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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 needed in part to avoid unresolvable dependency
989 loops on upgrade. If packages add unnecessary dependencies
990 on packages in this set, the chances that there
991 <strong>will</strong> be an unresolvable dependency loop
992 caused by forcing these Essential packages to be configured
993 first before they need to be is greatly increased. It also
994 increases the chances that frontends will be unable to
995 <strong>calculate</strong> an upgrade path, even if one
999 Also, functionality is rarely ever removed from the
1000 Essential set, but <em>packages</em> have been removed from
1001 the Essential set when the functionality moved to a
1002 different package. So depending on these packages <em>just
1003 in case</em> they stop being essential does way more harm
1010 Sometimes, a package requires another package to be installed
1011 <em>and</em> configured before it can be installed. In this
1012 case, you must specify a <tt>Pre-Depends</tt> entry for
1017 You should not specify a <tt>Pre-Depends</tt> entry for a
1018 package before this has been discussed on the
1019 <tt>debian-devel</tt> mailing list and a consensus about
1020 doing that has been reached.
1024 The format of the package interrelationship control fields is
1025 described in <ref id="relationships">.
1029 <sect id="virtual_pkg">
1030 <heading>Virtual packages</heading>
1033 Sometimes, there are several packages which offer
1034 more-or-less the same functionality. In this case, it's
1035 useful to define a <em>virtual package</em> whose name
1036 describes that common functionality. (The virtual
1037 packages only exist logically, not physically; that's why
1038 they are called <em>virtual</em>.) The packages with this
1039 particular function will then <em>provide</em> the virtual
1040 package. Thus, any other package requiring that function
1041 can simply depend on the virtual package without having to
1042 specify all possible packages individually.
1046 All packages should use virtual package names where
1047 appropriate, and arrange to create new ones if necessary.
1048 They should not use virtual package names (except privately,
1049 amongst a cooperating group of packages) unless they have
1050 been agreed upon and appear in the list of virtual package
1051 names. (See also <ref id="virtual">)
1055 The latest version of the authoritative list of virtual
1056 package names can be found in the <tt>debian-policy</tt> package.
1057 It is also available from the Debian web mirrors at
1058 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1059 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1063 The procedure for updating the list is described in the preface
1070 <heading>Base system</heading>
1073 The <tt>base system</tt> is a minimum subset of the Debian
1074 GNU/Linux system that is installed before everything else
1075 on a new system. Only very few packages are allowed to form
1076 part of the base system, in order to keep the required disk
1081 The base system consists of all those packages with priority
1082 <tt>required</tt> or <tt>important</tt>. Many of them will
1083 be tagged <tt>essential</tt> (see below).
1088 <heading>Essential packages</heading>
1091 Essential is defined as the minimal set of functionality that
1092 must be available and usable on the system at all times, even
1093 when packages are in an unconfigured (but unpacked) state.
1094 Packages are tagged <tt>essential</tt> for a system using the
1095 <tt>Essential</tt> control file field. The format of the
1096 <tt>Essential</tt> control field is described in <ref
1101 Since these packages cannot be easily removed (one has to
1102 specify an extra <em>force option</em> to
1103 <prgn>dpkg</prgn> to do so), this flag must not be used
1104 unless absolutely necessary. A shared library package
1105 must not be tagged <tt>essential</tt>; dependencies will
1106 prevent its premature removal, and we need to be able to
1107 remove it when it has been superseded.
1111 Since dpkg will not prevent upgrading of other packages
1112 while an <tt>essential</tt> package is in an unconfigured
1113 state, all <tt>essential</tt> packages must supply all of
1114 their core functionality even when unconfigured. If the
1115 package cannot satisfy this requirement it must not be
1116 tagged as essential, and any packages depending on this
1117 package must instead have explicit dependency fields as
1122 Maintainers should take great care in adding any programs,
1123 interfaces, or functionality to <tt>essential</tt> packages.
1124 Packages may assume that functionality provided by
1125 <tt>essential</tt> packages is always available without
1126 declaring explicit dependencies, which means that removing
1127 functionality from the Essential set is very difficult and is
1128 almost never done. Any capability added to an
1129 <tt>essential</tt> package therefore creates an obligation to
1130 support that capability as part of the Essential set in
1135 You must not tag any packages <tt>essential</tt> before
1136 this has been discussed on the <tt>debian-devel</tt>
1137 mailing list and a consensus about doing that has been
1142 <sect id="maintscripts">
1143 <heading>Maintainer Scripts</heading>
1146 The package installation scripts should avoid producing
1147 output which is unnecessary for the user to see and
1148 should rely on <prgn>dpkg</prgn> to stave off boredom on
1149 the part of a user installing many packages. This means,
1150 amongst other things, using the <tt>--quiet</tt> option on
1151 <prgn>install-info</prgn>.
1155 Errors which occur during the execution of an installation
1156 script must be checked and the installation must not
1157 continue after an error.
1161 Note that in general <ref id="scripts"> applies to package
1162 maintainer scripts, too.
1166 You should not use <prgn>dpkg-divert</prgn> on a file
1167 belonging to another package without consulting the
1168 maintainer of that package first.
1172 All packages which supply an instance of a common command
1173 name (or, in general, filename) should generally use
1174 <prgn>update-alternatives</prgn>, so that they may be
1175 installed together. If <prgn>update-alternatives</prgn>
1176 is not used, then each package must use
1177 <tt>Conflicts</tt> to ensure that other packages are
1178 de-installed. (In this case, it may be appropriate to
1179 specify a conflict against earlier versions of something
1180 that previously did not use
1181 <prgn>update-alternatives</prgn>; this is an exception to
1182 the usual rule that versioned conflicts should be
1186 <sect1 id="maintscriptprompt">
1187 <heading>Prompting in maintainer scripts</heading>
1189 Package maintainer scripts may prompt the user if
1190 necessary. Prompting should be done by communicating
1191 through a program, such as <prgn>debconf</prgn>, which
1192 conforms to the Debian Configuration management
1193 specification, version 2 or higher. Prompting the user by
1194 other means, such as by hand<footnote>
1195 From the Jargon file: by hand 2. By extension,
1196 writing code which does something in an explicit or
1197 low-level way for which a presupplied library
1198 (<em>debconf, in this instance</em>) routine ought
1199 to have been available.
1200 </footnote>, is now deprecated.
1204 The Debian Configuration management specification is included
1205 in the <file>debconf_specification</file> files in the
1206 <package>debian-policy</package> package.
1207 It is also available from the Debian web mirrors at
1208 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1209 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1213 Packages which use the Debian Configuration management
1214 specification may contain an additional
1215 <prgn>config</prgn> script and a <tt>templates</tt>
1216 file in their control archive<footnote>
1217 The control.tar.gz inside the .deb.
1218 See <manref name="deb" section="5">.
1220 The <prgn>config</prgn> script might be run before the
1221 <prgn>preinst</prgn> script, and before the package is unpacked
1222 or any of its dependencies or pre-dependencies are satisfied.
1223 Therefore it must work using only the tools present in
1224 <em>essential</em> packages.<footnote>
1225 <package>Debconf</package> or another tool that
1226 implements the Debian Configuration management
1227 specification will also be installed, and any
1228 versioned dependencies on it will be satisfied
1229 before preconfiguration begins.
1234 Packages which use the Debian Configuration management
1235 specification must allow for translation of their messages
1236 by using a gettext-based system such as the one provided by
1237 the <package>po-debconf</package> package.
1241 Packages should try to minimize the amount of prompting
1242 they need to do, and they should ensure that the user
1243 will only ever be asked each question once. This means
1244 that packages should try to use appropriate shared
1245 configuration files (such as <file>/etc/papersize</file> and
1246 <file>/etc/news/server</file>), and shared
1247 <package>debconf</package> variables rather than each
1248 prompting for their own list of required pieces of
1253 It also means that an upgrade should not ask the same
1254 questions again, unless the user has used
1255 <tt>dpkg --purge</tt> to remove the package's configuration.
1256 The answers to configuration questions should be stored in an
1257 appropriate place in <file>/etc</file> so that the user can
1258 modify them, and how this has been done should be
1263 If a package has a vitally important piece of
1264 information to pass to the user (such as "don't run me
1265 as I am, you must edit the following configuration files
1266 first or you risk your system emitting badly-formatted
1267 messages"), it should display this in the
1268 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1269 prompt the user to hit return to acknowledge the
1270 message. Copyright messages do not count as vitally
1271 important (they belong in
1272 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1273 neither do instructions on how to use a program (these
1274 should be in on-line documentation, where all the users
1279 Any necessary prompting should almost always be confined
1280 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1281 script. If it is done in the <prgn>postinst</prgn>, it
1282 should be protected with a conditional so that
1283 unnecessary prompting doesn't happen if a package's
1284 installation fails and the <prgn>postinst</prgn> is
1285 called with <tt>abort-upgrade</tt>,
1286 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1296 <heading>Source packages</heading>
1298 <sect id="standardsversion">
1299 <heading>Standards conformance</heading>
1302 Source packages should specify the most recent version number
1303 of this policy document with which your package complied
1304 when it was last updated.
1308 This information may be used to file bug reports
1309 automatically if your package becomes too much out of date.
1313 The version is specified in the <tt>Standards-Version</tt>
1315 The format of the <tt>Standards-Version</tt> field is
1316 described in <ref id="f-Standards-Version">.
1320 You should regularly, and especially if your package has
1321 become out of date, check for the newest Policy Manual
1322 available and update your package, if necessary. When your
1323 package complies with the new standards you should update the
1324 <tt>Standards-Version</tt> source package field and
1325 release it.<footnote>
1326 See the file <file>upgrading-checklist</file> for
1327 information about policy which has changed between
1328 different versions of this document.
1334 <sect id="pkg-relations">
1335 <heading>Package relationships</heading>
1338 Source packages should specify which binary packages they
1339 require to be installed or not to be installed in order to
1340 build correctly. For example, if building a package
1341 requires a certain compiler, then the compiler should be
1342 specified as a build-time dependency.
1346 It is not necessary to explicitly specify build-time
1347 relationships on a minimal set of packages that are always
1348 needed to compile, link and put in a Debian package a
1349 standard "Hello World!" program written in C or C++. The
1350 required packages are called <em>build-essential</em>, and
1351 an informational list can be found in
1352 <file>/usr/share/doc/build-essential/list</file> (which is
1353 contained in the <tt>build-essential</tt>
1356 <list compact="compact">
1358 This allows maintaining the list separately
1359 from the policy documents (the list does not
1360 need the kind of control that the policy
1364 Having a separate package allows one to install
1365 the build-essential packages on a machine, as
1366 well as allowing other packages such as tasks to
1367 require installation of the build-essential
1368 packages using the depends relation.
1371 The separate package allows bug reports against
1372 the list to be categorized separately from
1373 the policy management process in the BTS.
1380 When specifying the set of build-time dependencies, one
1381 should list only those packages explicitly required by the
1382 build. It is not necessary to list packages which are
1383 required merely because some other package in the list of
1384 build-time dependencies depends on them.<footnote>
1385 The reason for this is that dependencies change, and
1386 you should list all those packages, and <em>only</em>
1387 those packages that <em>you</em> need directly. What
1388 others need is their business. For example, if you
1389 only link against <file>libimlib</file>, you will need to
1390 build-depend on <package>libimlib2-dev</package> but
1391 not against any <tt>libjpeg*</tt> packages, even
1392 though <tt>libimlib2-dev</tt> currently depends on
1393 them: installation of <package>libimlib2-dev</package>
1394 will automatically ensure that all of its run-time
1395 dependencies are satisfied.
1400 If build-time dependencies are specified, it must be
1401 possible to build the package and produce working binaries
1402 on a system with only essential and build-essential
1403 packages installed and also those required to satisfy the
1404 build-time relationships (including any implied
1405 relationships). In particular, this means that version
1406 clauses should be used rigorously in build-time
1407 relationships so that one cannot produce bad or
1408 inconsistently configured packages when the relationships
1409 are properly satisfied.
1413 <ref id="relationships"> explains the technical details.
1418 <heading>Changes to the upstream sources</heading>
1421 If changes to the source code are made that are not
1422 specific to the needs of the Debian system, they should be
1423 sent to the upstream authors in whatever form they prefer
1424 so as to be included in the upstream version of the
1429 If you need to configure the package differently for
1430 Debian or for Linux, and the upstream source doesn't
1431 provide a way to do so, you should add such configuration
1432 facilities (for example, a new <prgn>autoconf</prgn> test
1433 or <tt>#define</tt>) and send the patch to the upstream
1434 authors, with the default set to the way they originally
1435 had it. You can then easily override the default in your
1436 <file>debian/rules</file> or wherever is appropriate.
1440 You should make sure that the <prgn>configure</prgn> utility
1441 detects the correct architecture specification string
1442 (refer to <ref id="arch-spec"> for details).
1446 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1447 <prgn>configure</prgn> scripts are used, you should edit the
1448 <file>.in</file> files rather than editing the
1449 <prgn>Makefile</prgn> directly. This allows the user to
1450 reconfigure the package if necessary. You should
1451 <em>not</em> configure the package and edit the generated
1452 <prgn>Makefile</prgn>! This makes it impossible for someone
1453 else to later reconfigure the package without losing the
1459 <sect id="dpkgchangelog">
1460 <heading>Debian changelog: <file>debian/changelog</file></heading>
1463 Changes in the Debian version of the package should be
1464 briefly explained in the Debian changelog file
1465 <file>debian/changelog</file>.<footnote>
1467 Mistakes in changelogs are usually best rectified by
1468 making a new changelog entry rather than "rewriting
1469 history" by editing old changelog entries.
1472 This includes modifications
1473 made in the Debian package compared to the upstream one
1474 as well as other changes and updates to the package.
1476 Although there is nothing stopping an author who is also
1477 the Debian maintainer from using this changelog for all
1478 their changes, it will have to be renamed if the Debian
1479 and upstream maintainers become different people. In such
1480 a case, however, it might be better to maintain the package
1481 as a non-native package.
1490 The format of the <file>debian/changelog</file> allows the
1491 package building tools to discover which version of the package
1492 is being built and find out other release-specific information.
1496 That format is a series of entries like this:
1498 <example compact="compact">
1499 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1501 [optional blank line(s), stripped]
1503 * <var>change details</var>
1504 <var>more change details</var>
1506 [blank line(s), included in output of dpkg-parsechangelog]
1508 * <var>even more change details</var>
1510 [optional blank line(s), stripped]
1512 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1517 <var>package</var> and <var>version</var> are the source
1518 package name and version number.
1522 <var>distribution(s)</var> lists the distributions where
1523 this version should be installed when it is uploaded - it
1524 is copied to the <tt>Distribution</tt> field in the
1525 <file>.changes</file> file. See <ref id="f-Distribution">.
1529 <var>urgency</var> is the value for the <tt>Urgency</tt>
1530 field in the <file>.changes</file> file for the upload
1531 (see <ref id="f-Urgency">). It is not possible to specify
1532 an urgency containing commas; commas are used to separate
1533 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1534 <prgn>dpkg</prgn> changelog format (though there is
1535 currently only one useful <var>keyword</var>,
1540 The change details may in fact be any series of lines
1541 starting with at least two spaces, but conventionally each
1542 change starts with an asterisk and a separating space and
1543 continuation lines are indented so as to bring them in
1544 line with the start of the text above. Blank lines may be
1545 used here to separate groups of changes, if desired.
1549 If this upload resolves bugs recorded in the Bug Tracking
1550 System (BTS), they may be automatically closed on the
1551 inclusion of this package into the Debian archive by
1552 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1553 in the change details.<footnote>
1554 To be precise, the string should match the following
1555 Perl regular expression:
1557 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1559 Then all of the bug numbers listed will be closed by the
1560 archive maintenance script (<prgn>katie</prgn>) using the
1561 <var>version</var> of the changelog entry.
1563 This information is conveyed via the <tt>Closes</tt> field
1564 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1568 The maintainer name and email address used in the changelog
1569 should be the details of the person uploading <em>this</em>
1570 version. They are <em>not</em> necessarily those of the
1571 usual package maintainer. The information here will be
1572 copied to the <tt>Changed-By</tt> field in the
1573 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1574 and then later used to send an acknowledgement when the
1575 upload has been installed.
1579 The <var>date</var> should be in RFC822 format<footnote>
1580 This is generated by <tt>date -R</tt>.
1581 </footnote>; it should include the time zone specified
1582 numerically, with the time zone name or abbreviation
1583 optionally present as a comment in parentheses.
1587 The first "title" line with the package name should start
1588 at the left hand margin; the "trailer" line with the
1589 maintainer and date details should be preceded by exactly
1590 one space. The maintainer details and the date must be
1591 separated by exactly two spaces.
1595 For more information on placement of the changelog files
1596 within binary packages, please see <ref id="changelogs">.
1599 <sect1><heading>Alternative changelog formats</heading>
1602 In non-experimental packages you must use a format for
1603 <file>debian/changelog</file> which is supported by the most
1604 recent released version of <prgn>dpkg</prgn>.
1608 It is possible to use a format different from the standard
1609 one by providing a changelog parser for the format you wish
1610 to use. The parser must have an API compatible with that
1611 expected by <prgn>dpkg-genchanges</prgn> and
1612 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1615 If there is general interest in the new format, you should
1616 contact the <package>dpkg</package> maintainer to have the
1617 parser script for it included in the <prgn>dpkg</prgn>
1618 package. (You will need to agree that the parser and its
1619 man page may be distributed under the GNU GPL, just as the rest
1620 of <prgn>dpkg</prgn> is.)
1625 <sect id="dpkgcopyright">
1626 <heading>Copyright: <file>debian/copyright</file></heading>
1628 Every package must be accompanied by a verbatim copy of
1629 its copyright and distribution license in the file
1630 <file>/usr/share/doc/<var>package</var>/copyright</file>
1631 (see <ref id="copyrightfile"> for further details). Also see
1632 <ref id="pkgcopyright"> for further considerations relayed
1633 to copyrights for packages.
1637 <heading>Error trapping in makefiles</heading>
1640 When <prgn>make</prgn> invokes a command in a makefile
1641 (including your package's upstream makefiles and
1642 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1643 means that <prgn>sh</prgn>'s usual bad error handling
1644 properties apply: if you include a miniature script as one
1645 of the commands in your makefile you'll find that if you
1646 don't do anything about it then errors are not detected
1647 and <prgn>make</prgn> will blithely continue after
1652 Every time you put more than one shell command (this
1653 includes using a loop) in a makefile command you
1654 must make sure that errors are trapped. For
1655 simple compound commands, such as changing directory and
1656 then running a program, using <tt>&&</tt> rather
1657 than semicolon as a command separator is sufficient. For
1658 more complex commands including most loops and
1659 conditionals you should include a separate <tt>set -e</tt>
1660 command at the start of every makefile command that's
1661 actually one of these miniature shell scripts.
1665 <sect id="timestamps">
1666 <heading>Time Stamps</heading>
1668 Maintainers should preserve the modification times of the
1669 upstream source files in a package, as far as is reasonably
1671 The rationale is that there is some information conveyed
1672 by knowing the age of the file, for example, you could
1673 recognize that some documentation is very old by looking
1674 at the modification time, so it would be nice if the
1675 modification time of the upstream source would be
1681 <sect id="restrictions">
1682 <heading>Restrictions on objects in source packages</heading>
1685 The source package may not contain any hard links<footnote>
1687 This is not currently detected when building source
1688 packages, but only when extracting
1692 Hard links may be permitted at some point in the
1693 future, but would require a fair amount of
1696 </footnote>, device special files, sockets or setuid or
1697 setgid files.<footnote>
1698 Setgid directories are allowed.
1703 <sect id="debianrules">
1704 <heading>Main building script: <file>debian/rules</file></heading>
1707 This file must be an executable makefile, and contains the
1708 package-specific recipes for compiling the package and
1709 building binary package(s) from the source.
1713 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1714 so that it can be invoked by saying its name rather than
1715 invoking <prgn>make</prgn> explicitly.
1719 Since an interactive <file>debian/rules</file> script makes it
1720 impossible to auto-compile that package and also makes it
1721 hard for other people to reproduce the same binary
1722 package, all <em>required targets</em> MUST be
1723 non-interactive. At a minimum, required targets are the
1724 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1725 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1726 <em>binary-indep</em>, and <em>build</em>. It also follows
1727 that any target that these targets depend on must also be
1732 The targets are as follows (required unless stated otherwise):
1734 <tag><tt>build</tt></tag>
1737 The <tt>build</tt> target should perform all the
1738 configuration and compilation of the package.
1739 If a package has an interactive pre-build
1740 configuration routine, the Debianized source package
1741 must either be built after this has taken place (so
1742 that the binary package can be built without rerunning
1743 the configuration) or the configuration routine
1744 modified to become non-interactive. (The latter is
1745 preferable if there are architecture-specific features
1746 detected by the configuration routine.)
1750 For some packages, notably ones where the same
1751 source tree is compiled in different ways to produce
1752 two binary packages, the <tt>build</tt> target
1753 does not make much sense. For these packages it is
1754 good enough to provide two (or more) targets
1755 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1756 for each of the ways of building the package, and a
1757 <tt>build</tt> target that does nothing. The
1758 <tt>binary</tt> target will have to build the
1759 package in each of the possible ways and make the
1760 binary package out of each.
1764 The <tt>build</tt> target must not do anything
1765 that might require root privilege.
1769 The <tt>build</tt> target may need to run the
1770 <tt>clean</tt> target first - see below.
1774 When a package has a configuration and build routine
1775 which takes a long time, or when the makefiles are
1776 poorly designed, or when <tt>build</tt> needs to
1777 run <tt>clean</tt> first, it is a good idea to
1778 <tt>touch build</tt> when the build process is
1779 complete. This will ensure that if <tt>debian/rules
1780 build</tt> is run again it will not rebuild the whole
1782 Another common way to do this is for <tt>build</tt>
1783 to depend on <prgn>build-stamp</prgn> and to do
1784 nothing else, and for the <prgn>build-stamp</prgn>
1785 target to do the building and to <tt>touch
1786 build-stamp</tt> on completion. This is
1787 especially useful if the build routine creates a
1788 file or directory called <tt>build</tt>; in such a
1789 case, <tt>build</tt> will need to be listed as
1790 a phony target (i.e., as a dependency of the
1791 <tt>.PHONY</tt> target). See the documentation of
1792 <prgn>make</prgn> for more information on phony
1798 <tag><tt>build-arch</tt> (optional),
1799 <tt>build-indep</tt> (optional)
1803 A package may also provide both of the targets
1804 <tt>build-arch</tt> and <tt>build-indep</tt>.
1805 The <tt>build-arch</tt> target, if provided, should
1806 perform all the configuration and compilation required
1807 for producing all architecture-dependant binary packages
1808 (those packages for which the body of the
1809 <tt>Architecture</tt> field in <tt>debian/control</tt>
1810 is not <tt>all</tt>).
1811 Similarly, the <tt>build-indep</tt> target, if
1812 provided, should perform all the configuration and
1813 compilation required for producing all
1814 architecture-independent binary packages
1815 (those packages for which the body of the
1816 <tt>Architecture</tt> field in <tt>debian/control</tt>
1818 The <tt>build</tt> target should depend on those of the
1819 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1820 are provided in the rules file.
1824 If one or both of the targets <tt>build-arch</tt> and
1825 <tt>build-indep</tt> are not provided, then invoking
1826 <file>debian/rules</file> with one of the not-provided
1827 targets as arguments should produce a exit status code
1828 of 2. Usually this is provided automatically by make
1829 if the target is missing.
1833 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1834 must not do anything that might require root privilege.
1838 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1839 <tt>binary-indep</tt>
1843 The <tt>binary</tt> target must be all that is
1844 necessary for the user to build the binary package(s)
1845 produced from this source package. It is
1846 split into two parts: <prgn>binary-arch</prgn> builds
1847 the binary packages which are specific to a particular
1848 architecture, and <tt>binary-indep</tt> builds
1849 those which are not.
1852 <tt>binary</tt> may be (and commonly is) a target with
1853 no commands which simply depends on
1854 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1857 Both <tt>binary-*</tt> targets should depend on the
1858 <tt>build</tt> target, or on the appropriate
1859 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1860 provided, so that the package is built if it has not
1861 been already. It should then create the relevant
1862 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1863 make their control files and <prgn>dpkg-deb</prgn> to
1864 build them and place them in the parent of the top
1869 Both the <tt>binary-arch</tt> and
1870 <tt>binary-indep</tt> targets <em>must</em> exist.
1871 If one of them has nothing to do (which will always be
1872 the case if the source generates only a single binary
1873 package, whether architecture-dependent or not), it
1874 must still exist and must always succeed.
1878 The <tt>binary</tt> targets must be invoked as
1880 The <prgn>fakeroot</prgn> package often allows one
1881 to build a package correctly even without being
1887 <tag><tt>clean</tt></tag>
1890 This must undo any effects that the <tt>build</tt>
1891 and <tt>binary</tt> targets may have had, except
1892 that it should leave alone any output files created in
1893 the parent directory by a run of a <tt>binary</tt>
1898 If a <tt>build</tt> file is touched at the end of
1899 the <tt>build</tt> target, as suggested above, it
1900 should be removed as the first action that
1901 <tt>clean</tt> performs, so that running
1902 <tt>build</tt> again after an interrupted
1903 <tt>clean</tt> doesn't think that everything is
1908 The <tt>clean</tt> target may need to be
1909 invoked as root if <tt>binary</tt> has been
1910 invoked since the last <tt>clean</tt>, or if
1911 <tt>build</tt> has been invoked as root (since
1912 <tt>build</tt> may create directories, for
1917 <tag><tt>get-orig-source</tt> (optional)</tag>
1920 This target fetches the most recent version of the
1921 original source package from a canonical archive site
1922 (via FTP or WWW, for example), does any necessary
1923 rearrangement to turn it into the original source
1924 tar file format described below, and leaves it in the
1929 This target may be invoked in any directory, and
1930 should take care to clean up any temporary files it
1935 This target is optional, but providing it if
1936 possible is a good idea.
1940 <tag><tt>patch</tt> (optional)</tag>
1943 This target performs whatever additional actions are
1944 required to make the source ready for editing (unpacking
1945 additional upstream archives, applying patches, etc.).
1946 It is recommended to be implemented for any package where
1947 <tt>dpkg-source -x</tt> does not result in source ready
1948 for additional modification. See
1949 <ref id="readmesource">.
1955 The <tt>build</tt>, <tt>binary</tt> and
1956 <tt>clean</tt> targets must be invoked with the current
1957 directory being the package's top-level directory.
1962 Additional targets may exist in <file>debian/rules</file>,
1963 either as published or undocumented interfaces or for the
1964 package's internal use.
1968 The architectures we build on and build for are determined
1969 by <prgn>make</prgn> variables using the utility
1970 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1971 You can determine the
1972 Debian architecture and the GNU style architecture
1973 specification string for the build machine (the machine type
1974 we are building on) as well as for the host machine (the
1975 machine type we are building for). Here is a list of
1976 supported <prgn>make</prgn> variables:
1977 <list compact="compact">
1979 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1982 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1983 specification string)
1986 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1987 <tt>DEB_*_GNU_TYPE</tt>)
1990 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1991 <tt>DEB_*_GNU_TYPE</tt>)
1993 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1994 the build machine or <tt>HOST</tt> for specification of the
1999 Backward compatibility can be provided in the rules file
2000 by setting the needed variables to suitable default
2001 values; please refer to the documentation of
2002 <prgn>dpkg-architecture</prgn> for details.
2006 It is important to understand that the <tt>DEB_*_ARCH</tt>
2007 string only determines which Debian architecture we are
2008 building on or for. It should not be used to get the CPU
2009 or system information; the GNU style variables should be
2013 <sect1 id="debianrules-options">
2014 <heading><file>debian/rules</file> and
2015 <tt>DEB_BUILD_OPTIONS</tt></heading>
2018 Supporting the standardized environment variable
2019 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2020 contain several flags to change how a package is compiled and
2021 built. Each flag must be in the form <var>flag</var> or
2022 <var>flag</var>=<var>options</var>. If multiple flags are
2023 given, they must be separated by whitespace.<footnote>
2024 Some packages support any delimiter, but whitespace is the
2025 easiest to parse inside a makefile and avoids ambiguity with
2026 flag values that contain commas.
2028 <var>flag</var> must start with a lowercase letter
2029 (<tt>a-z</tt>) and consist only of lowercase letters,
2030 numbers (<tt>0-9</tt>), and the characters
2031 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2032 <var>options</var> must not contain whitespace. The same
2033 tag should not be given multiple times with conflicting
2034 values. Package maintainers may assume that
2035 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2039 The meaning of the following tags has been standardized:
2043 The presence of this tag means that the package should
2044 be compiled with a minimum of optimization. For C
2045 programs, it is best to add <tt>-O0</tt> to
2046 <tt>CFLAGS</tt> (although this is usually the default).
2047 Some programs might fail to build or run at this level
2048 of optimization; it may be necessary to use
2049 <tt>-O1</tt>, for example.
2053 This tag means that the debugging symbols should not be
2054 stripped from the binary during installation, so that
2055 debugging information may be included in the package.
2057 <tag>parallel=n</tag>
2059 This tag means that the package should be built using up
2060 to <tt>n</tt> parallel processes if the package build
2061 system supports this.<footnote>
2062 Packages built with <tt>make</tt> can often implement
2063 this by passing the <tt>-j</tt><var>n</var> option to
2066 If the package build system does not support parallel
2067 builds, this string must be ignored. If the package
2068 build system only supports a lower level of concurrency
2069 than <var>n</var>, the package should be built using as
2070 many parallel processes as the package build system
2071 supports. It is up to the package maintainer to decide
2072 whether the package build times are long enough and the
2073 package build system is robust enough to make supporting
2074 parallel builds worthwhile.
2080 Unknown flags must be ignored by <file>debian/rules</file>.
2084 The following makefile snippet is an example of how one may
2085 implement the build options; you will probably have to
2086 massage this example in order to make it work for your
2088 <example compact="compact">
2091 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2092 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2093 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2094 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2096 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2101 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2102 INSTALL_PROGRAM += -s
2104 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2105 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2106 MAKEFLAGS += -j$(NUMJOBS)
2113 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2114 <sect id="substvars">
2115 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2118 When <prgn>dpkg-gencontrol</prgn>,
2119 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2120 generate control files they perform variable substitutions
2121 on their output just before writing it. Variable
2122 substitutions have the form <tt>${<var>variable</var>}</tt>.
2123 The optional file <file>debian/substvars</file> contains
2124 variable substitutions to be used; variables can also be set
2125 directly from <file>debian/rules</file> using the <tt>-V</tt>
2126 option to the source packaging commands, and certain
2127 predefined variables are also available.
2131 The <file>debian/substvars</file> file is usually generated and
2132 modified dynamically by <file>debian/rules</file> targets, in
2133 which case it must be removed by the <tt>clean</tt> target.
2137 See <manref name="deb-substvars" section="5"> for full
2138 details about source variable substitutions, including the
2139 format of <file>debian/substvars</file>.</p>
2142 <sect id="debianwatch">
2143 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2146 This is an optional, recommended control file for the
2147 <tt>uscan</tt> utility which defines how to automatically
2148 scan ftp or http sites for newly available updates of the
2149 package. This is used by <url id="
2150 http://dehs.alioth.debian.org/"> and other Debian QA tools
2151 to help with quality control and maintenance of the
2152 distribution as a whole.
2157 <sect id="debianfiles">
2158 <heading>Generated files list: <file>debian/files</file></heading>
2161 This file is not a permanent part of the source tree; it
2162 is used while building packages to record which files are
2163 being generated. <prgn>dpkg-genchanges</prgn> uses it
2164 when it generates a <file>.changes</file> file.
2168 It should not exist in a shipped source package, and so it
2169 (and any backup files or temporary files such as
2170 <file>files.new</file><footnote>
2171 <file>files.new</file> is used as a temporary file by
2172 <prgn>dpkg-gencontrol</prgn> and
2173 <prgn>dpkg-distaddfile</prgn> - they write a new
2174 version of <tt>files</tt> here before renaming it,
2175 to avoid leaving a corrupted copy if an error
2177 </footnote>) should be removed by the
2178 <tt>clean</tt> target. It may also be wise to
2179 ensure a fresh start by emptying or removing it at the
2180 start of the <tt>binary</tt> target.
2184 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2185 package, it adds an entry to <file>debian/files</file> for the
2186 <file>.deb</file> file that will be created when <tt>dpkg-deb
2187 --build</tt> is run for that binary package. So for most
2188 packages all that needs to be done with this file is to
2189 delete it in the <tt>clean</tt> target.
2193 If a package upload includes files besides the source
2194 package and any binary packages whose control files were
2195 made with <prgn>dpkg-gencontrol</prgn> then they should be
2196 placed in the parent of the package's top-level directory
2197 and <prgn>dpkg-distaddfile</prgn> should be called to add
2198 the file to the list in <file>debian/files</file>.</p>
2201 <sect id="embeddedfiles">
2202 <heading>Convenience copies of code</heading>
2205 Some software packages include in their distribution convenience
2206 copies of code from other software packages, generally so that
2207 users compiling from source don't have to download multiple
2208 packages. Debian packages should not make use of these
2209 convenience copies unless the included package is explicitly
2210 intended to be used in this way.<footnote>
2211 For example, parts of the GNU build system work like this.
2213 If the included code is already in the Debian archive in the
2214 form of a library, the Debian packaging should ensure that
2215 binary packages reference the libraries already in Debian and
2216 the convenience copy is not used. If the included code is not
2217 already in Debian, it should be packaged separately as a
2218 prerequisite if possible.
2220 Having multiple copies of the same code in Debian is
2221 inefficient, often creates either static linking or shared
2222 library conflicts, and, most importantly, increases the
2223 difficulty of handling security vulnerabilities in the
2229 <sect id="readmesource">
2230 <heading>Source package handling:
2231 <file>debian/README.source</file></heading>
2234 If running <prgn>dpkg-source -x</prgn> on a source package
2235 doesn't produce the source of the package, ready for editing,
2236 and allow one to make changes and run
2237 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2238 without taking any additional steps, creating a
2239 <file>debian/README.source</file> documentation file is
2240 recommended. This file should explain how to do all of the
2243 <item>Generate the fully patched source, in a form ready for
2244 editing, that would be built to create Debian
2245 packages. Doing this with a <tt>patch</tt> target in
2246 <file>debian/rules</file> is recommended; see
2247 <ref id="debianrules">.</item>
2248 <item>Modify the source and save those modifications so that
2249 they will be applied when building the package.</item>
2250 <item>Remove source modifications that are currently being
2251 applied when building the package.</item>
2252 <item>Optionally, document what steps are necessary to
2253 upgrade the Debian source package to a new upstream version,
2254 if applicable.</item>
2256 This explanation should include specific commands and mention
2257 any additional required Debian packages. It should not assume
2258 familiarity with any specific Debian packaging system or patch
2263 This explanation may refer to a documentation file installed by
2264 one of the package's build dependencies provided that the
2265 referenced documentation clearly explains these tasks and is not
2266 a general reference manual.
2270 <file>debian/README.source</file> may also include any other
2271 information that would be helpful to someone modifying the
2272 source package. Even if the package doesn't fit the above
2273 description, maintainers are encouraged to document in a
2274 <file>debian/README.source</file> file any source package with a
2275 particularly complex or unintuitive source layout or build
2276 system (for example, a package that builds the same source
2277 multiple times to generate different binary packages).
2283 <chapt id="controlfields">
2284 <heading>Control files and their fields</heading>
2287 The package management system manipulates data represented in
2288 a common format, known as <em>control data</em>, stored in
2289 <em>control files</em>.
2290 Control files are used for source packages, binary packages and
2291 the <file>.changes</file> files which control the installation
2292 of uploaded files<footnote>
2293 <prgn>dpkg</prgn>'s internal databases are in a similar
2298 <sect id="controlsyntax">
2299 <heading>Syntax of control files</heading>
2302 A control file consists of one or more paragraphs of
2304 The paragraphs are also sometimes referred to as stanzas.
2306 The paragraphs are separated by blank lines. Some control
2307 files allow only one paragraph; others allow several, in
2308 which case each paragraph usually refers to a different
2309 package. (For example, in source packages, the first
2310 paragraph refers to the source package, and later paragraphs
2311 refer to binary packages generated from the source.)
2315 Each paragraph consists of a series of data fields; each
2316 field consists of the field name, followed by a colon and
2317 then the data/value associated with that field. It ends at
2318 the end of the (logical) line. Horizontal whitespace
2319 (spaces and tabs) may occur immediately before or after the
2320 value and is ignored there; it is conventional to put a
2321 single space after the colon. For example, a field might
2323 <example compact="compact">
2326 the field name is <tt>Package</tt> and the field value
2331 Many fields' values may span several lines; in this case
2332 each continuation line must start with a space or a tab.
2333 Any trailing spaces or tabs at the end of individual
2334 lines of a field value are ignored.
2338 In fields where it is specified that lines may not wrap,
2339 only a single line of data is allowed and whitespace is not
2340 significant in a field body. Whitespace must not appear
2341 inside names (of packages, architectures, files or anything
2342 else) or version numbers, or between the characters of
2343 multi-character version relationships.
2347 Field names are not case-sensitive, but it is usual to
2348 capitalize the field names using mixed case as shown below.
2352 Blank lines, or lines consisting only of spaces and tabs,
2353 are not allowed within field values or between fields - that
2354 would mean a new paragraph.
2359 <sect id="sourcecontrolfiles">
2360 <heading>Source package control files -- <file>debian/control</file></heading>
2363 The <file>debian/control</file> file contains the most vital
2364 (and version-independent) information about the source package
2365 and about the binary packages it creates.
2369 The first paragraph of the control file contains information about
2370 the source package in general. The subsequent sets each describe a
2371 binary package that the source tree builds.
2375 The fields in the general paragraph (the first one, for the source
2378 <list compact="compact">
2379 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2380 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2381 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2382 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2383 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2384 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2385 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2386 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2391 The fields in the binary package paragraphs are:
2393 <list compact="compact">
2394 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2395 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2396 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2397 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2398 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2399 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2400 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2401 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2406 The syntax and semantics of the fields are described below.
2412 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2413 generate control files for binary packages (see below), by
2414 <prgn>dpkg-genchanges</prgn> to generate the
2415 <tt>.changes</tt> file to accompany the upload, and by
2416 <prgn>dpkg-source</prgn> when it creates the
2417 <file>.dsc</file> source control file as part of a source
2418 archive. Many fields are permitted to span multiple lines in
2419 <file>debian/control</file> but not in any other control
2420 file. These tools are responsible for removing the line
2421 breaks from such fields when using fields from
2422 <file>debian/control</file> to generate other control files.
2426 The fields here may contain variable references - their
2427 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2428 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2429 when they generate output control files.
2430 See <ref id="substvars"> for details.
2435 <sect id="binarycontrolfiles">
2436 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2439 The <file>DEBIAN/control</file> file contains the most vital
2440 (and version-dependent) information about a binary package.
2444 The fields in this file are:
2446 <list compact="compact">
2447 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2448 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2449 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2450 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2451 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2452 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2453 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2454 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2455 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2456 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2457 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2458 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2463 <sect id="debiansourcecontrolfiles">
2464 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2467 This file contains a series of fields, identified and
2468 separated just like the fields in the control file of
2469 a binary package. The fields are listed below; their
2470 syntax is described above, in <ref id="pkg-controlfields">.
2472 <list compact="compact">
2473 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2474 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2475 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2476 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2477 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2478 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2479 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2480 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2481 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2482 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2488 The source package control file is generated by
2489 <prgn>dpkg-source</prgn> when it builds the source
2490 archive, from other files in the source package,
2491 described above. When unpacking, it is checked against
2492 the files and directories in the other parts of the
2498 <sect id="debianchangesfiles">
2499 <heading>Debian changes files -- <file>.changes</file></heading>
2502 The .changes files are used by the Debian archive maintenance
2503 software to process updates to packages. They contain one
2504 paragraph which contains information from the
2505 <tt>debian/control</tt> file and other data about the
2506 source package gathered via <tt>debian/changelog</tt>
2507 and <tt>debian/rules</tt>.
2511 The fields in this file are:
2513 <list compact="compact">
2514 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2516 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2518 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2519 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2520 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2521 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2522 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2524 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2525 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2526 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2527 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2532 <sect id="controlfieldslist">
2533 <heading>List of fields</heading>
2535 <sect1 id="f-Source">
2536 <heading><tt>Source</tt></heading>
2539 This field identifies the source package name.
2543 In <file>debian/control</file> or a <file>.dsc</file> file,
2544 this field must contain only the name of the source package.
2548 In a binary package control file or a <file>.changes</file>
2549 file, the source package name may be followed by a version
2550 number in parentheses<footnote>
2551 It is customary to leave a space after the package name
2552 if a version number is specified.
2554 This version number may be omitted (and is, by
2555 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2556 the <tt>Version</tt> field of the binary package in
2557 question. The field itself may be omitted from a binary
2558 package control file when the source package has the same
2559 name and version as the binary package.
2563 <sect1 id="f-Maintainer">
2564 <heading><tt>Maintainer</tt></heading>
2567 The package maintainer's name and email address. The name
2568 should come first, then the email address inside angle
2569 brackets <tt><></tt> (in RFC822 format).
2573 If the maintainer's name contains a full stop then the
2574 whole field will not work directly as an email address due
2575 to a misfeature in the syntax specified in RFC822; a
2576 program using this field as an address must check for this
2577 and correct the problem if necessary (for example by
2578 putting the name in round brackets and moving it to the
2579 end, and bringing the email address forward).
2583 <sect1 id="f-Uploaders">
2584 <heading><tt>Uploaders</tt></heading>
2587 List of the names and email addresses of co-maintainers of
2588 the package, if any. If the package has other maintainers
2589 beside the one named in the
2590 <qref id="f-Maintainer">Maintainer field</qref>, their
2591 names and email addresses should be listed here. The
2592 format is the same as that of the Maintainer tag, and
2593 multiple entries should be comma separated. Currently,
2594 this field is restricted to a single line of data. This
2595 is an optional field.
2598 Any parser that interprets the Uploaders field in
2599 <file>debian/control</file> must permit it to span multiple
2600 lines. Line breaks in an Uploaders field that spans multiple
2601 lines are not significant and the semantics of the field are
2602 the same as if the line breaks had not been present.
2606 <sect1 id="f-Changed-By">
2607 <heading><tt>Changed-By</tt></heading>
2610 The name and email address of the person who changed the
2611 said package. Usually the name of the maintainer.
2612 All the rules for the Maintainer field apply here, too.
2616 <sect1 id="f-Section">
2617 <heading><tt>Section</tt></heading>
2620 This field specifies an application area into which the package
2621 has been classified. See <ref id="subsections">.
2625 When it appears in the <file>debian/control</file> file,
2626 it gives the value for the subfield of the same name in
2627 the <tt>Files</tt> field of the <file>.changes</file> file.
2628 It also gives the default for the same field in the binary
2633 <sect1 id="f-Priority">
2634 <heading><tt>Priority</tt></heading>
2637 This field represents how important that it is that the user
2638 have the package installed. See <ref id="priorities">.
2642 When it appears in the <file>debian/control</file> file,
2643 it gives the value for the subfield of the same name in
2644 the <tt>Files</tt> field of the <file>.changes</file> file.
2645 It also gives the default for the same field in the binary
2650 <sect1 id="f-Package">
2651 <heading><tt>Package</tt></heading>
2654 The name of the binary package.
2658 Package names must consist only of lower case letters
2659 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2660 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2661 They must be at least two characters long and must start
2662 with an alphanumeric character.
2666 <sect1 id="f-Architecture">
2667 <heading><tt>Architecture</tt></heading>
2670 Depending on context and the control file used, the
2671 <tt>Architecture</tt> field can include the following sets of
2674 <item>A unique single word identifying a Debian machine
2675 architecture, see <ref id="arch-spec">.
2676 <item><tt>all</tt>, which indicates an
2677 architecture-independent package.
2678 <item><tt>any</tt>, which indicates a package available
2679 for building on any architecture.
2680 <item><tt>source</tt>, which indicates a source package.
2685 In the main <file>debian/control</file> file in the source
2686 package, or in the source package control file
2687 <file>.dsc</file>, one may specify a list of architectures
2688 separated by spaces, or the special values <tt>any</tt> or
2693 Specifying <tt>any</tt> indicates that the source package
2694 isn't dependent on any particular architecture and should
2695 compile fine on any one. The produced binary package(s)
2696 will be specific to whatever the current build architecture
2698 This is the most often used setting, and is recommended
2699 for new packages that aren't <tt>Architecture: all</tt>.
2704 Specifying a list of architectures indicates that the source
2705 will build an architecture-dependent package, and will only
2706 work correctly on the listed architectures.<footnote>
2707 This is a setting used for a minority of cases where the
2708 program is not portable. Generally, it should not be used
2714 In a <file>.changes</file> file, the <tt>Architecture</tt>
2715 field lists the architecture(s) of the package(s)
2716 currently being uploaded. This will be a list; if the
2717 source for the package is also being uploaded, the special
2718 entry <tt>source</tt> is also present.
2722 See <ref id="debianrules"> for information how to get the
2723 architecture for the build process.
2727 <sect1 id="f-Essential">
2728 <heading><tt>Essential</tt></heading>
2731 This is a boolean field which may occur only in the
2732 control file of a binary package or in a per-package fields
2733 paragraph of a main source control data file.
2737 If set to <tt>yes</tt> then the package management system
2738 will refuse to remove the package (upgrading and replacing
2739 it is still possible). The other possible value is <tt>no</tt>,
2740 which is the same as not having the field at all.
2745 <heading>Package interrelationship fields:
2746 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2747 <tt>Recommends</tt>, <tt>Suggests</tt>,
2748 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2749 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2753 These fields describe the package's relationships with
2754 other packages. Their syntax and semantics are described
2755 in <ref id="relationships">.</p>
2758 <sect1 id="f-Standards-Version">
2759 <heading><tt>Standards-Version</tt></heading>
2762 The most recent version of the standards (the policy
2763 manual and associated texts) with which the package
2768 The version number has four components: major and minor
2769 version number and major and minor patch level. When the
2770 standards change in a way that requires every package to
2771 change the major number will be changed. Significant
2772 changes that will require work in many packages will be
2773 signaled by a change to the minor number. The major patch
2774 level will be changed for any change to the meaning of the
2775 standards, however small; the minor patch level will be
2776 changed when only cosmetic, typographical or other edits
2777 are made which neither change the meaning of the document
2778 nor affect the contents of packages.
2782 Thus only the first three components of the policy version
2783 are significant in the <em>Standards-Version</em> control
2784 field, and so either these three components or the all
2785 four components may be specified.<footnote>
2786 In the past, people specified the full version number
2787 in the Standards-Version field, for example "2.3.0.0".
2788 Since minor patch-level changes don't introduce new
2789 policy, it was thought it would be better to relax
2790 policy and only require the first 3 components to be
2791 specified, in this example "2.3.0". All four
2792 components may still be used if someone wishes to do so.
2798 <sect1 id="f-Version">
2799 <heading><tt>Version</tt></heading>
2802 The version number of a package. The format is:
2803 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2807 The three components here are:
2809 <tag><var>epoch</var></tag>
2812 This is a single (generally small) unsigned integer. It
2813 may be omitted, in which case zero is assumed. If it is
2814 omitted then the <var>upstream_version</var> may not
2819 It is provided to allow mistakes in the version numbers
2820 of older versions of a package, and also a package's
2821 previous version numbering schemes, to be left behind.
2825 <tag><var>upstream_version</var></tag>
2828 This is the main part of the version number. It is
2829 usually the version number of the original ("upstream")
2830 package from which the <file>.deb</file> file has been made,
2831 if this is applicable. Usually this will be in the same
2832 format as that specified by the upstream author(s);
2833 however, it may need to be reformatted to fit into the
2834 package management system's format and comparison
2839 The comparison behavior of the package management system
2840 with respect to the <var>upstream_version</var> is
2841 described below. The <var>upstream_version</var>
2842 portion of the version number is mandatory.
2846 The <var>upstream_version</var> may contain only
2847 alphanumerics<footnote>
2848 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2850 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2851 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2852 tilde) and should start with a digit. If there is no
2853 <var>debian_revision</var> then hyphens are not allowed;
2854 if there is no <var>epoch</var> then colons are not
2859 <tag><var>debian_revision</var></tag>
2862 This part of the version number specifies the version of
2863 the Debian package based on the upstream version. It
2864 may contain only alphanumerics and the characters
2865 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2866 tilde) and is compared in the same way as the
2867 <var>upstream_version</var> is.
2871 It is optional; if it isn't present then the
2872 <var>upstream_version</var> may not contain a hyphen.
2873 This format represents the case where a piece of
2874 software was written specifically to be turned into a
2875 Debian package, and so there is only one "debianisation"
2876 of it and therefore no revision indication is required.
2880 It is conventional to restart the
2881 <var>debian_revision</var> at <tt>1</tt> each time the
2882 <var>upstream_version</var> is increased.
2886 The package management system will break the version
2887 number apart at the last hyphen in the string (if there
2888 is one) to determine the <var>upstream_version</var> and
2889 <var>debian_revision</var>. The absence of a
2890 <var>debian_revision</var> is equivalent to a
2891 <var>debian_revision</var> of <tt>0</tt>.
2898 When comparing two version numbers, first the <var>epoch</var>
2899 of each are compared, then the <var>upstream_version</var> if
2900 <var>epoch</var> is equal, and then <var>debian_revision</var>
2901 if <var>upstream_version</var> is also equal.
2902 <var>epoch</var> is compared numerically. The
2903 <var>upstream_version</var> and <var>debian_revision</var>
2904 parts are compared by the package management system using the
2905 following algorithm:
2909 The strings are compared from left to right.
2913 First the initial part of each string consisting entirely of
2914 non-digit characters is determined. These two parts (one of
2915 which may be empty) are compared lexically. If a difference
2916 is found it is returned. The lexical comparison is a
2917 comparison of ASCII values modified so that all the letters
2918 sort earlier than all the non-letters and so that a tilde
2919 sorts before anything, even the end of a part. For example,
2920 the following parts are in sorted order from earliest to
2921 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2922 <tt>a</tt>.<footnote>
2923 One common use of <tt>~</tt> is for upstream pre-releases.
2924 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2925 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2930 Then the initial part of the remainder of each string which
2931 consists entirely of digit characters is determined. The
2932 numerical values of these two parts are compared, and any
2933 difference found is returned as the result of the comparison.
2934 For these purposes an empty string (which can only occur at
2935 the end of one or both version strings being compared) counts
2940 These two steps (comparing and removing initial non-digit
2941 strings and initial digit strings) are repeated until a
2942 difference is found or both strings are exhausted.
2946 Note that the purpose of epochs is to allow us to leave behind
2947 mistakes in version numbering, and to cope with situations
2948 where the version numbering scheme changes. It is
2949 <em>not</em> intended to cope with version numbers containing
2950 strings of letters which the package management system cannot
2951 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2952 silly orderings (the author of this manual has heard of a
2953 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2954 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2955 <tt>2</tt> and so forth).
2959 <sect1 id="f-Description">
2960 <heading><tt>Description</tt></heading>
2963 In a source or binary control file, the <tt>Description</tt>
2964 field contains a description of the binary package, consisting
2965 of two parts, the synopsis or the short description, and the
2966 long description. The field's format is as follows:
2971 Description: <single line synopsis>
2972 <extended description over several lines>
2977 The lines in the extended description can have these formats:
2983 Those starting with a single space are part of a paragraph.
2984 Successive lines of this form will be word-wrapped when
2985 displayed. The leading space will usually be stripped off.
2989 Those starting with two or more spaces. These will be
2990 displayed verbatim. If the display cannot be panned
2991 horizontally, the displaying program will line wrap them "hard"
2992 (i.e., without taking account of word breaks). If it can they
2993 will be allowed to trail off to the right. None, one or two
2994 initial spaces may be deleted, but the number of spaces
2995 deleted from each line will be the same (so that you can have
2996 indenting work correctly, for example).
3000 Those containing a single space followed by a single full stop
3001 character. These are rendered as blank lines. This is the
3002 <em>only</em> way to get a blank line<footnote>
3003 Completely empty lines will not be rendered as blank lines.
3004 Instead, they will cause the parser to think you're starting
3005 a whole new record in the control file, and will therefore
3006 likely abort with an error.
3011 Those containing a space, a full stop and some more characters.
3012 These are for future expansion. Do not use them.
3018 Do not use tab characters. Their effect is not predictable.
3022 See <ref id="descriptions"> for further information on this.
3026 In a <file>.changes</file> file, the <tt>Description</tt> field
3027 contains a summary of the descriptions for the packages being
3032 The part of the field before the first newline is empty;
3033 thereafter each line has the name of a binary package and
3034 the summary description line from that binary package.
3035 Each line is indented by one space.
3040 <sect1 id="f-Distribution">
3041 <heading><tt>Distribution</tt></heading>
3044 In a <file>.changes</file> file or parsed changelog output
3045 this contains the (space-separated) name(s) of the
3046 distribution(s) where this version of the package should
3047 be installed. Valid distributions are determined by the
3048 archive maintainers.<footnote>
3049 Current distribution names are:
3050 <taglist compact="compact">
3051 <tag><em>stable</em></tag>
3053 This is the current "released" version of Debian
3054 GNU/Linux. Once the distribution is
3055 <em>stable</em> only security fixes and other
3056 major bug fixes are allowed. When changes are
3057 made to this distribution, the release number is
3058 increased (for example: 2.2r1 becomes 2.2r2 then
3062 <tag><em>unstable</em></tag>
3064 This distribution value refers to the
3065 <em>developmental</em> part of the Debian
3066 distribution tree. New packages, new upstream
3067 versions of packages and bug fixes go into the
3068 <em>unstable</em> directory tree. Download from
3069 this distribution at your own risk.
3072 <tag><em>testing</em></tag>
3074 This distribution value refers to the
3075 <em>testing</em> part of the Debian distribution
3076 tree. It receives its packages from the
3077 unstable distribution after a short time lag to
3078 ensure that there are no major issues with the
3079 unstable packages. It is less prone to breakage
3080 than unstable, but still risky. It is not
3081 possible to upload packages directly to
3085 <tag><em>frozen</em></tag>
3087 From time to time, the <em>testing</em>
3088 distribution enters a state of "code-freeze" in
3089 anticipation of release as a <em>stable</em>
3090 version. During this period of testing only
3091 fixes for existing or newly-discovered bugs will
3092 be allowed. The exact details of this stage are
3093 determined by the Release Manager.
3096 <tag><em>experimental</em></tag>
3098 The packages with this distribution value are
3099 deemed by their maintainers to be high
3100 risk. Oftentimes they represent early beta or
3101 developmental packages from various sources that
3102 the maintainers want people to try, but are not
3103 ready to be a part of the other parts of the
3104 Debian distribution tree. Download at your own
3110 You should list <em>all</em> distributions that the
3111 package should be installed into.
3115 More information is available in the Debian Developer's
3116 Reference, section "The Debian archive".
3123 <heading><tt>Date</tt></heading>
3126 This field includes the date the package was built or last edited.
3130 The value of this field is usually extracted from the
3131 <file>debian/changelog</file> file - see
3132 <ref id="dpkgchangelog">).
3136 <sect1 id="f-Format">
3137 <heading><tt>Format</tt></heading>
3140 This field specifies a format revision for the file.
3141 The most current format described in the Policy Manual
3142 is version <strong>1.5</strong>. The syntax of the
3143 format value is the same as that of a package version
3144 number except that no epoch or Debian revision is allowed
3145 - see <ref id="f-Version">.
3149 <sect1 id="f-Urgency">
3150 <heading><tt>Urgency</tt></heading>
3153 This is a description of how important it is to upgrade to
3154 this version from previous ones. It consists of a single
3155 keyword taking one of the values <tt>low</tt>,
3156 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3157 <tt>critical</tt><footnote>
3158 Other urgency values are supported with configuration
3159 changes in the archive software but are not used in Debian.
3160 The urgency affects how quickly a package will be considered
3161 for inclusion into the <tt>testing</tt> distribution and
3162 gives an indication of the importance of any fixes included
3163 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3164 treated as synonymous.
3165 </footnote> (not case-sensitive) followed by an optional
3166 commentary (separated by a space) which is usually in
3167 parentheses. For example:
3170 Urgency: low (HIGH for users of diversions)
3176 The value of this field is usually extracted from the
3177 <file>debian/changelog</file> file - see
3178 <ref id="dpkgchangelog">.
3182 <sect1 id="f-Changes">
3183 <heading><tt>Changes</tt></heading>
3186 This field contains the human-readable changes data, describing
3187 the differences between the last version and the current one.
3191 There should be nothing in this field before the first
3192 newline; all the subsequent lines must be indented by at
3193 least one space; blank lines must be represented by a line
3194 consisting only of a space and a full stop.
3198 The value of this field is usually extracted from the
3199 <file>debian/changelog</file> file - see
3200 <ref id="dpkgchangelog">).
3204 Each version's change information should be preceded by a
3205 "title" line giving at least the version, distribution(s)
3206 and urgency, in a human-readable way.
3210 If data from several versions is being returned the entry
3211 for the most recent version should be returned first, and
3212 entries should be separated by the representation of a
3213 blank line (the "title" line may also be followed by the
3214 representation of blank line).
3218 <sect1 id="f-Binary">
3219 <heading><tt>Binary</tt></heading>
3222 This field is a list of binary packages.
3226 When it appears in the <file>.dsc</file> file it is the list
3227 of binary packages which a source package can produce. It
3228 does not necessarily produce all of these binary packages
3229 for every architecture. The source control file doesn't
3230 contain details of which architectures are appropriate for
3231 which of the binary packages.
3235 When it appears in a <file>.changes</file> file it lists the
3236 names of the binary packages actually being uploaded.
3240 The syntax is a list of binary packages separated by
3242 A space after each comma is conventional.
3243 </footnote>. Currently the packages must be separated using
3244 only spaces in the <file>.changes</file> file.
3248 <sect1 id="f-Installed-Size">
3249 <heading><tt>Installed-Size</tt></heading>
3252 This field appears in the control files of binary
3253 packages, and in the <file>Packages</file> files. It gives
3254 the total amount of disk space required to install the
3259 The disk space is represented in kilobytes as a simple
3264 <sect1 id="f-Files">
3265 <heading><tt>Files</tt></heading>
3268 This field contains a list of files with information about
3269 each one. The exact information and syntax varies with
3270 the context. In all cases the part of the field
3271 contents on the same line as the field name is empty. The
3272 remainder of the field is one line per file, each line
3273 being indented by one space and containing a number of
3274 sub-fields separated by spaces.
3278 In the <file>.dsc</file> file, each line contains the MD5
3279 checksum, size and filename of the tar file and (if applicable)
3280 diff file which make up the remainder of the source
3282 That is, the parts which are not the <tt>.dsc</tt>.
3284 The exact forms of the filenames are described
3285 in <ref id="pkg-sourcearchives">.
3289 In the <file>.changes</file> file this contains one line per
3290 file being uploaded. Each line contains the MD5 checksum,
3291 size, section and priority and the filename.
3292 The <qref id="f-Section">section</qref>
3293 and <qref id="f-Priority">priority</qref>
3294 are the values of the corresponding fields in
3295 the main source control file. If no section or priority is
3296 specified then <tt>-</tt> should be used, though section
3297 and priority values must be specified for new packages to
3298 be installed properly.
3302 The special value <tt>byhand</tt> for the section in a
3303 <tt>.changes</tt> file indicates that the file in question
3304 is not an ordinary package file and must by installed by
3305 hand by the distribution maintainers. If the section is
3306 <tt>byhand</tt> the priority should be <tt>-</tt>.
3310 If a new Debian revision of a package is being shipped and
3311 no new original source archive is being distributed the
3312 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3313 entry for the original source archive
3314 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3315 but the <file>.changes</file> file should leave it out. In
3316 this case the original source archive on the distribution
3317 site must match exactly, byte-for-byte, the original
3318 source archive which was used to generate the
3319 <file>.dsc</file> file and diff which are being uploaded.</p>
3322 <sect1 id="f-Closes">
3323 <heading><tt>Closes</tt></heading>
3326 A space-separated list of bug report numbers that the upload
3327 governed by the .changes file closes.
3331 <sect1 id="f-Homepage">
3332 <heading><tt>Homepage</tt></heading>
3335 The URL of the web site for this package, preferably (when
3336 applicable) the site from which the original source can be
3337 obtained and any additional upstream documentation or
3338 information may be found. The content of this field is a
3339 simple URL without any surrounding characters such as
3347 <heading>User-defined fields</heading>
3350 Additional user-defined fields may be added to the
3351 source package control file. Such fields will be
3352 ignored, and not copied to (for example) binary or
3353 source package control files or upload control files.
3357 If you wish to add additional unsupported fields to
3358 these output files you should use the mechanism
3363 Fields in the main source control information file with
3364 names starting <tt>X</tt>, followed by one or more of
3365 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3366 be copied to the output files. Only the part of the
3367 field name after the hyphen will be used in the output
3368 file. Where the letter <tt>B</tt> is used the field
3369 will appear in binary package control files, where the
3370 letter <tt>S</tt> is used in source package control
3371 files and where <tt>C</tt> is used in upload control
3372 (<tt>.changes</tt>) files.
3376 For example, if the main source information control file
3379 XBS-Comment: I stand between the candle and the star.
3381 then the binary and source package control files will contain the
3384 Comment: I stand between the candle and the star.
3393 <chapt id="maintainerscripts">
3394 <heading>Package maintainer scripts and installation procedure</heading>
3397 <heading>Introduction to package maintainer scripts</heading>
3400 It is possible to supply scripts as part of a package which
3401 the package management system will run for you when your
3402 package is installed, upgraded or removed.
3406 These scripts are the files <prgn>preinst</prgn>,
3407 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3408 <prgn>postrm</prgn> in the control area of the package.
3409 They must be proper executable files; if they are scripts
3410 (which is recommended), they must start with the usual
3411 <tt>#!</tt> convention. They should be readable and
3412 executable by anyone, and must not be world-writable.
3416 The package management system looks at the exit status from
3417 these scripts. It is important that they exit with a
3418 non-zero status if there is an error, so that the package
3419 management system can stop its processing. For shell
3420 scripts this means that you <em>almost always</em> need to
3421 use <tt>set -e</tt> (this is usually true when writing shell
3422 scripts, in fact). It is also important, of course, that
3423 they don't exit with a non-zero status if everything went
3428 Additionally, packages interacting with users using
3429 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3430 install a <prgn>config</prgn> script in the control area,
3431 see <ref id="maintscriptprompt"> for details.
3435 When a package is upgraded a combination of the scripts from
3436 the old and new packages is called during the upgrade
3437 procedure. If your scripts are going to be at all
3438 complicated you need to be aware of this, and may need to
3439 check the arguments to your scripts.
3443 Broadly speaking the <prgn>preinst</prgn> is called before
3444 (a particular version of) a package is installed, and the
3445 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3446 before (a version of) a package is removed and the
3447 <prgn>postrm</prgn> afterwards.
3451 Programs called from maintainer scripts should not normally
3452 have a path prepended to them. Before installation is
3453 started, the package management system checks to see if the
3454 programs <prgn>ldconfig</prgn>,
3455 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3456 and <prgn>update-rc.d</prgn> can be found via the
3457 <tt>PATH</tt> environment variable. Those programs, and any
3458 other program that one would expect to be in the
3459 <tt>PATH</tt>, should thus be invoked without an absolute
3460 pathname. Maintainer scripts should also not reset the
3461 <tt>PATH</tt>, though they might choose to modify it by
3462 prepending or appending package-specific directories. These
3463 considerations really apply to all shell scripts.</p>
3466 <sect id="idempotency">
3467 <heading>Maintainer scripts idempotency</heading>
3470 It is necessary for the error recovery procedures that the
3471 scripts be idempotent. This means that if it is run
3472 successfully, and then it is called again, it doesn't bomb
3473 out or cause any harm, but just ensures that everything is
3474 the way it ought to be. If the first call failed, or
3475 aborted half way through for some reason, the second call
3476 should merely do the things that were left undone the first
3477 time, if any, and exit with a success status if everything
3479 This is so that if an error occurs, the user interrupts
3480 <prgn>dpkg</prgn> or some other unforeseen circumstance
3481 happens you don't leave the user with a badly-broken
3482 package when <prgn>dpkg</prgn> attempts to repeat the
3488 <sect id="controllingterminal">
3489 <heading>Controlling terminal for maintainer scripts</heading>
3492 The maintainer scripts are guaranteed to run with a
3493 controlling terminal and can interact with the user.
3494 Because these scripts may be executed with standard output
3495 redirected into a pipe for logging purposes, Perl scripts
3496 should set unbuffered output by setting <tt>$|=1</tt> so
3497 that the output is printed immediately rather than being
3501 <sect id="exitstatus">
3502 <heading>Exit status</heading>
3505 Each script must return a zero exit status for
3506 success, or a nonzero one for failure, since the package
3507 management system looks for the exit status of these scripts
3508 and determines what action to take next based on that datum.
3512 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3517 <list compact="compact">
3519 <var>new-preinst</var> <tt>install</tt>
3522 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3525 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3528 <var>old-preinst</var> <tt>abort-upgrade</tt>
3529 <var>new-version</var>
3534 <list compact="compact">
3536 <var>postinst</var> <tt>configure</tt>
3537 <var>most-recently-configured-version</var>
3540 <var>old-postinst</var> <tt>abort-upgrade</tt>
3541 <var>new-version</var>
3544 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3545 <tt>in-favour</tt> <var>package</var>
3546 <var>new-version</var>
3549 <var>postinst</var> <tt>abort-remove</tt>
3552 <var>deconfigured's-postinst</var>
3553 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3554 <var>failed-install-package</var> <var>version</var>
3555 [<tt>removing</tt> <var>conflicting-package</var>
3561 <list compact="compact">
3563 <var>prerm</var> <tt>remove</tt>
3566 <var>old-prerm</var> <tt>upgrade</tt>
3567 <var>new-version</var>
3570 <var>new-prerm</var> <tt>failed-upgrade</tt>
3571 <var>old-version</var>
3574 <var>conflictor's-prerm</var> <tt>remove</tt>
3575 <tt>in-favour</tt> <var>package</var>
3576 <var>new-version</var>
3579 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3580 <tt>in-favour</tt> <var>package-being-installed</var>
3581 <var>version</var> [<tt>removing</tt>
3582 <var>conflicting-package</var>
3588 <list compact="compact">
3590 <var>postrm</var> <tt>remove</tt>
3593 <var>postrm</var> <tt>purge</tt>
3596 <var>old-postrm</var> <tt>upgrade</tt>
3597 <var>new-version</var>
3600 <var>new-postrm</var> <tt>failed-upgrade</tt>
3601 <var>old-version</var>
3604 <var>new-postrm</var> <tt>abort-install</tt>
3607 <var>new-postrm</var> <tt>abort-install</tt>
3608 <var>old-version</var>
3611 <var>new-postrm</var> <tt>abort-upgrade</tt>
3612 <var>old-version</var>
3615 <var>disappearer's-postrm</var> <tt>disappear</tt>
3616 <var>overwriter</var>
3617 <var>overwriter-version</var>
3623 <sect id="unpackphase">
3624 <heading>Details of unpack phase of installation or upgrade</heading>
3627 The procedure on installation/upgrade/overwrite/disappear
3628 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3629 stage of <tt>dpkg --install</tt>) is as follows. In each
3630 case, if a major error occurs (unless listed below) the
3631 actions are, in general, run backwards - this means that the
3632 maintainer scripts are run with different arguments in
3633 reverse order. These are the "error unwind" calls listed
3640 If a version of the package is already installed, call
3641 <example compact="compact">
3642 <var>old-prerm</var> upgrade <var>new-version</var>
3646 If the script runs but exits with a non-zero
3647 exit status, <prgn>dpkg</prgn> will attempt:
3648 <example compact="compact">
3649 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3651 If this works, the upgrade continues. If this
3652 does not work, the error unwind:
3653 <example compact="compact">
3654 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3656 If this works, then the old-version is
3657 "Installed", if not, the old version is in a
3658 "Failed-Config" state.
3664 If a "conflicting" package is being removed at the same time,
3665 or if any package will be broken (due to <tt>Breaks</tt>):
3668 If <tt>--auto-deconfigure</tt> is
3669 specified, call, for each package to be deconfigured
3670 due to <tt>Breaks</tt>:
3671 <example compact="compact">
3672 <var>deconfigured's-prerm</var> deconfigure \
3673 in-favour <var>package-being-installed</var> <var>version</var>
3676 <example compact="compact">
3677 <var>deconfigured's-postinst</var> abort-deconfigure \
3678 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3680 The deconfigured packages are marked as
3681 requiring configuration, so that if
3682 <tt>--install</tt> is used they will be
3683 configured again if possible.
3686 If any packages depended on a conflicting
3687 package being removed and <tt>--auto-deconfigure</tt> is
3688 specified, call, for each such package:
3689 <example compact="compact">
3690 <var>deconfigured's-prerm</var> deconfigure \
3691 in-favour <var>package-being-installed</var> <var>version</var> \
3692 removing <var>conflicting-package</var> <var>version</var>
3695 <example compact="compact">
3696 <var>deconfigured's-postinst</var> abort-deconfigure \
3697 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3698 removing <var>conflicting-package</var> <var>version</var>
3700 The deconfigured packages are marked as
3701 requiring configuration, so that if
3702 <tt>--install</tt> is used they will be
3703 configured again if possible.
3706 To prepare for removal of each conflicting package, call:
3707 <example compact="compact">
3708 <var>conflictor's-prerm</var> remove \
3709 in-favour <var>package</var> <var>new-version</var>
3712 <example compact="compact">
3713 <var>conflictor's-postinst</var> abort-remove \
3714 in-favour <var>package</var> <var>new-version</var>
3723 If the package is being upgraded, call:
3724 <example compact="compact">
3725 <var>new-preinst</var> upgrade <var>old-version</var>
3727 If this fails, we call:
3729 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3736 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3738 is called. If this works, then the old version
3739 is in an "Installed" state, or else it is left
3740 in an "Unpacked" state.
3745 If it fails, then the old version is left
3746 in an "Half-Installed" state.
3753 Otherwise, if the package had some configuration
3754 files from a previous version installed (i.e., it
3755 is in the "configuration files only" state):
3756 <example compact="compact">
3757 <var>new-preinst</var> install <var>old-version</var>
3761 <var>new-postrm</var> abort-install <var>old-version</var>
3763 If this fails, the package is left in a
3764 "Half-Installed" state, which requires a
3765 reinstall. If it works, the packages is left in
3766 a "Config Files" state.
3769 Otherwise (i.e., the package was completely purged):
3770 <example compact="compact">
3771 <var>new-preinst</var> install
3774 <example compact="compact">
3775 <var>new-postrm</var> abort-install
3777 If the error-unwind fails, the package is in a
3778 "Half Installed" phase, and requires a
3779 reinstall. If the error unwind works, the
3780 package is in a not installed state.
3787 The new package's files are unpacked, overwriting any
3788 that may be on the system already, for example any
3789 from the old version of the same package or from
3790 another package. Backups of the old files are kept
3791 temporarily, and if anything goes wrong the package
3792 management system will attempt to put them back as
3793 part of the error unwind.
3797 It is an error for a package to contain files which
3798 are on the system in another package, unless
3799 <tt>Replaces</tt> is used (see <ref id="replaces">).
3801 The following paragraph is not currently the case:
3802 Currently the <tt>- - force-overwrite</tt> flag is
3803 enabled, downgrading it to a warning, but this may not
3809 It is a more serious error for a package to contain a
3810 plain file or other kind of non-directory where another
3811 package has a directory (again, unless
3812 <tt>Replaces</tt> is used). This error can be
3813 overridden if desired using
3814 <tt>--force-overwrite-dir</tt>, but this is not
3819 Packages which overwrite each other's files produce
3820 behavior which, though deterministic, is hard for the
3821 system administrator to understand. It can easily
3822 lead to "missing" programs if, for example, a package
3823 is installed which overwrites a file from another
3824 package, and is then removed again.<footnote>
3825 Part of the problem is due to what is arguably a
3826 bug in <prgn>dpkg</prgn>.
3831 A directory will never be replaced by a symbolic link
3832 to a directory or vice versa; instead, the existing
3833 state (symlink or not) will be left alone and
3834 <prgn>dpkg</prgn> will follow the symlink if there is
3843 If the package is being upgraded, call
3844 <example compact="compact">
3845 <var>old-postrm</var> upgrade <var>new-version</var>
3849 If this fails, <prgn>dpkg</prgn> will attempt:
3850 <example compact="compact">
3851 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3853 If this works, installation continues. If not,
3855 <example compact="compact">
3856 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3858 If this fails, the old version is left in an
3859 "Half Installed" state. If it works, dpkg now
3861 <example compact="compact">
3862 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3864 If this fails, the old version is left in an
3865 "Half Installed" state. If it works, dpkg now
3867 <example compact="compact">
3868 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3870 If this fails, the old version is in an
3877 This is the point of no return - if
3878 <prgn>dpkg</prgn> gets this far, it won't back off
3879 past this point if an error occurs. This will
3880 leave the package in a fairly bad state, which
3881 will require a successful re-installation to clear
3882 up, but it's when <prgn>dpkg</prgn> starts doing
3883 things that are irreversible.
3888 Any files which were in the old version of the package
3889 but not in the new are removed.
3893 The new file list replaces the old.
3897 The new maintainer scripts replace the old.
3901 Any packages all of whose files have been overwritten
3902 during the installation, and which aren't required for
3903 dependencies, are considered to have been removed.
3904 For each such package
3907 <prgn>dpkg</prgn> calls:
3908 <example compact="compact">
3909 <var>disappearer's-postrm</var> disappear \
3910 <var>overwriter</var> <var>overwriter-version</var>
3914 The package's maintainer scripts are removed.
3917 It is noted in the status database as being in a
3918 sane state, namely not installed (any conffiles
3919 it may have are ignored, rather than being
3920 removed by <prgn>dpkg</prgn>). Note that
3921 disappearing packages do not have their prerm
3922 called, because <prgn>dpkg</prgn> doesn't know
3923 in advance that the package is going to
3930 Any files in the package we're unpacking that are also
3931 listed in the file lists of other packages are removed
3932 from those lists. (This will lobotomize the file list
3933 of the "conflicting" package if there is one.)
3937 The backup files made during installation, above, are
3943 The new package's status is now sane, and recorded as
3948 Here is another point of no return - if the
3949 conflicting package's removal fails we do not unwind
3950 the rest of the installation; the conflicting package
3951 is left in a half-removed limbo.
3956 If there was a conflicting package we go and do the
3957 removal actions (described below), starting with the
3958 removal of the conflicting package's files (any that
3959 are also in the package being installed have already
3960 been removed from the conflicting package's file list,
3961 and so do not get removed now).
3967 <sect id="configdetails"><heading>Details of configuration</heading>
3970 When we configure a package (this happens with <tt>dpkg
3971 --install</tt> and <tt>dpkg --configure</tt>), we first
3972 update any <tt>conffile</tt>s and then call:
3973 <example compact="compact">
3974 <var>postinst</var> configure <var>most-recently-configured-version</var>
3979 No attempt is made to unwind after errors during
3980 configuration. If the configuration fails, the package is in
3981 a "Failed Config" state, and an error message is generated.
3985 If there is no most recently configured version
3986 <prgn>dpkg</prgn> will pass a null argument.
3989 Historical note: Truly ancient (pre-1997) versions of
3990 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3991 (including the angle brackets) in this case. Even older
3992 ones did not pass a second argument at all, under any
3993 circumstance. Note that upgrades using such an old dpkg
3994 version are unlikely to work for other reasons, even if
3995 this old argument behavior is handled by your postinst script.
4001 <sect id="removedetails"><heading>Details of removal and/or
4002 configuration purging</heading>
4008 <example compact="compact">
4009 <var>prerm</var> remove
4013 If prerm fails during replacement due to conflict
4015 <var>conflictor's-postinst</var> abort-remove \
4016 in-favour <var>package</var> <var>new-version</var>
4020 <var>postinst</var> abort-remove
4024 If this fails, the package is in a "Failed-Config"
4025 state, or else it remains "Installed".
4029 The package's files are removed (except <tt>conffile</tt>s).
4032 <example compact="compact">
4033 <var>postrm</var> remove
4037 If it fails, there's no error unwind, and the package is in
4038 an "Half-Installed" state.
4043 All the maintainer scripts except the <prgn>postrm</prgn>
4048 If we aren't purging the package we stop here. Note
4049 that packages which have no <prgn>postrm</prgn> and no
4050 <tt>conffile</tt>s are automatically purged when
4051 removed, as there is no difference except for the
4052 <prgn>dpkg</prgn> status.
4056 The <tt>conffile</tt>s and any backup files
4057 (<tt>~</tt>-files, <tt>#*#</tt> files,
4058 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4063 <example compact="compact">
4064 <var>postrm</var> purge
4068 If this fails, the package remains in a "Config-Files"
4073 The package's file list is removed.
4082 <chapt id="relationships">
4083 <heading>Declaring relationships between packages</heading>
4085 <sect id="depsyntax">
4086 <heading>Syntax of relationship fields</heading>
4089 These fields all have a uniform syntax. They are a list of
4090 package names separated by commas.
4094 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4095 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4096 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4097 control file fields of the package, which declare
4098 dependencies on other packages, the package names listed may
4099 also include lists of alternative package names, separated
4100 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4101 if any one of the alternative packages is installed, that
4102 part of the dependency is considered to be satisfied.
4106 All of the fields except for <tt>Provides</tt> may restrict
4107 their applicability to particular versions of each named
4108 package. This is done in parentheses after each individual
4109 package name; the parentheses should contain a relation from
4110 the list below followed by a version number, in the format
4111 described in <ref id="f-Version">.
4115 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4116 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4117 strictly earlier, earlier or equal, exactly equal, later or
4118 equal and strictly later, respectively. The deprecated
4119 forms <tt><</tt> and <tt>></tt> were used to mean
4120 earlier/later or equal, rather than strictly earlier/later,
4121 so they should not appear in new packages (though
4122 <prgn>dpkg</prgn> still supports them).
4126 Whitespace may appear at any point in the version
4127 specification subject to the rules in <ref
4128 id="controlsyntax">, and must appear where it's necessary to
4129 disambiguate; it is not otherwise significant. All of the
4130 relationship fields may span multiple lines. For
4131 consistency and in case of future changes to
4132 <prgn>dpkg</prgn> it is recommended that a single space be
4133 used after a version relationship and before a version
4134 number; it is also conventional to put a single space after
4135 each comma, on either side of each vertical bar, and before
4136 each open parenthesis. When wrapping a relationship field, it
4137 is conventional to do so after a comma and before the space
4138 following that comma.
4142 For example, a list of dependencies might appear as:
4143 <example compact="compact">
4146 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4151 All fields that specify build-time relationships
4152 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4153 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4154 may be restricted to a certain set of architectures. This
4155 is indicated in brackets after each individual package name and
4156 the optional version specification. The brackets enclose a
4157 list of Debian architecture names separated by whitespace.
4158 Exclamation marks may be prepended to each of the names.
4159 (It is not permitted for some names to be prepended with
4160 exclamation marks while others aren't.) If the current Debian
4161 host architecture is not in this list and there are no
4162 exclamation marks in the list, or it is in the list with a
4163 prepended exclamation mark, the package name and the
4164 associated version specification are ignored completely for
4165 the purposes of defining the relationships.
4170 <example compact="compact">
4172 Build-Depends-Indep: texinfo
4173 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4174 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4179 Note that the binary package relationship fields such as
4180 <tt>Depends</tt> appear in one of the binary package
4181 sections of the control file, whereas the build-time
4182 relationships such as <tt>Build-Depends</tt> appear in the
4183 source package section of the control file (which is the
4188 <sect id="binarydeps">
4189 <heading>Binary Dependencies - <tt>Depends</tt>,
4190 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4191 <tt>Pre-Depends</tt>
4195 Packages can declare in their control file that they have
4196 certain relationships to other packages - for example, that
4197 they may not be installed at the same time as certain other
4198 packages, and/or that they depend on the presence of others.
4202 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4203 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4204 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4208 These seven fields are used to declare a dependency
4209 relationship by one package on another. Except for
4210 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4211 depending (binary) package's control file.
4212 (<tt>Enhances</tt> appears in the recommending package's
4213 control file, and <tt>Breaks</tt> appears in the version of
4214 depended-on package which causes the named package to
4219 A <tt>Depends</tt> field takes effect <em>only</em> when a
4220 package is to be configured. It does not prevent a package
4221 being on the system in an unconfigured state while its
4222 dependencies are unsatisfied, and it is possible to replace
4223 a package whose dependencies are satisfied and which is
4224 properly installed with a different version whose
4225 dependencies are not and cannot be satisfied; when this is
4226 done the depending package will be left unconfigured (since
4227 attempts to configure it will give errors) and will not
4228 function properly. If it is necessary, a
4229 <tt>Pre-Depends</tt> field can be used, which has a partial
4230 effect even when a package is being unpacked, as explained
4231 in detail below. (The other three dependency fields,
4232 <tt>Recommends</tt>, <tt>Suggests</tt> and
4233 <tt>Enhances</tt>, are only used by the various front-ends
4234 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4235 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4239 For this reason packages in an installation run are usually
4240 all unpacked first and all configured later; this gives
4241 later versions of packages with dependencies on later
4242 versions of other packages the opportunity to have their
4243 dependencies satisfied.
4247 In case of circular dependencies, since installation or
4248 removal order honoring the dependency order can't be
4249 established, dependency loops are broken at some point
4250 (based on rules below), and some packages may not be able to
4251 rely on their dependencies being present when being
4252 installed or removed, depending on which side of the break
4253 of the circular dependency loop they happen to be on. If one
4254 of the packages in the loop has no postinst script, then the
4255 cycle will be broken at that package, so as to ensure that
4256 all postinst scripts run with the dependencies properly
4257 configured if this is possible. Otherwise the breaking point
4262 The <tt>Depends</tt> field thus allows package maintainers
4263 to impose an order in which packages should be configured.
4267 The meaning of the five dependency fields is as follows:
4269 <tag><tt>Depends</tt></tag>
4272 This declares an absolute dependency. A package will
4273 not be configured unless all of the packages listed in
4274 its <tt>Depends</tt> field have been correctly
4279 The <tt>Depends</tt> field should be used if the
4280 depended-on package is required for the depending
4281 package to provide a significant amount of
4286 The <tt>Depends</tt> field should also be used if the
4287 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4288 <prgn>postrm</prgn> scripts require the package to be
4289 present in order to run. Note, however, that the
4290 <prgn>postrm</prgn> cannot rely on any non-essential
4291 packages to be present during the <tt>purge</tt>
4295 <tag><tt>Recommends</tt></tag>
4298 This declares a strong, but not absolute, dependency.
4302 The <tt>Recommends</tt> field should list packages
4303 that would be found together with this one in all but
4304 unusual installations.
4308 <tag><tt>Suggests</tt></tag>
4310 This is used to declare that one package may be more
4311 useful with one or more others. Using this field
4312 tells the packaging system and the user that the
4313 listed packages are related to this one and can
4314 perhaps enhance its usefulness, but that installing
4315 this one without them is perfectly reasonable.
4318 <tag><tt>Enhances</tt></tag>
4320 This field is similar to Suggests but works in the
4321 opposite direction. It is used to declare that a
4322 package can enhance the functionality of another
4326 <tag><tt>Pre-Depends</tt></tag>
4329 This field is like <tt>Depends</tt>, except that it
4330 also forces <prgn>dpkg</prgn> to complete installation
4331 of the packages named before even starting the
4332 installation of the package which declares the
4333 pre-dependency, as follows:
4337 When a package declaring a pre-dependency is about to
4338 be <em>unpacked</em> the pre-dependency can be
4339 satisfied if the depended-on package is either fully
4340 configured, <em>or even if</em> the depended-on
4341 package(s) are only unpacked or half-configured,
4342 provided that they have been configured correctly at
4343 some point in the past (and not removed or partially
4344 removed since). In this case, both the
4345 previously-configured and currently unpacked or
4346 half-configured versions must satisfy any version
4347 clause in the <tt>Pre-Depends</tt> field.
4351 When the package declaring a pre-dependency is about
4352 to be <em>configured</em>, the pre-dependency will be
4353 treated as a normal <tt>Depends</tt>, that is, it will
4354 be considered satisfied only if the depended-on
4355 package has been correctly configured.
4359 <tt>Pre-Depends</tt> should be used sparingly,
4360 preferably only by packages whose premature upgrade or
4361 installation would hamper the ability of the system to
4362 continue with any upgrade that might be in progress.
4366 <tt>Pre-Depends</tt> are also required if the
4367 <prgn>preinst</prgn> script depends on the named
4368 package. It is best to avoid this situation if
4376 When selecting which level of dependency to use you should
4377 consider how important the depended-on package is to the
4378 functionality of the one declaring the dependency. Some
4379 packages are composed of components of varying degrees of
4380 importance. Such a package should list using
4381 <tt>Depends</tt> the package(s) which are required by the
4382 more important components. The other components'
4383 requirements may be mentioned as Suggestions or
4384 Recommendations, as appropriate to the components' relative
4390 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4393 Using <tt>Breaks</tt> may cause problems for upgrades from older
4394 versions of Debian and should not be used until the stable
4395 release of Debian supports <tt>Breaks</tt>.
4399 When one binary package declares that it breaks another,
4400 <prgn>dpkg</prgn> will refuse to allow the package which
4401 declares <tt>Breaks</tt> be installed unless the broken
4402 package is deconfigured first, and it will refuse to
4403 allow the broken package to be reconfigured.
4407 A package will not be regarded as causing breakage merely
4408 because its configuration files are still installed; it must
4409 be at least half-installed.
4413 A special exception is made for packages which declare that
4414 they break their own package name or a virtual package which
4415 they provide (see below): this does not count as a real
4420 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4421 version clause; such a <tt>Breaks</tt> is introduced in the
4422 version of an (implicit or explicit) dependency which
4423 violates an assumption or reveals a bug in earlier versions
4424 of the broken package. This use of <tt>Breaks</tt> will
4425 inform higher-level package management tools that broken
4426 package must be upgraded before the new one.
4430 If the breaking package also overwrites some files from the
4431 older package, it should use <tt>Replaces</tt> (not
4432 <tt>Conflicts</tt>) to ensure this goes smoothly.
4436 <sect id="conflicts">
4437 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4440 When one binary package declares a conflict with another
4441 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4442 refuse to allow them to be installed on the system at the
4447 If one package is to be installed, the other must be removed
4448 first - if the package being installed is marked as
4449 replacing (see <ref id="replaces">) the one on the system,
4450 or the one on the system is marked as deselected, or both
4451 packages are marked <tt>Essential</tt>, then
4452 <prgn>dpkg</prgn> will automatically remove the package
4453 which is causing the conflict, otherwise it will halt the
4454 installation of the new package with an error. This
4455 mechanism is specifically designed to produce an error when
4456 the installed package is <tt>Essential</tt>, but the new
4461 A package will not cause a conflict merely because its
4462 configuration files are still installed; it must be at least
4467 A special exception is made for packages which declare a
4468 conflict with their own package name, or with a virtual
4469 package which they provide (see below): this does not
4470 prevent their installation, and allows a package to conflict
4471 with others providing a replacement for it. You use this
4472 feature when you want the package in question to be the only
4473 package providing some feature.
4477 A <tt>Conflicts</tt> entry should almost never have an
4478 "earlier than" version clause. This would prevent
4479 <prgn>dpkg</prgn> from upgrading or installing the package
4480 which declared such a conflict until the upgrade or removal
4481 of the conflicted-with package had been completed. Instead,
4482 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4483 by the stable release of Debian).
4487 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4491 As well as the names of actual ("concrete") packages, the
4492 package relationship fields <tt>Depends</tt>,
4493 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4494 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4495 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4496 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4497 may mention "virtual packages".
4501 A <em>virtual package</em> is one which appears in the
4502 <tt>Provides</tt> control file field of another package.
4503 The effect is as if the package(s) which provide a
4504 particular virtual package name had been listed by name
4505 everywhere the virtual package name appears. (See also <ref
4510 If there are both concrete and virtual packages of the same
4511 name, then the dependency may be satisfied (or the conflict
4512 caused) by either the concrete package with the name in
4513 question or any other concrete package which provides the
4514 virtual package with the name in question. This is so that,
4515 for example, supposing we have
4516 <example compact="compact">
4519 </example> and someone else releases an enhanced version of
4520 the <tt>bar</tt> package they can say:
4521 <example compact="compact">
4525 and the <tt>bar-plus</tt> package will now also satisfy the
4526 dependency for the <tt>foo</tt> package.
4530 If a relationship field has a version number attached
4531 then only real packages will be considered to see whether
4532 the relationship is satisfied (or the prohibition violated,
4533 for a conflict or breakage) - it is assumed that a real
4534 package which provides the virtual package is not of the
4535 "right" version. So, a <tt>Provides</tt> field may not
4536 contain version numbers, and the version number of the
4537 concrete package which provides a particular virtual package
4538 will not be looked at when considering a dependency on or
4539 conflict with the virtual package name.
4543 It is likely that the ability will be added in a future
4544 release of <prgn>dpkg</prgn> to specify a version number for
4545 each virtual package it provides. This feature is not yet
4546 present, however, and is expected to be used only
4551 If you want to specify which of a set of real packages
4552 should be the default to satisfy a particular dependency on
4553 a virtual package, you should list the real package as an
4554 alternative before the virtual one.
4559 <sect id="replaces"><heading>Overwriting files and replacing
4560 packages - <tt>Replaces</tt></heading>
4563 Packages can declare in their control file that they should
4564 overwrite files in certain other packages, or completely
4565 replace other packages. The <tt>Replaces</tt> control file
4566 field has these two distinct purposes.
4569 <sect1><heading>Overwriting files in other packages</heading>
4572 Firstly, as mentioned before, it is usually an error for a
4573 package to contain files which are on the system in
4578 However, if the overwriting package declares that it
4579 <tt>Replaces</tt> the one containing the file being
4580 overwritten, then <prgn>dpkg</prgn> will replace the file
4581 from the old package with that from the new. The file
4582 will no longer be listed as "owned" by the old package.
4586 If a package is completely replaced in this way, so that
4587 <prgn>dpkg</prgn> does not know of any files it still
4588 contains, it is considered to have "disappeared". It will
4589 be marked as not wanted on the system (selected for
4590 removal) and not installed. Any <tt>conffile</tt>s
4591 details noted for the package will be ignored, as they
4592 will have been taken over by the overwriting package. The
4593 package's <prgn>postrm</prgn> script will be run with a
4594 special argument to allow the package to do any final
4595 cleanup required. See <ref id="mscriptsinstact">.
4598 Replaces is a one way relationship -- you have to
4599 install the replacing package after the replaced
4606 For this usage of <tt>Replaces</tt>, virtual packages (see
4607 <ref id="virtual">) are not considered when looking at a
4608 <tt>Replaces</tt> field - the packages declared as being
4609 replaced must be mentioned by their real names.
4613 Furthermore, this usage of <tt>Replaces</tt> only takes
4614 effect when both packages are at least partially on the
4615 system at once, so that it can only happen if they do not
4616 conflict or if the conflict has been overridden.
4621 <sect1><heading>Replacing whole packages, forcing their
4625 Secondly, <tt>Replaces</tt> allows the packaging system to
4626 resolve which package should be removed when there is a
4627 conflict - see <ref id="conflicts">. This usage only
4628 takes effect when the two packages <em>do</em> conflict,
4629 so that the two usages of this field do not interfere with
4634 In this situation, the package declared as being replaced
4635 can be a virtual package, so for example, all mail
4636 transport agents (MTAs) would have the following fields in
4637 their control files:
4638 <example compact="compact">
4639 Provides: mail-transport-agent
4640 Conflicts: mail-transport-agent
4641 Replaces: mail-transport-agent
4643 ensuring that only one MTA can be installed at any one
4648 <sect id="sourcebinarydeps">
4649 <heading>Relationships between source and binary packages -
4650 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4651 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4655 Source packages that require certain binary packages to be
4656 installed or absent at the time of building the package
4657 can declare relationships to those binary packages.
4661 This is done using the <tt>Build-Depends</tt>,
4662 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4663 <tt>Build-Conflicts-Indep</tt> control file fields.
4667 Build-dependencies on "build-essential" binary packages can be
4668 omitted. Please see <ref id="pkg-relations"> for more information.
4672 The dependencies and conflicts they define must be satisfied
4673 (as defined earlier for binary packages) in order to invoke
4674 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4676 If you make "build-arch" or "binary-arch", you need
4677 Build-Depends. If you make "build-indep" or
4678 "binary-indep", you need Build-Depends and
4679 Build-Depends-Indep. If you make "build" or "binary",
4683 There is no Build-Depends-Arch; this role is essentially
4684 met with Build-Depends. Anyone building the
4685 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4686 is basically assumed to be building the whole package
4687 anyway and so installs all build dependencies. The
4688 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4689 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4690 does not yet know how to check for its existence) and
4691 <tt>binary-arch</tt>.
4694 The purpose of the original split, I recall, was so that
4695 the autobuilders wouldn't need to install extra packages
4696 needed only for the binary-indep targets. But without a
4697 build-arch/build-indep split, this didn't work, since
4698 most of the work is done in the build target, not in the
4704 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4706 The <tt>Build-Depends</tt> and
4707 <tt>Build-Conflicts</tt> fields must be satisfied when
4708 any of the following targets is invoked:
4709 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4710 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4711 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4713 <tag><tt>Build-Depends-Indep</tt>,
4714 <tt>Build-Conflicts-Indep</tt></tag>
4716 The <tt>Build-Depends-Indep</tt> and
4717 <tt>Build-Conflicts-Indep</tt> fields must be
4718 satisfied when any of the following targets is
4719 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4720 <tt>binary</tt> and <tt>binary-indep</tt>.
4730 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4733 Packages containing shared libraries must be constructed with
4734 a little care to make sure that the shared library is always
4735 available. This is especially important for packages whose
4736 shared libraries are vitally important, such as the C library
4737 (currently <tt>libc6</tt>).
4741 Packages involving shared libraries should be split up into
4742 several binary packages. This section mostly deals with how
4743 this separation is to be accomplished; rules for files within
4744 the shared library packages are in <ref id="libraries"> instead.
4747 <sect id="sharedlibs-runtime">
4748 <heading>Run-time shared libraries</heading>
4751 The run-time shared library needs to be placed in a package
4752 whose name changes whenever the shared object version
4755 Since it is common place to install several versions of a
4756 package that just provides shared libraries, it is a
4757 good idea that the library package should not
4758 contain any extraneous non-versioned files, unless they
4759 happen to be in versioned directories.</p>
4761 The most common mechanism is to place it in a package
4763 <package><var>libraryname</var><var>soversion</var></package>,
4764 where <file><var>soversion</var></file> is the version number
4765 in the soname of the shared library<footnote>
4766 The soname is the shared object name: it's the thing
4767 that has to match exactly between building an executable
4768 and running it for the dynamic linker to be able run the
4769 program. For example, if the soname of the library is
4770 <file>libfoo.so.6</file>, the library package would be
4771 called <file>libfoo6</file>.
4773 Alternatively, if it would be confusing to directly append
4774 <var>soversion</var> to <var>libraryname</var> (e.g. because
4775 <var>libraryname</var> itself ends in a number), you may use
4776 <package><var>libraryname</var>-<var>soversion</var></package> and
4777 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4782 If you have several shared libraries built from the same
4783 source tree you may lump them all together into a single
4784 shared library package, provided that you change all of
4785 their sonames at once (so that you don't get filename
4786 clashes if you try to install different versions of the
4787 combined shared libraries package).
4791 The package should install the shared libraries under
4792 their normal names. For example, the <package>libgdbm3</package>
4793 package should install <file>libgdbm.so.3.0.0</file> as
4794 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4795 renamed or re-linked by any <prgn>prerm</prgn> or
4796 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4797 of renaming things safely without affecting running programs,
4798 and attempts to interfere with this are likely to lead to
4803 Shared libraries should not be installed executable, since
4804 the dynamic linker does not require this and trying to
4805 execute a shared library usually results in a core dump.
4809 The run-time library package should include the symbolic link that
4810 <prgn>ldconfig</prgn> would create for the shared libraries.
4811 For example, the <package>libgdbm3</package> package should include
4812 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4813 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4814 linker (for example <prgn>ld.so</prgn> or
4815 <prgn>ld-linux.so.*</prgn>) can find the library between the
4816 time that <prgn>dpkg</prgn> installs it and the time that
4817 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4819 The package management system requires the library to be
4820 placed before the symbolic link pointing to it in the
4821 <file>.deb</file> file. This is so that when
4822 <prgn>dpkg</prgn> comes to install the symlink
4823 (overwriting the previous symlink pointing at an older
4824 version of the library), the new shared library is already
4825 in place. In the past, this was achieved by creating the
4826 library in the temporary packaging directory before
4827 creating the symlink. Unfortunately, this was not always
4828 effective, since the building of the tar file in the
4829 <file>.deb</file> depended on the behavior of the underlying
4830 file system. Some file systems (such as reiserfs) reorder
4831 the files so that the order of creation is forgotten.
4832 Since version 1.7.0, <prgn>dpkg</prgn>
4833 reorders the files itself as necessary when building a
4834 package. Thus it is no longer important to concern
4835 oneself with the order of file creation.
4839 <sect1 id="ldconfig">
4840 <heading><tt>ldconfig</tt></heading>
4843 Any package installing shared libraries in one of the default
4844 library directories of the dynamic linker (which are currently
4845 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4846 listed in <file>/etc/ld.so.conf</file><footnote>
4848 <list compact="compact">
4849 <item>/usr/local/lib</item>
4850 <item>/usr/lib/libc5-compat</item>
4851 <item>/lib/libc5-compat</item>
4854 must use <prgn>ldconfig</prgn> to update the shared library
4859 The package maintainer scripts must only call
4860 <prgn>ldconfig</prgn> under these circumstances:
4861 <list compact="compact">
4862 <item>When the <prgn>postinst</prgn> script is run with a
4863 first argument of <tt>configure</tt>, the script must call
4864 <prgn>ldconfig</prgn>, and may optionally invoke
4865 <prgn>ldconfig</prgn> at other times.
4867 <item>When the <prgn>postrm</prgn> script is run with a
4868 first argument of <tt>remove</tt>, the script should call
4869 <prgn>ldconfig</prgn>.
4874 During install or upgrade, the preinst is called before
4875 the new files are installed, so calling "ldconfig" is
4876 pointless. The preinst of an existing package can also be
4877 called if an upgrade fails. However, this happens during
4878 the critical time when a shared libs may exist on-disk
4879 under a temporary name. Thus, it is dangerous and
4880 forbidden by current policy to call "ldconfig" at this
4885 When a package is installed or upgraded, "postinst
4886 configure" runs after the new files are safely on-disk.
4887 Since it is perfectly safe to invoke ldconfig
4888 unconditionally in a postinst, it is OK for a package to
4889 simply put ldconfig in its postinst without checking the
4890 argument. The postinst can also be called to recover from
4891 a failed upgrade. This happens before any new files are
4892 unpacked, so there is no reason to call "ldconfig" at this
4897 For a package that is being removed, prerm is
4898 called with all the files intact, so calling ldconfig is
4899 useless. The other calls to "prerm" happen in the case of
4900 upgrade at a time when all the files of the old package
4901 are on-disk, so again calling "ldconfig" is pointless.
4905 postrm, on the other hand, is called with the "remove"
4906 argument just after the files are removed, so this is
4907 the proper time to call "ldconfig" to notify the system
4908 of the fact that the shared libraries from the package
4909 are removed. The postrm can be called at several other
4910 times. At the time of "postrm purge", "postrm
4911 abort-install", or "postrm abort-upgrade", calling
4912 "ldconfig" is useless because the shared lib files are
4913 not on-disk. However, when "postrm" is invoked with
4914 arguments "upgrade", "failed-upgrade", or "disappear", a
4915 shared lib may exist on-disk under a temporary filename.
4923 <sect id="sharedlibs-support-files">
4924 <heading>Shared library support files</heading>
4927 If your package contains files whose names do not change with
4928 each change in the library shared object version, you must not
4929 put them in the shared library package. Otherwise, several
4930 versions of the shared library cannot be installed at the same
4931 time without filename clashes, making upgrades and transitions
4932 unnecessarily difficult.
4936 It is recommended that supporting files and run-time support
4937 programs that do not need to be invoked manually by users, but
4938 are nevertheless required for the package to function, be placed
4939 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4940 preferably under <file>/usr/lib/</file><var>package-name</var>.
4941 If the program or file is architecture independent, the
4942 recommendation is for it to be placed in a subdirectory of
4943 <file>/usr/share</file> instead, preferably under
4944 <file>/usr/share/</file><var>package-name</var>. Following the
4945 <var>package-name</var> naming convention ensures that the file
4946 names change when the shared object version changes.
4950 Run-time support programs that use the shared library but are
4951 not required for the library to function or files used by the
4952 shared library that can be used by any version of the shared
4953 library package should instead be put in a separate package.
4954 This package might typically be named
4955 <package><var>libraryname</var>-tools</package>; note the
4956 absence of the <var>soversion</var> in the package name.
4960 Files and support programs only useful when compiling software
4961 against the library should be included in the development
4962 package for the library.<footnote>
4963 For example, a <file><var>package-name</var>-config</file>
4964 script or <package>pkg-config</package> configuration files.
4969 <sect id="sharedlibs-static">
4970 <heading>Static libraries</heading>
4973 The static library (<file><var>libraryname.a</var></file>)
4974 is usually provided in addition to the shared version.
4975 It is placed into the development package (see below).
4979 In some cases, it is acceptable for a library to be
4980 available in static form only; these cases include:
4982 <item>libraries for languages whose shared library support
4983 is immature or unstable</item>
4984 <item>libraries whose interfaces are in flux or under
4985 development (commonly the case when the library's
4986 major version number is zero, or where the ABI breaks
4987 across patchlevels)</item>
4988 <item>libraries which are explicitly intended to be
4989 available only in static form by their upstream
4994 <sect id="sharedlibs-dev">
4995 <heading>Development files</heading>
4998 The development files associated to a shared library need to be
4999 placed in a package called
5000 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5001 or if you prefer only to support one development version at a
5002 time, <package><var>libraryname</var>-dev</package>.
5006 In case several development versions of a library exist, you may
5007 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5008 <ref id="conflicts">) to ensure that the user only installs one
5009 development version at a time (as different development versions are
5010 likely to have the same header files in them, which would cause a
5011 filename clash if both were installed).
5015 The development package should contain a symlink for the associated
5016 shared library without a version number. For example, the
5017 <package>libgdbm-dev</package> package should include a symlink
5018 from <file>/usr/lib/libgdbm.so</file> to
5019 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5020 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5021 <file>libgdbm.so</file> when compiling dynamically.
5025 <sect id="sharedlibs-intradeps">
5026 <heading>Dependencies between the packages of the same library</heading>
5029 Typically the development version should have an exact
5030 version dependency on the runtime library, to make sure that
5031 compilation and linking happens correctly. The
5032 <tt>${binary:Version}</tt> substitution variable can be
5033 useful for this purpose.
5035 Previously, <tt>${Source-Version}</tt> was used, but its name
5036 was confusing and it has been deprecated since dpkg 1.13.19.
5041 <sect id="sharedlibs-shlibdeps">
5042 <heading>Dependencies between the library and other packages -
5043 the <tt>shlibs</tt> system</heading>
5046 If a package contains a binary or library which links to a
5047 shared library, we must ensure that when the package is
5048 installed on the system, all of the libraries needed are
5049 also installed. This requirement led to the creation of the
5050 <tt>shlibs</tt> system, which is very simple in its design:
5051 any package which <em>provides</em> a shared library also
5052 provides information on the package dependencies required to
5053 ensure the presence of this library, and any package which
5054 <em>uses</em> a shared library uses this information to
5055 determine the dependencies it requires. The files which
5056 contain the mapping from shared libraries to the necessary
5057 dependency information are called <file>shlibs</file> files.
5061 Thus, when a package is built which contains any shared
5062 libraries, it must provide a <file>shlibs</file> file for other
5063 packages to use, and when a package is built which contains
5064 any shared libraries or compiled binaries, it must run
5065 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5066 on these to determine the libraries used and hence the
5067 dependencies needed by this package.<footnote>
5069 In the past, the shared libraries linked to were
5070 determined by calling <prgn>ldd</prgn>, but now
5071 <prgn>objdump</prgn> is used to do this. The only
5072 change this makes to package building is that
5073 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5074 libraries, whereas in the past this was unnecessary.
5075 The rest of this footnote explains the advantage that
5080 We say that a binary <tt>foo</tt> <em>directly</em> uses
5081 a library <tt>libbar</tt> if it is explicitly linked
5082 with that library (that is, it uses the flag
5083 <tt>-lbar</tt> during the linking stage). Other
5084 libraries that are needed by <tt>libbar</tt> are linked
5085 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5086 linker will load them automatically when it loads
5087 <tt>libbar</tt>. A package should depend on
5088 the libraries it directly uses, and the dependencies for
5089 those libraries should automatically pull in the other
5094 Unfortunately, the <prgn>ldd</prgn> program shows both
5095 the directly and indirectly used libraries, meaning that
5096 the dependencies determined included both direct and
5097 indirect dependencies. The use of <prgn>objdump</prgn>
5098 avoids this problem by determining only the directly
5103 A good example of where this helps is the following. We
5104 could update <tt>libimlib</tt> with a new version that
5105 supports a new graphics format called dgf (but retaining
5106 the same major version number). If we used the old
5107 <prgn>ldd</prgn> method, every package that uses
5108 <tt>libimlib</tt> would need to be recompiled so it
5109 would also depend on <tt>libdgf</tt> or it wouldn't run
5110 due to missing symbols. However with the new system,
5111 packages using <tt>libimlib</tt> can rely on
5112 <tt>libimlib</tt> itself having the dependency on
5113 <tt>libdgf</tt> and so they would not need rebuilding.
5119 In the following sections, we will first describe where the
5120 various <tt>shlibs</tt> files are to be found, then how to
5121 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5122 file format and how to create them if your package contains a
5127 <heading>The <tt>shlibs</tt> files present on the system</heading>
5130 There are several places where <tt>shlibs</tt> files are
5131 found. The following list gives them in the order in which
5133 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5134 (The first one which gives the required information is used.)
5140 <p><file>debian/shlibs.local</file></p>
5143 This lists overrides for this package. Its use is
5144 described below (see <ref id="shlibslocal">).
5149 <p><file>/etc/dpkg/shlibs.override</file></p>
5152 This lists global overrides. This list is normally
5153 empty. It is maintained by the local system
5159 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5162 When packages are being built, any
5163 <file>debian/shlibs</file> files are copied into the
5164 control file area of the temporary build directory and
5165 given the name <file>shlibs</file>. These files give
5166 details of any shared libraries included in the
5168 An example may help here. Let us say that the
5169 source package <tt>foo</tt> generates two binary
5170 packages, <tt>libfoo2</tt> and
5171 <tt>foo-runtime</tt>. When building the binary
5172 packages, the two packages are created in the
5173 directories <file>debian/libfoo2</file> and
5174 <file>debian/foo-runtime</file> respectively.
5175 (<file>debian/tmp</file> could be used instead of one
5176 of these.) Since <tt>libfoo2</tt> provides the
5177 <tt>libfoo</tt> shared library, it will require a
5178 <tt>shlibs</tt> file, which will be installed in
5179 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5181 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5182 when <prgn>dpkg-shlibdeps</prgn> is run on the
5184 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5186 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5187 determine whether <tt>foo-prog</tt>'s library
5188 dependencies are satisfied by any of the libraries
5189 provided by <tt>libfoo2</tt>. For this reason,
5190 <prgn>dpkg-shlibdeps</prgn> must only be run once
5191 all of the individual binary packages'
5192 <tt>shlibs</tt> files have been installed into the
5199 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5202 These are the <file>shlibs</file> files corresponding to
5203 all of the packages installed on the system, and are
5204 maintained by the relevant package maintainers.
5209 <p><file>/etc/dpkg/shlibs.default</file></p>
5212 This file lists any shared libraries whose packages
5213 have failed to provide correct <file>shlibs</file> files.
5214 It was used when the <file>shlibs</file> setup was first
5215 introduced, but it is now normally empty. It is
5216 maintained by the <tt>dpkg</tt> maintainer.
5224 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5225 <file>shlibs</file> files</heading>
5229 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5230 into your <file>debian/rules</file> file. If your package
5231 contains only compiled binaries and libraries (but no scripts),
5232 you can use a command such as:
5233 <example compact="compact">
5234 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5235 debian/tmp/usr/lib/*
5237 Otherwise, you will need to explicitly list the compiled
5238 binaries and libraries.<footnote>
5239 If you are using <tt>debhelper</tt>, the
5240 <prgn>dh_shlibdeps</prgn> program will do this work for
5241 you. It will also correctly handle multi-binary
5247 This command puts the dependency information into the
5248 <file>debian/substvars</file> file, which is then used by
5249 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5250 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5251 field in the control file for this to work.
5255 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5256 done. If it does complain you might need to create your own
5257 <file>debian/shlibs.local</file> file, as explained below (see
5258 <ref id="shlibslocal">).
5262 If you have multiple binary packages, you will need to call
5263 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5264 compiled libraries or binaries. In such a case, you will
5265 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5266 utilities to specify a different <file>substvars</file> file.
5270 If you are creating a udeb for use in the Debian Installer, you
5271 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5272 the dependency line of type <tt>udeb</tt> by adding
5273 <tt>-tudeb</tt> as option<footnote>
5274 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5275 will automatically add this option if it knows it is
5277 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5278 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5279 fall back to the regular dependency line.
5283 For more details on dpkg-shlibdeps, please see
5284 <ref id="pkg-dpkg-shlibdeps"> and
5285 <manref name="dpkg-shlibdeps" section="1">.
5290 <heading>The <file>shlibs</file> File Format</heading>
5293 Each <file>shlibs</file> file has the same format. Lines
5294 beginning with <tt>#</tt> are considered to be comments and
5295 are ignored. Each line is of the form:
5296 <example compact="compact">
5297 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5302 We will explain this by reference to the example of the
5303 <tt>zlib1g</tt> package, which (at the time of writing)
5304 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5308 <var>type</var> is an optional element that indicates the type
5309 of package for which the line is valid. The only type currently
5310 in use is <tt>udeb</tt>. The colon and space after the type are
5315 <var>library-name</var> is the name of the shared library,
5316 in this case <tt>libz</tt>. (This must match the name part
5317 of the soname, see below.)
5321 <var>soname-version</var> is the version part of the soname of
5322 the library. The soname is the thing that must exactly match
5323 for the library to be recognized by the dynamic linker, and is
5325 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5326 example, <tt>libz.so.1</tt>.<footnote>
5327 This can be determined using the command
5328 <example compact="compact">
5329 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5332 The version part is the part which comes after
5333 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5337 <var>dependencies</var> has the same syntax as a dependency
5338 field in a binary package control file. It should give
5339 details of which packages are required to satisfy a binary
5340 built against the version of the library contained in the
5341 package. See <ref id="depsyntax"> for details.
5345 In our example, if the first version of the <tt>zlib1g</tt>
5346 package which contained a minor number of at least
5347 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5348 <tt>shlibs</tt> entry for this library could say:
5349 <example compact="compact">
5350 libz 1 zlib1g (>= 1:1.1.3)
5352 The version-specific dependency is to avoid warnings from
5353 the dynamic linker about using older shared libraries with
5358 As zlib1g also provides a udeb containing the shared library,
5359 there would also be a second line:
5360 <example compact="compact">
5361 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5367 <heading>Providing a <file>shlibs</file> file</heading>
5370 If your package provides a shared library, you need to create
5371 a <file>shlibs</file> file following the format described above.
5372 It is usual to call this file <file>debian/shlibs</file> (but if
5373 you have multiple binary packages, you might want to call it
5374 <file>debian/shlibs.<var>package</var></file> instead). Then
5375 let <file>debian/rules</file> install it in the control area:
5376 <example compact="compact">
5377 install -m644 debian/shlibs debian/tmp/DEBIAN
5379 or, in the case of a multi-binary package:
5380 <example compact="compact">
5381 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5383 An alternative way of doing this is to create the
5384 <file>shlibs</file> file in the control area directly from
5385 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5386 file at all,<footnote>
5387 This is what <prgn>dh_makeshlibs</prgn> in the
5388 <tt>debhelper</tt> suite does. If your package also has a udeb
5389 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5390 automatically generate the <tt>udeb:</tt> lines if you specify
5391 the name of the udeb with the <tt>--add-udeb</tt> option.
5393 since the <file>debian/shlibs</file> file itself is ignored by
5394 <prgn>dpkg-shlibdeps</prgn>.
5398 As <prgn>dpkg-shlibdeps</prgn> reads the
5399 <file>DEBIAN/shlibs</file> files in all of the binary packages
5400 being built from this source package, all of the
5401 <file>DEBIAN/shlibs</file> files should be installed before
5402 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5407 <sect1 id="shlibslocal">
5408 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5411 This file is intended only as a <em>temporary</em> fix if
5412 your binaries or libraries depend on a library whose package
5413 does not yet provide a correct <file>shlibs</file> file.
5417 We will assume that you are trying to package a binary
5418 <tt>foo</tt>. When you try running
5419 <prgn>dpkg-shlibdeps</prgn> you get the following error
5420 message (<tt>-O</tt> displays the dependency information on
5421 <tt>stdout</tt> instead of writing it to
5422 <tt>debian/substvars</tt>, and the lines have been wrapped
5423 for ease of reading):
5424 <example compact="compact">
5425 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5426 dpkg-shlibdeps: warning: unable to find dependency
5427 information for shared library libbar (soname 1,
5428 path /usr/lib/libbar.so.1, dependency field Depends)
5429 shlibs:Depends=libc6 (>= 2.2.2-2)
5431 You can then run <prgn>ldd</prgn> on the binary to find the
5432 full location of the library concerned:
5433 <example compact="compact">
5435 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5436 libc.so.6 => /lib/libc.so.6 (0x40032000)
5437 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5439 So the <prgn>foo</prgn> binary depends on the
5440 <prgn>libbar</prgn> shared library, but no package seems to
5441 provide a <file>*.shlibs</file> file handling
5442 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5443 determine the package responsible:
5444 <example compact="compact">
5445 $ dpkg -S /usr/lib/libbar.so.1
5446 bar1: /usr/lib/libbar.so.1
5447 $ dpkg -s bar1 | grep Version
5450 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5451 is the one we are using. Now we can file a bug against the
5452 <tt>bar1</tt> package and create our own
5453 <file>debian/shlibs.local</file> to locally fix the problem.
5454 Including the following line into your
5455 <file>debian/shlibs.local</file> file:
5456 <example compact="compact">
5457 libbar 1 bar1 (>= 1.0-1)
5459 should allow the package build to work.
5463 As soon as the maintainer of <tt>bar1</tt> provides a
5464 correct <file>shlibs</file> file, you should remove this line
5465 from your <file>debian/shlibs.local</file> file. (You should
5466 probably also then have a versioned <tt>Build-Depends</tt>
5467 on <tt>bar1</tt> to help ensure that others do not have the
5468 same problem building your package.)
5477 <chapt id="opersys"><heading>The Operating System</heading>
5480 <heading>File system hierarchy</heading>
5484 <heading>File system Structure</heading>
5487 The location of all installed files and directories must
5488 comply with the File system Hierarchy Standard (FHS),
5489 version 2.3, with the exceptions noted below, and except
5490 where doing so would violate other terms of Debian
5491 Policy. The following exceptions to the FHS apply:
5496 Legacy XFree86 servers are permitted to retain the
5497 configuration file location
5498 <file>/etc/X11/XF86Config-4</file>.
5503 The optional rules related to user specific
5504 configuration files for applications are stored in
5505 the user's home directory are relaxed. It is
5506 recommended that such files start with the
5507 '<tt>.</tt>' character (a "dot file"), and if an
5508 application needs to create more than one dot file
5509 then the preferred placement is in a subdirectory
5510 with a name starting with a '.' character, (a "dot
5511 directory"). In this case it is recommended the
5512 configuration files not start with the '.'
5518 The requirement for amd64 to use <file>/lib64</file>
5519 for 64 bit binaries is removed.
5524 The requirement that
5525 <file>/usr/local/share/man</file> be "synonymous"
5526 with <file>/usr/local/man</file> is relaxed to a
5531 The requirement that windowmanagers with a single
5532 configuration file call it <file>system.*wmrc</file>
5533 is removed, as is the restriction that the window
5534 manager subdirectory be named identically to the
5535 window manager name itself.
5540 The requirement that boot manager configuration
5541 files live in <file>/etc</file>, or at least are
5542 symlinked there, is relaxed to a recommendation.
5549 The version of this document referred here can be
5550 found in the <tt>debian-policy</tt> package or on <url
5551 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5552 name="FHS (Debian copy)"> alongside this manual (or, if
5553 you have the <package>debian-policy</package> installed,
5555 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5556 (local copy)">). The
5557 latest version, which may be a more recent version, may
5559 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5560 Specific questions about following the standard may be
5561 asked on the <tt>debian-devel</tt> mailing list, or
5562 referred to the FHS mailing list (see the
5563 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5569 <heading>Site-specific programs</heading>
5572 As mandated by the FHS, packages must not place any
5573 files in <file>/usr/local</file>, either by putting them in
5574 the file system archive to be unpacked by <prgn>dpkg</prgn>
5575 or by manipulating them in their maintainer scripts.
5579 However, the package may create empty directories below
5580 <file>/usr/local</file> so that the system administrator knows
5581 where to place site-specific files. These are not
5582 directories <em>in</em> <file>/usr/local</file>, but are
5583 children of directories in <file>/usr/local</file>. These
5584 directories (<file>/usr/local/*/dir/</file>)
5585 should be removed on package removal if they are
5590 Note, that this applies only to directories <em>below</em>
5591 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5592 Packages must not create sub-directories in the directory
5593 <file>/usr/local</file> itself, except those listed in FHS,
5594 section 4.5. However, you may create directories below
5595 them as you wish. You must not remove any of the
5596 directories listed in 4.5, even if you created them.
5600 Since <file>/usr/local</file> can be mounted read-only from a
5601 remote server, these directories must be created and
5602 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5603 maintainer scripts and not be included in the
5604 <file>.deb</file> archive. These scripts must not fail if
5605 either of these operations fail.
5609 For example, the <tt>emacsen-common</tt> package could
5610 contain something like
5611 <example compact="compact">
5612 if [ ! -e /usr/local/share/emacs ]
5614 if mkdir /usr/local/share/emacs 2>/dev/null
5616 chown root:staff /usr/local/share/emacs
5617 chmod 2775 /usr/local/share/emacs
5621 in its <prgn>postinst</prgn> script, and
5622 <example compact="compact">
5623 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5624 rmdir /usr/local/share/emacs 2>/dev/null || true
5626 in the <prgn>prerm</prgn> script. (Note that this form is
5627 used to ensure that if the script is interrupted, the
5628 directory <file>/usr/local/share/emacs</file> will still be
5633 If you do create a directory in <file>/usr/local</file> for
5634 local additions to a package, you should ensure that
5635 settings in <file>/usr/local</file> take precedence over the
5636 equivalents in <file>/usr</file>.
5640 However, because <file>/usr/local</file> and its contents are
5641 for exclusive use of the local administrator, a package
5642 must not rely on the presence or absence of files or
5643 directories in <file>/usr/local</file> for normal operation.
5647 The <file>/usr/local</file> directory itself and all the
5648 subdirectories created by the package should (by default) have
5649 permissions 2775 (group-writable and set-group-id) and be
5650 owned by <tt>root:staff</tt>.
5655 <heading>The system-wide mail directory</heading>
5657 The system-wide mail directory is <file>/var/mail</file>. This
5658 directory is part of the base system and should not owned
5659 by any particular mail agents. The use of the old
5660 location <file>/var/spool/mail</file> is deprecated, even
5661 though the spool may still be physically located there.
5662 To maintain partial upgrade compatibility for systems
5663 which have <file>/var/spool/mail</file> as their physical mail
5664 spool, packages using <file>/var/mail</file> must depend on
5665 either <package>libc6</package> (>= 2.1.3-13), or on
5666 <package>base-files</package> (>= 2.2.0), or on later
5667 versions of either one of these packages.
5673 <heading>Users and groups</heading>
5676 <heading>Introduction</heading>
5678 The Debian system can be configured to use either plain or
5683 Some user ids (UIDs) and group ids (GIDs) are reserved
5684 globally for use by certain packages. Because some
5685 packages need to include files which are owned by these
5686 users or groups, or need the ids compiled into binaries,
5687 these ids must be used on any Debian system only for the
5688 purpose for which they are allocated. This is a serious
5689 restriction, and we should avoid getting in the way of
5690 local administration policies. In particular, many sites
5691 allocate users and/or local system groups starting at 100.
5695 Apart from this we should have dynamically allocated ids,
5696 which should by default be arranged in some sensible
5697 order, but the behavior should be configurable.
5701 Packages other than <tt>base-passwd</tt> must not modify
5702 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5703 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5708 <heading>UID and GID classes</heading>
5710 The UID and GID numbers are divided into classes as
5716 Globally allocated by the Debian project, the same
5717 on every Debian system. These ids will appear in
5718 the <file>passwd</file> and <file>group</file> files of all
5719 Debian systems, new ids in this range being added
5720 automatically as the <tt>base-passwd</tt> package is
5725 Packages which need a single statically allocated
5726 uid or gid should use one of these; their
5727 maintainers should ask the <tt>base-passwd</tt>
5735 Dynamically allocated system users and groups.
5736 Packages which need a user or group, but can have
5737 this user or group allocated dynamically and
5738 differently on each system, should use <tt>adduser
5739 --system</tt> to create the group and/or user.
5740 <prgn>adduser</prgn> will check for the existence of
5741 the user or group, and if necessary choose an unused
5742 id based on the ranges specified in
5743 <file>adduser.conf</file>.
5747 <tag>1000-29999:</tag>
5750 Dynamically allocated user accounts. By default
5751 <prgn>adduser</prgn> will choose UIDs and GIDs for
5752 user accounts in this range, though
5753 <file>adduser.conf</file> may be used to modify this
5758 <tag>30000-59999:</tag>
5763 <tag>60000-64999:</tag>
5766 Globally allocated by the Debian project, but only
5767 created on demand. The ids are allocated centrally
5768 and statically, but the actual accounts are only
5769 created on users' systems on demand.
5773 These ids are for packages which are obscure or
5774 which require many statically-allocated ids. These
5775 packages should check for and create the accounts in
5776 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5777 <prgn>adduser</prgn> if it has this facility) if
5778 necessary. Packages which are likely to require
5779 further allocations should have a "hole" left after
5780 them in the allocation, to give them room to
5785 <tag>65000-65533:</tag>
5793 User <tt>nobody</tt>. The corresponding gid refers
5794 to the group <tt>nogroup</tt>.
5801 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5802 not</em> be used, because it is the error return
5811 <sect id="sysvinit">
5812 <heading>System run levels and <file>init.d</file> scripts</heading>
5814 <sect1 id="/etc/init.d">
5815 <heading>Introduction</heading>
5818 The <file>/etc/init.d</file> directory contains the scripts
5819 executed by <prgn>init</prgn> at boot time and when the
5820 init state (or "runlevel") is changed (see <manref
5821 name="init" section="8">).
5825 There are at least two different, yet functionally
5826 equivalent, ways of handling these scripts. For the sake
5827 of simplicity, this document describes only the symbolic
5828 link method. However, it must not be assumed by maintainer
5829 scripts that this method is being used, and any automated
5830 manipulation of the various runlevel behaviors by
5831 maintainer scripts must be performed using
5832 <prgn>update-rc.d</prgn> as described below and not by
5833 manually installing or removing symlinks. For information
5834 on the implementation details of the other method,
5835 implemented in the <tt>file-rc</tt> package, please refer
5836 to the documentation of that package.
5840 These scripts are referenced by symbolic links in the
5841 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5842 runlevels, <prgn>init</prgn> looks in the directory
5843 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5844 execute, where <tt><var>n</var></tt> is the runlevel that
5845 is being changed to, or <tt>S</tt> for the boot-up
5850 The names of the links all have the form
5851 <file>S<var>mm</var><var>script</var></file> or
5852 <file>K<var>mm</var><var>script</var></file> where
5853 <var>mm</var> is a two-digit number and <var>script</var>
5854 is the name of the script (this should be the same as the
5855 name of the actual script in <file>/etc/init.d</file>).
5859 When <prgn>init</prgn> changes runlevel first the targets
5860 of the links whose names start with a <tt>K</tt> are
5861 executed, each with the single argument <tt>stop</tt>,
5862 followed by the scripts prefixed with an <tt>S</tt>, each
5863 with the single argument <tt>start</tt>. (The links are
5864 those in the <file>/etc/rc<var>n</var>.d</file> directory
5865 corresponding to the new runlevel.) The <tt>K</tt> links
5866 are responsible for killing services and the <tt>S</tt>
5867 link for starting services upon entering the runlevel.
5871 For example, if we are changing from runlevel 2 to
5872 runlevel 3, init will first execute all of the <tt>K</tt>
5873 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5874 all of the <tt>S</tt> prefixed scripts in that directory.
5875 The links starting with <tt>K</tt> will cause the
5876 referred-to file to be executed with an argument of
5877 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5882 The two-digit number <var>mm</var> is used to determine
5883 the order in which to run the scripts: low-numbered links
5884 have their scripts run first. For example, the
5885 <tt>K20</tt> scripts will be executed before the
5886 <tt>K30</tt> scripts. This is used when a certain service
5887 must be started before another. For example, the name
5888 server <prgn>bind</prgn> might need to be started before
5889 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5890 can set up its access lists. In this case, the script
5891 that starts <prgn>bind</prgn> would have a lower number
5892 than the script that starts <prgn>inn</prgn> so that it
5894 <example compact="compact">
5901 The two runlevels 0 (halt) and 6 (reboot) are slightly
5902 different. In these runlevels, the links with an
5903 <tt>S</tt> prefix are still called after those with a
5904 <tt>K</tt> prefix, but they too are called with the single
5905 argument <tt>stop</tt>.
5909 Also, if the script name ends in <tt>.sh</tt>, the script
5910 will be sourced in runlevel <tt>S</tt> rather than being
5911 run in a forked subprocess, but will be explicitly run by
5912 <prgn>sh</prgn> in all other runlevels.
5917 <heading>Writing the scripts</heading>
5920 Packages that include daemons for system services should
5921 place scripts in <file>/etc/init.d</file> to start or stop
5922 services at boot time or during a change of runlevel.
5923 These scripts should be named
5924 <file>/etc/init.d/<var>package</var></file>, and they should
5925 accept one argument, saying what to do:
5928 <tag><tt>start</tt></tag>
5929 <item>start the service,</item>
5931 <tag><tt>stop</tt></tag>
5932 <item>stop the service,</item>
5934 <tag><tt>restart</tt></tag>
5935 <item>stop and restart the service if it's already running,
5936 otherwise start the service</item>
5938 <tag><tt>reload</tt></tag>
5939 <item><p>cause the configuration of the service to be
5940 reloaded without actually stopping and restarting
5943 <tag><tt>force-reload</tt></tag>
5944 <item>cause the configuration to be reloaded if the
5945 service supports this, otherwise restart the
5949 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5950 <tt>force-reload</tt> options should be supported by all
5951 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5956 The <file>init.d</file> scripts must ensure that they will
5957 behave sensibly if invoked with <tt>start</tt> when the
5958 service is already running, or with <tt>stop</tt> when it
5959 isn't, and that they don't kill unfortunately-named user
5960 processes. The best way to achieve this is usually to use
5961 <prgn>start-stop-daemon</prgn>.
5965 If a service reloads its configuration automatically (as
5966 in the case of <prgn>cron</prgn>, for example), the
5967 <tt>reload</tt> option of the <file>init.d</file> script
5968 should behave as if the configuration has been reloaded
5973 The <file>/etc/init.d</file> scripts must be treated as
5974 configuration files, either (if they are present in the
5975 package, that is, in the .deb file) by marking them as
5976 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5977 by managing them correctly in the maintainer scripts (see
5978 <ref id="config-files">). This is important since we want
5979 to give the local system administrator the chance to adapt
5980 the scripts to the local system, e.g., to disable a
5981 service without de-installing the package, or to specify
5982 some special command line options when starting a service,
5983 while making sure their changes aren't lost during the next
5988 These scripts should not fail obscurely when the
5989 configuration files remain but the package has been
5990 removed, as configuration files remain on the system after
5991 the package has been removed. Only when <prgn>dpkg</prgn>
5992 is executed with the <tt>--purge</tt> option will
5993 configuration files be removed. In particular, as the
5994 <file>/etc/init.d/<var>package</var></file> script itself is
5995 usually a <tt>conffile</tt>, it will remain on the system
5996 if the package is removed but not purged. Therefore, you
5997 should include a <tt>test</tt> statement at the top of the
5999 <example compact="compact">
6000 test -f <var>program-executed-later-in-script</var> || exit 0
6005 Often there are some variables in the <file>init.d</file>
6006 scripts whose values control the behavior of the scripts,
6007 and which a system administrator is likely to want to
6008 change. As the scripts themselves are frequently
6009 <tt>conffile</tt>s, modifying them requires that the
6010 administrator merge in their changes each time the package
6011 is upgraded and the <tt>conffile</tt> changes. To ease
6012 the burden on the system administrator, such configurable
6013 values should not be placed directly in the script.
6014 Instead, they should be placed in a file in
6015 <file>/etc/default</file>, which typically will have the same
6016 base name as the <file>init.d</file> script. This extra file
6017 should be sourced by the script when the script runs. It
6018 must contain only variable settings and comments in SUSv3
6019 <prgn>sh</prgn> format. It may either be a
6020 <tt>conffile</tt> or a configuration file maintained by
6021 the package maintainer scripts. See <ref id="config-files">
6026 To ensure that vital configurable values are always
6027 available, the <file>init.d</file> script should set default
6028 values for each of the shell variables it uses, either
6029 before sourcing the <file>/etc/default/</file> file or
6030 afterwards using something like the <tt>:
6031 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6032 script must behave sensibly and not fail if the
6033 <file>/etc/default</file> file is deleted.
6038 <heading>Interfacing with the initscript system</heading>
6041 Maintainers should use the abstraction layer provided by
6042 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6043 programs to deal with initscripts in their packages'
6044 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6045 and <prgn>postrm</prgn>.
6049 Directly managing the /etc/rc?.d links and directly
6050 invoking the <file>/etc/init.d/</file> initscripts should
6051 be done only by packages providing the initscript
6052 subsystem (such as <prgn>sysv-rc</prgn> and
6053 <prgn>file-rc</prgn>).
6057 <heading>Managing the links</heading>
6060 The program <prgn>update-rc.d</prgn> is provided for
6061 package maintainers to arrange for the proper creation and
6062 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6063 or their functional equivalent if another method is being
6064 used. This may be used by maintainers in their packages'
6065 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6069 You must not include any <file>/etc/rc<var>n</var>.d</file>
6070 symbolic links in the actual archive or manually create or
6071 remove the symbolic links in maintainer scripts; you must
6072 use the <prgn>update-rc.d</prgn> program instead. (The
6073 former will fail if an alternative method of maintaining
6074 runlevel information is being used.) You must not include
6075 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6076 in the archive either. (Only the <tt>sysvinit</tt>
6081 By default <prgn>update-rc.d</prgn> will start services in
6082 each of the multi-user state runlevels (2, 3, 4, and 5)
6083 and stop them in the halt runlevel (0), the single-user
6084 runlevel (1) and the reboot runlevel (6). The system
6085 administrator will have the opportunity to customize
6086 runlevels by simply adding, moving, or removing the
6087 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6088 symbolic links are being used, or by modifying
6089 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6094 To get the default behavior for your package, put in your
6095 <prgn>postinst</prgn> script
6096 <example compact="compact">
6097 update-rc.d <var>package</var> defaults
6099 and in your <prgn>postrm</prgn>
6100 <example compact="compact">
6101 if [ "$1" = purge ]; then
6102 update-rc.d <var>package</var> remove
6104 </example>. Note that if your package changes runlevels
6105 or priority, you may have to remove and recreate the links,
6106 since otherwise the old links may persist. Refer to the
6107 documentation of <prgn>update-rc.d</prgn>.
6111 This will use a default sequence number of 20. If it does
6112 not matter when or in which order the <file>init.d</file>
6113 script is run, use this default. If it does, then you
6114 should talk to the maintainer of the <prgn>sysvinit</prgn>
6115 package or post to <tt>debian-devel</tt>, and they will
6116 help you choose a number.
6120 For more information about using <tt>update-rc.d</tt>,
6121 please consult its man page <manref name="update-rc.d"
6127 <heading>Running initscripts</heading>
6129 The program <prgn>invoke-rc.d</prgn> is provided to make
6130 it easier for package maintainers to properly invoke an
6131 initscript, obeying runlevel and other locally-defined
6132 constraints that might limit a package's right to start,
6133 stop and otherwise manage services. This program may be
6134 used by maintainers in their packages' scripts.
6138 The package maintainer scripts must use
6139 <prgn>invoke-rc.d</prgn> to invoke the
6140 <file>/etc/init.d/*</file> initscripts, instead of
6141 calling them directly.
6145 By default, <prgn>invoke-rc.d</prgn> will pass any
6146 action requests (start, stop, reload, restart...) to the
6147 <file>/etc/init.d</file> script, filtering out requests
6148 to start or restart a service out of its intended
6153 Most packages will simply need to change:
6154 <example compact="compact">/etc/init.d/<package>
6155 <action></example> in their <prgn>postinst</prgn>
6156 and <prgn>prerm</prgn> scripts to:
6157 <example compact="compact">
6158 if which invoke-rc.d >/dev/null 2>&1; then
6159 invoke-rc.d <var>package</var> <action>
6161 /etc/init.d/<var>package</var> <action>
6167 A package should register its initscript services using
6168 <prgn>update-rc.d</prgn> before it tries to invoke them
6169 using <prgn>invoke-rc.d</prgn>. Invocation of
6170 unregistered services may fail.
6174 For more information about using
6175 <prgn>invoke-rc.d</prgn>, please consult its man page
6176 <manref name="invoke-rc.d" section="8">.
6182 <heading>Boot-time initialization</heading>
6185 There used to be another directory, <file>/etc/rc.boot</file>,
6186 which contained scripts which were run once per machine
6187 boot. This has been deprecated in favour of links from
6188 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6189 described in <ref id="/etc/init.d">. Packages must not
6190 place files in <file>/etc/rc.boot</file>.
6195 <heading>Example</heading>
6198 An example on which you can base your
6199 <file>/etc/init.d</file> scripts is found in
6200 <file>/etc/init.d/skeleton</file>.
6207 <heading>Console messages from <file>init.d</file> scripts</heading>
6210 This section describes the formats to be used for messages
6211 written to standard output by the <file>/etc/init.d</file>
6212 scripts. The intent is to improve the consistency of
6213 Debian's startup and shutdown look and feel. For this
6214 reason, please look very carefully at the details. We want
6215 the messages to have the same format in terms of wording,
6216 spaces, punctuation and case of letters.
6220 Here is a list of overall rules that should be used for
6221 messages generated by <file>/etc/init.d</file> scripts.
6227 The message should fit in one line (fewer than 80
6228 characters), start with a capital letter and end with
6229 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6233 If the script is performing some time consuming task in
6234 the background (not merely starting or stopping a
6235 program, for instance), an ellipsis (three dots:
6236 <tt>...</tt>) should be output to the screen, with no
6237 leading or tailing whitespace or line feeds.
6241 The messages should appear as if the computer is telling
6242 the user what it is doing (politely :-), but should not
6243 mention "it" directly. For example, instead of:
6244 <example compact="compact">
6245 I'm starting network daemons: nfsd mountd.
6247 the message should say
6248 <example compact="compact">
6249 Starting network daemons: nfsd mountd.
6256 <tt>init.d</tt> script should use the following standard
6257 message formats for the situations enumerated below.
6263 <p>When daemons are started</p>
6266 If the script starts one or more daemons, the output
6267 should look like this (a single line, no leading
6269 <example compact="compact">
6270 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6272 The <var>description</var> should describe the
6273 subsystem the daemon or set of daemons are part of,
6274 while <var>daemon-1</var> up to <var>daemon-n</var>
6275 denote each daemon's name (typically the file name of
6280 For example, the output of <file>/etc/init.d/lpd</file>
6282 <example compact="compact">
6283 Starting printer spooler: lpd.
6288 This can be achieved by saying
6289 <example compact="compact">
6290 echo -n "Starting printer spooler: lpd"
6291 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6294 in the script. If there are more than one daemon to
6295 start, the output should look like this:
6296 <example compact="compact">
6297 echo -n "Starting remote file system services:"
6298 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6299 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6300 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6303 This makes it possible for the user to see what is
6304 happening and when the final daemon has been started.
6305 Care should be taken in the placement of white spaces:
6306 in the example above the system administrators can
6307 easily comment out a line if they don't want to start
6308 a specific daemon, while the displayed message still
6314 <p>When a system parameter is being set</p>
6317 If you have to set up different system parameters
6318 during the system boot, you should use this format:
6319 <example compact="compact">
6320 Setting <var>parameter</var> to "<var>value</var>".
6325 You can use a statement such as the following to get
6327 <example compact="compact">
6328 echo "Setting DNS domainname to \"$domainname\"."
6333 Note that the same symbol (<tt>"</tt>) is used for the left
6334 and right quotation marks. A grave accent (<tt>`</tt>) is
6335 not a quote character; neither is an apostrophe
6341 <p>When a daemon is stopped or restarted</p>
6344 When you stop or restart a daemon, you should issue a
6345 message identical to the startup message, except that
6346 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6347 or <tt>Restarting</tt> respectively.
6351 For example, stopping the printer daemon will look like
6353 <example compact="compact">
6354 Stopping printer spooler: lpd.
6360 <p>When something is executed</p>
6363 There are several examples where you have to run a
6364 program at system startup or shutdown to perform a
6365 specific task, for example, setting the system's clock
6366 using <prgn>netdate</prgn> or killing all processes
6367 when the system shuts down. Your message should look
6369 <example compact="compact">
6370 Doing something very useful...done.
6372 You should print the <tt>done.</tt> immediately after
6373 the job has been completed, so that the user is
6374 informed why they have to wait. You can get this
6376 <example compact="compact">
6377 echo -n "Doing something very useful..."
6386 <p>When the configuration is reloaded</p>
6389 When a daemon is forced to reload its configuration
6390 files you should use the following format:
6391 <example compact="compact">
6392 Reloading <var>description</var> configuration...done.
6394 where <var>description</var> is the same as in the
6395 daemon starting message.
6403 <heading>Cron jobs</heading>
6406 Packages must not modify the configuration file
6407 <file>/etc/crontab</file>, and they must not modify the files in
6408 <file>/var/spool/cron/crontabs</file>.</p>
6411 If a package wants to install a job that has to be executed
6412 via cron, it should place a file with the name of the
6413 package in one or more of the following directories:
6414 <example compact="compact">
6420 As these directory names imply, the files within them are
6421 executed on an hourly, daily, weekly, or monthly basis,
6422 respectively. The exact times are listed in
6423 <file>/etc/crontab</file>.</p>
6426 All files installed in any of these directories must be
6427 scripts (e.g., shell scripts or Perl scripts) so that they
6428 can easily be modified by the local system administrator.
6429 In addition, they must be treated as configuration files.
6433 If a certain job has to be executed at some other frequency or
6434 at a specific time, the package should install a file
6435 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6436 same syntax as <file>/etc/crontab</file> and is processed by
6437 <prgn>cron</prgn> automatically. The file must also be
6438 treated as a configuration file. (Note that entries in the
6439 <file>/etc/cron.d</file> directory are not handled by
6440 <prgn>anacron</prgn>. Thus, you should only use this
6441 directory for jobs which may be skipped if the system is not
6445 The scripts or crontab entries in these directories should
6446 check if all necessary programs are installed before they
6447 try to execute them. Otherwise, problems will arise when a
6448 package was removed but not purged since configuration files
6449 are kept on the system in this situation.</p>
6453 <heading>Menus</heading>
6456 The Debian <tt>menu</tt> package provides a standard
6457 interface between packages providing applications and
6458 <em>menu programs</em> (either X window managers or
6459 text-based menu programs such as <prgn>pdmenu</prgn>).
6463 All packages that provide applications that need not be
6464 passed any special command line arguments for normal
6465 operation should register a menu entry for those
6466 applications, so that users of the <tt>menu</tt> package
6467 will automatically get menu entries in their window
6468 managers, as well in shells like <tt>pdmenu</tt>.
6472 Menu entries should follow the current menu policy.
6476 The menu policy can be found in the <tt>menu-policy</tt>
6477 files in the <tt>debian-policy</tt> package.
6478 It is also available from the Debian web mirrors at
6479 <tt><url name="/doc/packaging-manuals/menu-policy/"
6480 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6484 Please also refer to the <em>Debian Menu System</em>
6485 documentation that comes with the <package>menu</package>
6486 package for information about how to register your
6492 <heading>Multimedia handlers</heading>
6495 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6496 is a mechanism for encoding files and data streams and
6497 providing meta-information about them, in particular their
6498 type (e.g. audio or video) and format (e.g. PNG, HTML,
6503 Registration of MIME type handlers allows programs like mail
6504 user agents and web browsers to invoke these handlers to
6505 view, edit or display MIME types they don't support directly.
6509 Packages which provide the ability to view/show/play,
6510 compose, edit or print MIME types should register themselves
6511 as such following the current MIME support policy.
6515 The MIME support policy can be found in the <tt>mime-policy</tt>
6516 files in the <tt>debian-policy</tt> package.
6517 It is also available from the Debian web mirrors at
6518 <tt><url name="/doc/packaging-manuals/mime-policy/"
6519 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6525 <heading>Keyboard configuration</heading>
6528 To achieve a consistent keyboard configuration so that all
6529 applications interpret a keyboard event the same way, all
6530 programs in the Debian distribution must be configured to
6531 comply with the following guidelines.
6535 The following keys must have the specified interpretations:
6538 <tag><tt><--</tt></tag>
6539 <item>delete the character to the left of the cursor</item>
6541 <tag><tt>Delete</tt></tag>
6542 <item>delete the character to the right of the cursor</item>
6544 <tag><tt>Control+H</tt></tag>
6545 <item>emacs: the help prefix</item>
6548 The interpretation of any keyboard events should be
6549 independent of the terminal that is used, be it a virtual
6550 console, an X terminal emulator, an rlogin/telnet session,
6555 The following list explains how the different programs
6556 should be set up to achieve this:
6562 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6566 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6570 X translations are set up to make
6571 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6572 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6573 is the vt220 escape code for the "delete character"
6574 key). This must be done by loading the X resources
6575 using <prgn>xrdb</prgn> on all local X displays, not
6576 using the application defaults, so that the
6577 translation resources used correspond to the
6578 <prgn>xmodmap</prgn> settings.
6582 The Linux console is configured to make
6583 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6584 generate <tt>ESC [ 3 ~</tt>.
6588 X applications are configured so that <tt><</tt>
6589 deletes left, and <tt>Delete</tt> deletes right. Motif
6590 applications already work like this.
6594 Terminals should have <tt>stty erase ^?</tt> .
6598 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6599 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6600 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6604 Emacs is programmed to map <tt>KB_Backspace</tt> or
6605 the <tt>stty erase</tt> character to
6606 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6607 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6608 <tt>^H</tt> to <tt>help</tt> as always.
6612 Other applications use the <tt>stty erase</tt>
6613 character and <tt>kdch1</tt> for the two delete keys,
6614 with ASCII DEL being "delete previous character" and
6615 <tt>kdch1</tt> being "delete character under
6623 This will solve the problem except for the following
6630 Some terminals have a <tt><--</tt> key that cannot
6631 be made to produce anything except <tt>^H</tt>. On
6632 these terminals Emacs help will be unavailable on
6633 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6634 character takes precedence in Emacs, and has been set
6635 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6636 available) can be used instead.
6640 Some operating systems use <tt>^H</tt> for <tt>stty
6641 erase</tt>. However, modern telnet versions and all
6642 rlogin versions propagate <tt>stty</tt> settings, and
6643 almost all UNIX versions honour <tt>stty erase</tt>.
6644 Where the <tt>stty</tt> settings are not propagated
6645 correctly, things can be made to work by using
6646 <tt>stty</tt> manually.
6650 Some systems (including previous Debian versions) use
6651 <prgn>xmodmap</prgn> to arrange for both
6652 <tt><--</tt> and <tt>Delete</tt> to generate
6653 <tt>KB_Delete</tt>. We can change the behavior of
6654 their X clients using the same X resources that we use
6655 to do it for our own clients, or configure our clients
6656 using their resources when things are the other way
6657 around. On displays configured like this
6658 <tt>Delete</tt> will not work, but <tt><--</tt>
6663 Some operating systems have different <tt>kdch1</tt>
6664 settings in their <tt>terminfo</tt> database for
6665 <tt>xterm</tt> and others. On these systems the
6666 <tt>Delete</tt> key will not work correctly when you
6667 log in from a system conforming to our policy, but
6668 <tt><--</tt> will.
6675 <heading>Environment variables</heading>
6678 A program must not depend on environment variables to get
6679 reasonable defaults. (That's because these environment
6680 variables would have to be set in a system-wide
6681 configuration file like <file>/etc/profile</file>, which is not
6682 supported by all shells.)
6686 If a program usually depends on environment variables for its
6687 configuration, the program should be changed to fall back to
6688 a reasonable default configuration if these environment
6689 variables are not present. If this cannot be done easily
6690 (e.g., if the source code of a non-free program is not
6691 available), the program must be replaced by a small
6692 "wrapper" shell script which sets the environment variables
6693 if they are not already defined, and calls the original program.
6697 Here is an example of a wrapper script for this purpose:
6699 <example compact="compact">
6701 BAR=${BAR:-/var/lib/fubar}
6703 exec /usr/lib/foo/foo "$@"
6708 Furthermore, as <file>/etc/profile</file> is a configuration
6709 file of the <prgn>base-files</prgn> package, other packages must
6710 not put any environment variables or other commands into that
6715 <sect id="doc-base">
6716 <heading>Registering Documents using doc-base</heading>
6719 The <package>doc-base</package> package implements a
6720 flexible mechanism for handling and presenting
6721 documentation. The recommended practice is for every Debian
6722 package that provides online documentation (other than just
6723 manual pages) to register these documents with
6724 <package>doc-base</package> by installing a
6725 <package>doc-base</package> control file via the
6726 <prgn/install-docs/ script at installation time and
6727 de-register the manuals again when the package is removed.
6730 Please refer to the documentation that comes with the
6731 <package>doc-base</package> package for information and
6740 <heading>Files</heading>
6743 <heading>Binaries</heading>
6746 Two different packages must not install programs with
6747 different functionality but with the same filenames. (The
6748 case of two programs having the same functionality but
6749 different implementations is handled via "alternatives" or
6750 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6751 <ref id="conflicts"> respectively.) If this case happens,
6752 one of the programs must be renamed. The maintainers should
6753 report this to the <tt>debian-devel</tt> mailing list and
6754 try to find a consensus about which program will have to be
6755 renamed. If a consensus cannot be reached, <em>both</em>
6756 programs must be renamed.
6760 By default, when a package is being built, any binaries
6761 created should include debugging information, as well as
6762 being compiled with optimization. You should also turn on
6763 as many reasonable compilation warnings as possible; this
6764 makes life easier for porters, who can then look at build
6765 logs for possible problems. For the C programming language,
6766 this means the following compilation parameters should be
6768 <example compact="compact">
6770 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6772 INSTALL = install -s # (or use strip on the files in debian/tmp)
6777 Note that by default all installed binaries should be stripped,
6778 either by using the <tt>-s</tt> flag to
6779 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6780 the binaries after they have been copied into
6781 <file>debian/tmp</file> but before the tree is made into a
6786 Although binaries in the build tree should be compiled with
6787 debugging information by default, it can often be difficult to
6788 debug programs if they are also subjected to compiler
6789 optimization. For this reason, it is recommended to support the
6790 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6791 (see <ref id="debianrules-options">). This variable can contain
6792 several flags to change how a package is compiled and built.
6796 It is up to the package maintainer to decide what
6797 compilation options are best for the package. Certain
6798 binaries (such as computationally-intensive programs) will
6799 function better with certain flags (<tt>-O3</tt>, for
6800 example); feel free to use them. Please use good judgment
6801 here. Don't use flags for the sake of it; only use them
6802 if there is good reason to do so. Feel free to override
6803 the upstream author's ideas about which compilation
6804 options are best: they are often inappropriate for our
6810 <sect id="libraries">
6811 <heading>Libraries</heading>
6814 If the package is <strong>architecture: any</strong>, then
6815 the shared library compilation and linking flags must have
6816 <tt>-fPIC</tt>, or the package shall not build on some of
6817 the supported architectures<footnote>
6819 If you are using GCC, <tt>-fPIC</tt> produces code with
6820 relocatable position independent code, which is required for
6821 most architectures to create a shared library, with i386 and
6822 perhaps some others where non position independent code is
6823 permitted in a shared library.
6826 Position independent code may have a performance penalty,
6827 especially on <tt>i386</tt>. However, in most cases the
6828 speed penalty must be measured against the memory wasted on
6829 the few architectures where non position independent code is
6832 </footnote>. Any exception to this rule must be discussed on
6833 the mailing list <em>debian-devel@lists.debian.org</em>, and
6834 a rough consensus obtained. The reasons for not compiling
6835 with <tt>-fPIC</tt> flag must be recorded in the file
6836 <tt>README.Debian</tt>, and care must be taken to either
6837 restrict the architecture or arrange for <tt>-fPIC</tt> to
6838 be used on architectures where it is required.<footnote>
6840 Some of the reasons why this might be required is if the
6841 library contains hand crafted assembly code that is not
6842 relocatable, the speed penalty is excessive for compute
6843 intensive libs, and similar reasons.
6848 As to the static libraries, the common case is not to have
6849 relocatable code, since there is no benefit, unless in specific
6850 cases; therefore the static version must not be compiled
6851 with the <tt>-fPIC</tt> flag. Any exception to this rule
6852 should be discussed on the mailing list
6853 <em>debian-devel@lists.debian.org</em>, and the reasons for
6854 compiling with the <tt>-fPIC</tt> flag must be recorded in
6855 the file <tt>README.Debian</tt>. <footnote>
6857 Some of the reasons for linking static libraries with
6858 the <tt>-fPIC</tt> flag are if, for example, one needs a
6859 Perl API for a library that is under rapid development,
6860 and has an unstable API, so shared libraries are
6861 pointless at this phase of the library's development. In
6862 that case, since Perl needs a library with relocatable
6863 code, it may make sense to create a static library with
6864 relocatable code. Another reason cited is if you are
6865 distilling various libraries into a common shared
6866 library, like <tt>mklibs</tt> does in the Debian
6872 In other words, if both a shared and a static library is
6873 being built, each source unit (<tt>*.c</tt>, for example,
6874 for C files) will need to be compiled twice, for the normal
6878 You must specify the gcc option <tt>-D_REENTRANT</tt>
6879 when building a library (either static or shared) to make
6880 the library compatible with LinuxThreads.
6884 Although not enforced by the build tools, shared libraries
6885 must be linked against all libraries that they use symbols from
6886 in the same way that binaries are. This ensures the correct
6887 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6888 system and guarantees that all libraries can be safely opened
6889 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6890 option <tt>-Wl,-z,defs</tt> when building a shared library.
6891 Since this option enforces symbol resolution at build time,
6892 a missing library reference will be caught early as a fatal
6897 All installed shared libraries should be stripped with
6898 <example compact="compact">
6899 strip --strip-unneeded <var>your-lib</var>
6901 (The option <tt>--strip-unneeded</tt> makes
6902 <prgn>strip</prgn> remove only the symbols which aren't
6903 needed for relocation processing.) Shared libraries can
6904 function perfectly well when stripped, since the symbols for
6905 dynamic linking are in a separate part of the ELF object
6907 You might also want to use the options
6908 <tt>--remove-section=.comment</tt> and
6909 <tt>--remove-section=.note</tt> on both shared libraries
6910 and executables, and <tt>--strip-debug</tt> on static
6916 Note that under some circumstances it may be useful to
6917 install a shared library unstripped, for example when
6918 building a separate package to support debugging.
6922 Shared object files (often <file>.so</file> files) that are not
6923 public libraries, that is, they are not meant to be linked
6924 to by third party executables (binaries of other packages),
6925 should be installed in subdirectories of the
6926 <file>/usr/lib</file> directory. Such files are exempt from the
6927 rules that govern ordinary shared libraries, except that
6928 they must not be installed executable and should be
6930 A common example are the so-called "plug-ins",
6931 internal shared objects that are dynamically loaded by
6932 programs using <manref name="dlopen" section="3">.
6937 Packages containing shared libraries that may be linked to
6938 by other packages' binaries, but which for some
6939 <em>compelling</em> reason can not be installed in
6940 <file>/usr/lib</file> directory, may install the shared library
6941 files in subdirectories of the <file>/usr/lib</file> directory,
6942 in which case they should arrange to add that directory in
6943 <file>/etc/ld.so.conf</file> in the package's post-installation
6944 script, and remove it in the package's post-removal script.
6948 An ever increasing number of packages are using
6949 <prgn>libtool</prgn> to do their linking. The latest GNU
6950 libtools (>= 1.3a) can take advantage of the metadata in the
6951 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6952 files). The main advantage of <prgn>libtool</prgn>'s
6953 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6954 store and subsequently access metadata with respect to the
6955 libraries it builds. <prgn>libtool</prgn> will search for
6956 those files, which contain a lot of useful information about
6957 a library (such as library dependency information for static
6958 linking). Also, they're <em>essential</em> for programs
6959 using <tt>libltdl</tt>.<footnote>
6960 Although <prgn>libtool</prgn> is fully capable of
6961 linking against shared libraries which don't have
6962 <tt>.la</tt> files, as it is a mere shell script it can
6963 add considerably to the build time of a
6964 <prgn>libtool</prgn>-using package if that shell script
6965 has to derive all this information from first principles
6966 for each library every time it is linked. With the
6967 advent of <prgn>libtool</prgn> version 1.4 (and to a
6968 lesser extent <prgn>libtool</prgn> version 1.3), the
6969 <file>.la</file> files also store information about
6970 inter-library dependencies which cannot necessarily be
6971 derived after the <file>.la</file> file is deleted.
6976 Packages that use <prgn>libtool</prgn> to create shared
6977 libraries should include the <file>.la</file> files in the
6978 <tt>-dev</tt> package, unless the package relies on
6979 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6980 the <tt>.la</tt> files must go in the run-time library
6985 You must make sure that you use only released versions of
6986 shared libraries to build your packages; otherwise other
6987 users will not be able to run your binaries
6988 properly. Producing source packages that depend on
6989 unreleased compilers is also usually a bad
6996 <heading>Shared libraries</heading>
6998 This section has moved to <ref id="sharedlibs">.
7004 <heading>Scripts</heading>
7007 All command scripts, including the package maintainer
7008 scripts inside the package and used by <prgn>dpkg</prgn>,
7009 should have a <tt>#!</tt> line naming the shell to be used
7014 In the case of Perl scripts this should be
7015 <tt>#!/usr/bin/perl</tt>.
7019 When scripts are installed into a directory in the system
7020 PATH, the script name should not include an extension such
7021 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7022 language currently used to implement it.
7025 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7026 should almost certainly start with <tt>set -e</tt> so that
7027 errors are detected. Every script should use
7028 <tt>set -e</tt> or check the exit status of <em>every</em>
7033 Scripts may assume that <file>/bin/sh</file> implements the
7034 SUSv3 Shell Command Language<footnote>
7035 Single UNIX Specification, version 3, which is also IEEE
7036 1003.1-2004 (POSIX), and is available on the World Wide Web
7037 from <url id="http://www.unix.org/version3/online.html"
7038 name="The Open Group"> after free
7039 registration.</footnote>
7040 plus the following additional features not mandated by
7042 These features are in widespread use in the Linux community
7043 and are implemented in all of bash, dash, and ksh, the most
7044 common shells users may wish to use as <file>/bin/sh</file>.
7047 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7048 must not generate a newline.</item>
7049 <item><tt>test</tt>, if implemented as a shell built-in, must
7050 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7052 <item><tt>local</tt> to create a scoped variable must be
7053 supported; however, <tt>local</tt> may or may not preserve
7054 the variable value from an outer scope and may or may not
7055 support arguments more complex than simple variables. Only
7067 If a shell script requires non-SUSv3 features from the shell
7068 interpreter other than those listed above, the appropriate shell
7069 must be specified in the first line of the script (e.g.,
7070 <tt>#!/bin/bash</tt>) and the package must depend on the package
7071 providing the shell (unless the shell package is marked
7072 "Essential", as in the case of <prgn>bash</prgn>).
7076 You may wish to restrict your script to SUSv3 features plus the
7077 above set when possible so that it may use <file>/bin/sh</file>
7078 as its interpreter. If your script works with <prgn>dash</prgn>
7079 (originally called <prgn>ash</prgn>), it probably complies with
7080 the above requirements, but if you are in doubt, use
7081 <file>/bin/bash</file>.
7085 Perl scripts should check for errors when making any
7086 system calls, including <tt>open</tt>, <tt>print</tt>,
7087 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7091 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7092 scripting languages. See <em>Csh Programming Considered
7093 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7094 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7095 If an upstream package comes with <prgn>csh</prgn> scripts
7096 then you must make sure that they start with
7097 <tt>#!/bin/csh</tt> and make your package depend on the
7098 <prgn>c-shell</prgn> virtual package.
7102 Any scripts which create files in world-writeable
7103 directories (e.g., in <file>/tmp</file>) must use a
7104 mechanism which will fail atomically if a file with the same
7105 name already exists.
7109 The Debian base system provides the <prgn>tempfile</prgn>
7110 and <prgn>mktemp</prgn> utilities for use by scripts for
7117 <heading>Symbolic links</heading>
7120 In general, symbolic links within a top-level directory
7121 should be relative, and symbolic links pointing from one
7122 top-level directory into another should be absolute. (A
7123 top-level directory is a sub-directory of the root
7124 directory <file>/</file>.)
7128 In addition, symbolic links should be specified as short as
7129 possible, i.e., link targets like <file>foo/../bar</file> are
7134 Note that when creating a relative link using
7135 <prgn>ln</prgn> it is not necessary for the target of the
7136 link to exist relative to the working directory you're
7137 running <prgn>ln</prgn> from, nor is it necessary to change
7138 directory to the directory where the link is to be made.
7139 Simply include the string that should appear as the target
7140 of the link (this will be a pathname relative to the
7141 directory in which the link resides) as the first argument
7146 For example, in your <prgn>Makefile</prgn> or
7147 <file>debian/rules</file>, you can do things like:
7148 <example compact="compact">
7149 ln -fs gcc $(prefix)/bin/cc
7150 ln -fs gcc debian/tmp/usr/bin/cc
7151 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7152 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7157 A symbolic link pointing to a compressed file should always
7158 have the same file extension as the referenced file. (For
7159 example, if a file <file>foo.gz</file> is referenced by a
7160 symbolic link, the filename of the link has to end with
7161 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7166 <heading>Device files</heading>
7169 Packages must not include device files in the package file
7174 If a package needs any special device files that are not
7175 included in the base system, it must call
7176 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7177 after notifying the user<footnote>
7178 This notification could be done via a (low-priority)
7179 debconf message, or an echo (printf) statement.
7184 Packages must not remove any device files in the
7185 <prgn>postrm</prgn> or any other script. This is left to the
7186 system administrator.
7190 Debian uses the serial devices
7191 <file>/dev/ttyS*</file>. Programs using the old
7192 <file>/dev/cu*</file> devices should be changed to use
7193 <file>/dev/ttyS*</file>.
7197 <sect id="config-files">
7198 <heading>Configuration files</heading>
7201 <heading>Definitions</heading>
7205 <tag>configuration file</tag>
7207 A file that affects the operation of a program, or
7208 provides site- or host-specific information, or
7209 otherwise customizes the behavior of a program.
7210 Typically, configuration files are intended to be
7211 modified by the system administrator (if needed or
7212 desired) to conform to local policy or to provide
7213 more useful site-specific behavior.
7216 <tag><tt>conffile</tt></tag>
7218 A file listed in a package's <tt>conffiles</tt>
7219 file, and is treated specially by <prgn>dpkg</prgn>
7220 (see <ref id="configdetails">).
7226 The distinction between these two is important; they are
7227 not interchangeable concepts. Almost all
7228 <tt>conffile</tt>s are configuration files, but many
7229 configuration files are not <tt>conffiles</tt>.
7233 As noted elsewhere, <file>/etc/init.d</file> scripts,
7234 <file>/etc/default</file> files, scripts installed in
7235 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7236 configuration installed in <file>/etc/cron.d</file> must be
7237 treated as configuration files. In general, any script that
7238 embeds configuration information is de-facto a configuration
7239 file and should be treated as such.
7244 <heading>Location</heading>
7247 Any configuration files created or used by your package
7248 must reside in <file>/etc</file>. If there are several,
7249 consider creating a subdirectory of <file>/etc</file>
7250 named after your package.
7254 If your package creates or uses configuration files
7255 outside of <file>/etc</file>, and it is not feasible to modify
7256 the package to use <file>/etc</file> directly, put the files
7257 in <file>/etc</file> and create symbolic links to those files
7258 from the location that the package requires.
7263 <heading>Behavior</heading>
7266 Configuration file handling must conform to the following
7268 <list compact="compact">
7270 local changes must be preserved during a package
7274 configuration files must be preserved when the
7275 package is removed, and only deleted when the
7282 The easy way to achieve this behavior is to make the
7283 configuration file a <tt>conffile</tt>. This is
7284 appropriate only if it is possible to distribute a default
7285 version that will work for most installations, although
7286 some system administrators may choose to modify it. This
7287 implies that the default version will be part of the
7288 package distribution, and must not be modified by the
7289 maintainer scripts during installation (or at any other
7294 In order to ensure that local changes are preserved
7295 correctly, no package may contain or make hard links to
7296 conffiles.<footnote>
7297 Rationale: There are two problems with hard links.
7298 The first is that some editors break the link while
7299 editing one of the files, so that the two files may
7300 unwittingly become unlinked and different. The second
7301 is that <prgn>dpkg</prgn> might break the hard link
7302 while upgrading <tt>conffile</tt>s.
7307 The other way to do it is via the maintainer scripts. In
7308 this case, the configuration file must not be listed as a
7309 <tt>conffile</tt> and must not be part of the package
7310 distribution. If the existence of a file is required for
7311 the package to be sensibly configured it is the
7312 responsibility of the package maintainer to provide
7313 maintainer scripts which correctly create, update and
7314 maintain the file and remove it on purge. (See <ref
7315 id="maintainerscripts"> for more information.) These
7316 scripts must be idempotent (i.e., must work correctly if
7317 <prgn>dpkg</prgn> needs to re-run them due to errors
7318 during installation or removal), must cope with all the
7319 variety of ways <prgn>dpkg</prgn> can call maintainer
7320 scripts, must not overwrite or otherwise mangle the user's
7321 configuration without asking, must not ask unnecessary
7322 questions (particularly during upgrades), and must
7323 otherwise be good citizens.
7327 The scripts are not required to configure every possible
7328 option for the package, but only those necessary to get
7329 the package running on a given system. Ideally the
7330 sysadmin should not have to do any configuration other
7331 than that done (semi-)automatically by the
7332 <prgn>postinst</prgn> script.
7336 A common practice is to create a script called
7337 <file><var>package</var>-configure</file> and have the
7338 package's <prgn>postinst</prgn> call it if and only if the
7339 configuration file does not already exist. In certain
7340 cases it is useful for there to be an example or template
7341 file which the maintainer scripts use. Such files should
7342 be in <file>/usr/share/<var>package</var></file> or
7343 <file>/usr/lib/<var>package</var></file> (depending on whether
7344 they are architecture-independent or not). There should
7345 be symbolic links to them from
7346 <file>/usr/share/doc/<var>package</var>/examples</file> if
7347 they are examples, and should be perfectly ordinary
7348 <prgn>dpkg</prgn>-handled files (<em>not</em>
7349 configuration files).
7353 These two styles of configuration file handling must
7354 not be mixed, for that way lies madness:
7355 <prgn>dpkg</prgn> will ask about overwriting the file
7356 every time the package is upgraded.
7361 <heading>Sharing configuration files</heading>
7364 Packages which specify the same file as a
7365 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7366 with each other. (This is an instance of the general rule
7367 about not sharing files. Note that neither alternatives
7368 nor diversions are likely to be appropriate in this case;
7369 in particular, <prgn>dpkg</prgn> does not handle diverted
7370 <tt>conffile</tt>s well.)
7374 The maintainer scripts must not alter a <tt>conffile</tt>
7375 of <em>any</em> package, including the one the scripts
7380 If two or more packages use the same configuration file
7381 and it is reasonable for both to be installed at the same
7382 time, one of these packages must be defined as
7383 <em>owner</em> of the configuration file, i.e., it will be
7384 the package which handles that file as a configuration
7385 file. Other packages that use the configuration file must
7386 depend on the owning package if they require the
7387 configuration file to operate. If the other package will
7388 use the configuration file if present, but is capable of
7389 operating without it, no dependency need be declared.
7393 If it is desirable for two or more related packages to
7394 share a configuration file <em>and</em> for all of the
7395 related packages to be able to modify that configuration
7396 file, then the following should be done:
7397 <enumlist compact="compact">
7399 One of the related packages (the "owning" package)
7400 will manage the configuration file with maintainer
7401 scripts as described in the previous section.
7404 The owning package should also provide a program
7405 that the other packages may use to modify the
7409 The related packages must use the provided program
7410 to make any desired modifications to the
7411 configuration file. They should either depend on
7412 the core package to guarantee that the configuration
7413 modifier program is available or accept gracefully
7414 that they cannot modify the configuration file if it
7415 is not. (This is in addition to the fact that the
7416 configuration file may not even be present in the
7423 Sometimes it's appropriate to create a new package which
7424 provides the basic infrastructure for the other packages
7425 and which manages the shared configuration files. (The
7426 <tt>sgml-base</tt> package is a good example.)
7431 <heading>User configuration files ("dotfiles")</heading>
7434 The files in <file>/etc/skel</file> will automatically be
7435 copied into new user accounts by <prgn>adduser</prgn>.
7436 No other program should reference the files in
7437 <file>/etc/skel</file>.
7441 Therefore, if a program needs a dotfile to exist in
7442 advance in <file>$HOME</file> to work sensibly, that dotfile
7443 should be installed in <file>/etc/skel</file> and treated as a
7448 However, programs that require dotfiles in order to
7449 operate sensibly are a bad thing, unless they do create
7450 the dotfiles themselves automatically.
7454 Furthermore, programs should be configured by the Debian
7455 default installation to behave as closely to the upstream
7456 default behavior as possible.
7460 Therefore, if a program in a Debian package needs to be
7461 configured in some way in order to operate sensibly, that
7462 should be done using a site-wide configuration file placed
7463 in <file>/etc</file>. Only if the program doesn't support a
7464 site-wide default configuration and the package maintainer
7465 doesn't have time to add it may a default per-user file be
7466 placed in <file>/etc/skel</file>.
7470 <file>/etc/skel</file> should be as empty as we can make it.
7471 This is particularly true because there is no easy (or
7472 necessarily desirable) mechanism for ensuring that the
7473 appropriate dotfiles are copied into the accounts of
7474 existing users when a package is installed.
7480 <heading>Log files</heading>
7482 Log files should usually be named
7483 <file>/var/log/<var>package</var>.log</file>. If you have many
7484 log files, or need a separate directory for permission
7485 reasons (<file>/var/log</file> is writable only by
7486 <file>root</file>), you should usually create a directory named
7487 <file>/var/log/<var>package</var></file> and place your log
7492 Log files must be rotated occasionally so that they don't
7493 grow indefinitely; the best way to do this is to drop a log
7494 rotation configuration file into the directory
7495 <file>/etc/logrotate.d</file> and use the facilities provided by
7496 logrotate.<footnote>
7498 The traditional approach to log files has been to set up
7499 <em>ad hoc</em> log rotation schemes using simple shell
7500 scripts and cron. While this approach is highly
7501 customizable, it requires quite a lot of sysadmin work.
7502 Even though the original Debian system helped a little
7503 by automatically installing a system which can be used
7504 as a template, this was deemed not enough.
7508 The use of <prgn>logrotate</prgn>, a program developed
7509 by Red Hat, is better, as it centralizes log management.
7510 It has both a configuration file
7511 (<file>/etc/logrotate.conf</file>) and a directory where
7512 packages can drop their individual log rotation
7513 configurations (<file>/etc/logrotate.d</file>).
7516 Here is a good example for a logrotate config
7517 file (for more information see <manref name="logrotate"
7519 <example compact="compact">
7520 /var/log/foo/*.log {
7525 /etc/init.d/foo force-reload
7529 This rotates all files under <file>/var/log/foo</file>, saves 12
7530 compressed generations, and forces the daemon to reload its
7531 configuration information after the log rotation.
7535 Log files should be removed when the package is
7536 purged (but not when it is only removed). This should be
7537 done by the <prgn>postrm</prgn> script when it is called
7538 with the argument <tt>purge</tt> (see <ref
7539 id="removedetails">).
7544 <heading>Permissions and owners</heading>
7547 The rules in this section are guidelines for general use.
7548 If necessary you may deviate from the details below.
7549 However, if you do so you must make sure that what is done
7550 is secure and you should try to be as consistent as possible
7551 with the rest of the system. You should probably also
7552 discuss it on <prgn>debian-devel</prgn> first.
7556 Files should be owned by <tt>root:root</tt>, and made
7557 writable only by the owner and universally readable (and
7558 executable, if appropriate), that is mode 644 or 755.
7562 Directories should be mode 755 or (for group-writability)
7563 mode 2775. The ownership of the directory should be
7564 consistent with its mode: if a directory is mode 2775, it
7565 should be owned by the group that needs write access to
7568 When a package is upgraded, and the owner or permissions
7569 of a file included in the package has changed, dpkg
7570 arranges for the ownership and permissions to be
7571 correctly set upon installation. However, this does not
7572 extend to directories; the permissions and ownership of
7573 directories already on the system does not change on
7574 install or upgrade of packages. This makes sense, since
7575 otherwise common directories like <tt>/usr</tt> would
7576 always be in flux. To correctly change permissions of a
7577 directory the package owns, explicit action is required,
7578 usually in the <tt>postinst</tt> script. Care must be
7579 taken to handle downgrades as well, in that case.
7586 Setuid and setgid executables should be mode 4755 or 2755
7587 respectively, and owned by the appropriate user or group.
7588 They should not be made unreadable (modes like 4711 or
7589 2711 or even 4111); doing so achieves no extra security,
7590 because anyone can find the binary in the freely available
7591 Debian package; it is merely inconvenient. For the same
7592 reason you should not restrict read or execute permissions
7593 on non-set-id executables.
7597 Some setuid programs need to be restricted to particular
7598 sets of users, using file permissions. In this case they
7599 should be owned by the uid to which they are set-id, and by
7600 the group which should be allowed to execute them. They
7601 should have mode 4754; again there is no point in making
7602 them unreadable to those users who must not be allowed to
7607 It is possible to arrange that the system administrator can
7608 reconfigure the package to correspond to their local
7609 security policy by changing the permissions on a binary:
7610 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7611 described below.<footnote>
7612 Ordinary files installed by <prgn>dpkg</prgn> (as
7613 opposed to <tt>conffile</tt>s and other similar objects)
7614 normally have their permissions reset to the distributed
7615 permissions when the package is reinstalled. However,
7616 the use of <prgn>dpkg-statoverride</prgn> overrides this
7617 default behavior. If you use this method, you should
7618 remember to describe <prgn>dpkg-statoverride</prgn> in
7619 the package documentation; being a relatively new
7620 addition to Debian, it is probably not yet well-known.
7622 Another method you should consider is to create a group for
7623 people allowed to use the program(s) and make any setuid
7624 executables executable only by that group.
7628 If you need to create a new user or group for your package
7629 there are two possibilities. Firstly, you may need to
7630 make some files in the binary package be owned by this
7631 user or group, or you may need to compile the user or
7632 group id (rather than just the name) into the binary
7633 (though this latter should be avoided if possible, as in
7634 this case you need a statically allocated id).</p>
7637 If you need a statically allocated id, you must ask for a
7638 user or group id from the <tt>base-passwd</tt> maintainer,
7639 and must not release the package until you have been
7640 allocated one. Once you have been allocated one you must
7641 either make the package depend on a version of the
7642 <tt>base-passwd</tt> package with the id present in
7643 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7644 your package to create the user or group itself with the
7645 correct id (using <tt>adduser</tt>) in its
7646 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7647 the <prgn>postinst</prgn> is to be preferred if it is
7648 possible, otherwise a pre-dependency will be needed on the
7649 <tt>adduser</tt> package.)
7653 On the other hand, the program might be able to determine
7654 the uid or gid from the user or group name at runtime, so
7655 that a dynamically allocated id can be used. In this case
7656 you should choose an appropriate user or group name,
7657 discussing this on <prgn>debian-devel</prgn> and checking
7658 with the <package/base-passwd/ maintainer that it is unique and that
7659 they do not wish you to use a statically allocated id
7660 instead. When this has been checked you must arrange for
7661 your package to create the user or group if necessary using
7662 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7663 <prgn>postinst</prgn> script (again, the latter is to be
7664 preferred if it is possible).
7668 Note that changing the numeric value of an id associated
7669 with a name is very difficult, and involves searching the
7670 file system for all appropriate files. You need to think
7671 carefully whether a static or dynamic id is required, since
7672 changing your mind later will cause problems.
7675 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7677 This section is not intended as policy, but as a
7678 description of the use of <prgn>dpkg-statoverride</prgn>.
7682 If a system administrator wishes to have a file (or
7683 directory or other such thing) installed with owner and
7684 permissions different from those in the distributed Debian
7685 package, they can use the <prgn>dpkg-statoverride</prgn>
7686 program to instruct <prgn>dpkg</prgn> to use the different
7687 settings every time the file is installed. Thus the
7688 package maintainer should distribute the files with their
7689 normal permissions, and leave it for the system
7690 administrator to make any desired changes. For example, a
7691 daemon which is normally required to be setuid root, but
7692 in certain situations could be used without being setuid,
7693 should be installed setuid in the <tt>.deb</tt>. Then the
7694 local system administrator can change this if they wish.
7695 If there are two standard ways of doing it, the package
7696 maintainer can use <tt>debconf</tt> to find out the
7697 preference, and call <prgn>dpkg-statoverride</prgn> in the
7698 maintainer script if necessary to accommodate the system
7699 administrator's choice. Care must be taken during
7700 upgrades to not override an existing setting.
7704 Given the above, <prgn>dpkg-statoverride</prgn> is
7705 essentially a tool for system administrators and would not
7706 normally be needed in the maintainer scripts. There is
7707 one type of situation, though, where calls to
7708 <prgn>dpkg-statoverride</prgn> would be needed in the
7709 maintainer scripts, and that involves packages which use
7710 dynamically allocated user or group ids. In such a
7711 situation, something like the following idiom can be very
7712 helpful in the package's <prgn>postinst</prgn>, where
7713 <tt>sysuser</tt> is a dynamically allocated id:
7715 for i in /usr/bin/foo /usr/sbin/bar
7717 # only do something when no setting exists
7718 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7720 #include: debconf processing, question about foo and bar
7721 if [ "$RET" = "true" ] ; then
7722 dpkg-statoverride --update --add sysuser root 4755 $i
7727 The corresponding <tt>dpkg-statoverride --remove</tt>
7728 calls can then be made unconditionally when the package is
7736 <chapt id="customized-programs">
7737 <heading>Customized programs</heading>
7739 <sect id="arch-spec">
7740 <heading>Architecture specification strings</heading>
7743 If a program needs to specify an <em>architecture specification
7744 string</em> in some place, it should select one of the
7745 strings provided by <tt>dpkg-architecture -L</tt>. The
7746 strings are in the format
7747 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7748 is sometimes elided, as when the OS is Linux.<footnote>
7749 <p>Currently, the strings are:
7750 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7751 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7752 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7753 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7754 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7755 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7756 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7757 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7758 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7759 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7760 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7761 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7762 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7763 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7764 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7765 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7766 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7767 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7768 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7769 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7770 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7771 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7772 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7773 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7774 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7775 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7776 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7777 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7778 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7779 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7780 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7781 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7782 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7783 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7784 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7785 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7786 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7792 Note that we don't want to use
7793 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7794 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7795 since this would make our programs incompatible with other
7796 Linux distributions. We also don't use something like
7797 <tt><var>arch</var>-unknown-linux</tt>, since the
7798 <tt>unknown</tt> does not look very good.
7803 <heading>Daemons</heading>
7806 The configuration files <file>/etc/services</file>,
7807 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7808 by the <prgn>netbase</prgn> package and must not be modified
7813 If a package requires a new entry in one of these files, the
7814 maintainer should get in contact with the
7815 <prgn>netbase</prgn> maintainer, who will add the entries
7816 and release a new version of the <prgn>netbase</prgn>
7821 The configuration file <file>/etc/inetd.conf</file> must not be
7822 modified by the package's scripts except via the
7823 <prgn>update-inetd</prgn> script or the
7824 <file>DebianNet.pm</file> Perl module. See their documentation
7825 for details on how to add entries.
7829 If a package wants to install an example entry into
7830 <file>/etc/inetd.conf</file>, the entry must be preceded with
7831 exactly one hash character (<tt>#</tt>). Such lines are
7832 treated as "commented out by user" by the
7833 <prgn>update-inetd</prgn> script and are not changed or
7834 activated during package updates.
7839 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7843 Some programs need to create pseudo-ttys. This should be done
7844 using Unix98 ptys if the C library supports it. The resulting
7845 program must not be installed setuid root, unless that
7846 is required for other functionality.
7850 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7851 <file>/var/log/lastlog</file> must be installed writable by
7852 group <tt>utmp</tt>. Programs which need to modify those
7853 files must be installed setgid <tt>utmp</tt>.
7858 <heading>Editors and pagers</heading>
7861 Some programs have the ability to launch an editor or pager
7862 program to edit or display a text document. Since there are
7863 lots of different editors and pagers available in the Debian
7864 distribution, the system administrator and each user should
7865 have the possibility to choose their preferred editor and
7870 In addition, every program should choose a good default
7871 editor/pager if none is selected by the user or system
7876 Thus, every program that launches an editor or pager must
7877 use the EDITOR or PAGER environment variable to determine
7878 the editor or pager the user wishes to use. If these
7879 variables are not set, the programs <file>/usr/bin/editor</file>
7880 and <file>/usr/bin/pager</file> should be used, respectively.
7884 These two files are managed through the <prgn>dpkg</prgn>
7885 "alternatives" mechanism. Thus every package providing an
7886 editor or pager must call the
7887 <prgn>update-alternatives</prgn> script to register these
7892 If it is very hard to adapt a program to make use of the
7893 EDITOR or PAGER variables, that program may be configured to
7894 use <file>/usr/bin/sensible-editor</file> and
7895 <file>/usr/bin/sensible-pager</file> as the editor or pager
7896 program respectively. These are two scripts provided in the
7897 Debian base system that check the EDITOR and PAGER variables
7898 and launch the appropriate program, and fall back to
7899 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7900 variable is not set.
7904 A program may also use the VISUAL environment variable to
7905 determine the user's choice of editor. If it exists, it
7906 should take precedence over EDITOR. This is in fact what
7907 <file>/usr/bin/sensible-editor</file> does.
7911 It is not required for a package to depend on
7912 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7913 package to provide such virtual packages.<footnote>
7914 The Debian base system already provides an editor and a
7920 <sect id="web-appl">
7921 <heading>Web servers and applications</heading>
7924 This section describes the locations and URLs that should
7925 be used by all web servers and web applications in the
7932 Cgi-bin executable files are installed in the
7934 <example compact="compact">
7935 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7937 and should be referred to as
7938 <example compact="compact">
7939 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7945 <p>Access to HTML documents</p>
7948 HTML documents for a package are stored in
7949 <file>/usr/share/doc/<var>package</var></file>
7950 and can be referred to as
7951 <example compact="compact">
7952 http://localhost/doc/<var>package</var>/<var>filename</var>
7957 The web server should restrict access to the document
7958 tree so that only clients on the same host can read
7959 the documents. If the web server does not support such
7960 access controls, then it should not provide access at
7961 all, or ask about providing access during installation.
7966 <p>Access to images</p>
7968 It is recommended that images for a package be stored
7969 in <tt>/usr/share/images/<var>package</var></tt> and
7970 may be referred to through an alias <tt>/images/</tt>
7973 http://localhost/images/<package>/<filename>
7980 <p>Web Document Root</p>
7983 Web Applications should try to avoid storing files in
7984 the Web Document Root. Instead they should use the
7985 /usr/share/doc/<var>package</var> directory for
7986 documents and register the Web Application via the
7987 <package>doc-base</package> package. If access to the
7988 web document root is unavoidable then use
7989 <example compact="compact">
7992 as the Document Root. This might be just a symbolic
7993 link to the location where the system administrator
7994 has put the real document root.
7997 <item><p>Providing httpd and/or httpd-cgi</p>
7999 All web servers should provide the virtual package
8000 <tt>httpd</tt>. If a web server has CGI support it should
8001 provide <tt>httpd-cgi</tt> additionally.
8004 All web applications which do not contain CGI scripts should
8005 depend on <tt>httpd</tt>, all those web applications which
8006 <tt>do</tt> contain CGI scripts, should depend on
8014 <sect id="mail-transport-agents">
8015 <heading>Mail transport, delivery and user agents</heading>
8018 Debian packages which process electronic mail, whether mail
8019 user agents (MUAs) or mail transport agents (MTAs), must
8020 ensure that they are compatible with the configuration
8021 decisions below. Failure to do this may result in lost
8022 mail, broken <tt>From:</tt> lines, and other serious brain
8027 The mail spool is <file>/var/mail</file> and the interface to
8028 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8029 the FHS). On older systems, the mail spool may be
8030 physically located in <file>/var/spool/mail</file>, but all
8031 access to the mail spool should be via the
8032 <file>/var/mail</file> symlink. The mail spool is part of the
8033 base system and not part of the MTA package.
8037 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8038 programs (such as IMAP daemons) must lock the mailbox in an
8039 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8040 be combined with dot locking. To avoid deadlocks, a program
8041 should use <tt>fcntl()</tt> first and dot locking after
8042 this, or alternatively implement the two locking methods in
8043 a non blocking way<footnote>
8044 If it is not possible to establish both locks, the
8045 system shouldn't wait for the second lock to be
8046 established, but remove the first lock, wait a (random)
8047 time, and start over locking again.
8048 </footnote>. Using the functions <tt>maillock</tt> and
8049 <tt>mailunlock</tt> provided by the
8050 <tt>liblockfile*</tt><footnote>
8051 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8052 to use these functions.
8053 </footnote> packages is the recommended way to realize this.
8057 Mailboxes are generally mode 660
8058 <tt><var>user</var>:mail</tt> unless the system
8059 administrator has chosen otherwise. A MUA may remove a
8060 mailbox (unless it has nonstandard permissions) in which
8061 case the MTA or another MUA must recreate it if needed.
8062 Mailboxes must be writable by group mail.
8066 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8067 be setgid mail to do the locking mentioned above (and
8068 must obviously avoid accessing other users' mailboxes
8069 using this privilege).</p>
8072 <file>/etc/aliases</file> is the source file for the system mail
8073 aliases (e.g., postmaster, usenet, etc.), it is the one
8074 which the sysadmin and <prgn>postinst</prgn> scripts may
8075 edit. After <file>/etc/aliases</file> is edited the program or
8076 human editing it must call <prgn>newaliases</prgn>. All MTA
8077 packages must come with a <prgn>newaliases</prgn> program,
8078 even if it does nothing, but older MTA packages did not do
8079 this so programs should not fail if <prgn>newaliases</prgn>
8080 cannot be found. Note that because of this, all MTA
8081 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8082 <tt>Replaces: mail-transport-agent</tt> control file
8087 The convention of writing <tt>forward to
8088 <var>address</var></tt> in the mailbox itself is not
8089 supported. Use a <tt>.forward</tt> file instead.</p>
8092 The <prgn>rmail</prgn> program used by UUCP
8093 for incoming mail should be <file>/usr/sbin/rmail</file>.
8094 Likewise, <prgn>rsmtp</prgn>, for receiving
8095 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8099 If your package needs to know what hostname to use on (for
8100 example) outgoing news and mail messages which are generated
8101 locally, you should use the file <file>/etc/mailname</file>. It
8102 will contain the portion after the username and <tt>@</tt>
8103 (at) sign for email addresses of users on the machine
8104 (followed by a newline).
8108 Such a package should check for the existence of this file
8109 when it is being configured. If it exists, it should be
8110 used without comment, although an MTA's configuration script
8111 may wish to prompt the user even if it finds that this file
8112 exists. If the file does not exist, the package should
8113 prompt the user for the value (preferably using
8114 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8115 as well as using it in the package's configuration. The
8116 prompt should make it clear that the name will not just be
8117 used by that package. For example, in this situation the
8118 <tt>inn</tt> package could say something like:
8119 <example compact="compact">
8120 Please enter the "mail name" of your system. This is the
8121 hostname portion of the address to be shown on outgoing
8122 news and mail messages. The default is
8123 <var>syshostname</var>, your system's host name. Mail
8124 name ["<var>syshostname</var>"]:
8126 where <var>syshostname</var> is the output of <tt>hostname
8132 <heading>News system configuration</heading>
8135 All the configuration files related to the NNTP (news)
8136 servers and clients should be located under
8137 <file>/etc/news</file>.</p>
8140 There are some configuration issues that apply to a number
8141 of news clients and server packages on the machine. These
8145 <tag><file>/etc/news/organization</file></tag>
8147 A string which should appear as the
8148 organization header for all messages posted
8149 by NNTP clients on the machine
8152 <tag><file>/etc/news/server</file></tag>
8154 Contains the FQDN of the upstream NNTP
8155 server, or localhost if the local machine is
8160 Other global files may be added as required for cross-package news
8167 <heading>Programs for the X Window System</heading>
8170 <heading>Providing X support and package priorities</heading>
8173 Programs that can be configured with support for the X
8174 Window System must be configured to do so and must declare
8175 any package dependencies necessary to satisfy their
8176 runtime requirements when using the X Window System. If
8177 such a package is of higher priority than the X packages
8178 on which it depends, it is required that either the
8179 X-specific components be split into a separate package, or
8180 that an alternative version of the package, which includes
8181 X support, be provided, or that the package's priority be
8187 <heading>Packages providing an X server</heading>
8190 Packages that provide an X server that, directly or
8191 indirectly, communicates with real input and display
8192 hardware should declare in their control data that they
8193 provide the virtual package <tt>xserver</tt>.<footnote>
8194 This implements current practice, and provides an
8195 actual policy for usage of the <tt>xserver</tt>
8196 virtual package which appears in the virtual packages
8197 list. In a nutshell, X servers that interface
8198 directly with the display and input hardware or via
8199 another subsystem (e.g., GGI) should provide
8200 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8201 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8207 <heading>Packages providing a terminal emulator</heading>
8210 Packages that provide a terminal emulator for the X Window
8211 System which meet the criteria listed below should declare
8212 in their control data that they provide the virtual
8213 package <tt>x-terminal-emulator</tt>. They should also
8214 register themselves as an alternative for
8215 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8220 To be an <tt>x-terminal-emulator</tt>, a program must:
8221 <list compact="compact">
8223 Be able to emulate a DEC VT100 terminal, or a
8224 compatible terminal.
8228 Support the command-line option <tt>-e
8229 <var>command</var></tt>, which creates a new
8230 terminal window<footnote>
8231 "New terminal window" does not necessarily mean
8232 a new top-level X window directly parented by
8233 the window manager; it could, if the terminal
8234 emulator application were so coded, be a new
8235 "view" in a multiple-document interface (MDI).
8237 and runs the specified <var>command</var>,
8238 interpreting the entirety of the rest of the command
8239 line as a command to pass straight to exec, in the
8240 manner that <tt>xterm</tt> does.
8244 Support the command-line option <tt>-T
8245 <var>title</var></tt>, which creates a new terminal
8246 window with the window title <var>title</var>.
8253 <heading>Packages providing a window manager</heading>
8256 Packages that provide a window manager should declare in
8257 their control data that they provide the virtual package
8258 <tt>x-window-manager</tt>. They should also register
8259 themselves as an alternative for
8260 <file>/usr/bin/x-window-manager</file>, with a priority
8261 calculated as follows:
8262 <list compact="compact">
8264 Start with a priority of 20.
8268 If the window manager supports the Debian menu
8269 system, add 20 points if this support is available
8270 in the package's default configuration (i.e., no
8271 configuration files belonging to the system or user
8272 have to be edited to activate the feature); if
8273 configuration files must be modified, add only 10
8279 If the window manager complies with <url
8280 id="http://www.freedesktop.org/Standards/wm-spec"
8281 name="The Window Manager Specification Project">,
8282 written by the <url id="http://www.freedesktop.org/"
8283 name="Free Desktop Group">, add 40 points.
8287 If the window manager permits the X session to be
8288 restarted using a <em>different</em> window manager
8289 (without killing the X server) in its default
8290 configuration, add 10 points; otherwise add none.
8297 <heading>Packages providing fonts</heading>
8300 Packages that provide fonts for the X Window
8302 For the purposes of Debian Policy, a "font for the X
8303 Window System" is one which is accessed via X protocol
8304 requests. Fonts for the Linux console, for PostScript
8305 renderer, or any other purpose, do not fit this
8306 definition. Any tool which makes such fonts available
8307 to the X Window System, however, must abide by this
8310 must do a number of things to ensure that they are both
8311 available without modification of the X or font server
8312 configuration, and that they do not corrupt files used by
8313 other font packages to register information about
8317 Fonts of any type supported by the X Window System
8318 must be in a separate binary package from any
8319 executables, libraries, or documentation (except
8320 that specific to the fonts shipped, such as their
8321 license information). If one or more of the fonts
8322 so packaged are necessary for proper operation of
8323 the package with which they are associated the font
8324 package may be Recommended; if the fonts merely
8325 provide an enhancement, a Suggests relationship may
8326 be used. Packages must not Depend on font
8328 This is because the X server may retrieve fonts
8329 from the local file system or over the network
8330 from an X font server; the Debian package system
8331 is empowered to deal only with the local
8337 BDF fonts must be converted to PCF fonts with the
8338 <prgn>bdftopcf</prgn> utility (available in the
8339 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8340 placed in a directory that corresponds to their
8342 <list compact="compact">
8344 100 dpi fonts must be placed in
8345 <file>/usr/share/fonts/X11/100dpi/</file>.
8349 75 dpi fonts must be placed in
8350 <file>/usr/share/fonts/X11/75dpi/</file>.
8354 Character-cell fonts, cursor fonts, and other
8355 low-resolution fonts must be placed in
8356 <file>/usr/share/fonts/X11/misc/</file>.
8362 Speedo fonts must be placed in
8363 <file>/usr/share/fonts/X11/Speedo/</file>.
8367 Type 1 fonts must be placed in
8368 <file>/usr/share/fonts/X11/Type1/</file>. If font
8369 metric files are available, they must be placed here
8374 Subdirectories of <file>/usr/share/fonts/X11/</file>
8375 other than those listed above must be neither
8376 created nor used. (The <file>PEX</file>, <file>CID</file>,
8377 and <file>cyrillic</file> directories are excepted for
8378 historical reasons, but installation of files into
8379 these directories remains discouraged.)
8383 Font packages may, instead of placing files directly
8384 in the X font directories listed above, provide
8385 symbolic links in that font directory pointing to
8386 the files' actual location in the filesystem. Such
8387 a location must comply with the FHS.
8391 Font packages should not contain both 75dpi and
8392 100dpi versions of a font. If both are available,
8393 they should be provided in separate binary packages
8394 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8395 the names of the packages containing the
8396 corresponding fonts.
8400 Fonts destined for the <file>misc</file> subdirectory
8401 should not be included in the same package as 75dpi
8402 or 100dpi fonts; instead, they should be provided in
8403 a separate package with <tt>-misc</tt> appended to
8408 Font packages must not provide the files
8409 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8410 <file>fonts.scale</file> in a font directory:
8413 <file>fonts.dir</file> files must not be provided at all.
8417 <file>fonts.alias</file> and <file>fonts.scale</file>
8418 files, if needed, should be provided in the
8420 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8421 where <var>fontdir</var> is the name of the
8423 <file>/usr/share/fonts/X11/</file> where the
8424 package's corresponding fonts are stored
8425 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8426 <var>package</var> is the name of the package
8427 that provides these fonts, and
8428 <var>extension</var> is either <tt>scale</tt>
8429 or <tt>alias</tt>, whichever corresponds to
8436 Font packages must declare a dependency on
8437 <tt>xfonts-utils</tt> in their control
8442 Font packages that provide one or more
8443 <file>fonts.scale</file> files as described above must
8444 invoke <prgn>update-fonts-scale</prgn> on each
8445 directory into which they installed fonts
8446 <em>before</em> invoking
8447 <prgn>update-fonts-dir</prgn> on that directory.
8448 This invocation must occur in both the
8449 <prgn>postinst</prgn> (for all arguments) and
8450 <prgn>postrm</prgn> (for all arguments except
8451 <tt>upgrade</tt>) scripts.
8455 Font packages that provide one or more
8456 <file>fonts.alias</file> files as described above must
8457 invoke <prgn>update-fonts-alias</prgn> on each
8458 directory into which they installed fonts. This
8459 invocation must occur in both the
8460 <prgn>postinst</prgn> (for all arguments) and
8461 <prgn>postrm</prgn> (for all arguments except
8462 <tt>upgrade</tt>) scripts.
8466 Font packages must invoke
8467 <prgn>update-fonts-dir</prgn> on each directory into
8468 which they installed fonts. This invocation must
8469 occur in both the <prgn>postinst</prgn> (for all
8470 arguments) and <prgn>postrm</prgn> (for all
8471 arguments except <tt>upgrade</tt>) scripts.
8475 Font packages must not provide alias names for the
8476 fonts they include which collide with alias names
8477 already in use by fonts already packaged.
8481 Font packages must not provide fonts with the same
8482 XLFD registry name as another font already packaged.
8489 <heading>Application defaults files</heading>
8492 Application defaults files must be installed in the
8493 directory <file>/etc/X11/app-defaults/</file> (use of a
8494 localized subdirectory of <file>/etc/X11/</file> as described
8495 in the <em>X Toolkit Intrinsics - C Language
8496 Interface</em> manual is also permitted). They must be
8497 registered as <tt>conffile</tt>s or handled as
8498 configuration files.
8502 Customization of programs' X resources may also be
8503 supported with the provision of a file with the same name
8504 as that of the package placed in the
8505 <file>/etc/X11/Xresources/</file> directory, which must
8506 registered as a <tt>conffile</tt> or handled as a
8507 configuration file.<footnote>
8508 Note that this mechanism is not the same as using
8509 app-defaults; app-defaults are tied to the client
8510 binary on the local file system, whereas X resources
8511 are stored in the X server and affect all connecting
8518 <heading>Installation directory issues</heading>
8521 Packages using the X Window System should not be
8522 configured to install files under the
8523 <file>/usr/X11R6/</file> directory. The
8524 <file>/usr/X11R6/</file> directory hierarchy should be
8525 regarded as obsolete.
8529 Programs that use GNU <prgn>autoconf</prgn> and
8530 <prgn>automake</prgn> are usually easily configured at
8531 compile time to use <file>/usr/</file> instead of
8532 <file>/usr/X11R6/</file>, and this should be done whenever
8533 possible. Configuration files for window managers and
8534 display managers should be placed in a subdirectory of
8535 <file>/etc/X11/</file> corresponding to the package name due
8536 to these programs' tight integration with the mechanisms
8537 of the X Window System. Application-level programs should
8538 use the <file>/etc/</file> directory unless otherwise mandated
8543 The installation of files into subdirectories
8544 of <file>/usr/X11R6/include/X11/</file> and
8545 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8546 package maintainers should determine if subdirectories of
8547 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8552 Packages should install any relevant files into the
8553 directories <file>/usr/include/X11/</file> and
8554 <file>/usr/lib/X11/</file>, but if they do so, they must
8555 pre-depend on <tt>x11-common (>=
8556 1:7.0.0)</tt><footnote>
8558 These libraries used to be all symbolic
8559 links. However, with <tt>X11R7</tt>,
8560 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8561 are now real directories, and packages
8562 <strong>should</strong> ship their files here instead
8563 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8564 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8565 responsible for converting these symlinks into
8573 <heading>The OSF/Motif and OpenMotif libraries</heading>
8576 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8577 OpenMotif libraries</em><footnote>
8578 OSF/Motif and OpenMotif are collectively referred to as
8579 "Motif" in this policy document.
8581 should be compiled against and tested with LessTif (a free
8582 re-implementation of Motif) instead. If the maintainer
8583 judges that the program or programs do not work
8584 sufficiently well with LessTif to be distributed and
8585 supported, but do so when compiled against Motif, then two
8586 versions of the package should be created; one linked
8587 statically against Motif and with <tt>-smotif</tt>
8588 appended to the package name, and one linked dynamically
8589 against Motif and with <tt>-dmotif</tt> appended to the
8594 Both Motif-linked versions are dependent
8595 upon non-DFSG-compliant software and thus cannot be
8596 uploaded to the <em>main</em> distribution; if the
8597 software is itself DFSG-compliant it may be uploaded to
8598 the <em>contrib</em> distribution. While known existing
8599 versions of Motif permit unlimited redistribution of
8600 binaries linked against the library (whether statically or
8601 dynamically), it is the package maintainer's
8602 responsibility to determine whether this is permitted by
8603 the license of the copy of Motif in their possession.
8609 <heading>Perl programs and modules</heading>
8612 Perl programs and modules should follow the current Perl policy.
8616 The Perl policy can be found in the <tt>perl-policy</tt>
8617 files in the <tt>debian-policy</tt> package.
8618 It is also available from the Debian web mirrors at
8619 <tt><url name="/doc/packaging-manuals/perl-policy/"
8620 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8625 <heading>Emacs lisp programs</heading>
8628 Please refer to the "Debian Emacs Policy" for details of how to
8629 package emacs lisp programs.
8633 The Emacs policy is available in
8634 <file>debian-emacs-policy.gz</file> of the
8635 <package>emacsen-common</package> package.
8636 It is also available from the Debian web mirrors at
8637 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8638 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8643 <heading>Games</heading>
8646 The permissions on <file>/var/games</file> are mode 755, owner
8647 <tt>root</tt> and group <tt>root</tt>.
8651 Each game decides on its own security policy.</p>
8654 Games which require protected, privileged access to
8655 high-score files, saved games, etc., may be made
8656 set-<em>group</em>-id (mode 2755) and owned by
8657 <tt>root:games</tt>, and use files and directories with
8658 appropriate permissions (770 <tt>root:games</tt>, for
8659 example). They must not be made
8660 set-<em>user</em>-id, as this causes security problems. (If
8661 an attacker can subvert any set-user-id game they can
8662 overwrite the executable of any other, causing other players
8663 of these games to run a Trojan horse program. With a
8664 set-group-id game the attacker only gets access to less
8665 important game data, and if they can get at the other
8666 players' accounts at all it will take considerably more
8670 Some packages, for example some fortune cookie programs, are
8671 configured by the upstream authors to install with their
8672 data files or other static information made unreadable so
8673 that they can only be accessed through set-id programs
8674 provided. You should not do this in a Debian package: anyone can
8675 download the <file>.deb</file> file and read the data from it,
8676 so there is no point making the files unreadable. Not
8677 making the files unreadable also means that you don't have
8678 to make so many programs set-id, which reduces the risk of a
8682 As described in the FHS, binaries of games should be
8683 installed in the directory <file>/usr/games</file>. This also
8684 applies to games that use the X Window System. Manual pages
8685 for games (X and non-X games) should be installed in
8686 <file>/usr/share/man/man6</file>.</p>
8692 <heading>Documentation</heading>
8695 <heading>Manual pages</heading>
8698 You should install manual pages in <prgn>nroff</prgn> source
8699 form, in appropriate places under <file>/usr/share/man</file>.
8700 You should only use sections 1 to 9 (see the FHS for more
8701 details). You must not install a pre-formatted "cat page".
8705 Each program, utility, and function should have an
8706 associated manual page included in the same package. It is
8707 suggested that all configuration files also have a manual
8708 page included as well. Manual pages for protocols and other
8709 auxiliary things are optional.
8713 If no manual page is available, this is considered as a bug
8714 and should be reported to the Debian Bug Tracking System (the
8715 maintainer of the package is allowed to write this bug report
8716 themselves, if they so desire). Do not close the bug report
8717 until a proper man page is available.<footnote>
8718 It is not very hard to write a man page. See the
8719 <url id="http://www.schweikhardt.net/man_page_howto.html"
8720 name="Man-Page-HOWTO">,
8721 <manref name="man" section="7">, the examples
8722 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8723 the helper programs <prgn>help2man</prgn>, or the
8724 directory <file>/usr/share/doc/man-db/examples</file>.
8729 You may forward a complaint about a missing man page to the
8730 upstream authors, and mark the bug as forwarded in the
8731 Debian bug tracking system. Even though the GNU Project do
8732 not in general consider the lack of a man page to be a bug,
8733 we do; if they tell you that they don't consider it a bug
8734 you should leave the bug in our bug tracking system open
8739 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8743 If one man page needs to be accessible via several names it
8744 is better to use a symbolic link than the <file>.so</file>
8745 feature, but there is no need to fiddle with the relevant
8746 parts of the upstream source to change from <file>.so</file> to
8747 symlinks: don't do it unless it's easy. You should not
8748 create hard links in the manual page directories, nor put
8749 absolute filenames in <file>.so</file> directives. The filename
8750 in a <file>.so</file> in a man page should be relative to the
8751 base of the man page tree (usually
8752 <file>/usr/share/man</file>). If you do not create any links
8753 (whether symlinks, hard links, or <tt>.so</tt> directives)
8754 in the file system to the alternate names of the man page,
8755 then you should not rely on <prgn>man</prgn> finding your
8756 man page under those names based solely on the information in
8757 the man page's header.<footnote>
8758 Supporting this in <prgn>man</prgn> often requires
8759 unreasonable processing time to find a manual page or to
8760 report that none exists, and moves knowledge into man's
8761 database that would be better left in the file system.
8762 This support is therefore deprecated and will cease to
8763 be present in the future.
8768 Manual pages in locale-specific subdirectories of
8769 <file>/usr/share/man</file> should use either UTF-8 or the usual
8770 legacy encoding for that language (normally the one corresponding
8771 to the shortest relevant locale name in
8772 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8773 <file>/usr/share/man/fr</file> should use either UTF-8 or
8774 ISO-8859-1.<footnote>
8775 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8776 use. In future, all manual pages will be required to use
8782 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8783 included in the subdirectory name unless it indicates a
8784 significant difference in the language, as this excludes
8785 speakers of the language in other countries.<footnote>
8786 At the time of writing, Chinese and Portuguese are the main
8787 languages with such differences, so <file>pt_BR</file>,
8788 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8793 Due to limitations in current implementations, all characters
8794 in the manual page source should be representable in the usual
8795 legacy encoding for that language, even if the file is
8796 actually encoded in UTF-8. Safe alternative ways to write many
8797 characters outside that range may be found in
8798 <manref name="groff_char" section="7">.
8803 <heading>Info documents</heading>
8806 Info documents should be installed in <file>/usr/share/info</file>.
8807 They should be compressed with <tt>gzip -9</tt>.
8811 Your package should call <prgn>install-info</prgn> to update
8812 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8813 script when called with a <tt>configure</tt> argument, for
8815 <example compact="compact">
8816 install-info --quiet --section Development Development \
8817 /usr/share/info/foobar.info
8821 It is a good idea to specify a section for the location of
8822 your program; this is done with the <tt>--section</tt>
8823 switch. To determine which section to use, you should look
8824 at <file>/usr/share/info/dir</file> on your system and choose the most
8825 relevant (or create a new section if none of the current
8826 sections are relevant). Note that the <tt>--section</tt>
8827 flag takes two arguments; the first is a regular expression
8828 to match (case-insensitively) against an existing section,
8829 the second is used when creating a new one.</p>
8832 You should remove the entries in the <prgn>prerm</prgn>
8833 script when called with a <tt>remove</tt> argument:
8834 <example compact="compact">
8835 install-info --quiet --remove /usr/share/info/foobar.info
8839 If <prgn>install-info</prgn> cannot find a description entry
8840 in the Info file you must supply one. See <manref
8841 name="install-info" section="8"> for details.</p>
8845 <heading>Additional documentation</heading>
8848 Any additional documentation that comes with the package may
8849 be installed at the discretion of the package maintainer.
8850 Plain text documentation should be installed in the directory
8851 <file>/usr/share/doc/<var>package</var></file>, where
8852 <var>package</var> is the name of the package, and
8853 compressed with <tt>gzip -9</tt> unless it is small.
8857 If a package comes with large amounts of documentation which
8858 many users of the package will not require you should create
8859 a separate binary package to contain it, so that it does not
8860 take up disk space on the machines of users who do not need
8861 or want it installed.</p>
8864 It is often a good idea to put text information files
8865 (<file>README</file>s, changelogs, and so forth) that come with
8866 the source package in <file>/usr/share/doc/<var>package</var></file>
8867 in the binary package. However, you don't need to install
8868 the instructions for building and installing the package, of
8872 Packages must not require the existence of any files in
8873 <file>/usr/share/doc/</file> in order to function
8875 The system administrator should be able to
8876 delete files in <file>/usr/share/doc/</file> without causing
8877 any programs to break.
8879 Any files that are referenced by programs but are also
8880 useful as stand alone documentation should be installed under
8881 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8882 <file>/usr/share/doc/<var>package</var></file>.
8886 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8887 link to another directory in <file>/usr/share/doc</file> only if
8888 the two packages both come from the same source and the
8889 first package Depends on the second.<footnote>
8891 Please note that this does not override the section on
8892 changelog files below, so the file
8893 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8894 must refer to the changelog for the current version of
8895 <var>package</var> in question. In practice, this means
8896 that the sources of the target and the destination of the
8897 symlink must be the same (same source package and
8904 Former Debian releases placed all additional documentation
8905 in <file>/usr/doc/<var>package</var></file>. This has been
8906 changed to <file>/usr/share/doc/<var>package</var></file>,
8907 and packages must not put documentation in the directory
8908 <file>/usr/doc/<var>package</var></file>. <footnote>
8909 At this phase of the transition, we no longer require a
8910 symbolic link in <file>/usr/doc/</file>. At a later point,
8911 policy shall change to make the symbolic links a bug.
8917 <heading>Preferred documentation formats</heading>
8920 The unification of Debian documentation is being carried out
8924 If your package comes with extensive documentation in a
8925 markup format that can be converted to various other formats
8926 you should if possible ship HTML versions in a binary
8927 package, in the directory
8928 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8929 its subdirectories.<footnote>
8930 The rationale: The important thing here is that HTML
8931 docs should be available in <em>some</em> package, not
8932 necessarily in the main binary package.
8937 Other formats such as PostScript may be provided at the
8938 package maintainer's discretion.
8942 <sect id="copyrightfile">
8943 <heading>Copyright information</heading>
8946 Every package must be accompanied by a verbatim copy of its
8947 copyright and distribution license in the file
8948 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8949 file must neither be compressed nor be a symbolic link.
8953 In addition, the copyright file must say where the upstream
8954 sources (if any) were obtained. It should name the original
8955 authors of the package and the Debian maintainer(s) who were
8956 involved with its creation.
8960 Packages in the <em>contrib</em> or <em>non-free</em> categories
8961 should state in the copyright file that the package is not part
8962 of the Debian GNU/Linux distribution and briefly explain why.
8966 A copy of the file which will be installed in
8967 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8968 be in <file>debian/copyright</file> in the source package.
8972 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8973 link to another directory in <file>/usr/share/doc</file> only if
8974 the two packages both come from the same source and the
8975 first package Depends on the second. These rules are
8976 important because copyrights must be extractable by
8981 Packages distributed under the UCB BSD license, the Apache
8982 license (version 2.0), the Artistic license, the GNU GPL
8983 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8984 the GNU FDL (version 1.2) should refer to the corresponding
8985 files under <file>/usr/share/common-licenses</file>,<footnote>
8988 <file>/usr/share/common-licenses/BSD</file>,
8989 <file>/usr/share/common-licenses/Apache-2.0</file>,
8990 <file>/usr/share/common-licenses/Artistic</file>,
8991 <file>/usr/share/common-licenses/GPL-2</file>,
8992 <file>/usr/share/common-licenses/GPL-3</file>,
8993 <file>/usr/share/common-licenses/LGPL-2</file>,
8994 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8995 <file>/usr/share/common-licenses/LGPL-3</file>, and
8996 <file>/usr/share/common-licenses/GFDL-1.2</file>
8999 </footnote> rather than quoting them in the copyright
9004 You should not use the copyright file as a general <file>README</file>
9005 file. If your package has such a file it should be
9006 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9007 <file>README.Debian</file> or some other appropriate place.</p>
9011 <heading>Examples</heading>
9014 Any examples (configurations, source files, whatever),
9015 should be installed in a directory
9016 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9017 files should not be referenced by any program: they're there
9018 for the benefit of the system administrator and users as
9019 documentation only. Architecture-specific example files
9020 should be installed in a directory
9021 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9023 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9024 latter directory itself may be a symbolic link to the
9029 If the purpose of a package is to provide examples, then the
9030 example files may be installed into
9031 <file>/usr/share/doc/<var>package</var></file>.
9035 <sect id="changelogs">
9036 <heading>Changelog files</heading>
9039 Packages that are not Debian-native must contain a
9040 compressed copy of the <file>debian/changelog</file> file from
9041 the Debian source tree in
9042 <file>/usr/share/doc/<var>package</var></file> with the name
9043 <file>changelog.Debian.gz</file>.
9047 If an upstream changelog is available, it should be accessible as
9048 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9049 plain text. If the upstream changelog is distributed in
9050 HTML, it should be made available in that form as
9051 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9052 and a plain text <file>changelog.gz</file> should be generated
9053 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9054 the upstream changelog files do not already conform to this
9055 naming convention, then this may be achieved either by
9056 renaming the files, or by adding a symbolic link, at the
9057 maintainer's discretion.<footnote>
9058 Rationale: People should not have to look in places for
9059 upstream changelogs merely because they are given
9060 different names or are distributed in HTML format.
9065 All of these files should be installed compressed using
9066 <tt>gzip -9</tt>, as they will become large with time even
9067 if they start out small.
9071 If the package has only one changelog which is used both as
9072 the Debian changelog and the upstream one because there is
9073 no separate upstream maintainer then that changelog should
9074 usually be installed as
9075 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9076 there is a separate upstream maintainer, but no upstream
9077 changelog, then the Debian changelog should still be called
9078 <file>changelog.Debian.gz</file>.
9082 For details about the format and contents of the Debian
9083 changelog file, please see <ref id="dpkgchangelog">.
9088 <appendix id="pkg-scope">
9089 <heading>Introduction and scope of these appendices</heading>
9092 These appendices are taken essentially verbatim from the
9093 now-deprecated Packaging Manual, version 3.2.1.0. They are
9094 the chapters which are likely to be of use to package
9095 maintainers and which have not already been included in the
9096 policy document itself. Most of these sections are very likely
9097 not relevant to policy; they should be treated as
9098 documentation for the packaging system. Please note that these
9099 appendices are included for convenience, and for historical
9100 reasons: they used to be part of policy package, and they have
9101 not yet been incorporated into dpkg documentation. However,
9102 they still have value, and hence they are presented here.
9106 They have not yet been checked to ensure that they are
9107 compatible with the contents of policy, and if there are any
9108 contradictions, the version in the main policy document takes
9109 precedence. The remaining chapters of the old Packaging
9110 Manual have also not been read in detail to ensure that there
9111 are not parts which have been left out. Both of these will be
9116 Certain parts of the Packaging manual were integrated into the
9117 Policy Manual proper, and removed from the appendices. Links
9118 have been placed from the old locations to the new ones.
9122 <prgn>dpkg</prgn> is a suite of programs for creating binary
9123 package files and installing and removing them on Unix
9125 <prgn>dpkg</prgn> is targeted primarily at Debian
9126 GNU/Linux, but may work on or be ported to other
9132 The binary packages are designed for the management of
9133 installed executable programs (usually compiled binaries) and
9134 their associated data, though source code examples and
9135 documentation are provided as part of some packages.</p>
9138 This manual describes the technical aspects of creating Debian
9139 binary packages (<file>.deb</file> files). It documents the
9140 behavior of the package management programs
9141 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9142 they interact with packages.</p>
9145 It also documents the interaction between
9146 <prgn>dselect</prgn>'s core and the access method scripts it
9147 uses to actually install the selected packages, and describes
9148 how to create a new access method.</p>
9151 This manual does not go into detail about the options and
9152 usage of the package building and installation tools. It
9153 should therefore be read in conjunction with those programs'
9158 The utility programs which are provided with <prgn>dpkg</prgn>
9159 for managing various system configuration and similar issues,
9160 such as <prgn>update-rc.d</prgn> and
9161 <prgn>install-info</prgn>, are not described in detail here -
9162 please see their man pages.
9166 It is assumed that the reader is reasonably familiar with the
9167 <prgn>dpkg</prgn> System Administrators' manual.
9168 Unfortunately this manual does not yet exist.
9172 The Debian version of the FSF's GNU hello program is provided
9173 as an example for people wishing to create Debian
9174 packages. The Debian <prgn>debmake</prgn> package is
9175 recommended as a very helpful tool in creating and maintaining
9176 Debian packages. However, while the tools and examples are
9177 helpful, they do not replace the need to read and follow the
9178 Policy and Programmer's Manual.</p>
9181 <appendix id="pkg-binarypkg">
9182 <heading>Binary packages (from old Packaging Manual)</heading>
9185 The binary package has two main sections. The first part
9186 consists of various control information files and scripts used
9187 by <prgn>dpkg</prgn> when installing and removing. See <ref
9188 id="pkg-controlarea">.
9192 The second part is an archive containing the files and
9193 directories to be installed.
9197 In the future binary packages may also contain other
9198 components, such as checksums and digital signatures. The
9199 format for the archive is described in full in the
9200 <file>deb(5)</file> man page.
9204 <sect id="pkg-bincreating"><heading>Creating package files -
9205 <prgn>dpkg-deb</prgn>
9209 All manipulation of binary package files is done by
9210 <prgn>dpkg-deb</prgn>; it's the only program that has
9211 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9212 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9213 will spot that the options requested are appropriate to
9214 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9219 In order to create a binary package you must make a
9220 directory tree which contains all the files and directories
9221 you want to have in the file system data part of the package.
9222 In Debian-format source packages this directory is usually
9223 <file>debian/tmp</file>, relative to the top of the package's
9228 They should have the locations (relative to the root of the
9229 directory tree you're constructing) ownerships and
9230 permissions which you want them to have on the system when
9235 With current versions of <prgn>dpkg</prgn> the uid/username
9236 and gid/groupname mappings for the users and groups being
9237 used should be the same on the system where the package is
9238 built and the one where it is installed.
9242 You need to add one special directory to the root of the
9243 miniature file system tree you're creating:
9244 <prgn>DEBIAN</prgn>. It should contain the control
9245 information files, notably the binary package control file
9246 (see <ref id="pkg-controlfile">).
9250 The <prgn>DEBIAN</prgn> directory will not appear in the
9251 file system archive of the package, and so won't be installed
9252 by <prgn>dpkg</prgn> when the package is installed.
9256 When you've prepared the package, you should invoke:
9258 dpkg --build <var>directory</var>
9263 This will build the package in
9264 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9265 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9266 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9271 See the man page <manref name="dpkg-deb" section="8"> for details of how
9272 to examine the contents of this newly-created file. You may find the
9273 output of following commands enlightening:
9275 dpkg-deb --info <var>filename</var>.deb
9276 dpkg-deb --contents <var>filename</var>.deb
9277 dpkg --contents <var>filename</var>.deb
9279 To view the copyright file for a package you could use this command:
9281 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9286 <sect id="pkg-controlarea">
9287 <heading>Package control information files</heading>
9290 The control information portion of a binary package is a
9291 collection of files with names known to <prgn>dpkg</prgn>.
9292 It will treat the contents of these files specially - some
9293 of them contain information used by <prgn>dpkg</prgn> when
9294 installing or removing the package; others are scripts which
9295 the package maintainer wants <prgn>dpkg</prgn> to run.
9299 It is possible to put other files in the package control
9300 area, but this is not generally a good idea (though they
9301 will largely be ignored).
9305 Here is a brief list of the control info files supported by
9306 <prgn>dpkg</prgn> and a summary of what they're used for.
9311 <tag><tt>control</tt>
9314 This is the key description file used by
9315 <prgn>dpkg</prgn>. It specifies the package's name
9316 and version, gives its description for the user,
9317 states its relationships with other packages, and so
9318 forth. See <ref id="sourcecontrolfiles"> and
9319 <ref id="binarycontrolfiles">.
9323 It is usually generated automatically from information
9324 in the source package by the
9325 <prgn>dpkg-gencontrol</prgn> program, and with
9326 assistance from <prgn>dpkg-shlibdeps</prgn>.
9327 See <ref id="pkg-sourcetools">.
9331 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9336 These are executable files (usually scripts) which
9337 <prgn>dpkg</prgn> runs during installation, upgrade
9338 and removal of packages. They allow the package to
9339 deal with matters which are particular to that package
9340 or require more complicated processing than that
9341 provided by <prgn>dpkg</prgn>. Details of when and
9342 how they are called are in <ref id="maintainerscripts">.
9346 It is very important to make these scripts idempotent.
9347 See <ref id="idempotency">.
9351 The maintainer scripts are guaranteed to run with a
9352 controlling terminal and can interact with the user.
9353 See <ref id="controllingterminal">.
9357 <tag><tt>conffiles</tt>
9360 This file contains a list of configuration files which
9361 are to be handled automatically by <prgn>dpkg</prgn>
9362 (see <ref id="pkg-conffiles">). Note that not necessarily
9363 every configuration file should be listed here.
9366 <tag><tt>shlibs</tt>
9369 This file contains a list of the shared libraries
9370 supplied by the package, with dependency details for
9371 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9372 when it determines what dependencies are required in a
9373 package control file. The <tt>shlibs</tt> file format
9374 is described on <ref id="shlibs">.
9379 <sect id="pkg-controlfile">
9380 <heading>The main control information file: <tt>control</tt></heading>
9383 The most important control information file used by
9384 <prgn>dpkg</prgn> when it installs a package is
9385 <tt>control</tt>. It contains all the package's "vital
9390 The binary package control files of packages built from
9391 Debian sources are made by a special tool,
9392 <prgn>dpkg-gencontrol</prgn>, which reads
9393 <file>debian/control</file> and <file>debian/changelog</file> to
9394 find the information it needs. See <ref id="pkg-sourcepkg"> for
9399 The fields in binary package control files are listed in
9400 <ref id="binarycontrolfiles">.
9404 A description of the syntax of control files and the purpose
9405 of the fields is available in <ref id="controlfields">.
9410 <heading>Time Stamps</heading>
9413 See <ref id="timestamps">.
9418 <appendix id="pkg-sourcepkg">
9419 <heading>Source packages (from old Packaging Manual) </heading>
9422 The Debian binary packages in the distribution are generated
9423 from Debian sources, which are in a special format to assist
9424 the easy and automatic building of binaries.
9427 <sect id="pkg-sourcetools">
9428 <heading>Tools for processing source packages</heading>
9431 Various tools are provided for manipulating source packages;
9432 they pack and unpack sources and help build of binary
9433 packages and help manage the distribution of new versions.
9437 They are introduced and typical uses described here; see
9438 <manref name="dpkg-source" section="1"> for full
9439 documentation about their arguments and operation.
9443 For examples of how to construct a Debian source package,
9444 and how to use those utilities that are used by Debian
9445 source packages, please see the <prgn>hello</prgn> example
9449 <sect1 id="pkg-dpkg-source">
9451 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9456 This program is frequently used by hand, and is also
9457 called from package-independent automated building scripts
9458 such as <prgn>dpkg-buildpackage</prgn>.
9462 To unpack a package it is typically invoked with
9464 dpkg-source -x <var>.../path/to/filename</var>.dsc
9469 with the <file><var>filename</var>.tar.gz</file> and
9470 <file><var>filename</var>.diff.gz</file> (if applicable) in
9471 the same directory. It unpacks into
9472 <file><var>package</var>-<var>version</var></file>, and if
9474 <file><var>package</var>-<var>version</var>.orig</file>, in
9475 the current directory.
9479 To create a packed source archive it is typically invoked:
9481 dpkg-source -b <var>package</var>-<var>version</var>
9486 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9487 <file>.diff.gz</file> (if appropriate) in the current
9488 directory. <prgn>dpkg-source</prgn> does not clean the
9489 source tree first - this must be done separately if it is
9494 See also <ref id="pkg-sourcearchives">.</p>
9498 <sect1 id="pkg-dpkg-buildpackage">
9500 <prgn>dpkg-buildpackage</prgn> - overall package-building
9505 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9506 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9507 targets <tt>clean</tt>, <tt>build</tt> and
9508 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9509 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9510 source and binary package upload.
9514 It is usually invoked by hand from the top level of the
9515 built or unbuilt source directory. It may be invoked with
9516 no arguments; useful arguments include:
9517 <taglist compact="compact">
9518 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9521 Do not sign the <tt>.changes</tt> file or the
9522 source package <tt>.dsc</tt> file, respectively.</p>
9524 <tag><tt>-p<var>sign-command</var></tt></tag>
9527 Invoke <var>sign-command</var> instead of finding
9528 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9529 <var>sign-command</var> must behave just like
9530 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9532 <tag><tt>-r<var>root-command</var></tt></tag>
9535 When root privilege is required, invoke the command
9536 <var>root-command</var>. <var>root-command</var>
9537 should invoke its first argument as a command, from
9538 the <prgn>PATH</prgn> if necessary, and pass its
9539 second and subsequent arguments to the command it
9540 calls. If no <var>root-command</var> is supplied
9541 then <var>dpkg-buildpackage</var> will take no
9542 special action to gain root privilege, so that for
9543 most packages it will have to be invoked as root to
9546 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9549 Two types of binary-only build and upload - see
9550 <manref name="dpkg-source" section="1">.
9557 <sect1 id="pkg-dpkg-gencontrol">
9559 <prgn>dpkg-gencontrol</prgn> - generates binary package
9564 This program is usually called from <file>debian/rules</file>
9565 (see <ref id="pkg-sourcetree">) in the top level of the source
9570 This is usually done just before the files and directories in the
9571 temporary directory tree where the package is being built have their
9572 permissions and ownerships set and the package is constructed using
9573 <prgn>dpkg-deb/</prgn>
9575 This is so that the control file which is produced has
9576 the right permissions
9581 <prgn>dpkg-gencontrol</prgn> must be called after all the
9582 files which are to go into the package have been placed in
9583 the temporary build directory, so that its calculation of
9584 the installed size of a package is correct.
9588 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9589 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9590 variable substitutions created by
9591 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9596 For a package which generates only one binary package, and
9597 which builds it in <file>debian/tmp</file> relative to the top
9598 of the source package, it is usually sufficient to call
9599 <prgn>dpkg-gencontrol</prgn>.
9603 Sources which build several binaries will typically need
9606 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9607 </example> The <tt>-P</tt> tells
9608 <prgn>dpkg-gencontrol</prgn> that the package is being
9609 built in a non-default directory, and the <tt>-p</tt>
9610 tells it which package's control file should be generated.
9614 <prgn>dpkg-gencontrol</prgn> also adds information to the
9615 list of files in <file>debian/files</file>, for the benefit of
9616 (for example) a future invocation of
9617 <prgn>dpkg-genchanges</prgn>.</p>
9620 <sect1 id="pkg-dpkg-shlibdeps">
9622 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9627 This program is usually called from <file>debian/rules</file>
9628 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9629 id="pkg-sourcetree">), in the top level of the source tree.
9633 Its arguments are executables and shared libraries
9636 They may be specified either in the locations in the
9637 source tree where they are created or in the locations
9638 in the temporary build tree where they are installed
9639 prior to binary package creation.
9641 </footnote> for which shared library dependencies should
9642 be included in the binary package's control file.
9646 If some of the found shared libraries should only
9647 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9648 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9649 by using the <tt>-d<var>dependency-field</var></tt> option
9650 before those executable(s). (Each <tt>-d</tt> option
9651 takes effect until the next <tt>-d</tt>.)
9655 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9656 output control file to be modified. Instead by default it
9657 adds to the <file>debian/substvars</file> file variable
9658 settings like <tt>shlibs:Depends</tt>. These variable
9659 settings must be referenced in dependency fields in the
9660 appropriate per-binary-package sections of the source
9665 For example, a package that generates an essential part
9666 which requires dependencies, and optional parts that
9667 which only require a recommendation, would separate those
9668 two sets of dependencies into two different fields.<footnote>
9669 At the time of writing, an example for this was the
9670 <package/xmms/ package, with Depends used for the xmms
9671 executable, Recommends for the plug-ins and Suggests for
9672 even more optional features provided by unzip.
9674 It can say in its <file>debian/rules</file>:
9676 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9677 -dRecommends <var>optionalpart anotheroptionalpart</var>
9679 and then in its main control file <file>debian/control</file>:
9682 Depends: ${shlibs:Depends}
9683 Recommends: ${shlibs:Recommends}
9689 Sources which produce several binary packages with
9690 different shared library dependency requirements can use
9691 the <tt>-p<var>varnameprefix</var></tt> option to override
9692 the default <tt>shlibs:</tt> prefix (one invocation of
9693 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9694 They can thus produce several sets of dependency
9695 variables, each of the form
9696 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9697 which can be referred to in the appropriate parts of the
9698 binary package control files.
9703 <sect1 id="pkg-dpkg-distaddfile">
9705 <prgn>dpkg-distaddfile</prgn> - adds a file to
9706 <file>debian/files</file>
9710 Some packages' uploads need to include files other than
9711 the source and binary package files.
9715 <prgn>dpkg-distaddfile</prgn> adds a file to the
9716 <file>debian/files</file> file so that it will be included in
9717 the <file>.changes</file> file when
9718 <prgn>dpkg-genchanges</prgn> is run.
9722 It is usually invoked from the <tt>binary</tt> target of
9723 <file>debian/rules</file>:
9725 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9727 The <var>filename</var> is relative to the directory where
9728 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9729 is usually the directory above the top level of the source
9730 tree. The <file>debian/rules</file> target should put the
9731 file there just before or just after calling
9732 <prgn>dpkg-distaddfile</prgn>.
9736 The <var>section</var> and <var>priority</var> are passed
9737 unchanged into the resulting <file>.changes</file> file.
9742 <sect1 id="pkg-dpkg-genchanges">
9744 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9749 This program is usually called by package-independent
9750 automatic building scripts such as
9751 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9756 It is usually called in the top level of a built source
9757 tree, and when invoked with no arguments will print out a
9758 straightforward <file>.changes</file> file based on the
9759 information in the source package's changelog and control
9760 file and the binary and source packages which should have
9766 <sect1 id="pkg-dpkg-parsechangelog">
9768 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9769 representation of a changelog
9773 This program is used internally by
9774 <prgn>dpkg-source</prgn> et al. It may also occasionally
9775 be useful in <file>debian/rules</file> and elsewhere. It
9776 parses a changelog, <file>debian/changelog</file> by default,
9777 and prints a control-file format representation of the
9778 information in it to standard output.
9782 <sect1 id="pkg-dpkg-architecture">
9784 <prgn>dpkg-architecture</prgn> - information about the build and
9789 This program can be used manually, but is also invoked by
9790 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9791 environment or make variables which specify the build and host
9792 architecture for the package building process.
9797 <sect id="pkg-sourcetree">
9798 <heading>The Debianised source tree</heading>
9801 The source archive scheme described later is intended to
9802 allow a Debianised source tree with some associated control
9803 information to be reproduced and transported easily. The
9804 Debianised source tree is a version of the original program
9805 with certain files added for the benefit of the
9806 Debianisation process, and with any other changes required
9807 made to the rest of the source code and installation
9812 The extra files created for Debian are in the subdirectory
9813 <file>debian</file> of the top level of the Debianised source
9814 tree. They are described below.
9817 <sect1 id="pkg-debianrules">
9818 <heading><file>debian/rules</file> - the main building script</heading>
9821 See <ref id="debianrules">.
9826 <sect1 id="pkg-dpkgchangelog">
9827 <heading><file>debian/changelog</file></heading>
9830 See <ref id="dpkgchangelog">.
9834 It is recommended that the entire changelog be encoded in the
9835 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9837 <url id="http://www.unicode.org/"
9838 name="Unicode">.<footnote>
9840 I think it is fairly obvious that we need to
9841 eventually transition to UTF-8 for our package
9842 infrastructure; it is really the only sane char-set in
9843 an international environment. Now, we can't switch to
9844 using UTF-8 for package control fields and the like
9845 until dpkg has better support, but one thing we can
9846 start doing today is requesting that Debian changelogs
9847 are UTF-8 encoded. At some point in time, we can start
9848 requiring them to do so.
9851 Checking for non-UTF8 characters in a changelog is
9852 trivial. Dump the file through
9853 <example>iconv -f utf-8 -t ucs-4</example>
9854 discard the output, and check the return
9855 value. If there are any characters in the stream
9856 which are invalid UTF-8 sequences, iconv will exit
9857 with an error code; and this will be the case for the
9858 vast majority of other character sets.
9863 <sect2><heading>Defining alternative changelog formats
9867 It is possible to use a different format to the standard
9868 one, by providing a parser for the format you wish to
9873 In order to have <tt>dpkg-parsechangelog</tt> run your
9874 parser, you must include a line within the last 40 lines
9875 of your file matching the Perl regular expression:
9876 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9877 parentheses should be the name of the format. For
9878 example, you might say:
9880 @@@ changelog-format: joebloggs @@@
9882 Changelog format names are non-empty strings of alphanumerics.
9886 If such a line exists then <tt>dpkg-parsechangelog</tt>
9887 will look for the parser as
9888 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9890 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9891 it is an error for it not to find it, or for it not to
9892 be an executable program. The default changelog format
9893 is <tt>dpkg</tt>, and a parser for it is provided with
9894 the <tt>dpkg</tt> package.
9898 The parser will be invoked with the changelog open on
9899 standard input at the start of the file. It should read
9900 the file (it may seek if it wishes) to determine the
9901 information required and return the parsed information
9902 to standard output in the form of a series of control
9903 fields in the standard format. By default it should
9904 return information about only the most recent version in
9905 the changelog; it should accept a
9906 <tt>-v<var>version</var></tt> option to return changes
9907 information from all versions present <em>strictly
9908 after</em> <var>version</var>, and it should then be an
9909 error for <var>version</var> not to be present in the
9915 <list compact="compact">
9916 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9917 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9918 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9919 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9920 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9921 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9922 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9927 If several versions are being returned (due to the use
9928 of <tt>-v</tt>), the urgency value should be of the
9929 highest urgency code listed at the start of any of the
9930 versions requested followed by the concatenated
9931 (space-separated) comments from all the versions
9932 requested; the maintainer, version, distribution and
9933 date should always be from the most recent version.
9937 For the format of the <tt>Changes</tt> field see
9938 <ref id="f-Changes">.
9942 If the changelog format which is being parsed always or
9943 almost always leaves a blank line between individual
9944 change notes these blank lines should be stripped out,
9945 so as to make the resulting output compact.
9949 If the changelog format does not contain date or package
9950 name information this information should be omitted from
9951 the output. The parser should not attempt to synthesize
9952 it or find it from other sources.
9956 If the changelog does not have the expected format the
9957 parser should exit with a nonzero exit status, rather
9958 than trying to muddle through and possibly generating
9963 A changelog parser may not interact with the user at
9969 <sect1 id="pkg-srcsubstvars">
9970 <heading><file>debian/substvars</file> and variable substitutions</heading>
9973 See <ref id="substvars">.
9979 <heading><file>debian/files</file></heading>
9982 See <ref id="debianfiles">.
9986 <sect1><heading><file>debian/tmp</file>
9990 This is the canonical temporary location for the
9991 construction of binary packages by the <tt>binary</tt>
9992 target. The directory <file>tmp</file> serves as the root of
9993 the file system tree as it is being constructed (for
9994 example, by using the package's upstream makefiles install
9995 targets and redirecting the output there), and it also
9996 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9997 id="pkg-bincreating">.
10001 If several binary packages are generated from the same
10002 source tree it is usual to use several
10003 <file>debian/tmp<var>something</var></file> directories, for
10004 example <file>tmp-a</file> or <file>tmp-doc</file>.
10008 Whatever <file>tmp</file> directories are created and used by
10009 <tt>binary</tt> must of course be removed by the
10010 <tt>clean</tt> target.</p></sect1>
10014 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10018 As it exists on the FTP site, a Debian source package
10019 consists of three related files. You must have the right
10020 versions of all three to be able to use them.
10025 <tag>Debian source control file - <tt>.dsc</tt></tag>
10027 This file is a control file used by <prgn>dpkg-source</prgn>
10028 to extract a source package.
10029 See <ref id="debiansourcecontrolfiles">.
10033 Original source archive -
10035 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10041 This is a compressed (with <tt>gzip -9</tt>)
10042 <prgn>tar</prgn> file containing the source code from
10043 the upstream authors of the program.
10048 Debianisation diff -
10050 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10056 This is a unified context diff (<tt>diff -u</tt>)
10057 giving the changes which are required to turn the
10058 original source into the Debian source. These changes
10059 may only include editing and creating plain files.
10060 The permissions of files, the targets of symbolic
10061 links and the characteristics of special files or
10062 pipes may not be changed and no files may be removed
10067 All the directories in the diff must exist, except the
10068 <file>debian</file> subdirectory of the top of the source
10069 tree, which will be created by
10070 <prgn>dpkg-source</prgn> if necessary when unpacking.
10074 The <prgn>dpkg-source</prgn> program will
10075 automatically make the <file>debian/rules</file> file
10076 executable (see below).</p></item>
10081 If there is no original source code - for example, if the
10082 package is specially prepared for Debian or the Debian
10083 maintainer is the same as the upstream maintainer - the
10084 format is slightly different: then there is no diff, and the
10086 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10087 and preferably contains a directory named
10088 <file><var>package</var>-<var>version</var></file>.
10093 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10096 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10097 Debian source package. However, if it is not available it
10098 is possible to unpack a Debian source archive as follows:
10099 <enumlist compact="compact">
10102 Untar the tarfile, which will create a <file>.orig</file>
10106 <p>Rename the <file>.orig</file> directory to
10107 <file><var>package</var>-<var>version</var></file>.</p>
10111 Create the subdirectory <file>debian</file> at the top of
10112 the source tree.</p>
10114 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10116 <item><p>Untar the tarfile again if you want a copy of the original
10117 source code alongside the Debianised version.</p>
10122 It is not possible to generate a valid Debian source archive
10123 without using <prgn>dpkg-source</prgn>. In particular,
10124 attempting to use <prgn>diff</prgn> directly to generate the
10125 <file>.diff.gz</file> file will not work.
10129 <heading>Restrictions on objects in source packages</heading>
10132 The source package may not contain any hard links
10134 This is not currently detected when building source
10135 packages, but only when extracting
10139 Hard links may be permitted at some point in the
10140 future, but would require a fair amount of
10142 </footnote>, device special files, sockets or setuid or
10145 Setgid directories are allowed.
10150 The source packaging tools manage the changes between the
10151 original and Debianised source using <prgn>diff</prgn> and
10152 <prgn>patch</prgn>. Turning the original source tree as
10153 included in the <file>.orig.tar.gz</file> into the debianised
10154 source must not involve any changes which cannot be
10155 handled by these tools. Problematic changes which cause
10156 <prgn>dpkg-source</prgn> to halt with an error when
10157 building the source package are:
10158 <list compact="compact">
10159 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10161 <item><p>Changing the targets of symbolic links.</p>
10163 <item><p>Creating directories, other than <file>debian</file>.</p>
10165 <item><p>Changes to the contents of binary files.</p></item>
10166 </list> Changes which cause <prgn>dpkg-source</prgn> to
10167 print a warning but continue anyway are:
10168 <list compact="compact">
10171 Removing files, directories or symlinks.
10173 Renaming a file is not treated specially - it is
10174 seen as the removal of the old file (which
10175 generates a warning, but is otherwise ignored),
10176 and the creation of the new one.
10182 Changed text files which are missing the usual final
10183 newline (either in the original or the modified
10188 Changes which are not represented, but which are not detected by
10189 <prgn>dpkg-source</prgn>, are:
10190 <list compact="compact">
10191 <item><p>Changing the permissions of files (other than
10192 <file>debian/rules</file>) and directories.</p></item>
10197 The <file>debian</file> directory and <file>debian/rules</file>
10198 are handled specially by <prgn>dpkg-source</prgn> - before
10199 applying the changes it will create the <file>debian</file>
10200 directory, and afterwards it will make
10201 <file>debian/rules</file> world-executable.
10207 <appendix id="pkg-controlfields">
10208 <heading>Control files and their fields (from old Packaging Manual)</heading>
10211 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10212 data in a common format, known as control files. Binary and
10213 source packages have control data as do the <file>.changes</file>
10214 files which control the installation of uploaded files, and
10215 <prgn>dpkg</prgn>'s internal databases are in a similar
10220 <heading>Syntax of control files</heading>
10223 See <ref id="controlsyntax">.
10227 It is important to note that there are several fields which
10228 are optional as far as <prgn>dpkg</prgn> and the related
10229 tools are concerned, but which must appear in every Debian
10230 package, or whose omission may cause problems.
10235 <heading>List of fields</heading>
10238 See <ref id="controlfieldslist">.
10242 This section now contains only the fields that didn't belong
10243 to the Policy manual.
10246 <sect1 id="pkg-f-Filename">
10247 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10250 These fields in <tt>Packages</tt> files give the
10251 filename(s) of (the parts of) a package in the
10252 distribution directories, relative to the root of the
10253 Debian hierarchy. If the package has been split into
10254 several parts the parts are all listed in order, separated
10259 <sect1 id="pkg-f-Size">
10260 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10263 These fields in <file>Packages</file> files give the size (in
10264 bytes, expressed in decimal) and MD5 checksum of the
10265 file(s) which make(s) up a binary package in the
10266 distribution. If the package is split into several parts
10267 the values for the parts are listed in order, separated by
10272 <sect1 id="pkg-f-Status">
10273 <heading><tt>Status</tt></heading>
10276 This field in <prgn>dpkg</prgn>'s status file records
10277 whether the user wants a package installed, removed or
10278 left alone, whether it is broken (requiring
10279 re-installation) or not and what its current state on the
10280 system is. Each of these pieces of information is a
10285 <sect1 id="pkg-f-Config-Version">
10286 <heading><tt>Config-Version</tt></heading>
10289 If a package is not installed or not configured, this
10290 field in <prgn>dpkg</prgn>'s status file records the last
10291 version of the package which was successfully
10296 <sect1 id="pkg-f-Conffiles">
10297 <heading><tt>Conffiles</tt></heading>
10300 This field in <prgn>dpkg</prgn>'s status file contains
10301 information about the automatically-managed configuration
10302 files held by a package. This field should <em>not</em>
10303 appear anywhere in a package!
10308 <heading>Obsolete fields</heading>
10311 These are still recognized by <prgn>dpkg</prgn> but should
10312 not appear anywhere any more.
10314 <taglist compact="compact">
10316 <tag><tt>Revision</tt></tag>
10317 <tag><tt>Package-Revision</tt></tag>
10318 <tag><tt>Package_Revision</tt></tag>
10320 The Debian revision part of the package version was
10321 at one point in a separate control file field. This
10322 field went through several names.
10325 <tag><tt>Recommended</tt></tag>
10326 <item>Old name for <tt>Recommends</tt>.</item>
10328 <tag><tt>Optional</tt></tag>
10329 <item>Old name for <tt>Suggests</tt>.</item>
10331 <tag><tt>Class</tt></tag>
10332 <item>Old name for <tt>Priority</tt>.</item>
10341 <appendix id="pkg-conffiles">
10342 <heading>Configuration file handling (from old Packaging Manual)</heading>
10345 <prgn>dpkg</prgn> can do a certain amount of automatic
10346 handling of package configuration files.
10350 Whether this mechanism is appropriate depends on a number of
10351 factors, but basically there are two approaches to any
10352 particular configuration file.
10356 The easy method is to ship a best-effort configuration in the
10357 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10358 handle updates. If the user is unlikely to want to edit the
10359 file, but you need them to be able to without losing their
10360 changes, and a new package with a changed version of the file
10361 is only released infrequently, this is a good approach.
10365 The hard method is to build the configuration file from
10366 scratch in the <prgn>postinst</prgn> script, and to take the
10367 responsibility for fixing any mistakes made in earlier
10368 versions of the package automatically. This will be
10369 appropriate if the file is likely to need to be different on
10373 <sect><heading>Automatic handling of configuration files by
10378 A package may contain a control area file called
10379 <tt>conffiles</tt>. This file should be a list of filenames
10380 of configuration files needing automatic handling, separated
10381 by newlines. The filenames should be absolute pathnames,
10382 and the files referred to should actually exist in the
10387 When a package is upgraded <prgn>dpkg</prgn> will process
10388 the configuration files during the configuration stage,
10389 shortly before it runs the package's <prgn>postinst</prgn>
10394 For each file it checks to see whether the version of the
10395 file included in the package is the same as the one that was
10396 included in the last version of the package (the one that is
10397 being upgraded from); it also compares the version currently
10398 installed on the system with the one shipped with the last
10403 If neither the user nor the package maintainer has changed
10404 the file, it is left alone. If one or the other has changed
10405 their version, then the changed version is preferred - i.e.,
10406 if the user edits their file, but the package maintainer
10407 doesn't ship a different version, the user's changes will
10408 stay, silently, but if the maintainer ships a new version
10409 and the user hasn't edited it the new version will be
10410 installed (with an informative message). If both have
10411 changed their version the user is prompted about the problem
10412 and must resolve the differences themselves.
10416 The comparisons are done by calculating the MD5 message
10417 digests of the files, and storing the MD5 of the file as it
10418 was included in the most recent version of the package.
10422 When a package is installed for the first time
10423 <prgn>dpkg</prgn> will install the file that comes with it,
10424 unless that would mean overwriting a file already on the
10429 However, note that <prgn>dpkg</prgn> will <em>not</em>
10430 replace a conffile that was removed by the user (or by a
10431 script). This is necessary because with some programs a
10432 missing file produces an effect hard or impossible to
10433 achieve in another way, so that a missing file needs to be
10434 kept that way if the user did it.
10438 Note that a package should <em>not</em> modify a
10439 <prgn>dpkg</prgn>-handled conffile in its maintainer
10440 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10441 the user confusing and possibly dangerous options for
10442 conffile update when the package is upgraded.</p>
10445 <sect><heading>Fully-featured maintainer script configuration
10450 For files which contain site-specific information such as
10451 the hostname and networking details and so forth, it is
10452 better to create the file in the package's
10453 <prgn>postinst</prgn> script.
10457 This will typically involve examining the state of the rest
10458 of the system to determine values and other information, and
10459 may involve prompting the user for some information which
10460 can't be obtained some other way.
10464 When using this method there are a couple of important
10465 issues which should be considered:
10469 If you discover a bug in the program which generates the
10470 configuration file, or if the format of the file changes
10471 from one version to the next, you will have to arrange for
10472 the postinst script to do something sensible - usually this
10473 will mean editing the installed configuration file to remove
10474 the problem or change the syntax. You will have to do this
10475 very carefully, since the user may have changed the file,
10476 perhaps to fix the very problem that your script is trying
10477 to deal with - you will have to detect these situations and
10478 deal with them correctly.
10482 If you do go down this route it's probably a good idea to
10483 make the program that generates the configuration file(s) a
10484 separate program in <file>/usr/sbin</file>, by convention called
10485 <file><var>package</var>config</file> and then run that if
10486 appropriate from the post-installation script. The
10487 <tt><var>package</var>config</tt> program should not
10488 unquestioningly overwrite an existing configuration - if its
10489 mode of operation is geared towards setting up a package for
10490 the first time (rather than any arbitrary reconfiguration
10491 later) you should have it check whether the configuration
10492 already exists, and require a <tt>--force</tt> flag to
10493 overwrite it.</p></sect>
10496 <appendix id="pkg-alternatives"><heading>Alternative versions of
10497 an interface - <prgn>update-alternatives</prgn> (from old
10502 When several packages all provide different versions of the
10503 same program or file it is useful to have the system select a
10504 default, but to allow the system administrator to change it
10505 and have their decisions respected.
10509 For example, there are several versions of the <prgn>vi</prgn>
10510 editor, and there is no reason to prevent all of them from
10511 being installed at once, each under their own name
10512 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10513 Nevertheless it is desirable to have the name <tt>vi</tt>
10514 refer to something, at least by default.
10518 If all the packages involved cooperate, this can be done with
10519 <prgn>update-alternatives</prgn>.
10523 Each package provides its own version under its own name, and
10524 calls <prgn>update-alternatives</prgn> in its postinst to
10525 register its version (and again in its prerm to deregister
10530 See the man page <manref name="update-alternatives"
10531 section="8"> for details.
10535 If <prgn>update-alternatives</prgn> does not seem appropriate
10536 you may wish to consider using diversions instead.</p>
10539 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10540 package's version of a file (from old Packaging Manual)
10544 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10545 when it reinstalls the package it belongs to, and to have it
10546 put the file from the package somewhere else instead.
10550 This can be used locally to override a package's version of a
10551 file, or by one package to override another's version (or
10552 provide a wrapper for it).
10556 Before deciding to use a diversion, read <ref
10557 id="pkg-alternatives"> to see if you really want a diversion
10558 rather than several alternative versions of a program.
10562 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10563 and updated by a special program <prgn>dpkg-divert</prgn>.
10564 Please see <manref name="dpkg-divert" section="8"> for full
10565 details of its operation.
10569 When a package wishes to divert a file from another, it should
10570 call <prgn>dpkg-divert</prgn> in its preinst to add the
10571 diversion and rename the existing file. For example,
10572 supposing that a <prgn>smailwrapper</prgn> package wishes to
10573 install a wrapper around <file>/usr/sbin/smail</file>:
10575 if [ install = "$1" ]; then
10576 dpkg-divert --package smailwrapper --add --rename \
10577 --divert /usr/sbin/smail.real /usr/sbin/smail
10579 </example> Testing <tt>$1</tt> is necessary so that the script
10580 doesn't try to add the diversion again when
10581 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10582 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10583 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10584 get installed as the true version.
10588 The postrm has to do the reverse:
10590 if [ remove = "$1" ]; then
10591 dpkg-divert --package smailwrapper --remove --rename \
10592 --divert /usr/sbin/smail.real /usr/sbin/smail
10598 Do not attempt to divert a file which is vitally important for
10599 the system's operation - when using <prgn>dpkg-divert</prgn>
10600 there is a time, after it has been diverted but before
10601 <prgn>dpkg</prgn> has installed the new version, when the file
10602 does not exist.</p>
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