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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or categories based on their licenses and other restrictions.
300 The aims of this are:
302 <list compact="compact">
303 <item>to allow us to make as much software available as we can</item>
304 <item>to allow us to encourage everyone to write free software,
306 <item>to allow us to make it easy for people to produce
307 CD-ROMs of our system without violating any licenses,
308 import/export restrictions, or any other laws.</item>
313 The <em>main</em> category forms the
314 <em>Debian GNU/Linux distribution</em>.
318 Packages in the other distribution areas (<tt>contrib</tt>,
319 <tt>non-free</tt>) are not considered to be part of the Debian
320 distribution, although we support their use and provide
321 infrastructure for them (such as our bug-tracking system and
322 mailing lists). This Debian Policy Manual applies to these
327 <heading>The Debian Free Software Guidelines</heading>
329 The Debian Free Software Guidelines (DFSG) form our
330 definition of "free software". These are:
332 <tag>Free Redistribution
335 The license of a Debian component may not restrict any
336 party from selling or giving away the software as a
337 component of an aggregate software distribution
338 containing programs from several different
339 sources. The license may not require a royalty or
340 other fee for such sale.
345 The program must include source code, and must allow
346 distribution in source code as well as compiled form.
351 The license must allow modifications and derived
352 works, and must allow them to be distributed under the
353 same terms as the license of the original software.
355 <tag>Integrity of The Author's Source Code
358 The license may restrict source-code from being
359 distributed in modified form <em>only</em> if the
360 license allows the distribution of "patch files"
361 with the source code for the purpose of modifying the
362 program at build time. The license must explicitly
363 permit distribution of software built from modified
364 source code. The license may require derived works to
365 carry a different name or version number from the
366 original software. (This is a compromise. The Debian
367 Project encourages all authors to not restrict any
368 files, source or binary, from being modified.)
370 <tag>No Discrimination Against Persons or Groups
373 The license must not discriminate against any person
376 <tag>No Discrimination Against Fields of Endeavor
379 The license must not restrict anyone from making use
380 of the program in a specific field of endeavor. For
381 example, it may not restrict the program from being
382 used in a business, or from being used for genetic
385 <tag>Distribution of License
388 The rights attached to the program must apply to all
389 to whom the program is redistributed without the need
390 for execution of an additional license by those
393 <tag>License Must Not Be Specific to Debian
396 The rights attached to the program must not depend on
397 the program's being part of a Debian system. If the
398 program is extracted from Debian and used or
399 distributed without Debian but otherwise within the
400 terms of the program's license, all parties to whom
401 the program is redistributed must have the same
402 rights as those that are granted in conjunction with
405 <tag>License Must Not Contaminate Other Software
408 The license must not place restrictions on other
409 software that is distributed along with the licensed
410 software. For example, the license must not insist
411 that all other programs distributed on the same medium
412 must be free software.
414 <tag>Example Licenses
417 The "GPL," "BSD," and "Artistic" licenses are examples of
418 licenses that we consider <em>free</em>.
425 <heading>Categories</heading>
428 <heading>The main category</heading>
431 Every package in <em>main</em> must comply with the DFSG
432 (Debian Free Software Guidelines).
436 In addition, the packages in <em>main</em>
437 <list compact="compact">
439 must not require a package outside of <em>main</em>
440 for compilation or execution (thus, the package must
441 not declare a "Depends", "Recommends", or
442 "Build-Depends" relationship on a non-<em>main</em>
446 must not be so buggy that we refuse to support them,
450 must meet all policy requirements presented in this
459 <heading>The contrib category</heading>
462 Every package in <em>contrib</em> must comply with the DFSG.
466 In addition, the packages in <em>contrib</em>
467 <list compact="compact">
469 must not be so buggy that we refuse to support them,
473 must meet all policy requirements presented in this
481 Examples of packages which would be included in
482 <em>contrib</em> are:
483 <list compact="compact">
485 free packages which require <em>contrib</em>,
486 <em>non-free</em> packages or packages which are not
487 in our archive at all for compilation or execution,
491 wrapper packages or other sorts of free accessories for
498 <sect1 id="non-free">
499 <heading>The non-free category</heading>
502 Packages must be placed in <em>non-free</em> if they are
503 not compliant with the DFSG or are encumbered by patents
504 or other legal issues that make their distribution
509 In addition, the packages in <em>non-free</em>
510 <list compact="compact">
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
517 manual that it is possible for them to meet.
519 It is possible that there are policy
520 requirements which the package is unable to
521 meet, for example, if the source is
522 unavailable. These situations will need to be
523 handled on a case-by-case basis.
532 <sect id="pkgcopyright">
533 <heading>Copyright considerations</heading>
536 Every package must be accompanied by a verbatim copy of
537 its copyright and distribution license in the file
538 <file>/usr/share/doc/<var>package</var>/copyright</file>
539 (see <ref id="copyrightfile"> for further details).
543 We reserve the right to restrict files from being included
544 anywhere in our archives if
545 <list compact="compact">
547 their use or distribution would break a law,
550 there is an ethical conflict in their distribution or
554 we would have to sign a license for them, or
557 their distribution would conflict with other project
564 Programs whose authors encourage the user to make
565 donations are fine for the main distribution, provided
566 that the authors do not claim that not donating is
567 immoral, unethical, illegal or something similar; in such
568 a case they must go in <em>non-free</em>.
572 Packages whose copyright permission notices (or patent
573 problems) do not even allow redistribution of binaries
574 only, and where no special permission has been obtained,
575 must not be placed on the Debian FTP site and its mirrors
580 Note that under international copyright law (this applies
581 in the United States, too), <em>no</em> distribution or
582 modification of a work is allowed without an explicit
583 notice saying so. Therefore a program without a copyright
584 notice <em>is</em> copyrighted and you may not do anything
585 to it without risking being sued! Likewise if a program
586 has a copyright notice but no statement saying what is
587 permitted then nothing is permitted.
591 Many authors are unaware of the problems that restrictive
592 copyrights (or lack of copyright notices) can cause for
593 the users of their supposedly-free software. It is often
594 worthwhile contacting such authors diplomatically to ask
595 them to modify their license terms. However, this can be a
596 politically difficult thing to do and you should ask for
597 advice on the <tt>debian-legal</tt> mailing list first, as
602 When in doubt about a copyright, send mail to
603 <email>debian-legal@lists.debian.org</email>. Be prepared
604 to provide us with the copyright statement. Software
605 covered by the GPL, public domain software and BSD-like
606 copyrights are safe; be wary of the phrases "commercial
607 use prohibited" and "distribution restricted".
611 <sect id="subsections">
612 <heading>Sections</heading>
615 The packages in the categories <em>main</em>,
616 <em>contrib</em> and <em>non-free</em> are grouped further
617 into <em>sections</em> to simplify handling.
621 The category and section for each package should be
622 specified in the package's <tt>Section</tt> control record
623 (see <ref id="f-Section">). However, the maintainer of the
624 Debian archive may override this selection to ensure the
625 consistency of the Debian distribution. The
626 <tt>Section</tt> field should be of the form:
627 <list compact="compact">
629 <em>section</em> if the package is in the
630 <em>main</em> category,
633 <em>segment/section</em> if the package is in
634 the <em>contrib</em> or <em>non-free</em>
641 The Debian archive maintainers provide the authoritative
642 list of sections. At present, they are:
643 <em>admin</em>, <em>comm</em>,
644 <em>devel</em>, <em>doc</em>,
645 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
646 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
647 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
648 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
649 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Only very few packages are allowed to form
1082 part of the base system, in order to keep the required disk
1087 The base system consists of all those packages with priority
1088 <tt>required</tt> or <tt>important</tt>. Many of them will
1089 be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1480 The format of the <file>debian/changelog</file> allows the
1481 package building tools to discover which version of the package
1482 is being built and find out other release-specific information.
1486 That format is a series of entries like this:
1488 <example compact="compact">
1489 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1491 [optional blank line(s), stripped]
1493 * <var>change details</var>
1494 <var>more change details</var>
1496 [blank line(s), included in output of dpkg-parsechangelog]
1498 * <var>even more change details</var>
1500 [optional blank line(s), stripped]
1502 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1507 <var>package</var> and <var>version</var> are the source
1508 package name and version number.
1512 <var>distribution(s)</var> lists the distributions where
1513 this version should be installed when it is uploaded - it
1514 is copied to the <tt>Distribution</tt> field in the
1515 <file>.changes</file> file. See <ref id="f-Distribution">.
1519 <var>urgency</var> is the value for the <tt>Urgency</tt>
1520 field in the <file>.changes</file> file for the upload
1521 (see <ref id="f-Urgency">). It is not possible to specify
1522 an urgency containing commas; commas are used to separate
1523 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1524 <prgn>dpkg</prgn> changelog format (though there is
1525 currently only one useful <var>keyword</var>,
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>), or in
1551 the case of an NMU, marked as fixed.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1930 <tag><tt>patch</tt> (optional)</tag>
1933 This target performs whatever additional actions are
1934 required to make the source ready for editing (unpacking
1935 additional upstream archives, applying patches, etc.).
1936 It is recommended to be implemented for any package where
1937 <tt>dpkg-source -x</tt> does not result in source ready
1938 for additional modification. See
1939 <ref id="readmesource">.
1945 The <tt>build</tt>, <tt>binary</tt> and
1946 <tt>clean</tt> targets must be invoked with the current
1947 directory being the package's top-level directory.
1952 Additional targets may exist in <file>debian/rules</file>,
1953 either as published or undocumented interfaces or for the
1954 package's internal use.
1958 The architectures we build on and build for are determined
1959 by <prgn>make</prgn> variables using the utility
1960 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1961 You can determine the
1962 Debian architecture and the GNU style architecture
1963 specification string for the build machine (the machine type
1964 we are building on) as well as for the host machine (the
1965 machine type we are building for). Here is a list of
1966 supported <prgn>make</prgn> variables:
1967 <list compact="compact">
1969 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1972 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1973 specification string)
1976 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1977 <tt>DEB_*_GNU_TYPE</tt>)
1980 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1981 <tt>DEB_*_GNU_TYPE</tt>)
1983 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1984 the build machine or <tt>HOST</tt> for specification of the
1989 Backward compatibility can be provided in the rules file
1990 by setting the needed variables to suitable default
1991 values; please refer to the documentation of
1992 <prgn>dpkg-architecture</prgn> for details.
1996 It is important to understand that the <tt>DEB_*_ARCH</tt>
1997 string only determines which Debian architecture we are
1998 building on or for. It should not be used to get the CPU
1999 or system information; the GNU style variables should be
2003 <sect1 id="debianrules-options">
2004 <heading><file>debian/rules</file> and
2005 <tt>DEB_BUILD_OPTIONS</tt></heading>
2008 Supporting the standardized environment variable
2009 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2010 contain several flags to change how a package is compiled and
2011 built. Each flag must be in the form <var>flag</var> or
2012 <var>flag</var>=<var>options</var>. If multiple flags are
2013 given, they must be separated by whitespace.<footnote>
2014 Some packages support any delimiter, but whitespace is the
2015 easiest to parse inside a makefile and avoids ambiguity with
2016 flag values that contain commas.
2018 <var>flag</var> must start with a lowercase letter
2019 (<tt>a-z</tt>) and consist only of lowercase letters,
2020 numbers (<tt>0-9</tt>), and the characters
2021 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2022 <var>options</var> must not contain whitespace. The same
2023 tag should not be given multiple times with conflicting
2024 values. Package maintainers may assume that
2025 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2029 The meaning of the following tags has been standardized:
2033 The presence of this tag means that the package should
2034 be compiled with a minimum of optimization. For C
2035 programs, it is best to add <tt>-O0</tt> to
2036 <tt>CFLAGS</tt> (although this is usually the default).
2037 Some programs might fail to build or run at this level
2038 of optimization; it may be necessary to use
2039 <tt>-O1</tt>, for example.
2043 This tag means that the debugging symbols should not be
2044 stripped from the binary during installation, so that
2045 debugging information may be included in the package.
2047 <tag>parallel=n</tag>
2049 This tag means that the package should be built using up
2050 to <tt>n</tt> parallel processes if the package build
2051 system supports this.<footnote>
2052 Packages built with <tt>make</tt> can often implement
2053 this by passing the <tt>-j</tt><var>n</var> option to
2056 If the package build system does not support parallel
2057 builds, this string must be ignored. If the package
2058 build system only supports a lower level of concurrency
2059 than <var>n</var>, the package should be built using as
2060 many parallel processes as the package build system
2061 supports. It is up to the package maintainer to decide
2062 whether the package build times are long enough and the
2063 package build system is robust enough to make supporting
2064 parallel builds worthwhile.
2070 Unknown flags must be ignored by <file>debian/rules</file>.
2074 The following makefile snippet is an example of how one may
2075 implement the build options; you will probably have to
2076 massage this example in order to make it work for your
2078 <example compact="compact">
2081 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2082 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2083 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2084 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2086 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2091 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2092 INSTALL_PROGRAM += -s
2094 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2095 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2096 MAKEFLAGS += -j$(NUMJOBS)
2103 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2104 <sect id="substvars">
2105 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2108 When <prgn>dpkg-gencontrol</prgn>,
2109 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2110 generate control files they perform variable substitutions
2111 on their output just before writing it. Variable
2112 substitutions have the form <tt>${<var>variable</var>}</tt>.
2113 The optional file <file>debian/substvars</file> contains
2114 variable substitutions to be used; variables can also be set
2115 directly from <file>debian/rules</file> using the <tt>-V</tt>
2116 option to the source packaging commands, and certain
2117 predefined variables are also available.
2121 The <file>debian/substvars</file> file is usually generated and
2122 modified dynamically by <file>debian/rules</file> targets, in
2123 which case it must be removed by the <tt>clean</tt> target.
2127 See <manref name="deb-substvars" section="5"> for full
2128 details about source variable substitutions, including the
2129 format of <file>debian/substvars</file>.</p>
2132 <sect id="debianwatch">
2133 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2136 This is an optional, recommended control file for the
2137 <tt>uscan</tt> utility which defines how to automatically
2138 scan ftp or http sites for newly available updates of the
2139 package. This is used by <url id="
2140 http://dehs.alioth.debian.org/"> and other Debian QA tools
2141 to help with quality control and maintenance of the
2142 distribution as a whole.
2147 <sect id="debianfiles">
2148 <heading>Generated files list: <file>debian/files</file></heading>
2151 This file is not a permanent part of the source tree; it
2152 is used while building packages to record which files are
2153 being generated. <prgn>dpkg-genchanges</prgn> uses it
2154 when it generates a <file>.changes</file> file.
2158 It should not exist in a shipped source package, and so it
2159 (and any backup files or temporary files such as
2160 <file>files.new</file><footnote>
2161 <file>files.new</file> is used as a temporary file by
2162 <prgn>dpkg-gencontrol</prgn> and
2163 <prgn>dpkg-distaddfile</prgn> - they write a new
2164 version of <tt>files</tt> here before renaming it,
2165 to avoid leaving a corrupted copy if an error
2167 </footnote>) should be removed by the
2168 <tt>clean</tt> target. It may also be wise to
2169 ensure a fresh start by emptying or removing it at the
2170 start of the <tt>binary</tt> target.
2174 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2175 package, it adds an entry to <file>debian/files</file> for the
2176 <file>.deb</file> file that will be created when <tt>dpkg-deb
2177 --build</tt> is run for that binary package. So for most
2178 packages all that needs to be done with this file is to
2179 delete it in the <tt>clean</tt> target.
2183 If a package upload includes files besides the source
2184 package and any binary packages whose control files were
2185 made with <prgn>dpkg-gencontrol</prgn> then they should be
2186 placed in the parent of the package's top-level directory
2187 and <prgn>dpkg-distaddfile</prgn> should be called to add
2188 the file to the list in <file>debian/files</file>.</p>
2191 <sect id="embeddedfiles">
2192 <heading>Convenience copies of code</heading>
2195 Some software packages include in their distribution convenience
2196 copies of code from other software packages, generally so that
2197 users compiling from source don't have to download multiple
2198 packages. Debian packages should not make use of these
2199 convenience copies unless the included package is explicitly
2200 intended to be used in this way.<footnote>
2201 For example, parts of the GNU build system work like this.
2203 If the included code is already in the Debian archive in the
2204 form of a library, the Debian packaging should ensure that
2205 binary packages reference the libraries already in Debian and
2206 the convenience copy is not used. If the included code is not
2207 already in Debian, it should be packaged separately as a
2208 prerequisite if possible.
2210 Having multiple copies of the same code in Debian is
2211 inefficient, often creates either static linking or shared
2212 library conflicts, and, most importantly, increases the
2213 difficulty of handling security vulnerabilities in the
2219 <sect id="readmesource">
2220 <heading>Source package handling:
2221 <file>debian/README.source</file></heading>
2224 If running <prgn>dpkg-source -x</prgn> on a source package
2225 doesn't produce the source of the package, ready for editing,
2226 and allow one to make changes and run
2227 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2228 without taking any additional steps, creating a
2229 <file>debian/README.source</file> documentation file is
2230 recommended. This file should explain how to do all of the
2233 <item>Generate the fully patched source, in a form ready for
2234 editing, that would be built to create Debian
2235 packages. Doing this with a <tt>patch</tt> target in
2236 <file>debian/rules</file> is recommended; see
2237 <ref id="debianrules">.</item>
2238 <item>Modify the source and save those modifications so that
2239 they will be applied when building the package.</item>
2240 <item>Remove source modifications that are currently being
2241 applied when building the package.</item>
2242 <item>Optionally, document what steps are necessary to
2243 upgrade the Debian source package to a new upstream version,
2244 if applicable.</item>
2246 This explanation should include specific commands and mention
2247 any additional required Debian packages. It should not assume
2248 familiarity with any specific Debian packaging system or patch
2253 This explanation may refer to a documentation file installed by
2254 one of the package's build dependencies provided that the
2255 referenced documentation clearly explains these tasks and is not
2256 a general reference manual.
2260 <file>debian/README.source</file> may also include any other
2261 information that would be helpful to someone modifying the
2262 source package. Even if the package doesn't fit the above
2263 description, maintainers are encouraged to document in a
2264 <file>debian/README.source</file> file any source package with a
2265 particularly complex or unintuitive source layout or build
2266 system (for example, a package that builds the same source
2267 multiple times to generate different binary packages).
2273 <chapt id="controlfields">
2274 <heading>Control files and their fields</heading>
2277 The package management system manipulates data represented in
2278 a common format, known as <em>control data</em>, stored in
2279 <em>control files</em>.
2280 Control files are used for source packages, binary packages and
2281 the <file>.changes</file> files which control the installation
2282 of uploaded files<footnote>
2283 <prgn>dpkg</prgn>'s internal databases are in a similar
2288 <sect id="controlsyntax">
2289 <heading>Syntax of control files</heading>
2292 A control file consists of one or more paragraphs of
2294 The paragraphs are also sometimes referred to as stanzas.
2296 The paragraphs are separated by blank lines. Some control
2297 files allow only one paragraph; others allow several, in
2298 which case each paragraph usually refers to a different
2299 package. (For example, in source packages, the first
2300 paragraph refers to the source package, and later paragraphs
2301 refer to binary packages generated from the source.)
2305 Each paragraph consists of a series of data fields; each
2306 field consists of the field name, followed by a colon and
2307 then the data/value associated with that field. It ends at
2308 the end of the (logical) line. Horizontal whitespace
2309 (spaces and tabs) may occur immediately before or after the
2310 value and is ignored there; it is conventional to put a
2311 single space after the colon. For example, a field might
2313 <example compact="compact">
2316 the field name is <tt>Package</tt> and the field value
2321 Many fields' values may span several lines; in this case
2322 each continuation line must start with a space or a tab.
2323 Any trailing spaces or tabs at the end of individual
2324 lines of a field value are ignored.
2328 In fields where it is specified that lines may not wrap,
2329 only a single line of data is allowed and whitespace is not
2330 significant in a field body. Whitespace must not appear
2331 inside names (of packages, architectures, files or anything
2332 else) or version numbers, or between the characters of
2333 multi-character version relationships.
2337 Field names are not case-sensitive, but it is usual to
2338 capitalize the field names using mixed case as shown below.
2342 Blank lines, or lines consisting only of spaces and tabs,
2343 are not allowed within field values or between fields - that
2344 would mean a new paragraph.
2349 <sect id="sourcecontrolfiles">
2350 <heading>Source package control files -- <file>debian/control</file></heading>
2353 The <file>debian/control</file> file contains the most vital
2354 (and version-independent) information about the source package
2355 and about the binary packages it creates.
2359 The first paragraph of the control file contains information about
2360 the source package in general. The subsequent sets each describe a
2361 binary package that the source tree builds.
2365 The fields in the general paragraph (the first one, for the source
2368 <list compact="compact">
2369 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2370 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2371 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2372 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2373 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2374 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2375 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2376 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2381 The fields in the binary package paragraphs are:
2383 <list compact="compact">
2384 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2385 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2386 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2387 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2388 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2389 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2390 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2391 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2396 The syntax and semantics of the fields are described below.
2402 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2403 generate control files for binary packages (see below), by
2404 <prgn>dpkg-genchanges</prgn> to generate the
2405 <tt>.changes</tt> file to accompany the upload, and by
2406 <prgn>dpkg-source</prgn> when it creates the
2407 <file>.dsc</file> source control file as part of a source
2408 archive. Many fields are permitted to span multiple lines in
2409 <file>debian/control</file> but not in any other control
2410 file. These tools are responsible for removing the line
2411 breaks from such fields when using fields from
2412 <file>debian/control</file> to generate other control files.
2416 The fields here may contain variable references - their
2417 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2418 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2419 when they generate output control files.
2420 See <ref id="substvars"> for details.
2425 <sect id="binarycontrolfiles">
2426 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2429 The <file>DEBIAN/control</file> file contains the most vital
2430 (and version-dependent) information about a binary package.
2434 The fields in this file are:
2436 <list compact="compact">
2437 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2438 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2439 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2440 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2441 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2442 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2443 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2444 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2445 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2446 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2447 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2448 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2453 <sect id="debiansourcecontrolfiles">
2454 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2457 This file contains a series of fields, identified and
2458 separated just like the fields in the control file of
2459 a binary package. The fields are listed below; their
2460 syntax is described above, in <ref id="pkg-controlfields">.
2462 <list compact="compact">
2463 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2464 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2465 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2466 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2467 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2468 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2469 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2470 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2471 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2472 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2478 The source package control file is generated by
2479 <prgn>dpkg-source</prgn> when it builds the source
2480 archive, from other files in the source package,
2481 described above. When unpacking, it is checked against
2482 the files and directories in the other parts of the
2488 <sect id="debianchangesfiles">
2489 <heading>Debian changes files -- <file>.changes</file></heading>
2492 The .changes files are used by the Debian archive maintenance
2493 software to process updates to packages. They contain one
2494 paragraph which contains information from the
2495 <tt>debian/control</tt> file and other data about the
2496 source package gathered via <tt>debian/changelog</tt>
2497 and <tt>debian/rules</tt>.
2501 The fields in this file are:
2503 <list compact="compact">
2504 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2506 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2507 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2510 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2512 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2513 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2514 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2516 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2522 <sect id="controlfieldslist">
2523 <heading>List of fields</heading>
2525 <sect1 id="f-Source">
2526 <heading><tt>Source</tt></heading>
2529 This field identifies the source package name.
2533 In <file>debian/control</file> or a <file>.dsc</file> file,
2534 this field must contain only the name of the source package.
2538 In a binary package control file or a <file>.changes</file>
2539 file, the source package name may be followed by a version
2540 number in parentheses<footnote>
2541 It is customary to leave a space after the package name
2542 if a version number is specified.
2544 This version number may be omitted (and is, by
2545 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2546 the <tt>Version</tt> field of the binary package in
2547 question. The field itself may be omitted from a binary
2548 package control file when the source package has the same
2549 name and version as the binary package.
2553 <sect1 id="f-Maintainer">
2554 <heading><tt>Maintainer</tt></heading>
2557 The package maintainer's name and email address. The name
2558 should come first, then the email address inside angle
2559 brackets <tt><></tt> (in RFC822 format).
2563 If the maintainer's name contains a full stop then the
2564 whole field will not work directly as an email address due
2565 to a misfeature in the syntax specified in RFC822; a
2566 program using this field as an address must check for this
2567 and correct the problem if necessary (for example by
2568 putting the name in round brackets and moving it to the
2569 end, and bringing the email address forward).
2573 <sect1 id="f-Uploaders">
2574 <heading><tt>Uploaders</tt></heading>
2577 List of the names and email addresses of co-maintainers of
2578 the package, if any. If the package has other maintainers
2579 beside the one named in the
2580 <qref id="f-Maintainer">Maintainer field</qref>, their
2581 names and email addresses should be listed here. The
2582 format is the same as that of the Maintainer tag, and
2583 multiple entries should be comma separated. Currently,
2584 this field is restricted to a single line of data. This
2585 is an optional field.
2588 Any parser that interprets the Uploaders field in
2589 <file>debian/control</file> must permit it to span multiple
2590 lines. Line breaks in an Uploaders field that spans multiple
2591 lines are not significant and the semantics of the field are
2592 the same as if the line breaks had not been present.
2596 <sect1 id="f-Changed-By">
2597 <heading><tt>Changed-By</tt></heading>
2600 The name and email address of the person who changed the
2601 said package. Usually the name of the maintainer.
2602 All the rules for the Maintainer field apply here, too.
2606 <sect1 id="f-Section">
2607 <heading><tt>Section</tt></heading>
2610 This field specifies an application area into which the package
2611 has been classified. See <ref id="subsections">.
2615 When it appears in the <file>debian/control</file> file,
2616 it gives the value for the subfield of the same name in
2617 the <tt>Files</tt> field of the <file>.changes</file> file.
2618 It also gives the default for the same field in the binary
2623 <sect1 id="f-Priority">
2624 <heading><tt>Priority</tt></heading>
2627 This field represents how important that it is that the user
2628 have the package installed. See <ref id="priorities">.
2632 When it appears in the <file>debian/control</file> file,
2633 it gives the value for the subfield of the same name in
2634 the <tt>Files</tt> field of the <file>.changes</file> file.
2635 It also gives the default for the same field in the binary
2640 <sect1 id="f-Package">
2641 <heading><tt>Package</tt></heading>
2644 The name of the binary package.
2648 Package names must consist only of lower case letters
2649 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2650 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2651 They must be at least two characters long and must start
2652 with an alphanumeric character.
2656 <sect1 id="f-Architecture">
2657 <heading><tt>Architecture</tt></heading>
2660 Depending on context and the control file used, the
2661 <tt>Architecture</tt> field can include the following sets of
2664 <item>A unique single word identifying a Debian machine
2665 architecture, see <ref id="arch-spec">.
2666 <item><tt>all</tt>, which indicates an
2667 architecture-independent package.
2668 <item><tt>any</tt>, which indicates a package available
2669 for building on any architecture.
2670 <item><tt>source</tt>, which indicates a source package.
2675 In the main <file>debian/control</file> file in the source
2676 package, or in the source package control file
2677 <file>.dsc</file>, one may specify a list of architectures
2678 separated by spaces, or the special values <tt>any</tt> or
2683 Specifying <tt>any</tt> indicates that the source package
2684 isn't dependent on any particular architecture and should
2685 compile fine on any one. The produced binary package(s)
2686 will be specific to whatever the current build architecture
2688 This is the most often used setting, and is recommended
2689 for new packages that aren't <tt>Architecture: all</tt>.
2694 Specifying a list of architectures indicates that the source
2695 will build an architecture-dependent package, and will only
2696 work correctly on the listed architectures.<footnote>
2697 This is a setting used for a minority of cases where the
2698 program is not portable. Generally, it should not be used
2704 In a <file>.changes</file> file, the <tt>Architecture</tt>
2705 field lists the architecture(s) of the package(s)
2706 currently being uploaded. This will be a list; if the
2707 source for the package is also being uploaded, the special
2708 entry <tt>source</tt> is also present.
2712 See <ref id="debianrules"> for information how to get the
2713 architecture for the build process.
2717 <sect1 id="f-Essential">
2718 <heading><tt>Essential</tt></heading>
2721 This is a boolean field which may occur only in the
2722 control file of a binary package or in a per-package fields
2723 paragraph of a main source control data file.
2727 If set to <tt>yes</tt> then the package management system
2728 will refuse to remove the package (upgrading and replacing
2729 it is still possible). The other possible value is <tt>no</tt>,
2730 which is the same as not having the field at all.
2735 <heading>Package interrelationship fields:
2736 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2737 <tt>Recommends</tt>, <tt>Suggests</tt>,
2738 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2739 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2743 These fields describe the package's relationships with
2744 other packages. Their syntax and semantics are described
2745 in <ref id="relationships">.</p>
2748 <sect1 id="f-Standards-Version">
2749 <heading><tt>Standards-Version</tt></heading>
2752 The most recent version of the standards (the policy
2753 manual and associated texts) with which the package
2758 The version number has four components: major and minor
2759 version number and major and minor patch level. When the
2760 standards change in a way that requires every package to
2761 change the major number will be changed. Significant
2762 changes that will require work in many packages will be
2763 signaled by a change to the minor number. The major patch
2764 level will be changed for any change to the meaning of the
2765 standards, however small; the minor patch level will be
2766 changed when only cosmetic, typographical or other edits
2767 are made which neither change the meaning of the document
2768 nor affect the contents of packages.
2772 Thus only the first three components of the policy version
2773 are significant in the <em>Standards-Version</em> control
2774 field, and so either these three components or the all
2775 four components may be specified.<footnote>
2776 In the past, people specified the full version number
2777 in the Standards-Version field, for example "2.3.0.0".
2778 Since minor patch-level changes don't introduce new
2779 policy, it was thought it would be better to relax
2780 policy and only require the first 3 components to be
2781 specified, in this example "2.3.0". All four
2782 components may still be used if someone wishes to do so.
2788 <sect1 id="f-Version">
2789 <heading><tt>Version</tt></heading>
2792 The version number of a package. The format is:
2793 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2797 The three components here are:
2799 <tag><var>epoch</var></tag>
2802 This is a single (generally small) unsigned integer. It
2803 may be omitted, in which case zero is assumed. If it is
2804 omitted then the <var>upstream_version</var> may not
2809 It is provided to allow mistakes in the version numbers
2810 of older versions of a package, and also a package's
2811 previous version numbering schemes, to be left behind.
2815 <tag><var>upstream_version</var></tag>
2818 This is the main part of the version number. It is
2819 usually the version number of the original ("upstream")
2820 package from which the <file>.deb</file> file has been made,
2821 if this is applicable. Usually this will be in the same
2822 format as that specified by the upstream author(s);
2823 however, it may need to be reformatted to fit into the
2824 package management system's format and comparison
2829 The comparison behavior of the package management system
2830 with respect to the <var>upstream_version</var> is
2831 described below. The <var>upstream_version</var>
2832 portion of the version number is mandatory.
2836 The <var>upstream_version</var> may contain only
2837 alphanumerics<footnote>
2838 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2840 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2841 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2842 tilde) and should start with a digit. If there is no
2843 <var>debian_revision</var> then hyphens are not allowed;
2844 if there is no <var>epoch</var> then colons are not
2849 <tag><var>debian_revision</var></tag>
2852 This part of the version number specifies the version of
2853 the Debian package based on the upstream version. It
2854 may contain only alphanumerics and the characters
2855 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2856 tilde) and is compared in the same way as the
2857 <var>upstream_version</var> is.
2861 It is optional; if it isn't present then the
2862 <var>upstream_version</var> may not contain a hyphen.
2863 This format represents the case where a piece of
2864 software was written specifically to be turned into a
2865 Debian package, and so there is only one "debianisation"
2866 of it and therefore no revision indication is required.
2870 It is conventional to restart the
2871 <var>debian_revision</var> at <tt>1</tt> each time the
2872 <var>upstream_version</var> is increased.
2876 The package management system will break the version
2877 number apart at the last hyphen in the string (if there
2878 is one) to determine the <var>upstream_version</var> and
2879 <var>debian_revision</var>. The absence of a
2880 <var>debian_revision</var> compares earlier than the
2881 presence of one (but note that the
2882 <var>debian_revision</var> is the least significant part
2883 of the version number).
2890 The <var>upstream_version</var> and <var>debian_revision</var>
2891 parts are compared by the package management system using the
2896 The strings are compared from left to right.
2900 First the initial part of each string consisting entirely of
2901 non-digit characters is determined. These two parts (one of
2902 which may be empty) are compared lexically. If a difference
2903 is found it is returned. The lexical comparison is a
2904 comparison of ASCII values modified so that all the letters
2905 sort earlier than all the non-letters and so that a tilde
2906 sorts before anything, even the end of a part. For example,
2907 the following parts are in sorted order from earliest to
2908 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2909 <tt>a</tt>.<footnote>
2910 One common use of <tt>~</tt> is for upstream pre-releases.
2911 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2912 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2917 Then the initial part of the remainder of each string which
2918 consists entirely of digit characters is determined. The
2919 numerical values of these two parts are compared, and any
2920 difference found is returned as the result of the comparison.
2921 For these purposes an empty string (which can only occur at
2922 the end of one or both version strings being compared) counts
2927 These two steps (comparing and removing initial non-digit
2928 strings and initial digit strings) are repeated until a
2929 difference is found or both strings are exhausted.
2933 Note that the purpose of epochs is to allow us to leave behind
2934 mistakes in version numbering, and to cope with situations
2935 where the version numbering scheme changes. It is
2936 <em>not</em> intended to cope with version numbers containing
2937 strings of letters which the package management system cannot
2938 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2939 silly orderings (the author of this manual has heard of a
2940 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2941 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2942 <tt>2</tt> and so forth).
2946 <sect1 id="f-Description">
2947 <heading><tt>Description</tt></heading>
2950 In a source or binary control file, the <tt>Description</tt>
2951 field contains a description of the binary package, consisting
2952 of two parts, the synopsis or the short description, and the
2953 long description. The field's format is as follows:
2958 Description: <single line synopsis>
2959 <extended description over several lines>
2964 The lines in the extended description can have these formats:
2970 Those starting with a single space are part of a paragraph.
2971 Successive lines of this form will be word-wrapped when
2972 displayed. The leading space will usually be stripped off.
2976 Those starting with two or more spaces. These will be
2977 displayed verbatim. If the display cannot be panned
2978 horizontally, the displaying program will line wrap them "hard"
2979 (i.e., without taking account of word breaks). If it can they
2980 will be allowed to trail off to the right. None, one or two
2981 initial spaces may be deleted, but the number of spaces
2982 deleted from each line will be the same (so that you can have
2983 indenting work correctly, for example).
2987 Those containing a single space followed by a single full stop
2988 character. These are rendered as blank lines. This is the
2989 <em>only</em> way to get a blank line<footnote>
2990 Completely empty lines will not be rendered as blank lines.
2991 Instead, they will cause the parser to think you're starting
2992 a whole new record in the control file, and will therefore
2993 likely abort with an error.
2998 Those containing a space, a full stop and some more characters.
2999 These are for future expansion. Do not use them.
3005 Do not use tab characters. Their effect is not predictable.
3009 See <ref id="descriptions"> for further information on this.
3013 In a <file>.changes</file> file, the <tt>Description</tt> field
3014 contains a summary of the descriptions for the packages being
3019 The part of the field before the first newline is empty;
3020 thereafter each line has the name of a binary package and
3021 the summary description line from that binary package.
3022 Each line is indented by one space.
3027 <sect1 id="f-Distribution">
3028 <heading><tt>Distribution</tt></heading>
3031 In a <file>.changes</file> file or parsed changelog output
3032 this contains the (space-separated) name(s) of the
3033 distribution(s) where this version of the package should
3034 be installed. Valid distributions are determined by the
3035 archive maintainers.<footnote>
3036 Current distribution names are:
3037 <taglist compact="compact">
3038 <tag><em>stable</em></tag>
3040 This is the current "released" version of Debian
3041 GNU/Linux. Once the distribution is
3042 <em>stable</em> only security fixes and other
3043 major bug fixes are allowed. When changes are
3044 made to this distribution, the release number is
3045 increased (for example: 2.2r1 becomes 2.2r2 then
3049 <tag><em>unstable</em></tag>
3051 This distribution value refers to the
3052 <em>developmental</em> part of the Debian
3053 distribution tree. New packages, new upstream
3054 versions of packages and bug fixes go into the
3055 <em>unstable</em> directory tree. Download from
3056 this distribution at your own risk.
3059 <tag><em>testing</em></tag>
3061 This distribution value refers to the
3062 <em>testing</em> part of the Debian distribution
3063 tree. It receives its packages from the
3064 unstable distribution after a short time lag to
3065 ensure that there are no major issues with the
3066 unstable packages. It is less prone to breakage
3067 than unstable, but still risky. It is not
3068 possible to upload packages directly to
3072 <tag><em>frozen</em></tag>
3074 From time to time, the <em>testing</em>
3075 distribution enters a state of "code-freeze" in
3076 anticipation of release as a <em>stable</em>
3077 version. During this period of testing only
3078 fixes for existing or newly-discovered bugs will
3079 be allowed. The exact details of this stage are
3080 determined by the Release Manager.
3083 <tag><em>experimental</em></tag>
3085 The packages with this distribution value are
3086 deemed by their maintainers to be high
3087 risk. Oftentimes they represent early beta or
3088 developmental packages from various sources that
3089 the maintainers want people to try, but are not
3090 ready to be a part of the other parts of the
3091 Debian distribution tree. Download at your own
3097 You should list <em>all</em> distributions that the
3098 package should be installed into.
3102 More information is available in the Debian Developer's
3103 Reference, section "The Debian archive".
3110 <heading><tt>Date</tt></heading>
3113 This field includes the date the package was built or last edited.
3117 The value of this field is usually extracted from the
3118 <file>debian/changelog</file> file - see
3119 <ref id="dpkgchangelog">).
3123 <sect1 id="f-Format">
3124 <heading><tt>Format</tt></heading>
3127 This field specifies a format revision for the file.
3128 The most current format described in the Policy Manual
3129 is version <strong>1.5</strong>. The syntax of the
3130 format value is the same as that of a package version
3131 number except that no epoch or Debian revision is allowed
3132 - see <ref id="f-Version">.
3136 <sect1 id="f-Urgency">
3137 <heading><tt>Urgency</tt></heading>
3140 This is a description of how important it is to upgrade to
3141 this version from previous ones. It consists of a single
3142 keyword taking one of the values <tt>low</tt>,
3143 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3144 <tt>critical</tt><footnote>
3145 Other urgency values are supported with configuration
3146 changes in the archive software but are not used in Debian.
3147 The urgency affects how quickly a package will be considered
3148 for inclusion into the <tt>testing</tt> distribution and
3149 gives an indication of the importance of any fixes included
3150 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3151 treated as synonymous.
3152 </footnote> (not case-sensitive) followed by an optional
3153 commentary (separated by a space) which is usually in
3154 parentheses. For example:
3157 Urgency: low (HIGH for users of diversions)
3163 The value of this field is usually extracted from the
3164 <file>debian/changelog</file> file - see
3165 <ref id="dpkgchangelog">.
3169 <sect1 id="f-Changes">
3170 <heading><tt>Changes</tt></heading>
3173 This field contains the human-readable changes data, describing
3174 the differences between the last version and the current one.
3178 There should be nothing in this field before the first
3179 newline; all the subsequent lines must be indented by at
3180 least one space; blank lines must be represented by a line
3181 consisting only of a space and a full stop.
3185 The value of this field is usually extracted from the
3186 <file>debian/changelog</file> file - see
3187 <ref id="dpkgchangelog">).
3191 Each version's change information should be preceded by a
3192 "title" line giving at least the version, distribution(s)
3193 and urgency, in a human-readable way.
3197 If data from several versions is being returned the entry
3198 for the most recent version should be returned first, and
3199 entries should be separated by the representation of a
3200 blank line (the "title" line may also be followed by the
3201 representation of blank line).
3205 <sect1 id="f-Binary">
3206 <heading><tt>Binary</tt></heading>
3209 This field is a list of binary packages.
3213 When it appears in the <file>.dsc</file> file it is the list
3214 of binary packages which a source package can produce. It
3215 does not necessarily produce all of these binary packages
3216 for every architecture. The source control file doesn't
3217 contain details of which architectures are appropriate for
3218 which of the binary packages.
3222 When it appears in a <file>.changes</file> file it lists the
3223 names of the binary packages actually being uploaded.
3227 The syntax is a list of binary packages separated by
3229 A space after each comma is conventional.
3230 </footnote>. Currently the packages must be separated using
3231 only spaces in the <file>.changes</file> file.
3235 <sect1 id="f-Installed-Size">
3236 <heading><tt>Installed-Size</tt></heading>
3239 This field appears in the control files of binary
3240 packages, and in the <file>Packages</file> files. It gives
3241 the total amount of disk space required to install the
3246 The disk space is represented in kilobytes as a simple
3251 <sect1 id="f-Files">
3252 <heading><tt>Files</tt></heading>
3255 This field contains a list of files with information about
3256 each one. The exact information and syntax varies with
3257 the context. In all cases the part of the field
3258 contents on the same line as the field name is empty. The
3259 remainder of the field is one line per file, each line
3260 being indented by one space and containing a number of
3261 sub-fields separated by spaces.
3265 In the <file>.dsc</file> file, each line contains the MD5
3266 checksum, size and filename of the tar file and (if applicable)
3267 diff file which make up the remainder of the source
3269 That is, the parts which are not the <tt>.dsc</tt>.
3271 The exact forms of the filenames are described
3272 in <ref id="pkg-sourcearchives">.
3276 In the <file>.changes</file> file this contains one line per
3277 file being uploaded. Each line contains the MD5 checksum,
3278 size, section and priority and the filename.
3279 The <qref id="f-Section">section</qref>
3280 and <qref id="f-Priority">priority</qref>
3281 are the values of the corresponding fields in
3282 the main source control file. If no section or priority is
3283 specified then <tt>-</tt> should be used, though section
3284 and priority values must be specified for new packages to
3285 be installed properly.
3289 The special value <tt>byhand</tt> for the section in a
3290 <tt>.changes</tt> file indicates that the file in question
3291 is not an ordinary package file and must by installed by
3292 hand by the distribution maintainers. If the section is
3293 <tt>byhand</tt> the priority should be <tt>-</tt>.
3297 If a new Debian revision of a package is being shipped and
3298 no new original source archive is being distributed the
3299 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3300 entry for the original source archive
3301 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3302 but the <file>.changes</file> file should leave it out. In
3303 this case the original source archive on the distribution
3304 site must match exactly, byte-for-byte, the original
3305 source archive which was used to generate the
3306 <file>.dsc</file> file and diff which are being uploaded.</p>
3309 <sect1 id="f-Closes">
3310 <heading><tt>Closes</tt></heading>
3313 A space-separated list of bug report numbers that the upload
3314 governed by the .changes file closes.
3318 <sect1 id="f-Homepage">
3319 <heading><tt>Homepage</tt></heading>
3322 The URL of the web site for this package, preferably (when
3323 applicable) the site from which the original source can be
3324 obtained and any additional upstream documentation or
3325 information may be found. The content of this field is a
3326 simple URL without any surrounding characters such as
3334 <heading>User-defined fields</heading>
3337 Additional user-defined fields may be added to the
3338 source package control file. Such fields will be
3339 ignored, and not copied to (for example) binary or
3340 source package control files or upload control files.
3344 If you wish to add additional unsupported fields to
3345 these output files you should use the mechanism
3350 Fields in the main source control information file with
3351 names starting <tt>X</tt>, followed by one or more of
3352 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3353 be copied to the output files. Only the part of the
3354 field name after the hyphen will be used in the output
3355 file. Where the letter <tt>B</tt> is used the field
3356 will appear in binary package control files, where the
3357 letter <tt>S</tt> is used in source package control
3358 files and where <tt>C</tt> is used in upload control
3359 (<tt>.changes</tt>) files.
3363 For example, if the main source information control file
3366 XBS-Comment: I stand between the candle and the star.
3368 then the binary and source package control files will contain the
3371 Comment: I stand between the candle and the star.
3380 <chapt id="maintainerscripts">
3381 <heading>Package maintainer scripts and installation procedure</heading>
3384 <heading>Introduction to package maintainer scripts</heading>
3387 It is possible to supply scripts as part of a package which
3388 the package management system will run for you when your
3389 package is installed, upgraded or removed.
3393 These scripts are the files <prgn>preinst</prgn>,
3394 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3395 <prgn>postrm</prgn> in the control area of the package.
3396 They must be proper executable files; if they are scripts
3397 (which is recommended), they must start with the usual
3398 <tt>#!</tt> convention. They should be readable and
3399 executable by anyone, and must not be world-writable.
3403 The package management system looks at the exit status from
3404 these scripts. It is important that they exit with a
3405 non-zero status if there is an error, so that the package
3406 management system can stop its processing. For shell
3407 scripts this means that you <em>almost always</em> need to
3408 use <tt>set -e</tt> (this is usually true when writing shell
3409 scripts, in fact). It is also important, of course, that
3410 they don't exit with a non-zero status if everything went
3415 Additionally, packages interacting with users using
3416 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3417 install a <prgn>config</prgn> script in the control area,
3418 see <ref id="maintscriptprompt"> for details.
3422 When a package is upgraded a combination of the scripts from
3423 the old and new packages is called during the upgrade
3424 procedure. If your scripts are going to be at all
3425 complicated you need to be aware of this, and may need to
3426 check the arguments to your scripts.
3430 Broadly speaking the <prgn>preinst</prgn> is called before
3431 (a particular version of) a package is installed, and the
3432 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3433 before (a version of) a package is removed and the
3434 <prgn>postrm</prgn> afterwards.
3438 Programs called from maintainer scripts should not normally
3439 have a path prepended to them. Before installation is
3440 started, the package management system checks to see if the
3441 programs <prgn>ldconfig</prgn>,
3442 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3443 and <prgn>update-rc.d</prgn> can be found via the
3444 <tt>PATH</tt> environment variable. Those programs, and any
3445 other program that one would expect to be in the
3446 <tt>PATH</tt>, should thus be invoked without an absolute
3447 pathname. Maintainer scripts should also not reset the
3448 <tt>PATH</tt>, though they might choose to modify it by
3449 prepending or appending package-specific directories. These
3450 considerations really apply to all shell scripts.</p>
3453 <sect id="idempotency">
3454 <heading>Maintainer scripts idempotency</heading>
3457 It is necessary for the error recovery procedures that the
3458 scripts be idempotent. This means that if it is run
3459 successfully, and then it is called again, it doesn't bomb
3460 out or cause any harm, but just ensures that everything is
3461 the way it ought to be. If the first call failed, or
3462 aborted half way through for some reason, the second call
3463 should merely do the things that were left undone the first
3464 time, if any, and exit with a success status if everything
3466 This is so that if an error occurs, the user interrupts
3467 <prgn>dpkg</prgn> or some other unforeseen circumstance
3468 happens you don't leave the user with a badly-broken
3469 package when <prgn>dpkg</prgn> attempts to repeat the
3475 <sect id="controllingterminal">
3476 <heading>Controlling terminal for maintainer scripts</heading>
3479 The maintainer scripts are guaranteed to run with a
3480 controlling terminal and can interact with the user.
3481 Because these scripts may be executed with standard output
3482 redirected into a pipe for logging purposes, Perl scripts
3483 should set unbuffered output by setting <tt>$|=1</tt> so
3484 that the output is printed immediately rather than being
3488 <sect id="exitstatus">
3489 <heading>Exit status</heading>
3492 Each script must return a zero exit status for
3493 success, or a nonzero one for failure, since the package
3494 management system looks for the exit status of these scripts
3495 and determines what action to take next based on that datum.
3499 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3504 <list compact="compact">
3506 <var>new-preinst</var> <tt>install</tt>
3509 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3512 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3515 <var>old-preinst</var> <tt>abort-upgrade</tt>
3516 <var>new-version</var>
3521 <list compact="compact">
3523 <var>postinst</var> <tt>configure</tt>
3524 <var>most-recently-configured-version</var>
3527 <var>old-postinst</var> <tt>abort-upgrade</tt>
3528 <var>new-version</var>
3531 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3532 <tt>in-favour</tt> <var>package</var>
3533 <var>new-version</var>
3536 <var>postinst</var> <tt>abort-remove</tt>
3539 <var>deconfigured's-postinst</var>
3540 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3541 <var>failed-install-package</var> <var>version</var>
3542 [<tt>removing</tt> <var>conflicting-package</var>
3548 <list compact="compact">
3550 <var>prerm</var> <tt>remove</tt>
3553 <var>old-prerm</var> <tt>upgrade</tt>
3554 <var>new-version</var>
3557 <var>new-prerm</var> <tt>failed-upgrade</tt>
3558 <var>old-version</var>
3561 <var>conflictor's-prerm</var> <tt>remove</tt>
3562 <tt>in-favour</tt> <var>package</var>
3563 <var>new-version</var>
3566 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3567 <tt>in-favour</tt> <var>package-being-installed</var>
3568 <var>version</var> [<tt>removing</tt>
3569 <var>conflicting-package</var>
3575 <list compact="compact">
3577 <var>postrm</var> <tt>remove</tt>
3580 <var>postrm</var> <tt>purge</tt>
3583 <var>old-postrm</var> <tt>upgrade</tt>
3584 <var>new-version</var>
3587 <var>new-postrm</var> <tt>failed-upgrade</tt>
3588 <var>old-version</var>
3591 <var>new-postrm</var> <tt>abort-install</tt>
3594 <var>new-postrm</var> <tt>abort-install</tt>
3595 <var>old-version</var>
3598 <var>new-postrm</var> <tt>abort-upgrade</tt>
3599 <var>old-version</var>
3602 <var>disappearer's-postrm</var> <tt>disappear</tt>
3603 <var>overwriter</var>
3604 <var>overwriter-version</var>
3610 <sect id="unpackphase">
3611 <heading>Details of unpack phase of installation or upgrade</heading>
3614 The procedure on installation/upgrade/overwrite/disappear
3615 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3616 stage of <tt>dpkg --install</tt>) is as follows. In each
3617 case, if a major error occurs (unless listed below) the
3618 actions are, in general, run backwards - this means that the
3619 maintainer scripts are run with different arguments in
3620 reverse order. These are the "error unwind" calls listed
3627 If a version of the package is already installed, call
3628 <example compact="compact">
3629 <var>old-prerm</var> upgrade <var>new-version</var>
3633 If the script runs but exits with a non-zero
3634 exit status, <prgn>dpkg</prgn> will attempt:
3635 <example compact="compact">
3636 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3638 If this works, the upgrade continues. If this
3639 does not work, the error unwind:
3640 <example compact="compact">
3641 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3643 If this works, then the old-version is
3644 "Installed", if not, the old version is in a
3645 "Failed-Config" state.
3651 If a "conflicting" package is being removed at the same time,
3652 or if any package will be broken (due to <tt>Breaks</tt>):
3655 If <tt>--auto-deconfigure</tt> is
3656 specified, call, for each package to be deconfigured
3657 due to <tt>Breaks</tt>:
3658 <example compact="compact">
3659 <var>deconfigured's-prerm</var> deconfigure \
3660 in-favour <var>package-being-installed</var> <var>version</var>
3663 <example compact="compact">
3664 <var>deconfigured's-postinst</var> abort-deconfigure \
3665 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3667 The deconfigured packages are marked as
3668 requiring configuration, so that if
3669 <tt>--install</tt> is used they will be
3670 configured again if possible.
3673 If any packages depended on a conflicting
3674 package being removed and <tt>--auto-deconfigure</tt> is
3675 specified, call, for each such package:
3676 <example compact="compact">
3677 <var>deconfigured's-prerm</var> deconfigure \
3678 in-favour <var>package-being-installed</var> <var>version</var> \
3679 removing <var>conflicting-package</var> <var>version</var>
3682 <example compact="compact">
3683 <var>deconfigured's-postinst</var> abort-deconfigure \
3684 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3685 removing <var>conflicting-package</var> <var>version</var>
3687 The deconfigured packages are marked as
3688 requiring configuration, so that if
3689 <tt>--install</tt> is used they will be
3690 configured again if possible.
3693 To prepare for removal of each conflicting package, call:
3694 <example compact="compact">
3695 <var>conflictor's-prerm</var> remove \
3696 in-favour <var>package</var> <var>new-version</var>
3699 <example compact="compact">
3700 <var>conflictor's-postinst</var> abort-remove \
3701 in-favour <var>package</var> <var>new-version</var>
3710 If the package is being upgraded, call:
3711 <example compact="compact">
3712 <var>new-preinst</var> upgrade <var>old-version</var>
3714 If this fails, we call:
3716 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3723 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3725 is called. If this works, then the old version
3726 is in an "Installed" state, or else it is left
3727 in an "Unpacked" state.
3732 If it fails, then the old version is left
3733 in an "Half-Installed" state.
3740 Otherwise, if the package had some configuration
3741 files from a previous version installed (i.e., it
3742 is in the "configuration files only" state):
3743 <example compact="compact">
3744 <var>new-preinst</var> install <var>old-version</var>
3748 <var>new-postrm</var> abort-install <var>old-version</var>
3750 If this fails, the package is left in a
3751 "Half-Installed" state, which requires a
3752 reinstall. If it works, the packages is left in
3753 a "Config Files" state.
3756 Otherwise (i.e., the package was completely purged):
3757 <example compact="compact">
3758 <var>new-preinst</var> install
3761 <example compact="compact">
3762 <var>new-postrm</var> abort-install
3764 If the error-unwind fails, the package is in a
3765 "Half Installed" phase, and requires a
3766 reinstall. If the error unwind works, the
3767 package is in a not installed state.
3774 The new package's files are unpacked, overwriting any
3775 that may be on the system already, for example any
3776 from the old version of the same package or from
3777 another package. Backups of the old files are kept
3778 temporarily, and if anything goes wrong the package
3779 management system will attempt to put them back as
3780 part of the error unwind.
3784 It is an error for a package to contain files which
3785 are on the system in another package, unless
3786 <tt>Replaces</tt> is used (see <ref id="replaces">).
3788 The following paragraph is not currently the case:
3789 Currently the <tt>- - force-overwrite</tt> flag is
3790 enabled, downgrading it to a warning, but this may not
3796 It is a more serious error for a package to contain a
3797 plain file or other kind of non-directory where another
3798 package has a directory (again, unless
3799 <tt>Replaces</tt> is used). This error can be
3800 overridden if desired using
3801 <tt>--force-overwrite-dir</tt>, but this is not
3806 Packages which overwrite each other's files produce
3807 behavior which, though deterministic, is hard for the
3808 system administrator to understand. It can easily
3809 lead to "missing" programs if, for example, a package
3810 is installed which overwrites a file from another
3811 package, and is then removed again.<footnote>
3812 Part of the problem is due to what is arguably a
3813 bug in <prgn>dpkg</prgn>.
3818 A directory will never be replaced by a symbolic link
3819 to a directory or vice versa; instead, the existing
3820 state (symlink or not) will be left alone and
3821 <prgn>dpkg</prgn> will follow the symlink if there is
3830 If the package is being upgraded, call
3831 <example compact="compact">
3832 <var>old-postrm</var> upgrade <var>new-version</var>
3836 If this fails, <prgn>dpkg</prgn> will attempt:
3837 <example compact="compact">
3838 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3840 If this works, installation continues. If not,
3842 <example compact="compact">
3843 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3845 If this fails, the old version is left in an
3846 "Half Installed" state. If it works, dpkg now
3848 <example compact="compact">
3849 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3851 If this fails, the old version is left in an
3852 "Half Installed" state. If it works, dpkg now
3854 <example compact="compact">
3855 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3857 If this fails, the old version is in an
3864 This is the point of no return - if
3865 <prgn>dpkg</prgn> gets this far, it won't back off
3866 past this point if an error occurs. This will
3867 leave the package in a fairly bad state, which
3868 will require a successful re-installation to clear
3869 up, but it's when <prgn>dpkg</prgn> starts doing
3870 things that are irreversible.
3875 Any files which were in the old version of the package
3876 but not in the new are removed.
3880 The new file list replaces the old.
3884 The new maintainer scripts replace the old.
3888 Any packages all of whose files have been overwritten
3889 during the installation, and which aren't required for
3890 dependencies, are considered to have been removed.
3891 For each such package
3894 <prgn>dpkg</prgn> calls:
3895 <example compact="compact">
3896 <var>disappearer's-postrm</var> disappear \
3897 <var>overwriter</var> <var>overwriter-version</var>
3901 The package's maintainer scripts are removed.
3904 It is noted in the status database as being in a
3905 sane state, namely not installed (any conffiles
3906 it may have are ignored, rather than being
3907 removed by <prgn>dpkg</prgn>). Note that
3908 disappearing packages do not have their prerm
3909 called, because <prgn>dpkg</prgn> doesn't know
3910 in advance that the package is going to
3917 Any files in the package we're unpacking that are also
3918 listed in the file lists of other packages are removed
3919 from those lists. (This will lobotomize the file list
3920 of the "conflicting" package if there is one.)
3924 The backup files made during installation, above, are
3930 The new package's status is now sane, and recorded as
3935 Here is another point of no return - if the
3936 conflicting package's removal fails we do not unwind
3937 the rest of the installation; the conflicting package
3938 is left in a half-removed limbo.
3943 If there was a conflicting package we go and do the
3944 removal actions (described below), starting with the
3945 removal of the conflicting package's files (any that
3946 are also in the package being installed have already
3947 been removed from the conflicting package's file list,
3948 and so do not get removed now).
3954 <sect id="configdetails"><heading>Details of configuration</heading>
3957 When we configure a package (this happens with <tt>dpkg
3958 --install</tt> and <tt>dpkg --configure</tt>), we first
3959 update any <tt>conffile</tt>s and then call:
3960 <example compact="compact">
3961 <var>postinst</var> configure <var>most-recently-configured-version</var>
3966 No attempt is made to unwind after errors during
3967 configuration. If the configuration fails, the package is in
3968 a "Failed Config" state, and an error message is generated.
3972 If there is no most recently configured version
3973 <prgn>dpkg</prgn> will pass a null argument.
3976 Historical note: Truly ancient (pre-1997) versions of
3977 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3978 (including the angle brackets) in this case. Even older
3979 ones did not pass a second argument at all, under any
3980 circumstance. Note that upgrades using such an old dpkg
3981 version are unlikely to work for other reasons, even if
3982 this old argument behavior is handled by your postinst script.
3988 <sect id="removedetails"><heading>Details of removal and/or
3989 configuration purging</heading>
3995 <example compact="compact">
3996 <var>prerm</var> remove
4000 If prerm fails during replacement due to conflict
4002 <var>conflictor's-postinst</var> abort-remove \
4003 in-favour <var>package</var> <var>new-version</var>
4007 <var>postinst</var> abort-remove
4011 If this fails, the package is in a "Failed-Config"
4012 state, or else it remains "Installed".
4016 The package's files are removed (except <tt>conffile</tt>s).
4019 <example compact="compact">
4020 <var>postrm</var> remove
4024 If it fails, there's no error unwind, and the package is in
4025 an "Half-Installed" state.
4030 All the maintainer scripts except the <prgn>postrm</prgn>
4035 If we aren't purging the package we stop here. Note
4036 that packages which have no <prgn>postrm</prgn> and no
4037 <tt>conffile</tt>s are automatically purged when
4038 removed, as there is no difference except for the
4039 <prgn>dpkg</prgn> status.
4043 The <tt>conffile</tt>s and any backup files
4044 (<tt>~</tt>-files, <tt>#*#</tt> files,
4045 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4050 <example compact="compact">
4051 <var>postrm</var> purge
4055 If this fails, the package remains in a "Config-Files"
4060 The package's file list is removed.
4069 <chapt id="relationships">
4070 <heading>Declaring relationships between packages</heading>
4072 <sect id="depsyntax">
4073 <heading>Syntax of relationship fields</heading>
4076 These fields all have a uniform syntax. They are a list of
4077 package names separated by commas.
4081 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4082 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4083 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4084 control file fields of the package, which declare
4085 dependencies on other packages, the package names listed may
4086 also include lists of alternative package names, separated
4087 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4088 if any one of the alternative packages is installed, that
4089 part of the dependency is considered to be satisfied.
4093 All of the fields except for <tt>Provides</tt> may restrict
4094 their applicability to particular versions of each named
4095 package. This is done in parentheses after each individual
4096 package name; the parentheses should contain a relation from
4097 the list below followed by a version number, in the format
4098 described in <ref id="f-Version">.
4102 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4103 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4104 strictly earlier, earlier or equal, exactly equal, later or
4105 equal and strictly later, respectively. The deprecated
4106 forms <tt><</tt> and <tt>></tt> were used to mean
4107 earlier/later or equal, rather than strictly earlier/later,
4108 so they should not appear in new packages (though
4109 <prgn>dpkg</prgn> still supports them).
4113 Whitespace may appear at any point in the version
4114 specification subject to the rules in <ref
4115 id="controlsyntax">, and must appear where it's necessary to
4116 disambiguate; it is not otherwise significant. All of the
4117 relationship fields may span multiple lines. For
4118 consistency and in case of future changes to
4119 <prgn>dpkg</prgn> it is recommended that a single space be
4120 used after a version relationship and before a version
4121 number; it is also conventional to put a single space after
4122 each comma, on either side of each vertical bar, and before
4123 each open parenthesis. When wrapping a relationship field, it
4124 is conventional to do so after a comma and before the space
4125 following that comma.
4129 For example, a list of dependencies might appear as:
4130 <example compact="compact">
4133 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4138 All fields that specify build-time relationships
4139 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4140 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4141 may be restricted to a certain set of architectures. This
4142 is indicated in brackets after each individual package name and
4143 the optional version specification. The brackets enclose a
4144 list of Debian architecture names separated by whitespace.
4145 Exclamation marks may be prepended to each of the names.
4146 (It is not permitted for some names to be prepended with
4147 exclamation marks while others aren't.) If the current Debian
4148 host architecture is not in this list and there are no
4149 exclamation marks in the list, or it is in the list with a
4150 prepended exclamation mark, the package name and the
4151 associated version specification are ignored completely for
4152 the purposes of defining the relationships.
4157 <example compact="compact">
4159 Build-Depends-Indep: texinfo
4160 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4161 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4166 Note that the binary package relationship fields such as
4167 <tt>Depends</tt> appear in one of the binary package
4168 sections of the control file, whereas the build-time
4169 relationships such as <tt>Build-Depends</tt> appear in the
4170 source package section of the control file (which is the
4175 <sect id="binarydeps">
4176 <heading>Binary Dependencies - <tt>Depends</tt>,
4177 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4178 <tt>Pre-Depends</tt>
4182 Packages can declare in their control file that they have
4183 certain relationships to other packages - for example, that
4184 they may not be installed at the same time as certain other
4185 packages, and/or that they depend on the presence of others.
4189 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4190 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4191 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4195 These seven fields are used to declare a dependency
4196 relationship by one package on another. Except for
4197 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4198 depending (binary) package's control file.
4199 (<tt>Enhances</tt> appears in the recommending package's
4200 control file, and <tt>Breaks</tt> appears in the version of
4201 depended-on package which causes the named package to
4206 A <tt>Depends</tt> field takes effect <em>only</em> when a
4207 package is to be configured. It does not prevent a package
4208 being on the system in an unconfigured state while its
4209 dependencies are unsatisfied, and it is possible to replace
4210 a package whose dependencies are satisfied and which is
4211 properly installed with a different version whose
4212 dependencies are not and cannot be satisfied; when this is
4213 done the depending package will be left unconfigured (since
4214 attempts to configure it will give errors) and will not
4215 function properly. If it is necessary, a
4216 <tt>Pre-Depends</tt> field can be used, which has a partial
4217 effect even when a package is being unpacked, as explained
4218 in detail below. (The other three dependency fields,
4219 <tt>Recommends</tt>, <tt>Suggests</tt> and
4220 <tt>Enhances</tt>, are only used by the various front-ends
4221 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4222 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4226 For this reason packages in an installation run are usually
4227 all unpacked first and all configured later; this gives
4228 later versions of packages with dependencies on later
4229 versions of other packages the opportunity to have their
4230 dependencies satisfied.
4234 In case of circular dependencies, since installation or
4235 removal order honoring the dependency order can't be
4236 established, dependency loops are broken at some point
4237 (based on rules below), and some packages may not be able to
4238 rely on their dependencies being present when being
4239 installed or removed, depending on which side of the break
4240 of the circular dependency loop they happen to be on. If one
4241 of the packages in the loop has no postinst script, then the
4242 cycle will be broken at that package, so as to ensure that
4243 all postinst scripts run with the dependencies properly
4244 configured if this is possible. Otherwise the breaking point
4249 The <tt>Depends</tt> field thus allows package maintainers
4250 to impose an order in which packages should be configured.
4254 The meaning of the five dependency fields is as follows:
4256 <tag><tt>Depends</tt></tag>
4259 This declares an absolute dependency. A package will
4260 not be configured unless all of the packages listed in
4261 its <tt>Depends</tt> field have been correctly
4266 The <tt>Depends</tt> field should be used if the
4267 depended-on package is required for the depending
4268 package to provide a significant amount of
4273 The <tt>Depends</tt> field should also be used if the
4274 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4275 <prgn>postrm</prgn> scripts require the package to be
4276 present in order to run. Note, however, that the
4277 <prgn>postrm</prgn> cannot rely on any non-essential
4278 packages to be present during the <tt>purge</tt>
4282 <tag><tt>Recommends</tt></tag>
4285 This declares a strong, but not absolute, dependency.
4289 The <tt>Recommends</tt> field should list packages
4290 that would be found together with this one in all but
4291 unusual installations.
4295 <tag><tt>Suggests</tt></tag>
4297 This is used to declare that one package may be more
4298 useful with one or more others. Using this field
4299 tells the packaging system and the user that the
4300 listed packages are related to this one and can
4301 perhaps enhance its usefulness, but that installing
4302 this one without them is perfectly reasonable.
4305 <tag><tt>Enhances</tt></tag>
4307 This field is similar to Suggests but works in the
4308 opposite direction. It is used to declare that a
4309 package can enhance the functionality of another
4313 <tag><tt>Pre-Depends</tt></tag>
4316 This field is like <tt>Depends</tt>, except that it
4317 also forces <prgn>dpkg</prgn> to complete installation
4318 of the packages named before even starting the
4319 installation of the package which declares the
4320 pre-dependency, as follows:
4324 When a package declaring a pre-dependency is about to
4325 be <em>unpacked</em> the pre-dependency can be
4326 satisfied if the depended-on package is either fully
4327 configured, <em>or even if</em> the depended-on
4328 package(s) are only unpacked or half-configured,
4329 provided that they have been configured correctly at
4330 some point in the past (and not removed or partially
4331 removed since). In this case, both the
4332 previously-configured and currently unpacked or
4333 half-configured versions must satisfy any version
4334 clause in the <tt>Pre-Depends</tt> field.
4338 When the package declaring a pre-dependency is about
4339 to be <em>configured</em>, the pre-dependency will be
4340 treated as a normal <tt>Depends</tt>, that is, it will
4341 be considered satisfied only if the depended-on
4342 package has been correctly configured.
4346 <tt>Pre-Depends</tt> should be used sparingly,
4347 preferably only by packages whose premature upgrade or
4348 installation would hamper the ability of the system to
4349 continue with any upgrade that might be in progress.
4353 <tt>Pre-Depends</tt> are also required if the
4354 <prgn>preinst</prgn> script depends on the named
4355 package. It is best to avoid this situation if
4363 When selecting which level of dependency to use you should
4364 consider how important the depended-on package is to the
4365 functionality of the one declaring the dependency. Some
4366 packages are composed of components of varying degrees of
4367 importance. Such a package should list using
4368 <tt>Depends</tt> the package(s) which are required by the
4369 more important components. The other components'
4370 requirements may be mentioned as Suggestions or
4371 Recommendations, as appropriate to the components' relative
4377 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4380 Using <tt>Breaks</tt> may cause problems for upgrades from older
4381 versions of Debian and should not be used until the stable
4382 release of Debian supports <tt>Breaks</tt>.
4386 When one binary package declares that it breaks another,
4387 <prgn>dpkg</prgn> will refuse to allow the package which
4388 declares <tt>Breaks</tt> be installed unless the broken
4389 package is deconfigured first, and it will refuse to
4390 allow the broken package to be reconfigured.
4394 A package will not be regarded as causing breakage merely
4395 because its configuration files are still installed; it must
4396 be at least half-installed.
4400 A special exception is made for packages which declare that
4401 they break their own package name or a virtual package which
4402 they provide (see below): this does not count as a real
4407 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4408 version clause; such a <tt>Breaks</tt> is introduced in the
4409 version of an (implicit or explicit) dependency which
4410 violates an assumption or reveals a bug in earlier versions
4411 of the broken package. This use of <tt>Breaks</tt> will
4412 inform higher-level package management tools that broken
4413 package must be upgraded before the new one.
4417 If the breaking package also overwrites some files from the
4418 older package, it should use <tt>Replaces</tt> (not
4419 <tt>Conflicts</tt>) to ensure this goes smoothly.
4423 <sect id="conflicts">
4424 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4427 When one binary package declares a conflict with another
4428 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4429 refuse to allow them to be installed on the system at the
4434 If one package is to be installed, the other must be removed
4435 first - if the package being installed is marked as
4436 replacing (see <ref id="replaces">) the one on the system,
4437 or the one on the system is marked as deselected, or both
4438 packages are marked <tt>Essential</tt>, then
4439 <prgn>dpkg</prgn> will automatically remove the package
4440 which is causing the conflict, otherwise it will halt the
4441 installation of the new package with an error. This
4442 mechanism is specifically designed to produce an error when
4443 the installed package is <tt>Essential</tt>, but the new
4448 A package will not cause a conflict merely because its
4449 configuration files are still installed; it must be at least
4454 A special exception is made for packages which declare a
4455 conflict with their own package name, or with a virtual
4456 package which they provide (see below): this does not
4457 prevent their installation, and allows a package to conflict
4458 with others providing a replacement for it. You use this
4459 feature when you want the package in question to be the only
4460 package providing some feature.
4464 A <tt>Conflicts</tt> entry should almost never have an
4465 "earlier than" version clause. This would prevent
4466 <prgn>dpkg</prgn> from upgrading or installing the package
4467 which declared such a conflict until the upgrade or removal
4468 of the conflicted-with package had been completed. Instead,
4469 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4470 by the stable release of Debian).
4474 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4478 As well as the names of actual ("concrete") packages, the
4479 package relationship fields <tt>Depends</tt>,
4480 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4481 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4482 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4483 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4484 may mention "virtual packages".
4488 A <em>virtual package</em> is one which appears in the
4489 <tt>Provides</tt> control file field of another package.
4490 The effect is as if the package(s) which provide a
4491 particular virtual package name had been listed by name
4492 everywhere the virtual package name appears. (See also <ref
4497 If there are both concrete and virtual packages of the same
4498 name, then the dependency may be satisfied (or the conflict
4499 caused) by either the concrete package with the name in
4500 question or any other concrete package which provides the
4501 virtual package with the name in question. This is so that,
4502 for example, supposing we have
4503 <example compact="compact">
4506 </example> and someone else releases an enhanced version of
4507 the <tt>bar</tt> package they can say:
4508 <example compact="compact">
4512 and the <tt>bar-plus</tt> package will now also satisfy the
4513 dependency for the <tt>foo</tt> package.
4517 If a relationship field has a version number attached
4518 then only real packages will be considered to see whether
4519 the relationship is satisfied (or the prohibition violated,
4520 for a conflict or breakage) - it is assumed that a real
4521 package which provides the virtual package is not of the
4522 "right" version. So, a <tt>Provides</tt> field may not
4523 contain version numbers, and the version number of the
4524 concrete package which provides a particular virtual package
4525 will not be looked at when considering a dependency on or
4526 conflict with the virtual package name.
4530 It is likely that the ability will be added in a future
4531 release of <prgn>dpkg</prgn> to specify a version number for
4532 each virtual package it provides. This feature is not yet
4533 present, however, and is expected to be used only
4538 If you want to specify which of a set of real packages
4539 should be the default to satisfy a particular dependency on
4540 a virtual package, you should list the real package as an
4541 alternative before the virtual one.
4546 <sect id="replaces"><heading>Overwriting files and replacing
4547 packages - <tt>Replaces</tt></heading>
4550 Packages can declare in their control file that they should
4551 overwrite files in certain other packages, or completely
4552 replace other packages. The <tt>Replaces</tt> control file
4553 field has these two distinct purposes.
4556 <sect1><heading>Overwriting files in other packages</heading>
4559 Firstly, as mentioned before, it is usually an error for a
4560 package to contain files which are on the system in
4565 However, if the overwriting package declares that it
4566 <tt>Replaces</tt> the one containing the file being
4567 overwritten, then <prgn>dpkg</prgn> will replace the file
4568 from the old package with that from the new. The file
4569 will no longer be listed as "owned" by the old package.
4573 If a package is completely replaced in this way, so that
4574 <prgn>dpkg</prgn> does not know of any files it still
4575 contains, it is considered to have "disappeared". It will
4576 be marked as not wanted on the system (selected for
4577 removal) and not installed. Any <tt>conffile</tt>s
4578 details noted for the package will be ignored, as they
4579 will have been taken over by the overwriting package. The
4580 package's <prgn>postrm</prgn> script will be run with a
4581 special argument to allow the package to do any final
4582 cleanup required. See <ref id="mscriptsinstact">.
4585 Replaces is a one way relationship -- you have to
4586 install the replacing package after the replaced
4593 For this usage of <tt>Replaces</tt>, virtual packages (see
4594 <ref id="virtual">) are not considered when looking at a
4595 <tt>Replaces</tt> field - the packages declared as being
4596 replaced must be mentioned by their real names.
4600 Furthermore, this usage of <tt>Replaces</tt> only takes
4601 effect when both packages are at least partially on the
4602 system at once, so that it can only happen if they do not
4603 conflict or if the conflict has been overridden.
4608 <sect1><heading>Replacing whole packages, forcing their
4612 Secondly, <tt>Replaces</tt> allows the packaging system to
4613 resolve which package should be removed when there is a
4614 conflict - see <ref id="conflicts">. This usage only
4615 takes effect when the two packages <em>do</em> conflict,
4616 so that the two usages of this field do not interfere with
4621 In this situation, the package declared as being replaced
4622 can be a virtual package, so for example, all mail
4623 transport agents (MTAs) would have the following fields in
4624 their control files:
4625 <example compact="compact">
4626 Provides: mail-transport-agent
4627 Conflicts: mail-transport-agent
4628 Replaces: mail-transport-agent
4630 ensuring that only one MTA can be installed at any one
4635 <sect id="sourcebinarydeps">
4636 <heading>Relationships between source and binary packages -
4637 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4638 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4642 Source packages that require certain binary packages to be
4643 installed or absent at the time of building the package
4644 can declare relationships to those binary packages.
4648 This is done using the <tt>Build-Depends</tt>,
4649 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4650 <tt>Build-Conflicts-Indep</tt> control file fields.
4654 Build-dependencies on "build-essential" binary packages can be
4655 omitted. Please see <ref id="pkg-relations"> for more information.
4659 The dependencies and conflicts they define must be satisfied
4660 (as defined earlier for binary packages) in order to invoke
4661 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4663 If you make "build-arch" or "binary-arch", you need
4664 Build-Depends. If you make "build-indep" or
4665 "binary-indep", you need Build-Depends and
4666 Build-Depends-Indep. If you make "build" or "binary",
4670 There is no Build-Depends-Arch; this role is essentially
4671 met with Build-Depends. Anyone building the
4672 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4673 is basically assumed to be building the whole package
4674 anyway and so installs all build dependencies. The
4675 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4676 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4677 does not yet know how to check for its existence) and
4678 <tt>binary-arch</tt>.
4681 The purpose of the original split, I recall, was so that
4682 the autobuilders wouldn't need to install extra packages
4683 needed only for the binary-indep targets. But without a
4684 build-arch/build-indep split, this didn't work, since
4685 most of the work is done in the build target, not in the
4691 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4693 The <tt>Build-Depends</tt> and
4694 <tt>Build-Conflicts</tt> fields must be satisfied when
4695 any of the following targets is invoked:
4696 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4697 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4698 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4700 <tag><tt>Build-Depends-Indep</tt>,
4701 <tt>Build-Conflicts-Indep</tt></tag>
4703 The <tt>Build-Depends-Indep</tt> and
4704 <tt>Build-Conflicts-Indep</tt> fields must be
4705 satisfied when any of the following targets is
4706 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4707 <tt>binary</tt> and <tt>binary-indep</tt>.
4717 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4720 Packages containing shared libraries must be constructed with
4721 a little care to make sure that the shared library is always
4722 available. This is especially important for packages whose
4723 shared libraries are vitally important, such as the C library
4724 (currently <tt>libc6</tt>).
4728 Packages involving shared libraries should be split up into
4729 several binary packages. This section mostly deals with how
4730 this separation is to be accomplished; rules for files within
4731 the shared library packages are in <ref id="libraries"> instead.
4734 <sect id="sharedlibs-runtime">
4735 <heading>Run-time shared libraries</heading>
4738 The run-time shared library needs to be placed in a package
4739 whose name changes whenever the shared object version
4742 Since it is common place to install several versions of a
4743 package that just provides shared libraries, it is a
4744 good idea that the library package should not
4745 contain any extraneous non-versioned files, unless they
4746 happen to be in versioned directories.</p>
4748 The most common mechanism is to place it in a package
4750 <package><var>libraryname</var><var>soversion</var></package>,
4751 where <file><var>soversion</var></file> is the version number
4752 in the soname of the shared library<footnote>
4753 The soname is the shared object name: it's the thing
4754 that has to match exactly between building an executable
4755 and running it for the dynamic linker to be able run the
4756 program. For example, if the soname of the library is
4757 <file>libfoo.so.6</file>, the library package would be
4758 called <file>libfoo6</file>.
4760 Alternatively, if it would be confusing to directly append
4761 <var>soversion</var> to <var>libraryname</var> (e.g. because
4762 <var>libraryname</var> itself ends in a number), you may use
4763 <package><var>libraryname</var>-<var>soversion</var></package> and
4764 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4769 If you have several shared libraries built from the same
4770 source tree you may lump them all together into a single
4771 shared library package, provided that you change all of
4772 their sonames at once (so that you don't get filename
4773 clashes if you try to install different versions of the
4774 combined shared libraries package).
4778 The package should install the shared libraries under
4779 their normal names. For example, the <package>libgdbm3</package>
4780 package should install <file>libgdbm.so.3.0.0</file> as
4781 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4782 renamed or re-linked by any <prgn>prerm</prgn> or
4783 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4784 of renaming things safely without affecting running programs,
4785 and attempts to interfere with this are likely to lead to
4790 Shared libraries should not be installed executable, since
4791 the dynamic linker does not require this and trying to
4792 execute a shared library usually results in a core dump.
4796 The run-time library package should include the symbolic link that
4797 <prgn>ldconfig</prgn> would create for the shared libraries.
4798 For example, the <package>libgdbm3</package> package should include
4799 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4800 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4801 linker (for example <prgn>ld.so</prgn> or
4802 <prgn>ld-linux.so.*</prgn>) can find the library between the
4803 time that <prgn>dpkg</prgn> installs it and the time that
4804 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4806 The package management system requires the library to be
4807 placed before the symbolic link pointing to it in the
4808 <file>.deb</file> file. This is so that when
4809 <prgn>dpkg</prgn> comes to install the symlink
4810 (overwriting the previous symlink pointing at an older
4811 version of the library), the new shared library is already
4812 in place. In the past, this was achieved by creating the
4813 library in the temporary packaging directory before
4814 creating the symlink. Unfortunately, this was not always
4815 effective, since the building of the tar file in the
4816 <file>.deb</file> depended on the behavior of the underlying
4817 file system. Some file systems (such as reiserfs) reorder
4818 the files so that the order of creation is forgotten.
4819 Since version 1.7.0, <prgn>dpkg</prgn>
4820 reorders the files itself as necessary when building a
4821 package. Thus it is no longer important to concern
4822 oneself with the order of file creation.
4826 <sect1 id="ldconfig">
4827 <heading><tt>ldconfig</tt></heading>
4830 Any package installing shared libraries in one of the default
4831 library directories of the dynamic linker (which are currently
4832 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4833 listed in <file>/etc/ld.so.conf</file><footnote>
4835 <list compact="compact">
4836 <item>/usr/local/lib</item>
4837 <item>/usr/lib/libc5-compat</item>
4838 <item>/lib/libc5-compat</item>
4841 must use <prgn>ldconfig</prgn> to update the shared library
4846 The package maintainer scripts must only call
4847 <prgn>ldconfig</prgn> under these circumstances:
4848 <list compact="compact">
4849 <item>When the <prgn>postinst</prgn> script is run with a
4850 first argument of <tt>configure</tt>, the script must call
4851 <prgn>ldconfig</prgn>, and may optionally invoke
4852 <prgn>ldconfig</prgn> at other times.
4854 <item>When the <prgn>postrm</prgn> script is run with a
4855 first argument of <tt>remove</tt>, the script should call
4856 <prgn>ldconfig</prgn>.
4861 During install or upgrade, the preinst is called before
4862 the new files are installed, so calling "ldconfig" is
4863 pointless. The preinst of an existing package can also be
4864 called if an upgrade fails. However, this happens during
4865 the critical time when a shared libs may exist on-disk
4866 under a temporary name. Thus, it is dangerous and
4867 forbidden by current policy to call "ldconfig" at this
4872 When a package is installed or upgraded, "postinst
4873 configure" runs after the new files are safely on-disk.
4874 Since it is perfectly safe to invoke ldconfig
4875 unconditionally in a postinst, it is OK for a package to
4876 simply put ldconfig in its postinst without checking the
4877 argument. The postinst can also be called to recover from
4878 a failed upgrade. This happens before any new files are
4879 unpacked, so there is no reason to call "ldconfig" at this
4884 For a package that is being removed, prerm is
4885 called with all the files intact, so calling ldconfig is
4886 useless. The other calls to "prerm" happen in the case of
4887 upgrade at a time when all the files of the old package
4888 are on-disk, so again calling "ldconfig" is pointless.
4892 postrm, on the other hand, is called with the "remove"
4893 argument just after the files are removed, so this is
4894 the proper time to call "ldconfig" to notify the system
4895 of the fact that the shared libraries from the package
4896 are removed. The postrm can be called at several other
4897 times. At the time of "postrm purge", "postrm
4898 abort-install", or "postrm abort-upgrade", calling
4899 "ldconfig" is useless because the shared lib files are
4900 not on-disk. However, when "postrm" is invoked with
4901 arguments "upgrade", "failed-upgrade", or "disappear", a
4902 shared lib may exist on-disk under a temporary filename.
4910 <sect id="sharedlibs-support-files">
4911 <heading>Shared library support files</heading>
4914 If your package contains files whose names do not change with
4915 each change in the library shared object version, you must not
4916 put them in the shared library package. Otherwise, several
4917 versions of the shared library cannot be installed at the same
4918 time without filename clashes, making upgrades and transitions
4919 unnecessarily difficult.
4923 It is recommended that supporting files and run-time support
4924 programs that do not need to be invoked manually by users, but
4925 are nevertheless required for the package to function, be placed
4926 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4927 preferably under <file>/usr/lib/</file><var>package-name</var>.
4928 If the program or file is architecture independent, the
4929 recommendation is for it to be placed in a subdirectory of
4930 <file>/usr/share</file> instead, preferably under
4931 <file>/usr/share/</file><var>package-name</var>. Following the
4932 <var>package-name</var> naming convention ensures that the file
4933 names change when the shared object version changes.
4937 Run-time support programs that use the shared library but are
4938 not required for the library to function or files used by the
4939 shared library that can be used by any version of the shared
4940 library package should instead be put in a separate package.
4941 This package might typically be named
4942 <package><var>libraryname</var>-tools</package>; note the
4943 absence of the <var>soversion</var> in the package name.
4947 Files and support programs only useful when compiling software
4948 against the library should be included in the development
4949 package for the library.<footnote>
4950 For example, a <file><var>package-name</var>-config</file>
4951 script or <package>pkg-config</package> configuration files.
4956 <sect id="sharedlibs-static">
4957 <heading>Static libraries</heading>
4960 The static library (<file><var>libraryname.a</var></file>)
4961 is usually provided in addition to the shared version.
4962 It is placed into the development package (see below).
4966 In some cases, it is acceptable for a library to be
4967 available in static form only; these cases include:
4969 <item>libraries for languages whose shared library support
4970 is immature or unstable</item>
4971 <item>libraries whose interfaces are in flux or under
4972 development (commonly the case when the library's
4973 major version number is zero, or where the ABI breaks
4974 across patchlevels)</item>
4975 <item>libraries which are explicitly intended to be
4976 available only in static form by their upstream
4981 <sect id="sharedlibs-dev">
4982 <heading>Development files</heading>
4985 The development files associated to a shared library need to be
4986 placed in a package called
4987 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4988 or if you prefer only to support one development version at a
4989 time, <package><var>libraryname</var>-dev</package>.
4993 In case several development versions of a library exist, you may
4994 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4995 <ref id="conflicts">) to ensure that the user only installs one
4996 development version at a time (as different development versions are
4997 likely to have the same header files in them, which would cause a
4998 filename clash if both were installed).
5002 The development package should contain a symlink for the associated
5003 shared library without a version number. For example, the
5004 <package>libgdbm-dev</package> package should include a symlink
5005 from <file>/usr/lib/libgdbm.so</file> to
5006 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5007 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5008 <file>libgdbm.so</file> when compiling dynamically.
5012 <sect id="sharedlibs-intradeps">
5013 <heading>Dependencies between the packages of the same library</heading>
5016 Typically the development version should have an exact
5017 version dependency on the runtime library, to make sure that
5018 compilation and linking happens correctly. The
5019 <tt>${binary:Version}</tt> substitution variable can be
5020 useful for this purpose.
5022 Previously, <tt>${Source-Version}</tt> was used, but its name
5023 was confusing and it has been deprecated since dpkg 1.13.19.
5028 <sect id="sharedlibs-shlibdeps">
5029 <heading>Dependencies between the library and other packages -
5030 the <tt>shlibs</tt> system</heading>
5033 If a package contains a binary or library which links to a
5034 shared library, we must ensure that when the package is
5035 installed on the system, all of the libraries needed are
5036 also installed. This requirement led to the creation of the
5037 <tt>shlibs</tt> system, which is very simple in its design:
5038 any package which <em>provides</em> a shared library also
5039 provides information on the package dependencies required to
5040 ensure the presence of this library, and any package which
5041 <em>uses</em> a shared library uses this information to
5042 determine the dependencies it requires. The files which
5043 contain the mapping from shared libraries to the necessary
5044 dependency information are called <file>shlibs</file> files.
5048 Thus, when a package is built which contains any shared
5049 libraries, it must provide a <file>shlibs</file> file for other
5050 packages to use, and when a package is built which contains
5051 any shared libraries or compiled binaries, it must run
5052 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5053 on these to determine the libraries used and hence the
5054 dependencies needed by this package.<footnote>
5056 In the past, the shared libraries linked to were
5057 determined by calling <prgn>ldd</prgn>, but now
5058 <prgn>objdump</prgn> is used to do this. The only
5059 change this makes to package building is that
5060 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5061 libraries, whereas in the past this was unnecessary.
5062 The rest of this footnote explains the advantage that
5067 We say that a binary <tt>foo</tt> <em>directly</em> uses
5068 a library <tt>libbar</tt> if it is explicitly linked
5069 with that library (that is, it uses the flag
5070 <tt>-lbar</tt> during the linking stage). Other
5071 libraries that are needed by <tt>libbar</tt> are linked
5072 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5073 linker will load them automatically when it loads
5074 <tt>libbar</tt>. A package should depend on
5075 the libraries it directly uses, and the dependencies for
5076 those libraries should automatically pull in the other
5081 Unfortunately, the <prgn>ldd</prgn> program shows both
5082 the directly and indirectly used libraries, meaning that
5083 the dependencies determined included both direct and
5084 indirect dependencies. The use of <prgn>objdump</prgn>
5085 avoids this problem by determining only the directly
5090 A good example of where this helps is the following. We
5091 could update <tt>libimlib</tt> with a new version that
5092 supports a new graphics format called dgf (but retaining
5093 the same major version number). If we used the old
5094 <prgn>ldd</prgn> method, every package that uses
5095 <tt>libimlib</tt> would need to be recompiled so it
5096 would also depend on <tt>libdgf</tt> or it wouldn't run
5097 due to missing symbols. However with the new system,
5098 packages using <tt>libimlib</tt> can rely on
5099 <tt>libimlib</tt> itself having the dependency on
5100 <tt>libdgf</tt> and so they would not need rebuilding.
5106 In the following sections, we will first describe where the
5107 various <tt>shlibs</tt> files are to be found, then how to
5108 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5109 file format and how to create them if your package contains a
5114 <heading>The <tt>shlibs</tt> files present on the system</heading>
5117 There are several places where <tt>shlibs</tt> files are
5118 found. The following list gives them in the order in which
5120 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5121 (The first one which gives the required information is used.)
5127 <p><file>debian/shlibs.local</file></p>
5130 This lists overrides for this package. Its use is
5131 described below (see <ref id="shlibslocal">).
5136 <p><file>/etc/dpkg/shlibs.override</file></p>
5139 This lists global overrides. This list is normally
5140 empty. It is maintained by the local system
5146 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5149 When packages are being built, any
5150 <file>debian/shlibs</file> files are copied into the
5151 control file area of the temporary build directory and
5152 given the name <file>shlibs</file>. These files give
5153 details of any shared libraries included in the
5155 An example may help here. Let us say that the
5156 source package <tt>foo</tt> generates two binary
5157 packages, <tt>libfoo2</tt> and
5158 <tt>foo-runtime</tt>. When building the binary
5159 packages, the two packages are created in the
5160 directories <file>debian/libfoo2</file> and
5161 <file>debian/foo-runtime</file> respectively.
5162 (<file>debian/tmp</file> could be used instead of one
5163 of these.) Since <tt>libfoo2</tt> provides the
5164 <tt>libfoo</tt> shared library, it will require a
5165 <tt>shlibs</tt> file, which will be installed in
5166 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5168 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5169 when <prgn>dpkg-shlibdeps</prgn> is run on the
5171 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5173 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5174 determine whether <tt>foo-prog</tt>'s library
5175 dependencies are satisfied by any of the libraries
5176 provided by <tt>libfoo2</tt>. For this reason,
5177 <prgn>dpkg-shlibdeps</prgn> must only be run once
5178 all of the individual binary packages'
5179 <tt>shlibs</tt> files have been installed into the
5186 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5189 These are the <file>shlibs</file> files corresponding to
5190 all of the packages installed on the system, and are
5191 maintained by the relevant package maintainers.
5196 <p><file>/etc/dpkg/shlibs.default</file></p>
5199 This file lists any shared libraries whose packages
5200 have failed to provide correct <file>shlibs</file> files.
5201 It was used when the <file>shlibs</file> setup was first
5202 introduced, but it is now normally empty. It is
5203 maintained by the <tt>dpkg</tt> maintainer.
5211 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5212 <file>shlibs</file> files</heading>
5216 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5217 into your <file>debian/rules</file> file. If your package
5218 contains only compiled binaries and libraries (but no scripts),
5219 you can use a command such as:
5220 <example compact="compact">
5221 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5222 debian/tmp/usr/lib/*
5224 Otherwise, you will need to explicitly list the compiled
5225 binaries and libraries.<footnote>
5226 If you are using <tt>debhelper</tt>, the
5227 <prgn>dh_shlibdeps</prgn> program will do this work for
5228 you. It will also correctly handle multi-binary
5234 This command puts the dependency information into the
5235 <file>debian/substvars</file> file, which is then used by
5236 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5237 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5238 field in the control file for this to work.
5242 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5243 done. If it does complain you might need to create your own
5244 <file>debian/shlibs.local</file> file, as explained below (see
5245 <ref id="shlibslocal">).
5249 If you have multiple binary packages, you will need to call
5250 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5251 compiled libraries or binaries. In such a case, you will
5252 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5253 utilities to specify a different <file>substvars</file> file.
5257 If you are creating a udeb for use in the Debian Installer, you
5258 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5259 the dependency line of type <tt>udeb</tt> by adding
5260 <tt>-tudeb</tt> as option<footnote>
5261 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5262 will automatically add this option if it knows it is
5264 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5265 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5266 fall back to the regular dependency line.
5270 For more details on dpkg-shlibdeps, please see
5271 <ref id="pkg-dpkg-shlibdeps"> and
5272 <manref name="dpkg-shlibdeps" section="1">.
5277 <heading>The <file>shlibs</file> File Format</heading>
5280 Each <file>shlibs</file> file has the same format. Lines
5281 beginning with <tt>#</tt> are considered to be comments and
5282 are ignored. Each line is of the form:
5283 <example compact="compact">
5284 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5289 We will explain this by reference to the example of the
5290 <tt>zlib1g</tt> package, which (at the time of writing)
5291 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5295 <var>type</var> is an optional element that indicates the type
5296 of package for which the line is valid. The only type currently
5297 in use is <tt>udeb</tt>. The colon and space after the type are
5302 <var>library-name</var> is the name of the shared library,
5303 in this case <tt>libz</tt>. (This must match the name part
5304 of the soname, see below.)
5308 <var>soname-version</var> is the version part of the soname of
5309 the library. The soname is the thing that must exactly match
5310 for the library to be recognized by the dynamic linker, and is
5312 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5313 example, <tt>libz.so.1</tt>.<footnote>
5314 This can be determined using the command
5315 <example compact="compact">
5316 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5319 The version part is the part which comes after
5320 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5324 <var>dependencies</var> has the same syntax as a dependency
5325 field in a binary package control file. It should give
5326 details of which packages are required to satisfy a binary
5327 built against the version of the library contained in the
5328 package. See <ref id="depsyntax"> for details.
5332 In our example, if the first version of the <tt>zlib1g</tt>
5333 package which contained a minor number of at least
5334 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5335 <tt>shlibs</tt> entry for this library could say:
5336 <example compact="compact">
5337 libz 1 zlib1g (>= 1:1.1.3)
5339 The version-specific dependency is to avoid warnings from
5340 the dynamic linker about using older shared libraries with
5345 As zlib1g also provides a udeb containing the shared library,
5346 there would also be a second line:
5347 <example compact="compact">
5348 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5354 <heading>Providing a <file>shlibs</file> file</heading>
5357 If your package provides a shared library, you need to create
5358 a <file>shlibs</file> file following the format described above.
5359 It is usual to call this file <file>debian/shlibs</file> (but if
5360 you have multiple binary packages, you might want to call it
5361 <file>debian/shlibs.<var>package</var></file> instead). Then
5362 let <file>debian/rules</file> install it in the control area:
5363 <example compact="compact">
5364 install -m644 debian/shlibs debian/tmp/DEBIAN
5366 or, in the case of a multi-binary package:
5367 <example compact="compact">
5368 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5370 An alternative way of doing this is to create the
5371 <file>shlibs</file> file in the control area directly from
5372 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5373 file at all,<footnote>
5374 This is what <prgn>dh_makeshlibs</prgn> in the
5375 <tt>debhelper</tt> suite does. If your package also has a udeb
5376 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5377 automatically generate the <tt>udeb:</tt> lines if you specify
5378 the name of the udeb with the <tt>--add-udeb</tt> option.
5380 since the <file>debian/shlibs</file> file itself is ignored by
5381 <prgn>dpkg-shlibdeps</prgn>.
5385 As <prgn>dpkg-shlibdeps</prgn> reads the
5386 <file>DEBIAN/shlibs</file> files in all of the binary packages
5387 being built from this source package, all of the
5388 <file>DEBIAN/shlibs</file> files should be installed before
5389 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5394 <sect1 id="shlibslocal">
5395 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5398 This file is intended only as a <em>temporary</em> fix if
5399 your binaries or libraries depend on a library whose package
5400 does not yet provide a correct <file>shlibs</file> file.
5404 We will assume that you are trying to package a binary
5405 <tt>foo</tt>. When you try running
5406 <prgn>dpkg-shlibdeps</prgn> you get the following error
5407 message (<tt>-O</tt> displays the dependency information on
5408 <tt>stdout</tt> instead of writing it to
5409 <tt>debian/substvars</tt>, and the lines have been wrapped
5410 for ease of reading):
5411 <example compact="compact">
5412 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5413 dpkg-shlibdeps: warning: unable to find dependency
5414 information for shared library libbar (soname 1,
5415 path /usr/lib/libbar.so.1, dependency field Depends)
5416 shlibs:Depends=libc6 (>= 2.2.2-2)
5418 You can then run <prgn>ldd</prgn> on the binary to find the
5419 full location of the library concerned:
5420 <example compact="compact">
5422 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5423 libc.so.6 => /lib/libc.so.6 (0x40032000)
5424 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5426 So the <prgn>foo</prgn> binary depends on the
5427 <prgn>libbar</prgn> shared library, but no package seems to
5428 provide a <file>*.shlibs</file> file handling
5429 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5430 determine the package responsible:
5431 <example compact="compact">
5432 $ dpkg -S /usr/lib/libbar.so.1
5433 bar1: /usr/lib/libbar.so.1
5434 $ dpkg -s bar1 | grep Version
5437 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5438 is the one we are using. Now we can file a bug against the
5439 <tt>bar1</tt> package and create our own
5440 <file>debian/shlibs.local</file> to locally fix the problem.
5441 Including the following line into your
5442 <file>debian/shlibs.local</file> file:
5443 <example compact="compact">
5444 libbar 1 bar1 (>= 1.0-1)
5446 should allow the package build to work.
5450 As soon as the maintainer of <tt>bar1</tt> provides a
5451 correct <file>shlibs</file> file, you should remove this line
5452 from your <file>debian/shlibs.local</file> file. (You should
5453 probably also then have a versioned <tt>Build-Depends</tt>
5454 on <tt>bar1</tt> to help ensure that others do not have the
5455 same problem building your package.)
5464 <chapt id="opersys"><heading>The Operating System</heading>
5467 <heading>File system hierarchy</heading>
5471 <heading>File system Structure</heading>
5474 The location of all installed files and directories must
5475 comply with the File system Hierarchy Standard (FHS),
5476 version 2.3, with the exceptions noted below, and except
5477 where doing so would violate other terms of Debian
5478 Policy. The following exceptions to the FHS apply:
5483 Legacy XFree86 servers are permitted to retain the
5484 configuration file location
5485 <file>/etc/X11/XF86Config-4</file>.
5490 The optional rules related to user specific
5491 configuration files for applications are stored in
5492 the user's home directory are relaxed. It is
5493 recommended that such files start with the
5494 '<tt>.</tt>' character (a "dot file"), and if an
5495 application needs to create more than one dot file
5496 then the preferred placement is in a subdirectory
5497 with a name starting with a '.' character, (a "dot
5498 directory"). In this case it is recommended the
5499 configuration files not start with the '.'
5505 The requirement for amd64 to use <file>/lib64</file>
5506 for 64 bit binaries is removed.
5511 The requirement that
5512 <file>/usr/local/share/man</file> be "synonymous"
5513 with <file>/usr/local/man</file> is relaxed to a
5518 The requirement that windowmanagers with a single
5519 configuration file call it <file>system.*wmrc</file>
5520 is removed, as is the restriction that the window
5521 manager subdirectory be named identically to the
5522 window manager name itself.
5527 The requirement that boot manager configuration
5528 files live in <file>/etc</file>, or at least are
5529 symlinked there, is relaxed to a recommendation.
5536 The version of this document referred here can be
5537 found in the <tt>debian-policy</tt> package or on <url
5538 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5539 name="FHS (Debian copy)"> alongside this manual (or, if
5540 you have the <package>debian-policy</package> installed,
5542 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5543 (local copy)">). The
5544 latest version, which may be a more recent version, may
5546 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5547 Specific questions about following the standard may be
5548 asked on the <tt>debian-devel</tt> mailing list, or
5549 referred to the FHS mailing list (see the
5550 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5556 <heading>Site-specific programs</heading>
5559 As mandated by the FHS, packages must not place any
5560 files in <file>/usr/local</file>, either by putting them in
5561 the file system archive to be unpacked by <prgn>dpkg</prgn>
5562 or by manipulating them in their maintainer scripts.
5566 However, the package may create empty directories below
5567 <file>/usr/local</file> so that the system administrator knows
5568 where to place site-specific files. These are not
5569 directories <em>in</em> <file>/usr/local</file>, but are
5570 children of directories in <file>/usr/local</file>. These
5571 directories (<file>/usr/local/*/dir/</file>)
5572 should be removed on package removal if they are
5577 Note, that this applies only to directories <em>below</em>
5578 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5579 Packages must not create sub-directories in the directory
5580 <file>/usr/local</file> itself, except those listed in FHS,
5581 section 4.5. However, you may create directories below
5582 them as you wish. You must not remove any of the
5583 directories listed in 4.5, even if you created them.
5587 Since <file>/usr/local</file> can be mounted read-only from a
5588 remote server, these directories must be created and
5589 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5590 maintainer scripts and not be included in the
5591 <file>.deb</file> archive. These scripts must not fail if
5592 either of these operations fail.
5596 For example, the <tt>emacsen-common</tt> package could
5597 contain something like
5598 <example compact="compact">
5599 if [ ! -e /usr/local/share/emacs ]
5601 if mkdir /usr/local/share/emacs 2>/dev/null
5603 chown root:staff /usr/local/share/emacs
5604 chmod 2775 /usr/local/share/emacs
5608 in its <prgn>postinst</prgn> script, and
5609 <example compact="compact">
5610 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5611 rmdir /usr/local/share/emacs 2>/dev/null || true
5613 in the <prgn>prerm</prgn> script. (Note that this form is
5614 used to ensure that if the script is interrupted, the
5615 directory <file>/usr/local/share/emacs</file> will still be
5620 If you do create a directory in <file>/usr/local</file> for
5621 local additions to a package, you should ensure that
5622 settings in <file>/usr/local</file> take precedence over the
5623 equivalents in <file>/usr</file>.
5627 However, because <file>/usr/local</file> and its contents are
5628 for exclusive use of the local administrator, a package
5629 must not rely on the presence or absence of files or
5630 directories in <file>/usr/local</file> for normal operation.
5634 The <file>/usr/local</file> directory itself and all the
5635 subdirectories created by the package should (by default) have
5636 permissions 2775 (group-writable and set-group-id) and be
5637 owned by <tt>root.staff</tt>.
5642 <heading>The system-wide mail directory</heading>
5644 The system-wide mail directory is <file>/var/mail</file>. This
5645 directory is part of the base system and should not owned
5646 by any particular mail agents. The use of the old
5647 location <file>/var/spool/mail</file> is deprecated, even
5648 though the spool may still be physically located there.
5649 To maintain partial upgrade compatibility for systems
5650 which have <file>/var/spool/mail</file> as their physical mail
5651 spool, packages using <file>/var/mail</file> must depend on
5652 either <package>libc6</package> (>= 2.1.3-13), or on
5653 <package>base-files</package> (>= 2.2.0), or on later
5654 versions of either one of these packages.
5660 <heading>Users and groups</heading>
5663 <heading>Introduction</heading>
5665 The Debian system can be configured to use either plain or
5670 Some user ids (UIDs) and group ids (GIDs) are reserved
5671 globally for use by certain packages. Because some
5672 packages need to include files which are owned by these
5673 users or groups, or need the ids compiled into binaries,
5674 these ids must be used on any Debian system only for the
5675 purpose for which they are allocated. This is a serious
5676 restriction, and we should avoid getting in the way of
5677 local administration policies. In particular, many sites
5678 allocate users and/or local system groups starting at 100.
5682 Apart from this we should have dynamically allocated ids,
5683 which should by default be arranged in some sensible
5684 order, but the behavior should be configurable.
5688 Packages other than <tt>base-passwd</tt> must not modify
5689 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5690 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5695 <heading>UID and GID classes</heading>
5697 The UID and GID numbers are divided into classes as
5703 Globally allocated by the Debian project, the same
5704 on every Debian system. These ids will appear in
5705 the <file>passwd</file> and <file>group</file> files of all
5706 Debian systems, new ids in this range being added
5707 automatically as the <tt>base-passwd</tt> package is
5712 Packages which need a single statically allocated
5713 uid or gid should use one of these; their
5714 maintainers should ask the <tt>base-passwd</tt>
5722 Dynamically allocated system users and groups.
5723 Packages which need a user or group, but can have
5724 this user or group allocated dynamically and
5725 differently on each system, should use <tt>adduser
5726 --system</tt> to create the group and/or user.
5727 <prgn>adduser</prgn> will check for the existence of
5728 the user or group, and if necessary choose an unused
5729 id based on the ranges specified in
5730 <file>adduser.conf</file>.
5734 <tag>1000-29999:</tag>
5737 Dynamically allocated user accounts. By default
5738 <prgn>adduser</prgn> will choose UIDs and GIDs for
5739 user accounts in this range, though
5740 <file>adduser.conf</file> may be used to modify this
5745 <tag>30000-59999:</tag>
5750 <tag>60000-64999:</tag>
5753 Globally allocated by the Debian project, but only
5754 created on demand. The ids are allocated centrally
5755 and statically, but the actual accounts are only
5756 created on users' systems on demand.
5760 These ids are for packages which are obscure or
5761 which require many statically-allocated ids. These
5762 packages should check for and create the accounts in
5763 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5764 <prgn>adduser</prgn> if it has this facility) if
5765 necessary. Packages which are likely to require
5766 further allocations should have a "hole" left after
5767 them in the allocation, to give them room to
5772 <tag>65000-65533:</tag>
5780 User <tt>nobody</tt>. The corresponding gid refers
5781 to the group <tt>nogroup</tt>.
5788 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5789 not</em> be used, because it is the error return
5798 <sect id="sysvinit">
5799 <heading>System run levels and <file>init.d</file> scripts</heading>
5801 <sect1 id="/etc/init.d">
5802 <heading>Introduction</heading>
5805 The <file>/etc/init.d</file> directory contains the scripts
5806 executed by <prgn>init</prgn> at boot time and when the
5807 init state (or "runlevel") is changed (see <manref
5808 name="init" section="8">).
5812 There are at least two different, yet functionally
5813 equivalent, ways of handling these scripts. For the sake
5814 of simplicity, this document describes only the symbolic
5815 link method. However, it must not be assumed by maintainer
5816 scripts that this method is being used, and any automated
5817 manipulation of the various runlevel behaviors by
5818 maintainer scripts must be performed using
5819 <prgn>update-rc.d</prgn> as described below and not by
5820 manually installing or removing symlinks. For information
5821 on the implementation details of the other method,
5822 implemented in the <tt>file-rc</tt> package, please refer
5823 to the documentation of that package.
5827 These scripts are referenced by symbolic links in the
5828 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5829 runlevels, <prgn>init</prgn> looks in the directory
5830 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5831 execute, where <tt><var>n</var></tt> is the runlevel that
5832 is being changed to, or <tt>S</tt> for the boot-up
5837 The names of the links all have the form
5838 <file>S<var>mm</var><var>script</var></file> or
5839 <file>K<var>mm</var><var>script</var></file> where
5840 <var>mm</var> is a two-digit number and <var>script</var>
5841 is the name of the script (this should be the same as the
5842 name of the actual script in <file>/etc/init.d</file>).
5846 When <prgn>init</prgn> changes runlevel first the targets
5847 of the links whose names start with a <tt>K</tt> are
5848 executed, each with the single argument <tt>stop</tt>,
5849 followed by the scripts prefixed with an <tt>S</tt>, each
5850 with the single argument <tt>start</tt>. (The links are
5851 those in the <file>/etc/rc<var>n</var>.d</file> directory
5852 corresponding to the new runlevel.) The <tt>K</tt> links
5853 are responsible for killing services and the <tt>S</tt>
5854 link for starting services upon entering the runlevel.
5858 For example, if we are changing from runlevel 2 to
5859 runlevel 3, init will first execute all of the <tt>K</tt>
5860 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5861 all of the <tt>S</tt> prefixed scripts in that directory.
5862 The links starting with <tt>K</tt> will cause the
5863 referred-to file to be executed with an argument of
5864 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5869 The two-digit number <var>mm</var> is used to determine
5870 the order in which to run the scripts: low-numbered links
5871 have their scripts run first. For example, the
5872 <tt>K20</tt> scripts will be executed before the
5873 <tt>K30</tt> scripts. This is used when a certain service
5874 must be started before another. For example, the name
5875 server <prgn>bind</prgn> might need to be started before
5876 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5877 can set up its access lists. In this case, the script
5878 that starts <prgn>bind</prgn> would have a lower number
5879 than the script that starts <prgn>inn</prgn> so that it
5881 <example compact="compact">
5888 The two runlevels 0 (halt) and 6 (reboot) are slightly
5889 different. In these runlevels, the links with an
5890 <tt>S</tt> prefix are still called after those with a
5891 <tt>K</tt> prefix, but they too are called with the single
5892 argument <tt>stop</tt>.
5896 Also, if the script name ends in <tt>.sh</tt>, the script
5897 will be sourced in runlevel <tt>S</tt> rather than being
5898 run in a forked subprocess, but will be explicitly run by
5899 <prgn>sh</prgn> in all other runlevels.
5904 <heading>Writing the scripts</heading>
5907 Packages that include daemons for system services should
5908 place scripts in <file>/etc/init.d</file> to start or stop
5909 services at boot time or during a change of runlevel.
5910 These scripts should be named
5911 <file>/etc/init.d/<var>package</var></file>, and they should
5912 accept one argument, saying what to do:
5915 <tag><tt>start</tt></tag>
5916 <item>start the service,</item>
5918 <tag><tt>stop</tt></tag>
5919 <item>stop the service,</item>
5921 <tag><tt>restart</tt></tag>
5922 <item>stop and restart the service if it's already running,
5923 otherwise start the service</item>
5925 <tag><tt>reload</tt></tag>
5926 <item><p>cause the configuration of the service to be
5927 reloaded without actually stopping and restarting
5930 <tag><tt>force-reload</tt></tag>
5931 <item>cause the configuration to be reloaded if the
5932 service supports this, otherwise restart the
5936 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5937 <tt>force-reload</tt> options should be supported by all
5938 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5943 The <file>init.d</file> scripts must ensure that they will
5944 behave sensibly if invoked with <tt>start</tt> when the
5945 service is already running, or with <tt>stop</tt> when it
5946 isn't, and that they don't kill unfortunately-named user
5947 processes. The best way to achieve this is usually to use
5948 <prgn>start-stop-daemon</prgn>.
5952 If a service reloads its configuration automatically (as
5953 in the case of <prgn>cron</prgn>, for example), the
5954 <tt>reload</tt> option of the <file>init.d</file> script
5955 should behave as if the configuration has been reloaded
5960 The <file>/etc/init.d</file> scripts must be treated as
5961 configuration files, either (if they are present in the
5962 package, that is, in the .deb file) by marking them as
5963 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5964 by managing them correctly in the maintainer scripts (see
5965 <ref id="config-files">). This is important since we want
5966 to give the local system administrator the chance to adapt
5967 the scripts to the local system, e.g., to disable a
5968 service without de-installing the package, or to specify
5969 some special command line options when starting a service,
5970 while making sure their changes aren't lost during the next
5975 These scripts should not fail obscurely when the
5976 configuration files remain but the package has been
5977 removed, as configuration files remain on the system after
5978 the package has been removed. Only when <prgn>dpkg</prgn>
5979 is executed with the <tt>--purge</tt> option will
5980 configuration files be removed. In particular, as the
5981 <file>/etc/init.d/<var>package</var></file> script itself is
5982 usually a <tt>conffile</tt>, it will remain on the system
5983 if the package is removed but not purged. Therefore, you
5984 should include a <tt>test</tt> statement at the top of the
5986 <example compact="compact">
5987 test -f <var>program-executed-later-in-script</var> || exit 0
5992 Often there are some variables in the <file>init.d</file>
5993 scripts whose values control the behavior of the scripts,
5994 and which a system administrator is likely to want to
5995 change. As the scripts themselves are frequently
5996 <tt>conffile</tt>s, modifying them requires that the
5997 administrator merge in their changes each time the package
5998 is upgraded and the <tt>conffile</tt> changes. To ease
5999 the burden on the system administrator, such configurable
6000 values should not be placed directly in the script.
6001 Instead, they should be placed in a file in
6002 <file>/etc/default</file>, which typically will have the same
6003 base name as the <file>init.d</file> script. This extra file
6004 should be sourced by the script when the script runs. It
6005 must contain only variable settings and comments in SUSv3
6006 <prgn>sh</prgn> format. It may either be a
6007 <tt>conffile</tt> or a configuration file maintained by
6008 the package maintainer scripts. See <ref id="config-files">
6013 To ensure that vital configurable values are always
6014 available, the <file>init.d</file> script should set default
6015 values for each of the shell variables it uses, either
6016 before sourcing the <file>/etc/default/</file> file or
6017 afterwards using something like the <tt>:
6018 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6019 script must behave sensibly and not fail if the
6020 <file>/etc/default</file> file is deleted.
6025 <heading>Interfacing with the initscript system</heading>
6028 Maintainers should use the abstraction layer provided by
6029 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6030 programs to deal with initscripts in their packages'
6031 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6032 and <prgn>postrm</prgn>.
6036 Directly managing the /etc/rc?.d links and directly
6037 invoking the <file>/etc/init.d/</file> initscripts should
6038 be done only by packages providing the initscript
6039 subsystem (such as <prgn>sysv-rc</prgn> and
6040 <prgn>file-rc</prgn>).
6044 <heading>Managing the links</heading>
6047 The program <prgn>update-rc.d</prgn> is provided for
6048 package maintainers to arrange for the proper creation and
6049 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6050 or their functional equivalent if another method is being
6051 used. This may be used by maintainers in their packages'
6052 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6056 You must not include any <file>/etc/rc<var>n</var>.d</file>
6057 symbolic links in the actual archive or manually create or
6058 remove the symbolic links in maintainer scripts; you must
6059 use the <prgn>update-rc.d</prgn> program instead. (The
6060 former will fail if an alternative method of maintaining
6061 runlevel information is being used.) You must not include
6062 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6063 in the archive either. (Only the <tt>sysvinit</tt>
6068 By default <prgn>update-rc.d</prgn> will start services in
6069 each of the multi-user state runlevels (2, 3, 4, and 5)
6070 and stop them in the halt runlevel (0), the single-user
6071 runlevel (1) and the reboot runlevel (6). The system
6072 administrator will have the opportunity to customize
6073 runlevels by simply adding, moving, or removing the
6074 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6075 symbolic links are being used, or by modifying
6076 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6081 To get the default behavior for your package, put in your
6082 <prgn>postinst</prgn> script
6083 <example compact="compact">
6084 update-rc.d <var>package</var> defaults
6086 and in your <prgn>postrm</prgn>
6087 <example compact="compact">
6088 if [ "$1" = purge ]; then
6089 update-rc.d <var>package</var> remove
6091 </example>. Note that if your package changes runlevels
6092 or priority, you may have to remove and recreate the links,
6093 since otherwise the old links may persist. Refer to the
6094 documentation of <prgn>update-rc.d</prgn>.
6098 This will use a default sequence number of 20. If it does
6099 not matter when or in which order the <file>init.d</file>
6100 script is run, use this default. If it does, then you
6101 should talk to the maintainer of the <prgn>sysvinit</prgn>
6102 package or post to <tt>debian-devel</tt>, and they will
6103 help you choose a number.
6107 For more information about using <tt>update-rc.d</tt>,
6108 please consult its man page <manref name="update-rc.d"
6114 <heading>Running initscripts</heading>
6116 The program <prgn>invoke-rc.d</prgn> is provided to make
6117 it easier for package maintainers to properly invoke an
6118 initscript, obeying runlevel and other locally-defined
6119 constraints that might limit a package's right to start,
6120 stop and otherwise manage services. This program may be
6121 used by maintainers in their packages' scripts.
6125 The package maintainer scripts must use
6126 <prgn>invoke-rc.d</prgn> to invoke the
6127 <file>/etc/init.d/*</file> initscripts, instead of
6128 calling them directly.
6132 By default, <prgn>invoke-rc.d</prgn> will pass any
6133 action requests (start, stop, reload, restart...) to the
6134 <file>/etc/init.d</file> script, filtering out requests
6135 to start or restart a service out of its intended
6140 Most packages will simply need to change:
6141 <example compact="compact">/etc/init.d/<package>
6142 <action></example> in their <prgn>postinst</prgn>
6143 and <prgn>prerm</prgn> scripts to:
6144 <example compact="compact">
6145 if which invoke-rc.d >/dev/null 2>&1; then
6146 invoke-rc.d <var>package</var> <action>
6148 /etc/init.d/<var>package</var> <action>
6154 A package should register its initscript services using
6155 <prgn>update-rc.d</prgn> before it tries to invoke them
6156 using <prgn>invoke-rc.d</prgn>. Invocation of
6157 unregistered services may fail.
6161 For more information about using
6162 <prgn>invoke-rc.d</prgn>, please consult its man page
6163 <manref name="invoke-rc.d" section="8">.
6169 <heading>Boot-time initialization</heading>
6172 There used to be another directory, <file>/etc/rc.boot</file>,
6173 which contained scripts which were run once per machine
6174 boot. This has been deprecated in favour of links from
6175 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6176 described in <ref id="/etc/init.d">. Packages must not
6177 place files in <file>/etc/rc.boot</file>.
6182 <heading>Example</heading>
6185 An example on which you can base your
6186 <file>/etc/init.d</file> scripts is found in
6187 <file>/etc/init.d/skeleton</file>.
6194 <heading>Console messages from <file>init.d</file> scripts</heading>
6197 This section describes the formats to be used for messages
6198 written to standard output by the <file>/etc/init.d</file>
6199 scripts. The intent is to improve the consistency of
6200 Debian's startup and shutdown look and feel. For this
6201 reason, please look very carefully at the details. We want
6202 the messages to have the same format in terms of wording,
6203 spaces, punctuation and case of letters.
6207 Here is a list of overall rules that should be used for
6208 messages generated by <file>/etc/init.d</file> scripts.
6214 The message should fit in one line (fewer than 80
6215 characters), start with a capital letter and end with
6216 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6220 If the script is performing some time consuming task in
6221 the background (not merely starting or stopping a
6222 program, for instance), an ellipsis (three dots:
6223 <tt>...</tt>) should be output to the screen, with no
6224 leading or tailing whitespace or line feeds.
6228 The messages should appear as if the computer is telling
6229 the user what it is doing (politely :-), but should not
6230 mention "it" directly. For example, instead of:
6231 <example compact="compact">
6232 I'm starting network daemons: nfsd mountd.
6234 the message should say
6235 <example compact="compact">
6236 Starting network daemons: nfsd mountd.
6243 <tt>init.d</tt> script should use the following standard
6244 message formats for the situations enumerated below.
6250 <p>When daemons are started</p>
6253 If the script starts one or more daemons, the output
6254 should look like this (a single line, no leading
6256 <example compact="compact">
6257 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6259 The <var>description</var> should describe the
6260 subsystem the daemon or set of daemons are part of,
6261 while <var>daemon-1</var> up to <var>daemon-n</var>
6262 denote each daemon's name (typically the file name of
6267 For example, the output of <file>/etc/init.d/lpd</file>
6269 <example compact="compact">
6270 Starting printer spooler: lpd.
6275 This can be achieved by saying
6276 <example compact="compact">
6277 echo -n "Starting printer spooler: lpd"
6278 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6281 in the script. If there are more than one daemon to
6282 start, the output should look like this:
6283 <example compact="compact">
6284 echo -n "Starting remote file system services:"
6285 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6286 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6287 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6290 This makes it possible for the user to see what is
6291 happening and when the final daemon has been started.
6292 Care should be taken in the placement of white spaces:
6293 in the example above the system administrators can
6294 easily comment out a line if they don't want to start
6295 a specific daemon, while the displayed message still
6301 <p>When a system parameter is being set</p>
6304 If you have to set up different system parameters
6305 during the system boot, you should use this format:
6306 <example compact="compact">
6307 Setting <var>parameter</var> to "<var>value</var>".
6312 You can use a statement such as the following to get
6314 <example compact="compact">
6315 echo "Setting DNS domainname to \"$domainname\"."
6320 Note that the same symbol (<tt>"</tt>) is used for the left
6321 and right quotation marks. A grave accent (<tt>`</tt>) is
6322 not a quote character; neither is an apostrophe
6328 <p>When a daemon is stopped or restarted</p>
6331 When you stop or restart a daemon, you should issue a
6332 message identical to the startup message, except that
6333 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6334 or <tt>Restarting</tt> respectively.
6338 For example, stopping the printer daemon will look like
6340 <example compact="compact">
6341 Stopping printer spooler: lpd.
6347 <p>When something is executed</p>
6350 There are several examples where you have to run a
6351 program at system startup or shutdown to perform a
6352 specific task, for example, setting the system's clock
6353 using <prgn>netdate</prgn> or killing all processes
6354 when the system shuts down. Your message should look
6356 <example compact="compact">
6357 Doing something very useful...done.
6359 You should print the <tt>done.</tt> immediately after
6360 the job has been completed, so that the user is
6361 informed why they have to wait. You can get this
6363 <example compact="compact">
6364 echo -n "Doing something very useful..."
6373 <p>When the configuration is reloaded</p>
6376 When a daemon is forced to reload its configuration
6377 files you should use the following format:
6378 <example compact="compact">
6379 Reloading <var>description</var> configuration...done.
6381 where <var>description</var> is the same as in the
6382 daemon starting message.
6390 <heading>Cron jobs</heading>
6393 Packages must not modify the configuration file
6394 <file>/etc/crontab</file>, and they must not modify the files in
6395 <file>/var/spool/cron/crontabs</file>.</p>
6398 If a package wants to install a job that has to be executed
6399 via cron, it should place a file with the name of the
6400 package in one or more of the following directories:
6401 <example compact="compact">
6407 As these directory names imply, the files within them are
6408 executed on an hourly, daily, weekly, or monthly basis,
6409 respectively. The exact times are listed in
6410 <file>/etc/crontab</file>.</p>
6413 All files installed in any of these directories must be
6414 scripts (e.g., shell scripts or Perl scripts) so that they
6415 can easily be modified by the local system administrator.
6416 In addition, they must be treated as configuration files.
6420 If a certain job has to be executed at some other frequency or
6421 at a specific time, the package should install a file
6422 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6423 same syntax as <file>/etc/crontab</file> and is processed by
6424 <prgn>cron</prgn> automatically. The file must also be
6425 treated as a configuration file. (Note that entries in the
6426 <file>/etc/cron.d</file> directory are not handled by
6427 <prgn>anacron</prgn>. Thus, you should only use this
6428 directory for jobs which may be skipped if the system is not
6432 The scripts or crontab entries in these directories should
6433 check if all necessary programs are installed before they
6434 try to execute them. Otherwise, problems will arise when a
6435 package was removed but not purged since configuration files
6436 are kept on the system in this situation.</p>
6440 <heading>Menus</heading>
6443 The Debian <tt>menu</tt> package provides a standard
6444 interface between packages providing applications and
6445 <em>menu programs</em> (either X window managers or
6446 text-based menu programs such as <prgn>pdmenu</prgn>).
6450 All packages that provide applications that need not be
6451 passed any special command line arguments for normal
6452 operation should register a menu entry for those
6453 applications, so that users of the <tt>menu</tt> package
6454 will automatically get menu entries in their window
6455 managers, as well in shells like <tt>pdmenu</tt>.
6459 Menu entries should follow the current menu policy.
6463 The menu policy can be found in the <tt>menu-policy</tt>
6464 files in the <tt>debian-policy</tt> package.
6465 It is also available from the Debian web mirrors at
6466 <tt><url name="/doc/packaging-manuals/menu-policy/"
6467 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6471 Please also refer to the <em>Debian Menu System</em>
6472 documentation that comes with the <package>menu</package>
6473 package for information about how to register your
6479 <heading>Multimedia handlers</heading>
6482 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6483 is a mechanism for encoding files and data streams and
6484 providing meta-information about them, in particular their
6485 type (e.g. audio or video) and format (e.g. PNG, HTML,
6490 Registration of MIME type handlers allows programs like mail
6491 user agents and web browsers to invoke these handlers to
6492 view, edit or display MIME types they don't support directly.
6496 Packages which provide the ability to view/show/play,
6497 compose, edit or print MIME types should register themselves
6498 as such following the current MIME support policy.
6502 The MIME support policy can be found in the <tt>mime-policy</tt>
6503 files in the <tt>debian-policy</tt> package.
6504 It is also available from the Debian web mirrors at
6505 <tt><url name="/doc/packaging-manuals/mime-policy/"
6506 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6512 <heading>Keyboard configuration</heading>
6515 To achieve a consistent keyboard configuration so that all
6516 applications interpret a keyboard event the same way, all
6517 programs in the Debian distribution must be configured to
6518 comply with the following guidelines.
6522 The following keys must have the specified interpretations:
6525 <tag><tt><--</tt></tag>
6526 <item>delete the character to the left of the cursor</item>
6528 <tag><tt>Delete</tt></tag>
6529 <item>delete the character to the right of the cursor</item>
6531 <tag><tt>Control+H</tt></tag>
6532 <item>emacs: the help prefix</item>
6535 The interpretation of any keyboard events should be
6536 independent of the terminal that is used, be it a virtual
6537 console, an X terminal emulator, an rlogin/telnet session,
6542 The following list explains how the different programs
6543 should be set up to achieve this:
6549 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6553 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6557 X translations are set up to make
6558 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6559 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6560 is the vt220 escape code for the "delete character"
6561 key). This must be done by loading the X resources
6562 using <prgn>xrdb</prgn> on all local X displays, not
6563 using the application defaults, so that the
6564 translation resources used correspond to the
6565 <prgn>xmodmap</prgn> settings.
6569 The Linux console is configured to make
6570 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6571 generate <tt>ESC [ 3 ~</tt>.
6575 X applications are configured so that <tt><</tt>
6576 deletes left, and <tt>Delete</tt> deletes right. Motif
6577 applications already work like this.
6581 Terminals should have <tt>stty erase ^?</tt> .
6585 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6586 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6587 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6591 Emacs is programmed to map <tt>KB_Backspace</tt> or
6592 the <tt>stty erase</tt> character to
6593 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6594 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6595 <tt>^H</tt> to <tt>help</tt> as always.
6599 Other applications use the <tt>stty erase</tt>
6600 character and <tt>kdch1</tt> for the two delete keys,
6601 with ASCII DEL being "delete previous character" and
6602 <tt>kdch1</tt> being "delete character under
6610 This will solve the problem except for the following
6617 Some terminals have a <tt><--</tt> key that cannot
6618 be made to produce anything except <tt>^H</tt>. On
6619 these terminals Emacs help will be unavailable on
6620 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6621 character takes precedence in Emacs, and has been set
6622 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6623 available) can be used instead.
6627 Some operating systems use <tt>^H</tt> for <tt>stty
6628 erase</tt>. However, modern telnet versions and all
6629 rlogin versions propagate <tt>stty</tt> settings, and
6630 almost all UNIX versions honour <tt>stty erase</tt>.
6631 Where the <tt>stty</tt> settings are not propagated
6632 correctly, things can be made to work by using
6633 <tt>stty</tt> manually.
6637 Some systems (including previous Debian versions) use
6638 <prgn>xmodmap</prgn> to arrange for both
6639 <tt><--</tt> and <tt>Delete</tt> to generate
6640 <tt>KB_Delete</tt>. We can change the behavior of
6641 their X clients using the same X resources that we use
6642 to do it for our own clients, or configure our clients
6643 using their resources when things are the other way
6644 around. On displays configured like this
6645 <tt>Delete</tt> will not work, but <tt><--</tt>
6650 Some operating systems have different <tt>kdch1</tt>
6651 settings in their <tt>terminfo</tt> database for
6652 <tt>xterm</tt> and others. On these systems the
6653 <tt>Delete</tt> key will not work correctly when you
6654 log in from a system conforming to our policy, but
6655 <tt><--</tt> will.
6662 <heading>Environment variables</heading>
6665 A program must not depend on environment variables to get
6666 reasonable defaults. (That's because these environment
6667 variables would have to be set in a system-wide
6668 configuration file like <file>/etc/profile</file>, which is not
6669 supported by all shells.)
6673 If a program usually depends on environment variables for its
6674 configuration, the program should be changed to fall back to
6675 a reasonable default configuration if these environment
6676 variables are not present. If this cannot be done easily
6677 (e.g., if the source code of a non-free program is not
6678 available), the program must be replaced by a small
6679 "wrapper" shell script which sets the environment variables
6680 if they are not already defined, and calls the original program.
6684 Here is an example of a wrapper script for this purpose:
6686 <example compact="compact">
6688 BAR=${BAR:-/var/lib/fubar}
6690 exec /usr/lib/foo/foo "$@"
6695 Furthermore, as <file>/etc/profile</file> is a configuration
6696 file of the <prgn>base-files</prgn> package, other packages must
6697 not put any environment variables or other commands into that
6702 <sect id="doc-base">
6703 <heading>Registering Documents using doc-base</heading>
6706 The <package>doc-base</package> package implements a
6707 flexible mechanism for handling and presenting
6708 documentation. The recommended practice is for every Debian
6709 package that provides online documentation (other than just
6710 manual pages) to register these documents with
6711 <package>doc-base</package> by installing a
6712 <package>doc-base</package> control file via the
6713 <prgn/install-docs/ script at installation time and
6714 de-register the manuals again when the package is removed.
6717 Please refer to the documentation that comes with the
6718 <package>doc-base</package> package for information and
6727 <heading>Files</heading>
6730 <heading>Binaries</heading>
6733 Two different packages must not install programs with
6734 different functionality but with the same filenames. (The
6735 case of two programs having the same functionality but
6736 different implementations is handled via "alternatives" or
6737 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6738 <ref id="conflicts"> respectively.) If this case happens,
6739 one of the programs must be renamed. The maintainers should
6740 report this to the <tt>debian-devel</tt> mailing list and
6741 try to find a consensus about which program will have to be
6742 renamed. If a consensus cannot be reached, <em>both</em>
6743 programs must be renamed.
6747 By default, when a package is being built, any binaries
6748 created should include debugging information, as well as
6749 being compiled with optimization. You should also turn on
6750 as many reasonable compilation warnings as possible; this
6751 makes life easier for porters, who can then look at build
6752 logs for possible problems. For the C programming language,
6753 this means the following compilation parameters should be
6755 <example compact="compact">
6757 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6759 INSTALL = install -s # (or use strip on the files in debian/tmp)
6764 Note that by default all installed binaries should be stripped,
6765 either by using the <tt>-s</tt> flag to
6766 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6767 the binaries after they have been copied into
6768 <file>debian/tmp</file> but before the tree is made into a
6773 Although binaries in the build tree should be compiled with
6774 debugging information by default, it can often be difficult to
6775 debug programs if they are also subjected to compiler
6776 optimization. For this reason, it is recommended to support the
6777 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6778 (see <ref id="debianrules-options">). This variable can contain
6779 several flags to change how a package is compiled and built.
6783 It is up to the package maintainer to decide what
6784 compilation options are best for the package. Certain
6785 binaries (such as computationally-intensive programs) will
6786 function better with certain flags (<tt>-O3</tt>, for
6787 example); feel free to use them. Please use good judgment
6788 here. Don't use flags for the sake of it; only use them
6789 if there is good reason to do so. Feel free to override
6790 the upstream author's ideas about which compilation
6791 options are best: they are often inappropriate for our
6797 <sect id="libraries">
6798 <heading>Libraries</heading>
6801 If the package is <strong>architecture: any</strong>, then
6802 the shared library compilation and linking flags must have
6803 <tt>-fPIC</tt>, or the package shall not build on some of
6804 the supported architectures<footnote>
6806 If you are using GCC, <tt>-fPIC</tt> produces code with
6807 relocatable position independent code, which is required for
6808 most architectures to create a shared library, with i386 and
6809 perhaps some others where non position independent code is
6810 permitted in a shared library.
6813 Position independent code may have a performance penalty,
6814 especially on <tt>i386</tt>. However, in most cases the
6815 speed penalty must be measured against the memory wasted on
6816 the few architectures where non position independent code is
6819 </footnote>. Any exception to this rule must be discussed on
6820 the mailing list <em>debian-devel@lists.debian.org</em>, and
6821 a rough consensus obtained. The reasons for not compiling
6822 with <tt>-fPIC</tt> flag must be recorded in the file
6823 <tt>README.Debian</tt>, and care must be taken to either
6824 restrict the architecture or arrange for <tt>-fPIC</tt> to
6825 be used on architectures where it is required.<footnote>
6827 Some of the reasons why this might be required is if the
6828 library contains hand crafted assembly code that is not
6829 relocatable, the speed penalty is excessive for compute
6830 intensive libs, and similar reasons.
6835 As to the static libraries, the common case is not to have
6836 relocatable code, since there is no benefit, unless in specific
6837 cases; therefore the static version must not be compiled
6838 with the <tt>-fPIC</tt> flag. Any exception to this rule
6839 should be discussed on the mailing list
6840 <em>debian-devel@lists.debian.org</em>, and the reasons for
6841 compiling with the <tt>-fPIC</tt> flag must be recorded in
6842 the file <tt>README.Debian</tt>. <footnote>
6844 Some of the reasons for linking static libraries with
6845 the <tt>-fPIC</tt> flag are if, for example, one needs a
6846 Perl API for a library that is under rapid development,
6847 and has an unstable API, so shared libraries are
6848 pointless at this phase of the library's development. In
6849 that case, since Perl needs a library with relocatable
6850 code, it may make sense to create a static library with
6851 relocatable code. Another reason cited is if you are
6852 distilling various libraries into a common shared
6853 library, like <tt>mklibs</tt> does in the Debian
6859 In other words, if both a shared and a static library is
6860 being built, each source unit (<tt>*.c</tt>, for example,
6861 for C files) will need to be compiled twice, for the normal
6865 You must specify the gcc option <tt>-D_REENTRANT</tt>
6866 when building a library (either static or shared) to make
6867 the library compatible with LinuxThreads.
6871 Although not enforced by the build tools, shared libraries
6872 must be linked against all libraries that they use symbols from
6873 in the same way that binaries are. This ensures the correct
6874 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6875 system and guarantees that all libraries can be safely opened
6876 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6877 option <tt>-Wl,-z,defs</tt> when building a shared library.
6878 Since this option enforces symbol resolution at build time,
6879 a missing library reference will be caught early as a fatal
6884 All installed shared libraries should be stripped with
6885 <example compact="compact">
6886 strip --strip-unneeded <var>your-lib</var>
6888 (The option <tt>--strip-unneeded</tt> makes
6889 <prgn>strip</prgn> remove only the symbols which aren't
6890 needed for relocation processing.) Shared libraries can
6891 function perfectly well when stripped, since the symbols for
6892 dynamic linking are in a separate part of the ELF object
6894 You might also want to use the options
6895 <tt>--remove-section=.comment</tt> and
6896 <tt>--remove-section=.note</tt> on both shared libraries
6897 and executables, and <tt>--strip-debug</tt> on static
6903 Note that under some circumstances it may be useful to
6904 install a shared library unstripped, for example when
6905 building a separate package to support debugging.
6909 Shared object files (often <file>.so</file> files) that are not
6910 public libraries, that is, they are not meant to be linked
6911 to by third party executables (binaries of other packages),
6912 should be installed in subdirectories of the
6913 <file>/usr/lib</file> directory. Such files are exempt from the
6914 rules that govern ordinary shared libraries, except that
6915 they must not be installed executable and should be
6917 A common example are the so-called "plug-ins",
6918 internal shared objects that are dynamically loaded by
6919 programs using <manref name="dlopen" section="3">.
6924 Packages containing shared libraries that may be linked to
6925 by other packages' binaries, but which for some
6926 <em>compelling</em> reason can not be installed in
6927 <file>/usr/lib</file> directory, may install the shared library
6928 files in subdirectories of the <file>/usr/lib</file> directory,
6929 in which case they should arrange to add that directory in
6930 <file>/etc/ld.so.conf</file> in the package's post-installation
6931 script, and remove it in the package's post-removal script.
6935 An ever increasing number of packages are using
6936 <prgn>libtool</prgn> to do their linking. The latest GNU
6937 libtools (>= 1.3a) can take advantage of the metadata in the
6938 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6939 files). The main advantage of <prgn>libtool</prgn>'s
6940 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6941 store and subsequently access metadata with respect to the
6942 libraries it builds. <prgn>libtool</prgn> will search for
6943 those files, which contain a lot of useful information about
6944 a library (such as library dependency information for static
6945 linking). Also, they're <em>essential</em> for programs
6946 using <tt>libltdl</tt>.<footnote>
6947 Although <prgn>libtool</prgn> is fully capable of
6948 linking against shared libraries which don't have
6949 <tt>.la</tt> files, as it is a mere shell script it can
6950 add considerably to the build time of a
6951 <prgn>libtool</prgn>-using package if that shell script
6952 has to derive all this information from first principles
6953 for each library every time it is linked. With the
6954 advent of <prgn>libtool</prgn> version 1.4 (and to a
6955 lesser extent <prgn>libtool</prgn> version 1.3), the
6956 <file>.la</file> files also store information about
6957 inter-library dependencies which cannot necessarily be
6958 derived after the <file>.la</file> file is deleted.
6963 Packages that use <prgn>libtool</prgn> to create shared
6964 libraries should include the <file>.la</file> files in the
6965 <tt>-dev</tt> package, unless the package relies on
6966 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6967 the <tt>.la</tt> files must go in the run-time library
6972 You must make sure that you use only released versions of
6973 shared libraries to build your packages; otherwise other
6974 users will not be able to run your binaries
6975 properly. Producing source packages that depend on
6976 unreleased compilers is also usually a bad
6983 <heading>Shared libraries</heading>
6985 This section has moved to <ref id="sharedlibs">.
6991 <heading>Scripts</heading>
6994 All command scripts, including the package maintainer
6995 scripts inside the package and used by <prgn>dpkg</prgn>,
6996 should have a <tt>#!</tt> line naming the shell to be used
7001 In the case of Perl scripts this should be
7002 <tt>#!/usr/bin/perl</tt>.
7006 When scripts are installed into a directory in the system
7007 PATH, the script name should not include an extension such
7008 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7009 language currently used to implement it.
7012 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7013 should almost certainly start with <tt>set -e</tt> so that
7014 errors are detected. Every script should use
7015 <tt>set -e</tt> or check the exit status of <em>every</em>
7020 Scripts may assume that <file>/bin/sh</file> implements the
7021 SUSv3 Shell Command Language<footnote>
7022 Single UNIX Specification, version 3, which is also IEEE
7023 1003.1-2004 (POSIX), and is available on the World Wide Web
7024 from <url id="http://www.unix.org/version3/online.html"
7025 name="The Open Group"> after free
7026 registration.</footnote>
7027 plus the following additional features not mandated by
7029 These features are in widespread use in the Linux community
7030 and are implemented in all of bash, dash, and ksh, the most
7031 common shells users may wish to use as <file>/bin/sh</file>.
7034 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7035 must not generate a newline.</item>
7036 <item><tt>test</tt>, if implemented as a shell built-in, must
7037 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7039 <item><tt>local</tt> to create a scoped variable must be
7040 supported; however, <tt>local</tt> may or may not preserve
7041 the variable value from an outer scope and may or may not
7042 support arguments more complex than simple variables. Only
7054 If a shell script requires non-SUSv3 features from the shell
7055 interpreter other than those listed above, the appropriate shell
7056 must be specified in the first line of the script (e.g.,
7057 <tt>#!/bin/bash</tt>) and the package must depend on the package
7058 providing the shell (unless the shell package is marked
7059 "Essential", as in the case of <prgn>bash</prgn>).
7063 You may wish to restrict your script to SUSv3 features plus the
7064 above set when possible so that it may use <file>/bin/sh</file>
7065 as its interpreter. If your script works with <prgn>dash</prgn>
7066 (originally called <prgn>ash</prgn>), it probably complies with
7067 the above requirements, but if you are in doubt, use
7068 <file>/bin/bash</file>.
7072 Perl scripts should check for errors when making any
7073 system calls, including <tt>open</tt>, <tt>print</tt>,
7074 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7078 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7079 scripting languages. See <em>Csh Programming Considered
7080 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7081 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7082 If an upstream package comes with <prgn>csh</prgn> scripts
7083 then you must make sure that they start with
7084 <tt>#!/bin/csh</tt> and make your package depend on the
7085 <prgn>c-shell</prgn> virtual package.
7089 Any scripts which create files in world-writeable
7090 directories (e.g., in <file>/tmp</file>) must use a
7091 mechanism which will fail atomically if a file with the same
7092 name already exists.
7096 The Debian base system provides the <prgn>tempfile</prgn>
7097 and <prgn>mktemp</prgn> utilities for use by scripts for
7104 <heading>Symbolic links</heading>
7107 In general, symbolic links within a top-level directory
7108 should be relative, and symbolic links pointing from one
7109 top-level directory into another should be absolute. (A
7110 top-level directory is a sub-directory of the root
7111 directory <file>/</file>.)
7115 In addition, symbolic links should be specified as short as
7116 possible, i.e., link targets like <file>foo/../bar</file> are
7121 Note that when creating a relative link using
7122 <prgn>ln</prgn> it is not necessary for the target of the
7123 link to exist relative to the working directory you're
7124 running <prgn>ln</prgn> from, nor is it necessary to change
7125 directory to the directory where the link is to be made.
7126 Simply include the string that should appear as the target
7127 of the link (this will be a pathname relative to the
7128 directory in which the link resides) as the first argument
7133 For example, in your <prgn>Makefile</prgn> or
7134 <file>debian/rules</file>, you can do things like:
7135 <example compact="compact">
7136 ln -fs gcc $(prefix)/bin/cc
7137 ln -fs gcc debian/tmp/usr/bin/cc
7138 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7139 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7144 A symbolic link pointing to a compressed file should always
7145 have the same file extension as the referenced file. (For
7146 example, if a file <file>foo.gz</file> is referenced by a
7147 symbolic link, the filename of the link has to end with
7148 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7153 <heading>Device files</heading>
7156 Packages must not include device files in the package file
7161 If a package needs any special device files that are not
7162 included in the base system, it must call
7163 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7164 after notifying the user<footnote>
7165 This notification could be done via a (low-priority)
7166 debconf message, or an echo (printf) statement.
7171 Packages must not remove any device files in the
7172 <prgn>postrm</prgn> or any other script. This is left to the
7173 system administrator.
7177 Debian uses the serial devices
7178 <file>/dev/ttyS*</file>. Programs using the old
7179 <file>/dev/cu*</file> devices should be changed to use
7180 <file>/dev/ttyS*</file>.
7184 <sect id="config-files">
7185 <heading>Configuration files</heading>
7188 <heading>Definitions</heading>
7192 <tag>configuration file</tag>
7194 A file that affects the operation of a program, or
7195 provides site- or host-specific information, or
7196 otherwise customizes the behavior of a program.
7197 Typically, configuration files are intended to be
7198 modified by the system administrator (if needed or
7199 desired) to conform to local policy or to provide
7200 more useful site-specific behavior.
7203 <tag><tt>conffile</tt></tag>
7205 A file listed in a package's <tt>conffiles</tt>
7206 file, and is treated specially by <prgn>dpkg</prgn>
7207 (see <ref id="configdetails">).
7213 The distinction between these two is important; they are
7214 not interchangeable concepts. Almost all
7215 <tt>conffile</tt>s are configuration files, but many
7216 configuration files are not <tt>conffiles</tt>.
7220 As noted elsewhere, <file>/etc/init.d</file> scripts,
7221 <file>/etc/default</file> files, scripts installed in
7222 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7223 configuration installed in <file>/etc/cron.d</file> must be
7224 treated as configuration files. In general, any script that
7225 embeds configuration information is de-facto a configuration
7226 file and should be treated as such.
7231 <heading>Location</heading>
7234 Any configuration files created or used by your package
7235 must reside in <file>/etc</file>. If there are several,
7236 consider creating a subdirectory of <file>/etc</file>
7237 named after your package.
7241 If your package creates or uses configuration files
7242 outside of <file>/etc</file>, and it is not feasible to modify
7243 the package to use <file>/etc</file> directly, put the files
7244 in <file>/etc</file> and create symbolic links to those files
7245 from the location that the package requires.
7250 <heading>Behavior</heading>
7253 Configuration file handling must conform to the following
7255 <list compact="compact">
7257 local changes must be preserved during a package
7261 configuration files must be preserved when the
7262 package is removed, and only deleted when the
7269 The easy way to achieve this behavior is to make the
7270 configuration file a <tt>conffile</tt>. This is
7271 appropriate only if it is possible to distribute a default
7272 version that will work for most installations, although
7273 some system administrators may choose to modify it. This
7274 implies that the default version will be part of the
7275 package distribution, and must not be modified by the
7276 maintainer scripts during installation (or at any other
7281 In order to ensure that local changes are preserved
7282 correctly, no package may contain or make hard links to
7283 conffiles.<footnote>
7284 Rationale: There are two problems with hard links.
7285 The first is that some editors break the link while
7286 editing one of the files, so that the two files may
7287 unwittingly become unlinked and different. The second
7288 is that <prgn>dpkg</prgn> might break the hard link
7289 while upgrading <tt>conffile</tt>s.
7294 The other way to do it is via the maintainer scripts. In
7295 this case, the configuration file must not be listed as a
7296 <tt>conffile</tt> and must not be part of the package
7297 distribution. If the existence of a file is required for
7298 the package to be sensibly configured it is the
7299 responsibility of the package maintainer to provide
7300 maintainer scripts which correctly create, update and
7301 maintain the file and remove it on purge. (See <ref
7302 id="maintainerscripts"> for more information.) These
7303 scripts must be idempotent (i.e., must work correctly if
7304 <prgn>dpkg</prgn> needs to re-run them due to errors
7305 during installation or removal), must cope with all the
7306 variety of ways <prgn>dpkg</prgn> can call maintainer
7307 scripts, must not overwrite or otherwise mangle the user's
7308 configuration without asking, must not ask unnecessary
7309 questions (particularly during upgrades), and must
7310 otherwise be good citizens.
7314 The scripts are not required to configure every possible
7315 option for the package, but only those necessary to get
7316 the package running on a given system. Ideally the
7317 sysadmin should not have to do any configuration other
7318 than that done (semi-)automatically by the
7319 <prgn>postinst</prgn> script.
7323 A common practice is to create a script called
7324 <file><var>package</var>-configure</file> and have the
7325 package's <prgn>postinst</prgn> call it if and only if the
7326 configuration file does not already exist. In certain
7327 cases it is useful for there to be an example or template
7328 file which the maintainer scripts use. Such files should
7329 be in <file>/usr/share/<var>package</var></file> or
7330 <file>/usr/lib/<var>package</var></file> (depending on whether
7331 they are architecture-independent or not). There should
7332 be symbolic links to them from
7333 <file>/usr/share/doc/<var>package</var>/examples</file> if
7334 they are examples, and should be perfectly ordinary
7335 <prgn>dpkg</prgn>-handled files (<em>not</em>
7336 configuration files).
7340 These two styles of configuration file handling must
7341 not be mixed, for that way lies madness:
7342 <prgn>dpkg</prgn> will ask about overwriting the file
7343 every time the package is upgraded.
7348 <heading>Sharing configuration files</heading>
7351 Packages which specify the same file as a
7352 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7353 with each other. (This is an instance of the general rule
7354 about not sharing files. Note that neither alternatives
7355 nor diversions are likely to be appropriate in this case;
7356 in particular, <prgn>dpkg</prgn> does not handle diverted
7357 <tt>conffile</tt>s well.)
7361 The maintainer scripts must not alter a <tt>conffile</tt>
7362 of <em>any</em> package, including the one the scripts
7367 If two or more packages use the same configuration file
7368 and it is reasonable for both to be installed at the same
7369 time, one of these packages must be defined as
7370 <em>owner</em> of the configuration file, i.e., it will be
7371 the package which handles that file as a configuration
7372 file. Other packages that use the configuration file must
7373 depend on the owning package if they require the
7374 configuration file to operate. If the other package will
7375 use the configuration file if present, but is capable of
7376 operating without it, no dependency need be declared.
7380 If it is desirable for two or more related packages to
7381 share a configuration file <em>and</em> for all of the
7382 related packages to be able to modify that configuration
7383 file, then the following should be done:
7384 <enumlist compact="compact">
7386 One of the related packages (the "owning" package)
7387 will manage the configuration file with maintainer
7388 scripts as described in the previous section.
7391 The owning package should also provide a program
7392 that the other packages may use to modify the
7396 The related packages must use the provided program
7397 to make any desired modifications to the
7398 configuration file. They should either depend on
7399 the core package to guarantee that the configuration
7400 modifier program is available or accept gracefully
7401 that they cannot modify the configuration file if it
7402 is not. (This is in addition to the fact that the
7403 configuration file may not even be present in the
7410 Sometimes it's appropriate to create a new package which
7411 provides the basic infrastructure for the other packages
7412 and which manages the shared configuration files. (The
7413 <tt>sgml-base</tt> package is a good example.)
7418 <heading>User configuration files ("dotfiles")</heading>
7421 The files in <file>/etc/skel</file> will automatically be
7422 copied into new user accounts by <prgn>adduser</prgn>.
7423 No other program should reference the files in
7424 <file>/etc/skel</file>.
7428 Therefore, if a program needs a dotfile to exist in
7429 advance in <file>$HOME</file> to work sensibly, that dotfile
7430 should be installed in <file>/etc/skel</file> and treated as a
7435 However, programs that require dotfiles in order to
7436 operate sensibly are a bad thing, unless they do create
7437 the dotfiles themselves automatically.
7441 Furthermore, programs should be configured by the Debian
7442 default installation to behave as closely to the upstream
7443 default behavior as possible.
7447 Therefore, if a program in a Debian package needs to be
7448 configured in some way in order to operate sensibly, that
7449 should be done using a site-wide configuration file placed
7450 in <file>/etc</file>. Only if the program doesn't support a
7451 site-wide default configuration and the package maintainer
7452 doesn't have time to add it may a default per-user file be
7453 placed in <file>/etc/skel</file>.
7457 <file>/etc/skel</file> should be as empty as we can make it.
7458 This is particularly true because there is no easy (or
7459 necessarily desirable) mechanism for ensuring that the
7460 appropriate dotfiles are copied into the accounts of
7461 existing users when a package is installed.
7467 <heading>Log files</heading>
7469 Log files should usually be named
7470 <file>/var/log/<var>package</var>.log</file>. If you have many
7471 log files, or need a separate directory for permission
7472 reasons (<file>/var/log</file> is writable only by
7473 <file>root</file>), you should usually create a directory named
7474 <file>/var/log/<var>package</var></file> and place your log
7479 Log files must be rotated occasionally so that they don't
7480 grow indefinitely; the best way to do this is to drop a log
7481 rotation configuration file into the directory
7482 <file>/etc/logrotate.d</file> and use the facilities provided by
7483 logrotate.<footnote>
7485 The traditional approach to log files has been to set up
7486 <em>ad hoc</em> log rotation schemes using simple shell
7487 scripts and cron. While this approach is highly
7488 customizable, it requires quite a lot of sysadmin work.
7489 Even though the original Debian system helped a little
7490 by automatically installing a system which can be used
7491 as a template, this was deemed not enough.
7495 The use of <prgn>logrotate</prgn>, a program developed
7496 by Red Hat, is better, as it centralizes log management.
7497 It has both a configuration file
7498 (<file>/etc/logrotate.conf</file>) and a directory where
7499 packages can drop their individual log rotation
7500 configurations (<file>/etc/logrotate.d</file>).
7503 Here is a good example for a logrotate config
7504 file (for more information see <manref name="logrotate"
7506 <example compact="compact">
7507 /var/log/foo/*.log {
7512 /etc/init.d/foo force-reload
7516 This rotates all files under <file>/var/log/foo</file>, saves 12
7517 compressed generations, and forces the daemon to reload its
7518 configuration information after the log rotation.
7522 Log files should be removed when the package is
7523 purged (but not when it is only removed). This should be
7524 done by the <prgn>postrm</prgn> script when it is called
7525 with the argument <tt>purge</tt> (see <ref
7526 id="removedetails">).
7531 <heading>Permissions and owners</heading>
7534 The rules in this section are guidelines for general use.
7535 If necessary you may deviate from the details below.
7536 However, if you do so you must make sure that what is done
7537 is secure and you should try to be as consistent as possible
7538 with the rest of the system. You should probably also
7539 discuss it on <prgn>debian-devel</prgn> first.
7543 Files should be owned by <tt>root.root</tt>, and made
7544 writable only by the owner and universally readable (and
7545 executable, if appropriate), that is mode 644 or 755.
7549 Directories should be mode 755 or (for group-writability)
7550 mode 2775. The ownership of the directory should be
7551 consistent with its mode: if a directory is mode 2775, it
7552 should be owned by the group that needs write access to
7555 When a package is upgraded, and the owner or permissions
7556 of a file included in the package has changed, dpkg
7557 arranges for the ownership and permissions to be
7558 correctly set upon installation. However, this does not
7559 extend to directories; the permissions and ownership of
7560 directories already on the system does not change on
7561 install or upgrade of packages. This makes sense, since
7562 otherwise common directories like <tt>/usr</tt> would
7563 always be in flux. To correctly change permissions of a
7564 directory the package owns, explicit action is required,
7565 usually in the <tt>postinst</tt> script. Care must be
7566 taken to handle downgrades as well, in that case.
7573 Setuid and setgid executables should be mode 4755 or 2755
7574 respectively, and owned by the appropriate user or group.
7575 They should not be made unreadable (modes like 4711 or
7576 2711 or even 4111); doing so achieves no extra security,
7577 because anyone can find the binary in the freely available
7578 Debian package; it is merely inconvenient. For the same
7579 reason you should not restrict read or execute permissions
7580 on non-set-id executables.
7584 Some setuid programs need to be restricted to particular
7585 sets of users, using file permissions. In this case they
7586 should be owned by the uid to which they are set-id, and by
7587 the group which should be allowed to execute them. They
7588 should have mode 4754; again there is no point in making
7589 them unreadable to those users who must not be allowed to
7594 It is possible to arrange that the system administrator can
7595 reconfigure the package to correspond to their local
7596 security policy by changing the permissions on a binary:
7597 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7598 described below.<footnote>
7599 Ordinary files installed by <prgn>dpkg</prgn> (as
7600 opposed to <tt>conffile</tt>s and other similar objects)
7601 normally have their permissions reset to the distributed
7602 permissions when the package is reinstalled. However,
7603 the use of <prgn>dpkg-statoverride</prgn> overrides this
7604 default behavior. If you use this method, you should
7605 remember to describe <prgn>dpkg-statoverride</prgn> in
7606 the package documentation; being a relatively new
7607 addition to Debian, it is probably not yet well-known.
7609 Another method you should consider is to create a group for
7610 people allowed to use the program(s) and make any setuid
7611 executables executable only by that group.
7615 If you need to create a new user or group for your package
7616 there are two possibilities. Firstly, you may need to
7617 make some files in the binary package be owned by this
7618 user or group, or you may need to compile the user or
7619 group id (rather than just the name) into the binary
7620 (though this latter should be avoided if possible, as in
7621 this case you need a statically allocated id).</p>
7624 If you need a statically allocated id, you must ask for a
7625 user or group id from the <tt>base-passwd</tt> maintainer,
7626 and must not release the package until you have been
7627 allocated one. Once you have been allocated one you must
7628 either make the package depend on a version of the
7629 <tt>base-passwd</tt> package with the id present in
7630 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7631 your package to create the user or group itself with the
7632 correct id (using <tt>adduser</tt>) in its
7633 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7634 the <prgn>postinst</prgn> is to be preferred if it is
7635 possible, otherwise a pre-dependency will be needed on the
7636 <tt>adduser</tt> package.)
7640 On the other hand, the program might be able to determine
7641 the uid or gid from the user or group name at runtime, so
7642 that a dynamically allocated id can be used. In this case
7643 you should choose an appropriate user or group name,
7644 discussing this on <prgn>debian-devel</prgn> and checking
7645 with the <package/base-passwd/ maintainer that it is unique and that
7646 they do not wish you to use a statically allocated id
7647 instead. When this has been checked you must arrange for
7648 your package to create the user or group if necessary using
7649 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7650 <prgn>postinst</prgn> script (again, the latter is to be
7651 preferred if it is possible).
7655 Note that changing the numeric value of an id associated
7656 with a name is very difficult, and involves searching the
7657 file system for all appropriate files. You need to think
7658 carefully whether a static or dynamic id is required, since
7659 changing your mind later will cause problems.
7662 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7664 This section is not intended as policy, but as a
7665 description of the use of <prgn>dpkg-statoverride</prgn>.
7669 If a system administrator wishes to have a file (or
7670 directory or other such thing) installed with owner and
7671 permissions different from those in the distributed Debian
7672 package, they can use the <prgn>dpkg-statoverride</prgn>
7673 program to instruct <prgn>dpkg</prgn> to use the different
7674 settings every time the file is installed. Thus the
7675 package maintainer should distribute the files with their
7676 normal permissions, and leave it for the system
7677 administrator to make any desired changes. For example, a
7678 daemon which is normally required to be setuid root, but
7679 in certain situations could be used without being setuid,
7680 should be installed setuid in the <tt>.deb</tt>. Then the
7681 local system administrator can change this if they wish.
7682 If there are two standard ways of doing it, the package
7683 maintainer can use <tt>debconf</tt> to find out the
7684 preference, and call <prgn>dpkg-statoverride</prgn> in the
7685 maintainer script if necessary to accommodate the system
7686 administrator's choice. Care must be taken during
7687 upgrades to not override an existing setting.
7691 Given the above, <prgn>dpkg-statoverride</prgn> is
7692 essentially a tool for system administrators and would not
7693 normally be needed in the maintainer scripts. There is
7694 one type of situation, though, where calls to
7695 <prgn>dpkg-statoverride</prgn> would be needed in the
7696 maintainer scripts, and that involves packages which use
7697 dynamically allocated user or group ids. In such a
7698 situation, something like the following idiom can be very
7699 helpful in the package's <prgn>postinst</prgn>, where
7700 <tt>sysuser</tt> is a dynamically allocated id:
7702 for i in /usr/bin/foo /usr/sbin/bar
7704 # only do something when no setting exists
7705 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7707 #include: debconf processing, question about foo and bar
7708 if [ "$RET" = "true" ] ; then
7709 dpkg-statoverride --update --add sysuser root 4755 $i
7714 The corresponding <tt>dpkg-statoverride --remove</tt>
7715 calls can then be made unconditionally when the package is
7723 <chapt id="customized-programs">
7724 <heading>Customized programs</heading>
7726 <sect id="arch-spec">
7727 <heading>Architecture specification strings</heading>
7730 If a program needs to specify an <em>architecture specification
7731 string</em> in some place, it should select one of the
7732 strings provided by <tt>dpkg-architecture -L</tt>. The
7733 strings are in the format
7734 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7735 is sometimes elided, as when the OS is Linux.<footnote>
7736 <p>Currently, the strings are:
7737 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7738 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7739 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7740 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7741 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7742 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7743 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7744 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7745 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7746 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7747 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7748 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7749 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7750 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7751 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7752 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7753 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7754 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7755 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7756 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7757 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7758 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7759 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7760 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7761 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7762 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7763 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7764 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7765 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7766 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7767 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7768 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7769 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7770 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7771 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7772 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7773 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7779 Note that we don't want to use
7780 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7781 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7782 since this would make our programs incompatible with other
7783 Linux distributions. We also don't use something like
7784 <tt><var>arch</var>-unknown-linux</tt>, since the
7785 <tt>unknown</tt> does not look very good.
7790 <heading>Daemons</heading>
7793 The configuration files <file>/etc/services</file>,
7794 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7795 by the <prgn>netbase</prgn> package and must not be modified
7800 If a package requires a new entry in one of these files, the
7801 maintainer should get in contact with the
7802 <prgn>netbase</prgn> maintainer, who will add the entries
7803 and release a new version of the <prgn>netbase</prgn>
7808 The configuration file <file>/etc/inetd.conf</file> must not be
7809 modified by the package's scripts except via the
7810 <prgn>update-inetd</prgn> script or the
7811 <file>DebianNet.pm</file> Perl module. See their documentation
7812 for details on how to add entries.
7816 If a package wants to install an example entry into
7817 <file>/etc/inetd.conf</file>, the entry must be preceded with
7818 exactly one hash character (<tt>#</tt>). Such lines are
7819 treated as "commented out by user" by the
7820 <prgn>update-inetd</prgn> script and are not changed or
7821 activated during package updates.
7826 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7830 Some programs need to create pseudo-ttys. This should be done
7831 using Unix98 ptys if the C library supports it. The resulting
7832 program must not be installed setuid root, unless that
7833 is required for other functionality.
7837 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7838 <file>/var/log/lastlog</file> must be installed writable by
7839 group <tt>utmp</tt>. Programs which need to modify those
7840 files must be installed setgid <tt>utmp</tt>.
7845 <heading>Editors and pagers</heading>
7848 Some programs have the ability to launch an editor or pager
7849 program to edit or display a text document. Since there are
7850 lots of different editors and pagers available in the Debian
7851 distribution, the system administrator and each user should
7852 have the possibility to choose their preferred editor and
7857 In addition, every program should choose a good default
7858 editor/pager if none is selected by the user or system
7863 Thus, every program that launches an editor or pager must
7864 use the EDITOR or PAGER environment variable to determine
7865 the editor or pager the user wishes to use. If these
7866 variables are not set, the programs <file>/usr/bin/editor</file>
7867 and <file>/usr/bin/pager</file> should be used, respectively.
7871 These two files are managed through the <prgn>dpkg</prgn>
7872 "alternatives" mechanism. Thus every package providing an
7873 editor or pager must call the
7874 <prgn>update-alternatives</prgn> script to register these
7879 If it is very hard to adapt a program to make use of the
7880 EDITOR or PAGER variables, that program may be configured to
7881 use <file>/usr/bin/sensible-editor</file> and
7882 <file>/usr/bin/sensible-pager</file> as the editor or pager
7883 program respectively. These are two scripts provided in the
7884 Debian base system that check the EDITOR and PAGER variables
7885 and launch the appropriate program, and fall back to
7886 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7887 variable is not set.
7891 A program may also use the VISUAL environment variable to
7892 determine the user's choice of editor. If it exists, it
7893 should take precedence over EDITOR. This is in fact what
7894 <file>/usr/bin/sensible-editor</file> does.
7898 It is not required for a package to depend on
7899 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7900 package to provide such virtual packages.<footnote>
7901 The Debian base system already provides an editor and a
7907 <sect id="web-appl">
7908 <heading>Web servers and applications</heading>
7911 This section describes the locations and URLs that should
7912 be used by all web servers and web applications in the
7919 Cgi-bin executable files are installed in the
7921 <example compact="compact">
7922 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7924 and should be referred to as
7925 <example compact="compact">
7926 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7932 <p>Access to HTML documents</p>
7935 HTML documents for a package are stored in
7936 <file>/usr/share/doc/<var>package</var></file>
7937 and can be referred to as
7938 <example compact="compact">
7939 http://localhost/doc/<var>package</var>/<var>filename</var>
7944 The web server should restrict access to the document
7945 tree so that only clients on the same host can read
7946 the documents. If the web server does not support such
7947 access controls, then it should not provide access at
7948 all, or ask about providing access during installation.
7953 <p>Access to images</p>
7955 It is recommended that images for a package be stored
7956 in <tt>/usr/share/images/<var>package</var></tt> and
7957 may be referred to through an alias <tt>/images/</tt>
7960 http://localhost/images/<package>/<filename>
7967 <p>Web Document Root</p>
7970 Web Applications should try to avoid storing files in
7971 the Web Document Root. Instead they should use the
7972 /usr/share/doc/<var>package</var> directory for
7973 documents and register the Web Application via the
7974 <package>doc-base</package> package. If access to the
7975 web document root is unavoidable then use
7976 <example compact="compact">
7979 as the Document Root. This might be just a symbolic
7980 link to the location where the system administrator
7981 has put the real document root.
7984 <item><p>Providing httpd and/or httpd-cgi</p>
7986 All web servers should provide the virtual package
7987 <tt>httpd</tt>. If a web server has CGI support it should
7988 provide <tt>httpd-cgi</tt> additionally.
7991 All web applications which do not contain CGI scripts should
7992 depend on <tt>httpd</tt>, all those web applications which
7993 <tt>do</tt> contain CGI scripts, should depend on
8001 <sect id="mail-transport-agents">
8002 <heading>Mail transport, delivery and user agents</heading>
8005 Debian packages which process electronic mail, whether mail
8006 user agents (MUAs) or mail transport agents (MTAs), must
8007 ensure that they are compatible with the configuration
8008 decisions below. Failure to do this may result in lost
8009 mail, broken <tt>From:</tt> lines, and other serious brain
8014 The mail spool is <file>/var/mail</file> and the interface to
8015 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8016 the FHS). On older systems, the mail spool may be
8017 physically located in <file>/var/spool/mail</file>, but all
8018 access to the mail spool should be via the
8019 <file>/var/mail</file> symlink. The mail spool is part of the
8020 base system and not part of the MTA package.
8024 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8025 programs (such as IMAP daemons) must lock the mailbox in an
8026 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8027 be combined with dot locking. To avoid deadlocks, a program
8028 should use <tt>fcntl()</tt> first and dot locking after
8029 this, or alternatively implement the two locking methods in
8030 a non blocking way<footnote>
8031 If it is not possible to establish both locks, the
8032 system shouldn't wait for the second lock to be
8033 established, but remove the first lock, wait a (random)
8034 time, and start over locking again.
8035 </footnote>. Using the functions <tt>maillock</tt> and
8036 <tt>mailunlock</tt> provided by the
8037 <tt>liblockfile*</tt><footnote>
8038 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8039 to use these functions.
8040 </footnote> packages is the recommended way to realize this.
8044 Mailboxes are generally mode 660
8045 <tt><var>user</var>.mail</tt> unless the system
8046 administrator has chosen otherwise. A MUA may remove a
8047 mailbox (unless it has nonstandard permissions) in which
8048 case the MTA or another MUA must recreate it if needed.
8049 Mailboxes must be writable by group mail.
8053 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
8054 be setgid mail to do the locking mentioned above (and
8055 must obviously avoid accessing other users' mailboxes
8056 using this privilege).</p>
8059 <file>/etc/aliases</file> is the source file for the system mail
8060 aliases (e.g., postmaster, usenet, etc.), it is the one
8061 which the sysadmin and <prgn>postinst</prgn> scripts may
8062 edit. After <file>/etc/aliases</file> is edited the program or
8063 human editing it must call <prgn>newaliases</prgn>. All MTA
8064 packages must come with a <prgn>newaliases</prgn> program,
8065 even if it does nothing, but older MTA packages did not do
8066 this so programs should not fail if <prgn>newaliases</prgn>
8067 cannot be found. Note that because of this, all MTA
8068 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8069 <tt>Replaces: mail-transport-agent</tt> control file
8074 The convention of writing <tt>forward to
8075 <var>address</var></tt> in the mailbox itself is not
8076 supported. Use a <tt>.forward</tt> file instead.</p>
8079 The <prgn>rmail</prgn> program used by UUCP
8080 for incoming mail should be <file>/usr/sbin/rmail</file>.
8081 Likewise, <prgn>rsmtp</prgn>, for receiving
8082 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8086 If your package needs to know what hostname to use on (for
8087 example) outgoing news and mail messages which are generated
8088 locally, you should use the file <file>/etc/mailname</file>. It
8089 will contain the portion after the username and <tt>@</tt>
8090 (at) sign for email addresses of users on the machine
8091 (followed by a newline).
8095 Such a package should check for the existence of this file
8096 when it is being configured. If it exists, it should be
8097 used without comment, although an MTA's configuration script
8098 may wish to prompt the user even if it finds that this file
8099 exists. If the file does not exist, the package should
8100 prompt the user for the value (preferably using
8101 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8102 as well as using it in the package's configuration. The
8103 prompt should make it clear that the name will not just be
8104 used by that package. For example, in this situation the
8105 <tt>inn</tt> package could say something like:
8106 <example compact="compact">
8107 Please enter the "mail name" of your system. This is the
8108 hostname portion of the address to be shown on outgoing
8109 news and mail messages. The default is
8110 <var>syshostname</var>, your system's host name. Mail
8111 name ["<var>syshostname</var>"]:
8113 where <var>syshostname</var> is the output of <tt>hostname
8119 <heading>News system configuration</heading>
8122 All the configuration files related to the NNTP (news)
8123 servers and clients should be located under
8124 <file>/etc/news</file>.</p>
8127 There are some configuration issues that apply to a number
8128 of news clients and server packages on the machine. These
8132 <tag><file>/etc/news/organization</file></tag>
8134 A string which should appear as the
8135 organization header for all messages posted
8136 by NNTP clients on the machine
8139 <tag><file>/etc/news/server</file></tag>
8141 Contains the FQDN of the upstream NNTP
8142 server, or localhost if the local machine is
8147 Other global files may be added as required for cross-package news
8154 <heading>Programs for the X Window System</heading>
8157 <heading>Providing X support and package priorities</heading>
8160 Programs that can be configured with support for the X
8161 Window System must be configured to do so and must declare
8162 any package dependencies necessary to satisfy their
8163 runtime requirements when using the X Window System. If
8164 such a package is of higher priority than the X packages
8165 on which it depends, it is required that either the
8166 X-specific components be split into a separate package, or
8167 that an alternative version of the package, which includes
8168 X support, be provided, or that the package's priority be
8174 <heading>Packages providing an X server</heading>
8177 Packages that provide an X server that, directly or
8178 indirectly, communicates with real input and display
8179 hardware should declare in their control data that they
8180 provide the virtual package <tt>xserver</tt>.<footnote>
8181 This implements current practice, and provides an
8182 actual policy for usage of the <tt>xserver</tt>
8183 virtual package which appears in the virtual packages
8184 list. In a nutshell, X servers that interface
8185 directly with the display and input hardware or via
8186 another subsystem (e.g., GGI) should provide
8187 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8188 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8194 <heading>Packages providing a terminal emulator</heading>
8197 Packages that provide a terminal emulator for the X Window
8198 System which meet the criteria listed below should declare
8199 in their control data that they provide the virtual
8200 package <tt>x-terminal-emulator</tt>. They should also
8201 register themselves as an alternative for
8202 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8207 To be an <tt>x-terminal-emulator</tt>, a program must:
8208 <list compact="compact">
8210 Be able to emulate a DEC VT100 terminal, or a
8211 compatible terminal.
8215 Support the command-line option <tt>-e
8216 <var>command</var></tt>, which creates a new
8217 terminal window<footnote>
8218 "New terminal window" does not necessarily mean
8219 a new top-level X window directly parented by
8220 the window manager; it could, if the terminal
8221 emulator application were so coded, be a new
8222 "view" in a multiple-document interface (MDI).
8224 and runs the specified <var>command</var>,
8225 interpreting the entirety of the rest of the command
8226 line as a command to pass straight to exec, in the
8227 manner that <tt>xterm</tt> does.
8231 Support the command-line option <tt>-T
8232 <var>title</var></tt>, which creates a new terminal
8233 window with the window title <var>title</var>.
8240 <heading>Packages providing a window manager</heading>
8243 Packages that provide a window manager should declare in
8244 their control data that they provide the virtual package
8245 <tt>x-window-manager</tt>. They should also register
8246 themselves as an alternative for
8247 <file>/usr/bin/x-window-manager</file>, with a priority
8248 calculated as follows:
8249 <list compact="compact">
8251 Start with a priority of 20.
8255 If the window manager supports the Debian menu
8256 system, add 20 points if this support is available
8257 in the package's default configuration (i.e., no
8258 configuration files belonging to the system or user
8259 have to be edited to activate the feature); if
8260 configuration files must be modified, add only 10
8266 If the window manager complies with <url
8267 id="http://www.freedesktop.org/Standards/wm-spec"
8268 name="The Window Manager Specification Project">,
8269 written by the <url id="http://www.freedesktop.org/"
8270 name="Free Desktop Group">, add 40 points.
8274 If the window manager permits the X session to be
8275 restarted using a <em>different</em> window manager
8276 (without killing the X server) in its default
8277 configuration, add 10 points; otherwise add none.
8284 <heading>Packages providing fonts</heading>
8287 Packages that provide fonts for the X Window
8289 For the purposes of Debian Policy, a "font for the X
8290 Window System" is one which is accessed via X protocol
8291 requests. Fonts for the Linux console, for PostScript
8292 renderer, or any other purpose, do not fit this
8293 definition. Any tool which makes such fonts available
8294 to the X Window System, however, must abide by this
8297 must do a number of things to ensure that they are both
8298 available without modification of the X or font server
8299 configuration, and that they do not corrupt files used by
8300 other font packages to register information about
8304 Fonts of any type supported by the X Window System
8305 must be in a separate binary package from any
8306 executables, libraries, or documentation (except
8307 that specific to the fonts shipped, such as their
8308 license information). If one or more of the fonts
8309 so packaged are necessary for proper operation of
8310 the package with which they are associated the font
8311 package may be Recommended; if the fonts merely
8312 provide an enhancement, a Suggests relationship may
8313 be used. Packages must not Depend on font
8315 This is because the X server may retrieve fonts
8316 from the local file system or over the network
8317 from an X font server; the Debian package system
8318 is empowered to deal only with the local
8324 BDF fonts must be converted to PCF fonts with the
8325 <prgn>bdftopcf</prgn> utility (available in the
8326 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8327 placed in a directory that corresponds to their
8329 <list compact="compact">
8331 100 dpi fonts must be placed in
8332 <file>/usr/share/fonts/X11/100dpi/</file>.
8336 75 dpi fonts must be placed in
8337 <file>/usr/share/fonts/X11/75dpi/</file>.
8341 Character-cell fonts, cursor fonts, and other
8342 low-resolution fonts must be placed in
8343 <file>/usr/share/fonts/X11/misc/</file>.
8349 Speedo fonts must be placed in
8350 <file>/usr/share/fonts/X11/Speedo/</file>.
8354 Type 1 fonts must be placed in
8355 <file>/usr/share/fonts/X11/Type1/</file>. If font
8356 metric files are available, they must be placed here
8361 Subdirectories of <file>/usr/share/fonts/X11/</file>
8362 other than those listed above must be neither
8363 created nor used. (The <file>PEX</file>, <file>CID</file>,
8364 and <file>cyrillic</file> directories are excepted for
8365 historical reasons, but installation of files into
8366 these directories remains discouraged.)
8370 Font packages may, instead of placing files directly
8371 in the X font directories listed above, provide
8372 symbolic links in that font directory pointing to
8373 the files' actual location in the filesystem. Such
8374 a location must comply with the FHS.
8378 Font packages should not contain both 75dpi and
8379 100dpi versions of a font. If both are available,
8380 they should be provided in separate binary packages
8381 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8382 the names of the packages containing the
8383 corresponding fonts.
8387 Fonts destined for the <file>misc</file> subdirectory
8388 should not be included in the same package as 75dpi
8389 or 100dpi fonts; instead, they should be provided in
8390 a separate package with <tt>-misc</tt> appended to
8395 Font packages must not provide the files
8396 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8397 <file>fonts.scale</file> in a font directory:
8400 <file>fonts.dir</file> files must not be provided at all.
8404 <file>fonts.alias</file> and <file>fonts.scale</file>
8405 files, if needed, should be provided in the
8407 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8408 where <var>fontdir</var> is the name of the
8410 <file>/usr/share/fonts/X11/</file> where the
8411 package's corresponding fonts are stored
8412 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8413 <var>package</var> is the name of the package
8414 that provides these fonts, and
8415 <var>extension</var> is either <tt>scale</tt>
8416 or <tt>alias</tt>, whichever corresponds to
8423 Font packages must declare a dependency on
8424 <tt>xfonts-utils</tt> in their control
8429 Font packages that provide one or more
8430 <file>fonts.scale</file> files as described above must
8431 invoke <prgn>update-fonts-scale</prgn> on each
8432 directory into which they installed fonts
8433 <em>before</em> invoking
8434 <prgn>update-fonts-dir</prgn> on that directory.
8435 This invocation must occur in both the
8436 <prgn>postinst</prgn> (for all arguments) and
8437 <prgn>postrm</prgn> (for all arguments except
8438 <tt>upgrade</tt>) scripts.
8442 Font packages that provide one or more
8443 <file>fonts.alias</file> files as described above must
8444 invoke <prgn>update-fonts-alias</prgn> on each
8445 directory into which they installed fonts. This
8446 invocation must occur in both the
8447 <prgn>postinst</prgn> (for all arguments) and
8448 <prgn>postrm</prgn> (for all arguments except
8449 <tt>upgrade</tt>) scripts.
8453 Font packages must invoke
8454 <prgn>update-fonts-dir</prgn> on each directory into
8455 which they installed fonts. This invocation must
8456 occur in both the <prgn>postinst</prgn> (for all
8457 arguments) and <prgn>postrm</prgn> (for all
8458 arguments except <tt>upgrade</tt>) scripts.
8462 Font packages must not provide alias names for the
8463 fonts they include which collide with alias names
8464 already in use by fonts already packaged.
8468 Font packages must not provide fonts with the same
8469 XLFD registry name as another font already packaged.
8476 <heading>Application defaults files</heading>
8479 Application defaults files must be installed in the
8480 directory <file>/etc/X11/app-defaults/</file> (use of a
8481 localized subdirectory of <file>/etc/X11/</file> as described
8482 in the <em>X Toolkit Intrinsics - C Language
8483 Interface</em> manual is also permitted). They must be
8484 registered as <tt>conffile</tt>s or handled as
8485 configuration files. Packages must not provide the
8486 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8490 Customization of programs' X resources may also be
8491 supported with the provision of a file with the same name
8492 as that of the package placed in the
8493 <file>/etc/X11/Xresources/</file> directory, which must
8494 registered as a <tt>conffile</tt> or handled as a
8495 configuration file.<footnote>
8496 Note that this mechanism is not the same as using
8497 app-defaults; app-defaults are tied to the client
8498 binary on the local file system, whereas X resources
8499 are stored in the X server and affect all connecting
8502 <em>Important:</em> packages that install files into the
8503 <file>/etc/X11/Xresources/</file> directory must conflict with
8504 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8505 it is possible for the installing package to destroy a
8506 previously-existing <file>/etc/X11/Xresources</file> file
8507 which had been customized by the system administrator.
8512 <heading>Installation directory issues</heading>
8515 Packages using the X Window System should not be
8516 configured to install files under the
8517 <file>/usr/X11R6/</file> directory. The
8518 <file>/usr/X11R6/</file> directory hierarchy should be
8519 regarded as obsolete.
8523 Programs that use GNU <prgn>autoconf</prgn> and
8524 <prgn>automake</prgn> are usually easily configured at
8525 compile time to use <file>/usr/</file> instead of
8526 <file>/usr/X11R6/</file>, and this should be done whenever
8527 possible. Configuration files for window managers and
8528 display managers should be placed in a subdirectory of
8529 <file>/etc/X11/</file> corresponding to the package name due
8530 to these programs' tight integration with the mechanisms
8531 of the X Window System. Application-level programs should
8532 use the <file>/etc/</file> directory unless otherwise mandated
8537 The installation of files into subdirectories
8538 of <file>/usr/X11R6/include/X11/</file> and
8539 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8540 package maintainers should determine if subdirectories of
8541 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8546 Packages should install any relevant files into the
8547 directories <file>/usr/include/X11/</file> and
8548 <file>/usr/lib/X11/</file>, but if they do so, they must
8549 pre-depend on <tt>x11-common (>=
8550 1:7.0.0)</tt><footnote>
8552 These libraries used to be all symbolic
8553 links. However, with <tt>X11R7</tt>,
8554 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8555 are now real directories, and packages
8556 <strong>should</strong> ship their files here instead
8557 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8558 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8559 responsible for converting these symlinks into
8567 <heading>The OSF/Motif and OpenMotif libraries</heading>
8570 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8571 OpenMotif libraries</em><footnote>
8572 OSF/Motif and OpenMotif are collectively referred to as
8573 "Motif" in this policy document.
8575 should be compiled against and tested with LessTif (a free
8576 re-implementation of Motif) instead. If the maintainer
8577 judges that the program or programs do not work
8578 sufficiently well with LessTif to be distributed and
8579 supported, but do so when compiled against Motif, then two
8580 versions of the package should be created; one linked
8581 statically against Motif and with <tt>-smotif</tt>
8582 appended to the package name, and one linked dynamically
8583 against Motif and with <tt>-dmotif</tt> appended to the
8588 Both Motif-linked versions are dependent
8589 upon non-DFSG-compliant software and thus cannot be
8590 uploaded to the <em>main</em> distribution; if the
8591 software is itself DFSG-compliant it may be uploaded to
8592 the <em>contrib</em> distribution. While known existing
8593 versions of Motif permit unlimited redistribution of
8594 binaries linked against the library (whether statically or
8595 dynamically), it is the package maintainer's
8596 responsibility to determine whether this is permitted by
8597 the license of the copy of Motif in their possession.
8603 <heading>Perl programs and modules</heading>
8606 Perl programs and modules should follow the current Perl policy.
8610 The Perl policy can be found in the <tt>perl-policy</tt>
8611 files in the <tt>debian-policy</tt> package.
8612 It is also available from the Debian web mirrors at
8613 <tt><url name="/doc/packaging-manuals/perl-policy/"
8614 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8619 <heading>Emacs lisp programs</heading>
8622 Please refer to the "Debian Emacs Policy" for details of how to
8623 package emacs lisp programs.
8627 The Emacs policy is available in
8628 <file>debian-emacs-policy.gz</file> of the
8629 <package>emacsen-common</package> package.
8630 It is also available from the Debian web mirrors at
8631 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8632 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8637 <heading>Games</heading>
8640 The permissions on <file>/var/games</file> are mode 755, owner
8641 <tt>root</tt> and group <tt>root</tt>.
8645 Each game decides on its own security policy.</p>
8648 Games which require protected, privileged access to
8649 high-score files, saved games, etc., may be made
8650 set-<em>group</em>-id (mode 2755) and owned by
8651 <tt>root.games</tt>, and use files and directories with
8652 appropriate permissions (770 <tt>root.games</tt>, for
8653 example). They must not be made
8654 set-<em>user</em>-id, as this causes security problems. (If
8655 an attacker can subvert any set-user-id game they can
8656 overwrite the executable of any other, causing other players
8657 of these games to run a Trojan horse program. With a
8658 set-group-id game the attacker only gets access to less
8659 important game data, and if they can get at the other
8660 players' accounts at all it will take considerably more
8664 Some packages, for example some fortune cookie programs, are
8665 configured by the upstream authors to install with their
8666 data files or other static information made unreadable so
8667 that they can only be accessed through set-id programs
8668 provided. You should not do this in a Debian package: anyone can
8669 download the <file>.deb</file> file and read the data from it,
8670 so there is no point making the files unreadable. Not
8671 making the files unreadable also means that you don't have
8672 to make so many programs set-id, which reduces the risk of a
8676 As described in the FHS, binaries of games should be
8677 installed in the directory <file>/usr/games</file>. This also
8678 applies to games that use the X Window System. Manual pages
8679 for games (X and non-X games) should be installed in
8680 <file>/usr/share/man/man6</file>.</p>
8686 <heading>Documentation</heading>
8689 <heading>Manual pages</heading>
8692 You should install manual pages in <prgn>nroff</prgn> source
8693 form, in appropriate places under <file>/usr/share/man</file>.
8694 You should only use sections 1 to 9 (see the FHS for more
8695 details). You must not install a pre-formatted "cat page".
8699 Each program, utility, and function should have an
8700 associated manual page included in the same package. It is
8701 suggested that all configuration files also have a manual
8702 page included as well. Manual pages for protocols and other
8703 auxiliary things are optional.
8707 If no manual page is available, this is considered as a bug
8708 and should be reported to the Debian Bug Tracking System (the
8709 maintainer of the package is allowed to write this bug report
8710 themselves, if they so desire). Do not close the bug report
8711 until a proper man page is available.<footnote>
8712 It is not very hard to write a man page. See the
8713 <url id="http://www.schweikhardt.net/man_page_howto.html"
8714 name="Man-Page-HOWTO">,
8715 <manref name="man" section="7">, the examples
8716 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8717 the helper programs <prgn>help2man</prgn>, or the
8718 directory <file>/usr/share/doc/man-db/examples</file>.
8723 You may forward a complaint about a missing man page to the
8724 upstream authors, and mark the bug as forwarded in the
8725 Debian bug tracking system. Even though the GNU Project do
8726 not in general consider the lack of a man page to be a bug,
8727 we do; if they tell you that they don't consider it a bug
8728 you should leave the bug in our bug tracking system open
8733 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8737 If one man page needs to be accessible via several names it
8738 is better to use a symbolic link than the <file>.so</file>
8739 feature, but there is no need to fiddle with the relevant
8740 parts of the upstream source to change from <file>.so</file> to
8741 symlinks: don't do it unless it's easy. You should not
8742 create hard links in the manual page directories, nor put
8743 absolute filenames in <file>.so</file> directives. The filename
8744 in a <file>.so</file> in a man page should be relative to the
8745 base of the man page tree (usually
8746 <file>/usr/share/man</file>). If you do not create any links
8747 (whether symlinks, hard links, or <tt>.so</tt> directives)
8748 in the file system to the alternate names of the man page,
8749 then you should not rely on <prgn>man</prgn> finding your
8750 man page under those names based solely on the information in
8751 the man page's header.<footnote>
8752 Supporting this in <prgn>man</prgn> often requires
8753 unreasonable processing time to find a manual page or to
8754 report that none exists, and moves knowledge into man's
8755 database that would be better left in the file system.
8756 This support is therefore deprecated and will cease to
8757 be present in the future.
8762 Manual pages in locale-specific subdirectories of
8763 <file>/usr/share/man</file> should use either UTF-8 or the usual
8764 legacy encoding for that language (normally the one corresponding
8765 to the shortest relevant locale name in
8766 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8767 <file>/usr/share/man/fr</file> should use either UTF-8 or
8768 ISO-8859-1.<footnote>
8769 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8770 use. In future, all manual pages will be required to use
8776 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8777 included in the subdirectory name unless it indicates a
8778 significant difference in the language, as this excludes
8779 speakers of the language in other countries.<footnote>
8780 At the time of writing, Chinese and Portuguese are the main
8781 languages with such differences, so <file>pt_BR</file>,
8782 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8787 Due to limitations in current implementations, all characters
8788 in the manual page source should be representable in the usual
8789 legacy encoding for that language, even if the file is
8790 actually encoded in UTF-8. Safe alternative ways to write many
8791 characters outside that range may be found in
8792 <manref name="groff_char" section="7">.
8797 <heading>Info documents</heading>
8800 Info documents should be installed in <file>/usr/share/info</file>.
8801 They should be compressed with <tt>gzip -9</tt>.
8805 Your package should call <prgn>install-info</prgn> to update
8806 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8807 script when called with a <tt>configure</tt> argument, for
8809 <example compact="compact">
8810 install-info --quiet --section Development Development \
8811 /usr/share/info/foobar.info
8815 It is a good idea to specify a section for the location of
8816 your program; this is done with the <tt>--section</tt>
8817 switch. To determine which section to use, you should look
8818 at <file>/usr/share/info/dir</file> on your system and choose the most
8819 relevant (or create a new section if none of the current
8820 sections are relevant). Note that the <tt>--section</tt>
8821 flag takes two arguments; the first is a regular expression
8822 to match (case-insensitively) against an existing section,
8823 the second is used when creating a new one.</p>
8826 You should remove the entries in the <prgn>prerm</prgn>
8827 script when called with a <tt>remove</tt> argument:
8828 <example compact="compact">
8829 install-info --quiet --remove /usr/share/info/foobar.info
8833 If <prgn>install-info</prgn> cannot find a description entry
8834 in the Info file you must supply one. See <manref
8835 name="install-info" section="8"> for details.</p>
8839 <heading>Additional documentation</heading>
8842 Any additional documentation that comes with the package may
8843 be installed at the discretion of the package maintainer.
8844 Plain text documentation should be installed in the directory
8845 <file>/usr/share/doc/<var>package</var></file>, where
8846 <var>package</var> is the name of the package, and
8847 compressed with <tt>gzip -9</tt> unless it is small.
8851 If a package comes with large amounts of documentation which
8852 many users of the package will not require you should create
8853 a separate binary package to contain it, so that it does not
8854 take up disk space on the machines of users who do not need
8855 or want it installed.</p>
8858 It is often a good idea to put text information files
8859 (<file>README</file>s, changelogs, and so forth) that come with
8860 the source package in <file>/usr/share/doc/<var>package</var></file>
8861 in the binary package. However, you don't need to install
8862 the instructions for building and installing the package, of
8866 Packages must not require the existence of any files in
8867 <file>/usr/share/doc/</file> in order to function
8869 The system administrator should be able to
8870 delete files in <file>/usr/share/doc/</file> without causing
8871 any programs to break.
8873 Any files that are referenced by programs but are also
8874 useful as stand alone documentation should be installed under
8875 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8876 <file>/usr/share/doc/<var>package</var></file>.
8880 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8881 link to another directory in <file>/usr/share/doc</file> only if
8882 the two packages both come from the same source and the
8883 first package Depends on the second.<footnote>
8885 Please note that this does not override the section on
8886 changelog files below, so the file
8887 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8888 must refer to the changelog for the current version of
8889 <var>package</var> in question. In practice, this means
8890 that the sources of the target and the destination of the
8891 symlink must be the same (same source package and
8898 Former Debian releases placed all additional documentation
8899 in <file>/usr/doc/<var>package</var></file>. This has been
8900 changed to <file>/usr/share/doc/<var>package</var></file>,
8901 and packages must not put documentation in the directory
8902 <file>/usr/doc/<var>package</var></file>. <footnote>
8903 At this phase of the transition, we no longer require a
8904 symbolic link in <file>/usr/doc/</file>. At a later point,
8905 policy shall change to make the symbolic links a bug.
8911 <heading>Preferred documentation formats</heading>
8914 The unification of Debian documentation is being carried out
8918 If your package comes with extensive documentation in a
8919 markup format that can be converted to various other formats
8920 you should if possible ship HTML versions in a binary
8921 package, in the directory
8922 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8923 its subdirectories.<footnote>
8924 The rationale: The important thing here is that HTML
8925 docs should be available in <em>some</em> package, not
8926 necessarily in the main binary package.
8931 Other formats such as PostScript may be provided at the
8932 package maintainer's discretion.
8936 <sect id="copyrightfile">
8937 <heading>Copyright information</heading>
8940 Every package must be accompanied by a verbatim copy of its
8941 copyright and distribution license in the file
8942 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8943 file must neither be compressed nor be a symbolic link.
8947 In addition, the copyright file must say where the upstream
8948 sources (if any) were obtained. It should name the original
8949 authors of the package and the Debian maintainer(s) who were
8950 involved with its creation.
8954 Packages in the <em>contrib</em> or <em>non-free</em> categories
8955 should state in the copyright file that the package is not part
8956 of the Debian GNU/Linux distribution and briefly explain why.
8960 A copy of the file which will be installed in
8961 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8962 be in <file>debian/copyright</file> in the source package.
8966 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8967 link to another directory in <file>/usr/share/doc</file> only if
8968 the two packages both come from the same source and the
8969 first package Depends on the second. These rules are
8970 important because copyrights must be extractable by
8975 Packages distributed under the UCB BSD license, the Apache
8976 license (version 2.0), the Artistic license, the GNU GPL
8977 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8978 the GNU FDL (version 1.2) should refer to the corresponding
8979 files under <file>/usr/share/common-licenses</file>,<footnote>
8982 <file>/usr/share/common-licenses/BSD</file>,
8983 <file>/usr/share/common-licenses/Apache-2.0</file>,
8984 <file>/usr/share/common-licenses/Artistic</file>,
8985 <file>/usr/share/common-licenses/GPL-2</file>,
8986 <file>/usr/share/common-licenses/GPL-3</file>,
8987 <file>/usr/share/common-licenses/LGPL-2</file>,
8988 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8989 <file>/usr/share/common-licenses/LGPL-3</file>, and
8990 <file>/usr/share/common-licenses/GFDL-1.2</file>
8993 </footnote> rather than quoting them in the copyright
8998 You should not use the copyright file as a general <file>README</file>
8999 file. If your package has such a file it should be
9000 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9001 <file>README.Debian</file> or some other appropriate place.</p>
9005 <heading>Examples</heading>
9008 Any examples (configurations, source files, whatever),
9009 should be installed in a directory
9010 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9011 files should not be referenced by any program: they're there
9012 for the benefit of the system administrator and users as
9013 documentation only. Architecture-specific example files
9014 should be installed in a directory
9015 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9017 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9018 latter directory itself may be a symbolic link to the
9023 If the purpose of a package is to provide examples, then the
9024 example files may be installed into
9025 <file>/usr/share/doc/<var>package</var></file>.
9029 <sect id="changelogs">
9030 <heading>Changelog files</heading>
9033 Packages that are not Debian-native must contain a
9034 compressed copy of the <file>debian/changelog</file> file from
9035 the Debian source tree in
9036 <file>/usr/share/doc/<var>package</var></file> with the name
9037 <file>changelog.Debian.gz</file>.
9041 If an upstream changelog is available, it should be accessible as
9042 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9043 plain text. If the upstream changelog is distributed in
9044 HTML, it should be made available in that form as
9045 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9046 and a plain text <file>changelog.gz</file> should be generated
9047 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9048 the upstream changelog files do not already conform to this
9049 naming convention, then this may be achieved either by
9050 renaming the files, or by adding a symbolic link, at the
9051 maintainer's discretion.<footnote>
9052 Rationale: People should not have to look in places for
9053 upstream changelogs merely because they are given
9054 different names or are distributed in HTML format.
9059 All of these files should be installed compressed using
9060 <tt>gzip -9</tt>, as they will become large with time even
9061 if they start out small.
9065 If the package has only one changelog which is used both as
9066 the Debian changelog and the upstream one because there is
9067 no separate upstream maintainer then that changelog should
9068 usually be installed as
9069 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9070 there is a separate upstream maintainer, but no upstream
9071 changelog, then the Debian changelog should still be called
9072 <file>changelog.Debian.gz</file>.
9076 For details about the format and contents of the Debian
9077 changelog file, please see <ref id="dpkgchangelog">.
9082 <appendix id="pkg-scope">
9083 <heading>Introduction and scope of these appendices</heading>
9086 These appendices are taken essentially verbatim from the
9087 now-deprecated Packaging Manual, version 3.2.1.0. They are
9088 the chapters which are likely to be of use to package
9089 maintainers and which have not already been included in the
9090 policy document itself. Most of these sections are very likely
9091 not relevant to policy; they should be treated as
9092 documentation for the packaging system. Please note that these
9093 appendices are included for convenience, and for historical
9094 reasons: they used to be part of policy package, and they have
9095 not yet been incorporated into dpkg documentation. However,
9096 they still have value, and hence they are presented here.
9100 They have not yet been checked to ensure that they are
9101 compatible with the contents of policy, and if there are any
9102 contradictions, the version in the main policy document takes
9103 precedence. The remaining chapters of the old Packaging
9104 Manual have also not been read in detail to ensure that there
9105 are not parts which have been left out. Both of these will be
9110 Certain parts of the Packaging manual were integrated into the
9111 Policy Manual proper, and removed from the appendices. Links
9112 have been placed from the old locations to the new ones.
9116 <prgn>dpkg</prgn> is a suite of programs for creating binary
9117 package files and installing and removing them on Unix
9119 <prgn>dpkg</prgn> is targeted primarily at Debian
9120 GNU/Linux, but may work on or be ported to other
9126 The binary packages are designed for the management of
9127 installed executable programs (usually compiled binaries) and
9128 their associated data, though source code examples and
9129 documentation are provided as part of some packages.</p>
9132 This manual describes the technical aspects of creating Debian
9133 binary packages (<file>.deb</file> files). It documents the
9134 behavior of the package management programs
9135 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9136 they interact with packages.</p>
9139 It also documents the interaction between
9140 <prgn>dselect</prgn>'s core and the access method scripts it
9141 uses to actually install the selected packages, and describes
9142 how to create a new access method.</p>
9145 This manual does not go into detail about the options and
9146 usage of the package building and installation tools. It
9147 should therefore be read in conjunction with those programs'
9152 The utility programs which are provided with <prgn>dpkg</prgn>
9153 for managing various system configuration and similar issues,
9154 such as <prgn>update-rc.d</prgn> and
9155 <prgn>install-info</prgn>, are not described in detail here -
9156 please see their man pages.
9160 It is assumed that the reader is reasonably familiar with the
9161 <prgn>dpkg</prgn> System Administrators' manual.
9162 Unfortunately this manual does not yet exist.
9166 The Debian version of the FSF's GNU hello program is provided
9167 as an example for people wishing to create Debian
9168 packages. The Debian <prgn>debmake</prgn> package is
9169 recommended as a very helpful tool in creating and maintaining
9170 Debian packages. However, while the tools and examples are
9171 helpful, they do not replace the need to read and follow the
9172 Policy and Programmer's Manual.</p>
9175 <appendix id="pkg-binarypkg">
9176 <heading>Binary packages (from old Packaging Manual)</heading>
9179 The binary package has two main sections. The first part
9180 consists of various control information files and scripts used
9181 by <prgn>dpkg</prgn> when installing and removing. See <ref
9182 id="pkg-controlarea">.
9186 The second part is an archive containing the files and
9187 directories to be installed.
9191 In the future binary packages may also contain other
9192 components, such as checksums and digital signatures. The
9193 format for the archive is described in full in the
9194 <file>deb(5)</file> man page.
9198 <sect id="pkg-bincreating"><heading>Creating package files -
9199 <prgn>dpkg-deb</prgn>
9203 All manipulation of binary package files is done by
9204 <prgn>dpkg-deb</prgn>; it's the only program that has
9205 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9206 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9207 will spot that the options requested are appropriate to
9208 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9213 In order to create a binary package you must make a
9214 directory tree which contains all the files and directories
9215 you want to have in the file system data part of the package.
9216 In Debian-format source packages this directory is usually
9217 <file>debian/tmp</file>, relative to the top of the package's
9222 They should have the locations (relative to the root of the
9223 directory tree you're constructing) ownerships and
9224 permissions which you want them to have on the system when
9229 With current versions of <prgn>dpkg</prgn> the uid/username
9230 and gid/groupname mappings for the users and groups being
9231 used should be the same on the system where the package is
9232 built and the one where it is installed.
9236 You need to add one special directory to the root of the
9237 miniature file system tree you're creating:
9238 <prgn>DEBIAN</prgn>. It should contain the control
9239 information files, notably the binary package control file
9240 (see <ref id="pkg-controlfile">).
9244 The <prgn>DEBIAN</prgn> directory will not appear in the
9245 file system archive of the package, and so won't be installed
9246 by <prgn>dpkg</prgn> when the package is installed.
9250 When you've prepared the package, you should invoke:
9252 dpkg --build <var>directory</var>
9257 This will build the package in
9258 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9259 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9260 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9265 See the man page <manref name="dpkg-deb" section="8"> for details of how
9266 to examine the contents of this newly-created file. You may find the
9267 output of following commands enlightening:
9269 dpkg-deb --info <var>filename</var>.deb
9270 dpkg-deb --contents <var>filename</var>.deb
9271 dpkg --contents <var>filename</var>.deb
9273 To view the copyright file for a package you could use this command:
9275 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9280 <sect id="pkg-controlarea">
9281 <heading>Package control information files</heading>
9284 The control information portion of a binary package is a
9285 collection of files with names known to <prgn>dpkg</prgn>.
9286 It will treat the contents of these files specially - some
9287 of them contain information used by <prgn>dpkg</prgn> when
9288 installing or removing the package; others are scripts which
9289 the package maintainer wants <prgn>dpkg</prgn> to run.
9293 It is possible to put other files in the package control
9294 area, but this is not generally a good idea (though they
9295 will largely be ignored).
9299 Here is a brief list of the control info files supported by
9300 <prgn>dpkg</prgn> and a summary of what they're used for.
9305 <tag><tt>control</tt>
9308 This is the key description file used by
9309 <prgn>dpkg</prgn>. It specifies the package's name
9310 and version, gives its description for the user,
9311 states its relationships with other packages, and so
9312 forth. See <ref id="sourcecontrolfiles"> and
9313 <ref id="binarycontrolfiles">.
9317 It is usually generated automatically from information
9318 in the source package by the
9319 <prgn>dpkg-gencontrol</prgn> program, and with
9320 assistance from <prgn>dpkg-shlibdeps</prgn>.
9321 See <ref id="pkg-sourcetools">.
9325 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9330 These are executable files (usually scripts) which
9331 <prgn>dpkg</prgn> runs during installation, upgrade
9332 and removal of packages. They allow the package to
9333 deal with matters which are particular to that package
9334 or require more complicated processing than that
9335 provided by <prgn>dpkg</prgn>. Details of when and
9336 how they are called are in <ref id="maintainerscripts">.
9340 It is very important to make these scripts idempotent.
9341 See <ref id="idempotency">.
9345 The maintainer scripts are guaranteed to run with a
9346 controlling terminal and can interact with the user.
9347 See <ref id="controllingterminal">.
9351 <tag><tt>conffiles</tt>
9354 This file contains a list of configuration files which
9355 are to be handled automatically by <prgn>dpkg</prgn>
9356 (see <ref id="pkg-conffiles">). Note that not necessarily
9357 every configuration file should be listed here.
9360 <tag><tt>shlibs</tt>
9363 This file contains a list of the shared libraries
9364 supplied by the package, with dependency details for
9365 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9366 when it determines what dependencies are required in a
9367 package control file. The <tt>shlibs</tt> file format
9368 is described on <ref id="shlibs">.
9373 <sect id="pkg-controlfile">
9374 <heading>The main control information file: <tt>control</tt></heading>
9377 The most important control information file used by
9378 <prgn>dpkg</prgn> when it installs a package is
9379 <tt>control</tt>. It contains all the package's "vital
9384 The binary package control files of packages built from
9385 Debian sources are made by a special tool,
9386 <prgn>dpkg-gencontrol</prgn>, which reads
9387 <file>debian/control</file> and <file>debian/changelog</file> to
9388 find the information it needs. See <ref id="pkg-sourcepkg"> for
9393 The fields in binary package control files are listed in
9394 <ref id="binarycontrolfiles">.
9398 A description of the syntax of control files and the purpose
9399 of the fields is available in <ref id="controlfields">.
9404 <heading>Time Stamps</heading>
9407 See <ref id="timestamps">.
9412 <appendix id="pkg-sourcepkg">
9413 <heading>Source packages (from old Packaging Manual) </heading>
9416 The Debian binary packages in the distribution are generated
9417 from Debian sources, which are in a special format to assist
9418 the easy and automatic building of binaries.
9421 <sect id="pkg-sourcetools">
9422 <heading>Tools for processing source packages</heading>
9425 Various tools are provided for manipulating source packages;
9426 they pack and unpack sources and help build of binary
9427 packages and help manage the distribution of new versions.
9431 They are introduced and typical uses described here; see
9432 <manref name="dpkg-source" section="1"> for full
9433 documentation about their arguments and operation.
9437 For examples of how to construct a Debian source package,
9438 and how to use those utilities that are used by Debian
9439 source packages, please see the <prgn>hello</prgn> example
9443 <sect1 id="pkg-dpkg-source">
9445 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9450 This program is frequently used by hand, and is also
9451 called from package-independent automated building scripts
9452 such as <prgn>dpkg-buildpackage</prgn>.
9456 To unpack a package it is typically invoked with
9458 dpkg-source -x <var>.../path/to/filename</var>.dsc
9463 with the <file><var>filename</var>.tar.gz</file> and
9464 <file><var>filename</var>.diff.gz</file> (if applicable) in
9465 the same directory. It unpacks into
9466 <file><var>package</var>-<var>version</var></file>, and if
9468 <file><var>package</var>-<var>version</var>.orig</file>, in
9469 the current directory.
9473 To create a packed source archive it is typically invoked:
9475 dpkg-source -b <var>package</var>-<var>version</var>
9480 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9481 <file>.diff.gz</file> (if appropriate) in the current
9482 directory. <prgn>dpkg-source</prgn> does not clean the
9483 source tree first - this must be done separately if it is
9488 See also <ref id="pkg-sourcearchives">.</p>
9492 <sect1 id="pkg-dpkg-buildpackage">
9494 <prgn>dpkg-buildpackage</prgn> - overall package-building
9499 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9500 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9501 targets <tt>clean</tt>, <tt>build</tt> and
9502 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9503 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9504 source and binary package upload.
9508 It is usually invoked by hand from the top level of the
9509 built or unbuilt source directory. It may be invoked with
9510 no arguments; useful arguments include:
9511 <taglist compact="compact">
9512 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9515 Do not sign the <tt>.changes</tt> file or the
9516 source package <tt>.dsc</tt> file, respectively.</p>
9518 <tag><tt>-p<var>sign-command</var></tt></tag>
9521 Invoke <var>sign-command</var> instead of finding
9522 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9523 <var>sign-command</var> must behave just like
9524 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9526 <tag><tt>-r<var>root-command</var></tt></tag>
9529 When root privilege is required, invoke the command
9530 <var>root-command</var>. <var>root-command</var>
9531 should invoke its first argument as a command, from
9532 the <prgn>PATH</prgn> if necessary, and pass its
9533 second and subsequent arguments to the command it
9534 calls. If no <var>root-command</var> is supplied
9535 then <var>dpkg-buildpackage</var> will take no
9536 special action to gain root privilege, so that for
9537 most packages it will have to be invoked as root to
9540 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9543 Two types of binary-only build and upload - see
9544 <manref name="dpkg-source" section="1">.
9551 <sect1 id="pkg-dpkg-gencontrol">
9553 <prgn>dpkg-gencontrol</prgn> - generates binary package
9558 This program is usually called from <file>debian/rules</file>
9559 (see <ref id="pkg-sourcetree">) in the top level of the source
9564 This is usually done just before the files and directories in the
9565 temporary directory tree where the package is being built have their
9566 permissions and ownerships set and the package is constructed using
9567 <prgn>dpkg-deb/</prgn>
9569 This is so that the control file which is produced has
9570 the right permissions
9575 <prgn>dpkg-gencontrol</prgn> must be called after all the
9576 files which are to go into the package have been placed in
9577 the temporary build directory, so that its calculation of
9578 the installed size of a package is correct.
9582 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9583 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9584 variable substitutions created by
9585 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9590 For a package which generates only one binary package, and
9591 which builds it in <file>debian/tmp</file> relative to the top
9592 of the source package, it is usually sufficient to call
9593 <prgn>dpkg-gencontrol</prgn>.
9597 Sources which build several binaries will typically need
9600 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9601 </example> The <tt>-P</tt> tells
9602 <prgn>dpkg-gencontrol</prgn> that the package is being
9603 built in a non-default directory, and the <tt>-p</tt>
9604 tells it which package's control file should be generated.
9608 <prgn>dpkg-gencontrol</prgn> also adds information to the
9609 list of files in <file>debian/files</file>, for the benefit of
9610 (for example) a future invocation of
9611 <prgn>dpkg-genchanges</prgn>.</p>
9614 <sect1 id="pkg-dpkg-shlibdeps">
9616 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9621 This program is usually called from <file>debian/rules</file>
9622 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9623 id="pkg-sourcetree">), in the top level of the source tree.
9627 Its arguments are executables.
9630 In a forthcoming dpkg version,
9631 <prgn>dpkg-shlibdeps</prgn> would be required to be
9632 called on shared libraries as well.
9635 They may be specified either in the locations in the
9636 source tree where they are created or in the locations
9637 in the temporary build tree where they are installed
9638 prior to binary package creation.
9640 </footnote> for which shared library dependencies should
9641 be included in the binary package's control file.
9645 If some of the found shared libraries should only
9646 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9647 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9648 by using the <tt>-d<var>dependency-field</var></tt> option
9649 before those executable(s). (Each <tt>-d</tt> option
9650 takes effect until the next <tt>-d</tt>.)
9654 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9655 output control file to be modified. Instead by default it
9656 adds to the <file>debian/substvars</file> file variable
9657 settings like <tt>shlibs:Depends</tt>. These variable
9658 settings must be referenced in dependency fields in the
9659 appropriate per-binary-package sections of the source
9664 For example, a package that generates an essential part
9665 which requires dependencies, and optional parts that
9666 which only require a recommendation, would separate those
9667 two sets of dependencies into two different fields.<footnote>
9668 At the time of writing, an example for this was the
9669 <package/xmms/ package, with Depends used for the xmms
9670 executable, Recommends for the plug-ins and Suggests for
9671 even more optional features provided by unzip.
9673 It can say in its <file>debian/rules</file>:
9675 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9676 -dRecommends <var>optionalpart anotheroptionalpart</var>
9678 and then in its main control file <file>debian/control</file>:
9681 Depends: ${shlibs:Pre-Depends}
9682 Recommends: ${shlibs:Recommends}
9688 Sources which produce several binary packages with
9689 different shared library dependency requirements can use
9690 the <tt>-p<var>varnameprefix</var></tt> option to override
9691 the default <tt>shlibs:</tt> prefix (one invocation of
9692 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9693 They can thus produce several sets of dependency
9694 variables, each of the form
9695 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9696 which can be referred to in the appropriate parts of the
9697 binary package control files.
9702 <sect1 id="pkg-dpkg-distaddfile">
9704 <prgn>dpkg-distaddfile</prgn> - adds a file to
9705 <file>debian/files</file>
9709 Some packages' uploads need to include files other than
9710 the source and binary package files.
9714 <prgn>dpkg-distaddfile</prgn> adds a file to the
9715 <file>debian/files</file> file so that it will be included in
9716 the <file>.changes</file> file when
9717 <prgn>dpkg-genchanges</prgn> is run.
9721 It is usually invoked from the <tt>binary</tt> target of
9722 <file>debian/rules</file>:
9724 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9726 The <var>filename</var> is relative to the directory where
9727 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9728 is usually the directory above the top level of the source
9729 tree. The <file>debian/rules</file> target should put the
9730 file there just before or just after calling
9731 <prgn>dpkg-distaddfile</prgn>.
9735 The <var>section</var> and <var>priority</var> are passed
9736 unchanged into the resulting <file>.changes</file> file.
9741 <sect1 id="pkg-dpkg-genchanges">
9743 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9748 This program is usually called by package-independent
9749 automatic building scripts such as
9750 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9755 It is usually called in the top level of a built source
9756 tree, and when invoked with no arguments will print out a
9757 straightforward <file>.changes</file> file based on the
9758 information in the source package's changelog and control
9759 file and the binary and source packages which should have
9765 <sect1 id="pkg-dpkg-parsechangelog">
9767 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9768 representation of a changelog
9772 This program is used internally by
9773 <prgn>dpkg-source</prgn> et al. It may also occasionally
9774 be useful in <file>debian/rules</file> and elsewhere. It
9775 parses a changelog, <file>debian/changelog</file> by default,
9776 and prints a control-file format representation of the
9777 information in it to standard output.
9781 <sect1 id="pkg-dpkg-architecture">
9783 <prgn>dpkg-architecture</prgn> - information about the build and
9788 This program can be used manually, but is also invoked by
9789 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9790 to set environment or make variables which specify the build and
9791 host architecture for the package building process.
9796 <sect id="pkg-sourcetree">
9797 <heading>The Debianised source tree</heading>
9800 The source archive scheme described later is intended to
9801 allow a Debianised source tree with some associated control
9802 information to be reproduced and transported easily. The
9803 Debianised source tree is a version of the original program
9804 with certain files added for the benefit of the
9805 Debianisation process, and with any other changes required
9806 made to the rest of the source code and installation
9811 The extra files created for Debian are in the subdirectory
9812 <file>debian</file> of the top level of the Debianised source
9813 tree. They are described below.
9816 <sect1 id="pkg-debianrules">
9817 <heading><file>debian/rules</file> - the main building script</heading>
9820 See <ref id="debianrules">.
9825 <sect1 id="pkg-dpkgchangelog">
9826 <heading><file>debian/changelog</file></heading>
9829 See <ref id="dpkgchangelog">.
9833 It is recommended that the entire changelog be encoded in the
9834 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9836 <url id="http://www.unicode.org/"
9837 name="Unicode">.<footnote>
9839 I think it is fairly obvious that we need to
9840 eventually transition to UTF-8 for our package
9841 infrastructure; it is really the only sane char-set in
9842 an international environment. Now, we can't switch to
9843 using UTF-8 for package control fields and the like
9844 until dpkg has better support, but one thing we can
9845 start doing today is requesting that Debian changelogs
9846 are UTF-8 encoded. At some point in time, we can start
9847 requiring them to do so.
9850 Checking for non-UTF8 characters in a changelog is
9851 trivial. Dump the file through
9852 <example>iconv -f utf-8 -t ucs-4</example>
9853 discard the output, and check the return
9854 value. If there are any characters in the stream
9855 which are invalid UTF-8 sequences, iconv will exit
9856 with an error code; and this will be the case for the
9857 vast majority of other character sets.
9862 <sect2><heading>Defining alternative changelog formats
9866 It is possible to use a different format to the standard
9867 one, by providing a parser for the format you wish to
9872 In order to have <tt>dpkg-parsechangelog</tt> run your
9873 parser, you must include a line within the last 40 lines
9874 of your file matching the Perl regular expression:
9875 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9876 parentheses should be the name of the format. For
9877 example, you might say:
9879 @@@ changelog-format: joebloggs @@@
9881 Changelog format names are non-empty strings of alphanumerics.
9885 If such a line exists then <tt>dpkg-parsechangelog</tt>
9886 will look for the parser as
9887 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9889 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9890 it is an error for it not to find it, or for it not to
9891 be an executable program. The default changelog format
9892 is <tt>dpkg</tt>, and a parser for it is provided with
9893 the <tt>dpkg</tt> package.
9897 The parser will be invoked with the changelog open on
9898 standard input at the start of the file. It should read
9899 the file (it may seek if it wishes) to determine the
9900 information required and return the parsed information
9901 to standard output in the form of a series of control
9902 fields in the standard format. By default it should
9903 return information about only the most recent version in
9904 the changelog; it should accept a
9905 <tt>-v<var>version</var></tt> option to return changes
9906 information from all versions present <em>strictly
9907 after</em> <var>version</var>, and it should then be an
9908 error for <var>version</var> not to be present in the
9914 <list compact="compact">
9915 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9916 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9917 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9918 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9919 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9920 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9921 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9926 If several versions are being returned (due to the use
9927 of <tt>-v</tt>), the urgency value should be of the
9928 highest urgency code listed at the start of any of the
9929 versions requested followed by the concatenated
9930 (space-separated) comments from all the versions
9931 requested; the maintainer, version, distribution and
9932 date should always be from the most recent version.
9936 For the format of the <tt>Changes</tt> field see
9937 <ref id="f-Changes">.
9941 If the changelog format which is being parsed always or
9942 almost always leaves a blank line between individual
9943 change notes these blank lines should be stripped out,
9944 so as to make the resulting output compact.
9948 If the changelog format does not contain date or package
9949 name information this information should be omitted from
9950 the output. The parser should not attempt to synthesize
9951 it or find it from other sources.
9955 If the changelog does not have the expected format the
9956 parser should exit with a nonzero exit status, rather
9957 than trying to muddle through and possibly generating
9962 A changelog parser may not interact with the user at
9968 <sect1 id="pkg-srcsubstvars">
9969 <heading><file>debian/substvars</file> and variable substitutions</heading>
9972 See <ref id="substvars">.
9978 <heading><file>debian/files</file></heading>
9981 See <ref id="debianfiles">.
9985 <sect1><heading><file>debian/tmp</file>
9989 This is the canonical temporary location for the
9990 construction of binary packages by the <tt>binary</tt>
9991 target. The directory <file>tmp</file> serves as the root of
9992 the file system tree as it is being constructed (for
9993 example, by using the package's upstream makefiles install
9994 targets and redirecting the output there), and it also
9995 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9996 id="pkg-bincreating">.
10000 If several binary packages are generated from the same
10001 source tree it is usual to use several
10002 <file>debian/tmp<var>something</var></file> directories, for
10003 example <file>tmp-a</file> or <file>tmp-doc</file>.
10007 Whatever <file>tmp</file> directories are created and used by
10008 <tt>binary</tt> must of course be removed by the
10009 <tt>clean</tt> target.</p></sect1>
10013 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10017 As it exists on the FTP site, a Debian source package
10018 consists of three related files. You must have the right
10019 versions of all three to be able to use them.
10024 <tag>Debian source control file - <tt>.dsc</tt></tag>
10026 This file is a control file used by <prgn>dpkg-source</prgn>
10027 to extract a source package.
10028 See <ref id="debiansourcecontrolfiles">.
10032 Original source archive -
10034 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10040 This is a compressed (with <tt>gzip -9</tt>)
10041 <prgn>tar</prgn> file containing the source code from
10042 the upstream authors of the program.
10047 Debianisation diff -
10049 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10055 This is a unified context diff (<tt>diff -u</tt>)
10056 giving the changes which are required to turn the
10057 original source into the Debian source. These changes
10058 may only include editing and creating plain files.
10059 The permissions of files, the targets of symbolic
10060 links and the characteristics of special files or
10061 pipes may not be changed and no files may be removed
10066 All the directories in the diff must exist, except the
10067 <file>debian</file> subdirectory of the top of the source
10068 tree, which will be created by
10069 <prgn>dpkg-source</prgn> if necessary when unpacking.
10073 The <prgn>dpkg-source</prgn> program will
10074 automatically make the <file>debian/rules</file> file
10075 executable (see below).</p></item>
10080 If there is no original source code - for example, if the
10081 package is specially prepared for Debian or the Debian
10082 maintainer is the same as the upstream maintainer - the
10083 format is slightly different: then there is no diff, and the
10085 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10086 and preferably contains a directory named
10087 <file><var>package</var>-<var>version</var></file>.
10092 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10095 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10096 Debian source package. However, if it is not available it
10097 is possible to unpack a Debian source archive as follows:
10098 <enumlist compact="compact">
10101 Untar the tarfile, which will create a <file>.orig</file>
10105 <p>Rename the <file>.orig</file> directory to
10106 <file><var>package</var>-<var>version</var></file>.</p>
10110 Create the subdirectory <file>debian</file> at the top of
10111 the source tree.</p>
10113 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10115 <item><p>Untar the tarfile again if you want a copy of the original
10116 source code alongside the Debianised version.</p>
10121 It is not possible to generate a valid Debian source archive
10122 without using <prgn>dpkg-source</prgn>. In particular,
10123 attempting to use <prgn>diff</prgn> directly to generate the
10124 <file>.diff.gz</file> file will not work.
10128 <heading>Restrictions on objects in source packages</heading>
10131 The source package may not contain any hard links
10133 This is not currently detected when building source
10134 packages, but only when extracting
10138 Hard links may be permitted at some point in the
10139 future, but would require a fair amount of
10141 </footnote>, device special files, sockets or setuid or
10144 Setgid directories are allowed.
10149 The source packaging tools manage the changes between the
10150 original and Debianised source using <prgn>diff</prgn> and
10151 <prgn>patch</prgn>. Turning the original source tree as
10152 included in the <file>.orig.tar.gz</file> into the debianised
10153 source must not involve any changes which cannot be
10154 handled by these tools. Problematic changes which cause
10155 <prgn>dpkg-source</prgn> to halt with an error when
10156 building the source package are:
10157 <list compact="compact">
10158 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10160 <item><p>Changing the targets of symbolic links.</p>
10162 <item><p>Creating directories, other than <file>debian</file>.</p>
10164 <item><p>Changes to the contents of binary files.</p></item>
10165 </list> Changes which cause <prgn>dpkg-source</prgn> to
10166 print a warning but continue anyway are:
10167 <list compact="compact">
10170 Removing files, directories or symlinks.
10172 Renaming a file is not treated specially - it is
10173 seen as the removal of the old file (which
10174 generates a warning, but is otherwise ignored),
10175 and the creation of the new one.
10181 Changed text files which are missing the usual final
10182 newline (either in the original or the modified
10187 Changes which are not represented, but which are not detected by
10188 <prgn>dpkg-source</prgn>, are:
10189 <list compact="compact">
10190 <item><p>Changing the permissions of files (other than
10191 <file>debian/rules</file>) and directories.</p></item>
10196 The <file>debian</file> directory and <file>debian/rules</file>
10197 are handled specially by <prgn>dpkg-source</prgn> - before
10198 applying the changes it will create the <file>debian</file>
10199 directory, and afterwards it will make
10200 <file>debian/rules</file> world-executable.
10206 <appendix id="pkg-controlfields">
10207 <heading>Control files and their fields (from old Packaging Manual)</heading>
10210 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10211 data in a common format, known as control files. Binary and
10212 source packages have control data as do the <file>.changes</file>
10213 files which control the installation of uploaded files, and
10214 <prgn>dpkg</prgn>'s internal databases are in a similar
10219 <heading>Syntax of control files</heading>
10222 See <ref id="controlsyntax">.
10226 It is important to note that there are several fields which
10227 are optional as far as <prgn>dpkg</prgn> and the related
10228 tools are concerned, but which must appear in every Debian
10229 package, or whose omission may cause problems.
10234 <heading>List of fields</heading>
10237 See <ref id="controlfieldslist">.
10241 This section now contains only the fields that didn't belong
10242 to the Policy manual.
10245 <sect1 id="pkg-f-Filename">
10246 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10249 These fields in <tt>Packages</tt> files give the
10250 filename(s) of (the parts of) a package in the
10251 distribution directories, relative to the root of the
10252 Debian hierarchy. If the package has been split into
10253 several parts the parts are all listed in order, separated
10258 <sect1 id="pkg-f-Size">
10259 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10262 These fields in <file>Packages</file> files give the size (in
10263 bytes, expressed in decimal) and MD5 checksum of the
10264 file(s) which make(s) up a binary package in the
10265 distribution. If the package is split into several parts
10266 the values for the parts are listed in order, separated by
10271 <sect1 id="pkg-f-Status">
10272 <heading><tt>Status</tt></heading>
10275 This field in <prgn>dpkg</prgn>'s status file records
10276 whether the user wants a package installed, removed or
10277 left alone, whether it is broken (requiring
10278 re-installation) or not and what its current state on the
10279 system is. Each of these pieces of information is a
10284 <sect1 id="pkg-f-Config-Version">
10285 <heading><tt>Config-Version</tt></heading>
10288 If a package is not installed or not configured, this
10289 field in <prgn>dpkg</prgn>'s status file records the last
10290 version of the package which was successfully
10295 <sect1 id="pkg-f-Conffiles">
10296 <heading><tt>Conffiles</tt></heading>
10299 This field in <prgn>dpkg</prgn>'s status file contains
10300 information about the automatically-managed configuration
10301 files held by a package. This field should <em>not</em>
10302 appear anywhere in a package!
10307 <heading>Obsolete fields</heading>
10310 These are still recognized by <prgn>dpkg</prgn> but should
10311 not appear anywhere any more.
10313 <taglist compact="compact">
10315 <tag><tt>Revision</tt></tag>
10316 <tag><tt>Package-Revision</tt></tag>
10317 <tag><tt>Package_Revision</tt></tag>
10319 The Debian revision part of the package version was
10320 at one point in a separate control file field. This
10321 field went through several names.
10324 <tag><tt>Recommended</tt></tag>
10325 <item>Old name for <tt>Recommends</tt>.</item>
10327 <tag><tt>Optional</tt></tag>
10328 <item>Old name for <tt>Suggests</tt>.</item>
10330 <tag><tt>Class</tt></tag>
10331 <item>Old name for <tt>Priority</tt>.</item>
10340 <appendix id="pkg-conffiles">
10341 <heading>Configuration file handling (from old Packaging Manual)</heading>
10344 <prgn>dpkg</prgn> can do a certain amount of automatic
10345 handling of package configuration files.
10349 Whether this mechanism is appropriate depends on a number of
10350 factors, but basically there are two approaches to any
10351 particular configuration file.
10355 The easy method is to ship a best-effort configuration in the
10356 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10357 handle updates. If the user is unlikely to want to edit the
10358 file, but you need them to be able to without losing their
10359 changes, and a new package with a changed version of the file
10360 is only released infrequently, this is a good approach.
10364 The hard method is to build the configuration file from
10365 scratch in the <prgn>postinst</prgn> script, and to take the
10366 responsibility for fixing any mistakes made in earlier
10367 versions of the package automatically. This will be
10368 appropriate if the file is likely to need to be different on
10372 <sect><heading>Automatic handling of configuration files by
10377 A package may contain a control area file called
10378 <tt>conffiles</tt>. This file should be a list of filenames
10379 of configuration files needing automatic handling, separated
10380 by newlines. The filenames should be absolute pathnames,
10381 and the files referred to should actually exist in the
10386 When a package is upgraded <prgn>dpkg</prgn> will process
10387 the configuration files during the configuration stage,
10388 shortly before it runs the package's <prgn>postinst</prgn>
10393 For each file it checks to see whether the version of the
10394 file included in the package is the same as the one that was
10395 included in the last version of the package (the one that is
10396 being upgraded from); it also compares the version currently
10397 installed on the system with the one shipped with the last
10402 If neither the user nor the package maintainer has changed
10403 the file, it is left alone. If one or the other has changed
10404 their version, then the changed version is preferred - i.e.,
10405 if the user edits their file, but the package maintainer
10406 doesn't ship a different version, the user's changes will
10407 stay, silently, but if the maintainer ships a new version
10408 and the user hasn't edited it the new version will be
10409 installed (with an informative message). If both have
10410 changed their version the user is prompted about the problem
10411 and must resolve the differences themselves.
10415 The comparisons are done by calculating the MD5 message
10416 digests of the files, and storing the MD5 of the file as it
10417 was included in the most recent version of the package.
10421 When a package is installed for the first time
10422 <prgn>dpkg</prgn> will install the file that comes with it,
10423 unless that would mean overwriting a file already on the
10428 However, note that <prgn>dpkg</prgn> will <em>not</em>
10429 replace a conffile that was removed by the user (or by a
10430 script). This is necessary because with some programs a
10431 missing file produces an effect hard or impossible to
10432 achieve in another way, so that a missing file needs to be
10433 kept that way if the user did it.
10437 Note that a package should <em>not</em> modify a
10438 <prgn>dpkg</prgn>-handled conffile in its maintainer
10439 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10440 the user confusing and possibly dangerous options for
10441 conffile update when the package is upgraded.</p>
10444 <sect><heading>Fully-featured maintainer script configuration
10449 For files which contain site-specific information such as
10450 the hostname and networking details and so forth, it is
10451 better to create the file in the package's
10452 <prgn>postinst</prgn> script.
10456 This will typically involve examining the state of the rest
10457 of the system to determine values and other information, and
10458 may involve prompting the user for some information which
10459 can't be obtained some other way.
10463 When using this method there are a couple of important
10464 issues which should be considered:
10468 If you discover a bug in the program which generates the
10469 configuration file, or if the format of the file changes
10470 from one version to the next, you will have to arrange for
10471 the postinst script to do something sensible - usually this
10472 will mean editing the installed configuration file to remove
10473 the problem or change the syntax. You will have to do this
10474 very carefully, since the user may have changed the file,
10475 perhaps to fix the very problem that your script is trying
10476 to deal with - you will have to detect these situations and
10477 deal with them correctly.
10481 If you do go down this route it's probably a good idea to
10482 make the program that generates the configuration file(s) a
10483 separate program in <file>/usr/sbin</file>, by convention called
10484 <file><var>package</var>config</file> and then run that if
10485 appropriate from the post-installation script. The
10486 <tt><var>package</var>config</tt> program should not
10487 unquestioningly overwrite an existing configuration - if its
10488 mode of operation is geared towards setting up a package for
10489 the first time (rather than any arbitrary reconfiguration
10490 later) you should have it check whether the configuration
10491 already exists, and require a <tt>--force</tt> flag to
10492 overwrite it.</p></sect>
10495 <appendix id="pkg-alternatives"><heading>Alternative versions of
10496 an interface - <prgn>update-alternatives</prgn> (from old
10501 When several packages all provide different versions of the
10502 same program or file it is useful to have the system select a
10503 default, but to allow the system administrator to change it
10504 and have their decisions respected.
10508 For example, there are several versions of the <prgn>vi</prgn>
10509 editor, and there is no reason to prevent all of them from
10510 being installed at once, each under their own name
10511 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10512 Nevertheless it is desirable to have the name <tt>vi</tt>
10513 refer to something, at least by default.
10517 If all the packages involved cooperate, this can be done with
10518 <prgn>update-alternatives</prgn>.
10522 Each package provides its own version under its own name, and
10523 calls <prgn>update-alternatives</prgn> in its postinst to
10524 register its version (and again in its prerm to deregister
10529 See the man page <manref name="update-alternatives"
10530 section="8"> for details.
10534 If <prgn>update-alternatives</prgn> does not seem appropriate
10535 you may wish to consider using diversions instead.</p>
10538 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10539 package's version of a file (from old Packaging Manual)
10543 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10544 when it reinstalls the package it belongs to, and to have it
10545 put the file from the package somewhere else instead.
10549 This can be used locally to override a package's version of a
10550 file, or by one package to override another's version (or
10551 provide a wrapper for it).
10555 Before deciding to use a diversion, read <ref
10556 id="pkg-alternatives"> to see if you really want a diversion
10557 rather than several alternative versions of a program.
10561 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10562 and updated by a special program <prgn>dpkg-divert</prgn>.
10563 Please see <manref name="dpkg-divert" section="8"> for full
10564 details of its operation.
10568 When a package wishes to divert a file from another, it should
10569 call <prgn>dpkg-divert</prgn> in its preinst to add the
10570 diversion and rename the existing file. For example,
10571 supposing that a <prgn>smailwrapper</prgn> package wishes to
10572 install a wrapper around <file>/usr/sbin/smail</file>:
10574 if [ install = "$1" ]; then
10575 dpkg-divert --package smailwrapper --add --rename \
10576 --divert /usr/sbin/smail.real /usr/sbin/smail
10578 </example> Testing <tt>$1</tt> is necessary so that the script
10579 doesn't try to add the diversion again when
10580 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10581 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10582 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10583 get installed as the true version.
10587 The postrm has to do the reverse:
10589 if [ remove = "$1" ]; then
10590 dpkg-divert --package smailwrapper --remove --rename \
10591 --divert /usr/sbin/smail.real /usr/sbin/smail
10597 Do not attempt to divert a file which is vitally important for
10598 the system's operation - when using <prgn>dpkg-divert</prgn>
10599 there is a time, after it has been diverted but before
10600 <prgn>dpkg</prgn> has installed the new version, when the file
10601 does not exist.</p>
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