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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.
1486 The format of the <file>debian/changelog</file> allows the
1487 package building tools to discover which version of the package
1488 is being built and find out other release-specific information.
1492 That format is a series of entries like this:
1494 <example compact="compact">
1495 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1497 [optional blank line(s), stripped]
1499 * <var>change details</var>
1500 <var>more change details</var>
1502 [blank line(s), included in output of dpkg-parsechangelog]
1504 * <var>even more change details</var>
1506 [optional blank line(s), stripped]
1508 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1513 <var>package</var> and <var>version</var> are the source
1514 package name and version number.
1518 <var>distribution(s)</var> lists the distributions where
1519 this version should be installed when it is uploaded - it
1520 is copied to the <tt>Distribution</tt> field in the
1521 <file>.changes</file> file. See <ref id="f-Distribution">.
1525 <var>urgency</var> is the value for the <tt>Urgency</tt>
1526 field in the <file>.changes</file> file for the upload
1527 (see <ref id="f-Urgency">). It is not possible to specify
1528 an urgency containing commas; commas are used to separate
1529 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1530 <prgn>dpkg</prgn> changelog format (though there is
1531 currently only one useful <var>keyword</var>,
1536 The change details may in fact be any series of lines
1537 starting with at least two spaces, but conventionally each
1538 change starts with an asterisk and a separating space and
1539 continuation lines are indented so as to bring them in
1540 line with the start of the text above. Blank lines may be
1541 used here to separate groups of changes, if desired.
1545 If this upload resolves bugs recorded in the Bug Tracking
1546 System (BTS), they may be automatically closed on the
1547 inclusion of this package into the Debian archive by
1548 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1549 in the change details.<footnote>
1550 To be precise, the string should match the following
1551 Perl regular expression:
1553 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1555 Then all of the bug numbers listed will be closed by the
1556 archive maintenance script (<prgn>katie</prgn>) using the
1557 <var>version</var> of the changelog entry.
1559 This information is conveyed via the <tt>Closes</tt> field
1560 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1564 The maintainer name and email address used in the changelog
1565 should be the details of the person uploading <em>this</em>
1566 version. They are <em>not</em> necessarily those of the
1567 usual package maintainer. The information here will be
1568 copied to the <tt>Changed-By</tt> field in the
1569 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1570 and then later used to send an acknowledgement when the
1571 upload has been installed.
1575 The <var>date</var> must be in RFC822 format<footnote>
1576 This is generated by <tt>date -R</tt>.
1577 </footnote>; it must include the time zone specified
1578 numerically, with the time zone name or abbreviation
1579 optionally present as a comment in parentheses.
1583 The first "title" line with the package name must start
1584 at the left hand margin. The "trailer" line with the
1585 maintainer and date details must be preceded by exactly
1586 one space. The maintainer details and the date must be
1587 separated by exactly two spaces.
1591 For more information on placement of the changelog files
1592 within binary packages, please see <ref id="changelogs">.
1596 <sect id="dpkgcopyright">
1597 <heading>Copyright: <file>debian/copyright</file></heading>
1599 Every package must be accompanied by a verbatim copy of
1600 its copyright and distribution license in the file
1601 <file>/usr/share/doc/<var>package</var>/copyright</file>
1602 (see <ref id="copyrightfile"> for further details). Also see
1603 <ref id="pkgcopyright"> for further considerations relayed
1604 to copyrights for packages.
1608 <heading>Error trapping in makefiles</heading>
1611 When <prgn>make</prgn> invokes a command in a makefile
1612 (including your package's upstream makefiles and
1613 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1614 means that <prgn>sh</prgn>'s usual bad error handling
1615 properties apply: if you include a miniature script as one
1616 of the commands in your makefile you'll find that if you
1617 don't do anything about it then errors are not detected
1618 and <prgn>make</prgn> will blithely continue after
1623 Every time you put more than one shell command (this
1624 includes using a loop) in a makefile command you
1625 must make sure that errors are trapped. For
1626 simple compound commands, such as changing directory and
1627 then running a program, using <tt>&&</tt> rather
1628 than semicolon as a command separator is sufficient. For
1629 more complex commands including most loops and
1630 conditionals you should include a separate <tt>set -e</tt>
1631 command at the start of every makefile command that's
1632 actually one of these miniature shell scripts.
1636 <sect id="timestamps">
1637 <heading>Time Stamps</heading>
1639 Maintainers should preserve the modification times of the
1640 upstream source files in a package, as far as is reasonably
1642 The rationale is that there is some information conveyed
1643 by knowing the age of the file, for example, you could
1644 recognize that some documentation is very old by looking
1645 at the modification time, so it would be nice if the
1646 modification time of the upstream source would be
1652 <sect id="restrictions">
1653 <heading>Restrictions on objects in source packages</heading>
1656 The source package may not contain any hard links<footnote>
1658 This is not currently detected when building source
1659 packages, but only when extracting
1663 Hard links may be permitted at some point in the
1664 future, but would require a fair amount of
1667 </footnote>, device special files, sockets or setuid or
1668 setgid files.<footnote>
1669 Setgid directories are allowed.
1674 <sect id="debianrules">
1675 <heading>Main building script: <file>debian/rules</file></heading>
1678 This file must be an executable makefile, and contains the
1679 package-specific recipes for compiling the package and
1680 building binary package(s) from the source.
1684 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1685 so that it can be invoked by saying its name rather than
1686 invoking <prgn>make</prgn> explicitly.
1690 Since an interactive <file>debian/rules</file> script makes it
1691 impossible to auto-compile that package and also makes it
1692 hard for other people to reproduce the same binary
1693 package, all <em>required targets</em> MUST be
1694 non-interactive. At a minimum, required targets are the
1695 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1696 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1697 <em>binary-indep</em>, and <em>build</em>. It also follows
1698 that any target that these targets depend on must also be
1703 The targets are as follows (required unless stated otherwise):
1705 <tag><tt>build</tt></tag>
1708 The <tt>build</tt> target should perform all the
1709 configuration and compilation of the package.
1710 If a package has an interactive pre-build
1711 configuration routine, the Debianized source package
1712 must either be built after this has taken place (so
1713 that the binary package can be built without rerunning
1714 the configuration) or the configuration routine
1715 modified to become non-interactive. (The latter is
1716 preferable if there are architecture-specific features
1717 detected by the configuration routine.)
1721 For some packages, notably ones where the same
1722 source tree is compiled in different ways to produce
1723 two binary packages, the <tt>build</tt> target
1724 does not make much sense. For these packages it is
1725 good enough to provide two (or more) targets
1726 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1727 for each of the ways of building the package, and a
1728 <tt>build</tt> target that does nothing. The
1729 <tt>binary</tt> target will have to build the
1730 package in each of the possible ways and make the
1731 binary package out of each.
1735 The <tt>build</tt> target must not do anything
1736 that might require root privilege.
1740 The <tt>build</tt> target may need to run the
1741 <tt>clean</tt> target first - see below.
1745 When a package has a configuration and build routine
1746 which takes a long time, or when the makefiles are
1747 poorly designed, or when <tt>build</tt> needs to
1748 run <tt>clean</tt> first, it is a good idea to
1749 <tt>touch build</tt> when the build process is
1750 complete. This will ensure that if <tt>debian/rules
1751 build</tt> is run again it will not rebuild the whole
1753 Another common way to do this is for <tt>build</tt>
1754 to depend on <prgn>build-stamp</prgn> and to do
1755 nothing else, and for the <prgn>build-stamp</prgn>
1756 target to do the building and to <tt>touch
1757 build-stamp</tt> on completion. This is
1758 especially useful if the build routine creates a
1759 file or directory called <tt>build</tt>; in such a
1760 case, <tt>build</tt> will need to be listed as
1761 a phony target (i.e., as a dependency of the
1762 <tt>.PHONY</tt> target). See the documentation of
1763 <prgn>make</prgn> for more information on phony
1769 <tag><tt>build-arch</tt> (optional),
1770 <tt>build-indep</tt> (optional)
1774 A package may also provide both of the targets
1775 <tt>build-arch</tt> and <tt>build-indep</tt>.
1776 The <tt>build-arch</tt> target, if provided, should
1777 perform all the configuration and compilation required
1778 for producing all architecture-dependant binary packages
1779 (those packages for which the body of the
1780 <tt>Architecture</tt> field in <tt>debian/control</tt>
1781 is not <tt>all</tt>).
1782 Similarly, the <tt>build-indep</tt> target, if
1783 provided, should perform all the configuration and
1784 compilation required for producing all
1785 architecture-independent binary packages
1786 (those packages for which the body of the
1787 <tt>Architecture</tt> field in <tt>debian/control</tt>
1789 The <tt>build</tt> target should depend on those of the
1790 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1791 are provided in the rules file.
1795 If one or both of the targets <tt>build-arch</tt> and
1796 <tt>build-indep</tt> are not provided, then invoking
1797 <file>debian/rules</file> with one of the not-provided
1798 targets as arguments should produce a exit status code
1799 of 2. Usually this is provided automatically by make
1800 if the target is missing.
1804 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1805 must not do anything that might require root privilege.
1809 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1810 <tt>binary-indep</tt>
1814 The <tt>binary</tt> target must be all that is
1815 necessary for the user to build the binary package(s)
1816 produced from this source package. It is
1817 split into two parts: <prgn>binary-arch</prgn> builds
1818 the binary packages which are specific to a particular
1819 architecture, and <tt>binary-indep</tt> builds
1820 those which are not.
1823 <tt>binary</tt> may be (and commonly is) a target with
1824 no commands which simply depends on
1825 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1828 Both <tt>binary-*</tt> targets should depend on the
1829 <tt>build</tt> target, or on the appropriate
1830 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1831 provided, so that the package is built if it has not
1832 been already. It should then create the relevant
1833 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1834 make their control files and <prgn>dpkg-deb</prgn> to
1835 build them and place them in the parent of the top
1840 Both the <tt>binary-arch</tt> and
1841 <tt>binary-indep</tt> targets <em>must</em> exist.
1842 If one of them has nothing to do (which will always be
1843 the case if the source generates only a single binary
1844 package, whether architecture-dependent or not), it
1845 must still exist and must always succeed.
1849 The <tt>binary</tt> targets must be invoked as
1851 The <prgn>fakeroot</prgn> package often allows one
1852 to build a package correctly even without being
1858 <tag><tt>clean</tt></tag>
1861 This must undo any effects that the <tt>build</tt>
1862 and <tt>binary</tt> targets may have had, except
1863 that it should leave alone any output files created in
1864 the parent directory by a run of a <tt>binary</tt>
1869 If a <tt>build</tt> file is touched at the end of
1870 the <tt>build</tt> target, as suggested above, it
1871 should be removed as the first action that
1872 <tt>clean</tt> performs, so that running
1873 <tt>build</tt> again after an interrupted
1874 <tt>clean</tt> doesn't think that everything is
1879 The <tt>clean</tt> target may need to be
1880 invoked as root if <tt>binary</tt> has been
1881 invoked since the last <tt>clean</tt>, or if
1882 <tt>build</tt> has been invoked as root (since
1883 <tt>build</tt> may create directories, for
1888 <tag><tt>get-orig-source</tt> (optional)</tag>
1891 This target fetches the most recent version of the
1892 original source package from a canonical archive site
1893 (via FTP or WWW, for example), does any necessary
1894 rearrangement to turn it into the original source
1895 tar file format described below, and leaves it in the
1900 This target may be invoked in any directory, and
1901 should take care to clean up any temporary files it
1906 This target is optional, but providing it if
1907 possible is a good idea.
1911 <tag><tt>patch</tt> (optional)</tag>
1914 This target performs whatever additional actions are
1915 required to make the source ready for editing (unpacking
1916 additional upstream archives, applying patches, etc.).
1917 It is recommended to be implemented for any package where
1918 <tt>dpkg-source -x</tt> does not result in source ready
1919 for additional modification. See
1920 <ref id="readmesource">.
1926 The <tt>build</tt>, <tt>binary</tt> and
1927 <tt>clean</tt> targets must be invoked with the current
1928 directory being the package's top-level directory.
1933 Additional targets may exist in <file>debian/rules</file>,
1934 either as published or undocumented interfaces or for the
1935 package's internal use.
1939 The architectures we build on and build for are determined
1940 by <prgn>make</prgn> variables using the utility
1941 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1942 You can determine the
1943 Debian architecture and the GNU style architecture
1944 specification string for the build machine (the machine type
1945 we are building on) as well as for the host machine (the
1946 machine type we are building for). Here is a list of
1947 supported <prgn>make</prgn> variables:
1948 <list compact="compact">
1950 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1953 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1954 specification string)
1957 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1958 <tt>DEB_*_GNU_TYPE</tt>)
1961 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1962 <tt>DEB_*_GNU_TYPE</tt>)
1964 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1965 the build machine or <tt>HOST</tt> for specification of the
1970 Backward compatibility can be provided in the rules file
1971 by setting the needed variables to suitable default
1972 values; please refer to the documentation of
1973 <prgn>dpkg-architecture</prgn> for details.
1977 It is important to understand that the <tt>DEB_*_ARCH</tt>
1978 string only determines which Debian architecture we are
1979 building on or for. It should not be used to get the CPU
1980 or system information; the GNU style variables should be
1984 <sect1 id="debianrules-options">
1985 <heading><file>debian/rules</file> and
1986 <tt>DEB_BUILD_OPTIONS</tt></heading>
1989 Supporting the standardized environment variable
1990 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
1991 contain several flags to change how a package is compiled and
1992 built. Each flag must be in the form <var>flag</var> or
1993 <var>flag</var>=<var>options</var>. If multiple flags are
1994 given, they must be separated by whitespace.<footnote>
1995 Some packages support any delimiter, but whitespace is the
1996 easiest to parse inside a makefile and avoids ambiguity with
1997 flag values that contain commas.
1999 <var>flag</var> must start with a lowercase letter
2000 (<tt>a-z</tt>) and consist only of lowercase letters,
2001 numbers (<tt>0-9</tt>), and the characters
2002 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2003 <var>options</var> must not contain whitespace. The same
2004 tag should not be given multiple times with conflicting
2005 values. Package maintainers may assume that
2006 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2010 The meaning of the following tags has been standardized:
2014 The presence of this tag means that the package should
2015 be compiled with a minimum of optimization. For C
2016 programs, it is best to add <tt>-O0</tt> to
2017 <tt>CFLAGS</tt> (although this is usually the default).
2018 Some programs might fail to build or run at this level
2019 of optimization; it may be necessary to use
2020 <tt>-O1</tt>, for example.
2024 This tag means that the debugging symbols should not be
2025 stripped from the binary during installation, so that
2026 debugging information may be included in the package.
2028 <tag>parallel=n</tag>
2030 This tag means that the package should be built using up
2031 to <tt>n</tt> parallel processes if the package build
2032 system supports this.<footnote>
2033 Packages built with <tt>make</tt> can often implement
2034 this by passing the <tt>-j</tt><var>n</var> option to
2037 If the package build system does not support parallel
2038 builds, this string must be ignored. If the package
2039 build system only supports a lower level of concurrency
2040 than <var>n</var>, the package should be built using as
2041 many parallel processes as the package build system
2042 supports. It is up to the package maintainer to decide
2043 whether the package build times are long enough and the
2044 package build system is robust enough to make supporting
2045 parallel builds worthwhile.
2051 Unknown flags must be ignored by <file>debian/rules</file>.
2055 The following makefile snippet is an example of how one may
2056 implement the build options; you will probably have to
2057 massage this example in order to make it work for your
2059 <example compact="compact">
2062 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2063 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2064 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2065 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2067 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2072 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2073 INSTALL_PROGRAM += -s
2075 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2076 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2077 MAKEFLAGS += -j$(NUMJOBS)
2084 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2085 <sect id="substvars">
2086 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2089 When <prgn>dpkg-gencontrol</prgn>,
2090 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2091 generate control files they perform variable substitutions
2092 on their output just before writing it. Variable
2093 substitutions have the form <tt>${<var>variable</var>}</tt>.
2094 The optional file <file>debian/substvars</file> contains
2095 variable substitutions to be used; variables can also be set
2096 directly from <file>debian/rules</file> using the <tt>-V</tt>
2097 option to the source packaging commands, and certain
2098 predefined variables are also available.
2102 The <file>debian/substvars</file> file is usually generated and
2103 modified dynamically by <file>debian/rules</file> targets, in
2104 which case it must be removed by the <tt>clean</tt> target.
2108 See <manref name="deb-substvars" section="5"> for full
2109 details about source variable substitutions, including the
2110 format of <file>debian/substvars</file>.</p>
2113 <sect id="debianwatch">
2114 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2117 This is an optional, recommended control file for the
2118 <tt>uscan</tt> utility which defines how to automatically
2119 scan ftp or http sites for newly available updates of the
2120 package. This is used by <url id="
2121 http://dehs.alioth.debian.org/"> and other Debian QA tools
2122 to help with quality control and maintenance of the
2123 distribution as a whole.
2128 <sect id="debianfiles">
2129 <heading>Generated files list: <file>debian/files</file></heading>
2132 This file is not a permanent part of the source tree; it
2133 is used while building packages to record which files are
2134 being generated. <prgn>dpkg-genchanges</prgn> uses it
2135 when it generates a <file>.changes</file> file.
2139 It should not exist in a shipped source package, and so it
2140 (and any backup files or temporary files such as
2141 <file>files.new</file><footnote>
2142 <file>files.new</file> is used as a temporary file by
2143 <prgn>dpkg-gencontrol</prgn> and
2144 <prgn>dpkg-distaddfile</prgn> - they write a new
2145 version of <tt>files</tt> here before renaming it,
2146 to avoid leaving a corrupted copy if an error
2148 </footnote>) should be removed by the
2149 <tt>clean</tt> target. It may also be wise to
2150 ensure a fresh start by emptying or removing it at the
2151 start of the <tt>binary</tt> target.
2155 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2156 package, it adds an entry to <file>debian/files</file> for the
2157 <file>.deb</file> file that will be created when <tt>dpkg-deb
2158 --build</tt> is run for that binary package. So for most
2159 packages all that needs to be done with this file is to
2160 delete it in the <tt>clean</tt> target.
2164 If a package upload includes files besides the source
2165 package and any binary packages whose control files were
2166 made with <prgn>dpkg-gencontrol</prgn> then they should be
2167 placed in the parent of the package's top-level directory
2168 and <prgn>dpkg-distaddfile</prgn> should be called to add
2169 the file to the list in <file>debian/files</file>.</p>
2172 <sect id="embeddedfiles">
2173 <heading>Convenience copies of code</heading>
2176 Some software packages include in their distribution convenience
2177 copies of code from other software packages, generally so that
2178 users compiling from source don't have to download multiple
2179 packages. Debian packages should not make use of these
2180 convenience copies unless the included package is explicitly
2181 intended to be used in this way.<footnote>
2182 For example, parts of the GNU build system work like this.
2184 If the included code is already in the Debian archive in the
2185 form of a library, the Debian packaging should ensure that
2186 binary packages reference the libraries already in Debian and
2187 the convenience copy is not used. If the included code is not
2188 already in Debian, it should be packaged separately as a
2189 prerequisite if possible.
2191 Having multiple copies of the same code in Debian is
2192 inefficient, often creates either static linking or shared
2193 library conflicts, and, most importantly, increases the
2194 difficulty of handling security vulnerabilities in the
2200 <sect id="readmesource">
2201 <heading>Source package handling:
2202 <file>debian/README.source</file></heading>
2205 If running <prgn>dpkg-source -x</prgn> on a source package
2206 doesn't produce the source of the package, ready for editing,
2207 and allow one to make changes and run
2208 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2209 without taking any additional steps, creating a
2210 <file>debian/README.source</file> documentation file is
2211 recommended. This file should explain how to do all of the
2214 <item>Generate the fully patched source, in a form ready for
2215 editing, that would be built to create Debian
2216 packages. Doing this with a <tt>patch</tt> target in
2217 <file>debian/rules</file> is recommended; see
2218 <ref id="debianrules">.</item>
2219 <item>Modify the source and save those modifications so that
2220 they will be applied when building the package.</item>
2221 <item>Remove source modifications that are currently being
2222 applied when building the package.</item>
2223 <item>Optionally, document what steps are necessary to
2224 upgrade the Debian source package to a new upstream version,
2225 if applicable.</item>
2227 This explanation should include specific commands and mention
2228 any additional required Debian packages. It should not assume
2229 familiarity with any specific Debian packaging system or patch
2234 This explanation may refer to a documentation file installed by
2235 one of the package's build dependencies provided that the
2236 referenced documentation clearly explains these tasks and is not
2237 a general reference manual.
2241 <file>debian/README.source</file> may also include any other
2242 information that would be helpful to someone modifying the
2243 source package. Even if the package doesn't fit the above
2244 description, maintainers are encouraged to document in a
2245 <file>debian/README.source</file> file any source package with a
2246 particularly complex or unintuitive source layout or build
2247 system (for example, a package that builds the same source
2248 multiple times to generate different binary packages).
2254 <chapt id="controlfields">
2255 <heading>Control files and their fields</heading>
2258 The package management system manipulates data represented in
2259 a common format, known as <em>control data</em>, stored in
2260 <em>control files</em>.
2261 Control files are used for source packages, binary packages and
2262 the <file>.changes</file> files which control the installation
2263 of uploaded files<footnote>
2264 <prgn>dpkg</prgn>'s internal databases are in a similar
2269 <sect id="controlsyntax">
2270 <heading>Syntax of control files</heading>
2273 A control file consists of one or more paragraphs of
2275 The paragraphs are also sometimes referred to as stanzas.
2277 The paragraphs are separated by blank lines. Some control
2278 files allow only one paragraph; others allow several, in
2279 which case each paragraph usually refers to a different
2280 package. (For example, in source packages, the first
2281 paragraph refers to the source package, and later paragraphs
2282 refer to binary packages generated from the source.)
2286 Each paragraph consists of a series of data fields; each
2287 field consists of the field name, followed by a colon and
2288 then the data/value associated with that field. It ends at
2289 the end of the (logical) line. Horizontal whitespace
2290 (spaces and tabs) may occur immediately before or after the
2291 value and is ignored there; it is conventional to put a
2292 single space after the colon. For example, a field might
2294 <example compact="compact">
2297 the field name is <tt>Package</tt> and the field value
2302 Many fields' values may span several lines; in this case
2303 each continuation line must start with a space or a tab.
2304 Any trailing spaces or tabs at the end of individual
2305 lines of a field value are ignored.
2309 In fields where it is specified that lines may not wrap,
2310 only a single line of data is allowed and whitespace is not
2311 significant in a field body. Whitespace must not appear
2312 inside names (of packages, architectures, files or anything
2313 else) or version numbers, or between the characters of
2314 multi-character version relationships.
2318 Field names are not case-sensitive, but it is usual to
2319 capitalize the field names using mixed case as shown below.
2323 Blank lines, or lines consisting only of spaces and tabs,
2324 are not allowed within field values or between fields - that
2325 would mean a new paragraph.
2330 <sect id="sourcecontrolfiles">
2331 <heading>Source package control files -- <file>debian/control</file></heading>
2334 The <file>debian/control</file> file contains the most vital
2335 (and version-independent) information about the source package
2336 and about the binary packages it creates.
2340 The first paragraph of the control file contains information about
2341 the source package in general. The subsequent sets each describe a
2342 binary package that the source tree builds.
2346 The fields in the general paragraph (the first one, for the source
2349 <list compact="compact">
2350 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2351 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2352 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2353 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2354 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2355 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2356 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2357 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2362 The fields in the binary package paragraphs are:
2364 <list compact="compact">
2365 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2366 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2367 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2368 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2369 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2370 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2371 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2372 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2377 The syntax and semantics of the fields are described below.
2383 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2384 generate control files for binary packages (see below), by
2385 <prgn>dpkg-genchanges</prgn> to generate the
2386 <tt>.changes</tt> file to accompany the upload, and by
2387 <prgn>dpkg-source</prgn> when it creates the
2388 <file>.dsc</file> source control file as part of a source
2389 archive. Many fields are permitted to span multiple lines in
2390 <file>debian/control</file> but not in any other control
2391 file. These tools are responsible for removing the line
2392 breaks from such fields when using fields from
2393 <file>debian/control</file> to generate other control files.
2397 The fields here may contain variable references - their
2398 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2399 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2400 when they generate output control files.
2401 See <ref id="substvars"> for details.
2406 <sect id="binarycontrolfiles">
2407 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2410 The <file>DEBIAN/control</file> file contains the most vital
2411 (and version-dependent) information about a binary package.
2415 The fields in this file are:
2417 <list compact="compact">
2418 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2419 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2420 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2421 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2422 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2423 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2424 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2425 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2426 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2427 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2428 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2429 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2434 <sect id="debiansourcecontrolfiles">
2435 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2438 This file contains a series of fields, identified and
2439 separated just like the fields in the control file of
2440 a binary package. The fields are listed below; their
2441 syntax is described above, in <ref id="pkg-controlfields">.
2443 <list compact="compact">
2444 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2445 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2446 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2447 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2448 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2449 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2450 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2451 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2452 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2453 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2454 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2459 The source package control file is generated by
2460 <prgn>dpkg-source</prgn> when it builds the source
2461 archive, from other files in the source package,
2462 described above. When unpacking, it is checked against
2463 the files and directories in the other parts of the
2469 <sect id="debianchangesfiles">
2470 <heading>Debian changes files -- <file>.changes</file></heading>
2473 The .changes files are used by the Debian archive maintenance
2474 software to process updates to packages. They contain one
2475 paragraph which contains information from the
2476 <tt>debian/control</tt> file and other data about the
2477 source package gathered via <tt>debian/changelog</tt>
2478 and <tt>debian/rules</tt>.
2482 The fields in this file are:
2484 <list compact="compact">
2485 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2489 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2490 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2491 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2492 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2493 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2495 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2496 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2497 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2498 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2503 <sect id="controlfieldslist">
2504 <heading>List of fields</heading>
2506 <sect1 id="f-Source">
2507 <heading><tt>Source</tt></heading>
2510 This field identifies the source package name.
2514 In <file>debian/control</file> or a <file>.dsc</file> file,
2515 this field must contain only the name of the source package.
2519 In a binary package control file or a <file>.changes</file>
2520 file, the source package name may be followed by a version
2521 number in parentheses<footnote>
2522 It is customary to leave a space after the package name
2523 if a version number is specified.
2525 This version number may be omitted (and is, by
2526 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2527 the <tt>Version</tt> field of the binary package in
2528 question. The field itself may be omitted from a binary
2529 package control file when the source package has the same
2530 name and version as the binary package.
2534 <sect1 id="f-Maintainer">
2535 <heading><tt>Maintainer</tt></heading>
2538 The package maintainer's name and email address. The name
2539 should come first, then the email address inside angle
2540 brackets <tt><></tt> (in RFC822 format).
2544 If the maintainer's name contains a full stop then the
2545 whole field will not work directly as an email address due
2546 to a misfeature in the syntax specified in RFC822; a
2547 program using this field as an address must check for this
2548 and correct the problem if necessary (for example by
2549 putting the name in round brackets and moving it to the
2550 end, and bringing the email address forward).
2554 <sect1 id="f-Uploaders">
2555 <heading><tt>Uploaders</tt></heading>
2558 List of the names and email addresses of co-maintainers of
2559 the package, if any. If the package has other maintainers
2560 beside the one named in the
2561 <qref id="f-Maintainer">Maintainer field</qref>, their
2562 names and email addresses should be listed here. The
2563 format is the same as that of the Maintainer tag, and
2564 multiple entries should be comma separated. Currently,
2565 this field is restricted to a single line of data. This
2566 is an optional field.
2569 Any parser that interprets the Uploaders field in
2570 <file>debian/control</file> must permit it to span multiple
2571 lines. Line breaks in an Uploaders field that spans multiple
2572 lines are not significant and the semantics of the field are
2573 the same as if the line breaks had not been present.
2577 <sect1 id="f-Changed-By">
2578 <heading><tt>Changed-By</tt></heading>
2581 The name and email address of the person who changed the
2582 said package. Usually the name of the maintainer.
2583 All the rules for the Maintainer field apply here, too.
2587 <sect1 id="f-Section">
2588 <heading><tt>Section</tt></heading>
2591 This field specifies an application area into which the package
2592 has been classified. See <ref id="subsections">.
2596 When it appears in the <file>debian/control</file> file,
2597 it gives the value for the subfield of the same name in
2598 the <tt>Files</tt> field of the <file>.changes</file> file.
2599 It also gives the default for the same field in the binary
2604 <sect1 id="f-Priority">
2605 <heading><tt>Priority</tt></heading>
2608 This field represents how important that it is that the user
2609 have the package installed. See <ref id="priorities">.
2613 When it appears in the <file>debian/control</file> file,
2614 it gives the value for the subfield of the same name in
2615 the <tt>Files</tt> field of the <file>.changes</file> file.
2616 It also gives the default for the same field in the binary
2621 <sect1 id="f-Package">
2622 <heading><tt>Package</tt></heading>
2625 The name of the binary package.
2629 Package names must consist only of lower case letters
2630 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2631 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2632 They must be at least two characters long and must start
2633 with an alphanumeric character.
2637 <sect1 id="f-Architecture">
2638 <heading><tt>Architecture</tt></heading>
2641 Depending on context and the control file used, the
2642 <tt>Architecture</tt> field can include the following sets of
2645 <item>A unique single word identifying a Debian machine
2646 architecture, see <ref id="arch-spec">.
2647 <item><tt>all</tt>, which indicates an
2648 architecture-independent package.
2649 <item><tt>any</tt>, which indicates a package available
2650 for building on any architecture.
2651 <item><tt>source</tt>, which indicates a source package.
2656 In the main <file>debian/control</file> file in the source
2657 package, or in the source package control file
2658 <file>.dsc</file>, one may specify a list of architectures
2659 separated by spaces, or the special values <tt>any</tt> or
2664 Specifying <tt>any</tt> indicates that the source package
2665 isn't dependent on any particular architecture and should
2666 compile fine on any one. The produced binary package(s)
2667 will be specific to whatever the current build architecture
2669 This is the most often used setting, and is recommended
2670 for new packages that aren't <tt>Architecture: all</tt>.
2675 Specifying a list of architectures indicates that the source
2676 will build an architecture-dependent package, and will only
2677 work correctly on the listed architectures.<footnote>
2678 This is a setting used for a minority of cases where the
2679 program is not portable. Generally, it should not be used
2685 In a <file>.changes</file> file, the <tt>Architecture</tt>
2686 field lists the architecture(s) of the package(s)
2687 currently being uploaded. This will be a list; if the
2688 source for the package is also being uploaded, the special
2689 entry <tt>source</tt> is also present.
2693 See <ref id="debianrules"> for information how to get the
2694 architecture for the build process.
2698 <sect1 id="f-Essential">
2699 <heading><tt>Essential</tt></heading>
2702 This is a boolean field which may occur only in the
2703 control file of a binary package or in a per-package fields
2704 paragraph of a main source control data file.
2708 If set to <tt>yes</tt> then the package management system
2709 will refuse to remove the package (upgrading and replacing
2710 it is still possible). The other possible value is <tt>no</tt>,
2711 which is the same as not having the field at all.
2716 <heading>Package interrelationship fields:
2717 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2718 <tt>Recommends</tt>, <tt>Suggests</tt>,
2719 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2720 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2724 These fields describe the package's relationships with
2725 other packages. Their syntax and semantics are described
2726 in <ref id="relationships">.</p>
2729 <sect1 id="f-Standards-Version">
2730 <heading><tt>Standards-Version</tt></heading>
2733 The most recent version of the standards (the policy
2734 manual and associated texts) with which the package
2739 The version number has four components: major and minor
2740 version number and major and minor patch level. When the
2741 standards change in a way that requires every package to
2742 change the major number will be changed. Significant
2743 changes that will require work in many packages will be
2744 signaled by a change to the minor number. The major patch
2745 level will be changed for any change to the meaning of the
2746 standards, however small; the minor patch level will be
2747 changed when only cosmetic, typographical or other edits
2748 are made which neither change the meaning of the document
2749 nor affect the contents of packages.
2753 Thus only the first three components of the policy version
2754 are significant in the <em>Standards-Version</em> control
2755 field, and so either these three components or the all
2756 four components may be specified.<footnote>
2757 In the past, people specified the full version number
2758 in the Standards-Version field, for example "2.3.0.0".
2759 Since minor patch-level changes don't introduce new
2760 policy, it was thought it would be better to relax
2761 policy and only require the first 3 components to be
2762 specified, in this example "2.3.0". All four
2763 components may still be used if someone wishes to do so.
2769 <sect1 id="f-Version">
2770 <heading><tt>Version</tt></heading>
2773 The version number of a package. The format is:
2774 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2778 The three components here are:
2780 <tag><var>epoch</var></tag>
2783 This is a single (generally small) unsigned integer. It
2784 may be omitted, in which case zero is assumed. If it is
2785 omitted then the <var>upstream_version</var> may not
2790 It is provided to allow mistakes in the version numbers
2791 of older versions of a package, and also a package's
2792 previous version numbering schemes, to be left behind.
2796 <tag><var>upstream_version</var></tag>
2799 This is the main part of the version number. It is
2800 usually the version number of the original ("upstream")
2801 package from which the <file>.deb</file> file has been made,
2802 if this is applicable. Usually this will be in the same
2803 format as that specified by the upstream author(s);
2804 however, it may need to be reformatted to fit into the
2805 package management system's format and comparison
2810 The comparison behavior of the package management system
2811 with respect to the <var>upstream_version</var> is
2812 described below. The <var>upstream_version</var>
2813 portion of the version number is mandatory.
2817 The <var>upstream_version</var> may contain only
2818 alphanumerics<footnote>
2819 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2821 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2822 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2823 tilde) and should start with a digit. If there is no
2824 <var>debian_revision</var> then hyphens are not allowed;
2825 if there is no <var>epoch</var> then colons are not
2830 <tag><var>debian_revision</var></tag>
2833 This part of the version number specifies the version of
2834 the Debian package based on the upstream version. It
2835 may contain only alphanumerics and the characters
2836 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2837 tilde) and is compared in the same way as the
2838 <var>upstream_version</var> is.
2842 It is optional; if it isn't present then the
2843 <var>upstream_version</var> may not contain a hyphen.
2844 This format represents the case where a piece of
2845 software was written specifically to be turned into a
2846 Debian package, and so there is only one "debianisation"
2847 of it and therefore no revision indication is required.
2851 It is conventional to restart the
2852 <var>debian_revision</var> at <tt>1</tt> each time the
2853 <var>upstream_version</var> is increased.
2857 The package management system will break the version
2858 number apart at the last hyphen in the string (if there
2859 is one) to determine the <var>upstream_version</var> and
2860 <var>debian_revision</var>. The absence of a
2861 <var>debian_revision</var> is equivalent to a
2862 <var>debian_revision</var> of <tt>0</tt>.
2869 When comparing two version numbers, first the <var>epoch</var>
2870 of each are compared, then the <var>upstream_version</var> if
2871 <var>epoch</var> is equal, and then <var>debian_revision</var>
2872 if <var>upstream_version</var> is also equal.
2873 <var>epoch</var> is compared numerically. The
2874 <var>upstream_version</var> and <var>debian_revision</var>
2875 parts are compared by the package management system using the
2876 following algorithm:
2880 The strings are compared from left to right.
2884 First the initial part of each string consisting entirely of
2885 non-digit characters is determined. These two parts (one of
2886 which may be empty) are compared lexically. If a difference
2887 is found it is returned. The lexical comparison is a
2888 comparison of ASCII values modified so that all the letters
2889 sort earlier than all the non-letters and so that a tilde
2890 sorts before anything, even the end of a part. For example,
2891 the following parts are in sorted order from earliest to
2892 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2893 <tt>a</tt>.<footnote>
2894 One common use of <tt>~</tt> is for upstream pre-releases.
2895 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2896 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2901 Then the initial part of the remainder of each string which
2902 consists entirely of digit characters is determined. The
2903 numerical values of these two parts are compared, and any
2904 difference found is returned as the result of the comparison.
2905 For these purposes an empty string (which can only occur at
2906 the end of one or both version strings being compared) counts
2911 These two steps (comparing and removing initial non-digit
2912 strings and initial digit strings) are repeated until a
2913 difference is found or both strings are exhausted.
2917 Note that the purpose of epochs is to allow us to leave behind
2918 mistakes in version numbering, and to cope with situations
2919 where the version numbering scheme changes. It is
2920 <em>not</em> intended to cope with version numbers containing
2921 strings of letters which the package management system cannot
2922 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2923 silly orderings (the author of this manual has heard of a
2924 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2925 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2926 <tt>2</tt> and so forth).
2930 <sect1 id="f-Description">
2931 <heading><tt>Description</tt></heading>
2934 In a source or binary control file, the <tt>Description</tt>
2935 field contains a description of the binary package, consisting
2936 of two parts, the synopsis or the short description, and the
2937 long description. The field's format is as follows:
2942 Description: <single line synopsis>
2943 <extended description over several lines>
2948 The lines in the extended description can have these formats:
2954 Those starting with a single space are part of a paragraph.
2955 Successive lines of this form will be word-wrapped when
2956 displayed. The leading space will usually be stripped off.
2960 Those starting with two or more spaces. These will be
2961 displayed verbatim. If the display cannot be panned
2962 horizontally, the displaying program will line wrap them "hard"
2963 (i.e., without taking account of word breaks). If it can they
2964 will be allowed to trail off to the right. None, one or two
2965 initial spaces may be deleted, but the number of spaces
2966 deleted from each line will be the same (so that you can have
2967 indenting work correctly, for example).
2971 Those containing a single space followed by a single full stop
2972 character. These are rendered as blank lines. This is the
2973 <em>only</em> way to get a blank line<footnote>
2974 Completely empty lines will not be rendered as blank lines.
2975 Instead, they will cause the parser to think you're starting
2976 a whole new record in the control file, and will therefore
2977 likely abort with an error.
2982 Those containing a space, a full stop and some more characters.
2983 These are for future expansion. Do not use them.
2989 Do not use tab characters. Their effect is not predictable.
2993 See <ref id="descriptions"> for further information on this.
2997 In a <file>.changes</file> file, the <tt>Description</tt> field
2998 contains a summary of the descriptions for the packages being
3003 The part of the field before the first newline is empty;
3004 thereafter each line has the name of a binary package and
3005 the summary description line from that binary package.
3006 Each line is indented by one space.
3011 <sect1 id="f-Distribution">
3012 <heading><tt>Distribution</tt></heading>
3015 In a <file>.changes</file> file or parsed changelog output
3016 this contains the (space-separated) name(s) of the
3017 distribution(s) where this version of the package should
3018 be installed. Valid distributions are determined by the
3019 archive maintainers.<footnote>
3020 Current distribution names are:
3021 <taglist compact="compact">
3022 <tag><em>stable</em></tag>
3024 This is the current "released" version of Debian
3025 GNU/Linux. Once the distribution is
3026 <em>stable</em> only security fixes and other
3027 major bug fixes are allowed. When changes are
3028 made to this distribution, the release number is
3029 increased (for example: 2.2r1 becomes 2.2r2 then
3033 <tag><em>unstable</em></tag>
3035 This distribution value refers to the
3036 <em>developmental</em> part of the Debian
3037 distribution tree. New packages, new upstream
3038 versions of packages and bug fixes go into the
3039 <em>unstable</em> directory tree. Download from
3040 this distribution at your own risk.
3043 <tag><em>testing</em></tag>
3045 This distribution value refers to the
3046 <em>testing</em> part of the Debian distribution
3047 tree. It receives its packages from the
3048 unstable distribution after a short time lag to
3049 ensure that there are no major issues with the
3050 unstable packages. It is less prone to breakage
3051 than unstable, but still risky. It is not
3052 possible to upload packages directly to
3056 <tag><em>frozen</em></tag>
3058 From time to time, the <em>testing</em>
3059 distribution enters a state of "code-freeze" in
3060 anticipation of release as a <em>stable</em>
3061 version. During this period of testing only
3062 fixes for existing or newly-discovered bugs will
3063 be allowed. The exact details of this stage are
3064 determined by the Release Manager.
3067 <tag><em>experimental</em></tag>
3069 The packages with this distribution value are
3070 deemed by their maintainers to be high
3071 risk. Oftentimes they represent early beta or
3072 developmental packages from various sources that
3073 the maintainers want people to try, but are not
3074 ready to be a part of the other parts of the
3075 Debian distribution tree. Download at your own
3081 You should list <em>all</em> distributions that the
3082 package should be installed into.
3086 More information is available in the Debian Developer's
3087 Reference, section "The Debian archive".
3094 <heading><tt>Date</tt></heading>
3097 This field includes the date the package was built or last edited.
3101 The value of this field is usually extracted from the
3102 <file>debian/changelog</file> file - see
3103 <ref id="dpkgchangelog">).
3107 <sect1 id="f-Format">
3108 <heading><tt>Format</tt></heading>
3111 This field specifies a format revision for the file.
3112 The most current format described in the Policy Manual
3113 is version <strong>1.5</strong>. The syntax of the
3114 format value is the same as that of a package version
3115 number except that no epoch or Debian revision is allowed
3116 - see <ref id="f-Version">.
3120 <sect1 id="f-Urgency">
3121 <heading><tt>Urgency</tt></heading>
3124 This is a description of how important it is to upgrade to
3125 this version from previous ones. It consists of a single
3126 keyword taking one of the values <tt>low</tt>,
3127 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3128 <tt>critical</tt><footnote>
3129 Other urgency values are supported with configuration
3130 changes in the archive software but are not used in Debian.
3131 The urgency affects how quickly a package will be considered
3132 for inclusion into the <tt>testing</tt> distribution and
3133 gives an indication of the importance of any fixes included
3134 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3135 treated as synonymous.
3136 </footnote> (not case-sensitive) followed by an optional
3137 commentary (separated by a space) which is usually in
3138 parentheses. For example:
3141 Urgency: low (HIGH for users of diversions)
3147 The value of this field is usually extracted from the
3148 <file>debian/changelog</file> file - see
3149 <ref id="dpkgchangelog">.
3153 <sect1 id="f-Changes">
3154 <heading><tt>Changes</tt></heading>
3157 This field contains the human-readable changes data, describing
3158 the differences between the last version and the current one.
3162 There should be nothing in this field before the first
3163 newline; all the subsequent lines must be indented by at
3164 least one space; blank lines must be represented by a line
3165 consisting only of a space and a full stop.
3169 The value of this field is usually extracted from the
3170 <file>debian/changelog</file> file - see
3171 <ref id="dpkgchangelog">).
3175 Each version's change information should be preceded by a
3176 "title" line giving at least the version, distribution(s)
3177 and urgency, in a human-readable way.
3181 If data from several versions is being returned the entry
3182 for the most recent version should be returned first, and
3183 entries should be separated by the representation of a
3184 blank line (the "title" line may also be followed by the
3185 representation of blank line).
3189 <sect1 id="f-Binary">
3190 <heading><tt>Binary</tt></heading>
3193 This field is a list of binary packages.
3197 When it appears in the <file>.dsc</file> file it is the list
3198 of binary packages which a source package can produce. It
3199 does not necessarily produce all of these binary packages
3200 for every architecture. The source control file doesn't
3201 contain details of which architectures are appropriate for
3202 which of the binary packages.
3206 When it appears in a <file>.changes</file> file it lists the
3207 names of the binary packages actually being uploaded.
3211 The syntax is a list of binary packages separated by
3213 A space after each comma is conventional.
3214 </footnote>. Currently the packages must be separated using
3215 only spaces in the <file>.changes</file> file.
3219 <sect1 id="f-Installed-Size">
3220 <heading><tt>Installed-Size</tt></heading>
3223 This field appears in the control files of binary
3224 packages, and in the <file>Packages</file> files. It gives
3225 the total amount of disk space required to install the
3230 The disk space is represented in kilobytes as a simple
3235 <sect1 id="f-Files">
3236 <heading><tt>Files</tt></heading>
3239 This field contains a list of files with information about
3240 each one. The exact information and syntax varies with
3241 the context. In all cases the part of the field
3242 contents on the same line as the field name is empty. The
3243 remainder of the field is one line per file, each line
3244 being indented by one space and containing a number of
3245 sub-fields separated by spaces.
3249 In the <file>.dsc</file> file, each line contains the MD5
3250 checksum, size and filename of the tar file and (if applicable)
3251 diff file which make up the remainder of the source
3253 That is, the parts which are not the <tt>.dsc</tt>.
3255 The exact forms of the filenames are described
3256 in <ref id="pkg-sourcearchives">.
3260 In the <file>.changes</file> file this contains one line per
3261 file being uploaded. Each line contains the MD5 checksum,
3262 size, section and priority and the filename.
3263 The <qref id="f-Section">section</qref>
3264 and <qref id="f-Priority">priority</qref>
3265 are the values of the corresponding fields in
3266 the main source control file. If no section or priority is
3267 specified then <tt>-</tt> should be used, though section
3268 and priority values must be specified for new packages to
3269 be installed properly.
3273 The special value <tt>byhand</tt> for the section in a
3274 <tt>.changes</tt> file indicates that the file in question
3275 is not an ordinary package file and must by installed by
3276 hand by the distribution maintainers. If the section is
3277 <tt>byhand</tt> the priority should be <tt>-</tt>.
3281 If a new Debian revision of a package is being shipped and
3282 no new original source archive is being distributed the
3283 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3284 entry for the original source archive
3285 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3286 but the <file>.changes</file> file should leave it out. In
3287 this case the original source archive on the distribution
3288 site must match exactly, byte-for-byte, the original
3289 source archive which was used to generate the
3290 <file>.dsc</file> file and diff which are being uploaded.</p>
3293 <sect1 id="f-Closes">
3294 <heading><tt>Closes</tt></heading>
3297 A space-separated list of bug report numbers that the upload
3298 governed by the .changes file closes.
3302 <sect1 id="f-Homepage">
3303 <heading><tt>Homepage</tt></heading>
3306 The URL of the web site for this package, preferably (when
3307 applicable) the site from which the original source can be
3308 obtained and any additional upstream documentation or
3309 information may be found. The content of this field is a
3310 simple URL without any surrounding characters such as
3318 <heading>User-defined fields</heading>
3321 Additional user-defined fields may be added to the
3322 source package control file. Such fields will be
3323 ignored, and not copied to (for example) binary or
3324 source package control files or upload control files.
3328 If you wish to add additional unsupported fields to
3329 these output files you should use the mechanism
3334 Fields in the main source control information file with
3335 names starting <tt>X</tt>, followed by one or more of
3336 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3337 be copied to the output files. Only the part of the
3338 field name after the hyphen will be used in the output
3339 file. Where the letter <tt>B</tt> is used the field
3340 will appear in binary package control files, where the
3341 letter <tt>S</tt> is used in source package control
3342 files and where <tt>C</tt> is used in upload control
3343 (<tt>.changes</tt>) files.
3347 For example, if the main source information control file
3350 XBS-Comment: I stand between the candle and the star.
3352 then the binary and source package control files will contain the
3355 Comment: I stand between the candle and the star.
3364 <chapt id="maintainerscripts">
3365 <heading>Package maintainer scripts and installation procedure</heading>
3368 <heading>Introduction to package maintainer scripts</heading>
3371 It is possible to supply scripts as part of a package which
3372 the package management system will run for you when your
3373 package is installed, upgraded or removed.
3377 These scripts are the files <prgn>preinst</prgn>,
3378 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3379 <prgn>postrm</prgn> in the control area of the package.
3380 They must be proper executable files; if they are scripts
3381 (which is recommended), they must start with the usual
3382 <tt>#!</tt> convention. They should be readable and
3383 executable by anyone, and must not be world-writable.
3387 The package management system looks at the exit status from
3388 these scripts. It is important that they exit with a
3389 non-zero status if there is an error, so that the package
3390 management system can stop its processing. For shell
3391 scripts this means that you <em>almost always</em> need to
3392 use <tt>set -e</tt> (this is usually true when writing shell
3393 scripts, in fact). It is also important, of course, that
3394 they don't exit with a non-zero status if everything went
3399 Additionally, packages interacting with users using
3400 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3401 install a <prgn>config</prgn> script in the control area,
3402 see <ref id="maintscriptprompt"> for details.
3406 When a package is upgraded a combination of the scripts from
3407 the old and new packages is called during the upgrade
3408 procedure. If your scripts are going to be at all
3409 complicated you need to be aware of this, and may need to
3410 check the arguments to your scripts.
3414 Broadly speaking the <prgn>preinst</prgn> is called before
3415 (a particular version of) a package is installed, and the
3416 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3417 before (a version of) a package is removed and the
3418 <prgn>postrm</prgn> afterwards.
3422 Programs called from maintainer scripts should not normally
3423 have a path prepended to them. Before installation is
3424 started, the package management system checks to see if the
3425 programs <prgn>ldconfig</prgn>,
3426 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3427 and <prgn>update-rc.d</prgn> can be found via the
3428 <tt>PATH</tt> environment variable. Those programs, and any
3429 other program that one would expect to be in the
3430 <tt>PATH</tt>, should thus be invoked without an absolute
3431 pathname. Maintainer scripts should also not reset the
3432 <tt>PATH</tt>, though they might choose to modify it by
3433 prepending or appending package-specific directories. These
3434 considerations really apply to all shell scripts.</p>
3437 <sect id="idempotency">
3438 <heading>Maintainer scripts idempotency</heading>
3441 It is necessary for the error recovery procedures that the
3442 scripts be idempotent. This means that if it is run
3443 successfully, and then it is called again, it doesn't bomb
3444 out or cause any harm, but just ensures that everything is
3445 the way it ought to be. If the first call failed, or
3446 aborted half way through for some reason, the second call
3447 should merely do the things that were left undone the first
3448 time, if any, and exit with a success status if everything
3450 This is so that if an error occurs, the user interrupts
3451 <prgn>dpkg</prgn> or some other unforeseen circumstance
3452 happens you don't leave the user with a badly-broken
3453 package when <prgn>dpkg</prgn> attempts to repeat the
3459 <sect id="controllingterminal">
3460 <heading>Controlling terminal for maintainer scripts</heading>
3463 The maintainer scripts are guaranteed to run with a
3464 controlling terminal and can interact with the user.
3465 Because these scripts may be executed with standard output
3466 redirected into a pipe for logging purposes, Perl scripts
3467 should set unbuffered output by setting <tt>$|=1</tt> so
3468 that the output is printed immediately rather than being
3472 <sect id="exitstatus">
3473 <heading>Exit status</heading>
3476 Each script must return a zero exit status for
3477 success, or a nonzero one for failure, since the package
3478 management system looks for the exit status of these scripts
3479 and determines what action to take next based on that datum.
3483 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3488 <list compact="compact">
3490 <var>new-preinst</var> <tt>install</tt>
3493 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3496 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3499 <var>old-preinst</var> <tt>abort-upgrade</tt>
3500 <var>new-version</var>
3505 <list compact="compact">
3507 <var>postinst</var> <tt>configure</tt>
3508 <var>most-recently-configured-version</var>
3511 <var>old-postinst</var> <tt>abort-upgrade</tt>
3512 <var>new-version</var>
3515 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3516 <tt>in-favour</tt> <var>package</var>
3517 <var>new-version</var>
3520 <var>postinst</var> <tt>abort-remove</tt>
3523 <var>deconfigured's-postinst</var>
3524 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3525 <var>failed-install-package</var> <var>version</var>
3526 [<tt>removing</tt> <var>conflicting-package</var>
3532 <list compact="compact">
3534 <var>prerm</var> <tt>remove</tt>
3537 <var>old-prerm</var> <tt>upgrade</tt>
3538 <var>new-version</var>
3541 <var>new-prerm</var> <tt>failed-upgrade</tt>
3542 <var>old-version</var>
3545 <var>conflictor's-prerm</var> <tt>remove</tt>
3546 <tt>in-favour</tt> <var>package</var>
3547 <var>new-version</var>
3550 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3551 <tt>in-favour</tt> <var>package-being-installed</var>
3552 <var>version</var> [<tt>removing</tt>
3553 <var>conflicting-package</var>
3559 <list compact="compact">
3561 <var>postrm</var> <tt>remove</tt>
3564 <var>postrm</var> <tt>purge</tt>
3567 <var>old-postrm</var> <tt>upgrade</tt>
3568 <var>new-version</var>
3571 <var>new-postrm</var> <tt>failed-upgrade</tt>
3572 <var>old-version</var>
3575 <var>new-postrm</var> <tt>abort-install</tt>
3578 <var>new-postrm</var> <tt>abort-install</tt>
3579 <var>old-version</var>
3582 <var>new-postrm</var> <tt>abort-upgrade</tt>
3583 <var>old-version</var>
3586 <var>disappearer's-postrm</var> <tt>disappear</tt>
3587 <var>overwriter</var>
3588 <var>overwriter-version</var>
3594 <sect id="unpackphase">
3595 <heading>Details of unpack phase of installation or upgrade</heading>
3598 The procedure on installation/upgrade/overwrite/disappear
3599 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3600 stage of <tt>dpkg --install</tt>) is as follows. In each
3601 case, if a major error occurs (unless listed below) the
3602 actions are, in general, run backwards - this means that the
3603 maintainer scripts are run with different arguments in
3604 reverse order. These are the "error unwind" calls listed
3611 If a version of the package is already installed, call
3612 <example compact="compact">
3613 <var>old-prerm</var> upgrade <var>new-version</var>
3617 If the script runs but exits with a non-zero
3618 exit status, <prgn>dpkg</prgn> will attempt:
3619 <example compact="compact">
3620 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3622 If this works, the upgrade continues. If this
3623 does not work, the error unwind:
3624 <example compact="compact">
3625 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3627 If this works, then the old-version is
3628 "Installed", if not, the old version is in a
3629 "Failed-Config" state.
3635 If a "conflicting" package is being removed at the same time,
3636 or if any package will be broken (due to <tt>Breaks</tt>):
3639 If <tt>--auto-deconfigure</tt> is
3640 specified, call, for each package to be deconfigured
3641 due to <tt>Breaks</tt>:
3642 <example compact="compact">
3643 <var>deconfigured's-prerm</var> deconfigure \
3644 in-favour <var>package-being-installed</var> <var>version</var>
3647 <example compact="compact">
3648 <var>deconfigured's-postinst</var> abort-deconfigure \
3649 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3651 The deconfigured packages are marked as
3652 requiring configuration, so that if
3653 <tt>--install</tt> is used they will be
3654 configured again if possible.
3657 If any packages depended on a conflicting
3658 package being removed and <tt>--auto-deconfigure</tt> is
3659 specified, call, for each such package:
3660 <example compact="compact">
3661 <var>deconfigured's-prerm</var> deconfigure \
3662 in-favour <var>package-being-installed</var> <var>version</var> \
3663 removing <var>conflicting-package</var> <var>version</var>
3666 <example compact="compact">
3667 <var>deconfigured's-postinst</var> abort-deconfigure \
3668 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3669 removing <var>conflicting-package</var> <var>version</var>
3671 The deconfigured packages are marked as
3672 requiring configuration, so that if
3673 <tt>--install</tt> is used they will be
3674 configured again if possible.
3677 To prepare for removal of each conflicting package, call:
3678 <example compact="compact">
3679 <var>conflictor's-prerm</var> remove \
3680 in-favour <var>package</var> <var>new-version</var>
3683 <example compact="compact">
3684 <var>conflictor's-postinst</var> abort-remove \
3685 in-favour <var>package</var> <var>new-version</var>
3694 If the package is being upgraded, call:
3695 <example compact="compact">
3696 <var>new-preinst</var> upgrade <var>old-version</var>
3698 If this fails, we call:
3700 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3707 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3709 is called. If this works, then the old version
3710 is in an "Installed" state, or else it is left
3711 in an "Unpacked" state.
3716 If it fails, then the old version is left
3717 in an "Half-Installed" state.
3724 Otherwise, if the package had some configuration
3725 files from a previous version installed (i.e., it
3726 is in the "configuration files only" state):
3727 <example compact="compact">
3728 <var>new-preinst</var> install <var>old-version</var>
3732 <var>new-postrm</var> abort-install <var>old-version</var>
3734 If this fails, the package is left in a
3735 "Half-Installed" state, which requires a
3736 reinstall. If it works, the packages is left in
3737 a "Config Files" state.
3740 Otherwise (i.e., the package was completely purged):
3741 <example compact="compact">
3742 <var>new-preinst</var> install
3745 <example compact="compact">
3746 <var>new-postrm</var> abort-install
3748 If the error-unwind fails, the package is in a
3749 "Half Installed" phase, and requires a
3750 reinstall. If the error unwind works, the
3751 package is in a not installed state.
3758 The new package's files are unpacked, overwriting any
3759 that may be on the system already, for example any
3760 from the old version of the same package or from
3761 another package. Backups of the old files are kept
3762 temporarily, and if anything goes wrong the package
3763 management system will attempt to put them back as
3764 part of the error unwind.
3768 It is an error for a package to contain files which
3769 are on the system in another package, unless
3770 <tt>Replaces</tt> is used (see <ref id="replaces">).
3772 The following paragraph is not currently the case:
3773 Currently the <tt>- - force-overwrite</tt> flag is
3774 enabled, downgrading it to a warning, but this may not
3780 It is a more serious error for a package to contain a
3781 plain file or other kind of non-directory where another
3782 package has a directory (again, unless
3783 <tt>Replaces</tt> is used). This error can be
3784 overridden if desired using
3785 <tt>--force-overwrite-dir</tt>, but this is not
3790 Packages which overwrite each other's files produce
3791 behavior which, though deterministic, is hard for the
3792 system administrator to understand. It can easily
3793 lead to "missing" programs if, for example, a package
3794 is installed which overwrites a file from another
3795 package, and is then removed again.<footnote>
3796 Part of the problem is due to what is arguably a
3797 bug in <prgn>dpkg</prgn>.
3802 A directory will never be replaced by a symbolic link
3803 to a directory or vice versa; instead, the existing
3804 state (symlink or not) will be left alone and
3805 <prgn>dpkg</prgn> will follow the symlink if there is
3814 If the package is being upgraded, call
3815 <example compact="compact">
3816 <var>old-postrm</var> upgrade <var>new-version</var>
3820 If this fails, <prgn>dpkg</prgn> will attempt:
3821 <example compact="compact">
3822 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3824 If this works, installation continues. If not,
3826 <example compact="compact">
3827 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3829 If this fails, the old version is left in an
3830 "Half Installed" state. If it works, dpkg now
3832 <example compact="compact">
3833 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3835 If this fails, the old version is left in an
3836 "Half Installed" state. If it works, dpkg now
3838 <example compact="compact">
3839 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3841 If this fails, the old version is in an
3848 This is the point of no return - if
3849 <prgn>dpkg</prgn> gets this far, it won't back off
3850 past this point if an error occurs. This will
3851 leave the package in a fairly bad state, which
3852 will require a successful re-installation to clear
3853 up, but it's when <prgn>dpkg</prgn> starts doing
3854 things that are irreversible.
3859 Any files which were in the old version of the package
3860 but not in the new are removed.
3864 The new file list replaces the old.
3868 The new maintainer scripts replace the old.
3872 Any packages all of whose files have been overwritten
3873 during the installation, and which aren't required for
3874 dependencies, are considered to have been removed.
3875 For each such package
3878 <prgn>dpkg</prgn> calls:
3879 <example compact="compact">
3880 <var>disappearer's-postrm</var> disappear \
3881 <var>overwriter</var> <var>overwriter-version</var>
3885 The package's maintainer scripts are removed.
3888 It is noted in the status database as being in a
3889 sane state, namely not installed (any conffiles
3890 it may have are ignored, rather than being
3891 removed by <prgn>dpkg</prgn>). Note that
3892 disappearing packages do not have their prerm
3893 called, because <prgn>dpkg</prgn> doesn't know
3894 in advance that the package is going to
3901 Any files in the package we're unpacking that are also
3902 listed in the file lists of other packages are removed
3903 from those lists. (This will lobotomize the file list
3904 of the "conflicting" package if there is one.)
3908 The backup files made during installation, above, are
3914 The new package's status is now sane, and recorded as
3919 Here is another point of no return - if the
3920 conflicting package's removal fails we do not unwind
3921 the rest of the installation; the conflicting package
3922 is left in a half-removed limbo.
3927 If there was a conflicting package we go and do the
3928 removal actions (described below), starting with the
3929 removal of the conflicting package's files (any that
3930 are also in the package being installed have already
3931 been removed from the conflicting package's file list,
3932 and so do not get removed now).
3938 <sect id="configdetails"><heading>Details of configuration</heading>
3941 When we configure a package (this happens with <tt>dpkg
3942 --install</tt> and <tt>dpkg --configure</tt>), we first
3943 update any <tt>conffile</tt>s and then call:
3944 <example compact="compact">
3945 <var>postinst</var> configure <var>most-recently-configured-version</var>
3950 No attempt is made to unwind after errors during
3951 configuration. If the configuration fails, the package is in
3952 a "Failed Config" state, and an error message is generated.
3956 If there is no most recently configured version
3957 <prgn>dpkg</prgn> will pass a null argument.
3960 Historical note: Truly ancient (pre-1997) versions of
3961 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3962 (including the angle brackets) in this case. Even older
3963 ones did not pass a second argument at all, under any
3964 circumstance. Note that upgrades using such an old dpkg
3965 version are unlikely to work for other reasons, even if
3966 this old argument behavior is handled by your postinst script.
3972 <sect id="removedetails"><heading>Details of removal and/or
3973 configuration purging</heading>
3979 <example compact="compact">
3980 <var>prerm</var> remove
3984 If prerm fails during replacement due to conflict
3986 <var>conflictor's-postinst</var> abort-remove \
3987 in-favour <var>package</var> <var>new-version</var>
3991 <var>postinst</var> abort-remove
3995 If this fails, the package is in a "Failed-Config"
3996 state, or else it remains "Installed".
4000 The package's files are removed (except <tt>conffile</tt>s).
4003 <example compact="compact">
4004 <var>postrm</var> remove
4008 If it fails, there's no error unwind, and the package is in
4009 an "Half-Installed" state.
4014 All the maintainer scripts except the <prgn>postrm</prgn>
4019 If we aren't purging the package we stop here. Note
4020 that packages which have no <prgn>postrm</prgn> and no
4021 <tt>conffile</tt>s are automatically purged when
4022 removed, as there is no difference except for the
4023 <prgn>dpkg</prgn> status.
4027 The <tt>conffile</tt>s and any backup files
4028 (<tt>~</tt>-files, <tt>#*#</tt> files,
4029 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4034 <example compact="compact">
4035 <var>postrm</var> purge
4039 If this fails, the package remains in a "Config-Files"
4044 The package's file list is removed.
4053 <chapt id="relationships">
4054 <heading>Declaring relationships between packages</heading>
4056 <sect id="depsyntax">
4057 <heading>Syntax of relationship fields</heading>
4060 These fields all have a uniform syntax. They are a list of
4061 package names separated by commas.
4065 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4066 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4067 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4068 control file fields of the package, which declare
4069 dependencies on other packages, the package names listed may
4070 also include lists of alternative package names, separated
4071 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4072 if any one of the alternative packages is installed, that
4073 part of the dependency is considered to be satisfied.
4077 All of the fields except for <tt>Provides</tt> may restrict
4078 their applicability to particular versions of each named
4079 package. This is done in parentheses after each individual
4080 package name; the parentheses should contain a relation from
4081 the list below followed by a version number, in the format
4082 described in <ref id="f-Version">.
4086 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4087 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4088 strictly earlier, earlier or equal, exactly equal, later or
4089 equal and strictly later, respectively. The deprecated
4090 forms <tt><</tt> and <tt>></tt> were used to mean
4091 earlier/later or equal, rather than strictly earlier/later,
4092 so they should not appear in new packages (though
4093 <prgn>dpkg</prgn> still supports them).
4097 Whitespace may appear at any point in the version
4098 specification subject to the rules in <ref
4099 id="controlsyntax">, and must appear where it's necessary to
4100 disambiguate; it is not otherwise significant. All of the
4101 relationship fields may span multiple lines. For
4102 consistency and in case of future changes to
4103 <prgn>dpkg</prgn> it is recommended that a single space be
4104 used after a version relationship and before a version
4105 number; it is also conventional to put a single space after
4106 each comma, on either side of each vertical bar, and before
4107 each open parenthesis. When wrapping a relationship field, it
4108 is conventional to do so after a comma and before the space
4109 following that comma.
4113 For example, a list of dependencies might appear as:
4114 <example compact="compact">
4117 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4122 All fields that specify build-time relationships
4123 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4124 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4125 may be restricted to a certain set of architectures. This
4126 is indicated in brackets after each individual package name and
4127 the optional version specification. The brackets enclose a
4128 list of Debian architecture names separated by whitespace.
4129 Exclamation marks may be prepended to each of the names.
4130 (It is not permitted for some names to be prepended with
4131 exclamation marks while others aren't.) If the current Debian
4132 host architecture is not in this list and there are no
4133 exclamation marks in the list, or it is in the list with a
4134 prepended exclamation mark, the package name and the
4135 associated version specification are ignored completely for
4136 the purposes of defining the relationships.
4141 <example compact="compact">
4143 Build-Depends-Indep: texinfo
4144 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4145 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4150 Note that the binary package relationship fields such as
4151 <tt>Depends</tt> appear in one of the binary package
4152 sections of the control file, whereas the build-time
4153 relationships such as <tt>Build-Depends</tt> appear in the
4154 source package section of the control file (which is the
4159 <sect id="binarydeps">
4160 <heading>Binary Dependencies - <tt>Depends</tt>,
4161 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4162 <tt>Pre-Depends</tt>
4166 Packages can declare in their control file that they have
4167 certain relationships to other packages - for example, that
4168 they may not be installed at the same time as certain other
4169 packages, and/or that they depend on the presence of others.
4173 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4174 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4175 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4179 These seven fields are used to declare a dependency
4180 relationship by one package on another. Except for
4181 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4182 depending (binary) package's control file.
4183 (<tt>Enhances</tt> appears in the recommending package's
4184 control file, and <tt>Breaks</tt> appears in the version of
4185 depended-on package which causes the named package to
4190 A <tt>Depends</tt> field takes effect <em>only</em> when a
4191 package is to be configured. It does not prevent a package
4192 being on the system in an unconfigured state while its
4193 dependencies are unsatisfied, and it is possible to replace
4194 a package whose dependencies are satisfied and which is
4195 properly installed with a different version whose
4196 dependencies are not and cannot be satisfied; when this is
4197 done the depending package will be left unconfigured (since
4198 attempts to configure it will give errors) and will not
4199 function properly. If it is necessary, a
4200 <tt>Pre-Depends</tt> field can be used, which has a partial
4201 effect even when a package is being unpacked, as explained
4202 in detail below. (The other three dependency fields,
4203 <tt>Recommends</tt>, <tt>Suggests</tt> and
4204 <tt>Enhances</tt>, are only used by the various front-ends
4205 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4206 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4210 For this reason packages in an installation run are usually
4211 all unpacked first and all configured later; this gives
4212 later versions of packages with dependencies on later
4213 versions of other packages the opportunity to have their
4214 dependencies satisfied.
4218 In case of circular dependencies, since installation or
4219 removal order honoring the dependency order can't be
4220 established, dependency loops are broken at some point
4221 (based on rules below), and some packages may not be able to
4222 rely on their dependencies being present when being
4223 installed or removed, depending on which side of the break
4224 of the circular dependency loop they happen to be on. If one
4225 of the packages in the loop has no postinst script, then the
4226 cycle will be broken at that package, so as to ensure that
4227 all postinst scripts run with the dependencies properly
4228 configured if this is possible. Otherwise the breaking point
4233 The <tt>Depends</tt> field thus allows package maintainers
4234 to impose an order in which packages should be configured.
4238 The meaning of the five dependency fields is as follows:
4240 <tag><tt>Depends</tt></tag>
4243 This declares an absolute dependency. A package will
4244 not be configured unless all of the packages listed in
4245 its <tt>Depends</tt> field have been correctly
4250 The <tt>Depends</tt> field should be used if the
4251 depended-on package is required for the depending
4252 package to provide a significant amount of
4257 The <tt>Depends</tt> field should also be used if the
4258 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4259 <prgn>postrm</prgn> scripts require the package to be
4260 present in order to run. Note, however, that the
4261 <prgn>postrm</prgn> cannot rely on any non-essential
4262 packages to be present during the <tt>purge</tt>
4266 <tag><tt>Recommends</tt></tag>
4269 This declares a strong, but not absolute, dependency.
4273 The <tt>Recommends</tt> field should list packages
4274 that would be found together with this one in all but
4275 unusual installations.
4279 <tag><tt>Suggests</tt></tag>
4281 This is used to declare that one package may be more
4282 useful with one or more others. Using this field
4283 tells the packaging system and the user that the
4284 listed packages are related to this one and can
4285 perhaps enhance its usefulness, but that installing
4286 this one without them is perfectly reasonable.
4289 <tag><tt>Enhances</tt></tag>
4291 This field is similar to Suggests but works in the
4292 opposite direction. It is used to declare that a
4293 package can enhance the functionality of another
4297 <tag><tt>Pre-Depends</tt></tag>
4300 This field is like <tt>Depends</tt>, except that it
4301 also forces <prgn>dpkg</prgn> to complete installation
4302 of the packages named before even starting the
4303 installation of the package which declares the
4304 pre-dependency, as follows:
4308 When a package declaring a pre-dependency is about to
4309 be <em>unpacked</em> the pre-dependency can be
4310 satisfied if the depended-on package is either fully
4311 configured, <em>or even if</em> the depended-on
4312 package(s) are only unpacked or half-configured,
4313 provided that they have been configured correctly at
4314 some point in the past (and not removed or partially
4315 removed since). In this case, both the
4316 previously-configured and currently unpacked or
4317 half-configured versions must satisfy any version
4318 clause in the <tt>Pre-Depends</tt> field.
4322 When the package declaring a pre-dependency is about
4323 to be <em>configured</em>, the pre-dependency will be
4324 treated as a normal <tt>Depends</tt>, that is, it will
4325 be considered satisfied only if the depended-on
4326 package has been correctly configured.
4330 <tt>Pre-Depends</tt> should be used sparingly,
4331 preferably only by packages whose premature upgrade or
4332 installation would hamper the ability of the system to
4333 continue with any upgrade that might be in progress.
4337 <tt>Pre-Depends</tt> are also required if the
4338 <prgn>preinst</prgn> script depends on the named
4339 package. It is best to avoid this situation if
4347 When selecting which level of dependency to use you should
4348 consider how important the depended-on package is to the
4349 functionality of the one declaring the dependency. Some
4350 packages are composed of components of varying degrees of
4351 importance. Such a package should list using
4352 <tt>Depends</tt> the package(s) which are required by the
4353 more important components. The other components'
4354 requirements may be mentioned as Suggestions or
4355 Recommendations, as appropriate to the components' relative
4361 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4364 Using <tt>Breaks</tt> may cause problems for upgrades from older
4365 versions of Debian and should not be used until the stable
4366 release of Debian supports <tt>Breaks</tt>.
4370 When one binary package declares that it breaks another,
4371 <prgn>dpkg</prgn> will refuse to allow the package which
4372 declares <tt>Breaks</tt> be installed unless the broken
4373 package is deconfigured first, and it will refuse to
4374 allow the broken package to be reconfigured.
4378 A package will not be regarded as causing breakage merely
4379 because its configuration files are still installed; it must
4380 be at least half-installed.
4384 A special exception is made for packages which declare that
4385 they break their own package name or a virtual package which
4386 they provide (see below): this does not count as a real
4391 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4392 version clause; such a <tt>Breaks</tt> is introduced in the
4393 version of an (implicit or explicit) dependency which
4394 violates an assumption or reveals a bug in earlier versions
4395 of the broken package. This use of <tt>Breaks</tt> will
4396 inform higher-level package management tools that broken
4397 package must be upgraded before the new one.
4401 If the breaking package also overwrites some files from the
4402 older package, it should use <tt>Replaces</tt> (not
4403 <tt>Conflicts</tt>) to ensure this goes smoothly.
4407 <sect id="conflicts">
4408 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4411 When one binary package declares a conflict with another
4412 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4413 refuse to allow them to be installed on the system at the
4418 If one package is to be installed, the other must be removed
4419 first - if the package being installed is marked as
4420 replacing (see <ref id="replaces">) the one on the system,
4421 or the one on the system is marked as deselected, or both
4422 packages are marked <tt>Essential</tt>, then
4423 <prgn>dpkg</prgn> will automatically remove the package
4424 which is causing the conflict, otherwise it will halt the
4425 installation of the new package with an error. This
4426 mechanism is specifically designed to produce an error when
4427 the installed package is <tt>Essential</tt>, but the new
4432 A package will not cause a conflict merely because its
4433 configuration files are still installed; it must be at least
4438 A special exception is made for packages which declare a
4439 conflict with their own package name, or with a virtual
4440 package which they provide (see below): this does not
4441 prevent their installation, and allows a package to conflict
4442 with others providing a replacement for it. You use this
4443 feature when you want the package in question to be the only
4444 package providing some feature.
4448 A <tt>Conflicts</tt> entry should almost never have an
4449 "earlier than" version clause. This would prevent
4450 <prgn>dpkg</prgn> from upgrading or installing the package
4451 which declared such a conflict until the upgrade or removal
4452 of the conflicted-with package had been completed. Instead,
4453 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4454 by the stable release of Debian).
4458 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4462 As well as the names of actual ("concrete") packages, the
4463 package relationship fields <tt>Depends</tt>,
4464 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4465 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4466 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4467 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4468 may mention "virtual packages".
4472 A <em>virtual package</em> is one which appears in the
4473 <tt>Provides</tt> control file field of another package.
4474 The effect is as if the package(s) which provide a
4475 particular virtual package name had been listed by name
4476 everywhere the virtual package name appears. (See also <ref
4481 If there are both concrete and virtual packages of the same
4482 name, then the dependency may be satisfied (or the conflict
4483 caused) by either the concrete package with the name in
4484 question or any other concrete package which provides the
4485 virtual package with the name in question. This is so that,
4486 for example, supposing we have
4487 <example compact="compact">
4490 </example> and someone else releases an enhanced version of
4491 the <tt>bar</tt> package they can say:
4492 <example compact="compact">
4496 and the <tt>bar-plus</tt> package will now also satisfy the
4497 dependency for the <tt>foo</tt> package.
4501 If a relationship field has a version number attached
4502 then only real packages will be considered to see whether
4503 the relationship is satisfied (or the prohibition violated,
4504 for a conflict or breakage) - it is assumed that a real
4505 package which provides the virtual package is not of the
4506 "right" version. So, a <tt>Provides</tt> field may not
4507 contain version numbers, and the version number of the
4508 concrete package which provides a particular virtual package
4509 will not be looked at when considering a dependency on or
4510 conflict with the virtual package name.
4514 It is likely that the ability will be added in a future
4515 release of <prgn>dpkg</prgn> to specify a version number for
4516 each virtual package it provides. This feature is not yet
4517 present, however, and is expected to be used only
4522 If you want to specify which of a set of real packages
4523 should be the default to satisfy a particular dependency on
4524 a virtual package, you should list the real package as an
4525 alternative before the virtual one.
4530 <sect id="replaces"><heading>Overwriting files and replacing
4531 packages - <tt>Replaces</tt></heading>
4534 Packages can declare in their control file that they should
4535 overwrite files in certain other packages, or completely
4536 replace other packages. The <tt>Replaces</tt> control file
4537 field has these two distinct purposes.
4540 <sect1><heading>Overwriting files in other packages</heading>
4543 Firstly, as mentioned before, it is usually an error for a
4544 package to contain files which are on the system in
4549 However, if the overwriting package declares that it
4550 <tt>Replaces</tt> the one containing the file being
4551 overwritten, then <prgn>dpkg</prgn> will replace the file
4552 from the old package with that from the new. The file
4553 will no longer be listed as "owned" by the old package.
4557 If a package is completely replaced in this way, so that
4558 <prgn>dpkg</prgn> does not know of any files it still
4559 contains, it is considered to have "disappeared". It will
4560 be marked as not wanted on the system (selected for
4561 removal) and not installed. Any <tt>conffile</tt>s
4562 details noted for the package will be ignored, as they
4563 will have been taken over by the overwriting package. The
4564 package's <prgn>postrm</prgn> script will be run with a
4565 special argument to allow the package to do any final
4566 cleanup required. See <ref id="mscriptsinstact">.
4569 Replaces is a one way relationship -- you have to
4570 install the replacing package after the replaced
4577 For this usage of <tt>Replaces</tt>, virtual packages (see
4578 <ref id="virtual">) are not considered when looking at a
4579 <tt>Replaces</tt> field - the packages declared as being
4580 replaced must be mentioned by their real names.
4584 Furthermore, this usage of <tt>Replaces</tt> only takes
4585 effect when both packages are at least partially on the
4586 system at once, so that it can only happen if they do not
4587 conflict or if the conflict has been overridden.
4592 <sect1><heading>Replacing whole packages, forcing their
4596 Secondly, <tt>Replaces</tt> allows the packaging system to
4597 resolve which package should be removed when there is a
4598 conflict - see <ref id="conflicts">. This usage only
4599 takes effect when the two packages <em>do</em> conflict,
4600 so that the two usages of this field do not interfere with
4605 In this situation, the package declared as being replaced
4606 can be a virtual package, so for example, all mail
4607 transport agents (MTAs) would have the following fields in
4608 their control files:
4609 <example compact="compact">
4610 Provides: mail-transport-agent
4611 Conflicts: mail-transport-agent
4612 Replaces: mail-transport-agent
4614 ensuring that only one MTA can be installed at any one
4619 <sect id="sourcebinarydeps">
4620 <heading>Relationships between source and binary packages -
4621 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4622 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4626 Source packages that require certain binary packages to be
4627 installed or absent at the time of building the package
4628 can declare relationships to those binary packages.
4632 This is done using the <tt>Build-Depends</tt>,
4633 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4634 <tt>Build-Conflicts-Indep</tt> control file fields.
4638 Build-dependencies on "build-essential" binary packages can be
4639 omitted. Please see <ref id="pkg-relations"> for more information.
4643 The dependencies and conflicts they define must be satisfied
4644 (as defined earlier for binary packages) in order to invoke
4645 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4647 If you make "build-arch" or "binary-arch", you need
4648 Build-Depends. If you make "build-indep" or
4649 "binary-indep", you need Build-Depends and
4650 Build-Depends-Indep. If you make "build" or "binary",
4654 There is no Build-Depends-Arch; this role is essentially
4655 met with Build-Depends. Anyone building the
4656 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4657 is basically assumed to be building the whole package
4658 anyway and so installs all build dependencies. The
4659 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4660 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4661 does not yet know how to check for its existence) and
4662 <tt>binary-arch</tt>.
4665 The purpose of the original split, I recall, was so that
4666 the autobuilders wouldn't need to install extra packages
4667 needed only for the binary-indep targets. But without a
4668 build-arch/build-indep split, this didn't work, since
4669 most of the work is done in the build target, not in the
4675 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4677 The <tt>Build-Depends</tt> and
4678 <tt>Build-Conflicts</tt> fields must be satisfied when
4679 any of the following targets is invoked:
4680 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4681 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4682 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4684 <tag><tt>Build-Depends-Indep</tt>,
4685 <tt>Build-Conflicts-Indep</tt></tag>
4687 The <tt>Build-Depends-Indep</tt> and
4688 <tt>Build-Conflicts-Indep</tt> fields must be
4689 satisfied when any of the following targets is
4690 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4691 <tt>binary</tt> and <tt>binary-indep</tt>.
4701 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4704 Packages containing shared libraries must be constructed with
4705 a little care to make sure that the shared library is always
4706 available. This is especially important for packages whose
4707 shared libraries are vitally important, such as the C library
4708 (currently <tt>libc6</tt>).
4712 Packages involving shared libraries should be split up into
4713 several binary packages. This section mostly deals with how
4714 this separation is to be accomplished; rules for files within
4715 the shared library packages are in <ref id="libraries"> instead.
4718 <sect id="sharedlibs-runtime">
4719 <heading>Run-time shared libraries</heading>
4722 The run-time shared library needs to be placed in a package
4723 whose name changes whenever the shared object version
4726 Since it is common place to install several versions of a
4727 package that just provides shared libraries, it is a
4728 good idea that the library package should not
4729 contain any extraneous non-versioned files, unless they
4730 happen to be in versioned directories.</p>
4732 The most common mechanism is to place it in a package
4734 <package><var>libraryname</var><var>soversion</var></package>,
4735 where <file><var>soversion</var></file> is the version number
4736 in the soname of the shared library<footnote>
4737 The soname is the shared object name: it's the thing
4738 that has to match exactly between building an executable
4739 and running it for the dynamic linker to be able run the
4740 program. For example, if the soname of the library is
4741 <file>libfoo.so.6</file>, the library package would be
4742 called <file>libfoo6</file>.
4744 Alternatively, if it would be confusing to directly append
4745 <var>soversion</var> to <var>libraryname</var> (e.g. because
4746 <var>libraryname</var> itself ends in a number), you may use
4747 <package><var>libraryname</var>-<var>soversion</var></package> and
4748 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4753 If you have several shared libraries built from the same
4754 source tree you may lump them all together into a single
4755 shared library package, provided that you change all of
4756 their sonames at once (so that you don't get filename
4757 clashes if you try to install different versions of the
4758 combined shared libraries package).
4762 The package should install the shared libraries under
4763 their normal names. For example, the <package>libgdbm3</package>
4764 package should install <file>libgdbm.so.3.0.0</file> as
4765 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4766 renamed or re-linked by any <prgn>prerm</prgn> or
4767 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4768 of renaming things safely without affecting running programs,
4769 and attempts to interfere with this are likely to lead to
4774 Shared libraries should not be installed executable, since
4775 the dynamic linker does not require this and trying to
4776 execute a shared library usually results in a core dump.
4780 The run-time library package should include the symbolic link that
4781 <prgn>ldconfig</prgn> would create for the shared libraries.
4782 For example, the <package>libgdbm3</package> package should include
4783 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4784 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4785 linker (for example <prgn>ld.so</prgn> or
4786 <prgn>ld-linux.so.*</prgn>) can find the library between the
4787 time that <prgn>dpkg</prgn> installs it and the time that
4788 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4790 The package management system requires the library to be
4791 placed before the symbolic link pointing to it in the
4792 <file>.deb</file> file. This is so that when
4793 <prgn>dpkg</prgn> comes to install the symlink
4794 (overwriting the previous symlink pointing at an older
4795 version of the library), the new shared library is already
4796 in place. In the past, this was achieved by creating the
4797 library in the temporary packaging directory before
4798 creating the symlink. Unfortunately, this was not always
4799 effective, since the building of the tar file in the
4800 <file>.deb</file> depended on the behavior of the underlying
4801 file system. Some file systems (such as reiserfs) reorder
4802 the files so that the order of creation is forgotten.
4803 Since version 1.7.0, <prgn>dpkg</prgn>
4804 reorders the files itself as necessary when building a
4805 package. Thus it is no longer important to concern
4806 oneself with the order of file creation.
4810 <sect1 id="ldconfig">
4811 <heading><tt>ldconfig</tt></heading>
4814 Any package installing shared libraries in one of the default
4815 library directories of the dynamic linker (which are currently
4816 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4817 listed in <file>/etc/ld.so.conf</file><footnote>
4819 <list compact="compact">
4820 <item>/usr/local/lib</item>
4821 <item>/usr/lib/libc5-compat</item>
4822 <item>/lib/libc5-compat</item>
4825 must use <prgn>ldconfig</prgn> to update the shared library
4830 The package maintainer scripts must only call
4831 <prgn>ldconfig</prgn> under these circumstances:
4832 <list compact="compact">
4833 <item>When the <prgn>postinst</prgn> script is run with a
4834 first argument of <tt>configure</tt>, the script must call
4835 <prgn>ldconfig</prgn>, and may optionally invoke
4836 <prgn>ldconfig</prgn> at other times.
4838 <item>When the <prgn>postrm</prgn> script is run with a
4839 first argument of <tt>remove</tt>, the script should call
4840 <prgn>ldconfig</prgn>.
4845 During install or upgrade, the preinst is called before
4846 the new files are installed, so calling "ldconfig" is
4847 pointless. The preinst of an existing package can also be
4848 called if an upgrade fails. However, this happens during
4849 the critical time when a shared libs may exist on-disk
4850 under a temporary name. Thus, it is dangerous and
4851 forbidden by current policy to call "ldconfig" at this
4856 When a package is installed or upgraded, "postinst
4857 configure" runs after the new files are safely on-disk.
4858 Since it is perfectly safe to invoke ldconfig
4859 unconditionally in a postinst, it is OK for a package to
4860 simply put ldconfig in its postinst without checking the
4861 argument. The postinst can also be called to recover from
4862 a failed upgrade. This happens before any new files are
4863 unpacked, so there is no reason to call "ldconfig" at this
4868 For a package that is being removed, prerm is
4869 called with all the files intact, so calling ldconfig is
4870 useless. The other calls to "prerm" happen in the case of
4871 upgrade at a time when all the files of the old package
4872 are on-disk, so again calling "ldconfig" is pointless.
4876 postrm, on the other hand, is called with the "remove"
4877 argument just after the files are removed, so this is
4878 the proper time to call "ldconfig" to notify the system
4879 of the fact that the shared libraries from the package
4880 are removed. The postrm can be called at several other
4881 times. At the time of "postrm purge", "postrm
4882 abort-install", or "postrm abort-upgrade", calling
4883 "ldconfig" is useless because the shared lib files are
4884 not on-disk. However, when "postrm" is invoked with
4885 arguments "upgrade", "failed-upgrade", or "disappear", a
4886 shared lib may exist on-disk under a temporary filename.
4894 <sect id="sharedlibs-support-files">
4895 <heading>Shared library support files</heading>
4898 If your package contains files whose names do not change with
4899 each change in the library shared object version, you must not
4900 put them in the shared library package. Otherwise, several
4901 versions of the shared library cannot be installed at the same
4902 time without filename clashes, making upgrades and transitions
4903 unnecessarily difficult.
4907 It is recommended that supporting files and run-time support
4908 programs that do not need to be invoked manually by users, but
4909 are nevertheless required for the package to function, be placed
4910 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4911 preferably under <file>/usr/lib/</file><var>package-name</var>.
4912 If the program or file is architecture independent, the
4913 recommendation is for it to be placed in a subdirectory of
4914 <file>/usr/share</file> instead, preferably under
4915 <file>/usr/share/</file><var>package-name</var>. Following the
4916 <var>package-name</var> naming convention ensures that the file
4917 names change when the shared object version changes.
4921 Run-time support programs that use the shared library but are
4922 not required for the library to function or files used by the
4923 shared library that can be used by any version of the shared
4924 library package should instead be put in a separate package.
4925 This package might typically be named
4926 <package><var>libraryname</var>-tools</package>; note the
4927 absence of the <var>soversion</var> in the package name.
4931 Files and support programs only useful when compiling software
4932 against the library should be included in the development
4933 package for the library.<footnote>
4934 For example, a <file><var>package-name</var>-config</file>
4935 script or <package>pkg-config</package> configuration files.
4940 <sect id="sharedlibs-static">
4941 <heading>Static libraries</heading>
4944 The static library (<file><var>libraryname.a</var></file>)
4945 is usually provided in addition to the shared version.
4946 It is placed into the development package (see below).
4950 In some cases, it is acceptable for a library to be
4951 available in static form only; these cases include:
4953 <item>libraries for languages whose shared library support
4954 is immature or unstable</item>
4955 <item>libraries whose interfaces are in flux or under
4956 development (commonly the case when the library's
4957 major version number is zero, or where the ABI breaks
4958 across patchlevels)</item>
4959 <item>libraries which are explicitly intended to be
4960 available only in static form by their upstream
4965 <sect id="sharedlibs-dev">
4966 <heading>Development files</heading>
4969 The development files associated to a shared library need to be
4970 placed in a package called
4971 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4972 or if you prefer only to support one development version at a
4973 time, <package><var>libraryname</var>-dev</package>.
4977 In case several development versions of a library exist, you may
4978 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4979 <ref id="conflicts">) to ensure that the user only installs one
4980 development version at a time (as different development versions are
4981 likely to have the same header files in them, which would cause a
4982 filename clash if both were installed).
4986 The development package should contain a symlink for the associated
4987 shared library without a version number. For example, the
4988 <package>libgdbm-dev</package> package should include a symlink
4989 from <file>/usr/lib/libgdbm.so</file> to
4990 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4991 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4992 <file>libgdbm.so</file> when compiling dynamically.
4996 <sect id="sharedlibs-intradeps">
4997 <heading>Dependencies between the packages of the same library</heading>
5000 Typically the development version should have an exact
5001 version dependency on the runtime library, to make sure that
5002 compilation and linking happens correctly. The
5003 <tt>${binary:Version}</tt> substitution variable can be
5004 useful for this purpose.
5006 Previously, <tt>${Source-Version}</tt> was used, but its name
5007 was confusing and it has been deprecated since dpkg 1.13.19.
5012 <sect id="sharedlibs-shlibdeps">
5013 <heading>Dependencies between the library and other packages -
5014 the <tt>shlibs</tt> system</heading>
5017 If a package contains a binary or library which links to a
5018 shared library, we must ensure that when the package is
5019 installed on the system, all of the libraries needed are
5020 also installed. This requirement led to the creation of the
5021 <tt>shlibs</tt> system, which is very simple in its design:
5022 any package which <em>provides</em> a shared library also
5023 provides information on the package dependencies required to
5024 ensure the presence of this library, and any package which
5025 <em>uses</em> a shared library uses this information to
5026 determine the dependencies it requires. The files which
5027 contain the mapping from shared libraries to the necessary
5028 dependency information are called <file>shlibs</file> files.
5032 Thus, when a package is built which contains any shared
5033 libraries, it must provide a <file>shlibs</file> file for other
5034 packages to use, and when a package is built which contains
5035 any shared libraries or compiled binaries, it must run
5036 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5037 on these to determine the libraries used and hence the
5038 dependencies needed by this package.<footnote>
5040 In the past, the shared libraries linked to were
5041 determined by calling <prgn>ldd</prgn>, but now
5042 <prgn>objdump</prgn> is used to do this. The only
5043 change this makes to package building is that
5044 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5045 libraries, whereas in the past this was unnecessary.
5046 The rest of this footnote explains the advantage that
5051 We say that a binary <tt>foo</tt> <em>directly</em> uses
5052 a library <tt>libbar</tt> if it is explicitly linked
5053 with that library (that is, it uses the flag
5054 <tt>-lbar</tt> during the linking stage). Other
5055 libraries that are needed by <tt>libbar</tt> are linked
5056 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5057 linker will load them automatically when it loads
5058 <tt>libbar</tt>. A package should depend on
5059 the libraries it directly uses, and the dependencies for
5060 those libraries should automatically pull in the other
5065 Unfortunately, the <prgn>ldd</prgn> program shows both
5066 the directly and indirectly used libraries, meaning that
5067 the dependencies determined included both direct and
5068 indirect dependencies. The use of <prgn>objdump</prgn>
5069 avoids this problem by determining only the directly
5074 A good example of where this helps is the following. We
5075 could update <tt>libimlib</tt> with a new version that
5076 supports a new graphics format called dgf (but retaining
5077 the same major version number). If we used the old
5078 <prgn>ldd</prgn> method, every package that uses
5079 <tt>libimlib</tt> would need to be recompiled so it
5080 would also depend on <tt>libdgf</tt> or it wouldn't run
5081 due to missing symbols. However with the new system,
5082 packages using <tt>libimlib</tt> can rely on
5083 <tt>libimlib</tt> itself having the dependency on
5084 <tt>libdgf</tt> and so they would not need rebuilding.
5090 In the following sections, we will first describe where the
5091 various <tt>shlibs</tt> files are to be found, then how to
5092 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5093 file format and how to create them if your package contains a
5098 <heading>The <tt>shlibs</tt> files present on the system</heading>
5101 There are several places where <tt>shlibs</tt> files are
5102 found. The following list gives them in the order in which
5104 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5105 (The first one which gives the required information is used.)
5111 <p><file>debian/shlibs.local</file></p>
5114 This lists overrides for this package. Its use is
5115 described below (see <ref id="shlibslocal">).
5120 <p><file>/etc/dpkg/shlibs.override</file></p>
5123 This lists global overrides. This list is normally
5124 empty. It is maintained by the local system
5130 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5133 When packages are being built, any
5134 <file>debian/shlibs</file> files are copied into the
5135 control file area of the temporary build directory and
5136 given the name <file>shlibs</file>. These files give
5137 details of any shared libraries included in the
5139 An example may help here. Let us say that the
5140 source package <tt>foo</tt> generates two binary
5141 packages, <tt>libfoo2</tt> and
5142 <tt>foo-runtime</tt>. When building the binary
5143 packages, the two packages are created in the
5144 directories <file>debian/libfoo2</file> and
5145 <file>debian/foo-runtime</file> respectively.
5146 (<file>debian/tmp</file> could be used instead of one
5147 of these.) Since <tt>libfoo2</tt> provides the
5148 <tt>libfoo</tt> shared library, it will require a
5149 <tt>shlibs</tt> file, which will be installed in
5150 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5152 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5153 when <prgn>dpkg-shlibdeps</prgn> is run on the
5155 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5157 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5158 determine whether <tt>foo-prog</tt>'s library
5159 dependencies are satisfied by any of the libraries
5160 provided by <tt>libfoo2</tt>. For this reason,
5161 <prgn>dpkg-shlibdeps</prgn> must only be run once
5162 all of the individual binary packages'
5163 <tt>shlibs</tt> files have been installed into the
5170 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5173 These are the <file>shlibs</file> files corresponding to
5174 all of the packages installed on the system, and are
5175 maintained by the relevant package maintainers.
5180 <p><file>/etc/dpkg/shlibs.default</file></p>
5183 This file lists any shared libraries whose packages
5184 have failed to provide correct <file>shlibs</file> files.
5185 It was used when the <file>shlibs</file> setup was first
5186 introduced, but it is now normally empty. It is
5187 maintained by the <tt>dpkg</tt> maintainer.
5195 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5196 <file>shlibs</file> files</heading>
5200 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5201 into your <file>debian/rules</file> file. If your package
5202 contains only compiled binaries and libraries (but no scripts),
5203 you can use a command such as:
5204 <example compact="compact">
5205 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5206 debian/tmp/usr/lib/*
5208 Otherwise, you will need to explicitly list the compiled
5209 binaries and libraries.<footnote>
5210 If you are using <tt>debhelper</tt>, the
5211 <prgn>dh_shlibdeps</prgn> program will do this work for
5212 you. It will also correctly handle multi-binary
5218 This command puts the dependency information into the
5219 <file>debian/substvars</file> file, which is then used by
5220 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5221 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5222 field in the control file for this to work.
5226 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5227 done. If it does complain you might need to create your own
5228 <file>debian/shlibs.local</file> file, as explained below (see
5229 <ref id="shlibslocal">).
5233 If you have multiple binary packages, you will need to call
5234 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5235 compiled libraries or binaries. In such a case, you will
5236 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5237 utilities to specify a different <file>substvars</file> file.
5241 If you are creating a udeb for use in the Debian Installer, you
5242 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5243 the dependency line of type <tt>udeb</tt> by adding
5244 <tt>-tudeb</tt> as option<footnote>
5245 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5246 will automatically add this option if it knows it is
5248 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5249 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5250 fall back to the regular dependency line.
5254 For more details on dpkg-shlibdeps, please see
5255 <ref id="pkg-dpkg-shlibdeps"> and
5256 <manref name="dpkg-shlibdeps" section="1">.
5261 <heading>The <file>shlibs</file> File Format</heading>
5264 Each <file>shlibs</file> file has the same format. Lines
5265 beginning with <tt>#</tt> are considered to be comments and
5266 are ignored. Each line is of the form:
5267 <example compact="compact">
5268 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5273 We will explain this by reference to the example of the
5274 <tt>zlib1g</tt> package, which (at the time of writing)
5275 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5279 <var>type</var> is an optional element that indicates the type
5280 of package for which the line is valid. The only type currently
5281 in use is <tt>udeb</tt>. The colon and space after the type are
5286 <var>library-name</var> is the name of the shared library,
5287 in this case <tt>libz</tt>. (This must match the name part
5288 of the soname, see below.)
5292 <var>soname-version</var> is the version part of the soname of
5293 the library. The soname is the thing that must exactly match
5294 for the library to be recognized by the dynamic linker, and is
5296 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5297 example, <tt>libz.so.1</tt>.<footnote>
5298 This can be determined using the command
5299 <example compact="compact">
5300 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5303 The version part is the part which comes after
5304 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5308 <var>dependencies</var> has the same syntax as a dependency
5309 field in a binary package control file. It should give
5310 details of which packages are required to satisfy a binary
5311 built against the version of the library contained in the
5312 package. See <ref id="depsyntax"> for details.
5316 In our example, if the first version of the <tt>zlib1g</tt>
5317 package which contained a minor number of at least
5318 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5319 <tt>shlibs</tt> entry for this library could say:
5320 <example compact="compact">
5321 libz 1 zlib1g (>= 1:1.1.3)
5323 The version-specific dependency is to avoid warnings from
5324 the dynamic linker about using older shared libraries with
5329 As zlib1g also provides a udeb containing the shared library,
5330 there would also be a second line:
5331 <example compact="compact">
5332 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5338 <heading>Providing a <file>shlibs</file> file</heading>
5341 If your package provides a shared library, you need to create
5342 a <file>shlibs</file> file following the format described above.
5343 It is usual to call this file <file>debian/shlibs</file> (but if
5344 you have multiple binary packages, you might want to call it
5345 <file>debian/shlibs.<var>package</var></file> instead). Then
5346 let <file>debian/rules</file> install it in the control area:
5347 <example compact="compact">
5348 install -m644 debian/shlibs debian/tmp/DEBIAN
5350 or, in the case of a multi-binary package:
5351 <example compact="compact">
5352 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5354 An alternative way of doing this is to create the
5355 <file>shlibs</file> file in the control area directly from
5356 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5357 file at all,<footnote>
5358 This is what <prgn>dh_makeshlibs</prgn> in the
5359 <tt>debhelper</tt> suite does. If your package also has a udeb
5360 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5361 automatically generate the <tt>udeb:</tt> lines if you specify
5362 the name of the udeb with the <tt>--add-udeb</tt> option.
5364 since the <file>debian/shlibs</file> file itself is ignored by
5365 <prgn>dpkg-shlibdeps</prgn>.
5369 As <prgn>dpkg-shlibdeps</prgn> reads the
5370 <file>DEBIAN/shlibs</file> files in all of the binary packages
5371 being built from this source package, all of the
5372 <file>DEBIAN/shlibs</file> files should be installed before
5373 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5378 <sect1 id="shlibslocal">
5379 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5382 This file is intended only as a <em>temporary</em> fix if
5383 your binaries or libraries depend on a library whose package
5384 does not yet provide a correct <file>shlibs</file> file.
5388 We will assume that you are trying to package a binary
5389 <tt>foo</tt>. When you try running
5390 <prgn>dpkg-shlibdeps</prgn> you get the following error
5391 message (<tt>-O</tt> displays the dependency information on
5392 <tt>stdout</tt> instead of writing it to
5393 <tt>debian/substvars</tt>, and the lines have been wrapped
5394 for ease of reading):
5395 <example compact="compact">
5396 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5397 dpkg-shlibdeps: warning: unable to find dependency
5398 information for shared library libbar (soname 1,
5399 path /usr/lib/libbar.so.1, dependency field Depends)
5400 shlibs:Depends=libc6 (>= 2.2.2-2)
5402 You can then run <prgn>ldd</prgn> on the binary to find the
5403 full location of the library concerned:
5404 <example compact="compact">
5406 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5407 libc.so.6 => /lib/libc.so.6 (0x40032000)
5408 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5410 So the <prgn>foo</prgn> binary depends on the
5411 <prgn>libbar</prgn> shared library, but no package seems to
5412 provide a <file>*.shlibs</file> file handling
5413 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5414 determine the package responsible:
5415 <example compact="compact">
5416 $ dpkg -S /usr/lib/libbar.so.1
5417 bar1: /usr/lib/libbar.so.1
5418 $ dpkg -s bar1 | grep Version
5421 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5422 is the one we are using. Now we can file a bug against the
5423 <tt>bar1</tt> package and create our own
5424 <file>debian/shlibs.local</file> to locally fix the problem.
5425 Including the following line into your
5426 <file>debian/shlibs.local</file> file:
5427 <example compact="compact">
5428 libbar 1 bar1 (>= 1.0-1)
5430 should allow the package build to work.
5434 As soon as the maintainer of <tt>bar1</tt> provides a
5435 correct <file>shlibs</file> file, you should remove this line
5436 from your <file>debian/shlibs.local</file> file. (You should
5437 probably also then have a versioned <tt>Build-Depends</tt>
5438 on <tt>bar1</tt> to help ensure that others do not have the
5439 same problem building your package.)
5448 <chapt id="opersys"><heading>The Operating System</heading>
5451 <heading>File system hierarchy</heading>
5455 <heading>File system Structure</heading>
5458 The location of all installed files and directories must
5459 comply with the File system Hierarchy Standard (FHS),
5460 version 2.3, with the exceptions noted below, and except
5461 where doing so would violate other terms of Debian
5462 Policy. The following exceptions to the FHS apply:
5467 Legacy XFree86 servers are permitted to retain the
5468 configuration file location
5469 <file>/etc/X11/XF86Config-4</file>.
5474 The optional rules related to user specific
5475 configuration files for applications are stored in
5476 the user's home directory are relaxed. It is
5477 recommended that such files start with the
5478 '<tt>.</tt>' character (a "dot file"), and if an
5479 application needs to create more than one dot file
5480 then the preferred placement is in a subdirectory
5481 with a name starting with a '.' character, (a "dot
5482 directory"). In this case it is recommended the
5483 configuration files not start with the '.'
5489 The requirement for amd64 to use <file>/lib64</file>
5490 for 64 bit binaries is removed.
5495 The requirement that
5496 <file>/usr/local/share/man</file> be "synonymous"
5497 with <file>/usr/local/man</file> is relaxed to a
5502 The requirement that windowmanagers with a single
5503 configuration file call it <file>system.*wmrc</file>
5504 is removed, as is the restriction that the window
5505 manager subdirectory be named identically to the
5506 window manager name itself.
5511 The requirement that boot manager configuration
5512 files live in <file>/etc</file>, or at least are
5513 symlinked there, is relaxed to a recommendation.
5520 The version of this document referred here can be
5521 found in the <tt>debian-policy</tt> package or on <url
5522 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5523 name="FHS (Debian copy)"> alongside this manual (or, if
5524 you have the <package>debian-policy</package> installed,
5526 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5527 (local copy)">). The
5528 latest version, which may be a more recent version, may
5530 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5531 Specific questions about following the standard may be
5532 asked on the <tt>debian-devel</tt> mailing list, or
5533 referred to the FHS mailing list (see the
5534 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5540 <heading>Site-specific programs</heading>
5543 As mandated by the FHS, packages must not place any
5544 files in <file>/usr/local</file>, either by putting them in
5545 the file system archive to be unpacked by <prgn>dpkg</prgn>
5546 or by manipulating them in their maintainer scripts.
5550 However, the package may create empty directories below
5551 <file>/usr/local</file> so that the system administrator knows
5552 where to place site-specific files. These are not
5553 directories <em>in</em> <file>/usr/local</file>, but are
5554 children of directories in <file>/usr/local</file>. These
5555 directories (<file>/usr/local/*/dir/</file>)
5556 should be removed on package removal if they are
5561 Note, that this applies only to directories <em>below</em>
5562 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5563 Packages must not create sub-directories in the directory
5564 <file>/usr/local</file> itself, except those listed in FHS,
5565 section 4.5. However, you may create directories below
5566 them as you wish. You must not remove any of the
5567 directories listed in 4.5, even if you created them.
5571 Since <file>/usr/local</file> can be mounted read-only from a
5572 remote server, these directories must be created and
5573 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5574 maintainer scripts and not be included in the
5575 <file>.deb</file> archive. These scripts must not fail if
5576 either of these operations fail.
5580 For example, the <tt>emacsen-common</tt> package could
5581 contain something like
5582 <example compact="compact">
5583 if [ ! -e /usr/local/share/emacs ]
5585 if mkdir /usr/local/share/emacs 2>/dev/null
5587 chown root:staff /usr/local/share/emacs
5588 chmod 2775 /usr/local/share/emacs
5592 in its <prgn>postinst</prgn> script, and
5593 <example compact="compact">
5594 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5595 rmdir /usr/local/share/emacs 2>/dev/null || true
5597 in the <prgn>prerm</prgn> script. (Note that this form is
5598 used to ensure that if the script is interrupted, the
5599 directory <file>/usr/local/share/emacs</file> will still be
5604 If you do create a directory in <file>/usr/local</file> for
5605 local additions to a package, you should ensure that
5606 settings in <file>/usr/local</file> take precedence over the
5607 equivalents in <file>/usr</file>.
5611 However, because <file>/usr/local</file> and its contents are
5612 for exclusive use of the local administrator, a package
5613 must not rely on the presence or absence of files or
5614 directories in <file>/usr/local</file> for normal operation.
5618 The <file>/usr/local</file> directory itself and all the
5619 subdirectories created by the package should (by default) have
5620 permissions 2775 (group-writable and set-group-id) and be
5621 owned by <tt>root:staff</tt>.
5626 <heading>The system-wide mail directory</heading>
5628 The system-wide mail directory is <file>/var/mail</file>. This
5629 directory is part of the base system and should not owned
5630 by any particular mail agents. The use of the old
5631 location <file>/var/spool/mail</file> is deprecated, even
5632 though the spool may still be physically located there.
5633 To maintain partial upgrade compatibility for systems
5634 which have <file>/var/spool/mail</file> as their physical mail
5635 spool, packages using <file>/var/mail</file> must depend on
5636 either <package>libc6</package> (>= 2.1.3-13), or on
5637 <package>base-files</package> (>= 2.2.0), or on later
5638 versions of either one of these packages.
5644 <heading>Users and groups</heading>
5647 <heading>Introduction</heading>
5649 The Debian system can be configured to use either plain or
5654 Some user ids (UIDs) and group ids (GIDs) are reserved
5655 globally for use by certain packages. Because some
5656 packages need to include files which are owned by these
5657 users or groups, or need the ids compiled into binaries,
5658 these ids must be used on any Debian system only for the
5659 purpose for which they are allocated. This is a serious
5660 restriction, and we should avoid getting in the way of
5661 local administration policies. In particular, many sites
5662 allocate users and/or local system groups starting at 100.
5666 Apart from this we should have dynamically allocated ids,
5667 which should by default be arranged in some sensible
5668 order, but the behavior should be configurable.
5672 Packages other than <tt>base-passwd</tt> must not modify
5673 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5674 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5679 <heading>UID and GID classes</heading>
5681 The UID and GID numbers are divided into classes as
5687 Globally allocated by the Debian project, the same
5688 on every Debian system. These ids will appear in
5689 the <file>passwd</file> and <file>group</file> files of all
5690 Debian systems, new ids in this range being added
5691 automatically as the <tt>base-passwd</tt> package is
5696 Packages which need a single statically allocated
5697 uid or gid should use one of these; their
5698 maintainers should ask the <tt>base-passwd</tt>
5706 Dynamically allocated system users and groups.
5707 Packages which need a user or group, but can have
5708 this user or group allocated dynamically and
5709 differently on each system, should use <tt>adduser
5710 --system</tt> to create the group and/or user.
5711 <prgn>adduser</prgn> will check for the existence of
5712 the user or group, and if necessary choose an unused
5713 id based on the ranges specified in
5714 <file>adduser.conf</file>.
5718 <tag>1000-29999:</tag>
5721 Dynamically allocated user accounts. By default
5722 <prgn>adduser</prgn> will choose UIDs and GIDs for
5723 user accounts in this range, though
5724 <file>adduser.conf</file> may be used to modify this
5729 <tag>30000-59999:</tag>
5734 <tag>60000-64999:</tag>
5737 Globally allocated by the Debian project, but only
5738 created on demand. The ids are allocated centrally
5739 and statically, but the actual accounts are only
5740 created on users' systems on demand.
5744 These ids are for packages which are obscure or
5745 which require many statically-allocated ids. These
5746 packages should check for and create the accounts in
5747 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5748 <prgn>adduser</prgn> if it has this facility) if
5749 necessary. Packages which are likely to require
5750 further allocations should have a "hole" left after
5751 them in the allocation, to give them room to
5756 <tag>65000-65533:</tag>
5764 User <tt>nobody</tt>. The corresponding gid refers
5765 to the group <tt>nogroup</tt>.
5772 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5773 not</em> be used, because it is the error return
5782 <sect id="sysvinit">
5783 <heading>System run levels and <file>init.d</file> scripts</heading>
5785 <sect1 id="/etc/init.d">
5786 <heading>Introduction</heading>
5789 The <file>/etc/init.d</file> directory contains the scripts
5790 executed by <prgn>init</prgn> at boot time and when the
5791 init state (or "runlevel") is changed (see <manref
5792 name="init" section="8">).
5796 There are at least two different, yet functionally
5797 equivalent, ways of handling these scripts. For the sake
5798 of simplicity, this document describes only the symbolic
5799 link method. However, it must not be assumed by maintainer
5800 scripts that this method is being used, and any automated
5801 manipulation of the various runlevel behaviors by
5802 maintainer scripts must be performed using
5803 <prgn>update-rc.d</prgn> as described below and not by
5804 manually installing or removing symlinks. For information
5805 on the implementation details of the other method,
5806 implemented in the <tt>file-rc</tt> package, please refer
5807 to the documentation of that package.
5811 These scripts are referenced by symbolic links in the
5812 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5813 runlevels, <prgn>init</prgn> looks in the directory
5814 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5815 execute, where <tt><var>n</var></tt> is the runlevel that
5816 is being changed to, or <tt>S</tt> for the boot-up
5821 The names of the links all have the form
5822 <file>S<var>mm</var><var>script</var></file> or
5823 <file>K<var>mm</var><var>script</var></file> where
5824 <var>mm</var> is a two-digit number and <var>script</var>
5825 is the name of the script (this should be the same as the
5826 name of the actual script in <file>/etc/init.d</file>).
5830 When <prgn>init</prgn> changes runlevel first the targets
5831 of the links whose names start with a <tt>K</tt> are
5832 executed, each with the single argument <tt>stop</tt>,
5833 followed by the scripts prefixed with an <tt>S</tt>, each
5834 with the single argument <tt>start</tt>. (The links are
5835 those in the <file>/etc/rc<var>n</var>.d</file> directory
5836 corresponding to the new runlevel.) The <tt>K</tt> links
5837 are responsible for killing services and the <tt>S</tt>
5838 link for starting services upon entering the runlevel.
5842 For example, if we are changing from runlevel 2 to
5843 runlevel 3, init will first execute all of the <tt>K</tt>
5844 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5845 all of the <tt>S</tt> prefixed scripts in that directory.
5846 The links starting with <tt>K</tt> will cause the
5847 referred-to file to be executed with an argument of
5848 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5853 The two-digit number <var>mm</var> is used to determine
5854 the order in which to run the scripts: low-numbered links
5855 have their scripts run first. For example, the
5856 <tt>K20</tt> scripts will be executed before the
5857 <tt>K30</tt> scripts. This is used when a certain service
5858 must be started before another. For example, the name
5859 server <prgn>bind</prgn> might need to be started before
5860 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5861 can set up its access lists. In this case, the script
5862 that starts <prgn>bind</prgn> would have a lower number
5863 than the script that starts <prgn>inn</prgn> so that it
5865 <example compact="compact">
5872 The two runlevels 0 (halt) and 6 (reboot) are slightly
5873 different. In these runlevels, the links with an
5874 <tt>S</tt> prefix are still called after those with a
5875 <tt>K</tt> prefix, but they too are called with the single
5876 argument <tt>stop</tt>.
5880 Also, if the script name ends in <tt>.sh</tt>, the script
5881 will be sourced in runlevel <tt>S</tt> rather than being
5882 run in a forked subprocess, but will be explicitly run by
5883 <prgn>sh</prgn> in all other runlevels.
5888 <heading>Writing the scripts</heading>
5891 Packages that include daemons for system services should
5892 place scripts in <file>/etc/init.d</file> to start or stop
5893 services at boot time or during a change of runlevel.
5894 These scripts should be named
5895 <file>/etc/init.d/<var>package</var></file>, and they should
5896 accept one argument, saying what to do:
5899 <tag><tt>start</tt></tag>
5900 <item>start the service,</item>
5902 <tag><tt>stop</tt></tag>
5903 <item>stop the service,</item>
5905 <tag><tt>restart</tt></tag>
5906 <item>stop and restart the service if it's already running,
5907 otherwise start the service</item>
5909 <tag><tt>reload</tt></tag>
5910 <item><p>cause the configuration of the service to be
5911 reloaded without actually stopping and restarting
5914 <tag><tt>force-reload</tt></tag>
5915 <item>cause the configuration to be reloaded if the
5916 service supports this, otherwise restart the
5920 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5921 <tt>force-reload</tt> options should be supported by all
5922 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5927 The <file>init.d</file> scripts must ensure that they will
5928 behave sensibly (i.e., returning success and not starting
5929 multiple copies of a service) if invoked with <tt>start</tt>
5930 when the service is already running, or with <tt>stop</tt>
5931 when it isn't, and that they don't kill unfortunately-named
5932 user processes. The best way to achieve this is usually to
5933 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5938 If a service reloads its configuration automatically (as
5939 in the case of <prgn>cron</prgn>, for example), the
5940 <tt>reload</tt> option of the <file>init.d</file> script
5941 should behave as if the configuration has been reloaded
5946 The <file>/etc/init.d</file> scripts must be treated as
5947 configuration files, either (if they are present in the
5948 package, that is, in the .deb file) by marking them as
5949 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5950 by managing them correctly in the maintainer scripts (see
5951 <ref id="config-files">). This is important since we want
5952 to give the local system administrator the chance to adapt
5953 the scripts to the local system, e.g., to disable a
5954 service without de-installing the package, or to specify
5955 some special command line options when starting a service,
5956 while making sure their changes aren't lost during the next
5961 These scripts should not fail obscurely when the
5962 configuration files remain but the package has been
5963 removed, as configuration files remain on the system after
5964 the package has been removed. Only when <prgn>dpkg</prgn>
5965 is executed with the <tt>--purge</tt> option will
5966 configuration files be removed. In particular, as the
5967 <file>/etc/init.d/<var>package</var></file> script itself is
5968 usually a <tt>conffile</tt>, it will remain on the system
5969 if the package is removed but not purged. Therefore, you
5970 should include a <tt>test</tt> statement at the top of the
5972 <example compact="compact">
5973 test -f <var>program-executed-later-in-script</var> || exit 0
5978 Often there are some variables in the <file>init.d</file>
5979 scripts whose values control the behavior of the scripts,
5980 and which a system administrator is likely to want to
5981 change. As the scripts themselves are frequently
5982 <tt>conffile</tt>s, modifying them requires that the
5983 administrator merge in their changes each time the package
5984 is upgraded and the <tt>conffile</tt> changes. To ease
5985 the burden on the system administrator, such configurable
5986 values should not be placed directly in the script.
5987 Instead, they should be placed in a file in
5988 <file>/etc/default</file>, which typically will have the same
5989 base name as the <file>init.d</file> script. This extra file
5990 should be sourced by the script when the script runs. It
5991 must contain only variable settings and comments in SUSv3
5992 <prgn>sh</prgn> format. It may either be a
5993 <tt>conffile</tt> or a configuration file maintained by
5994 the package maintainer scripts. See <ref id="config-files">
5999 To ensure that vital configurable values are always
6000 available, the <file>init.d</file> script should set default
6001 values for each of the shell variables it uses, either
6002 before sourcing the <file>/etc/default/</file> file or
6003 afterwards using something like the <tt>:
6004 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6005 script must behave sensibly and not fail if the
6006 <file>/etc/default</file> file is deleted.
6011 <heading>Interfacing with the initscript system</heading>
6014 Maintainers should use the abstraction layer provided by
6015 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6016 programs to deal with initscripts in their packages'
6017 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6018 and <prgn>postrm</prgn>.
6022 Directly managing the /etc/rc?.d links and directly
6023 invoking the <file>/etc/init.d/</file> initscripts should
6024 be done only by packages providing the initscript
6025 subsystem (such as <prgn>sysv-rc</prgn> and
6026 <prgn>file-rc</prgn>).
6030 <heading>Managing the links</heading>
6033 The program <prgn>update-rc.d</prgn> is provided for
6034 package maintainers to arrange for the proper creation and
6035 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6036 or their functional equivalent if another method is being
6037 used. This may be used by maintainers in their packages'
6038 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6042 You must not include any <file>/etc/rc<var>n</var>.d</file>
6043 symbolic links in the actual archive or manually create or
6044 remove the symbolic links in maintainer scripts; you must
6045 use the <prgn>update-rc.d</prgn> program instead. (The
6046 former will fail if an alternative method of maintaining
6047 runlevel information is being used.) You must not include
6048 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6049 in the archive either. (Only the <tt>sysvinit</tt>
6054 By default <prgn>update-rc.d</prgn> will start services in
6055 each of the multi-user state runlevels (2, 3, 4, and 5)
6056 and stop them in the halt runlevel (0), the single-user
6057 runlevel (1) and the reboot runlevel (6). The system
6058 administrator will have the opportunity to customize
6059 runlevels by simply adding, moving, or removing the
6060 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6061 symbolic links are being used, or by modifying
6062 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6067 To get the default behavior for your package, put in your
6068 <prgn>postinst</prgn> script
6069 <example compact="compact">
6070 update-rc.d <var>package</var> defaults
6072 and in your <prgn>postrm</prgn>
6073 <example compact="compact">
6074 if [ "$1" = purge ]; then
6075 update-rc.d <var>package</var> remove
6077 </example>. Note that if your package changes runlevels
6078 or priority, you may have to remove and recreate the links,
6079 since otherwise the old links may persist. Refer to the
6080 documentation of <prgn>update-rc.d</prgn>.
6084 This will use a default sequence number of 20. If it does
6085 not matter when or in which order the <file>init.d</file>
6086 script is run, use this default. If it does, then you
6087 should talk to the maintainer of the <prgn>sysvinit</prgn>
6088 package or post to <tt>debian-devel</tt>, and they will
6089 help you choose a number.
6093 For more information about using <tt>update-rc.d</tt>,
6094 please consult its man page <manref name="update-rc.d"
6100 <heading>Running initscripts</heading>
6102 The program <prgn>invoke-rc.d</prgn> is provided to make
6103 it easier for package maintainers to properly invoke an
6104 initscript, obeying runlevel and other locally-defined
6105 constraints that might limit a package's right to start,
6106 stop and otherwise manage services. This program may be
6107 used by maintainers in their packages' scripts.
6111 The package maintainer scripts must use
6112 <prgn>invoke-rc.d</prgn> to invoke the
6113 <file>/etc/init.d/*</file> initscripts, instead of
6114 calling them directly.
6118 By default, <prgn>invoke-rc.d</prgn> will pass any
6119 action requests (start, stop, reload, restart...) to the
6120 <file>/etc/init.d</file> script, filtering out requests
6121 to start or restart a service out of its intended
6126 Most packages will simply need to change:
6127 <example compact="compact">/etc/init.d/<package>
6128 <action></example> in their <prgn>postinst</prgn>
6129 and <prgn>prerm</prgn> scripts to:
6130 <example compact="compact">
6131 if which invoke-rc.d >/dev/null 2>&1; then
6132 invoke-rc.d <var>package</var> <action>
6134 /etc/init.d/<var>package</var> <action>
6140 A package should register its initscript services using
6141 <prgn>update-rc.d</prgn> before it tries to invoke them
6142 using <prgn>invoke-rc.d</prgn>. Invocation of
6143 unregistered services may fail.
6147 For more information about using
6148 <prgn>invoke-rc.d</prgn>, please consult its man page
6149 <manref name="invoke-rc.d" section="8">.
6155 <heading>Boot-time initialization</heading>
6158 There used to be another directory, <file>/etc/rc.boot</file>,
6159 which contained scripts which were run once per machine
6160 boot. This has been deprecated in favour of links from
6161 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6162 described in <ref id="/etc/init.d">. Packages must not
6163 place files in <file>/etc/rc.boot</file>.
6168 <heading>Example</heading>
6171 An example on which you can base your
6172 <file>/etc/init.d</file> scripts is found in
6173 <file>/etc/init.d/skeleton</file>.
6180 <heading>Console messages from <file>init.d</file> scripts</heading>
6183 This section describes the formats to be used for messages
6184 written to standard output by the <file>/etc/init.d</file>
6185 scripts. The intent is to improve the consistency of
6186 Debian's startup and shutdown look and feel. For this
6187 reason, please look very carefully at the details. We want
6188 the messages to have the same format in terms of wording,
6189 spaces, punctuation and case of letters.
6193 Here is a list of overall rules that should be used for
6194 messages generated by <file>/etc/init.d</file> scripts.
6200 The message should fit in one line (fewer than 80
6201 characters), start with a capital letter and end with
6202 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6206 If the script is performing some time consuming task in
6207 the background (not merely starting or stopping a
6208 program, for instance), an ellipsis (three dots:
6209 <tt>...</tt>) should be output to the screen, with no
6210 leading or tailing whitespace or line feeds.
6214 The messages should appear as if the computer is telling
6215 the user what it is doing (politely :-), but should not
6216 mention "it" directly. For example, instead of:
6217 <example compact="compact">
6218 I'm starting network daemons: nfsd mountd.
6220 the message should say
6221 <example compact="compact">
6222 Starting network daemons: nfsd mountd.
6229 <tt>init.d</tt> script should use the following standard
6230 message formats for the situations enumerated below.
6236 <p>When daemons are started</p>
6239 If the script starts one or more daemons, the output
6240 should look like this (a single line, no leading
6242 <example compact="compact">
6243 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6245 The <var>description</var> should describe the
6246 subsystem the daemon or set of daemons are part of,
6247 while <var>daemon-1</var> up to <var>daemon-n</var>
6248 denote each daemon's name (typically the file name of
6253 For example, the output of <file>/etc/init.d/lpd</file>
6255 <example compact="compact">
6256 Starting printer spooler: lpd.
6261 This can be achieved by saying
6262 <example compact="compact">
6263 echo -n "Starting printer spooler: lpd"
6264 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6267 in the script. If there are more than one daemon to
6268 start, the output should look like this:
6269 <example compact="compact">
6270 echo -n "Starting remote file system services:"
6271 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6272 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6273 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6276 This makes it possible for the user to see what is
6277 happening and when the final daemon has been started.
6278 Care should be taken in the placement of white spaces:
6279 in the example above the system administrators can
6280 easily comment out a line if they don't want to start
6281 a specific daemon, while the displayed message still
6287 <p>When a system parameter is being set</p>
6290 If you have to set up different system parameters
6291 during the system boot, you should use this format:
6292 <example compact="compact">
6293 Setting <var>parameter</var> to "<var>value</var>".
6298 You can use a statement such as the following to get
6300 <example compact="compact">
6301 echo "Setting DNS domainname to \"$domainname\"."
6306 Note that the same symbol (<tt>"</tt>) is used for the left
6307 and right quotation marks. A grave accent (<tt>`</tt>) is
6308 not a quote character; neither is an apostrophe
6314 <p>When a daemon is stopped or restarted</p>
6317 When you stop or restart a daemon, you should issue a
6318 message identical to the startup message, except that
6319 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6320 or <tt>Restarting</tt> respectively.
6324 For example, stopping the printer daemon will look like
6326 <example compact="compact">
6327 Stopping printer spooler: lpd.
6333 <p>When something is executed</p>
6336 There are several examples where you have to run a
6337 program at system startup or shutdown to perform a
6338 specific task, for example, setting the system's clock
6339 using <prgn>netdate</prgn> or killing all processes
6340 when the system shuts down. Your message should look
6342 <example compact="compact">
6343 Doing something very useful...done.
6345 You should print the <tt>done.</tt> immediately after
6346 the job has been completed, so that the user is
6347 informed why they have to wait. You can get this
6349 <example compact="compact">
6350 echo -n "Doing something very useful..."
6359 <p>When the configuration is reloaded</p>
6362 When a daemon is forced to reload its configuration
6363 files you should use the following format:
6364 <example compact="compact">
6365 Reloading <var>description</var> configuration...done.
6367 where <var>description</var> is the same as in the
6368 daemon starting message.
6376 <heading>Cron jobs</heading>
6379 Packages must not modify the configuration file
6380 <file>/etc/crontab</file>, and they must not modify the files in
6381 <file>/var/spool/cron/crontabs</file>.</p>
6384 If a package wants to install a job that has to be executed
6385 via cron, it should place a file with the name of the
6386 package in one or more of the following directories:
6387 <example compact="compact">
6393 As these directory names imply, the files within them are
6394 executed on an hourly, daily, weekly, or monthly basis,
6395 respectively. The exact times are listed in
6396 <file>/etc/crontab</file>.</p>
6399 All files installed in any of these directories must be
6400 scripts (e.g., shell scripts or Perl scripts) so that they
6401 can easily be modified by the local system administrator.
6402 In addition, they must be treated as configuration files.
6406 If a certain job has to be executed at some other frequency or
6407 at a specific time, the package should install a file
6408 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6409 same syntax as <file>/etc/crontab</file> and is processed by
6410 <prgn>cron</prgn> automatically. The file must also be
6411 treated as a configuration file. (Note that entries in the
6412 <file>/etc/cron.d</file> directory are not handled by
6413 <prgn>anacron</prgn>. Thus, you should only use this
6414 directory for jobs which may be skipped if the system is not
6418 The scripts or crontab entries in these directories should
6419 check if all necessary programs are installed before they
6420 try to execute them. Otherwise, problems will arise when a
6421 package was removed but not purged since configuration files
6422 are kept on the system in this situation.</p>
6426 <heading>Menus</heading>
6429 The Debian <tt>menu</tt> package provides a standard
6430 interface between packages providing applications and
6431 <em>menu programs</em> (either X window managers or
6432 text-based menu programs such as <prgn>pdmenu</prgn>).
6436 All packages that provide applications that need not be
6437 passed any special command line arguments for normal
6438 operation should register a menu entry for those
6439 applications, so that users of the <tt>menu</tt> package
6440 will automatically get menu entries in their window
6441 managers, as well in shells like <tt>pdmenu</tt>.
6445 Menu entries should follow the current menu policy.
6449 The menu policy can be found in the <tt>menu-policy</tt>
6450 files in the <tt>debian-policy</tt> package.
6451 It is also available from the Debian web mirrors at
6452 <tt><url name="/doc/packaging-manuals/menu-policy/"
6453 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6457 Please also refer to the <em>Debian Menu System</em>
6458 documentation that comes with the <package>menu</package>
6459 package for information about how to register your
6465 <heading>Multimedia handlers</heading>
6468 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6469 is a mechanism for encoding files and data streams and
6470 providing meta-information about them, in particular their
6471 type (e.g. audio or video) and format (e.g. PNG, HTML,
6476 Registration of MIME type handlers allows programs like mail
6477 user agents and web browsers to invoke these handlers to
6478 view, edit or display MIME types they don't support directly.
6482 Packages which provide the ability to view/show/play,
6483 compose, edit or print MIME types should register themselves
6484 as such following the current MIME support policy.
6488 The MIME support policy can be found in the <tt>mime-policy</tt>
6489 files in the <tt>debian-policy</tt> package.
6490 It is also available from the Debian web mirrors at
6491 <tt><url name="/doc/packaging-manuals/mime-policy/"
6492 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6498 <heading>Keyboard configuration</heading>
6501 To achieve a consistent keyboard configuration so that all
6502 applications interpret a keyboard event the same way, all
6503 programs in the Debian distribution must be configured to
6504 comply with the following guidelines.
6508 The following keys must have the specified interpretations:
6511 <tag><tt><--</tt></tag>
6512 <item>delete the character to the left of the cursor</item>
6514 <tag><tt>Delete</tt></tag>
6515 <item>delete the character to the right of the cursor</item>
6517 <tag><tt>Control+H</tt></tag>
6518 <item>emacs: the help prefix</item>
6521 The interpretation of any keyboard events should be
6522 independent of the terminal that is used, be it a virtual
6523 console, an X terminal emulator, an rlogin/telnet session,
6528 The following list explains how the different programs
6529 should be set up to achieve this:
6535 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6539 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6543 X translations are set up to make
6544 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6545 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6546 is the vt220 escape code for the "delete character"
6547 key). This must be done by loading the X resources
6548 using <prgn>xrdb</prgn> on all local X displays, not
6549 using the application defaults, so that the
6550 translation resources used correspond to the
6551 <prgn>xmodmap</prgn> settings.
6555 The Linux console is configured to make
6556 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6557 generate <tt>ESC [ 3 ~</tt>.
6561 X applications are configured so that <tt><</tt>
6562 deletes left, and <tt>Delete</tt> deletes right. Motif
6563 applications already work like this.
6567 Terminals should have <tt>stty erase ^?</tt> .
6571 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6572 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6573 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6577 Emacs is programmed to map <tt>KB_Backspace</tt> or
6578 the <tt>stty erase</tt> character to
6579 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6580 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6581 <tt>^H</tt> to <tt>help</tt> as always.
6585 Other applications use the <tt>stty erase</tt>
6586 character and <tt>kdch1</tt> for the two delete keys,
6587 with ASCII DEL being "delete previous character" and
6588 <tt>kdch1</tt> being "delete character under
6596 This will solve the problem except for the following
6603 Some terminals have a <tt><--</tt> key that cannot
6604 be made to produce anything except <tt>^H</tt>. On
6605 these terminals Emacs help will be unavailable on
6606 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6607 character takes precedence in Emacs, and has been set
6608 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6609 available) can be used instead.
6613 Some operating systems use <tt>^H</tt> for <tt>stty
6614 erase</tt>. However, modern telnet versions and all
6615 rlogin versions propagate <tt>stty</tt> settings, and
6616 almost all UNIX versions honour <tt>stty erase</tt>.
6617 Where the <tt>stty</tt> settings are not propagated
6618 correctly, things can be made to work by using
6619 <tt>stty</tt> manually.
6623 Some systems (including previous Debian versions) use
6624 <prgn>xmodmap</prgn> to arrange for both
6625 <tt><--</tt> and <tt>Delete</tt> to generate
6626 <tt>KB_Delete</tt>. We can change the behavior of
6627 their X clients using the same X resources that we use
6628 to do it for our own clients, or configure our clients
6629 using their resources when things are the other way
6630 around. On displays configured like this
6631 <tt>Delete</tt> will not work, but <tt><--</tt>
6636 Some operating systems have different <tt>kdch1</tt>
6637 settings in their <tt>terminfo</tt> database for
6638 <tt>xterm</tt> and others. On these systems the
6639 <tt>Delete</tt> key will not work correctly when you
6640 log in from a system conforming to our policy, but
6641 <tt><--</tt> will.
6648 <heading>Environment variables</heading>
6651 A program must not depend on environment variables to get
6652 reasonable defaults. (That's because these environment
6653 variables would have to be set in a system-wide
6654 configuration file like <file>/etc/profile</file>, which is not
6655 supported by all shells.)
6659 If a program usually depends on environment variables for its
6660 configuration, the program should be changed to fall back to
6661 a reasonable default configuration if these environment
6662 variables are not present. If this cannot be done easily
6663 (e.g., if the source code of a non-free program is not
6664 available), the program must be replaced by a small
6665 "wrapper" shell script which sets the environment variables
6666 if they are not already defined, and calls the original program.
6670 Here is an example of a wrapper script for this purpose:
6672 <example compact="compact">
6674 BAR=${BAR:-/var/lib/fubar}
6676 exec /usr/lib/foo/foo "$@"
6681 Furthermore, as <file>/etc/profile</file> is a configuration
6682 file of the <prgn>base-files</prgn> package, other packages must
6683 not put any environment variables or other commands into that
6688 <sect id="doc-base">
6689 <heading>Registering Documents using doc-base</heading>
6692 The <package>doc-base</package> package implements a
6693 flexible mechanism for handling and presenting
6694 documentation. The recommended practice is for every Debian
6695 package that provides online documentation (other than just
6696 manual pages) to register these documents with
6697 <package>doc-base</package> by installing a
6698 <package>doc-base</package> control file via the
6699 <prgn/install-docs/ script at installation time and
6700 de-register the manuals again when the package is removed.
6703 Please refer to the documentation that comes with the
6704 <package>doc-base</package> package for information and
6713 <heading>Files</heading>
6716 <heading>Binaries</heading>
6719 Two different packages must not install programs with
6720 different functionality but with the same filenames. (The
6721 case of two programs having the same functionality but
6722 different implementations is handled via "alternatives" or
6723 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6724 <ref id="conflicts"> respectively.) If this case happens,
6725 one of the programs must be renamed. The maintainers should
6726 report this to the <tt>debian-devel</tt> mailing list and
6727 try to find a consensus about which program will have to be
6728 renamed. If a consensus cannot be reached, <em>both</em>
6729 programs must be renamed.
6733 By default, when a package is being built, any binaries
6734 created should include debugging information, as well as
6735 being compiled with optimization. You should also turn on
6736 as many reasonable compilation warnings as possible; this
6737 makes life easier for porters, who can then look at build
6738 logs for possible problems. For the C programming language,
6739 this means the following compilation parameters should be
6741 <example compact="compact">
6743 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6745 INSTALL = install -s # (or use strip on the files in debian/tmp)
6750 Note that by default all installed binaries should be stripped,
6751 either by using the <tt>-s</tt> flag to
6752 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6753 the binaries after they have been copied into
6754 <file>debian/tmp</file> but before the tree is made into a
6759 Although binaries in the build tree should be compiled with
6760 debugging information by default, it can often be difficult to
6761 debug programs if they are also subjected to compiler
6762 optimization. For this reason, it is recommended to support the
6763 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6764 (see <ref id="debianrules-options">). This variable can contain
6765 several flags to change how a package is compiled and built.
6769 It is up to the package maintainer to decide what
6770 compilation options are best for the package. Certain
6771 binaries (such as computationally-intensive programs) will
6772 function better with certain flags (<tt>-O3</tt>, for
6773 example); feel free to use them. Please use good judgment
6774 here. Don't use flags for the sake of it; only use them
6775 if there is good reason to do so. Feel free to override
6776 the upstream author's ideas about which compilation
6777 options are best: they are often inappropriate for our
6783 <sect id="libraries">
6784 <heading>Libraries</heading>
6787 If the package is <strong>architecture: any</strong>, then
6788 the shared library compilation and linking flags must have
6789 <tt>-fPIC</tt>, or the package shall not build on some of
6790 the supported architectures<footnote>
6792 If you are using GCC, <tt>-fPIC</tt> produces code with
6793 relocatable position independent code, which is required for
6794 most architectures to create a shared library, with i386 and
6795 perhaps some others where non position independent code is
6796 permitted in a shared library.
6799 Position independent code may have a performance penalty,
6800 especially on <tt>i386</tt>. However, in most cases the
6801 speed penalty must be measured against the memory wasted on
6802 the few architectures where non position independent code is
6805 </footnote>. Any exception to this rule must be discussed on
6806 the mailing list <em>debian-devel@lists.debian.org</em>, and
6807 a rough consensus obtained. The reasons for not compiling
6808 with <tt>-fPIC</tt> flag must be recorded in the file
6809 <tt>README.Debian</tt>, and care must be taken to either
6810 restrict the architecture or arrange for <tt>-fPIC</tt> to
6811 be used on architectures where it is required.<footnote>
6813 Some of the reasons why this might be required is if the
6814 library contains hand crafted assembly code that is not
6815 relocatable, the speed penalty is excessive for compute
6816 intensive libs, and similar reasons.
6821 As to the static libraries, the common case is not to have
6822 relocatable code, since there is no benefit, unless in specific
6823 cases; therefore the static version must not be compiled
6824 with the <tt>-fPIC</tt> flag. Any exception to this rule
6825 should be discussed on the mailing list
6826 <em>debian-devel@lists.debian.org</em>, and the reasons for
6827 compiling with the <tt>-fPIC</tt> flag must be recorded in
6828 the file <tt>README.Debian</tt>. <footnote>
6830 Some of the reasons for linking static libraries with
6831 the <tt>-fPIC</tt> flag are if, for example, one needs a
6832 Perl API for a library that is under rapid development,
6833 and has an unstable API, so shared libraries are
6834 pointless at this phase of the library's development. In
6835 that case, since Perl needs a library with relocatable
6836 code, it may make sense to create a static library with
6837 relocatable code. Another reason cited is if you are
6838 distilling various libraries into a common shared
6839 library, like <tt>mklibs</tt> does in the Debian
6845 In other words, if both a shared and a static library is
6846 being built, each source unit (<tt>*.c</tt>, for example,
6847 for C files) will need to be compiled twice, for the normal
6851 You must specify the gcc option <tt>-D_REENTRANT</tt>
6852 when building a library (either static or shared) to make
6853 the library compatible with LinuxThreads.
6857 Although not enforced by the build tools, shared libraries
6858 must be linked against all libraries that they use symbols from
6859 in the same way that binaries are. This ensures the correct
6860 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6861 system and guarantees that all libraries can be safely opened
6862 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6863 option <tt>-Wl,-z,defs</tt> when building a shared library.
6864 Since this option enforces symbol resolution at build time,
6865 a missing library reference will be caught early as a fatal
6870 All installed shared libraries should be stripped with
6871 <example compact="compact">
6872 strip --strip-unneeded <var>your-lib</var>
6874 (The option <tt>--strip-unneeded</tt> makes
6875 <prgn>strip</prgn> remove only the symbols which aren't
6876 needed for relocation processing.) Shared libraries can
6877 function perfectly well when stripped, since the symbols for
6878 dynamic linking are in a separate part of the ELF object
6880 You might also want to use the options
6881 <tt>--remove-section=.comment</tt> and
6882 <tt>--remove-section=.note</tt> on both shared libraries
6883 and executables, and <tt>--strip-debug</tt> on static
6889 Note that under some circumstances it may be useful to
6890 install a shared library unstripped, for example when
6891 building a separate package to support debugging.
6895 Shared object files (often <file>.so</file> files) that are not
6896 public libraries, that is, they are not meant to be linked
6897 to by third party executables (binaries of other packages),
6898 should be installed in subdirectories of the
6899 <file>/usr/lib</file> directory. Such files are exempt from the
6900 rules that govern ordinary shared libraries, except that
6901 they must not be installed executable and should be
6903 A common example are the so-called "plug-ins",
6904 internal shared objects that are dynamically loaded by
6905 programs using <manref name="dlopen" section="3">.
6910 Packages containing shared libraries that may be linked to
6911 by other packages' binaries, but which for some
6912 <em>compelling</em> reason can not be installed in
6913 <file>/usr/lib</file> directory, may install the shared library
6914 files in subdirectories of the <file>/usr/lib</file> directory,
6915 in which case they should arrange to add that directory in
6916 <file>/etc/ld.so.conf</file> in the package's post-installation
6917 script, and remove it in the package's post-removal script.
6921 An ever increasing number of packages are using
6922 <prgn>libtool</prgn> to do their linking. The latest GNU
6923 libtools (>= 1.3a) can take advantage of the metadata in the
6924 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6925 files). The main advantage of <prgn>libtool</prgn>'s
6926 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6927 store and subsequently access metadata with respect to the
6928 libraries it builds. <prgn>libtool</prgn> will search for
6929 those files, which contain a lot of useful information about
6930 a library (such as library dependency information for static
6931 linking). Also, they're <em>essential</em> for programs
6932 using <tt>libltdl</tt>.<footnote>
6933 Although <prgn>libtool</prgn> is fully capable of
6934 linking against shared libraries which don't have
6935 <tt>.la</tt> files, as it is a mere shell script it can
6936 add considerably to the build time of a
6937 <prgn>libtool</prgn>-using package if that shell script
6938 has to derive all this information from first principles
6939 for each library every time it is linked. With the
6940 advent of <prgn>libtool</prgn> version 1.4 (and to a
6941 lesser extent <prgn>libtool</prgn> version 1.3), the
6942 <file>.la</file> files also store information about
6943 inter-library dependencies which cannot necessarily be
6944 derived after the <file>.la</file> file is deleted.
6949 Packages that use <prgn>libtool</prgn> to create shared
6950 libraries should include the <file>.la</file> files in the
6951 <tt>-dev</tt> package, unless the package relies on
6952 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6953 the <tt>.la</tt> files must go in the run-time library
6958 You must make sure that you use only released versions of
6959 shared libraries to build your packages; otherwise other
6960 users will not be able to run your binaries
6961 properly. Producing source packages that depend on
6962 unreleased compilers is also usually a bad
6969 <heading>Shared libraries</heading>
6971 This section has moved to <ref id="sharedlibs">.
6977 <heading>Scripts</heading>
6980 All command scripts, including the package maintainer
6981 scripts inside the package and used by <prgn>dpkg</prgn>,
6982 should have a <tt>#!</tt> line naming the shell to be used
6987 In the case of Perl scripts this should be
6988 <tt>#!/usr/bin/perl</tt>.
6992 When scripts are installed into a directory in the system
6993 PATH, the script name should not include an extension such
6994 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6995 language currently used to implement it.
6998 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6999 should almost certainly start with <tt>set -e</tt> so that
7000 errors are detected. Every script should use
7001 <tt>set -e</tt> or check the exit status of <em>every</em>
7006 Scripts may assume that <file>/bin/sh</file> implements the
7007 SUSv3 Shell Command Language<footnote>
7008 Single UNIX Specification, version 3, which is also IEEE
7009 1003.1-2004 (POSIX), and is available on the World Wide Web
7010 from <url id="http://www.unix.org/version3/online.html"
7011 name="The Open Group"> after free
7012 registration.</footnote>
7013 plus the following additional features not mandated by
7015 These features are in widespread use in the Linux community
7016 and are implemented in all of bash, dash, and ksh, the most
7017 common shells users may wish to use as <file>/bin/sh</file>.
7020 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7021 must not generate a newline.</item>
7022 <item><tt>test</tt>, if implemented as a shell built-in, must
7023 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7025 <item><tt>local</tt> to create a scoped variable must be
7026 supported; however, <tt>local</tt> may or may not preserve
7027 the variable value from an outer scope and may or may not
7028 support arguments more complex than simple variables. Only
7040 If a shell script requires non-SUSv3 features from the shell
7041 interpreter other than those listed above, the appropriate shell
7042 must be specified in the first line of the script (e.g.,
7043 <tt>#!/bin/bash</tt>) and the package must depend on the package
7044 providing the shell (unless the shell package is marked
7045 "Essential", as in the case of <prgn>bash</prgn>).
7049 You may wish to restrict your script to SUSv3 features plus the
7050 above set when possible so that it may use <file>/bin/sh</file>
7051 as its interpreter. If your script works with <prgn>dash</prgn>
7052 (originally called <prgn>ash</prgn>), it probably complies with
7053 the above requirements, but if you are in doubt, use
7054 <file>/bin/bash</file>.
7058 Perl scripts should check for errors when making any
7059 system calls, including <tt>open</tt>, <tt>print</tt>,
7060 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7064 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7065 scripting languages. See <em>Csh Programming Considered
7066 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7067 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7068 If an upstream package comes with <prgn>csh</prgn> scripts
7069 then you must make sure that they start with
7070 <tt>#!/bin/csh</tt> and make your package depend on the
7071 <prgn>c-shell</prgn> virtual package.
7075 Any scripts which create files in world-writeable
7076 directories (e.g., in <file>/tmp</file>) must use a
7077 mechanism which will fail atomically if a file with the same
7078 name already exists.
7082 The Debian base system provides the <prgn>tempfile</prgn>
7083 and <prgn>mktemp</prgn> utilities for use by scripts for
7090 <heading>Symbolic links</heading>
7093 In general, symbolic links within a top-level directory
7094 should be relative, and symbolic links pointing from one
7095 top-level directory into another should be absolute. (A
7096 top-level directory is a sub-directory of the root
7097 directory <file>/</file>.)
7101 In addition, symbolic links should be specified as short as
7102 possible, i.e., link targets like <file>foo/../bar</file> are
7107 Note that when creating a relative link using
7108 <prgn>ln</prgn> it is not necessary for the target of the
7109 link to exist relative to the working directory you're
7110 running <prgn>ln</prgn> from, nor is it necessary to change
7111 directory to the directory where the link is to be made.
7112 Simply include the string that should appear as the target
7113 of the link (this will be a pathname relative to the
7114 directory in which the link resides) as the first argument
7119 For example, in your <prgn>Makefile</prgn> or
7120 <file>debian/rules</file>, you can do things like:
7121 <example compact="compact">
7122 ln -fs gcc $(prefix)/bin/cc
7123 ln -fs gcc debian/tmp/usr/bin/cc
7124 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7125 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7130 A symbolic link pointing to a compressed file should always
7131 have the same file extension as the referenced file. (For
7132 example, if a file <file>foo.gz</file> is referenced by a
7133 symbolic link, the filename of the link has to end with
7134 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7139 <heading>Device files</heading>
7142 Packages must not include device files in the package file
7147 If a package needs any special device files that are not
7148 included in the base system, it must call
7149 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7150 after notifying the user<footnote>
7151 This notification could be done via a (low-priority)
7152 debconf message, or an echo (printf) statement.
7157 Packages must not remove any device files in the
7158 <prgn>postrm</prgn> or any other script. This is left to the
7159 system administrator.
7163 Debian uses the serial devices
7164 <file>/dev/ttyS*</file>. Programs using the old
7165 <file>/dev/cu*</file> devices should be changed to use
7166 <file>/dev/ttyS*</file>.
7170 <sect id="config-files">
7171 <heading>Configuration files</heading>
7174 <heading>Definitions</heading>
7178 <tag>configuration file</tag>
7180 A file that affects the operation of a program, or
7181 provides site- or host-specific information, or
7182 otherwise customizes the behavior of a program.
7183 Typically, configuration files are intended to be
7184 modified by the system administrator (if needed or
7185 desired) to conform to local policy or to provide
7186 more useful site-specific behavior.
7189 <tag><tt>conffile</tt></tag>
7191 A file listed in a package's <tt>conffiles</tt>
7192 file, and is treated specially by <prgn>dpkg</prgn>
7193 (see <ref id="configdetails">).
7199 The distinction between these two is important; they are
7200 not interchangeable concepts. Almost all
7201 <tt>conffile</tt>s are configuration files, but many
7202 configuration files are not <tt>conffiles</tt>.
7206 As noted elsewhere, <file>/etc/init.d</file> scripts,
7207 <file>/etc/default</file> files, scripts installed in
7208 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7209 configuration installed in <file>/etc/cron.d</file> must be
7210 treated as configuration files. In general, any script that
7211 embeds configuration information is de-facto a configuration
7212 file and should be treated as such.
7217 <heading>Location</heading>
7220 Any configuration files created or used by your package
7221 must reside in <file>/etc</file>. If there are several,
7222 consider creating a subdirectory of <file>/etc</file>
7223 named after your package.
7227 If your package creates or uses configuration files
7228 outside of <file>/etc</file>, and it is not feasible to modify
7229 the package to use <file>/etc</file> directly, put the files
7230 in <file>/etc</file> and create symbolic links to those files
7231 from the location that the package requires.
7236 <heading>Behavior</heading>
7239 Configuration file handling must conform to the following
7241 <list compact="compact">
7243 local changes must be preserved during a package
7247 configuration files must be preserved when the
7248 package is removed, and only deleted when the
7255 The easy way to achieve this behavior is to make the
7256 configuration file a <tt>conffile</tt>. This is
7257 appropriate only if it is possible to distribute a default
7258 version that will work for most installations, although
7259 some system administrators may choose to modify it. This
7260 implies that the default version will be part of the
7261 package distribution, and must not be modified by the
7262 maintainer scripts during installation (or at any other
7267 In order to ensure that local changes are preserved
7268 correctly, no package may contain or make hard links to
7269 conffiles.<footnote>
7270 Rationale: There are two problems with hard links.
7271 The first is that some editors break the link while
7272 editing one of the files, so that the two files may
7273 unwittingly become unlinked and different. The second
7274 is that <prgn>dpkg</prgn> might break the hard link
7275 while upgrading <tt>conffile</tt>s.
7280 The other way to do it is via the maintainer scripts. In
7281 this case, the configuration file must not be listed as a
7282 <tt>conffile</tt> and must not be part of the package
7283 distribution. If the existence of a file is required for
7284 the package to be sensibly configured it is the
7285 responsibility of the package maintainer to provide
7286 maintainer scripts which correctly create, update and
7287 maintain the file and remove it on purge. (See <ref
7288 id="maintainerscripts"> for more information.) These
7289 scripts must be idempotent (i.e., must work correctly if
7290 <prgn>dpkg</prgn> needs to re-run them due to errors
7291 during installation or removal), must cope with all the
7292 variety of ways <prgn>dpkg</prgn> can call maintainer
7293 scripts, must not overwrite or otherwise mangle the user's
7294 configuration without asking, must not ask unnecessary
7295 questions (particularly during upgrades), and must
7296 otherwise be good citizens.
7300 The scripts are not required to configure every possible
7301 option for the package, but only those necessary to get
7302 the package running on a given system. Ideally the
7303 sysadmin should not have to do any configuration other
7304 than that done (semi-)automatically by the
7305 <prgn>postinst</prgn> script.
7309 A common practice is to create a script called
7310 <file><var>package</var>-configure</file> and have the
7311 package's <prgn>postinst</prgn> call it if and only if the
7312 configuration file does not already exist. In certain
7313 cases it is useful for there to be an example or template
7314 file which the maintainer scripts use. Such files should
7315 be in <file>/usr/share/<var>package</var></file> or
7316 <file>/usr/lib/<var>package</var></file> (depending on whether
7317 they are architecture-independent or not). There should
7318 be symbolic links to them from
7319 <file>/usr/share/doc/<var>package</var>/examples</file> if
7320 they are examples, and should be perfectly ordinary
7321 <prgn>dpkg</prgn>-handled files (<em>not</em>
7322 configuration files).
7326 These two styles of configuration file handling must
7327 not be mixed, for that way lies madness:
7328 <prgn>dpkg</prgn> will ask about overwriting the file
7329 every time the package is upgraded.
7334 <heading>Sharing configuration files</heading>
7337 Packages which specify the same file as a
7338 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7339 with each other. (This is an instance of the general rule
7340 about not sharing files. Note that neither alternatives
7341 nor diversions are likely to be appropriate in this case;
7342 in particular, <prgn>dpkg</prgn> does not handle diverted
7343 <tt>conffile</tt>s well.)
7347 The maintainer scripts must not alter a <tt>conffile</tt>
7348 of <em>any</em> package, including the one the scripts
7353 If two or more packages use the same configuration file
7354 and it is reasonable for both to be installed at the same
7355 time, one of these packages must be defined as
7356 <em>owner</em> of the configuration file, i.e., it will be
7357 the package which handles that file as a configuration
7358 file. Other packages that use the configuration file must
7359 depend on the owning package if they require the
7360 configuration file to operate. If the other package will
7361 use the configuration file if present, but is capable of
7362 operating without it, no dependency need be declared.
7366 If it is desirable for two or more related packages to
7367 share a configuration file <em>and</em> for all of the
7368 related packages to be able to modify that configuration
7369 file, then the following should be done:
7370 <enumlist compact="compact">
7372 One of the related packages (the "owning" package)
7373 will manage the configuration file with maintainer
7374 scripts as described in the previous section.
7377 The owning package should also provide a program
7378 that the other packages may use to modify the
7382 The related packages must use the provided program
7383 to make any desired modifications to the
7384 configuration file. They should either depend on
7385 the core package to guarantee that the configuration
7386 modifier program is available or accept gracefully
7387 that they cannot modify the configuration file if it
7388 is not. (This is in addition to the fact that the
7389 configuration file may not even be present in the
7396 Sometimes it's appropriate to create a new package which
7397 provides the basic infrastructure for the other packages
7398 and which manages the shared configuration files. (The
7399 <tt>sgml-base</tt> package is a good example.)
7404 <heading>User configuration files ("dotfiles")</heading>
7407 The files in <file>/etc/skel</file> will automatically be
7408 copied into new user accounts by <prgn>adduser</prgn>.
7409 No other program should reference the files in
7410 <file>/etc/skel</file>.
7414 Therefore, if a program needs a dotfile to exist in
7415 advance in <file>$HOME</file> to work sensibly, that dotfile
7416 should be installed in <file>/etc/skel</file> and treated as a
7421 However, programs that require dotfiles in order to
7422 operate sensibly are a bad thing, unless they do create
7423 the dotfiles themselves automatically.
7427 Furthermore, programs should be configured by the Debian
7428 default installation to behave as closely to the upstream
7429 default behavior as possible.
7433 Therefore, if a program in a Debian package needs to be
7434 configured in some way in order to operate sensibly, that
7435 should be done using a site-wide configuration file placed
7436 in <file>/etc</file>. Only if the program doesn't support a
7437 site-wide default configuration and the package maintainer
7438 doesn't have time to add it may a default per-user file be
7439 placed in <file>/etc/skel</file>.
7443 <file>/etc/skel</file> should be as empty as we can make it.
7444 This is particularly true because there is no easy (or
7445 necessarily desirable) mechanism for ensuring that the
7446 appropriate dotfiles are copied into the accounts of
7447 existing users when a package is installed.
7453 <heading>Log files</heading>
7455 Log files should usually be named
7456 <file>/var/log/<var>package</var>.log</file>. If you have many
7457 log files, or need a separate directory for permission
7458 reasons (<file>/var/log</file> is writable only by
7459 <file>root</file>), you should usually create a directory named
7460 <file>/var/log/<var>package</var></file> and place your log
7465 Log files must be rotated occasionally so that they don't
7466 grow indefinitely; the best way to do this is to drop a log
7467 rotation configuration file into the directory
7468 <file>/etc/logrotate.d</file> and use the facilities provided by
7469 logrotate.<footnote>
7471 The traditional approach to log files has been to set up
7472 <em>ad hoc</em> log rotation schemes using simple shell
7473 scripts and cron. While this approach is highly
7474 customizable, it requires quite a lot of sysadmin work.
7475 Even though the original Debian system helped a little
7476 by automatically installing a system which can be used
7477 as a template, this was deemed not enough.
7481 The use of <prgn>logrotate</prgn>, a program developed
7482 by Red Hat, is better, as it centralizes log management.
7483 It has both a configuration file
7484 (<file>/etc/logrotate.conf</file>) and a directory where
7485 packages can drop their individual log rotation
7486 configurations (<file>/etc/logrotate.d</file>).
7489 Here is a good example for a logrotate config
7490 file (for more information see <manref name="logrotate"
7492 <example compact="compact">
7493 /var/log/foo/*.log {
7498 /etc/init.d/foo force-reload
7502 This rotates all files under <file>/var/log/foo</file>, saves 12
7503 compressed generations, and forces the daemon to reload its
7504 configuration information after the log rotation.
7508 Log files should be removed when the package is
7509 purged (but not when it is only removed). This should be
7510 done by the <prgn>postrm</prgn> script when it is called
7511 with the argument <tt>purge</tt> (see <ref
7512 id="removedetails">).
7517 <heading>Permissions and owners</heading>
7520 The rules in this section are guidelines for general use.
7521 If necessary you may deviate from the details below.
7522 However, if you do so you must make sure that what is done
7523 is secure and you should try to be as consistent as possible
7524 with the rest of the system. You should probably also
7525 discuss it on <prgn>debian-devel</prgn> first.
7529 Files should be owned by <tt>root:root</tt>, and made
7530 writable only by the owner and universally readable (and
7531 executable, if appropriate), that is mode 644 or 755.
7535 Directories should be mode 755 or (for group-writability)
7536 mode 2775. The ownership of the directory should be
7537 consistent with its mode: if a directory is mode 2775, it
7538 should be owned by the group that needs write access to
7541 When a package is upgraded, and the owner or permissions
7542 of a file included in the package has changed, dpkg
7543 arranges for the ownership and permissions to be
7544 correctly set upon installation. However, this does not
7545 extend to directories; the permissions and ownership of
7546 directories already on the system does not change on
7547 install or upgrade of packages. This makes sense, since
7548 otherwise common directories like <tt>/usr</tt> would
7549 always be in flux. To correctly change permissions of a
7550 directory the package owns, explicit action is required,
7551 usually in the <tt>postinst</tt> script. Care must be
7552 taken to handle downgrades as well, in that case.
7559 Setuid and setgid executables should be mode 4755 or 2755
7560 respectively, and owned by the appropriate user or group.
7561 They should not be made unreadable (modes like 4711 or
7562 2711 or even 4111); doing so achieves no extra security,
7563 because anyone can find the binary in the freely available
7564 Debian package; it is merely inconvenient. For the same
7565 reason you should not restrict read or execute permissions
7566 on non-set-id executables.
7570 Some setuid programs need to be restricted to particular
7571 sets of users, using file permissions. In this case they
7572 should be owned by the uid to which they are set-id, and by
7573 the group which should be allowed to execute them. They
7574 should have mode 4754; again there is no point in making
7575 them unreadable to those users who must not be allowed to
7580 It is possible to arrange that the system administrator can
7581 reconfigure the package to correspond to their local
7582 security policy by changing the permissions on a binary:
7583 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7584 described below.<footnote>
7585 Ordinary files installed by <prgn>dpkg</prgn> (as
7586 opposed to <tt>conffile</tt>s and other similar objects)
7587 normally have their permissions reset to the distributed
7588 permissions when the package is reinstalled. However,
7589 the use of <prgn>dpkg-statoverride</prgn> overrides this
7590 default behavior. If you use this method, you should
7591 remember to describe <prgn>dpkg-statoverride</prgn> in
7592 the package documentation; being a relatively new
7593 addition to Debian, it is probably not yet well-known.
7595 Another method you should consider is to create a group for
7596 people allowed to use the program(s) and make any setuid
7597 executables executable only by that group.
7601 If you need to create a new user or group for your package
7602 there are two possibilities. Firstly, you may need to
7603 make some files in the binary package be owned by this
7604 user or group, or you may need to compile the user or
7605 group id (rather than just the name) into the binary
7606 (though this latter should be avoided if possible, as in
7607 this case you need a statically allocated id).</p>
7610 If you need a statically allocated id, you must ask for a
7611 user or group id from the <tt>base-passwd</tt> maintainer,
7612 and must not release the package until you have been
7613 allocated one. Once you have been allocated one you must
7614 either make the package depend on a version of the
7615 <tt>base-passwd</tt> package with the id present in
7616 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7617 your package to create the user or group itself with the
7618 correct id (using <tt>adduser</tt>) in its
7619 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7620 the <prgn>postinst</prgn> is to be preferred if it is
7621 possible, otherwise a pre-dependency will be needed on the
7622 <tt>adduser</tt> package.)
7626 On the other hand, the program might be able to determine
7627 the uid or gid from the user or group name at runtime, so
7628 that a dynamically allocated id can be used. In this case
7629 you should choose an appropriate user or group name,
7630 discussing this on <prgn>debian-devel</prgn> and checking
7631 with the <package/base-passwd/ maintainer that it is unique and that
7632 they do not wish you to use a statically allocated id
7633 instead. When this has been checked you must arrange for
7634 your package to create the user or group if necessary using
7635 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7636 <prgn>postinst</prgn> script (again, the latter is to be
7637 preferred if it is possible).
7641 Note that changing the numeric value of an id associated
7642 with a name is very difficult, and involves searching the
7643 file system for all appropriate files. You need to think
7644 carefully whether a static or dynamic id is required, since
7645 changing your mind later will cause problems.
7648 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7650 This section is not intended as policy, but as a
7651 description of the use of <prgn>dpkg-statoverride</prgn>.
7655 If a system administrator wishes to have a file (or
7656 directory or other such thing) installed with owner and
7657 permissions different from those in the distributed Debian
7658 package, they can use the <prgn>dpkg-statoverride</prgn>
7659 program to instruct <prgn>dpkg</prgn> to use the different
7660 settings every time the file is installed. Thus the
7661 package maintainer should distribute the files with their
7662 normal permissions, and leave it for the system
7663 administrator to make any desired changes. For example, a
7664 daemon which is normally required to be setuid root, but
7665 in certain situations could be used without being setuid,
7666 should be installed setuid in the <tt>.deb</tt>. Then the
7667 local system administrator can change this if they wish.
7668 If there are two standard ways of doing it, the package
7669 maintainer can use <tt>debconf</tt> to find out the
7670 preference, and call <prgn>dpkg-statoverride</prgn> in the
7671 maintainer script if necessary to accommodate the system
7672 administrator's choice. Care must be taken during
7673 upgrades to not override an existing setting.
7677 Given the above, <prgn>dpkg-statoverride</prgn> is
7678 essentially a tool for system administrators and would not
7679 normally be needed in the maintainer scripts. There is
7680 one type of situation, though, where calls to
7681 <prgn>dpkg-statoverride</prgn> would be needed in the
7682 maintainer scripts, and that involves packages which use
7683 dynamically allocated user or group ids. In such a
7684 situation, something like the following idiom can be very
7685 helpful in the package's <prgn>postinst</prgn>, where
7686 <tt>sysuser</tt> is a dynamically allocated id:
7688 for i in /usr/bin/foo /usr/sbin/bar
7690 # only do something when no setting exists
7691 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7693 #include: debconf processing, question about foo and bar
7694 if [ "$RET" = "true" ] ; then
7695 dpkg-statoverride --update --add sysuser root 4755 $i
7700 The corresponding <tt>dpkg-statoverride --remove</tt>
7701 calls can then be made unconditionally when the package is
7709 <chapt id="customized-programs">
7710 <heading>Customized programs</heading>
7712 <sect id="arch-spec">
7713 <heading>Architecture specification strings</heading>
7716 If a program needs to specify an <em>architecture specification
7717 string</em> in some place, it should select one of the
7718 strings provided by <tt>dpkg-architecture -L</tt>. The
7719 strings are in the format
7720 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7721 is sometimes elided, as when the OS is Linux.<footnote>
7722 <p>Currently, the strings are:
7723 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7724 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7725 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7726 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7727 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7728 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7729 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7730 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7731 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7732 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7733 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7734 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7735 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7736 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7737 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7738 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7739 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7740 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7741 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7742 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7743 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7744 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7745 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7746 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7747 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7748 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7749 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7750 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7751 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7752 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7753 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7754 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7755 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7756 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7757 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7758 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7759 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7765 Note that we don't want to use
7766 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7767 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7768 since this would make our programs incompatible with other
7769 Linux distributions. We also don't use something like
7770 <tt><var>arch</var>-unknown-linux</tt>, since the
7771 <tt>unknown</tt> does not look very good.
7776 <heading>Daemons</heading>
7779 The configuration files <file>/etc/services</file>,
7780 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7781 by the <prgn>netbase</prgn> package and must not be modified
7786 If a package requires a new entry in one of these files, the
7787 maintainer should get in contact with the
7788 <prgn>netbase</prgn> maintainer, who will add the entries
7789 and release a new version of the <prgn>netbase</prgn>
7794 The configuration file <file>/etc/inetd.conf</file> must not be
7795 modified by the package's scripts except via the
7796 <prgn>update-inetd</prgn> script or the
7797 <file>DebianNet.pm</file> Perl module. See their documentation
7798 for details on how to add entries.
7802 If a package wants to install an example entry into
7803 <file>/etc/inetd.conf</file>, the entry must be preceded with
7804 exactly one hash character (<tt>#</tt>). Such lines are
7805 treated as "commented out by user" by the
7806 <prgn>update-inetd</prgn> script and are not changed or
7807 activated during package updates.
7812 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7816 Some programs need to create pseudo-ttys. This should be done
7817 using Unix98 ptys if the C library supports it. The resulting
7818 program must not be installed setuid root, unless that
7819 is required for other functionality.
7823 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7824 <file>/var/log/lastlog</file> must be installed writable by
7825 group <tt>utmp</tt>. Programs which need to modify those
7826 files must be installed setgid <tt>utmp</tt>.
7831 <heading>Editors and pagers</heading>
7834 Some programs have the ability to launch an editor or pager
7835 program to edit or display a text document. Since there are
7836 lots of different editors and pagers available in the Debian
7837 distribution, the system administrator and each user should
7838 have the possibility to choose their preferred editor and
7843 In addition, every program should choose a good default
7844 editor/pager if none is selected by the user or system
7849 Thus, every program that launches an editor or pager must
7850 use the EDITOR or PAGER environment variable to determine
7851 the editor or pager the user wishes to use. If these
7852 variables are not set, the programs <file>/usr/bin/editor</file>
7853 and <file>/usr/bin/pager</file> should be used, respectively.
7857 These two files are managed through the <prgn>dpkg</prgn>
7858 "alternatives" mechanism. Thus every package providing an
7859 editor or pager must call the
7860 <prgn>update-alternatives</prgn> script to register these
7865 If it is very hard to adapt a program to make use of the
7866 EDITOR or PAGER variables, that program may be configured to
7867 use <file>/usr/bin/sensible-editor</file> and
7868 <file>/usr/bin/sensible-pager</file> as the editor or pager
7869 program respectively. These are two scripts provided in the
7870 Debian base system that check the EDITOR and PAGER variables
7871 and launch the appropriate program, and fall back to
7872 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7873 variable is not set.
7877 A program may also use the VISUAL environment variable to
7878 determine the user's choice of editor. If it exists, it
7879 should take precedence over EDITOR. This is in fact what
7880 <file>/usr/bin/sensible-editor</file> does.
7884 It is not required for a package to depend on
7885 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7886 package to provide such virtual packages.<footnote>
7887 The Debian base system already provides an editor and a
7893 <sect id="web-appl">
7894 <heading>Web servers and applications</heading>
7897 This section describes the locations and URLs that should
7898 be used by all web servers and web applications in the
7905 Cgi-bin executable files are installed in the
7907 <example compact="compact">
7908 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7910 and should be referred to as
7911 <example compact="compact">
7912 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7918 <p>Access to HTML documents</p>
7921 HTML documents for a package are stored in
7922 <file>/usr/share/doc/<var>package</var></file>
7923 and can be referred to as
7924 <example compact="compact">
7925 http://localhost/doc/<var>package</var>/<var>filename</var>
7930 The web server should restrict access to the document
7931 tree so that only clients on the same host can read
7932 the documents. If the web server does not support such
7933 access controls, then it should not provide access at
7934 all, or ask about providing access during installation.
7939 <p>Access to images</p>
7941 It is recommended that images for a package be stored
7942 in <tt>/usr/share/images/<var>package</var></tt> and
7943 may be referred to through an alias <tt>/images/</tt>
7946 http://localhost/images/<package>/<filename>
7953 <p>Web Document Root</p>
7956 Web Applications should try to avoid storing files in
7957 the Web Document Root. Instead they should use the
7958 /usr/share/doc/<var>package</var> directory for
7959 documents and register the Web Application via the
7960 <package>doc-base</package> package. If access to the
7961 web document root is unavoidable then use
7962 <example compact="compact">
7965 as the Document Root. This might be just a symbolic
7966 link to the location where the system administrator
7967 has put the real document root.
7970 <item><p>Providing httpd and/or httpd-cgi</p>
7972 All web servers should provide the virtual package
7973 <tt>httpd</tt>. If a web server has CGI support it should
7974 provide <tt>httpd-cgi</tt> additionally.
7977 All web applications which do not contain CGI scripts should
7978 depend on <tt>httpd</tt>, all those web applications which
7979 <tt>do</tt> contain CGI scripts, should depend on
7987 <sect id="mail-transport-agents">
7988 <heading>Mail transport, delivery and user agents</heading>
7991 Debian packages which process electronic mail, whether mail
7992 user agents (MUAs) or mail transport agents (MTAs), must
7993 ensure that they are compatible with the configuration
7994 decisions below. Failure to do this may result in lost
7995 mail, broken <tt>From:</tt> lines, and other serious brain
8000 The mail spool is <file>/var/mail</file> and the interface to
8001 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8002 the FHS). On older systems, the mail spool may be
8003 physically located in <file>/var/spool/mail</file>, but all
8004 access to the mail spool should be via the
8005 <file>/var/mail</file> symlink. The mail spool is part of the
8006 base system and not part of the MTA package.
8010 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8011 programs (such as IMAP daemons) must lock the mailbox in an
8012 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8013 be combined with dot locking. To avoid deadlocks, a program
8014 should use <tt>fcntl()</tt> first and dot locking after
8015 this, or alternatively implement the two locking methods in
8016 a non blocking way<footnote>
8017 If it is not possible to establish both locks, the
8018 system shouldn't wait for the second lock to be
8019 established, but remove the first lock, wait a (random)
8020 time, and start over locking again.
8021 </footnote>. Using the functions <tt>maillock</tt> and
8022 <tt>mailunlock</tt> provided by the
8023 <tt>liblockfile*</tt><footnote>
8024 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8025 to use these functions.
8026 </footnote> packages is the recommended way to realize this.
8030 Mailboxes are generally mode 660
8031 <tt><var>user</var>:mail</tt> unless the system
8032 administrator has chosen otherwise. A MUA may remove a
8033 mailbox (unless it has nonstandard permissions) in which
8034 case the MTA or another MUA must recreate it if needed.
8035 Mailboxes must be writable by group mail.
8039 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8040 be setgid mail to do the locking mentioned above (and
8041 must obviously avoid accessing other users' mailboxes
8042 using this privilege).</p>
8045 <file>/etc/aliases</file> is the source file for the system mail
8046 aliases (e.g., postmaster, usenet, etc.), it is the one
8047 which the sysadmin and <prgn>postinst</prgn> scripts may
8048 edit. After <file>/etc/aliases</file> is edited the program or
8049 human editing it must call <prgn>newaliases</prgn>. All MTA
8050 packages must come with a <prgn>newaliases</prgn> program,
8051 even if it does nothing, but older MTA packages did not do
8052 this so programs should not fail if <prgn>newaliases</prgn>
8053 cannot be found. Note that because of this, all MTA
8054 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8055 <tt>Replaces: mail-transport-agent</tt> control file
8060 The convention of writing <tt>forward to
8061 <var>address</var></tt> in the mailbox itself is not
8062 supported. Use a <tt>.forward</tt> file instead.</p>
8065 The <prgn>rmail</prgn> program used by UUCP
8066 for incoming mail should be <file>/usr/sbin/rmail</file>.
8067 Likewise, <prgn>rsmtp</prgn>, for receiving
8068 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8072 If your package needs to know what hostname to use on (for
8073 example) outgoing news and mail messages which are generated
8074 locally, you should use the file <file>/etc/mailname</file>. It
8075 will contain the portion after the username and <tt>@</tt>
8076 (at) sign for email addresses of users on the machine
8077 (followed by a newline).
8081 Such a package should check for the existence of this file
8082 when it is being configured. If it exists, it should be
8083 used without comment, although an MTA's configuration script
8084 may wish to prompt the user even if it finds that this file
8085 exists. If the file does not exist, the package should
8086 prompt the user for the value (preferably using
8087 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8088 as well as using it in the package's configuration. The
8089 prompt should make it clear that the name will not just be
8090 used by that package. For example, in this situation the
8091 <tt>inn</tt> package could say something like:
8092 <example compact="compact">
8093 Please enter the "mail name" of your system. This is the
8094 hostname portion of the address to be shown on outgoing
8095 news and mail messages. The default is
8096 <var>syshostname</var>, your system's host name. Mail
8097 name ["<var>syshostname</var>"]:
8099 where <var>syshostname</var> is the output of <tt>hostname
8105 <heading>News system configuration</heading>
8108 All the configuration files related to the NNTP (news)
8109 servers and clients should be located under
8110 <file>/etc/news</file>.</p>
8113 There are some configuration issues that apply to a number
8114 of news clients and server packages on the machine. These
8118 <tag><file>/etc/news/organization</file></tag>
8120 A string which should appear as the
8121 organization header for all messages posted
8122 by NNTP clients on the machine
8125 <tag><file>/etc/news/server</file></tag>
8127 Contains the FQDN of the upstream NNTP
8128 server, or localhost if the local machine is
8133 Other global files may be added as required for cross-package news
8140 <heading>Programs for the X Window System</heading>
8143 <heading>Providing X support and package priorities</heading>
8146 Programs that can be configured with support for the X
8147 Window System must be configured to do so and must declare
8148 any package dependencies necessary to satisfy their
8149 runtime requirements when using the X Window System. If
8150 such a package is of higher priority than the X packages
8151 on which it depends, it is required that either the
8152 X-specific components be split into a separate package, or
8153 that an alternative version of the package, which includes
8154 X support, be provided, or that the package's priority be
8160 <heading>Packages providing an X server</heading>
8163 Packages that provide an X server that, directly or
8164 indirectly, communicates with real input and display
8165 hardware should declare in their control data that they
8166 provide the virtual package <tt>xserver</tt>.<footnote>
8167 This implements current practice, and provides an
8168 actual policy for usage of the <tt>xserver</tt>
8169 virtual package which appears in the virtual packages
8170 list. In a nutshell, X servers that interface
8171 directly with the display and input hardware or via
8172 another subsystem (e.g., GGI) should provide
8173 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8174 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8180 <heading>Packages providing a terminal emulator</heading>
8183 Packages that provide a terminal emulator for the X Window
8184 System which meet the criteria listed below should declare
8185 in their control data that they provide the virtual
8186 package <tt>x-terminal-emulator</tt>. They should also
8187 register themselves as an alternative for
8188 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8193 To be an <tt>x-terminal-emulator</tt>, a program must:
8194 <list compact="compact">
8196 Be able to emulate a DEC VT100 terminal, or a
8197 compatible terminal.
8201 Support the command-line option <tt>-e
8202 <var>command</var></tt>, which creates a new
8203 terminal window<footnote>
8204 "New terminal window" does not necessarily mean
8205 a new top-level X window directly parented by
8206 the window manager; it could, if the terminal
8207 emulator application were so coded, be a new
8208 "view" in a multiple-document interface (MDI).
8210 and runs the specified <var>command</var>,
8211 interpreting the entirety of the rest of the command
8212 line as a command to pass straight to exec, in the
8213 manner that <tt>xterm</tt> does.
8217 Support the command-line option <tt>-T
8218 <var>title</var></tt>, which creates a new terminal
8219 window with the window title <var>title</var>.
8226 <heading>Packages providing a window manager</heading>
8229 Packages that provide a window manager should declare in
8230 their control data that they provide the virtual package
8231 <tt>x-window-manager</tt>. They should also register
8232 themselves as an alternative for
8233 <file>/usr/bin/x-window-manager</file>, with a priority
8234 calculated as follows:
8235 <list compact="compact">
8237 Start with a priority of 20.
8241 If the window manager supports the Debian menu
8242 system, add 20 points if this support is available
8243 in the package's default configuration (i.e., no
8244 configuration files belonging to the system or user
8245 have to be edited to activate the feature); if
8246 configuration files must be modified, add only 10
8252 If the window manager complies with <url
8253 id="http://www.freedesktop.org/Standards/wm-spec"
8254 name="The Window Manager Specification Project">,
8255 written by the <url id="http://www.freedesktop.org/"
8256 name="Free Desktop Group">, add 40 points.
8260 If the window manager permits the X session to be
8261 restarted using a <em>different</em> window manager
8262 (without killing the X server) in its default
8263 configuration, add 10 points; otherwise add none.
8270 <heading>Packages providing fonts</heading>
8273 Packages that provide fonts for the X Window
8275 For the purposes of Debian Policy, a "font for the X
8276 Window System" is one which is accessed via X protocol
8277 requests. Fonts for the Linux console, for PostScript
8278 renderer, or any other purpose, do not fit this
8279 definition. Any tool which makes such fonts available
8280 to the X Window System, however, must abide by this
8283 must do a number of things to ensure that they are both
8284 available without modification of the X or font server
8285 configuration, and that they do not corrupt files used by
8286 other font packages to register information about
8290 Fonts of any type supported by the X Window System
8291 must be in a separate binary package from any
8292 executables, libraries, or documentation (except
8293 that specific to the fonts shipped, such as their
8294 license information). If one or more of the fonts
8295 so packaged are necessary for proper operation of
8296 the package with which they are associated the font
8297 package may be Recommended; if the fonts merely
8298 provide an enhancement, a Suggests relationship may
8299 be used. Packages must not Depend on font
8301 This is because the X server may retrieve fonts
8302 from the local file system or over the network
8303 from an X font server; the Debian package system
8304 is empowered to deal only with the local
8310 BDF fonts must be converted to PCF fonts with the
8311 <prgn>bdftopcf</prgn> utility (available in the
8312 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8313 placed in a directory that corresponds to their
8315 <list compact="compact">
8317 100 dpi fonts must be placed in
8318 <file>/usr/share/fonts/X11/100dpi/</file>.
8322 75 dpi fonts must be placed in
8323 <file>/usr/share/fonts/X11/75dpi/</file>.
8327 Character-cell fonts, cursor fonts, and other
8328 low-resolution fonts must be placed in
8329 <file>/usr/share/fonts/X11/misc/</file>.
8335 Speedo fonts must be placed in
8336 <file>/usr/share/fonts/X11/Speedo/</file>.
8340 Type 1 fonts must be placed in
8341 <file>/usr/share/fonts/X11/Type1/</file>. If font
8342 metric files are available, they must be placed here
8347 Subdirectories of <file>/usr/share/fonts/X11/</file>
8348 other than those listed above must be neither
8349 created nor used. (The <file>PEX</file>, <file>CID</file>,
8350 and <file>cyrillic</file> directories are excepted for
8351 historical reasons, but installation of files into
8352 these directories remains discouraged.)
8356 Font packages may, instead of placing files directly
8357 in the X font directories listed above, provide
8358 symbolic links in that font directory pointing to
8359 the files' actual location in the filesystem. Such
8360 a location must comply with the FHS.
8364 Font packages should not contain both 75dpi and
8365 100dpi versions of a font. If both are available,
8366 they should be provided in separate binary packages
8367 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8368 the names of the packages containing the
8369 corresponding fonts.
8373 Fonts destined for the <file>misc</file> subdirectory
8374 should not be included in the same package as 75dpi
8375 or 100dpi fonts; instead, they should be provided in
8376 a separate package with <tt>-misc</tt> appended to
8381 Font packages must not provide the files
8382 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8383 <file>fonts.scale</file> in a font directory:
8386 <file>fonts.dir</file> files must not be provided at all.
8390 <file>fonts.alias</file> and <file>fonts.scale</file>
8391 files, if needed, should be provided in the
8393 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8394 where <var>fontdir</var> is the name of the
8396 <file>/usr/share/fonts/X11/</file> where the
8397 package's corresponding fonts are stored
8398 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8399 <var>package</var> is the name of the package
8400 that provides these fonts, and
8401 <var>extension</var> is either <tt>scale</tt>
8402 or <tt>alias</tt>, whichever corresponds to
8409 Font packages must declare a dependency on
8410 <tt>xfonts-utils</tt> in their control
8415 Font packages that provide one or more
8416 <file>fonts.scale</file> files as described above must
8417 invoke <prgn>update-fonts-scale</prgn> on each
8418 directory into which they installed fonts
8419 <em>before</em> invoking
8420 <prgn>update-fonts-dir</prgn> on that directory.
8421 This invocation must occur in both the
8422 <prgn>postinst</prgn> (for all arguments) and
8423 <prgn>postrm</prgn> (for all arguments except
8424 <tt>upgrade</tt>) scripts.
8428 Font packages that provide one or more
8429 <file>fonts.alias</file> files as described above must
8430 invoke <prgn>update-fonts-alias</prgn> on each
8431 directory into which they installed fonts. This
8432 invocation must occur in both the
8433 <prgn>postinst</prgn> (for all arguments) and
8434 <prgn>postrm</prgn> (for all arguments except
8435 <tt>upgrade</tt>) scripts.
8439 Font packages must invoke
8440 <prgn>update-fonts-dir</prgn> on each directory into
8441 which they installed fonts. This invocation must
8442 occur in both the <prgn>postinst</prgn> (for all
8443 arguments) and <prgn>postrm</prgn> (for all
8444 arguments except <tt>upgrade</tt>) scripts.
8448 Font packages must not provide alias names for the
8449 fonts they include which collide with alias names
8450 already in use by fonts already packaged.
8454 Font packages must not provide fonts with the same
8455 XLFD registry name as another font already packaged.
8462 <heading>Application defaults files</heading>
8465 Application defaults files must be installed in the
8466 directory <file>/etc/X11/app-defaults/</file> (use of a
8467 localized subdirectory of <file>/etc/X11/</file> as described
8468 in the <em>X Toolkit Intrinsics - C Language
8469 Interface</em> manual is also permitted). They must be
8470 registered as <tt>conffile</tt>s or handled as
8471 configuration files.
8475 Customization of programs' X resources may also be
8476 supported with the provision of a file with the same name
8477 as that of the package placed in the
8478 <file>/etc/X11/Xresources/</file> directory, which must
8479 registered as a <tt>conffile</tt> or handled as a
8480 configuration file.<footnote>
8481 Note that this mechanism is not the same as using
8482 app-defaults; app-defaults are tied to the client
8483 binary on the local file system, whereas X resources
8484 are stored in the X server and affect all connecting
8491 <heading>Installation directory issues</heading>
8494 Packages using the X Window System should not be
8495 configured to install files under the
8496 <file>/usr/X11R6/</file> directory. The
8497 <file>/usr/X11R6/</file> directory hierarchy should be
8498 regarded as obsolete.
8502 Programs that use GNU <prgn>autoconf</prgn> and
8503 <prgn>automake</prgn> are usually easily configured at
8504 compile time to use <file>/usr/</file> instead of
8505 <file>/usr/X11R6/</file>, and this should be done whenever
8506 possible. Configuration files for window managers and
8507 display managers should be placed in a subdirectory of
8508 <file>/etc/X11/</file> corresponding to the package name due
8509 to these programs' tight integration with the mechanisms
8510 of the X Window System. Application-level programs should
8511 use the <file>/etc/</file> directory unless otherwise mandated
8516 The installation of files into subdirectories
8517 of <file>/usr/X11R6/include/X11/</file> and
8518 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8519 package maintainers should determine if subdirectories of
8520 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8525 Packages should install any relevant files into the
8526 directories <file>/usr/include/X11/</file> and
8527 <file>/usr/lib/X11/</file>, but if they do so, they must
8528 pre-depend on <tt>x11-common (>=
8529 1:7.0.0)</tt><footnote>
8531 These libraries used to be all symbolic
8532 links. However, with <tt>X11R7</tt>,
8533 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8534 are now real directories, and packages
8535 <strong>should</strong> ship their files here instead
8536 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8537 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8538 responsible for converting these symlinks into
8546 <heading>The OSF/Motif and OpenMotif libraries</heading>
8549 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8550 OpenMotif libraries</em><footnote>
8551 OSF/Motif and OpenMotif are collectively referred to as
8552 "Motif" in this policy document.
8554 should be compiled against and tested with LessTif (a free
8555 re-implementation of Motif) instead. If the maintainer
8556 judges that the program or programs do not work
8557 sufficiently well with LessTif to be distributed and
8558 supported, but do so when compiled against Motif, then two
8559 versions of the package should be created; one linked
8560 statically against Motif and with <tt>-smotif</tt>
8561 appended to the package name, and one linked dynamically
8562 against Motif and with <tt>-dmotif</tt> appended to the
8567 Both Motif-linked versions are dependent
8568 upon non-DFSG-compliant software and thus cannot be
8569 uploaded to the <em>main</em> distribution; if the
8570 software is itself DFSG-compliant it may be uploaded to
8571 the <em>contrib</em> distribution. While known existing
8572 versions of Motif permit unlimited redistribution of
8573 binaries linked against the library (whether statically or
8574 dynamically), it is the package maintainer's
8575 responsibility to determine whether this is permitted by
8576 the license of the copy of Motif in their possession.
8582 <heading>Perl programs and modules</heading>
8585 Perl programs and modules should follow the current Perl policy.
8589 The Perl policy can be found in the <tt>perl-policy</tt>
8590 files in the <tt>debian-policy</tt> package.
8591 It is also available from the Debian web mirrors at
8592 <tt><url name="/doc/packaging-manuals/perl-policy/"
8593 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8598 <heading>Emacs lisp programs</heading>
8601 Please refer to the "Debian Emacs Policy" for details of how to
8602 package emacs lisp programs.
8606 The Emacs policy is available in
8607 <file>debian-emacs-policy.gz</file> of the
8608 <package>emacsen-common</package> package.
8609 It is also available from the Debian web mirrors at
8610 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8611 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8616 <heading>Games</heading>
8619 The permissions on <file>/var/games</file> are mode 755, owner
8620 <tt>root</tt> and group <tt>root</tt>.
8624 Each game decides on its own security policy.</p>
8627 Games which require protected, privileged access to
8628 high-score files, saved games, etc., may be made
8629 set-<em>group</em>-id (mode 2755) and owned by
8630 <tt>root:games</tt>, and use files and directories with
8631 appropriate permissions (770 <tt>root:games</tt>, for
8632 example). They must not be made
8633 set-<em>user</em>-id, as this causes security problems. (If
8634 an attacker can subvert any set-user-id game they can
8635 overwrite the executable of any other, causing other players
8636 of these games to run a Trojan horse program. With a
8637 set-group-id game the attacker only gets access to less
8638 important game data, and if they can get at the other
8639 players' accounts at all it will take considerably more
8643 Some packages, for example some fortune cookie programs, are
8644 configured by the upstream authors to install with their
8645 data files or other static information made unreadable so
8646 that they can only be accessed through set-id programs
8647 provided. You should not do this in a Debian package: anyone can
8648 download the <file>.deb</file> file and read the data from it,
8649 so there is no point making the files unreadable. Not
8650 making the files unreadable also means that you don't have
8651 to make so many programs set-id, which reduces the risk of a
8655 As described in the FHS, binaries of games should be
8656 installed in the directory <file>/usr/games</file>. This also
8657 applies to games that use the X Window System. Manual pages
8658 for games (X and non-X games) should be installed in
8659 <file>/usr/share/man/man6</file>.</p>
8665 <heading>Documentation</heading>
8668 <heading>Manual pages</heading>
8671 You should install manual pages in <prgn>nroff</prgn> source
8672 form, in appropriate places under <file>/usr/share/man</file>.
8673 You should only use sections 1 to 9 (see the FHS for more
8674 details). You must not install a pre-formatted "cat page".
8678 Each program, utility, and function should have an
8679 associated manual page included in the same package. It is
8680 suggested that all configuration files also have a manual
8681 page included as well. Manual pages for protocols and other
8682 auxiliary things are optional.
8686 If no manual page is available, this is considered as a bug
8687 and should be reported to the Debian Bug Tracking System (the
8688 maintainer of the package is allowed to write this bug report
8689 themselves, if they so desire). Do not close the bug report
8690 until a proper man page is available.<footnote>
8691 It is not very hard to write a man page. See the
8692 <url id="http://www.schweikhardt.net/man_page_howto.html"
8693 name="Man-Page-HOWTO">,
8694 <manref name="man" section="7">, the examples
8695 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8696 the helper programs <prgn>help2man</prgn>, or the
8697 directory <file>/usr/share/doc/man-db/examples</file>.
8702 You may forward a complaint about a missing man page to the
8703 upstream authors, and mark the bug as forwarded in the
8704 Debian bug tracking system. Even though the GNU Project do
8705 not in general consider the lack of a man page to be a bug,
8706 we do; if they tell you that they don't consider it a bug
8707 you should leave the bug in our bug tracking system open
8712 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8716 If one man page needs to be accessible via several names it
8717 is better to use a symbolic link than the <file>.so</file>
8718 feature, but there is no need to fiddle with the relevant
8719 parts of the upstream source to change from <file>.so</file> to
8720 symlinks: don't do it unless it's easy. You should not
8721 create hard links in the manual page directories, nor put
8722 absolute filenames in <file>.so</file> directives. The filename
8723 in a <file>.so</file> in a man page should be relative to the
8724 base of the man page tree (usually
8725 <file>/usr/share/man</file>). If you do not create any links
8726 (whether symlinks, hard links, or <tt>.so</tt> directives)
8727 in the file system to the alternate names of the man page,
8728 then you should not rely on <prgn>man</prgn> finding your
8729 man page under those names based solely on the information in
8730 the man page's header.<footnote>
8731 Supporting this in <prgn>man</prgn> often requires
8732 unreasonable processing time to find a manual page or to
8733 report that none exists, and moves knowledge into man's
8734 database that would be better left in the file system.
8735 This support is therefore deprecated and will cease to
8736 be present in the future.
8741 Manual pages in locale-specific subdirectories of
8742 <file>/usr/share/man</file> should use either UTF-8 or the usual
8743 legacy encoding for that language (normally the one corresponding
8744 to the shortest relevant locale name in
8745 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8746 <file>/usr/share/man/fr</file> should use either UTF-8 or
8747 ISO-8859-1.<footnote>
8748 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8749 use. In future, all manual pages will be required to use
8755 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8756 included in the subdirectory name unless it indicates a
8757 significant difference in the language, as this excludes
8758 speakers of the language in other countries.<footnote>
8759 At the time of writing, Chinese and Portuguese are the main
8760 languages with such differences, so <file>pt_BR</file>,
8761 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8766 Due to limitations in current implementations, all characters
8767 in the manual page source should be representable in the usual
8768 legacy encoding for that language, even if the file is
8769 actually encoded in UTF-8. Safe alternative ways to write many
8770 characters outside that range may be found in
8771 <manref name="groff_char" section="7">.
8776 <heading>Info documents</heading>
8779 Info documents should be installed in <file>/usr/share/info</file>.
8780 They should be compressed with <tt>gzip -9</tt>.
8784 Your package should call <prgn>install-info</prgn> to update
8785 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8786 script when called with a <tt>configure</tt> argument, for
8788 <example compact="compact">
8789 install-info --quiet --section Development Development \
8790 /usr/share/info/foobar.info
8794 It is a good idea to specify a section for the location of
8795 your program; this is done with the <tt>--section</tt>
8796 switch. To determine which section to use, you should look
8797 at <file>/usr/share/info/dir</file> on your system and choose the most
8798 relevant (or create a new section if none of the current
8799 sections are relevant). Note that the <tt>--section</tt>
8800 flag takes two arguments; the first is a regular expression
8801 to match (case-insensitively) against an existing section,
8802 the second is used when creating a new one.</p>
8805 You should remove the entries in the <prgn>prerm</prgn>
8806 script when called with a <tt>remove</tt> argument:
8807 <example compact="compact">
8808 install-info --quiet --remove /usr/share/info/foobar.info
8812 If <prgn>install-info</prgn> cannot find a description entry
8813 in the Info file you must supply one. See <manref
8814 name="install-info" section="8"> for details.</p>
8818 <heading>Additional documentation</heading>
8821 Any additional documentation that comes with the package may
8822 be installed at the discretion of the package maintainer.
8823 Plain text documentation should be installed in the directory
8824 <file>/usr/share/doc/<var>package</var></file>, where
8825 <var>package</var> is the name of the package, and
8826 compressed with <tt>gzip -9</tt> unless it is small.
8830 If a package comes with large amounts of documentation which
8831 many users of the package will not require you should create
8832 a separate binary package to contain it, so that it does not
8833 take up disk space on the machines of users who do not need
8834 or want it installed.</p>
8837 It is often a good idea to put text information files
8838 (<file>README</file>s, changelogs, and so forth) that come with
8839 the source package in <file>/usr/share/doc/<var>package</var></file>
8840 in the binary package. However, you don't need to install
8841 the instructions for building and installing the package, of
8845 Packages must not require the existence of any files in
8846 <file>/usr/share/doc/</file> in order to function
8848 The system administrator should be able to
8849 delete files in <file>/usr/share/doc/</file> without causing
8850 any programs to break.
8852 Any files that are referenced by programs but are also
8853 useful as stand alone documentation should be installed under
8854 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8855 <file>/usr/share/doc/<var>package</var></file>.
8859 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8860 link to another directory in <file>/usr/share/doc</file> only if
8861 the two packages both come from the same source and the
8862 first package Depends on the second.<footnote>
8864 Please note that this does not override the section on
8865 changelog files below, so the file
8866 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8867 must refer to the changelog for the current version of
8868 <var>package</var> in question. In practice, this means
8869 that the sources of the target and the destination of the
8870 symlink must be the same (same source package and
8877 Former Debian releases placed all additional documentation
8878 in <file>/usr/doc/<var>package</var></file>. This has been
8879 changed to <file>/usr/share/doc/<var>package</var></file>,
8880 and packages must not put documentation in the directory
8881 <file>/usr/doc/<var>package</var></file>. <footnote>
8882 At this phase of the transition, we no longer require a
8883 symbolic link in <file>/usr/doc/</file>. At a later point,
8884 policy shall change to make the symbolic links a bug.
8890 <heading>Preferred documentation formats</heading>
8893 The unification of Debian documentation is being carried out
8897 If your package comes with extensive documentation in a
8898 markup format that can be converted to various other formats
8899 you should if possible ship HTML versions in a binary
8900 package, in the directory
8901 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8902 its subdirectories.<footnote>
8903 The rationale: The important thing here is that HTML
8904 docs should be available in <em>some</em> package, not
8905 necessarily in the main binary package.
8910 Other formats such as PostScript may be provided at the
8911 package maintainer's discretion.
8915 <sect id="copyrightfile">
8916 <heading>Copyright information</heading>
8919 Every package must be accompanied by a verbatim copy of its
8920 copyright and distribution license in the file
8921 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8922 file must neither be compressed nor be a symbolic link.
8926 In addition, the copyright file must say where the upstream
8927 sources (if any) were obtained. It should name the original
8928 authors of the package and the Debian maintainer(s) who were
8929 involved with its creation.
8933 Packages in the <em>contrib</em> or <em>non-free</em> categories
8934 should state in the copyright file that the package is not part
8935 of the Debian GNU/Linux distribution and briefly explain why.
8939 A copy of the file which will be installed in
8940 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8941 be in <file>debian/copyright</file> in the source package.
8945 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8946 link to another directory in <file>/usr/share/doc</file> only if
8947 the two packages both come from the same source and the
8948 first package Depends on the second. These rules are
8949 important because copyrights must be extractable by
8954 Packages distributed under the UCB BSD license, the Apache
8955 license (version 2.0), the Artistic license, the GNU GPL
8956 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8957 the GNU FDL (version 1.2) should refer to the corresponding
8958 files under <file>/usr/share/common-licenses</file>,<footnote>
8961 <file>/usr/share/common-licenses/BSD</file>,
8962 <file>/usr/share/common-licenses/Apache-2.0</file>,
8963 <file>/usr/share/common-licenses/Artistic</file>,
8964 <file>/usr/share/common-licenses/GPL-2</file>,
8965 <file>/usr/share/common-licenses/GPL-3</file>,
8966 <file>/usr/share/common-licenses/LGPL-2</file>,
8967 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8968 <file>/usr/share/common-licenses/LGPL-3</file>, and
8969 <file>/usr/share/common-licenses/GFDL-1.2</file>
8972 </footnote> rather than quoting them in the copyright
8977 You should not use the copyright file as a general <file>README</file>
8978 file. If your package has such a file it should be
8979 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8980 <file>README.Debian</file> or some other appropriate place.</p>
8984 <heading>Examples</heading>
8987 Any examples (configurations, source files, whatever),
8988 should be installed in a directory
8989 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8990 files should not be referenced by any program: they're there
8991 for the benefit of the system administrator and users as
8992 documentation only. Architecture-specific example files
8993 should be installed in a directory
8994 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8996 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8997 latter directory itself may be a symbolic link to the
9002 If the purpose of a package is to provide examples, then the
9003 example files may be installed into
9004 <file>/usr/share/doc/<var>package</var></file>.
9008 <sect id="changelogs">
9009 <heading>Changelog files</heading>
9012 Packages that are not Debian-native must contain a
9013 compressed copy of the <file>debian/changelog</file> file from
9014 the Debian source tree in
9015 <file>/usr/share/doc/<var>package</var></file> with the name
9016 <file>changelog.Debian.gz</file>.
9020 If an upstream changelog is available, it should be accessible as
9021 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9022 plain text. If the upstream changelog is distributed in
9023 HTML, it should be made available in that form as
9024 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9025 and a plain text <file>changelog.gz</file> should be generated
9026 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9027 the upstream changelog files do not already conform to this
9028 naming convention, then this may be achieved either by
9029 renaming the files, or by adding a symbolic link, at the
9030 maintainer's discretion.<footnote>
9031 Rationale: People should not have to look in places for
9032 upstream changelogs merely because they are given
9033 different names or are distributed in HTML format.
9038 All of these files should be installed compressed using
9039 <tt>gzip -9</tt>, as they will become large with time even
9040 if they start out small.
9044 If the package has only one changelog which is used both as
9045 the Debian changelog and the upstream one because there is
9046 no separate upstream maintainer then that changelog should
9047 usually be installed as
9048 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9049 there is a separate upstream maintainer, but no upstream
9050 changelog, then the Debian changelog should still be called
9051 <file>changelog.Debian.gz</file>.
9055 For details about the format and contents of the Debian
9056 changelog file, please see <ref id="dpkgchangelog">.
9061 <appendix id="pkg-scope">
9062 <heading>Introduction and scope of these appendices</heading>
9065 These appendices are taken essentially verbatim from the
9066 now-deprecated Packaging Manual, version 3.2.1.0. They are
9067 the chapters which are likely to be of use to package
9068 maintainers and which have not already been included in the
9069 policy document itself. Most of these sections are very likely
9070 not relevant to policy; they should be treated as
9071 documentation for the packaging system. Please note that these
9072 appendices are included for convenience, and for historical
9073 reasons: they used to be part of policy package, and they have
9074 not yet been incorporated into dpkg documentation. However,
9075 they still have value, and hence they are presented here.
9079 They have not yet been checked to ensure that they are
9080 compatible with the contents of policy, and if there are any
9081 contradictions, the version in the main policy document takes
9082 precedence. The remaining chapters of the old Packaging
9083 Manual have also not been read in detail to ensure that there
9084 are not parts which have been left out. Both of these will be
9089 Certain parts of the Packaging manual were integrated into the
9090 Policy Manual proper, and removed from the appendices. Links
9091 have been placed from the old locations to the new ones.
9095 <prgn>dpkg</prgn> is a suite of programs for creating binary
9096 package files and installing and removing them on Unix
9098 <prgn>dpkg</prgn> is targeted primarily at Debian
9099 GNU/Linux, but may work on or be ported to other
9105 The binary packages are designed for the management of
9106 installed executable programs (usually compiled binaries) and
9107 their associated data, though source code examples and
9108 documentation are provided as part of some packages.</p>
9111 This manual describes the technical aspects of creating Debian
9112 binary packages (<file>.deb</file> files). It documents the
9113 behavior of the package management programs
9114 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9115 they interact with packages.</p>
9118 It also documents the interaction between
9119 <prgn>dselect</prgn>'s core and the access method scripts it
9120 uses to actually install the selected packages, and describes
9121 how to create a new access method.</p>
9124 This manual does not go into detail about the options and
9125 usage of the package building and installation tools. It
9126 should therefore be read in conjunction with those programs'
9131 The utility programs which are provided with <prgn>dpkg</prgn>
9132 for managing various system configuration and similar issues,
9133 such as <prgn>update-rc.d</prgn> and
9134 <prgn>install-info</prgn>, are not described in detail here -
9135 please see their man pages.
9139 It is assumed that the reader is reasonably familiar with the
9140 <prgn>dpkg</prgn> System Administrators' manual.
9141 Unfortunately this manual does not yet exist.
9145 The Debian version of the FSF's GNU hello program is provided
9146 as an example for people wishing to create Debian
9147 packages. The Debian <prgn>debmake</prgn> package is
9148 recommended as a very helpful tool in creating and maintaining
9149 Debian packages. However, while the tools and examples are
9150 helpful, they do not replace the need to read and follow the
9151 Policy and Programmer's Manual.</p>
9154 <appendix id="pkg-binarypkg">
9155 <heading>Binary packages (from old Packaging Manual)</heading>
9158 The binary package has two main sections. The first part
9159 consists of various control information files and scripts used
9160 by <prgn>dpkg</prgn> when installing and removing. See <ref
9161 id="pkg-controlarea">.
9165 The second part is an archive containing the files and
9166 directories to be installed.
9170 In the future binary packages may also contain other
9171 components, such as checksums and digital signatures. The
9172 format for the archive is described in full in the
9173 <file>deb(5)</file> man page.
9177 <sect id="pkg-bincreating"><heading>Creating package files -
9178 <prgn>dpkg-deb</prgn>
9182 All manipulation of binary package files is done by
9183 <prgn>dpkg-deb</prgn>; it's the only program that has
9184 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9185 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9186 will spot that the options requested are appropriate to
9187 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9192 In order to create a binary package you must make a
9193 directory tree which contains all the files and directories
9194 you want to have in the file system data part of the package.
9195 In Debian-format source packages this directory is usually
9196 <file>debian/tmp</file>, relative to the top of the package's
9201 They should have the locations (relative to the root of the
9202 directory tree you're constructing) ownerships and
9203 permissions which you want them to have on the system when
9208 With current versions of <prgn>dpkg</prgn> the uid/username
9209 and gid/groupname mappings for the users and groups being
9210 used should be the same on the system where the package is
9211 built and the one where it is installed.
9215 You need to add one special directory to the root of the
9216 miniature file system tree you're creating:
9217 <prgn>DEBIAN</prgn>. It should contain the control
9218 information files, notably the binary package control file
9219 (see <ref id="pkg-controlfile">).
9223 The <prgn>DEBIAN</prgn> directory will not appear in the
9224 file system archive of the package, and so won't be installed
9225 by <prgn>dpkg</prgn> when the package is installed.
9229 When you've prepared the package, you should invoke:
9231 dpkg --build <var>directory</var>
9236 This will build the package in
9237 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9238 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9239 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9244 See the man page <manref name="dpkg-deb" section="8"> for details of how
9245 to examine the contents of this newly-created file. You may find the
9246 output of following commands enlightening:
9248 dpkg-deb --info <var>filename</var>.deb
9249 dpkg-deb --contents <var>filename</var>.deb
9250 dpkg --contents <var>filename</var>.deb
9252 To view the copyright file for a package you could use this command:
9254 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9259 <sect id="pkg-controlarea">
9260 <heading>Package control information files</heading>
9263 The control information portion of a binary package is a
9264 collection of files with names known to <prgn>dpkg</prgn>.
9265 It will treat the contents of these files specially - some
9266 of them contain information used by <prgn>dpkg</prgn> when
9267 installing or removing the package; others are scripts which
9268 the package maintainer wants <prgn>dpkg</prgn> to run.
9272 It is possible to put other files in the package control
9273 area, but this is not generally a good idea (though they
9274 will largely be ignored).
9278 Here is a brief list of the control info files supported by
9279 <prgn>dpkg</prgn> and a summary of what they're used for.
9284 <tag><tt>control</tt>
9287 This is the key description file used by
9288 <prgn>dpkg</prgn>. It specifies the package's name
9289 and version, gives its description for the user,
9290 states its relationships with other packages, and so
9291 forth. See <ref id="sourcecontrolfiles"> and
9292 <ref id="binarycontrolfiles">.
9296 It is usually generated automatically from information
9297 in the source package by the
9298 <prgn>dpkg-gencontrol</prgn> program, and with
9299 assistance from <prgn>dpkg-shlibdeps</prgn>.
9300 See <ref id="pkg-sourcetools">.
9304 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9309 These are executable files (usually scripts) which
9310 <prgn>dpkg</prgn> runs during installation, upgrade
9311 and removal of packages. They allow the package to
9312 deal with matters which are particular to that package
9313 or require more complicated processing than that
9314 provided by <prgn>dpkg</prgn>. Details of when and
9315 how they are called are in <ref id="maintainerscripts">.
9319 It is very important to make these scripts idempotent.
9320 See <ref id="idempotency">.
9324 The maintainer scripts are guaranteed to run with a
9325 controlling terminal and can interact with the user.
9326 See <ref id="controllingterminal">.
9330 <tag><tt>conffiles</tt>
9333 This file contains a list of configuration files which
9334 are to be handled automatically by <prgn>dpkg</prgn>
9335 (see <ref id="pkg-conffiles">). Note that not necessarily
9336 every configuration file should be listed here.
9339 <tag><tt>shlibs</tt>
9342 This file contains a list of the shared libraries
9343 supplied by the package, with dependency details for
9344 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9345 when it determines what dependencies are required in a
9346 package control file. The <tt>shlibs</tt> file format
9347 is described on <ref id="shlibs">.
9352 <sect id="pkg-controlfile">
9353 <heading>The main control information file: <tt>control</tt></heading>
9356 The most important control information file used by
9357 <prgn>dpkg</prgn> when it installs a package is
9358 <tt>control</tt>. It contains all the package's "vital
9363 The binary package control files of packages built from
9364 Debian sources are made by a special tool,
9365 <prgn>dpkg-gencontrol</prgn>, which reads
9366 <file>debian/control</file> and <file>debian/changelog</file> to
9367 find the information it needs. See <ref id="pkg-sourcepkg"> for
9372 The fields in binary package control files are listed in
9373 <ref id="binarycontrolfiles">.
9377 A description of the syntax of control files and the purpose
9378 of the fields is available in <ref id="controlfields">.
9383 <heading>Time Stamps</heading>
9386 See <ref id="timestamps">.
9391 <appendix id="pkg-sourcepkg">
9392 <heading>Source packages (from old Packaging Manual) </heading>
9395 The Debian binary packages in the distribution are generated
9396 from Debian sources, which are in a special format to assist
9397 the easy and automatic building of binaries.
9400 <sect id="pkg-sourcetools">
9401 <heading>Tools for processing source packages</heading>
9404 Various tools are provided for manipulating source packages;
9405 they pack and unpack sources and help build of binary
9406 packages and help manage the distribution of new versions.
9410 They are introduced and typical uses described here; see
9411 <manref name="dpkg-source" section="1"> for full
9412 documentation about their arguments and operation.
9416 For examples of how to construct a Debian source package,
9417 and how to use those utilities that are used by Debian
9418 source packages, please see the <prgn>hello</prgn> example
9422 <sect1 id="pkg-dpkg-source">
9424 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9429 This program is frequently used by hand, and is also
9430 called from package-independent automated building scripts
9431 such as <prgn>dpkg-buildpackage</prgn>.
9435 To unpack a package it is typically invoked with
9437 dpkg-source -x <var>.../path/to/filename</var>.dsc
9442 with the <file><var>filename</var>.tar.gz</file> and
9443 <file><var>filename</var>.diff.gz</file> (if applicable) in
9444 the same directory. It unpacks into
9445 <file><var>package</var>-<var>version</var></file>, and if
9447 <file><var>package</var>-<var>version</var>.orig</file>, in
9448 the current directory.
9452 To create a packed source archive it is typically invoked:
9454 dpkg-source -b <var>package</var>-<var>version</var>
9459 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9460 <file>.diff.gz</file> (if appropriate) in the current
9461 directory. <prgn>dpkg-source</prgn> does not clean the
9462 source tree first - this must be done separately if it is
9467 See also <ref id="pkg-sourcearchives">.</p>
9471 <sect1 id="pkg-dpkg-buildpackage">
9473 <prgn>dpkg-buildpackage</prgn> - overall package-building
9478 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9479 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9480 targets <tt>clean</tt>, <tt>build</tt> and
9481 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9482 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9483 source and binary package upload.
9487 It is usually invoked by hand from the top level of the
9488 built or unbuilt source directory. It may be invoked with
9489 no arguments; useful arguments include:
9490 <taglist compact="compact">
9491 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9494 Do not sign the <tt>.changes</tt> file or the
9495 source package <tt>.dsc</tt> file, respectively.</p>
9497 <tag><tt>-p<var>sign-command</var></tt></tag>
9500 Invoke <var>sign-command</var> instead of finding
9501 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9502 <var>sign-command</var> must behave just like
9503 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9505 <tag><tt>-r<var>root-command</var></tt></tag>
9508 When root privilege is required, invoke the command
9509 <var>root-command</var>. <var>root-command</var>
9510 should invoke its first argument as a command, from
9511 the <prgn>PATH</prgn> if necessary, and pass its
9512 second and subsequent arguments to the command it
9513 calls. If no <var>root-command</var> is supplied
9514 then <var>dpkg-buildpackage</var> will take no
9515 special action to gain root privilege, so that for
9516 most packages it will have to be invoked as root to
9519 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9522 Two types of binary-only build and upload - see
9523 <manref name="dpkg-source" section="1">.
9530 <sect1 id="pkg-dpkg-gencontrol">
9532 <prgn>dpkg-gencontrol</prgn> - generates binary package
9537 This program is usually called from <file>debian/rules</file>
9538 (see <ref id="pkg-sourcetree">) in the top level of the source
9543 This is usually done just before the files and directories in the
9544 temporary directory tree where the package is being built have their
9545 permissions and ownerships set and the package is constructed using
9546 <prgn>dpkg-deb/</prgn>
9548 This is so that the control file which is produced has
9549 the right permissions
9554 <prgn>dpkg-gencontrol</prgn> must be called after all the
9555 files which are to go into the package have been placed in
9556 the temporary build directory, so that its calculation of
9557 the installed size of a package is correct.
9561 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9562 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9563 variable substitutions created by
9564 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9569 For a package which generates only one binary package, and
9570 which builds it in <file>debian/tmp</file> relative to the top
9571 of the source package, it is usually sufficient to call
9572 <prgn>dpkg-gencontrol</prgn>.
9576 Sources which build several binaries will typically need
9579 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9580 </example> The <tt>-P</tt> tells
9581 <prgn>dpkg-gencontrol</prgn> that the package is being
9582 built in a non-default directory, and the <tt>-p</tt>
9583 tells it which package's control file should be generated.
9587 <prgn>dpkg-gencontrol</prgn> also adds information to the
9588 list of files in <file>debian/files</file>, for the benefit of
9589 (for example) a future invocation of
9590 <prgn>dpkg-genchanges</prgn>.</p>
9593 <sect1 id="pkg-dpkg-shlibdeps">
9595 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9600 This program is usually called from <file>debian/rules</file>
9601 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9602 id="pkg-sourcetree">), in the top level of the source tree.
9606 Its arguments are executables and shared libraries
9609 They may be specified either in the locations in the
9610 source tree where they are created or in the locations
9611 in the temporary build tree where they are installed
9612 prior to binary package creation.
9614 </footnote> for which shared library dependencies should
9615 be included in the binary package's control file.
9619 If some of the found shared libraries should only
9620 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9621 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9622 by using the <tt>-d<var>dependency-field</var></tt> option
9623 before those executable(s). (Each <tt>-d</tt> option
9624 takes effect until the next <tt>-d</tt>.)
9628 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9629 output control file to be modified. Instead by default it
9630 adds to the <file>debian/substvars</file> file variable
9631 settings like <tt>shlibs:Depends</tt>. These variable
9632 settings must be referenced in dependency fields in the
9633 appropriate per-binary-package sections of the source
9638 For example, a package that generates an essential part
9639 which requires dependencies, and optional parts that
9640 which only require a recommendation, would separate those
9641 two sets of dependencies into two different fields.<footnote>
9642 At the time of writing, an example for this was the
9643 <package/xmms/ package, with Depends used for the xmms
9644 executable, Recommends for the plug-ins and Suggests for
9645 even more optional features provided by unzip.
9647 It can say in its <file>debian/rules</file>:
9649 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9650 -dRecommends <var>optionalpart anotheroptionalpart</var>
9652 and then in its main control file <file>debian/control</file>:
9655 Depends: ${shlibs:Depends}
9656 Recommends: ${shlibs:Recommends}
9662 Sources which produce several binary packages with
9663 different shared library dependency requirements can use
9664 the <tt>-p<var>varnameprefix</var></tt> option to override
9665 the default <tt>shlibs:</tt> prefix (one invocation of
9666 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9667 They can thus produce several sets of dependency
9668 variables, each of the form
9669 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9670 which can be referred to in the appropriate parts of the
9671 binary package control files.
9676 <sect1 id="pkg-dpkg-distaddfile">
9678 <prgn>dpkg-distaddfile</prgn> - adds a file to
9679 <file>debian/files</file>
9683 Some packages' uploads need to include files other than
9684 the source and binary package files.
9688 <prgn>dpkg-distaddfile</prgn> adds a file to the
9689 <file>debian/files</file> file so that it will be included in
9690 the <file>.changes</file> file when
9691 <prgn>dpkg-genchanges</prgn> is run.
9695 It is usually invoked from the <tt>binary</tt> target of
9696 <file>debian/rules</file>:
9698 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9700 The <var>filename</var> is relative to the directory where
9701 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9702 is usually the directory above the top level of the source
9703 tree. The <file>debian/rules</file> target should put the
9704 file there just before or just after calling
9705 <prgn>dpkg-distaddfile</prgn>.
9709 The <var>section</var> and <var>priority</var> are passed
9710 unchanged into the resulting <file>.changes</file> file.
9715 <sect1 id="pkg-dpkg-genchanges">
9717 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9722 This program is usually called by package-independent
9723 automatic building scripts such as
9724 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9729 It is usually called in the top level of a built source
9730 tree, and when invoked with no arguments will print out a
9731 straightforward <file>.changes</file> file based on the
9732 information in the source package's changelog and control
9733 file and the binary and source packages which should have
9739 <sect1 id="pkg-dpkg-parsechangelog">
9741 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9742 representation of a changelog
9746 This program is used internally by
9747 <prgn>dpkg-source</prgn> et al. It may also occasionally
9748 be useful in <file>debian/rules</file> and elsewhere. It
9749 parses a changelog, <file>debian/changelog</file> by default,
9750 and prints a control-file format representation of the
9751 information in it to standard output.
9755 <sect1 id="pkg-dpkg-architecture">
9757 <prgn>dpkg-architecture</prgn> - information about the build and
9762 This program can be used manually, but is also invoked by
9763 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9764 environment or make variables which specify the build and host
9765 architecture for the package building process.
9770 <sect id="pkg-sourcetree">
9771 <heading>The Debianised source tree</heading>
9774 The source archive scheme described later is intended to
9775 allow a Debianised source tree with some associated control
9776 information to be reproduced and transported easily. The
9777 Debianised source tree is a version of the original program
9778 with certain files added for the benefit of the
9779 Debianisation process, and with any other changes required
9780 made to the rest of the source code and installation
9785 The extra files created for Debian are in the subdirectory
9786 <file>debian</file> of the top level of the Debianised source
9787 tree. They are described below.
9790 <sect1 id="pkg-debianrules">
9791 <heading><file>debian/rules</file> - the main building script</heading>
9794 See <ref id="debianrules">.
9799 <sect1 id="pkg-dpkgchangelog">
9800 <heading><file>debian/changelog</file></heading>
9803 See <ref id="dpkgchangelog">.
9807 It is recommended that the entire changelog be encoded in the
9808 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9810 <url id="http://www.unicode.org/"
9811 name="Unicode">.<footnote>
9813 I think it is fairly obvious that we need to
9814 eventually transition to UTF-8 for our package
9815 infrastructure; it is really the only sane char-set in
9816 an international environment. Now, we can't switch to
9817 using UTF-8 for package control fields and the like
9818 until dpkg has better support, but one thing we can
9819 start doing today is requesting that Debian changelogs
9820 are UTF-8 encoded. At some point in time, we can start
9821 requiring them to do so.
9824 Checking for non-UTF8 characters in a changelog is
9825 trivial. Dump the file through
9826 <example>iconv -f utf-8 -t ucs-4</example>
9827 discard the output, and check the return
9828 value. If there are any characters in the stream
9829 which are invalid UTF-8 sequences, iconv will exit
9830 with an error code; and this will be the case for the
9831 vast majority of other character sets.
9836 <sect2><heading>Defining alternative changelog formats
9840 It is possible to use a different format to the standard
9841 one, by providing a parser for the format you wish to
9846 In order to have <tt>dpkg-parsechangelog</tt> run your
9847 parser, you must include a line within the last 40 lines
9848 of your file matching the Perl regular expression:
9849 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9850 parentheses should be the name of the format. For
9851 example, you might say:
9853 @@@ changelog-format: joebloggs @@@
9855 Changelog format names are non-empty strings of alphanumerics.
9859 If such a line exists then <tt>dpkg-parsechangelog</tt>
9860 will look for the parser as
9861 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9863 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9864 it is an error for it not to find it, or for it not to
9865 be an executable program. The default changelog format
9866 is <tt>dpkg</tt>, and a parser for it is provided with
9867 the <tt>dpkg</tt> package.
9871 The parser will be invoked with the changelog open on
9872 standard input at the start of the file. It should read
9873 the file (it may seek if it wishes) to determine the
9874 information required and return the parsed information
9875 to standard output in the form of a series of control
9876 fields in the standard format. By default it should
9877 return information about only the most recent version in
9878 the changelog; it should accept a
9879 <tt>-v<var>version</var></tt> option to return changes
9880 information from all versions present <em>strictly
9881 after</em> <var>version</var>, and it should then be an
9882 error for <var>version</var> not to be present in the
9888 <list compact="compact">
9889 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9890 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9891 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9892 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9893 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9894 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9895 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9900 If several versions are being returned (due to the use
9901 of <tt>-v</tt>), the urgency value should be of the
9902 highest urgency code listed at the start of any of the
9903 versions requested followed by the concatenated
9904 (space-separated) comments from all the versions
9905 requested; the maintainer, version, distribution and
9906 date should always be from the most recent version.
9910 For the format of the <tt>Changes</tt> field see
9911 <ref id="f-Changes">.
9915 If the changelog format which is being parsed always or
9916 almost always leaves a blank line between individual
9917 change notes these blank lines should be stripped out,
9918 so as to make the resulting output compact.
9922 If the changelog format does not contain date or package
9923 name information this information should be omitted from
9924 the output. The parser should not attempt to synthesize
9925 it or find it from other sources.
9929 If the changelog does not have the expected format the
9930 parser should exit with a nonzero exit status, rather
9931 than trying to muddle through and possibly generating
9936 A changelog parser may not interact with the user at
9942 <sect1 id="pkg-srcsubstvars">
9943 <heading><file>debian/substvars</file> and variable substitutions</heading>
9946 See <ref id="substvars">.
9952 <heading><file>debian/files</file></heading>
9955 See <ref id="debianfiles">.
9959 <sect1><heading><file>debian/tmp</file>
9963 This is the canonical temporary location for the
9964 construction of binary packages by the <tt>binary</tt>
9965 target. The directory <file>tmp</file> serves as the root of
9966 the file system tree as it is being constructed (for
9967 example, by using the package's upstream makefiles install
9968 targets and redirecting the output there), and it also
9969 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9970 id="pkg-bincreating">.
9974 If several binary packages are generated from the same
9975 source tree it is usual to use several
9976 <file>debian/tmp<var>something</var></file> directories, for
9977 example <file>tmp-a</file> or <file>tmp-doc</file>.
9981 Whatever <file>tmp</file> directories are created and used by
9982 <tt>binary</tt> must of course be removed by the
9983 <tt>clean</tt> target.</p></sect1>
9987 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9991 As it exists on the FTP site, a Debian source package
9992 consists of three related files. You must have the right
9993 versions of all three to be able to use them.
9998 <tag>Debian source control file - <tt>.dsc</tt></tag>
10000 This file is a control file used by <prgn>dpkg-source</prgn>
10001 to extract a source package.
10002 See <ref id="debiansourcecontrolfiles">.
10006 Original source archive -
10008 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10014 This is a compressed (with <tt>gzip -9</tt>)
10015 <prgn>tar</prgn> file containing the source code from
10016 the upstream authors of the program.
10021 Debianisation diff -
10023 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10029 This is a unified context diff (<tt>diff -u</tt>)
10030 giving the changes which are required to turn the
10031 original source into the Debian source. These changes
10032 may only include editing and creating plain files.
10033 The permissions of files, the targets of symbolic
10034 links and the characteristics of special files or
10035 pipes may not be changed and no files may be removed
10040 All the directories in the diff must exist, except the
10041 <file>debian</file> subdirectory of the top of the source
10042 tree, which will be created by
10043 <prgn>dpkg-source</prgn> if necessary when unpacking.
10047 The <prgn>dpkg-source</prgn> program will
10048 automatically make the <file>debian/rules</file> file
10049 executable (see below).</p></item>
10054 If there is no original source code - for example, if the
10055 package is specially prepared for Debian or the Debian
10056 maintainer is the same as the upstream maintainer - the
10057 format is slightly different: then there is no diff, and the
10059 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10060 and preferably contains a directory named
10061 <file><var>package</var>-<var>version</var></file>.
10066 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10069 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10070 Debian source package. However, if it is not available it
10071 is possible to unpack a Debian source archive as follows:
10072 <enumlist compact="compact">
10075 Untar the tarfile, which will create a <file>.orig</file>
10079 <p>Rename the <file>.orig</file> directory to
10080 <file><var>package</var>-<var>version</var></file>.</p>
10084 Create the subdirectory <file>debian</file> at the top of
10085 the source tree.</p>
10087 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10089 <item><p>Untar the tarfile again if you want a copy of the original
10090 source code alongside the Debianised version.</p>
10095 It is not possible to generate a valid Debian source archive
10096 without using <prgn>dpkg-source</prgn>. In particular,
10097 attempting to use <prgn>diff</prgn> directly to generate the
10098 <file>.diff.gz</file> file will not work.
10102 <heading>Restrictions on objects in source packages</heading>
10105 The source package may not contain any hard links
10107 This is not currently detected when building source
10108 packages, but only when extracting
10112 Hard links may be permitted at some point in the
10113 future, but would require a fair amount of
10115 </footnote>, device special files, sockets or setuid or
10118 Setgid directories are allowed.
10123 The source packaging tools manage the changes between the
10124 original and Debianised source using <prgn>diff</prgn> and
10125 <prgn>patch</prgn>. Turning the original source tree as
10126 included in the <file>.orig.tar.gz</file> into the debianised
10127 source must not involve any changes which cannot be
10128 handled by these tools. Problematic changes which cause
10129 <prgn>dpkg-source</prgn> to halt with an error when
10130 building the source package are:
10131 <list compact="compact">
10132 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10134 <item><p>Changing the targets of symbolic links.</p>
10136 <item><p>Creating directories, other than <file>debian</file>.</p>
10138 <item><p>Changes to the contents of binary files.</p></item>
10139 </list> Changes which cause <prgn>dpkg-source</prgn> to
10140 print a warning but continue anyway are:
10141 <list compact="compact">
10144 Removing files, directories or symlinks.
10146 Renaming a file is not treated specially - it is
10147 seen as the removal of the old file (which
10148 generates a warning, but is otherwise ignored),
10149 and the creation of the new one.
10155 Changed text files which are missing the usual final
10156 newline (either in the original or the modified
10161 Changes which are not represented, but which are not detected by
10162 <prgn>dpkg-source</prgn>, are:
10163 <list compact="compact">
10164 <item><p>Changing the permissions of files (other than
10165 <file>debian/rules</file>) and directories.</p></item>
10170 The <file>debian</file> directory and <file>debian/rules</file>
10171 are handled specially by <prgn>dpkg-source</prgn> - before
10172 applying the changes it will create the <file>debian</file>
10173 directory, and afterwards it will make
10174 <file>debian/rules</file> world-executable.
10180 <appendix id="pkg-controlfields">
10181 <heading>Control files and their fields (from old Packaging Manual)</heading>
10184 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10185 data in a common format, known as control files. Binary and
10186 source packages have control data as do the <file>.changes</file>
10187 files which control the installation of uploaded files, and
10188 <prgn>dpkg</prgn>'s internal databases are in a similar
10193 <heading>Syntax of control files</heading>
10196 See <ref id="controlsyntax">.
10200 It is important to note that there are several fields which
10201 are optional as far as <prgn>dpkg</prgn> and the related
10202 tools are concerned, but which must appear in every Debian
10203 package, or whose omission may cause problems.
10208 <heading>List of fields</heading>
10211 See <ref id="controlfieldslist">.
10215 This section now contains only the fields that didn't belong
10216 to the Policy manual.
10219 <sect1 id="pkg-f-Filename">
10220 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10223 These fields in <tt>Packages</tt> files give the
10224 filename(s) of (the parts of) a package in the
10225 distribution directories, relative to the root of the
10226 Debian hierarchy. If the package has been split into
10227 several parts the parts are all listed in order, separated
10232 <sect1 id="pkg-f-Size">
10233 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10236 These fields in <file>Packages</file> files give the size (in
10237 bytes, expressed in decimal) and MD5 checksum of the
10238 file(s) which make(s) up a binary package in the
10239 distribution. If the package is split into several parts
10240 the values for the parts are listed in order, separated by
10245 <sect1 id="pkg-f-Status">
10246 <heading><tt>Status</tt></heading>
10249 This field in <prgn>dpkg</prgn>'s status file records
10250 whether the user wants a package installed, removed or
10251 left alone, whether it is broken (requiring
10252 re-installation) or not and what its current state on the
10253 system is. Each of these pieces of information is a
10258 <sect1 id="pkg-f-Config-Version">
10259 <heading><tt>Config-Version</tt></heading>
10262 If a package is not installed or not configured, this
10263 field in <prgn>dpkg</prgn>'s status file records the last
10264 version of the package which was successfully
10269 <sect1 id="pkg-f-Conffiles">
10270 <heading><tt>Conffiles</tt></heading>
10273 This field in <prgn>dpkg</prgn>'s status file contains
10274 information about the automatically-managed configuration
10275 files held by a package. This field should <em>not</em>
10276 appear anywhere in a package!
10281 <heading>Obsolete fields</heading>
10284 These are still recognized by <prgn>dpkg</prgn> but should
10285 not appear anywhere any more.
10287 <taglist compact="compact">
10289 <tag><tt>Revision</tt></tag>
10290 <tag><tt>Package-Revision</tt></tag>
10291 <tag><tt>Package_Revision</tt></tag>
10293 The Debian revision part of the package version was
10294 at one point in a separate control file field. This
10295 field went through several names.
10298 <tag><tt>Recommended</tt></tag>
10299 <item>Old name for <tt>Recommends</tt>.</item>
10301 <tag><tt>Optional</tt></tag>
10302 <item>Old name for <tt>Suggests</tt>.</item>
10304 <tag><tt>Class</tt></tag>
10305 <item>Old name for <tt>Priority</tt>.</item>
10314 <appendix id="pkg-conffiles">
10315 <heading>Configuration file handling (from old Packaging Manual)</heading>
10318 <prgn>dpkg</prgn> can do a certain amount of automatic
10319 handling of package configuration files.
10323 Whether this mechanism is appropriate depends on a number of
10324 factors, but basically there are two approaches to any
10325 particular configuration file.
10329 The easy method is to ship a best-effort configuration in the
10330 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10331 handle updates. If the user is unlikely to want to edit the
10332 file, but you need them to be able to without losing their
10333 changes, and a new package with a changed version of the file
10334 is only released infrequently, this is a good approach.
10338 The hard method is to build the configuration file from
10339 scratch in the <prgn>postinst</prgn> script, and to take the
10340 responsibility for fixing any mistakes made in earlier
10341 versions of the package automatically. This will be
10342 appropriate if the file is likely to need to be different on
10346 <sect><heading>Automatic handling of configuration files by
10351 A package may contain a control area file called
10352 <tt>conffiles</tt>. This file should be a list of filenames
10353 of configuration files needing automatic handling, separated
10354 by newlines. The filenames should be absolute pathnames,
10355 and the files referred to should actually exist in the
10360 When a package is upgraded <prgn>dpkg</prgn> will process
10361 the configuration files during the configuration stage,
10362 shortly before it runs the package's <prgn>postinst</prgn>
10367 For each file it checks to see whether the version of the
10368 file included in the package is the same as the one that was
10369 included in the last version of the package (the one that is
10370 being upgraded from); it also compares the version currently
10371 installed on the system with the one shipped with the last
10376 If neither the user nor the package maintainer has changed
10377 the file, it is left alone. If one or the other has changed
10378 their version, then the changed version is preferred - i.e.,
10379 if the user edits their file, but the package maintainer
10380 doesn't ship a different version, the user's changes will
10381 stay, silently, but if the maintainer ships a new version
10382 and the user hasn't edited it the new version will be
10383 installed (with an informative message). If both have
10384 changed their version the user is prompted about the problem
10385 and must resolve the differences themselves.
10389 The comparisons are done by calculating the MD5 message
10390 digests of the files, and storing the MD5 of the file as it
10391 was included in the most recent version of the package.
10395 When a package is installed for the first time
10396 <prgn>dpkg</prgn> will install the file that comes with it,
10397 unless that would mean overwriting a file already on the
10402 However, note that <prgn>dpkg</prgn> will <em>not</em>
10403 replace a conffile that was removed by the user (or by a
10404 script). This is necessary because with some programs a
10405 missing file produces an effect hard or impossible to
10406 achieve in another way, so that a missing file needs to be
10407 kept that way if the user did it.
10411 Note that a package should <em>not</em> modify a
10412 <prgn>dpkg</prgn>-handled conffile in its maintainer
10413 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10414 the user confusing and possibly dangerous options for
10415 conffile update when the package is upgraded.</p>
10418 <sect><heading>Fully-featured maintainer script configuration
10423 For files which contain site-specific information such as
10424 the hostname and networking details and so forth, it is
10425 better to create the file in the package's
10426 <prgn>postinst</prgn> script.
10430 This will typically involve examining the state of the rest
10431 of the system to determine values and other information, and
10432 may involve prompting the user for some information which
10433 can't be obtained some other way.
10437 When using this method there are a couple of important
10438 issues which should be considered:
10442 If you discover a bug in the program which generates the
10443 configuration file, or if the format of the file changes
10444 from one version to the next, you will have to arrange for
10445 the postinst script to do something sensible - usually this
10446 will mean editing the installed configuration file to remove
10447 the problem or change the syntax. You will have to do this
10448 very carefully, since the user may have changed the file,
10449 perhaps to fix the very problem that your script is trying
10450 to deal with - you will have to detect these situations and
10451 deal with them correctly.
10455 If you do go down this route it's probably a good idea to
10456 make the program that generates the configuration file(s) a
10457 separate program in <file>/usr/sbin</file>, by convention called
10458 <file><var>package</var>config</file> and then run that if
10459 appropriate from the post-installation script. The
10460 <tt><var>package</var>config</tt> program should not
10461 unquestioningly overwrite an existing configuration - if its
10462 mode of operation is geared towards setting up a package for
10463 the first time (rather than any arbitrary reconfiguration
10464 later) you should have it check whether the configuration
10465 already exists, and require a <tt>--force</tt> flag to
10466 overwrite it.</p></sect>
10469 <appendix id="pkg-alternatives"><heading>Alternative versions of
10470 an interface - <prgn>update-alternatives</prgn> (from old
10475 When several packages all provide different versions of the
10476 same program or file it is useful to have the system select a
10477 default, but to allow the system administrator to change it
10478 and have their decisions respected.
10482 For example, there are several versions of the <prgn>vi</prgn>
10483 editor, and there is no reason to prevent all of them from
10484 being installed at once, each under their own name
10485 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10486 Nevertheless it is desirable to have the name <tt>vi</tt>
10487 refer to something, at least by default.
10491 If all the packages involved cooperate, this can be done with
10492 <prgn>update-alternatives</prgn>.
10496 Each package provides its own version under its own name, and
10497 calls <prgn>update-alternatives</prgn> in its postinst to
10498 register its version (and again in its prerm to deregister
10503 See the man page <manref name="update-alternatives"
10504 section="8"> for details.
10508 If <prgn>update-alternatives</prgn> does not seem appropriate
10509 you may wish to consider using diversions instead.</p>
10512 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10513 package's version of a file (from old Packaging Manual)
10517 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10518 when it reinstalls the package it belongs to, and to have it
10519 put the file from the package somewhere else instead.
10523 This can be used locally to override a package's version of a
10524 file, or by one package to override another's version (or
10525 provide a wrapper for it).
10529 Before deciding to use a diversion, read <ref
10530 id="pkg-alternatives"> to see if you really want a diversion
10531 rather than several alternative versions of a program.
10535 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10536 and updated by a special program <prgn>dpkg-divert</prgn>.
10537 Please see <manref name="dpkg-divert" section="8"> for full
10538 details of its operation.
10542 When a package wishes to divert a file from another, it should
10543 call <prgn>dpkg-divert</prgn> in its preinst to add the
10544 diversion and rename the existing file. For example,
10545 supposing that a <prgn>smailwrapper</prgn> package wishes to
10546 install a wrapper around <file>/usr/sbin/smail</file>:
10548 if [ install = "$1" ]; then
10549 dpkg-divert --package smailwrapper --add --rename \
10550 --divert /usr/sbin/smail.real /usr/sbin/smail
10552 </example> Testing <tt>$1</tt> is necessary so that the script
10553 doesn't try to add the diversion again when
10554 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10555 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10556 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10557 get installed as the true version.
10561 The postrm has to do the reverse:
10563 if [ remove = "$1" ]; then
10564 dpkg-divert --package smailwrapper --remove --rename \
10565 --divert /usr/sbin/smail.real /usr/sbin/smail
10571 Do not attempt to divert a file which is vitally important for
10572 the system's operation - when using <prgn>dpkg-divert</prgn>
10573 there is a time, after it has been diverted but before
10574 <prgn>dpkg</prgn> has installed the new version, when the file
10575 does not exist.</p>
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