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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.
1476 The format of the <file>debian/changelog</file> allows the
1477 package building tools to discover which version of the package
1478 is being built and find out other release-specific information.
1482 That format is a series of entries like this:
1484 <example compact="compact">
1485 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1487 [optional blank line(s), stripped]
1489 * <var>change details</var>
1490 <var>more change details</var>
1492 [blank line(s), included in output of dpkg-parsechangelog]
1494 * <var>even more change details</var>
1496 [optional blank line(s), stripped]
1498 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1503 <var>package</var> and <var>version</var> are the source
1504 package name and version number.
1508 <var>distribution(s)</var> lists the distributions where
1509 this version should be installed when it is uploaded - it
1510 is copied to the <tt>Distribution</tt> field in the
1511 <file>.changes</file> file. See <ref id="f-Distribution">.
1515 <var>urgency</var> is the value for the <tt>Urgency</tt>
1516 field in the <file>.changes</file> file for the upload
1517 (see <ref id="f-Urgency">). It is not possible to specify
1518 an urgency containing commas; commas are used to separate
1519 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1520 <prgn>dpkg</prgn> changelog format (though there is
1521 currently only one useful <var>keyword</var>,
1526 The change details may in fact be any series of lines
1527 starting with at least two spaces, but conventionally each
1528 change starts with an asterisk and a separating space and
1529 continuation lines are indented so as to bring them in
1530 line with the start of the text above. Blank lines may be
1531 used here to separate groups of changes, if desired.
1535 If this upload resolves bugs recorded in the Bug Tracking
1536 System (BTS), they may be automatically closed on the
1537 inclusion of this package into the Debian archive by
1538 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1539 in the change details.<footnote>
1540 To be precise, the string should match the following
1541 Perl regular expression:
1543 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1545 Then all of the bug numbers listed will be closed by the
1546 archive maintenance script (<prgn>katie</prgn>) using the
1547 <var>version</var> of the changelog entry.
1549 This information is conveyed via the <tt>Closes</tt> field
1550 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1554 The maintainer name and email address used in the changelog
1555 should be the details of the person uploading <em>this</em>
1556 version. They are <em>not</em> necessarily those of the
1557 usual package maintainer. The information here will be
1558 copied to the <tt>Changed-By</tt> field in the
1559 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1560 and then later used to send an acknowledgement when the
1561 upload has been installed.
1565 The <var>date</var> must be in RFC822 format<footnote>
1566 This is generated by <tt>date -R</tt>.
1567 </footnote>; it must include the time zone specified
1568 numerically, with the time zone name or abbreviation
1569 optionally present as a comment in parentheses.
1573 The first "title" line with the package name must start
1574 at the left hand margin. The "trailer" line with the
1575 maintainer and date details must be preceded by exactly
1576 one space. The maintainer details and the date must be
1577 separated by exactly two spaces.
1581 For more information on placement of the changelog files
1582 within binary packages, please see <ref id="changelogs">.
1586 <sect id="dpkgcopyright">
1587 <heading>Copyright: <file>debian/copyright</file></heading>
1589 Every package must be accompanied by a verbatim copy of
1590 its copyright and distribution license in the file
1591 <file>/usr/share/doc/<var>package</var>/copyright</file>
1592 (see <ref id="copyrightfile"> for further details). Also see
1593 <ref id="pkgcopyright"> for further considerations relayed
1594 to copyrights for packages.
1598 <heading>Error trapping in makefiles</heading>
1601 When <prgn>make</prgn> invokes a command in a makefile
1602 (including your package's upstream makefiles and
1603 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1604 means that <prgn>sh</prgn>'s usual bad error handling
1605 properties apply: if you include a miniature script as one
1606 of the commands in your makefile you'll find that if you
1607 don't do anything about it then errors are not detected
1608 and <prgn>make</prgn> will blithely continue after
1613 Every time you put more than one shell command (this
1614 includes using a loop) in a makefile command you
1615 must make sure that errors are trapped. For
1616 simple compound commands, such as changing directory and
1617 then running a program, using <tt>&&</tt> rather
1618 than semicolon as a command separator is sufficient. For
1619 more complex commands including most loops and
1620 conditionals you should include a separate <tt>set -e</tt>
1621 command at the start of every makefile command that's
1622 actually one of these miniature shell scripts.
1626 <sect id="timestamps">
1627 <heading>Time Stamps</heading>
1629 Maintainers should preserve the modification times of the
1630 upstream source files in a package, as far as is reasonably
1632 The rationale is that there is some information conveyed
1633 by knowing the age of the file, for example, you could
1634 recognize that some documentation is very old by looking
1635 at the modification time, so it would be nice if the
1636 modification time of the upstream source would be
1642 <sect id="restrictions">
1643 <heading>Restrictions on objects in source packages</heading>
1646 The source package may not contain any hard links<footnote>
1648 This is not currently detected when building source
1649 packages, but only when extracting
1653 Hard links may be permitted at some point in the
1654 future, but would require a fair amount of
1657 </footnote>, device special files, sockets or setuid or
1658 setgid files.<footnote>
1659 Setgid directories are allowed.
1664 <sect id="debianrules">
1665 <heading>Main building script: <file>debian/rules</file></heading>
1668 This file must be an executable makefile, and contains the
1669 package-specific recipes for compiling the package and
1670 building binary package(s) from the source.
1674 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1675 so that it can be invoked by saying its name rather than
1676 invoking <prgn>make</prgn> explicitly.
1680 Since an interactive <file>debian/rules</file> script makes it
1681 impossible to auto-compile that package and also makes it
1682 hard for other people to reproduce the same binary
1683 package, all <em>required targets</em> MUST be
1684 non-interactive. At a minimum, required targets are the
1685 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1686 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1687 <em>binary-indep</em>, and <em>build</em>. It also follows
1688 that any target that these targets depend on must also be
1693 The targets are as follows (required unless stated otherwise):
1695 <tag><tt>build</tt></tag>
1698 The <tt>build</tt> target should perform all the
1699 configuration and compilation of the package.
1700 If a package has an interactive pre-build
1701 configuration routine, the Debianized source package
1702 must either be built after this has taken place (so
1703 that the binary package can be built without rerunning
1704 the configuration) or the configuration routine
1705 modified to become non-interactive. (The latter is
1706 preferable if there are architecture-specific features
1707 detected by the configuration routine.)
1711 For some packages, notably ones where the same
1712 source tree is compiled in different ways to produce
1713 two binary packages, the <tt>build</tt> target
1714 does not make much sense. For these packages it is
1715 good enough to provide two (or more) targets
1716 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1717 for each of the ways of building the package, and a
1718 <tt>build</tt> target that does nothing. The
1719 <tt>binary</tt> target will have to build the
1720 package in each of the possible ways and make the
1721 binary package out of each.
1725 The <tt>build</tt> target must not do anything
1726 that might require root privilege.
1730 The <tt>build</tt> target may need to run the
1731 <tt>clean</tt> target first - see below.
1735 When a package has a configuration and build routine
1736 which takes a long time, or when the makefiles are
1737 poorly designed, or when <tt>build</tt> needs to
1738 run <tt>clean</tt> first, it is a good idea to
1739 <tt>touch build</tt> when the build process is
1740 complete. This will ensure that if <tt>debian/rules
1741 build</tt> is run again it will not rebuild the whole
1743 Another common way to do this is for <tt>build</tt>
1744 to depend on <prgn>build-stamp</prgn> and to do
1745 nothing else, and for the <prgn>build-stamp</prgn>
1746 target to do the building and to <tt>touch
1747 build-stamp</tt> on completion. This is
1748 especially useful if the build routine creates a
1749 file or directory called <tt>build</tt>; in such a
1750 case, <tt>build</tt> will need to be listed as
1751 a phony target (i.e., as a dependency of the
1752 <tt>.PHONY</tt> target). See the documentation of
1753 <prgn>make</prgn> for more information on phony
1759 <tag><tt>build-arch</tt> (optional),
1760 <tt>build-indep</tt> (optional)
1764 A package may also provide both of the targets
1765 <tt>build-arch</tt> and <tt>build-indep</tt>.
1766 The <tt>build-arch</tt> target, if provided, should
1767 perform all the configuration and compilation required
1768 for producing all architecture-dependant binary packages
1769 (those packages for which the body of the
1770 <tt>Architecture</tt> field in <tt>debian/control</tt>
1771 is not <tt>all</tt>).
1772 Similarly, the <tt>build-indep</tt> target, if
1773 provided, should perform all the configuration and
1774 compilation required for producing all
1775 architecture-independent binary packages
1776 (those packages for which the body of the
1777 <tt>Architecture</tt> field in <tt>debian/control</tt>
1779 The <tt>build</tt> target should depend on those of the
1780 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1781 are provided in the rules file.
1785 If one or both of the targets <tt>build-arch</tt> and
1786 <tt>build-indep</tt> are not provided, then invoking
1787 <file>debian/rules</file> with one of the not-provided
1788 targets as arguments should produce a exit status code
1789 of 2. Usually this is provided automatically by make
1790 if the target is missing.
1794 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1795 must not do anything that might require root privilege.
1799 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1800 <tt>binary-indep</tt>
1804 The <tt>binary</tt> target must be all that is
1805 necessary for the user to build the binary package(s)
1806 produced from this source package. It is
1807 split into two parts: <prgn>binary-arch</prgn> builds
1808 the binary packages which are specific to a particular
1809 architecture, and <tt>binary-indep</tt> builds
1810 those which are not.
1813 <tt>binary</tt> may be (and commonly is) a target with
1814 no commands which simply depends on
1815 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1818 Both <tt>binary-*</tt> targets should depend on the
1819 <tt>build</tt> target, or on the appropriate
1820 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1821 provided, so that the package is built if it has not
1822 been already. It should then create the relevant
1823 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1824 make their control files and <prgn>dpkg-deb</prgn> to
1825 build them and place them in the parent of the top
1830 Both the <tt>binary-arch</tt> and
1831 <tt>binary-indep</tt> targets <em>must</em> exist.
1832 If one of them has nothing to do (which will always be
1833 the case if the source generates only a single binary
1834 package, whether architecture-dependent or not), it
1835 must still exist and must always succeed.
1839 The <tt>binary</tt> targets must be invoked as
1841 The <prgn>fakeroot</prgn> package often allows one
1842 to build a package correctly even without being
1848 <tag><tt>clean</tt></tag>
1851 This must undo any effects that the <tt>build</tt>
1852 and <tt>binary</tt> targets may have had, except
1853 that it should leave alone any output files created in
1854 the parent directory by a run of a <tt>binary</tt>
1859 If a <tt>build</tt> file is touched at the end of
1860 the <tt>build</tt> target, as suggested above, it
1861 should be removed as the first action that
1862 <tt>clean</tt> performs, so that running
1863 <tt>build</tt> again after an interrupted
1864 <tt>clean</tt> doesn't think that everything is
1869 The <tt>clean</tt> target may need to be
1870 invoked as root if <tt>binary</tt> has been
1871 invoked since the last <tt>clean</tt>, or if
1872 <tt>build</tt> has been invoked as root (since
1873 <tt>build</tt> may create directories, for
1878 <tag><tt>get-orig-source</tt> (optional)</tag>
1881 This target fetches the most recent version of the
1882 original source package from a canonical archive site
1883 (via FTP or WWW, for example), does any necessary
1884 rearrangement to turn it into the original source
1885 tar file format described below, and leaves it in the
1890 This target may be invoked in any directory, and
1891 should take care to clean up any temporary files it
1896 This target is optional, but providing it if
1897 possible is a good idea.
1901 <tag><tt>patch</tt> (optional)</tag>
1904 This target performs whatever additional actions are
1905 required to make the source ready for editing (unpacking
1906 additional upstream archives, applying patches, etc.).
1907 It is recommended to be implemented for any package where
1908 <tt>dpkg-source -x</tt> does not result in source ready
1909 for additional modification. See
1910 <ref id="readmesource">.
1916 The <tt>build</tt>, <tt>binary</tt> and
1917 <tt>clean</tt> targets must be invoked with the current
1918 directory being the package's top-level directory.
1923 Additional targets may exist in <file>debian/rules</file>,
1924 either as published or undocumented interfaces or for the
1925 package's internal use.
1929 The architectures we build on and build for are determined
1930 by <prgn>make</prgn> variables using the utility
1931 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1932 You can determine the
1933 Debian architecture and the GNU style architecture
1934 specification string for the build machine (the machine type
1935 we are building on) as well as for the host machine (the
1936 machine type we are building for). Here is a list of
1937 supported <prgn>make</prgn> variables:
1938 <list compact="compact">
1940 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1943 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1944 specification string)
1947 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1948 <tt>DEB_*_GNU_TYPE</tt>)
1951 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1952 <tt>DEB_*_GNU_TYPE</tt>)
1954 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1955 the build machine or <tt>HOST</tt> for specification of the
1960 Backward compatibility can be provided in the rules file
1961 by setting the needed variables to suitable default
1962 values; please refer to the documentation of
1963 <prgn>dpkg-architecture</prgn> for details.
1967 It is important to understand that the <tt>DEB_*_ARCH</tt>
1968 string only determines which Debian architecture we are
1969 building on or for. It should not be used to get the CPU
1970 or system information; the GNU style variables should be
1974 <sect1 id="debianrules-options">
1975 <heading><file>debian/rules</file> and
1976 <tt>DEB_BUILD_OPTIONS</tt></heading>
1979 Supporting the standardized environment variable
1980 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
1981 contain several flags to change how a package is compiled and
1982 built. Each flag must be in the form <var>flag</var> or
1983 <var>flag</var>=<var>options</var>. If multiple flags are
1984 given, they must be separated by whitespace.<footnote>
1985 Some packages support any delimiter, but whitespace is the
1986 easiest to parse inside a makefile and avoids ambiguity with
1987 flag values that contain commas.
1989 <var>flag</var> must start with a lowercase letter
1990 (<tt>a-z</tt>) and consist only of lowercase letters,
1991 numbers (<tt>0-9</tt>), and the characters
1992 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
1993 <var>options</var> must not contain whitespace. The same
1994 tag should not be given multiple times with conflicting
1995 values. Package maintainers may assume that
1996 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2000 The meaning of the following tags has been standardized:
2004 The presence of this tag means that the package should
2005 be compiled with a minimum of optimization. For C
2006 programs, it is best to add <tt>-O0</tt> to
2007 <tt>CFLAGS</tt> (although this is usually the default).
2008 Some programs might fail to build or run at this level
2009 of optimization; it may be necessary to use
2010 <tt>-O1</tt>, for example.
2014 This tag means that the debugging symbols should not be
2015 stripped from the binary during installation, so that
2016 debugging information may be included in the package.
2018 <tag>parallel=n</tag>
2020 This tag means that the package should be built using up
2021 to <tt>n</tt> parallel processes if the package build
2022 system supports this.<footnote>
2023 Packages built with <tt>make</tt> can often implement
2024 this by passing the <tt>-j</tt><var>n</var> option to
2027 If the package build system does not support parallel
2028 builds, this string must be ignored. If the package
2029 build system only supports a lower level of concurrency
2030 than <var>n</var>, the package should be built using as
2031 many parallel processes as the package build system
2032 supports. It is up to the package maintainer to decide
2033 whether the package build times are long enough and the
2034 package build system is robust enough to make supporting
2035 parallel builds worthwhile.
2041 Unknown flags must be ignored by <file>debian/rules</file>.
2045 The following makefile snippet is an example of how one may
2046 implement the build options; you will probably have to
2047 massage this example in order to make it work for your
2049 <example compact="compact">
2052 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2053 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2054 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2055 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2057 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2062 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2063 INSTALL_PROGRAM += -s
2065 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2066 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2067 MAKEFLAGS += -j$(NUMJOBS)
2074 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2075 <sect id="substvars">
2076 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2079 When <prgn>dpkg-gencontrol</prgn>,
2080 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2081 generate control files they perform variable substitutions
2082 on their output just before writing it. Variable
2083 substitutions have the form <tt>${<var>variable</var>}</tt>.
2084 The optional file <file>debian/substvars</file> contains
2085 variable substitutions to be used; variables can also be set
2086 directly from <file>debian/rules</file> using the <tt>-V</tt>
2087 option to the source packaging commands, and certain
2088 predefined variables are also available.
2092 The <file>debian/substvars</file> file is usually generated and
2093 modified dynamically by <file>debian/rules</file> targets, in
2094 which case it must be removed by the <tt>clean</tt> target.
2098 See <manref name="deb-substvars" section="5"> for full
2099 details about source variable substitutions, including the
2100 format of <file>debian/substvars</file>.</p>
2103 <sect id="debianwatch">
2104 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2107 This is an optional, recommended control file for the
2108 <tt>uscan</tt> utility which defines how to automatically
2109 scan ftp or http sites for newly available updates of the
2110 package. This is used by <url id="
2111 http://dehs.alioth.debian.org/"> and other Debian QA tools
2112 to help with quality control and maintenance of the
2113 distribution as a whole.
2118 <sect id="debianfiles">
2119 <heading>Generated files list: <file>debian/files</file></heading>
2122 This file is not a permanent part of the source tree; it
2123 is used while building packages to record which files are
2124 being generated. <prgn>dpkg-genchanges</prgn> uses it
2125 when it generates a <file>.changes</file> file.
2129 It should not exist in a shipped source package, and so it
2130 (and any backup files or temporary files such as
2131 <file>files.new</file><footnote>
2132 <file>files.new</file> is used as a temporary file by
2133 <prgn>dpkg-gencontrol</prgn> and
2134 <prgn>dpkg-distaddfile</prgn> - they write a new
2135 version of <tt>files</tt> here before renaming it,
2136 to avoid leaving a corrupted copy if an error
2138 </footnote>) should be removed by the
2139 <tt>clean</tt> target. It may also be wise to
2140 ensure a fresh start by emptying or removing it at the
2141 start of the <tt>binary</tt> target.
2145 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2146 package, it adds an entry to <file>debian/files</file> for the
2147 <file>.deb</file> file that will be created when <tt>dpkg-deb
2148 --build</tt> is run for that binary package. So for most
2149 packages all that needs to be done with this file is to
2150 delete it in the <tt>clean</tt> target.
2154 If a package upload includes files besides the source
2155 package and any binary packages whose control files were
2156 made with <prgn>dpkg-gencontrol</prgn> then they should be
2157 placed in the parent of the package's top-level directory
2158 and <prgn>dpkg-distaddfile</prgn> should be called to add
2159 the file to the list in <file>debian/files</file>.</p>
2162 <sect id="embeddedfiles">
2163 <heading>Convenience copies of code</heading>
2166 Some software packages include in their distribution convenience
2167 copies of code from other software packages, generally so that
2168 users compiling from source don't have to download multiple
2169 packages. Debian packages should not make use of these
2170 convenience copies unless the included package is explicitly
2171 intended to be used in this way.<footnote>
2172 For example, parts of the GNU build system work like this.
2174 If the included code is already in the Debian archive in the
2175 form of a library, the Debian packaging should ensure that
2176 binary packages reference the libraries already in Debian and
2177 the convenience copy is not used. If the included code is not
2178 already in Debian, it should be packaged separately as a
2179 prerequisite if possible.
2181 Having multiple copies of the same code in Debian is
2182 inefficient, often creates either static linking or shared
2183 library conflicts, and, most importantly, increases the
2184 difficulty of handling security vulnerabilities in the
2190 <sect id="readmesource">
2191 <heading>Source package handling:
2192 <file>debian/README.source</file></heading>
2195 If running <prgn>dpkg-source -x</prgn> on a source package
2196 doesn't produce the source of the package, ready for editing,
2197 and allow one to make changes and run
2198 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2199 without taking any additional steps, creating a
2200 <file>debian/README.source</file> documentation file is
2201 recommended. This file should explain how to do all of the
2204 <item>Generate the fully patched source, in a form ready for
2205 editing, that would be built to create Debian
2206 packages. Doing this with a <tt>patch</tt> target in
2207 <file>debian/rules</file> is recommended; see
2208 <ref id="debianrules">.</item>
2209 <item>Modify the source and save those modifications so that
2210 they will be applied when building the package.</item>
2211 <item>Remove source modifications that are currently being
2212 applied when building the package.</item>
2213 <item>Optionally, document what steps are necessary to
2214 upgrade the Debian source package to a new upstream version,
2215 if applicable.</item>
2217 This explanation should include specific commands and mention
2218 any additional required Debian packages. It should not assume
2219 familiarity with any specific Debian packaging system or patch
2224 This explanation may refer to a documentation file installed by
2225 one of the package's build dependencies provided that the
2226 referenced documentation clearly explains these tasks and is not
2227 a general reference manual.
2231 <file>debian/README.source</file> may also include any other
2232 information that would be helpful to someone modifying the
2233 source package. Even if the package doesn't fit the above
2234 description, maintainers are encouraged to document in a
2235 <file>debian/README.source</file> file any source package with a
2236 particularly complex or unintuitive source layout or build
2237 system (for example, a package that builds the same source
2238 multiple times to generate different binary packages).
2244 <chapt id="controlfields">
2245 <heading>Control files and their fields</heading>
2248 The package management system manipulates data represented in
2249 a common format, known as <em>control data</em>, stored in
2250 <em>control files</em>.
2251 Control files are used for source packages, binary packages and
2252 the <file>.changes</file> files which control the installation
2253 of uploaded files<footnote>
2254 <prgn>dpkg</prgn>'s internal databases are in a similar
2259 <sect id="controlsyntax">
2260 <heading>Syntax of control files</heading>
2263 A control file consists of one or more paragraphs of
2265 The paragraphs are also sometimes referred to as stanzas.
2267 The paragraphs are separated by blank lines. Some control
2268 files allow only one paragraph; others allow several, in
2269 which case each paragraph usually refers to a different
2270 package. (For example, in source packages, the first
2271 paragraph refers to the source package, and later paragraphs
2272 refer to binary packages generated from the source.)
2276 Each paragraph consists of a series of data fields; each
2277 field consists of the field name, followed by a colon and
2278 then the data/value associated with that field. It ends at
2279 the end of the (logical) line. Horizontal whitespace
2280 (spaces and tabs) may occur immediately before or after the
2281 value and is ignored there; it is conventional to put a
2282 single space after the colon. For example, a field might
2284 <example compact="compact">
2287 the field name is <tt>Package</tt> and the field value
2292 Many fields' values may span several lines; in this case
2293 each continuation line must start with a space or a tab.
2294 Any trailing spaces or tabs at the end of individual
2295 lines of a field value are ignored.
2299 In fields where it is specified that lines may not wrap,
2300 only a single line of data is allowed and whitespace is not
2301 significant in a field body. Whitespace must not appear
2302 inside names (of packages, architectures, files or anything
2303 else) or version numbers, or between the characters of
2304 multi-character version relationships.
2308 Field names are not case-sensitive, but it is usual to
2309 capitalize the field names using mixed case as shown below.
2313 Blank lines, or lines consisting only of spaces and tabs,
2314 are not allowed within field values or between fields - that
2315 would mean a new paragraph.
2319 All control files must be encoded in UTF-8.
2323 <sect id="sourcecontrolfiles">
2324 <heading>Source package control files -- <file>debian/control</file></heading>
2327 The <file>debian/control</file> file contains the most vital
2328 (and version-independent) information about the source package
2329 and about the binary packages it creates.
2333 The first paragraph of the control file contains information about
2334 the source package in general. The subsequent sets each describe a
2335 binary package that the source tree builds.
2339 The fields in the general paragraph (the first one, for the source
2342 <list compact="compact">
2343 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2344 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2345 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2346 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2347 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2348 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2349 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2350 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2355 The fields in the binary package paragraphs are:
2357 <list compact="compact">
2358 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2359 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2360 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2361 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2362 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2363 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2364 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2365 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2370 The syntax and semantics of the fields are described below.
2376 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2377 generate control files for binary packages (see below), by
2378 <prgn>dpkg-genchanges</prgn> to generate the
2379 <tt>.changes</tt> file to accompany the upload, and by
2380 <prgn>dpkg-source</prgn> when it creates the
2381 <file>.dsc</file> source control file as part of a source
2382 archive. Many fields are permitted to span multiple lines in
2383 <file>debian/control</file> but not in any other control
2384 file. These tools are responsible for removing the line
2385 breaks from such fields when using fields from
2386 <file>debian/control</file> to generate other control files.
2390 The fields here may contain variable references - their
2391 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2392 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2393 when they generate output control files.
2394 See <ref id="substvars"> for details.
2399 <sect id="binarycontrolfiles">
2400 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2403 The <file>DEBIAN/control</file> file contains the most vital
2404 (and version-dependent) information about a binary package.
2408 The fields in this file are:
2410 <list compact="compact">
2411 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2412 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2413 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2414 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2415 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2416 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2417 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2418 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2419 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2420 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2421 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2422 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2427 <sect id="debiansourcecontrolfiles">
2428 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2431 This file contains a series of fields, identified and
2432 separated just like the fields in the control file of
2433 a binary package. The fields are listed below; their
2434 syntax is described above, in <ref id="pkg-controlfields">.
2436 <list compact="compact">
2437 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2438 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2439 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2440 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2441 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2442 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2443 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2444 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2445 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2446 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2447 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2452 The source package control file is generated by
2453 <prgn>dpkg-source</prgn> when it builds the source
2454 archive, from other files in the source package,
2455 described above. When unpacking, it is checked against
2456 the files and directories in the other parts of the
2462 <sect id="debianchangesfiles">
2463 <heading>Debian changes files -- <file>.changes</file></heading>
2466 The .changes files are used by the Debian archive maintenance
2467 software to process updates to packages. They contain one
2468 paragraph which contains information from the
2469 <tt>debian/control</tt> file and other data about the
2470 source package gathered via <tt>debian/changelog</tt>
2471 and <tt>debian/rules</tt>.
2475 The fields in this file are:
2477 <list compact="compact">
2478 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2479 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2480 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2481 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2484 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2485 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2486 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2488 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2489 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2490 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2491 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2496 <sect id="controlfieldslist">
2497 <heading>List of fields</heading>
2499 <sect1 id="f-Source">
2500 <heading><tt>Source</tt></heading>
2503 This field identifies the source package name.
2507 In <file>debian/control</file> or a <file>.dsc</file> file,
2508 this field must contain only the name of the source package.
2512 In a binary package control file or a <file>.changes</file>
2513 file, the source package name may be followed by a version
2514 number in parentheses<footnote>
2515 It is customary to leave a space after the package name
2516 if a version number is specified.
2518 This version number may be omitted (and is, by
2519 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2520 the <tt>Version</tt> field of the binary package in
2521 question. The field itself may be omitted from a binary
2522 package control file when the source package has the same
2523 name and version as the binary package.
2527 <sect1 id="f-Maintainer">
2528 <heading><tt>Maintainer</tt></heading>
2531 The package maintainer's name and email address. The name
2532 should come first, then the email address inside angle
2533 brackets <tt><></tt> (in RFC822 format).
2537 If the maintainer's name contains a full stop then the
2538 whole field will not work directly as an email address due
2539 to a misfeature in the syntax specified in RFC822; a
2540 program using this field as an address must check for this
2541 and correct the problem if necessary (for example by
2542 putting the name in round brackets and moving it to the
2543 end, and bringing the email address forward).
2547 <sect1 id="f-Uploaders">
2548 <heading><tt>Uploaders</tt></heading>
2551 List of the names and email addresses of co-maintainers of
2552 the package, if any. If the package has other maintainers
2553 beside the one named in the
2554 <qref id="f-Maintainer">Maintainer field</qref>, their
2555 names and email addresses should be listed here. The
2556 format is the same as that of the Maintainer tag, and
2557 multiple entries should be comma separated. Currently,
2558 this field is restricted to a single line of data. This
2559 is an optional field.
2562 Any parser that interprets the Uploaders field in
2563 <file>debian/control</file> must permit it to span multiple
2564 lines. Line breaks in an Uploaders field that spans multiple
2565 lines are not significant and the semantics of the field are
2566 the same as if the line breaks had not been present.
2570 <sect1 id="f-Changed-By">
2571 <heading><tt>Changed-By</tt></heading>
2574 The name and email address of the person who changed the
2575 said package. Usually the name of the maintainer.
2576 All the rules for the Maintainer field apply here, too.
2580 <sect1 id="f-Section">
2581 <heading><tt>Section</tt></heading>
2584 This field specifies an application area into which the package
2585 has been classified. See <ref id="subsections">.
2589 When it appears in the <file>debian/control</file> file,
2590 it gives the value for the subfield of the same name in
2591 the <tt>Files</tt> field of the <file>.changes</file> file.
2592 It also gives the default for the same field in the binary
2597 <sect1 id="f-Priority">
2598 <heading><tt>Priority</tt></heading>
2601 This field represents how important that it is that the user
2602 have the package installed. See <ref id="priorities">.
2606 When it appears in the <file>debian/control</file> file,
2607 it gives the value for the subfield of the same name in
2608 the <tt>Files</tt> field of the <file>.changes</file> file.
2609 It also gives the default for the same field in the binary
2614 <sect1 id="f-Package">
2615 <heading><tt>Package</tt></heading>
2618 The name of the binary package.
2622 Package names must consist only of lower case letters
2623 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2624 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2625 They must be at least two characters long and must start
2626 with an alphanumeric character.
2630 <sect1 id="f-Architecture">
2631 <heading><tt>Architecture</tt></heading>
2634 Depending on context and the control file used, the
2635 <tt>Architecture</tt> field can include the following sets of
2638 <item>A unique single word identifying a Debian machine
2639 architecture, see <ref id="arch-spec">.
2640 <item><tt>all</tt>, which indicates an
2641 architecture-independent package.
2642 <item><tt>any</tt>, which indicates a package available
2643 for building on any architecture.
2644 <item><tt>source</tt>, which indicates a source package.
2649 In the main <file>debian/control</file> file in the source
2650 package, or in the source package control file
2651 <file>.dsc</file>, one may specify a list of architectures
2652 separated by spaces, or the special values <tt>any</tt> or
2657 Specifying <tt>any</tt> indicates that the source package
2658 isn't dependent on any particular architecture and should
2659 compile fine on any one. The produced binary package(s)
2660 will be specific to whatever the current build architecture
2662 This is the most often used setting, and is recommended
2663 for new packages that aren't <tt>Architecture: all</tt>.
2668 Specifying a list of architectures indicates that the source
2669 will build an architecture-dependent package, and will only
2670 work correctly on the listed architectures.<footnote>
2671 This is a setting used for a minority of cases where the
2672 program is not portable. Generally, it should not be used
2678 In a <file>.changes</file> file, the <tt>Architecture</tt>
2679 field lists the architecture(s) of the package(s)
2680 currently being uploaded. This will be a list; if the
2681 source for the package is also being uploaded, the special
2682 entry <tt>source</tt> is also present.
2686 See <ref id="debianrules"> for information how to get the
2687 architecture for the build process.
2691 <sect1 id="f-Essential">
2692 <heading><tt>Essential</tt></heading>
2695 This is a boolean field which may occur only in the
2696 control file of a binary package or in a per-package fields
2697 paragraph of a main source control data file.
2701 If set to <tt>yes</tt> then the package management system
2702 will refuse to remove the package (upgrading and replacing
2703 it is still possible). The other possible value is <tt>no</tt>,
2704 which is the same as not having the field at all.
2709 <heading>Package interrelationship fields:
2710 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2711 <tt>Recommends</tt>, <tt>Suggests</tt>,
2712 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2713 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2717 These fields describe the package's relationships with
2718 other packages. Their syntax and semantics are described
2719 in <ref id="relationships">.</p>
2722 <sect1 id="f-Standards-Version">
2723 <heading><tt>Standards-Version</tt></heading>
2726 The most recent version of the standards (the policy
2727 manual and associated texts) with which the package
2732 The version number has four components: major and minor
2733 version number and major and minor patch level. When the
2734 standards change in a way that requires every package to
2735 change the major number will be changed. Significant
2736 changes that will require work in many packages will be
2737 signaled by a change to the minor number. The major patch
2738 level will be changed for any change to the meaning of the
2739 standards, however small; the minor patch level will be
2740 changed when only cosmetic, typographical or other edits
2741 are made which neither change the meaning of the document
2742 nor affect the contents of packages.
2746 Thus only the first three components of the policy version
2747 are significant in the <em>Standards-Version</em> control
2748 field, and so either these three components or the all
2749 four components may be specified.<footnote>
2750 In the past, people specified the full version number
2751 in the Standards-Version field, for example "2.3.0.0".
2752 Since minor patch-level changes don't introduce new
2753 policy, it was thought it would be better to relax
2754 policy and only require the first 3 components to be
2755 specified, in this example "2.3.0". All four
2756 components may still be used if someone wishes to do so.
2762 <sect1 id="f-Version">
2763 <heading><tt>Version</tt></heading>
2766 The version number of a package. The format is:
2767 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2771 The three components here are:
2773 <tag><var>epoch</var></tag>
2776 This is a single (generally small) unsigned integer. It
2777 may be omitted, in which case zero is assumed. If it is
2778 omitted then the <var>upstream_version</var> may not
2783 It is provided to allow mistakes in the version numbers
2784 of older versions of a package, and also a package's
2785 previous version numbering schemes, to be left behind.
2789 <tag><var>upstream_version</var></tag>
2792 This is the main part of the version number. It is
2793 usually the version number of the original ("upstream")
2794 package from which the <file>.deb</file> file has been made,
2795 if this is applicable. Usually this will be in the same
2796 format as that specified by the upstream author(s);
2797 however, it may need to be reformatted to fit into the
2798 package management system's format and comparison
2803 The comparison behavior of the package management system
2804 with respect to the <var>upstream_version</var> is
2805 described below. The <var>upstream_version</var>
2806 portion of the version number is mandatory.
2810 The <var>upstream_version</var> may contain only
2811 alphanumerics<footnote>
2812 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2814 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2815 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2816 tilde) and should start with a digit. If there is no
2817 <var>debian_revision</var> then hyphens are not allowed;
2818 if there is no <var>epoch</var> then colons are not
2823 <tag><var>debian_revision</var></tag>
2826 This part of the version number specifies the version of
2827 the Debian package based on the upstream version. It
2828 may contain only alphanumerics and the characters
2829 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2830 tilde) and is compared in the same way as the
2831 <var>upstream_version</var> is.
2835 It is optional; if it isn't present then the
2836 <var>upstream_version</var> may not contain a hyphen.
2837 This format represents the case where a piece of
2838 software was written specifically to be turned into a
2839 Debian package, and so there is only one "debianisation"
2840 of it and therefore no revision indication is required.
2844 It is conventional to restart the
2845 <var>debian_revision</var> at <tt>1</tt> each time the
2846 <var>upstream_version</var> is increased.
2850 The package management system will break the version
2851 number apart at the last hyphen in the string (if there
2852 is one) to determine the <var>upstream_version</var> and
2853 <var>debian_revision</var>. The absence of a
2854 <var>debian_revision</var> is equivalent to a
2855 <var>debian_revision</var> of <tt>0</tt>.
2862 When comparing two version numbers, first the <var>epoch</var>
2863 of each are compared, then the <var>upstream_version</var> if
2864 <var>epoch</var> is equal, and then <var>debian_revision</var>
2865 if <var>upstream_version</var> is also equal.
2866 <var>epoch</var> is compared numerically. The
2867 <var>upstream_version</var> and <var>debian_revision</var>
2868 parts are compared by the package management system using the
2869 following algorithm:
2873 The strings are compared from left to right.
2877 First the initial part of each string consisting entirely of
2878 non-digit characters is determined. These two parts (one of
2879 which may be empty) are compared lexically. If a difference
2880 is found it is returned. The lexical comparison is a
2881 comparison of ASCII values modified so that all the letters
2882 sort earlier than all the non-letters and so that a tilde
2883 sorts before anything, even the end of a part. For example,
2884 the following parts are in sorted order from earliest to
2885 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2886 <tt>a</tt>.<footnote>
2887 One common use of <tt>~</tt> is for upstream pre-releases.
2888 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2889 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2894 Then the initial part of the remainder of each string which
2895 consists entirely of digit characters is determined. The
2896 numerical values of these two parts are compared, and any
2897 difference found is returned as the result of the comparison.
2898 For these purposes an empty string (which can only occur at
2899 the end of one or both version strings being compared) counts
2904 These two steps (comparing and removing initial non-digit
2905 strings and initial digit strings) are repeated until a
2906 difference is found or both strings are exhausted.
2910 Note that the purpose of epochs is to allow us to leave behind
2911 mistakes in version numbering, and to cope with situations
2912 where the version numbering scheme changes. It is
2913 <em>not</em> intended to cope with version numbers containing
2914 strings of letters which the package management system cannot
2915 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2916 silly orderings (the author of this manual has heard of a
2917 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2918 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2919 <tt>2</tt> and so forth).
2923 <sect1 id="f-Description">
2924 <heading><tt>Description</tt></heading>
2927 In a source or binary control file, the <tt>Description</tt>
2928 field contains a description of the binary package, consisting
2929 of two parts, the synopsis or the short description, and the
2930 long description. The field's format is as follows:
2935 Description: <single line synopsis>
2936 <extended description over several lines>
2941 The lines in the extended description can have these formats:
2947 Those starting with a single space are part of a paragraph.
2948 Successive lines of this form will be word-wrapped when
2949 displayed. The leading space will usually be stripped off.
2953 Those starting with two or more spaces. These will be
2954 displayed verbatim. If the display cannot be panned
2955 horizontally, the displaying program will line wrap them "hard"
2956 (i.e., without taking account of word breaks). If it can they
2957 will be allowed to trail off to the right. None, one or two
2958 initial spaces may be deleted, but the number of spaces
2959 deleted from each line will be the same (so that you can have
2960 indenting work correctly, for example).
2964 Those containing a single space followed by a single full stop
2965 character. These are rendered as blank lines. This is the
2966 <em>only</em> way to get a blank line<footnote>
2967 Completely empty lines will not be rendered as blank lines.
2968 Instead, they will cause the parser to think you're starting
2969 a whole new record in the control file, and will therefore
2970 likely abort with an error.
2975 Those containing a space, a full stop and some more characters.
2976 These are for future expansion. Do not use them.
2982 Do not use tab characters. Their effect is not predictable.
2986 See <ref id="descriptions"> for further information on this.
2990 In a <file>.changes</file> file, the <tt>Description</tt> field
2991 contains a summary of the descriptions for the packages being
2996 The part of the field before the first newline is empty;
2997 thereafter each line has the name of a binary package and
2998 the summary description line from that binary package.
2999 Each line is indented by one space.
3004 <sect1 id="f-Distribution">
3005 <heading><tt>Distribution</tt></heading>
3008 In a <file>.changes</file> file or parsed changelog output
3009 this contains the (space-separated) name(s) of the
3010 distribution(s) where this version of the package should
3011 be installed. Valid distributions are determined by the
3012 archive maintainers.<footnote>
3013 Current distribution names are:
3014 <taglist compact="compact">
3015 <tag><em>stable</em></tag>
3017 This is the current "released" version of Debian
3018 GNU/Linux. Once the distribution is
3019 <em>stable</em> only security fixes and other
3020 major bug fixes are allowed. When changes are
3021 made to this distribution, the release number is
3022 increased (for example: 2.2r1 becomes 2.2r2 then
3026 <tag><em>unstable</em></tag>
3028 This distribution value refers to the
3029 <em>developmental</em> part of the Debian
3030 distribution tree. New packages, new upstream
3031 versions of packages and bug fixes go into the
3032 <em>unstable</em> directory tree. Download from
3033 this distribution at your own risk.
3036 <tag><em>testing</em></tag>
3038 This distribution value refers to the
3039 <em>testing</em> part of the Debian distribution
3040 tree. It receives its packages from the
3041 unstable distribution after a short time lag to
3042 ensure that there are no major issues with the
3043 unstable packages. It is less prone to breakage
3044 than unstable, but still risky. It is not
3045 possible to upload packages directly to
3049 <tag><em>frozen</em></tag>
3051 From time to time, the <em>testing</em>
3052 distribution enters a state of "code-freeze" in
3053 anticipation of release as a <em>stable</em>
3054 version. During this period of testing only
3055 fixes for existing or newly-discovered bugs will
3056 be allowed. The exact details of this stage are
3057 determined by the Release Manager.
3060 <tag><em>experimental</em></tag>
3062 The packages with this distribution value are
3063 deemed by their maintainers to be high
3064 risk. Oftentimes they represent early beta or
3065 developmental packages from various sources that
3066 the maintainers want people to try, but are not
3067 ready to be a part of the other parts of the
3068 Debian distribution tree. Download at your own
3074 You should list <em>all</em> distributions that the
3075 package should be installed into.
3079 More information is available in the Debian Developer's
3080 Reference, section "The Debian archive".
3087 <heading><tt>Date</tt></heading>
3090 This field includes the date the package was built or last edited.
3094 The value of this field is usually extracted from the
3095 <file>debian/changelog</file> file - see
3096 <ref id="dpkgchangelog">).
3100 <sect1 id="f-Format">
3101 <heading><tt>Format</tt></heading>
3104 This field specifies a format revision for the file.
3105 The most current format described in the Policy Manual
3106 is version <strong>1.5</strong>. The syntax of the
3107 format value is the same as that of a package version
3108 number except that no epoch or Debian revision is allowed
3109 - see <ref id="f-Version">.
3113 <sect1 id="f-Urgency">
3114 <heading><tt>Urgency</tt></heading>
3117 This is a description of how important it is to upgrade to
3118 this version from previous ones. It consists of a single
3119 keyword taking one of the values <tt>low</tt>,
3120 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3121 <tt>critical</tt><footnote>
3122 Other urgency values are supported with configuration
3123 changes in the archive software but are not used in Debian.
3124 The urgency affects how quickly a package will be considered
3125 for inclusion into the <tt>testing</tt> distribution and
3126 gives an indication of the importance of any fixes included
3127 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3128 treated as synonymous.
3129 </footnote> (not case-sensitive) followed by an optional
3130 commentary (separated by a space) which is usually in
3131 parentheses. For example:
3134 Urgency: low (HIGH for users of diversions)
3140 The value of this field is usually extracted from the
3141 <file>debian/changelog</file> file - see
3142 <ref id="dpkgchangelog">.
3146 <sect1 id="f-Changes">
3147 <heading><tt>Changes</tt></heading>
3150 This field contains the human-readable changes data, describing
3151 the differences between the last version and the current one.
3155 There should be nothing in this field before the first
3156 newline; all the subsequent lines must be indented by at
3157 least one space; blank lines must be represented by a line
3158 consisting only of a space and a full stop.
3162 The value of this field is usually extracted from the
3163 <file>debian/changelog</file> file - see
3164 <ref id="dpkgchangelog">).
3168 Each version's change information should be preceded by a
3169 "title" line giving at least the version, distribution(s)
3170 and urgency, in a human-readable way.
3174 If data from several versions is being returned the entry
3175 for the most recent version should be returned first, and
3176 entries should be separated by the representation of a
3177 blank line (the "title" line may also be followed by the
3178 representation of blank line).
3182 <sect1 id="f-Binary">
3183 <heading><tt>Binary</tt></heading>
3186 This field is a list of binary packages.
3190 When it appears in the <file>.dsc</file> file it is the list
3191 of binary packages which a source package can produce. It
3192 does not necessarily produce all of these binary packages
3193 for every architecture. The source control file doesn't
3194 contain details of which architectures are appropriate for
3195 which of the binary packages.
3199 When it appears in a <file>.changes</file> file it lists the
3200 names of the binary packages actually being uploaded.
3204 The syntax is a list of binary packages separated by
3206 A space after each comma is conventional.
3207 </footnote>. Currently the packages must be separated using
3208 only spaces in the <file>.changes</file> file.
3212 <sect1 id="f-Installed-Size">
3213 <heading><tt>Installed-Size</tt></heading>
3216 This field appears in the control files of binary
3217 packages, and in the <file>Packages</file> files. It gives
3218 the total amount of disk space required to install the
3223 The disk space is represented in kilobytes as a simple
3228 <sect1 id="f-Files">
3229 <heading><tt>Files</tt></heading>
3232 This field contains a list of files with information about
3233 each one. The exact information and syntax varies with
3234 the context. In all cases the part of the field
3235 contents on the same line as the field name is empty. The
3236 remainder of the field is one line per file, each line
3237 being indented by one space and containing a number of
3238 sub-fields separated by spaces.
3242 In the <file>.dsc</file> file, each line contains the MD5
3243 checksum, size and filename of the tar file and (if applicable)
3244 diff file which make up the remainder of the source
3246 That is, the parts which are not the <tt>.dsc</tt>.
3248 The exact forms of the filenames are described
3249 in <ref id="pkg-sourcearchives">.
3253 In the <file>.changes</file> file this contains one line per
3254 file being uploaded. Each line contains the MD5 checksum,
3255 size, section and priority and the filename.
3256 The <qref id="f-Section">section</qref>
3257 and <qref id="f-Priority">priority</qref>
3258 are the values of the corresponding fields in
3259 the main source control file. If no section or priority is
3260 specified then <tt>-</tt> should be used, though section
3261 and priority values must be specified for new packages to
3262 be installed properly.
3266 The special value <tt>byhand</tt> for the section in a
3267 <tt>.changes</tt> file indicates that the file in question
3268 is not an ordinary package file and must by installed by
3269 hand by the distribution maintainers. If the section is
3270 <tt>byhand</tt> the priority should be <tt>-</tt>.
3274 If a new Debian revision of a package is being shipped and
3275 no new original source archive is being distributed the
3276 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3277 entry for the original source archive
3278 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3279 but the <file>.changes</file> file should leave it out. In
3280 this case the original source archive on the distribution
3281 site must match exactly, byte-for-byte, the original
3282 source archive which was used to generate the
3283 <file>.dsc</file> file and diff which are being uploaded.</p>
3286 <sect1 id="f-Closes">
3287 <heading><tt>Closes</tt></heading>
3290 A space-separated list of bug report numbers that the upload
3291 governed by the .changes file closes.
3295 <sect1 id="f-Homepage">
3296 <heading><tt>Homepage</tt></heading>
3299 The URL of the web site for this package, preferably (when
3300 applicable) the site from which the original source can be
3301 obtained and any additional upstream documentation or
3302 information may be found. The content of this field is a
3303 simple URL without any surrounding characters such as
3311 <heading>User-defined fields</heading>
3314 Additional user-defined fields may be added to the
3315 source package control file. Such fields will be
3316 ignored, and not copied to (for example) binary or
3317 source package control files or upload control files.
3321 If you wish to add additional unsupported fields to
3322 these output files you should use the mechanism
3327 Fields in the main source control information file with
3328 names starting <tt>X</tt>, followed by one or more of
3329 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3330 be copied to the output files. Only the part of the
3331 field name after the hyphen will be used in the output
3332 file. Where the letter <tt>B</tt> is used the field
3333 will appear in binary package control files, where the
3334 letter <tt>S</tt> is used in source package control
3335 files and where <tt>C</tt> is used in upload control
3336 (<tt>.changes</tt>) files.
3340 For example, if the main source information control file
3343 XBS-Comment: I stand between the candle and the star.
3345 then the binary and source package control files will contain the
3348 Comment: I stand between the candle and the star.
3357 <chapt id="maintainerscripts">
3358 <heading>Package maintainer scripts and installation procedure</heading>
3361 <heading>Introduction to package maintainer scripts</heading>
3364 It is possible to supply scripts as part of a package which
3365 the package management system will run for you when your
3366 package is installed, upgraded or removed.
3370 These scripts are the files <prgn>preinst</prgn>,
3371 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3372 <prgn>postrm</prgn> in the control area of the package.
3373 They must be proper executable files; if they are scripts
3374 (which is recommended), they must start with the usual
3375 <tt>#!</tt> convention. They should be readable and
3376 executable by anyone, and must not be world-writable.
3380 The package management system looks at the exit status from
3381 these scripts. It is important that they exit with a
3382 non-zero status if there is an error, so that the package
3383 management system can stop its processing. For shell
3384 scripts this means that you <em>almost always</em> need to
3385 use <tt>set -e</tt> (this is usually true when writing shell
3386 scripts, in fact). It is also important, of course, that
3387 they don't exit with a non-zero status if everything went
3392 Additionally, packages interacting with users using
3393 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3394 install a <prgn>config</prgn> script in the control area,
3395 see <ref id="maintscriptprompt"> for details.
3399 When a package is upgraded a combination of the scripts from
3400 the old and new packages is called during the upgrade
3401 procedure. If your scripts are going to be at all
3402 complicated you need to be aware of this, and may need to
3403 check the arguments to your scripts.
3407 Broadly speaking the <prgn>preinst</prgn> is called before
3408 (a particular version of) a package is installed, and the
3409 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3410 before (a version of) a package is removed and the
3411 <prgn>postrm</prgn> afterwards.
3415 Programs called from maintainer scripts should not normally
3416 have a path prepended to them. Before installation is
3417 started, the package management system checks to see if the
3418 programs <prgn>ldconfig</prgn>,
3419 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3420 and <prgn>update-rc.d</prgn> can be found via the
3421 <tt>PATH</tt> environment variable. Those programs, and any
3422 other program that one would expect to be in the
3423 <tt>PATH</tt>, should thus be invoked without an absolute
3424 pathname. Maintainer scripts should also not reset the
3425 <tt>PATH</tt>, though they might choose to modify it by
3426 prepending or appending package-specific directories. These
3427 considerations really apply to all shell scripts.</p>
3430 <sect id="idempotency">
3431 <heading>Maintainer scripts idempotency</heading>
3434 It is necessary for the error recovery procedures that the
3435 scripts be idempotent. This means that if it is run
3436 successfully, and then it is called again, it doesn't bomb
3437 out or cause any harm, but just ensures that everything is
3438 the way it ought to be. If the first call failed, or
3439 aborted half way through for some reason, the second call
3440 should merely do the things that were left undone the first
3441 time, if any, and exit with a success status if everything
3443 This is so that if an error occurs, the user interrupts
3444 <prgn>dpkg</prgn> or some other unforeseen circumstance
3445 happens you don't leave the user with a badly-broken
3446 package when <prgn>dpkg</prgn> attempts to repeat the
3452 <sect id="controllingterminal">
3453 <heading>Controlling terminal for maintainer scripts</heading>
3456 The maintainer scripts are guaranteed to run with a
3457 controlling terminal and can interact with the user.
3458 Because these scripts may be executed with standard output
3459 redirected into a pipe for logging purposes, Perl scripts
3460 should set unbuffered output by setting <tt>$|=1</tt> so
3461 that the output is printed immediately rather than being
3465 <sect id="exitstatus">
3466 <heading>Exit status</heading>
3469 Each script must return a zero exit status for
3470 success, or a nonzero one for failure, since the package
3471 management system looks for the exit status of these scripts
3472 and determines what action to take next based on that datum.
3476 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3481 <list compact="compact">
3483 <var>new-preinst</var> <tt>install</tt>
3486 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3489 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3492 <var>old-preinst</var> <tt>abort-upgrade</tt>
3493 <var>new-version</var>
3498 <list compact="compact">
3500 <var>postinst</var> <tt>configure</tt>
3501 <var>most-recently-configured-version</var>
3504 <var>old-postinst</var> <tt>abort-upgrade</tt>
3505 <var>new-version</var>
3508 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3509 <tt>in-favour</tt> <var>package</var>
3510 <var>new-version</var>
3513 <var>postinst</var> <tt>abort-remove</tt>
3516 <var>deconfigured's-postinst</var>
3517 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3518 <var>failed-install-package</var> <var>version</var>
3519 [<tt>removing</tt> <var>conflicting-package</var>
3525 <list compact="compact">
3527 <var>prerm</var> <tt>remove</tt>
3530 <var>old-prerm</var> <tt>upgrade</tt>
3531 <var>new-version</var>
3534 <var>new-prerm</var> <tt>failed-upgrade</tt>
3535 <var>old-version</var>
3538 <var>conflictor's-prerm</var> <tt>remove</tt>
3539 <tt>in-favour</tt> <var>package</var>
3540 <var>new-version</var>
3543 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3544 <tt>in-favour</tt> <var>package-being-installed</var>
3545 <var>version</var> [<tt>removing</tt>
3546 <var>conflicting-package</var>
3552 <list compact="compact">
3554 <var>postrm</var> <tt>remove</tt>
3557 <var>postrm</var> <tt>purge</tt>
3560 <var>old-postrm</var> <tt>upgrade</tt>
3561 <var>new-version</var>
3564 <var>new-postrm</var> <tt>failed-upgrade</tt>
3565 <var>old-version</var>
3568 <var>new-postrm</var> <tt>abort-install</tt>
3571 <var>new-postrm</var> <tt>abort-install</tt>
3572 <var>old-version</var>
3575 <var>new-postrm</var> <tt>abort-upgrade</tt>
3576 <var>old-version</var>
3579 <var>disappearer's-postrm</var> <tt>disappear</tt>
3580 <var>overwriter</var>
3581 <var>overwriter-version</var>
3587 <sect id="unpackphase">
3588 <heading>Details of unpack phase of installation or upgrade</heading>
3591 The procedure on installation/upgrade/overwrite/disappear
3592 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3593 stage of <tt>dpkg --install</tt>) is as follows. In each
3594 case, if a major error occurs (unless listed below) the
3595 actions are, in general, run backwards - this means that the
3596 maintainer scripts are run with different arguments in
3597 reverse order. These are the "error unwind" calls listed
3604 If a version of the package is already installed, call
3605 <example compact="compact">
3606 <var>old-prerm</var> upgrade <var>new-version</var>
3610 If the script runs but exits with a non-zero
3611 exit status, <prgn>dpkg</prgn> will attempt:
3612 <example compact="compact">
3613 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3615 If this works, the upgrade continues. If this
3616 does not work, the error unwind:
3617 <example compact="compact">
3618 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3620 If this works, then the old-version is
3621 "Installed", if not, the old version is in a
3622 "Failed-Config" state.
3628 If a "conflicting" package is being removed at the same time,
3629 or if any package will be broken (due to <tt>Breaks</tt>):
3632 If <tt>--auto-deconfigure</tt> is
3633 specified, call, for each package to be deconfigured
3634 due to <tt>Breaks</tt>:
3635 <example compact="compact">
3636 <var>deconfigured's-prerm</var> deconfigure \
3637 in-favour <var>package-being-installed</var> <var>version</var>
3640 <example compact="compact">
3641 <var>deconfigured's-postinst</var> abort-deconfigure \
3642 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3644 The deconfigured packages are marked as
3645 requiring configuration, so that if
3646 <tt>--install</tt> is used they will be
3647 configured again if possible.
3650 If any packages depended on a conflicting
3651 package being removed and <tt>--auto-deconfigure</tt> is
3652 specified, call, for each such package:
3653 <example compact="compact">
3654 <var>deconfigured's-prerm</var> deconfigure \
3655 in-favour <var>package-being-installed</var> <var>version</var> \
3656 removing <var>conflicting-package</var> <var>version</var>
3659 <example compact="compact">
3660 <var>deconfigured's-postinst</var> abort-deconfigure \
3661 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3662 removing <var>conflicting-package</var> <var>version</var>
3664 The deconfigured packages are marked as
3665 requiring configuration, so that if
3666 <tt>--install</tt> is used they will be
3667 configured again if possible.
3670 To prepare for removal of each conflicting package, call:
3671 <example compact="compact">
3672 <var>conflictor's-prerm</var> remove \
3673 in-favour <var>package</var> <var>new-version</var>
3676 <example compact="compact">
3677 <var>conflictor's-postinst</var> abort-remove \
3678 in-favour <var>package</var> <var>new-version</var>
3687 If the package is being upgraded, call:
3688 <example compact="compact">
3689 <var>new-preinst</var> upgrade <var>old-version</var>
3691 If this fails, we call:
3693 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3700 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3702 is called. If this works, then the old version
3703 is in an "Installed" state, or else it is left
3704 in an "Unpacked" state.
3709 If it fails, then the old version is left
3710 in an "Half-Installed" state.
3717 Otherwise, if the package had some configuration
3718 files from a previous version installed (i.e., it
3719 is in the "configuration files only" state):
3720 <example compact="compact">
3721 <var>new-preinst</var> install <var>old-version</var>
3725 <var>new-postrm</var> abort-install <var>old-version</var>
3727 If this fails, the package is left in a
3728 "Half-Installed" state, which requires a
3729 reinstall. If it works, the packages is left in
3730 a "Config Files" state.
3733 Otherwise (i.e., the package was completely purged):
3734 <example compact="compact">
3735 <var>new-preinst</var> install
3738 <example compact="compact">
3739 <var>new-postrm</var> abort-install
3741 If the error-unwind fails, the package is in a
3742 "Half Installed" phase, and requires a
3743 reinstall. If the error unwind works, the
3744 package is in a not installed state.
3751 The new package's files are unpacked, overwriting any
3752 that may be on the system already, for example any
3753 from the old version of the same package or from
3754 another package. Backups of the old files are kept
3755 temporarily, and if anything goes wrong the package
3756 management system will attempt to put them back as
3757 part of the error unwind.
3761 It is an error for a package to contain files which
3762 are on the system in another package, unless
3763 <tt>Replaces</tt> is used (see <ref id="replaces">).
3765 The following paragraph is not currently the case:
3766 Currently the <tt>- - force-overwrite</tt> flag is
3767 enabled, downgrading it to a warning, but this may not
3773 It is a more serious error for a package to contain a
3774 plain file or other kind of non-directory where another
3775 package has a directory (again, unless
3776 <tt>Replaces</tt> is used). This error can be
3777 overridden if desired using
3778 <tt>--force-overwrite-dir</tt>, but this is not
3783 Packages which overwrite each other's files produce
3784 behavior which, though deterministic, is hard for the
3785 system administrator to understand. It can easily
3786 lead to "missing" programs if, for example, a package
3787 is installed which overwrites a file from another
3788 package, and is then removed again.<footnote>
3789 Part of the problem is due to what is arguably a
3790 bug in <prgn>dpkg</prgn>.
3795 A directory will never be replaced by a symbolic link
3796 to a directory or vice versa; instead, the existing
3797 state (symlink or not) will be left alone and
3798 <prgn>dpkg</prgn> will follow the symlink if there is
3807 If the package is being upgraded, call
3808 <example compact="compact">
3809 <var>old-postrm</var> upgrade <var>new-version</var>
3813 If this fails, <prgn>dpkg</prgn> will attempt:
3814 <example compact="compact">
3815 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3817 If this works, installation continues. If not,
3819 <example compact="compact">
3820 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3822 If this fails, the old version is left in an
3823 "Half Installed" state. If it works, dpkg now
3825 <example compact="compact">
3826 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3828 If this fails, the old version is left in an
3829 "Half Installed" state. If it works, dpkg now
3831 <example compact="compact">
3832 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3834 If this fails, the old version is in an
3841 This is the point of no return - if
3842 <prgn>dpkg</prgn> gets this far, it won't back off
3843 past this point if an error occurs. This will
3844 leave the package in a fairly bad state, which
3845 will require a successful re-installation to clear
3846 up, but it's when <prgn>dpkg</prgn> starts doing
3847 things that are irreversible.
3852 Any files which were in the old version of the package
3853 but not in the new are removed.
3857 The new file list replaces the old.
3861 The new maintainer scripts replace the old.
3865 Any packages all of whose files have been overwritten
3866 during the installation, and which aren't required for
3867 dependencies, are considered to have been removed.
3868 For each such package
3871 <prgn>dpkg</prgn> calls:
3872 <example compact="compact">
3873 <var>disappearer's-postrm</var> disappear \
3874 <var>overwriter</var> <var>overwriter-version</var>
3878 The package's maintainer scripts are removed.
3881 It is noted in the status database as being in a
3882 sane state, namely not installed (any conffiles
3883 it may have are ignored, rather than being
3884 removed by <prgn>dpkg</prgn>). Note that
3885 disappearing packages do not have their prerm
3886 called, because <prgn>dpkg</prgn> doesn't know
3887 in advance that the package is going to
3894 Any files in the package we're unpacking that are also
3895 listed in the file lists of other packages are removed
3896 from those lists. (This will lobotomize the file list
3897 of the "conflicting" package if there is one.)
3901 The backup files made during installation, above, are
3907 The new package's status is now sane, and recorded as
3912 Here is another point of no return - if the
3913 conflicting package's removal fails we do not unwind
3914 the rest of the installation; the conflicting package
3915 is left in a half-removed limbo.
3920 If there was a conflicting package we go and do the
3921 removal actions (described below), starting with the
3922 removal of the conflicting package's files (any that
3923 are also in the package being installed have already
3924 been removed from the conflicting package's file list,
3925 and so do not get removed now).
3931 <sect id="configdetails"><heading>Details of configuration</heading>
3934 When we configure a package (this happens with <tt>dpkg
3935 --install</tt> and <tt>dpkg --configure</tt>), we first
3936 update any <tt>conffile</tt>s and then call:
3937 <example compact="compact">
3938 <var>postinst</var> configure <var>most-recently-configured-version</var>
3943 No attempt is made to unwind after errors during
3944 configuration. If the configuration fails, the package is in
3945 a "Failed Config" state, and an error message is generated.
3949 If there is no most recently configured version
3950 <prgn>dpkg</prgn> will pass a null argument.
3953 Historical note: Truly ancient (pre-1997) versions of
3954 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3955 (including the angle brackets) in this case. Even older
3956 ones did not pass a second argument at all, under any
3957 circumstance. Note that upgrades using such an old dpkg
3958 version are unlikely to work for other reasons, even if
3959 this old argument behavior is handled by your postinst script.
3965 <sect id="removedetails"><heading>Details of removal and/or
3966 configuration purging</heading>
3972 <example compact="compact">
3973 <var>prerm</var> remove
3977 If prerm fails during replacement due to conflict
3979 <var>conflictor's-postinst</var> abort-remove \
3980 in-favour <var>package</var> <var>new-version</var>
3984 <var>postinst</var> abort-remove
3988 If this fails, the package is in a "Failed-Config"
3989 state, or else it remains "Installed".
3993 The package's files are removed (except <tt>conffile</tt>s).
3996 <example compact="compact">
3997 <var>postrm</var> remove
4001 If it fails, there's no error unwind, and the package is in
4002 an "Half-Installed" state.
4007 All the maintainer scripts except the <prgn>postrm</prgn>
4012 If we aren't purging the package we stop here. Note
4013 that packages which have no <prgn>postrm</prgn> and no
4014 <tt>conffile</tt>s are automatically purged when
4015 removed, as there is no difference except for the
4016 <prgn>dpkg</prgn> status.
4020 The <tt>conffile</tt>s and any backup files
4021 (<tt>~</tt>-files, <tt>#*#</tt> files,
4022 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4027 <example compact="compact">
4028 <var>postrm</var> purge
4032 If this fails, the package remains in a "Config-Files"
4037 The package's file list is removed.
4046 <chapt id="relationships">
4047 <heading>Declaring relationships between packages</heading>
4049 <sect id="depsyntax">
4050 <heading>Syntax of relationship fields</heading>
4053 These fields all have a uniform syntax. They are a list of
4054 package names separated by commas.
4058 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4059 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4060 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4061 control file fields of the package, which declare
4062 dependencies on other packages, the package names listed may
4063 also include lists of alternative package names, separated
4064 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4065 if any one of the alternative packages is installed, that
4066 part of the dependency is considered to be satisfied.
4070 All of the fields except for <tt>Provides</tt> may restrict
4071 their applicability to particular versions of each named
4072 package. This is done in parentheses after each individual
4073 package name; the parentheses should contain a relation from
4074 the list below followed by a version number, in the format
4075 described in <ref id="f-Version">.
4079 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4080 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4081 strictly earlier, earlier or equal, exactly equal, later or
4082 equal and strictly later, respectively. The deprecated
4083 forms <tt><</tt> and <tt>></tt> were used to mean
4084 earlier/later or equal, rather than strictly earlier/later,
4085 so they should not appear in new packages (though
4086 <prgn>dpkg</prgn> still supports them).
4090 Whitespace may appear at any point in the version
4091 specification subject to the rules in <ref
4092 id="controlsyntax">, and must appear where it's necessary to
4093 disambiguate; it is not otherwise significant. All of the
4094 relationship fields may span multiple lines. For
4095 consistency and in case of future changes to
4096 <prgn>dpkg</prgn> it is recommended that a single space be
4097 used after a version relationship and before a version
4098 number; it is also conventional to put a single space after
4099 each comma, on either side of each vertical bar, and before
4100 each open parenthesis. When wrapping a relationship field, it
4101 is conventional to do so after a comma and before the space
4102 following that comma.
4106 For example, a list of dependencies might appear as:
4107 <example compact="compact">
4110 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4115 All fields that specify build-time relationships
4116 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4117 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4118 may be restricted to a certain set of architectures. This
4119 is indicated in brackets after each individual package name and
4120 the optional version specification. The brackets enclose a
4121 list of Debian architecture names separated by whitespace.
4122 Exclamation marks may be prepended to each of the names.
4123 (It is not permitted for some names to be prepended with
4124 exclamation marks while others aren't.) If the current Debian
4125 host architecture is not in this list and there are no
4126 exclamation marks in the list, or it is in the list with a
4127 prepended exclamation mark, the package name and the
4128 associated version specification are ignored completely for
4129 the purposes of defining the relationships.
4134 <example compact="compact">
4136 Build-Depends-Indep: texinfo
4137 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4138 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4143 Note that the binary package relationship fields such as
4144 <tt>Depends</tt> appear in one of the binary package
4145 sections of the control file, whereas the build-time
4146 relationships such as <tt>Build-Depends</tt> appear in the
4147 source package section of the control file (which is the
4152 <sect id="binarydeps">
4153 <heading>Binary Dependencies - <tt>Depends</tt>,
4154 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4155 <tt>Pre-Depends</tt>
4159 Packages can declare in their control file that they have
4160 certain relationships to other packages - for example, that
4161 they may not be installed at the same time as certain other
4162 packages, and/or that they depend on the presence of others.
4166 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4167 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4168 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4172 These seven fields are used to declare a dependency
4173 relationship by one package on another. Except for
4174 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4175 depending (binary) package's control file.
4176 (<tt>Enhances</tt> appears in the recommending package's
4177 control file, and <tt>Breaks</tt> appears in the version of
4178 depended-on package which causes the named package to
4183 A <tt>Depends</tt> field takes effect <em>only</em> when a
4184 package is to be configured. It does not prevent a package
4185 being on the system in an unconfigured state while its
4186 dependencies are unsatisfied, and it is possible to replace
4187 a package whose dependencies are satisfied and which is
4188 properly installed with a different version whose
4189 dependencies are not and cannot be satisfied; when this is
4190 done the depending package will be left unconfigured (since
4191 attempts to configure it will give errors) and will not
4192 function properly. If it is necessary, a
4193 <tt>Pre-Depends</tt> field can be used, which has a partial
4194 effect even when a package is being unpacked, as explained
4195 in detail below. (The other three dependency fields,
4196 <tt>Recommends</tt>, <tt>Suggests</tt> and
4197 <tt>Enhances</tt>, are only used by the various front-ends
4198 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4199 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4203 For this reason packages in an installation run are usually
4204 all unpacked first and all configured later; this gives
4205 later versions of packages with dependencies on later
4206 versions of other packages the opportunity to have their
4207 dependencies satisfied.
4211 In case of circular dependencies, since installation or
4212 removal order honoring the dependency order can't be
4213 established, dependency loops are broken at some point
4214 (based on rules below), and some packages may not be able to
4215 rely on their dependencies being present when being
4216 installed or removed, depending on which side of the break
4217 of the circular dependency loop they happen to be on. If one
4218 of the packages in the loop has no postinst script, then the
4219 cycle will be broken at that package, so as to ensure that
4220 all postinst scripts run with the dependencies properly
4221 configured if this is possible. Otherwise the breaking point
4226 The <tt>Depends</tt> field thus allows package maintainers
4227 to impose an order in which packages should be configured.
4231 The meaning of the five dependency fields is as follows:
4233 <tag><tt>Depends</tt></tag>
4236 This declares an absolute dependency. A package will
4237 not be configured unless all of the packages listed in
4238 its <tt>Depends</tt> field have been correctly
4243 The <tt>Depends</tt> field should be used if the
4244 depended-on package is required for the depending
4245 package to provide a significant amount of
4250 The <tt>Depends</tt> field should also be used if the
4251 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4252 <prgn>postrm</prgn> scripts require the package to be
4253 present in order to run. Note, however, that the
4254 <prgn>postrm</prgn> cannot rely on any non-essential
4255 packages to be present during the <tt>purge</tt>
4259 <tag><tt>Recommends</tt></tag>
4262 This declares a strong, but not absolute, dependency.
4266 The <tt>Recommends</tt> field should list packages
4267 that would be found together with this one in all but
4268 unusual installations.
4272 <tag><tt>Suggests</tt></tag>
4274 This is used to declare that one package may be more
4275 useful with one or more others. Using this field
4276 tells the packaging system and the user that the
4277 listed packages are related to this one and can
4278 perhaps enhance its usefulness, but that installing
4279 this one without them is perfectly reasonable.
4282 <tag><tt>Enhances</tt></tag>
4284 This field is similar to Suggests but works in the
4285 opposite direction. It is used to declare that a
4286 package can enhance the functionality of another
4290 <tag><tt>Pre-Depends</tt></tag>
4293 This field is like <tt>Depends</tt>, except that it
4294 also forces <prgn>dpkg</prgn> to complete installation
4295 of the packages named before even starting the
4296 installation of the package which declares the
4297 pre-dependency, as follows:
4301 When a package declaring a pre-dependency is about to
4302 be <em>unpacked</em> the pre-dependency can be
4303 satisfied if the depended-on package is either fully
4304 configured, <em>or even if</em> the depended-on
4305 package(s) are only unpacked or half-configured,
4306 provided that they have been configured correctly at
4307 some point in the past (and not removed or partially
4308 removed since). In this case, both the
4309 previously-configured and currently unpacked or
4310 half-configured versions must satisfy any version
4311 clause in the <tt>Pre-Depends</tt> field.
4315 When the package declaring a pre-dependency is about
4316 to be <em>configured</em>, the pre-dependency will be
4317 treated as a normal <tt>Depends</tt>, that is, it will
4318 be considered satisfied only if the depended-on
4319 package has been correctly configured.
4323 <tt>Pre-Depends</tt> should be used sparingly,
4324 preferably only by packages whose premature upgrade or
4325 installation would hamper the ability of the system to
4326 continue with any upgrade that might be in progress.
4330 <tt>Pre-Depends</tt> are also required if the
4331 <prgn>preinst</prgn> script depends on the named
4332 package. It is best to avoid this situation if
4340 When selecting which level of dependency to use you should
4341 consider how important the depended-on package is to the
4342 functionality of the one declaring the dependency. Some
4343 packages are composed of components of varying degrees of
4344 importance. Such a package should list using
4345 <tt>Depends</tt> the package(s) which are required by the
4346 more important components. The other components'
4347 requirements may be mentioned as Suggestions or
4348 Recommendations, as appropriate to the components' relative
4354 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4357 Using <tt>Breaks</tt> may cause problems for upgrades from older
4358 versions of Debian and should not be used until the stable
4359 release of Debian supports <tt>Breaks</tt>.
4363 When one binary package declares that it breaks another,
4364 <prgn>dpkg</prgn> will refuse to allow the package which
4365 declares <tt>Breaks</tt> be installed unless the broken
4366 package is deconfigured first, and it will refuse to
4367 allow the broken package to be reconfigured.
4371 A package will not be regarded as causing breakage merely
4372 because its configuration files are still installed; it must
4373 be at least half-installed.
4377 A special exception is made for packages which declare that
4378 they break their own package name or a virtual package which
4379 they provide (see below): this does not count as a real
4384 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4385 version clause; such a <tt>Breaks</tt> is introduced in the
4386 version of an (implicit or explicit) dependency which
4387 violates an assumption or reveals a bug in earlier versions
4388 of the broken package. This use of <tt>Breaks</tt> will
4389 inform higher-level package management tools that broken
4390 package must be upgraded before the new one.
4394 If the breaking package also overwrites some files from the
4395 older package, it should use <tt>Replaces</tt> (not
4396 <tt>Conflicts</tt>) to ensure this goes smoothly.
4400 <sect id="conflicts">
4401 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4404 When one binary package declares a conflict with another
4405 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4406 refuse to allow them to be installed on the system at the
4411 If one package is to be installed, the other must be removed
4412 first - if the package being installed is marked as
4413 replacing (see <ref id="replaces">) the one on the system,
4414 or the one on the system is marked as deselected, or both
4415 packages are marked <tt>Essential</tt>, then
4416 <prgn>dpkg</prgn> will automatically remove the package
4417 which is causing the conflict, otherwise it will halt the
4418 installation of the new package with an error. This
4419 mechanism is specifically designed to produce an error when
4420 the installed package is <tt>Essential</tt>, but the new
4425 A package will not cause a conflict merely because its
4426 configuration files are still installed; it must be at least
4431 A special exception is made for packages which declare a
4432 conflict with their own package name, or with a virtual
4433 package which they provide (see below): this does not
4434 prevent their installation, and allows a package to conflict
4435 with others providing a replacement for it. You use this
4436 feature when you want the package in question to be the only
4437 package providing some feature.
4441 A <tt>Conflicts</tt> entry should almost never have an
4442 "earlier than" version clause. This would prevent
4443 <prgn>dpkg</prgn> from upgrading or installing the package
4444 which declared such a conflict until the upgrade or removal
4445 of the conflicted-with package had been completed. Instead,
4446 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4447 by the stable release of Debian).
4451 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4455 As well as the names of actual ("concrete") packages, the
4456 package relationship fields <tt>Depends</tt>,
4457 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4458 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4459 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4460 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4461 may mention "virtual packages".
4465 A <em>virtual package</em> is one which appears in the
4466 <tt>Provides</tt> control file field of another package.
4467 The effect is as if the package(s) which provide a
4468 particular virtual package name had been listed by name
4469 everywhere the virtual package name appears. (See also <ref
4474 If there are both concrete and virtual packages of the same
4475 name, then the dependency may be satisfied (or the conflict
4476 caused) by either the concrete package with the name in
4477 question or any other concrete package which provides the
4478 virtual package with the name in question. This is so that,
4479 for example, supposing we have
4480 <example compact="compact">
4483 </example> and someone else releases an enhanced version of
4484 the <tt>bar</tt> package they can say:
4485 <example compact="compact">
4489 and the <tt>bar-plus</tt> package will now also satisfy the
4490 dependency for the <tt>foo</tt> package.
4494 If a relationship field has a version number attached
4495 then only real packages will be considered to see whether
4496 the relationship is satisfied (or the prohibition violated,
4497 for a conflict or breakage) - it is assumed that a real
4498 package which provides the virtual package is not of the
4499 "right" version. So, a <tt>Provides</tt> field may not
4500 contain version numbers, and the version number of the
4501 concrete package which provides a particular virtual package
4502 will not be looked at when considering a dependency on or
4503 conflict with the virtual package name.
4507 It is likely that the ability will be added in a future
4508 release of <prgn>dpkg</prgn> to specify a version number for
4509 each virtual package it provides. This feature is not yet
4510 present, however, and is expected to be used only
4515 If you want to specify which of a set of real packages
4516 should be the default to satisfy a particular dependency on
4517 a virtual package, you should list the real package as an
4518 alternative before the virtual one.
4523 <sect id="replaces"><heading>Overwriting files and replacing
4524 packages - <tt>Replaces</tt></heading>
4527 Packages can declare in their control file that they should
4528 overwrite files in certain other packages, or completely
4529 replace other packages. The <tt>Replaces</tt> control file
4530 field has these two distinct purposes.
4533 <sect1><heading>Overwriting files in other packages</heading>
4536 Firstly, as mentioned before, it is usually an error for a
4537 package to contain files which are on the system in
4542 However, if the overwriting package declares that it
4543 <tt>Replaces</tt> the one containing the file being
4544 overwritten, then <prgn>dpkg</prgn> will replace the file
4545 from the old package with that from the new. The file
4546 will no longer be listed as "owned" by the old package.
4550 If a package is completely replaced in this way, so that
4551 <prgn>dpkg</prgn> does not know of any files it still
4552 contains, it is considered to have "disappeared". It will
4553 be marked as not wanted on the system (selected for
4554 removal) and not installed. Any <tt>conffile</tt>s
4555 details noted for the package will be ignored, as they
4556 will have been taken over by the overwriting package. The
4557 package's <prgn>postrm</prgn> script will be run with a
4558 special argument to allow the package to do any final
4559 cleanup required. See <ref id="mscriptsinstact">.
4562 Replaces is a one way relationship -- you have to
4563 install the replacing package after the replaced
4570 For this usage of <tt>Replaces</tt>, virtual packages (see
4571 <ref id="virtual">) are not considered when looking at a
4572 <tt>Replaces</tt> field - the packages declared as being
4573 replaced must be mentioned by their real names.
4577 Furthermore, this usage of <tt>Replaces</tt> only takes
4578 effect when both packages are at least partially on the
4579 system at once, so that it can only happen if they do not
4580 conflict or if the conflict has been overridden.
4585 <sect1><heading>Replacing whole packages, forcing their
4589 Secondly, <tt>Replaces</tt> allows the packaging system to
4590 resolve which package should be removed when there is a
4591 conflict - see <ref id="conflicts">. This usage only
4592 takes effect when the two packages <em>do</em> conflict,
4593 so that the two usages of this field do not interfere with
4598 In this situation, the package declared as being replaced
4599 can be a virtual package, so for example, all mail
4600 transport agents (MTAs) would have the following fields in
4601 their control files:
4602 <example compact="compact">
4603 Provides: mail-transport-agent
4604 Conflicts: mail-transport-agent
4605 Replaces: mail-transport-agent
4607 ensuring that only one MTA can be installed at any one
4612 <sect id="sourcebinarydeps">
4613 <heading>Relationships between source and binary packages -
4614 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4615 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4619 Source packages that require certain binary packages to be
4620 installed or absent at the time of building the package
4621 can declare relationships to those binary packages.
4625 This is done using the <tt>Build-Depends</tt>,
4626 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4627 <tt>Build-Conflicts-Indep</tt> control file fields.
4631 Build-dependencies on "build-essential" binary packages can be
4632 omitted. Please see <ref id="pkg-relations"> for more information.
4636 The dependencies and conflicts they define must be satisfied
4637 (as defined earlier for binary packages) in order to invoke
4638 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4640 If you make "build-arch" or "binary-arch", you need
4641 Build-Depends. If you make "build-indep" or
4642 "binary-indep", you need Build-Depends and
4643 Build-Depends-Indep. If you make "build" or "binary",
4647 There is no Build-Depends-Arch; this role is essentially
4648 met with Build-Depends. Anyone building the
4649 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4650 is basically assumed to be building the whole package
4651 anyway and so installs all build dependencies. The
4652 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4653 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4654 does not yet know how to check for its existence) and
4655 <tt>binary-arch</tt>.
4658 The purpose of the original split, I recall, was so that
4659 the autobuilders wouldn't need to install extra packages
4660 needed only for the binary-indep targets. But without a
4661 build-arch/build-indep split, this didn't work, since
4662 most of the work is done in the build target, not in the
4668 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4670 The <tt>Build-Depends</tt> and
4671 <tt>Build-Conflicts</tt> fields must be satisfied when
4672 any of the following targets is invoked:
4673 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4674 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4675 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4677 <tag><tt>Build-Depends-Indep</tt>,
4678 <tt>Build-Conflicts-Indep</tt></tag>
4680 The <tt>Build-Depends-Indep</tt> and
4681 <tt>Build-Conflicts-Indep</tt> fields must be
4682 satisfied when any of the following targets is
4683 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4684 <tt>binary</tt> and <tt>binary-indep</tt>.
4694 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4697 Packages containing shared libraries must be constructed with
4698 a little care to make sure that the shared library is always
4699 available. This is especially important for packages whose
4700 shared libraries are vitally important, such as the C library
4701 (currently <tt>libc6</tt>).
4705 Packages involving shared libraries should be split up into
4706 several binary packages. This section mostly deals with how
4707 this separation is to be accomplished; rules for files within
4708 the shared library packages are in <ref id="libraries"> instead.
4711 <sect id="sharedlibs-runtime">
4712 <heading>Run-time shared libraries</heading>
4715 The run-time shared library needs to be placed in a package
4716 whose name changes whenever the shared object version
4719 Since it is common place to install several versions of a
4720 package that just provides shared libraries, it is a
4721 good idea that the library package should not
4722 contain any extraneous non-versioned files, unless they
4723 happen to be in versioned directories.</p>
4725 The most common mechanism is to place it in a package
4727 <package><var>libraryname</var><var>soversion</var></package>,
4728 where <file><var>soversion</var></file> is the version number
4729 in the soname of the shared library<footnote>
4730 The soname is the shared object name: it's the thing
4731 that has to match exactly between building an executable
4732 and running it for the dynamic linker to be able run the
4733 program. For example, if the soname of the library is
4734 <file>libfoo.so.6</file>, the library package would be
4735 called <file>libfoo6</file>.
4737 Alternatively, if it would be confusing to directly append
4738 <var>soversion</var> to <var>libraryname</var> (e.g. because
4739 <var>libraryname</var> itself ends in a number), you may use
4740 <package><var>libraryname</var>-<var>soversion</var></package> and
4741 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4746 If you have several shared libraries built from the same
4747 source tree you may lump them all together into a single
4748 shared library package, provided that you change all of
4749 their sonames at once (so that you don't get filename
4750 clashes if you try to install different versions of the
4751 combined shared libraries package).
4755 The package should install the shared libraries under
4756 their normal names. For example, the <package>libgdbm3</package>
4757 package should install <file>libgdbm.so.3.0.0</file> as
4758 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4759 renamed or re-linked by any <prgn>prerm</prgn> or
4760 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4761 of renaming things safely without affecting running programs,
4762 and attempts to interfere with this are likely to lead to
4767 Shared libraries should not be installed executable, since
4768 the dynamic linker does not require this and trying to
4769 execute a shared library usually results in a core dump.
4773 The run-time library package should include the symbolic link that
4774 <prgn>ldconfig</prgn> would create for the shared libraries.
4775 For example, the <package>libgdbm3</package> package should include
4776 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4777 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4778 linker (for example <prgn>ld.so</prgn> or
4779 <prgn>ld-linux.so.*</prgn>) can find the library between the
4780 time that <prgn>dpkg</prgn> installs it and the time that
4781 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4783 The package management system requires the library to be
4784 placed before the symbolic link pointing to it in the
4785 <file>.deb</file> file. This is so that when
4786 <prgn>dpkg</prgn> comes to install the symlink
4787 (overwriting the previous symlink pointing at an older
4788 version of the library), the new shared library is already
4789 in place. In the past, this was achieved by creating the
4790 library in the temporary packaging directory before
4791 creating the symlink. Unfortunately, this was not always
4792 effective, since the building of the tar file in the
4793 <file>.deb</file> depended on the behavior of the underlying
4794 file system. Some file systems (such as reiserfs) reorder
4795 the files so that the order of creation is forgotten.
4796 Since version 1.7.0, <prgn>dpkg</prgn>
4797 reorders the files itself as necessary when building a
4798 package. Thus it is no longer important to concern
4799 oneself with the order of file creation.
4803 <sect1 id="ldconfig">
4804 <heading><tt>ldconfig</tt></heading>
4807 Any package installing shared libraries in one of the default
4808 library directories of the dynamic linker (which are currently
4809 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4810 listed in <file>/etc/ld.so.conf</file><footnote>
4812 <list compact="compact">
4813 <item>/usr/local/lib</item>
4814 <item>/usr/lib/libc5-compat</item>
4815 <item>/lib/libc5-compat</item>
4818 must use <prgn>ldconfig</prgn> to update the shared library
4823 The package maintainer scripts must only call
4824 <prgn>ldconfig</prgn> under these circumstances:
4825 <list compact="compact">
4826 <item>When the <prgn>postinst</prgn> script is run with a
4827 first argument of <tt>configure</tt>, the script must call
4828 <prgn>ldconfig</prgn>, and may optionally invoke
4829 <prgn>ldconfig</prgn> at other times.
4831 <item>When the <prgn>postrm</prgn> script is run with a
4832 first argument of <tt>remove</tt>, the script should call
4833 <prgn>ldconfig</prgn>.
4838 During install or upgrade, the preinst is called before
4839 the new files are installed, so calling "ldconfig" is
4840 pointless. The preinst of an existing package can also be
4841 called if an upgrade fails. However, this happens during
4842 the critical time when a shared libs may exist on-disk
4843 under a temporary name. Thus, it is dangerous and
4844 forbidden by current policy to call "ldconfig" at this
4849 When a package is installed or upgraded, "postinst
4850 configure" runs after the new files are safely on-disk.
4851 Since it is perfectly safe to invoke ldconfig
4852 unconditionally in a postinst, it is OK for a package to
4853 simply put ldconfig in its postinst without checking the
4854 argument. The postinst can also be called to recover from
4855 a failed upgrade. This happens before any new files are
4856 unpacked, so there is no reason to call "ldconfig" at this
4861 For a package that is being removed, prerm is
4862 called with all the files intact, so calling ldconfig is
4863 useless. The other calls to "prerm" happen in the case of
4864 upgrade at a time when all the files of the old package
4865 are on-disk, so again calling "ldconfig" is pointless.
4869 postrm, on the other hand, is called with the "remove"
4870 argument just after the files are removed, so this is
4871 the proper time to call "ldconfig" to notify the system
4872 of the fact that the shared libraries from the package
4873 are removed. The postrm can be called at several other
4874 times. At the time of "postrm purge", "postrm
4875 abort-install", or "postrm abort-upgrade", calling
4876 "ldconfig" is useless because the shared lib files are
4877 not on-disk. However, when "postrm" is invoked with
4878 arguments "upgrade", "failed-upgrade", or "disappear", a
4879 shared lib may exist on-disk under a temporary filename.
4887 <sect id="sharedlibs-support-files">
4888 <heading>Shared library support files</heading>
4891 If your package contains files whose names do not change with
4892 each change in the library shared object version, you must not
4893 put them in the shared library package. Otherwise, several
4894 versions of the shared library cannot be installed at the same
4895 time without filename clashes, making upgrades and transitions
4896 unnecessarily difficult.
4900 It is recommended that supporting files and run-time support
4901 programs that do not need to be invoked manually by users, but
4902 are nevertheless required for the package to function, be placed
4903 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4904 preferably under <file>/usr/lib/</file><var>package-name</var>.
4905 If the program or file is architecture independent, the
4906 recommendation is for it to be placed in a subdirectory of
4907 <file>/usr/share</file> instead, preferably under
4908 <file>/usr/share/</file><var>package-name</var>. Following the
4909 <var>package-name</var> naming convention ensures that the file
4910 names change when the shared object version changes.
4914 Run-time support programs that use the shared library but are
4915 not required for the library to function or files used by the
4916 shared library that can be used by any version of the shared
4917 library package should instead be put in a separate package.
4918 This package might typically be named
4919 <package><var>libraryname</var>-tools</package>; note the
4920 absence of the <var>soversion</var> in the package name.
4924 Files and support programs only useful when compiling software
4925 against the library should be included in the development
4926 package for the library.<footnote>
4927 For example, a <file><var>package-name</var>-config</file>
4928 script or <package>pkg-config</package> configuration files.
4933 <sect id="sharedlibs-static">
4934 <heading>Static libraries</heading>
4937 The static library (<file><var>libraryname.a</var></file>)
4938 is usually provided in addition to the shared version.
4939 It is placed into the development package (see below).
4943 In some cases, it is acceptable for a library to be
4944 available in static form only; these cases include:
4946 <item>libraries for languages whose shared library support
4947 is immature or unstable</item>
4948 <item>libraries whose interfaces are in flux or under
4949 development (commonly the case when the library's
4950 major version number is zero, or where the ABI breaks
4951 across patchlevels)</item>
4952 <item>libraries which are explicitly intended to be
4953 available only in static form by their upstream
4958 <sect id="sharedlibs-dev">
4959 <heading>Development files</heading>
4962 The development files associated to a shared library need to be
4963 placed in a package called
4964 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4965 or if you prefer only to support one development version at a
4966 time, <package><var>libraryname</var>-dev</package>.
4970 In case several development versions of a library exist, you may
4971 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4972 <ref id="conflicts">) to ensure that the user only installs one
4973 development version at a time (as different development versions are
4974 likely to have the same header files in them, which would cause a
4975 filename clash if both were installed).
4979 The development package should contain a symlink for the associated
4980 shared library without a version number. For example, the
4981 <package>libgdbm-dev</package> package should include a symlink
4982 from <file>/usr/lib/libgdbm.so</file> to
4983 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4984 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4985 <file>libgdbm.so</file> when compiling dynamically.
4989 <sect id="sharedlibs-intradeps">
4990 <heading>Dependencies between the packages of the same library</heading>
4993 Typically the development version should have an exact
4994 version dependency on the runtime library, to make sure that
4995 compilation and linking happens correctly. The
4996 <tt>${binary:Version}</tt> substitution variable can be
4997 useful for this purpose.
4999 Previously, <tt>${Source-Version}</tt> was used, but its name
5000 was confusing and it has been deprecated since dpkg 1.13.19.
5005 <sect id="sharedlibs-shlibdeps">
5006 <heading>Dependencies between the library and other packages -
5007 the <tt>shlibs</tt> system</heading>
5010 If a package contains a binary or library which links to a
5011 shared library, we must ensure that when the package is
5012 installed on the system, all of the libraries needed are
5013 also installed. This requirement led to the creation of the
5014 <tt>shlibs</tt> system, which is very simple in its design:
5015 any package which <em>provides</em> a shared library also
5016 provides information on the package dependencies required to
5017 ensure the presence of this library, and any package which
5018 <em>uses</em> a shared library uses this information to
5019 determine the dependencies it requires. The files which
5020 contain the mapping from shared libraries to the necessary
5021 dependency information are called <file>shlibs</file> files.
5025 Thus, when a package is built which contains any shared
5026 libraries, it must provide a <file>shlibs</file> file for other
5027 packages to use, and when a package is built which contains
5028 any shared libraries or compiled binaries, it must run
5029 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5030 on these to determine the libraries used and hence the
5031 dependencies needed by this package.<footnote>
5033 In the past, the shared libraries linked to were
5034 determined by calling <prgn>ldd</prgn>, but now
5035 <prgn>objdump</prgn> is used to do this. The only
5036 change this makes to package building is that
5037 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5038 libraries, whereas in the past this was unnecessary.
5039 The rest of this footnote explains the advantage that
5044 We say that a binary <tt>foo</tt> <em>directly</em> uses
5045 a library <tt>libbar</tt> if it is explicitly linked
5046 with that library (that is, it uses the flag
5047 <tt>-lbar</tt> during the linking stage). Other
5048 libraries that are needed by <tt>libbar</tt> are linked
5049 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5050 linker will load them automatically when it loads
5051 <tt>libbar</tt>. A package should depend on
5052 the libraries it directly uses, and the dependencies for
5053 those libraries should automatically pull in the other
5058 Unfortunately, the <prgn>ldd</prgn> program shows both
5059 the directly and indirectly used libraries, meaning that
5060 the dependencies determined included both direct and
5061 indirect dependencies. The use of <prgn>objdump</prgn>
5062 avoids this problem by determining only the directly
5067 A good example of where this helps is the following. We
5068 could update <tt>libimlib</tt> with a new version that
5069 supports a new graphics format called dgf (but retaining
5070 the same major version number). If we used the old
5071 <prgn>ldd</prgn> method, every package that uses
5072 <tt>libimlib</tt> would need to be recompiled so it
5073 would also depend on <tt>libdgf</tt> or it wouldn't run
5074 due to missing symbols. However with the new system,
5075 packages using <tt>libimlib</tt> can rely on
5076 <tt>libimlib</tt> itself having the dependency on
5077 <tt>libdgf</tt> and so they would not need rebuilding.
5083 In the following sections, we will first describe where the
5084 various <tt>shlibs</tt> files are to be found, then how to
5085 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5086 file format and how to create them if your package contains a
5091 <heading>The <tt>shlibs</tt> files present on the system</heading>
5094 There are several places where <tt>shlibs</tt> files are
5095 found. The following list gives them in the order in which
5097 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5098 (The first one which gives the required information is used.)
5104 <p><file>debian/shlibs.local</file></p>
5107 This lists overrides for this package. Its use is
5108 described below (see <ref id="shlibslocal">).
5113 <p><file>/etc/dpkg/shlibs.override</file></p>
5116 This lists global overrides. This list is normally
5117 empty. It is maintained by the local system
5123 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5126 When packages are being built, any
5127 <file>debian/shlibs</file> files are copied into the
5128 control file area of the temporary build directory and
5129 given the name <file>shlibs</file>. These files give
5130 details of any shared libraries included in the
5132 An example may help here. Let us say that the
5133 source package <tt>foo</tt> generates two binary
5134 packages, <tt>libfoo2</tt> and
5135 <tt>foo-runtime</tt>. When building the binary
5136 packages, the two packages are created in the
5137 directories <file>debian/libfoo2</file> and
5138 <file>debian/foo-runtime</file> respectively.
5139 (<file>debian/tmp</file> could be used instead of one
5140 of these.) Since <tt>libfoo2</tt> provides the
5141 <tt>libfoo</tt> shared library, it will require a
5142 <tt>shlibs</tt> file, which will be installed in
5143 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5145 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5146 when <prgn>dpkg-shlibdeps</prgn> is run on the
5148 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5150 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5151 determine whether <tt>foo-prog</tt>'s library
5152 dependencies are satisfied by any of the libraries
5153 provided by <tt>libfoo2</tt>. For this reason,
5154 <prgn>dpkg-shlibdeps</prgn> must only be run once
5155 all of the individual binary packages'
5156 <tt>shlibs</tt> files have been installed into the
5163 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5166 These are the <file>shlibs</file> files corresponding to
5167 all of the packages installed on the system, and are
5168 maintained by the relevant package maintainers.
5173 <p><file>/etc/dpkg/shlibs.default</file></p>
5176 This file lists any shared libraries whose packages
5177 have failed to provide correct <file>shlibs</file> files.
5178 It was used when the <file>shlibs</file> setup was first
5179 introduced, but it is now normally empty. It is
5180 maintained by the <tt>dpkg</tt> maintainer.
5188 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5189 <file>shlibs</file> files</heading>
5193 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5194 into your <file>debian/rules</file> file. If your package
5195 contains only compiled binaries and libraries (but no scripts),
5196 you can use a command such as:
5197 <example compact="compact">
5198 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5199 debian/tmp/usr/lib/*
5201 Otherwise, you will need to explicitly list the compiled
5202 binaries and libraries.<footnote>
5203 If you are using <tt>debhelper</tt>, the
5204 <prgn>dh_shlibdeps</prgn> program will do this work for
5205 you. It will also correctly handle multi-binary
5211 This command puts the dependency information into the
5212 <file>debian/substvars</file> file, which is then used by
5213 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5214 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5215 field in the control file for this to work.
5219 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5220 done. If it does complain you might need to create your own
5221 <file>debian/shlibs.local</file> file, as explained below (see
5222 <ref id="shlibslocal">).
5226 If you have multiple binary packages, you will need to call
5227 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5228 compiled libraries or binaries. In such a case, you will
5229 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5230 utilities to specify a different <file>substvars</file> file.
5234 If you are creating a udeb for use in the Debian Installer, you
5235 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5236 the dependency line of type <tt>udeb</tt> by adding
5237 <tt>-tudeb</tt> as option<footnote>
5238 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5239 will automatically add this option if it knows it is
5241 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5242 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5243 fall back to the regular dependency line.
5247 For more details on dpkg-shlibdeps, please see
5248 <ref id="pkg-dpkg-shlibdeps"> and
5249 <manref name="dpkg-shlibdeps" section="1">.
5254 <heading>The <file>shlibs</file> File Format</heading>
5257 Each <file>shlibs</file> file has the same format. Lines
5258 beginning with <tt>#</tt> are considered to be comments and
5259 are ignored. Each line is of the form:
5260 <example compact="compact">
5261 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5266 We will explain this by reference to the example of the
5267 <tt>zlib1g</tt> package, which (at the time of writing)
5268 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5272 <var>type</var> is an optional element that indicates the type
5273 of package for which the line is valid. The only type currently
5274 in use is <tt>udeb</tt>. The colon and space after the type are
5279 <var>library-name</var> is the name of the shared library,
5280 in this case <tt>libz</tt>. (This must match the name part
5281 of the soname, see below.)
5285 <var>soname-version</var> is the version part of the soname of
5286 the library. The soname is the thing that must exactly match
5287 for the library to be recognized by the dynamic linker, and is
5289 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5290 example, <tt>libz.so.1</tt>.<footnote>
5291 This can be determined using the command
5292 <example compact="compact">
5293 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5296 The version part is the part which comes after
5297 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5301 <var>dependencies</var> has the same syntax as a dependency
5302 field in a binary package control file. It should give
5303 details of which packages are required to satisfy a binary
5304 built against the version of the library contained in the
5305 package. See <ref id="depsyntax"> for details.
5309 In our example, if the first version of the <tt>zlib1g</tt>
5310 package which contained a minor number of at least
5311 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5312 <tt>shlibs</tt> entry for this library could say:
5313 <example compact="compact">
5314 libz 1 zlib1g (>= 1:1.1.3)
5316 The version-specific dependency is to avoid warnings from
5317 the dynamic linker about using older shared libraries with
5322 As zlib1g also provides a udeb containing the shared library,
5323 there would also be a second line:
5324 <example compact="compact">
5325 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5331 <heading>Providing a <file>shlibs</file> file</heading>
5334 If your package provides a shared library, you need to create
5335 a <file>shlibs</file> file following the format described above.
5336 It is usual to call this file <file>debian/shlibs</file> (but if
5337 you have multiple binary packages, you might want to call it
5338 <file>debian/shlibs.<var>package</var></file> instead). Then
5339 let <file>debian/rules</file> install it in the control area:
5340 <example compact="compact">
5341 install -m644 debian/shlibs debian/tmp/DEBIAN
5343 or, in the case of a multi-binary package:
5344 <example compact="compact">
5345 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5347 An alternative way of doing this is to create the
5348 <file>shlibs</file> file in the control area directly from
5349 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5350 file at all,<footnote>
5351 This is what <prgn>dh_makeshlibs</prgn> in the
5352 <tt>debhelper</tt> suite does. If your package also has a udeb
5353 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5354 automatically generate the <tt>udeb:</tt> lines if you specify
5355 the name of the udeb with the <tt>--add-udeb</tt> option.
5357 since the <file>debian/shlibs</file> file itself is ignored by
5358 <prgn>dpkg-shlibdeps</prgn>.
5362 As <prgn>dpkg-shlibdeps</prgn> reads the
5363 <file>DEBIAN/shlibs</file> files in all of the binary packages
5364 being built from this source package, all of the
5365 <file>DEBIAN/shlibs</file> files should be installed before
5366 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5371 <sect1 id="shlibslocal">
5372 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5375 This file is intended only as a <em>temporary</em> fix if
5376 your binaries or libraries depend on a library whose package
5377 does not yet provide a correct <file>shlibs</file> file.
5381 We will assume that you are trying to package a binary
5382 <tt>foo</tt>. When you try running
5383 <prgn>dpkg-shlibdeps</prgn> you get the following error
5384 message (<tt>-O</tt> displays the dependency information on
5385 <tt>stdout</tt> instead of writing it to
5386 <tt>debian/substvars</tt>, and the lines have been wrapped
5387 for ease of reading):
5388 <example compact="compact">
5389 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5390 dpkg-shlibdeps: warning: unable to find dependency
5391 information for shared library libbar (soname 1,
5392 path /usr/lib/libbar.so.1, dependency field Depends)
5393 shlibs:Depends=libc6 (>= 2.2.2-2)
5395 You can then run <prgn>ldd</prgn> on the binary to find the
5396 full location of the library concerned:
5397 <example compact="compact">
5399 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5400 libc.so.6 => /lib/libc.so.6 (0x40032000)
5401 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5403 So the <prgn>foo</prgn> binary depends on the
5404 <prgn>libbar</prgn> shared library, but no package seems to
5405 provide a <file>*.shlibs</file> file handling
5406 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5407 determine the package responsible:
5408 <example compact="compact">
5409 $ dpkg -S /usr/lib/libbar.so.1
5410 bar1: /usr/lib/libbar.so.1
5411 $ dpkg -s bar1 | grep Version
5414 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5415 is the one we are using. Now we can file a bug against the
5416 <tt>bar1</tt> package and create our own
5417 <file>debian/shlibs.local</file> to locally fix the problem.
5418 Including the following line into your
5419 <file>debian/shlibs.local</file> file:
5420 <example compact="compact">
5421 libbar 1 bar1 (>= 1.0-1)
5423 should allow the package build to work.
5427 As soon as the maintainer of <tt>bar1</tt> provides a
5428 correct <file>shlibs</file> file, you should remove this line
5429 from your <file>debian/shlibs.local</file> file. (You should
5430 probably also then have a versioned <tt>Build-Depends</tt>
5431 on <tt>bar1</tt> to help ensure that others do not have the
5432 same problem building your package.)
5441 <chapt id="opersys"><heading>The Operating System</heading>
5444 <heading>File system hierarchy</heading>
5448 <heading>File system Structure</heading>
5451 The location of all installed files and directories must
5452 comply with the File system Hierarchy Standard (FHS),
5453 version 2.3, with the exceptions noted below, and except
5454 where doing so would violate other terms of Debian
5455 Policy. The following exceptions to the FHS apply:
5460 Legacy XFree86 servers are permitted to retain the
5461 configuration file location
5462 <file>/etc/X11/XF86Config-4</file>.
5467 The optional rules related to user specific
5468 configuration files for applications are stored in
5469 the user's home directory are relaxed. It is
5470 recommended that such files start with the
5471 '<tt>.</tt>' character (a "dot file"), and if an
5472 application needs to create more than one dot file
5473 then the preferred placement is in a subdirectory
5474 with a name starting with a '.' character, (a "dot
5475 directory"). In this case it is recommended the
5476 configuration files not start with the '.'
5482 The requirement for amd64 to use <file>/lib64</file>
5483 for 64 bit binaries is removed.
5488 The requirement that
5489 <file>/usr/local/share/man</file> be "synonymous"
5490 with <file>/usr/local/man</file> is relaxed to a
5495 The requirement that windowmanagers with a single
5496 configuration file call it <file>system.*wmrc</file>
5497 is removed, as is the restriction that the window
5498 manager subdirectory be named identically to the
5499 window manager name itself.
5504 The requirement that boot manager configuration
5505 files live in <file>/etc</file>, or at least are
5506 symlinked there, is relaxed to a recommendation.
5513 The version of this document referred here can be
5514 found in the <tt>debian-policy</tt> package or on <url
5515 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5516 name="FHS (Debian copy)"> alongside this manual (or, if
5517 you have the <package>debian-policy</package> installed,
5519 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5520 (local copy)">). The
5521 latest version, which may be a more recent version, may
5523 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5524 Specific questions about following the standard may be
5525 asked on the <tt>debian-devel</tt> mailing list, or
5526 referred to the FHS mailing list (see the
5527 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5533 <heading>Site-specific programs</heading>
5536 As mandated by the FHS, packages must not place any
5537 files in <file>/usr/local</file>, either by putting them in
5538 the file system archive to be unpacked by <prgn>dpkg</prgn>
5539 or by manipulating them in their maintainer scripts.
5543 However, the package may create empty directories below
5544 <file>/usr/local</file> so that the system administrator knows
5545 where to place site-specific files. These are not
5546 directories <em>in</em> <file>/usr/local</file>, but are
5547 children of directories in <file>/usr/local</file>. These
5548 directories (<file>/usr/local/*/dir/</file>)
5549 should be removed on package removal if they are
5554 Note, that this applies only to directories <em>below</em>
5555 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5556 Packages must not create sub-directories in the directory
5557 <file>/usr/local</file> itself, except those listed in FHS,
5558 section 4.5. However, you may create directories below
5559 them as you wish. You must not remove any of the
5560 directories listed in 4.5, even if you created them.
5564 Since <file>/usr/local</file> can be mounted read-only from a
5565 remote server, these directories must be created and
5566 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5567 maintainer scripts and not be included in the
5568 <file>.deb</file> archive. These scripts must not fail if
5569 either of these operations fail.
5573 For example, the <tt>emacsen-common</tt> package could
5574 contain something like
5575 <example compact="compact">
5576 if [ ! -e /usr/local/share/emacs ]
5578 if mkdir /usr/local/share/emacs 2>/dev/null
5580 chown root:staff /usr/local/share/emacs
5581 chmod 2775 /usr/local/share/emacs
5585 in its <prgn>postinst</prgn> script, and
5586 <example compact="compact">
5587 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5588 rmdir /usr/local/share/emacs 2>/dev/null || true
5590 in the <prgn>prerm</prgn> script. (Note that this form is
5591 used to ensure that if the script is interrupted, the
5592 directory <file>/usr/local/share/emacs</file> will still be
5597 If you do create a directory in <file>/usr/local</file> for
5598 local additions to a package, you should ensure that
5599 settings in <file>/usr/local</file> take precedence over the
5600 equivalents in <file>/usr</file>.
5604 However, because <file>/usr/local</file> and its contents are
5605 for exclusive use of the local administrator, a package
5606 must not rely on the presence or absence of files or
5607 directories in <file>/usr/local</file> for normal operation.
5611 The <file>/usr/local</file> directory itself and all the
5612 subdirectories created by the package should (by default) have
5613 permissions 2775 (group-writable and set-group-id) and be
5614 owned by <tt>root:staff</tt>.
5619 <heading>The system-wide mail directory</heading>
5621 The system-wide mail directory is <file>/var/mail</file>. This
5622 directory is part of the base system and should not owned
5623 by any particular mail agents. The use of the old
5624 location <file>/var/spool/mail</file> is deprecated, even
5625 though the spool may still be physically located there.
5626 To maintain partial upgrade compatibility for systems
5627 which have <file>/var/spool/mail</file> as their physical mail
5628 spool, packages using <file>/var/mail</file> must depend on
5629 either <package>libc6</package> (>= 2.1.3-13), or on
5630 <package>base-files</package> (>= 2.2.0), or on later
5631 versions of either one of these packages.
5637 <heading>Users and groups</heading>
5640 <heading>Introduction</heading>
5642 The Debian system can be configured to use either plain or
5647 Some user ids (UIDs) and group ids (GIDs) are reserved
5648 globally for use by certain packages. Because some
5649 packages need to include files which are owned by these
5650 users or groups, or need the ids compiled into binaries,
5651 these ids must be used on any Debian system only for the
5652 purpose for which they are allocated. This is a serious
5653 restriction, and we should avoid getting in the way of
5654 local administration policies. In particular, many sites
5655 allocate users and/or local system groups starting at 100.
5659 Apart from this we should have dynamically allocated ids,
5660 which should by default be arranged in some sensible
5661 order, but the behavior should be configurable.
5665 Packages other than <tt>base-passwd</tt> must not modify
5666 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5667 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5672 <heading>UID and GID classes</heading>
5674 The UID and GID numbers are divided into classes as
5680 Globally allocated by the Debian project, the same
5681 on every Debian system. These ids will appear in
5682 the <file>passwd</file> and <file>group</file> files of all
5683 Debian systems, new ids in this range being added
5684 automatically as the <tt>base-passwd</tt> package is
5689 Packages which need a single statically allocated
5690 uid or gid should use one of these; their
5691 maintainers should ask the <tt>base-passwd</tt>
5699 Dynamically allocated system users and groups.
5700 Packages which need a user or group, but can have
5701 this user or group allocated dynamically and
5702 differently on each system, should use <tt>adduser
5703 --system</tt> to create the group and/or user.
5704 <prgn>adduser</prgn> will check for the existence of
5705 the user or group, and if necessary choose an unused
5706 id based on the ranges specified in
5707 <file>adduser.conf</file>.
5711 <tag>1000-29999:</tag>
5714 Dynamically allocated user accounts. By default
5715 <prgn>adduser</prgn> will choose UIDs and GIDs for
5716 user accounts in this range, though
5717 <file>adduser.conf</file> may be used to modify this
5722 <tag>30000-59999:</tag>
5727 <tag>60000-64999:</tag>
5730 Globally allocated by the Debian project, but only
5731 created on demand. The ids are allocated centrally
5732 and statically, but the actual accounts are only
5733 created on users' systems on demand.
5737 These ids are for packages which are obscure or
5738 which require many statically-allocated ids. These
5739 packages should check for and create the accounts in
5740 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5741 <prgn>adduser</prgn> if it has this facility) if
5742 necessary. Packages which are likely to require
5743 further allocations should have a "hole" left after
5744 them in the allocation, to give them room to
5749 <tag>65000-65533:</tag>
5757 User <tt>nobody</tt>. The corresponding gid refers
5758 to the group <tt>nogroup</tt>.
5765 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5766 not</em> be used, because it is the error return
5775 <sect id="sysvinit">
5776 <heading>System run levels and <file>init.d</file> scripts</heading>
5778 <sect1 id="/etc/init.d">
5779 <heading>Introduction</heading>
5782 The <file>/etc/init.d</file> directory contains the scripts
5783 executed by <prgn>init</prgn> at boot time and when the
5784 init state (or "runlevel") is changed (see <manref
5785 name="init" section="8">).
5789 There are at least two different, yet functionally
5790 equivalent, ways of handling these scripts. For the sake
5791 of simplicity, this document describes only the symbolic
5792 link method. However, it must not be assumed by maintainer
5793 scripts that this method is being used, and any automated
5794 manipulation of the various runlevel behaviors by
5795 maintainer scripts must be performed using
5796 <prgn>update-rc.d</prgn> as described below and not by
5797 manually installing or removing symlinks. For information
5798 on the implementation details of the other method,
5799 implemented in the <tt>file-rc</tt> package, please refer
5800 to the documentation of that package.
5804 These scripts are referenced by symbolic links in the
5805 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5806 runlevels, <prgn>init</prgn> looks in the directory
5807 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5808 execute, where <tt><var>n</var></tt> is the runlevel that
5809 is being changed to, or <tt>S</tt> for the boot-up
5814 The names of the links all have the form
5815 <file>S<var>mm</var><var>script</var></file> or
5816 <file>K<var>mm</var><var>script</var></file> where
5817 <var>mm</var> is a two-digit number and <var>script</var>
5818 is the name of the script (this should be the same as the
5819 name of the actual script in <file>/etc/init.d</file>).
5823 When <prgn>init</prgn> changes runlevel first the targets
5824 of the links whose names start with a <tt>K</tt> are
5825 executed, each with the single argument <tt>stop</tt>,
5826 followed by the scripts prefixed with an <tt>S</tt>, each
5827 with the single argument <tt>start</tt>. (The links are
5828 those in the <file>/etc/rc<var>n</var>.d</file> directory
5829 corresponding to the new runlevel.) The <tt>K</tt> links
5830 are responsible for killing services and the <tt>S</tt>
5831 link for starting services upon entering the runlevel.
5835 For example, if we are changing from runlevel 2 to
5836 runlevel 3, init will first execute all of the <tt>K</tt>
5837 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5838 all of the <tt>S</tt> prefixed scripts in that directory.
5839 The links starting with <tt>K</tt> will cause the
5840 referred-to file to be executed with an argument of
5841 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5846 The two-digit number <var>mm</var> is used to determine
5847 the order in which to run the scripts: low-numbered links
5848 have their scripts run first. For example, the
5849 <tt>K20</tt> scripts will be executed before the
5850 <tt>K30</tt> scripts. This is used when a certain service
5851 must be started before another. For example, the name
5852 server <prgn>bind</prgn> might need to be started before
5853 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5854 can set up its access lists. In this case, the script
5855 that starts <prgn>bind</prgn> would have a lower number
5856 than the script that starts <prgn>inn</prgn> so that it
5858 <example compact="compact">
5865 The two runlevels 0 (halt) and 6 (reboot) are slightly
5866 different. In these runlevels, the links with an
5867 <tt>S</tt> prefix are still called after those with a
5868 <tt>K</tt> prefix, but they too are called with the single
5869 argument <tt>stop</tt>.
5873 Also, if the script name ends in <tt>.sh</tt>, the script
5874 will be sourced in runlevel <tt>S</tt> rather than being
5875 run in a forked subprocess, but will be explicitly run by
5876 <prgn>sh</prgn> in all other runlevels.
5881 <heading>Writing the scripts</heading>
5884 Packages that include daemons for system services should
5885 place scripts in <file>/etc/init.d</file> to start or stop
5886 services at boot time or during a change of runlevel.
5887 These scripts should be named
5888 <file>/etc/init.d/<var>package</var></file>, and they should
5889 accept one argument, saying what to do:
5892 <tag><tt>start</tt></tag>
5893 <item>start the service,</item>
5895 <tag><tt>stop</tt></tag>
5896 <item>stop the service,</item>
5898 <tag><tt>restart</tt></tag>
5899 <item>stop and restart the service if it's already running,
5900 otherwise start the service</item>
5902 <tag><tt>reload</tt></tag>
5903 <item><p>cause the configuration of the service to be
5904 reloaded without actually stopping and restarting
5907 <tag><tt>force-reload</tt></tag>
5908 <item>cause the configuration to be reloaded if the
5909 service supports this, otherwise restart the
5913 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5914 <tt>force-reload</tt> options should be supported by all
5915 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5920 The <file>init.d</file> scripts must ensure that they will
5921 behave sensibly (i.e., returning success and not starting
5922 multiple copies of a service) if invoked with <tt>start</tt>
5923 when the service is already running, or with <tt>stop</tt>
5924 when it isn't, and that they don't kill unfortunately-named
5925 user processes. The best way to achieve this is usually to
5926 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5931 If a service reloads its configuration automatically (as
5932 in the case of <prgn>cron</prgn>, for example), the
5933 <tt>reload</tt> option of the <file>init.d</file> script
5934 should behave as if the configuration has been reloaded
5939 The <file>/etc/init.d</file> scripts must be treated as
5940 configuration files, either (if they are present in the
5941 package, that is, in the .deb file) by marking them as
5942 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5943 by managing them correctly in the maintainer scripts (see
5944 <ref id="config-files">). This is important since we want
5945 to give the local system administrator the chance to adapt
5946 the scripts to the local system, e.g., to disable a
5947 service without de-installing the package, or to specify
5948 some special command line options when starting a service,
5949 while making sure their changes aren't lost during the next
5954 These scripts should not fail obscurely when the
5955 configuration files remain but the package has been
5956 removed, as configuration files remain on the system after
5957 the package has been removed. Only when <prgn>dpkg</prgn>
5958 is executed with the <tt>--purge</tt> option will
5959 configuration files be removed. In particular, as the
5960 <file>/etc/init.d/<var>package</var></file> script itself is
5961 usually a <tt>conffile</tt>, it will remain on the system
5962 if the package is removed but not purged. Therefore, you
5963 should include a <tt>test</tt> statement at the top of the
5965 <example compact="compact">
5966 test -f <var>program-executed-later-in-script</var> || exit 0
5971 Often there are some variables in the <file>init.d</file>
5972 scripts whose values control the behavior of the scripts,
5973 and which a system administrator is likely to want to
5974 change. As the scripts themselves are frequently
5975 <tt>conffile</tt>s, modifying them requires that the
5976 administrator merge in their changes each time the package
5977 is upgraded and the <tt>conffile</tt> changes. To ease
5978 the burden on the system administrator, such configurable
5979 values should not be placed directly in the script.
5980 Instead, they should be placed in a file in
5981 <file>/etc/default</file>, which typically will have the same
5982 base name as the <file>init.d</file> script. This extra file
5983 should be sourced by the script when the script runs. It
5984 must contain only variable settings and comments in SUSv3
5985 <prgn>sh</prgn> format. It may either be a
5986 <tt>conffile</tt> or a configuration file maintained by
5987 the package maintainer scripts. See <ref id="config-files">
5992 To ensure that vital configurable values are always
5993 available, the <file>init.d</file> script should set default
5994 values for each of the shell variables it uses, either
5995 before sourcing the <file>/etc/default/</file> file or
5996 afterwards using something like the <tt>:
5997 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5998 script must behave sensibly and not fail if the
5999 <file>/etc/default</file> file is deleted.
6004 <heading>Interfacing with the initscript system</heading>
6007 Maintainers should use the abstraction layer provided by
6008 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6009 programs to deal with initscripts in their packages'
6010 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6011 and <prgn>postrm</prgn>.
6015 Directly managing the /etc/rc?.d links and directly
6016 invoking the <file>/etc/init.d/</file> initscripts should
6017 be done only by packages providing the initscript
6018 subsystem (such as <prgn>sysv-rc</prgn> and
6019 <prgn>file-rc</prgn>).
6023 <heading>Managing the links</heading>
6026 The program <prgn>update-rc.d</prgn> is provided for
6027 package maintainers to arrange for the proper creation and
6028 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6029 or their functional equivalent if another method is being
6030 used. This may be used by maintainers in their packages'
6031 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6035 You must not include any <file>/etc/rc<var>n</var>.d</file>
6036 symbolic links in the actual archive or manually create or
6037 remove the symbolic links in maintainer scripts; you must
6038 use the <prgn>update-rc.d</prgn> program instead. (The
6039 former will fail if an alternative method of maintaining
6040 runlevel information is being used.) You must not include
6041 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6042 in the archive either. (Only the <tt>sysvinit</tt>
6047 By default <prgn>update-rc.d</prgn> will start services in
6048 each of the multi-user state runlevels (2, 3, 4, and 5)
6049 and stop them in the halt runlevel (0), the single-user
6050 runlevel (1) and the reboot runlevel (6). The system
6051 administrator will have the opportunity to customize
6052 runlevels by simply adding, moving, or removing the
6053 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6054 symbolic links are being used, or by modifying
6055 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6060 To get the default behavior for your package, put in your
6061 <prgn>postinst</prgn> script
6062 <example compact="compact">
6063 update-rc.d <var>package</var> defaults
6065 and in your <prgn>postrm</prgn>
6066 <example compact="compact">
6067 if [ "$1" = purge ]; then
6068 update-rc.d <var>package</var> remove
6070 </example>. Note that if your package changes runlevels
6071 or priority, you may have to remove and recreate the links,
6072 since otherwise the old links may persist. Refer to the
6073 documentation of <prgn>update-rc.d</prgn>.
6077 This will use a default sequence number of 20. If it does
6078 not matter when or in which order the <file>init.d</file>
6079 script is run, use this default. If it does, then you
6080 should talk to the maintainer of the <prgn>sysvinit</prgn>
6081 package or post to <tt>debian-devel</tt>, and they will
6082 help you choose a number.
6086 For more information about using <tt>update-rc.d</tt>,
6087 please consult its man page <manref name="update-rc.d"
6093 <heading>Running initscripts</heading>
6095 The program <prgn>invoke-rc.d</prgn> is provided to make
6096 it easier for package maintainers to properly invoke an
6097 initscript, obeying runlevel and other locally-defined
6098 constraints that might limit a package's right to start,
6099 stop and otherwise manage services. This program may be
6100 used by maintainers in their packages' scripts.
6104 The package maintainer scripts must use
6105 <prgn>invoke-rc.d</prgn> to invoke the
6106 <file>/etc/init.d/*</file> initscripts, instead of
6107 calling them directly.
6111 By default, <prgn>invoke-rc.d</prgn> will pass any
6112 action requests (start, stop, reload, restart...) to the
6113 <file>/etc/init.d</file> script, filtering out requests
6114 to start or restart a service out of its intended
6119 Most packages will simply need to change:
6120 <example compact="compact">/etc/init.d/<package>
6121 <action></example> in their <prgn>postinst</prgn>
6122 and <prgn>prerm</prgn> scripts to:
6123 <example compact="compact">
6124 if which invoke-rc.d >/dev/null 2>&1; then
6125 invoke-rc.d <var>package</var> <action>
6127 /etc/init.d/<var>package</var> <action>
6133 A package should register its initscript services using
6134 <prgn>update-rc.d</prgn> before it tries to invoke them
6135 using <prgn>invoke-rc.d</prgn>. Invocation of
6136 unregistered services may fail.
6140 For more information about using
6141 <prgn>invoke-rc.d</prgn>, please consult its man page
6142 <manref name="invoke-rc.d" section="8">.
6148 <heading>Boot-time initialization</heading>
6151 There used to be another directory, <file>/etc/rc.boot</file>,
6152 which contained scripts which were run once per machine
6153 boot. This has been deprecated in favour of links from
6154 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6155 described in <ref id="/etc/init.d">. Packages must not
6156 place files in <file>/etc/rc.boot</file>.
6161 <heading>Example</heading>
6164 An example on which you can base your
6165 <file>/etc/init.d</file> scripts is found in
6166 <file>/etc/init.d/skeleton</file>.
6173 <heading>Console messages from <file>init.d</file> scripts</heading>
6176 This section describes the formats to be used for messages
6177 written to standard output by the <file>/etc/init.d</file>
6178 scripts. The intent is to improve the consistency of
6179 Debian's startup and shutdown look and feel. For this
6180 reason, please look very carefully at the details. We want
6181 the messages to have the same format in terms of wording,
6182 spaces, punctuation and case of letters.
6186 Here is a list of overall rules that should be used for
6187 messages generated by <file>/etc/init.d</file> scripts.
6193 The message should fit in one line (fewer than 80
6194 characters), start with a capital letter and end with
6195 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6199 If the script is performing some time consuming task in
6200 the background (not merely starting or stopping a
6201 program, for instance), an ellipsis (three dots:
6202 <tt>...</tt>) should be output to the screen, with no
6203 leading or tailing whitespace or line feeds.
6207 The messages should appear as if the computer is telling
6208 the user what it is doing (politely :-), but should not
6209 mention "it" directly. For example, instead of:
6210 <example compact="compact">
6211 I'm starting network daemons: nfsd mountd.
6213 the message should say
6214 <example compact="compact">
6215 Starting network daemons: nfsd mountd.
6222 <tt>init.d</tt> script should use the following standard
6223 message formats for the situations enumerated below.
6229 <p>When daemons are started</p>
6232 If the script starts one or more daemons, the output
6233 should look like this (a single line, no leading
6235 <example compact="compact">
6236 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6238 The <var>description</var> should describe the
6239 subsystem the daemon or set of daemons are part of,
6240 while <var>daemon-1</var> up to <var>daemon-n</var>
6241 denote each daemon's name (typically the file name of
6246 For example, the output of <file>/etc/init.d/lpd</file>
6248 <example compact="compact">
6249 Starting printer spooler: lpd.
6254 This can be achieved by saying
6255 <example compact="compact">
6256 echo -n "Starting printer spooler: lpd"
6257 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6260 in the script. If there are more than one daemon to
6261 start, the output should look like this:
6262 <example compact="compact">
6263 echo -n "Starting remote file system services:"
6264 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6265 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6266 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6269 This makes it possible for the user to see what is
6270 happening and when the final daemon has been started.
6271 Care should be taken in the placement of white spaces:
6272 in the example above the system administrators can
6273 easily comment out a line if they don't want to start
6274 a specific daemon, while the displayed message still
6280 <p>When a system parameter is being set</p>
6283 If you have to set up different system parameters
6284 during the system boot, you should use this format:
6285 <example compact="compact">
6286 Setting <var>parameter</var> to "<var>value</var>".
6291 You can use a statement such as the following to get
6293 <example compact="compact">
6294 echo "Setting DNS domainname to \"$domainname\"."
6299 Note that the same symbol (<tt>"</tt>) is used for the left
6300 and right quotation marks. A grave accent (<tt>`</tt>) is
6301 not a quote character; neither is an apostrophe
6307 <p>When a daemon is stopped or restarted</p>
6310 When you stop or restart a daemon, you should issue a
6311 message identical to the startup message, except that
6312 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6313 or <tt>Restarting</tt> respectively.
6317 For example, stopping the printer daemon will look like
6319 <example compact="compact">
6320 Stopping printer spooler: lpd.
6326 <p>When something is executed</p>
6329 There are several examples where you have to run a
6330 program at system startup or shutdown to perform a
6331 specific task, for example, setting the system's clock
6332 using <prgn>netdate</prgn> or killing all processes
6333 when the system shuts down. Your message should look
6335 <example compact="compact">
6336 Doing something very useful...done.
6338 You should print the <tt>done.</tt> immediately after
6339 the job has been completed, so that the user is
6340 informed why they have to wait. You can get this
6342 <example compact="compact">
6343 echo -n "Doing something very useful..."
6352 <p>When the configuration is reloaded</p>
6355 When a daemon is forced to reload its configuration
6356 files you should use the following format:
6357 <example compact="compact">
6358 Reloading <var>description</var> configuration...done.
6360 where <var>description</var> is the same as in the
6361 daemon starting message.
6369 <heading>Cron jobs</heading>
6372 Packages must not modify the configuration file
6373 <file>/etc/crontab</file>, and they must not modify the files in
6374 <file>/var/spool/cron/crontabs</file>.</p>
6377 If a package wants to install a job that has to be executed
6378 via cron, it should place a file with the name of the
6379 package in one or more of the following directories:
6380 <example compact="compact">
6386 As these directory names imply, the files within them are
6387 executed on an hourly, daily, weekly, or monthly basis,
6388 respectively. The exact times are listed in
6389 <file>/etc/crontab</file>.</p>
6392 All files installed in any of these directories must be
6393 scripts (e.g., shell scripts or Perl scripts) so that they
6394 can easily be modified by the local system administrator.
6395 In addition, they must be treated as configuration files.
6399 If a certain job has to be executed at some other frequency or
6400 at a specific time, the package should install a file
6401 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6402 same syntax as <file>/etc/crontab</file> and is processed by
6403 <prgn>cron</prgn> automatically. The file must also be
6404 treated as a configuration file. (Note that entries in the
6405 <file>/etc/cron.d</file> directory are not handled by
6406 <prgn>anacron</prgn>. Thus, you should only use this
6407 directory for jobs which may be skipped if the system is not
6411 The scripts or crontab entries in these directories should
6412 check if all necessary programs are installed before they
6413 try to execute them. Otherwise, problems will arise when a
6414 package was removed but not purged since configuration files
6415 are kept on the system in this situation.</p>
6419 <heading>Menus</heading>
6422 The Debian <tt>menu</tt> package provides a standard
6423 interface between packages providing applications and
6424 <em>menu programs</em> (either X window managers or
6425 text-based menu programs such as <prgn>pdmenu</prgn>).
6429 All packages that provide applications that need not be
6430 passed any special command line arguments for normal
6431 operation should register a menu entry for those
6432 applications, so that users of the <tt>menu</tt> package
6433 will automatically get menu entries in their window
6434 managers, as well in shells like <tt>pdmenu</tt>.
6438 Menu entries should follow the current menu policy.
6442 The menu policy can be found in the <tt>menu-policy</tt>
6443 files in the <tt>debian-policy</tt> package.
6444 It is also available from the Debian web mirrors at
6445 <tt><url name="/doc/packaging-manuals/menu-policy/"
6446 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6450 Please also refer to the <em>Debian Menu System</em>
6451 documentation that comes with the <package>menu</package>
6452 package for information about how to register your
6458 <heading>Multimedia handlers</heading>
6461 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6462 is a mechanism for encoding files and data streams and
6463 providing meta-information about them, in particular their
6464 type (e.g. audio or video) and format (e.g. PNG, HTML,
6469 Registration of MIME type handlers allows programs like mail
6470 user agents and web browsers to invoke these handlers to
6471 view, edit or display MIME types they don't support directly.
6475 Packages which provide the ability to view/show/play,
6476 compose, edit or print MIME types should register themselves
6477 as such following the current MIME support policy.
6481 The MIME support policy can be found in the <tt>mime-policy</tt>
6482 files in the <tt>debian-policy</tt> package.
6483 It is also available from the Debian web mirrors at
6484 <tt><url name="/doc/packaging-manuals/mime-policy/"
6485 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6491 <heading>Keyboard configuration</heading>
6494 To achieve a consistent keyboard configuration so that all
6495 applications interpret a keyboard event the same way, all
6496 programs in the Debian distribution must be configured to
6497 comply with the following guidelines.
6501 The following keys must have the specified interpretations:
6504 <tag><tt><--</tt></tag>
6505 <item>delete the character to the left of the cursor</item>
6507 <tag><tt>Delete</tt></tag>
6508 <item>delete the character to the right of the cursor</item>
6510 <tag><tt>Control+H</tt></tag>
6511 <item>emacs: the help prefix</item>
6514 The interpretation of any keyboard events should be
6515 independent of the terminal that is used, be it a virtual
6516 console, an X terminal emulator, an rlogin/telnet session,
6521 The following list explains how the different programs
6522 should be set up to achieve this:
6528 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6532 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6536 X translations are set up to make
6537 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6538 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6539 is the vt220 escape code for the "delete character"
6540 key). This must be done by loading the X resources
6541 using <prgn>xrdb</prgn> on all local X displays, not
6542 using the application defaults, so that the
6543 translation resources used correspond to the
6544 <prgn>xmodmap</prgn> settings.
6548 The Linux console is configured to make
6549 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6550 generate <tt>ESC [ 3 ~</tt>.
6554 X applications are configured so that <tt><</tt>
6555 deletes left, and <tt>Delete</tt> deletes right. Motif
6556 applications already work like this.
6560 Terminals should have <tt>stty erase ^?</tt> .
6564 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6565 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6566 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6570 Emacs is programmed to map <tt>KB_Backspace</tt> or
6571 the <tt>stty erase</tt> character to
6572 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6573 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6574 <tt>^H</tt> to <tt>help</tt> as always.
6578 Other applications use the <tt>stty erase</tt>
6579 character and <tt>kdch1</tt> for the two delete keys,
6580 with ASCII DEL being "delete previous character" and
6581 <tt>kdch1</tt> being "delete character under
6589 This will solve the problem except for the following
6596 Some terminals have a <tt><--</tt> key that cannot
6597 be made to produce anything except <tt>^H</tt>. On
6598 these terminals Emacs help will be unavailable on
6599 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6600 character takes precedence in Emacs, and has been set
6601 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6602 available) can be used instead.
6606 Some operating systems use <tt>^H</tt> for <tt>stty
6607 erase</tt>. However, modern telnet versions and all
6608 rlogin versions propagate <tt>stty</tt> settings, and
6609 almost all UNIX versions honour <tt>stty erase</tt>.
6610 Where the <tt>stty</tt> settings are not propagated
6611 correctly, things can be made to work by using
6612 <tt>stty</tt> manually.
6616 Some systems (including previous Debian versions) use
6617 <prgn>xmodmap</prgn> to arrange for both
6618 <tt><--</tt> and <tt>Delete</tt> to generate
6619 <tt>KB_Delete</tt>. We can change the behavior of
6620 their X clients using the same X resources that we use
6621 to do it for our own clients, or configure our clients
6622 using their resources when things are the other way
6623 around. On displays configured like this
6624 <tt>Delete</tt> will not work, but <tt><--</tt>
6629 Some operating systems have different <tt>kdch1</tt>
6630 settings in their <tt>terminfo</tt> database for
6631 <tt>xterm</tt> and others. On these systems the
6632 <tt>Delete</tt> key will not work correctly when you
6633 log in from a system conforming to our policy, but
6634 <tt><--</tt> will.
6641 <heading>Environment variables</heading>
6644 A program must not depend on environment variables to get
6645 reasonable defaults. (That's because these environment
6646 variables would have to be set in a system-wide
6647 configuration file like <file>/etc/profile</file>, which is not
6648 supported by all shells.)
6652 If a program usually depends on environment variables for its
6653 configuration, the program should be changed to fall back to
6654 a reasonable default configuration if these environment
6655 variables are not present. If this cannot be done easily
6656 (e.g., if the source code of a non-free program is not
6657 available), the program must be replaced by a small
6658 "wrapper" shell script which sets the environment variables
6659 if they are not already defined, and calls the original program.
6663 Here is an example of a wrapper script for this purpose:
6665 <example compact="compact">
6667 BAR=${BAR:-/var/lib/fubar}
6669 exec /usr/lib/foo/foo "$@"
6674 Furthermore, as <file>/etc/profile</file> is a configuration
6675 file of the <prgn>base-files</prgn> package, other packages must
6676 not put any environment variables or other commands into that
6681 <sect id="doc-base">
6682 <heading>Registering Documents using doc-base</heading>
6685 The <package>doc-base</package> package implements a
6686 flexible mechanism for handling and presenting
6687 documentation. The recommended practice is for every Debian
6688 package that provides online documentation (other than just
6689 manual pages) to register these documents with
6690 <package>doc-base</package> by installing a
6691 <package>doc-base</package> control file via the
6692 <prgn/install-docs/ script at installation time and
6693 de-register the manuals again when the package is removed.
6696 Please refer to the documentation that comes with the
6697 <package>doc-base</package> package for information and
6706 <heading>Files</heading>
6709 <heading>Binaries</heading>
6712 Two different packages must not install programs with
6713 different functionality but with the same filenames. (The
6714 case of two programs having the same functionality but
6715 different implementations is handled via "alternatives" or
6716 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6717 <ref id="conflicts"> respectively.) If this case happens,
6718 one of the programs must be renamed. The maintainers should
6719 report this to the <tt>debian-devel</tt> mailing list and
6720 try to find a consensus about which program will have to be
6721 renamed. If a consensus cannot be reached, <em>both</em>
6722 programs must be renamed.
6726 By default, when a package is being built, any binaries
6727 created should include debugging information, as well as
6728 being compiled with optimization. You should also turn on
6729 as many reasonable compilation warnings as possible; this
6730 makes life easier for porters, who can then look at build
6731 logs for possible problems. For the C programming language,
6732 this means the following compilation parameters should be
6734 <example compact="compact">
6736 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6738 INSTALL = install -s # (or use strip on the files in debian/tmp)
6743 Note that by default all installed binaries should be stripped,
6744 either by using the <tt>-s</tt> flag to
6745 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6746 the binaries after they have been copied into
6747 <file>debian/tmp</file> but before the tree is made into a
6752 Although binaries in the build tree should be compiled with
6753 debugging information by default, it can often be difficult to
6754 debug programs if they are also subjected to compiler
6755 optimization. For this reason, it is recommended to support the
6756 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6757 (see <ref id="debianrules-options">). This variable can contain
6758 several flags to change how a package is compiled and built.
6762 It is up to the package maintainer to decide what
6763 compilation options are best for the package. Certain
6764 binaries (such as computationally-intensive programs) will
6765 function better with certain flags (<tt>-O3</tt>, for
6766 example); feel free to use them. Please use good judgment
6767 here. Don't use flags for the sake of it; only use them
6768 if there is good reason to do so. Feel free to override
6769 the upstream author's ideas about which compilation
6770 options are best: they are often inappropriate for our
6776 <sect id="libraries">
6777 <heading>Libraries</heading>
6780 If the package is <strong>architecture: any</strong>, then
6781 the shared library compilation and linking flags must have
6782 <tt>-fPIC</tt>, or the package shall not build on some of
6783 the supported architectures<footnote>
6785 If you are using GCC, <tt>-fPIC</tt> produces code with
6786 relocatable position independent code, which is required for
6787 most architectures to create a shared library, with i386 and
6788 perhaps some others where non position independent code is
6789 permitted in a shared library.
6792 Position independent code may have a performance penalty,
6793 especially on <tt>i386</tt>. However, in most cases the
6794 speed penalty must be measured against the memory wasted on
6795 the few architectures where non position independent code is
6798 </footnote>. Any exception to this rule must be discussed on
6799 the mailing list <em>debian-devel@lists.debian.org</em>, and
6800 a rough consensus obtained. The reasons for not compiling
6801 with <tt>-fPIC</tt> flag must be recorded in the file
6802 <tt>README.Debian</tt>, and care must be taken to either
6803 restrict the architecture or arrange for <tt>-fPIC</tt> to
6804 be used on architectures where it is required.<footnote>
6806 Some of the reasons why this might be required is if the
6807 library contains hand crafted assembly code that is not
6808 relocatable, the speed penalty is excessive for compute
6809 intensive libs, and similar reasons.
6814 As to the static libraries, the common case is not to have
6815 relocatable code, since there is no benefit, unless in specific
6816 cases; therefore the static version must not be compiled
6817 with the <tt>-fPIC</tt> flag. Any exception to this rule
6818 should be discussed on the mailing list
6819 <em>debian-devel@lists.debian.org</em>, and the reasons for
6820 compiling with the <tt>-fPIC</tt> flag must be recorded in
6821 the file <tt>README.Debian</tt>. <footnote>
6823 Some of the reasons for linking static libraries with
6824 the <tt>-fPIC</tt> flag are if, for example, one needs a
6825 Perl API for a library that is under rapid development,
6826 and has an unstable API, so shared libraries are
6827 pointless at this phase of the library's development. In
6828 that case, since Perl needs a library with relocatable
6829 code, it may make sense to create a static library with
6830 relocatable code. Another reason cited is if you are
6831 distilling various libraries into a common shared
6832 library, like <tt>mklibs</tt> does in the Debian
6838 In other words, if both a shared and a static library is
6839 being built, each source unit (<tt>*.c</tt>, for example,
6840 for C files) will need to be compiled twice, for the normal
6844 You must specify the gcc option <tt>-D_REENTRANT</tt>
6845 when building a library (either static or shared) to make
6846 the library compatible with LinuxThreads.
6850 Although not enforced by the build tools, shared libraries
6851 must be linked against all libraries that they use symbols from
6852 in the same way that binaries are. This ensures the correct
6853 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6854 system and guarantees that all libraries can be safely opened
6855 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6856 option <tt>-Wl,-z,defs</tt> when building a shared library.
6857 Since this option enforces symbol resolution at build time,
6858 a missing library reference will be caught early as a fatal
6863 All installed shared libraries should be stripped with
6864 <example compact="compact">
6865 strip --strip-unneeded <var>your-lib</var>
6867 (The option <tt>--strip-unneeded</tt> makes
6868 <prgn>strip</prgn> remove only the symbols which aren't
6869 needed for relocation processing.) Shared libraries can
6870 function perfectly well when stripped, since the symbols for
6871 dynamic linking are in a separate part of the ELF object
6873 You might also want to use the options
6874 <tt>--remove-section=.comment</tt> and
6875 <tt>--remove-section=.note</tt> on both shared libraries
6876 and executables, and <tt>--strip-debug</tt> on static
6882 Note that under some circumstances it may be useful to
6883 install a shared library unstripped, for example when
6884 building a separate package to support debugging.
6888 Shared object files (often <file>.so</file> files) that are not
6889 public libraries, that is, they are not meant to be linked
6890 to by third party executables (binaries of other packages),
6891 should be installed in subdirectories of the
6892 <file>/usr/lib</file> directory. Such files are exempt from the
6893 rules that govern ordinary shared libraries, except that
6894 they must not be installed executable and should be
6896 A common example are the so-called "plug-ins",
6897 internal shared objects that are dynamically loaded by
6898 programs using <manref name="dlopen" section="3">.
6903 Packages containing shared libraries that may be linked to
6904 by other packages' binaries, but which for some
6905 <em>compelling</em> reason can not be installed in
6906 <file>/usr/lib</file> directory, may install the shared library
6907 files in subdirectories of the <file>/usr/lib</file> directory,
6908 in which case they should arrange to add that directory in
6909 <file>/etc/ld.so.conf</file> in the package's post-installation
6910 script, and remove it in the package's post-removal script.
6914 An ever increasing number of packages are using
6915 <prgn>libtool</prgn> to do their linking. The latest GNU
6916 libtools (>= 1.3a) can take advantage of the metadata in the
6917 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6918 files). The main advantage of <prgn>libtool</prgn>'s
6919 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6920 store and subsequently access metadata with respect to the
6921 libraries it builds. <prgn>libtool</prgn> will search for
6922 those files, which contain a lot of useful information about
6923 a library (such as library dependency information for static
6924 linking). Also, they're <em>essential</em> for programs
6925 using <tt>libltdl</tt>.<footnote>
6926 Although <prgn>libtool</prgn> is fully capable of
6927 linking against shared libraries which don't have
6928 <tt>.la</tt> files, as it is a mere shell script it can
6929 add considerably to the build time of a
6930 <prgn>libtool</prgn>-using package if that shell script
6931 has to derive all this information from first principles
6932 for each library every time it is linked. With the
6933 advent of <prgn>libtool</prgn> version 1.4 (and to a
6934 lesser extent <prgn>libtool</prgn> version 1.3), the
6935 <file>.la</file> files also store information about
6936 inter-library dependencies which cannot necessarily be
6937 derived after the <file>.la</file> file is deleted.
6942 Packages that use <prgn>libtool</prgn> to create shared
6943 libraries should include the <file>.la</file> files in the
6944 <tt>-dev</tt> package, unless the package relies on
6945 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6946 the <tt>.la</tt> files must go in the run-time library
6951 You must make sure that you use only released versions of
6952 shared libraries to build your packages; otherwise other
6953 users will not be able to run your binaries
6954 properly. Producing source packages that depend on
6955 unreleased compilers is also usually a bad
6962 <heading>Shared libraries</heading>
6964 This section has moved to <ref id="sharedlibs">.
6970 <heading>Scripts</heading>
6973 All command scripts, including the package maintainer
6974 scripts inside the package and used by <prgn>dpkg</prgn>,
6975 should have a <tt>#!</tt> line naming the shell to be used
6980 In the case of Perl scripts this should be
6981 <tt>#!/usr/bin/perl</tt>.
6985 When scripts are installed into a directory in the system
6986 PATH, the script name should not include an extension such
6987 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6988 language currently used to implement it.
6991 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6992 should almost certainly start with <tt>set -e</tt> so that
6993 errors are detected. Every script should use
6994 <tt>set -e</tt> or check the exit status of <em>every</em>
6999 Scripts may assume that <file>/bin/sh</file> implements the
7000 SUSv3 Shell Command Language<footnote>
7001 Single UNIX Specification, version 3, which is also IEEE
7002 1003.1-2004 (POSIX), and is available on the World Wide Web
7003 from <url id="http://www.unix.org/version3/online.html"
7004 name="The Open Group"> after free
7005 registration.</footnote>
7006 plus the following additional features not mandated by
7008 These features are in widespread use in the Linux community
7009 and are implemented in all of bash, dash, and ksh, the most
7010 common shells users may wish to use as <file>/bin/sh</file>.
7013 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7014 must not generate a newline.</item>
7015 <item><tt>test</tt>, if implemented as a shell built-in, must
7016 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7018 <item><tt>local</tt> to create a scoped variable must be
7019 supported; however, <tt>local</tt> may or may not preserve
7020 the variable value from an outer scope and may or may not
7021 support arguments more complex than simple variables. Only
7033 If a shell script requires non-SUSv3 features from the shell
7034 interpreter other than those listed above, the appropriate shell
7035 must be specified in the first line of the script (e.g.,
7036 <tt>#!/bin/bash</tt>) and the package must depend on the package
7037 providing the shell (unless the shell package is marked
7038 "Essential", as in the case of <prgn>bash</prgn>).
7042 You may wish to restrict your script to SUSv3 features plus the
7043 above set when possible so that it may use <file>/bin/sh</file>
7044 as its interpreter. If your script works with <prgn>dash</prgn>
7045 (originally called <prgn>ash</prgn>), it probably complies with
7046 the above requirements, but if you are in doubt, use
7047 <file>/bin/bash</file>.
7051 Perl scripts should check for errors when making any
7052 system calls, including <tt>open</tt>, <tt>print</tt>,
7053 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7057 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7058 scripting languages. See <em>Csh Programming Considered
7059 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7060 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7061 If an upstream package comes with <prgn>csh</prgn> scripts
7062 then you must make sure that they start with
7063 <tt>#!/bin/csh</tt> and make your package depend on the
7064 <prgn>c-shell</prgn> virtual package.
7068 Any scripts which create files in world-writeable
7069 directories (e.g., in <file>/tmp</file>) must use a
7070 mechanism which will fail atomically if a file with the same
7071 name already exists.
7075 The Debian base system provides the <prgn>tempfile</prgn>
7076 and <prgn>mktemp</prgn> utilities for use by scripts for
7083 <heading>Symbolic links</heading>
7086 In general, symbolic links within a top-level directory
7087 should be relative, and symbolic links pointing from one
7088 top-level directory into another should be absolute. (A
7089 top-level directory is a sub-directory of the root
7090 directory <file>/</file>.)
7094 In addition, symbolic links should be specified as short as
7095 possible, i.e., link targets like <file>foo/../bar</file> are
7100 Note that when creating a relative link using
7101 <prgn>ln</prgn> it is not necessary for the target of the
7102 link to exist relative to the working directory you're
7103 running <prgn>ln</prgn> from, nor is it necessary to change
7104 directory to the directory where the link is to be made.
7105 Simply include the string that should appear as the target
7106 of the link (this will be a pathname relative to the
7107 directory in which the link resides) as the first argument
7112 For example, in your <prgn>Makefile</prgn> or
7113 <file>debian/rules</file>, you can do things like:
7114 <example compact="compact">
7115 ln -fs gcc $(prefix)/bin/cc
7116 ln -fs gcc debian/tmp/usr/bin/cc
7117 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7118 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7123 A symbolic link pointing to a compressed file should always
7124 have the same file extension as the referenced file. (For
7125 example, if a file <file>foo.gz</file> is referenced by a
7126 symbolic link, the filename of the link has to end with
7127 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7132 <heading>Device files</heading>
7135 Packages must not include device files in the package file
7140 If a package needs any special device files that are not
7141 included in the base system, it must call
7142 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7143 after notifying the user<footnote>
7144 This notification could be done via a (low-priority)
7145 debconf message, or an echo (printf) statement.
7150 Packages must not remove any device files in the
7151 <prgn>postrm</prgn> or any other script. This is left to the
7152 system administrator.
7156 Debian uses the serial devices
7157 <file>/dev/ttyS*</file>. Programs using the old
7158 <file>/dev/cu*</file> devices should be changed to use
7159 <file>/dev/ttyS*</file>.
7163 <sect id="config-files">
7164 <heading>Configuration files</heading>
7167 <heading>Definitions</heading>
7171 <tag>configuration file</tag>
7173 A file that affects the operation of a program, or
7174 provides site- or host-specific information, or
7175 otherwise customizes the behavior of a program.
7176 Typically, configuration files are intended to be
7177 modified by the system administrator (if needed or
7178 desired) to conform to local policy or to provide
7179 more useful site-specific behavior.
7182 <tag><tt>conffile</tt></tag>
7184 A file listed in a package's <tt>conffiles</tt>
7185 file, and is treated specially by <prgn>dpkg</prgn>
7186 (see <ref id="configdetails">).
7192 The distinction between these two is important; they are
7193 not interchangeable concepts. Almost all
7194 <tt>conffile</tt>s are configuration files, but many
7195 configuration files are not <tt>conffiles</tt>.
7199 As noted elsewhere, <file>/etc/init.d</file> scripts,
7200 <file>/etc/default</file> files, scripts installed in
7201 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7202 configuration installed in <file>/etc/cron.d</file> must be
7203 treated as configuration files. In general, any script that
7204 embeds configuration information is de-facto a configuration
7205 file and should be treated as such.
7210 <heading>Location</heading>
7213 Any configuration files created or used by your package
7214 must reside in <file>/etc</file>. If there are several,
7215 consider creating a subdirectory of <file>/etc</file>
7216 named after your package.
7220 If your package creates or uses configuration files
7221 outside of <file>/etc</file>, and it is not feasible to modify
7222 the package to use <file>/etc</file> directly, put the files
7223 in <file>/etc</file> and create symbolic links to those files
7224 from the location that the package requires.
7229 <heading>Behavior</heading>
7232 Configuration file handling must conform to the following
7234 <list compact="compact">
7236 local changes must be preserved during a package
7240 configuration files must be preserved when the
7241 package is removed, and only deleted when the
7248 The easy way to achieve this behavior is to make the
7249 configuration file a <tt>conffile</tt>. This is
7250 appropriate only if it is possible to distribute a default
7251 version that will work for most installations, although
7252 some system administrators may choose to modify it. This
7253 implies that the default version will be part of the
7254 package distribution, and must not be modified by the
7255 maintainer scripts during installation (or at any other
7260 In order to ensure that local changes are preserved
7261 correctly, no package may contain or make hard links to
7262 conffiles.<footnote>
7263 Rationale: There are two problems with hard links.
7264 The first is that some editors break the link while
7265 editing one of the files, so that the two files may
7266 unwittingly become unlinked and different. The second
7267 is that <prgn>dpkg</prgn> might break the hard link
7268 while upgrading <tt>conffile</tt>s.
7273 The other way to do it is via the maintainer scripts. In
7274 this case, the configuration file must not be listed as a
7275 <tt>conffile</tt> and must not be part of the package
7276 distribution. If the existence of a file is required for
7277 the package to be sensibly configured it is the
7278 responsibility of the package maintainer to provide
7279 maintainer scripts which correctly create, update and
7280 maintain the file and remove it on purge. (See <ref
7281 id="maintainerscripts"> for more information.) These
7282 scripts must be idempotent (i.e., must work correctly if
7283 <prgn>dpkg</prgn> needs to re-run them due to errors
7284 during installation or removal), must cope with all the
7285 variety of ways <prgn>dpkg</prgn> can call maintainer
7286 scripts, must not overwrite or otherwise mangle the user's
7287 configuration without asking, must not ask unnecessary
7288 questions (particularly during upgrades), and must
7289 otherwise be good citizens.
7293 The scripts are not required to configure every possible
7294 option for the package, but only those necessary to get
7295 the package running on a given system. Ideally the
7296 sysadmin should not have to do any configuration other
7297 than that done (semi-)automatically by the
7298 <prgn>postinst</prgn> script.
7302 A common practice is to create a script called
7303 <file><var>package</var>-configure</file> and have the
7304 package's <prgn>postinst</prgn> call it if and only if the
7305 configuration file does not already exist. In certain
7306 cases it is useful for there to be an example or template
7307 file which the maintainer scripts use. Such files should
7308 be in <file>/usr/share/<var>package</var></file> or
7309 <file>/usr/lib/<var>package</var></file> (depending on whether
7310 they are architecture-independent or not). There should
7311 be symbolic links to them from
7312 <file>/usr/share/doc/<var>package</var>/examples</file> if
7313 they are examples, and should be perfectly ordinary
7314 <prgn>dpkg</prgn>-handled files (<em>not</em>
7315 configuration files).
7319 These two styles of configuration file handling must
7320 not be mixed, for that way lies madness:
7321 <prgn>dpkg</prgn> will ask about overwriting the file
7322 every time the package is upgraded.
7327 <heading>Sharing configuration files</heading>
7330 Packages which specify the same file as a
7331 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7332 with each other. (This is an instance of the general rule
7333 about not sharing files. Note that neither alternatives
7334 nor diversions are likely to be appropriate in this case;
7335 in particular, <prgn>dpkg</prgn> does not handle diverted
7336 <tt>conffile</tt>s well.)
7340 The maintainer scripts must not alter a <tt>conffile</tt>
7341 of <em>any</em> package, including the one the scripts
7346 If two or more packages use the same configuration file
7347 and it is reasonable for both to be installed at the same
7348 time, one of these packages must be defined as
7349 <em>owner</em> of the configuration file, i.e., it will be
7350 the package which handles that file as a configuration
7351 file. Other packages that use the configuration file must
7352 depend on the owning package if they require the
7353 configuration file to operate. If the other package will
7354 use the configuration file if present, but is capable of
7355 operating without it, no dependency need be declared.
7359 If it is desirable for two or more related packages to
7360 share a configuration file <em>and</em> for all of the
7361 related packages to be able to modify that configuration
7362 file, then the following should be done:
7363 <enumlist compact="compact">
7365 One of the related packages (the "owning" package)
7366 will manage the configuration file with maintainer
7367 scripts as described in the previous section.
7370 The owning package should also provide a program
7371 that the other packages may use to modify the
7375 The related packages must use the provided program
7376 to make any desired modifications to the
7377 configuration file. They should either depend on
7378 the core package to guarantee that the configuration
7379 modifier program is available or accept gracefully
7380 that they cannot modify the configuration file if it
7381 is not. (This is in addition to the fact that the
7382 configuration file may not even be present in the
7389 Sometimes it's appropriate to create a new package which
7390 provides the basic infrastructure for the other packages
7391 and which manages the shared configuration files. (The
7392 <tt>sgml-base</tt> package is a good example.)
7397 <heading>User configuration files ("dotfiles")</heading>
7400 The files in <file>/etc/skel</file> will automatically be
7401 copied into new user accounts by <prgn>adduser</prgn>.
7402 No other program should reference the files in
7403 <file>/etc/skel</file>.
7407 Therefore, if a program needs a dotfile to exist in
7408 advance in <file>$HOME</file> to work sensibly, that dotfile
7409 should be installed in <file>/etc/skel</file> and treated as a
7414 However, programs that require dotfiles in order to
7415 operate sensibly are a bad thing, unless they do create
7416 the dotfiles themselves automatically.
7420 Furthermore, programs should be configured by the Debian
7421 default installation to behave as closely to the upstream
7422 default behavior as possible.
7426 Therefore, if a program in a Debian package needs to be
7427 configured in some way in order to operate sensibly, that
7428 should be done using a site-wide configuration file placed
7429 in <file>/etc</file>. Only if the program doesn't support a
7430 site-wide default configuration and the package maintainer
7431 doesn't have time to add it may a default per-user file be
7432 placed in <file>/etc/skel</file>.
7436 <file>/etc/skel</file> should be as empty as we can make it.
7437 This is particularly true because there is no easy (or
7438 necessarily desirable) mechanism for ensuring that the
7439 appropriate dotfiles are copied into the accounts of
7440 existing users when a package is installed.
7446 <heading>Log files</heading>
7448 Log files should usually be named
7449 <file>/var/log/<var>package</var>.log</file>. If you have many
7450 log files, or need a separate directory for permission
7451 reasons (<file>/var/log</file> is writable only by
7452 <file>root</file>), you should usually create a directory named
7453 <file>/var/log/<var>package</var></file> and place your log
7458 Log files must be rotated occasionally so that they don't
7459 grow indefinitely; the best way to do this is to drop a log
7460 rotation configuration file into the directory
7461 <file>/etc/logrotate.d</file> and use the facilities provided by
7462 logrotate.<footnote>
7464 The traditional approach to log files has been to set up
7465 <em>ad hoc</em> log rotation schemes using simple shell
7466 scripts and cron. While this approach is highly
7467 customizable, it requires quite a lot of sysadmin work.
7468 Even though the original Debian system helped a little
7469 by automatically installing a system which can be used
7470 as a template, this was deemed not enough.
7474 The use of <prgn>logrotate</prgn>, a program developed
7475 by Red Hat, is better, as it centralizes log management.
7476 It has both a configuration file
7477 (<file>/etc/logrotate.conf</file>) and a directory where
7478 packages can drop their individual log rotation
7479 configurations (<file>/etc/logrotate.d</file>).
7482 Here is a good example for a logrotate config
7483 file (for more information see <manref name="logrotate"
7485 <example compact="compact">
7486 /var/log/foo/*.log {
7491 /etc/init.d/foo force-reload
7495 This rotates all files under <file>/var/log/foo</file>, saves 12
7496 compressed generations, and forces the daemon to reload its
7497 configuration information after the log rotation.
7501 Log files should be removed when the package is
7502 purged (but not when it is only removed). This should be
7503 done by the <prgn>postrm</prgn> script when it is called
7504 with the argument <tt>purge</tt> (see <ref
7505 id="removedetails">).
7510 <heading>Permissions and owners</heading>
7513 The rules in this section are guidelines for general use.
7514 If necessary you may deviate from the details below.
7515 However, if you do so you must make sure that what is done
7516 is secure and you should try to be as consistent as possible
7517 with the rest of the system. You should probably also
7518 discuss it on <prgn>debian-devel</prgn> first.
7522 Files should be owned by <tt>root:root</tt>, and made
7523 writable only by the owner and universally readable (and
7524 executable, if appropriate), that is mode 644 or 755.
7528 Directories should be mode 755 or (for group-writability)
7529 mode 2775. The ownership of the directory should be
7530 consistent with its mode: if a directory is mode 2775, it
7531 should be owned by the group that needs write access to
7534 When a package is upgraded, and the owner or permissions
7535 of a file included in the package has changed, dpkg
7536 arranges for the ownership and permissions to be
7537 correctly set upon installation. However, this does not
7538 extend to directories; the permissions and ownership of
7539 directories already on the system does not change on
7540 install or upgrade of packages. This makes sense, since
7541 otherwise common directories like <tt>/usr</tt> would
7542 always be in flux. To correctly change permissions of a
7543 directory the package owns, explicit action is required,
7544 usually in the <tt>postinst</tt> script. Care must be
7545 taken to handle downgrades as well, in that case.
7552 Setuid and setgid executables should be mode 4755 or 2755
7553 respectively, and owned by the appropriate user or group.
7554 They should not be made unreadable (modes like 4711 or
7555 2711 or even 4111); doing so achieves no extra security,
7556 because anyone can find the binary in the freely available
7557 Debian package; it is merely inconvenient. For the same
7558 reason you should not restrict read or execute permissions
7559 on non-set-id executables.
7563 Some setuid programs need to be restricted to particular
7564 sets of users, using file permissions. In this case they
7565 should be owned by the uid to which they are set-id, and by
7566 the group which should be allowed to execute them. They
7567 should have mode 4754; again there is no point in making
7568 them unreadable to those users who must not be allowed to
7573 It is possible to arrange that the system administrator can
7574 reconfigure the package to correspond to their local
7575 security policy by changing the permissions on a binary:
7576 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7577 described below.<footnote>
7578 Ordinary files installed by <prgn>dpkg</prgn> (as
7579 opposed to <tt>conffile</tt>s and other similar objects)
7580 normally have their permissions reset to the distributed
7581 permissions when the package is reinstalled. However,
7582 the use of <prgn>dpkg-statoverride</prgn> overrides this
7583 default behavior. If you use this method, you should
7584 remember to describe <prgn>dpkg-statoverride</prgn> in
7585 the package documentation; being a relatively new
7586 addition to Debian, it is probably not yet well-known.
7588 Another method you should consider is to create a group for
7589 people allowed to use the program(s) and make any setuid
7590 executables executable only by that group.
7594 If you need to create a new user or group for your package
7595 there are two possibilities. Firstly, you may need to
7596 make some files in the binary package be owned by this
7597 user or group, or you may need to compile the user or
7598 group id (rather than just the name) into the binary
7599 (though this latter should be avoided if possible, as in
7600 this case you need a statically allocated id).</p>
7603 If you need a statically allocated id, you must ask for a
7604 user or group id from the <tt>base-passwd</tt> maintainer,
7605 and must not release the package until you have been
7606 allocated one. Once you have been allocated one you must
7607 either make the package depend on a version of the
7608 <tt>base-passwd</tt> package with the id present in
7609 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7610 your package to create the user or group itself with the
7611 correct id (using <tt>adduser</tt>) in its
7612 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7613 the <prgn>postinst</prgn> is to be preferred if it is
7614 possible, otherwise a pre-dependency will be needed on the
7615 <tt>adduser</tt> package.)
7619 On the other hand, the program might be able to determine
7620 the uid or gid from the user or group name at runtime, so
7621 that a dynamically allocated id can be used. In this case
7622 you should choose an appropriate user or group name,
7623 discussing this on <prgn>debian-devel</prgn> and checking
7624 with the <package/base-passwd/ maintainer that it is unique and that
7625 they do not wish you to use a statically allocated id
7626 instead. When this has been checked you must arrange for
7627 your package to create the user or group if necessary using
7628 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7629 <prgn>postinst</prgn> script (again, the latter is to be
7630 preferred if it is possible).
7634 Note that changing the numeric value of an id associated
7635 with a name is very difficult, and involves searching the
7636 file system for all appropriate files. You need to think
7637 carefully whether a static or dynamic id is required, since
7638 changing your mind later will cause problems.
7641 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7643 This section is not intended as policy, but as a
7644 description of the use of <prgn>dpkg-statoverride</prgn>.
7648 If a system administrator wishes to have a file (or
7649 directory or other such thing) installed with owner and
7650 permissions different from those in the distributed Debian
7651 package, they can use the <prgn>dpkg-statoverride</prgn>
7652 program to instruct <prgn>dpkg</prgn> to use the different
7653 settings every time the file is installed. Thus the
7654 package maintainer should distribute the files with their
7655 normal permissions, and leave it for the system
7656 administrator to make any desired changes. For example, a
7657 daemon which is normally required to be setuid root, but
7658 in certain situations could be used without being setuid,
7659 should be installed setuid in the <tt>.deb</tt>. Then the
7660 local system administrator can change this if they wish.
7661 If there are two standard ways of doing it, the package
7662 maintainer can use <tt>debconf</tt> to find out the
7663 preference, and call <prgn>dpkg-statoverride</prgn> in the
7664 maintainer script if necessary to accommodate the system
7665 administrator's choice. Care must be taken during
7666 upgrades to not override an existing setting.
7670 Given the above, <prgn>dpkg-statoverride</prgn> is
7671 essentially a tool for system administrators and would not
7672 normally be needed in the maintainer scripts. There is
7673 one type of situation, though, where calls to
7674 <prgn>dpkg-statoverride</prgn> would be needed in the
7675 maintainer scripts, and that involves packages which use
7676 dynamically allocated user or group ids. In such a
7677 situation, something like the following idiom can be very
7678 helpful in the package's <prgn>postinst</prgn>, where
7679 <tt>sysuser</tt> is a dynamically allocated id:
7681 for i in /usr/bin/foo /usr/sbin/bar
7683 # only do something when no setting exists
7684 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7686 #include: debconf processing, question about foo and bar
7687 if [ "$RET" = "true" ] ; then
7688 dpkg-statoverride --update --add sysuser root 4755 $i
7693 The corresponding <tt>dpkg-statoverride --remove</tt>
7694 calls can then be made unconditionally when the package is
7702 <chapt id="customized-programs">
7703 <heading>Customized programs</heading>
7705 <sect id="arch-spec">
7706 <heading>Architecture specification strings</heading>
7709 If a program needs to specify an <em>architecture specification
7710 string</em> in some place, it should select one of the
7711 strings provided by <tt>dpkg-architecture -L</tt>. The
7712 strings are in the format
7713 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7714 is sometimes elided, as when the OS is Linux.<footnote>
7715 <p>Currently, the strings are:
7716 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7717 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7718 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7719 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7720 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7721 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7722 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7723 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7724 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7725 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7726 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7727 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7728 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7729 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7730 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7731 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7732 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7733 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7734 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7735 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7736 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7737 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7738 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7739 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7740 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7741 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7742 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7743 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7744 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7745 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7746 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7747 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7748 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7749 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7750 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7751 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7752 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7758 Note that we don't want to use
7759 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7760 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7761 since this would make our programs incompatible with other
7762 Linux distributions. We also don't use something like
7763 <tt><var>arch</var>-unknown-linux</tt>, since the
7764 <tt>unknown</tt> does not look very good.
7769 <heading>Daemons</heading>
7772 The configuration files <file>/etc/services</file>,
7773 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7774 by the <prgn>netbase</prgn> package and must not be modified
7779 If a package requires a new entry in one of these files, the
7780 maintainer should get in contact with the
7781 <prgn>netbase</prgn> maintainer, who will add the entries
7782 and release a new version of the <prgn>netbase</prgn>
7787 The configuration file <file>/etc/inetd.conf</file> must not be
7788 modified by the package's scripts except via the
7789 <prgn>update-inetd</prgn> script or the
7790 <file>DebianNet.pm</file> Perl module. See their documentation
7791 for details on how to add entries.
7795 If a package wants to install an example entry into
7796 <file>/etc/inetd.conf</file>, the entry must be preceded with
7797 exactly one hash character (<tt>#</tt>). Such lines are
7798 treated as "commented out by user" by the
7799 <prgn>update-inetd</prgn> script and are not changed or
7800 activated during package updates.
7805 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7809 Some programs need to create pseudo-ttys. This should be done
7810 using Unix98 ptys if the C library supports it. The resulting
7811 program must not be installed setuid root, unless that
7812 is required for other functionality.
7816 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7817 <file>/var/log/lastlog</file> must be installed writable by
7818 group <tt>utmp</tt>. Programs which need to modify those
7819 files must be installed setgid <tt>utmp</tt>.
7824 <heading>Editors and pagers</heading>
7827 Some programs have the ability to launch an editor or pager
7828 program to edit or display a text document. Since there are
7829 lots of different editors and pagers available in the Debian
7830 distribution, the system administrator and each user should
7831 have the possibility to choose their preferred editor and
7836 In addition, every program should choose a good default
7837 editor/pager if none is selected by the user or system
7842 Thus, every program that launches an editor or pager must
7843 use the EDITOR or PAGER environment variable to determine
7844 the editor or pager the user wishes to use. If these
7845 variables are not set, the programs <file>/usr/bin/editor</file>
7846 and <file>/usr/bin/pager</file> should be used, respectively.
7850 These two files are managed through the <prgn>dpkg</prgn>
7851 "alternatives" mechanism. Thus every package providing an
7852 editor or pager must call the
7853 <prgn>update-alternatives</prgn> script to register these
7858 If it is very hard to adapt a program to make use of the
7859 EDITOR or PAGER variables, that program may be configured to
7860 use <file>/usr/bin/sensible-editor</file> and
7861 <file>/usr/bin/sensible-pager</file> as the editor or pager
7862 program respectively. These are two scripts provided in the
7863 Debian base system that check the EDITOR and PAGER variables
7864 and launch the appropriate program, and fall back to
7865 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7866 variable is not set.
7870 A program may also use the VISUAL environment variable to
7871 determine the user's choice of editor. If it exists, it
7872 should take precedence over EDITOR. This is in fact what
7873 <file>/usr/bin/sensible-editor</file> does.
7877 It is not required for a package to depend on
7878 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7879 package to provide such virtual packages.<footnote>
7880 The Debian base system already provides an editor and a
7886 <sect id="web-appl">
7887 <heading>Web servers and applications</heading>
7890 This section describes the locations and URLs that should
7891 be used by all web servers and web applications in the
7898 Cgi-bin executable files are installed in the
7900 <example compact="compact">
7901 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7903 and should be referred to as
7904 <example compact="compact">
7905 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7911 <p>Access to HTML documents</p>
7914 HTML documents for a package are stored in
7915 <file>/usr/share/doc/<var>package</var></file>
7916 and can be referred to as
7917 <example compact="compact">
7918 http://localhost/doc/<var>package</var>/<var>filename</var>
7923 The web server should restrict access to the document
7924 tree so that only clients on the same host can read
7925 the documents. If the web server does not support such
7926 access controls, then it should not provide access at
7927 all, or ask about providing access during installation.
7932 <p>Access to images</p>
7934 It is recommended that images for a package be stored
7935 in <tt>/usr/share/images/<var>package</var></tt> and
7936 may be referred to through an alias <tt>/images/</tt>
7939 http://localhost/images/<package>/<filename>
7946 <p>Web Document Root</p>
7949 Web Applications should try to avoid storing files in
7950 the Web Document Root. Instead they should use the
7951 /usr/share/doc/<var>package</var> directory for
7952 documents and register the Web Application via the
7953 <package>doc-base</package> package. If access to the
7954 web document root is unavoidable then use
7955 <example compact="compact">
7958 as the Document Root. This might be just a symbolic
7959 link to the location where the system administrator
7960 has put the real document root.
7963 <item><p>Providing httpd and/or httpd-cgi</p>
7965 All web servers should provide the virtual package
7966 <tt>httpd</tt>. If a web server has CGI support it should
7967 provide <tt>httpd-cgi</tt> additionally.
7970 All web applications which do not contain CGI scripts should
7971 depend on <tt>httpd</tt>, all those web applications which
7972 <tt>do</tt> contain CGI scripts, should depend on
7980 <sect id="mail-transport-agents">
7981 <heading>Mail transport, delivery and user agents</heading>
7984 Debian packages which process electronic mail, whether mail
7985 user agents (MUAs) or mail transport agents (MTAs), must
7986 ensure that they are compatible with the configuration
7987 decisions below. Failure to do this may result in lost
7988 mail, broken <tt>From:</tt> lines, and other serious brain
7993 The mail spool is <file>/var/mail</file> and the interface to
7994 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7995 the FHS). On older systems, the mail spool may be
7996 physically located in <file>/var/spool/mail</file>, but all
7997 access to the mail spool should be via the
7998 <file>/var/mail</file> symlink. The mail spool is part of the
7999 base system and not part of the MTA package.
8003 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8004 programs (such as IMAP daemons) must lock the mailbox in an
8005 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8006 be combined with dot locking. To avoid deadlocks, a program
8007 should use <tt>fcntl()</tt> first and dot locking after
8008 this, or alternatively implement the two locking methods in
8009 a non blocking way<footnote>
8010 If it is not possible to establish both locks, the
8011 system shouldn't wait for the second lock to be
8012 established, but remove the first lock, wait a (random)
8013 time, and start over locking again.
8014 </footnote>. Using the functions <tt>maillock</tt> and
8015 <tt>mailunlock</tt> provided by the
8016 <tt>liblockfile*</tt><footnote>
8017 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8018 to use these functions.
8019 </footnote> packages is the recommended way to realize this.
8023 Mailboxes are generally mode 660
8024 <tt><var>user</var>:mail</tt> unless the system
8025 administrator has chosen otherwise. A MUA may remove a
8026 mailbox (unless it has nonstandard permissions) in which
8027 case the MTA or another MUA must recreate it if needed.
8028 Mailboxes must be writable by group mail.
8032 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8033 be setgid mail to do the locking mentioned above (and
8034 must obviously avoid accessing other users' mailboxes
8035 using this privilege).</p>
8038 <file>/etc/aliases</file> is the source file for the system mail
8039 aliases (e.g., postmaster, usenet, etc.), it is the one
8040 which the sysadmin and <prgn>postinst</prgn> scripts may
8041 edit. After <file>/etc/aliases</file> is edited the program or
8042 human editing it must call <prgn>newaliases</prgn>. All MTA
8043 packages must come with a <prgn>newaliases</prgn> program,
8044 even if it does nothing, but older MTA packages did not do
8045 this so programs should not fail if <prgn>newaliases</prgn>
8046 cannot be found. Note that because of this, all MTA
8047 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8048 <tt>Replaces: mail-transport-agent</tt> control file
8053 The convention of writing <tt>forward to
8054 <var>address</var></tt> in the mailbox itself is not
8055 supported. Use a <tt>.forward</tt> file instead.</p>
8058 The <prgn>rmail</prgn> program used by UUCP
8059 for incoming mail should be <file>/usr/sbin/rmail</file>.
8060 Likewise, <prgn>rsmtp</prgn>, for receiving
8061 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8065 If your package needs to know what hostname to use on (for
8066 example) outgoing news and mail messages which are generated
8067 locally, you should use the file <file>/etc/mailname</file>. It
8068 will contain the portion after the username and <tt>@</tt>
8069 (at) sign for email addresses of users on the machine
8070 (followed by a newline).
8074 Such a package should check for the existence of this file
8075 when it is being configured. If it exists, it should be
8076 used without comment, although an MTA's configuration script
8077 may wish to prompt the user even if it finds that this file
8078 exists. If the file does not exist, the package should
8079 prompt the user for the value (preferably using
8080 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8081 as well as using it in the package's configuration. The
8082 prompt should make it clear that the name will not just be
8083 used by that package. For example, in this situation the
8084 <tt>inn</tt> package could say something like:
8085 <example compact="compact">
8086 Please enter the "mail name" of your system. This is the
8087 hostname portion of the address to be shown on outgoing
8088 news and mail messages. The default is
8089 <var>syshostname</var>, your system's host name. Mail
8090 name ["<var>syshostname</var>"]:
8092 where <var>syshostname</var> is the output of <tt>hostname
8098 <heading>News system configuration</heading>
8101 All the configuration files related to the NNTP (news)
8102 servers and clients should be located under
8103 <file>/etc/news</file>.</p>
8106 There are some configuration issues that apply to a number
8107 of news clients and server packages on the machine. These
8111 <tag><file>/etc/news/organization</file></tag>
8113 A string which should appear as the
8114 organization header for all messages posted
8115 by NNTP clients on the machine
8118 <tag><file>/etc/news/server</file></tag>
8120 Contains the FQDN of the upstream NNTP
8121 server, or localhost if the local machine is
8126 Other global files may be added as required for cross-package news
8133 <heading>Programs for the X Window System</heading>
8136 <heading>Providing X support and package priorities</heading>
8139 Programs that can be configured with support for the X
8140 Window System must be configured to do so and must declare
8141 any package dependencies necessary to satisfy their
8142 runtime requirements when using the X Window System. If
8143 such a package is of higher priority than the X packages
8144 on which it depends, it is required that either the
8145 X-specific components be split into a separate package, or
8146 that an alternative version of the package, which includes
8147 X support, be provided, or that the package's priority be
8153 <heading>Packages providing an X server</heading>
8156 Packages that provide an X server that, directly or
8157 indirectly, communicates with real input and display
8158 hardware should declare in their control data that they
8159 provide the virtual package <tt>xserver</tt>.<footnote>
8160 This implements current practice, and provides an
8161 actual policy for usage of the <tt>xserver</tt>
8162 virtual package which appears in the virtual packages
8163 list. In a nutshell, X servers that interface
8164 directly with the display and input hardware or via
8165 another subsystem (e.g., GGI) should provide
8166 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8167 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8173 <heading>Packages providing a terminal emulator</heading>
8176 Packages that provide a terminal emulator for the X Window
8177 System which meet the criteria listed below should declare
8178 in their control data that they provide the virtual
8179 package <tt>x-terminal-emulator</tt>. They should also
8180 register themselves as an alternative for
8181 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8186 To be an <tt>x-terminal-emulator</tt>, a program must:
8187 <list compact="compact">
8189 Be able to emulate a DEC VT100 terminal, or a
8190 compatible terminal.
8194 Support the command-line option <tt>-e
8195 <var>command</var></tt>, which creates a new
8196 terminal window<footnote>
8197 "New terminal window" does not necessarily mean
8198 a new top-level X window directly parented by
8199 the window manager; it could, if the terminal
8200 emulator application were so coded, be a new
8201 "view" in a multiple-document interface (MDI).
8203 and runs the specified <var>command</var>,
8204 interpreting the entirety of the rest of the command
8205 line as a command to pass straight to exec, in the
8206 manner that <tt>xterm</tt> does.
8210 Support the command-line option <tt>-T
8211 <var>title</var></tt>, which creates a new terminal
8212 window with the window title <var>title</var>.
8219 <heading>Packages providing a window manager</heading>
8222 Packages that provide a window manager should declare in
8223 their control data that they provide the virtual package
8224 <tt>x-window-manager</tt>. They should also register
8225 themselves as an alternative for
8226 <file>/usr/bin/x-window-manager</file>, with a priority
8227 calculated as follows:
8228 <list compact="compact">
8230 Start with a priority of 20.
8234 If the window manager supports the Debian menu
8235 system, add 20 points if this support is available
8236 in the package's default configuration (i.e., no
8237 configuration files belonging to the system or user
8238 have to be edited to activate the feature); if
8239 configuration files must be modified, add only 10
8245 If the window manager complies with <url
8246 id="http://www.freedesktop.org/Standards/wm-spec"
8247 name="The Window Manager Specification Project">,
8248 written by the <url id="http://www.freedesktop.org/"
8249 name="Free Desktop Group">, add 40 points.
8253 If the window manager permits the X session to be
8254 restarted using a <em>different</em> window manager
8255 (without killing the X server) in its default
8256 configuration, add 10 points; otherwise add none.
8263 <heading>Packages providing fonts</heading>
8266 Packages that provide fonts for the X Window
8268 For the purposes of Debian Policy, a "font for the X
8269 Window System" is one which is accessed via X protocol
8270 requests. Fonts for the Linux console, for PostScript
8271 renderer, or any other purpose, do not fit this
8272 definition. Any tool which makes such fonts available
8273 to the X Window System, however, must abide by this
8276 must do a number of things to ensure that they are both
8277 available without modification of the X or font server
8278 configuration, and that they do not corrupt files used by
8279 other font packages to register information about
8283 Fonts of any type supported by the X Window System
8284 must be in a separate binary package from any
8285 executables, libraries, or documentation (except
8286 that specific to the fonts shipped, such as their
8287 license information). If one or more of the fonts
8288 so packaged are necessary for proper operation of
8289 the package with which they are associated the font
8290 package may be Recommended; if the fonts merely
8291 provide an enhancement, a Suggests relationship may
8292 be used. Packages must not Depend on font
8294 This is because the X server may retrieve fonts
8295 from the local file system or over the network
8296 from an X font server; the Debian package system
8297 is empowered to deal only with the local
8303 BDF fonts must be converted to PCF fonts with the
8304 <prgn>bdftopcf</prgn> utility (available in the
8305 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8306 placed in a directory that corresponds to their
8308 <list compact="compact">
8310 100 dpi fonts must be placed in
8311 <file>/usr/share/fonts/X11/100dpi/</file>.
8315 75 dpi fonts must be placed in
8316 <file>/usr/share/fonts/X11/75dpi/</file>.
8320 Character-cell fonts, cursor fonts, and other
8321 low-resolution fonts must be placed in
8322 <file>/usr/share/fonts/X11/misc/</file>.
8328 Speedo fonts must be placed in
8329 <file>/usr/share/fonts/X11/Speedo/</file>.
8333 Type 1 fonts must be placed in
8334 <file>/usr/share/fonts/X11/Type1/</file>. If font
8335 metric files are available, they must be placed here
8340 Subdirectories of <file>/usr/share/fonts/X11/</file>
8341 other than those listed above must be neither
8342 created nor used. (The <file>PEX</file>, <file>CID</file>,
8343 and <file>cyrillic</file> directories are excepted for
8344 historical reasons, but installation of files into
8345 these directories remains discouraged.)
8349 Font packages may, instead of placing files directly
8350 in the X font directories listed above, provide
8351 symbolic links in that font directory pointing to
8352 the files' actual location in the filesystem. Such
8353 a location must comply with the FHS.
8357 Font packages should not contain both 75dpi and
8358 100dpi versions of a font. If both are available,
8359 they should be provided in separate binary packages
8360 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8361 the names of the packages containing the
8362 corresponding fonts.
8366 Fonts destined for the <file>misc</file> subdirectory
8367 should not be included in the same package as 75dpi
8368 or 100dpi fonts; instead, they should be provided in
8369 a separate package with <tt>-misc</tt> appended to
8374 Font packages must not provide the files
8375 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8376 <file>fonts.scale</file> in a font directory:
8379 <file>fonts.dir</file> files must not be provided at all.
8383 <file>fonts.alias</file> and <file>fonts.scale</file>
8384 files, if needed, should be provided in the
8386 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8387 where <var>fontdir</var> is the name of the
8389 <file>/usr/share/fonts/X11/</file> where the
8390 package's corresponding fonts are stored
8391 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8392 <var>package</var> is the name of the package
8393 that provides these fonts, and
8394 <var>extension</var> is either <tt>scale</tt>
8395 or <tt>alias</tt>, whichever corresponds to
8402 Font packages must declare a dependency on
8403 <tt>xfonts-utils</tt> in their control
8408 Font packages that provide one or more
8409 <file>fonts.scale</file> files as described above must
8410 invoke <prgn>update-fonts-scale</prgn> on each
8411 directory into which they installed fonts
8412 <em>before</em> invoking
8413 <prgn>update-fonts-dir</prgn> on that directory.
8414 This invocation must occur in both the
8415 <prgn>postinst</prgn> (for all arguments) and
8416 <prgn>postrm</prgn> (for all arguments except
8417 <tt>upgrade</tt>) scripts.
8421 Font packages that provide one or more
8422 <file>fonts.alias</file> files as described above must
8423 invoke <prgn>update-fonts-alias</prgn> on each
8424 directory into which they installed fonts. This
8425 invocation must occur in both the
8426 <prgn>postinst</prgn> (for all arguments) and
8427 <prgn>postrm</prgn> (for all arguments except
8428 <tt>upgrade</tt>) scripts.
8432 Font packages must invoke
8433 <prgn>update-fonts-dir</prgn> on each directory into
8434 which they installed fonts. This invocation must
8435 occur in both the <prgn>postinst</prgn> (for all
8436 arguments) and <prgn>postrm</prgn> (for all
8437 arguments except <tt>upgrade</tt>) scripts.
8441 Font packages must not provide alias names for the
8442 fonts they include which collide with alias names
8443 already in use by fonts already packaged.
8447 Font packages must not provide fonts with the same
8448 XLFD registry name as another font already packaged.
8455 <heading>Application defaults files</heading>
8458 Application defaults files must be installed in the
8459 directory <file>/etc/X11/app-defaults/</file> (use of a
8460 localized subdirectory of <file>/etc/X11/</file> as described
8461 in the <em>X Toolkit Intrinsics - C Language
8462 Interface</em> manual is also permitted). They must be
8463 registered as <tt>conffile</tt>s or handled as
8464 configuration files.
8468 Customization of programs' X resources may also be
8469 supported with the provision of a file with the same name
8470 as that of the package placed in the
8471 <file>/etc/X11/Xresources/</file> directory, which must
8472 registered as a <tt>conffile</tt> or handled as a
8473 configuration file.<footnote>
8474 Note that this mechanism is not the same as using
8475 app-defaults; app-defaults are tied to the client
8476 binary on the local file system, whereas X resources
8477 are stored in the X server and affect all connecting
8484 <heading>Installation directory issues</heading>
8487 Packages using the X Window System should not be
8488 configured to install files under the
8489 <file>/usr/X11R6/</file> directory. The
8490 <file>/usr/X11R6/</file> directory hierarchy should be
8491 regarded as obsolete.
8495 Programs that use GNU <prgn>autoconf</prgn> and
8496 <prgn>automake</prgn> are usually easily configured at
8497 compile time to use <file>/usr/</file> instead of
8498 <file>/usr/X11R6/</file>, and this should be done whenever
8499 possible. Configuration files for window managers and
8500 display managers should be placed in a subdirectory of
8501 <file>/etc/X11/</file> corresponding to the package name due
8502 to these programs' tight integration with the mechanisms
8503 of the X Window System. Application-level programs should
8504 use the <file>/etc/</file> directory unless otherwise mandated
8509 The installation of files into subdirectories
8510 of <file>/usr/X11R6/include/X11/</file> and
8511 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8512 package maintainers should determine if subdirectories of
8513 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8518 Packages should install any relevant files into the
8519 directories <file>/usr/include/X11/</file> and
8520 <file>/usr/lib/X11/</file>, but if they do so, they must
8521 pre-depend on <tt>x11-common (>=
8522 1:7.0.0)</tt><footnote>
8524 These libraries used to be all symbolic
8525 links. However, with <tt>X11R7</tt>,
8526 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8527 are now real directories, and packages
8528 <strong>should</strong> ship their files here instead
8529 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8530 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8531 responsible for converting these symlinks into
8539 <heading>The OSF/Motif and OpenMotif libraries</heading>
8542 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8543 OpenMotif libraries</em><footnote>
8544 OSF/Motif and OpenMotif are collectively referred to as
8545 "Motif" in this policy document.
8547 should be compiled against and tested with LessTif (a free
8548 re-implementation of Motif) instead. If the maintainer
8549 judges that the program or programs do not work
8550 sufficiently well with LessTif to be distributed and
8551 supported, but do so when compiled against Motif, then two
8552 versions of the package should be created; one linked
8553 statically against Motif and with <tt>-smotif</tt>
8554 appended to the package name, and one linked dynamically
8555 against Motif and with <tt>-dmotif</tt> appended to the
8560 Both Motif-linked versions are dependent
8561 upon non-DFSG-compliant software and thus cannot be
8562 uploaded to the <em>main</em> distribution; if the
8563 software is itself DFSG-compliant it may be uploaded to
8564 the <em>contrib</em> distribution. While known existing
8565 versions of Motif permit unlimited redistribution of
8566 binaries linked against the library (whether statically or
8567 dynamically), it is the package maintainer's
8568 responsibility to determine whether this is permitted by
8569 the license of the copy of Motif in their possession.
8575 <heading>Perl programs and modules</heading>
8578 Perl programs and modules should follow the current Perl policy.
8582 The Perl policy can be found in the <tt>perl-policy</tt>
8583 files in the <tt>debian-policy</tt> package.
8584 It is also available from the Debian web mirrors at
8585 <tt><url name="/doc/packaging-manuals/perl-policy/"
8586 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8591 <heading>Emacs lisp programs</heading>
8594 Please refer to the "Debian Emacs Policy" for details of how to
8595 package emacs lisp programs.
8599 The Emacs policy is available in
8600 <file>debian-emacs-policy.gz</file> of the
8601 <package>emacsen-common</package> package.
8602 It is also available from the Debian web mirrors at
8603 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8604 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8609 <heading>Games</heading>
8612 The permissions on <file>/var/games</file> are mode 755, owner
8613 <tt>root</tt> and group <tt>root</tt>.
8617 Each game decides on its own security policy.</p>
8620 Games which require protected, privileged access to
8621 high-score files, saved games, etc., may be made
8622 set-<em>group</em>-id (mode 2755) and owned by
8623 <tt>root:games</tt>, and use files and directories with
8624 appropriate permissions (770 <tt>root:games</tt>, for
8625 example). They must not be made
8626 set-<em>user</em>-id, as this causes security problems. (If
8627 an attacker can subvert any set-user-id game they can
8628 overwrite the executable of any other, causing other players
8629 of these games to run a Trojan horse program. With a
8630 set-group-id game the attacker only gets access to less
8631 important game data, and if they can get at the other
8632 players' accounts at all it will take considerably more
8636 Some packages, for example some fortune cookie programs, are
8637 configured by the upstream authors to install with their
8638 data files or other static information made unreadable so
8639 that they can only be accessed through set-id programs
8640 provided. You should not do this in a Debian package: anyone can
8641 download the <file>.deb</file> file and read the data from it,
8642 so there is no point making the files unreadable. Not
8643 making the files unreadable also means that you don't have
8644 to make so many programs set-id, which reduces the risk of a
8648 As described in the FHS, binaries of games should be
8649 installed in the directory <file>/usr/games</file>. This also
8650 applies to games that use the X Window System. Manual pages
8651 for games (X and non-X games) should be installed in
8652 <file>/usr/share/man/man6</file>.</p>
8658 <heading>Documentation</heading>
8661 <heading>Manual pages</heading>
8664 You should install manual pages in <prgn>nroff</prgn> source
8665 form, in appropriate places under <file>/usr/share/man</file>.
8666 You should only use sections 1 to 9 (see the FHS for more
8667 details). You must not install a pre-formatted "cat page".
8671 Each program, utility, and function should have an
8672 associated manual page included in the same package. It is
8673 suggested that all configuration files also have a manual
8674 page included as well. Manual pages for protocols and other
8675 auxiliary things are optional.
8679 If no manual page is available, this is considered as a bug
8680 and should be reported to the Debian Bug Tracking System (the
8681 maintainer of the package is allowed to write this bug report
8682 themselves, if they so desire). Do not close the bug report
8683 until a proper man page is available.<footnote>
8684 It is not very hard to write a man page. See the
8685 <url id="http://www.schweikhardt.net/man_page_howto.html"
8686 name="Man-Page-HOWTO">,
8687 <manref name="man" section="7">, the examples
8688 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8689 the helper programs <prgn>help2man</prgn>, or the
8690 directory <file>/usr/share/doc/man-db/examples</file>.
8695 You may forward a complaint about a missing man page to the
8696 upstream authors, and mark the bug as forwarded in the
8697 Debian bug tracking system. Even though the GNU Project do
8698 not in general consider the lack of a man page to be a bug,
8699 we do; if they tell you that they don't consider it a bug
8700 you should leave the bug in our bug tracking system open
8705 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8709 If one man page needs to be accessible via several names it
8710 is better to use a symbolic link than the <file>.so</file>
8711 feature, but there is no need to fiddle with the relevant
8712 parts of the upstream source to change from <file>.so</file> to
8713 symlinks: don't do it unless it's easy. You should not
8714 create hard links in the manual page directories, nor put
8715 absolute filenames in <file>.so</file> directives. The filename
8716 in a <file>.so</file> in a man page should be relative to the
8717 base of the man page tree (usually
8718 <file>/usr/share/man</file>). If you do not create any links
8719 (whether symlinks, hard links, or <tt>.so</tt> directives)
8720 in the file system to the alternate names of the man page,
8721 then you should not rely on <prgn>man</prgn> finding your
8722 man page under those names based solely on the information in
8723 the man page's header.<footnote>
8724 Supporting this in <prgn>man</prgn> often requires
8725 unreasonable processing time to find a manual page or to
8726 report that none exists, and moves knowledge into man's
8727 database that would be better left in the file system.
8728 This support is therefore deprecated and will cease to
8729 be present in the future.
8734 Manual pages in locale-specific subdirectories of
8735 <file>/usr/share/man</file> should use either UTF-8 or the usual
8736 legacy encoding for that language (normally the one corresponding
8737 to the shortest relevant locale name in
8738 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8739 <file>/usr/share/man/fr</file> should use either UTF-8 or
8740 ISO-8859-1.<footnote>
8741 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8742 use. In future, all manual pages will be required to use
8748 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8749 included in the subdirectory name unless it indicates a
8750 significant difference in the language, as this excludes
8751 speakers of the language in other countries.<footnote>
8752 At the time of writing, Chinese and Portuguese are the main
8753 languages with such differences, so <file>pt_BR</file>,
8754 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8759 Due to limitations in current implementations, all characters
8760 in the manual page source should be representable in the usual
8761 legacy encoding for that language, even if the file is
8762 actually encoded in UTF-8. Safe alternative ways to write many
8763 characters outside that range may be found in
8764 <manref name="groff_char" section="7">.
8769 <heading>Info documents</heading>
8772 Info documents should be installed in <file>/usr/share/info</file>.
8773 They should be compressed with <tt>gzip -9</tt>.
8777 Your package should call <prgn>install-info</prgn> to update
8778 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8779 script when called with a <tt>configure</tt> argument, for
8781 <example compact="compact">
8782 install-info --quiet --section Development Development \
8783 /usr/share/info/foobar.info
8787 It is a good idea to specify a section for the location of
8788 your program; this is done with the <tt>--section</tt>
8789 switch. To determine which section to use, you should look
8790 at <file>/usr/share/info/dir</file> on your system and choose the most
8791 relevant (or create a new section if none of the current
8792 sections are relevant). Note that the <tt>--section</tt>
8793 flag takes two arguments; the first is a regular expression
8794 to match (case-insensitively) against an existing section,
8795 the second is used when creating a new one.</p>
8798 You should remove the entries in the <prgn>prerm</prgn>
8799 script when called with a <tt>remove</tt> argument:
8800 <example compact="compact">
8801 install-info --quiet --remove /usr/share/info/foobar.info
8805 If <prgn>install-info</prgn> cannot find a description entry
8806 in the Info file you must supply one. See <manref
8807 name="install-info" section="8"> for details.</p>
8811 <heading>Additional documentation</heading>
8814 Any additional documentation that comes with the package may
8815 be installed at the discretion of the package maintainer.
8816 Plain text documentation should be installed in the directory
8817 <file>/usr/share/doc/<var>package</var></file>, where
8818 <var>package</var> is the name of the package, and
8819 compressed with <tt>gzip -9</tt> unless it is small.
8823 If a package comes with large amounts of documentation which
8824 many users of the package will not require you should create
8825 a separate binary package to contain it, so that it does not
8826 take up disk space on the machines of users who do not need
8827 or want it installed.</p>
8830 It is often a good idea to put text information files
8831 (<file>README</file>s, changelogs, and so forth) that come with
8832 the source package in <file>/usr/share/doc/<var>package</var></file>
8833 in the binary package. However, you don't need to install
8834 the instructions for building and installing the package, of
8838 Packages must not require the existence of any files in
8839 <file>/usr/share/doc/</file> in order to function
8841 The system administrator should be able to
8842 delete files in <file>/usr/share/doc/</file> without causing
8843 any programs to break.
8845 Any files that are referenced by programs but are also
8846 useful as stand alone documentation should be installed under
8847 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8848 <file>/usr/share/doc/<var>package</var></file>.
8852 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8853 link to another directory in <file>/usr/share/doc</file> only if
8854 the two packages both come from the same source and the
8855 first package Depends on the second.<footnote>
8857 Please note that this does not override the section on
8858 changelog files below, so the file
8859 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8860 must refer to the changelog for the current version of
8861 <var>package</var> in question. In practice, this means
8862 that the sources of the target and the destination of the
8863 symlink must be the same (same source package and
8870 Former Debian releases placed all additional documentation
8871 in <file>/usr/doc/<var>package</var></file>. This has been
8872 changed to <file>/usr/share/doc/<var>package</var></file>,
8873 and packages must not put documentation in the directory
8874 <file>/usr/doc/<var>package</var></file>. <footnote>
8875 At this phase of the transition, we no longer require a
8876 symbolic link in <file>/usr/doc/</file>. At a later point,
8877 policy shall change to make the symbolic links a bug.
8883 <heading>Preferred documentation formats</heading>
8886 The unification of Debian documentation is being carried out
8890 If your package comes with extensive documentation in a
8891 markup format that can be converted to various other formats
8892 you should if possible ship HTML versions in a binary
8893 package, in the directory
8894 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8895 its subdirectories.<footnote>
8896 The rationale: The important thing here is that HTML
8897 docs should be available in <em>some</em> package, not
8898 necessarily in the main binary package.
8903 Other formats such as PostScript may be provided at the
8904 package maintainer's discretion.
8908 <sect id="copyrightfile">
8909 <heading>Copyright information</heading>
8912 Every package must be accompanied by a verbatim copy of its
8913 copyright and distribution license in the file
8914 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8915 file must neither be compressed nor be a symbolic link.
8919 In addition, the copyright file must say where the upstream
8920 sources (if any) were obtained. It should name the original
8921 authors of the package and the Debian maintainer(s) who were
8922 involved with its creation.
8926 Packages in the <em>contrib</em> or <em>non-free</em> categories
8927 should state in the copyright file that the package is not part
8928 of the Debian GNU/Linux distribution and briefly explain why.
8932 A copy of the file which will be installed in
8933 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8934 be in <file>debian/copyright</file> in the source package.
8938 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8939 link to another directory in <file>/usr/share/doc</file> only if
8940 the two packages both come from the same source and the
8941 first package Depends on the second. These rules are
8942 important because copyrights must be extractable by
8947 Packages distributed under the UCB BSD license, the Apache
8948 license (version 2.0), the Artistic license, the GNU GPL
8949 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8950 the GNU FDL (version 1.2) should refer to the corresponding
8951 files under <file>/usr/share/common-licenses</file>,<footnote>
8954 <file>/usr/share/common-licenses/BSD</file>,
8955 <file>/usr/share/common-licenses/Apache-2.0</file>,
8956 <file>/usr/share/common-licenses/Artistic</file>,
8957 <file>/usr/share/common-licenses/GPL-2</file>,
8958 <file>/usr/share/common-licenses/GPL-3</file>,
8959 <file>/usr/share/common-licenses/LGPL-2</file>,
8960 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8961 <file>/usr/share/common-licenses/LGPL-3</file>, and
8962 <file>/usr/share/common-licenses/GFDL-1.2</file>
8965 </footnote> rather than quoting them in the copyright
8970 You should not use the copyright file as a general <file>README</file>
8971 file. If your package has such a file it should be
8972 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8973 <file>README.Debian</file> or some other appropriate place.</p>
8977 <heading>Examples</heading>
8980 Any examples (configurations, source files, whatever),
8981 should be installed in a directory
8982 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8983 files should not be referenced by any program: they're there
8984 for the benefit of the system administrator and users as
8985 documentation only. Architecture-specific example files
8986 should be installed in a directory
8987 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8989 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8990 latter directory itself may be a symbolic link to the
8995 If the purpose of a package is to provide examples, then the
8996 example files may be installed into
8997 <file>/usr/share/doc/<var>package</var></file>.
9001 <sect id="changelogs">
9002 <heading>Changelog files</heading>
9005 Packages that are not Debian-native must contain a
9006 compressed copy of the <file>debian/changelog</file> file from
9007 the Debian source tree in
9008 <file>/usr/share/doc/<var>package</var></file> with the name
9009 <file>changelog.Debian.gz</file>.
9013 If an upstream changelog is available, it should be accessible as
9014 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9015 plain text. If the upstream changelog is distributed in
9016 HTML, it should be made available in that form as
9017 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9018 and a plain text <file>changelog.gz</file> should be generated
9019 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9020 the upstream changelog files do not already conform to this
9021 naming convention, then this may be achieved either by
9022 renaming the files, or by adding a symbolic link, at the
9023 maintainer's discretion.<footnote>
9024 Rationale: People should not have to look in places for
9025 upstream changelogs merely because they are given
9026 different names or are distributed in HTML format.
9031 All of these files should be installed compressed using
9032 <tt>gzip -9</tt>, as they will become large with time even
9033 if they start out small.
9037 If the package has only one changelog which is used both as
9038 the Debian changelog and the upstream one because there is
9039 no separate upstream maintainer then that changelog should
9040 usually be installed as
9041 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9042 there is a separate upstream maintainer, but no upstream
9043 changelog, then the Debian changelog should still be called
9044 <file>changelog.Debian.gz</file>.
9048 For details about the format and contents of the Debian
9049 changelog file, please see <ref id="dpkgchangelog">.
9054 <appendix id="pkg-scope">
9055 <heading>Introduction and scope of these appendices</heading>
9058 These appendices are taken essentially verbatim from the
9059 now-deprecated Packaging Manual, version 3.2.1.0. They are
9060 the chapters which are likely to be of use to package
9061 maintainers and which have not already been included in the
9062 policy document itself. Most of these sections are very likely
9063 not relevant to policy; they should be treated as
9064 documentation for the packaging system. Please note that these
9065 appendices are included for convenience, and for historical
9066 reasons: they used to be part of policy package, and they have
9067 not yet been incorporated into dpkg documentation. However,
9068 they still have value, and hence they are presented here.
9072 They have not yet been checked to ensure that they are
9073 compatible with the contents of policy, and if there are any
9074 contradictions, the version in the main policy document takes
9075 precedence. The remaining chapters of the old Packaging
9076 Manual have also not been read in detail to ensure that there
9077 are not parts which have been left out. Both of these will be
9082 Certain parts of the Packaging manual were integrated into the
9083 Policy Manual proper, and removed from the appendices. Links
9084 have been placed from the old locations to the new ones.
9088 <prgn>dpkg</prgn> is a suite of programs for creating binary
9089 package files and installing and removing them on Unix
9091 <prgn>dpkg</prgn> is targeted primarily at Debian
9092 GNU/Linux, but may work on or be ported to other
9098 The binary packages are designed for the management of
9099 installed executable programs (usually compiled binaries) and
9100 their associated data, though source code examples and
9101 documentation are provided as part of some packages.</p>
9104 This manual describes the technical aspects of creating Debian
9105 binary packages (<file>.deb</file> files). It documents the
9106 behavior of the package management programs
9107 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9108 they interact with packages.</p>
9111 It also documents the interaction between
9112 <prgn>dselect</prgn>'s core and the access method scripts it
9113 uses to actually install the selected packages, and describes
9114 how to create a new access method.</p>
9117 This manual does not go into detail about the options and
9118 usage of the package building and installation tools. It
9119 should therefore be read in conjunction with those programs'
9124 The utility programs which are provided with <prgn>dpkg</prgn>
9125 for managing various system configuration and similar issues,
9126 such as <prgn>update-rc.d</prgn> and
9127 <prgn>install-info</prgn>, are not described in detail here -
9128 please see their man pages.
9132 It is assumed that the reader is reasonably familiar with the
9133 <prgn>dpkg</prgn> System Administrators' manual.
9134 Unfortunately this manual does not yet exist.
9138 The Debian version of the FSF's GNU hello program is provided
9139 as an example for people wishing to create Debian
9140 packages. The Debian <prgn>debmake</prgn> package is
9141 recommended as a very helpful tool in creating and maintaining
9142 Debian packages. However, while the tools and examples are
9143 helpful, they do not replace the need to read and follow the
9144 Policy and Programmer's Manual.</p>
9147 <appendix id="pkg-binarypkg">
9148 <heading>Binary packages (from old Packaging Manual)</heading>
9151 The binary package has two main sections. The first part
9152 consists of various control information files and scripts used
9153 by <prgn>dpkg</prgn> when installing and removing. See <ref
9154 id="pkg-controlarea">.
9158 The second part is an archive containing the files and
9159 directories to be installed.
9163 In the future binary packages may also contain other
9164 components, such as checksums and digital signatures. The
9165 format for the archive is described in full in the
9166 <file>deb(5)</file> man page.
9170 <sect id="pkg-bincreating"><heading>Creating package files -
9171 <prgn>dpkg-deb</prgn>
9175 All manipulation of binary package files is done by
9176 <prgn>dpkg-deb</prgn>; it's the only program that has
9177 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9178 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9179 will spot that the options requested are appropriate to
9180 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9185 In order to create a binary package you must make a
9186 directory tree which contains all the files and directories
9187 you want to have in the file system data part of the package.
9188 In Debian-format source packages this directory is usually
9189 <file>debian/tmp</file>, relative to the top of the package's
9194 They should have the locations (relative to the root of the
9195 directory tree you're constructing) ownerships and
9196 permissions which you want them to have on the system when
9201 With current versions of <prgn>dpkg</prgn> the uid/username
9202 and gid/groupname mappings for the users and groups being
9203 used should be the same on the system where the package is
9204 built and the one where it is installed.
9208 You need to add one special directory to the root of the
9209 miniature file system tree you're creating:
9210 <prgn>DEBIAN</prgn>. It should contain the control
9211 information files, notably the binary package control file
9212 (see <ref id="pkg-controlfile">).
9216 The <prgn>DEBIAN</prgn> directory will not appear in the
9217 file system archive of the package, and so won't be installed
9218 by <prgn>dpkg</prgn> when the package is installed.
9222 When you've prepared the package, you should invoke:
9224 dpkg --build <var>directory</var>
9229 This will build the package in
9230 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9231 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9232 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9237 See the man page <manref name="dpkg-deb" section="8"> for details of how
9238 to examine the contents of this newly-created file. You may find the
9239 output of following commands enlightening:
9241 dpkg-deb --info <var>filename</var>.deb
9242 dpkg-deb --contents <var>filename</var>.deb
9243 dpkg --contents <var>filename</var>.deb
9245 To view the copyright file for a package you could use this command:
9247 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9252 <sect id="pkg-controlarea">
9253 <heading>Package control information files</heading>
9256 The control information portion of a binary package is a
9257 collection of files with names known to <prgn>dpkg</prgn>.
9258 It will treat the contents of these files specially - some
9259 of them contain information used by <prgn>dpkg</prgn> when
9260 installing or removing the package; others are scripts which
9261 the package maintainer wants <prgn>dpkg</prgn> to run.
9265 It is possible to put other files in the package control
9266 area, but this is not generally a good idea (though they
9267 will largely be ignored).
9271 Here is a brief list of the control info files supported by
9272 <prgn>dpkg</prgn> and a summary of what they're used for.
9277 <tag><tt>control</tt>
9280 This is the key description file used by
9281 <prgn>dpkg</prgn>. It specifies the package's name
9282 and version, gives its description for the user,
9283 states its relationships with other packages, and so
9284 forth. See <ref id="sourcecontrolfiles"> and
9285 <ref id="binarycontrolfiles">.
9289 It is usually generated automatically from information
9290 in the source package by the
9291 <prgn>dpkg-gencontrol</prgn> program, and with
9292 assistance from <prgn>dpkg-shlibdeps</prgn>.
9293 See <ref id="pkg-sourcetools">.
9297 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9302 These are executable files (usually scripts) which
9303 <prgn>dpkg</prgn> runs during installation, upgrade
9304 and removal of packages. They allow the package to
9305 deal with matters which are particular to that package
9306 or require more complicated processing than that
9307 provided by <prgn>dpkg</prgn>. Details of when and
9308 how they are called are in <ref id="maintainerscripts">.
9312 It is very important to make these scripts idempotent.
9313 See <ref id="idempotency">.
9317 The maintainer scripts are guaranteed to run with a
9318 controlling terminal and can interact with the user.
9319 See <ref id="controllingterminal">.
9323 <tag><tt>conffiles</tt>
9326 This file contains a list of configuration files which
9327 are to be handled automatically by <prgn>dpkg</prgn>
9328 (see <ref id="pkg-conffiles">). Note that not necessarily
9329 every configuration file should be listed here.
9332 <tag><tt>shlibs</tt>
9335 This file contains a list of the shared libraries
9336 supplied by the package, with dependency details for
9337 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9338 when it determines what dependencies are required in a
9339 package control file. The <tt>shlibs</tt> file format
9340 is described on <ref id="shlibs">.
9345 <sect id="pkg-controlfile">
9346 <heading>The main control information file: <tt>control</tt></heading>
9349 The most important control information file used by
9350 <prgn>dpkg</prgn> when it installs a package is
9351 <tt>control</tt>. It contains all the package's "vital
9356 The binary package control files of packages built from
9357 Debian sources are made by a special tool,
9358 <prgn>dpkg-gencontrol</prgn>, which reads
9359 <file>debian/control</file> and <file>debian/changelog</file> to
9360 find the information it needs. See <ref id="pkg-sourcepkg"> for
9365 The fields in binary package control files are listed in
9366 <ref id="binarycontrolfiles">.
9370 A description of the syntax of control files and the purpose
9371 of the fields is available in <ref id="controlfields">.
9376 <heading>Time Stamps</heading>
9379 See <ref id="timestamps">.
9384 <appendix id="pkg-sourcepkg">
9385 <heading>Source packages (from old Packaging Manual) </heading>
9388 The Debian binary packages in the distribution are generated
9389 from Debian sources, which are in a special format to assist
9390 the easy and automatic building of binaries.
9393 <sect id="pkg-sourcetools">
9394 <heading>Tools for processing source packages</heading>
9397 Various tools are provided for manipulating source packages;
9398 they pack and unpack sources and help build of binary
9399 packages and help manage the distribution of new versions.
9403 They are introduced and typical uses described here; see
9404 <manref name="dpkg-source" section="1"> for full
9405 documentation about their arguments and operation.
9409 For examples of how to construct a Debian source package,
9410 and how to use those utilities that are used by Debian
9411 source packages, please see the <prgn>hello</prgn> example
9415 <sect1 id="pkg-dpkg-source">
9417 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9422 This program is frequently used by hand, and is also
9423 called from package-independent automated building scripts
9424 such as <prgn>dpkg-buildpackage</prgn>.
9428 To unpack a package it is typically invoked with
9430 dpkg-source -x <var>.../path/to/filename</var>.dsc
9435 with the <file><var>filename</var>.tar.gz</file> and
9436 <file><var>filename</var>.diff.gz</file> (if applicable) in
9437 the same directory. It unpacks into
9438 <file><var>package</var>-<var>version</var></file>, and if
9440 <file><var>package</var>-<var>version</var>.orig</file>, in
9441 the current directory.
9445 To create a packed source archive it is typically invoked:
9447 dpkg-source -b <var>package</var>-<var>version</var>
9452 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9453 <file>.diff.gz</file> (if appropriate) in the current
9454 directory. <prgn>dpkg-source</prgn> does not clean the
9455 source tree first - this must be done separately if it is
9460 See also <ref id="pkg-sourcearchives">.</p>
9464 <sect1 id="pkg-dpkg-buildpackage">
9466 <prgn>dpkg-buildpackage</prgn> - overall package-building
9471 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9472 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9473 targets <tt>clean</tt>, <tt>build</tt> and
9474 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9475 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9476 source and binary package upload.
9480 It is usually invoked by hand from the top level of the
9481 built or unbuilt source directory. It may be invoked with
9482 no arguments; useful arguments include:
9483 <taglist compact="compact">
9484 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9487 Do not sign the <tt>.changes</tt> file or the
9488 source package <tt>.dsc</tt> file, respectively.</p>
9490 <tag><tt>-p<var>sign-command</var></tt></tag>
9493 Invoke <var>sign-command</var> instead of finding
9494 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9495 <var>sign-command</var> must behave just like
9496 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9498 <tag><tt>-r<var>root-command</var></tt></tag>
9501 When root privilege is required, invoke the command
9502 <var>root-command</var>. <var>root-command</var>
9503 should invoke its first argument as a command, from
9504 the <prgn>PATH</prgn> if necessary, and pass its
9505 second and subsequent arguments to the command it
9506 calls. If no <var>root-command</var> is supplied
9507 then <var>dpkg-buildpackage</var> will take no
9508 special action to gain root privilege, so that for
9509 most packages it will have to be invoked as root to
9512 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9515 Two types of binary-only build and upload - see
9516 <manref name="dpkg-source" section="1">.
9523 <sect1 id="pkg-dpkg-gencontrol">
9525 <prgn>dpkg-gencontrol</prgn> - generates binary package
9530 This program is usually called from <file>debian/rules</file>
9531 (see <ref id="pkg-sourcetree">) in the top level of the source
9536 This is usually done just before the files and directories in the
9537 temporary directory tree where the package is being built have their
9538 permissions and ownerships set and the package is constructed using
9539 <prgn>dpkg-deb/</prgn>
9541 This is so that the control file which is produced has
9542 the right permissions
9547 <prgn>dpkg-gencontrol</prgn> must be called after all the
9548 files which are to go into the package have been placed in
9549 the temporary build directory, so that its calculation of
9550 the installed size of a package is correct.
9554 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9555 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9556 variable substitutions created by
9557 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9562 For a package which generates only one binary package, and
9563 which builds it in <file>debian/tmp</file> relative to the top
9564 of the source package, it is usually sufficient to call
9565 <prgn>dpkg-gencontrol</prgn>.
9569 Sources which build several binaries will typically need
9572 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9573 </example> The <tt>-P</tt> tells
9574 <prgn>dpkg-gencontrol</prgn> that the package is being
9575 built in a non-default directory, and the <tt>-p</tt>
9576 tells it which package's control file should be generated.
9580 <prgn>dpkg-gencontrol</prgn> also adds information to the
9581 list of files in <file>debian/files</file>, for the benefit of
9582 (for example) a future invocation of
9583 <prgn>dpkg-genchanges</prgn>.</p>
9586 <sect1 id="pkg-dpkg-shlibdeps">
9588 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9593 This program is usually called from <file>debian/rules</file>
9594 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9595 id="pkg-sourcetree">), in the top level of the source tree.
9599 Its arguments are executables and shared libraries
9602 They may be specified either in the locations in the
9603 source tree where they are created or in the locations
9604 in the temporary build tree where they are installed
9605 prior to binary package creation.
9607 </footnote> for which shared library dependencies should
9608 be included in the binary package's control file.
9612 If some of the found shared libraries should only
9613 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9614 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9615 by using the <tt>-d<var>dependency-field</var></tt> option
9616 before those executable(s). (Each <tt>-d</tt> option
9617 takes effect until the next <tt>-d</tt>.)
9621 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9622 output control file to be modified. Instead by default it
9623 adds to the <file>debian/substvars</file> file variable
9624 settings like <tt>shlibs:Depends</tt>. These variable
9625 settings must be referenced in dependency fields in the
9626 appropriate per-binary-package sections of the source
9631 For example, a package that generates an essential part
9632 which requires dependencies, and optional parts that
9633 which only require a recommendation, would separate those
9634 two sets of dependencies into two different fields.<footnote>
9635 At the time of writing, an example for this was the
9636 <package/xmms/ package, with Depends used for the xmms
9637 executable, Recommends for the plug-ins and Suggests for
9638 even more optional features provided by unzip.
9640 It can say in its <file>debian/rules</file>:
9642 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9643 -dRecommends <var>optionalpart anotheroptionalpart</var>
9645 and then in its main control file <file>debian/control</file>:
9648 Depends: ${shlibs:Depends}
9649 Recommends: ${shlibs:Recommends}
9655 Sources which produce several binary packages with
9656 different shared library dependency requirements can use
9657 the <tt>-p<var>varnameprefix</var></tt> option to override
9658 the default <tt>shlibs:</tt> prefix (one invocation of
9659 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9660 They can thus produce several sets of dependency
9661 variables, each of the form
9662 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9663 which can be referred to in the appropriate parts of the
9664 binary package control files.
9669 <sect1 id="pkg-dpkg-distaddfile">
9671 <prgn>dpkg-distaddfile</prgn> - adds a file to
9672 <file>debian/files</file>
9676 Some packages' uploads need to include files other than
9677 the source and binary package files.
9681 <prgn>dpkg-distaddfile</prgn> adds a file to the
9682 <file>debian/files</file> file so that it will be included in
9683 the <file>.changes</file> file when
9684 <prgn>dpkg-genchanges</prgn> is run.
9688 It is usually invoked from the <tt>binary</tt> target of
9689 <file>debian/rules</file>:
9691 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9693 The <var>filename</var> is relative to the directory where
9694 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9695 is usually the directory above the top level of the source
9696 tree. The <file>debian/rules</file> target should put the
9697 file there just before or just after calling
9698 <prgn>dpkg-distaddfile</prgn>.
9702 The <var>section</var> and <var>priority</var> are passed
9703 unchanged into the resulting <file>.changes</file> file.
9708 <sect1 id="pkg-dpkg-genchanges">
9710 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9715 This program is usually called by package-independent
9716 automatic building scripts such as
9717 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9722 It is usually called in the top level of a built source
9723 tree, and when invoked with no arguments will print out a
9724 straightforward <file>.changes</file> file based on the
9725 information in the source package's changelog and control
9726 file and the binary and source packages which should have
9732 <sect1 id="pkg-dpkg-parsechangelog">
9734 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9735 representation of a changelog
9739 This program is used internally by
9740 <prgn>dpkg-source</prgn> et al. It may also occasionally
9741 be useful in <file>debian/rules</file> and elsewhere. It
9742 parses a changelog, <file>debian/changelog</file> by default,
9743 and prints a control-file format representation of the
9744 information in it to standard output.
9748 <sect1 id="pkg-dpkg-architecture">
9750 <prgn>dpkg-architecture</prgn> - information about the build and
9755 This program can be used manually, but is also invoked by
9756 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9757 environment or make variables which specify the build and host
9758 architecture for the package building process.
9763 <sect id="pkg-sourcetree">
9764 <heading>The Debianised source tree</heading>
9767 The source archive scheme described later is intended to
9768 allow a Debianised source tree with some associated control
9769 information to be reproduced and transported easily. The
9770 Debianised source tree is a version of the original program
9771 with certain files added for the benefit of the
9772 Debianisation process, and with any other changes required
9773 made to the rest of the source code and installation
9778 The extra files created for Debian are in the subdirectory
9779 <file>debian</file> of the top level of the Debianised source
9780 tree. They are described below.
9783 <sect1 id="pkg-debianrules">
9784 <heading><file>debian/rules</file> - the main building script</heading>
9787 See <ref id="debianrules">.
9792 <sect1 id="pkg-dpkgchangelog">
9793 <heading><file>debian/changelog</file></heading>
9796 See <ref id="dpkgchangelog">.
9800 It is recommended that the entire changelog be encoded in the
9801 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9803 <url id="http://www.unicode.org/"
9804 name="Unicode">.<footnote>
9806 I think it is fairly obvious that we need to
9807 eventually transition to UTF-8 for our package
9808 infrastructure; it is really the only sane char-set in
9809 an international environment. Now, we can't switch to
9810 using UTF-8 for package control fields and the like
9811 until dpkg has better support, but one thing we can
9812 start doing today is requesting that Debian changelogs
9813 are UTF-8 encoded. At some point in time, we can start
9814 requiring them to do so.
9817 Checking for non-UTF8 characters in a changelog is
9818 trivial. Dump the file through
9819 <example>iconv -f utf-8 -t ucs-4</example>
9820 discard the output, and check the return
9821 value. If there are any characters in the stream
9822 which are invalid UTF-8 sequences, iconv will exit
9823 with an error code; and this will be the case for the
9824 vast majority of other character sets.
9829 <sect2><heading>Defining alternative changelog formats
9833 It is possible to use a different format to the standard
9834 one, by providing a parser for the format you wish to
9839 In order to have <tt>dpkg-parsechangelog</tt> run your
9840 parser, you must include a line within the last 40 lines
9841 of your file matching the Perl regular expression:
9842 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9843 parentheses should be the name of the format. For
9844 example, you might say:
9846 @@@ changelog-format: joebloggs @@@
9848 Changelog format names are non-empty strings of alphanumerics.
9852 If such a line exists then <tt>dpkg-parsechangelog</tt>
9853 will look for the parser as
9854 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9856 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9857 it is an error for it not to find it, or for it not to
9858 be an executable program. The default changelog format
9859 is <tt>dpkg</tt>, and a parser for it is provided with
9860 the <tt>dpkg</tt> package.
9864 The parser will be invoked with the changelog open on
9865 standard input at the start of the file. It should read
9866 the file (it may seek if it wishes) to determine the
9867 information required and return the parsed information
9868 to standard output in the form of a series of control
9869 fields in the standard format. By default it should
9870 return information about only the most recent version in
9871 the changelog; it should accept a
9872 <tt>-v<var>version</var></tt> option to return changes
9873 information from all versions present <em>strictly
9874 after</em> <var>version</var>, and it should then be an
9875 error for <var>version</var> not to be present in the
9881 <list compact="compact">
9882 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9883 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9884 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9885 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9886 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9887 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9888 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9893 If several versions are being returned (due to the use
9894 of <tt>-v</tt>), the urgency value should be of the
9895 highest urgency code listed at the start of any of the
9896 versions requested followed by the concatenated
9897 (space-separated) comments from all the versions
9898 requested; the maintainer, version, distribution and
9899 date should always be from the most recent version.
9903 For the format of the <tt>Changes</tt> field see
9904 <ref id="f-Changes">.
9908 If the changelog format which is being parsed always or
9909 almost always leaves a blank line between individual
9910 change notes these blank lines should be stripped out,
9911 so as to make the resulting output compact.
9915 If the changelog format does not contain date or package
9916 name information this information should be omitted from
9917 the output. The parser should not attempt to synthesize
9918 it or find it from other sources.
9922 If the changelog does not have the expected format the
9923 parser should exit with a nonzero exit status, rather
9924 than trying to muddle through and possibly generating
9929 A changelog parser may not interact with the user at
9935 <sect1 id="pkg-srcsubstvars">
9936 <heading><file>debian/substvars</file> and variable substitutions</heading>
9939 See <ref id="substvars">.
9945 <heading><file>debian/files</file></heading>
9948 See <ref id="debianfiles">.
9952 <sect1><heading><file>debian/tmp</file>
9956 This is the canonical temporary location for the
9957 construction of binary packages by the <tt>binary</tt>
9958 target. The directory <file>tmp</file> serves as the root of
9959 the file system tree as it is being constructed (for
9960 example, by using the package's upstream makefiles install
9961 targets and redirecting the output there), and it also
9962 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9963 id="pkg-bincreating">.
9967 If several binary packages are generated from the same
9968 source tree it is usual to use several
9969 <file>debian/tmp<var>something</var></file> directories, for
9970 example <file>tmp-a</file> or <file>tmp-doc</file>.
9974 Whatever <file>tmp</file> directories are created and used by
9975 <tt>binary</tt> must of course be removed by the
9976 <tt>clean</tt> target.</p></sect1>
9980 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9984 As it exists on the FTP site, a Debian source package
9985 consists of three related files. You must have the right
9986 versions of all three to be able to use them.
9991 <tag>Debian source control file - <tt>.dsc</tt></tag>
9993 This file is a control file used by <prgn>dpkg-source</prgn>
9994 to extract a source package.
9995 See <ref id="debiansourcecontrolfiles">.
9999 Original source archive -
10001 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10007 This is a compressed (with <tt>gzip -9</tt>)
10008 <prgn>tar</prgn> file containing the source code from
10009 the upstream authors of the program.
10014 Debianisation diff -
10016 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10022 This is a unified context diff (<tt>diff -u</tt>)
10023 giving the changes which are required to turn the
10024 original source into the Debian source. These changes
10025 may only include editing and creating plain files.
10026 The permissions of files, the targets of symbolic
10027 links and the characteristics of special files or
10028 pipes may not be changed and no files may be removed
10033 All the directories in the diff must exist, except the
10034 <file>debian</file> subdirectory of the top of the source
10035 tree, which will be created by
10036 <prgn>dpkg-source</prgn> if necessary when unpacking.
10040 The <prgn>dpkg-source</prgn> program will
10041 automatically make the <file>debian/rules</file> file
10042 executable (see below).</p></item>
10047 If there is no original source code - for example, if the
10048 package is specially prepared for Debian or the Debian
10049 maintainer is the same as the upstream maintainer - the
10050 format is slightly different: then there is no diff, and the
10052 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10053 and preferably contains a directory named
10054 <file><var>package</var>-<var>version</var></file>.
10059 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10062 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10063 Debian source package. However, if it is not available it
10064 is possible to unpack a Debian source archive as follows:
10065 <enumlist compact="compact">
10068 Untar the tarfile, which will create a <file>.orig</file>
10072 <p>Rename the <file>.orig</file> directory to
10073 <file><var>package</var>-<var>version</var></file>.</p>
10077 Create the subdirectory <file>debian</file> at the top of
10078 the source tree.</p>
10080 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10082 <item><p>Untar the tarfile again if you want a copy of the original
10083 source code alongside the Debianised version.</p>
10088 It is not possible to generate a valid Debian source archive
10089 without using <prgn>dpkg-source</prgn>. In particular,
10090 attempting to use <prgn>diff</prgn> directly to generate the
10091 <file>.diff.gz</file> file will not work.
10095 <heading>Restrictions on objects in source packages</heading>
10098 The source package may not contain any hard links
10100 This is not currently detected when building source
10101 packages, but only when extracting
10105 Hard links may be permitted at some point in the
10106 future, but would require a fair amount of
10108 </footnote>, device special files, sockets or setuid or
10111 Setgid directories are allowed.
10116 The source packaging tools manage the changes between the
10117 original and Debianised source using <prgn>diff</prgn> and
10118 <prgn>patch</prgn>. Turning the original source tree as
10119 included in the <file>.orig.tar.gz</file> into the debianised
10120 source must not involve any changes which cannot be
10121 handled by these tools. Problematic changes which cause
10122 <prgn>dpkg-source</prgn> to halt with an error when
10123 building the source package are:
10124 <list compact="compact">
10125 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10127 <item><p>Changing the targets of symbolic links.</p>
10129 <item><p>Creating directories, other than <file>debian</file>.</p>
10131 <item><p>Changes to the contents of binary files.</p></item>
10132 </list> Changes which cause <prgn>dpkg-source</prgn> to
10133 print a warning but continue anyway are:
10134 <list compact="compact">
10137 Removing files, directories or symlinks.
10139 Renaming a file is not treated specially - it is
10140 seen as the removal of the old file (which
10141 generates a warning, but is otherwise ignored),
10142 and the creation of the new one.
10148 Changed text files which are missing the usual final
10149 newline (either in the original or the modified
10154 Changes which are not represented, but which are not detected by
10155 <prgn>dpkg-source</prgn>, are:
10156 <list compact="compact">
10157 <item><p>Changing the permissions of files (other than
10158 <file>debian/rules</file>) and directories.</p></item>
10163 The <file>debian</file> directory and <file>debian/rules</file>
10164 are handled specially by <prgn>dpkg-source</prgn> - before
10165 applying the changes it will create the <file>debian</file>
10166 directory, and afterwards it will make
10167 <file>debian/rules</file> world-executable.
10173 <appendix id="pkg-controlfields">
10174 <heading>Control files and their fields (from old Packaging Manual)</heading>
10177 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10178 data in a common format, known as control files. Binary and
10179 source packages have control data as do the <file>.changes</file>
10180 files which control the installation of uploaded files, and
10181 <prgn>dpkg</prgn>'s internal databases are in a similar
10186 <heading>Syntax of control files</heading>
10189 See <ref id="controlsyntax">.
10193 It is important to note that there are several fields which
10194 are optional as far as <prgn>dpkg</prgn> and the related
10195 tools are concerned, but which must appear in every Debian
10196 package, or whose omission may cause problems.
10201 <heading>List of fields</heading>
10204 See <ref id="controlfieldslist">.
10208 This section now contains only the fields that didn't belong
10209 to the Policy manual.
10212 <sect1 id="pkg-f-Filename">
10213 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10216 These fields in <tt>Packages</tt> files give the
10217 filename(s) of (the parts of) a package in the
10218 distribution directories, relative to the root of the
10219 Debian hierarchy. If the package has been split into
10220 several parts the parts are all listed in order, separated
10225 <sect1 id="pkg-f-Size">
10226 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10229 These fields in <file>Packages</file> files give the size (in
10230 bytes, expressed in decimal) and MD5 checksum of the
10231 file(s) which make(s) up a binary package in the
10232 distribution. If the package is split into several parts
10233 the values for the parts are listed in order, separated by
10238 <sect1 id="pkg-f-Status">
10239 <heading><tt>Status</tt></heading>
10242 This field in <prgn>dpkg</prgn>'s status file records
10243 whether the user wants a package installed, removed or
10244 left alone, whether it is broken (requiring
10245 re-installation) or not and what its current state on the
10246 system is. Each of these pieces of information is a
10251 <sect1 id="pkg-f-Config-Version">
10252 <heading><tt>Config-Version</tt></heading>
10255 If a package is not installed or not configured, this
10256 field in <prgn>dpkg</prgn>'s status file records the last
10257 version of the package which was successfully
10262 <sect1 id="pkg-f-Conffiles">
10263 <heading><tt>Conffiles</tt></heading>
10266 This field in <prgn>dpkg</prgn>'s status file contains
10267 information about the automatically-managed configuration
10268 files held by a package. This field should <em>not</em>
10269 appear anywhere in a package!
10274 <heading>Obsolete fields</heading>
10277 These are still recognized by <prgn>dpkg</prgn> but should
10278 not appear anywhere any more.
10280 <taglist compact="compact">
10282 <tag><tt>Revision</tt></tag>
10283 <tag><tt>Package-Revision</tt></tag>
10284 <tag><tt>Package_Revision</tt></tag>
10286 The Debian revision part of the package version was
10287 at one point in a separate control file field. This
10288 field went through several names.
10291 <tag><tt>Recommended</tt></tag>
10292 <item>Old name for <tt>Recommends</tt>.</item>
10294 <tag><tt>Optional</tt></tag>
10295 <item>Old name for <tt>Suggests</tt>.</item>
10297 <tag><tt>Class</tt></tag>
10298 <item>Old name for <tt>Priority</tt>.</item>
10307 <appendix id="pkg-conffiles">
10308 <heading>Configuration file handling (from old Packaging Manual)</heading>
10311 <prgn>dpkg</prgn> can do a certain amount of automatic
10312 handling of package configuration files.
10316 Whether this mechanism is appropriate depends on a number of
10317 factors, but basically there are two approaches to any
10318 particular configuration file.
10322 The easy method is to ship a best-effort configuration in the
10323 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10324 handle updates. If the user is unlikely to want to edit the
10325 file, but you need them to be able to without losing their
10326 changes, and a new package with a changed version of the file
10327 is only released infrequently, this is a good approach.
10331 The hard method is to build the configuration file from
10332 scratch in the <prgn>postinst</prgn> script, and to take the
10333 responsibility for fixing any mistakes made in earlier
10334 versions of the package automatically. This will be
10335 appropriate if the file is likely to need to be different on
10339 <sect><heading>Automatic handling of configuration files by
10344 A package may contain a control area file called
10345 <tt>conffiles</tt>. This file should be a list of filenames
10346 of configuration files needing automatic handling, separated
10347 by newlines. The filenames should be absolute pathnames,
10348 and the files referred to should actually exist in the
10353 When a package is upgraded <prgn>dpkg</prgn> will process
10354 the configuration files during the configuration stage,
10355 shortly before it runs the package's <prgn>postinst</prgn>
10360 For each file it checks to see whether the version of the
10361 file included in the package is the same as the one that was
10362 included in the last version of the package (the one that is
10363 being upgraded from); it also compares the version currently
10364 installed on the system with the one shipped with the last
10369 If neither the user nor the package maintainer has changed
10370 the file, it is left alone. If one or the other has changed
10371 their version, then the changed version is preferred - i.e.,
10372 if the user edits their file, but the package maintainer
10373 doesn't ship a different version, the user's changes will
10374 stay, silently, but if the maintainer ships a new version
10375 and the user hasn't edited it the new version will be
10376 installed (with an informative message). If both have
10377 changed their version the user is prompted about the problem
10378 and must resolve the differences themselves.
10382 The comparisons are done by calculating the MD5 message
10383 digests of the files, and storing the MD5 of the file as it
10384 was included in the most recent version of the package.
10388 When a package is installed for the first time
10389 <prgn>dpkg</prgn> will install the file that comes with it,
10390 unless that would mean overwriting a file already on the
10395 However, note that <prgn>dpkg</prgn> will <em>not</em>
10396 replace a conffile that was removed by the user (or by a
10397 script). This is necessary because with some programs a
10398 missing file produces an effect hard or impossible to
10399 achieve in another way, so that a missing file needs to be
10400 kept that way if the user did it.
10404 Note that a package should <em>not</em> modify a
10405 <prgn>dpkg</prgn>-handled conffile in its maintainer
10406 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10407 the user confusing and possibly dangerous options for
10408 conffile update when the package is upgraded.</p>
10411 <sect><heading>Fully-featured maintainer script configuration
10416 For files which contain site-specific information such as
10417 the hostname and networking details and so forth, it is
10418 better to create the file in the package's
10419 <prgn>postinst</prgn> script.
10423 This will typically involve examining the state of the rest
10424 of the system to determine values and other information, and
10425 may involve prompting the user for some information which
10426 can't be obtained some other way.
10430 When using this method there are a couple of important
10431 issues which should be considered:
10435 If you discover a bug in the program which generates the
10436 configuration file, or if the format of the file changes
10437 from one version to the next, you will have to arrange for
10438 the postinst script to do something sensible - usually this
10439 will mean editing the installed configuration file to remove
10440 the problem or change the syntax. You will have to do this
10441 very carefully, since the user may have changed the file,
10442 perhaps to fix the very problem that your script is trying
10443 to deal with - you will have to detect these situations and
10444 deal with them correctly.
10448 If you do go down this route it's probably a good idea to
10449 make the program that generates the configuration file(s) a
10450 separate program in <file>/usr/sbin</file>, by convention called
10451 <file><var>package</var>config</file> and then run that if
10452 appropriate from the post-installation script. The
10453 <tt><var>package</var>config</tt> program should not
10454 unquestioningly overwrite an existing configuration - if its
10455 mode of operation is geared towards setting up a package for
10456 the first time (rather than any arbitrary reconfiguration
10457 later) you should have it check whether the configuration
10458 already exists, and require a <tt>--force</tt> flag to
10459 overwrite it.</p></sect>
10462 <appendix id="pkg-alternatives"><heading>Alternative versions of
10463 an interface - <prgn>update-alternatives</prgn> (from old
10468 When several packages all provide different versions of the
10469 same program or file it is useful to have the system select a
10470 default, but to allow the system administrator to change it
10471 and have their decisions respected.
10475 For example, there are several versions of the <prgn>vi</prgn>
10476 editor, and there is no reason to prevent all of them from
10477 being installed at once, each under their own name
10478 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10479 Nevertheless it is desirable to have the name <tt>vi</tt>
10480 refer to something, at least by default.
10484 If all the packages involved cooperate, this can be done with
10485 <prgn>update-alternatives</prgn>.
10489 Each package provides its own version under its own name, and
10490 calls <prgn>update-alternatives</prgn> in its postinst to
10491 register its version (and again in its prerm to deregister
10496 See the man page <manref name="update-alternatives"
10497 section="8"> for details.
10501 If <prgn>update-alternatives</prgn> does not seem appropriate
10502 you may wish to consider using diversions instead.</p>
10505 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10506 package's version of a file (from old Packaging Manual)
10510 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10511 when it reinstalls the package it belongs to, and to have it
10512 put the file from the package somewhere else instead.
10516 This can be used locally to override a package's version of a
10517 file, or by one package to override another's version (or
10518 provide a wrapper for it).
10522 Before deciding to use a diversion, read <ref
10523 id="pkg-alternatives"> to see if you really want a diversion
10524 rather than several alternative versions of a program.
10528 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10529 and updated by a special program <prgn>dpkg-divert</prgn>.
10530 Please see <manref name="dpkg-divert" section="8"> for full
10531 details of its operation.
10535 When a package wishes to divert a file from another, it should
10536 call <prgn>dpkg-divert</prgn> in its preinst to add the
10537 diversion and rename the existing file. For example,
10538 supposing that a <prgn>smailwrapper</prgn> package wishes to
10539 install a wrapper around <file>/usr/sbin/smail</file>:
10541 if [ install = "$1" ]; then
10542 dpkg-divert --package smailwrapper --add --rename \
10543 --divert /usr/sbin/smail.real /usr/sbin/smail
10545 </example> Testing <tt>$1</tt> is necessary so that the script
10546 doesn't try to add the diversion again when
10547 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10548 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10549 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10550 get installed as the true version.
10554 The postrm has to do the reverse:
10556 if [ remove = "$1" ]; then
10557 dpkg-divert --package smailwrapper --remove --rename \
10558 --divert /usr/sbin/smail.real /usr/sbin/smail
10564 Do not attempt to divert a file which is vitally important for
10565 the system's operation - when using <prgn>dpkg-divert</prgn>
10566 there is a time, after it has been diverted but before
10567 <prgn>dpkg</prgn> has installed the new version, when the file
10568 does not exist.</p>
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