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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or categories based on their licenses and other restrictions.
300 The aims of this are:
302 <list compact="compact">
303 <item>to allow us to make as much software available as we can</item>
304 <item>to allow us to encourage everyone to write free software,
306 <item>to allow us to make it easy for people to produce
307 CD-ROMs of our system without violating any licenses,
308 import/export restrictions, or any other laws.</item>
313 The <em>main</em> category forms the
314 <em>Debian GNU/Linux distribution</em>.
318 Packages in the other distribution areas (<tt>contrib</tt>,
319 <tt>non-free</tt>) are not considered to be part of the Debian
320 distribution, although we support their use and provide
321 infrastructure for them (such as our bug-tracking system and
322 mailing lists). This Debian Policy Manual applies to these
327 <heading>The Debian Free Software Guidelines</heading>
329 The Debian Free Software Guidelines (DFSG) form our
330 definition of "free software". These are:
332 <tag>Free Redistribution
335 The license of a Debian component may not restrict any
336 party from selling or giving away the software as a
337 component of an aggregate software distribution
338 containing programs from several different
339 sources. The license may not require a royalty or
340 other fee for such sale.
345 The program must include source code, and must allow
346 distribution in source code as well as compiled form.
351 The license must allow modifications and derived
352 works, and must allow them to be distributed under the
353 same terms as the license of the original software.
355 <tag>Integrity of The Author's Source Code
358 The license may restrict source-code from being
359 distributed in modified form <em>only</em> if the
360 license allows the distribution of "patch files"
361 with the source code for the purpose of modifying the
362 program at build time. The license must explicitly
363 permit distribution of software built from modified
364 source code. The license may require derived works to
365 carry a different name or version number from the
366 original software. (This is a compromise. The Debian
367 Project encourages all authors to not restrict any
368 files, source or binary, from being modified.)
370 <tag>No Discrimination Against Persons or Groups
373 The license must not discriminate against any person
376 <tag>No Discrimination Against Fields of Endeavor
379 The license must not restrict anyone from making use
380 of the program in a specific field of endeavor. For
381 example, it may not restrict the program from being
382 used in a business, or from being used for genetic
385 <tag>Distribution of License
388 The rights attached to the program must apply to all
389 to whom the program is redistributed without the need
390 for execution of an additional license by those
393 <tag>License Must Not Be Specific to Debian
396 The rights attached to the program must not depend on
397 the program's being part of a Debian system. If the
398 program is extracted from Debian and used or
399 distributed without Debian but otherwise within the
400 terms of the program's license, all parties to whom
401 the program is redistributed must have the same
402 rights as those that are granted in conjunction with
405 <tag>License Must Not Contaminate Other Software
408 The license must not place restrictions on other
409 software that is distributed along with the licensed
410 software. For example, the license must not insist
411 that all other programs distributed on the same medium
412 must be free software.
414 <tag>Example Licenses
417 The "GPL," "BSD," and "Artistic" licenses are examples of
418 licenses that we consider <em>free</em>.
425 <heading>Categories</heading>
428 <heading>The main category</heading>
431 Every package in <em>main</em> must comply with the DFSG
432 (Debian Free Software Guidelines).
436 In addition, the packages in <em>main</em>
437 <list compact="compact">
439 must not require a package outside of <em>main</em>
440 for compilation or execution (thus, the package must
441 not declare a "Depends", "Recommends", or
442 "Build-Depends" relationship on a non-<em>main</em>
446 must not be so buggy that we refuse to support them,
450 must meet all policy requirements presented in this
459 <heading>The contrib category</heading>
462 Every package in <em>contrib</em> must comply with the DFSG.
466 In addition, the packages in <em>contrib</em>
467 <list compact="compact">
469 must not be so buggy that we refuse to support them,
473 must meet all policy requirements presented in this
481 Examples of packages which would be included in
482 <em>contrib</em> are:
483 <list compact="compact">
485 free packages which require <em>contrib</em>,
486 <em>non-free</em> packages or packages which are not
487 in our archive at all for compilation or execution,
491 wrapper packages or other sorts of free accessories for
498 <sect1 id="non-free">
499 <heading>The non-free category</heading>
502 Packages must be placed in <em>non-free</em> if they are
503 not compliant with the DFSG or are encumbered by patents
504 or other legal issues that make their distribution
509 In addition, the packages in <em>non-free</em>
510 <list compact="compact">
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
517 manual that it is possible for them to meet.
519 It is possible that there are policy
520 requirements which the package is unable to
521 meet, for example, if the source is
522 unavailable. These situations will need to be
523 handled on a case-by-case basis.
532 <sect id="pkgcopyright">
533 <heading>Copyright considerations</heading>
536 Every package must be accompanied by a verbatim copy of
537 its copyright and distribution license in the file
538 <file>/usr/share/doc/<var>package</var>/copyright</file>
539 (see <ref id="copyrightfile"> for further details).
543 We reserve the right to restrict files from being included
544 anywhere in our archives if
545 <list compact="compact">
547 their use or distribution would break a law,
550 there is an ethical conflict in their distribution or
554 we would have to sign a license for them, or
557 their distribution would conflict with other project
564 Programs whose authors encourage the user to make
565 donations are fine for the main distribution, provided
566 that the authors do not claim that not donating is
567 immoral, unethical, illegal or something similar; in such
568 a case they must go in <em>non-free</em>.
572 Packages whose copyright permission notices (or patent
573 problems) do not even allow redistribution of binaries
574 only, and where no special permission has been obtained,
575 must not be placed on the Debian FTP site and its mirrors
580 Note that under international copyright law (this applies
581 in the United States, too), <em>no</em> distribution or
582 modification of a work is allowed without an explicit
583 notice saying so. Therefore a program without a copyright
584 notice <em>is</em> copyrighted and you may not do anything
585 to it without risking being sued! Likewise if a program
586 has a copyright notice but no statement saying what is
587 permitted then nothing is permitted.
591 Many authors are unaware of the problems that restrictive
592 copyrights (or lack of copyright notices) can cause for
593 the users of their supposedly-free software. It is often
594 worthwhile contacting such authors diplomatically to ask
595 them to modify their license terms. However, this can be a
596 politically difficult thing to do and you should ask for
597 advice on the <tt>debian-legal</tt> mailing list first, as
602 When in doubt about a copyright, send mail to
603 <email>debian-legal@lists.debian.org</email>. Be prepared
604 to provide us with the copyright statement. Software
605 covered by the GPL, public domain software and BSD-like
606 copyrights are safe; be wary of the phrases "commercial
607 use prohibited" and "distribution restricted".
611 <sect id="subsections">
612 <heading>Sections</heading>
615 The packages in the categories <em>main</em>,
616 <em>contrib</em> and <em>non-free</em> are grouped further
617 into <em>sections</em> to simplify handling.
621 The category and section for each package should be
622 specified in the package's <tt>Section</tt> control record
623 (see <ref id="f-Section">). However, the maintainer of the
624 Debian archive may override this selection to ensure the
625 consistency of the Debian distribution. The
626 <tt>Section</tt> field should be of the form:
627 <list compact="compact">
629 <em>section</em> if the package is in the
630 <em>main</em> category,
633 <em>segment/section</em> if the package is in
634 the <em>contrib</em> or <em>non-free</em>
641 The Debian archive maintainers provide the authoritative
642 list of sections. At present, they are:
643 <em>admin</em>, <em>comm</em>,
644 <em>devel</em>, <em>doc</em>,
645 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
646 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
647 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
648 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
649 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Only very few packages are allowed to form
1082 part of the base system, in order to keep the required disk
1087 The base system consists of all those packages with priority
1088 <tt>required</tt> or <tt>important</tt>. Many of them will
1089 be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1480 The format of the <file>debian/changelog</file> allows the
1481 package building tools to discover which version of the package
1482 is being built and find out other release-specific information.
1486 That format is a series of entries like this:
1488 <example compact="compact">
1489 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1491 [optional blank line(s), stripped]
1493 * <var>change details</var>
1494 <var>more change details</var>
1496 [blank line(s), included in output of dpkg-parsechangelog]
1498 * <var>even more change details</var>
1500 [optional blank line(s), stripped]
1502 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1507 <var>package</var> and <var>version</var> are the source
1508 package name and version number.
1512 <var>distribution(s)</var> lists the distributions where
1513 this version should be installed when it is uploaded - it
1514 is copied to the <tt>Distribution</tt> field in the
1515 <file>.changes</file> file. See <ref id="f-Distribution">.
1519 <var>urgency</var> is the value for the <tt>Urgency</tt>
1520 field in the <file>.changes</file> file for the upload
1521 (see <ref id="f-Urgency">). It is not possible to specify
1522 an urgency containing commas; commas are used to separate
1523 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1524 <prgn>dpkg</prgn> changelog format (though there is
1525 currently only one useful <var>keyword</var>,
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>) using the
1551 <var>version</var> of the changelog entry.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1930 <tag><tt>patch</tt> (optional)</tag>
1933 This target performs whatever additional actions are
1934 required to make the source ready for editing (unpacking
1935 additional upstream archives, applying patches, etc.).
1936 It is recommended to be implemented for any package where
1937 <tt>dpkg-source -x</tt> does not result in source ready
1938 for additional modification. See
1939 <ref id="readmesource">.
1945 The <tt>build</tt>, <tt>binary</tt> and
1946 <tt>clean</tt> targets must be invoked with the current
1947 directory being the package's top-level directory.
1952 Additional targets may exist in <file>debian/rules</file>,
1953 either as published or undocumented interfaces or for the
1954 package's internal use.
1958 The architectures we build on and build for are determined
1959 by <prgn>make</prgn> variables using the utility
1960 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1961 You can determine the
1962 Debian architecture and the GNU style architecture
1963 specification string for the build machine (the machine type
1964 we are building on) as well as for the host machine (the
1965 machine type we are building for). Here is a list of
1966 supported <prgn>make</prgn> variables:
1967 <list compact="compact">
1969 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1972 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1973 specification string)
1976 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1977 <tt>DEB_*_GNU_TYPE</tt>)
1980 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1981 <tt>DEB_*_GNU_TYPE</tt>)
1983 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1984 the build machine or <tt>HOST</tt> for specification of the
1989 Backward compatibility can be provided in the rules file
1990 by setting the needed variables to suitable default
1991 values; please refer to the documentation of
1992 <prgn>dpkg-architecture</prgn> for details.
1996 It is important to understand that the <tt>DEB_*_ARCH</tt>
1997 string only determines which Debian architecture we are
1998 building on or for. It should not be used to get the CPU
1999 or system information; the GNU style variables should be
2003 <sect1 id="debianrules-options">
2004 <heading><file>debian/rules</file> and
2005 <tt>DEB_BUILD_OPTIONS</tt></heading>
2008 Supporting the standardized environment variable
2009 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2010 contain several flags to change how a package is compiled and
2011 built. Each flag must be in the form <var>flag</var> or
2012 <var>flag</var>=<var>options</var>. If multiple flags are
2013 given, they must be separated by whitespace.<footnote>
2014 Some packages support any delimiter, but whitespace is the
2015 easiest to parse inside a makefile and avoids ambiguity with
2016 flag values that contain commas.
2018 <var>flag</var> must start with a lowercase letter
2019 (<tt>a-z</tt>) and consist only of lowercase letters,
2020 numbers (<tt>0-9</tt>), and the characters
2021 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2022 <var>options</var> must not contain whitespace. The same
2023 tag should not be given multiple times with conflicting
2024 values. Package maintainers may assume that
2025 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2029 The meaning of the following tags has been standardized:
2033 The presence of this tag means that the package should
2034 be compiled with a minimum of optimization. For C
2035 programs, it is best to add <tt>-O0</tt> to
2036 <tt>CFLAGS</tt> (although this is usually the default).
2037 Some programs might fail to build or run at this level
2038 of optimization; it may be necessary to use
2039 <tt>-O1</tt>, for example.
2043 This tag means that the debugging symbols should not be
2044 stripped from the binary during installation, so that
2045 debugging information may be included in the package.
2047 <tag>parallel=n</tag>
2049 This tag means that the package should be built using up
2050 to <tt>n</tt> parallel processes if the package build
2051 system supports this.<footnote>
2052 Packages built with <tt>make</tt> can often implement
2053 this by passing the <tt>-j</tt><var>n</var> option to
2056 If the package build system does not support parallel
2057 builds, this string must be ignored. If the package
2058 build system only supports a lower level of concurrency
2059 than <var>n</var>, the package should be built using as
2060 many parallel processes as the package build system
2061 supports. It is up to the package maintainer to decide
2062 whether the package build times are long enough and the
2063 package build system is robust enough to make supporting
2064 parallel builds worthwhile.
2070 Unknown flags must be ignored by <file>debian/rules</file>.
2074 The following makefile snippet is an example of how one may
2075 implement the build options; you will probably have to
2076 massage this example in order to make it work for your
2078 <example compact="compact">
2081 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2082 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2083 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2084 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2086 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2091 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2092 INSTALL_PROGRAM += -s
2094 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2095 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2096 MAKEFLAGS += -j$(NUMJOBS)
2103 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2104 <sect id="substvars">
2105 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2108 When <prgn>dpkg-gencontrol</prgn>,
2109 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2110 generate control files they perform variable substitutions
2111 on their output just before writing it. Variable
2112 substitutions have the form <tt>${<var>variable</var>}</tt>.
2113 The optional file <file>debian/substvars</file> contains
2114 variable substitutions to be used; variables can also be set
2115 directly from <file>debian/rules</file> using the <tt>-V</tt>
2116 option to the source packaging commands, and certain
2117 predefined variables are also available.
2121 The <file>debian/substvars</file> file is usually generated and
2122 modified dynamically by <file>debian/rules</file> targets, in
2123 which case it must be removed by the <tt>clean</tt> target.
2127 See <manref name="deb-substvars" section="5"> for full
2128 details about source variable substitutions, including the
2129 format of <file>debian/substvars</file>.</p>
2132 <sect id="debianwatch">
2133 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2136 This is an optional, recommended control file for the
2137 <tt>uscan</tt> utility which defines how to automatically
2138 scan ftp or http sites for newly available updates of the
2139 package. This is used by <url id="
2140 http://dehs.alioth.debian.org/"> and other Debian QA tools
2141 to help with quality control and maintenance of the
2142 distribution as a whole.
2147 <sect id="debianfiles">
2148 <heading>Generated files list: <file>debian/files</file></heading>
2151 This file is not a permanent part of the source tree; it
2152 is used while building packages to record which files are
2153 being generated. <prgn>dpkg-genchanges</prgn> uses it
2154 when it generates a <file>.changes</file> file.
2158 It should not exist in a shipped source package, and so it
2159 (and any backup files or temporary files such as
2160 <file>files.new</file><footnote>
2161 <file>files.new</file> is used as a temporary file by
2162 <prgn>dpkg-gencontrol</prgn> and
2163 <prgn>dpkg-distaddfile</prgn> - they write a new
2164 version of <tt>files</tt> here before renaming it,
2165 to avoid leaving a corrupted copy if an error
2167 </footnote>) should be removed by the
2168 <tt>clean</tt> target. It may also be wise to
2169 ensure a fresh start by emptying or removing it at the
2170 start of the <tt>binary</tt> target.
2174 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2175 package, it adds an entry to <file>debian/files</file> for the
2176 <file>.deb</file> file that will be created when <tt>dpkg-deb
2177 --build</tt> is run for that binary package. So for most
2178 packages all that needs to be done with this file is to
2179 delete it in the <tt>clean</tt> target.
2183 If a package upload includes files besides the source
2184 package and any binary packages whose control files were
2185 made with <prgn>dpkg-gencontrol</prgn> then they should be
2186 placed in the parent of the package's top-level directory
2187 and <prgn>dpkg-distaddfile</prgn> should be called to add
2188 the file to the list in <file>debian/files</file>.</p>
2191 <sect id="embeddedfiles">
2192 <heading>Convenience copies of code</heading>
2195 Some software packages include in their distribution convenience
2196 copies of code from other software packages, generally so that
2197 users compiling from source don't have to download multiple
2198 packages. Debian packages should not make use of these
2199 convenience copies unless the included package is explicitly
2200 intended to be used in this way.<footnote>
2201 For example, parts of the GNU build system work like this.
2203 If the included code is already in the Debian archive in the
2204 form of a library, the Debian packaging should ensure that
2205 binary packages reference the libraries already in Debian and
2206 the convenience copy is not used. If the included code is not
2207 already in Debian, it should be packaged separately as a
2208 prerequisite if possible.
2210 Having multiple copies of the same code in Debian is
2211 inefficient, often creates either static linking or shared
2212 library conflicts, and, most importantly, increases the
2213 difficulty of handling security vulnerabilities in the
2219 <sect id="readmesource">
2220 <heading>Source package handling:
2221 <file>debian/README.source</file></heading>
2224 If running <prgn>dpkg-source -x</prgn> on a source package
2225 doesn't produce the source of the package, ready for editing,
2226 and allow one to make changes and run
2227 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2228 without taking any additional steps, creating a
2229 <file>debian/README.source</file> documentation file is
2230 recommended. This file should explain how to do all of the
2233 <item>Generate the fully patched source, in a form ready for
2234 editing, that would be built to create Debian
2235 packages. Doing this with a <tt>patch</tt> target in
2236 <file>debian/rules</file> is recommended; see
2237 <ref id="debianrules">.</item>
2238 <item>Modify the source and save those modifications so that
2239 they will be applied when building the package.</item>
2240 <item>Remove source modifications that are currently being
2241 applied when building the package.</item>
2242 <item>Optionally, document what steps are necessary to
2243 upgrade the Debian source package to a new upstream version,
2244 if applicable.</item>
2246 This explanation should include specific commands and mention
2247 any additional required Debian packages. It should not assume
2248 familiarity with any specific Debian packaging system or patch
2253 This explanation may refer to a documentation file installed by
2254 one of the package's build dependencies provided that the
2255 referenced documentation clearly explains these tasks and is not
2256 a general reference manual.
2260 <file>debian/README.source</file> may also include any other
2261 information that would be helpful to someone modifying the
2262 source package. Even if the package doesn't fit the above
2263 description, maintainers are encouraged to document in a
2264 <file>debian/README.source</file> file any source package with a
2265 particularly complex or unintuitive source layout or build
2266 system (for example, a package that builds the same source
2267 multiple times to generate different binary packages).
2273 <chapt id="controlfields">
2274 <heading>Control files and their fields</heading>
2277 The package management system manipulates data represented in
2278 a common format, known as <em>control data</em>, stored in
2279 <em>control files</em>.
2280 Control files are used for source packages, binary packages and
2281 the <file>.changes</file> files which control the installation
2282 of uploaded files<footnote>
2283 <prgn>dpkg</prgn>'s internal databases are in a similar
2288 <sect id="controlsyntax">
2289 <heading>Syntax of control files</heading>
2292 A control file consists of one or more paragraphs of
2294 The paragraphs are also sometimes referred to as stanzas.
2296 The paragraphs are separated by blank lines. Some control
2297 files allow only one paragraph; others allow several, in
2298 which case each paragraph usually refers to a different
2299 package. (For example, in source packages, the first
2300 paragraph refers to the source package, and later paragraphs
2301 refer to binary packages generated from the source.)
2305 Each paragraph consists of a series of data fields; each
2306 field consists of the field name, followed by a colon and
2307 then the data/value associated with that field. It ends at
2308 the end of the (logical) line. Horizontal whitespace
2309 (spaces and tabs) may occur immediately before or after the
2310 value and is ignored there; it is conventional to put a
2311 single space after the colon. For example, a field might
2313 <example compact="compact">
2316 the field name is <tt>Package</tt> and the field value
2321 Many fields' values may span several lines; in this case
2322 each continuation line must start with a space or a tab.
2323 Any trailing spaces or tabs at the end of individual
2324 lines of a field value are ignored.
2328 In fields where it is specified that lines may not wrap,
2329 only a single line of data is allowed and whitespace is not
2330 significant in a field body. Whitespace must not appear
2331 inside names (of packages, architectures, files or anything
2332 else) or version numbers, or between the characters of
2333 multi-character version relationships.
2337 Field names are not case-sensitive, but it is usual to
2338 capitalize the field names using mixed case as shown below.
2342 Blank lines, or lines consisting only of spaces and tabs,
2343 are not allowed within field values or between fields - that
2344 would mean a new paragraph.
2349 <sect id="sourcecontrolfiles">
2350 <heading>Source package control files -- <file>debian/control</file></heading>
2353 The <file>debian/control</file> file contains the most vital
2354 (and version-independent) information about the source package
2355 and about the binary packages it creates.
2359 The first paragraph of the control file contains information about
2360 the source package in general. The subsequent sets each describe a
2361 binary package that the source tree builds.
2365 The fields in the general paragraph (the first one, for the source
2368 <list compact="compact">
2369 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2370 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2371 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2372 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2373 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2374 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2375 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2376 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2381 The fields in the binary package paragraphs are:
2383 <list compact="compact">
2384 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2385 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2386 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2387 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2388 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2389 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2390 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2391 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2396 The syntax and semantics of the fields are described below.
2402 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2403 generate control files for binary packages (see below), by
2404 <prgn>dpkg-genchanges</prgn> to generate the
2405 <tt>.changes</tt> file to accompany the upload, and by
2406 <prgn>dpkg-source</prgn> when it creates the
2407 <file>.dsc</file> source control file as part of a source
2408 archive. Many fields are permitted to span multiple lines in
2409 <file>debian/control</file> but not in any other control
2410 file. These tools are responsible for removing the line
2411 breaks from such fields when using fields from
2412 <file>debian/control</file> to generate other control files.
2416 The fields here may contain variable references - their
2417 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2418 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2419 when they generate output control files.
2420 See <ref id="substvars"> for details.
2425 <sect id="binarycontrolfiles">
2426 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2429 The <file>DEBIAN/control</file> file contains the most vital
2430 (and version-dependent) information about a binary package.
2434 The fields in this file are:
2436 <list compact="compact">
2437 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2438 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2439 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2440 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2441 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2442 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2443 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2444 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2445 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2446 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2447 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2448 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2453 <sect id="debiansourcecontrolfiles">
2454 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2457 This file contains a series of fields, identified and
2458 separated just like the fields in the control file of
2459 a binary package. The fields are listed below; their
2460 syntax is described above, in <ref id="pkg-controlfields">.
2462 <list compact="compact">
2463 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2464 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2465 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2466 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2467 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2468 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2469 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2470 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2471 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2472 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2478 The source package control file is generated by
2479 <prgn>dpkg-source</prgn> when it builds the source
2480 archive, from other files in the source package,
2481 described above. When unpacking, it is checked against
2482 the files and directories in the other parts of the
2488 <sect id="debianchangesfiles">
2489 <heading>Debian changes files -- <file>.changes</file></heading>
2492 The .changes files are used by the Debian archive maintenance
2493 software to process updates to packages. They contain one
2494 paragraph which contains information from the
2495 <tt>debian/control</tt> file and other data about the
2496 source package gathered via <tt>debian/changelog</tt>
2497 and <tt>debian/rules</tt>.
2501 The fields in this file are:
2503 <list compact="compact">
2504 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2506 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2507 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2510 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2512 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2513 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2514 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2516 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2522 <sect id="controlfieldslist">
2523 <heading>List of fields</heading>
2525 <sect1 id="f-Source">
2526 <heading><tt>Source</tt></heading>
2529 This field identifies the source package name.
2533 In <file>debian/control</file> or a <file>.dsc</file> file,
2534 this field must contain only the name of the source package.
2538 In a binary package control file or a <file>.changes</file>
2539 file, the source package name may be followed by a version
2540 number in parentheses<footnote>
2541 It is customary to leave a space after the package name
2542 if a version number is specified.
2544 This version number may be omitted (and is, by
2545 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2546 the <tt>Version</tt> field of the binary package in
2547 question. The field itself may be omitted from a binary
2548 package control file when the source package has the same
2549 name and version as the binary package.
2553 <sect1 id="f-Maintainer">
2554 <heading><tt>Maintainer</tt></heading>
2557 The package maintainer's name and email address. The name
2558 should come first, then the email address inside angle
2559 brackets <tt><></tt> (in RFC822 format).
2563 If the maintainer's name contains a full stop then the
2564 whole field will not work directly as an email address due
2565 to a misfeature in the syntax specified in RFC822; a
2566 program using this field as an address must check for this
2567 and correct the problem if necessary (for example by
2568 putting the name in round brackets and moving it to the
2569 end, and bringing the email address forward).
2573 <sect1 id="f-Uploaders">
2574 <heading><tt>Uploaders</tt></heading>
2577 List of the names and email addresses of co-maintainers of
2578 the package, if any. If the package has other maintainers
2579 beside the one named in the
2580 <qref id="f-Maintainer">Maintainer field</qref>, their
2581 names and email addresses should be listed here. The
2582 format is the same as that of the Maintainer tag, and
2583 multiple entries should be comma separated. Currently,
2584 this field is restricted to a single line of data. This
2585 is an optional field.
2588 Any parser that interprets the Uploaders field in
2589 <file>debian/control</file> must permit it to span multiple
2590 lines. Line breaks in an Uploaders field that spans multiple
2591 lines are not significant and the semantics of the field are
2592 the same as if the line breaks had not been present.
2596 <sect1 id="f-Changed-By">
2597 <heading><tt>Changed-By</tt></heading>
2600 The name and email address of the person who changed the
2601 said package. Usually the name of the maintainer.
2602 All the rules for the Maintainer field apply here, too.
2606 <sect1 id="f-Section">
2607 <heading><tt>Section</tt></heading>
2610 This field specifies an application area into which the package
2611 has been classified. See <ref id="subsections">.
2615 When it appears in the <file>debian/control</file> file,
2616 it gives the value for the subfield of the same name in
2617 the <tt>Files</tt> field of the <file>.changes</file> file.
2618 It also gives the default for the same field in the binary
2623 <sect1 id="f-Priority">
2624 <heading><tt>Priority</tt></heading>
2627 This field represents how important that it is that the user
2628 have the package installed. See <ref id="priorities">.
2632 When it appears in the <file>debian/control</file> file,
2633 it gives the value for the subfield of the same name in
2634 the <tt>Files</tt> field of the <file>.changes</file> file.
2635 It also gives the default for the same field in the binary
2640 <sect1 id="f-Package">
2641 <heading><tt>Package</tt></heading>
2644 The name of the binary package.
2648 Package names must consist only of lower case letters
2649 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2650 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2651 They must be at least two characters long and must start
2652 with an alphanumeric character.
2656 <sect1 id="f-Architecture">
2657 <heading><tt>Architecture</tt></heading>
2660 Depending on context and the control file used, the
2661 <tt>Architecture</tt> field can include the following sets of
2664 <item>A unique single word identifying a Debian machine
2665 architecture, see <ref id="arch-spec">.
2666 <item><tt>all</tt>, which indicates an
2667 architecture-independent package.
2668 <item><tt>any</tt>, which indicates a package available
2669 for building on any architecture.
2670 <item><tt>source</tt>, which indicates a source package.
2675 In the main <file>debian/control</file> file in the source
2676 package, or in the source package control file
2677 <file>.dsc</file>, one may specify a list of architectures
2678 separated by spaces, or the special values <tt>any</tt> or
2683 Specifying <tt>any</tt> indicates that the source package
2684 isn't dependent on any particular architecture and should
2685 compile fine on any one. The produced binary package(s)
2686 will be specific to whatever the current build architecture
2688 This is the most often used setting, and is recommended
2689 for new packages that aren't <tt>Architecture: all</tt>.
2694 Specifying a list of architectures indicates that the source
2695 will build an architecture-dependent package, and will only
2696 work correctly on the listed architectures.<footnote>
2697 This is a setting used for a minority of cases where the
2698 program is not portable. Generally, it should not be used
2704 In a <file>.changes</file> file, the <tt>Architecture</tt>
2705 field lists the architecture(s) of the package(s)
2706 currently being uploaded. This will be a list; if the
2707 source for the package is also being uploaded, the special
2708 entry <tt>source</tt> is also present.
2712 See <ref id="debianrules"> for information how to get the
2713 architecture for the build process.
2717 <sect1 id="f-Essential">
2718 <heading><tt>Essential</tt></heading>
2721 This is a boolean field which may occur only in the
2722 control file of a binary package or in a per-package fields
2723 paragraph of a main source control data file.
2727 If set to <tt>yes</tt> then the package management system
2728 will refuse to remove the package (upgrading and replacing
2729 it is still possible). The other possible value is <tt>no</tt>,
2730 which is the same as not having the field at all.
2735 <heading>Package interrelationship fields:
2736 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2737 <tt>Recommends</tt>, <tt>Suggests</tt>,
2738 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2739 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2743 These fields describe the package's relationships with
2744 other packages. Their syntax and semantics are described
2745 in <ref id="relationships">.</p>
2748 <sect1 id="f-Standards-Version">
2749 <heading><tt>Standards-Version</tt></heading>
2752 The most recent version of the standards (the policy
2753 manual and associated texts) with which the package
2758 The version number has four components: major and minor
2759 version number and major and minor patch level. When the
2760 standards change in a way that requires every package to
2761 change the major number will be changed. Significant
2762 changes that will require work in many packages will be
2763 signaled by a change to the minor number. The major patch
2764 level will be changed for any change to the meaning of the
2765 standards, however small; the minor patch level will be
2766 changed when only cosmetic, typographical or other edits
2767 are made which neither change the meaning of the document
2768 nor affect the contents of packages.
2772 Thus only the first three components of the policy version
2773 are significant in the <em>Standards-Version</em> control
2774 field, and so either these three components or the all
2775 four components may be specified.<footnote>
2776 In the past, people specified the full version number
2777 in the Standards-Version field, for example "2.3.0.0".
2778 Since minor patch-level changes don't introduce new
2779 policy, it was thought it would be better to relax
2780 policy and only require the first 3 components to be
2781 specified, in this example "2.3.0". All four
2782 components may still be used if someone wishes to do so.
2788 <sect1 id="f-Version">
2789 <heading><tt>Version</tt></heading>
2792 The version number of a package. The format is:
2793 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2797 The three components here are:
2799 <tag><var>epoch</var></tag>
2802 This is a single (generally small) unsigned integer. It
2803 may be omitted, in which case zero is assumed. If it is
2804 omitted then the <var>upstream_version</var> may not
2809 It is provided to allow mistakes in the version numbers
2810 of older versions of a package, and also a package's
2811 previous version numbering schemes, to be left behind.
2815 <tag><var>upstream_version</var></tag>
2818 This is the main part of the version number. It is
2819 usually the version number of the original ("upstream")
2820 package from which the <file>.deb</file> file has been made,
2821 if this is applicable. Usually this will be in the same
2822 format as that specified by the upstream author(s);
2823 however, it may need to be reformatted to fit into the
2824 package management system's format and comparison
2829 The comparison behavior of the package management system
2830 with respect to the <var>upstream_version</var> is
2831 described below. The <var>upstream_version</var>
2832 portion of the version number is mandatory.
2836 The <var>upstream_version</var> may contain only
2837 alphanumerics<footnote>
2838 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2840 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2841 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2842 tilde) and should start with a digit. If there is no
2843 <var>debian_revision</var> then hyphens are not allowed;
2844 if there is no <var>epoch</var> then colons are not
2849 <tag><var>debian_revision</var></tag>
2852 This part of the version number specifies the version of
2853 the Debian package based on the upstream version. It
2854 may contain only alphanumerics and the characters
2855 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2856 tilde) and is compared in the same way as the
2857 <var>upstream_version</var> is.
2861 It is optional; if it isn't present then the
2862 <var>upstream_version</var> may not contain a hyphen.
2863 This format represents the case where a piece of
2864 software was written specifically to be turned into a
2865 Debian package, and so there is only one "debianisation"
2866 of it and therefore no revision indication is required.
2870 It is conventional to restart the
2871 <var>debian_revision</var> at <tt>1</tt> each time the
2872 <var>upstream_version</var> is increased.
2876 The package management system will break the version
2877 number apart at the last hyphen in the string (if there
2878 is one) to determine the <var>upstream_version</var> and
2879 <var>debian_revision</var>. The absence of a
2880 <var>debian_revision</var> is equivalent to a
2881 <var>debian_revision</var> of <tt>0</tt>.
2888 When comparing two version numbers, first the <var>epoch</var>
2889 of each are compared, then the <var>upstream_version</var> if
2890 <var>epoch</var> is equal, and then <var>debian_revision</var>
2891 if <var>upstream_version</var> is also equal.
2892 <var>epoch</var> is compared numerically. The
2893 <var>upstream_version</var> and <var>debian_revision</var>
2894 parts are compared by the package management system using the
2895 following algorithm:
2899 The strings are compared from left to right.
2903 First the initial part of each string consisting entirely of
2904 non-digit characters is determined. These two parts (one of
2905 which may be empty) are compared lexically. If a difference
2906 is found it is returned. The lexical comparison is a
2907 comparison of ASCII values modified so that all the letters
2908 sort earlier than all the non-letters and so that a tilde
2909 sorts before anything, even the end of a part. For example,
2910 the following parts are in sorted order from earliest to
2911 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2912 <tt>a</tt>.<footnote>
2913 One common use of <tt>~</tt> is for upstream pre-releases.
2914 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2915 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2920 Then the initial part of the remainder of each string which
2921 consists entirely of digit characters is determined. The
2922 numerical values of these two parts are compared, and any
2923 difference found is returned as the result of the comparison.
2924 For these purposes an empty string (which can only occur at
2925 the end of one or both version strings being compared) counts
2930 These two steps (comparing and removing initial non-digit
2931 strings and initial digit strings) are repeated until a
2932 difference is found or both strings are exhausted.
2936 Note that the purpose of epochs is to allow us to leave behind
2937 mistakes in version numbering, and to cope with situations
2938 where the version numbering scheme changes. It is
2939 <em>not</em> intended to cope with version numbers containing
2940 strings of letters which the package management system cannot
2941 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2942 silly orderings (the author of this manual has heard of a
2943 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2944 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2945 <tt>2</tt> and so forth).
2949 <sect1 id="f-Description">
2950 <heading><tt>Description</tt></heading>
2953 In a source or binary control file, the <tt>Description</tt>
2954 field contains a description of the binary package, consisting
2955 of two parts, the synopsis or the short description, and the
2956 long description. The field's format is as follows:
2961 Description: <single line synopsis>
2962 <extended description over several lines>
2967 The lines in the extended description can have these formats:
2973 Those starting with a single space are part of a paragraph.
2974 Successive lines of this form will be word-wrapped when
2975 displayed. The leading space will usually be stripped off.
2979 Those starting with two or more spaces. These will be
2980 displayed verbatim. If the display cannot be panned
2981 horizontally, the displaying program will line wrap them "hard"
2982 (i.e., without taking account of word breaks). If it can they
2983 will be allowed to trail off to the right. None, one or two
2984 initial spaces may be deleted, but the number of spaces
2985 deleted from each line will be the same (so that you can have
2986 indenting work correctly, for example).
2990 Those containing a single space followed by a single full stop
2991 character. These are rendered as blank lines. This is the
2992 <em>only</em> way to get a blank line<footnote>
2993 Completely empty lines will not be rendered as blank lines.
2994 Instead, they will cause the parser to think you're starting
2995 a whole new record in the control file, and will therefore
2996 likely abort with an error.
3001 Those containing a space, a full stop and some more characters.
3002 These are for future expansion. Do not use them.
3008 Do not use tab characters. Their effect is not predictable.
3012 See <ref id="descriptions"> for further information on this.
3016 In a <file>.changes</file> file, the <tt>Description</tt> field
3017 contains a summary of the descriptions for the packages being
3022 The part of the field before the first newline is empty;
3023 thereafter each line has the name of a binary package and
3024 the summary description line from that binary package.
3025 Each line is indented by one space.
3030 <sect1 id="f-Distribution">
3031 <heading><tt>Distribution</tt></heading>
3034 In a <file>.changes</file> file or parsed changelog output
3035 this contains the (space-separated) name(s) of the
3036 distribution(s) where this version of the package should
3037 be installed. Valid distributions are determined by the
3038 archive maintainers.<footnote>
3039 Current distribution names are:
3040 <taglist compact="compact">
3041 <tag><em>stable</em></tag>
3043 This is the current "released" version of Debian
3044 GNU/Linux. Once the distribution is
3045 <em>stable</em> only security fixes and other
3046 major bug fixes are allowed. When changes are
3047 made to this distribution, the release number is
3048 increased (for example: 2.2r1 becomes 2.2r2 then
3052 <tag><em>unstable</em></tag>
3054 This distribution value refers to the
3055 <em>developmental</em> part of the Debian
3056 distribution tree. New packages, new upstream
3057 versions of packages and bug fixes go into the
3058 <em>unstable</em> directory tree. Download from
3059 this distribution at your own risk.
3062 <tag><em>testing</em></tag>
3064 This distribution value refers to the
3065 <em>testing</em> part of the Debian distribution
3066 tree. It receives its packages from the
3067 unstable distribution after a short time lag to
3068 ensure that there are no major issues with the
3069 unstable packages. It is less prone to breakage
3070 than unstable, but still risky. It is not
3071 possible to upload packages directly to
3075 <tag><em>frozen</em></tag>
3077 From time to time, the <em>testing</em>
3078 distribution enters a state of "code-freeze" in
3079 anticipation of release as a <em>stable</em>
3080 version. During this period of testing only
3081 fixes for existing or newly-discovered bugs will
3082 be allowed. The exact details of this stage are
3083 determined by the Release Manager.
3086 <tag><em>experimental</em></tag>
3088 The packages with this distribution value are
3089 deemed by their maintainers to be high
3090 risk. Oftentimes they represent early beta or
3091 developmental packages from various sources that
3092 the maintainers want people to try, but are not
3093 ready to be a part of the other parts of the
3094 Debian distribution tree. Download at your own
3100 You should list <em>all</em> distributions that the
3101 package should be installed into.
3105 More information is available in the Debian Developer's
3106 Reference, section "The Debian archive".
3113 <heading><tt>Date</tt></heading>
3116 This field includes the date the package was built or last edited.
3120 The value of this field is usually extracted from the
3121 <file>debian/changelog</file> file - see
3122 <ref id="dpkgchangelog">).
3126 <sect1 id="f-Format">
3127 <heading><tt>Format</tt></heading>
3130 This field specifies a format revision for the file.
3131 The most current format described in the Policy Manual
3132 is version <strong>1.5</strong>. The syntax of the
3133 format value is the same as that of a package version
3134 number except that no epoch or Debian revision is allowed
3135 - see <ref id="f-Version">.
3139 <sect1 id="f-Urgency">
3140 <heading><tt>Urgency</tt></heading>
3143 This is a description of how important it is to upgrade to
3144 this version from previous ones. It consists of a single
3145 keyword taking one of the values <tt>low</tt>,
3146 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3147 <tt>critical</tt><footnote>
3148 Other urgency values are supported with configuration
3149 changes in the archive software but are not used in Debian.
3150 The urgency affects how quickly a package will be considered
3151 for inclusion into the <tt>testing</tt> distribution and
3152 gives an indication of the importance of any fixes included
3153 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3154 treated as synonymous.
3155 </footnote> (not case-sensitive) followed by an optional
3156 commentary (separated by a space) which is usually in
3157 parentheses. For example:
3160 Urgency: low (HIGH for users of diversions)
3166 The value of this field is usually extracted from the
3167 <file>debian/changelog</file> file - see
3168 <ref id="dpkgchangelog">.
3172 <sect1 id="f-Changes">
3173 <heading><tt>Changes</tt></heading>
3176 This field contains the human-readable changes data, describing
3177 the differences between the last version and the current one.
3181 There should be nothing in this field before the first
3182 newline; all the subsequent lines must be indented by at
3183 least one space; blank lines must be represented by a line
3184 consisting only of a space and a full stop.
3188 The value of this field is usually extracted from the
3189 <file>debian/changelog</file> file - see
3190 <ref id="dpkgchangelog">).
3194 Each version's change information should be preceded by a
3195 "title" line giving at least the version, distribution(s)
3196 and urgency, in a human-readable way.
3200 If data from several versions is being returned the entry
3201 for the most recent version should be returned first, and
3202 entries should be separated by the representation of a
3203 blank line (the "title" line may also be followed by the
3204 representation of blank line).
3208 <sect1 id="f-Binary">
3209 <heading><tt>Binary</tt></heading>
3212 This field is a list of binary packages.
3216 When it appears in the <file>.dsc</file> file it is the list
3217 of binary packages which a source package can produce. It
3218 does not necessarily produce all of these binary packages
3219 for every architecture. The source control file doesn't
3220 contain details of which architectures are appropriate for
3221 which of the binary packages.
3225 When it appears in a <file>.changes</file> file it lists the
3226 names of the binary packages actually being uploaded.
3230 The syntax is a list of binary packages separated by
3232 A space after each comma is conventional.
3233 </footnote>. Currently the packages must be separated using
3234 only spaces in the <file>.changes</file> file.
3238 <sect1 id="f-Installed-Size">
3239 <heading><tt>Installed-Size</tt></heading>
3242 This field appears in the control files of binary
3243 packages, and in the <file>Packages</file> files. It gives
3244 the total amount of disk space required to install the
3249 The disk space is represented in kilobytes as a simple
3254 <sect1 id="f-Files">
3255 <heading><tt>Files</tt></heading>
3258 This field contains a list of files with information about
3259 each one. The exact information and syntax varies with
3260 the context. In all cases the part of the field
3261 contents on the same line as the field name is empty. The
3262 remainder of the field is one line per file, each line
3263 being indented by one space and containing a number of
3264 sub-fields separated by spaces.
3268 In the <file>.dsc</file> file, each line contains the MD5
3269 checksum, size and filename of the tar file and (if applicable)
3270 diff file which make up the remainder of the source
3272 That is, the parts which are not the <tt>.dsc</tt>.
3274 The exact forms of the filenames are described
3275 in <ref id="pkg-sourcearchives">.
3279 In the <file>.changes</file> file this contains one line per
3280 file being uploaded. Each line contains the MD5 checksum,
3281 size, section and priority and the filename.
3282 The <qref id="f-Section">section</qref>
3283 and <qref id="f-Priority">priority</qref>
3284 are the values of the corresponding fields in
3285 the main source control file. If no section or priority is
3286 specified then <tt>-</tt> should be used, though section
3287 and priority values must be specified for new packages to
3288 be installed properly.
3292 The special value <tt>byhand</tt> for the section in a
3293 <tt>.changes</tt> file indicates that the file in question
3294 is not an ordinary package file and must by installed by
3295 hand by the distribution maintainers. If the section is
3296 <tt>byhand</tt> the priority should be <tt>-</tt>.
3300 If a new Debian revision of a package is being shipped and
3301 no new original source archive is being distributed the
3302 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3303 entry for the original source archive
3304 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3305 but the <file>.changes</file> file should leave it out. In
3306 this case the original source archive on the distribution
3307 site must match exactly, byte-for-byte, the original
3308 source archive which was used to generate the
3309 <file>.dsc</file> file and diff which are being uploaded.</p>
3312 <sect1 id="f-Closes">
3313 <heading><tt>Closes</tt></heading>
3316 A space-separated list of bug report numbers that the upload
3317 governed by the .changes file closes.
3321 <sect1 id="f-Homepage">
3322 <heading><tt>Homepage</tt></heading>
3325 The URL of the web site for this package, preferably (when
3326 applicable) the site from which the original source can be
3327 obtained and any additional upstream documentation or
3328 information may be found. The content of this field is a
3329 simple URL without any surrounding characters such as
3337 <heading>User-defined fields</heading>
3340 Additional user-defined fields may be added to the
3341 source package control file. Such fields will be
3342 ignored, and not copied to (for example) binary or
3343 source package control files or upload control files.
3347 If you wish to add additional unsupported fields to
3348 these output files you should use the mechanism
3353 Fields in the main source control information file with
3354 names starting <tt>X</tt>, followed by one or more of
3355 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3356 be copied to the output files. Only the part of the
3357 field name after the hyphen will be used in the output
3358 file. Where the letter <tt>B</tt> is used the field
3359 will appear in binary package control files, where the
3360 letter <tt>S</tt> is used in source package control
3361 files and where <tt>C</tt> is used in upload control
3362 (<tt>.changes</tt>) files.
3366 For example, if the main source information control file
3369 XBS-Comment: I stand between the candle and the star.
3371 then the binary and source package control files will contain the
3374 Comment: I stand between the candle and the star.
3383 <chapt id="maintainerscripts">
3384 <heading>Package maintainer scripts and installation procedure</heading>
3387 <heading>Introduction to package maintainer scripts</heading>
3390 It is possible to supply scripts as part of a package which
3391 the package management system will run for you when your
3392 package is installed, upgraded or removed.
3396 These scripts are the files <prgn>preinst</prgn>,
3397 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3398 <prgn>postrm</prgn> in the control area of the package.
3399 They must be proper executable files; if they are scripts
3400 (which is recommended), they must start with the usual
3401 <tt>#!</tt> convention. They should be readable and
3402 executable by anyone, and must not be world-writable.
3406 The package management system looks at the exit status from
3407 these scripts. It is important that they exit with a
3408 non-zero status if there is an error, so that the package
3409 management system can stop its processing. For shell
3410 scripts this means that you <em>almost always</em> need to
3411 use <tt>set -e</tt> (this is usually true when writing shell
3412 scripts, in fact). It is also important, of course, that
3413 they don't exit with a non-zero status if everything went
3418 Additionally, packages interacting with users using
3419 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3420 install a <prgn>config</prgn> script in the control area,
3421 see <ref id="maintscriptprompt"> for details.
3425 When a package is upgraded a combination of the scripts from
3426 the old and new packages is called during the upgrade
3427 procedure. If your scripts are going to be at all
3428 complicated you need to be aware of this, and may need to
3429 check the arguments to your scripts.
3433 Broadly speaking the <prgn>preinst</prgn> is called before
3434 (a particular version of) a package is installed, and the
3435 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3436 before (a version of) a package is removed and the
3437 <prgn>postrm</prgn> afterwards.
3441 Programs called from maintainer scripts should not normally
3442 have a path prepended to them. Before installation is
3443 started, the package management system checks to see if the
3444 programs <prgn>ldconfig</prgn>,
3445 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3446 and <prgn>update-rc.d</prgn> can be found via the
3447 <tt>PATH</tt> environment variable. Those programs, and any
3448 other program that one would expect to be in the
3449 <tt>PATH</tt>, should thus be invoked without an absolute
3450 pathname. Maintainer scripts should also not reset the
3451 <tt>PATH</tt>, though they might choose to modify it by
3452 prepending or appending package-specific directories. These
3453 considerations really apply to all shell scripts.</p>
3456 <sect id="idempotency">
3457 <heading>Maintainer scripts idempotency</heading>
3460 It is necessary for the error recovery procedures that the
3461 scripts be idempotent. This means that if it is run
3462 successfully, and then it is called again, it doesn't bomb
3463 out or cause any harm, but just ensures that everything is
3464 the way it ought to be. If the first call failed, or
3465 aborted half way through for some reason, the second call
3466 should merely do the things that were left undone the first
3467 time, if any, and exit with a success status if everything
3469 This is so that if an error occurs, the user interrupts
3470 <prgn>dpkg</prgn> or some other unforeseen circumstance
3471 happens you don't leave the user with a badly-broken
3472 package when <prgn>dpkg</prgn> attempts to repeat the
3478 <sect id="controllingterminal">
3479 <heading>Controlling terminal for maintainer scripts</heading>
3482 The maintainer scripts are guaranteed to run with a
3483 controlling terminal and can interact with the user.
3484 Because these scripts may be executed with standard output
3485 redirected into a pipe for logging purposes, Perl scripts
3486 should set unbuffered output by setting <tt>$|=1</tt> so
3487 that the output is printed immediately rather than being
3491 <sect id="exitstatus">
3492 <heading>Exit status</heading>
3495 Each script must return a zero exit status for
3496 success, or a nonzero one for failure, since the package
3497 management system looks for the exit status of these scripts
3498 and determines what action to take next based on that datum.
3502 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3507 <list compact="compact">
3509 <var>new-preinst</var> <tt>install</tt>
3512 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3515 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3518 <var>old-preinst</var> <tt>abort-upgrade</tt>
3519 <var>new-version</var>
3524 <list compact="compact">
3526 <var>postinst</var> <tt>configure</tt>
3527 <var>most-recently-configured-version</var>
3530 <var>old-postinst</var> <tt>abort-upgrade</tt>
3531 <var>new-version</var>
3534 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3535 <tt>in-favour</tt> <var>package</var>
3536 <var>new-version</var>
3539 <var>postinst</var> <tt>abort-remove</tt>
3542 <var>deconfigured's-postinst</var>
3543 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3544 <var>failed-install-package</var> <var>version</var>
3545 [<tt>removing</tt> <var>conflicting-package</var>
3551 <list compact="compact">
3553 <var>prerm</var> <tt>remove</tt>
3556 <var>old-prerm</var> <tt>upgrade</tt>
3557 <var>new-version</var>
3560 <var>new-prerm</var> <tt>failed-upgrade</tt>
3561 <var>old-version</var>
3564 <var>conflictor's-prerm</var> <tt>remove</tt>
3565 <tt>in-favour</tt> <var>package</var>
3566 <var>new-version</var>
3569 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3570 <tt>in-favour</tt> <var>package-being-installed</var>
3571 <var>version</var> [<tt>removing</tt>
3572 <var>conflicting-package</var>
3578 <list compact="compact">
3580 <var>postrm</var> <tt>remove</tt>
3583 <var>postrm</var> <tt>purge</tt>
3586 <var>old-postrm</var> <tt>upgrade</tt>
3587 <var>new-version</var>
3590 <var>new-postrm</var> <tt>failed-upgrade</tt>
3591 <var>old-version</var>
3594 <var>new-postrm</var> <tt>abort-install</tt>
3597 <var>new-postrm</var> <tt>abort-install</tt>
3598 <var>old-version</var>
3601 <var>new-postrm</var> <tt>abort-upgrade</tt>
3602 <var>old-version</var>
3605 <var>disappearer's-postrm</var> <tt>disappear</tt>
3606 <var>overwriter</var>
3607 <var>overwriter-version</var>
3613 <sect id="unpackphase">
3614 <heading>Details of unpack phase of installation or upgrade</heading>
3617 The procedure on installation/upgrade/overwrite/disappear
3618 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3619 stage of <tt>dpkg --install</tt>) is as follows. In each
3620 case, if a major error occurs (unless listed below) the
3621 actions are, in general, run backwards - this means that the
3622 maintainer scripts are run with different arguments in
3623 reverse order. These are the "error unwind" calls listed
3630 If a version of the package is already installed, call
3631 <example compact="compact">
3632 <var>old-prerm</var> upgrade <var>new-version</var>
3636 If the script runs but exits with a non-zero
3637 exit status, <prgn>dpkg</prgn> will attempt:
3638 <example compact="compact">
3639 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3641 If this works, the upgrade continues. If this
3642 does not work, the error unwind:
3643 <example compact="compact">
3644 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3646 If this works, then the old-version is
3647 "Installed", if not, the old version is in a
3648 "Failed-Config" state.
3654 If a "conflicting" package is being removed at the same time,
3655 or if any package will be broken (due to <tt>Breaks</tt>):
3658 If <tt>--auto-deconfigure</tt> is
3659 specified, call, for each package to be deconfigured
3660 due to <tt>Breaks</tt>:
3661 <example compact="compact">
3662 <var>deconfigured's-prerm</var> deconfigure \
3663 in-favour <var>package-being-installed</var> <var>version</var>
3666 <example compact="compact">
3667 <var>deconfigured's-postinst</var> abort-deconfigure \
3668 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3670 The deconfigured packages are marked as
3671 requiring configuration, so that if
3672 <tt>--install</tt> is used they will be
3673 configured again if possible.
3676 If any packages depended on a conflicting
3677 package being removed and <tt>--auto-deconfigure</tt> is
3678 specified, call, for each such package:
3679 <example compact="compact">
3680 <var>deconfigured's-prerm</var> deconfigure \
3681 in-favour <var>package-being-installed</var> <var>version</var> \
3682 removing <var>conflicting-package</var> <var>version</var>
3685 <example compact="compact">
3686 <var>deconfigured's-postinst</var> abort-deconfigure \
3687 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3688 removing <var>conflicting-package</var> <var>version</var>
3690 The deconfigured packages are marked as
3691 requiring configuration, so that if
3692 <tt>--install</tt> is used they will be
3693 configured again if possible.
3696 To prepare for removal of each conflicting package, call:
3697 <example compact="compact">
3698 <var>conflictor's-prerm</var> remove \
3699 in-favour <var>package</var> <var>new-version</var>
3702 <example compact="compact">
3703 <var>conflictor's-postinst</var> abort-remove \
3704 in-favour <var>package</var> <var>new-version</var>
3713 If the package is being upgraded, call:
3714 <example compact="compact">
3715 <var>new-preinst</var> upgrade <var>old-version</var>
3717 If this fails, we call:
3719 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3726 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3728 is called. If this works, then the old version
3729 is in an "Installed" state, or else it is left
3730 in an "Unpacked" state.
3735 If it fails, then the old version is left
3736 in an "Half-Installed" state.
3743 Otherwise, if the package had some configuration
3744 files from a previous version installed (i.e., it
3745 is in the "configuration files only" state):
3746 <example compact="compact">
3747 <var>new-preinst</var> install <var>old-version</var>
3751 <var>new-postrm</var> abort-install <var>old-version</var>
3753 If this fails, the package is left in a
3754 "Half-Installed" state, which requires a
3755 reinstall. If it works, the packages is left in
3756 a "Config Files" state.
3759 Otherwise (i.e., the package was completely purged):
3760 <example compact="compact">
3761 <var>new-preinst</var> install
3764 <example compact="compact">
3765 <var>new-postrm</var> abort-install
3767 If the error-unwind fails, the package is in a
3768 "Half Installed" phase, and requires a
3769 reinstall. If the error unwind works, the
3770 package is in a not installed state.
3777 The new package's files are unpacked, overwriting any
3778 that may be on the system already, for example any
3779 from the old version of the same package or from
3780 another package. Backups of the old files are kept
3781 temporarily, and if anything goes wrong the package
3782 management system will attempt to put them back as
3783 part of the error unwind.
3787 It is an error for a package to contain files which
3788 are on the system in another package, unless
3789 <tt>Replaces</tt> is used (see <ref id="replaces">).
3791 The following paragraph is not currently the case:
3792 Currently the <tt>- - force-overwrite</tt> flag is
3793 enabled, downgrading it to a warning, but this may not
3799 It is a more serious error for a package to contain a
3800 plain file or other kind of non-directory where another
3801 package has a directory (again, unless
3802 <tt>Replaces</tt> is used). This error can be
3803 overridden if desired using
3804 <tt>--force-overwrite-dir</tt>, but this is not
3809 Packages which overwrite each other's files produce
3810 behavior which, though deterministic, is hard for the
3811 system administrator to understand. It can easily
3812 lead to "missing" programs if, for example, a package
3813 is installed which overwrites a file from another
3814 package, and is then removed again.<footnote>
3815 Part of the problem is due to what is arguably a
3816 bug in <prgn>dpkg</prgn>.
3821 A directory will never be replaced by a symbolic link
3822 to a directory or vice versa; instead, the existing
3823 state (symlink or not) will be left alone and
3824 <prgn>dpkg</prgn> will follow the symlink if there is
3833 If the package is being upgraded, call
3834 <example compact="compact">
3835 <var>old-postrm</var> upgrade <var>new-version</var>
3839 If this fails, <prgn>dpkg</prgn> will attempt:
3840 <example compact="compact">
3841 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3843 If this works, installation continues. If not,
3845 <example compact="compact">
3846 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3848 If this fails, the old version is left in an
3849 "Half Installed" state. If it works, dpkg now
3851 <example compact="compact">
3852 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3854 If this fails, the old version is left in an
3855 "Half Installed" state. If it works, dpkg now
3857 <example compact="compact">
3858 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3860 If this fails, the old version is in an
3867 This is the point of no return - if
3868 <prgn>dpkg</prgn> gets this far, it won't back off
3869 past this point if an error occurs. This will
3870 leave the package in a fairly bad state, which
3871 will require a successful re-installation to clear
3872 up, but it's when <prgn>dpkg</prgn> starts doing
3873 things that are irreversible.
3878 Any files which were in the old version of the package
3879 but not in the new are removed.
3883 The new file list replaces the old.
3887 The new maintainer scripts replace the old.
3891 Any packages all of whose files have been overwritten
3892 during the installation, and which aren't required for
3893 dependencies, are considered to have been removed.
3894 For each such package
3897 <prgn>dpkg</prgn> calls:
3898 <example compact="compact">
3899 <var>disappearer's-postrm</var> disappear \
3900 <var>overwriter</var> <var>overwriter-version</var>
3904 The package's maintainer scripts are removed.
3907 It is noted in the status database as being in a
3908 sane state, namely not installed (any conffiles
3909 it may have are ignored, rather than being
3910 removed by <prgn>dpkg</prgn>). Note that
3911 disappearing packages do not have their prerm
3912 called, because <prgn>dpkg</prgn> doesn't know
3913 in advance that the package is going to
3920 Any files in the package we're unpacking that are also
3921 listed in the file lists of other packages are removed
3922 from those lists. (This will lobotomize the file list
3923 of the "conflicting" package if there is one.)
3927 The backup files made during installation, above, are
3933 The new package's status is now sane, and recorded as
3938 Here is another point of no return - if the
3939 conflicting package's removal fails we do not unwind
3940 the rest of the installation; the conflicting package
3941 is left in a half-removed limbo.
3946 If there was a conflicting package we go and do the
3947 removal actions (described below), starting with the
3948 removal of the conflicting package's files (any that
3949 are also in the package being installed have already
3950 been removed from the conflicting package's file list,
3951 and so do not get removed now).
3957 <sect id="configdetails"><heading>Details of configuration</heading>
3960 When we configure a package (this happens with <tt>dpkg
3961 --install</tt> and <tt>dpkg --configure</tt>), we first
3962 update any <tt>conffile</tt>s and then call:
3963 <example compact="compact">
3964 <var>postinst</var> configure <var>most-recently-configured-version</var>
3969 No attempt is made to unwind after errors during
3970 configuration. If the configuration fails, the package is in
3971 a "Failed Config" state, and an error message is generated.
3975 If there is no most recently configured version
3976 <prgn>dpkg</prgn> will pass a null argument.
3979 Historical note: Truly ancient (pre-1997) versions of
3980 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3981 (including the angle brackets) in this case. Even older
3982 ones did not pass a second argument at all, under any
3983 circumstance. Note that upgrades using such an old dpkg
3984 version are unlikely to work for other reasons, even if
3985 this old argument behavior is handled by your postinst script.
3991 <sect id="removedetails"><heading>Details of removal and/or
3992 configuration purging</heading>
3998 <example compact="compact">
3999 <var>prerm</var> remove
4003 If prerm fails during replacement due to conflict
4005 <var>conflictor's-postinst</var> abort-remove \
4006 in-favour <var>package</var> <var>new-version</var>
4010 <var>postinst</var> abort-remove
4014 If this fails, the package is in a "Failed-Config"
4015 state, or else it remains "Installed".
4019 The package's files are removed (except <tt>conffile</tt>s).
4022 <example compact="compact">
4023 <var>postrm</var> remove
4027 If it fails, there's no error unwind, and the package is in
4028 an "Half-Installed" state.
4033 All the maintainer scripts except the <prgn>postrm</prgn>
4038 If we aren't purging the package we stop here. Note
4039 that packages which have no <prgn>postrm</prgn> and no
4040 <tt>conffile</tt>s are automatically purged when
4041 removed, as there is no difference except for the
4042 <prgn>dpkg</prgn> status.
4046 The <tt>conffile</tt>s and any backup files
4047 (<tt>~</tt>-files, <tt>#*#</tt> files,
4048 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4053 <example compact="compact">
4054 <var>postrm</var> purge
4058 If this fails, the package remains in a "Config-Files"
4063 The package's file list is removed.
4072 <chapt id="relationships">
4073 <heading>Declaring relationships between packages</heading>
4075 <sect id="depsyntax">
4076 <heading>Syntax of relationship fields</heading>
4079 These fields all have a uniform syntax. They are a list of
4080 package names separated by commas.
4084 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4085 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4086 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4087 control file fields of the package, which declare
4088 dependencies on other packages, the package names listed may
4089 also include lists of alternative package names, separated
4090 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4091 if any one of the alternative packages is installed, that
4092 part of the dependency is considered to be satisfied.
4096 All of the fields except for <tt>Provides</tt> may restrict
4097 their applicability to particular versions of each named
4098 package. This is done in parentheses after each individual
4099 package name; the parentheses should contain a relation from
4100 the list below followed by a version number, in the format
4101 described in <ref id="f-Version">.
4105 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4106 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4107 strictly earlier, earlier or equal, exactly equal, later or
4108 equal and strictly later, respectively. The deprecated
4109 forms <tt><</tt> and <tt>></tt> were used to mean
4110 earlier/later or equal, rather than strictly earlier/later,
4111 so they should not appear in new packages (though
4112 <prgn>dpkg</prgn> still supports them).
4116 Whitespace may appear at any point in the version
4117 specification subject to the rules in <ref
4118 id="controlsyntax">, and must appear where it's necessary to
4119 disambiguate; it is not otherwise significant. All of the
4120 relationship fields may span multiple lines. For
4121 consistency and in case of future changes to
4122 <prgn>dpkg</prgn> it is recommended that a single space be
4123 used after a version relationship and before a version
4124 number; it is also conventional to put a single space after
4125 each comma, on either side of each vertical bar, and before
4126 each open parenthesis. When wrapping a relationship field, it
4127 is conventional to do so after a comma and before the space
4128 following that comma.
4132 For example, a list of dependencies might appear as:
4133 <example compact="compact">
4136 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4141 All fields that specify build-time relationships
4142 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4143 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4144 may be restricted to a certain set of architectures. This
4145 is indicated in brackets after each individual package name and
4146 the optional version specification. The brackets enclose a
4147 list of Debian architecture names separated by whitespace.
4148 Exclamation marks may be prepended to each of the names.
4149 (It is not permitted for some names to be prepended with
4150 exclamation marks while others aren't.) If the current Debian
4151 host architecture is not in this list and there are no
4152 exclamation marks in the list, or it is in the list with a
4153 prepended exclamation mark, the package name and the
4154 associated version specification are ignored completely for
4155 the purposes of defining the relationships.
4160 <example compact="compact">
4162 Build-Depends-Indep: texinfo
4163 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4164 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4169 Note that the binary package relationship fields such as
4170 <tt>Depends</tt> appear in one of the binary package
4171 sections of the control file, whereas the build-time
4172 relationships such as <tt>Build-Depends</tt> appear in the
4173 source package section of the control file (which is the
4178 <sect id="binarydeps">
4179 <heading>Binary Dependencies - <tt>Depends</tt>,
4180 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4181 <tt>Pre-Depends</tt>
4185 Packages can declare in their control file that they have
4186 certain relationships to other packages - for example, that
4187 they may not be installed at the same time as certain other
4188 packages, and/or that they depend on the presence of others.
4192 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4193 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4194 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4198 These seven fields are used to declare a dependency
4199 relationship by one package on another. Except for
4200 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4201 depending (binary) package's control file.
4202 (<tt>Enhances</tt> appears in the recommending package's
4203 control file, and <tt>Breaks</tt> appears in the version of
4204 depended-on package which causes the named package to
4209 A <tt>Depends</tt> field takes effect <em>only</em> when a
4210 package is to be configured. It does not prevent a package
4211 being on the system in an unconfigured state while its
4212 dependencies are unsatisfied, and it is possible to replace
4213 a package whose dependencies are satisfied and which is
4214 properly installed with a different version whose
4215 dependencies are not and cannot be satisfied; when this is
4216 done the depending package will be left unconfigured (since
4217 attempts to configure it will give errors) and will not
4218 function properly. If it is necessary, a
4219 <tt>Pre-Depends</tt> field can be used, which has a partial
4220 effect even when a package is being unpacked, as explained
4221 in detail below. (The other three dependency fields,
4222 <tt>Recommends</tt>, <tt>Suggests</tt> and
4223 <tt>Enhances</tt>, are only used by the various front-ends
4224 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4225 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4229 For this reason packages in an installation run are usually
4230 all unpacked first and all configured later; this gives
4231 later versions of packages with dependencies on later
4232 versions of other packages the opportunity to have their
4233 dependencies satisfied.
4237 In case of circular dependencies, since installation or
4238 removal order honoring the dependency order can't be
4239 established, dependency loops are broken at some point
4240 (based on rules below), and some packages may not be able to
4241 rely on their dependencies being present when being
4242 installed or removed, depending on which side of the break
4243 of the circular dependency loop they happen to be on. If one
4244 of the packages in the loop has no postinst script, then the
4245 cycle will be broken at that package, so as to ensure that
4246 all postinst scripts run with the dependencies properly
4247 configured if this is possible. Otherwise the breaking point
4252 The <tt>Depends</tt> field thus allows package maintainers
4253 to impose an order in which packages should be configured.
4257 The meaning of the five dependency fields is as follows:
4259 <tag><tt>Depends</tt></tag>
4262 This declares an absolute dependency. A package will
4263 not be configured unless all of the packages listed in
4264 its <tt>Depends</tt> field have been correctly
4269 The <tt>Depends</tt> field should be used if the
4270 depended-on package is required for the depending
4271 package to provide a significant amount of
4276 The <tt>Depends</tt> field should also be used if the
4277 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4278 <prgn>postrm</prgn> scripts require the package to be
4279 present in order to run. Note, however, that the
4280 <prgn>postrm</prgn> cannot rely on any non-essential
4281 packages to be present during the <tt>purge</tt>
4285 <tag><tt>Recommends</tt></tag>
4288 This declares a strong, but not absolute, dependency.
4292 The <tt>Recommends</tt> field should list packages
4293 that would be found together with this one in all but
4294 unusual installations.
4298 <tag><tt>Suggests</tt></tag>
4300 This is used to declare that one package may be more
4301 useful with one or more others. Using this field
4302 tells the packaging system and the user that the
4303 listed packages are related to this one and can
4304 perhaps enhance its usefulness, but that installing
4305 this one without them is perfectly reasonable.
4308 <tag><tt>Enhances</tt></tag>
4310 This field is similar to Suggests but works in the
4311 opposite direction. It is used to declare that a
4312 package can enhance the functionality of another
4316 <tag><tt>Pre-Depends</tt></tag>
4319 This field is like <tt>Depends</tt>, except that it
4320 also forces <prgn>dpkg</prgn> to complete installation
4321 of the packages named before even starting the
4322 installation of the package which declares the
4323 pre-dependency, as follows:
4327 When a package declaring a pre-dependency is about to
4328 be <em>unpacked</em> the pre-dependency can be
4329 satisfied if the depended-on package is either fully
4330 configured, <em>or even if</em> the depended-on
4331 package(s) are only unpacked or half-configured,
4332 provided that they have been configured correctly at
4333 some point in the past (and not removed or partially
4334 removed since). In this case, both the
4335 previously-configured and currently unpacked or
4336 half-configured versions must satisfy any version
4337 clause in the <tt>Pre-Depends</tt> field.
4341 When the package declaring a pre-dependency is about
4342 to be <em>configured</em>, the pre-dependency will be
4343 treated as a normal <tt>Depends</tt>, that is, it will
4344 be considered satisfied only if the depended-on
4345 package has been correctly configured.
4349 <tt>Pre-Depends</tt> should be used sparingly,
4350 preferably only by packages whose premature upgrade or
4351 installation would hamper the ability of the system to
4352 continue with any upgrade that might be in progress.
4356 <tt>Pre-Depends</tt> are also required if the
4357 <prgn>preinst</prgn> script depends on the named
4358 package. It is best to avoid this situation if
4366 When selecting which level of dependency to use you should
4367 consider how important the depended-on package is to the
4368 functionality of the one declaring the dependency. Some
4369 packages are composed of components of varying degrees of
4370 importance. Such a package should list using
4371 <tt>Depends</tt> the package(s) which are required by the
4372 more important components. The other components'
4373 requirements may be mentioned as Suggestions or
4374 Recommendations, as appropriate to the components' relative
4380 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4383 Using <tt>Breaks</tt> may cause problems for upgrades from older
4384 versions of Debian and should not be used until the stable
4385 release of Debian supports <tt>Breaks</tt>.
4389 When one binary package declares that it breaks another,
4390 <prgn>dpkg</prgn> will refuse to allow the package which
4391 declares <tt>Breaks</tt> be installed unless the broken
4392 package is deconfigured first, and it will refuse to
4393 allow the broken package to be reconfigured.
4397 A package will not be regarded as causing breakage merely
4398 because its configuration files are still installed; it must
4399 be at least half-installed.
4403 A special exception is made for packages which declare that
4404 they break their own package name or a virtual package which
4405 they provide (see below): this does not count as a real
4410 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4411 version clause; such a <tt>Breaks</tt> is introduced in the
4412 version of an (implicit or explicit) dependency which
4413 violates an assumption or reveals a bug in earlier versions
4414 of the broken package. This use of <tt>Breaks</tt> will
4415 inform higher-level package management tools that broken
4416 package must be upgraded before the new one.
4420 If the breaking package also overwrites some files from the
4421 older package, it should use <tt>Replaces</tt> (not
4422 <tt>Conflicts</tt>) to ensure this goes smoothly.
4426 <sect id="conflicts">
4427 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4430 When one binary package declares a conflict with another
4431 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4432 refuse to allow them to be installed on the system at the
4437 If one package is to be installed, the other must be removed
4438 first - if the package being installed is marked as
4439 replacing (see <ref id="replaces">) the one on the system,
4440 or the one on the system is marked as deselected, or both
4441 packages are marked <tt>Essential</tt>, then
4442 <prgn>dpkg</prgn> will automatically remove the package
4443 which is causing the conflict, otherwise it will halt the
4444 installation of the new package with an error. This
4445 mechanism is specifically designed to produce an error when
4446 the installed package is <tt>Essential</tt>, but the new
4451 A package will not cause a conflict merely because its
4452 configuration files are still installed; it must be at least
4457 A special exception is made for packages which declare a
4458 conflict with their own package name, or with a virtual
4459 package which they provide (see below): this does not
4460 prevent their installation, and allows a package to conflict
4461 with others providing a replacement for it. You use this
4462 feature when you want the package in question to be the only
4463 package providing some feature.
4467 A <tt>Conflicts</tt> entry should almost never have an
4468 "earlier than" version clause. This would prevent
4469 <prgn>dpkg</prgn> from upgrading or installing the package
4470 which declared such a conflict until the upgrade or removal
4471 of the conflicted-with package had been completed. Instead,
4472 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4473 by the stable release of Debian).
4477 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4481 As well as the names of actual ("concrete") packages, the
4482 package relationship fields <tt>Depends</tt>,
4483 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4484 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4485 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4486 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4487 may mention "virtual packages".
4491 A <em>virtual package</em> is one which appears in the
4492 <tt>Provides</tt> control file field of another package.
4493 The effect is as if the package(s) which provide a
4494 particular virtual package name had been listed by name
4495 everywhere the virtual package name appears. (See also <ref
4500 If there are both concrete and virtual packages of the same
4501 name, then the dependency may be satisfied (or the conflict
4502 caused) by either the concrete package with the name in
4503 question or any other concrete package which provides the
4504 virtual package with the name in question. This is so that,
4505 for example, supposing we have
4506 <example compact="compact">
4509 </example> and someone else releases an enhanced version of
4510 the <tt>bar</tt> package they can say:
4511 <example compact="compact">
4515 and the <tt>bar-plus</tt> package will now also satisfy the
4516 dependency for the <tt>foo</tt> package.
4520 If a relationship field has a version number attached
4521 then only real packages will be considered to see whether
4522 the relationship is satisfied (or the prohibition violated,
4523 for a conflict or breakage) - it is assumed that a real
4524 package which provides the virtual package is not of the
4525 "right" version. So, a <tt>Provides</tt> field may not
4526 contain version numbers, and the version number of the
4527 concrete package which provides a particular virtual package
4528 will not be looked at when considering a dependency on or
4529 conflict with the virtual package name.
4533 It is likely that the ability will be added in a future
4534 release of <prgn>dpkg</prgn> to specify a version number for
4535 each virtual package it provides. This feature is not yet
4536 present, however, and is expected to be used only
4541 If you want to specify which of a set of real packages
4542 should be the default to satisfy a particular dependency on
4543 a virtual package, you should list the real package as an
4544 alternative before the virtual one.
4549 <sect id="replaces"><heading>Overwriting files and replacing
4550 packages - <tt>Replaces</tt></heading>
4553 Packages can declare in their control file that they should
4554 overwrite files in certain other packages, or completely
4555 replace other packages. The <tt>Replaces</tt> control file
4556 field has these two distinct purposes.
4559 <sect1><heading>Overwriting files in other packages</heading>
4562 Firstly, as mentioned before, it is usually an error for a
4563 package to contain files which are on the system in
4568 However, if the overwriting package declares that it
4569 <tt>Replaces</tt> the one containing the file being
4570 overwritten, then <prgn>dpkg</prgn> will replace the file
4571 from the old package with that from the new. The file
4572 will no longer be listed as "owned" by the old package.
4576 If a package is completely replaced in this way, so that
4577 <prgn>dpkg</prgn> does not know of any files it still
4578 contains, it is considered to have "disappeared". It will
4579 be marked as not wanted on the system (selected for
4580 removal) and not installed. Any <tt>conffile</tt>s
4581 details noted for the package will be ignored, as they
4582 will have been taken over by the overwriting package. The
4583 package's <prgn>postrm</prgn> script will be run with a
4584 special argument to allow the package to do any final
4585 cleanup required. See <ref id="mscriptsinstact">.
4588 Replaces is a one way relationship -- you have to
4589 install the replacing package after the replaced
4596 For this usage of <tt>Replaces</tt>, virtual packages (see
4597 <ref id="virtual">) are not considered when looking at a
4598 <tt>Replaces</tt> field - the packages declared as being
4599 replaced must be mentioned by their real names.
4603 Furthermore, this usage of <tt>Replaces</tt> only takes
4604 effect when both packages are at least partially on the
4605 system at once, so that it can only happen if they do not
4606 conflict or if the conflict has been overridden.
4611 <sect1><heading>Replacing whole packages, forcing their
4615 Secondly, <tt>Replaces</tt> allows the packaging system to
4616 resolve which package should be removed when there is a
4617 conflict - see <ref id="conflicts">. This usage only
4618 takes effect when the two packages <em>do</em> conflict,
4619 so that the two usages of this field do not interfere with
4624 In this situation, the package declared as being replaced
4625 can be a virtual package, so for example, all mail
4626 transport agents (MTAs) would have the following fields in
4627 their control files:
4628 <example compact="compact">
4629 Provides: mail-transport-agent
4630 Conflicts: mail-transport-agent
4631 Replaces: mail-transport-agent
4633 ensuring that only one MTA can be installed at any one
4638 <sect id="sourcebinarydeps">
4639 <heading>Relationships between source and binary packages -
4640 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4641 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4645 Source packages that require certain binary packages to be
4646 installed or absent at the time of building the package
4647 can declare relationships to those binary packages.
4651 This is done using the <tt>Build-Depends</tt>,
4652 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4653 <tt>Build-Conflicts-Indep</tt> control file fields.
4657 Build-dependencies on "build-essential" binary packages can be
4658 omitted. Please see <ref id="pkg-relations"> for more information.
4662 The dependencies and conflicts they define must be satisfied
4663 (as defined earlier for binary packages) in order to invoke
4664 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4666 If you make "build-arch" or "binary-arch", you need
4667 Build-Depends. If you make "build-indep" or
4668 "binary-indep", you need Build-Depends and
4669 Build-Depends-Indep. If you make "build" or "binary",
4673 There is no Build-Depends-Arch; this role is essentially
4674 met with Build-Depends. Anyone building the
4675 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4676 is basically assumed to be building the whole package
4677 anyway and so installs all build dependencies. The
4678 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4679 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4680 does not yet know how to check for its existence) and
4681 <tt>binary-arch</tt>.
4684 The purpose of the original split, I recall, was so that
4685 the autobuilders wouldn't need to install extra packages
4686 needed only for the binary-indep targets. But without a
4687 build-arch/build-indep split, this didn't work, since
4688 most of the work is done in the build target, not in the
4694 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4696 The <tt>Build-Depends</tt> and
4697 <tt>Build-Conflicts</tt> fields must be satisfied when
4698 any of the following targets is invoked:
4699 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4700 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4701 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4703 <tag><tt>Build-Depends-Indep</tt>,
4704 <tt>Build-Conflicts-Indep</tt></tag>
4706 The <tt>Build-Depends-Indep</tt> and
4707 <tt>Build-Conflicts-Indep</tt> fields must be
4708 satisfied when any of the following targets is
4709 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4710 <tt>binary</tt> and <tt>binary-indep</tt>.
4720 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4723 Packages containing shared libraries must be constructed with
4724 a little care to make sure that the shared library is always
4725 available. This is especially important for packages whose
4726 shared libraries are vitally important, such as the C library
4727 (currently <tt>libc6</tt>).
4731 Packages involving shared libraries should be split up into
4732 several binary packages. This section mostly deals with how
4733 this separation is to be accomplished; rules for files within
4734 the shared library packages are in <ref id="libraries"> instead.
4737 <sect id="sharedlibs-runtime">
4738 <heading>Run-time shared libraries</heading>
4741 The run-time shared library needs to be placed in a package
4742 whose name changes whenever the shared object version
4745 Since it is common place to install several versions of a
4746 package that just provides shared libraries, it is a
4747 good idea that the library package should not
4748 contain any extraneous non-versioned files, unless they
4749 happen to be in versioned directories.</p>
4751 The most common mechanism is to place it in a package
4753 <package><var>libraryname</var><var>soversion</var></package>,
4754 where <file><var>soversion</var></file> is the version number
4755 in the soname of the shared library<footnote>
4756 The soname is the shared object name: it's the thing
4757 that has to match exactly between building an executable
4758 and running it for the dynamic linker to be able run the
4759 program. For example, if the soname of the library is
4760 <file>libfoo.so.6</file>, the library package would be
4761 called <file>libfoo6</file>.
4763 Alternatively, if it would be confusing to directly append
4764 <var>soversion</var> to <var>libraryname</var> (e.g. because
4765 <var>libraryname</var> itself ends in a number), you may use
4766 <package><var>libraryname</var>-<var>soversion</var></package> and
4767 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4772 If you have several shared libraries built from the same
4773 source tree you may lump them all together into a single
4774 shared library package, provided that you change all of
4775 their sonames at once (so that you don't get filename
4776 clashes if you try to install different versions of the
4777 combined shared libraries package).
4781 The package should install the shared libraries under
4782 their normal names. For example, the <package>libgdbm3</package>
4783 package should install <file>libgdbm.so.3.0.0</file> as
4784 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4785 renamed or re-linked by any <prgn>prerm</prgn> or
4786 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4787 of renaming things safely without affecting running programs,
4788 and attempts to interfere with this are likely to lead to
4793 Shared libraries should not be installed executable, since
4794 the dynamic linker does not require this and trying to
4795 execute a shared library usually results in a core dump.
4799 The run-time library package should include the symbolic link that
4800 <prgn>ldconfig</prgn> would create for the shared libraries.
4801 For example, the <package>libgdbm3</package> package should include
4802 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4803 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4804 linker (for example <prgn>ld.so</prgn> or
4805 <prgn>ld-linux.so.*</prgn>) can find the library between the
4806 time that <prgn>dpkg</prgn> installs it and the time that
4807 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4809 The package management system requires the library to be
4810 placed before the symbolic link pointing to it in the
4811 <file>.deb</file> file. This is so that when
4812 <prgn>dpkg</prgn> comes to install the symlink
4813 (overwriting the previous symlink pointing at an older
4814 version of the library), the new shared library is already
4815 in place. In the past, this was achieved by creating the
4816 library in the temporary packaging directory before
4817 creating the symlink. Unfortunately, this was not always
4818 effective, since the building of the tar file in the
4819 <file>.deb</file> depended on the behavior of the underlying
4820 file system. Some file systems (such as reiserfs) reorder
4821 the files so that the order of creation is forgotten.
4822 Since version 1.7.0, <prgn>dpkg</prgn>
4823 reorders the files itself as necessary when building a
4824 package. Thus it is no longer important to concern
4825 oneself with the order of file creation.
4829 <sect1 id="ldconfig">
4830 <heading><tt>ldconfig</tt></heading>
4833 Any package installing shared libraries in one of the default
4834 library directories of the dynamic linker (which are currently
4835 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4836 listed in <file>/etc/ld.so.conf</file><footnote>
4838 <list compact="compact">
4839 <item>/usr/local/lib</item>
4840 <item>/usr/lib/libc5-compat</item>
4841 <item>/lib/libc5-compat</item>
4844 must use <prgn>ldconfig</prgn> to update the shared library
4849 The package maintainer scripts must only call
4850 <prgn>ldconfig</prgn> under these circumstances:
4851 <list compact="compact">
4852 <item>When the <prgn>postinst</prgn> script is run with a
4853 first argument of <tt>configure</tt>, the script must call
4854 <prgn>ldconfig</prgn>, and may optionally invoke
4855 <prgn>ldconfig</prgn> at other times.
4857 <item>When the <prgn>postrm</prgn> script is run with a
4858 first argument of <tt>remove</tt>, the script should call
4859 <prgn>ldconfig</prgn>.
4864 During install or upgrade, the preinst is called before
4865 the new files are installed, so calling "ldconfig" is
4866 pointless. The preinst of an existing package can also be
4867 called if an upgrade fails. However, this happens during
4868 the critical time when a shared libs may exist on-disk
4869 under a temporary name. Thus, it is dangerous and
4870 forbidden by current policy to call "ldconfig" at this
4875 When a package is installed or upgraded, "postinst
4876 configure" runs after the new files are safely on-disk.
4877 Since it is perfectly safe to invoke ldconfig
4878 unconditionally in a postinst, it is OK for a package to
4879 simply put ldconfig in its postinst without checking the
4880 argument. The postinst can also be called to recover from
4881 a failed upgrade. This happens before any new files are
4882 unpacked, so there is no reason to call "ldconfig" at this
4887 For a package that is being removed, prerm is
4888 called with all the files intact, so calling ldconfig is
4889 useless. The other calls to "prerm" happen in the case of
4890 upgrade at a time when all the files of the old package
4891 are on-disk, so again calling "ldconfig" is pointless.
4895 postrm, on the other hand, is called with the "remove"
4896 argument just after the files are removed, so this is
4897 the proper time to call "ldconfig" to notify the system
4898 of the fact that the shared libraries from the package
4899 are removed. The postrm can be called at several other
4900 times. At the time of "postrm purge", "postrm
4901 abort-install", or "postrm abort-upgrade", calling
4902 "ldconfig" is useless because the shared lib files are
4903 not on-disk. However, when "postrm" is invoked with
4904 arguments "upgrade", "failed-upgrade", or "disappear", a
4905 shared lib may exist on-disk under a temporary filename.
4913 <sect id="sharedlibs-support-files">
4914 <heading>Shared library support files</heading>
4917 If your package contains files whose names do not change with
4918 each change in the library shared object version, you must not
4919 put them in the shared library package. Otherwise, several
4920 versions of the shared library cannot be installed at the same
4921 time without filename clashes, making upgrades and transitions
4922 unnecessarily difficult.
4926 It is recommended that supporting files and run-time support
4927 programs that do not need to be invoked manually by users, but
4928 are nevertheless required for the package to function, be placed
4929 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4930 preferably under <file>/usr/lib/</file><var>package-name</var>.
4931 If the program or file is architecture independent, the
4932 recommendation is for it to be placed in a subdirectory of
4933 <file>/usr/share</file> instead, preferably under
4934 <file>/usr/share/</file><var>package-name</var>. Following the
4935 <var>package-name</var> naming convention ensures that the file
4936 names change when the shared object version changes.
4940 Run-time support programs that use the shared library but are
4941 not required for the library to function or files used by the
4942 shared library that can be used by any version of the shared
4943 library package should instead be put in a separate package.
4944 This package might typically be named
4945 <package><var>libraryname</var>-tools</package>; note the
4946 absence of the <var>soversion</var> in the package name.
4950 Files and support programs only useful when compiling software
4951 against the library should be included in the development
4952 package for the library.<footnote>
4953 For example, a <file><var>package-name</var>-config</file>
4954 script or <package>pkg-config</package> configuration files.
4959 <sect id="sharedlibs-static">
4960 <heading>Static libraries</heading>
4963 The static library (<file><var>libraryname.a</var></file>)
4964 is usually provided in addition to the shared version.
4965 It is placed into the development package (see below).
4969 In some cases, it is acceptable for a library to be
4970 available in static form only; these cases include:
4972 <item>libraries for languages whose shared library support
4973 is immature or unstable</item>
4974 <item>libraries whose interfaces are in flux or under
4975 development (commonly the case when the library's
4976 major version number is zero, or where the ABI breaks
4977 across patchlevels)</item>
4978 <item>libraries which are explicitly intended to be
4979 available only in static form by their upstream
4984 <sect id="sharedlibs-dev">
4985 <heading>Development files</heading>
4988 The development files associated to a shared library need to be
4989 placed in a package called
4990 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4991 or if you prefer only to support one development version at a
4992 time, <package><var>libraryname</var>-dev</package>.
4996 In case several development versions of a library exist, you may
4997 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4998 <ref id="conflicts">) to ensure that the user only installs one
4999 development version at a time (as different development versions are
5000 likely to have the same header files in them, which would cause a
5001 filename clash if both were installed).
5005 The development package should contain a symlink for the associated
5006 shared library without a version number. For example, the
5007 <package>libgdbm-dev</package> package should include a symlink
5008 from <file>/usr/lib/libgdbm.so</file> to
5009 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5010 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5011 <file>libgdbm.so</file> when compiling dynamically.
5015 <sect id="sharedlibs-intradeps">
5016 <heading>Dependencies between the packages of the same library</heading>
5019 Typically the development version should have an exact
5020 version dependency on the runtime library, to make sure that
5021 compilation and linking happens correctly. The
5022 <tt>${binary:Version}</tt> substitution variable can be
5023 useful for this purpose.
5025 Previously, <tt>${Source-Version}</tt> was used, but its name
5026 was confusing and it has been deprecated since dpkg 1.13.19.
5031 <sect id="sharedlibs-shlibdeps">
5032 <heading>Dependencies between the library and other packages -
5033 the <tt>shlibs</tt> system</heading>
5036 If a package contains a binary or library which links to a
5037 shared library, we must ensure that when the package is
5038 installed on the system, all of the libraries needed are
5039 also installed. This requirement led to the creation of the
5040 <tt>shlibs</tt> system, which is very simple in its design:
5041 any package which <em>provides</em> a shared library also
5042 provides information on the package dependencies required to
5043 ensure the presence of this library, and any package which
5044 <em>uses</em> a shared library uses this information to
5045 determine the dependencies it requires. The files which
5046 contain the mapping from shared libraries to the necessary
5047 dependency information are called <file>shlibs</file> files.
5051 Thus, when a package is built which contains any shared
5052 libraries, it must provide a <file>shlibs</file> file for other
5053 packages to use, and when a package is built which contains
5054 any shared libraries or compiled binaries, it must run
5055 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5056 on these to determine the libraries used and hence the
5057 dependencies needed by this package.<footnote>
5059 In the past, the shared libraries linked to were
5060 determined by calling <prgn>ldd</prgn>, but now
5061 <prgn>objdump</prgn> is used to do this. The only
5062 change this makes to package building is that
5063 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5064 libraries, whereas in the past this was unnecessary.
5065 The rest of this footnote explains the advantage that
5070 We say that a binary <tt>foo</tt> <em>directly</em> uses
5071 a library <tt>libbar</tt> if it is explicitly linked
5072 with that library (that is, it uses the flag
5073 <tt>-lbar</tt> during the linking stage). Other
5074 libraries that are needed by <tt>libbar</tt> are linked
5075 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5076 linker will load them automatically when it loads
5077 <tt>libbar</tt>. A package should depend on
5078 the libraries it directly uses, and the dependencies for
5079 those libraries should automatically pull in the other
5084 Unfortunately, the <prgn>ldd</prgn> program shows both
5085 the directly and indirectly used libraries, meaning that
5086 the dependencies determined included both direct and
5087 indirect dependencies. The use of <prgn>objdump</prgn>
5088 avoids this problem by determining only the directly
5093 A good example of where this helps is the following. We
5094 could update <tt>libimlib</tt> with a new version that
5095 supports a new graphics format called dgf (but retaining
5096 the same major version number). If we used the old
5097 <prgn>ldd</prgn> method, every package that uses
5098 <tt>libimlib</tt> would need to be recompiled so it
5099 would also depend on <tt>libdgf</tt> or it wouldn't run
5100 due to missing symbols. However with the new system,
5101 packages using <tt>libimlib</tt> can rely on
5102 <tt>libimlib</tt> itself having the dependency on
5103 <tt>libdgf</tt> and so they would not need rebuilding.
5109 In the following sections, we will first describe where the
5110 various <tt>shlibs</tt> files are to be found, then how to
5111 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5112 file format and how to create them if your package contains a
5117 <heading>The <tt>shlibs</tt> files present on the system</heading>
5120 There are several places where <tt>shlibs</tt> files are
5121 found. The following list gives them in the order in which
5123 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5124 (The first one which gives the required information is used.)
5130 <p><file>debian/shlibs.local</file></p>
5133 This lists overrides for this package. Its use is
5134 described below (see <ref id="shlibslocal">).
5139 <p><file>/etc/dpkg/shlibs.override</file></p>
5142 This lists global overrides. This list is normally
5143 empty. It is maintained by the local system
5149 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5152 When packages are being built, any
5153 <file>debian/shlibs</file> files are copied into the
5154 control file area of the temporary build directory and
5155 given the name <file>shlibs</file>. These files give
5156 details of any shared libraries included in the
5158 An example may help here. Let us say that the
5159 source package <tt>foo</tt> generates two binary
5160 packages, <tt>libfoo2</tt> and
5161 <tt>foo-runtime</tt>. When building the binary
5162 packages, the two packages are created in the
5163 directories <file>debian/libfoo2</file> and
5164 <file>debian/foo-runtime</file> respectively.
5165 (<file>debian/tmp</file> could be used instead of one
5166 of these.) Since <tt>libfoo2</tt> provides the
5167 <tt>libfoo</tt> shared library, it will require a
5168 <tt>shlibs</tt> file, which will be installed in
5169 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5171 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5172 when <prgn>dpkg-shlibdeps</prgn> is run on the
5174 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5176 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5177 determine whether <tt>foo-prog</tt>'s library
5178 dependencies are satisfied by any of the libraries
5179 provided by <tt>libfoo2</tt>. For this reason,
5180 <prgn>dpkg-shlibdeps</prgn> must only be run once
5181 all of the individual binary packages'
5182 <tt>shlibs</tt> files have been installed into the
5189 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5192 These are the <file>shlibs</file> files corresponding to
5193 all of the packages installed on the system, and are
5194 maintained by the relevant package maintainers.
5199 <p><file>/etc/dpkg/shlibs.default</file></p>
5202 This file lists any shared libraries whose packages
5203 have failed to provide correct <file>shlibs</file> files.
5204 It was used when the <file>shlibs</file> setup was first
5205 introduced, but it is now normally empty. It is
5206 maintained by the <tt>dpkg</tt> maintainer.
5214 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5215 <file>shlibs</file> files</heading>
5219 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5220 into your <file>debian/rules</file> file. If your package
5221 contains only compiled binaries and libraries (but no scripts),
5222 you can use a command such as:
5223 <example compact="compact">
5224 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5225 debian/tmp/usr/lib/*
5227 Otherwise, you will need to explicitly list the compiled
5228 binaries and libraries.<footnote>
5229 If you are using <tt>debhelper</tt>, the
5230 <prgn>dh_shlibdeps</prgn> program will do this work for
5231 you. It will also correctly handle multi-binary
5237 This command puts the dependency information into the
5238 <file>debian/substvars</file> file, which is then used by
5239 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5240 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5241 field in the control file for this to work.
5245 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5246 done. If it does complain you might need to create your own
5247 <file>debian/shlibs.local</file> file, as explained below (see
5248 <ref id="shlibslocal">).
5252 If you have multiple binary packages, you will need to call
5253 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5254 compiled libraries or binaries. In such a case, you will
5255 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5256 utilities to specify a different <file>substvars</file> file.
5260 If you are creating a udeb for use in the Debian Installer, you
5261 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5262 the dependency line of type <tt>udeb</tt> by adding
5263 <tt>-tudeb</tt> as option<footnote>
5264 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5265 will automatically add this option if it knows it is
5267 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5268 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5269 fall back to the regular dependency line.
5273 For more details on dpkg-shlibdeps, please see
5274 <ref id="pkg-dpkg-shlibdeps"> and
5275 <manref name="dpkg-shlibdeps" section="1">.
5280 <heading>The <file>shlibs</file> File Format</heading>
5283 Each <file>shlibs</file> file has the same format. Lines
5284 beginning with <tt>#</tt> are considered to be comments and
5285 are ignored. Each line is of the form:
5286 <example compact="compact">
5287 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5292 We will explain this by reference to the example of the
5293 <tt>zlib1g</tt> package, which (at the time of writing)
5294 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5298 <var>type</var> is an optional element that indicates the type
5299 of package for which the line is valid. The only type currently
5300 in use is <tt>udeb</tt>. The colon and space after the type are
5305 <var>library-name</var> is the name of the shared library,
5306 in this case <tt>libz</tt>. (This must match the name part
5307 of the soname, see below.)
5311 <var>soname-version</var> is the version part of the soname of
5312 the library. The soname is the thing that must exactly match
5313 for the library to be recognized by the dynamic linker, and is
5315 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5316 example, <tt>libz.so.1</tt>.<footnote>
5317 This can be determined using the command
5318 <example compact="compact">
5319 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5322 The version part is the part which comes after
5323 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5327 <var>dependencies</var> has the same syntax as a dependency
5328 field in a binary package control file. It should give
5329 details of which packages are required to satisfy a binary
5330 built against the version of the library contained in the
5331 package. See <ref id="depsyntax"> for details.
5335 In our example, if the first version of the <tt>zlib1g</tt>
5336 package which contained a minor number of at least
5337 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5338 <tt>shlibs</tt> entry for this library could say:
5339 <example compact="compact">
5340 libz 1 zlib1g (>= 1:1.1.3)
5342 The version-specific dependency is to avoid warnings from
5343 the dynamic linker about using older shared libraries with
5348 As zlib1g also provides a udeb containing the shared library,
5349 there would also be a second line:
5350 <example compact="compact">
5351 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5357 <heading>Providing a <file>shlibs</file> file</heading>
5360 If your package provides a shared library, you need to create
5361 a <file>shlibs</file> file following the format described above.
5362 It is usual to call this file <file>debian/shlibs</file> (but if
5363 you have multiple binary packages, you might want to call it
5364 <file>debian/shlibs.<var>package</var></file> instead). Then
5365 let <file>debian/rules</file> install it in the control area:
5366 <example compact="compact">
5367 install -m644 debian/shlibs debian/tmp/DEBIAN
5369 or, in the case of a multi-binary package:
5370 <example compact="compact">
5371 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5373 An alternative way of doing this is to create the
5374 <file>shlibs</file> file in the control area directly from
5375 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5376 file at all,<footnote>
5377 This is what <prgn>dh_makeshlibs</prgn> in the
5378 <tt>debhelper</tt> suite does. If your package also has a udeb
5379 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5380 automatically generate the <tt>udeb:</tt> lines if you specify
5381 the name of the udeb with the <tt>--add-udeb</tt> option.
5383 since the <file>debian/shlibs</file> file itself is ignored by
5384 <prgn>dpkg-shlibdeps</prgn>.
5388 As <prgn>dpkg-shlibdeps</prgn> reads the
5389 <file>DEBIAN/shlibs</file> files in all of the binary packages
5390 being built from this source package, all of the
5391 <file>DEBIAN/shlibs</file> files should be installed before
5392 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5397 <sect1 id="shlibslocal">
5398 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5401 This file is intended only as a <em>temporary</em> fix if
5402 your binaries or libraries depend on a library whose package
5403 does not yet provide a correct <file>shlibs</file> file.
5407 We will assume that you are trying to package a binary
5408 <tt>foo</tt>. When you try running
5409 <prgn>dpkg-shlibdeps</prgn> you get the following error
5410 message (<tt>-O</tt> displays the dependency information on
5411 <tt>stdout</tt> instead of writing it to
5412 <tt>debian/substvars</tt>, and the lines have been wrapped
5413 for ease of reading):
5414 <example compact="compact">
5415 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5416 dpkg-shlibdeps: warning: unable to find dependency
5417 information for shared library libbar (soname 1,
5418 path /usr/lib/libbar.so.1, dependency field Depends)
5419 shlibs:Depends=libc6 (>= 2.2.2-2)
5421 You can then run <prgn>ldd</prgn> on the binary to find the
5422 full location of the library concerned:
5423 <example compact="compact">
5425 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5426 libc.so.6 => /lib/libc.so.6 (0x40032000)
5427 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5429 So the <prgn>foo</prgn> binary depends on the
5430 <prgn>libbar</prgn> shared library, but no package seems to
5431 provide a <file>*.shlibs</file> file handling
5432 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5433 determine the package responsible:
5434 <example compact="compact">
5435 $ dpkg -S /usr/lib/libbar.so.1
5436 bar1: /usr/lib/libbar.so.1
5437 $ dpkg -s bar1 | grep Version
5440 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5441 is the one we are using. Now we can file a bug against the
5442 <tt>bar1</tt> package and create our own
5443 <file>debian/shlibs.local</file> to locally fix the problem.
5444 Including the following line into your
5445 <file>debian/shlibs.local</file> file:
5446 <example compact="compact">
5447 libbar 1 bar1 (>= 1.0-1)
5449 should allow the package build to work.
5453 As soon as the maintainer of <tt>bar1</tt> provides a
5454 correct <file>shlibs</file> file, you should remove this line
5455 from your <file>debian/shlibs.local</file> file. (You should
5456 probably also then have a versioned <tt>Build-Depends</tt>
5457 on <tt>bar1</tt> to help ensure that others do not have the
5458 same problem building your package.)
5467 <chapt id="opersys"><heading>The Operating System</heading>
5470 <heading>File system hierarchy</heading>
5474 <heading>File system Structure</heading>
5477 The location of all installed files and directories must
5478 comply with the File system Hierarchy Standard (FHS),
5479 version 2.3, with the exceptions noted below, and except
5480 where doing so would violate other terms of Debian
5481 Policy. The following exceptions to the FHS apply:
5486 Legacy XFree86 servers are permitted to retain the
5487 configuration file location
5488 <file>/etc/X11/XF86Config-4</file>.
5493 The optional rules related to user specific
5494 configuration files for applications are stored in
5495 the user's home directory are relaxed. It is
5496 recommended that such files start with the
5497 '<tt>.</tt>' character (a "dot file"), and if an
5498 application needs to create more than one dot file
5499 then the preferred placement is in a subdirectory
5500 with a name starting with a '.' character, (a "dot
5501 directory"). In this case it is recommended the
5502 configuration files not start with the '.'
5508 The requirement for amd64 to use <file>/lib64</file>
5509 for 64 bit binaries is removed.
5514 The requirement that
5515 <file>/usr/local/share/man</file> be "synonymous"
5516 with <file>/usr/local/man</file> is relaxed to a
5521 The requirement that windowmanagers with a single
5522 configuration file call it <file>system.*wmrc</file>
5523 is removed, as is the restriction that the window
5524 manager subdirectory be named identically to the
5525 window manager name itself.
5530 The requirement that boot manager configuration
5531 files live in <file>/etc</file>, or at least are
5532 symlinked there, is relaxed to a recommendation.
5539 The version of this document referred here can be
5540 found in the <tt>debian-policy</tt> package or on <url
5541 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5542 name="FHS (Debian copy)"> alongside this manual (or, if
5543 you have the <package>debian-policy</package> installed,
5545 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5546 (local copy)">). The
5547 latest version, which may be a more recent version, may
5549 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5550 Specific questions about following the standard may be
5551 asked on the <tt>debian-devel</tt> mailing list, or
5552 referred to the FHS mailing list (see the
5553 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5559 <heading>Site-specific programs</heading>
5562 As mandated by the FHS, packages must not place any
5563 files in <file>/usr/local</file>, either by putting them in
5564 the file system archive to be unpacked by <prgn>dpkg</prgn>
5565 or by manipulating them in their maintainer scripts.
5569 However, the package may create empty directories below
5570 <file>/usr/local</file> so that the system administrator knows
5571 where to place site-specific files. These are not
5572 directories <em>in</em> <file>/usr/local</file>, but are
5573 children of directories in <file>/usr/local</file>. These
5574 directories (<file>/usr/local/*/dir/</file>)
5575 should be removed on package removal if they are
5580 Note, that this applies only to directories <em>below</em>
5581 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5582 Packages must not create sub-directories in the directory
5583 <file>/usr/local</file> itself, except those listed in FHS,
5584 section 4.5. However, you may create directories below
5585 them as you wish. You must not remove any of the
5586 directories listed in 4.5, even if you created them.
5590 Since <file>/usr/local</file> can be mounted read-only from a
5591 remote server, these directories must be created and
5592 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5593 maintainer scripts and not be included in the
5594 <file>.deb</file> archive. These scripts must not fail if
5595 either of these operations fail.
5599 For example, the <tt>emacsen-common</tt> package could
5600 contain something like
5601 <example compact="compact">
5602 if [ ! -e /usr/local/share/emacs ]
5604 if mkdir /usr/local/share/emacs 2>/dev/null
5606 chown root:staff /usr/local/share/emacs
5607 chmod 2775 /usr/local/share/emacs
5611 in its <prgn>postinst</prgn> script, and
5612 <example compact="compact">
5613 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5614 rmdir /usr/local/share/emacs 2>/dev/null || true
5616 in the <prgn>prerm</prgn> script. (Note that this form is
5617 used to ensure that if the script is interrupted, the
5618 directory <file>/usr/local/share/emacs</file> will still be
5623 If you do create a directory in <file>/usr/local</file> for
5624 local additions to a package, you should ensure that
5625 settings in <file>/usr/local</file> take precedence over the
5626 equivalents in <file>/usr</file>.
5630 However, because <file>/usr/local</file> and its contents are
5631 for exclusive use of the local administrator, a package
5632 must not rely on the presence or absence of files or
5633 directories in <file>/usr/local</file> for normal operation.
5637 The <file>/usr/local</file> directory itself and all the
5638 subdirectories created by the package should (by default) have
5639 permissions 2775 (group-writable and set-group-id) and be
5640 owned by <tt>root:staff</tt>.
5645 <heading>The system-wide mail directory</heading>
5647 The system-wide mail directory is <file>/var/mail</file>. This
5648 directory is part of the base system and should not owned
5649 by any particular mail agents. The use of the old
5650 location <file>/var/spool/mail</file> is deprecated, even
5651 though the spool may still be physically located there.
5652 To maintain partial upgrade compatibility for systems
5653 which have <file>/var/spool/mail</file> as their physical mail
5654 spool, packages using <file>/var/mail</file> must depend on
5655 either <package>libc6</package> (>= 2.1.3-13), or on
5656 <package>base-files</package> (>= 2.2.0), or on later
5657 versions of either one of these packages.
5663 <heading>Users and groups</heading>
5666 <heading>Introduction</heading>
5668 The Debian system can be configured to use either plain or
5673 Some user ids (UIDs) and group ids (GIDs) are reserved
5674 globally for use by certain packages. Because some
5675 packages need to include files which are owned by these
5676 users or groups, or need the ids compiled into binaries,
5677 these ids must be used on any Debian system only for the
5678 purpose for which they are allocated. This is a serious
5679 restriction, and we should avoid getting in the way of
5680 local administration policies. In particular, many sites
5681 allocate users and/or local system groups starting at 100.
5685 Apart from this we should have dynamically allocated ids,
5686 which should by default be arranged in some sensible
5687 order, but the behavior should be configurable.
5691 Packages other than <tt>base-passwd</tt> must not modify
5692 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5693 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5698 <heading>UID and GID classes</heading>
5700 The UID and GID numbers are divided into classes as
5706 Globally allocated by the Debian project, the same
5707 on every Debian system. These ids will appear in
5708 the <file>passwd</file> and <file>group</file> files of all
5709 Debian systems, new ids in this range being added
5710 automatically as the <tt>base-passwd</tt> package is
5715 Packages which need a single statically allocated
5716 uid or gid should use one of these; their
5717 maintainers should ask the <tt>base-passwd</tt>
5725 Dynamically allocated system users and groups.
5726 Packages which need a user or group, but can have
5727 this user or group allocated dynamically and
5728 differently on each system, should use <tt>adduser
5729 --system</tt> to create the group and/or user.
5730 <prgn>adduser</prgn> will check for the existence of
5731 the user or group, and if necessary choose an unused
5732 id based on the ranges specified in
5733 <file>adduser.conf</file>.
5737 <tag>1000-29999:</tag>
5740 Dynamically allocated user accounts. By default
5741 <prgn>adduser</prgn> will choose UIDs and GIDs for
5742 user accounts in this range, though
5743 <file>adduser.conf</file> may be used to modify this
5748 <tag>30000-59999:</tag>
5753 <tag>60000-64999:</tag>
5756 Globally allocated by the Debian project, but only
5757 created on demand. The ids are allocated centrally
5758 and statically, but the actual accounts are only
5759 created on users' systems on demand.
5763 These ids are for packages which are obscure or
5764 which require many statically-allocated ids. These
5765 packages should check for and create the accounts in
5766 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5767 <prgn>adduser</prgn> if it has this facility) if
5768 necessary. Packages which are likely to require
5769 further allocations should have a "hole" left after
5770 them in the allocation, to give them room to
5775 <tag>65000-65533:</tag>
5783 User <tt>nobody</tt>. The corresponding gid refers
5784 to the group <tt>nogroup</tt>.
5791 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5792 not</em> be used, because it is the error return
5801 <sect id="sysvinit">
5802 <heading>System run levels and <file>init.d</file> scripts</heading>
5804 <sect1 id="/etc/init.d">
5805 <heading>Introduction</heading>
5808 The <file>/etc/init.d</file> directory contains the scripts
5809 executed by <prgn>init</prgn> at boot time and when the
5810 init state (or "runlevel") is changed (see <manref
5811 name="init" section="8">).
5815 There are at least two different, yet functionally
5816 equivalent, ways of handling these scripts. For the sake
5817 of simplicity, this document describes only the symbolic
5818 link method. However, it must not be assumed by maintainer
5819 scripts that this method is being used, and any automated
5820 manipulation of the various runlevel behaviors by
5821 maintainer scripts must be performed using
5822 <prgn>update-rc.d</prgn> as described below and not by
5823 manually installing or removing symlinks. For information
5824 on the implementation details of the other method,
5825 implemented in the <tt>file-rc</tt> package, please refer
5826 to the documentation of that package.
5830 These scripts are referenced by symbolic links in the
5831 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5832 runlevels, <prgn>init</prgn> looks in the directory
5833 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5834 execute, where <tt><var>n</var></tt> is the runlevel that
5835 is being changed to, or <tt>S</tt> for the boot-up
5840 The names of the links all have the form
5841 <file>S<var>mm</var><var>script</var></file> or
5842 <file>K<var>mm</var><var>script</var></file> where
5843 <var>mm</var> is a two-digit number and <var>script</var>
5844 is the name of the script (this should be the same as the
5845 name of the actual script in <file>/etc/init.d</file>).
5849 When <prgn>init</prgn> changes runlevel first the targets
5850 of the links whose names start with a <tt>K</tt> are
5851 executed, each with the single argument <tt>stop</tt>,
5852 followed by the scripts prefixed with an <tt>S</tt>, each
5853 with the single argument <tt>start</tt>. (The links are
5854 those in the <file>/etc/rc<var>n</var>.d</file> directory
5855 corresponding to the new runlevel.) The <tt>K</tt> links
5856 are responsible for killing services and the <tt>S</tt>
5857 link for starting services upon entering the runlevel.
5861 For example, if we are changing from runlevel 2 to
5862 runlevel 3, init will first execute all of the <tt>K</tt>
5863 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5864 all of the <tt>S</tt> prefixed scripts in that directory.
5865 The links starting with <tt>K</tt> will cause the
5866 referred-to file to be executed with an argument of
5867 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5872 The two-digit number <var>mm</var> is used to determine
5873 the order in which to run the scripts: low-numbered links
5874 have their scripts run first. For example, the
5875 <tt>K20</tt> scripts will be executed before the
5876 <tt>K30</tt> scripts. This is used when a certain service
5877 must be started before another. For example, the name
5878 server <prgn>bind</prgn> might need to be started before
5879 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5880 can set up its access lists. In this case, the script
5881 that starts <prgn>bind</prgn> would have a lower number
5882 than the script that starts <prgn>inn</prgn> so that it
5884 <example compact="compact">
5891 The two runlevels 0 (halt) and 6 (reboot) are slightly
5892 different. In these runlevels, the links with an
5893 <tt>S</tt> prefix are still called after those with a
5894 <tt>K</tt> prefix, but they too are called with the single
5895 argument <tt>stop</tt>.
5899 Also, if the script name ends in <tt>.sh</tt>, the script
5900 will be sourced in runlevel <tt>S</tt> rather than being
5901 run in a forked subprocess, but will be explicitly run by
5902 <prgn>sh</prgn> in all other runlevels.
5907 <heading>Writing the scripts</heading>
5910 Packages that include daemons for system services should
5911 place scripts in <file>/etc/init.d</file> to start or stop
5912 services at boot time or during a change of runlevel.
5913 These scripts should be named
5914 <file>/etc/init.d/<var>package</var></file>, and they should
5915 accept one argument, saying what to do:
5918 <tag><tt>start</tt></tag>
5919 <item>start the service,</item>
5921 <tag><tt>stop</tt></tag>
5922 <item>stop the service,</item>
5924 <tag><tt>restart</tt></tag>
5925 <item>stop and restart the service if it's already running,
5926 otherwise start the service</item>
5928 <tag><tt>reload</tt></tag>
5929 <item><p>cause the configuration of the service to be
5930 reloaded without actually stopping and restarting
5933 <tag><tt>force-reload</tt></tag>
5934 <item>cause the configuration to be reloaded if the
5935 service supports this, otherwise restart the
5939 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5940 <tt>force-reload</tt> options should be supported by all
5941 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5946 The <file>init.d</file> scripts must ensure that they will
5947 behave sensibly if invoked with <tt>start</tt> when the
5948 service is already running, or with <tt>stop</tt> when it
5949 isn't, and that they don't kill unfortunately-named user
5950 processes. The best way to achieve this is usually to use
5951 <prgn>start-stop-daemon</prgn>.
5955 If a service reloads its configuration automatically (as
5956 in the case of <prgn>cron</prgn>, for example), the
5957 <tt>reload</tt> option of the <file>init.d</file> script
5958 should behave as if the configuration has been reloaded
5963 The <file>/etc/init.d</file> scripts must be treated as
5964 configuration files, either (if they are present in the
5965 package, that is, in the .deb file) by marking them as
5966 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5967 by managing them correctly in the maintainer scripts (see
5968 <ref id="config-files">). This is important since we want
5969 to give the local system administrator the chance to adapt
5970 the scripts to the local system, e.g., to disable a
5971 service without de-installing the package, or to specify
5972 some special command line options when starting a service,
5973 while making sure their changes aren't lost during the next
5978 These scripts should not fail obscurely when the
5979 configuration files remain but the package has been
5980 removed, as configuration files remain on the system after
5981 the package has been removed. Only when <prgn>dpkg</prgn>
5982 is executed with the <tt>--purge</tt> option will
5983 configuration files be removed. In particular, as the
5984 <file>/etc/init.d/<var>package</var></file> script itself is
5985 usually a <tt>conffile</tt>, it will remain on the system
5986 if the package is removed but not purged. Therefore, you
5987 should include a <tt>test</tt> statement at the top of the
5989 <example compact="compact">
5990 test -f <var>program-executed-later-in-script</var> || exit 0
5995 Often there are some variables in the <file>init.d</file>
5996 scripts whose values control the behavior of the scripts,
5997 and which a system administrator is likely to want to
5998 change. As the scripts themselves are frequently
5999 <tt>conffile</tt>s, modifying them requires that the
6000 administrator merge in their changes each time the package
6001 is upgraded and the <tt>conffile</tt> changes. To ease
6002 the burden on the system administrator, such configurable
6003 values should not be placed directly in the script.
6004 Instead, they should be placed in a file in
6005 <file>/etc/default</file>, which typically will have the same
6006 base name as the <file>init.d</file> script. This extra file
6007 should be sourced by the script when the script runs. It
6008 must contain only variable settings and comments in SUSv3
6009 <prgn>sh</prgn> format. It may either be a
6010 <tt>conffile</tt> or a configuration file maintained by
6011 the package maintainer scripts. See <ref id="config-files">
6016 To ensure that vital configurable values are always
6017 available, the <file>init.d</file> script should set default
6018 values for each of the shell variables it uses, either
6019 before sourcing the <file>/etc/default/</file> file or
6020 afterwards using something like the <tt>:
6021 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6022 script must behave sensibly and not fail if the
6023 <file>/etc/default</file> file is deleted.
6028 <heading>Interfacing with the initscript system</heading>
6031 Maintainers should use the abstraction layer provided by
6032 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6033 programs to deal with initscripts in their packages'
6034 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6035 and <prgn>postrm</prgn>.
6039 Directly managing the /etc/rc?.d links and directly
6040 invoking the <file>/etc/init.d/</file> initscripts should
6041 be done only by packages providing the initscript
6042 subsystem (such as <prgn>sysv-rc</prgn> and
6043 <prgn>file-rc</prgn>).
6047 <heading>Managing the links</heading>
6050 The program <prgn>update-rc.d</prgn> is provided for
6051 package maintainers to arrange for the proper creation and
6052 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6053 or their functional equivalent if another method is being
6054 used. This may be used by maintainers in their packages'
6055 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6059 You must not include any <file>/etc/rc<var>n</var>.d</file>
6060 symbolic links in the actual archive or manually create or
6061 remove the symbolic links in maintainer scripts; you must
6062 use the <prgn>update-rc.d</prgn> program instead. (The
6063 former will fail if an alternative method of maintaining
6064 runlevel information is being used.) You must not include
6065 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6066 in the archive either. (Only the <tt>sysvinit</tt>
6071 By default <prgn>update-rc.d</prgn> will start services in
6072 each of the multi-user state runlevels (2, 3, 4, and 5)
6073 and stop them in the halt runlevel (0), the single-user
6074 runlevel (1) and the reboot runlevel (6). The system
6075 administrator will have the opportunity to customize
6076 runlevels by simply adding, moving, or removing the
6077 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6078 symbolic links are being used, or by modifying
6079 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6084 To get the default behavior for your package, put in your
6085 <prgn>postinst</prgn> script
6086 <example compact="compact">
6087 update-rc.d <var>package</var> defaults
6089 and in your <prgn>postrm</prgn>
6090 <example compact="compact">
6091 if [ "$1" = purge ]; then
6092 update-rc.d <var>package</var> remove
6094 </example>. Note that if your package changes runlevels
6095 or priority, you may have to remove and recreate the links,
6096 since otherwise the old links may persist. Refer to the
6097 documentation of <prgn>update-rc.d</prgn>.
6101 This will use a default sequence number of 20. If it does
6102 not matter when or in which order the <file>init.d</file>
6103 script is run, use this default. If it does, then you
6104 should talk to the maintainer of the <prgn>sysvinit</prgn>
6105 package or post to <tt>debian-devel</tt>, and they will
6106 help you choose a number.
6110 For more information about using <tt>update-rc.d</tt>,
6111 please consult its man page <manref name="update-rc.d"
6117 <heading>Running initscripts</heading>
6119 The program <prgn>invoke-rc.d</prgn> is provided to make
6120 it easier for package maintainers to properly invoke an
6121 initscript, obeying runlevel and other locally-defined
6122 constraints that might limit a package's right to start,
6123 stop and otherwise manage services. This program may be
6124 used by maintainers in their packages' scripts.
6128 The package maintainer scripts must use
6129 <prgn>invoke-rc.d</prgn> to invoke the
6130 <file>/etc/init.d/*</file> initscripts, instead of
6131 calling them directly.
6135 By default, <prgn>invoke-rc.d</prgn> will pass any
6136 action requests (start, stop, reload, restart...) to the
6137 <file>/etc/init.d</file> script, filtering out requests
6138 to start or restart a service out of its intended
6143 Most packages will simply need to change:
6144 <example compact="compact">/etc/init.d/<package>
6145 <action></example> in their <prgn>postinst</prgn>
6146 and <prgn>prerm</prgn> scripts to:
6147 <example compact="compact">
6148 if which invoke-rc.d >/dev/null 2>&1; then
6149 invoke-rc.d <var>package</var> <action>
6151 /etc/init.d/<var>package</var> <action>
6157 A package should register its initscript services using
6158 <prgn>update-rc.d</prgn> before it tries to invoke them
6159 using <prgn>invoke-rc.d</prgn>. Invocation of
6160 unregistered services may fail.
6164 For more information about using
6165 <prgn>invoke-rc.d</prgn>, please consult its man page
6166 <manref name="invoke-rc.d" section="8">.
6172 <heading>Boot-time initialization</heading>
6175 There used to be another directory, <file>/etc/rc.boot</file>,
6176 which contained scripts which were run once per machine
6177 boot. This has been deprecated in favour of links from
6178 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6179 described in <ref id="/etc/init.d">. Packages must not
6180 place files in <file>/etc/rc.boot</file>.
6185 <heading>Example</heading>
6188 An example on which you can base your
6189 <file>/etc/init.d</file> scripts is found in
6190 <file>/etc/init.d/skeleton</file>.
6197 <heading>Console messages from <file>init.d</file> scripts</heading>
6200 This section describes the formats to be used for messages
6201 written to standard output by the <file>/etc/init.d</file>
6202 scripts. The intent is to improve the consistency of
6203 Debian's startup and shutdown look and feel. For this
6204 reason, please look very carefully at the details. We want
6205 the messages to have the same format in terms of wording,
6206 spaces, punctuation and case of letters.
6210 Here is a list of overall rules that should be used for
6211 messages generated by <file>/etc/init.d</file> scripts.
6217 The message should fit in one line (fewer than 80
6218 characters), start with a capital letter and end with
6219 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6223 If the script is performing some time consuming task in
6224 the background (not merely starting or stopping a
6225 program, for instance), an ellipsis (three dots:
6226 <tt>...</tt>) should be output to the screen, with no
6227 leading or tailing whitespace or line feeds.
6231 The messages should appear as if the computer is telling
6232 the user what it is doing (politely :-), but should not
6233 mention "it" directly. For example, instead of:
6234 <example compact="compact">
6235 I'm starting network daemons: nfsd mountd.
6237 the message should say
6238 <example compact="compact">
6239 Starting network daemons: nfsd mountd.
6246 <tt>init.d</tt> script should use the following standard
6247 message formats for the situations enumerated below.
6253 <p>When daemons are started</p>
6256 If the script starts one or more daemons, the output
6257 should look like this (a single line, no leading
6259 <example compact="compact">
6260 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6262 The <var>description</var> should describe the
6263 subsystem the daemon or set of daemons are part of,
6264 while <var>daemon-1</var> up to <var>daemon-n</var>
6265 denote each daemon's name (typically the file name of
6270 For example, the output of <file>/etc/init.d/lpd</file>
6272 <example compact="compact">
6273 Starting printer spooler: lpd.
6278 This can be achieved by saying
6279 <example compact="compact">
6280 echo -n "Starting printer spooler: lpd"
6281 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6284 in the script. If there are more than one daemon to
6285 start, the output should look like this:
6286 <example compact="compact">
6287 echo -n "Starting remote file system services:"
6288 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6289 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6290 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6293 This makes it possible for the user to see what is
6294 happening and when the final daemon has been started.
6295 Care should be taken in the placement of white spaces:
6296 in the example above the system administrators can
6297 easily comment out a line if they don't want to start
6298 a specific daemon, while the displayed message still
6304 <p>When a system parameter is being set</p>
6307 If you have to set up different system parameters
6308 during the system boot, you should use this format:
6309 <example compact="compact">
6310 Setting <var>parameter</var> to "<var>value</var>".
6315 You can use a statement such as the following to get
6317 <example compact="compact">
6318 echo "Setting DNS domainname to \"$domainname\"."
6323 Note that the same symbol (<tt>"</tt>) is used for the left
6324 and right quotation marks. A grave accent (<tt>`</tt>) is
6325 not a quote character; neither is an apostrophe
6331 <p>When a daemon is stopped or restarted</p>
6334 When you stop or restart a daemon, you should issue a
6335 message identical to the startup message, except that
6336 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6337 or <tt>Restarting</tt> respectively.
6341 For example, stopping the printer daemon will look like
6343 <example compact="compact">
6344 Stopping printer spooler: lpd.
6350 <p>When something is executed</p>
6353 There are several examples where you have to run a
6354 program at system startup or shutdown to perform a
6355 specific task, for example, setting the system's clock
6356 using <prgn>netdate</prgn> or killing all processes
6357 when the system shuts down. Your message should look
6359 <example compact="compact">
6360 Doing something very useful...done.
6362 You should print the <tt>done.</tt> immediately after
6363 the job has been completed, so that the user is
6364 informed why they have to wait. You can get this
6366 <example compact="compact">
6367 echo -n "Doing something very useful..."
6376 <p>When the configuration is reloaded</p>
6379 When a daemon is forced to reload its configuration
6380 files you should use the following format:
6381 <example compact="compact">
6382 Reloading <var>description</var> configuration...done.
6384 where <var>description</var> is the same as in the
6385 daemon starting message.
6393 <heading>Cron jobs</heading>
6396 Packages must not modify the configuration file
6397 <file>/etc/crontab</file>, and they must not modify the files in
6398 <file>/var/spool/cron/crontabs</file>.</p>
6401 If a package wants to install a job that has to be executed
6402 via cron, it should place a file with the name of the
6403 package in one or more of the following directories:
6404 <example compact="compact">
6410 As these directory names imply, the files within them are
6411 executed on an hourly, daily, weekly, or monthly basis,
6412 respectively. The exact times are listed in
6413 <file>/etc/crontab</file>.</p>
6416 All files installed in any of these directories must be
6417 scripts (e.g., shell scripts or Perl scripts) so that they
6418 can easily be modified by the local system administrator.
6419 In addition, they must be treated as configuration files.
6423 If a certain job has to be executed at some other frequency or
6424 at a specific time, the package should install a file
6425 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6426 same syntax as <file>/etc/crontab</file> and is processed by
6427 <prgn>cron</prgn> automatically. The file must also be
6428 treated as a configuration file. (Note that entries in the
6429 <file>/etc/cron.d</file> directory are not handled by
6430 <prgn>anacron</prgn>. Thus, you should only use this
6431 directory for jobs which may be skipped if the system is not
6435 The scripts or crontab entries in these directories should
6436 check if all necessary programs are installed before they
6437 try to execute them. Otherwise, problems will arise when a
6438 package was removed but not purged since configuration files
6439 are kept on the system in this situation.</p>
6443 <heading>Menus</heading>
6446 The Debian <tt>menu</tt> package provides a standard
6447 interface between packages providing applications and
6448 <em>menu programs</em> (either X window managers or
6449 text-based menu programs such as <prgn>pdmenu</prgn>).
6453 All packages that provide applications that need not be
6454 passed any special command line arguments for normal
6455 operation should register a menu entry for those
6456 applications, so that users of the <tt>menu</tt> package
6457 will automatically get menu entries in their window
6458 managers, as well in shells like <tt>pdmenu</tt>.
6462 Menu entries should follow the current menu policy.
6466 The menu policy can be found in the <tt>menu-policy</tt>
6467 files in the <tt>debian-policy</tt> package.
6468 It is also available from the Debian web mirrors at
6469 <tt><url name="/doc/packaging-manuals/menu-policy/"
6470 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6474 Please also refer to the <em>Debian Menu System</em>
6475 documentation that comes with the <package>menu</package>
6476 package for information about how to register your
6482 <heading>Multimedia handlers</heading>
6485 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6486 is a mechanism for encoding files and data streams and
6487 providing meta-information about them, in particular their
6488 type (e.g. audio or video) and format (e.g. PNG, HTML,
6493 Registration of MIME type handlers allows programs like mail
6494 user agents and web browsers to invoke these handlers to
6495 view, edit or display MIME types they don't support directly.
6499 Packages which provide the ability to view/show/play,
6500 compose, edit or print MIME types should register themselves
6501 as such following the current MIME support policy.
6505 The MIME support policy can be found in the <tt>mime-policy</tt>
6506 files in the <tt>debian-policy</tt> package.
6507 It is also available from the Debian web mirrors at
6508 <tt><url name="/doc/packaging-manuals/mime-policy/"
6509 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6515 <heading>Keyboard configuration</heading>
6518 To achieve a consistent keyboard configuration so that all
6519 applications interpret a keyboard event the same way, all
6520 programs in the Debian distribution must be configured to
6521 comply with the following guidelines.
6525 The following keys must have the specified interpretations:
6528 <tag><tt><--</tt></tag>
6529 <item>delete the character to the left of the cursor</item>
6531 <tag><tt>Delete</tt></tag>
6532 <item>delete the character to the right of the cursor</item>
6534 <tag><tt>Control+H</tt></tag>
6535 <item>emacs: the help prefix</item>
6538 The interpretation of any keyboard events should be
6539 independent of the terminal that is used, be it a virtual
6540 console, an X terminal emulator, an rlogin/telnet session,
6545 The following list explains how the different programs
6546 should be set up to achieve this:
6552 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6556 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6560 X translations are set up to make
6561 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6562 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6563 is the vt220 escape code for the "delete character"
6564 key). This must be done by loading the X resources
6565 using <prgn>xrdb</prgn> on all local X displays, not
6566 using the application defaults, so that the
6567 translation resources used correspond to the
6568 <prgn>xmodmap</prgn> settings.
6572 The Linux console is configured to make
6573 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6574 generate <tt>ESC [ 3 ~</tt>.
6578 X applications are configured so that <tt><</tt>
6579 deletes left, and <tt>Delete</tt> deletes right. Motif
6580 applications already work like this.
6584 Terminals should have <tt>stty erase ^?</tt> .
6588 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6589 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6590 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6594 Emacs is programmed to map <tt>KB_Backspace</tt> or
6595 the <tt>stty erase</tt> character to
6596 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6597 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6598 <tt>^H</tt> to <tt>help</tt> as always.
6602 Other applications use the <tt>stty erase</tt>
6603 character and <tt>kdch1</tt> for the two delete keys,
6604 with ASCII DEL being "delete previous character" and
6605 <tt>kdch1</tt> being "delete character under
6613 This will solve the problem except for the following
6620 Some terminals have a <tt><--</tt> key that cannot
6621 be made to produce anything except <tt>^H</tt>. On
6622 these terminals Emacs help will be unavailable on
6623 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6624 character takes precedence in Emacs, and has been set
6625 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6626 available) can be used instead.
6630 Some operating systems use <tt>^H</tt> for <tt>stty
6631 erase</tt>. However, modern telnet versions and all
6632 rlogin versions propagate <tt>stty</tt> settings, and
6633 almost all UNIX versions honour <tt>stty erase</tt>.
6634 Where the <tt>stty</tt> settings are not propagated
6635 correctly, things can be made to work by using
6636 <tt>stty</tt> manually.
6640 Some systems (including previous Debian versions) use
6641 <prgn>xmodmap</prgn> to arrange for both
6642 <tt><--</tt> and <tt>Delete</tt> to generate
6643 <tt>KB_Delete</tt>. We can change the behavior of
6644 their X clients using the same X resources that we use
6645 to do it for our own clients, or configure our clients
6646 using their resources when things are the other way
6647 around. On displays configured like this
6648 <tt>Delete</tt> will not work, but <tt><--</tt>
6653 Some operating systems have different <tt>kdch1</tt>
6654 settings in their <tt>terminfo</tt> database for
6655 <tt>xterm</tt> and others. On these systems the
6656 <tt>Delete</tt> key will not work correctly when you
6657 log in from a system conforming to our policy, but
6658 <tt><--</tt> will.
6665 <heading>Environment variables</heading>
6668 A program must not depend on environment variables to get
6669 reasonable defaults. (That's because these environment
6670 variables would have to be set in a system-wide
6671 configuration file like <file>/etc/profile</file>, which is not
6672 supported by all shells.)
6676 If a program usually depends on environment variables for its
6677 configuration, the program should be changed to fall back to
6678 a reasonable default configuration if these environment
6679 variables are not present. If this cannot be done easily
6680 (e.g., if the source code of a non-free program is not
6681 available), the program must be replaced by a small
6682 "wrapper" shell script which sets the environment variables
6683 if they are not already defined, and calls the original program.
6687 Here is an example of a wrapper script for this purpose:
6689 <example compact="compact">
6691 BAR=${BAR:-/var/lib/fubar}
6693 exec /usr/lib/foo/foo "$@"
6698 Furthermore, as <file>/etc/profile</file> is a configuration
6699 file of the <prgn>base-files</prgn> package, other packages must
6700 not put any environment variables or other commands into that
6705 <sect id="doc-base">
6706 <heading>Registering Documents using doc-base</heading>
6709 The <package>doc-base</package> package implements a
6710 flexible mechanism for handling and presenting
6711 documentation. The recommended practice is for every Debian
6712 package that provides online documentation (other than just
6713 manual pages) to register these documents with
6714 <package>doc-base</package> by installing a
6715 <package>doc-base</package> control file via the
6716 <prgn/install-docs/ script at installation time and
6717 de-register the manuals again when the package is removed.
6720 Please refer to the documentation that comes with the
6721 <package>doc-base</package> package for information and
6730 <heading>Files</heading>
6733 <heading>Binaries</heading>
6736 Two different packages must not install programs with
6737 different functionality but with the same filenames. (The
6738 case of two programs having the same functionality but
6739 different implementations is handled via "alternatives" or
6740 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6741 <ref id="conflicts"> respectively.) If this case happens,
6742 one of the programs must be renamed. The maintainers should
6743 report this to the <tt>debian-devel</tt> mailing list and
6744 try to find a consensus about which program will have to be
6745 renamed. If a consensus cannot be reached, <em>both</em>
6746 programs must be renamed.
6750 By default, when a package is being built, any binaries
6751 created should include debugging information, as well as
6752 being compiled with optimization. You should also turn on
6753 as many reasonable compilation warnings as possible; this
6754 makes life easier for porters, who can then look at build
6755 logs for possible problems. For the C programming language,
6756 this means the following compilation parameters should be
6758 <example compact="compact">
6760 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6762 INSTALL = install -s # (or use strip on the files in debian/tmp)
6767 Note that by default all installed binaries should be stripped,
6768 either by using the <tt>-s</tt> flag to
6769 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6770 the binaries after they have been copied into
6771 <file>debian/tmp</file> but before the tree is made into a
6776 Although binaries in the build tree should be compiled with
6777 debugging information by default, it can often be difficult to
6778 debug programs if they are also subjected to compiler
6779 optimization. For this reason, it is recommended to support the
6780 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6781 (see <ref id="debianrules-options">). This variable can contain
6782 several flags to change how a package is compiled and built.
6786 It is up to the package maintainer to decide what
6787 compilation options are best for the package. Certain
6788 binaries (such as computationally-intensive programs) will
6789 function better with certain flags (<tt>-O3</tt>, for
6790 example); feel free to use them. Please use good judgment
6791 here. Don't use flags for the sake of it; only use them
6792 if there is good reason to do so. Feel free to override
6793 the upstream author's ideas about which compilation
6794 options are best: they are often inappropriate for our
6800 <sect id="libraries">
6801 <heading>Libraries</heading>
6804 If the package is <strong>architecture: any</strong>, then
6805 the shared library compilation and linking flags must have
6806 <tt>-fPIC</tt>, or the package shall not build on some of
6807 the supported architectures<footnote>
6809 If you are using GCC, <tt>-fPIC</tt> produces code with
6810 relocatable position independent code, which is required for
6811 most architectures to create a shared library, with i386 and
6812 perhaps some others where non position independent code is
6813 permitted in a shared library.
6816 Position independent code may have a performance penalty,
6817 especially on <tt>i386</tt>. However, in most cases the
6818 speed penalty must be measured against the memory wasted on
6819 the few architectures where non position independent code is
6822 </footnote>. Any exception to this rule must be discussed on
6823 the mailing list <em>debian-devel@lists.debian.org</em>, and
6824 a rough consensus obtained. The reasons for not compiling
6825 with <tt>-fPIC</tt> flag must be recorded in the file
6826 <tt>README.Debian</tt>, and care must be taken to either
6827 restrict the architecture or arrange for <tt>-fPIC</tt> to
6828 be used on architectures where it is required.<footnote>
6830 Some of the reasons why this might be required is if the
6831 library contains hand crafted assembly code that is not
6832 relocatable, the speed penalty is excessive for compute
6833 intensive libs, and similar reasons.
6838 As to the static libraries, the common case is not to have
6839 relocatable code, since there is no benefit, unless in specific
6840 cases; therefore the static version must not be compiled
6841 with the <tt>-fPIC</tt> flag. Any exception to this rule
6842 should be discussed on the mailing list
6843 <em>debian-devel@lists.debian.org</em>, and the reasons for
6844 compiling with the <tt>-fPIC</tt> flag must be recorded in
6845 the file <tt>README.Debian</tt>. <footnote>
6847 Some of the reasons for linking static libraries with
6848 the <tt>-fPIC</tt> flag are if, for example, one needs a
6849 Perl API for a library that is under rapid development,
6850 and has an unstable API, so shared libraries are
6851 pointless at this phase of the library's development. In
6852 that case, since Perl needs a library with relocatable
6853 code, it may make sense to create a static library with
6854 relocatable code. Another reason cited is if you are
6855 distilling various libraries into a common shared
6856 library, like <tt>mklibs</tt> does in the Debian
6862 In other words, if both a shared and a static library is
6863 being built, each source unit (<tt>*.c</tt>, for example,
6864 for C files) will need to be compiled twice, for the normal
6868 You must specify the gcc option <tt>-D_REENTRANT</tt>
6869 when building a library (either static or shared) to make
6870 the library compatible with LinuxThreads.
6874 Although not enforced by the build tools, shared libraries
6875 must be linked against all libraries that they use symbols from
6876 in the same way that binaries are. This ensures the correct
6877 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6878 system and guarantees that all libraries can be safely opened
6879 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6880 option <tt>-Wl,-z,defs</tt> when building a shared library.
6881 Since this option enforces symbol resolution at build time,
6882 a missing library reference will be caught early as a fatal
6887 All installed shared libraries should be stripped with
6888 <example compact="compact">
6889 strip --strip-unneeded <var>your-lib</var>
6891 (The option <tt>--strip-unneeded</tt> makes
6892 <prgn>strip</prgn> remove only the symbols which aren't
6893 needed for relocation processing.) Shared libraries can
6894 function perfectly well when stripped, since the symbols for
6895 dynamic linking are in a separate part of the ELF object
6897 You might also want to use the options
6898 <tt>--remove-section=.comment</tt> and
6899 <tt>--remove-section=.note</tt> on both shared libraries
6900 and executables, and <tt>--strip-debug</tt> on static
6906 Note that under some circumstances it may be useful to
6907 install a shared library unstripped, for example when
6908 building a separate package to support debugging.
6912 Shared object files (often <file>.so</file> files) that are not
6913 public libraries, that is, they are not meant to be linked
6914 to by third party executables (binaries of other packages),
6915 should be installed in subdirectories of the
6916 <file>/usr/lib</file> directory. Such files are exempt from the
6917 rules that govern ordinary shared libraries, except that
6918 they must not be installed executable and should be
6920 A common example are the so-called "plug-ins",
6921 internal shared objects that are dynamically loaded by
6922 programs using <manref name="dlopen" section="3">.
6927 Packages containing shared libraries that may be linked to
6928 by other packages' binaries, but which for some
6929 <em>compelling</em> reason can not be installed in
6930 <file>/usr/lib</file> directory, may install the shared library
6931 files in subdirectories of the <file>/usr/lib</file> directory,
6932 in which case they should arrange to add that directory in
6933 <file>/etc/ld.so.conf</file> in the package's post-installation
6934 script, and remove it in the package's post-removal script.
6938 An ever increasing number of packages are using
6939 <prgn>libtool</prgn> to do their linking. The latest GNU
6940 libtools (>= 1.3a) can take advantage of the metadata in the
6941 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6942 files). The main advantage of <prgn>libtool</prgn>'s
6943 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6944 store and subsequently access metadata with respect to the
6945 libraries it builds. <prgn>libtool</prgn> will search for
6946 those files, which contain a lot of useful information about
6947 a library (such as library dependency information for static
6948 linking). Also, they're <em>essential</em> for programs
6949 using <tt>libltdl</tt>.<footnote>
6950 Although <prgn>libtool</prgn> is fully capable of
6951 linking against shared libraries which don't have
6952 <tt>.la</tt> files, as it is a mere shell script it can
6953 add considerably to the build time of a
6954 <prgn>libtool</prgn>-using package if that shell script
6955 has to derive all this information from first principles
6956 for each library every time it is linked. With the
6957 advent of <prgn>libtool</prgn> version 1.4 (and to a
6958 lesser extent <prgn>libtool</prgn> version 1.3), the
6959 <file>.la</file> files also store information about
6960 inter-library dependencies which cannot necessarily be
6961 derived after the <file>.la</file> file is deleted.
6966 Packages that use <prgn>libtool</prgn> to create shared
6967 libraries should include the <file>.la</file> files in the
6968 <tt>-dev</tt> package, unless the package relies on
6969 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6970 the <tt>.la</tt> files must go in the run-time library
6975 You must make sure that you use only released versions of
6976 shared libraries to build your packages; otherwise other
6977 users will not be able to run your binaries
6978 properly. Producing source packages that depend on
6979 unreleased compilers is also usually a bad
6986 <heading>Shared libraries</heading>
6988 This section has moved to <ref id="sharedlibs">.
6994 <heading>Scripts</heading>
6997 All command scripts, including the package maintainer
6998 scripts inside the package and used by <prgn>dpkg</prgn>,
6999 should have a <tt>#!</tt> line naming the shell to be used
7004 In the case of Perl scripts this should be
7005 <tt>#!/usr/bin/perl</tt>.
7009 When scripts are installed into a directory in the system
7010 PATH, the script name should not include an extension such
7011 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7012 language currently used to implement it.
7015 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7016 should almost certainly start with <tt>set -e</tt> so that
7017 errors are detected. Every script should use
7018 <tt>set -e</tt> or check the exit status of <em>every</em>
7023 Scripts may assume that <file>/bin/sh</file> implements the
7024 SUSv3 Shell Command Language<footnote>
7025 Single UNIX Specification, version 3, which is also IEEE
7026 1003.1-2004 (POSIX), and is available on the World Wide Web
7027 from <url id="http://www.unix.org/version3/online.html"
7028 name="The Open Group"> after free
7029 registration.</footnote>
7030 plus the following additional features not mandated by
7032 These features are in widespread use in the Linux community
7033 and are implemented in all of bash, dash, and ksh, the most
7034 common shells users may wish to use as <file>/bin/sh</file>.
7037 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7038 must not generate a newline.</item>
7039 <item><tt>test</tt>, if implemented as a shell built-in, must
7040 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7042 <item><tt>local</tt> to create a scoped variable must be
7043 supported, including listing multiple variables in a single
7044 local command and assigning a value to a variable at the
7045 same time as localizing it. <tt>local</tt> may or
7046 may not preserve the variable value from an outer scope if
7047 no assignment is present. Uses such as:
7051 # ... use a, b, c, d ...
7054 must be supported and must set the value of <tt>c</tt> to
7058 If a shell script requires non-SUSv3 features from the shell
7059 interpreter other than those listed above, the appropriate shell
7060 must be specified in the first line of the script (e.g.,
7061 <tt>#!/bin/bash</tt>) and the package must depend on the package
7062 providing the shell (unless the shell package is marked
7063 "Essential", as in the case of <prgn>bash</prgn>).
7067 You may wish to restrict your script to SUSv3 features plus the
7068 above set when possible so that it may use <file>/bin/sh</file>
7069 as its interpreter. If your script works with <prgn>dash</prgn>
7070 (originally called <prgn>ash</prgn>), it probably complies with
7071 the above requirements, but if you are in doubt, use
7072 <file>/bin/bash</file>.
7076 Perl scripts should check for errors when making any
7077 system calls, including <tt>open</tt>, <tt>print</tt>,
7078 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7082 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7083 scripting languages. See <em>Csh Programming Considered
7084 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7085 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7086 If an upstream package comes with <prgn>csh</prgn> scripts
7087 then you must make sure that they start with
7088 <tt>#!/bin/csh</tt> and make your package depend on the
7089 <prgn>c-shell</prgn> virtual package.
7093 Any scripts which create files in world-writeable
7094 directories (e.g., in <file>/tmp</file>) must use a
7095 mechanism which will fail atomically if a file with the same
7096 name already exists.
7100 The Debian base system provides the <prgn>tempfile</prgn>
7101 and <prgn>mktemp</prgn> utilities for use by scripts for
7108 <heading>Symbolic links</heading>
7111 In general, symbolic links within a top-level directory
7112 should be relative, and symbolic links pointing from one
7113 top-level directory into another should be absolute. (A
7114 top-level directory is a sub-directory of the root
7115 directory <file>/</file>.)
7119 In addition, symbolic links should be specified as short as
7120 possible, i.e., link targets like <file>foo/../bar</file> are
7125 Note that when creating a relative link using
7126 <prgn>ln</prgn> it is not necessary for the target of the
7127 link to exist relative to the working directory you're
7128 running <prgn>ln</prgn> from, nor is it necessary to change
7129 directory to the directory where the link is to be made.
7130 Simply include the string that should appear as the target
7131 of the link (this will be a pathname relative to the
7132 directory in which the link resides) as the first argument
7137 For example, in your <prgn>Makefile</prgn> or
7138 <file>debian/rules</file>, you can do things like:
7139 <example compact="compact">
7140 ln -fs gcc $(prefix)/bin/cc
7141 ln -fs gcc debian/tmp/usr/bin/cc
7142 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7143 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7148 A symbolic link pointing to a compressed file should always
7149 have the same file extension as the referenced file. (For
7150 example, if a file <file>foo.gz</file> is referenced by a
7151 symbolic link, the filename of the link has to end with
7152 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7157 <heading>Device files</heading>
7160 Packages must not include device files in the package file
7165 If a package needs any special device files that are not
7166 included in the base system, it must call
7167 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7168 after notifying the user<footnote>
7169 This notification could be done via a (low-priority)
7170 debconf message, or an echo (printf) statement.
7175 Packages must not remove any device files in the
7176 <prgn>postrm</prgn> or any other script. This is left to the
7177 system administrator.
7181 Debian uses the serial devices
7182 <file>/dev/ttyS*</file>. Programs using the old
7183 <file>/dev/cu*</file> devices should be changed to use
7184 <file>/dev/ttyS*</file>.
7188 <sect id="config-files">
7189 <heading>Configuration files</heading>
7192 <heading>Definitions</heading>
7196 <tag>configuration file</tag>
7198 A file that affects the operation of a program, or
7199 provides site- or host-specific information, or
7200 otherwise customizes the behavior of a program.
7201 Typically, configuration files are intended to be
7202 modified by the system administrator (if needed or
7203 desired) to conform to local policy or to provide
7204 more useful site-specific behavior.
7207 <tag><tt>conffile</tt></tag>
7209 A file listed in a package's <tt>conffiles</tt>
7210 file, and is treated specially by <prgn>dpkg</prgn>
7211 (see <ref id="configdetails">).
7217 The distinction between these two is important; they are
7218 not interchangeable concepts. Almost all
7219 <tt>conffile</tt>s are configuration files, but many
7220 configuration files are not <tt>conffiles</tt>.
7224 As noted elsewhere, <file>/etc/init.d</file> scripts,
7225 <file>/etc/default</file> files, scripts installed in
7226 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7227 configuration installed in <file>/etc/cron.d</file> must be
7228 treated as configuration files. In general, any script that
7229 embeds configuration information is de-facto a configuration
7230 file and should be treated as such.
7235 <heading>Location</heading>
7238 Any configuration files created or used by your package
7239 must reside in <file>/etc</file>. If there are several,
7240 consider creating a subdirectory of <file>/etc</file>
7241 named after your package.
7245 If your package creates or uses configuration files
7246 outside of <file>/etc</file>, and it is not feasible to modify
7247 the package to use <file>/etc</file> directly, put the files
7248 in <file>/etc</file> and create symbolic links to those files
7249 from the location that the package requires.
7254 <heading>Behavior</heading>
7257 Configuration file handling must conform to the following
7259 <list compact="compact">
7261 local changes must be preserved during a package
7265 configuration files must be preserved when the
7266 package is removed, and only deleted when the
7273 The easy way to achieve this behavior is to make the
7274 configuration file a <tt>conffile</tt>. This is
7275 appropriate only if it is possible to distribute a default
7276 version that will work for most installations, although
7277 some system administrators may choose to modify it. This
7278 implies that the default version will be part of the
7279 package distribution, and must not be modified by the
7280 maintainer scripts during installation (or at any other
7285 In order to ensure that local changes are preserved
7286 correctly, no package may contain or make hard links to
7287 conffiles.<footnote>
7288 Rationale: There are two problems with hard links.
7289 The first is that some editors break the link while
7290 editing one of the files, so that the two files may
7291 unwittingly become unlinked and different. The second
7292 is that <prgn>dpkg</prgn> might break the hard link
7293 while upgrading <tt>conffile</tt>s.
7298 The other way to do it is via the maintainer scripts. In
7299 this case, the configuration file must not be listed as a
7300 <tt>conffile</tt> and must not be part of the package
7301 distribution. If the existence of a file is required for
7302 the package to be sensibly configured it is the
7303 responsibility of the package maintainer to provide
7304 maintainer scripts which correctly create, update and
7305 maintain the file and remove it on purge. (See <ref
7306 id="maintainerscripts"> for more information.) These
7307 scripts must be idempotent (i.e., must work correctly if
7308 <prgn>dpkg</prgn> needs to re-run them due to errors
7309 during installation or removal), must cope with all the
7310 variety of ways <prgn>dpkg</prgn> can call maintainer
7311 scripts, must not overwrite or otherwise mangle the user's
7312 configuration without asking, must not ask unnecessary
7313 questions (particularly during upgrades), and must
7314 otherwise be good citizens.
7318 The scripts are not required to configure every possible
7319 option for the package, but only those necessary to get
7320 the package running on a given system. Ideally the
7321 sysadmin should not have to do any configuration other
7322 than that done (semi-)automatically by the
7323 <prgn>postinst</prgn> script.
7327 A common practice is to create a script called
7328 <file><var>package</var>-configure</file> and have the
7329 package's <prgn>postinst</prgn> call it if and only if the
7330 configuration file does not already exist. In certain
7331 cases it is useful for there to be an example or template
7332 file which the maintainer scripts use. Such files should
7333 be in <file>/usr/share/<var>package</var></file> or
7334 <file>/usr/lib/<var>package</var></file> (depending on whether
7335 they are architecture-independent or not). There should
7336 be symbolic links to them from
7337 <file>/usr/share/doc/<var>package</var>/examples</file> if
7338 they are examples, and should be perfectly ordinary
7339 <prgn>dpkg</prgn>-handled files (<em>not</em>
7340 configuration files).
7344 These two styles of configuration file handling must
7345 not be mixed, for that way lies madness:
7346 <prgn>dpkg</prgn> will ask about overwriting the file
7347 every time the package is upgraded.
7352 <heading>Sharing configuration files</heading>
7355 Packages which specify the same file as a
7356 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7357 with each other. (This is an instance of the general rule
7358 about not sharing files. Note that neither alternatives
7359 nor diversions are likely to be appropriate in this case;
7360 in particular, <prgn>dpkg</prgn> does not handle diverted
7361 <tt>conffile</tt>s well.)
7365 The maintainer scripts must not alter a <tt>conffile</tt>
7366 of <em>any</em> package, including the one the scripts
7371 If two or more packages use the same configuration file
7372 and it is reasonable for both to be installed at the same
7373 time, one of these packages must be defined as
7374 <em>owner</em> of the configuration file, i.e., it will be
7375 the package which handles that file as a configuration
7376 file. Other packages that use the configuration file must
7377 depend on the owning package if they require the
7378 configuration file to operate. If the other package will
7379 use the configuration file if present, but is capable of
7380 operating without it, no dependency need be declared.
7384 If it is desirable for two or more related packages to
7385 share a configuration file <em>and</em> for all of the
7386 related packages to be able to modify that configuration
7387 file, then the following should be done:
7388 <enumlist compact="compact">
7390 One of the related packages (the "owning" package)
7391 will manage the configuration file with maintainer
7392 scripts as described in the previous section.
7395 The owning package should also provide a program
7396 that the other packages may use to modify the
7400 The related packages must use the provided program
7401 to make any desired modifications to the
7402 configuration file. They should either depend on
7403 the core package to guarantee that the configuration
7404 modifier program is available or accept gracefully
7405 that they cannot modify the configuration file if it
7406 is not. (This is in addition to the fact that the
7407 configuration file may not even be present in the
7414 Sometimes it's appropriate to create a new package which
7415 provides the basic infrastructure for the other packages
7416 and which manages the shared configuration files. (The
7417 <tt>sgml-base</tt> package is a good example.)
7422 <heading>User configuration files ("dotfiles")</heading>
7425 The files in <file>/etc/skel</file> will automatically be
7426 copied into new user accounts by <prgn>adduser</prgn>.
7427 No other program should reference the files in
7428 <file>/etc/skel</file>.
7432 Therefore, if a program needs a dotfile to exist in
7433 advance in <file>$HOME</file> to work sensibly, that dotfile
7434 should be installed in <file>/etc/skel</file> and treated as a
7439 However, programs that require dotfiles in order to
7440 operate sensibly are a bad thing, unless they do create
7441 the dotfiles themselves automatically.
7445 Furthermore, programs should be configured by the Debian
7446 default installation to behave as closely to the upstream
7447 default behavior as possible.
7451 Therefore, if a program in a Debian package needs to be
7452 configured in some way in order to operate sensibly, that
7453 should be done using a site-wide configuration file placed
7454 in <file>/etc</file>. Only if the program doesn't support a
7455 site-wide default configuration and the package maintainer
7456 doesn't have time to add it may a default per-user file be
7457 placed in <file>/etc/skel</file>.
7461 <file>/etc/skel</file> should be as empty as we can make it.
7462 This is particularly true because there is no easy (or
7463 necessarily desirable) mechanism for ensuring that the
7464 appropriate dotfiles are copied into the accounts of
7465 existing users when a package is installed.
7471 <heading>Log files</heading>
7473 Log files should usually be named
7474 <file>/var/log/<var>package</var>.log</file>. If you have many
7475 log files, or need a separate directory for permission
7476 reasons (<file>/var/log</file> is writable only by
7477 <file>root</file>), you should usually create a directory named
7478 <file>/var/log/<var>package</var></file> and place your log
7483 Log files must be rotated occasionally so that they don't
7484 grow indefinitely; the best way to do this is to drop a log
7485 rotation configuration file into the directory
7486 <file>/etc/logrotate.d</file> and use the facilities provided by
7487 logrotate.<footnote>
7489 The traditional approach to log files has been to set up
7490 <em>ad hoc</em> log rotation schemes using simple shell
7491 scripts and cron. While this approach is highly
7492 customizable, it requires quite a lot of sysadmin work.
7493 Even though the original Debian system helped a little
7494 by automatically installing a system which can be used
7495 as a template, this was deemed not enough.
7499 The use of <prgn>logrotate</prgn>, a program developed
7500 by Red Hat, is better, as it centralizes log management.
7501 It has both a configuration file
7502 (<file>/etc/logrotate.conf</file>) and a directory where
7503 packages can drop their individual log rotation
7504 configurations (<file>/etc/logrotate.d</file>).
7507 Here is a good example for a logrotate config
7508 file (for more information see <manref name="logrotate"
7510 <example compact="compact">
7511 /var/log/foo/*.log {
7516 /etc/init.d/foo force-reload
7520 This rotates all files under <file>/var/log/foo</file>, saves 12
7521 compressed generations, and forces the daemon to reload its
7522 configuration information after the log rotation.
7526 Log files should be removed when the package is
7527 purged (but not when it is only removed). This should be
7528 done by the <prgn>postrm</prgn> script when it is called
7529 with the argument <tt>purge</tt> (see <ref
7530 id="removedetails">).
7535 <heading>Permissions and owners</heading>
7538 The rules in this section are guidelines for general use.
7539 If necessary you may deviate from the details below.
7540 However, if you do so you must make sure that what is done
7541 is secure and you should try to be as consistent as possible
7542 with the rest of the system. You should probably also
7543 discuss it on <prgn>debian-devel</prgn> first.
7547 Files should be owned by <tt>root:root</tt>, and made
7548 writable only by the owner and universally readable (and
7549 executable, if appropriate), that is mode 644 or 755.
7553 Directories should be mode 755 or (for group-writability)
7554 mode 2775. The ownership of the directory should be
7555 consistent with its mode: if a directory is mode 2775, it
7556 should be owned by the group that needs write access to
7559 When a package is upgraded, and the owner or permissions
7560 of a file included in the package has changed, dpkg
7561 arranges for the ownership and permissions to be
7562 correctly set upon installation. However, this does not
7563 extend to directories; the permissions and ownership of
7564 directories already on the system does not change on
7565 install or upgrade of packages. This makes sense, since
7566 otherwise common directories like <tt>/usr</tt> would
7567 always be in flux. To correctly change permissions of a
7568 directory the package owns, explicit action is required,
7569 usually in the <tt>postinst</tt> script. Care must be
7570 taken to handle downgrades as well, in that case.
7577 Setuid and setgid executables should be mode 4755 or 2755
7578 respectively, and owned by the appropriate user or group.
7579 They should not be made unreadable (modes like 4711 or
7580 2711 or even 4111); doing so achieves no extra security,
7581 because anyone can find the binary in the freely available
7582 Debian package; it is merely inconvenient. For the same
7583 reason you should not restrict read or execute permissions
7584 on non-set-id executables.
7588 Some setuid programs need to be restricted to particular
7589 sets of users, using file permissions. In this case they
7590 should be owned by the uid to which they are set-id, and by
7591 the group which should be allowed to execute them. They
7592 should have mode 4754; again there is no point in making
7593 them unreadable to those users who must not be allowed to
7598 It is possible to arrange that the system administrator can
7599 reconfigure the package to correspond to their local
7600 security policy by changing the permissions on a binary:
7601 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7602 described below.<footnote>
7603 Ordinary files installed by <prgn>dpkg</prgn> (as
7604 opposed to <tt>conffile</tt>s and other similar objects)
7605 normally have their permissions reset to the distributed
7606 permissions when the package is reinstalled. However,
7607 the use of <prgn>dpkg-statoverride</prgn> overrides this
7608 default behavior. If you use this method, you should
7609 remember to describe <prgn>dpkg-statoverride</prgn> in
7610 the package documentation; being a relatively new
7611 addition to Debian, it is probably not yet well-known.
7613 Another method you should consider is to create a group for
7614 people allowed to use the program(s) and make any setuid
7615 executables executable only by that group.
7619 If you need to create a new user or group for your package
7620 there are two possibilities. Firstly, you may need to
7621 make some files in the binary package be owned by this
7622 user or group, or you may need to compile the user or
7623 group id (rather than just the name) into the binary
7624 (though this latter should be avoided if possible, as in
7625 this case you need a statically allocated id).</p>
7628 If you need a statically allocated id, you must ask for a
7629 user or group id from the <tt>base-passwd</tt> maintainer,
7630 and must not release the package until you have been
7631 allocated one. Once you have been allocated one you must
7632 either make the package depend on a version of the
7633 <tt>base-passwd</tt> package with the id present in
7634 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7635 your package to create the user or group itself with the
7636 correct id (using <tt>adduser</tt>) in its
7637 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7638 the <prgn>postinst</prgn> is to be preferred if it is
7639 possible, otherwise a pre-dependency will be needed on the
7640 <tt>adduser</tt> package.)
7644 On the other hand, the program might be able to determine
7645 the uid or gid from the user or group name at runtime, so
7646 that a dynamically allocated id can be used. In this case
7647 you should choose an appropriate user or group name,
7648 discussing this on <prgn>debian-devel</prgn> and checking
7649 with the <package/base-passwd/ maintainer that it is unique and that
7650 they do not wish you to use a statically allocated id
7651 instead. When this has been checked you must arrange for
7652 your package to create the user or group if necessary using
7653 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7654 <prgn>postinst</prgn> script (again, the latter is to be
7655 preferred if it is possible).
7659 Note that changing the numeric value of an id associated
7660 with a name is very difficult, and involves searching the
7661 file system for all appropriate files. You need to think
7662 carefully whether a static or dynamic id is required, since
7663 changing your mind later will cause problems.
7666 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7668 This section is not intended as policy, but as a
7669 description of the use of <prgn>dpkg-statoverride</prgn>.
7673 If a system administrator wishes to have a file (or
7674 directory or other such thing) installed with owner and
7675 permissions different from those in the distributed Debian
7676 package, they can use the <prgn>dpkg-statoverride</prgn>
7677 program to instruct <prgn>dpkg</prgn> to use the different
7678 settings every time the file is installed. Thus the
7679 package maintainer should distribute the files with their
7680 normal permissions, and leave it for the system
7681 administrator to make any desired changes. For example, a
7682 daemon which is normally required to be setuid root, but
7683 in certain situations could be used without being setuid,
7684 should be installed setuid in the <tt>.deb</tt>. Then the
7685 local system administrator can change this if they wish.
7686 If there are two standard ways of doing it, the package
7687 maintainer can use <tt>debconf</tt> to find out the
7688 preference, and call <prgn>dpkg-statoverride</prgn> in the
7689 maintainer script if necessary to accommodate the system
7690 administrator's choice. Care must be taken during
7691 upgrades to not override an existing setting.
7695 Given the above, <prgn>dpkg-statoverride</prgn> is
7696 essentially a tool for system administrators and would not
7697 normally be needed in the maintainer scripts. There is
7698 one type of situation, though, where calls to
7699 <prgn>dpkg-statoverride</prgn> would be needed in the
7700 maintainer scripts, and that involves packages which use
7701 dynamically allocated user or group ids. In such a
7702 situation, something like the following idiom can be very
7703 helpful in the package's <prgn>postinst</prgn>, where
7704 <tt>sysuser</tt> is a dynamically allocated id:
7706 for i in /usr/bin/foo /usr/sbin/bar
7708 # only do something when no setting exists
7709 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7711 #include: debconf processing, question about foo and bar
7712 if [ "$RET" = "true" ] ; then
7713 dpkg-statoverride --update --add sysuser root 4755 $i
7718 The corresponding <tt>dpkg-statoverride --remove</tt>
7719 calls can then be made unconditionally when the package is
7727 <chapt id="customized-programs">
7728 <heading>Customized programs</heading>
7730 <sect id="arch-spec">
7731 <heading>Architecture specification strings</heading>
7734 If a program needs to specify an <em>architecture specification
7735 string</em> in some place, it should select one of the
7736 strings provided by <tt>dpkg-architecture -L</tt>. The
7737 strings are in the format
7738 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7739 is sometimes elided, as when the OS is Linux.<footnote>
7740 <p>Currently, the strings are:
7741 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7742 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7743 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7744 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7745 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7746 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7747 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7748 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7749 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7750 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7751 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7752 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7753 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7754 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7755 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7756 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7757 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7758 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7759 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7760 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7761 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7762 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7763 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7764 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7765 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7766 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7767 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7768 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7769 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7770 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7771 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7772 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7773 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7774 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7775 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7776 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7777 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7783 Note that we don't want to use
7784 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7785 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7786 since this would make our programs incompatible with other
7787 Linux distributions. We also don't use something like
7788 <tt><var>arch</var>-unknown-linux</tt>, since the
7789 <tt>unknown</tt> does not look very good.
7794 <heading>Daemons</heading>
7797 The configuration files <file>/etc/services</file>,
7798 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7799 by the <prgn>netbase</prgn> package and must not be modified
7804 If a package requires a new entry in one of these files, the
7805 maintainer should get in contact with the
7806 <prgn>netbase</prgn> maintainer, who will add the entries
7807 and release a new version of the <prgn>netbase</prgn>
7812 The configuration file <file>/etc/inetd.conf</file> must not be
7813 modified by the package's scripts except via the
7814 <prgn>update-inetd</prgn> script or the
7815 <file>DebianNet.pm</file> Perl module. See their documentation
7816 for details on how to add entries.
7820 If a package wants to install an example entry into
7821 <file>/etc/inetd.conf</file>, the entry must be preceded with
7822 exactly one hash character (<tt>#</tt>). Such lines are
7823 treated as "commented out by user" by the
7824 <prgn>update-inetd</prgn> script and are not changed or
7825 activated during package updates.
7830 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7834 Some programs need to create pseudo-ttys. This should be done
7835 using Unix98 ptys if the C library supports it. The resulting
7836 program must not be installed setuid root, unless that
7837 is required for other functionality.
7841 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7842 <file>/var/log/lastlog</file> must be installed writable by
7843 group <tt>utmp</tt>. Programs which need to modify those
7844 files must be installed setgid <tt>utmp</tt>.
7849 <heading>Editors and pagers</heading>
7852 Some programs have the ability to launch an editor or pager
7853 program to edit or display a text document. Since there are
7854 lots of different editors and pagers available in the Debian
7855 distribution, the system administrator and each user should
7856 have the possibility to choose their preferred editor and
7861 In addition, every program should choose a good default
7862 editor/pager if none is selected by the user or system
7867 Thus, every program that launches an editor or pager must
7868 use the EDITOR or PAGER environment variable to determine
7869 the editor or pager the user wishes to use. If these
7870 variables are not set, the programs <file>/usr/bin/editor</file>
7871 and <file>/usr/bin/pager</file> should be used, respectively.
7875 These two files are managed through the <prgn>dpkg</prgn>
7876 "alternatives" mechanism. Thus every package providing an
7877 editor or pager must call the
7878 <prgn>update-alternatives</prgn> script to register these
7883 If it is very hard to adapt a program to make use of the
7884 EDITOR or PAGER variables, that program may be configured to
7885 use <file>/usr/bin/sensible-editor</file> and
7886 <file>/usr/bin/sensible-pager</file> as the editor or pager
7887 program respectively. These are two scripts provided in the
7888 Debian base system that check the EDITOR and PAGER variables
7889 and launch the appropriate program, and fall back to
7890 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7891 variable is not set.
7895 A program may also use the VISUAL environment variable to
7896 determine the user's choice of editor. If it exists, it
7897 should take precedence over EDITOR. This is in fact what
7898 <file>/usr/bin/sensible-editor</file> does.
7902 It is not required for a package to depend on
7903 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7904 package to provide such virtual packages.<footnote>
7905 The Debian base system already provides an editor and a
7911 <sect id="web-appl">
7912 <heading>Web servers and applications</heading>
7915 This section describes the locations and URLs that should
7916 be used by all web servers and web applications in the
7923 Cgi-bin executable files are installed in the
7925 <example compact="compact">
7926 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7928 and should be referred to as
7929 <example compact="compact">
7930 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7936 <p>Access to HTML documents</p>
7939 HTML documents for a package are stored in
7940 <file>/usr/share/doc/<var>package</var></file>
7941 and can be referred to as
7942 <example compact="compact">
7943 http://localhost/doc/<var>package</var>/<var>filename</var>
7948 The web server should restrict access to the document
7949 tree so that only clients on the same host can read
7950 the documents. If the web server does not support such
7951 access controls, then it should not provide access at
7952 all, or ask about providing access during installation.
7957 <p>Access to images</p>
7959 It is recommended that images for a package be stored
7960 in <tt>/usr/share/images/<var>package</var></tt> and
7961 may be referred to through an alias <tt>/images/</tt>
7964 http://localhost/images/<package>/<filename>
7971 <p>Web Document Root</p>
7974 Web Applications should try to avoid storing files in
7975 the Web Document Root. Instead they should use the
7976 /usr/share/doc/<var>package</var> directory for
7977 documents and register the Web Application via the
7978 <package>doc-base</package> package. If access to the
7979 web document root is unavoidable then use
7980 <example compact="compact">
7983 as the Document Root. This might be just a symbolic
7984 link to the location where the system administrator
7985 has put the real document root.
7988 <item><p>Providing httpd and/or httpd-cgi</p>
7990 All web servers should provide the virtual package
7991 <tt>httpd</tt>. If a web server has CGI support it should
7992 provide <tt>httpd-cgi</tt> additionally.
7995 All web applications which do not contain CGI scripts should
7996 depend on <tt>httpd</tt>, all those web applications which
7997 <tt>do</tt> contain CGI scripts, should depend on
8005 <sect id="mail-transport-agents">
8006 <heading>Mail transport, delivery and user agents</heading>
8009 Debian packages which process electronic mail, whether mail
8010 user agents (MUAs) or mail transport agents (MTAs), must
8011 ensure that they are compatible with the configuration
8012 decisions below. Failure to do this may result in lost
8013 mail, broken <tt>From:</tt> lines, and other serious brain
8018 The mail spool is <file>/var/mail</file> and the interface to
8019 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8020 the FHS). On older systems, the mail spool may be
8021 physically located in <file>/var/spool/mail</file>, but all
8022 access to the mail spool should be via the
8023 <file>/var/mail</file> symlink. The mail spool is part of the
8024 base system and not part of the MTA package.
8028 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8029 programs (such as IMAP daemons) must lock the mailbox in an
8030 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8031 be combined with dot locking. To avoid deadlocks, a program
8032 should use <tt>fcntl()</tt> first and dot locking after
8033 this, or alternatively implement the two locking methods in
8034 a non blocking way<footnote>
8035 If it is not possible to establish both locks, the
8036 system shouldn't wait for the second lock to be
8037 established, but remove the first lock, wait a (random)
8038 time, and start over locking again.
8039 </footnote>. Using the functions <tt>maillock</tt> and
8040 <tt>mailunlock</tt> provided by the
8041 <tt>liblockfile*</tt><footnote>
8042 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8043 to use these functions.
8044 </footnote> packages is the recommended way to realize this.
8048 Mailboxes are generally mode 660
8049 <tt><var>user</var>:mail</tt> unless the system
8050 administrator has chosen otherwise. A MUA may remove a
8051 mailbox (unless it has nonstandard permissions) in which
8052 case the MTA or another MUA must recreate it if needed.
8053 Mailboxes must be writable by group mail.
8057 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8058 be setgid mail to do the locking mentioned above (and
8059 must obviously avoid accessing other users' mailboxes
8060 using this privilege).</p>
8063 <file>/etc/aliases</file> is the source file for the system mail
8064 aliases (e.g., postmaster, usenet, etc.), it is the one
8065 which the sysadmin and <prgn>postinst</prgn> scripts may
8066 edit. After <file>/etc/aliases</file> is edited the program or
8067 human editing it must call <prgn>newaliases</prgn>. All MTA
8068 packages must come with a <prgn>newaliases</prgn> program,
8069 even if it does nothing, but older MTA packages did not do
8070 this so programs should not fail if <prgn>newaliases</prgn>
8071 cannot be found. Note that because of this, all MTA
8072 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8073 <tt>Replaces: mail-transport-agent</tt> control file
8078 The convention of writing <tt>forward to
8079 <var>address</var></tt> in the mailbox itself is not
8080 supported. Use a <tt>.forward</tt> file instead.</p>
8083 The <prgn>rmail</prgn> program used by UUCP
8084 for incoming mail should be <file>/usr/sbin/rmail</file>.
8085 Likewise, <prgn>rsmtp</prgn>, for receiving
8086 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8090 If your package needs to know what hostname to use on (for
8091 example) outgoing news and mail messages which are generated
8092 locally, you should use the file <file>/etc/mailname</file>. It
8093 will contain the portion after the username and <tt>@</tt>
8094 (at) sign for email addresses of users on the machine
8095 (followed by a newline).
8099 Such a package should check for the existence of this file
8100 when it is being configured. If it exists, it should be
8101 used without comment, although an MTA's configuration script
8102 may wish to prompt the user even if it finds that this file
8103 exists. If the file does not exist, the package should
8104 prompt the user for the value (preferably using
8105 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8106 as well as using it in the package's configuration. The
8107 prompt should make it clear that the name will not just be
8108 used by that package. For example, in this situation the
8109 <tt>inn</tt> package could say something like:
8110 <example compact="compact">
8111 Please enter the "mail name" of your system. This is the
8112 hostname portion of the address to be shown on outgoing
8113 news and mail messages. The default is
8114 <var>syshostname</var>, your system's host name. Mail
8115 name ["<var>syshostname</var>"]:
8117 where <var>syshostname</var> is the output of <tt>hostname
8123 <heading>News system configuration</heading>
8126 All the configuration files related to the NNTP (news)
8127 servers and clients should be located under
8128 <file>/etc/news</file>.</p>
8131 There are some configuration issues that apply to a number
8132 of news clients and server packages on the machine. These
8136 <tag><file>/etc/news/organization</file></tag>
8138 A string which should appear as the
8139 organization header for all messages posted
8140 by NNTP clients on the machine
8143 <tag><file>/etc/news/server</file></tag>
8145 Contains the FQDN of the upstream NNTP
8146 server, or localhost if the local machine is
8151 Other global files may be added as required for cross-package news
8158 <heading>Programs for the X Window System</heading>
8161 <heading>Providing X support and package priorities</heading>
8164 Programs that can be configured with support for the X
8165 Window System must be configured to do so and must declare
8166 any package dependencies necessary to satisfy their
8167 runtime requirements when using the X Window System. If
8168 such a package is of higher priority than the X packages
8169 on which it depends, it is required that either the
8170 X-specific components be split into a separate package, or
8171 that an alternative version of the package, which includes
8172 X support, be provided, or that the package's priority be
8178 <heading>Packages providing an X server</heading>
8181 Packages that provide an X server that, directly or
8182 indirectly, communicates with real input and display
8183 hardware should declare in their control data that they
8184 provide the virtual package <tt>xserver</tt>.<footnote>
8185 This implements current practice, and provides an
8186 actual policy for usage of the <tt>xserver</tt>
8187 virtual package which appears in the virtual packages
8188 list. In a nutshell, X servers that interface
8189 directly with the display and input hardware or via
8190 another subsystem (e.g., GGI) should provide
8191 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8192 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8198 <heading>Packages providing a terminal emulator</heading>
8201 Packages that provide a terminal emulator for the X Window
8202 System which meet the criteria listed below should declare
8203 in their control data that they provide the virtual
8204 package <tt>x-terminal-emulator</tt>. They should also
8205 register themselves as an alternative for
8206 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8211 To be an <tt>x-terminal-emulator</tt>, a program must:
8212 <list compact="compact">
8214 Be able to emulate a DEC VT100 terminal, or a
8215 compatible terminal.
8219 Support the command-line option <tt>-e
8220 <var>command</var></tt>, which creates a new
8221 terminal window<footnote>
8222 "New terminal window" does not necessarily mean
8223 a new top-level X window directly parented by
8224 the window manager; it could, if the terminal
8225 emulator application were so coded, be a new
8226 "view" in a multiple-document interface (MDI).
8228 and runs the specified <var>command</var>,
8229 interpreting the entirety of the rest of the command
8230 line as a command to pass straight to exec, in the
8231 manner that <tt>xterm</tt> does.
8235 Support the command-line option <tt>-T
8236 <var>title</var></tt>, which creates a new terminal
8237 window with the window title <var>title</var>.
8244 <heading>Packages providing a window manager</heading>
8247 Packages that provide a window manager should declare in
8248 their control data that they provide the virtual package
8249 <tt>x-window-manager</tt>. They should also register
8250 themselves as an alternative for
8251 <file>/usr/bin/x-window-manager</file>, with a priority
8252 calculated as follows:
8253 <list compact="compact">
8255 Start with a priority of 20.
8259 If the window manager supports the Debian menu
8260 system, add 20 points if this support is available
8261 in the package's default configuration (i.e., no
8262 configuration files belonging to the system or user
8263 have to be edited to activate the feature); if
8264 configuration files must be modified, add only 10
8270 If the window manager complies with <url
8271 id="http://www.freedesktop.org/Standards/wm-spec"
8272 name="The Window Manager Specification Project">,
8273 written by the <url id="http://www.freedesktop.org/"
8274 name="Free Desktop Group">, add 40 points.
8278 If the window manager permits the X session to be
8279 restarted using a <em>different</em> window manager
8280 (without killing the X server) in its default
8281 configuration, add 10 points; otherwise add none.
8288 <heading>Packages providing fonts</heading>
8291 Packages that provide fonts for the X Window
8293 For the purposes of Debian Policy, a "font for the X
8294 Window System" is one which is accessed via X protocol
8295 requests. Fonts for the Linux console, for PostScript
8296 renderer, or any other purpose, do not fit this
8297 definition. Any tool which makes such fonts available
8298 to the X Window System, however, must abide by this
8301 must do a number of things to ensure that they are both
8302 available without modification of the X or font server
8303 configuration, and that they do not corrupt files used by
8304 other font packages to register information about
8308 Fonts of any type supported by the X Window System
8309 must be in a separate binary package from any
8310 executables, libraries, or documentation (except
8311 that specific to the fonts shipped, such as their
8312 license information). If one or more of the fonts
8313 so packaged are necessary for proper operation of
8314 the package with which they are associated the font
8315 package may be Recommended; if the fonts merely
8316 provide an enhancement, a Suggests relationship may
8317 be used. Packages must not Depend on font
8319 This is because the X server may retrieve fonts
8320 from the local file system or over the network
8321 from an X font server; the Debian package system
8322 is empowered to deal only with the local
8328 BDF fonts must be converted to PCF fonts with the
8329 <prgn>bdftopcf</prgn> utility (available in the
8330 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8331 placed in a directory that corresponds to their
8333 <list compact="compact">
8335 100 dpi fonts must be placed in
8336 <file>/usr/share/fonts/X11/100dpi/</file>.
8340 75 dpi fonts must be placed in
8341 <file>/usr/share/fonts/X11/75dpi/</file>.
8345 Character-cell fonts, cursor fonts, and other
8346 low-resolution fonts must be placed in
8347 <file>/usr/share/fonts/X11/misc/</file>.
8353 Speedo fonts must be placed in
8354 <file>/usr/share/fonts/X11/Speedo/</file>.
8358 Type 1 fonts must be placed in
8359 <file>/usr/share/fonts/X11/Type1/</file>. If font
8360 metric files are available, they must be placed here
8365 Subdirectories of <file>/usr/share/fonts/X11/</file>
8366 other than those listed above must be neither
8367 created nor used. (The <file>PEX</file>, <file>CID</file>,
8368 and <file>cyrillic</file> directories are excepted for
8369 historical reasons, but installation of files into
8370 these directories remains discouraged.)
8374 Font packages may, instead of placing files directly
8375 in the X font directories listed above, provide
8376 symbolic links in that font directory pointing to
8377 the files' actual location in the filesystem. Such
8378 a location must comply with the FHS.
8382 Font packages should not contain both 75dpi and
8383 100dpi versions of a font. If both are available,
8384 they should be provided in separate binary packages
8385 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8386 the names of the packages containing the
8387 corresponding fonts.
8391 Fonts destined for the <file>misc</file> subdirectory
8392 should not be included in the same package as 75dpi
8393 or 100dpi fonts; instead, they should be provided in
8394 a separate package with <tt>-misc</tt> appended to
8399 Font packages must not provide the files
8400 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8401 <file>fonts.scale</file> in a font directory:
8404 <file>fonts.dir</file> files must not be provided at all.
8408 <file>fonts.alias</file> and <file>fonts.scale</file>
8409 files, if needed, should be provided in the
8411 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8412 where <var>fontdir</var> is the name of the
8414 <file>/usr/share/fonts/X11/</file> where the
8415 package's corresponding fonts are stored
8416 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8417 <var>package</var> is the name of the package
8418 that provides these fonts, and
8419 <var>extension</var> is either <tt>scale</tt>
8420 or <tt>alias</tt>, whichever corresponds to
8427 Font packages must declare a dependency on
8428 <tt>xfonts-utils</tt> in their control
8433 Font packages that provide one or more
8434 <file>fonts.scale</file> files as described above must
8435 invoke <prgn>update-fonts-scale</prgn> on each
8436 directory into which they installed fonts
8437 <em>before</em> invoking
8438 <prgn>update-fonts-dir</prgn> on that directory.
8439 This invocation must occur in both the
8440 <prgn>postinst</prgn> (for all arguments) and
8441 <prgn>postrm</prgn> (for all arguments except
8442 <tt>upgrade</tt>) scripts.
8446 Font packages that provide one or more
8447 <file>fonts.alias</file> files as described above must
8448 invoke <prgn>update-fonts-alias</prgn> on each
8449 directory into which they installed fonts. This
8450 invocation must occur in both the
8451 <prgn>postinst</prgn> (for all arguments) and
8452 <prgn>postrm</prgn> (for all arguments except
8453 <tt>upgrade</tt>) scripts.
8457 Font packages must invoke
8458 <prgn>update-fonts-dir</prgn> on each directory into
8459 which they installed fonts. This invocation must
8460 occur in both the <prgn>postinst</prgn> (for all
8461 arguments) and <prgn>postrm</prgn> (for all
8462 arguments except <tt>upgrade</tt>) scripts.
8466 Font packages must not provide alias names for the
8467 fonts they include which collide with alias names
8468 already in use by fonts already packaged.
8472 Font packages must not provide fonts with the same
8473 XLFD registry name as another font already packaged.
8480 <heading>Application defaults files</heading>
8483 Application defaults files must be installed in the
8484 directory <file>/etc/X11/app-defaults/</file> (use of a
8485 localized subdirectory of <file>/etc/X11/</file> as described
8486 in the <em>X Toolkit Intrinsics - C Language
8487 Interface</em> manual is also permitted). They must be
8488 registered as <tt>conffile</tt>s or handled as
8489 configuration files.
8493 Customization of programs' X resources may also be
8494 supported with the provision of a file with the same name
8495 as that of the package placed in the
8496 <file>/etc/X11/Xresources/</file> directory, which must
8497 registered as a <tt>conffile</tt> or handled as a
8498 configuration file.<footnote>
8499 Note that this mechanism is not the same as using
8500 app-defaults; app-defaults are tied to the client
8501 binary on the local file system, whereas X resources
8502 are stored in the X server and affect all connecting
8509 <heading>Installation directory issues</heading>
8512 Packages using the X Window System should not be
8513 configured to install files under the
8514 <file>/usr/X11R6/</file> directory. The
8515 <file>/usr/X11R6/</file> directory hierarchy should be
8516 regarded as obsolete.
8520 Programs that use GNU <prgn>autoconf</prgn> and
8521 <prgn>automake</prgn> are usually easily configured at
8522 compile time to use <file>/usr/</file> instead of
8523 <file>/usr/X11R6/</file>, and this should be done whenever
8524 possible. Configuration files for window managers and
8525 display managers should be placed in a subdirectory of
8526 <file>/etc/X11/</file> corresponding to the package name due
8527 to these programs' tight integration with the mechanisms
8528 of the X Window System. Application-level programs should
8529 use the <file>/etc/</file> directory unless otherwise mandated
8534 The installation of files into subdirectories
8535 of <file>/usr/X11R6/include/X11/</file> and
8536 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8537 package maintainers should determine if subdirectories of
8538 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8543 Packages should install any relevant files into the
8544 directories <file>/usr/include/X11/</file> and
8545 <file>/usr/lib/X11/</file>, but if they do so, they must
8546 pre-depend on <tt>x11-common (>=
8547 1:7.0.0)</tt><footnote>
8549 These libraries used to be all symbolic
8550 links. However, with <tt>X11R7</tt>,
8551 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8552 are now real directories, and packages
8553 <strong>should</strong> ship their files here instead
8554 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8555 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8556 responsible for converting these symlinks into
8564 <heading>The OSF/Motif and OpenMotif libraries</heading>
8567 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8568 OpenMotif libraries</em><footnote>
8569 OSF/Motif and OpenMotif are collectively referred to as
8570 "Motif" in this policy document.
8572 should be compiled against and tested with LessTif (a free
8573 re-implementation of Motif) instead. If the maintainer
8574 judges that the program or programs do not work
8575 sufficiently well with LessTif to be distributed and
8576 supported, but do so when compiled against Motif, then two
8577 versions of the package should be created; one linked
8578 statically against Motif and with <tt>-smotif</tt>
8579 appended to the package name, and one linked dynamically
8580 against Motif and with <tt>-dmotif</tt> appended to the
8585 Both Motif-linked versions are dependent
8586 upon non-DFSG-compliant software and thus cannot be
8587 uploaded to the <em>main</em> distribution; if the
8588 software is itself DFSG-compliant it may be uploaded to
8589 the <em>contrib</em> distribution. While known existing
8590 versions of Motif permit unlimited redistribution of
8591 binaries linked against the library (whether statically or
8592 dynamically), it is the package maintainer's
8593 responsibility to determine whether this is permitted by
8594 the license of the copy of Motif in their possession.
8600 <heading>Perl programs and modules</heading>
8603 Perl programs and modules should follow the current Perl policy.
8607 The Perl policy can be found in the <tt>perl-policy</tt>
8608 files in the <tt>debian-policy</tt> package.
8609 It is also available from the Debian web mirrors at
8610 <tt><url name="/doc/packaging-manuals/perl-policy/"
8611 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8616 <heading>Emacs lisp programs</heading>
8619 Please refer to the "Debian Emacs Policy" for details of how to
8620 package emacs lisp programs.
8624 The Emacs policy is available in
8625 <file>debian-emacs-policy.gz</file> of the
8626 <package>emacsen-common</package> package.
8627 It is also available from the Debian web mirrors at
8628 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8629 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8634 <heading>Games</heading>
8637 The permissions on <file>/var/games</file> are mode 755, owner
8638 <tt>root</tt> and group <tt>root</tt>.
8642 Each game decides on its own security policy.</p>
8645 Games which require protected, privileged access to
8646 high-score files, saved games, etc., may be made
8647 set-<em>group</em>-id (mode 2755) and owned by
8648 <tt>root:games</tt>, and use files and directories with
8649 appropriate permissions (770 <tt>root:games</tt>, for
8650 example). They must not be made
8651 set-<em>user</em>-id, as this causes security problems. (If
8652 an attacker can subvert any set-user-id game they can
8653 overwrite the executable of any other, causing other players
8654 of these games to run a Trojan horse program. With a
8655 set-group-id game the attacker only gets access to less
8656 important game data, and if they can get at the other
8657 players' accounts at all it will take considerably more
8661 Some packages, for example some fortune cookie programs, are
8662 configured by the upstream authors to install with their
8663 data files or other static information made unreadable so
8664 that they can only be accessed through set-id programs
8665 provided. You should not do this in a Debian package: anyone can
8666 download the <file>.deb</file> file and read the data from it,
8667 so there is no point making the files unreadable. Not
8668 making the files unreadable also means that you don't have
8669 to make so many programs set-id, which reduces the risk of a
8673 As described in the FHS, binaries of games should be
8674 installed in the directory <file>/usr/games</file>. This also
8675 applies to games that use the X Window System. Manual pages
8676 for games (X and non-X games) should be installed in
8677 <file>/usr/share/man/man6</file>.</p>
8683 <heading>Documentation</heading>
8686 <heading>Manual pages</heading>
8689 You should install manual pages in <prgn>nroff</prgn> source
8690 form, in appropriate places under <file>/usr/share/man</file>.
8691 You should only use sections 1 to 9 (see the FHS for more
8692 details). You must not install a pre-formatted "cat page".
8696 Each program, utility, and function should have an
8697 associated manual page included in the same package. It is
8698 suggested that all configuration files also have a manual
8699 page included as well. Manual pages for protocols and other
8700 auxiliary things are optional.
8704 If no manual page is available, this is considered as a bug
8705 and should be reported to the Debian Bug Tracking System (the
8706 maintainer of the package is allowed to write this bug report
8707 themselves, if they so desire). Do not close the bug report
8708 until a proper man page is available.<footnote>
8709 It is not very hard to write a man page. See the
8710 <url id="http://www.schweikhardt.net/man_page_howto.html"
8711 name="Man-Page-HOWTO">,
8712 <manref name="man" section="7">, the examples
8713 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8714 the helper programs <prgn>help2man</prgn>, or the
8715 directory <file>/usr/share/doc/man-db/examples</file>.
8720 You may forward a complaint about a missing man page to the
8721 upstream authors, and mark the bug as forwarded in the
8722 Debian bug tracking system. Even though the GNU Project do
8723 not in general consider the lack of a man page to be a bug,
8724 we do; if they tell you that they don't consider it a bug
8725 you should leave the bug in our bug tracking system open
8730 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8734 If one man page needs to be accessible via several names it
8735 is better to use a symbolic link than the <file>.so</file>
8736 feature, but there is no need to fiddle with the relevant
8737 parts of the upstream source to change from <file>.so</file> to
8738 symlinks: don't do it unless it's easy. You should not
8739 create hard links in the manual page directories, nor put
8740 absolute filenames in <file>.so</file> directives. The filename
8741 in a <file>.so</file> in a man page should be relative to the
8742 base of the man page tree (usually
8743 <file>/usr/share/man</file>). If you do not create any links
8744 (whether symlinks, hard links, or <tt>.so</tt> directives)
8745 in the file system to the alternate names of the man page,
8746 then you should not rely on <prgn>man</prgn> finding your
8747 man page under those names based solely on the information in
8748 the man page's header.<footnote>
8749 Supporting this in <prgn>man</prgn> often requires
8750 unreasonable processing time to find a manual page or to
8751 report that none exists, and moves knowledge into man's
8752 database that would be better left in the file system.
8753 This support is therefore deprecated and will cease to
8754 be present in the future.
8759 Manual pages in locale-specific subdirectories of
8760 <file>/usr/share/man</file> should use either UTF-8 or the usual
8761 legacy encoding for that language (normally the one corresponding
8762 to the shortest relevant locale name in
8763 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8764 <file>/usr/share/man/fr</file> should use either UTF-8 or
8765 ISO-8859-1.<footnote>
8766 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8767 use. In future, all manual pages will be required to use
8773 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8774 included in the subdirectory name unless it indicates a
8775 significant difference in the language, as this excludes
8776 speakers of the language in other countries.<footnote>
8777 At the time of writing, Chinese and Portuguese are the main
8778 languages with such differences, so <file>pt_BR</file>,
8779 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8784 Due to limitations in current implementations, all characters
8785 in the manual page source should be representable in the usual
8786 legacy encoding for that language, even if the file is
8787 actually encoded in UTF-8. Safe alternative ways to write many
8788 characters outside that range may be found in
8789 <manref name="groff_char" section="7">.
8794 <heading>Info documents</heading>
8797 Info documents should be installed in <file>/usr/share/info</file>.
8798 They should be compressed with <tt>gzip -9</tt>.
8802 Your package should call <prgn>install-info</prgn> to update
8803 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8804 script when called with a <tt>configure</tt> argument, for
8806 <example compact="compact">
8807 install-info --quiet --section Development Development \
8808 /usr/share/info/foobar.info
8812 It is a good idea to specify a section for the location of
8813 your program; this is done with the <tt>--section</tt>
8814 switch. To determine which section to use, you should look
8815 at <file>/usr/share/info/dir</file> on your system and choose the most
8816 relevant (or create a new section if none of the current
8817 sections are relevant). Note that the <tt>--section</tt>
8818 flag takes two arguments; the first is a regular expression
8819 to match (case-insensitively) against an existing section,
8820 the second is used when creating a new one.</p>
8823 You should remove the entries in the <prgn>prerm</prgn>
8824 script when called with a <tt>remove</tt> argument:
8825 <example compact="compact">
8826 install-info --quiet --remove /usr/share/info/foobar.info
8830 If <prgn>install-info</prgn> cannot find a description entry
8831 in the Info file you must supply one. See <manref
8832 name="install-info" section="8"> for details.</p>
8836 <heading>Additional documentation</heading>
8839 Any additional documentation that comes with the package may
8840 be installed at the discretion of the package maintainer.
8841 Plain text documentation should be installed in the directory
8842 <file>/usr/share/doc/<var>package</var></file>, where
8843 <var>package</var> is the name of the package, and
8844 compressed with <tt>gzip -9</tt> unless it is small.
8848 If a package comes with large amounts of documentation which
8849 many users of the package will not require you should create
8850 a separate binary package to contain it, so that it does not
8851 take up disk space on the machines of users who do not need
8852 or want it installed.</p>
8855 It is often a good idea to put text information files
8856 (<file>README</file>s, changelogs, and so forth) that come with
8857 the source package in <file>/usr/share/doc/<var>package</var></file>
8858 in the binary package. However, you don't need to install
8859 the instructions for building and installing the package, of
8863 Packages must not require the existence of any files in
8864 <file>/usr/share/doc/</file> in order to function
8866 The system administrator should be able to
8867 delete files in <file>/usr/share/doc/</file> without causing
8868 any programs to break.
8870 Any files that are referenced by programs but are also
8871 useful as stand alone documentation should be installed under
8872 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8873 <file>/usr/share/doc/<var>package</var></file>.
8877 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8878 link to another directory in <file>/usr/share/doc</file> only if
8879 the two packages both come from the same source and the
8880 first package Depends on the second.<footnote>
8882 Please note that this does not override the section on
8883 changelog files below, so the file
8884 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8885 must refer to the changelog for the current version of
8886 <var>package</var> in question. In practice, this means
8887 that the sources of the target and the destination of the
8888 symlink must be the same (same source package and
8895 Former Debian releases placed all additional documentation
8896 in <file>/usr/doc/<var>package</var></file>. This has been
8897 changed to <file>/usr/share/doc/<var>package</var></file>,
8898 and packages must not put documentation in the directory
8899 <file>/usr/doc/<var>package</var></file>. <footnote>
8900 At this phase of the transition, we no longer require a
8901 symbolic link in <file>/usr/doc/</file>. At a later point,
8902 policy shall change to make the symbolic links a bug.
8908 <heading>Preferred documentation formats</heading>
8911 The unification of Debian documentation is being carried out
8915 If your package comes with extensive documentation in a
8916 markup format that can be converted to various other formats
8917 you should if possible ship HTML versions in a binary
8918 package, in the directory
8919 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8920 its subdirectories.<footnote>
8921 The rationale: The important thing here is that HTML
8922 docs should be available in <em>some</em> package, not
8923 necessarily in the main binary package.
8928 Other formats such as PostScript may be provided at the
8929 package maintainer's discretion.
8933 <sect id="copyrightfile">
8934 <heading>Copyright information</heading>
8937 Every package must be accompanied by a verbatim copy of its
8938 copyright and distribution license in the file
8939 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8940 file must neither be compressed nor be a symbolic link.
8944 In addition, the copyright file must say where the upstream
8945 sources (if any) were obtained. It should name the original
8946 authors of the package and the Debian maintainer(s) who were
8947 involved with its creation.
8951 Packages in the <em>contrib</em> or <em>non-free</em> categories
8952 should state in the copyright file that the package is not part
8953 of the Debian GNU/Linux distribution and briefly explain why.
8957 A copy of the file which will be installed in
8958 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8959 be in <file>debian/copyright</file> in the source package.
8963 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8964 link to another directory in <file>/usr/share/doc</file> only if
8965 the two packages both come from the same source and the
8966 first package Depends on the second. These rules are
8967 important because copyrights must be extractable by
8972 Packages distributed under the UCB BSD license, the Apache
8973 license (version 2.0), the Artistic license, the GNU GPL
8974 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8975 the GNU FDL (version 1.2) should refer to the corresponding
8976 files under <file>/usr/share/common-licenses</file>,<footnote>
8979 <file>/usr/share/common-licenses/BSD</file>,
8980 <file>/usr/share/common-licenses/Apache-2.0</file>,
8981 <file>/usr/share/common-licenses/Artistic</file>,
8982 <file>/usr/share/common-licenses/GPL-2</file>,
8983 <file>/usr/share/common-licenses/GPL-3</file>,
8984 <file>/usr/share/common-licenses/LGPL-2</file>,
8985 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8986 <file>/usr/share/common-licenses/LGPL-3</file>, and
8987 <file>/usr/share/common-licenses/GFDL-1.2</file>
8990 </footnote> rather than quoting them in the copyright
8995 You should not use the copyright file as a general <file>README</file>
8996 file. If your package has such a file it should be
8997 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8998 <file>README.Debian</file> or some other appropriate place.</p>
9002 <heading>Examples</heading>
9005 Any examples (configurations, source files, whatever),
9006 should be installed in a directory
9007 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9008 files should not be referenced by any program: they're there
9009 for the benefit of the system administrator and users as
9010 documentation only. Architecture-specific example files
9011 should be installed in a directory
9012 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9014 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9015 latter directory itself may be a symbolic link to the
9020 If the purpose of a package is to provide examples, then the
9021 example files may be installed into
9022 <file>/usr/share/doc/<var>package</var></file>.
9026 <sect id="changelogs">
9027 <heading>Changelog files</heading>
9030 Packages that are not Debian-native must contain a
9031 compressed copy of the <file>debian/changelog</file> file from
9032 the Debian source tree in
9033 <file>/usr/share/doc/<var>package</var></file> with the name
9034 <file>changelog.Debian.gz</file>.
9038 If an upstream changelog is available, it should be accessible as
9039 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9040 plain text. If the upstream changelog is distributed in
9041 HTML, it should be made available in that form as
9042 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9043 and a plain text <file>changelog.gz</file> should be generated
9044 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9045 the upstream changelog files do not already conform to this
9046 naming convention, then this may be achieved either by
9047 renaming the files, or by adding a symbolic link, at the
9048 maintainer's discretion.<footnote>
9049 Rationale: People should not have to look in places for
9050 upstream changelogs merely because they are given
9051 different names or are distributed in HTML format.
9056 All of these files should be installed compressed using
9057 <tt>gzip -9</tt>, as they will become large with time even
9058 if they start out small.
9062 If the package has only one changelog which is used both as
9063 the Debian changelog and the upstream one because there is
9064 no separate upstream maintainer then that changelog should
9065 usually be installed as
9066 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9067 there is a separate upstream maintainer, but no upstream
9068 changelog, then the Debian changelog should still be called
9069 <file>changelog.Debian.gz</file>.
9073 For details about the format and contents of the Debian
9074 changelog file, please see <ref id="dpkgchangelog">.
9079 <appendix id="pkg-scope">
9080 <heading>Introduction and scope of these appendices</heading>
9083 These appendices are taken essentially verbatim from the
9084 now-deprecated Packaging Manual, version 3.2.1.0. They are
9085 the chapters which are likely to be of use to package
9086 maintainers and which have not already been included in the
9087 policy document itself. Most of these sections are very likely
9088 not relevant to policy; they should be treated as
9089 documentation for the packaging system. Please note that these
9090 appendices are included for convenience, and for historical
9091 reasons: they used to be part of policy package, and they have
9092 not yet been incorporated into dpkg documentation. However,
9093 they still have value, and hence they are presented here.
9097 They have not yet been checked to ensure that they are
9098 compatible with the contents of policy, and if there are any
9099 contradictions, the version in the main policy document takes
9100 precedence. The remaining chapters of the old Packaging
9101 Manual have also not been read in detail to ensure that there
9102 are not parts which have been left out. Both of these will be
9107 Certain parts of the Packaging manual were integrated into the
9108 Policy Manual proper, and removed from the appendices. Links
9109 have been placed from the old locations to the new ones.
9113 <prgn>dpkg</prgn> is a suite of programs for creating binary
9114 package files and installing and removing them on Unix
9116 <prgn>dpkg</prgn> is targeted primarily at Debian
9117 GNU/Linux, but may work on or be ported to other
9123 The binary packages are designed for the management of
9124 installed executable programs (usually compiled binaries) and
9125 their associated data, though source code examples and
9126 documentation are provided as part of some packages.</p>
9129 This manual describes the technical aspects of creating Debian
9130 binary packages (<file>.deb</file> files). It documents the
9131 behavior of the package management programs
9132 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9133 they interact with packages.</p>
9136 It also documents the interaction between
9137 <prgn>dselect</prgn>'s core and the access method scripts it
9138 uses to actually install the selected packages, and describes
9139 how to create a new access method.</p>
9142 This manual does not go into detail about the options and
9143 usage of the package building and installation tools. It
9144 should therefore be read in conjunction with those programs'
9149 The utility programs which are provided with <prgn>dpkg</prgn>
9150 for managing various system configuration and similar issues,
9151 such as <prgn>update-rc.d</prgn> and
9152 <prgn>install-info</prgn>, are not described in detail here -
9153 please see their man pages.
9157 It is assumed that the reader is reasonably familiar with the
9158 <prgn>dpkg</prgn> System Administrators' manual.
9159 Unfortunately this manual does not yet exist.
9163 The Debian version of the FSF's GNU hello program is provided
9164 as an example for people wishing to create Debian
9165 packages. The Debian <prgn>debmake</prgn> package is
9166 recommended as a very helpful tool in creating and maintaining
9167 Debian packages. However, while the tools and examples are
9168 helpful, they do not replace the need to read and follow the
9169 Policy and Programmer's Manual.</p>
9172 <appendix id="pkg-binarypkg">
9173 <heading>Binary packages (from old Packaging Manual)</heading>
9176 The binary package has two main sections. The first part
9177 consists of various control information files and scripts used
9178 by <prgn>dpkg</prgn> when installing and removing. See <ref
9179 id="pkg-controlarea">.
9183 The second part is an archive containing the files and
9184 directories to be installed.
9188 In the future binary packages may also contain other
9189 components, such as checksums and digital signatures. The
9190 format for the archive is described in full in the
9191 <file>deb(5)</file> man page.
9195 <sect id="pkg-bincreating"><heading>Creating package files -
9196 <prgn>dpkg-deb</prgn>
9200 All manipulation of binary package files is done by
9201 <prgn>dpkg-deb</prgn>; it's the only program that has
9202 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9203 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9204 will spot that the options requested are appropriate to
9205 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9210 In order to create a binary package you must make a
9211 directory tree which contains all the files and directories
9212 you want to have in the file system data part of the package.
9213 In Debian-format source packages this directory is usually
9214 <file>debian/tmp</file>, relative to the top of the package's
9219 They should have the locations (relative to the root of the
9220 directory tree you're constructing) ownerships and
9221 permissions which you want them to have on the system when
9226 With current versions of <prgn>dpkg</prgn> the uid/username
9227 and gid/groupname mappings for the users and groups being
9228 used should be the same on the system where the package is
9229 built and the one where it is installed.
9233 You need to add one special directory to the root of the
9234 miniature file system tree you're creating:
9235 <prgn>DEBIAN</prgn>. It should contain the control
9236 information files, notably the binary package control file
9237 (see <ref id="pkg-controlfile">).
9241 The <prgn>DEBIAN</prgn> directory will not appear in the
9242 file system archive of the package, and so won't be installed
9243 by <prgn>dpkg</prgn> when the package is installed.
9247 When you've prepared the package, you should invoke:
9249 dpkg --build <var>directory</var>
9254 This will build the package in
9255 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9256 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9257 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9262 See the man page <manref name="dpkg-deb" section="8"> for details of how
9263 to examine the contents of this newly-created file. You may find the
9264 output of following commands enlightening:
9266 dpkg-deb --info <var>filename</var>.deb
9267 dpkg-deb --contents <var>filename</var>.deb
9268 dpkg --contents <var>filename</var>.deb
9270 To view the copyright file for a package you could use this command:
9272 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9277 <sect id="pkg-controlarea">
9278 <heading>Package control information files</heading>
9281 The control information portion of a binary package is a
9282 collection of files with names known to <prgn>dpkg</prgn>.
9283 It will treat the contents of these files specially - some
9284 of them contain information used by <prgn>dpkg</prgn> when
9285 installing or removing the package; others are scripts which
9286 the package maintainer wants <prgn>dpkg</prgn> to run.
9290 It is possible to put other files in the package control
9291 area, but this is not generally a good idea (though they
9292 will largely be ignored).
9296 Here is a brief list of the control info files supported by
9297 <prgn>dpkg</prgn> and a summary of what they're used for.
9302 <tag><tt>control</tt>
9305 This is the key description file used by
9306 <prgn>dpkg</prgn>. It specifies the package's name
9307 and version, gives its description for the user,
9308 states its relationships with other packages, and so
9309 forth. See <ref id="sourcecontrolfiles"> and
9310 <ref id="binarycontrolfiles">.
9314 It is usually generated automatically from information
9315 in the source package by the
9316 <prgn>dpkg-gencontrol</prgn> program, and with
9317 assistance from <prgn>dpkg-shlibdeps</prgn>.
9318 See <ref id="pkg-sourcetools">.
9322 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9327 These are executable files (usually scripts) which
9328 <prgn>dpkg</prgn> runs during installation, upgrade
9329 and removal of packages. They allow the package to
9330 deal with matters which are particular to that package
9331 or require more complicated processing than that
9332 provided by <prgn>dpkg</prgn>. Details of when and
9333 how they are called are in <ref id="maintainerscripts">.
9337 It is very important to make these scripts idempotent.
9338 See <ref id="idempotency">.
9342 The maintainer scripts are guaranteed to run with a
9343 controlling terminal and can interact with the user.
9344 See <ref id="controllingterminal">.
9348 <tag><tt>conffiles</tt>
9351 This file contains a list of configuration files which
9352 are to be handled automatically by <prgn>dpkg</prgn>
9353 (see <ref id="pkg-conffiles">). Note that not necessarily
9354 every configuration file should be listed here.
9357 <tag><tt>shlibs</tt>
9360 This file contains a list of the shared libraries
9361 supplied by the package, with dependency details for
9362 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9363 when it determines what dependencies are required in a
9364 package control file. The <tt>shlibs</tt> file format
9365 is described on <ref id="shlibs">.
9370 <sect id="pkg-controlfile">
9371 <heading>The main control information file: <tt>control</tt></heading>
9374 The most important control information file used by
9375 <prgn>dpkg</prgn> when it installs a package is
9376 <tt>control</tt>. It contains all the package's "vital
9381 The binary package control files of packages built from
9382 Debian sources are made by a special tool,
9383 <prgn>dpkg-gencontrol</prgn>, which reads
9384 <file>debian/control</file> and <file>debian/changelog</file> to
9385 find the information it needs. See <ref id="pkg-sourcepkg"> for
9390 The fields in binary package control files are listed in
9391 <ref id="binarycontrolfiles">.
9395 A description of the syntax of control files and the purpose
9396 of the fields is available in <ref id="controlfields">.
9401 <heading>Time Stamps</heading>
9404 See <ref id="timestamps">.
9409 <appendix id="pkg-sourcepkg">
9410 <heading>Source packages (from old Packaging Manual) </heading>
9413 The Debian binary packages in the distribution are generated
9414 from Debian sources, which are in a special format to assist
9415 the easy and automatic building of binaries.
9418 <sect id="pkg-sourcetools">
9419 <heading>Tools for processing source packages</heading>
9422 Various tools are provided for manipulating source packages;
9423 they pack and unpack sources and help build of binary
9424 packages and help manage the distribution of new versions.
9428 They are introduced and typical uses described here; see
9429 <manref name="dpkg-source" section="1"> for full
9430 documentation about their arguments and operation.
9434 For examples of how to construct a Debian source package,
9435 and how to use those utilities that are used by Debian
9436 source packages, please see the <prgn>hello</prgn> example
9440 <sect1 id="pkg-dpkg-source">
9442 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9447 This program is frequently used by hand, and is also
9448 called from package-independent automated building scripts
9449 such as <prgn>dpkg-buildpackage</prgn>.
9453 To unpack a package it is typically invoked with
9455 dpkg-source -x <var>.../path/to/filename</var>.dsc
9460 with the <file><var>filename</var>.tar.gz</file> and
9461 <file><var>filename</var>.diff.gz</file> (if applicable) in
9462 the same directory. It unpacks into
9463 <file><var>package</var>-<var>version</var></file>, and if
9465 <file><var>package</var>-<var>version</var>.orig</file>, in
9466 the current directory.
9470 To create a packed source archive it is typically invoked:
9472 dpkg-source -b <var>package</var>-<var>version</var>
9477 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9478 <file>.diff.gz</file> (if appropriate) in the current
9479 directory. <prgn>dpkg-source</prgn> does not clean the
9480 source tree first - this must be done separately if it is
9485 See also <ref id="pkg-sourcearchives">.</p>
9489 <sect1 id="pkg-dpkg-buildpackage">
9491 <prgn>dpkg-buildpackage</prgn> - overall package-building
9496 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9497 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9498 targets <tt>clean</tt>, <tt>build</tt> and
9499 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9500 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9501 source and binary package upload.
9505 It is usually invoked by hand from the top level of the
9506 built or unbuilt source directory. It may be invoked with
9507 no arguments; useful arguments include:
9508 <taglist compact="compact">
9509 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9512 Do not sign the <tt>.changes</tt> file or the
9513 source package <tt>.dsc</tt> file, respectively.</p>
9515 <tag><tt>-p<var>sign-command</var></tt></tag>
9518 Invoke <var>sign-command</var> instead of finding
9519 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9520 <var>sign-command</var> must behave just like
9521 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9523 <tag><tt>-r<var>root-command</var></tt></tag>
9526 When root privilege is required, invoke the command
9527 <var>root-command</var>. <var>root-command</var>
9528 should invoke its first argument as a command, from
9529 the <prgn>PATH</prgn> if necessary, and pass its
9530 second and subsequent arguments to the command it
9531 calls. If no <var>root-command</var> is supplied
9532 then <var>dpkg-buildpackage</var> will take no
9533 special action to gain root privilege, so that for
9534 most packages it will have to be invoked as root to
9537 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9540 Two types of binary-only build and upload - see
9541 <manref name="dpkg-source" section="1">.
9548 <sect1 id="pkg-dpkg-gencontrol">
9550 <prgn>dpkg-gencontrol</prgn> - generates binary package
9555 This program is usually called from <file>debian/rules</file>
9556 (see <ref id="pkg-sourcetree">) in the top level of the source
9561 This is usually done just before the files and directories in the
9562 temporary directory tree where the package is being built have their
9563 permissions and ownerships set and the package is constructed using
9564 <prgn>dpkg-deb/</prgn>
9566 This is so that the control file which is produced has
9567 the right permissions
9572 <prgn>dpkg-gencontrol</prgn> must be called after all the
9573 files which are to go into the package have been placed in
9574 the temporary build directory, so that its calculation of
9575 the installed size of a package is correct.
9579 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9580 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9581 variable substitutions created by
9582 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9587 For a package which generates only one binary package, and
9588 which builds it in <file>debian/tmp</file> relative to the top
9589 of the source package, it is usually sufficient to call
9590 <prgn>dpkg-gencontrol</prgn>.
9594 Sources which build several binaries will typically need
9597 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9598 </example> The <tt>-P</tt> tells
9599 <prgn>dpkg-gencontrol</prgn> that the package is being
9600 built in a non-default directory, and the <tt>-p</tt>
9601 tells it which package's control file should be generated.
9605 <prgn>dpkg-gencontrol</prgn> also adds information to the
9606 list of files in <file>debian/files</file>, for the benefit of
9607 (for example) a future invocation of
9608 <prgn>dpkg-genchanges</prgn>.</p>
9611 <sect1 id="pkg-dpkg-shlibdeps">
9613 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9618 This program is usually called from <file>debian/rules</file>
9619 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9620 id="pkg-sourcetree">), in the top level of the source tree.
9624 Its arguments are executables and shared libraries
9627 They may be specified either in the locations in the
9628 source tree where they are created or in the locations
9629 in the temporary build tree where they are installed
9630 prior to binary package creation.
9632 </footnote> for which shared library dependencies should
9633 be included in the binary package's control file.
9637 If some of the found shared libraries should only
9638 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9639 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9640 by using the <tt>-d<var>dependency-field</var></tt> option
9641 before those executable(s). (Each <tt>-d</tt> option
9642 takes effect until the next <tt>-d</tt>.)
9646 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9647 output control file to be modified. Instead by default it
9648 adds to the <file>debian/substvars</file> file variable
9649 settings like <tt>shlibs:Depends</tt>. These variable
9650 settings must be referenced in dependency fields in the
9651 appropriate per-binary-package sections of the source
9656 For example, a package that generates an essential part
9657 which requires dependencies, and optional parts that
9658 which only require a recommendation, would separate those
9659 two sets of dependencies into two different fields.<footnote>
9660 At the time of writing, an example for this was the
9661 <package/xmms/ package, with Depends used for the xmms
9662 executable, Recommends for the plug-ins and Suggests for
9663 even more optional features provided by unzip.
9665 It can say in its <file>debian/rules</file>:
9667 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9668 -dRecommends <var>optionalpart anotheroptionalpart</var>
9670 and then in its main control file <file>debian/control</file>:
9673 Depends: ${shlibs:Depends}
9674 Recommends: ${shlibs:Recommends}
9680 Sources which produce several binary packages with
9681 different shared library dependency requirements can use
9682 the <tt>-p<var>varnameprefix</var></tt> option to override
9683 the default <tt>shlibs:</tt> prefix (one invocation of
9684 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9685 They can thus produce several sets of dependency
9686 variables, each of the form
9687 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9688 which can be referred to in the appropriate parts of the
9689 binary package control files.
9694 <sect1 id="pkg-dpkg-distaddfile">
9696 <prgn>dpkg-distaddfile</prgn> - adds a file to
9697 <file>debian/files</file>
9701 Some packages' uploads need to include files other than
9702 the source and binary package files.
9706 <prgn>dpkg-distaddfile</prgn> adds a file to the
9707 <file>debian/files</file> file so that it will be included in
9708 the <file>.changes</file> file when
9709 <prgn>dpkg-genchanges</prgn> is run.
9713 It is usually invoked from the <tt>binary</tt> target of
9714 <file>debian/rules</file>:
9716 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9718 The <var>filename</var> is relative to the directory where
9719 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9720 is usually the directory above the top level of the source
9721 tree. The <file>debian/rules</file> target should put the
9722 file there just before or just after calling
9723 <prgn>dpkg-distaddfile</prgn>.
9727 The <var>section</var> and <var>priority</var> are passed
9728 unchanged into the resulting <file>.changes</file> file.
9733 <sect1 id="pkg-dpkg-genchanges">
9735 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9740 This program is usually called by package-independent
9741 automatic building scripts such as
9742 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9747 It is usually called in the top level of a built source
9748 tree, and when invoked with no arguments will print out a
9749 straightforward <file>.changes</file> file based on the
9750 information in the source package's changelog and control
9751 file and the binary and source packages which should have
9757 <sect1 id="pkg-dpkg-parsechangelog">
9759 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9760 representation of a changelog
9764 This program is used internally by
9765 <prgn>dpkg-source</prgn> et al. It may also occasionally
9766 be useful in <file>debian/rules</file> and elsewhere. It
9767 parses a changelog, <file>debian/changelog</file> by default,
9768 and prints a control-file format representation of the
9769 information in it to standard output.
9773 <sect1 id="pkg-dpkg-architecture">
9775 <prgn>dpkg-architecture</prgn> - information about the build and
9780 This program can be used manually, but is also invoked by
9781 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9782 environment or make variables which specify the build and host
9783 architecture for the package building process.
9788 <sect id="pkg-sourcetree">
9789 <heading>The Debianised source tree</heading>
9792 The source archive scheme described later is intended to
9793 allow a Debianised source tree with some associated control
9794 information to be reproduced and transported easily. The
9795 Debianised source tree is a version of the original program
9796 with certain files added for the benefit of the
9797 Debianisation process, and with any other changes required
9798 made to the rest of the source code and installation
9803 The extra files created for Debian are in the subdirectory
9804 <file>debian</file> of the top level of the Debianised source
9805 tree. They are described below.
9808 <sect1 id="pkg-debianrules">
9809 <heading><file>debian/rules</file> - the main building script</heading>
9812 See <ref id="debianrules">.
9817 <sect1 id="pkg-dpkgchangelog">
9818 <heading><file>debian/changelog</file></heading>
9821 See <ref id="dpkgchangelog">.
9825 It is recommended that the entire changelog be encoded in the
9826 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9828 <url id="http://www.unicode.org/"
9829 name="Unicode">.<footnote>
9831 I think it is fairly obvious that we need to
9832 eventually transition to UTF-8 for our package
9833 infrastructure; it is really the only sane char-set in
9834 an international environment. Now, we can't switch to
9835 using UTF-8 for package control fields and the like
9836 until dpkg has better support, but one thing we can
9837 start doing today is requesting that Debian changelogs
9838 are UTF-8 encoded. At some point in time, we can start
9839 requiring them to do so.
9842 Checking for non-UTF8 characters in a changelog is
9843 trivial. Dump the file through
9844 <example>iconv -f utf-8 -t ucs-4</example>
9845 discard the output, and check the return
9846 value. If there are any characters in the stream
9847 which are invalid UTF-8 sequences, iconv will exit
9848 with an error code; and this will be the case for the
9849 vast majority of other character sets.
9854 <sect2><heading>Defining alternative changelog formats
9858 It is possible to use a different format to the standard
9859 one, by providing a parser for the format you wish to
9864 In order to have <tt>dpkg-parsechangelog</tt> run your
9865 parser, you must include a line within the last 40 lines
9866 of your file matching the Perl regular expression:
9867 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9868 parentheses should be the name of the format. For
9869 example, you might say:
9871 @@@ changelog-format: joebloggs @@@
9873 Changelog format names are non-empty strings of alphanumerics.
9877 If such a line exists then <tt>dpkg-parsechangelog</tt>
9878 will look for the parser as
9879 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9881 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9882 it is an error for it not to find it, or for it not to
9883 be an executable program. The default changelog format
9884 is <tt>dpkg</tt>, and a parser for it is provided with
9885 the <tt>dpkg</tt> package.
9889 The parser will be invoked with the changelog open on
9890 standard input at the start of the file. It should read
9891 the file (it may seek if it wishes) to determine the
9892 information required and return the parsed information
9893 to standard output in the form of a series of control
9894 fields in the standard format. By default it should
9895 return information about only the most recent version in
9896 the changelog; it should accept a
9897 <tt>-v<var>version</var></tt> option to return changes
9898 information from all versions present <em>strictly
9899 after</em> <var>version</var>, and it should then be an
9900 error for <var>version</var> not to be present in the
9906 <list compact="compact">
9907 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9908 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9909 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9910 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9911 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9912 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9913 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9918 If several versions are being returned (due to the use
9919 of <tt>-v</tt>), the urgency value should be of the
9920 highest urgency code listed at the start of any of the
9921 versions requested followed by the concatenated
9922 (space-separated) comments from all the versions
9923 requested; the maintainer, version, distribution and
9924 date should always be from the most recent version.
9928 For the format of the <tt>Changes</tt> field see
9929 <ref id="f-Changes">.
9933 If the changelog format which is being parsed always or
9934 almost always leaves a blank line between individual
9935 change notes these blank lines should be stripped out,
9936 so as to make the resulting output compact.
9940 If the changelog format does not contain date or package
9941 name information this information should be omitted from
9942 the output. The parser should not attempt to synthesize
9943 it or find it from other sources.
9947 If the changelog does not have the expected format the
9948 parser should exit with a nonzero exit status, rather
9949 than trying to muddle through and possibly generating
9954 A changelog parser may not interact with the user at
9960 <sect1 id="pkg-srcsubstvars">
9961 <heading><file>debian/substvars</file> and variable substitutions</heading>
9964 See <ref id="substvars">.
9970 <heading><file>debian/files</file></heading>
9973 See <ref id="debianfiles">.
9977 <sect1><heading><file>debian/tmp</file>
9981 This is the canonical temporary location for the
9982 construction of binary packages by the <tt>binary</tt>
9983 target. The directory <file>tmp</file> serves as the root of
9984 the file system tree as it is being constructed (for
9985 example, by using the package's upstream makefiles install
9986 targets and redirecting the output there), and it also
9987 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9988 id="pkg-bincreating">.
9992 If several binary packages are generated from the same
9993 source tree it is usual to use several
9994 <file>debian/tmp<var>something</var></file> directories, for
9995 example <file>tmp-a</file> or <file>tmp-doc</file>.
9999 Whatever <file>tmp</file> directories are created and used by
10000 <tt>binary</tt> must of course be removed by the
10001 <tt>clean</tt> target.</p></sect1>
10005 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10009 As it exists on the FTP site, a Debian source package
10010 consists of three related files. You must have the right
10011 versions of all three to be able to use them.
10016 <tag>Debian source control file - <tt>.dsc</tt></tag>
10018 This file is a control file used by <prgn>dpkg-source</prgn>
10019 to extract a source package.
10020 See <ref id="debiansourcecontrolfiles">.
10024 Original source archive -
10026 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10032 This is a compressed (with <tt>gzip -9</tt>)
10033 <prgn>tar</prgn> file containing the source code from
10034 the upstream authors of the program.
10039 Debianisation diff -
10041 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10047 This is a unified context diff (<tt>diff -u</tt>)
10048 giving the changes which are required to turn the
10049 original source into the Debian source. These changes
10050 may only include editing and creating plain files.
10051 The permissions of files, the targets of symbolic
10052 links and the characteristics of special files or
10053 pipes may not be changed and no files may be removed
10058 All the directories in the diff must exist, except the
10059 <file>debian</file> subdirectory of the top of the source
10060 tree, which will be created by
10061 <prgn>dpkg-source</prgn> if necessary when unpacking.
10065 The <prgn>dpkg-source</prgn> program will
10066 automatically make the <file>debian/rules</file> file
10067 executable (see below).</p></item>
10072 If there is no original source code - for example, if the
10073 package is specially prepared for Debian or the Debian
10074 maintainer is the same as the upstream maintainer - the
10075 format is slightly different: then there is no diff, and the
10077 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10078 and preferably contains a directory named
10079 <file><var>package</var>-<var>version</var></file>.
10084 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10087 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10088 Debian source package. However, if it is not available it
10089 is possible to unpack a Debian source archive as follows:
10090 <enumlist compact="compact">
10093 Untar the tarfile, which will create a <file>.orig</file>
10097 <p>Rename the <file>.orig</file> directory to
10098 <file><var>package</var>-<var>version</var></file>.</p>
10102 Create the subdirectory <file>debian</file> at the top of
10103 the source tree.</p>
10105 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10107 <item><p>Untar the tarfile again if you want a copy of the original
10108 source code alongside the Debianised version.</p>
10113 It is not possible to generate a valid Debian source archive
10114 without using <prgn>dpkg-source</prgn>. In particular,
10115 attempting to use <prgn>diff</prgn> directly to generate the
10116 <file>.diff.gz</file> file will not work.
10120 <heading>Restrictions on objects in source packages</heading>
10123 The source package may not contain any hard links
10125 This is not currently detected when building source
10126 packages, but only when extracting
10130 Hard links may be permitted at some point in the
10131 future, but would require a fair amount of
10133 </footnote>, device special files, sockets or setuid or
10136 Setgid directories are allowed.
10141 The source packaging tools manage the changes between the
10142 original and Debianised source using <prgn>diff</prgn> and
10143 <prgn>patch</prgn>. Turning the original source tree as
10144 included in the <file>.orig.tar.gz</file> into the debianised
10145 source must not involve any changes which cannot be
10146 handled by these tools. Problematic changes which cause
10147 <prgn>dpkg-source</prgn> to halt with an error when
10148 building the source package are:
10149 <list compact="compact">
10150 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10152 <item><p>Changing the targets of symbolic links.</p>
10154 <item><p>Creating directories, other than <file>debian</file>.</p>
10156 <item><p>Changes to the contents of binary files.</p></item>
10157 </list> Changes which cause <prgn>dpkg-source</prgn> to
10158 print a warning but continue anyway are:
10159 <list compact="compact">
10162 Removing files, directories or symlinks.
10164 Renaming a file is not treated specially - it is
10165 seen as the removal of the old file (which
10166 generates a warning, but is otherwise ignored),
10167 and the creation of the new one.
10173 Changed text files which are missing the usual final
10174 newline (either in the original or the modified
10179 Changes which are not represented, but which are not detected by
10180 <prgn>dpkg-source</prgn>, are:
10181 <list compact="compact">
10182 <item><p>Changing the permissions of files (other than
10183 <file>debian/rules</file>) and directories.</p></item>
10188 The <file>debian</file> directory and <file>debian/rules</file>
10189 are handled specially by <prgn>dpkg-source</prgn> - before
10190 applying the changes it will create the <file>debian</file>
10191 directory, and afterwards it will make
10192 <file>debian/rules</file> world-executable.
10198 <appendix id="pkg-controlfields">
10199 <heading>Control files and their fields (from old Packaging Manual)</heading>
10202 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10203 data in a common format, known as control files. Binary and
10204 source packages have control data as do the <file>.changes</file>
10205 files which control the installation of uploaded files, and
10206 <prgn>dpkg</prgn>'s internal databases are in a similar
10211 <heading>Syntax of control files</heading>
10214 See <ref id="controlsyntax">.
10218 It is important to note that there are several fields which
10219 are optional as far as <prgn>dpkg</prgn> and the related
10220 tools are concerned, but which must appear in every Debian
10221 package, or whose omission may cause problems.
10226 <heading>List of fields</heading>
10229 See <ref id="controlfieldslist">.
10233 This section now contains only the fields that didn't belong
10234 to the Policy manual.
10237 <sect1 id="pkg-f-Filename">
10238 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10241 These fields in <tt>Packages</tt> files give the
10242 filename(s) of (the parts of) a package in the
10243 distribution directories, relative to the root of the
10244 Debian hierarchy. If the package has been split into
10245 several parts the parts are all listed in order, separated
10250 <sect1 id="pkg-f-Size">
10251 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10254 These fields in <file>Packages</file> files give the size (in
10255 bytes, expressed in decimal) and MD5 checksum of the
10256 file(s) which make(s) up a binary package in the
10257 distribution. If the package is split into several parts
10258 the values for the parts are listed in order, separated by
10263 <sect1 id="pkg-f-Status">
10264 <heading><tt>Status</tt></heading>
10267 This field in <prgn>dpkg</prgn>'s status file records
10268 whether the user wants a package installed, removed or
10269 left alone, whether it is broken (requiring
10270 re-installation) or not and what its current state on the
10271 system is. Each of these pieces of information is a
10276 <sect1 id="pkg-f-Config-Version">
10277 <heading><tt>Config-Version</tt></heading>
10280 If a package is not installed or not configured, this
10281 field in <prgn>dpkg</prgn>'s status file records the last
10282 version of the package which was successfully
10287 <sect1 id="pkg-f-Conffiles">
10288 <heading><tt>Conffiles</tt></heading>
10291 This field in <prgn>dpkg</prgn>'s status file contains
10292 information about the automatically-managed configuration
10293 files held by a package. This field should <em>not</em>
10294 appear anywhere in a package!
10299 <heading>Obsolete fields</heading>
10302 These are still recognized by <prgn>dpkg</prgn> but should
10303 not appear anywhere any more.
10305 <taglist compact="compact">
10307 <tag><tt>Revision</tt></tag>
10308 <tag><tt>Package-Revision</tt></tag>
10309 <tag><tt>Package_Revision</tt></tag>
10311 The Debian revision part of the package version was
10312 at one point in a separate control file field. This
10313 field went through several names.
10316 <tag><tt>Recommended</tt></tag>
10317 <item>Old name for <tt>Recommends</tt>.</item>
10319 <tag><tt>Optional</tt></tag>
10320 <item>Old name for <tt>Suggests</tt>.</item>
10322 <tag><tt>Class</tt></tag>
10323 <item>Old name for <tt>Priority</tt>.</item>
10332 <appendix id="pkg-conffiles">
10333 <heading>Configuration file handling (from old Packaging Manual)</heading>
10336 <prgn>dpkg</prgn> can do a certain amount of automatic
10337 handling of package configuration files.
10341 Whether this mechanism is appropriate depends on a number of
10342 factors, but basically there are two approaches to any
10343 particular configuration file.
10347 The easy method is to ship a best-effort configuration in the
10348 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10349 handle updates. If the user is unlikely to want to edit the
10350 file, but you need them to be able to without losing their
10351 changes, and a new package with a changed version of the file
10352 is only released infrequently, this is a good approach.
10356 The hard method is to build the configuration file from
10357 scratch in the <prgn>postinst</prgn> script, and to take the
10358 responsibility for fixing any mistakes made in earlier
10359 versions of the package automatically. This will be
10360 appropriate if the file is likely to need to be different on
10364 <sect><heading>Automatic handling of configuration files by
10369 A package may contain a control area file called
10370 <tt>conffiles</tt>. This file should be a list of filenames
10371 of configuration files needing automatic handling, separated
10372 by newlines. The filenames should be absolute pathnames,
10373 and the files referred to should actually exist in the
10378 When a package is upgraded <prgn>dpkg</prgn> will process
10379 the configuration files during the configuration stage,
10380 shortly before it runs the package's <prgn>postinst</prgn>
10385 For each file it checks to see whether the version of the
10386 file included in the package is the same as the one that was
10387 included in the last version of the package (the one that is
10388 being upgraded from); it also compares the version currently
10389 installed on the system with the one shipped with the last
10394 If neither the user nor the package maintainer has changed
10395 the file, it is left alone. If one or the other has changed
10396 their version, then the changed version is preferred - i.e.,
10397 if the user edits their file, but the package maintainer
10398 doesn't ship a different version, the user's changes will
10399 stay, silently, but if the maintainer ships a new version
10400 and the user hasn't edited it the new version will be
10401 installed (with an informative message). If both have
10402 changed their version the user is prompted about the problem
10403 and must resolve the differences themselves.
10407 The comparisons are done by calculating the MD5 message
10408 digests of the files, and storing the MD5 of the file as it
10409 was included in the most recent version of the package.
10413 When a package is installed for the first time
10414 <prgn>dpkg</prgn> will install the file that comes with it,
10415 unless that would mean overwriting a file already on the
10420 However, note that <prgn>dpkg</prgn> will <em>not</em>
10421 replace a conffile that was removed by the user (or by a
10422 script). This is necessary because with some programs a
10423 missing file produces an effect hard or impossible to
10424 achieve in another way, so that a missing file needs to be
10425 kept that way if the user did it.
10429 Note that a package should <em>not</em> modify a
10430 <prgn>dpkg</prgn>-handled conffile in its maintainer
10431 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10432 the user confusing and possibly dangerous options for
10433 conffile update when the package is upgraded.</p>
10436 <sect><heading>Fully-featured maintainer script configuration
10441 For files which contain site-specific information such as
10442 the hostname and networking details and so forth, it is
10443 better to create the file in the package's
10444 <prgn>postinst</prgn> script.
10448 This will typically involve examining the state of the rest
10449 of the system to determine values and other information, and
10450 may involve prompting the user for some information which
10451 can't be obtained some other way.
10455 When using this method there are a couple of important
10456 issues which should be considered:
10460 If you discover a bug in the program which generates the
10461 configuration file, or if the format of the file changes
10462 from one version to the next, you will have to arrange for
10463 the postinst script to do something sensible - usually this
10464 will mean editing the installed configuration file to remove
10465 the problem or change the syntax. You will have to do this
10466 very carefully, since the user may have changed the file,
10467 perhaps to fix the very problem that your script is trying
10468 to deal with - you will have to detect these situations and
10469 deal with them correctly.
10473 If you do go down this route it's probably a good idea to
10474 make the program that generates the configuration file(s) a
10475 separate program in <file>/usr/sbin</file>, by convention called
10476 <file><var>package</var>config</file> and then run that if
10477 appropriate from the post-installation script. The
10478 <tt><var>package</var>config</tt> program should not
10479 unquestioningly overwrite an existing configuration - if its
10480 mode of operation is geared towards setting up a package for
10481 the first time (rather than any arbitrary reconfiguration
10482 later) you should have it check whether the configuration
10483 already exists, and require a <tt>--force</tt> flag to
10484 overwrite it.</p></sect>
10487 <appendix id="pkg-alternatives"><heading>Alternative versions of
10488 an interface - <prgn>update-alternatives</prgn> (from old
10493 When several packages all provide different versions of the
10494 same program or file it is useful to have the system select a
10495 default, but to allow the system administrator to change it
10496 and have their decisions respected.
10500 For example, there are several versions of the <prgn>vi</prgn>
10501 editor, and there is no reason to prevent all of them from
10502 being installed at once, each under their own name
10503 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10504 Nevertheless it is desirable to have the name <tt>vi</tt>
10505 refer to something, at least by default.
10509 If all the packages involved cooperate, this can be done with
10510 <prgn>update-alternatives</prgn>.
10514 Each package provides its own version under its own name, and
10515 calls <prgn>update-alternatives</prgn> in its postinst to
10516 register its version (and again in its prerm to deregister
10521 See the man page <manref name="update-alternatives"
10522 section="8"> for details.
10526 If <prgn>update-alternatives</prgn> does not seem appropriate
10527 you may wish to consider using diversions instead.</p>
10530 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10531 package's version of a file (from old Packaging Manual)
10535 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10536 when it reinstalls the package it belongs to, and to have it
10537 put the file from the package somewhere else instead.
10541 This can be used locally to override a package's version of a
10542 file, or by one package to override another's version (or
10543 provide a wrapper for it).
10547 Before deciding to use a diversion, read <ref
10548 id="pkg-alternatives"> to see if you really want a diversion
10549 rather than several alternative versions of a program.
10553 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10554 and updated by a special program <prgn>dpkg-divert</prgn>.
10555 Please see <manref name="dpkg-divert" section="8"> for full
10556 details of its operation.
10560 When a package wishes to divert a file from another, it should
10561 call <prgn>dpkg-divert</prgn> in its preinst to add the
10562 diversion and rename the existing file. For example,
10563 supposing that a <prgn>smailwrapper</prgn> package wishes to
10564 install a wrapper around <file>/usr/sbin/smail</file>:
10566 if [ install = "$1" ]; then
10567 dpkg-divert --package smailwrapper --add --rename \
10568 --divert /usr/sbin/smail.real /usr/sbin/smail
10570 </example> Testing <tt>$1</tt> is necessary so that the script
10571 doesn't try to add the diversion again when
10572 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10573 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10574 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10575 get installed as the true version.
10579 The postrm has to do the reverse:
10581 if [ remove = "$1" ]; then
10582 dpkg-divert --package smailwrapper --remove --rename \
10583 --divert /usr/sbin/smail.real /usr/sbin/smail
10589 Do not attempt to divert a file which is vitally important for
10590 the system's operation - when using <prgn>dpkg-divert</prgn>
10591 there is a time, after it has been diverted but before
10592 <prgn>dpkg</prgn> has installed the new version, when the file
10593 does not exist.</p>
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