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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or categories based on their licenses and other restrictions.
300 The aims of this are:
302 <list compact="compact">
303 <item>to allow us to make as much software available as we can</item>
304 <item>to allow us to encourage everyone to write free software,
306 <item>to allow us to make it easy for people to produce
307 CD-ROMs of our system without violating any licenses,
308 import/export restrictions, or any other laws.</item>
313 The <em>main</em> category forms the
314 <em>Debian GNU/Linux distribution</em>.
318 Packages in the other distribution areas (<tt>contrib</tt>,
319 <tt>non-free</tt>) are not considered to be part of the Debian
320 distribution, although we support their use and provide
321 infrastructure for them (such as our bug-tracking system and
322 mailing lists). This Debian Policy Manual applies to these
327 <heading>The Debian Free Software Guidelines</heading>
329 The Debian Free Software Guidelines (DFSG) form our
330 definition of "free software". These are:
332 <tag>Free Redistribution
335 The license of a Debian component may not restrict any
336 party from selling or giving away the software as a
337 component of an aggregate software distribution
338 containing programs from several different
339 sources. The license may not require a royalty or
340 other fee for such sale.
345 The program must include source code, and must allow
346 distribution in source code as well as compiled form.
351 The license must allow modifications and derived
352 works, and must allow them to be distributed under the
353 same terms as the license of the original software.
355 <tag>Integrity of The Author's Source Code
358 The license may restrict source-code from being
359 distributed in modified form <em>only</em> if the
360 license allows the distribution of "patch files"
361 with the source code for the purpose of modifying the
362 program at build time. The license must explicitly
363 permit distribution of software built from modified
364 source code. The license may require derived works to
365 carry a different name or version number from the
366 original software. (This is a compromise. The Debian
367 Project encourages all authors to not restrict any
368 files, source or binary, from being modified.)
370 <tag>No Discrimination Against Persons or Groups
373 The license must not discriminate against any person
376 <tag>No Discrimination Against Fields of Endeavor
379 The license must not restrict anyone from making use
380 of the program in a specific field of endeavor. For
381 example, it may not restrict the program from being
382 used in a business, or from being used for genetic
385 <tag>Distribution of License
388 The rights attached to the program must apply to all
389 to whom the program is redistributed without the need
390 for execution of an additional license by those
393 <tag>License Must Not Be Specific to Debian
396 The rights attached to the program must not depend on
397 the program's being part of a Debian system. If the
398 program is extracted from Debian and used or
399 distributed without Debian but otherwise within the
400 terms of the program's license, all parties to whom
401 the program is redistributed must have the same
402 rights as those that are granted in conjunction with
405 <tag>License Must Not Contaminate Other Software
408 The license must not place restrictions on other
409 software that is distributed along with the licensed
410 software. For example, the license must not insist
411 that all other programs distributed on the same medium
412 must be free software.
414 <tag>Example Licenses
417 The "GPL," "BSD," and "Artistic" licenses are examples of
418 licenses that we consider <em>free</em>.
425 <heading>Categories</heading>
428 <heading>The main category</heading>
431 Every package in <em>main</em> must comply with the DFSG
432 (Debian Free Software Guidelines).
436 In addition, the packages in <em>main</em>
437 <list compact="compact">
439 must not require a package outside of <em>main</em>
440 for compilation or execution (thus, the package must
441 not declare a "Depends", "Recommends", or
442 "Build-Depends" relationship on a non-<em>main</em>
446 must not be so buggy that we refuse to support them,
450 must meet all policy requirements presented in this
459 <heading>The contrib category</heading>
462 Every package in <em>contrib</em> must comply with the DFSG.
466 In addition, the packages in <em>contrib</em>
467 <list compact="compact">
469 must not be so buggy that we refuse to support them,
473 must meet all policy requirements presented in this
481 Examples of packages which would be included in
482 <em>contrib</em> are:
483 <list compact="compact">
485 free packages which require <em>contrib</em>,
486 <em>non-free</em> packages or packages which are not
487 in our archive at all for compilation or execution,
491 wrapper packages or other sorts of free accessories for
498 <sect1 id="non-free">
499 <heading>The non-free category</heading>
502 Packages must be placed in <em>non-free</em> if they are
503 not compliant with the DFSG or are encumbered by patents
504 or other legal issues that make their distribution
509 In addition, the packages in <em>non-free</em>
510 <list compact="compact">
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
517 manual that it is possible for them to meet.
519 It is possible that there are policy
520 requirements which the package is unable to
521 meet, for example, if the source is
522 unavailable. These situations will need to be
523 handled on a case-by-case basis.
532 <sect id="pkgcopyright">
533 <heading>Copyright considerations</heading>
536 Every package must be accompanied by a verbatim copy of
537 its copyright and distribution license in the file
538 <file>/usr/share/doc/<var>package</var>/copyright</file>
539 (see <ref id="copyrightfile"> for further details).
543 We reserve the right to restrict files from being included
544 anywhere in our archives if
545 <list compact="compact">
547 their use or distribution would break a law,
550 there is an ethical conflict in their distribution or
554 we would have to sign a license for them, or
557 their distribution would conflict with other project
564 Programs whose authors encourage the user to make
565 donations are fine for the main distribution, provided
566 that the authors do not claim that not donating is
567 immoral, unethical, illegal or something similar; in such
568 a case they must go in <em>non-free</em>.
572 Packages whose copyright permission notices (or patent
573 problems) do not even allow redistribution of binaries
574 only, and where no special permission has been obtained,
575 must not be placed on the Debian FTP site and its mirrors
580 Note that under international copyright law (this applies
581 in the United States, too), <em>no</em> distribution or
582 modification of a work is allowed without an explicit
583 notice saying so. Therefore a program without a copyright
584 notice <em>is</em> copyrighted and you may not do anything
585 to it without risking being sued! Likewise if a program
586 has a copyright notice but no statement saying what is
587 permitted then nothing is permitted.
591 Many authors are unaware of the problems that restrictive
592 copyrights (or lack of copyright notices) can cause for
593 the users of their supposedly-free software. It is often
594 worthwhile contacting such authors diplomatically to ask
595 them to modify their license terms. However, this can be a
596 politically difficult thing to do and you should ask for
597 advice on the <tt>debian-legal</tt> mailing list first, as
602 When in doubt about a copyright, send mail to
603 <email>debian-legal@lists.debian.org</email>. Be prepared
604 to provide us with the copyright statement. Software
605 covered by the GPL, public domain software and BSD-like
606 copyrights are safe; be wary of the phrases "commercial
607 use prohibited" and "distribution restricted".
611 <sect id="subsections">
612 <heading>Sections</heading>
615 The packages in the categories <em>main</em>,
616 <em>contrib</em> and <em>non-free</em> are grouped further
617 into <em>sections</em> to simplify handling.
621 The category and section for each package should be
622 specified in the package's <tt>Section</tt> control record
623 (see <ref id="f-Section">). However, the maintainer of the
624 Debian archive may override this selection to ensure the
625 consistency of the Debian distribution. The
626 <tt>Section</tt> field should be of the form:
627 <list compact="compact">
629 <em>section</em> if the package is in the
630 <em>main</em> category,
633 <em>segment/section</em> if the package is in
634 the <em>contrib</em> or <em>non-free</em>
641 The Debian archive maintainers provide the authoritative
642 list of sections. At present, they are:
643 <em>admin</em>, <em>comm</em>,
644 <em>devel</em>, <em>doc</em>,
645 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
646 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
647 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
648 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
649 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Only very few packages are allowed to form
1082 part of the base system, in order to keep the required disk
1087 The base system consists of all those packages with priority
1088 <tt>required</tt> or <tt>important</tt>. Many of them will
1089 be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1476 The format of the <file>debian/changelog</file> allows the
1477 package building tools to discover which version of the package
1478 is being built and find out other release-specific information.
1482 That format is a series of entries like this:
1484 <example compact="compact">
1485 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1487 [optional blank line(s), stripped]
1489 * <var>change details</var>
1490 <var>more change details</var>
1492 [blank line(s), included in output of dpkg-parsechangelog]
1494 * <var>even more change details</var>
1496 [optional blank line(s), stripped]
1498 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1503 <var>package</var> and <var>version</var> are the source
1504 package name and version number.
1508 <var>distribution(s)</var> lists the distributions where
1509 this version should be installed when it is uploaded - it
1510 is copied to the <tt>Distribution</tt> field in the
1511 <file>.changes</file> file. See <ref id="f-Distribution">.
1515 <var>urgency</var> is the value for the <tt>Urgency</tt>
1516 field in the <file>.changes</file> file for the upload
1517 (see <ref id="f-Urgency">). It is not possible to specify
1518 an urgency containing commas; commas are used to separate
1519 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1520 <prgn>dpkg</prgn> changelog format (though there is
1521 currently only one useful <var>keyword</var>,
1526 The change details may in fact be any series of lines
1527 starting with at least two spaces, but conventionally each
1528 change starts with an asterisk and a separating space and
1529 continuation lines are indented so as to bring them in
1530 line with the start of the text above. Blank lines may be
1531 used here to separate groups of changes, if desired.
1535 If this upload resolves bugs recorded in the Bug Tracking
1536 System (BTS), they may be automatically closed on the
1537 inclusion of this package into the Debian archive by
1538 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1539 in the change details.<footnote>
1540 To be precise, the string should match the following
1541 Perl regular expression:
1543 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1545 Then all of the bug numbers listed will be closed by the
1546 archive maintenance script (<prgn>katie</prgn>) using the
1547 <var>version</var> of the changelog entry.
1549 This information is conveyed via the <tt>Closes</tt> field
1550 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1554 The maintainer name and email address used in the changelog
1555 should be the details of the person uploading <em>this</em>
1556 version. They are <em>not</em> necessarily those of the
1557 usual package maintainer. The information here will be
1558 copied to the <tt>Changed-By</tt> field in the
1559 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1560 and then later used to send an acknowledgement when the
1561 upload has been installed.
1565 The <var>date</var> must be in RFC822 format<footnote>
1566 This is generated by <tt>date -R</tt>.
1567 </footnote>; it must include the time zone specified
1568 numerically, with the time zone name or abbreviation
1569 optionally present as a comment in parentheses.
1573 The first "title" line with the package name must start
1574 at the left hand margin. The "trailer" line with the
1575 maintainer and date details must be preceded by exactly
1576 one space. The maintainer details and the date must be
1577 separated by exactly two spaces.
1581 For more information on placement of the changelog files
1582 within binary packages, please see <ref id="changelogs">.
1586 <sect id="dpkgcopyright">
1587 <heading>Copyright: <file>debian/copyright</file></heading>
1589 Every package must be accompanied by a verbatim copy of
1590 its copyright and distribution license in the file
1591 <file>/usr/share/doc/<var>package</var>/copyright</file>
1592 (see <ref id="copyrightfile"> for further details). Also see
1593 <ref id="pkgcopyright"> for further considerations relayed
1594 to copyrights for packages.
1598 <heading>Error trapping in makefiles</heading>
1601 When <prgn>make</prgn> invokes a command in a makefile
1602 (including your package's upstream makefiles and
1603 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1604 means that <prgn>sh</prgn>'s usual bad error handling
1605 properties apply: if you include a miniature script as one
1606 of the commands in your makefile you'll find that if you
1607 don't do anything about it then errors are not detected
1608 and <prgn>make</prgn> will blithely continue after
1613 Every time you put more than one shell command (this
1614 includes using a loop) in a makefile command you
1615 must make sure that errors are trapped. For
1616 simple compound commands, such as changing directory and
1617 then running a program, using <tt>&&</tt> rather
1618 than semicolon as a command separator is sufficient. For
1619 more complex commands including most loops and
1620 conditionals you should include a separate <tt>set -e</tt>
1621 command at the start of every makefile command that's
1622 actually one of these miniature shell scripts.
1626 <sect id="timestamps">
1627 <heading>Time Stamps</heading>
1629 Maintainers should preserve the modification times of the
1630 upstream source files in a package, as far as is reasonably
1632 The rationale is that there is some information conveyed
1633 by knowing the age of the file, for example, you could
1634 recognize that some documentation is very old by looking
1635 at the modification time, so it would be nice if the
1636 modification time of the upstream source would be
1642 <sect id="restrictions">
1643 <heading>Restrictions on objects in source packages</heading>
1646 The source package may not contain any hard links<footnote>
1648 This is not currently detected when building source
1649 packages, but only when extracting
1653 Hard links may be permitted at some point in the
1654 future, but would require a fair amount of
1657 </footnote>, device special files, sockets or setuid or
1658 setgid files.<footnote>
1659 Setgid directories are allowed.
1664 <sect id="debianrules">
1665 <heading>Main building script: <file>debian/rules</file></heading>
1668 This file must be an executable makefile, and contains the
1669 package-specific recipes for compiling the package and
1670 building binary package(s) from the source.
1674 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1675 so that it can be invoked by saying its name rather than
1676 invoking <prgn>make</prgn> explicitly.
1680 Since an interactive <file>debian/rules</file> script makes it
1681 impossible to auto-compile that package and also makes it
1682 hard for other people to reproduce the same binary
1683 package, all <em>required targets</em> MUST be
1684 non-interactive. At a minimum, required targets are the
1685 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1686 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1687 <em>binary-indep</em>, and <em>build</em>. It also follows
1688 that any target that these targets depend on must also be
1693 The targets are as follows (required unless stated otherwise):
1695 <tag><tt>build</tt></tag>
1698 The <tt>build</tt> target should perform all the
1699 configuration and compilation of the package.
1700 If a package has an interactive pre-build
1701 configuration routine, the Debianized source package
1702 must either be built after this has taken place (so
1703 that the binary package can be built without rerunning
1704 the configuration) or the configuration routine
1705 modified to become non-interactive. (The latter is
1706 preferable if there are architecture-specific features
1707 detected by the configuration routine.)
1711 For some packages, notably ones where the same
1712 source tree is compiled in different ways to produce
1713 two binary packages, the <tt>build</tt> target
1714 does not make much sense. For these packages it is
1715 good enough to provide two (or more) targets
1716 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1717 for each of the ways of building the package, and a
1718 <tt>build</tt> target that does nothing. The
1719 <tt>binary</tt> target will have to build the
1720 package in each of the possible ways and make the
1721 binary package out of each.
1725 The <tt>build</tt> target must not do anything
1726 that might require root privilege.
1730 The <tt>build</tt> target may need to run the
1731 <tt>clean</tt> target first - see below.
1735 When a package has a configuration and build routine
1736 which takes a long time, or when the makefiles are
1737 poorly designed, or when <tt>build</tt> needs to
1738 run <tt>clean</tt> first, it is a good idea to
1739 <tt>touch build</tt> when the build process is
1740 complete. This will ensure that if <tt>debian/rules
1741 build</tt> is run again it will not rebuild the whole
1743 Another common way to do this is for <tt>build</tt>
1744 to depend on <prgn>build-stamp</prgn> and to do
1745 nothing else, and for the <prgn>build-stamp</prgn>
1746 target to do the building and to <tt>touch
1747 build-stamp</tt> on completion. This is
1748 especially useful if the build routine creates a
1749 file or directory called <tt>build</tt>; in such a
1750 case, <tt>build</tt> will need to be listed as
1751 a phony target (i.e., as a dependency of the
1752 <tt>.PHONY</tt> target). See the documentation of
1753 <prgn>make</prgn> for more information on phony
1759 <tag><tt>build-arch</tt> (optional),
1760 <tt>build-indep</tt> (optional)
1764 A package may also provide both of the targets
1765 <tt>build-arch</tt> and <tt>build-indep</tt>.
1766 The <tt>build-arch</tt> target, if provided, should
1767 perform all the configuration and compilation required
1768 for producing all architecture-dependant binary packages
1769 (those packages for which the body of the
1770 <tt>Architecture</tt> field in <tt>debian/control</tt>
1771 is not <tt>all</tt>).
1772 Similarly, the <tt>build-indep</tt> target, if
1773 provided, should perform all the configuration and
1774 compilation required for producing all
1775 architecture-independent binary packages
1776 (those packages for which the body of the
1777 <tt>Architecture</tt> field in <tt>debian/control</tt>
1779 The <tt>build</tt> target should depend on those of the
1780 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1781 are provided in the rules file.
1785 If one or both of the targets <tt>build-arch</tt> and
1786 <tt>build-indep</tt> are not provided, then invoking
1787 <file>debian/rules</file> with one of the not-provided
1788 targets as arguments should produce a exit status code
1789 of 2. Usually this is provided automatically by make
1790 if the target is missing.
1794 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1795 must not do anything that might require root privilege.
1799 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1800 <tt>binary-indep</tt>
1804 The <tt>binary</tt> target must be all that is
1805 necessary for the user to build the binary package(s)
1806 produced from this source package. It is
1807 split into two parts: <prgn>binary-arch</prgn> builds
1808 the binary packages which are specific to a particular
1809 architecture, and <tt>binary-indep</tt> builds
1810 those which are not.
1813 <tt>binary</tt> may be (and commonly is) a target with
1814 no commands which simply depends on
1815 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1818 Both <tt>binary-*</tt> targets should depend on the
1819 <tt>build</tt> target, or on the appropriate
1820 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1821 provided, so that the package is built if it has not
1822 been already. It should then create the relevant
1823 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1824 make their control files and <prgn>dpkg-deb</prgn> to
1825 build them and place them in the parent of the top
1830 Both the <tt>binary-arch</tt> and
1831 <tt>binary-indep</tt> targets <em>must</em> exist.
1832 If one of them has nothing to do (which will always be
1833 the case if the source generates only a single binary
1834 package, whether architecture-dependent or not), it
1835 must still exist and must always succeed.
1839 The <tt>binary</tt> targets must be invoked as
1841 The <prgn>fakeroot</prgn> package often allows one
1842 to build a package correctly even without being
1848 <tag><tt>clean</tt></tag>
1851 This must undo any effects that the <tt>build</tt>
1852 and <tt>binary</tt> targets may have had, except
1853 that it should leave alone any output files created in
1854 the parent directory by a run of a <tt>binary</tt>
1859 If a <tt>build</tt> file is touched at the end of
1860 the <tt>build</tt> target, as suggested above, it
1861 should be removed as the first action that
1862 <tt>clean</tt> performs, so that running
1863 <tt>build</tt> again after an interrupted
1864 <tt>clean</tt> doesn't think that everything is
1869 The <tt>clean</tt> target may need to be
1870 invoked as root if <tt>binary</tt> has been
1871 invoked since the last <tt>clean</tt>, or if
1872 <tt>build</tt> has been invoked as root (since
1873 <tt>build</tt> may create directories, for
1878 <tag><tt>get-orig-source</tt> (optional)</tag>
1881 This target fetches the most recent version of the
1882 original source package from a canonical archive site
1883 (via FTP or WWW, for example), does any necessary
1884 rearrangement to turn it into the original source
1885 tar file format described below, and leaves it in the
1890 This target may be invoked in any directory, and
1891 should take care to clean up any temporary files it
1896 This target is optional, but providing it if
1897 possible is a good idea.
1901 <tag><tt>patch</tt> (optional)</tag>
1904 This target performs whatever additional actions are
1905 required to make the source ready for editing (unpacking
1906 additional upstream archives, applying patches, etc.).
1907 It is recommended to be implemented for any package where
1908 <tt>dpkg-source -x</tt> does not result in source ready
1909 for additional modification. See
1910 <ref id="readmesource">.
1916 The <tt>build</tt>, <tt>binary</tt> and
1917 <tt>clean</tt> targets must be invoked with the current
1918 directory being the package's top-level directory.
1923 Additional targets may exist in <file>debian/rules</file>,
1924 either as published or undocumented interfaces or for the
1925 package's internal use.
1929 The architectures we build on and build for are determined
1930 by <prgn>make</prgn> variables using the utility
1931 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1932 You can determine the
1933 Debian architecture and the GNU style architecture
1934 specification string for the build machine (the machine type
1935 we are building on) as well as for the host machine (the
1936 machine type we are building for). Here is a list of
1937 supported <prgn>make</prgn> variables:
1938 <list compact="compact">
1940 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1943 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1944 specification string)
1947 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1948 <tt>DEB_*_GNU_TYPE</tt>)
1951 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1952 <tt>DEB_*_GNU_TYPE</tt>)
1954 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1955 the build machine or <tt>HOST</tt> for specification of the
1960 Backward compatibility can be provided in the rules file
1961 by setting the needed variables to suitable default
1962 values; please refer to the documentation of
1963 <prgn>dpkg-architecture</prgn> for details.
1967 It is important to understand that the <tt>DEB_*_ARCH</tt>
1968 string only determines which Debian architecture we are
1969 building on or for. It should not be used to get the CPU
1970 or system information; the GNU style variables should be
1974 <sect1 id="debianrules-options">
1975 <heading><file>debian/rules</file> and
1976 <tt>DEB_BUILD_OPTIONS</tt></heading>
1979 Supporting the standardized environment variable
1980 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
1981 contain several flags to change how a package is compiled and
1982 built. Each flag must be in the form <var>flag</var> or
1983 <var>flag</var>=<var>options</var>. If multiple flags are
1984 given, they must be separated by whitespace.<footnote>
1985 Some packages support any delimiter, but whitespace is the
1986 easiest to parse inside a makefile and avoids ambiguity with
1987 flag values that contain commas.
1989 <var>flag</var> must start with a lowercase letter
1990 (<tt>a-z</tt>) and consist only of lowercase letters,
1991 numbers (<tt>0-9</tt>), and the characters
1992 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
1993 <var>options</var> must not contain whitespace. The same
1994 tag should not be given multiple times with conflicting
1995 values. Package maintainers may assume that
1996 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2000 The meaning of the following tags has been standardized:
2004 This tag says to not run any build-time test suite
2005 provided by the package.
2009 The presence of this tag means that the package should
2010 be compiled with a minimum of optimization. For C
2011 programs, it is best to add <tt>-O0</tt> to
2012 <tt>CFLAGS</tt> (although this is usually the default).
2013 Some programs might fail to build or run at this level
2014 of optimization; it may be necessary to use
2015 <tt>-O1</tt>, for example.
2019 This tag means that the debugging symbols should not be
2020 stripped from the binary during installation, so that
2021 debugging information may be included in the package.
2023 <tag>parallel=n</tag>
2025 This tag means that the package should be built using up
2026 to <tt>n</tt> parallel processes if the package build
2027 system supports this.<footnote>
2028 Packages built with <tt>make</tt> can often implement
2029 this by passing the <tt>-j</tt><var>n</var> option to
2032 If the package build system does not support parallel
2033 builds, this string must be ignored. If the package
2034 build system only supports a lower level of concurrency
2035 than <var>n</var>, the package should be built using as
2036 many parallel processes as the package build system
2037 supports. It is up to the package maintainer to decide
2038 whether the package build times are long enough and the
2039 package build system is robust enough to make supporting
2040 parallel builds worthwhile.
2046 Unknown flags must be ignored by <file>debian/rules</file>.
2050 The following makefile snippet is an example of how one may
2051 implement the build options; you will probably have to
2052 massage this example in order to make it work for your
2054 <example compact="compact">
2057 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2058 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2059 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2060 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2062 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2067 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2068 INSTALL_PROGRAM += -s
2070 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2071 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2072 MAKEFLAGS += -j$(NUMJOBS)
2077 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2078 # Code to run the package test suite.
2085 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2086 <sect id="substvars">
2087 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2090 When <prgn>dpkg-gencontrol</prgn>,
2091 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2092 generate control files they perform variable substitutions
2093 on their output just before writing it. Variable
2094 substitutions have the form <tt>${<var>variable</var>}</tt>.
2095 The optional file <file>debian/substvars</file> contains
2096 variable substitutions to be used; variables can also be set
2097 directly from <file>debian/rules</file> using the <tt>-V</tt>
2098 option to the source packaging commands, and certain
2099 predefined variables are also available.
2103 The <file>debian/substvars</file> file is usually generated and
2104 modified dynamically by <file>debian/rules</file> targets, in
2105 which case it must be removed by the <tt>clean</tt> target.
2109 See <manref name="deb-substvars" section="5"> for full
2110 details about source variable substitutions, including the
2111 format of <file>debian/substvars</file>.</p>
2114 <sect id="debianwatch">
2115 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2118 This is an optional, recommended control file for the
2119 <tt>uscan</tt> utility which defines how to automatically
2120 scan ftp or http sites for newly available updates of the
2121 package. This is used by <url id="
2122 http://dehs.alioth.debian.org/"> and other Debian QA tools
2123 to help with quality control and maintenance of the
2124 distribution as a whole.
2129 <sect id="debianfiles">
2130 <heading>Generated files list: <file>debian/files</file></heading>
2133 This file is not a permanent part of the source tree; it
2134 is used while building packages to record which files are
2135 being generated. <prgn>dpkg-genchanges</prgn> uses it
2136 when it generates a <file>.changes</file> file.
2140 It should not exist in a shipped source package, and so it
2141 (and any backup files or temporary files such as
2142 <file>files.new</file><footnote>
2143 <file>files.new</file> is used as a temporary file by
2144 <prgn>dpkg-gencontrol</prgn> and
2145 <prgn>dpkg-distaddfile</prgn> - they write a new
2146 version of <tt>files</tt> here before renaming it,
2147 to avoid leaving a corrupted copy if an error
2149 </footnote>) should be removed by the
2150 <tt>clean</tt> target. It may also be wise to
2151 ensure a fresh start by emptying or removing it at the
2152 start of the <tt>binary</tt> target.
2156 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2157 package, it adds an entry to <file>debian/files</file> for the
2158 <file>.deb</file> file that will be created when <tt>dpkg-deb
2159 --build</tt> is run for that binary package. So for most
2160 packages all that needs to be done with this file is to
2161 delete it in the <tt>clean</tt> target.
2165 If a package upload includes files besides the source
2166 package and any binary packages whose control files were
2167 made with <prgn>dpkg-gencontrol</prgn> then they should be
2168 placed in the parent of the package's top-level directory
2169 and <prgn>dpkg-distaddfile</prgn> should be called to add
2170 the file to the list in <file>debian/files</file>.</p>
2173 <sect id="embeddedfiles">
2174 <heading>Convenience copies of code</heading>
2177 Some software packages include in their distribution convenience
2178 copies of code from other software packages, generally so that
2179 users compiling from source don't have to download multiple
2180 packages. Debian packages should not make use of these
2181 convenience copies unless the included package is explicitly
2182 intended to be used in this way.<footnote>
2183 For example, parts of the GNU build system work like this.
2185 If the included code is already in the Debian archive in the
2186 form of a library, the Debian packaging should ensure that
2187 binary packages reference the libraries already in Debian and
2188 the convenience copy is not used. If the included code is not
2189 already in Debian, it should be packaged separately as a
2190 prerequisite if possible.
2192 Having multiple copies of the same code in Debian is
2193 inefficient, often creates either static linking or shared
2194 library conflicts, and, most importantly, increases the
2195 difficulty of handling security vulnerabilities in the
2201 <sect id="readmesource">
2202 <heading>Source package handling:
2203 <file>debian/README.source</file></heading>
2206 If running <prgn>dpkg-source -x</prgn> on a source package
2207 doesn't produce the source of the package, ready for editing,
2208 and allow one to make changes and run
2209 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2210 without taking any additional steps, creating a
2211 <file>debian/README.source</file> documentation file is
2212 recommended. This file should explain how to do all of the
2215 <item>Generate the fully patched source, in a form ready for
2216 editing, that would be built to create Debian
2217 packages. Doing this with a <tt>patch</tt> target in
2218 <file>debian/rules</file> is recommended; see
2219 <ref id="debianrules">.</item>
2220 <item>Modify the source and save those modifications so that
2221 they will be applied when building the package.</item>
2222 <item>Remove source modifications that are currently being
2223 applied when building the package.</item>
2224 <item>Optionally, document what steps are necessary to
2225 upgrade the Debian source package to a new upstream version,
2226 if applicable.</item>
2228 This explanation should include specific commands and mention
2229 any additional required Debian packages. It should not assume
2230 familiarity with any specific Debian packaging system or patch
2235 This explanation may refer to a documentation file installed by
2236 one of the package's build dependencies provided that the
2237 referenced documentation clearly explains these tasks and is not
2238 a general reference manual.
2242 <file>debian/README.source</file> may also include any other
2243 information that would be helpful to someone modifying the
2244 source package. Even if the package doesn't fit the above
2245 description, maintainers are encouraged to document in a
2246 <file>debian/README.source</file> file any source package with a
2247 particularly complex or unintuitive source layout or build
2248 system (for example, a package that builds the same source
2249 multiple times to generate different binary packages).
2255 <chapt id="controlfields">
2256 <heading>Control files and their fields</heading>
2259 The package management system manipulates data represented in
2260 a common format, known as <em>control data</em>, stored in
2261 <em>control files</em>.
2262 Control files are used for source packages, binary packages and
2263 the <file>.changes</file> files which control the installation
2264 of uploaded files<footnote>
2265 <prgn>dpkg</prgn>'s internal databases are in a similar
2270 <sect id="controlsyntax">
2271 <heading>Syntax of control files</heading>
2274 A control file consists of one or more paragraphs of
2276 The paragraphs are also sometimes referred to as stanzas.
2278 The paragraphs are separated by blank lines. Some control
2279 files allow only one paragraph; others allow several, in
2280 which case each paragraph usually refers to a different
2281 package. (For example, in source packages, the first
2282 paragraph refers to the source package, and later paragraphs
2283 refer to binary packages generated from the source.)
2287 Each paragraph consists of a series of data fields; each
2288 field consists of the field name, followed by a colon and
2289 then the data/value associated with that field. It ends at
2290 the end of the (logical) line. Horizontal whitespace
2291 (spaces and tabs) may occur immediately before or after the
2292 value and is ignored there; it is conventional to put a
2293 single space after the colon. For example, a field might
2295 <example compact="compact">
2298 the field name is <tt>Package</tt> and the field value
2303 Many fields' values may span several lines; in this case
2304 each continuation line must start with a space or a tab.
2305 Any trailing spaces or tabs at the end of individual
2306 lines of a field value are ignored.
2310 In fields where it is specified that lines may not wrap,
2311 only a single line of data is allowed and whitespace is not
2312 significant in a field body. Whitespace must not appear
2313 inside names (of packages, architectures, files or anything
2314 else) or version numbers, or between the characters of
2315 multi-character version relationships.
2319 Field names are not case-sensitive, but it is usual to
2320 capitalize the field names using mixed case as shown below.
2324 Blank lines, or lines consisting only of spaces and tabs,
2325 are not allowed within field values or between fields - that
2326 would mean a new paragraph.
2331 <sect id="sourcecontrolfiles">
2332 <heading>Source package control files -- <file>debian/control</file></heading>
2335 The <file>debian/control</file> file contains the most vital
2336 (and version-independent) information about the source package
2337 and about the binary packages it creates.
2341 The first paragraph of the control file contains information about
2342 the source package in general. The subsequent sets each describe a
2343 binary package that the source tree builds.
2347 The fields in the general paragraph (the first one, for the source
2350 <list compact="compact">
2351 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2352 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2353 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2354 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2355 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2356 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2357 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2358 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2363 The fields in the binary package paragraphs are:
2365 <list compact="compact">
2366 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2367 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2368 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2369 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2370 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2371 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2372 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2373 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2378 The syntax and semantics of the fields are described below.
2384 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2385 generate control files for binary packages (see below), by
2386 <prgn>dpkg-genchanges</prgn> to generate the
2387 <tt>.changes</tt> file to accompany the upload, and by
2388 <prgn>dpkg-source</prgn> when it creates the
2389 <file>.dsc</file> source control file as part of a source
2390 archive. Many fields are permitted to span multiple lines in
2391 <file>debian/control</file> but not in any other control
2392 file. These tools are responsible for removing the line
2393 breaks from such fields when using fields from
2394 <file>debian/control</file> to generate other control files.
2398 The fields here may contain variable references - their
2399 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2400 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2401 when they generate output control files.
2402 See <ref id="substvars"> for details.
2407 <sect id="binarycontrolfiles">
2408 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2411 The <file>DEBIAN/control</file> file contains the most vital
2412 (and version-dependent) information about a binary package.
2416 The fields in this file are:
2418 <list compact="compact">
2419 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2420 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2421 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2422 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2423 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2424 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2425 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2426 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2427 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2428 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2429 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2430 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2435 <sect id="debiansourcecontrolfiles">
2436 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2439 This file contains a series of fields, identified and
2440 separated just like the fields in the control file of
2441 a binary package. The fields are listed below; their
2442 syntax is described above, in <ref id="pkg-controlfields">.
2444 <list compact="compact">
2445 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2446 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2447 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2448 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2449 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2450 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2451 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2452 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2453 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2454 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2455 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2460 The source package control file is generated by
2461 <prgn>dpkg-source</prgn> when it builds the source
2462 archive, from other files in the source package,
2463 described above. When unpacking, it is checked against
2464 the files and directories in the other parts of the
2470 <sect id="debianchangesfiles">
2471 <heading>Debian changes files -- <file>.changes</file></heading>
2474 The .changes files are used by the Debian archive maintenance
2475 software to process updates to packages. They contain one
2476 paragraph which contains information from the
2477 <tt>debian/control</tt> file and other data about the
2478 source package gathered via <tt>debian/changelog</tt>
2479 and <tt>debian/rules</tt>.
2483 The fields in this file are:
2485 <list compact="compact">
2486 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2489 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2490 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2491 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2492 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2493 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2494 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2495 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2496 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2497 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2498 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2499 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2504 <sect id="controlfieldslist">
2505 <heading>List of fields</heading>
2507 <sect1 id="f-Source">
2508 <heading><tt>Source</tt></heading>
2511 This field identifies the source package name.
2515 In <file>debian/control</file> or a <file>.dsc</file> file,
2516 this field must contain only the name of the source package.
2520 In a binary package control file or a <file>.changes</file>
2521 file, the source package name may be followed by a version
2522 number in parentheses<footnote>
2523 It is customary to leave a space after the package name
2524 if a version number is specified.
2526 This version number may be omitted (and is, by
2527 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2528 the <tt>Version</tt> field of the binary package in
2529 question. The field itself may be omitted from a binary
2530 package control file when the source package has the same
2531 name and version as the binary package.
2535 <sect1 id="f-Maintainer">
2536 <heading><tt>Maintainer</tt></heading>
2539 The package maintainer's name and email address. The name
2540 should come first, then the email address inside angle
2541 brackets <tt><></tt> (in RFC822 format).
2545 If the maintainer's name contains a full stop then the
2546 whole field will not work directly as an email address due
2547 to a misfeature in the syntax specified in RFC822; a
2548 program using this field as an address must check for this
2549 and correct the problem if necessary (for example by
2550 putting the name in round brackets and moving it to the
2551 end, and bringing the email address forward).
2555 <sect1 id="f-Uploaders">
2556 <heading><tt>Uploaders</tt></heading>
2559 List of the names and email addresses of co-maintainers of
2560 the package, if any. If the package has other maintainers
2561 beside the one named in the
2562 <qref id="f-Maintainer">Maintainer field</qref>, their
2563 names and email addresses should be listed here. The
2564 format is the same as that of the Maintainer tag, and
2565 multiple entries should be comma separated. Currently,
2566 this field is restricted to a single line of data. This
2567 is an optional field.
2570 Any parser that interprets the Uploaders field in
2571 <file>debian/control</file> must permit it to span multiple
2572 lines. Line breaks in an Uploaders field that spans multiple
2573 lines are not significant and the semantics of the field are
2574 the same as if the line breaks had not been present.
2578 <sect1 id="f-Changed-By">
2579 <heading><tt>Changed-By</tt></heading>
2582 The name and email address of the person who changed the
2583 said package. Usually the name of the maintainer.
2584 All the rules for the Maintainer field apply here, too.
2588 <sect1 id="f-Section">
2589 <heading><tt>Section</tt></heading>
2592 This field specifies an application area into which the package
2593 has been classified. See <ref id="subsections">.
2597 When it appears in the <file>debian/control</file> file,
2598 it gives the value for the subfield of the same name in
2599 the <tt>Files</tt> field of the <file>.changes</file> file.
2600 It also gives the default for the same field in the binary
2605 <sect1 id="f-Priority">
2606 <heading><tt>Priority</tt></heading>
2609 This field represents how important that it is that the user
2610 have the package installed. See <ref id="priorities">.
2614 When it appears in the <file>debian/control</file> file,
2615 it gives the value for the subfield of the same name in
2616 the <tt>Files</tt> field of the <file>.changes</file> file.
2617 It also gives the default for the same field in the binary
2622 <sect1 id="f-Package">
2623 <heading><tt>Package</tt></heading>
2626 The name of the binary package.
2630 Package names must consist only of lower case letters
2631 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2632 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2633 They must be at least two characters long and must start
2634 with an alphanumeric character.
2638 <sect1 id="f-Architecture">
2639 <heading><tt>Architecture</tt></heading>
2642 Depending on context and the control file used, the
2643 <tt>Architecture</tt> field can include the following sets of
2646 <item>A unique single word identifying a Debian machine
2647 architecture, see <ref id="arch-spec">.
2648 <item><tt>all</tt>, which indicates an
2649 architecture-independent package.
2650 <item><tt>any</tt>, which indicates a package available
2651 for building on any architecture.
2652 <item><tt>source</tt>, which indicates a source package.
2657 In the main <file>debian/control</file> file in the source
2658 package, or in the source package control file
2659 <file>.dsc</file>, one may specify a list of architectures
2660 separated by spaces, or the special values <tt>any</tt> or
2665 Specifying <tt>any</tt> indicates that the source package
2666 isn't dependent on any particular architecture and should
2667 compile fine on any one. The produced binary package(s)
2668 will be specific to whatever the current build architecture
2670 This is the most often used setting, and is recommended
2671 for new packages that aren't <tt>Architecture: all</tt>.
2676 Specifying a list of architectures indicates that the source
2677 will build an architecture-dependent package, and will only
2678 work correctly on the listed architectures.<footnote>
2679 This is a setting used for a minority of cases where the
2680 program is not portable. Generally, it should not be used
2686 In a <file>.changes</file> file, the <tt>Architecture</tt>
2687 field lists the architecture(s) of the package(s)
2688 currently being uploaded. This will be a list; if the
2689 source for the package is also being uploaded, the special
2690 entry <tt>source</tt> is also present.
2694 See <ref id="debianrules"> for information how to get the
2695 architecture for the build process.
2699 <sect1 id="f-Essential">
2700 <heading><tt>Essential</tt></heading>
2703 This is a boolean field which may occur only in the
2704 control file of a binary package or in a per-package fields
2705 paragraph of a main source control data file.
2709 If set to <tt>yes</tt> then the package management system
2710 will refuse to remove the package (upgrading and replacing
2711 it is still possible). The other possible value is <tt>no</tt>,
2712 which is the same as not having the field at all.
2717 <heading>Package interrelationship fields:
2718 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2719 <tt>Recommends</tt>, <tt>Suggests</tt>,
2720 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2721 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2725 These fields describe the package's relationships with
2726 other packages. Their syntax and semantics are described
2727 in <ref id="relationships">.</p>
2730 <sect1 id="f-Standards-Version">
2731 <heading><tt>Standards-Version</tt></heading>
2734 The most recent version of the standards (the policy
2735 manual and associated texts) with which the package
2740 The version number has four components: major and minor
2741 version number and major and minor patch level. When the
2742 standards change in a way that requires every package to
2743 change the major number will be changed. Significant
2744 changes that will require work in many packages will be
2745 signaled by a change to the minor number. The major patch
2746 level will be changed for any change to the meaning of the
2747 standards, however small; the minor patch level will be
2748 changed when only cosmetic, typographical or other edits
2749 are made which neither change the meaning of the document
2750 nor affect the contents of packages.
2754 Thus only the first three components of the policy version
2755 are significant in the <em>Standards-Version</em> control
2756 field, and so either these three components or the all
2757 four components may be specified.<footnote>
2758 In the past, people specified the full version number
2759 in the Standards-Version field, for example "2.3.0.0".
2760 Since minor patch-level changes don't introduce new
2761 policy, it was thought it would be better to relax
2762 policy and only require the first 3 components to be
2763 specified, in this example "2.3.0". All four
2764 components may still be used if someone wishes to do so.
2770 <sect1 id="f-Version">
2771 <heading><tt>Version</tt></heading>
2774 The version number of a package. The format is:
2775 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2779 The three components here are:
2781 <tag><var>epoch</var></tag>
2784 This is a single (generally small) unsigned integer. It
2785 may be omitted, in which case zero is assumed. If it is
2786 omitted then the <var>upstream_version</var> may not
2791 It is provided to allow mistakes in the version numbers
2792 of older versions of a package, and also a package's
2793 previous version numbering schemes, to be left behind.
2797 <tag><var>upstream_version</var></tag>
2800 This is the main part of the version number. It is
2801 usually the version number of the original ("upstream")
2802 package from which the <file>.deb</file> file has been made,
2803 if this is applicable. Usually this will be in the same
2804 format as that specified by the upstream author(s);
2805 however, it may need to be reformatted to fit into the
2806 package management system's format and comparison
2811 The comparison behavior of the package management system
2812 with respect to the <var>upstream_version</var> is
2813 described below. The <var>upstream_version</var>
2814 portion of the version number is mandatory.
2818 The <var>upstream_version</var> may contain only
2819 alphanumerics<footnote>
2820 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2822 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2823 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2824 tilde) and should start with a digit. If there is no
2825 <var>debian_revision</var> then hyphens are not allowed;
2826 if there is no <var>epoch</var> then colons are not
2831 <tag><var>debian_revision</var></tag>
2834 This part of the version number specifies the version of
2835 the Debian package based on the upstream version. It
2836 may contain only alphanumerics and the characters
2837 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2838 tilde) and is compared in the same way as the
2839 <var>upstream_version</var> is.
2843 It is optional; if it isn't present then the
2844 <var>upstream_version</var> may not contain a hyphen.
2845 This format represents the case where a piece of
2846 software was written specifically to be turned into a
2847 Debian package, and so there is only one "debianisation"
2848 of it and therefore no revision indication is required.
2852 It is conventional to restart the
2853 <var>debian_revision</var> at <tt>1</tt> each time the
2854 <var>upstream_version</var> is increased.
2858 The package management system will break the version
2859 number apart at the last hyphen in the string (if there
2860 is one) to determine the <var>upstream_version</var> and
2861 <var>debian_revision</var>. The absence of a
2862 <var>debian_revision</var> is equivalent to a
2863 <var>debian_revision</var> of <tt>0</tt>.
2870 When comparing two version numbers, first the <var>epoch</var>
2871 of each are compared, then the <var>upstream_version</var> if
2872 <var>epoch</var> is equal, and then <var>debian_revision</var>
2873 if <var>upstream_version</var> is also equal.
2874 <var>epoch</var> is compared numerically. The
2875 <var>upstream_version</var> and <var>debian_revision</var>
2876 parts are compared by the package management system using the
2877 following algorithm:
2881 The strings are compared from left to right.
2885 First the initial part of each string consisting entirely of
2886 non-digit characters is determined. These two parts (one of
2887 which may be empty) are compared lexically. If a difference
2888 is found it is returned. The lexical comparison is a
2889 comparison of ASCII values modified so that all the letters
2890 sort earlier than all the non-letters and so that a tilde
2891 sorts before anything, even the end of a part. For example,
2892 the following parts are in sorted order from earliest to
2893 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2894 <tt>a</tt>.<footnote>
2895 One common use of <tt>~</tt> is for upstream pre-releases.
2896 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2897 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2902 Then the initial part of the remainder of each string which
2903 consists entirely of digit characters is determined. The
2904 numerical values of these two parts are compared, and any
2905 difference found is returned as the result of the comparison.
2906 For these purposes an empty string (which can only occur at
2907 the end of one or both version strings being compared) counts
2912 These two steps (comparing and removing initial non-digit
2913 strings and initial digit strings) are repeated until a
2914 difference is found or both strings are exhausted.
2918 Note that the purpose of epochs is to allow us to leave behind
2919 mistakes in version numbering, and to cope with situations
2920 where the version numbering scheme changes. It is
2921 <em>not</em> intended to cope with version numbers containing
2922 strings of letters which the package management system cannot
2923 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2924 silly orderings (the author of this manual has heard of a
2925 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2926 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2927 <tt>2</tt> and so forth).
2931 <sect1 id="f-Description">
2932 <heading><tt>Description</tt></heading>
2935 In a source or binary control file, the <tt>Description</tt>
2936 field contains a description of the binary package, consisting
2937 of two parts, the synopsis or the short description, and the
2938 long description. The field's format is as follows:
2943 Description: <single line synopsis>
2944 <extended description over several lines>
2949 The lines in the extended description can have these formats:
2955 Those starting with a single space are part of a paragraph.
2956 Successive lines of this form will be word-wrapped when
2957 displayed. The leading space will usually be stripped off.
2961 Those starting with two or more spaces. These will be
2962 displayed verbatim. If the display cannot be panned
2963 horizontally, the displaying program will line wrap them "hard"
2964 (i.e., without taking account of word breaks). If it can they
2965 will be allowed to trail off to the right. None, one or two
2966 initial spaces may be deleted, but the number of spaces
2967 deleted from each line will be the same (so that you can have
2968 indenting work correctly, for example).
2972 Those containing a single space followed by a single full stop
2973 character. These are rendered as blank lines. This is the
2974 <em>only</em> way to get a blank line<footnote>
2975 Completely empty lines will not be rendered as blank lines.
2976 Instead, they will cause the parser to think you're starting
2977 a whole new record in the control file, and will therefore
2978 likely abort with an error.
2983 Those containing a space, a full stop and some more characters.
2984 These are for future expansion. Do not use them.
2990 Do not use tab characters. Their effect is not predictable.
2994 See <ref id="descriptions"> for further information on this.
2998 In a <file>.changes</file> file, the <tt>Description</tt> field
2999 contains a summary of the descriptions for the packages being
3004 The part of the field before the first newline is empty;
3005 thereafter each line has the name of a binary package and
3006 the summary description line from that binary package.
3007 Each line is indented by one space.
3012 <sect1 id="f-Distribution">
3013 <heading><tt>Distribution</tt></heading>
3016 In a <file>.changes</file> file or parsed changelog output
3017 this contains the (space-separated) name(s) of the
3018 distribution(s) where this version of the package should
3019 be installed. Valid distributions are determined by the
3020 archive maintainers.<footnote>
3021 Current distribution names are:
3022 <taglist compact="compact">
3023 <tag><em>stable</em></tag>
3025 This is the current "released" version of Debian
3026 GNU/Linux. Once the distribution is
3027 <em>stable</em> only security fixes and other
3028 major bug fixes are allowed. When changes are
3029 made to this distribution, the release number is
3030 increased (for example: 2.2r1 becomes 2.2r2 then
3034 <tag><em>unstable</em></tag>
3036 This distribution value refers to the
3037 <em>developmental</em> part of the Debian
3038 distribution tree. New packages, new upstream
3039 versions of packages and bug fixes go into the
3040 <em>unstable</em> directory tree. Download from
3041 this distribution at your own risk.
3044 <tag><em>testing</em></tag>
3046 This distribution value refers to the
3047 <em>testing</em> part of the Debian distribution
3048 tree. It receives its packages from the
3049 unstable distribution after a short time lag to
3050 ensure that there are no major issues with the
3051 unstable packages. It is less prone to breakage
3052 than unstable, but still risky. It is not
3053 possible to upload packages directly to
3057 <tag><em>frozen</em></tag>
3059 From time to time, the <em>testing</em>
3060 distribution enters a state of "code-freeze" in
3061 anticipation of release as a <em>stable</em>
3062 version. During this period of testing only
3063 fixes for existing or newly-discovered bugs will
3064 be allowed. The exact details of this stage are
3065 determined by the Release Manager.
3068 <tag><em>experimental</em></tag>
3070 The packages with this distribution value are
3071 deemed by their maintainers to be high
3072 risk. Oftentimes they represent early beta or
3073 developmental packages from various sources that
3074 the maintainers want people to try, but are not
3075 ready to be a part of the other parts of the
3076 Debian distribution tree. Download at your own
3082 You should list <em>all</em> distributions that the
3083 package should be installed into.
3087 More information is available in the Debian Developer's
3088 Reference, section "The Debian archive".
3095 <heading><tt>Date</tt></heading>
3098 This field includes the date the package was built or last edited.
3102 The value of this field is usually extracted from the
3103 <file>debian/changelog</file> file - see
3104 <ref id="dpkgchangelog">).
3108 <sect1 id="f-Format">
3109 <heading><tt>Format</tt></heading>
3112 This field specifies a format revision for the file.
3113 The most current format described in the Policy Manual
3114 is version <strong>1.5</strong>. The syntax of the
3115 format value is the same as that of a package version
3116 number except that no epoch or Debian revision is allowed
3117 - see <ref id="f-Version">.
3121 <sect1 id="f-Urgency">
3122 <heading><tt>Urgency</tt></heading>
3125 This is a description of how important it is to upgrade to
3126 this version from previous ones. It consists of a single
3127 keyword taking one of the values <tt>low</tt>,
3128 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3129 <tt>critical</tt><footnote>
3130 Other urgency values are supported with configuration
3131 changes in the archive software but are not used in Debian.
3132 The urgency affects how quickly a package will be considered
3133 for inclusion into the <tt>testing</tt> distribution and
3134 gives an indication of the importance of any fixes included
3135 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3136 treated as synonymous.
3137 </footnote> (not case-sensitive) followed by an optional
3138 commentary (separated by a space) which is usually in
3139 parentheses. For example:
3142 Urgency: low (HIGH for users of diversions)
3148 The value of this field is usually extracted from the
3149 <file>debian/changelog</file> file - see
3150 <ref id="dpkgchangelog">.
3154 <sect1 id="f-Changes">
3155 <heading><tt>Changes</tt></heading>
3158 This field contains the human-readable changes data, describing
3159 the differences between the last version and the current one.
3163 There should be nothing in this field before the first
3164 newline; all the subsequent lines must be indented by at
3165 least one space; blank lines must be represented by a line
3166 consisting only of a space and a full stop.
3170 The value of this field is usually extracted from the
3171 <file>debian/changelog</file> file - see
3172 <ref id="dpkgchangelog">).
3176 Each version's change information should be preceded by a
3177 "title" line giving at least the version, distribution(s)
3178 and urgency, in a human-readable way.
3182 If data from several versions is being returned the entry
3183 for the most recent version should be returned first, and
3184 entries should be separated by the representation of a
3185 blank line (the "title" line may also be followed by the
3186 representation of blank line).
3190 <sect1 id="f-Binary">
3191 <heading><tt>Binary</tt></heading>
3194 This field is a list of binary packages.
3198 When it appears in the <file>.dsc</file> file it is the list
3199 of binary packages which a source package can produce. It
3200 does not necessarily produce all of these binary packages
3201 for every architecture. The source control file doesn't
3202 contain details of which architectures are appropriate for
3203 which of the binary packages.
3207 When it appears in a <file>.changes</file> file it lists the
3208 names of the binary packages actually being uploaded.
3212 The syntax is a list of binary packages separated by
3214 A space after each comma is conventional.
3215 </footnote>. Currently the packages must be separated using
3216 only spaces in the <file>.changes</file> file.
3220 <sect1 id="f-Installed-Size">
3221 <heading><tt>Installed-Size</tt></heading>
3224 This field appears in the control files of binary
3225 packages, and in the <file>Packages</file> files. It gives
3226 the total amount of disk space required to install the
3231 The disk space is represented in kilobytes as a simple
3236 <sect1 id="f-Files">
3237 <heading><tt>Files</tt></heading>
3240 This field contains a list of files with information about
3241 each one. The exact information and syntax varies with
3242 the context. In all cases the part of the field
3243 contents on the same line as the field name is empty. The
3244 remainder of the field is one line per file, each line
3245 being indented by one space and containing a number of
3246 sub-fields separated by spaces.
3250 In the <file>.dsc</file> file, each line contains the MD5
3251 checksum, size and filename of the tar file and (if applicable)
3252 diff file which make up the remainder of the source
3254 That is, the parts which are not the <tt>.dsc</tt>.
3256 The exact forms of the filenames are described
3257 in <ref id="pkg-sourcearchives">.
3261 In the <file>.changes</file> file this contains one line per
3262 file being uploaded. Each line contains the MD5 checksum,
3263 size, section and priority and the filename.
3264 The <qref id="f-Section">section</qref>
3265 and <qref id="f-Priority">priority</qref>
3266 are the values of the corresponding fields in
3267 the main source control file. If no section or priority is
3268 specified then <tt>-</tt> should be used, though section
3269 and priority values must be specified for new packages to
3270 be installed properly.
3274 The special value <tt>byhand</tt> for the section in a
3275 <tt>.changes</tt> file indicates that the file in question
3276 is not an ordinary package file and must by installed by
3277 hand by the distribution maintainers. If the section is
3278 <tt>byhand</tt> the priority should be <tt>-</tt>.
3282 If a new Debian revision of a package is being shipped and
3283 no new original source archive is being distributed the
3284 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3285 entry for the original source archive
3286 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3287 but the <file>.changes</file> file should leave it out. In
3288 this case the original source archive on the distribution
3289 site must match exactly, byte-for-byte, the original
3290 source archive which was used to generate the
3291 <file>.dsc</file> file and diff which are being uploaded.</p>
3294 <sect1 id="f-Closes">
3295 <heading><tt>Closes</tt></heading>
3298 A space-separated list of bug report numbers that the upload
3299 governed by the .changes file closes.
3303 <sect1 id="f-Homepage">
3304 <heading><tt>Homepage</tt></heading>
3307 The URL of the web site for this package, preferably (when
3308 applicable) the site from which the original source can be
3309 obtained and any additional upstream documentation or
3310 information may be found. The content of this field is a
3311 simple URL without any surrounding characters such as
3319 <heading>User-defined fields</heading>
3322 Additional user-defined fields may be added to the
3323 source package control file. Such fields will be
3324 ignored, and not copied to (for example) binary or
3325 source package control files or upload control files.
3329 If you wish to add additional unsupported fields to
3330 these output files you should use the mechanism
3335 Fields in the main source control information file with
3336 names starting <tt>X</tt>, followed by one or more of
3337 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3338 be copied to the output files. Only the part of the
3339 field name after the hyphen will be used in the output
3340 file. Where the letter <tt>B</tt> is used the field
3341 will appear in binary package control files, where the
3342 letter <tt>S</tt> is used in source package control
3343 files and where <tt>C</tt> is used in upload control
3344 (<tt>.changes</tt>) files.
3348 For example, if the main source information control file
3351 XBS-Comment: I stand between the candle and the star.
3353 then the binary and source package control files will contain the
3356 Comment: I stand between the candle and the star.
3365 <chapt id="maintainerscripts">
3366 <heading>Package maintainer scripts and installation procedure</heading>
3369 <heading>Introduction to package maintainer scripts</heading>
3372 It is possible to supply scripts as part of a package which
3373 the package management system will run for you when your
3374 package is installed, upgraded or removed.
3378 These scripts are the files <prgn>preinst</prgn>,
3379 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3380 <prgn>postrm</prgn> in the control area of the package.
3381 They must be proper executable files; if they are scripts
3382 (which is recommended), they must start with the usual
3383 <tt>#!</tt> convention. They should be readable and
3384 executable by anyone, and must not be world-writable.
3388 The package management system looks at the exit status from
3389 these scripts. It is important that they exit with a
3390 non-zero status if there is an error, so that the package
3391 management system can stop its processing. For shell
3392 scripts this means that you <em>almost always</em> need to
3393 use <tt>set -e</tt> (this is usually true when writing shell
3394 scripts, in fact). It is also important, of course, that
3395 they don't exit with a non-zero status if everything went
3400 Additionally, packages interacting with users using
3401 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3402 install a <prgn>config</prgn> script in the control area,
3403 see <ref id="maintscriptprompt"> for details.
3407 When a package is upgraded a combination of the scripts from
3408 the old and new packages is called during the upgrade
3409 procedure. If your scripts are going to be at all
3410 complicated you need to be aware of this, and may need to
3411 check the arguments to your scripts.
3415 Broadly speaking the <prgn>preinst</prgn> is called before
3416 (a particular version of) a package is installed, and the
3417 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3418 before (a version of) a package is removed and the
3419 <prgn>postrm</prgn> afterwards.
3423 Programs called from maintainer scripts should not normally
3424 have a path prepended to them. Before installation is
3425 started, the package management system checks to see if the
3426 programs <prgn>ldconfig</prgn>,
3427 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3428 and <prgn>update-rc.d</prgn> can be found via the
3429 <tt>PATH</tt> environment variable. Those programs, and any
3430 other program that one would expect to be in the
3431 <tt>PATH</tt>, should thus be invoked without an absolute
3432 pathname. Maintainer scripts should also not reset the
3433 <tt>PATH</tt>, though they might choose to modify it by
3434 prepending or appending package-specific directories. These
3435 considerations really apply to all shell scripts.</p>
3438 <sect id="idempotency">
3439 <heading>Maintainer scripts idempotency</heading>
3442 It is necessary for the error recovery procedures that the
3443 scripts be idempotent. This means that if it is run
3444 successfully, and then it is called again, it doesn't bomb
3445 out or cause any harm, but just ensures that everything is
3446 the way it ought to be. If the first call failed, or
3447 aborted half way through for some reason, the second call
3448 should merely do the things that were left undone the first
3449 time, if any, and exit with a success status if everything
3451 This is so that if an error occurs, the user interrupts
3452 <prgn>dpkg</prgn> or some other unforeseen circumstance
3453 happens you don't leave the user with a badly-broken
3454 package when <prgn>dpkg</prgn> attempts to repeat the
3460 <sect id="controllingterminal">
3461 <heading>Controlling terminal for maintainer scripts</heading>
3464 The maintainer scripts are guaranteed to run with a
3465 controlling terminal and can interact with the user.
3466 Because these scripts may be executed with standard output
3467 redirected into a pipe for logging purposes, Perl scripts
3468 should set unbuffered output by setting <tt>$|=1</tt> so
3469 that the output is printed immediately rather than being
3473 <sect id="exitstatus">
3474 <heading>Exit status</heading>
3477 Each script must return a zero exit status for
3478 success, or a nonzero one for failure, since the package
3479 management system looks for the exit status of these scripts
3480 and determines what action to take next based on that datum.
3484 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3489 <list compact="compact">
3491 <var>new-preinst</var> <tt>install</tt>
3494 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3497 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3500 <var>old-preinst</var> <tt>abort-upgrade</tt>
3501 <var>new-version</var>
3506 <list compact="compact">
3508 <var>postinst</var> <tt>configure</tt>
3509 <var>most-recently-configured-version</var>
3512 <var>old-postinst</var> <tt>abort-upgrade</tt>
3513 <var>new-version</var>
3516 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3517 <tt>in-favour</tt> <var>package</var>
3518 <var>new-version</var>
3521 <var>postinst</var> <tt>abort-remove</tt>
3524 <var>deconfigured's-postinst</var>
3525 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3526 <var>failed-install-package</var> <var>version</var>
3527 [<tt>removing</tt> <var>conflicting-package</var>
3533 <list compact="compact">
3535 <var>prerm</var> <tt>remove</tt>
3538 <var>old-prerm</var> <tt>upgrade</tt>
3539 <var>new-version</var>
3542 <var>new-prerm</var> <tt>failed-upgrade</tt>
3543 <var>old-version</var>
3546 <var>conflictor's-prerm</var> <tt>remove</tt>
3547 <tt>in-favour</tt> <var>package</var>
3548 <var>new-version</var>
3551 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3552 <tt>in-favour</tt> <var>package-being-installed</var>
3553 <var>version</var> [<tt>removing</tt>
3554 <var>conflicting-package</var>
3560 <list compact="compact">
3562 <var>postrm</var> <tt>remove</tt>
3565 <var>postrm</var> <tt>purge</tt>
3568 <var>old-postrm</var> <tt>upgrade</tt>
3569 <var>new-version</var>
3572 <var>new-postrm</var> <tt>failed-upgrade</tt>
3573 <var>old-version</var>
3576 <var>new-postrm</var> <tt>abort-install</tt>
3579 <var>new-postrm</var> <tt>abort-install</tt>
3580 <var>old-version</var>
3583 <var>new-postrm</var> <tt>abort-upgrade</tt>
3584 <var>old-version</var>
3587 <var>disappearer's-postrm</var> <tt>disappear</tt>
3588 <var>overwriter</var>
3589 <var>overwriter-version</var>
3595 <sect id="unpackphase">
3596 <heading>Details of unpack phase of installation or upgrade</heading>
3599 The procedure on installation/upgrade/overwrite/disappear
3600 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3601 stage of <tt>dpkg --install</tt>) is as follows. In each
3602 case, if a major error occurs (unless listed below) the
3603 actions are, in general, run backwards - this means that the
3604 maintainer scripts are run with different arguments in
3605 reverse order. These are the "error unwind" calls listed
3612 If a version of the package is already installed, call
3613 <example compact="compact">
3614 <var>old-prerm</var> upgrade <var>new-version</var>
3618 If the script runs but exits with a non-zero
3619 exit status, <prgn>dpkg</prgn> will attempt:
3620 <example compact="compact">
3621 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3623 If this works, the upgrade continues. If this
3624 does not work, the error unwind:
3625 <example compact="compact">
3626 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3628 If this works, then the old-version is
3629 "Installed", if not, the old version is in a
3630 "Failed-Config" state.
3636 If a "conflicting" package is being removed at the same time,
3637 or if any package will be broken (due to <tt>Breaks</tt>):
3640 If <tt>--auto-deconfigure</tt> is
3641 specified, call, for each package to be deconfigured
3642 due to <tt>Breaks</tt>:
3643 <example compact="compact">
3644 <var>deconfigured's-prerm</var> deconfigure \
3645 in-favour <var>package-being-installed</var> <var>version</var>
3648 <example compact="compact">
3649 <var>deconfigured's-postinst</var> abort-deconfigure \
3650 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3652 The deconfigured packages are marked as
3653 requiring configuration, so that if
3654 <tt>--install</tt> is used they will be
3655 configured again if possible.
3658 If any packages depended on a conflicting
3659 package being removed and <tt>--auto-deconfigure</tt> is
3660 specified, call, for each such package:
3661 <example compact="compact">
3662 <var>deconfigured's-prerm</var> deconfigure \
3663 in-favour <var>package-being-installed</var> <var>version</var> \
3664 removing <var>conflicting-package</var> <var>version</var>
3667 <example compact="compact">
3668 <var>deconfigured's-postinst</var> abort-deconfigure \
3669 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3670 removing <var>conflicting-package</var> <var>version</var>
3672 The deconfigured packages are marked as
3673 requiring configuration, so that if
3674 <tt>--install</tt> is used they will be
3675 configured again if possible.
3678 To prepare for removal of each conflicting package, call:
3679 <example compact="compact">
3680 <var>conflictor's-prerm</var> remove \
3681 in-favour <var>package</var> <var>new-version</var>
3684 <example compact="compact">
3685 <var>conflictor's-postinst</var> abort-remove \
3686 in-favour <var>package</var> <var>new-version</var>
3695 If the package is being upgraded, call:
3696 <example compact="compact">
3697 <var>new-preinst</var> upgrade <var>old-version</var>
3699 If this fails, we call:
3701 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3708 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3710 is called. If this works, then the old version
3711 is in an "Installed" state, or else it is left
3712 in an "Unpacked" state.
3717 If it fails, then the old version is left
3718 in an "Half-Installed" state.
3725 Otherwise, if the package had some configuration
3726 files from a previous version installed (i.e., it
3727 is in the "configuration files only" state):
3728 <example compact="compact">
3729 <var>new-preinst</var> install <var>old-version</var>
3733 <var>new-postrm</var> abort-install <var>old-version</var>
3735 If this fails, the package is left in a
3736 "Half-Installed" state, which requires a
3737 reinstall. If it works, the packages is left in
3738 a "Config Files" state.
3741 Otherwise (i.e., the package was completely purged):
3742 <example compact="compact">
3743 <var>new-preinst</var> install
3746 <example compact="compact">
3747 <var>new-postrm</var> abort-install
3749 If the error-unwind fails, the package is in a
3750 "Half Installed" phase, and requires a
3751 reinstall. If the error unwind works, the
3752 package is in a not installed state.
3759 The new package's files are unpacked, overwriting any
3760 that may be on the system already, for example any
3761 from the old version of the same package or from
3762 another package. Backups of the old files are kept
3763 temporarily, and if anything goes wrong the package
3764 management system will attempt to put them back as
3765 part of the error unwind.
3769 It is an error for a package to contain files which
3770 are on the system in another package, unless
3771 <tt>Replaces</tt> is used (see <ref id="replaces">).
3773 The following paragraph is not currently the case:
3774 Currently the <tt>- - force-overwrite</tt> flag is
3775 enabled, downgrading it to a warning, but this may not
3781 It is a more serious error for a package to contain a
3782 plain file or other kind of non-directory where another
3783 package has a directory (again, unless
3784 <tt>Replaces</tt> is used). This error can be
3785 overridden if desired using
3786 <tt>--force-overwrite-dir</tt>, but this is not
3791 Packages which overwrite each other's files produce
3792 behavior which, though deterministic, is hard for the
3793 system administrator to understand. It can easily
3794 lead to "missing" programs if, for example, a package
3795 is installed which overwrites a file from another
3796 package, and is then removed again.<footnote>
3797 Part of the problem is due to what is arguably a
3798 bug in <prgn>dpkg</prgn>.
3803 A directory will never be replaced by a symbolic link
3804 to a directory or vice versa; instead, the existing
3805 state (symlink or not) will be left alone and
3806 <prgn>dpkg</prgn> will follow the symlink if there is
3815 If the package is being upgraded, call
3816 <example compact="compact">
3817 <var>old-postrm</var> upgrade <var>new-version</var>
3821 If this fails, <prgn>dpkg</prgn> will attempt:
3822 <example compact="compact">
3823 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3825 If this works, installation continues. If not,
3827 <example compact="compact">
3828 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3830 If this fails, the old version is left in an
3831 "Half Installed" state. If it works, dpkg now
3833 <example compact="compact">
3834 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3836 If this fails, the old version is left in an
3837 "Half Installed" state. If it works, dpkg now
3839 <example compact="compact">
3840 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3842 If this fails, the old version is in an
3849 This is the point of no return - if
3850 <prgn>dpkg</prgn> gets this far, it won't back off
3851 past this point if an error occurs. This will
3852 leave the package in a fairly bad state, which
3853 will require a successful re-installation to clear
3854 up, but it's when <prgn>dpkg</prgn> starts doing
3855 things that are irreversible.
3860 Any files which were in the old version of the package
3861 but not in the new are removed.
3865 The new file list replaces the old.
3869 The new maintainer scripts replace the old.
3873 Any packages all of whose files have been overwritten
3874 during the installation, and which aren't required for
3875 dependencies, are considered to have been removed.
3876 For each such package
3879 <prgn>dpkg</prgn> calls:
3880 <example compact="compact">
3881 <var>disappearer's-postrm</var> disappear \
3882 <var>overwriter</var> <var>overwriter-version</var>
3886 The package's maintainer scripts are removed.
3889 It is noted in the status database as being in a
3890 sane state, namely not installed (any conffiles
3891 it may have are ignored, rather than being
3892 removed by <prgn>dpkg</prgn>). Note that
3893 disappearing packages do not have their prerm
3894 called, because <prgn>dpkg</prgn> doesn't know
3895 in advance that the package is going to
3902 Any files in the package we're unpacking that are also
3903 listed in the file lists of other packages are removed
3904 from those lists. (This will lobotomize the file list
3905 of the "conflicting" package if there is one.)
3909 The backup files made during installation, above, are
3915 The new package's status is now sane, and recorded as
3920 Here is another point of no return - if the
3921 conflicting package's removal fails we do not unwind
3922 the rest of the installation; the conflicting package
3923 is left in a half-removed limbo.
3928 If there was a conflicting package we go and do the
3929 removal actions (described below), starting with the
3930 removal of the conflicting package's files (any that
3931 are also in the package being installed have already
3932 been removed from the conflicting package's file list,
3933 and so do not get removed now).
3939 <sect id="configdetails"><heading>Details of configuration</heading>
3942 When we configure a package (this happens with <tt>dpkg
3943 --install</tt> and <tt>dpkg --configure</tt>), we first
3944 update any <tt>conffile</tt>s and then call:
3945 <example compact="compact">
3946 <var>postinst</var> configure <var>most-recently-configured-version</var>
3951 No attempt is made to unwind after errors during
3952 configuration. If the configuration fails, the package is in
3953 a "Failed Config" state, and an error message is generated.
3957 If there is no most recently configured version
3958 <prgn>dpkg</prgn> will pass a null argument.
3961 Historical note: Truly ancient (pre-1997) versions of
3962 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3963 (including the angle brackets) in this case. Even older
3964 ones did not pass a second argument at all, under any
3965 circumstance. Note that upgrades using such an old dpkg
3966 version are unlikely to work for other reasons, even if
3967 this old argument behavior is handled by your postinst script.
3973 <sect id="removedetails"><heading>Details of removal and/or
3974 configuration purging</heading>
3980 <example compact="compact">
3981 <var>prerm</var> remove
3985 If prerm fails during replacement due to conflict
3987 <var>conflictor's-postinst</var> abort-remove \
3988 in-favour <var>package</var> <var>new-version</var>
3992 <var>postinst</var> abort-remove
3996 If this fails, the package is in a "Failed-Config"
3997 state, or else it remains "Installed".
4001 The package's files are removed (except <tt>conffile</tt>s).
4004 <example compact="compact">
4005 <var>postrm</var> remove
4009 If it fails, there's no error unwind, and the package is in
4010 an "Half-Installed" state.
4015 All the maintainer scripts except the <prgn>postrm</prgn>
4020 If we aren't purging the package we stop here. Note
4021 that packages which have no <prgn>postrm</prgn> and no
4022 <tt>conffile</tt>s are automatically purged when
4023 removed, as there is no difference except for the
4024 <prgn>dpkg</prgn> status.
4028 The <tt>conffile</tt>s and any backup files
4029 (<tt>~</tt>-files, <tt>#*#</tt> files,
4030 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4035 <example compact="compact">
4036 <var>postrm</var> purge
4040 If this fails, the package remains in a "Config-Files"
4045 The package's file list is removed.
4054 <chapt id="relationships">
4055 <heading>Declaring relationships between packages</heading>
4057 <sect id="depsyntax">
4058 <heading>Syntax of relationship fields</heading>
4061 These fields all have a uniform syntax. They are a list of
4062 package names separated by commas.
4066 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4067 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4068 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4069 control file fields of the package, which declare
4070 dependencies on other packages, the package names listed may
4071 also include lists of alternative package names, separated
4072 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4073 if any one of the alternative packages is installed, that
4074 part of the dependency is considered to be satisfied.
4078 All of the fields except for <tt>Provides</tt> may restrict
4079 their applicability to particular versions of each named
4080 package. This is done in parentheses after each individual
4081 package name; the parentheses should contain a relation from
4082 the list below followed by a version number, in the format
4083 described in <ref id="f-Version">.
4087 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4088 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4089 strictly earlier, earlier or equal, exactly equal, later or
4090 equal and strictly later, respectively. The deprecated
4091 forms <tt><</tt> and <tt>></tt> were used to mean
4092 earlier/later or equal, rather than strictly earlier/later,
4093 so they should not appear in new packages (though
4094 <prgn>dpkg</prgn> still supports them).
4098 Whitespace may appear at any point in the version
4099 specification subject to the rules in <ref
4100 id="controlsyntax">, and must appear where it's necessary to
4101 disambiguate; it is not otherwise significant. All of the
4102 relationship fields may span multiple lines. For
4103 consistency and in case of future changes to
4104 <prgn>dpkg</prgn> it is recommended that a single space be
4105 used after a version relationship and before a version
4106 number; it is also conventional to put a single space after
4107 each comma, on either side of each vertical bar, and before
4108 each open parenthesis. When wrapping a relationship field, it
4109 is conventional to do so after a comma and before the space
4110 following that comma.
4114 For example, a list of dependencies might appear as:
4115 <example compact="compact">
4118 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4123 All fields that specify build-time relationships
4124 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4125 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4126 may be restricted to a certain set of architectures. This
4127 is indicated in brackets after each individual package name and
4128 the optional version specification. The brackets enclose a
4129 list of Debian architecture names separated by whitespace.
4130 Exclamation marks may be prepended to each of the names.
4131 (It is not permitted for some names to be prepended with
4132 exclamation marks while others aren't.) If the current Debian
4133 host architecture is not in this list and there are no
4134 exclamation marks in the list, or it is in the list with a
4135 prepended exclamation mark, the package name and the
4136 associated version specification are ignored completely for
4137 the purposes of defining the relationships.
4142 <example compact="compact">
4144 Build-Depends-Indep: texinfo
4145 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4146 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4151 Note that the binary package relationship fields such as
4152 <tt>Depends</tt> appear in one of the binary package
4153 sections of the control file, whereas the build-time
4154 relationships such as <tt>Build-Depends</tt> appear in the
4155 source package section of the control file (which is the
4160 <sect id="binarydeps">
4161 <heading>Binary Dependencies - <tt>Depends</tt>,
4162 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4163 <tt>Pre-Depends</tt>
4167 Packages can declare in their control file that they have
4168 certain relationships to other packages - for example, that
4169 they may not be installed at the same time as certain other
4170 packages, and/or that they depend on the presence of others.
4174 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4175 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4176 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4180 These seven fields are used to declare a dependency
4181 relationship by one package on another. Except for
4182 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4183 depending (binary) package's control file.
4184 (<tt>Enhances</tt> appears in the recommending package's
4185 control file, and <tt>Breaks</tt> appears in the version of
4186 depended-on package which causes the named package to
4191 A <tt>Depends</tt> field takes effect <em>only</em> when a
4192 package is to be configured. It does not prevent a package
4193 being on the system in an unconfigured state while its
4194 dependencies are unsatisfied, and it is possible to replace
4195 a package whose dependencies are satisfied and which is
4196 properly installed with a different version whose
4197 dependencies are not and cannot be satisfied; when this is
4198 done the depending package will be left unconfigured (since
4199 attempts to configure it will give errors) and will not
4200 function properly. If it is necessary, a
4201 <tt>Pre-Depends</tt> field can be used, which has a partial
4202 effect even when a package is being unpacked, as explained
4203 in detail below. (The other three dependency fields,
4204 <tt>Recommends</tt>, <tt>Suggests</tt> and
4205 <tt>Enhances</tt>, are only used by the various front-ends
4206 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4207 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4211 For this reason packages in an installation run are usually
4212 all unpacked first and all configured later; this gives
4213 later versions of packages with dependencies on later
4214 versions of other packages the opportunity to have their
4215 dependencies satisfied.
4219 In case of circular dependencies, since installation or
4220 removal order honoring the dependency order can't be
4221 established, dependency loops are broken at some point
4222 (based on rules below), and some packages may not be able to
4223 rely on their dependencies being present when being
4224 installed or removed, depending on which side of the break
4225 of the circular dependency loop they happen to be on. If one
4226 of the packages in the loop has no postinst script, then the
4227 cycle will be broken at that package, so as to ensure that
4228 all postinst scripts run with the dependencies properly
4229 configured if this is possible. Otherwise the breaking point
4234 The <tt>Depends</tt> field thus allows package maintainers
4235 to impose an order in which packages should be configured.
4239 The meaning of the five dependency fields is as follows:
4241 <tag><tt>Depends</tt></tag>
4244 This declares an absolute dependency. A package will
4245 not be configured unless all of the packages listed in
4246 its <tt>Depends</tt> field have been correctly
4251 The <tt>Depends</tt> field should be used if the
4252 depended-on package is required for the depending
4253 package to provide a significant amount of
4258 The <tt>Depends</tt> field should also be used if the
4259 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4260 <prgn>postrm</prgn> scripts require the package to be
4261 present in order to run. Note, however, that the
4262 <prgn>postrm</prgn> cannot rely on any non-essential
4263 packages to be present during the <tt>purge</tt>
4267 <tag><tt>Recommends</tt></tag>
4270 This declares a strong, but not absolute, dependency.
4274 The <tt>Recommends</tt> field should list packages
4275 that would be found together with this one in all but
4276 unusual installations.
4280 <tag><tt>Suggests</tt></tag>
4282 This is used to declare that one package may be more
4283 useful with one or more others. Using this field
4284 tells the packaging system and the user that the
4285 listed packages are related to this one and can
4286 perhaps enhance its usefulness, but that installing
4287 this one without them is perfectly reasonable.
4290 <tag><tt>Enhances</tt></tag>
4292 This field is similar to Suggests but works in the
4293 opposite direction. It is used to declare that a
4294 package can enhance the functionality of another
4298 <tag><tt>Pre-Depends</tt></tag>
4301 This field is like <tt>Depends</tt>, except that it
4302 also forces <prgn>dpkg</prgn> to complete installation
4303 of the packages named before even starting the
4304 installation of the package which declares the
4305 pre-dependency, as follows:
4309 When a package declaring a pre-dependency is about to
4310 be <em>unpacked</em> the pre-dependency can be
4311 satisfied if the depended-on package is either fully
4312 configured, <em>or even if</em> the depended-on
4313 package(s) are only unpacked or half-configured,
4314 provided that they have been configured correctly at
4315 some point in the past (and not removed or partially
4316 removed since). In this case, both the
4317 previously-configured and currently unpacked or
4318 half-configured versions must satisfy any version
4319 clause in the <tt>Pre-Depends</tt> field.
4323 When the package declaring a pre-dependency is about
4324 to be <em>configured</em>, the pre-dependency will be
4325 treated as a normal <tt>Depends</tt>, that is, it will
4326 be considered satisfied only if the depended-on
4327 package has been correctly configured.
4331 <tt>Pre-Depends</tt> should be used sparingly,
4332 preferably only by packages whose premature upgrade or
4333 installation would hamper the ability of the system to
4334 continue with any upgrade that might be in progress.
4338 <tt>Pre-Depends</tt> are also required if the
4339 <prgn>preinst</prgn> script depends on the named
4340 package. It is best to avoid this situation if
4348 When selecting which level of dependency to use you should
4349 consider how important the depended-on package is to the
4350 functionality of the one declaring the dependency. Some
4351 packages are composed of components of varying degrees of
4352 importance. Such a package should list using
4353 <tt>Depends</tt> the package(s) which are required by the
4354 more important components. The other components'
4355 requirements may be mentioned as Suggestions or
4356 Recommendations, as appropriate to the components' relative
4362 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4365 Using <tt>Breaks</tt> may cause problems for upgrades from older
4366 versions of Debian and should not be used until the stable
4367 release of Debian supports <tt>Breaks</tt>.
4371 When one binary package declares that it breaks another,
4372 <prgn>dpkg</prgn> will refuse to allow the package which
4373 declares <tt>Breaks</tt> be installed unless the broken
4374 package is deconfigured first, and it will refuse to
4375 allow the broken package to be reconfigured.
4379 A package will not be regarded as causing breakage merely
4380 because its configuration files are still installed; it must
4381 be at least half-installed.
4385 A special exception is made for packages which declare that
4386 they break their own package name or a virtual package which
4387 they provide (see below): this does not count as a real
4392 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4393 version clause; such a <tt>Breaks</tt> is introduced in the
4394 version of an (implicit or explicit) dependency which
4395 violates an assumption or reveals a bug in earlier versions
4396 of the broken package. This use of <tt>Breaks</tt> will
4397 inform higher-level package management tools that broken
4398 package must be upgraded before the new one.
4402 If the breaking package also overwrites some files from the
4403 older package, it should use <tt>Replaces</tt> (not
4404 <tt>Conflicts</tt>) to ensure this goes smoothly.
4408 <sect id="conflicts">
4409 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4412 When one binary package declares a conflict with another
4413 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4414 refuse to allow them to be installed on the system at the
4419 If one package is to be installed, the other must be removed
4420 first - if the package being installed is marked as
4421 replacing (see <ref id="replaces">) the one on the system,
4422 or the one on the system is marked as deselected, or both
4423 packages are marked <tt>Essential</tt>, then
4424 <prgn>dpkg</prgn> will automatically remove the package
4425 which is causing the conflict, otherwise it will halt the
4426 installation of the new package with an error. This
4427 mechanism is specifically designed to produce an error when
4428 the installed package is <tt>Essential</tt>, but the new
4433 A package will not cause a conflict merely because its
4434 configuration files are still installed; it must be at least
4439 A special exception is made for packages which declare a
4440 conflict with their own package name, or with a virtual
4441 package which they provide (see below): this does not
4442 prevent their installation, and allows a package to conflict
4443 with others providing a replacement for it. You use this
4444 feature when you want the package in question to be the only
4445 package providing some feature.
4449 A <tt>Conflicts</tt> entry should almost never have an
4450 "earlier than" version clause. This would prevent
4451 <prgn>dpkg</prgn> from upgrading or installing the package
4452 which declared such a conflict until the upgrade or removal
4453 of the conflicted-with package had been completed. Instead,
4454 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4455 by the stable release of Debian).
4459 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4463 As well as the names of actual ("concrete") packages, the
4464 package relationship fields <tt>Depends</tt>,
4465 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4466 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4467 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4468 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4469 may mention "virtual packages".
4473 A <em>virtual package</em> is one which appears in the
4474 <tt>Provides</tt> control file field of another package.
4475 The effect is as if the package(s) which provide a
4476 particular virtual package name had been listed by name
4477 everywhere the virtual package name appears. (See also <ref
4482 If there are both concrete and virtual packages of the same
4483 name, then the dependency may be satisfied (or the conflict
4484 caused) by either the concrete package with the name in
4485 question or any other concrete package which provides the
4486 virtual package with the name in question. This is so that,
4487 for example, supposing we have
4488 <example compact="compact">
4491 </example> and someone else releases an enhanced version of
4492 the <tt>bar</tt> package they can say:
4493 <example compact="compact">
4497 and the <tt>bar-plus</tt> package will now also satisfy the
4498 dependency for the <tt>foo</tt> package.
4502 If a relationship field has a version number attached
4503 then only real packages will be considered to see whether
4504 the relationship is satisfied (or the prohibition violated,
4505 for a conflict or breakage) - it is assumed that a real
4506 package which provides the virtual package is not of the
4507 "right" version. So, a <tt>Provides</tt> field may not
4508 contain version numbers, and the version number of the
4509 concrete package which provides a particular virtual package
4510 will not be looked at when considering a dependency on or
4511 conflict with the virtual package name.
4515 It is likely that the ability will be added in a future
4516 release of <prgn>dpkg</prgn> to specify a version number for
4517 each virtual package it provides. This feature is not yet
4518 present, however, and is expected to be used only
4523 If you want to specify which of a set of real packages
4524 should be the default to satisfy a particular dependency on
4525 a virtual package, you should list the real package as an
4526 alternative before the virtual one.
4531 <sect id="replaces"><heading>Overwriting files and replacing
4532 packages - <tt>Replaces</tt></heading>
4535 Packages can declare in their control file that they should
4536 overwrite files in certain other packages, or completely
4537 replace other packages. The <tt>Replaces</tt> control file
4538 field has these two distinct purposes.
4541 <sect1><heading>Overwriting files in other packages</heading>
4544 Firstly, as mentioned before, it is usually an error for a
4545 package to contain files which are on the system in
4550 However, if the overwriting package declares that it
4551 <tt>Replaces</tt> the one containing the file being
4552 overwritten, then <prgn>dpkg</prgn> will replace the file
4553 from the old package with that from the new. The file
4554 will no longer be listed as "owned" by the old package.
4558 If a package is completely replaced in this way, so that
4559 <prgn>dpkg</prgn> does not know of any files it still
4560 contains, it is considered to have "disappeared". It will
4561 be marked as not wanted on the system (selected for
4562 removal) and not installed. Any <tt>conffile</tt>s
4563 details noted for the package will be ignored, as they
4564 will have been taken over by the overwriting package. The
4565 package's <prgn>postrm</prgn> script will be run with a
4566 special argument to allow the package to do any final
4567 cleanup required. See <ref id="mscriptsinstact">.
4570 Replaces is a one way relationship -- you have to
4571 install the replacing package after the replaced
4578 For this usage of <tt>Replaces</tt>, virtual packages (see
4579 <ref id="virtual">) are not considered when looking at a
4580 <tt>Replaces</tt> field - the packages declared as being
4581 replaced must be mentioned by their real names.
4585 Furthermore, this usage of <tt>Replaces</tt> only takes
4586 effect when both packages are at least partially on the
4587 system at once, so that it can only happen if they do not
4588 conflict or if the conflict has been overridden.
4593 <sect1><heading>Replacing whole packages, forcing their
4597 Secondly, <tt>Replaces</tt> allows the packaging system to
4598 resolve which package should be removed when there is a
4599 conflict - see <ref id="conflicts">. This usage only
4600 takes effect when the two packages <em>do</em> conflict,
4601 so that the two usages of this field do not interfere with
4606 In this situation, the package declared as being replaced
4607 can be a virtual package, so for example, all mail
4608 transport agents (MTAs) would have the following fields in
4609 their control files:
4610 <example compact="compact">
4611 Provides: mail-transport-agent
4612 Conflicts: mail-transport-agent
4613 Replaces: mail-transport-agent
4615 ensuring that only one MTA can be installed at any one
4620 <sect id="sourcebinarydeps">
4621 <heading>Relationships between source and binary packages -
4622 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4623 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4627 Source packages that require certain binary packages to be
4628 installed or absent at the time of building the package
4629 can declare relationships to those binary packages.
4633 This is done using the <tt>Build-Depends</tt>,
4634 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4635 <tt>Build-Conflicts-Indep</tt> control file fields.
4639 Build-dependencies on "build-essential" binary packages can be
4640 omitted. Please see <ref id="pkg-relations"> for more information.
4644 The dependencies and conflicts they define must be satisfied
4645 (as defined earlier for binary packages) in order to invoke
4646 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4648 If you make "build-arch" or "binary-arch", you need
4649 Build-Depends. If you make "build-indep" or
4650 "binary-indep", you need Build-Depends and
4651 Build-Depends-Indep. If you make "build" or "binary",
4655 There is no Build-Depends-Arch; this role is essentially
4656 met with Build-Depends. Anyone building the
4657 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4658 is basically assumed to be building the whole package
4659 anyway and so installs all build dependencies. The
4660 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4661 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4662 does not yet know how to check for its existence) and
4663 <tt>binary-arch</tt>.
4666 The purpose of the original split, I recall, was so that
4667 the autobuilders wouldn't need to install extra packages
4668 needed only for the binary-indep targets. But without a
4669 build-arch/build-indep split, this didn't work, since
4670 most of the work is done in the build target, not in the
4676 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4678 The <tt>Build-Depends</tt> and
4679 <tt>Build-Conflicts</tt> fields must be satisfied when
4680 any of the following targets is invoked:
4681 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4682 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4683 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4685 <tag><tt>Build-Depends-Indep</tt>,
4686 <tt>Build-Conflicts-Indep</tt></tag>
4688 The <tt>Build-Depends-Indep</tt> and
4689 <tt>Build-Conflicts-Indep</tt> fields must be
4690 satisfied when any of the following targets is
4691 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4692 <tt>binary</tt> and <tt>binary-indep</tt>.
4702 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4705 Packages containing shared libraries must be constructed with
4706 a little care to make sure that the shared library is always
4707 available. This is especially important for packages whose
4708 shared libraries are vitally important, such as the C library
4709 (currently <tt>libc6</tt>).
4713 Packages involving shared libraries should be split up into
4714 several binary packages. This section mostly deals with how
4715 this separation is to be accomplished; rules for files within
4716 the shared library packages are in <ref id="libraries"> instead.
4719 <sect id="sharedlibs-runtime">
4720 <heading>Run-time shared libraries</heading>
4723 The run-time shared library needs to be placed in a package
4724 whose name changes whenever the shared object version
4727 Since it is common place to install several versions of a
4728 package that just provides shared libraries, it is a
4729 good idea that the library package should not
4730 contain any extraneous non-versioned files, unless they
4731 happen to be in versioned directories.</p>
4733 The most common mechanism is to place it in a package
4735 <package><var>libraryname</var><var>soversion</var></package>,
4736 where <file><var>soversion</var></file> is the version number
4737 in the soname of the shared library<footnote>
4738 The soname is the shared object name: it's the thing
4739 that has to match exactly between building an executable
4740 and running it for the dynamic linker to be able run the
4741 program. For example, if the soname of the library is
4742 <file>libfoo.so.6</file>, the library package would be
4743 called <file>libfoo6</file>.
4745 Alternatively, if it would be confusing to directly append
4746 <var>soversion</var> to <var>libraryname</var> (e.g. because
4747 <var>libraryname</var> itself ends in a number), you may use
4748 <package><var>libraryname</var>-<var>soversion</var></package> and
4749 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4754 If you have several shared libraries built from the same
4755 source tree you may lump them all together into a single
4756 shared library package, provided that you change all of
4757 their sonames at once (so that you don't get filename
4758 clashes if you try to install different versions of the
4759 combined shared libraries package).
4763 The package should install the shared libraries under
4764 their normal names. For example, the <package>libgdbm3</package>
4765 package should install <file>libgdbm.so.3.0.0</file> as
4766 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4767 renamed or re-linked by any <prgn>prerm</prgn> or
4768 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4769 of renaming things safely without affecting running programs,
4770 and attempts to interfere with this are likely to lead to
4775 Shared libraries should not be installed executable, since
4776 the dynamic linker does not require this and trying to
4777 execute a shared library usually results in a core dump.
4781 The run-time library package should include the symbolic link that
4782 <prgn>ldconfig</prgn> would create for the shared libraries.
4783 For example, the <package>libgdbm3</package> package should include
4784 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4785 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4786 linker (for example <prgn>ld.so</prgn> or
4787 <prgn>ld-linux.so.*</prgn>) can find the library between the
4788 time that <prgn>dpkg</prgn> installs it and the time that
4789 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4791 The package management system requires the library to be
4792 placed before the symbolic link pointing to it in the
4793 <file>.deb</file> file. This is so that when
4794 <prgn>dpkg</prgn> comes to install the symlink
4795 (overwriting the previous symlink pointing at an older
4796 version of the library), the new shared library is already
4797 in place. In the past, this was achieved by creating the
4798 library in the temporary packaging directory before
4799 creating the symlink. Unfortunately, this was not always
4800 effective, since the building of the tar file in the
4801 <file>.deb</file> depended on the behavior of the underlying
4802 file system. Some file systems (such as reiserfs) reorder
4803 the files so that the order of creation is forgotten.
4804 Since version 1.7.0, <prgn>dpkg</prgn>
4805 reorders the files itself as necessary when building a
4806 package. Thus it is no longer important to concern
4807 oneself with the order of file creation.
4811 <sect1 id="ldconfig">
4812 <heading><tt>ldconfig</tt></heading>
4815 Any package installing shared libraries in one of the default
4816 library directories of the dynamic linker (which are currently
4817 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4818 listed in <file>/etc/ld.so.conf</file><footnote>
4820 <list compact="compact">
4821 <item>/usr/local/lib</item>
4822 <item>/usr/lib/libc5-compat</item>
4823 <item>/lib/libc5-compat</item>
4826 must use <prgn>ldconfig</prgn> to update the shared library
4831 The package maintainer scripts must only call
4832 <prgn>ldconfig</prgn> under these circumstances:
4833 <list compact="compact">
4834 <item>When the <prgn>postinst</prgn> script is run with a
4835 first argument of <tt>configure</tt>, the script must call
4836 <prgn>ldconfig</prgn>, and may optionally invoke
4837 <prgn>ldconfig</prgn> at other times.
4839 <item>When the <prgn>postrm</prgn> script is run with a
4840 first argument of <tt>remove</tt>, the script should call
4841 <prgn>ldconfig</prgn>.
4846 During install or upgrade, the preinst is called before
4847 the new files are installed, so calling "ldconfig" is
4848 pointless. The preinst of an existing package can also be
4849 called if an upgrade fails. However, this happens during
4850 the critical time when a shared libs may exist on-disk
4851 under a temporary name. Thus, it is dangerous and
4852 forbidden by current policy to call "ldconfig" at this
4857 When a package is installed or upgraded, "postinst
4858 configure" runs after the new files are safely on-disk.
4859 Since it is perfectly safe to invoke ldconfig
4860 unconditionally in a postinst, it is OK for a package to
4861 simply put ldconfig in its postinst without checking the
4862 argument. The postinst can also be called to recover from
4863 a failed upgrade. This happens before any new files are
4864 unpacked, so there is no reason to call "ldconfig" at this
4869 For a package that is being removed, prerm is
4870 called with all the files intact, so calling ldconfig is
4871 useless. The other calls to "prerm" happen in the case of
4872 upgrade at a time when all the files of the old package
4873 are on-disk, so again calling "ldconfig" is pointless.
4877 postrm, on the other hand, is called with the "remove"
4878 argument just after the files are removed, so this is
4879 the proper time to call "ldconfig" to notify the system
4880 of the fact that the shared libraries from the package
4881 are removed. The postrm can be called at several other
4882 times. At the time of "postrm purge", "postrm
4883 abort-install", or "postrm abort-upgrade", calling
4884 "ldconfig" is useless because the shared lib files are
4885 not on-disk. However, when "postrm" is invoked with
4886 arguments "upgrade", "failed-upgrade", or "disappear", a
4887 shared lib may exist on-disk under a temporary filename.
4895 <sect id="sharedlibs-support-files">
4896 <heading>Shared library support files</heading>
4899 If your package contains files whose names do not change with
4900 each change in the library shared object version, you must not
4901 put them in the shared library package. Otherwise, several
4902 versions of the shared library cannot be installed at the same
4903 time without filename clashes, making upgrades and transitions
4904 unnecessarily difficult.
4908 It is recommended that supporting files and run-time support
4909 programs that do not need to be invoked manually by users, but
4910 are nevertheless required for the package to function, be placed
4911 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4912 preferably under <file>/usr/lib/</file><var>package-name</var>.
4913 If the program or file is architecture independent, the
4914 recommendation is for it to be placed in a subdirectory of
4915 <file>/usr/share</file> instead, preferably under
4916 <file>/usr/share/</file><var>package-name</var>. Following the
4917 <var>package-name</var> naming convention ensures that the file
4918 names change when the shared object version changes.
4922 Run-time support programs that use the shared library but are
4923 not required for the library to function or files used by the
4924 shared library that can be used by any version of the shared
4925 library package should instead be put in a separate package.
4926 This package might typically be named
4927 <package><var>libraryname</var>-tools</package>; note the
4928 absence of the <var>soversion</var> in the package name.
4932 Files and support programs only useful when compiling software
4933 against the library should be included in the development
4934 package for the library.<footnote>
4935 For example, a <file><var>package-name</var>-config</file>
4936 script or <package>pkg-config</package> configuration files.
4941 <sect id="sharedlibs-static">
4942 <heading>Static libraries</heading>
4945 The static library (<file><var>libraryname.a</var></file>)
4946 is usually provided in addition to the shared version.
4947 It is placed into the development package (see below).
4951 In some cases, it is acceptable for a library to be
4952 available in static form only; these cases include:
4954 <item>libraries for languages whose shared library support
4955 is immature or unstable</item>
4956 <item>libraries whose interfaces are in flux or under
4957 development (commonly the case when the library's
4958 major version number is zero, or where the ABI breaks
4959 across patchlevels)</item>
4960 <item>libraries which are explicitly intended to be
4961 available only in static form by their upstream
4966 <sect id="sharedlibs-dev">
4967 <heading>Development files</heading>
4970 The development files associated to a shared library need to be
4971 placed in a package called
4972 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4973 or if you prefer only to support one development version at a
4974 time, <package><var>libraryname</var>-dev</package>.
4978 In case several development versions of a library exist, you may
4979 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4980 <ref id="conflicts">) to ensure that the user only installs one
4981 development version at a time (as different development versions are
4982 likely to have the same header files in them, which would cause a
4983 filename clash if both were installed).
4987 The development package should contain a symlink for the associated
4988 shared library without a version number. For example, the
4989 <package>libgdbm-dev</package> package should include a symlink
4990 from <file>/usr/lib/libgdbm.so</file> to
4991 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4992 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4993 <file>libgdbm.so</file> when compiling dynamically.
4997 <sect id="sharedlibs-intradeps">
4998 <heading>Dependencies between the packages of the same library</heading>
5001 Typically the development version should have an exact
5002 version dependency on the runtime library, to make sure that
5003 compilation and linking happens correctly. The
5004 <tt>${binary:Version}</tt> substitution variable can be
5005 useful for this purpose.
5007 Previously, <tt>${Source-Version}</tt> was used, but its name
5008 was confusing and it has been deprecated since dpkg 1.13.19.
5013 <sect id="sharedlibs-shlibdeps">
5014 <heading>Dependencies between the library and other packages -
5015 the <tt>shlibs</tt> system</heading>
5018 If a package contains a binary or library which links to a
5019 shared library, we must ensure that when the package is
5020 installed on the system, all of the libraries needed are
5021 also installed. This requirement led to the creation of the
5022 <tt>shlibs</tt> system, which is very simple in its design:
5023 any package which <em>provides</em> a shared library also
5024 provides information on the package dependencies required to
5025 ensure the presence of this library, and any package which
5026 <em>uses</em> a shared library uses this information to
5027 determine the dependencies it requires. The files which
5028 contain the mapping from shared libraries to the necessary
5029 dependency information are called <file>shlibs</file> files.
5033 Thus, when a package is built which contains any shared
5034 libraries, it must provide a <file>shlibs</file> file for other
5035 packages to use, and when a package is built which contains
5036 any shared libraries or compiled binaries, it must run
5037 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5038 on these to determine the libraries used and hence the
5039 dependencies needed by this package.<footnote>
5041 In the past, the shared libraries linked to were
5042 determined by calling <prgn>ldd</prgn>, but now
5043 <prgn>objdump</prgn> is used to do this. The only
5044 change this makes to package building is that
5045 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5046 libraries, whereas in the past this was unnecessary.
5047 The rest of this footnote explains the advantage that
5052 We say that a binary <tt>foo</tt> <em>directly</em> uses
5053 a library <tt>libbar</tt> if it is explicitly linked
5054 with that library (that is, it uses the flag
5055 <tt>-lbar</tt> during the linking stage). Other
5056 libraries that are needed by <tt>libbar</tt> are linked
5057 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5058 linker will load them automatically when it loads
5059 <tt>libbar</tt>. A package should depend on
5060 the libraries it directly uses, and the dependencies for
5061 those libraries should automatically pull in the other
5066 Unfortunately, the <prgn>ldd</prgn> program shows both
5067 the directly and indirectly used libraries, meaning that
5068 the dependencies determined included both direct and
5069 indirect dependencies. The use of <prgn>objdump</prgn>
5070 avoids this problem by determining only the directly
5075 A good example of where this helps is the following. We
5076 could update <tt>libimlib</tt> with a new version that
5077 supports a new graphics format called dgf (but retaining
5078 the same major version number). If we used the old
5079 <prgn>ldd</prgn> method, every package that uses
5080 <tt>libimlib</tt> would need to be recompiled so it
5081 would also depend on <tt>libdgf</tt> or it wouldn't run
5082 due to missing symbols. However with the new system,
5083 packages using <tt>libimlib</tt> can rely on
5084 <tt>libimlib</tt> itself having the dependency on
5085 <tt>libdgf</tt> and so they would not need rebuilding.
5091 In the following sections, we will first describe where the
5092 various <tt>shlibs</tt> files are to be found, then how to
5093 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5094 file format and how to create them if your package contains a
5099 <heading>The <tt>shlibs</tt> files present on the system</heading>
5102 There are several places where <tt>shlibs</tt> files are
5103 found. The following list gives them in the order in which
5105 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5106 (The first one which gives the required information is used.)
5112 <p><file>debian/shlibs.local</file></p>
5115 This lists overrides for this package. Its use is
5116 described below (see <ref id="shlibslocal">).
5121 <p><file>/etc/dpkg/shlibs.override</file></p>
5124 This lists global overrides. This list is normally
5125 empty. It is maintained by the local system
5131 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5134 When packages are being built, any
5135 <file>debian/shlibs</file> files are copied into the
5136 control file area of the temporary build directory and
5137 given the name <file>shlibs</file>. These files give
5138 details of any shared libraries included in the
5140 An example may help here. Let us say that the
5141 source package <tt>foo</tt> generates two binary
5142 packages, <tt>libfoo2</tt> and
5143 <tt>foo-runtime</tt>. When building the binary
5144 packages, the two packages are created in the
5145 directories <file>debian/libfoo2</file> and
5146 <file>debian/foo-runtime</file> respectively.
5147 (<file>debian/tmp</file> could be used instead of one
5148 of these.) Since <tt>libfoo2</tt> provides the
5149 <tt>libfoo</tt> shared library, it will require a
5150 <tt>shlibs</tt> file, which will be installed in
5151 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5153 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5154 when <prgn>dpkg-shlibdeps</prgn> is run on the
5156 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5158 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5159 determine whether <tt>foo-prog</tt>'s library
5160 dependencies are satisfied by any of the libraries
5161 provided by <tt>libfoo2</tt>. For this reason,
5162 <prgn>dpkg-shlibdeps</prgn> must only be run once
5163 all of the individual binary packages'
5164 <tt>shlibs</tt> files have been installed into the
5171 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5174 These are the <file>shlibs</file> files corresponding to
5175 all of the packages installed on the system, and are
5176 maintained by the relevant package maintainers.
5181 <p><file>/etc/dpkg/shlibs.default</file></p>
5184 This file lists any shared libraries whose packages
5185 have failed to provide correct <file>shlibs</file> files.
5186 It was used when the <file>shlibs</file> setup was first
5187 introduced, but it is now normally empty. It is
5188 maintained by the <tt>dpkg</tt> maintainer.
5196 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5197 <file>shlibs</file> files</heading>
5201 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5202 into your <file>debian/rules</file> file. If your package
5203 contains only compiled binaries and libraries (but no scripts),
5204 you can use a command such as:
5205 <example compact="compact">
5206 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5207 debian/tmp/usr/lib/*
5209 Otherwise, you will need to explicitly list the compiled
5210 binaries and libraries.<footnote>
5211 If you are using <tt>debhelper</tt>, the
5212 <prgn>dh_shlibdeps</prgn> program will do this work for
5213 you. It will also correctly handle multi-binary
5219 This command puts the dependency information into the
5220 <file>debian/substvars</file> file, which is then used by
5221 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5222 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5223 field in the control file for this to work.
5227 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5228 done. If it does complain you might need to create your own
5229 <file>debian/shlibs.local</file> file, as explained below (see
5230 <ref id="shlibslocal">).
5234 If you have multiple binary packages, you will need to call
5235 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5236 compiled libraries or binaries. In such a case, you will
5237 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5238 utilities to specify a different <file>substvars</file> file.
5242 If you are creating a udeb for use in the Debian Installer, you
5243 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5244 the dependency line of type <tt>udeb</tt> by adding
5245 <tt>-tudeb</tt> as option<footnote>
5246 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5247 will automatically add this option if it knows it is
5249 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5250 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5251 fall back to the regular dependency line.
5255 For more details on dpkg-shlibdeps, please see
5256 <ref id="pkg-dpkg-shlibdeps"> and
5257 <manref name="dpkg-shlibdeps" section="1">.
5262 <heading>The <file>shlibs</file> File Format</heading>
5265 Each <file>shlibs</file> file has the same format. Lines
5266 beginning with <tt>#</tt> are considered to be comments and
5267 are ignored. Each line is of the form:
5268 <example compact="compact">
5269 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5274 We will explain this by reference to the example of the
5275 <tt>zlib1g</tt> package, which (at the time of writing)
5276 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5280 <var>type</var> is an optional element that indicates the type
5281 of package for which the line is valid. The only type currently
5282 in use is <tt>udeb</tt>. The colon and space after the type are
5287 <var>library-name</var> is the name of the shared library,
5288 in this case <tt>libz</tt>. (This must match the name part
5289 of the soname, see below.)
5293 <var>soname-version</var> is the version part of the soname of
5294 the library. The soname is the thing that must exactly match
5295 for the library to be recognized by the dynamic linker, and is
5297 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5298 example, <tt>libz.so.1</tt>.<footnote>
5299 This can be determined using the command
5300 <example compact="compact">
5301 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5304 The version part is the part which comes after
5305 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5309 <var>dependencies</var> has the same syntax as a dependency
5310 field in a binary package control file. It should give
5311 details of which packages are required to satisfy a binary
5312 built against the version of the library contained in the
5313 package. See <ref id="depsyntax"> for details.
5317 In our example, if the first version of the <tt>zlib1g</tt>
5318 package which contained a minor number of at least
5319 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5320 <tt>shlibs</tt> entry for this library could say:
5321 <example compact="compact">
5322 libz 1 zlib1g (>= 1:1.1.3)
5324 The version-specific dependency is to avoid warnings from
5325 the dynamic linker about using older shared libraries with
5330 As zlib1g also provides a udeb containing the shared library,
5331 there would also be a second line:
5332 <example compact="compact">
5333 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5339 <heading>Providing a <file>shlibs</file> file</heading>
5342 If your package provides a shared library, you need to create
5343 a <file>shlibs</file> file following the format described above.
5344 It is usual to call this file <file>debian/shlibs</file> (but if
5345 you have multiple binary packages, you might want to call it
5346 <file>debian/shlibs.<var>package</var></file> instead). Then
5347 let <file>debian/rules</file> install it in the control area:
5348 <example compact="compact">
5349 install -m644 debian/shlibs debian/tmp/DEBIAN
5351 or, in the case of a multi-binary package:
5352 <example compact="compact">
5353 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5355 An alternative way of doing this is to create the
5356 <file>shlibs</file> file in the control area directly from
5357 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5358 file at all,<footnote>
5359 This is what <prgn>dh_makeshlibs</prgn> in the
5360 <tt>debhelper</tt> suite does. If your package also has a udeb
5361 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5362 automatically generate the <tt>udeb:</tt> lines if you specify
5363 the name of the udeb with the <tt>--add-udeb</tt> option.
5365 since the <file>debian/shlibs</file> file itself is ignored by
5366 <prgn>dpkg-shlibdeps</prgn>.
5370 As <prgn>dpkg-shlibdeps</prgn> reads the
5371 <file>DEBIAN/shlibs</file> files in all of the binary packages
5372 being built from this source package, all of the
5373 <file>DEBIAN/shlibs</file> files should be installed before
5374 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5379 <sect1 id="shlibslocal">
5380 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5383 This file is intended only as a <em>temporary</em> fix if
5384 your binaries or libraries depend on a library whose package
5385 does not yet provide a correct <file>shlibs</file> file.
5389 We will assume that you are trying to package a binary
5390 <tt>foo</tt>. When you try running
5391 <prgn>dpkg-shlibdeps</prgn> you get the following error
5392 message (<tt>-O</tt> displays the dependency information on
5393 <tt>stdout</tt> instead of writing it to
5394 <tt>debian/substvars</tt>, and the lines have been wrapped
5395 for ease of reading):
5396 <example compact="compact">
5397 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5398 dpkg-shlibdeps: warning: unable to find dependency
5399 information for shared library libbar (soname 1,
5400 path /usr/lib/libbar.so.1, dependency field Depends)
5401 shlibs:Depends=libc6 (>= 2.2.2-2)
5403 You can then run <prgn>ldd</prgn> on the binary to find the
5404 full location of the library concerned:
5405 <example compact="compact">
5407 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5408 libc.so.6 => /lib/libc.so.6 (0x40032000)
5409 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5411 So the <prgn>foo</prgn> binary depends on the
5412 <prgn>libbar</prgn> shared library, but no package seems to
5413 provide a <file>*.shlibs</file> file handling
5414 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5415 determine the package responsible:
5416 <example compact="compact">
5417 $ dpkg -S /usr/lib/libbar.so.1
5418 bar1: /usr/lib/libbar.so.1
5419 $ dpkg -s bar1 | grep Version
5422 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5423 is the one we are using. Now we can file a bug against the
5424 <tt>bar1</tt> package and create our own
5425 <file>debian/shlibs.local</file> to locally fix the problem.
5426 Including the following line into your
5427 <file>debian/shlibs.local</file> file:
5428 <example compact="compact">
5429 libbar 1 bar1 (>= 1.0-1)
5431 should allow the package build to work.
5435 As soon as the maintainer of <tt>bar1</tt> provides a
5436 correct <file>shlibs</file> file, you should remove this line
5437 from your <file>debian/shlibs.local</file> file. (You should
5438 probably also then have a versioned <tt>Build-Depends</tt>
5439 on <tt>bar1</tt> to help ensure that others do not have the
5440 same problem building your package.)
5449 <chapt id="opersys"><heading>The Operating System</heading>
5452 <heading>File system hierarchy</heading>
5456 <heading>File system Structure</heading>
5459 The location of all installed files and directories must
5460 comply with the File system Hierarchy Standard (FHS),
5461 version 2.3, with the exceptions noted below, and except
5462 where doing so would violate other terms of Debian
5463 Policy. The following exceptions to the FHS apply:
5468 Legacy XFree86 servers are permitted to retain the
5469 configuration file location
5470 <file>/etc/X11/XF86Config-4</file>.
5475 The optional rules related to user specific
5476 configuration files for applications are stored in
5477 the user's home directory are relaxed. It is
5478 recommended that such files start with the
5479 '<tt>.</tt>' character (a "dot file"), and if an
5480 application needs to create more than one dot file
5481 then the preferred placement is in a subdirectory
5482 with a name starting with a '.' character, (a "dot
5483 directory"). In this case it is recommended the
5484 configuration files not start with the '.'
5490 The requirement for amd64 to use <file>/lib64</file>
5491 for 64 bit binaries is removed.
5496 The requirement that
5497 <file>/usr/local/share/man</file> be "synonymous"
5498 with <file>/usr/local/man</file> is relaxed to a
5503 The requirement that windowmanagers with a single
5504 configuration file call it <file>system.*wmrc</file>
5505 is removed, as is the restriction that the window
5506 manager subdirectory be named identically to the
5507 window manager name itself.
5512 The requirement that boot manager configuration
5513 files live in <file>/etc</file>, or at least are
5514 symlinked there, is relaxed to a recommendation.
5521 The version of this document referred here can be
5522 found in the <tt>debian-policy</tt> package or on <url
5523 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5524 name="FHS (Debian copy)"> alongside this manual (or, if
5525 you have the <package>debian-policy</package> installed,
5527 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5528 (local copy)">). The
5529 latest version, which may be a more recent version, may
5531 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5532 Specific questions about following the standard may be
5533 asked on the <tt>debian-devel</tt> mailing list, or
5534 referred to the FHS mailing list (see the
5535 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5541 <heading>Site-specific programs</heading>
5544 As mandated by the FHS, packages must not place any
5545 files in <file>/usr/local</file>, either by putting them in
5546 the file system archive to be unpacked by <prgn>dpkg</prgn>
5547 or by manipulating them in their maintainer scripts.
5551 However, the package may create empty directories below
5552 <file>/usr/local</file> so that the system administrator knows
5553 where to place site-specific files. These are not
5554 directories <em>in</em> <file>/usr/local</file>, but are
5555 children of directories in <file>/usr/local</file>. These
5556 directories (<file>/usr/local/*/dir/</file>)
5557 should be removed on package removal if they are
5562 Note, that this applies only to directories <em>below</em>
5563 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5564 Packages must not create sub-directories in the directory
5565 <file>/usr/local</file> itself, except those listed in FHS,
5566 section 4.5. However, you may create directories below
5567 them as you wish. You must not remove any of the
5568 directories listed in 4.5, even if you created them.
5572 Since <file>/usr/local</file> can be mounted read-only from a
5573 remote server, these directories must be created and
5574 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5575 maintainer scripts and not be included in the
5576 <file>.deb</file> archive. These scripts must not fail if
5577 either of these operations fail.
5581 For example, the <tt>emacsen-common</tt> package could
5582 contain something like
5583 <example compact="compact">
5584 if [ ! -e /usr/local/share/emacs ]
5586 if mkdir /usr/local/share/emacs 2>/dev/null
5588 chown root:staff /usr/local/share/emacs
5589 chmod 2775 /usr/local/share/emacs
5593 in its <prgn>postinst</prgn> script, and
5594 <example compact="compact">
5595 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5596 rmdir /usr/local/share/emacs 2>/dev/null || true
5598 in the <prgn>prerm</prgn> script. (Note that this form is
5599 used to ensure that if the script is interrupted, the
5600 directory <file>/usr/local/share/emacs</file> will still be
5605 If you do create a directory in <file>/usr/local</file> for
5606 local additions to a package, you should ensure that
5607 settings in <file>/usr/local</file> take precedence over the
5608 equivalents in <file>/usr</file>.
5612 However, because <file>/usr/local</file> and its contents are
5613 for exclusive use of the local administrator, a package
5614 must not rely on the presence or absence of files or
5615 directories in <file>/usr/local</file> for normal operation.
5619 The <file>/usr/local</file> directory itself and all the
5620 subdirectories created by the package should (by default) have
5621 permissions 2775 (group-writable and set-group-id) and be
5622 owned by <tt>root:staff</tt>.
5627 <heading>The system-wide mail directory</heading>
5629 The system-wide mail directory is <file>/var/mail</file>. This
5630 directory is part of the base system and should not owned
5631 by any particular mail agents. The use of the old
5632 location <file>/var/spool/mail</file> is deprecated, even
5633 though the spool may still be physically located there.
5634 To maintain partial upgrade compatibility for systems
5635 which have <file>/var/spool/mail</file> as their physical mail
5636 spool, packages using <file>/var/mail</file> must depend on
5637 either <package>libc6</package> (>= 2.1.3-13), or on
5638 <package>base-files</package> (>= 2.2.0), or on later
5639 versions of either one of these packages.
5645 <heading>Users and groups</heading>
5648 <heading>Introduction</heading>
5650 The Debian system can be configured to use either plain or
5655 Some user ids (UIDs) and group ids (GIDs) are reserved
5656 globally for use by certain packages. Because some
5657 packages need to include files which are owned by these
5658 users or groups, or need the ids compiled into binaries,
5659 these ids must be used on any Debian system only for the
5660 purpose for which they are allocated. This is a serious
5661 restriction, and we should avoid getting in the way of
5662 local administration policies. In particular, many sites
5663 allocate users and/or local system groups starting at 100.
5667 Apart from this we should have dynamically allocated ids,
5668 which should by default be arranged in some sensible
5669 order, but the behavior should be configurable.
5673 Packages other than <tt>base-passwd</tt> must not modify
5674 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5675 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5680 <heading>UID and GID classes</heading>
5682 The UID and GID numbers are divided into classes as
5688 Globally allocated by the Debian project, the same
5689 on every Debian system. These ids will appear in
5690 the <file>passwd</file> and <file>group</file> files of all
5691 Debian systems, new ids in this range being added
5692 automatically as the <tt>base-passwd</tt> package is
5697 Packages which need a single statically allocated
5698 uid or gid should use one of these; their
5699 maintainers should ask the <tt>base-passwd</tt>
5707 Dynamically allocated system users and groups.
5708 Packages which need a user or group, but can have
5709 this user or group allocated dynamically and
5710 differently on each system, should use <tt>adduser
5711 --system</tt> to create the group and/or user.
5712 <prgn>adduser</prgn> will check for the existence of
5713 the user or group, and if necessary choose an unused
5714 id based on the ranges specified in
5715 <file>adduser.conf</file>.
5719 <tag>1000-29999:</tag>
5722 Dynamically allocated user accounts. By default
5723 <prgn>adduser</prgn> will choose UIDs and GIDs for
5724 user accounts in this range, though
5725 <file>adduser.conf</file> may be used to modify this
5730 <tag>30000-59999:</tag>
5735 <tag>60000-64999:</tag>
5738 Globally allocated by the Debian project, but only
5739 created on demand. The ids are allocated centrally
5740 and statically, but the actual accounts are only
5741 created on users' systems on demand.
5745 These ids are for packages which are obscure or
5746 which require many statically-allocated ids. These
5747 packages should check for and create the accounts in
5748 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5749 <prgn>adduser</prgn> if it has this facility) if
5750 necessary. Packages which are likely to require
5751 further allocations should have a "hole" left after
5752 them in the allocation, to give them room to
5757 <tag>65000-65533:</tag>
5765 User <tt>nobody</tt>. The corresponding gid refers
5766 to the group <tt>nogroup</tt>.
5773 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5774 not</em> be used, because it is the error return
5783 <sect id="sysvinit">
5784 <heading>System run levels and <file>init.d</file> scripts</heading>
5786 <sect1 id="/etc/init.d">
5787 <heading>Introduction</heading>
5790 The <file>/etc/init.d</file> directory contains the scripts
5791 executed by <prgn>init</prgn> at boot time and when the
5792 init state (or "runlevel") is changed (see <manref
5793 name="init" section="8">).
5797 There are at least two different, yet functionally
5798 equivalent, ways of handling these scripts. For the sake
5799 of simplicity, this document describes only the symbolic
5800 link method. However, it must not be assumed by maintainer
5801 scripts that this method is being used, and any automated
5802 manipulation of the various runlevel behaviors by
5803 maintainer scripts must be performed using
5804 <prgn>update-rc.d</prgn> as described below and not by
5805 manually installing or removing symlinks. For information
5806 on the implementation details of the other method,
5807 implemented in the <tt>file-rc</tt> package, please refer
5808 to the documentation of that package.
5812 These scripts are referenced by symbolic links in the
5813 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5814 runlevels, <prgn>init</prgn> looks in the directory
5815 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5816 execute, where <tt><var>n</var></tt> is the runlevel that
5817 is being changed to, or <tt>S</tt> for the boot-up
5822 The names of the links all have the form
5823 <file>S<var>mm</var><var>script</var></file> or
5824 <file>K<var>mm</var><var>script</var></file> where
5825 <var>mm</var> is a two-digit number and <var>script</var>
5826 is the name of the script (this should be the same as the
5827 name of the actual script in <file>/etc/init.d</file>).
5831 When <prgn>init</prgn> changes runlevel first the targets
5832 of the links whose names start with a <tt>K</tt> are
5833 executed, each with the single argument <tt>stop</tt>,
5834 followed by the scripts prefixed with an <tt>S</tt>, each
5835 with the single argument <tt>start</tt>. (The links are
5836 those in the <file>/etc/rc<var>n</var>.d</file> directory
5837 corresponding to the new runlevel.) The <tt>K</tt> links
5838 are responsible for killing services and the <tt>S</tt>
5839 link for starting services upon entering the runlevel.
5843 For example, if we are changing from runlevel 2 to
5844 runlevel 3, init will first execute all of the <tt>K</tt>
5845 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5846 all of the <tt>S</tt> prefixed scripts in that directory.
5847 The links starting with <tt>K</tt> will cause the
5848 referred-to file to be executed with an argument of
5849 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5854 The two-digit number <var>mm</var> is used to determine
5855 the order in which to run the scripts: low-numbered links
5856 have their scripts run first. For example, the
5857 <tt>K20</tt> scripts will be executed before the
5858 <tt>K30</tt> scripts. This is used when a certain service
5859 must be started before another. For example, the name
5860 server <prgn>bind</prgn> might need to be started before
5861 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5862 can set up its access lists. In this case, the script
5863 that starts <prgn>bind</prgn> would have a lower number
5864 than the script that starts <prgn>inn</prgn> so that it
5866 <example compact="compact">
5873 The two runlevels 0 (halt) and 6 (reboot) are slightly
5874 different. In these runlevels, the links with an
5875 <tt>S</tt> prefix are still called after those with a
5876 <tt>K</tt> prefix, but they too are called with the single
5877 argument <tt>stop</tt>.
5881 Also, if the script name ends in <tt>.sh</tt>, the script
5882 will be sourced in runlevel <tt>S</tt> rather than being
5883 run in a forked subprocess, but will be explicitly run by
5884 <prgn>sh</prgn> in all other runlevels.
5889 <heading>Writing the scripts</heading>
5892 Packages that include daemons for system services should
5893 place scripts in <file>/etc/init.d</file> to start or stop
5894 services at boot time or during a change of runlevel.
5895 These scripts should be named
5896 <file>/etc/init.d/<var>package</var></file>, and they should
5897 accept one argument, saying what to do:
5900 <tag><tt>start</tt></tag>
5901 <item>start the service,</item>
5903 <tag><tt>stop</tt></tag>
5904 <item>stop the service,</item>
5906 <tag><tt>restart</tt></tag>
5907 <item>stop and restart the service if it's already running,
5908 otherwise start the service</item>
5910 <tag><tt>reload</tt></tag>
5911 <item><p>cause the configuration of the service to be
5912 reloaded without actually stopping and restarting
5915 <tag><tt>force-reload</tt></tag>
5916 <item>cause the configuration to be reloaded if the
5917 service supports this, otherwise restart the
5921 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5922 <tt>force-reload</tt> options should be supported by all
5923 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5928 The <file>init.d</file> scripts must ensure that they will
5929 behave sensibly (i.e., returning success and not starting
5930 multiple copies of a service) if invoked with <tt>start</tt>
5931 when the service is already running, or with <tt>stop</tt>
5932 when it isn't, and that they don't kill unfortunately-named
5933 user processes. The best way to achieve this is usually to
5934 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5939 If a service reloads its configuration automatically (as
5940 in the case of <prgn>cron</prgn>, for example), the
5941 <tt>reload</tt> option of the <file>init.d</file> script
5942 should behave as if the configuration has been reloaded
5947 The <file>/etc/init.d</file> scripts must be treated as
5948 configuration files, either (if they are present in the
5949 package, that is, in the .deb file) by marking them as
5950 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5951 by managing them correctly in the maintainer scripts (see
5952 <ref id="config-files">). This is important since we want
5953 to give the local system administrator the chance to adapt
5954 the scripts to the local system, e.g., to disable a
5955 service without de-installing the package, or to specify
5956 some special command line options when starting a service,
5957 while making sure their changes aren't lost during the next
5962 These scripts should not fail obscurely when the
5963 configuration files remain but the package has been
5964 removed, as configuration files remain on the system after
5965 the package has been removed. Only when <prgn>dpkg</prgn>
5966 is executed with the <tt>--purge</tt> option will
5967 configuration files be removed. In particular, as the
5968 <file>/etc/init.d/<var>package</var></file> script itself is
5969 usually a <tt>conffile</tt>, it will remain on the system
5970 if the package is removed but not purged. Therefore, you
5971 should include a <tt>test</tt> statement at the top of the
5973 <example compact="compact">
5974 test -f <var>program-executed-later-in-script</var> || exit 0
5979 Often there are some variables in the <file>init.d</file>
5980 scripts whose values control the behavior of the scripts,
5981 and which a system administrator is likely to want to
5982 change. As the scripts themselves are frequently
5983 <tt>conffile</tt>s, modifying them requires that the
5984 administrator merge in their changes each time the package
5985 is upgraded and the <tt>conffile</tt> changes. To ease
5986 the burden on the system administrator, such configurable
5987 values should not be placed directly in the script.
5988 Instead, they should be placed in a file in
5989 <file>/etc/default</file>, which typically will have the same
5990 base name as the <file>init.d</file> script. This extra file
5991 should be sourced by the script when the script runs. It
5992 must contain only variable settings and comments in SUSv3
5993 <prgn>sh</prgn> format. It may either be a
5994 <tt>conffile</tt> or a configuration file maintained by
5995 the package maintainer scripts. See <ref id="config-files">
6000 To ensure that vital configurable values are always
6001 available, the <file>init.d</file> script should set default
6002 values for each of the shell variables it uses, either
6003 before sourcing the <file>/etc/default/</file> file or
6004 afterwards using something like the <tt>:
6005 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6006 script must behave sensibly and not fail if the
6007 <file>/etc/default</file> file is deleted.
6012 <heading>Interfacing with the initscript system</heading>
6015 Maintainers should use the abstraction layer provided by
6016 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6017 programs to deal with initscripts in their packages'
6018 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6019 and <prgn>postrm</prgn>.
6023 Directly managing the /etc/rc?.d links and directly
6024 invoking the <file>/etc/init.d/</file> initscripts should
6025 be done only by packages providing the initscript
6026 subsystem (such as <prgn>sysv-rc</prgn> and
6027 <prgn>file-rc</prgn>).
6031 <heading>Managing the links</heading>
6034 The program <prgn>update-rc.d</prgn> is provided for
6035 package maintainers to arrange for the proper creation and
6036 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6037 or their functional equivalent if another method is being
6038 used. This may be used by maintainers in their packages'
6039 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6043 You must not include any <file>/etc/rc<var>n</var>.d</file>
6044 symbolic links in the actual archive or manually create or
6045 remove the symbolic links in maintainer scripts; you must
6046 use the <prgn>update-rc.d</prgn> program instead. (The
6047 former will fail if an alternative method of maintaining
6048 runlevel information is being used.) You must not include
6049 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6050 in the archive either. (Only the <tt>sysvinit</tt>
6055 By default <prgn>update-rc.d</prgn> will start services in
6056 each of the multi-user state runlevels (2, 3, 4, and 5)
6057 and stop them in the halt runlevel (0), the single-user
6058 runlevel (1) and the reboot runlevel (6). The system
6059 administrator will have the opportunity to customize
6060 runlevels by simply adding, moving, or removing the
6061 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6062 symbolic links are being used, or by modifying
6063 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6068 To get the default behavior for your package, put in your
6069 <prgn>postinst</prgn> script
6070 <example compact="compact">
6071 update-rc.d <var>package</var> defaults
6073 and in your <prgn>postrm</prgn>
6074 <example compact="compact">
6075 if [ "$1" = purge ]; then
6076 update-rc.d <var>package</var> remove
6078 </example>. Note that if your package changes runlevels
6079 or priority, you may have to remove and recreate the links,
6080 since otherwise the old links may persist. Refer to the
6081 documentation of <prgn>update-rc.d</prgn>.
6085 This will use a default sequence number of 20. If it does
6086 not matter when or in which order the <file>init.d</file>
6087 script is run, use this default. If it does, then you
6088 should talk to the maintainer of the <prgn>sysvinit</prgn>
6089 package or post to <tt>debian-devel</tt>, and they will
6090 help you choose a number.
6094 For more information about using <tt>update-rc.d</tt>,
6095 please consult its man page <manref name="update-rc.d"
6101 <heading>Running initscripts</heading>
6103 The program <prgn>invoke-rc.d</prgn> is provided to make
6104 it easier for package maintainers to properly invoke an
6105 initscript, obeying runlevel and other locally-defined
6106 constraints that might limit a package's right to start,
6107 stop and otherwise manage services. This program may be
6108 used by maintainers in their packages' scripts.
6112 The package maintainer scripts must use
6113 <prgn>invoke-rc.d</prgn> to invoke the
6114 <file>/etc/init.d/*</file> initscripts, instead of
6115 calling them directly.
6119 By default, <prgn>invoke-rc.d</prgn> will pass any
6120 action requests (start, stop, reload, restart...) to the
6121 <file>/etc/init.d</file> script, filtering out requests
6122 to start or restart a service out of its intended
6127 Most packages will simply need to change:
6128 <example compact="compact">/etc/init.d/<package>
6129 <action></example> in their <prgn>postinst</prgn>
6130 and <prgn>prerm</prgn> scripts to:
6131 <example compact="compact">
6132 if which invoke-rc.d >/dev/null 2>&1; then
6133 invoke-rc.d <var>package</var> <action>
6135 /etc/init.d/<var>package</var> <action>
6141 A package should register its initscript services using
6142 <prgn>update-rc.d</prgn> before it tries to invoke them
6143 using <prgn>invoke-rc.d</prgn>. Invocation of
6144 unregistered services may fail.
6148 For more information about using
6149 <prgn>invoke-rc.d</prgn>, please consult its man page
6150 <manref name="invoke-rc.d" section="8">.
6156 <heading>Boot-time initialization</heading>
6159 There used to be another directory, <file>/etc/rc.boot</file>,
6160 which contained scripts which were run once per machine
6161 boot. This has been deprecated in favour of links from
6162 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6163 described in <ref id="/etc/init.d">. Packages must not
6164 place files in <file>/etc/rc.boot</file>.
6169 <heading>Example</heading>
6172 An example on which you can base your
6173 <file>/etc/init.d</file> scripts is found in
6174 <file>/etc/init.d/skeleton</file>.
6181 <heading>Console messages from <file>init.d</file> scripts</heading>
6184 This section describes the formats to be used for messages
6185 written to standard output by the <file>/etc/init.d</file>
6186 scripts. The intent is to improve the consistency of
6187 Debian's startup and shutdown look and feel. For this
6188 reason, please look very carefully at the details. We want
6189 the messages to have the same format in terms of wording,
6190 spaces, punctuation and case of letters.
6194 Here is a list of overall rules that should be used for
6195 messages generated by <file>/etc/init.d</file> scripts.
6201 The message should fit in one line (fewer than 80
6202 characters), start with a capital letter and end with
6203 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6207 If the script is performing some time consuming task in
6208 the background (not merely starting or stopping a
6209 program, for instance), an ellipsis (three dots:
6210 <tt>...</tt>) should be output to the screen, with no
6211 leading or tailing whitespace or line feeds.
6215 The messages should appear as if the computer is telling
6216 the user what it is doing (politely :-), but should not
6217 mention "it" directly. For example, instead of:
6218 <example compact="compact">
6219 I'm starting network daemons: nfsd mountd.
6221 the message should say
6222 <example compact="compact">
6223 Starting network daemons: nfsd mountd.
6230 <tt>init.d</tt> script should use the following standard
6231 message formats for the situations enumerated below.
6237 <p>When daemons are started</p>
6240 If the script starts one or more daemons, the output
6241 should look like this (a single line, no leading
6243 <example compact="compact">
6244 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6246 The <var>description</var> should describe the
6247 subsystem the daemon or set of daemons are part of,
6248 while <var>daemon-1</var> up to <var>daemon-n</var>
6249 denote each daemon's name (typically the file name of
6254 For example, the output of <file>/etc/init.d/lpd</file>
6256 <example compact="compact">
6257 Starting printer spooler: lpd.
6262 This can be achieved by saying
6263 <example compact="compact">
6264 echo -n "Starting printer spooler: lpd"
6265 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6268 in the script. If there are more than one daemon to
6269 start, the output should look like this:
6270 <example compact="compact">
6271 echo -n "Starting remote file system services:"
6272 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6273 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6274 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6277 This makes it possible for the user to see what is
6278 happening and when the final daemon has been started.
6279 Care should be taken in the placement of white spaces:
6280 in the example above the system administrators can
6281 easily comment out a line if they don't want to start
6282 a specific daemon, while the displayed message still
6288 <p>When a system parameter is being set</p>
6291 If you have to set up different system parameters
6292 during the system boot, you should use this format:
6293 <example compact="compact">
6294 Setting <var>parameter</var> to "<var>value</var>".
6299 You can use a statement such as the following to get
6301 <example compact="compact">
6302 echo "Setting DNS domainname to \"$domainname\"."
6307 Note that the same symbol (<tt>"</tt>) is used for the left
6308 and right quotation marks. A grave accent (<tt>`</tt>) is
6309 not a quote character; neither is an apostrophe
6315 <p>When a daemon is stopped or restarted</p>
6318 When you stop or restart a daemon, you should issue a
6319 message identical to the startup message, except that
6320 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6321 or <tt>Restarting</tt> respectively.
6325 For example, stopping the printer daemon will look like
6327 <example compact="compact">
6328 Stopping printer spooler: lpd.
6334 <p>When something is executed</p>
6337 There are several examples where you have to run a
6338 program at system startup or shutdown to perform a
6339 specific task, for example, setting the system's clock
6340 using <prgn>netdate</prgn> or killing all processes
6341 when the system shuts down. Your message should look
6343 <example compact="compact">
6344 Doing something very useful...done.
6346 You should print the <tt>done.</tt> immediately after
6347 the job has been completed, so that the user is
6348 informed why they have to wait. You can get this
6350 <example compact="compact">
6351 echo -n "Doing something very useful..."
6360 <p>When the configuration is reloaded</p>
6363 When a daemon is forced to reload its configuration
6364 files you should use the following format:
6365 <example compact="compact">
6366 Reloading <var>description</var> configuration...done.
6368 where <var>description</var> is the same as in the
6369 daemon starting message.
6377 <heading>Cron jobs</heading>
6380 Packages must not modify the configuration file
6381 <file>/etc/crontab</file>, and they must not modify the files in
6382 <file>/var/spool/cron/crontabs</file>.</p>
6385 If a package wants to install a job that has to be executed
6386 via cron, it should place a file with the name of the
6387 package in one or more of the following directories:
6388 <example compact="compact">
6394 As these directory names imply, the files within them are
6395 executed on an hourly, daily, weekly, or monthly basis,
6396 respectively. The exact times are listed in
6397 <file>/etc/crontab</file>.</p>
6400 All files installed in any of these directories must be
6401 scripts (e.g., shell scripts or Perl scripts) so that they
6402 can easily be modified by the local system administrator.
6403 In addition, they must be treated as configuration files.
6407 If a certain job has to be executed at some other frequency or
6408 at a specific time, the package should install a file
6409 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6410 same syntax as <file>/etc/crontab</file> and is processed by
6411 <prgn>cron</prgn> automatically. The file must also be
6412 treated as a configuration file. (Note that entries in the
6413 <file>/etc/cron.d</file> directory are not handled by
6414 <prgn>anacron</prgn>. Thus, you should only use this
6415 directory for jobs which may be skipped if the system is not
6419 The scripts or crontab entries in these directories should
6420 check if all necessary programs are installed before they
6421 try to execute them. Otherwise, problems will arise when a
6422 package was removed but not purged since configuration files
6423 are kept on the system in this situation.</p>
6427 <heading>Menus</heading>
6430 The Debian <tt>menu</tt> package provides a standard
6431 interface between packages providing applications and
6432 <em>menu programs</em> (either X window managers or
6433 text-based menu programs such as <prgn>pdmenu</prgn>).
6437 All packages that provide applications that need not be
6438 passed any special command line arguments for normal
6439 operation should register a menu entry for those
6440 applications, so that users of the <tt>menu</tt> package
6441 will automatically get menu entries in their window
6442 managers, as well in shells like <tt>pdmenu</tt>.
6446 Menu entries should follow the current menu policy.
6450 The menu policy can be found in the <tt>menu-policy</tt>
6451 files in the <tt>debian-policy</tt> package.
6452 It is also available from the Debian web mirrors at
6453 <tt><url name="/doc/packaging-manuals/menu-policy/"
6454 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6458 Please also refer to the <em>Debian Menu System</em>
6459 documentation that comes with the <package>menu</package>
6460 package for information about how to register your
6466 <heading>Multimedia handlers</heading>
6469 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6470 is a mechanism for encoding files and data streams and
6471 providing meta-information about them, in particular their
6472 type (e.g. audio or video) and format (e.g. PNG, HTML,
6477 Registration of MIME type handlers allows programs like mail
6478 user agents and web browsers to invoke these handlers to
6479 view, edit or display MIME types they don't support directly.
6483 Packages which provide the ability to view/show/play,
6484 compose, edit or print MIME types should register themselves
6485 as such following the current MIME support policy.
6489 The MIME support policy can be found in the <tt>mime-policy</tt>
6490 files in the <tt>debian-policy</tt> package.
6491 It is also available from the Debian web mirrors at
6492 <tt><url name="/doc/packaging-manuals/mime-policy/"
6493 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6499 <heading>Keyboard configuration</heading>
6502 To achieve a consistent keyboard configuration so that all
6503 applications interpret a keyboard event the same way, all
6504 programs in the Debian distribution must be configured to
6505 comply with the following guidelines.
6509 The following keys must have the specified interpretations:
6512 <tag><tt><--</tt></tag>
6513 <item>delete the character to the left of the cursor</item>
6515 <tag><tt>Delete</tt></tag>
6516 <item>delete the character to the right of the cursor</item>
6518 <tag><tt>Control+H</tt></tag>
6519 <item>emacs: the help prefix</item>
6522 The interpretation of any keyboard events should be
6523 independent of the terminal that is used, be it a virtual
6524 console, an X terminal emulator, an rlogin/telnet session,
6529 The following list explains how the different programs
6530 should be set up to achieve this:
6536 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6540 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6544 X translations are set up to make
6545 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6546 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6547 is the vt220 escape code for the "delete character"
6548 key). This must be done by loading the X resources
6549 using <prgn>xrdb</prgn> on all local X displays, not
6550 using the application defaults, so that the
6551 translation resources used correspond to the
6552 <prgn>xmodmap</prgn> settings.
6556 The Linux console is configured to make
6557 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6558 generate <tt>ESC [ 3 ~</tt>.
6562 X applications are configured so that <tt><</tt>
6563 deletes left, and <tt>Delete</tt> deletes right. Motif
6564 applications already work like this.
6568 Terminals should have <tt>stty erase ^?</tt> .
6572 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6573 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6574 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6578 Emacs is programmed to map <tt>KB_Backspace</tt> or
6579 the <tt>stty erase</tt> character to
6580 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6581 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6582 <tt>^H</tt> to <tt>help</tt> as always.
6586 Other applications use the <tt>stty erase</tt>
6587 character and <tt>kdch1</tt> for the two delete keys,
6588 with ASCII DEL being "delete previous character" and
6589 <tt>kdch1</tt> being "delete character under
6597 This will solve the problem except for the following
6604 Some terminals have a <tt><--</tt> key that cannot
6605 be made to produce anything except <tt>^H</tt>. On
6606 these terminals Emacs help will be unavailable on
6607 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6608 character takes precedence in Emacs, and has been set
6609 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6610 available) can be used instead.
6614 Some operating systems use <tt>^H</tt> for <tt>stty
6615 erase</tt>. However, modern telnet versions and all
6616 rlogin versions propagate <tt>stty</tt> settings, and
6617 almost all UNIX versions honour <tt>stty erase</tt>.
6618 Where the <tt>stty</tt> settings are not propagated
6619 correctly, things can be made to work by using
6620 <tt>stty</tt> manually.
6624 Some systems (including previous Debian versions) use
6625 <prgn>xmodmap</prgn> to arrange for both
6626 <tt><--</tt> and <tt>Delete</tt> to generate
6627 <tt>KB_Delete</tt>. We can change the behavior of
6628 their X clients using the same X resources that we use
6629 to do it for our own clients, or configure our clients
6630 using their resources when things are the other way
6631 around. On displays configured like this
6632 <tt>Delete</tt> will not work, but <tt><--</tt>
6637 Some operating systems have different <tt>kdch1</tt>
6638 settings in their <tt>terminfo</tt> database for
6639 <tt>xterm</tt> and others. On these systems the
6640 <tt>Delete</tt> key will not work correctly when you
6641 log in from a system conforming to our policy, but
6642 <tt><--</tt> will.
6649 <heading>Environment variables</heading>
6652 A program must not depend on environment variables to get
6653 reasonable defaults. (That's because these environment
6654 variables would have to be set in a system-wide
6655 configuration file like <file>/etc/profile</file>, which is not
6656 supported by all shells.)
6660 If a program usually depends on environment variables for its
6661 configuration, the program should be changed to fall back to
6662 a reasonable default configuration if these environment
6663 variables are not present. If this cannot be done easily
6664 (e.g., if the source code of a non-free program is not
6665 available), the program must be replaced by a small
6666 "wrapper" shell script which sets the environment variables
6667 if they are not already defined, and calls the original program.
6671 Here is an example of a wrapper script for this purpose:
6673 <example compact="compact">
6675 BAR=${BAR:-/var/lib/fubar}
6677 exec /usr/lib/foo/foo "$@"
6682 Furthermore, as <file>/etc/profile</file> is a configuration
6683 file of the <prgn>base-files</prgn> package, other packages must
6684 not put any environment variables or other commands into that
6689 <sect id="doc-base">
6690 <heading>Registering Documents using doc-base</heading>
6693 The <package>doc-base</package> package implements a
6694 flexible mechanism for handling and presenting
6695 documentation. The recommended practice is for every Debian
6696 package that provides online documentation (other than just
6697 manual pages) to register these documents with
6698 <package>doc-base</package> by installing a
6699 <package>doc-base</package> control file via the
6700 <prgn/install-docs/ script at installation time and
6701 de-register the manuals again when the package is removed.
6704 Please refer to the documentation that comes with the
6705 <package>doc-base</package> package for information and
6714 <heading>Files</heading>
6717 <heading>Binaries</heading>
6720 Two different packages must not install programs with
6721 different functionality but with the same filenames. (The
6722 case of two programs having the same functionality but
6723 different implementations is handled via "alternatives" or
6724 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6725 <ref id="conflicts"> respectively.) If this case happens,
6726 one of the programs must be renamed. The maintainers should
6727 report this to the <tt>debian-devel</tt> mailing list and
6728 try to find a consensus about which program will have to be
6729 renamed. If a consensus cannot be reached, <em>both</em>
6730 programs must be renamed.
6734 By default, when a package is being built, any binaries
6735 created should include debugging information, as well as
6736 being compiled with optimization. You should also turn on
6737 as many reasonable compilation warnings as possible; this
6738 makes life easier for porters, who can then look at build
6739 logs for possible problems. For the C programming language,
6740 this means the following compilation parameters should be
6742 <example compact="compact">
6744 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6746 INSTALL = install -s # (or use strip on the files in debian/tmp)
6751 Note that by default all installed binaries should be stripped,
6752 either by using the <tt>-s</tt> flag to
6753 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6754 the binaries after they have been copied into
6755 <file>debian/tmp</file> but before the tree is made into a
6760 Although binaries in the build tree should be compiled with
6761 debugging information by default, it can often be difficult to
6762 debug programs if they are also subjected to compiler
6763 optimization. For this reason, it is recommended to support the
6764 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6765 (see <ref id="debianrules-options">). This variable can contain
6766 several flags to change how a package is compiled and built.
6770 It is up to the package maintainer to decide what
6771 compilation options are best for the package. Certain
6772 binaries (such as computationally-intensive programs) will
6773 function better with certain flags (<tt>-O3</tt>, for
6774 example); feel free to use them. Please use good judgment
6775 here. Don't use flags for the sake of it; only use them
6776 if there is good reason to do so. Feel free to override
6777 the upstream author's ideas about which compilation
6778 options are best: they are often inappropriate for our
6784 <sect id="libraries">
6785 <heading>Libraries</heading>
6788 If the package is <strong>architecture: any</strong>, then
6789 the shared library compilation and linking flags must have
6790 <tt>-fPIC</tt>, or the package shall not build on some of
6791 the supported architectures<footnote>
6793 If you are using GCC, <tt>-fPIC</tt> produces code with
6794 relocatable position independent code, which is required for
6795 most architectures to create a shared library, with i386 and
6796 perhaps some others where non position independent code is
6797 permitted in a shared library.
6800 Position independent code may have a performance penalty,
6801 especially on <tt>i386</tt>. However, in most cases the
6802 speed penalty must be measured against the memory wasted on
6803 the few architectures where non position independent code is
6806 </footnote>. Any exception to this rule must be discussed on
6807 the mailing list <em>debian-devel@lists.debian.org</em>, and
6808 a rough consensus obtained. The reasons for not compiling
6809 with <tt>-fPIC</tt> flag must be recorded in the file
6810 <tt>README.Debian</tt>, and care must be taken to either
6811 restrict the architecture or arrange for <tt>-fPIC</tt> to
6812 be used on architectures where it is required.<footnote>
6814 Some of the reasons why this might be required is if the
6815 library contains hand crafted assembly code that is not
6816 relocatable, the speed penalty is excessive for compute
6817 intensive libs, and similar reasons.
6822 As to the static libraries, the common case is not to have
6823 relocatable code, since there is no benefit, unless in specific
6824 cases; therefore the static version must not be compiled
6825 with the <tt>-fPIC</tt> flag. Any exception to this rule
6826 should be discussed on the mailing list
6827 <em>debian-devel@lists.debian.org</em>, and the reasons for
6828 compiling with the <tt>-fPIC</tt> flag must be recorded in
6829 the file <tt>README.Debian</tt>. <footnote>
6831 Some of the reasons for linking static libraries with
6832 the <tt>-fPIC</tt> flag are if, for example, one needs a
6833 Perl API for a library that is under rapid development,
6834 and has an unstable API, so shared libraries are
6835 pointless at this phase of the library's development. In
6836 that case, since Perl needs a library with relocatable
6837 code, it may make sense to create a static library with
6838 relocatable code. Another reason cited is if you are
6839 distilling various libraries into a common shared
6840 library, like <tt>mklibs</tt> does in the Debian
6846 In other words, if both a shared and a static library is
6847 being built, each source unit (<tt>*.c</tt>, for example,
6848 for C files) will need to be compiled twice, for the normal
6852 You must specify the gcc option <tt>-D_REENTRANT</tt>
6853 when building a library (either static or shared) to make
6854 the library compatible with LinuxThreads.
6858 Although not enforced by the build tools, shared libraries
6859 must be linked against all libraries that they use symbols from
6860 in the same way that binaries are. This ensures the correct
6861 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6862 system and guarantees that all libraries can be safely opened
6863 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6864 option <tt>-Wl,-z,defs</tt> when building a shared library.
6865 Since this option enforces symbol resolution at build time,
6866 a missing library reference will be caught early as a fatal
6871 All installed shared libraries should be stripped with
6872 <example compact="compact">
6873 strip --strip-unneeded <var>your-lib</var>
6875 (The option <tt>--strip-unneeded</tt> makes
6876 <prgn>strip</prgn> remove only the symbols which aren't
6877 needed for relocation processing.) Shared libraries can
6878 function perfectly well when stripped, since the symbols for
6879 dynamic linking are in a separate part of the ELF object
6881 You might also want to use the options
6882 <tt>--remove-section=.comment</tt> and
6883 <tt>--remove-section=.note</tt> on both shared libraries
6884 and executables, and <tt>--strip-debug</tt> on static
6890 Note that under some circumstances it may be useful to
6891 install a shared library unstripped, for example when
6892 building a separate package to support debugging.
6896 Shared object files (often <file>.so</file> files) that are not
6897 public libraries, that is, they are not meant to be linked
6898 to by third party executables (binaries of other packages),
6899 should be installed in subdirectories of the
6900 <file>/usr/lib</file> directory. Such files are exempt from the
6901 rules that govern ordinary shared libraries, except that
6902 they must not be installed executable and should be
6904 A common example are the so-called "plug-ins",
6905 internal shared objects that are dynamically loaded by
6906 programs using <manref name="dlopen" section="3">.
6911 Packages containing shared libraries that may be linked to
6912 by other packages' binaries, but which for some
6913 <em>compelling</em> reason can not be installed in
6914 <file>/usr/lib</file> directory, may install the shared library
6915 files in subdirectories of the <file>/usr/lib</file> directory,
6916 in which case they should arrange to add that directory in
6917 <file>/etc/ld.so.conf</file> in the package's post-installation
6918 script, and remove it in the package's post-removal script.
6922 An ever increasing number of packages are using
6923 <prgn>libtool</prgn> to do their linking. The latest GNU
6924 libtools (>= 1.3a) can take advantage of the metadata in the
6925 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6926 files). The main advantage of <prgn>libtool</prgn>'s
6927 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6928 store and subsequently access metadata with respect to the
6929 libraries it builds. <prgn>libtool</prgn> will search for
6930 those files, which contain a lot of useful information about
6931 a library (such as library dependency information for static
6932 linking). Also, they're <em>essential</em> for programs
6933 using <tt>libltdl</tt>.<footnote>
6934 Although <prgn>libtool</prgn> is fully capable of
6935 linking against shared libraries which don't have
6936 <tt>.la</tt> files, as it is a mere shell script it can
6937 add considerably to the build time of a
6938 <prgn>libtool</prgn>-using package if that shell script
6939 has to derive all this information from first principles
6940 for each library every time it is linked. With the
6941 advent of <prgn>libtool</prgn> version 1.4 (and to a
6942 lesser extent <prgn>libtool</prgn> version 1.3), the
6943 <file>.la</file> files also store information about
6944 inter-library dependencies which cannot necessarily be
6945 derived after the <file>.la</file> file is deleted.
6950 Packages that use <prgn>libtool</prgn> to create shared
6951 libraries should include the <file>.la</file> files in the
6952 <tt>-dev</tt> package, unless the package relies on
6953 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6954 the <tt>.la</tt> files must go in the run-time library
6959 You must make sure that you use only released versions of
6960 shared libraries to build your packages; otherwise other
6961 users will not be able to run your binaries
6962 properly. Producing source packages that depend on
6963 unreleased compilers is also usually a bad
6970 <heading>Shared libraries</heading>
6972 This section has moved to <ref id="sharedlibs">.
6978 <heading>Scripts</heading>
6981 All command scripts, including the package maintainer
6982 scripts inside the package and used by <prgn>dpkg</prgn>,
6983 should have a <tt>#!</tt> line naming the shell to be used
6988 In the case of Perl scripts this should be
6989 <tt>#!/usr/bin/perl</tt>.
6993 When scripts are installed into a directory in the system
6994 PATH, the script name should not include an extension such
6995 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6996 language currently used to implement it.
6999 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7000 should almost certainly start with <tt>set -e</tt> so that
7001 errors are detected. Every script should use
7002 <tt>set -e</tt> or check the exit status of <em>every</em>
7007 Scripts may assume that <file>/bin/sh</file> implements the
7008 SUSv3 Shell Command Language<footnote>
7009 Single UNIX Specification, version 3, which is also IEEE
7010 1003.1-2004 (POSIX), and is available on the World Wide Web
7011 from <url id="http://www.unix.org/version3/online.html"
7012 name="The Open Group"> after free
7013 registration.</footnote>
7014 plus the following additional features not mandated by
7016 These features are in widespread use in the Linux community
7017 and are implemented in all of bash, dash, and ksh, the most
7018 common shells users may wish to use as <file>/bin/sh</file>.
7021 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7022 must not generate a newline.</item>
7023 <item><tt>test</tt>, if implemented as a shell built-in, must
7024 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7026 <item><tt>local</tt> to create a scoped variable must be
7027 supported; however, <tt>local</tt> may or may not preserve
7028 the variable value from an outer scope and may or may not
7029 support arguments more complex than simple variables. Only
7041 If a shell script requires non-SUSv3 features from the shell
7042 interpreter other than those listed above, the appropriate shell
7043 must be specified in the first line of the script (e.g.,
7044 <tt>#!/bin/bash</tt>) and the package must depend on the package
7045 providing the shell (unless the shell package is marked
7046 "Essential", as in the case of <prgn>bash</prgn>).
7050 You may wish to restrict your script to SUSv3 features plus the
7051 above set when possible so that it may use <file>/bin/sh</file>
7052 as its interpreter. If your script works with <prgn>dash</prgn>
7053 (originally called <prgn>ash</prgn>), it probably complies with
7054 the above requirements, but if you are in doubt, use
7055 <file>/bin/bash</file>.
7059 Perl scripts should check for errors when making any
7060 system calls, including <tt>open</tt>, <tt>print</tt>,
7061 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7065 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7066 scripting languages. See <em>Csh Programming Considered
7067 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7068 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7069 If an upstream package comes with <prgn>csh</prgn> scripts
7070 then you must make sure that they start with
7071 <tt>#!/bin/csh</tt> and make your package depend on the
7072 <prgn>c-shell</prgn> virtual package.
7076 Any scripts which create files in world-writeable
7077 directories (e.g., in <file>/tmp</file>) must use a
7078 mechanism which will fail atomically if a file with the same
7079 name already exists.
7083 The Debian base system provides the <prgn>tempfile</prgn>
7084 and <prgn>mktemp</prgn> utilities for use by scripts for
7091 <heading>Symbolic links</heading>
7094 In general, symbolic links within a top-level directory
7095 should be relative, and symbolic links pointing from one
7096 top-level directory into another should be absolute. (A
7097 top-level directory is a sub-directory of the root
7098 directory <file>/</file>.)
7102 In addition, symbolic links should be specified as short as
7103 possible, i.e., link targets like <file>foo/../bar</file> are
7108 Note that when creating a relative link using
7109 <prgn>ln</prgn> it is not necessary for the target of the
7110 link to exist relative to the working directory you're
7111 running <prgn>ln</prgn> from, nor is it necessary to change
7112 directory to the directory where the link is to be made.
7113 Simply include the string that should appear as the target
7114 of the link (this will be a pathname relative to the
7115 directory in which the link resides) as the first argument
7120 For example, in your <prgn>Makefile</prgn> or
7121 <file>debian/rules</file>, you can do things like:
7122 <example compact="compact">
7123 ln -fs gcc $(prefix)/bin/cc
7124 ln -fs gcc debian/tmp/usr/bin/cc
7125 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7126 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7131 A symbolic link pointing to a compressed file should always
7132 have the same file extension as the referenced file. (For
7133 example, if a file <file>foo.gz</file> is referenced by a
7134 symbolic link, the filename of the link has to end with
7135 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7140 <heading>Device files</heading>
7143 Packages must not include device files in the package file
7148 If a package needs any special device files that are not
7149 included in the base system, it must call
7150 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7151 after notifying the user<footnote>
7152 This notification could be done via a (low-priority)
7153 debconf message, or an echo (printf) statement.
7158 Packages must not remove any device files in the
7159 <prgn>postrm</prgn> or any other script. This is left to the
7160 system administrator.
7164 Debian uses the serial devices
7165 <file>/dev/ttyS*</file>. Programs using the old
7166 <file>/dev/cu*</file> devices should be changed to use
7167 <file>/dev/ttyS*</file>.
7171 <sect id="config-files">
7172 <heading>Configuration files</heading>
7175 <heading>Definitions</heading>
7179 <tag>configuration file</tag>
7181 A file that affects the operation of a program, or
7182 provides site- or host-specific information, or
7183 otherwise customizes the behavior of a program.
7184 Typically, configuration files are intended to be
7185 modified by the system administrator (if needed or
7186 desired) to conform to local policy or to provide
7187 more useful site-specific behavior.
7190 <tag><tt>conffile</tt></tag>
7192 A file listed in a package's <tt>conffiles</tt>
7193 file, and is treated specially by <prgn>dpkg</prgn>
7194 (see <ref id="configdetails">).
7200 The distinction between these two is important; they are
7201 not interchangeable concepts. Almost all
7202 <tt>conffile</tt>s are configuration files, but many
7203 configuration files are not <tt>conffiles</tt>.
7207 As noted elsewhere, <file>/etc/init.d</file> scripts,
7208 <file>/etc/default</file> files, scripts installed in
7209 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7210 configuration installed in <file>/etc/cron.d</file> must be
7211 treated as configuration files. In general, any script that
7212 embeds configuration information is de-facto a configuration
7213 file and should be treated as such.
7218 <heading>Location</heading>
7221 Any configuration files created or used by your package
7222 must reside in <file>/etc</file>. If there are several,
7223 consider creating a subdirectory of <file>/etc</file>
7224 named after your package.
7228 If your package creates or uses configuration files
7229 outside of <file>/etc</file>, and it is not feasible to modify
7230 the package to use <file>/etc</file> directly, put the files
7231 in <file>/etc</file> and create symbolic links to those files
7232 from the location that the package requires.
7237 <heading>Behavior</heading>
7240 Configuration file handling must conform to the following
7242 <list compact="compact">
7244 local changes must be preserved during a package
7248 configuration files must be preserved when the
7249 package is removed, and only deleted when the
7256 The easy way to achieve this behavior is to make the
7257 configuration file a <tt>conffile</tt>. This is
7258 appropriate only if it is possible to distribute a default
7259 version that will work for most installations, although
7260 some system administrators may choose to modify it. This
7261 implies that the default version will be part of the
7262 package distribution, and must not be modified by the
7263 maintainer scripts during installation (or at any other
7268 In order to ensure that local changes are preserved
7269 correctly, no package may contain or make hard links to
7270 conffiles.<footnote>
7271 Rationale: There are two problems with hard links.
7272 The first is that some editors break the link while
7273 editing one of the files, so that the two files may
7274 unwittingly become unlinked and different. The second
7275 is that <prgn>dpkg</prgn> might break the hard link
7276 while upgrading <tt>conffile</tt>s.
7281 The other way to do it is via the maintainer scripts. In
7282 this case, the configuration file must not be listed as a
7283 <tt>conffile</tt> and must not be part of the package
7284 distribution. If the existence of a file is required for
7285 the package to be sensibly configured it is the
7286 responsibility of the package maintainer to provide
7287 maintainer scripts which correctly create, update and
7288 maintain the file and remove it on purge. (See <ref
7289 id="maintainerscripts"> for more information.) These
7290 scripts must be idempotent (i.e., must work correctly if
7291 <prgn>dpkg</prgn> needs to re-run them due to errors
7292 during installation or removal), must cope with all the
7293 variety of ways <prgn>dpkg</prgn> can call maintainer
7294 scripts, must not overwrite or otherwise mangle the user's
7295 configuration without asking, must not ask unnecessary
7296 questions (particularly during upgrades), and must
7297 otherwise be good citizens.
7301 The scripts are not required to configure every possible
7302 option for the package, but only those necessary to get
7303 the package running on a given system. Ideally the
7304 sysadmin should not have to do any configuration other
7305 than that done (semi-)automatically by the
7306 <prgn>postinst</prgn> script.
7310 A common practice is to create a script called
7311 <file><var>package</var>-configure</file> and have the
7312 package's <prgn>postinst</prgn> call it if and only if the
7313 configuration file does not already exist. In certain
7314 cases it is useful for there to be an example or template
7315 file which the maintainer scripts use. Such files should
7316 be in <file>/usr/share/<var>package</var></file> or
7317 <file>/usr/lib/<var>package</var></file> (depending on whether
7318 they are architecture-independent or not). There should
7319 be symbolic links to them from
7320 <file>/usr/share/doc/<var>package</var>/examples</file> if
7321 they are examples, and should be perfectly ordinary
7322 <prgn>dpkg</prgn>-handled files (<em>not</em>
7323 configuration files).
7327 These two styles of configuration file handling must
7328 not be mixed, for that way lies madness:
7329 <prgn>dpkg</prgn> will ask about overwriting the file
7330 every time the package is upgraded.
7335 <heading>Sharing configuration files</heading>
7338 Packages which specify the same file as a
7339 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7340 with each other. (This is an instance of the general rule
7341 about not sharing files. Note that neither alternatives
7342 nor diversions are likely to be appropriate in this case;
7343 in particular, <prgn>dpkg</prgn> does not handle diverted
7344 <tt>conffile</tt>s well.)
7348 The maintainer scripts must not alter a <tt>conffile</tt>
7349 of <em>any</em> package, including the one the scripts
7354 If two or more packages use the same configuration file
7355 and it is reasonable for both to be installed at the same
7356 time, one of these packages must be defined as
7357 <em>owner</em> of the configuration file, i.e., it will be
7358 the package which handles that file as a configuration
7359 file. Other packages that use the configuration file must
7360 depend on the owning package if they require the
7361 configuration file to operate. If the other package will
7362 use the configuration file if present, but is capable of
7363 operating without it, no dependency need be declared.
7367 If it is desirable for two or more related packages to
7368 share a configuration file <em>and</em> for all of the
7369 related packages to be able to modify that configuration
7370 file, then the following should be done:
7371 <enumlist compact="compact">
7373 One of the related packages (the "owning" package)
7374 will manage the configuration file with maintainer
7375 scripts as described in the previous section.
7378 The owning package should also provide a program
7379 that the other packages may use to modify the
7383 The related packages must use the provided program
7384 to make any desired modifications to the
7385 configuration file. They should either depend on
7386 the core package to guarantee that the configuration
7387 modifier program is available or accept gracefully
7388 that they cannot modify the configuration file if it
7389 is not. (This is in addition to the fact that the
7390 configuration file may not even be present in the
7397 Sometimes it's appropriate to create a new package which
7398 provides the basic infrastructure for the other packages
7399 and which manages the shared configuration files. (The
7400 <tt>sgml-base</tt> package is a good example.)
7405 <heading>User configuration files ("dotfiles")</heading>
7408 The files in <file>/etc/skel</file> will automatically be
7409 copied into new user accounts by <prgn>adduser</prgn>.
7410 No other program should reference the files in
7411 <file>/etc/skel</file>.
7415 Therefore, if a program needs a dotfile to exist in
7416 advance in <file>$HOME</file> to work sensibly, that dotfile
7417 should be installed in <file>/etc/skel</file> and treated as a
7422 However, programs that require dotfiles in order to
7423 operate sensibly are a bad thing, unless they do create
7424 the dotfiles themselves automatically.
7428 Furthermore, programs should be configured by the Debian
7429 default installation to behave as closely to the upstream
7430 default behavior as possible.
7434 Therefore, if a program in a Debian package needs to be
7435 configured in some way in order to operate sensibly, that
7436 should be done using a site-wide configuration file placed
7437 in <file>/etc</file>. Only if the program doesn't support a
7438 site-wide default configuration and the package maintainer
7439 doesn't have time to add it may a default per-user file be
7440 placed in <file>/etc/skel</file>.
7444 <file>/etc/skel</file> should be as empty as we can make it.
7445 This is particularly true because there is no easy (or
7446 necessarily desirable) mechanism for ensuring that the
7447 appropriate dotfiles are copied into the accounts of
7448 existing users when a package is installed.
7454 <heading>Log files</heading>
7456 Log files should usually be named
7457 <file>/var/log/<var>package</var>.log</file>. If you have many
7458 log files, or need a separate directory for permission
7459 reasons (<file>/var/log</file> is writable only by
7460 <file>root</file>), you should usually create a directory named
7461 <file>/var/log/<var>package</var></file> and place your log
7466 Log files must be rotated occasionally so that they don't
7467 grow indefinitely; the best way to do this is to drop a log
7468 rotation configuration file into the directory
7469 <file>/etc/logrotate.d</file> and use the facilities provided by
7470 logrotate.<footnote>
7472 The traditional approach to log files has been to set up
7473 <em>ad hoc</em> log rotation schemes using simple shell
7474 scripts and cron. While this approach is highly
7475 customizable, it requires quite a lot of sysadmin work.
7476 Even though the original Debian system helped a little
7477 by automatically installing a system which can be used
7478 as a template, this was deemed not enough.
7482 The use of <prgn>logrotate</prgn>, a program developed
7483 by Red Hat, is better, as it centralizes log management.
7484 It has both a configuration file
7485 (<file>/etc/logrotate.conf</file>) and a directory where
7486 packages can drop their individual log rotation
7487 configurations (<file>/etc/logrotate.d</file>).
7490 Here is a good example for a logrotate config
7491 file (for more information see <manref name="logrotate"
7493 <example compact="compact">
7494 /var/log/foo/*.log {
7499 /etc/init.d/foo force-reload
7503 This rotates all files under <file>/var/log/foo</file>, saves 12
7504 compressed generations, and forces the daemon to reload its
7505 configuration information after the log rotation.
7509 Log files should be removed when the package is
7510 purged (but not when it is only removed). This should be
7511 done by the <prgn>postrm</prgn> script when it is called
7512 with the argument <tt>purge</tt> (see <ref
7513 id="removedetails">).
7518 <heading>Permissions and owners</heading>
7521 The rules in this section are guidelines for general use.
7522 If necessary you may deviate from the details below.
7523 However, if you do so you must make sure that what is done
7524 is secure and you should try to be as consistent as possible
7525 with the rest of the system. You should probably also
7526 discuss it on <prgn>debian-devel</prgn> first.
7530 Files should be owned by <tt>root:root</tt>, and made
7531 writable only by the owner and universally readable (and
7532 executable, if appropriate), that is mode 644 or 755.
7536 Directories should be mode 755 or (for group-writability)
7537 mode 2775. The ownership of the directory should be
7538 consistent with its mode: if a directory is mode 2775, it
7539 should be owned by the group that needs write access to
7542 When a package is upgraded, and the owner or permissions
7543 of a file included in the package has changed, dpkg
7544 arranges for the ownership and permissions to be
7545 correctly set upon installation. However, this does not
7546 extend to directories; the permissions and ownership of
7547 directories already on the system does not change on
7548 install or upgrade of packages. This makes sense, since
7549 otherwise common directories like <tt>/usr</tt> would
7550 always be in flux. To correctly change permissions of a
7551 directory the package owns, explicit action is required,
7552 usually in the <tt>postinst</tt> script. Care must be
7553 taken to handle downgrades as well, in that case.
7560 Setuid and setgid executables should be mode 4755 or 2755
7561 respectively, and owned by the appropriate user or group.
7562 They should not be made unreadable (modes like 4711 or
7563 2711 or even 4111); doing so achieves no extra security,
7564 because anyone can find the binary in the freely available
7565 Debian package; it is merely inconvenient. For the same
7566 reason you should not restrict read or execute permissions
7567 on non-set-id executables.
7571 Some setuid programs need to be restricted to particular
7572 sets of users, using file permissions. In this case they
7573 should be owned by the uid to which they are set-id, and by
7574 the group which should be allowed to execute them. They
7575 should have mode 4754; again there is no point in making
7576 them unreadable to those users who must not be allowed to
7581 It is possible to arrange that the system administrator can
7582 reconfigure the package to correspond to their local
7583 security policy by changing the permissions on a binary:
7584 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7585 described below.<footnote>
7586 Ordinary files installed by <prgn>dpkg</prgn> (as
7587 opposed to <tt>conffile</tt>s and other similar objects)
7588 normally have their permissions reset to the distributed
7589 permissions when the package is reinstalled. However,
7590 the use of <prgn>dpkg-statoverride</prgn> overrides this
7591 default behavior. If you use this method, you should
7592 remember to describe <prgn>dpkg-statoverride</prgn> in
7593 the package documentation; being a relatively new
7594 addition to Debian, it is probably not yet well-known.
7596 Another method you should consider is to create a group for
7597 people allowed to use the program(s) and make any setuid
7598 executables executable only by that group.
7602 If you need to create a new user or group for your package
7603 there are two possibilities. Firstly, you may need to
7604 make some files in the binary package be owned by this
7605 user or group, or you may need to compile the user or
7606 group id (rather than just the name) into the binary
7607 (though this latter should be avoided if possible, as in
7608 this case you need a statically allocated id).</p>
7611 If you need a statically allocated id, you must ask for a
7612 user or group id from the <tt>base-passwd</tt> maintainer,
7613 and must not release the package until you have been
7614 allocated one. Once you have been allocated one you must
7615 either make the package depend on a version of the
7616 <tt>base-passwd</tt> package with the id present in
7617 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7618 your package to create the user or group itself with the
7619 correct id (using <tt>adduser</tt>) in its
7620 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7621 the <prgn>postinst</prgn> is to be preferred if it is
7622 possible, otherwise a pre-dependency will be needed on the
7623 <tt>adduser</tt> package.)
7627 On the other hand, the program might be able to determine
7628 the uid or gid from the user or group name at runtime, so
7629 that a dynamically allocated id can be used. In this case
7630 you should choose an appropriate user or group name,
7631 discussing this on <prgn>debian-devel</prgn> and checking
7632 with the <package/base-passwd/ maintainer that it is unique and that
7633 they do not wish you to use a statically allocated id
7634 instead. When this has been checked you must arrange for
7635 your package to create the user or group if necessary using
7636 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7637 <prgn>postinst</prgn> script (again, the latter is to be
7638 preferred if it is possible).
7642 Note that changing the numeric value of an id associated
7643 with a name is very difficult, and involves searching the
7644 file system for all appropriate files. You need to think
7645 carefully whether a static or dynamic id is required, since
7646 changing your mind later will cause problems.
7649 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7651 This section is not intended as policy, but as a
7652 description of the use of <prgn>dpkg-statoverride</prgn>.
7656 If a system administrator wishes to have a file (or
7657 directory or other such thing) installed with owner and
7658 permissions different from those in the distributed Debian
7659 package, they can use the <prgn>dpkg-statoverride</prgn>
7660 program to instruct <prgn>dpkg</prgn> to use the different
7661 settings every time the file is installed. Thus the
7662 package maintainer should distribute the files with their
7663 normal permissions, and leave it for the system
7664 administrator to make any desired changes. For example, a
7665 daemon which is normally required to be setuid root, but
7666 in certain situations could be used without being setuid,
7667 should be installed setuid in the <tt>.deb</tt>. Then the
7668 local system administrator can change this if they wish.
7669 If there are two standard ways of doing it, the package
7670 maintainer can use <tt>debconf</tt> to find out the
7671 preference, and call <prgn>dpkg-statoverride</prgn> in the
7672 maintainer script if necessary to accommodate the system
7673 administrator's choice. Care must be taken during
7674 upgrades to not override an existing setting.
7678 Given the above, <prgn>dpkg-statoverride</prgn> is
7679 essentially a tool for system administrators and would not
7680 normally be needed in the maintainer scripts. There is
7681 one type of situation, though, where calls to
7682 <prgn>dpkg-statoverride</prgn> would be needed in the
7683 maintainer scripts, and that involves packages which use
7684 dynamically allocated user or group ids. In such a
7685 situation, something like the following idiom can be very
7686 helpful in the package's <prgn>postinst</prgn>, where
7687 <tt>sysuser</tt> is a dynamically allocated id:
7689 for i in /usr/bin/foo /usr/sbin/bar
7691 # only do something when no setting exists
7692 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7694 #include: debconf processing, question about foo and bar
7695 if [ "$RET" = "true" ] ; then
7696 dpkg-statoverride --update --add sysuser root 4755 $i
7701 The corresponding <tt>dpkg-statoverride --remove</tt>
7702 calls can then be made unconditionally when the package is
7710 <chapt id="customized-programs">
7711 <heading>Customized programs</heading>
7713 <sect id="arch-spec">
7714 <heading>Architecture specification strings</heading>
7717 If a program needs to specify an <em>architecture specification
7718 string</em> in some place, it should select one of the
7719 strings provided by <tt>dpkg-architecture -L</tt>. The
7720 strings are in the format
7721 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7722 is sometimes elided, as when the OS is Linux.<footnote>
7723 <p>Currently, the strings are:
7724 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7725 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7726 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7727 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7728 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7729 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7730 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7731 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7732 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7733 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7734 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7735 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7736 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7737 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7738 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7739 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7740 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7741 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7742 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7743 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7744 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7745 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7746 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7747 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7748 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7749 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7750 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7751 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7752 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7753 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7754 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7755 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7756 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7757 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7758 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7759 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7760 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7766 Note that we don't want to use
7767 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7768 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7769 since this would make our programs incompatible with other
7770 Linux distributions. We also don't use something like
7771 <tt><var>arch</var>-unknown-linux</tt>, since the
7772 <tt>unknown</tt> does not look very good.
7777 <heading>Daemons</heading>
7780 The configuration files <file>/etc/services</file>,
7781 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7782 by the <prgn>netbase</prgn> package and must not be modified
7787 If a package requires a new entry in one of these files, the
7788 maintainer should get in contact with the
7789 <prgn>netbase</prgn> maintainer, who will add the entries
7790 and release a new version of the <prgn>netbase</prgn>
7795 The configuration file <file>/etc/inetd.conf</file> must not be
7796 modified by the package's scripts except via the
7797 <prgn>update-inetd</prgn> script or the
7798 <file>DebianNet.pm</file> Perl module. See their documentation
7799 for details on how to add entries.
7803 If a package wants to install an example entry into
7804 <file>/etc/inetd.conf</file>, the entry must be preceded with
7805 exactly one hash character (<tt>#</tt>). Such lines are
7806 treated as "commented out by user" by the
7807 <prgn>update-inetd</prgn> script and are not changed or
7808 activated during package updates.
7813 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7817 Some programs need to create pseudo-ttys. This should be done
7818 using Unix98 ptys if the C library supports it. The resulting
7819 program must not be installed setuid root, unless that
7820 is required for other functionality.
7824 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7825 <file>/var/log/lastlog</file> must be installed writable by
7826 group <tt>utmp</tt>. Programs which need to modify those
7827 files must be installed setgid <tt>utmp</tt>.
7832 <heading>Editors and pagers</heading>
7835 Some programs have the ability to launch an editor or pager
7836 program to edit or display a text document. Since there are
7837 lots of different editors and pagers available in the Debian
7838 distribution, the system administrator and each user should
7839 have the possibility to choose their preferred editor and
7844 In addition, every program should choose a good default
7845 editor/pager if none is selected by the user or system
7850 Thus, every program that launches an editor or pager must
7851 use the EDITOR or PAGER environment variable to determine
7852 the editor or pager the user wishes to use. If these
7853 variables are not set, the programs <file>/usr/bin/editor</file>
7854 and <file>/usr/bin/pager</file> should be used, respectively.
7858 These two files are managed through the <prgn>dpkg</prgn>
7859 "alternatives" mechanism. Thus every package providing an
7860 editor or pager must call the
7861 <prgn>update-alternatives</prgn> script to register these
7866 If it is very hard to adapt a program to make use of the
7867 EDITOR or PAGER variables, that program may be configured to
7868 use <file>/usr/bin/sensible-editor</file> and
7869 <file>/usr/bin/sensible-pager</file> as the editor or pager
7870 program respectively. These are two scripts provided in the
7871 Debian base system that check the EDITOR and PAGER variables
7872 and launch the appropriate program, and fall back to
7873 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7874 variable is not set.
7878 A program may also use the VISUAL environment variable to
7879 determine the user's choice of editor. If it exists, it
7880 should take precedence over EDITOR. This is in fact what
7881 <file>/usr/bin/sensible-editor</file> does.
7885 It is not required for a package to depend on
7886 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7887 package to provide such virtual packages.<footnote>
7888 The Debian base system already provides an editor and a
7894 <sect id="web-appl">
7895 <heading>Web servers and applications</heading>
7898 This section describes the locations and URLs that should
7899 be used by all web servers and web applications in the
7906 Cgi-bin executable files are installed in the
7908 <example compact="compact">
7909 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7911 and should be referred to as
7912 <example compact="compact">
7913 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7919 <p>Access to HTML documents</p>
7922 HTML documents for a package are stored in
7923 <file>/usr/share/doc/<var>package</var></file>
7924 and can be referred to as
7925 <example compact="compact">
7926 http://localhost/doc/<var>package</var>/<var>filename</var>
7931 The web server should restrict access to the document
7932 tree so that only clients on the same host can read
7933 the documents. If the web server does not support such
7934 access controls, then it should not provide access at
7935 all, or ask about providing access during installation.
7940 <p>Access to images</p>
7942 It is recommended that images for a package be stored
7943 in <tt>/usr/share/images/<var>package</var></tt> and
7944 may be referred to through an alias <tt>/images/</tt>
7947 http://localhost/images/<package>/<filename>
7954 <p>Web Document Root</p>
7957 Web Applications should try to avoid storing files in
7958 the Web Document Root. Instead they should use the
7959 /usr/share/doc/<var>package</var> directory for
7960 documents and register the Web Application via the
7961 <package>doc-base</package> package. If access to the
7962 web document root is unavoidable then use
7963 <example compact="compact">
7966 as the Document Root. This might be just a symbolic
7967 link to the location where the system administrator
7968 has put the real document root.
7971 <item><p>Providing httpd and/or httpd-cgi</p>
7973 All web servers should provide the virtual package
7974 <tt>httpd</tt>. If a web server has CGI support it should
7975 provide <tt>httpd-cgi</tt> additionally.
7978 All web applications which do not contain CGI scripts should
7979 depend on <tt>httpd</tt>, all those web applications which
7980 <tt>do</tt> contain CGI scripts, should depend on
7988 <sect id="mail-transport-agents">
7989 <heading>Mail transport, delivery and user agents</heading>
7992 Debian packages which process electronic mail, whether mail
7993 user agents (MUAs) or mail transport agents (MTAs), must
7994 ensure that they are compatible with the configuration
7995 decisions below. Failure to do this may result in lost
7996 mail, broken <tt>From:</tt> lines, and other serious brain
8001 The mail spool is <file>/var/mail</file> and the interface to
8002 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8003 the FHS). On older systems, the mail spool may be
8004 physically located in <file>/var/spool/mail</file>, but all
8005 access to the mail spool should be via the
8006 <file>/var/mail</file> symlink. The mail spool is part of the
8007 base system and not part of the MTA package.
8011 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8012 programs (such as IMAP daemons) must lock the mailbox in an
8013 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8014 be combined with dot locking. To avoid deadlocks, a program
8015 should use <tt>fcntl()</tt> first and dot locking after
8016 this, or alternatively implement the two locking methods in
8017 a non blocking way<footnote>
8018 If it is not possible to establish both locks, the
8019 system shouldn't wait for the second lock to be
8020 established, but remove the first lock, wait a (random)
8021 time, and start over locking again.
8022 </footnote>. Using the functions <tt>maillock</tt> and
8023 <tt>mailunlock</tt> provided by the
8024 <tt>liblockfile*</tt><footnote>
8025 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8026 to use these functions.
8027 </footnote> packages is the recommended way to realize this.
8031 Mailboxes are generally mode 660
8032 <tt><var>user</var>:mail</tt> unless the system
8033 administrator has chosen otherwise. A MUA may remove a
8034 mailbox (unless it has nonstandard permissions) in which
8035 case the MTA or another MUA must recreate it if needed.
8036 Mailboxes must be writable by group mail.
8040 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8041 be setgid mail to do the locking mentioned above (and
8042 must obviously avoid accessing other users' mailboxes
8043 using this privilege).</p>
8046 <file>/etc/aliases</file> is the source file for the system mail
8047 aliases (e.g., postmaster, usenet, etc.), it is the one
8048 which the sysadmin and <prgn>postinst</prgn> scripts may
8049 edit. After <file>/etc/aliases</file> is edited the program or
8050 human editing it must call <prgn>newaliases</prgn>. All MTA
8051 packages must come with a <prgn>newaliases</prgn> program,
8052 even if it does nothing, but older MTA packages did not do
8053 this so programs should not fail if <prgn>newaliases</prgn>
8054 cannot be found. Note that because of this, all MTA
8055 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8056 <tt>Replaces: mail-transport-agent</tt> control file
8061 The convention of writing <tt>forward to
8062 <var>address</var></tt> in the mailbox itself is not
8063 supported. Use a <tt>.forward</tt> file instead.</p>
8066 The <prgn>rmail</prgn> program used by UUCP
8067 for incoming mail should be <file>/usr/sbin/rmail</file>.
8068 Likewise, <prgn>rsmtp</prgn>, for receiving
8069 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8073 If your package needs to know what hostname to use on (for
8074 example) outgoing news and mail messages which are generated
8075 locally, you should use the file <file>/etc/mailname</file>. It
8076 will contain the portion after the username and <tt>@</tt>
8077 (at) sign for email addresses of users on the machine
8078 (followed by a newline).
8082 Such a package should check for the existence of this file
8083 when it is being configured. If it exists, it should be
8084 used without comment, although an MTA's configuration script
8085 may wish to prompt the user even if it finds that this file
8086 exists. If the file does not exist, the package should
8087 prompt the user for the value (preferably using
8088 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8089 as well as using it in the package's configuration. The
8090 prompt should make it clear that the name will not just be
8091 used by that package. For example, in this situation the
8092 <tt>inn</tt> package could say something like:
8093 <example compact="compact">
8094 Please enter the "mail name" of your system. This is the
8095 hostname portion of the address to be shown on outgoing
8096 news and mail messages. The default is
8097 <var>syshostname</var>, your system's host name. Mail
8098 name ["<var>syshostname</var>"]:
8100 where <var>syshostname</var> is the output of <tt>hostname
8106 <heading>News system configuration</heading>
8109 All the configuration files related to the NNTP (news)
8110 servers and clients should be located under
8111 <file>/etc/news</file>.</p>
8114 There are some configuration issues that apply to a number
8115 of news clients and server packages on the machine. These
8119 <tag><file>/etc/news/organization</file></tag>
8121 A string which should appear as the
8122 organization header for all messages posted
8123 by NNTP clients on the machine
8126 <tag><file>/etc/news/server</file></tag>
8128 Contains the FQDN of the upstream NNTP
8129 server, or localhost if the local machine is
8134 Other global files may be added as required for cross-package news
8141 <heading>Programs for the X Window System</heading>
8144 <heading>Providing X support and package priorities</heading>
8147 Programs that can be configured with support for the X
8148 Window System must be configured to do so and must declare
8149 any package dependencies necessary to satisfy their
8150 runtime requirements when using the X Window System. If
8151 such a package is of higher priority than the X packages
8152 on which it depends, it is required that either the
8153 X-specific components be split into a separate package, or
8154 that an alternative version of the package, which includes
8155 X support, be provided, or that the package's priority be
8161 <heading>Packages providing an X server</heading>
8164 Packages that provide an X server that, directly or
8165 indirectly, communicates with real input and display
8166 hardware should declare in their control data that they
8167 provide the virtual package <tt>xserver</tt>.<footnote>
8168 This implements current practice, and provides an
8169 actual policy for usage of the <tt>xserver</tt>
8170 virtual package which appears in the virtual packages
8171 list. In a nutshell, X servers that interface
8172 directly with the display and input hardware or via
8173 another subsystem (e.g., GGI) should provide
8174 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8175 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8181 <heading>Packages providing a terminal emulator</heading>
8184 Packages that provide a terminal emulator for the X Window
8185 System which meet the criteria listed below should declare
8186 in their control data that they provide the virtual
8187 package <tt>x-terminal-emulator</tt>. They should also
8188 register themselves as an alternative for
8189 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8194 To be an <tt>x-terminal-emulator</tt>, a program must:
8195 <list compact="compact">
8197 Be able to emulate a DEC VT100 terminal, or a
8198 compatible terminal.
8202 Support the command-line option <tt>-e
8203 <var>command</var></tt>, which creates a new
8204 terminal window<footnote>
8205 "New terminal window" does not necessarily mean
8206 a new top-level X window directly parented by
8207 the window manager; it could, if the terminal
8208 emulator application were so coded, be a new
8209 "view" in a multiple-document interface (MDI).
8211 and runs the specified <var>command</var>,
8212 interpreting the entirety of the rest of the command
8213 line as a command to pass straight to exec, in the
8214 manner that <tt>xterm</tt> does.
8218 Support the command-line option <tt>-T
8219 <var>title</var></tt>, which creates a new terminal
8220 window with the window title <var>title</var>.
8227 <heading>Packages providing a window manager</heading>
8230 Packages that provide a window manager should declare in
8231 their control data that they provide the virtual package
8232 <tt>x-window-manager</tt>. They should also register
8233 themselves as an alternative for
8234 <file>/usr/bin/x-window-manager</file>, with a priority
8235 calculated as follows:
8236 <list compact="compact">
8238 Start with a priority of 20.
8242 If the window manager supports the Debian menu
8243 system, add 20 points if this support is available
8244 in the package's default configuration (i.e., no
8245 configuration files belonging to the system or user
8246 have to be edited to activate the feature); if
8247 configuration files must be modified, add only 10
8253 If the window manager complies with <url
8254 id="http://www.freedesktop.org/Standards/wm-spec"
8255 name="The Window Manager Specification Project">,
8256 written by the <url id="http://www.freedesktop.org/"
8257 name="Free Desktop Group">, add 40 points.
8261 If the window manager permits the X session to be
8262 restarted using a <em>different</em> window manager
8263 (without killing the X server) in its default
8264 configuration, add 10 points; otherwise add none.
8271 <heading>Packages providing fonts</heading>
8274 Packages that provide fonts for the X Window
8276 For the purposes of Debian Policy, a "font for the X
8277 Window System" is one which is accessed via X protocol
8278 requests. Fonts for the Linux console, for PostScript
8279 renderer, or any other purpose, do not fit this
8280 definition. Any tool which makes such fonts available
8281 to the X Window System, however, must abide by this
8284 must do a number of things to ensure that they are both
8285 available without modification of the X or font server
8286 configuration, and that they do not corrupt files used by
8287 other font packages to register information about
8291 Fonts of any type supported by the X Window System
8292 must be in a separate binary package from any
8293 executables, libraries, or documentation (except
8294 that specific to the fonts shipped, such as their
8295 license information). If one or more of the fonts
8296 so packaged are necessary for proper operation of
8297 the package with which they are associated the font
8298 package may be Recommended; if the fonts merely
8299 provide an enhancement, a Suggests relationship may
8300 be used. Packages must not Depend on font
8302 This is because the X server may retrieve fonts
8303 from the local file system or over the network
8304 from an X font server; the Debian package system
8305 is empowered to deal only with the local
8311 BDF fonts must be converted to PCF fonts with the
8312 <prgn>bdftopcf</prgn> utility (available in the
8313 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8314 placed in a directory that corresponds to their
8316 <list compact="compact">
8318 100 dpi fonts must be placed in
8319 <file>/usr/share/fonts/X11/100dpi/</file>.
8323 75 dpi fonts must be placed in
8324 <file>/usr/share/fonts/X11/75dpi/</file>.
8328 Character-cell fonts, cursor fonts, and other
8329 low-resolution fonts must be placed in
8330 <file>/usr/share/fonts/X11/misc/</file>.
8336 Speedo fonts must be placed in
8337 <file>/usr/share/fonts/X11/Speedo/</file>.
8341 Type 1 fonts must be placed in
8342 <file>/usr/share/fonts/X11/Type1/</file>. If font
8343 metric files are available, they must be placed here
8348 Subdirectories of <file>/usr/share/fonts/X11/</file>
8349 other than those listed above must be neither
8350 created nor used. (The <file>PEX</file>, <file>CID</file>,
8351 and <file>cyrillic</file> directories are excepted for
8352 historical reasons, but installation of files into
8353 these directories remains discouraged.)
8357 Font packages may, instead of placing files directly
8358 in the X font directories listed above, provide
8359 symbolic links in that font directory pointing to
8360 the files' actual location in the filesystem. Such
8361 a location must comply with the FHS.
8365 Font packages should not contain both 75dpi and
8366 100dpi versions of a font. If both are available,
8367 they should be provided in separate binary packages
8368 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8369 the names of the packages containing the
8370 corresponding fonts.
8374 Fonts destined for the <file>misc</file> subdirectory
8375 should not be included in the same package as 75dpi
8376 or 100dpi fonts; instead, they should be provided in
8377 a separate package with <tt>-misc</tt> appended to
8382 Font packages must not provide the files
8383 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8384 <file>fonts.scale</file> in a font directory:
8387 <file>fonts.dir</file> files must not be provided at all.
8391 <file>fonts.alias</file> and <file>fonts.scale</file>
8392 files, if needed, should be provided in the
8394 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8395 where <var>fontdir</var> is the name of the
8397 <file>/usr/share/fonts/X11/</file> where the
8398 package's corresponding fonts are stored
8399 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8400 <var>package</var> is the name of the package
8401 that provides these fonts, and
8402 <var>extension</var> is either <tt>scale</tt>
8403 or <tt>alias</tt>, whichever corresponds to
8410 Font packages must declare a dependency on
8411 <tt>xfonts-utils</tt> in their control
8416 Font packages that provide one or more
8417 <file>fonts.scale</file> files as described above must
8418 invoke <prgn>update-fonts-scale</prgn> on each
8419 directory into which they installed fonts
8420 <em>before</em> invoking
8421 <prgn>update-fonts-dir</prgn> on that directory.
8422 This invocation must occur in both the
8423 <prgn>postinst</prgn> (for all arguments) and
8424 <prgn>postrm</prgn> (for all arguments except
8425 <tt>upgrade</tt>) scripts.
8429 Font packages that provide one or more
8430 <file>fonts.alias</file> files as described above must
8431 invoke <prgn>update-fonts-alias</prgn> on each
8432 directory into which they installed fonts. This
8433 invocation must occur in both the
8434 <prgn>postinst</prgn> (for all arguments) and
8435 <prgn>postrm</prgn> (for all arguments except
8436 <tt>upgrade</tt>) scripts.
8440 Font packages must invoke
8441 <prgn>update-fonts-dir</prgn> on each directory into
8442 which they installed fonts. This invocation must
8443 occur in both the <prgn>postinst</prgn> (for all
8444 arguments) and <prgn>postrm</prgn> (for all
8445 arguments except <tt>upgrade</tt>) scripts.
8449 Font packages must not provide alias names for the
8450 fonts they include which collide with alias names
8451 already in use by fonts already packaged.
8455 Font packages must not provide fonts with the same
8456 XLFD registry name as another font already packaged.
8463 <heading>Application defaults files</heading>
8466 Application defaults files must be installed in the
8467 directory <file>/etc/X11/app-defaults/</file> (use of a
8468 localized subdirectory of <file>/etc/X11/</file> as described
8469 in the <em>X Toolkit Intrinsics - C Language
8470 Interface</em> manual is also permitted). They must be
8471 registered as <tt>conffile</tt>s or handled as
8472 configuration files.
8476 Customization of programs' X resources may also be
8477 supported with the provision of a file with the same name
8478 as that of the package placed in the
8479 <file>/etc/X11/Xresources/</file> directory, which must
8480 registered as a <tt>conffile</tt> or handled as a
8481 configuration file.<footnote>
8482 Note that this mechanism is not the same as using
8483 app-defaults; app-defaults are tied to the client
8484 binary on the local file system, whereas X resources
8485 are stored in the X server and affect all connecting
8492 <heading>Installation directory issues</heading>
8495 Packages using the X Window System should not be
8496 configured to install files under the
8497 <file>/usr/X11R6/</file> directory. The
8498 <file>/usr/X11R6/</file> directory hierarchy should be
8499 regarded as obsolete.
8503 Programs that use GNU <prgn>autoconf</prgn> and
8504 <prgn>automake</prgn> are usually easily configured at
8505 compile time to use <file>/usr/</file> instead of
8506 <file>/usr/X11R6/</file>, and this should be done whenever
8507 possible. Configuration files for window managers and
8508 display managers should be placed in a subdirectory of
8509 <file>/etc/X11/</file> corresponding to the package name due
8510 to these programs' tight integration with the mechanisms
8511 of the X Window System. Application-level programs should
8512 use the <file>/etc/</file> directory unless otherwise mandated
8517 The installation of files into subdirectories
8518 of <file>/usr/X11R6/include/X11/</file> and
8519 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8520 package maintainers should determine if subdirectories of
8521 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8526 Packages should install any relevant files into the
8527 directories <file>/usr/include/X11/</file> and
8528 <file>/usr/lib/X11/</file>, but if they do so, they must
8529 pre-depend on <tt>x11-common (>=
8530 1:7.0.0)</tt><footnote>
8532 These libraries used to be all symbolic
8533 links. However, with <tt>X11R7</tt>,
8534 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8535 are now real directories, and packages
8536 <strong>should</strong> ship their files here instead
8537 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8538 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8539 responsible for converting these symlinks into
8547 <heading>The OSF/Motif and OpenMotif libraries</heading>
8550 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8551 OpenMotif libraries</em><footnote>
8552 OSF/Motif and OpenMotif are collectively referred to as
8553 "Motif" in this policy document.
8555 should be compiled against and tested with LessTif (a free
8556 re-implementation of Motif) instead. If the maintainer
8557 judges that the program or programs do not work
8558 sufficiently well with LessTif to be distributed and
8559 supported, but do so when compiled against Motif, then two
8560 versions of the package should be created; one linked
8561 statically against Motif and with <tt>-smotif</tt>
8562 appended to the package name, and one linked dynamically
8563 against Motif and with <tt>-dmotif</tt> appended to the
8568 Both Motif-linked versions are dependent
8569 upon non-DFSG-compliant software and thus cannot be
8570 uploaded to the <em>main</em> distribution; if the
8571 software is itself DFSG-compliant it may be uploaded to
8572 the <em>contrib</em> distribution. While known existing
8573 versions of Motif permit unlimited redistribution of
8574 binaries linked against the library (whether statically or
8575 dynamically), it is the package maintainer's
8576 responsibility to determine whether this is permitted by
8577 the license of the copy of Motif in their possession.
8583 <heading>Perl programs and modules</heading>
8586 Perl programs and modules should follow the current Perl policy.
8590 The Perl policy can be found in the <tt>perl-policy</tt>
8591 files in the <tt>debian-policy</tt> package.
8592 It is also available from the Debian web mirrors at
8593 <tt><url name="/doc/packaging-manuals/perl-policy/"
8594 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8599 <heading>Emacs lisp programs</heading>
8602 Please refer to the "Debian Emacs Policy" for details of how to
8603 package emacs lisp programs.
8607 The Emacs policy is available in
8608 <file>debian-emacs-policy.gz</file> of the
8609 <package>emacsen-common</package> package.
8610 It is also available from the Debian web mirrors at
8611 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8612 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8617 <heading>Games</heading>
8620 The permissions on <file>/var/games</file> are mode 755, owner
8621 <tt>root</tt> and group <tt>root</tt>.
8625 Each game decides on its own security policy.</p>
8628 Games which require protected, privileged access to
8629 high-score files, saved games, etc., may be made
8630 set-<em>group</em>-id (mode 2755) and owned by
8631 <tt>root:games</tt>, and use files and directories with
8632 appropriate permissions (770 <tt>root:games</tt>, for
8633 example). They must not be made
8634 set-<em>user</em>-id, as this causes security problems. (If
8635 an attacker can subvert any set-user-id game they can
8636 overwrite the executable of any other, causing other players
8637 of these games to run a Trojan horse program. With a
8638 set-group-id game the attacker only gets access to less
8639 important game data, and if they can get at the other
8640 players' accounts at all it will take considerably more
8644 Some packages, for example some fortune cookie programs, are
8645 configured by the upstream authors to install with their
8646 data files or other static information made unreadable so
8647 that they can only be accessed through set-id programs
8648 provided. You should not do this in a Debian package: anyone can
8649 download the <file>.deb</file> file and read the data from it,
8650 so there is no point making the files unreadable. Not
8651 making the files unreadable also means that you don't have
8652 to make so many programs set-id, which reduces the risk of a
8656 As described in the FHS, binaries of games should be
8657 installed in the directory <file>/usr/games</file>. This also
8658 applies to games that use the X Window System. Manual pages
8659 for games (X and non-X games) should be installed in
8660 <file>/usr/share/man/man6</file>.</p>
8666 <heading>Documentation</heading>
8669 <heading>Manual pages</heading>
8672 You should install manual pages in <prgn>nroff</prgn> source
8673 form, in appropriate places under <file>/usr/share/man</file>.
8674 You should only use sections 1 to 9 (see the FHS for more
8675 details). You must not install a pre-formatted "cat page".
8679 Each program, utility, and function should have an
8680 associated manual page included in the same package. It is
8681 suggested that all configuration files also have a manual
8682 page included as well. Manual pages for protocols and other
8683 auxiliary things are optional.
8687 If no manual page is available, this is considered as a bug
8688 and should be reported to the Debian Bug Tracking System (the
8689 maintainer of the package is allowed to write this bug report
8690 themselves, if they so desire). Do not close the bug report
8691 until a proper man page is available.<footnote>
8692 It is not very hard to write a man page. See the
8693 <url id="http://www.schweikhardt.net/man_page_howto.html"
8694 name="Man-Page-HOWTO">,
8695 <manref name="man" section="7">, the examples
8696 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8697 the helper programs <prgn>help2man</prgn>, or the
8698 directory <file>/usr/share/doc/man-db/examples</file>.
8703 You may forward a complaint about a missing man page to the
8704 upstream authors, and mark the bug as forwarded in the
8705 Debian bug tracking system. Even though the GNU Project do
8706 not in general consider the lack of a man page to be a bug,
8707 we do; if they tell you that they don't consider it a bug
8708 you should leave the bug in our bug tracking system open
8713 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8717 If one man page needs to be accessible via several names it
8718 is better to use a symbolic link than the <file>.so</file>
8719 feature, but there is no need to fiddle with the relevant
8720 parts of the upstream source to change from <file>.so</file> to
8721 symlinks: don't do it unless it's easy. You should not
8722 create hard links in the manual page directories, nor put
8723 absolute filenames in <file>.so</file> directives. The filename
8724 in a <file>.so</file> in a man page should be relative to the
8725 base of the man page tree (usually
8726 <file>/usr/share/man</file>). If you do not create any links
8727 (whether symlinks, hard links, or <tt>.so</tt> directives)
8728 in the file system to the alternate names of the man page,
8729 then you should not rely on <prgn>man</prgn> finding your
8730 man page under those names based solely on the information in
8731 the man page's header.<footnote>
8732 Supporting this in <prgn>man</prgn> often requires
8733 unreasonable processing time to find a manual page or to
8734 report that none exists, and moves knowledge into man's
8735 database that would be better left in the file system.
8736 This support is therefore deprecated and will cease to
8737 be present in the future.
8742 Manual pages in locale-specific subdirectories of
8743 <file>/usr/share/man</file> should use either UTF-8 or the usual
8744 legacy encoding for that language (normally the one corresponding
8745 to the shortest relevant locale name in
8746 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8747 <file>/usr/share/man/fr</file> should use either UTF-8 or
8748 ISO-8859-1.<footnote>
8749 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8750 use. In future, all manual pages will be required to use
8756 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8757 included in the subdirectory name unless it indicates a
8758 significant difference in the language, as this excludes
8759 speakers of the language in other countries.<footnote>
8760 At the time of writing, Chinese and Portuguese are the main
8761 languages with such differences, so <file>pt_BR</file>,
8762 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8767 Due to limitations in current implementations, all characters
8768 in the manual page source should be representable in the usual
8769 legacy encoding for that language, even if the file is
8770 actually encoded in UTF-8. Safe alternative ways to write many
8771 characters outside that range may be found in
8772 <manref name="groff_char" section="7">.
8777 <heading>Info documents</heading>
8780 Info documents should be installed in <file>/usr/share/info</file>.
8781 They should be compressed with <tt>gzip -9</tt>.
8785 Your package should call <prgn>install-info</prgn> to update
8786 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8787 script when called with a <tt>configure</tt> argument, for
8789 <example compact="compact">
8790 install-info --quiet --section Development Development \
8791 /usr/share/info/foobar.info
8795 It is a good idea to specify a section for the location of
8796 your program; this is done with the <tt>--section</tt>
8797 switch. To determine which section to use, you should look
8798 at <file>/usr/share/info/dir</file> on your system and choose the most
8799 relevant (or create a new section if none of the current
8800 sections are relevant). Note that the <tt>--section</tt>
8801 flag takes two arguments; the first is a regular expression
8802 to match (case-insensitively) against an existing section,
8803 the second is used when creating a new one.</p>
8806 You should remove the entries in the <prgn>prerm</prgn>
8807 script when called with a <tt>remove</tt> argument:
8808 <example compact="compact">
8809 install-info --quiet --remove /usr/share/info/foobar.info
8813 If <prgn>install-info</prgn> cannot find a description entry
8814 in the Info file you must supply one. See <manref
8815 name="install-info" section="8"> for details.</p>
8819 <heading>Additional documentation</heading>
8822 Any additional documentation that comes with the package may
8823 be installed at the discretion of the package maintainer.
8824 Plain text documentation should be installed in the directory
8825 <file>/usr/share/doc/<var>package</var></file>, where
8826 <var>package</var> is the name of the package, and
8827 compressed with <tt>gzip -9</tt> unless it is small.
8831 If a package comes with large amounts of documentation which
8832 many users of the package will not require you should create
8833 a separate binary package to contain it, so that it does not
8834 take up disk space on the machines of users who do not need
8835 or want it installed.</p>
8838 It is often a good idea to put text information files
8839 (<file>README</file>s, changelogs, and so forth) that come with
8840 the source package in <file>/usr/share/doc/<var>package</var></file>
8841 in the binary package. However, you don't need to install
8842 the instructions for building and installing the package, of
8846 Packages must not require the existence of any files in
8847 <file>/usr/share/doc/</file> in order to function
8849 The system administrator should be able to
8850 delete files in <file>/usr/share/doc/</file> without causing
8851 any programs to break.
8853 Any files that are referenced by programs but are also
8854 useful as stand alone documentation should be installed under
8855 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8856 <file>/usr/share/doc/<var>package</var></file>.
8860 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8861 link to another directory in <file>/usr/share/doc</file> only if
8862 the two packages both come from the same source and the
8863 first package Depends on the second.<footnote>
8865 Please note that this does not override the section on
8866 changelog files below, so the file
8867 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8868 must refer to the changelog for the current version of
8869 <var>package</var> in question. In practice, this means
8870 that the sources of the target and the destination of the
8871 symlink must be the same (same source package and
8878 Former Debian releases placed all additional documentation
8879 in <file>/usr/doc/<var>package</var></file>. This has been
8880 changed to <file>/usr/share/doc/<var>package</var></file>,
8881 and packages must not put documentation in the directory
8882 <file>/usr/doc/<var>package</var></file>. <footnote>
8883 At this phase of the transition, we no longer require a
8884 symbolic link in <file>/usr/doc/</file>. At a later point,
8885 policy shall change to make the symbolic links a bug.
8891 <heading>Preferred documentation formats</heading>
8894 The unification of Debian documentation is being carried out
8898 If your package comes with extensive documentation in a
8899 markup format that can be converted to various other formats
8900 you should if possible ship HTML versions in a binary
8901 package, in the directory
8902 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8903 its subdirectories.<footnote>
8904 The rationale: The important thing here is that HTML
8905 docs should be available in <em>some</em> package, not
8906 necessarily in the main binary package.
8911 Other formats such as PostScript may be provided at the
8912 package maintainer's discretion.
8916 <sect id="copyrightfile">
8917 <heading>Copyright information</heading>
8920 Every package must be accompanied by a verbatim copy of its
8921 copyright and distribution license in the file
8922 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8923 file must neither be compressed nor be a symbolic link.
8927 In addition, the copyright file must say where the upstream
8928 sources (if any) were obtained. It should name the original
8929 authors of the package and the Debian maintainer(s) who were
8930 involved with its creation.
8934 Packages in the <em>contrib</em> or <em>non-free</em> categories
8935 should state in the copyright file that the package is not part
8936 of the Debian GNU/Linux distribution and briefly explain why.
8940 A copy of the file which will be installed in
8941 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8942 be in <file>debian/copyright</file> in the source package.
8946 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8947 link to another directory in <file>/usr/share/doc</file> only if
8948 the two packages both come from the same source and the
8949 first package Depends on the second. These rules are
8950 important because copyrights must be extractable by
8955 Packages distributed under the UCB BSD license, the Apache
8956 license (version 2.0), the Artistic license, the GNU GPL
8957 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8958 the GNU FDL (version 1.2) should refer to the corresponding
8959 files under <file>/usr/share/common-licenses</file>,<footnote>
8962 <file>/usr/share/common-licenses/BSD</file>,
8963 <file>/usr/share/common-licenses/Apache-2.0</file>,
8964 <file>/usr/share/common-licenses/Artistic</file>,
8965 <file>/usr/share/common-licenses/GPL-2</file>,
8966 <file>/usr/share/common-licenses/GPL-3</file>,
8967 <file>/usr/share/common-licenses/LGPL-2</file>,
8968 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8969 <file>/usr/share/common-licenses/LGPL-3</file>, and
8970 <file>/usr/share/common-licenses/GFDL-1.2</file>
8973 </footnote> rather than quoting them in the copyright
8978 You should not use the copyright file as a general <file>README</file>
8979 file. If your package has such a file it should be
8980 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8981 <file>README.Debian</file> or some other appropriate place.</p>
8985 <heading>Examples</heading>
8988 Any examples (configurations, source files, whatever),
8989 should be installed in a directory
8990 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8991 files should not be referenced by any program: they're there
8992 for the benefit of the system administrator and users as
8993 documentation only. Architecture-specific example files
8994 should be installed in a directory
8995 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8997 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8998 latter directory itself may be a symbolic link to the
9003 If the purpose of a package is to provide examples, then the
9004 example files may be installed into
9005 <file>/usr/share/doc/<var>package</var></file>.
9009 <sect id="changelogs">
9010 <heading>Changelog files</heading>
9013 Packages that are not Debian-native must contain a
9014 compressed copy of the <file>debian/changelog</file> file from
9015 the Debian source tree in
9016 <file>/usr/share/doc/<var>package</var></file> with the name
9017 <file>changelog.Debian.gz</file>.
9021 If an upstream changelog is available, it should be accessible as
9022 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9023 plain text. If the upstream changelog is distributed in
9024 HTML, it should be made available in that form as
9025 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9026 and a plain text <file>changelog.gz</file> should be generated
9027 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9028 the upstream changelog files do not already conform to this
9029 naming convention, then this may be achieved either by
9030 renaming the files, or by adding a symbolic link, at the
9031 maintainer's discretion.<footnote>
9032 Rationale: People should not have to look in places for
9033 upstream changelogs merely because they are given
9034 different names or are distributed in HTML format.
9039 All of these files should be installed compressed using
9040 <tt>gzip -9</tt>, as they will become large with time even
9041 if they start out small.
9045 If the package has only one changelog which is used both as
9046 the Debian changelog and the upstream one because there is
9047 no separate upstream maintainer then that changelog should
9048 usually be installed as
9049 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9050 there is a separate upstream maintainer, but no upstream
9051 changelog, then the Debian changelog should still be called
9052 <file>changelog.Debian.gz</file>.
9056 For details about the format and contents of the Debian
9057 changelog file, please see <ref id="dpkgchangelog">.
9062 <appendix id="pkg-scope">
9063 <heading>Introduction and scope of these appendices</heading>
9066 These appendices are taken essentially verbatim from the
9067 now-deprecated Packaging Manual, version 3.2.1.0. They are
9068 the chapters which are likely to be of use to package
9069 maintainers and which have not already been included in the
9070 policy document itself. Most of these sections are very likely
9071 not relevant to policy; they should be treated as
9072 documentation for the packaging system. Please note that these
9073 appendices are included for convenience, and for historical
9074 reasons: they used to be part of policy package, and they have
9075 not yet been incorporated into dpkg documentation. However,
9076 they still have value, and hence they are presented here.
9080 They have not yet been checked to ensure that they are
9081 compatible with the contents of policy, and if there are any
9082 contradictions, the version in the main policy document takes
9083 precedence. The remaining chapters of the old Packaging
9084 Manual have also not been read in detail to ensure that there
9085 are not parts which have been left out. Both of these will be
9090 Certain parts of the Packaging manual were integrated into the
9091 Policy Manual proper, and removed from the appendices. Links
9092 have been placed from the old locations to the new ones.
9096 <prgn>dpkg</prgn> is a suite of programs for creating binary
9097 package files and installing and removing them on Unix
9099 <prgn>dpkg</prgn> is targeted primarily at Debian
9100 GNU/Linux, but may work on or be ported to other
9106 The binary packages are designed for the management of
9107 installed executable programs (usually compiled binaries) and
9108 their associated data, though source code examples and
9109 documentation are provided as part of some packages.</p>
9112 This manual describes the technical aspects of creating Debian
9113 binary packages (<file>.deb</file> files). It documents the
9114 behavior of the package management programs
9115 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9116 they interact with packages.</p>
9119 It also documents the interaction between
9120 <prgn>dselect</prgn>'s core and the access method scripts it
9121 uses to actually install the selected packages, and describes
9122 how to create a new access method.</p>
9125 This manual does not go into detail about the options and
9126 usage of the package building and installation tools. It
9127 should therefore be read in conjunction with those programs'
9132 The utility programs which are provided with <prgn>dpkg</prgn>
9133 for managing various system configuration and similar issues,
9134 such as <prgn>update-rc.d</prgn> and
9135 <prgn>install-info</prgn>, are not described in detail here -
9136 please see their man pages.
9140 It is assumed that the reader is reasonably familiar with the
9141 <prgn>dpkg</prgn> System Administrators' manual.
9142 Unfortunately this manual does not yet exist.
9146 The Debian version of the FSF's GNU hello program is provided
9147 as an example for people wishing to create Debian
9148 packages. The Debian <prgn>debmake</prgn> package is
9149 recommended as a very helpful tool in creating and maintaining
9150 Debian packages. However, while the tools and examples are
9151 helpful, they do not replace the need to read and follow the
9152 Policy and Programmer's Manual.</p>
9155 <appendix id="pkg-binarypkg">
9156 <heading>Binary packages (from old Packaging Manual)</heading>
9159 The binary package has two main sections. The first part
9160 consists of various control information files and scripts used
9161 by <prgn>dpkg</prgn> when installing and removing. See <ref
9162 id="pkg-controlarea">.
9166 The second part is an archive containing the files and
9167 directories to be installed.
9171 In the future binary packages may also contain other
9172 components, such as checksums and digital signatures. The
9173 format for the archive is described in full in the
9174 <file>deb(5)</file> man page.
9178 <sect id="pkg-bincreating"><heading>Creating package files -
9179 <prgn>dpkg-deb</prgn>
9183 All manipulation of binary package files is done by
9184 <prgn>dpkg-deb</prgn>; it's the only program that has
9185 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9186 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9187 will spot that the options requested are appropriate to
9188 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9193 In order to create a binary package you must make a
9194 directory tree which contains all the files and directories
9195 you want to have in the file system data part of the package.
9196 In Debian-format source packages this directory is usually
9197 <file>debian/tmp</file>, relative to the top of the package's
9202 They should have the locations (relative to the root of the
9203 directory tree you're constructing) ownerships and
9204 permissions which you want them to have on the system when
9209 With current versions of <prgn>dpkg</prgn> the uid/username
9210 and gid/groupname mappings for the users and groups being
9211 used should be the same on the system where the package is
9212 built and the one where it is installed.
9216 You need to add one special directory to the root of the
9217 miniature file system tree you're creating:
9218 <prgn>DEBIAN</prgn>. It should contain the control
9219 information files, notably the binary package control file
9220 (see <ref id="pkg-controlfile">).
9224 The <prgn>DEBIAN</prgn> directory will not appear in the
9225 file system archive of the package, and so won't be installed
9226 by <prgn>dpkg</prgn> when the package is installed.
9230 When you've prepared the package, you should invoke:
9232 dpkg --build <var>directory</var>
9237 This will build the package in
9238 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9239 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9240 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9245 See the man page <manref name="dpkg-deb" section="8"> for details of how
9246 to examine the contents of this newly-created file. You may find the
9247 output of following commands enlightening:
9249 dpkg-deb --info <var>filename</var>.deb
9250 dpkg-deb --contents <var>filename</var>.deb
9251 dpkg --contents <var>filename</var>.deb
9253 To view the copyright file for a package you could use this command:
9255 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9260 <sect id="pkg-controlarea">
9261 <heading>Package control information files</heading>
9264 The control information portion of a binary package is a
9265 collection of files with names known to <prgn>dpkg</prgn>.
9266 It will treat the contents of these files specially - some
9267 of them contain information used by <prgn>dpkg</prgn> when
9268 installing or removing the package; others are scripts which
9269 the package maintainer wants <prgn>dpkg</prgn> to run.
9273 It is possible to put other files in the package control
9274 area, but this is not generally a good idea (though they
9275 will largely be ignored).
9279 Here is a brief list of the control info files supported by
9280 <prgn>dpkg</prgn> and a summary of what they're used for.
9285 <tag><tt>control</tt>
9288 This is the key description file used by
9289 <prgn>dpkg</prgn>. It specifies the package's name
9290 and version, gives its description for the user,
9291 states its relationships with other packages, and so
9292 forth. See <ref id="sourcecontrolfiles"> and
9293 <ref id="binarycontrolfiles">.
9297 It is usually generated automatically from information
9298 in the source package by the
9299 <prgn>dpkg-gencontrol</prgn> program, and with
9300 assistance from <prgn>dpkg-shlibdeps</prgn>.
9301 See <ref id="pkg-sourcetools">.
9305 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9310 These are executable files (usually scripts) which
9311 <prgn>dpkg</prgn> runs during installation, upgrade
9312 and removal of packages. They allow the package to
9313 deal with matters which are particular to that package
9314 or require more complicated processing than that
9315 provided by <prgn>dpkg</prgn>. Details of when and
9316 how they are called are in <ref id="maintainerscripts">.
9320 It is very important to make these scripts idempotent.
9321 See <ref id="idempotency">.
9325 The maintainer scripts are guaranteed to run with a
9326 controlling terminal and can interact with the user.
9327 See <ref id="controllingterminal">.
9331 <tag><tt>conffiles</tt>
9334 This file contains a list of configuration files which
9335 are to be handled automatically by <prgn>dpkg</prgn>
9336 (see <ref id="pkg-conffiles">). Note that not necessarily
9337 every configuration file should be listed here.
9340 <tag><tt>shlibs</tt>
9343 This file contains a list of the shared libraries
9344 supplied by the package, with dependency details for
9345 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9346 when it determines what dependencies are required in a
9347 package control file. The <tt>shlibs</tt> file format
9348 is described on <ref id="shlibs">.
9353 <sect id="pkg-controlfile">
9354 <heading>The main control information file: <tt>control</tt></heading>
9357 The most important control information file used by
9358 <prgn>dpkg</prgn> when it installs a package is
9359 <tt>control</tt>. It contains all the package's "vital
9364 The binary package control files of packages built from
9365 Debian sources are made by a special tool,
9366 <prgn>dpkg-gencontrol</prgn>, which reads
9367 <file>debian/control</file> and <file>debian/changelog</file> to
9368 find the information it needs. See <ref id="pkg-sourcepkg"> for
9373 The fields in binary package control files are listed in
9374 <ref id="binarycontrolfiles">.
9378 A description of the syntax of control files and the purpose
9379 of the fields is available in <ref id="controlfields">.
9384 <heading>Time Stamps</heading>
9387 See <ref id="timestamps">.
9392 <appendix id="pkg-sourcepkg">
9393 <heading>Source packages (from old Packaging Manual) </heading>
9396 The Debian binary packages in the distribution are generated
9397 from Debian sources, which are in a special format to assist
9398 the easy and automatic building of binaries.
9401 <sect id="pkg-sourcetools">
9402 <heading>Tools for processing source packages</heading>
9405 Various tools are provided for manipulating source packages;
9406 they pack and unpack sources and help build of binary
9407 packages and help manage the distribution of new versions.
9411 They are introduced and typical uses described here; see
9412 <manref name="dpkg-source" section="1"> for full
9413 documentation about their arguments and operation.
9417 For examples of how to construct a Debian source package,
9418 and how to use those utilities that are used by Debian
9419 source packages, please see the <prgn>hello</prgn> example
9423 <sect1 id="pkg-dpkg-source">
9425 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9430 This program is frequently used by hand, and is also
9431 called from package-independent automated building scripts
9432 such as <prgn>dpkg-buildpackage</prgn>.
9436 To unpack a package it is typically invoked with
9438 dpkg-source -x <var>.../path/to/filename</var>.dsc
9443 with the <file><var>filename</var>.tar.gz</file> and
9444 <file><var>filename</var>.diff.gz</file> (if applicable) in
9445 the same directory. It unpacks into
9446 <file><var>package</var>-<var>version</var></file>, and if
9448 <file><var>package</var>-<var>version</var>.orig</file>, in
9449 the current directory.
9453 To create a packed source archive it is typically invoked:
9455 dpkg-source -b <var>package</var>-<var>version</var>
9460 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9461 <file>.diff.gz</file> (if appropriate) in the current
9462 directory. <prgn>dpkg-source</prgn> does not clean the
9463 source tree first - this must be done separately if it is
9468 See also <ref id="pkg-sourcearchives">.</p>
9472 <sect1 id="pkg-dpkg-buildpackage">
9474 <prgn>dpkg-buildpackage</prgn> - overall package-building
9479 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9480 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9481 targets <tt>clean</tt>, <tt>build</tt> and
9482 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9483 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9484 source and binary package upload.
9488 It is usually invoked by hand from the top level of the
9489 built or unbuilt source directory. It may be invoked with
9490 no arguments; useful arguments include:
9491 <taglist compact="compact">
9492 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9495 Do not sign the <tt>.changes</tt> file or the
9496 source package <tt>.dsc</tt> file, respectively.</p>
9498 <tag><tt>-p<var>sign-command</var></tt></tag>
9501 Invoke <var>sign-command</var> instead of finding
9502 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9503 <var>sign-command</var> must behave just like
9504 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9506 <tag><tt>-r<var>root-command</var></tt></tag>
9509 When root privilege is required, invoke the command
9510 <var>root-command</var>. <var>root-command</var>
9511 should invoke its first argument as a command, from
9512 the <prgn>PATH</prgn> if necessary, and pass its
9513 second and subsequent arguments to the command it
9514 calls. If no <var>root-command</var> is supplied
9515 then <var>dpkg-buildpackage</var> will take no
9516 special action to gain root privilege, so that for
9517 most packages it will have to be invoked as root to
9520 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9523 Two types of binary-only build and upload - see
9524 <manref name="dpkg-source" section="1">.
9531 <sect1 id="pkg-dpkg-gencontrol">
9533 <prgn>dpkg-gencontrol</prgn> - generates binary package
9538 This program is usually called from <file>debian/rules</file>
9539 (see <ref id="pkg-sourcetree">) in the top level of the source
9544 This is usually done just before the files and directories in the
9545 temporary directory tree where the package is being built have their
9546 permissions and ownerships set and the package is constructed using
9547 <prgn>dpkg-deb/</prgn>
9549 This is so that the control file which is produced has
9550 the right permissions
9555 <prgn>dpkg-gencontrol</prgn> must be called after all the
9556 files which are to go into the package have been placed in
9557 the temporary build directory, so that its calculation of
9558 the installed size of a package is correct.
9562 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9563 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9564 variable substitutions created by
9565 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9570 For a package which generates only one binary package, and
9571 which builds it in <file>debian/tmp</file> relative to the top
9572 of the source package, it is usually sufficient to call
9573 <prgn>dpkg-gencontrol</prgn>.
9577 Sources which build several binaries will typically need
9580 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9581 </example> The <tt>-P</tt> tells
9582 <prgn>dpkg-gencontrol</prgn> that the package is being
9583 built in a non-default directory, and the <tt>-p</tt>
9584 tells it which package's control file should be generated.
9588 <prgn>dpkg-gencontrol</prgn> also adds information to the
9589 list of files in <file>debian/files</file>, for the benefit of
9590 (for example) a future invocation of
9591 <prgn>dpkg-genchanges</prgn>.</p>
9594 <sect1 id="pkg-dpkg-shlibdeps">
9596 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9601 This program is usually called from <file>debian/rules</file>
9602 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9603 id="pkg-sourcetree">), in the top level of the source tree.
9607 Its arguments are executables and shared libraries
9610 They may be specified either in the locations in the
9611 source tree where they are created or in the locations
9612 in the temporary build tree where they are installed
9613 prior to binary package creation.
9615 </footnote> for which shared library dependencies should
9616 be included in the binary package's control file.
9620 If some of the found shared libraries should only
9621 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9622 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9623 by using the <tt>-d<var>dependency-field</var></tt> option
9624 before those executable(s). (Each <tt>-d</tt> option
9625 takes effect until the next <tt>-d</tt>.)
9629 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9630 output control file to be modified. Instead by default it
9631 adds to the <file>debian/substvars</file> file variable
9632 settings like <tt>shlibs:Depends</tt>. These variable
9633 settings must be referenced in dependency fields in the
9634 appropriate per-binary-package sections of the source
9639 For example, a package that generates an essential part
9640 which requires dependencies, and optional parts that
9641 which only require a recommendation, would separate those
9642 two sets of dependencies into two different fields.<footnote>
9643 At the time of writing, an example for this was the
9644 <package/xmms/ package, with Depends used for the xmms
9645 executable, Recommends for the plug-ins and Suggests for
9646 even more optional features provided by unzip.
9648 It can say in its <file>debian/rules</file>:
9650 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9651 -dRecommends <var>optionalpart anotheroptionalpart</var>
9653 and then in its main control file <file>debian/control</file>:
9656 Depends: ${shlibs:Depends}
9657 Recommends: ${shlibs:Recommends}
9663 Sources which produce several binary packages with
9664 different shared library dependency requirements can use
9665 the <tt>-p<var>varnameprefix</var></tt> option to override
9666 the default <tt>shlibs:</tt> prefix (one invocation of
9667 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9668 They can thus produce several sets of dependency
9669 variables, each of the form
9670 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9671 which can be referred to in the appropriate parts of the
9672 binary package control files.
9677 <sect1 id="pkg-dpkg-distaddfile">
9679 <prgn>dpkg-distaddfile</prgn> - adds a file to
9680 <file>debian/files</file>
9684 Some packages' uploads need to include files other than
9685 the source and binary package files.
9689 <prgn>dpkg-distaddfile</prgn> adds a file to the
9690 <file>debian/files</file> file so that it will be included in
9691 the <file>.changes</file> file when
9692 <prgn>dpkg-genchanges</prgn> is run.
9696 It is usually invoked from the <tt>binary</tt> target of
9697 <file>debian/rules</file>:
9699 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9701 The <var>filename</var> is relative to the directory where
9702 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9703 is usually the directory above the top level of the source
9704 tree. The <file>debian/rules</file> target should put the
9705 file there just before or just after calling
9706 <prgn>dpkg-distaddfile</prgn>.
9710 The <var>section</var> and <var>priority</var> are passed
9711 unchanged into the resulting <file>.changes</file> file.
9716 <sect1 id="pkg-dpkg-genchanges">
9718 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9723 This program is usually called by package-independent
9724 automatic building scripts such as
9725 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9730 It is usually called in the top level of a built source
9731 tree, and when invoked with no arguments will print out a
9732 straightforward <file>.changes</file> file based on the
9733 information in the source package's changelog and control
9734 file and the binary and source packages which should have
9740 <sect1 id="pkg-dpkg-parsechangelog">
9742 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9743 representation of a changelog
9747 This program is used internally by
9748 <prgn>dpkg-source</prgn> et al. It may also occasionally
9749 be useful in <file>debian/rules</file> and elsewhere. It
9750 parses a changelog, <file>debian/changelog</file> by default,
9751 and prints a control-file format representation of the
9752 information in it to standard output.
9756 <sect1 id="pkg-dpkg-architecture">
9758 <prgn>dpkg-architecture</prgn> - information about the build and
9763 This program can be used manually, but is also invoked by
9764 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9765 environment or make variables which specify the build and host
9766 architecture for the package building process.
9771 <sect id="pkg-sourcetree">
9772 <heading>The Debianised source tree</heading>
9775 The source archive scheme described later is intended to
9776 allow a Debianised source tree with some associated control
9777 information to be reproduced and transported easily. The
9778 Debianised source tree is a version of the original program
9779 with certain files added for the benefit of the
9780 Debianisation process, and with any other changes required
9781 made to the rest of the source code and installation
9786 The extra files created for Debian are in the subdirectory
9787 <file>debian</file> of the top level of the Debianised source
9788 tree. They are described below.
9791 <sect1 id="pkg-debianrules">
9792 <heading><file>debian/rules</file> - the main building script</heading>
9795 See <ref id="debianrules">.
9800 <sect1 id="pkg-dpkgchangelog">
9801 <heading><file>debian/changelog</file></heading>
9804 See <ref id="dpkgchangelog">.
9808 It is recommended that the entire changelog be encoded in the
9809 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9811 <url id="http://www.unicode.org/"
9812 name="Unicode">.<footnote>
9814 I think it is fairly obvious that we need to
9815 eventually transition to UTF-8 for our package
9816 infrastructure; it is really the only sane char-set in
9817 an international environment. Now, we can't switch to
9818 using UTF-8 for package control fields and the like
9819 until dpkg has better support, but one thing we can
9820 start doing today is requesting that Debian changelogs
9821 are UTF-8 encoded. At some point in time, we can start
9822 requiring them to do so.
9825 Checking for non-UTF8 characters in a changelog is
9826 trivial. Dump the file through
9827 <example>iconv -f utf-8 -t ucs-4</example>
9828 discard the output, and check the return
9829 value. If there are any characters in the stream
9830 which are invalid UTF-8 sequences, iconv will exit
9831 with an error code; and this will be the case for the
9832 vast majority of other character sets.
9837 <sect2><heading>Defining alternative changelog formats
9841 It is possible to use a different format to the standard
9842 one, by providing a parser for the format you wish to
9847 In order to have <tt>dpkg-parsechangelog</tt> run your
9848 parser, you must include a line within the last 40 lines
9849 of your file matching the Perl regular expression:
9850 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9851 parentheses should be the name of the format. For
9852 example, you might say:
9854 @@@ changelog-format: joebloggs @@@
9856 Changelog format names are non-empty strings of alphanumerics.
9860 If such a line exists then <tt>dpkg-parsechangelog</tt>
9861 will look for the parser as
9862 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9864 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9865 it is an error for it not to find it, or for it not to
9866 be an executable program. The default changelog format
9867 is <tt>dpkg</tt>, and a parser for it is provided with
9868 the <tt>dpkg</tt> package.
9872 The parser will be invoked with the changelog open on
9873 standard input at the start of the file. It should read
9874 the file (it may seek if it wishes) to determine the
9875 information required and return the parsed information
9876 to standard output in the form of a series of control
9877 fields in the standard format. By default it should
9878 return information about only the most recent version in
9879 the changelog; it should accept a
9880 <tt>-v<var>version</var></tt> option to return changes
9881 information from all versions present <em>strictly
9882 after</em> <var>version</var>, and it should then be an
9883 error for <var>version</var> not to be present in the
9889 <list compact="compact">
9890 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9891 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9892 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9893 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9894 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9895 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9896 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9901 If several versions are being returned (due to the use
9902 of <tt>-v</tt>), the urgency value should be of the
9903 highest urgency code listed at the start of any of the
9904 versions requested followed by the concatenated
9905 (space-separated) comments from all the versions
9906 requested; the maintainer, version, distribution and
9907 date should always be from the most recent version.
9911 For the format of the <tt>Changes</tt> field see
9912 <ref id="f-Changes">.
9916 If the changelog format which is being parsed always or
9917 almost always leaves a blank line between individual
9918 change notes these blank lines should be stripped out,
9919 so as to make the resulting output compact.
9923 If the changelog format does not contain date or package
9924 name information this information should be omitted from
9925 the output. The parser should not attempt to synthesize
9926 it or find it from other sources.
9930 If the changelog does not have the expected format the
9931 parser should exit with a nonzero exit status, rather
9932 than trying to muddle through and possibly generating
9937 A changelog parser may not interact with the user at
9943 <sect1 id="pkg-srcsubstvars">
9944 <heading><file>debian/substvars</file> and variable substitutions</heading>
9947 See <ref id="substvars">.
9953 <heading><file>debian/files</file></heading>
9956 See <ref id="debianfiles">.
9960 <sect1><heading><file>debian/tmp</file>
9964 This is the canonical temporary location for the
9965 construction of binary packages by the <tt>binary</tt>
9966 target. The directory <file>tmp</file> serves as the root of
9967 the file system tree as it is being constructed (for
9968 example, by using the package's upstream makefiles install
9969 targets and redirecting the output there), and it also
9970 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9971 id="pkg-bincreating">.
9975 If several binary packages are generated from the same
9976 source tree it is usual to use several
9977 <file>debian/tmp<var>something</var></file> directories, for
9978 example <file>tmp-a</file> or <file>tmp-doc</file>.
9982 Whatever <file>tmp</file> directories are created and used by
9983 <tt>binary</tt> must of course be removed by the
9984 <tt>clean</tt> target.</p></sect1>
9988 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9992 As it exists on the FTP site, a Debian source package
9993 consists of three related files. You must have the right
9994 versions of all three to be able to use them.
9999 <tag>Debian source control file - <tt>.dsc</tt></tag>
10001 This file is a control file used by <prgn>dpkg-source</prgn>
10002 to extract a source package.
10003 See <ref id="debiansourcecontrolfiles">.
10007 Original source archive -
10009 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10015 This is a compressed (with <tt>gzip -9</tt>)
10016 <prgn>tar</prgn> file containing the source code from
10017 the upstream authors of the program.
10022 Debianisation diff -
10024 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10030 This is a unified context diff (<tt>diff -u</tt>)
10031 giving the changes which are required to turn the
10032 original source into the Debian source. These changes
10033 may only include editing and creating plain files.
10034 The permissions of files, the targets of symbolic
10035 links and the characteristics of special files or
10036 pipes may not be changed and no files may be removed
10041 All the directories in the diff must exist, except the
10042 <file>debian</file> subdirectory of the top of the source
10043 tree, which will be created by
10044 <prgn>dpkg-source</prgn> if necessary when unpacking.
10048 The <prgn>dpkg-source</prgn> program will
10049 automatically make the <file>debian/rules</file> file
10050 executable (see below).</p></item>
10055 If there is no original source code - for example, if the
10056 package is specially prepared for Debian or the Debian
10057 maintainer is the same as the upstream maintainer - the
10058 format is slightly different: then there is no diff, and the
10060 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10061 and preferably contains a directory named
10062 <file><var>package</var>-<var>version</var></file>.
10067 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10070 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10071 Debian source package. However, if it is not available it
10072 is possible to unpack a Debian source archive as follows:
10073 <enumlist compact="compact">
10076 Untar the tarfile, which will create a <file>.orig</file>
10080 <p>Rename the <file>.orig</file> directory to
10081 <file><var>package</var>-<var>version</var></file>.</p>
10085 Create the subdirectory <file>debian</file> at the top of
10086 the source tree.</p>
10088 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10090 <item><p>Untar the tarfile again if you want a copy of the original
10091 source code alongside the Debianised version.</p>
10096 It is not possible to generate a valid Debian source archive
10097 without using <prgn>dpkg-source</prgn>. In particular,
10098 attempting to use <prgn>diff</prgn> directly to generate the
10099 <file>.diff.gz</file> file will not work.
10103 <heading>Restrictions on objects in source packages</heading>
10106 The source package may not contain any hard links
10108 This is not currently detected when building source
10109 packages, but only when extracting
10113 Hard links may be permitted at some point in the
10114 future, but would require a fair amount of
10116 </footnote>, device special files, sockets or setuid or
10119 Setgid directories are allowed.
10124 The source packaging tools manage the changes between the
10125 original and Debianised source using <prgn>diff</prgn> and
10126 <prgn>patch</prgn>. Turning the original source tree as
10127 included in the <file>.orig.tar.gz</file> into the debianised
10128 source must not involve any changes which cannot be
10129 handled by these tools. Problematic changes which cause
10130 <prgn>dpkg-source</prgn> to halt with an error when
10131 building the source package are:
10132 <list compact="compact">
10133 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10135 <item><p>Changing the targets of symbolic links.</p>
10137 <item><p>Creating directories, other than <file>debian</file>.</p>
10139 <item><p>Changes to the contents of binary files.</p></item>
10140 </list> Changes which cause <prgn>dpkg-source</prgn> to
10141 print a warning but continue anyway are:
10142 <list compact="compact">
10145 Removing files, directories or symlinks.
10147 Renaming a file is not treated specially - it is
10148 seen as the removal of the old file (which
10149 generates a warning, but is otherwise ignored),
10150 and the creation of the new one.
10156 Changed text files which are missing the usual final
10157 newline (either in the original or the modified
10162 Changes which are not represented, but which are not detected by
10163 <prgn>dpkg-source</prgn>, are:
10164 <list compact="compact">
10165 <item><p>Changing the permissions of files (other than
10166 <file>debian/rules</file>) and directories.</p></item>
10171 The <file>debian</file> directory and <file>debian/rules</file>
10172 are handled specially by <prgn>dpkg-source</prgn> - before
10173 applying the changes it will create the <file>debian</file>
10174 directory, and afterwards it will make
10175 <file>debian/rules</file> world-executable.
10181 <appendix id="pkg-controlfields">
10182 <heading>Control files and their fields (from old Packaging Manual)</heading>
10185 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10186 data in a common format, known as control files. Binary and
10187 source packages have control data as do the <file>.changes</file>
10188 files which control the installation of uploaded files, and
10189 <prgn>dpkg</prgn>'s internal databases are in a similar
10194 <heading>Syntax of control files</heading>
10197 See <ref id="controlsyntax">.
10201 It is important to note that there are several fields which
10202 are optional as far as <prgn>dpkg</prgn> and the related
10203 tools are concerned, but which must appear in every Debian
10204 package, or whose omission may cause problems.
10209 <heading>List of fields</heading>
10212 See <ref id="controlfieldslist">.
10216 This section now contains only the fields that didn't belong
10217 to the Policy manual.
10220 <sect1 id="pkg-f-Filename">
10221 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10224 These fields in <tt>Packages</tt> files give the
10225 filename(s) of (the parts of) a package in the
10226 distribution directories, relative to the root of the
10227 Debian hierarchy. If the package has been split into
10228 several parts the parts are all listed in order, separated
10233 <sect1 id="pkg-f-Size">
10234 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10237 These fields in <file>Packages</file> files give the size (in
10238 bytes, expressed in decimal) and MD5 checksum of the
10239 file(s) which make(s) up a binary package in the
10240 distribution. If the package is split into several parts
10241 the values for the parts are listed in order, separated by
10246 <sect1 id="pkg-f-Status">
10247 <heading><tt>Status</tt></heading>
10250 This field in <prgn>dpkg</prgn>'s status file records
10251 whether the user wants a package installed, removed or
10252 left alone, whether it is broken (requiring
10253 re-installation) or not and what its current state on the
10254 system is. Each of these pieces of information is a
10259 <sect1 id="pkg-f-Config-Version">
10260 <heading><tt>Config-Version</tt></heading>
10263 If a package is not installed or not configured, this
10264 field in <prgn>dpkg</prgn>'s status file records the last
10265 version of the package which was successfully
10270 <sect1 id="pkg-f-Conffiles">
10271 <heading><tt>Conffiles</tt></heading>
10274 This field in <prgn>dpkg</prgn>'s status file contains
10275 information about the automatically-managed configuration
10276 files held by a package. This field should <em>not</em>
10277 appear anywhere in a package!
10282 <heading>Obsolete fields</heading>
10285 These are still recognized by <prgn>dpkg</prgn> but should
10286 not appear anywhere any more.
10288 <taglist compact="compact">
10290 <tag><tt>Revision</tt></tag>
10291 <tag><tt>Package-Revision</tt></tag>
10292 <tag><tt>Package_Revision</tt></tag>
10294 The Debian revision part of the package version was
10295 at one point in a separate control file field. This
10296 field went through several names.
10299 <tag><tt>Recommended</tt></tag>
10300 <item>Old name for <tt>Recommends</tt>.</item>
10302 <tag><tt>Optional</tt></tag>
10303 <item>Old name for <tt>Suggests</tt>.</item>
10305 <tag><tt>Class</tt></tag>
10306 <item>Old name for <tt>Priority</tt>.</item>
10315 <appendix id="pkg-conffiles">
10316 <heading>Configuration file handling (from old Packaging Manual)</heading>
10319 <prgn>dpkg</prgn> can do a certain amount of automatic
10320 handling of package configuration files.
10324 Whether this mechanism is appropriate depends on a number of
10325 factors, but basically there are two approaches to any
10326 particular configuration file.
10330 The easy method is to ship a best-effort configuration in the
10331 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10332 handle updates. If the user is unlikely to want to edit the
10333 file, but you need them to be able to without losing their
10334 changes, and a new package with a changed version of the file
10335 is only released infrequently, this is a good approach.
10339 The hard method is to build the configuration file from
10340 scratch in the <prgn>postinst</prgn> script, and to take the
10341 responsibility for fixing any mistakes made in earlier
10342 versions of the package automatically. This will be
10343 appropriate if the file is likely to need to be different on
10347 <sect><heading>Automatic handling of configuration files by
10352 A package may contain a control area file called
10353 <tt>conffiles</tt>. This file should be a list of filenames
10354 of configuration files needing automatic handling, separated
10355 by newlines. The filenames should be absolute pathnames,
10356 and the files referred to should actually exist in the
10361 When a package is upgraded <prgn>dpkg</prgn> will process
10362 the configuration files during the configuration stage,
10363 shortly before it runs the package's <prgn>postinst</prgn>
10368 For each file it checks to see whether the version of the
10369 file included in the package is the same as the one that was
10370 included in the last version of the package (the one that is
10371 being upgraded from); it also compares the version currently
10372 installed on the system with the one shipped with the last
10377 If neither the user nor the package maintainer has changed
10378 the file, it is left alone. If one or the other has changed
10379 their version, then the changed version is preferred - i.e.,
10380 if the user edits their file, but the package maintainer
10381 doesn't ship a different version, the user's changes will
10382 stay, silently, but if the maintainer ships a new version
10383 and the user hasn't edited it the new version will be
10384 installed (with an informative message). If both have
10385 changed their version the user is prompted about the problem
10386 and must resolve the differences themselves.
10390 The comparisons are done by calculating the MD5 message
10391 digests of the files, and storing the MD5 of the file as it
10392 was included in the most recent version of the package.
10396 When a package is installed for the first time
10397 <prgn>dpkg</prgn> will install the file that comes with it,
10398 unless that would mean overwriting a file already on the
10403 However, note that <prgn>dpkg</prgn> will <em>not</em>
10404 replace a conffile that was removed by the user (or by a
10405 script). This is necessary because with some programs a
10406 missing file produces an effect hard or impossible to
10407 achieve in another way, so that a missing file needs to be
10408 kept that way if the user did it.
10412 Note that a package should <em>not</em> modify a
10413 <prgn>dpkg</prgn>-handled conffile in its maintainer
10414 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10415 the user confusing and possibly dangerous options for
10416 conffile update when the package is upgraded.</p>
10419 <sect><heading>Fully-featured maintainer script configuration
10424 For files which contain site-specific information such as
10425 the hostname and networking details and so forth, it is
10426 better to create the file in the package's
10427 <prgn>postinst</prgn> script.
10431 This will typically involve examining the state of the rest
10432 of the system to determine values and other information, and
10433 may involve prompting the user for some information which
10434 can't be obtained some other way.
10438 When using this method there are a couple of important
10439 issues which should be considered:
10443 If you discover a bug in the program which generates the
10444 configuration file, or if the format of the file changes
10445 from one version to the next, you will have to arrange for
10446 the postinst script to do something sensible - usually this
10447 will mean editing the installed configuration file to remove
10448 the problem or change the syntax. You will have to do this
10449 very carefully, since the user may have changed the file,
10450 perhaps to fix the very problem that your script is trying
10451 to deal with - you will have to detect these situations and
10452 deal with them correctly.
10456 If you do go down this route it's probably a good idea to
10457 make the program that generates the configuration file(s) a
10458 separate program in <file>/usr/sbin</file>, by convention called
10459 <file><var>package</var>config</file> and then run that if
10460 appropriate from the post-installation script. The
10461 <tt><var>package</var>config</tt> program should not
10462 unquestioningly overwrite an existing configuration - if its
10463 mode of operation is geared towards setting up a package for
10464 the first time (rather than any arbitrary reconfiguration
10465 later) you should have it check whether the configuration
10466 already exists, and require a <tt>--force</tt> flag to
10467 overwrite it.</p></sect>
10470 <appendix id="pkg-alternatives"><heading>Alternative versions of
10471 an interface - <prgn>update-alternatives</prgn> (from old
10476 When several packages all provide different versions of the
10477 same program or file it is useful to have the system select a
10478 default, but to allow the system administrator to change it
10479 and have their decisions respected.
10483 For example, there are several versions of the <prgn>vi</prgn>
10484 editor, and there is no reason to prevent all of them from
10485 being installed at once, each under their own name
10486 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10487 Nevertheless it is desirable to have the name <tt>vi</tt>
10488 refer to something, at least by default.
10492 If all the packages involved cooperate, this can be done with
10493 <prgn>update-alternatives</prgn>.
10497 Each package provides its own version under its own name, and
10498 calls <prgn>update-alternatives</prgn> in its postinst to
10499 register its version (and again in its prerm to deregister
10504 See the man page <manref name="update-alternatives"
10505 section="8"> for details.
10509 If <prgn>update-alternatives</prgn> does not seem appropriate
10510 you may wish to consider using diversions instead.</p>
10513 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10514 package's version of a file (from old Packaging Manual)
10518 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10519 when it reinstalls the package it belongs to, and to have it
10520 put the file from the package somewhere else instead.
10524 This can be used locally to override a package's version of a
10525 file, or by one package to override another's version (or
10526 provide a wrapper for it).
10530 Before deciding to use a diversion, read <ref
10531 id="pkg-alternatives"> to see if you really want a diversion
10532 rather than several alternative versions of a program.
10536 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10537 and updated by a special program <prgn>dpkg-divert</prgn>.
10538 Please see <manref name="dpkg-divert" section="8"> for full
10539 details of its operation.
10543 When a package wishes to divert a file from another, it should
10544 call <prgn>dpkg-divert</prgn> in its preinst to add the
10545 diversion and rename the existing file. For example,
10546 supposing that a <prgn>smailwrapper</prgn> package wishes to
10547 install a wrapper around <file>/usr/sbin/smail</file>:
10549 if [ install = "$1" ]; then
10550 dpkg-divert --package smailwrapper --add --rename \
10551 --divert /usr/sbin/smail.real /usr/sbin/smail
10553 </example> Testing <tt>$1</tt> is necessary so that the script
10554 doesn't try to add the diversion again when
10555 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10556 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10557 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10558 get installed as the true version.
10562 The postrm has to do the reverse:
10564 if [ remove = "$1" ]; then
10565 dpkg-divert --package smailwrapper --remove --rename \
10566 --divert /usr/sbin/smail.real /usr/sbin/smail
10572 Do not attempt to divert a file which is vitally important for
10573 the system's operation - when using <prgn>dpkg-divert</prgn>
10574 there is a time, after it has been diverted but before
10575 <prgn>dpkg</prgn> has installed the new version, when the file
10576 does not exist.</p>
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