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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>base</em>, <em>comm</em>,
644 <em>contrib</em>, <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>,
650 <em>non-free</em>, <em>oldlibs</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Thus, only very few packages are allowed
1082 to go into the <tt>base</tt> section to keep the required
1083 disk usage very small.
1087 Most of these packages will have the priority value
1088 <tt>required</tt> or at least <tt>important</tt>, and many
1089 of them will be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1480 The format of the <file>debian/changelog</file> allows the
1481 package building tools to discover which version of the package
1482 is being built and find out other release-specific information.
1486 That format is a series of entries like this:
1488 <example compact="compact">
1489 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1491 [optional blank line(s), stripped]
1493 * <var>change details</var>
1494 <var>more change details</var>
1496 [blank line(s), included in output of dpkg-parsechangelog]
1498 * <var>even more change details</var>
1500 [optional blank line(s), stripped]
1502 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1507 <var>package</var> and <var>version</var> are the source
1508 package name and version number.
1512 <var>distribution(s)</var> lists the distributions where
1513 this version should be installed when it is uploaded - it
1514 is copied to the <tt>Distribution</tt> field in the
1515 <file>.changes</file> file. See <ref id="f-Distribution">.
1519 <var>urgency</var> is the value for the <tt>Urgency</tt>
1520 field in the <file>.changes</file> file for the upload
1521 (see <ref id="f-Urgency">). It is not possible to specify
1522 an urgency containing commas; commas are used to separate
1523 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1524 <prgn>dpkg</prgn> changelog format (though there is
1525 currently only one useful <var>keyword</var>,
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>), or in
1551 the case of an NMU, marked as fixed.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1932 The <tt>build</tt>, <tt>binary</tt> and
1933 <tt>clean</tt> targets must be invoked with the current
1934 directory being the package's top-level directory.
1939 Additional targets may exist in <file>debian/rules</file>,
1940 either as published or undocumented interfaces or for the
1941 package's internal use.
1945 The architectures we build on and build for are determined
1946 by <prgn>make</prgn> variables using the utility
1947 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1948 You can determine the
1949 Debian architecture and the GNU style architecture
1950 specification string for the build machine (the machine type
1951 we are building on) as well as for the host machine (the
1952 machine type we are building for). Here is a list of
1953 supported <prgn>make</prgn> variables:
1954 <list compact="compact">
1956 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1959 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1960 specification string)
1963 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1964 <tt>DEB_*_GNU_TYPE</tt>)
1967 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1968 <tt>DEB_*_GNU_TYPE</tt>)
1970 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1971 the build machine or <tt>HOST</tt> for specification of the
1976 Backward compatibility can be provided in the rules file
1977 by setting the needed variables to suitable default
1978 values; please refer to the documentation of
1979 <prgn>dpkg-architecture</prgn> for details.
1983 It is important to understand that the <tt>DEB_*_ARCH</tt>
1984 string only determines which Debian architecture we are
1985 building on or for. It should not be used to get the CPU
1986 or system information; the GNU style variables should be
1991 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
1992 <sect id="substvars">
1993 <heading>Variable substitutions: <file>debian/substvars</file></heading>
1996 When <prgn>dpkg-gencontrol</prgn>,
1997 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
1998 generate control files they perform variable substitutions
1999 on their output just before writing it. Variable
2000 substitutions have the form <tt>${<var>variable</var>}</tt>.
2001 The optional file <file>debian/substvars</file> contains
2002 variable substitutions to be used; variables can also be set
2003 directly from <file>debian/rules</file> using the <tt>-V</tt>
2004 option to the source packaging commands, and certain
2005 predefined variables are also available.
2009 The <file>debian/substvars</file> file is usually generated and
2010 modified dynamically by <file>debian/rules</file> targets, in
2011 which case it must be removed by the <tt>clean</tt> target.
2015 See <manref name="dpkg-source" section="1"> for full
2016 details about source variable substitutions, including the
2017 format of <file>debian/substvars</file>.</p>
2020 <sect id="debianwatch">
2021 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2024 This is an optional, recommended control file for the
2025 <tt>uscan</tt> utility which defines how to automatically
2026 scan ftp or http sites for newly available updates of the
2027 package. This is used by <url id="
2028 http://dehs.alioth.debian.org/"> and other Debian QA tools
2029 to help with quality control and maintenance of the
2030 distribution as a whole.
2035 <sect id="debianfiles">
2036 <heading>Generated files list: <file>debian/files</file></heading>
2039 This file is not a permanent part of the source tree; it
2040 is used while building packages to record which files are
2041 being generated. <prgn>dpkg-genchanges</prgn> uses it
2042 when it generates a <file>.changes</file> file.
2046 It should not exist in a shipped source package, and so it
2047 (and any backup files or temporary files such as
2048 <file>files.new</file><footnote>
2049 <file>files.new</file> is used as a temporary file by
2050 <prgn>dpkg-gencontrol</prgn> and
2051 <prgn>dpkg-distaddfile</prgn> - they write a new
2052 version of <tt>files</tt> here before renaming it,
2053 to avoid leaving a corrupted copy if an error
2055 </footnote>) should be removed by the
2056 <tt>clean</tt> target. It may also be wise to
2057 ensure a fresh start by emptying or removing it at the
2058 start of the <tt>binary</tt> target.
2062 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2063 package, it adds an entry to <file>debian/files</file> for the
2064 <file>.deb</file> file that will be created when <tt>dpkg-deb
2065 --build</tt> is run for that binary package. So for most
2066 packages all that needs to be done with this file is to
2067 delete it in the <tt>clean</tt> target.
2071 If a package upload includes files besides the source
2072 package and any binary packages whose control files were
2073 made with <prgn>dpkg-gencontrol</prgn> then they should be
2074 placed in the parent of the package's top-level directory
2075 and <prgn>dpkg-distaddfile</prgn> should be called to add
2076 the file to the list in <file>debian/files</file>.</p>
2079 <sect id="embeddedfiles">
2080 <heading>Convenience copies of code</heading>
2083 Some software packages include in their distribution convenience
2084 copies of code from other software packages, generally so that
2085 users compiling from source don't have to download multiple
2086 packages. Debian packages should not make use of these
2087 convenience copies unless the included package is explicitly
2088 intended to be used in this way.<footnote>
2089 For example, parts of the GNU build system work like this.
2091 If the included code is already in the Debian archive in the
2092 form of a library, the Debian packaging should ensure that
2093 binary packages reference the libraries already in Debian and
2094 the convenience copy is not used. If the included code is not
2095 already in Debian, it should be packaged separately as a
2096 prerequisite if possible.
2098 Having multiple copies of the same code in Debian is
2099 inefficient, often creates either static linking or shared
2100 library conflicts, and, most importantly, increases the
2101 difficulty of handling security vulnerabilities in the
2110 <chapt id="controlfields">
2111 <heading>Control files and their fields</heading>
2114 The package management system manipulates data represented in
2115 a common format, known as <em>control data</em>, stored in
2116 <em>control files</em>.
2117 Control files are used for source packages, binary packages and
2118 the <file>.changes</file> files which control the installation
2119 of uploaded files<footnote>
2120 <prgn>dpkg</prgn>'s internal databases are in a similar
2125 <sect id="controlsyntax">
2126 <heading>Syntax of control files</heading>
2129 A control file consists of one or more paragraphs of
2131 The paragraphs are also sometimes referred to as stanzas.
2133 The paragraphs are separated by blank lines. Some control
2134 files allow only one paragraph; others allow several, in
2135 which case each paragraph usually refers to a different
2136 package. (For example, in source packages, the first
2137 paragraph refers to the source package, and later paragraphs
2138 refer to binary packages generated from the source.)
2142 Each paragraph consists of a series of data fields; each
2143 field consists of the field name, followed by a colon and
2144 then the data/value associated with that field. It ends at
2145 the end of the (logical) line. Horizontal whitespace
2146 (spaces and tabs) may occur immediately before or after the
2147 value and is ignored there; it is conventional to put a
2148 single space after the colon. For example, a field might
2150 <example compact="compact">
2153 the field name is <tt>Package</tt> and the field value
2158 Many fields' values may span several lines; in this case
2159 each continuation line must start with a space or a tab.
2160 Any trailing spaces or tabs at the end of individual
2161 lines of a field value are ignored.
2165 In fields where it is specified that lines may not wrap,
2166 only a single line of data is allowed and whitespace is not
2167 significant in a field body. Whitespace must not appear
2168 inside names (of packages, architectures, files or anything
2169 else) or version numbers, or between the characters of
2170 multi-character version relationships.
2174 Field names are not case-sensitive, but it is usual to
2175 capitalize the field names using mixed case as shown below.
2179 Blank lines, or lines consisting only of spaces and tabs,
2180 are not allowed within field values or between fields - that
2181 would mean a new paragraph.
2186 <sect id="sourcecontrolfiles">
2187 <heading>Source package control files -- <file>debian/control</file></heading>
2190 The <file>debian/control</file> file contains the most vital
2191 (and version-independent) information about the source package
2192 and about the binary packages it creates.
2196 The first paragraph of the control file contains information about
2197 the source package in general. The subsequent sets each describe a
2198 binary package that the source tree builds.
2202 The fields in the general paragraph (the first one, for the source
2205 <list compact="compact">
2206 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2207 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2208 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2209 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2210 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2211 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2212 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2217 The fields in the binary package paragraphs are:
2219 <list compact="compact">
2220 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2221 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2222 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2223 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2224 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2225 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2226 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2231 The syntax and semantics of the fields are described below.
2237 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2238 generate control files for binary packages (see below), by
2239 <prgn>dpkg-genchanges</prgn> to generate the
2240 <tt>.changes</tt> file to accompany the upload, and by
2241 <prgn>dpkg-source</prgn> when it creates the
2242 <file>.dsc</file> source control file as part of a source
2243 archive. Many fields are permitted to span multiple lines in
2244 <file>debian/control</file> but not in any other control
2245 file. These tools are responsible for removing the line
2246 breaks from such fields when using fields from
2247 <file>debian/control</file> to generate other control files.
2251 The fields here may contain variable references - their
2252 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2253 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2254 when they generate output control files.
2255 See <ref id="substvars"> for details.
2260 <sect id="binarycontrolfiles">
2261 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2264 The <file>DEBIAN/control</file> file contains the most vital
2265 (and version-dependent) information about a binary package.
2269 The fields in this file are:
2271 <list compact="compact">
2272 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2273 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2274 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2275 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2276 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2277 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2278 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2279 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2280 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2281 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2282 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2287 <sect id="debiansourcecontrolfiles">
2288 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2291 This file contains a series of fields, identified and
2292 separated just like the fields in the control file of
2293 a binary package. The fields are listed below; their
2294 syntax is described above, in <ref id="pkg-controlfields">.
2296 <list compact="compact">
2297 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2298 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2299 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2300 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2301 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2302 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2303 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2304 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2305 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2306 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2311 The source package control file is generated by
2312 <prgn>dpkg-source</prgn> when it builds the source
2313 archive, from other files in the source package,
2314 described above. When unpacking, it is checked against
2315 the files and directories in the other parts of the
2321 <sect id="debianchangesfiles">
2322 <heading>Debian changes files -- <file>.changes</file></heading>
2325 The .changes files are used by the Debian archive maintenance
2326 software to process updates to packages. They contain one
2327 paragraph which contains information from the
2328 <tt>debian/control</tt> file and other data about the
2329 source package gathered via <tt>debian/changelog</tt>
2330 and <tt>debian/rules</tt>.
2334 The fields in this file are:
2336 <list compact="compact">
2337 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2338 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2339 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2340 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2341 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2342 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2343 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2344 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2345 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2346 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2347 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2348 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2349 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2350 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2355 <sect id="controlfieldslist">
2356 <heading>List of fields</heading>
2358 <sect1 id="f-Source">
2359 <heading><tt>Source</tt></heading>
2362 This field identifies the source package name.
2366 In <file>debian/control</file> or a <file>.dsc</file> file,
2367 this field must contain only the name of the source package.
2371 In a binary package control file or a <file>.changes</file>
2372 file, the source package name may be followed by a version
2373 number in parentheses<footnote>
2374 It is customary to leave a space after the package name
2375 if a version number is specified.
2377 This version number may be omitted (and is, by
2378 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2379 the <tt>Version</tt> field of the binary package in
2380 question. The field itself may be omitted from a binary
2381 package control file when the source package has the same
2382 name and version as the binary package.
2386 <sect1 id="f-Maintainer">
2387 <heading><tt>Maintainer</tt></heading>
2390 The package maintainer's name and email address. The name
2391 should come first, then the email address inside angle
2392 brackets <tt><></tt> (in RFC822 format).
2396 If the maintainer's name contains a full stop then the
2397 whole field will not work directly as an email address due
2398 to a misfeature in the syntax specified in RFC822; a
2399 program using this field as an address must check for this
2400 and correct the problem if necessary (for example by
2401 putting the name in round brackets and moving it to the
2402 end, and bringing the email address forward).
2406 <sect1 id="f-Uploaders">
2407 <heading><tt>Uploaders</tt></heading>
2410 List of the names and email addresses of co-maintainers of
2411 the package, if any. If the package has other maintainers
2412 beside the one named in the
2413 <qref id="f-Maintainer">Maintainer field</qref>, their
2414 names and email addresses should be listed here. The
2415 format is the same as that of the Maintainer tag, and
2416 multiple entries should be comma separated. Currently,
2417 this field is restricted to a single line of data. This
2418 is an optional field.
2421 Any parser that interprets the Uploaders field in
2422 <file>debian/control</file> must permit it to span multiple
2423 lines. Line breaks in an Uploaders field that spans multiple
2424 lines are not significant and the semantics of the field are
2425 the same as if the line breaks had not been present.
2429 <sect1 id="f-Changed-By">
2430 <heading><tt>Changed-By</tt></heading>
2433 The name and email address of the person who changed the
2434 said package. Usually the name of the maintainer.
2435 All the rules for the Maintainer field apply here, too.
2439 <sect1 id="f-Section">
2440 <heading><tt>Section</tt></heading>
2443 This field specifies an application area into which the package
2444 has been classified. See <ref id="subsections">.
2448 When it appears in the <file>debian/control</file> file,
2449 it gives the value for the subfield of the same name in
2450 the <tt>Files</tt> field of the <file>.changes</file> file.
2451 It also gives the default for the same field in the binary
2456 <sect1 id="f-Priority">
2457 <heading><tt>Priority</tt></heading>
2460 This field represents how important that it is that the user
2461 have the package installed. See <ref id="priorities">.
2465 When it appears in the <file>debian/control</file> file,
2466 it gives the value for the subfield of the same name in
2467 the <tt>Files</tt> field of the <file>.changes</file> file.
2468 It also gives the default for the same field in the binary
2473 <sect1 id="f-Package">
2474 <heading><tt>Package</tt></heading>
2477 The name of the binary package.
2481 Package names must consist only of lower case letters
2482 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2483 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2484 They must be at least two characters long and must start
2485 with an alphanumeric character.
2489 <sect1 id="f-Architecture">
2490 <heading><tt>Architecture</tt></heading>
2493 Depending on context and the control file used, the
2494 <tt>Architecture</tt> field can include the following sets of
2497 <item>A unique single word identifying a Debian machine
2498 architecture, see <ref id="arch-spec">.
2499 <item><tt>all</tt>, which indicates an
2500 architecture-independent package.
2501 <item><tt>any</tt>, which indicates a package available
2502 for building on any architecture.
2503 <item><tt>source</tt>, which indicates a source package.
2508 In the main <file>debian/control</file> file in the source
2509 package, or in the source package control file
2510 <file>.dsc</file>, one may specify a list of architectures
2511 separated by spaces, or the special values <tt>any</tt> or
2516 Specifying <tt>any</tt> indicates that the source package
2517 isn't dependent on any particular architecture and should
2518 compile fine on any one. The produced binary package(s)
2519 will be specific to whatever the current build architecture
2521 This is the most often used setting, and is recommended
2522 for new packages that aren't <tt>Architecture: all</tt>.
2527 Specifying a list of architectures indicates that the source
2528 will build an architecture-dependent package, and will only
2529 work correctly on the listed architectures.<footnote>
2530 This is a setting used for a minority of cases where the
2531 program is not portable. Generally, it should not be used
2537 In a <file>.changes</file> file, the <tt>Architecture</tt>
2538 field lists the architecture(s) of the package(s)
2539 currently being uploaded. This will be a list; if the
2540 source for the package is also being uploaded, the special
2541 entry <tt>source</tt> is also present.
2545 See <ref id="debianrules"> for information how to get the
2546 architecture for the build process.
2550 <sect1 id="f-Essential">
2551 <heading><tt>Essential</tt></heading>
2554 This is a boolean field which may occur only in the
2555 control file of a binary package or in a per-package fields
2556 paragraph of a main source control data file.
2560 If set to <tt>yes</tt> then the package management system
2561 will refuse to remove the package (upgrading and replacing
2562 it is still possible). The other possible value is <tt>no</tt>,
2563 which is the same as not having the field at all.
2568 <heading>Package interrelationship fields:
2569 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2570 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Conflicts</tt>,
2571 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2575 These fields describe the package's relationships with
2576 other packages. Their syntax and semantics are described
2577 in <ref id="relationships">.</p>
2580 <sect1 id="f-Standards-Version">
2581 <heading><tt>Standards-Version</tt></heading>
2584 The most recent version of the standards (the policy
2585 manual and associated texts) with which the package
2590 The version number has four components: major and minor
2591 version number and major and minor patch level. When the
2592 standards change in a way that requires every package to
2593 change the major number will be changed. Significant
2594 changes that will require work in many packages will be
2595 signaled by a change to the minor number. The major patch
2596 level will be changed for any change to the meaning of the
2597 standards, however small; the minor patch level will be
2598 changed when only cosmetic, typographical or other edits
2599 are made which neither change the meaning of the document
2600 nor affect the contents of packages.
2604 Thus only the first three components of the policy version
2605 are significant in the <em>Standards-Version</em> control
2606 field, and so either these three components or the all
2607 four components may be specified.<footnote>
2608 In the past, people specified the full version number
2609 in the Standards-Version field, for example "2.3.0.0".
2610 Since minor patch-level changes don't introduce new
2611 policy, it was thought it would be better to relax
2612 policy and only require the first 3 components to be
2613 specified, in this example "2.3.0". All four
2614 components may still be used if someone wishes to do so.
2620 <sect1 id="f-Version">
2621 <heading><tt>Version</tt></heading>
2624 The version number of a package. The format is:
2625 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2629 The three components here are:
2631 <tag><var>epoch</var></tag>
2634 This is a single (generally small) unsigned integer. It
2635 may be omitted, in which case zero is assumed. If it is
2636 omitted then the <var>upstream_version</var> may not
2641 It is provided to allow mistakes in the version numbers
2642 of older versions of a package, and also a package's
2643 previous version numbering schemes, to be left behind.
2647 <tag><var>upstream_version</var></tag>
2650 This is the main part of the version number. It is
2651 usually the version number of the original ("upstream")
2652 package from which the <file>.deb</file> file has been made,
2653 if this is applicable. Usually this will be in the same
2654 format as that specified by the upstream author(s);
2655 however, it may need to be reformatted to fit into the
2656 package management system's format and comparison
2661 The comparison behavior of the package management system
2662 with respect to the <var>upstream_version</var> is
2663 described below. The <var>upstream_version</var>
2664 portion of the version number is mandatory.
2668 The <var>upstream_version</var> may contain only
2669 alphanumerics<footnote>
2670 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2672 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2673 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2674 tilde) and should start with a digit. If there is no
2675 <var>debian_revision</var> then hyphens are not allowed;
2676 if there is no <var>epoch</var> then colons are not
2681 <tag><var>debian_revision</var></tag>
2684 This part of the version number specifies the version of
2685 the Debian package based on the upstream version. It
2686 may contain only alphanumerics and the characters
2687 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2688 tilde) and is compared in the same way as the
2689 <var>upstream_version</var> is.
2693 It is optional; if it isn't present then the
2694 <var>upstream_version</var> may not contain a hyphen.
2695 This format represents the case where a piece of
2696 software was written specifically to be turned into a
2697 Debian package, and so there is only one "debianisation"
2698 of it and therefore no revision indication is required.
2702 It is conventional to restart the
2703 <var>debian_revision</var> at <tt>1</tt> each time the
2704 <var>upstream_version</var> is increased.
2708 The package management system will break the version
2709 number apart at the last hyphen in the string (if there
2710 is one) to determine the <var>upstream_version</var> and
2711 <var>debian_revision</var>. The absence of a
2712 <var>debian_revision</var> compares earlier than the
2713 presence of one (but note that the
2714 <var>debian_revision</var> is the least significant part
2715 of the version number).
2722 The <var>upstream_version</var> and <var>debian_revision</var>
2723 parts are compared by the package management system using the
2728 The strings are compared from left to right.
2732 First the initial part of each string consisting entirely of
2733 non-digit characters is determined. These two parts (one of
2734 which may be empty) are compared lexically. If a difference
2735 is found it is returned. The lexical comparison is a
2736 comparison of ASCII values modified so that all the letters
2737 sort earlier than all the non-letters and so that a tilde
2738 sorts before anything, even the end of a part. For example,
2739 the following parts are in sorted order from earliest to
2740 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2741 <tt>a</tt>.<footnote>
2742 One common use of <tt>~</tt> is for upstream pre-releases.
2743 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2744 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2749 Then the initial part of the remainder of each string which
2750 consists entirely of digit characters is determined. The
2751 numerical values of these two parts are compared, and any
2752 difference found is returned as the result of the comparison.
2753 For these purposes an empty string (which can only occur at
2754 the end of one or both version strings being compared) counts
2759 These two steps (comparing and removing initial non-digit
2760 strings and initial digit strings) are repeated until a
2761 difference is found or both strings are exhausted.
2765 Note that the purpose of epochs is to allow us to leave behind
2766 mistakes in version numbering, and to cope with situations
2767 where the version numbering scheme changes. It is
2768 <em>not</em> intended to cope with version numbers containing
2769 strings of letters which the package management system cannot
2770 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2771 silly orderings (the author of this manual has heard of a
2772 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2773 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2774 <tt>2</tt> and so forth).
2778 <sect1 id="f-Description">
2779 <heading><tt>Description</tt></heading>
2782 In a source or binary control file, the <tt>Description</tt>
2783 field contains a description of the binary package, consisting
2784 of two parts, the synopsis or the short description, and the
2785 long description. The field's format is as follows:
2790 Description: <single line synopsis>
2791 <extended description over several lines>
2796 The lines in the extended description can have these formats:
2802 Those starting with a single space are part of a paragraph.
2803 Successive lines of this form will be word-wrapped when
2804 displayed. The leading space will usually be stripped off.
2808 Those starting with two or more spaces. These will be
2809 displayed verbatim. If the display cannot be panned
2810 horizontally, the displaying program will line wrap them "hard"
2811 (i.e., without taking account of word breaks). If it can they
2812 will be allowed to trail off to the right. None, one or two
2813 initial spaces may be deleted, but the number of spaces
2814 deleted from each line will be the same (so that you can have
2815 indenting work correctly, for example).
2819 Those containing a single space followed by a single full stop
2820 character. These are rendered as blank lines. This is the
2821 <em>only</em> way to get a blank line<footnote>
2822 Completely empty lines will not be rendered as blank lines.
2823 Instead, they will cause the parser to think you're starting
2824 a whole new record in the control file, and will therefore
2825 likely abort with an error.
2830 Those containing a space, a full stop and some more characters.
2831 These are for future expansion. Do not use them.
2837 Do not use tab characters. Their effect is not predictable.
2841 See <ref id="descriptions"> for further information on this.
2845 In a <file>.changes</file> file, the <tt>Description</tt> field
2846 contains a summary of the descriptions for the packages being
2851 The part of the field before the first newline is empty;
2852 thereafter each line has the name of a binary package and
2853 the summary description line from that binary package.
2854 Each line is indented by one space.
2859 <sect1 id="f-Distribution">
2860 <heading><tt>Distribution</tt></heading>
2863 In a <file>.changes</file> file or parsed changelog output
2864 this contains the (space-separated) name(s) of the
2865 distribution(s) where this version of the package should
2866 be installed. Valid distributions are determined by the
2867 archive maintainers.<footnote>
2868 Current distribution names are:
2869 <taglist compact="compact">
2870 <tag><em>stable</em></tag>
2872 This is the current "released" version of Debian
2873 GNU/Linux. Once the distribution is
2874 <em>stable</em> only security fixes and other
2875 major bug fixes are allowed. When changes are
2876 made to this distribution, the release number is
2877 increased (for example: 2.2r1 becomes 2.2r2 then
2881 <tag><em>unstable</em></tag>
2883 This distribution value refers to the
2884 <em>developmental</em> part of the Debian
2885 distribution tree. New packages, new upstream
2886 versions of packages and bug fixes go into the
2887 <em>unstable</em> directory tree. Download from
2888 this distribution at your own risk.
2891 <tag><em>testing</em></tag>
2893 This distribution value refers to the
2894 <em>testing</em> part of the Debian distribution
2895 tree. It receives its packages from the
2896 unstable distribution after a short time lag to
2897 ensure that there are no major issues with the
2898 unstable packages. It is less prone to breakage
2899 than unstable, but still risky. It is not
2900 possible to upload packages directly to
2904 <tag><em>frozen</em></tag>
2906 From time to time, the <em>testing</em>
2907 distribution enters a state of "code-freeze" in
2908 anticipation of release as a <em>stable</em>
2909 version. During this period of testing only
2910 fixes for existing or newly-discovered bugs will
2911 be allowed. The exact details of this stage are
2912 determined by the Release Manager.
2915 <tag><em>experimental</em></tag>
2917 The packages with this distribution value are
2918 deemed by their maintainers to be high
2919 risk. Oftentimes they represent early beta or
2920 developmental packages from various sources that
2921 the maintainers want people to try, but are not
2922 ready to be a part of the other parts of the
2923 Debian distribution tree. Download at your own
2929 You should list <em>all</em> distributions that the
2930 package should be installed into.
2934 More information is available in the Debian Developer's
2935 Reference, section "The Debian archive".
2942 <heading><tt>Date</tt></heading>
2945 This field includes the date the package was built or last edited.
2949 The value of this field is usually extracted from the
2950 <file>debian/changelog</file> file - see
2951 <ref id="dpkgchangelog">).
2955 <sect1 id="f-Format">
2956 <heading><tt>Format</tt></heading>
2959 This field specifies a format revision for the file.
2960 The most current format described in the Policy Manual
2961 is version <strong>1.5</strong>. The syntax of the
2962 format value is the same as that of a package version
2963 number except that no epoch or Debian revision is allowed
2964 - see <ref id="f-Version">.
2968 <sect1 id="f-Urgency">
2969 <heading><tt>Urgency</tt></heading>
2972 This is a description of how important it is to upgrade to
2973 this version from previous ones. It consists of a single
2974 keyword taking one of the values <tt>low</tt>,
2975 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
2976 <tt>critical</tt><footnote>
2977 Other urgency values are supported with configuration
2978 changes in the archive software but are not used in Debian.
2979 The urgency affects how quickly a package will be considered
2980 for inclusion into the <tt>testing</tt> distribution and
2981 gives an indication of the importance of any fixes included
2982 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
2983 treated as synonymous.
2984 </footnote> (not case-sensitive) followed by an optional
2985 commentary (separated by a space) which is usually in
2986 parentheses. For example:
2989 Urgency: low (HIGH for users of diversions)
2995 The value of this field is usually extracted from the
2996 <file>debian/changelog</file> file - see
2997 <ref id="dpkgchangelog">.
3001 <sect1 id="f-Changes">
3002 <heading><tt>Changes</tt></heading>
3005 This field contains the human-readable changes data, describing
3006 the differences between the last version and the current one.
3010 There should be nothing in this field before the first
3011 newline; all the subsequent lines must be indented by at
3012 least one space; blank lines must be represented by a line
3013 consisting only of a space and a full stop.
3017 The value of this field is usually extracted from the
3018 <file>debian/changelog</file> file - see
3019 <ref id="dpkgchangelog">).
3023 Each version's change information should be preceded by a
3024 "title" line giving at least the version, distribution(s)
3025 and urgency, in a human-readable way.
3029 If data from several versions is being returned the entry
3030 for the most recent version should be returned first, and
3031 entries should be separated by the representation of a
3032 blank line (the "title" line may also be followed by the
3033 representation of blank line).
3037 <sect1 id="f-Binary">
3038 <heading><tt>Binary</tt></heading>
3041 This field is a list of binary packages.
3045 When it appears in the <file>.dsc</file> file it is the list
3046 of binary packages which a source package can produce. It
3047 does not necessarily produce all of these binary packages
3048 for every architecture. The source control file doesn't
3049 contain details of which architectures are appropriate for
3050 which of the binary packages.
3054 When it appears in a <file>.changes</file> file it lists the
3055 names of the binary packages actually being uploaded.
3059 The syntax is a list of binary packages separated by
3061 A space after each comma is conventional.
3062 </footnote>. Currently the packages must be separated using
3063 only spaces in the <file>.changes</file> file.
3067 <sect1 id="f-Installed-Size">
3068 <heading><tt>Installed-Size</tt></heading>
3071 This field appears in the control files of binary
3072 packages, and in the <file>Packages</file> files. It gives
3073 the total amount of disk space required to install the
3078 The disk space is represented in kilobytes as a simple
3083 <sect1 id="f-Files">
3084 <heading><tt>Files</tt></heading>
3087 This field contains a list of files with information about
3088 each one. The exact information and syntax varies with
3089 the context. In all cases the part of the field
3090 contents on the same line as the field name is empty. The
3091 remainder of the field is one line per file, each line
3092 being indented by one space and containing a number of
3093 sub-fields separated by spaces.
3097 In the <file>.dsc</file> file, each line contains the MD5
3098 checksum, size and filename of the tar file and (if applicable)
3099 diff file which make up the remainder of the source
3101 That is, the parts which are not the <tt>.dsc</tt>.
3103 The exact forms of the filenames are described
3104 in <ref id="pkg-sourcearchives">.
3108 In the <file>.changes</file> file this contains one line per
3109 file being uploaded. Each line contains the MD5 checksum,
3110 size, section and priority and the filename.
3111 The <qref id="f-Section">section</qref>
3112 and <qref id="f-Priority">priority</qref>
3113 are the values of the corresponding fields in
3114 the main source control file. If no section or priority is
3115 specified then <tt>-</tt> should be used, though section
3116 and priority values must be specified for new packages to
3117 be installed properly.
3121 The special value <tt>byhand</tt> for the section in a
3122 <tt>.changes</tt> file indicates that the file in question
3123 is not an ordinary package file and must by installed by
3124 hand by the distribution maintainers. If the section is
3125 <tt>byhand</tt> the priority should be <tt>-</tt>.
3129 If a new Debian revision of a package is being shipped and
3130 no new original source archive is being distributed the
3131 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3132 entry for the original source archive
3133 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3134 but the <file>.changes</file> file should leave it out. In
3135 this case the original source archive on the distribution
3136 site must match exactly, byte-for-byte, the original
3137 source archive which was used to generate the
3138 <file>.dsc</file> file and diff which are being uploaded.</p>
3141 <sect1 id="f-Closes">
3142 <heading><tt>Closes</tt></heading>
3145 A space-separated list of bug report numbers that the upload
3146 governed by the .changes file closes.
3153 <heading>User-defined fields</heading>
3156 Additional user-defined fields may be added to the
3157 source package control file. Such fields will be
3158 ignored, and not copied to (for example) binary or
3159 source package control files or upload control files.
3163 If you wish to add additional unsupported fields to
3164 these output files you should use the mechanism
3169 Fields in the main source control information file with
3170 names starting <tt>X</tt>, followed by one or more of
3171 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3172 be copied to the output files. Only the part of the
3173 field name after the hyphen will be used in the output
3174 file. Where the letter <tt>B</tt> is used the field
3175 will appear in binary package control files, where the
3176 letter <tt>S</tt> is used in source package control
3177 files and where <tt>C</tt> is used in upload control
3178 (<tt>.changes</tt>) files.
3182 For example, if the main source information control file
3185 XBS-Comment: I stand between the candle and the star.
3187 then the binary and source package control files will contain the
3190 Comment: I stand between the candle and the star.
3199 <chapt id="maintainerscripts">
3200 <heading>Package maintainer scripts and installation procedure</heading>
3203 <heading>Introduction to package maintainer scripts</heading>
3206 It is possible to supply scripts as part of a package which
3207 the package management system will run for you when your
3208 package is installed, upgraded or removed.
3212 These scripts are the files <prgn>preinst</prgn>,
3213 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3214 <prgn>postrm</prgn> in the control area of the package.
3215 They must be proper executable files; if they are scripts
3216 (which is recommended), they must start with the usual
3217 <tt>#!</tt> convention. They should be readable and
3218 executable by anyone, and must not be world-writable.
3222 The package management system looks at the exit status from
3223 these scripts. It is important that they exit with a
3224 non-zero status if there is an error, so that the package
3225 management system can stop its processing. For shell
3226 scripts this means that you <em>almost always</em> need to
3227 use <tt>set -e</tt> (this is usually true when writing shell
3228 scripts, in fact). It is also important, of course, that
3229 they don't exit with a non-zero status if everything went
3234 Additionally, packages interacting with users using
3235 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3236 install a <prgn>config</prgn> script in the control area,
3237 see <ref id="maintscriptprompt"> for details.
3241 When a package is upgraded a combination of the scripts from
3242 the old and new packages is called during the upgrade
3243 procedure. If your scripts are going to be at all
3244 complicated you need to be aware of this, and may need to
3245 check the arguments to your scripts.
3249 Broadly speaking the <prgn>preinst</prgn> is called before
3250 (a particular version of) a package is installed, and the
3251 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3252 before (a version of) a package is removed and the
3253 <prgn>postrm</prgn> afterwards.
3257 Programs called from maintainer scripts should not normally
3258 have a path prepended to them. Before installation is
3259 started, the package management system checks to see if the
3260 programs <prgn>ldconfig</prgn>,
3261 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3262 and <prgn>update-rc.d</prgn> can be found via the
3263 <tt>PATH</tt> environment variable. Those programs, and any
3264 other program that one would expect to be in the
3265 <tt>PATH</tt>, should thus be invoked without an absolute
3266 pathname. Maintainer scripts should also not reset the
3267 <tt>PATH</tt>, though they might choose to modify it by
3268 prepending or appending package-specific directories. These
3269 considerations really apply to all shell scripts.</p>
3272 <sect id="idempotency">
3273 <heading>Maintainer scripts idempotency</heading>
3276 It is necessary for the error recovery procedures that the
3277 scripts be idempotent. This means that if it is run
3278 successfully, and then it is called again, it doesn't bomb
3279 out or cause any harm, but just ensures that everything is
3280 the way it ought to be. If the first call failed, or
3281 aborted half way through for some reason, the second call
3282 should merely do the things that were left undone the first
3283 time, if any, and exit with a success status if everything
3285 This is so that if an error occurs, the user interrupts
3286 <prgn>dpkg</prgn> or some other unforeseen circumstance
3287 happens you don't leave the user with a badly-broken
3288 package when <prgn>dpkg</prgn> attempts to repeat the
3294 <sect id="controllingterminal">
3295 <heading>Controlling terminal for maintainer scripts</heading>
3298 The maintainer scripts are guaranteed to run with a
3299 controlling terminal and can interact with the user.
3300 Because these scripts may be executed with standard output
3301 redirected into a pipe for logging purposes, Perl scripts
3302 should set unbuffered output by setting <tt>$|=1</tt> so
3303 that the output is printed immediately rather than being
3307 <sect id="exitstatus">
3308 <heading>Exit status</heading>
3311 Each script must return a zero exit status for
3312 success, or a nonzero one for failure, since the package
3313 management system looks for the exit status of these scripts
3314 and determines what action to take next based on that datum.
3318 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3323 <list compact="compact">
3325 <var>new-preinst</var> <tt>install</tt>
3328 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3331 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3334 <var>old-preinst</var> <tt>abort-upgrade</tt>
3335 <var>new-version</var>
3340 <list compact="compact">
3342 <var>postinst</var> <tt>configure</tt>
3343 <var>most-recently-configured-version</var>
3346 <var>old-postinst</var> <tt>abort-upgrade</tt>
3347 <var>new-version</var>
3350 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3351 <tt>in-favour</tt> <var>package</var>
3352 <var>new-version</var>
3355 <var>postinst</var> <tt>abort-remove</tt>
3358 <var>deconfigured's-postinst</var>
3359 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3360 <var>failed-install-package</var> <var>version</var>
3361 <tt>removing</tt> <var>conflicting-package</var>
3367 <list compact="compact">
3369 <var>prerm</var> <tt>remove</tt>
3372 <var>old-prerm</var> <tt>upgrade</tt>
3373 <var>new-version</var>
3376 <var>new-prerm</var> <tt>failed-upgrade</tt>
3377 <var>old-version</var>
3380 <var>conflictor's-prerm</var> <tt>remove</tt>
3381 <tt>in-favour</tt> <var>package</var>
3382 <var>new-version</var>
3385 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3386 <tt>in-favour</tt> <var>package-being-installed</var>
3387 <var>version</var> <tt>removing</tt>
3388 <var>conflicting-package</var>
3394 <list compact="compact">
3396 <var>postrm</var> <tt>remove</tt>
3399 <var>postrm</var> <tt>purge</tt>
3402 <var>old-postrm</var> <tt>upgrade</tt>
3403 <var>new-version</var>
3406 <var>new-postrm</var> <tt>failed-upgrade</tt>
3407 <var>old-version</var>
3410 <var>new-postrm</var> <tt>abort-install</tt>
3413 <var>new-postrm</var> <tt>abort-install</tt>
3414 <var>old-version</var>
3417 <var>new-postrm</var> <tt>abort-upgrade</tt>
3418 <var>old-version</var>
3421 <var>disappearer's-postrm</var> <tt>disappear</tt>
3422 <var>overwriter</var>
3423 <var>overwriter-version</var>
3429 <sect id="unpackphase">
3430 <heading>Details of unpack phase of installation or upgrade</heading>
3433 The procedure on installation/upgrade/overwrite/disappear
3434 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3435 stage of <tt>dpkg --install</tt>) is as follows. In each
3436 case, if a major error occurs (unless listed below) the
3437 actions are, in general, run backwards - this means that the
3438 maintainer scripts are run with different arguments in
3439 reverse order. These are the "error unwind" calls listed
3446 If a version of the package is already installed, call
3447 <example compact="compact">
3448 <var>old-prerm</var> upgrade <var>new-version</var>
3452 If the script runs but exits with a non-zero
3453 exit status, <prgn>dpkg</prgn> will attempt:
3454 <example compact="compact">
3455 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3457 If this works, the upgrade continues. If this
3458 does not work, the error unwind:
3459 <example compact="compact">
3460 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3462 If this works, then the old-version is
3463 "Installed", if not, the old version is in a
3464 "Failed-Config" state.
3470 If a "conflicting" package is being removed at the same time:
3473 If any packages depended on that conflicting
3474 package and <tt>--auto-deconfigure</tt> is
3475 specified, call, for each such package:
3476 <example compact="compact">
3477 <var>deconfigured's-prerm</var> deconfigure \
3478 in-favour <var>package-being-installed</var> <var>version</var> \
3479 removing <var>conflicting-package</var> <var>version</var>
3482 <example compact="compact">
3483 <var>deconfigured's-postinst</var> abort-deconfigure \
3484 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3485 removing <var>conflicting-package</var> <var>version</var>
3487 The deconfigured packages are marked as
3488 requiring configuration, so that if
3489 <tt>--install</tt> is used they will be
3490 configured again if possible.
3493 To prepare for removal of the conflicting package, call:
3494 <example compact="compact">
3495 <var>conflictor's-prerm</var> remove \
3496 in-favour <var>package</var> <var>new-version</var>
3499 <example compact="compact">
3500 <var>conflictor's-postinst</var> abort-remove \
3501 in-favour <var>package</var> <var>new-version</var>
3510 If the package is being upgraded, call:
3511 <example compact="compact">
3512 <var>new-preinst</var> upgrade <var>old-version</var>
3514 If this fails, we call:
3516 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3523 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3525 is called. If this works, then the old version
3526 is in an "Installed" state, or else it is left
3527 in an "Unpacked" state.
3532 If it fails, then the old version is left
3533 in an "Half-Installed" state.
3540 Otherwise, if the package had some configuration
3541 files from a previous version installed (i.e., it
3542 is in the "configuration files only" state):
3543 <example compact="compact">
3544 <var>new-preinst</var> install <var>old-version</var>
3548 <var>new-postrm</var> abort-install <var>old-version</var>
3550 If this fails, the package is left in a
3551 "Half-Installed" state, which requires a
3552 reinstall. If it works, the packages is left in
3553 a "Config Files" state.
3556 Otherwise (i.e., the package was completely purged):
3557 <example compact="compact">
3558 <var>new-preinst</var> install
3561 <example compact="compact">
3562 <var>new-postrm</var> abort-install
3564 If the error-unwind fails, the package is in a
3565 "Half Installed" phase, and requires a
3566 reinstall. If the error unwind works, the
3567 package is in a not installed state.
3574 The new package's files are unpacked, overwriting any
3575 that may be on the system already, for example any
3576 from the old version of the same package or from
3577 another package. Backups of the old files are kept
3578 temporarily, and if anything goes wrong the package
3579 management system will attempt to put them back as
3580 part of the error unwind.
3584 It is an error for a package to contain files which
3585 are on the system in another package, unless
3586 <tt>Replaces</tt> is used (see <ref id="replaces">).
3588 The following paragraph is not currently the case:
3589 Currently the <tt>- - force-overwrite</tt> flag is
3590 enabled, downgrading it to a warning, but this may not
3596 It is a more serious error for a package to contain a
3597 plain file or other kind of non-directory where another
3598 package has a directory (again, unless
3599 <tt>Replaces</tt> is used). This error can be
3600 overridden if desired using
3601 <tt>--force-overwrite-dir</tt>, but this is not
3606 Packages which overwrite each other's files produce
3607 behavior which, though deterministic, is hard for the
3608 system administrator to understand. It can easily
3609 lead to "missing" programs if, for example, a package
3610 is installed which overwrites a file from another
3611 package, and is then removed again.<footnote>
3612 Part of the problem is due to what is arguably a
3613 bug in <prgn>dpkg</prgn>.
3618 A directory will never be replaced by a symbolic link
3619 to a directory or vice versa; instead, the existing
3620 state (symlink or not) will be left alone and
3621 <prgn>dpkg</prgn> will follow the symlink if there is
3630 If the package is being upgraded, call
3631 <example compact="compact">
3632 <var>old-postrm</var> upgrade <var>new-version</var>
3636 If this fails, <prgn>dpkg</prgn> will attempt:
3637 <example compact="compact">
3638 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3640 If this works, installation continues. If not,
3642 <example compact="compact">
3643 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3645 If this fails, the old version is left in an
3646 "Half Installed" state. If it works, dpkg now
3648 <example compact="compact">
3649 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3651 If this fails, the old version is left in an
3652 "Half Installed" state. If it works, dpkg now
3654 <example compact="compact">
3655 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3657 If this fails, the old version is in an
3664 This is the point of no return - if
3665 <prgn>dpkg</prgn> gets this far, it won't back off
3666 past this point if an error occurs. This will
3667 leave the package in a fairly bad state, which
3668 will require a successful re-installation to clear
3669 up, but it's when <prgn>dpkg</prgn> starts doing
3670 things that are irreversible.
3675 Any files which were in the old version of the package
3676 but not in the new are removed.
3680 The new file list replaces the old.
3684 The new maintainer scripts replace the old.
3688 Any packages all of whose files have been overwritten
3689 during the installation, and which aren't required for
3690 dependencies, are considered to have been removed.
3691 For each such package
3694 <prgn>dpkg</prgn> calls:
3695 <example compact="compact">
3696 <var>disappearer's-postrm</var> disappear \
3697 <var>overwriter</var> <var>overwriter-version</var>
3701 The package's maintainer scripts are removed.
3704 It is noted in the status database as being in a
3705 sane state, namely not installed (any conffiles
3706 it may have are ignored, rather than being
3707 removed by <prgn>dpkg</prgn>). Note that
3708 disappearing packages do not have their prerm
3709 called, because <prgn>dpkg</prgn> doesn't know
3710 in advance that the package is going to
3717 Any files in the package we're unpacking that are also
3718 listed in the file lists of other packages are removed
3719 from those lists. (This will lobotomize the file list
3720 of the "conflicting" package if there is one.)
3724 The backup files made during installation, above, are
3730 The new package's status is now sane, and recorded as
3735 Here is another point of no return - if the
3736 conflicting package's removal fails we do not unwind
3737 the rest of the installation; the conflicting package
3738 is left in a half-removed limbo.
3743 If there was a conflicting package we go and do the
3744 removal actions (described below), starting with the
3745 removal of the conflicting package's files (any that
3746 are also in the package being installed have already
3747 been removed from the conflicting package's file list,
3748 and so do not get removed now).
3754 <sect id="configdetails"><heading>Details of configuration</heading>
3757 When we configure a package (this happens with <tt>dpkg
3758 --install</tt> and <tt>dpkg --configure</tt>), we first
3759 update any <tt>conffile</tt>s and then call:
3760 <example compact="compact">
3761 <var>postinst</var> configure <var>most-recently-configured-version</var>
3766 No attempt is made to unwind after errors during
3767 configuration. If the configuration fails, the package is in
3768 a "Failed Config" state, and an error message is generated.
3772 If there is no most recently configured version
3773 <prgn>dpkg</prgn> will pass a null argument.
3776 Historical note: Truly ancient (pre-1997) versions of
3777 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3778 (including the angle brackets) in this case. Even older
3779 ones did not pass a second argument at all, under any
3780 circumstance. Note that upgrades using such an old dpkg
3781 version are unlikely to work for other reasons, even if
3782 this old argument behavior is handled by your postinst script.
3788 <sect id="removedetails"><heading>Details of removal and/or
3789 configuration purging</heading>
3795 <example compact="compact">
3796 <var>prerm</var> remove
3800 If prerm fails during replacement due to conflict
3802 <var>conflictor's-postinst</var> abort-remove \
3803 in-favour <var>package</var> <var>new-version</var>
3807 <var>postinst</var> abort-remove
3811 If this fails, the package is in a "Failed-Config"
3812 state, or else it remains "Installed".
3816 The package's files are removed (except <tt>conffile</tt>s).
3819 <example compact="compact">
3820 <var>postrm</var> remove
3824 If it fails, there's no error unwind, and the package is in
3825 an "Half-Installed" state.
3830 All the maintainer scripts except the <prgn>postrm</prgn>
3835 If we aren't purging the package we stop here. Note
3836 that packages which have no <prgn>postrm</prgn> and no
3837 <tt>conffile</tt>s are automatically purged when
3838 removed, as there is no difference except for the
3839 <prgn>dpkg</prgn> status.
3843 The <tt>conffile</tt>s and any backup files
3844 (<tt>~</tt>-files, <tt>#*#</tt> files,
3845 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3850 <example compact="compact">
3851 <var>postrm</var> purge
3855 If this fails, the package remains in a "Config-Files"
3860 The package's file list is removed.
3869 <chapt id="relationships">
3870 <heading>Declaring relationships between packages</heading>
3872 <sect id="depsyntax">
3873 <heading>Syntax of relationship fields</heading>
3876 These fields all have a uniform syntax. They are a list of
3877 package names separated by commas.
3881 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3882 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3883 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3884 control file fields of the package, which declare
3885 dependencies on other packages, the package names listed may
3886 also include lists of alternative package names, separated
3887 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3888 if any one of the alternative packages is installed, that
3889 part of the dependency is considered to be satisfied.
3893 All of the fields except for <tt>Provides</tt> may restrict
3894 their applicability to particular versions of each named
3895 package. This is done in parentheses after each individual
3896 package name; the parentheses should contain a relation from
3897 the list below followed by a version number, in the format
3898 described in <ref id="f-Version">.
3902 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3903 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3904 strictly earlier, earlier or equal, exactly equal, later or
3905 equal and strictly later, respectively. The deprecated
3906 forms <tt><</tt> and <tt>></tt> were used to mean
3907 earlier/later or equal, rather than strictly earlier/later,
3908 so they should not appear in new packages (though
3909 <prgn>dpkg</prgn> still supports them).
3913 Whitespace may appear at any point in the version
3914 specification subject to the rules in <ref
3915 id="controlsyntax">, and must appear where it's necessary to
3916 disambiguate; it is not otherwise significant. All of the
3917 relationship fields may span multiple lines. For
3918 consistency and in case of future changes to
3919 <prgn>dpkg</prgn> it is recommended that a single space be
3920 used after a version relationship and before a version
3921 number; it is also conventional to put a single space after
3922 each comma, on either side of each vertical bar, and before
3923 each open parenthesis. When wrapping a relationship field, it
3924 is conventional to do so after a comma and before the space
3925 following that comma.
3929 For example, a list of dependencies might appear as:
3930 <example compact="compact">
3933 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3938 All fields that specify build-time relationships
3939 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3940 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3941 may be restricted to a certain set of architectures. This
3942 is indicated in brackets after each individual package name and
3943 the optional version specification. The brackets enclose a
3944 list of Debian architecture names separated by whitespace.
3945 Exclamation marks may be prepended to each of the names.
3946 (It is not permitted for some names to be prepended with
3947 exclamation marks while others aren't.) If the current Debian
3948 host architecture is not in this list and there are no
3949 exclamation marks in the list, or it is in the list with a
3950 prepended exclamation mark, the package name and the
3951 associated version specification are ignored completely for
3952 the purposes of defining the relationships.
3957 <example compact="compact">
3959 Build-Depends-Indep: texinfo
3960 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3961 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3966 Note that the binary package relationship fields such as
3967 <tt>Depends</tt> appear in one of the binary package
3968 sections of the control file, whereas the build-time
3969 relationships such as <tt>Build-Depends</tt> appear in the
3970 source package section of the control file (which is the
3975 <sect id="binarydeps">
3976 <heading>Binary Dependencies - <tt>Depends</tt>,
3977 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3978 <tt>Pre-Depends</tt>
3982 Packages can declare in their control file that they have
3983 certain relationships to other packages - for example, that
3984 they may not be installed at the same time as certain other
3985 packages, and/or that they depend on the presence of others.
3989 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3990 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3991 <tt>Conflicts</tt> control file fields.
3995 These six fields are used to declare a dependency
3996 relationship by one package on another. Except for
3997 <tt>Enhances</tt>, they appear in the depending (binary)
3998 package's control file. (<tt>Enhances</tt> appears in the
3999 recommending package's control file.)
4003 A <tt>Depends</tt> field takes effect <em>only</em> when a
4004 package is to be configured. It does not prevent a package
4005 being on the system in an unconfigured state while its
4006 dependencies are unsatisfied, and it is possible to replace
4007 a package whose dependencies are satisfied and which is
4008 properly installed with a different version whose
4009 dependencies are not and cannot be satisfied; when this is
4010 done the depending package will be left unconfigured (since
4011 attempts to configure it will give errors) and will not
4012 function properly. If it is necessary, a
4013 <tt>Pre-Depends</tt> field can be used, which has a partial
4014 effect even when a package is being unpacked, as explained
4015 in detail below. (The other three dependency fields,
4016 <tt>Recommends</tt>, <tt>Suggests</tt> and
4017 <tt>Enhances</tt>, are only used by the various front-ends
4018 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4019 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4023 For this reason packages in an installation run are usually
4024 all unpacked first and all configured later; this gives
4025 later versions of packages with dependencies on later
4026 versions of other packages the opportunity to have their
4027 dependencies satisfied.
4031 In case of circular dependencies, since installation or
4032 removal order honoring the dependency order can't be
4033 established, dependency loops are broken at some point
4034 (based on rules below), and some packages may not be able to
4035 rely on their dependencies being present when being
4036 installed or removed, depending on which side of the break
4037 of the circular dependcy loop they happen to be on. If one
4038 of the packages in the loop has no postinst script, then the
4039 cycle will be broken at that package, so as to ensure that
4040 all postinst scripts run with the dependencies properly
4041 configured if this is possible. Otherwise the breaking point
4046 The <tt>Depends</tt> field thus allows package maintainers
4047 to impose an order in which packages should be configured.
4051 The meaning of the five dependency fields is as follows:
4053 <tag><tt>Depends</tt></tag>
4056 This declares an absolute dependency. A package will
4057 not be configured unless all of the packages listed in
4058 its <tt>Depends</tt> field have been correctly
4063 The <tt>Depends</tt> field should be used if the
4064 depended-on package is required for the depending
4065 package to provide a significant amount of
4070 The <tt>Depends</tt> field should also be used if the
4071 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4072 <prgn>postrm</prgn> scripts require the package to be
4073 present in order to run. Note, however, that the
4074 <prgn>postrm</prgn> cannot rely on any non-essential
4075 packages to be present during the <tt>purge</tt>
4079 <tag><tt>Recommends</tt></tag>
4082 This declares a strong, but not absolute, dependency.
4086 The <tt>Recommends</tt> field should list packages
4087 that would be found together with this one in all but
4088 unusual installations.
4092 <tag><tt>Suggests</tt></tag>
4094 This is used to declare that one package may be more
4095 useful with one or more others. Using this field
4096 tells the packaging system and the user that the
4097 listed packages are related to this one and can
4098 perhaps enhance its usefulness, but that installing
4099 this one without them is perfectly reasonable.
4102 <tag><tt>Enhances</tt></tag>
4104 This field is similar to Suggests but works in the
4105 opposite direction. It is used to declare that a
4106 package can enhance the functionality of another
4110 <tag><tt>Pre-Depends</tt></tag>
4113 This field is like <tt>Depends</tt>, except that it
4114 also forces <prgn>dpkg</prgn> to complete installation
4115 of the packages named before even starting the
4116 installation of the package which declares the
4117 pre-dependency, as follows:
4121 When a package declaring a pre-dependency is about to
4122 be <em>unpacked</em> the pre-dependency can be
4123 satisfied if the depended-on package is either fully
4124 configured, <em>or even if</em> the depended-on
4125 package(s) are only unpacked or half-configured,
4126 provided that they have been configured correctly at
4127 some point in the past (and not removed or partially
4128 removed since). In this case, both the
4129 previously-configured and currently unpacked or
4130 half-configured versions must satisfy any version
4131 clause in the <tt>Pre-Depends</tt> field.
4135 When the package declaring a pre-dependency is about
4136 to be <em>configured</em>, the pre-dependency will be
4137 treated as a normal <tt>Depends</tt>, that is, it will
4138 be considered satisfied only if the depended-on
4139 package has been correctly configured.
4143 <tt>Pre-Depends</tt> should be used sparingly,
4144 preferably only by packages whose premature upgrade or
4145 installation would hamper the ability of the system to
4146 continue with any upgrade that might be in progress.
4150 <tt>Pre-Depends</tt> are also required if the
4151 <prgn>preinst</prgn> script depends on the named
4152 package. It is best to avoid this situation if
4160 When selecting which level of dependency to use you should
4161 consider how important the depended-on package is to the
4162 functionality of the one declaring the dependency. Some
4163 packages are composed of components of varying degrees of
4164 importance. Such a package should list using
4165 <tt>Depends</tt> the package(s) which are required by the
4166 more important components. The other components'
4167 requirements may be mentioned as Suggestions or
4168 Recommendations, as appropriate to the components' relative
4173 <sect id="conflicts">
4174 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4177 When one binary package declares a conflict with another
4178 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4179 refuse to allow them to be installed on the system at the
4184 If one package is to be installed, the other must be removed
4185 first - if the package being installed is marked as
4186 replacing (see <ref id="replaces">) the one on the system,
4187 or the one on the system is marked as deselected, or both
4188 packages are marked <tt>Essential</tt>, then
4189 <prgn>dpkg</prgn> will automatically remove the package
4190 which is causing the conflict, otherwise it will halt the
4191 installation of the new package with an error. This
4192 mechanism is specifically designed to produce an error when
4193 the installed package is <tt>Essential</tt>, but the new
4198 A package will not cause a conflict merely because its
4199 configuration files are still installed; it must be at least
4204 A special exception is made for packages which declare a
4205 conflict with their own package name, or with a virtual
4206 package which they provide (see below): this does not
4207 prevent their installation, and allows a package to conflict
4208 with others providing a replacement for it. You use this
4209 feature when you want the package in question to be the only
4210 package providing some feature.
4214 A <tt>Conflicts</tt> entry should almost never have an
4215 "earlier than" version clause. This would prevent
4216 <prgn>dpkg</prgn> from upgrading or installing the package
4217 which declared such a conflict until the upgrade or removal
4218 of the conflicted-with package had been completed.
4222 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4226 As well as the names of actual ("concrete") packages, the
4227 package relationship fields <tt>Depends</tt>,
4228 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4229 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4230 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4231 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4232 may mention "virtual packages".
4236 A <em>virtual package</em> is one which appears in the
4237 <tt>Provides</tt> control file field of another package.
4238 The effect is as if the package(s) which provide a
4239 particular virtual package name had been listed by name
4240 everywhere the virtual package name appears. (See also <ref
4245 If there are both concrete and virtual packages of the same
4246 name, then the dependency may be satisfied (or the conflict
4247 caused) by either the concrete package with the name in
4248 question or any other concrete package which provides the
4249 virtual package with the name in question. This is so that,
4250 for example, supposing we have
4251 <example compact="compact">
4254 </example> and someone else releases an enhanced version of
4255 the <tt>bar</tt> package they can say:
4256 <example compact="compact">
4260 and the <tt>bar-plus</tt> package will now also satisfy the
4261 dependency for the <tt>foo</tt> package.
4265 If a dependency or a conflict has a version number attached
4266 then only real packages will be considered to see whether
4267 the relationship is satisfied (or the prohibition violated,
4268 for a conflict) - it is assumed that a real package which
4269 provides the virtual package is not of the "right" version.
4270 So, a <tt>Provides</tt> field may not contain version
4271 numbers, and the version number of the concrete package
4272 which provides a particular virtual package will not be
4273 looked at when considering a dependency on or conflict with
4274 the virtual package name.
4278 It is likely that the ability will be added in a future
4279 release of <prgn>dpkg</prgn> to specify a version number for
4280 each virtual package it provides. This feature is not yet
4281 present, however, and is expected to be used only
4286 If you want to specify which of a set of real packages
4287 should be the default to satisfy a particular dependency on
4288 a virtual package, you should list the real package as an
4289 alternative before the virtual one.
4294 <sect id="replaces"><heading>Overwriting files and replacing
4295 packages - <tt>Replaces</tt></heading>
4298 Packages can declare in their control file that they should
4299 overwrite files in certain other packages, or completely
4300 replace other packages. The <tt>Replaces</tt> control file
4301 field has these two distinct purposes.
4304 <sect1><heading>Overwriting files in other packages</heading>
4307 Firstly, as mentioned before, it is usually an error for a
4308 package to contain files which are on the system in
4313 However, if the overwriting package declares that it
4314 <tt>Replaces</tt> the one containing the file being
4315 overwritten, then <prgn>dpkg</prgn> will replace the file
4316 from the old package with that from the new. The file
4317 will no longer be listed as "owned" by the old package.
4321 If a package is completely replaced in this way, so that
4322 <prgn>dpkg</prgn> does not know of any files it still
4323 contains, it is considered to have "disappeared". It will
4324 be marked as not wanted on the system (selected for
4325 removal) and not installed. Any <tt>conffile</tt>s
4326 details noted for the package will be ignored, as they
4327 will have been taken over by the overwriting package. The
4328 package's <prgn>postrm</prgn> script will be run with a
4329 special argument to allow the package to do any final
4330 cleanup required. See <ref id="mscriptsinstact">.
4333 Replaces is a one way relationship -- you have to
4334 install the replacing package after the replaced
4341 For this usage of <tt>Replaces</tt>, virtual packages (see
4342 <ref id="virtual">) are not considered when looking at a
4343 <tt>Replaces</tt> field - the packages declared as being
4344 replaced must be mentioned by their real names.
4348 Furthermore, this usage of <tt>Replaces</tt> only takes
4349 effect when both packages are at least partially on the
4350 system at once, so that it can only happen if they do not
4351 conflict or if the conflict has been overridden.
4356 <sect1><heading>Replacing whole packages, forcing their
4360 Secondly, <tt>Replaces</tt> allows the packaging system to
4361 resolve which package should be removed when there is a
4362 conflict - see <ref id="conflicts">. This usage only
4363 takes effect when the two packages <em>do</em> conflict,
4364 so that the two usages of this field do not interfere with
4369 In this situation, the package declared as being replaced
4370 can be a virtual package, so for example, all mail
4371 transport agents (MTAs) would have the following fields in
4372 their control files:
4373 <example compact="compact">
4374 Provides: mail-transport-agent
4375 Conflicts: mail-transport-agent
4376 Replaces: mail-transport-agent
4378 ensuring that only one MTA can be installed at any one
4383 <sect id="sourcebinarydeps">
4384 <heading>Relationships between source and binary packages -
4385 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4386 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4390 Source packages that require certain binary packages to be
4391 installed or absent at the time of building the package
4392 can declare relationships to those binary packages.
4396 This is done using the <tt>Build-Depends</tt>,
4397 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4398 <tt>Build-Conflicts-Indep</tt> control file fields.
4402 Build-dependencies on "build-essential" binary packages can be
4403 omitted. Please see <ref id="pkg-relations"> for more information.
4407 The dependencies and conflicts they define must be satisfied
4408 (as defined earlier for binary packages) in order to invoke
4409 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4411 If you make "build-arch" or "binary-arch", you need
4412 Build-Depends. If you make "build-indep" or
4413 "binary-indep", you need Build-Depends and
4414 Build-Depends-Indep. If you make "build" or "binary",
4418 There is no Build-Depends-Arch; this role is essentially
4419 met with Build-Depends. Anyone building the
4420 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4421 is basically assumed to be building the whole package
4422 anyway and so installs all build dependencies. The
4423 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4424 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4425 does not yet know how to check for its existence) and
4426 <tt>binary-arch</tt>.
4429 The purpose of the original split, I recall, was so that
4430 the autobuilders wouldn't need to install extra packages
4431 needed only for the binary-indep targets. But without a
4432 build-arch/build-indep split, this didn't work, since
4433 most of the work is done in the build target, not in the
4439 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4441 The <tt>Build-Depends</tt> and
4442 <tt>Build-Conflicts</tt> fields must be satisfied when
4443 any of the following targets is invoked:
4444 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4445 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4446 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4448 <tag><tt>Build-Depends-Indep</tt>,
4449 <tt>Build-Conflicts-Indep</tt></tag>
4451 The <tt>Build-Depends-Indep</tt> and
4452 <tt>Build-Conflicts-Indep</tt> fields must be
4453 satisfied when any of the following targets is
4454 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4455 <tt>binary</tt> and <tt>binary-indep</tt>.
4465 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4468 Packages containing shared libraries must be constructed with
4469 a little care to make sure that the shared library is always
4470 available. This is especially important for packages whose
4471 shared libraries are vitally important, such as the C library
4472 (currently <tt>libc6</tt>).
4476 Packages involving shared libraries should be split up into
4477 several binary packages. This section mostly deals with how
4478 this separation is to be accomplished; rules for files within
4479 the shared library packages are in <ref id="libraries"> instead.
4482 <sect id="sharedlibs-runtime">
4483 <heading>Run-time shared libraries</heading>
4486 The run-time shared library needs to be placed in a package
4487 whose name changes whenever the shared object version
4490 Since it is common place to install several versions of a
4491 package that just provides shared libraries, it is a
4492 good idea that the library package should not
4493 contain any extraneous non-versioned files, unless they
4494 happen to be in versioned directories.</p>
4496 The most common mechanism is to place it in a package
4498 <package><var>libraryname</var><var>soversion</var></package>,
4499 where <file><var>soversion</var></file> is the version number
4500 in the soname of the shared library<footnote>
4501 The soname is the shared object name: it's the thing
4502 that has to match exactly between building an executable
4503 and running it for the dynamic linker to be able run the
4504 program. For example, if the soname of the library is
4505 <file>libfoo.so.6</file>, the library package would be
4506 called <file>libfoo6</file>.
4508 Alternatively, if it would be confusing to directly append
4509 <var>soversion</var> to <var>libraryname</var> (e.g. because
4510 <var>libraryname</var> itself ends in a number), you may use
4511 <package><var>libraryname</var>-<var>soversion</var></package> and
4512 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4517 If your package includes run-time support programs that
4518 do not need to be invoked manually by users, but are
4519 nevertheless required for the package to function, then it
4520 is recommended that these programs are placed
4521 (if they are binary) in a subdirectory of
4522 <file>/usr/lib</file>, preferably under
4523 <file>/usr/lib/</file><var>package-name</var>.
4524 If the program is architecture independent, the
4525 recommendation is for it to be placed in a subdirectory of
4526 <file>/usr/share</file> instead, preferably under
4527 <file>/usr/share/</file><var>package-name</var>.
4532 If you have several shared libraries built from the same
4533 source tree you may lump them all together into a single
4534 shared library package, provided that you change all of
4535 their sonames at once (so that you don't get filename
4536 clashes if you try to install different versions of the
4537 combined shared libraries package).
4541 The package should install the shared libraries under
4542 their normal names. For example, the <package>libgdbm3</package>
4543 package should install <file>libgdbm.so.3.0.0</file> as
4544 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4545 renamed or re-linked by any <prgn>prerm</prgn> or
4546 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4547 of renaming things safely without affecting running programs,
4548 and attempts to interfere with this are likely to lead to
4553 Shared libraries should not be installed executable, since
4554 the dynamic linker does not require this and trying to
4555 execute a shared library usually results in a core dump.
4559 The run-time library package should include the symbolic link that
4560 <prgn>ldconfig</prgn> would create for the shared libraries.
4561 For example, the <package>libgdbm3</package> package should include
4562 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4563 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4564 linker (for example <prgn>ld.so</prgn> or
4565 <prgn>ld-linux.so.*</prgn>) can find the library between the
4566 time that <prgn>dpkg</prgn> installs it and the time that
4567 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4569 The package management system requires the library to be
4570 placed before the symbolic link pointing to it in the
4571 <file>.deb</file> file. This is so that when
4572 <prgn>dpkg</prgn> comes to install the symlink
4573 (overwriting the previous symlink pointing at an older
4574 version of the library), the new shared library is already
4575 in place. In the past, this was achieved by creating the
4576 library in the temporary packaging directory before
4577 creating the symlink. Unfortunately, this was not always
4578 effective, since the building of the tar file in the
4579 <file>.deb</file> depended on the behavior of the underlying
4580 file system. Some file systems (such as reiserfs) reorder
4581 the files so that the order of creation is forgotten.
4582 Since version 1.7.0, <prgn>dpkg</prgn>
4583 reorders the files itself as necessary when building a
4584 package. Thus it is no longer important to concern
4585 oneself with the order of file creation.
4589 <sect1 id="ldconfig">
4590 <heading><tt>ldconfig</tt></heading>
4593 Any package installing shared libraries in one of the default
4594 library directories of the dynamic linker (which are currently
4595 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4596 listed in <file>/etc/ld.so.conf</file><footnote>
4598 <list compact="compact">
4599 <item>/usr/local/lib</item>
4600 <item>/usr/lib/libc5-compat</item>
4601 <item>/lib/libc5-compat</item>
4604 must use <prgn>ldconfig</prgn> to update the shared library
4609 The package maintainer scripts must only call
4610 <prgn>ldconfig</prgn> under these circumstances:
4611 <list compact="compact">
4612 <item>When the <prgn>postinst</prgn> script is run with a
4613 first argument of <tt>configure</tt>, the script must call
4614 <prgn>ldconfig</prgn>, and may optionally invoke
4615 <prgn>ldconfig</prgn> at other times.
4617 <item>When the <prgn>postrm</prgn> script is run with a
4618 first argument of <tt>remove</tt>, the script should call
4619 <prgn>ldconfig</prgn>.
4624 During install or upgrade, the preinst is called before
4625 the new files are installed, so calling "ldconfig" is
4626 pointless. The preinst of an existing package can also be
4627 called if an upgrade fails. However, this happens during
4628 the critical time when a shared libs may exist on-disk
4629 under a temporary name. Thus, it is dangerous and
4630 forbidden by current policy to call "ldconfig" at this
4635 When a package is installed or upgraded, "postinst
4636 configure" runs after the new files are safely on-disk.
4637 Since it is perfectly safe to invoke ldconfig
4638 unconditionally in a postinst, it is OK for a package to
4639 simply put ldconfig in its postinst without checking the
4640 argument. The postinst can also be called to recover from
4641 a failed upgrade. This happens before any new files are
4642 unpacked, so there is no reason to call "ldconfig" at this
4647 For a package that is being removed, prerm is
4648 called with all the files intact, so calling ldconfig is
4649 useless. The other calls to "prerm" happen in the case of
4650 upgrade at a time when all the files of the old package
4651 are on-disk, so again calling "ldconfig" is pointless.
4655 postrm, on the other hand, is called with the "remove"
4656 argument just after the files are removed, so this is
4657 the proper time to call "ldconfig" to notify the system
4658 of the fact that the shared libraries from the package
4659 are removed. The postrm can be called at several other
4660 times. At the time of "postrm purge", "postrm
4661 abort-install", or "postrm abort-upgrade", calling
4662 "ldconfig" is useless because the shared lib files are
4663 not on-disk. However, when "postrm" is invoked with
4664 arguments "upgrade", "failed-upgrade", or "disappear", a
4665 shared lib may exist on-disk under a temporary filename.
4673 <sect id="sharedlibs-runtime-progs">
4674 <heading>Run-time support programs</heading>
4677 If your package has some run-time support programs which use
4678 the shared library you must not put them in the shared
4679 library package. If you do that then you won't be able to
4680 install several versions of the shared library without
4681 getting filename clashes.
4685 Instead, either create another package for the runtime binaries
4686 (this package might typically be named
4687 <package><var>libraryname</var>-runtime</package>; note the absence
4688 of the <var>soversion</var> in the package name), or if the
4689 development package is small, include them in there.
4693 <sect id="sharedlibs-static">
4694 <heading>Static libraries</heading>
4697 The static library (<file><var>libraryname.a</var></file>)
4698 is usually provided in addition to the shared version.
4699 It is placed into the development package (see below).
4703 In some cases, it is acceptable for a library to be
4704 available in static form only; these cases include:
4706 <item>libraries for languages whose shared library support
4707 is immature or unstable</item>
4708 <item>libraries whose interfaces are in flux or under
4709 development (commonly the case when the library's
4710 major version number is zero, or where the ABI breaks
4711 across patchlevels)</item>
4712 <item>libraries which are explicitly intended to be
4713 available only in static form by their upstream
4718 <sect id="sharedlibs-dev">
4719 <heading>Development files</heading>
4722 The development files associated to a shared library need to be
4723 placed in a package called
4724 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4725 or if you prefer only to support one development version at a
4726 time, <package><var>libraryname</var>-dev</package>.
4730 In case several development versions of a library exist, you may
4731 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4732 <ref id="conflicts">) to ensure that the user only installs one
4733 development version at a time (as different development versions are
4734 likely to have the same header files in them, which would cause a
4735 filename clash if both were installed).
4739 The development package should contain a symlink for the associated
4740 shared library without a version number. For example, the
4741 <package>libgdbm-dev</package> package should include a symlink
4742 from <file>/usr/lib/libgdbm.so</file> to
4743 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4744 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4745 <file>libgdbm.so</file> when compiling dynamically.
4749 <sect id="sharedlibs-intradeps">
4750 <heading>Dependencies between the packages of the same library</heading>
4753 Typically the development version should have an exact
4754 version dependency on the runtime library, to make sure that
4755 compilation and linking happens correctly. The
4756 <tt>${binary:Version}</tt> substitution variable can be
4757 useful for this purpose.
4759 Previously, <tt>${Source-Version}</tt> was used, but its name
4760 was confusing and it has been deprecated since dpkg 1.13.19.
4765 <sect id="sharedlibs-shlibdeps">
4766 <heading>Dependencies between the library and other packages -
4767 the <tt>shlibs</tt> system</heading>
4770 If a package contains a binary or library which links to a
4771 shared library, we must ensure that when the package is
4772 installed on the system, all of the libraries needed are
4773 also installed. This requirement led to the creation of the
4774 <tt>shlibs</tt> system, which is very simple in its design:
4775 any package which <em>provides</em> a shared library also
4776 provides information on the package dependencies required to
4777 ensure the presence of this library, and any package which
4778 <em>uses</em> a shared library uses this information to
4779 determine the dependencies it requires. The files which
4780 contain the mapping from shared libraries to the necessary
4781 dependency information are called <file>shlibs</file> files.
4785 Thus, when a package is built which contains any shared
4786 libraries, it must provide a <file>shlibs</file> file for other
4787 packages to use, and when a package is built which contains
4788 any shared libraries or compiled binaries, it must run
4789 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4790 on these to determine the libraries used and hence the
4791 dependencies needed by this package.<footnote>
4793 In the past, the shared libraries linked to were
4794 determined by calling <prgn>ldd</prgn>, but now
4795 <prgn>objdump</prgn> is used to do this. The only
4796 change this makes to package building is that
4797 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4798 libraries, whereas in the past this was unnecessary.
4799 The rest of this footnote explains the advantage that
4804 We say that a binary <tt>foo</tt> <em>directly</em> uses
4805 a library <tt>libbar</tt> if it is explicitly linked
4806 with that library (that is, it uses the flag
4807 <tt>-lbar</tt> during the linking stage). Other
4808 libraries that are needed by <tt>libbar</tt> are linked
4809 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4810 linker will load them automatically when it loads
4811 <tt>libbar</tt>. A package should depend on
4812 the libraries it directly uses, and the dependencies for
4813 those libraries should automatically pull in the other
4818 Unfortunately, the <prgn>ldd</prgn> program shows both
4819 the directly and indirectly used libraries, meaning that
4820 the dependencies determined included both direct and
4821 indirect dependencies. The use of <prgn>objdump</prgn>
4822 avoids this problem by determining only the directly
4827 A good example of where this helps is the following. We
4828 could update <tt>libimlib</tt> with a new version that
4829 supports a new graphics format called dgf (but retaining
4830 the same major version number). If we used the old
4831 <prgn>ldd</prgn> method, every package that uses
4832 <tt>libimlib</tt> would need to be recompiled so it
4833 would also depend on <tt>libdgf</tt> or it wouldn't run
4834 due to missing symbols. However with the new system,
4835 packages using <tt>libimlib</tt> can rely on
4836 <tt>libimlib</tt> itself having the dependency on
4837 <tt>libdgf</tt> and so they would not need rebuilding.
4843 In the following sections, we will first describe where the
4844 various <tt>shlibs</tt> files are to be found, then how to
4845 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4846 file format and how to create them if your package contains a
4851 <heading>The <tt>shlibs</tt> files present on the system</heading>
4854 There are several places where <tt>shlibs</tt> files are
4855 found. The following list gives them in the order in which
4857 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4858 (The first one which gives the required information is used.)
4864 <p><file>debian/shlibs.local</file></p>
4867 This lists overrides for this package. Its use is
4868 described below (see <ref id="shlibslocal">).
4873 <p><file>/etc/dpkg/shlibs.override</file></p>
4876 This lists global overrides. This list is normally
4877 empty. It is maintained by the local system
4883 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4886 When packages are being built, any
4887 <file>debian/shlibs</file> files are copied into the
4888 control file area of the temporary build directory and
4889 given the name <file>shlibs</file>. These files give
4890 details of any shared libraries included in the
4892 An example may help here. Let us say that the
4893 source package <tt>foo</tt> generates two binary
4894 packages, <tt>libfoo2</tt> and
4895 <tt>foo-runtime</tt>. When building the binary
4896 packages, the two packages are created in the
4897 directories <file>debian/libfoo2</file> and
4898 <file>debian/foo-runtime</file> respectively.
4899 (<file>debian/tmp</file> could be used instead of one
4900 of these.) Since <tt>libfoo2</tt> provides the
4901 <tt>libfoo</tt> shared library, it will require a
4902 <tt>shlibs</tt> file, which will be installed in
4903 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4905 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4906 when <prgn>dpkg-shlibdeps</prgn> is run on the
4908 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4910 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4911 determine whether <tt>foo-prog</tt>'s library
4912 dependencies are satisfied by any of the libraries
4913 provided by <tt>libfoo2</tt>. For this reason,
4914 <prgn>dpkg-shlibdeps</prgn> must only be run once
4915 all of the individual binary packages'
4916 <tt>shlibs</tt> files have been installed into the
4923 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4926 These are the <file>shlibs</file> files corresponding to
4927 all of the packages installed on the system, and are
4928 maintained by the relevant package maintainers.
4933 <p><file>/etc/dpkg/shlibs.default</file></p>
4936 This file lists any shared libraries whose packages
4937 have failed to provide correct <file>shlibs</file> files.
4938 It was used when the <file>shlibs</file> setup was first
4939 introduced, but it is now normally empty. It is
4940 maintained by the <tt>dpkg</tt> maintainer.
4948 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4949 <file>shlibs</file> files</heading>
4953 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4954 into your <file>debian/rules</file> file. If your package
4955 contains only compiled binaries and libraries (but no scripts),
4956 you can use a command such as:
4957 <example compact="compact">
4958 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4959 debian/tmp/usr/lib/*
4961 Otherwise, you will need to explicitly list the compiled
4962 binaries and libraries.<footnote>
4963 If you are using <tt>debhelper</tt>, the
4964 <prgn>dh_shlibdeps</prgn> program will do this work for
4965 you. It will also correctly handle multi-binary
4971 This command puts the dependency information into the
4972 <file>debian/substvars</file> file, which is then used by
4973 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4974 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4975 field in the control file for this to work.
4979 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4980 done. If it does complain you might need to create your own
4981 <file>debian/shlibs.local</file> file, as explained below (see
4982 <ref id="shlibslocal">).
4986 If you have multiple binary packages, you will need to call
4987 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4988 compiled libraries or binaries. In such a case, you will
4989 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4990 utilities to specify a different <file>substvars</file> file.
4994 If you are creating a udeb for use in the Debian Installer, you
4995 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
4996 the dependency line of type <tt>udeb</tt> by adding
4997 <tt>-tudeb</tt> as option<footnote>
4998 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
4999 will automatically add this option if it knows it is
5001 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5002 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5003 fall back to the regular dependency line.
5007 For more details on dpkg-shlibdeps, please see
5008 <ref id="pkg-dpkg-shlibdeps"> and
5009 <manref name="dpkg-shlibdeps" section="1">.
5014 <heading>The <file>shlibs</file> File Format</heading>
5017 Each <file>shlibs</file> file has the same format. Lines
5018 beginning with <tt>#</tt> are considered to be comments and
5019 are ignored. Each line is of the form:
5020 <example compact="compact">
5021 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5026 We will explain this by reference to the example of the
5027 <tt>zlib1g</tt> package, which (at the time of writing)
5028 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5032 <var>type</var> is an optional element that indicates the type
5033 of package for which the line is valid. The only type currently
5034 in use is <tt>udeb</tt>. The colon and space after the type are
5039 <var>library-name</var> is the name of the shared library,
5040 in this case <tt>libz</tt>. (This must match the name part
5041 of the soname, see below.)
5045 <var>soname-version</var> is the version part of the soname of
5046 the library. The soname is the thing that must exactly match
5047 for the library to be recognized by the dynamic linker, and is
5049 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5050 example, <tt>libz.so.1</tt>.<footnote>
5051 This can be determined using the command
5052 <example compact="compact">
5053 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5056 The version part is the part which comes after
5057 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5061 <var>dependencies</var> has the same syntax as a dependency
5062 field in a binary package control file. It should give
5063 details of which packages are required to satisfy a binary
5064 built against the version of the library contained in the
5065 package. See <ref id="depsyntax"> for details.
5069 In our example, if the first version of the <tt>zlib1g</tt>
5070 package which contained a minor number of at least
5071 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5072 <tt>shlibs</tt> entry for this library could say:
5073 <example compact="compact">
5074 libz 1 zlib1g (>= 1:1.1.3)
5076 The version-specific dependency is to avoid warnings from
5077 the dynamic linker about using older shared libraries with
5082 As zlib1g also provides a udeb containing the shared library,
5083 there would also be a second line:
5084 <example compact="compact">
5085 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5091 <heading>Providing a <file>shlibs</file> file</heading>
5094 If your package provides a shared library, you need to create
5095 a <file>shlibs</file> file following the format described above.
5096 It is usual to call this file <file>debian/shlibs</file> (but if
5097 you have multiple binary packages, you might want to call it
5098 <file>debian/shlibs.<var>package</var></file> instead). Then
5099 let <file>debian/rules</file> install it in the control area:
5100 <example compact="compact">
5101 install -m644 debian/shlibs debian/tmp/DEBIAN
5103 or, in the case of a multi-binary package:
5104 <example compact="compact">
5105 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5107 An alternative way of doing this is to create the
5108 <file>shlibs</file> file in the control area directly from
5109 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5110 file at all,<footnote>
5111 This is what <prgn>dh_makeshlibs</prgn> in the
5112 <tt>debhelper</tt> suite does. If your package also has a udeb
5113 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5114 automatically generate the <tt>udeb:</tt> lines if you specify
5115 the name of the udeb with the <tt>--add-udeb</tt> option.
5117 since the <file>debian/shlibs</file> file itself is ignored by
5118 <prgn>dpkg-shlibdeps</prgn>.
5122 As <prgn>dpkg-shlibdeps</prgn> reads the
5123 <file>DEBIAN/shlibs</file> files in all of the binary packages
5124 being built from this source package, all of the
5125 <file>DEBIAN/shlibs</file> files should be installed before
5126 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5131 <sect1 id="shlibslocal">
5132 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5135 This file is intended only as a <em>temporary</em> fix if
5136 your binaries or libraries depend on a library whose package
5137 does not yet provide a correct <file>shlibs</file> file.
5141 We will assume that you are trying to package a binary
5142 <tt>foo</tt>. When you try running
5143 <prgn>dpkg-shlibdeps</prgn> you get the following error
5144 message (<tt>-O</tt> displays the dependency information on
5145 <tt>stdout</tt> instead of writing it to
5146 <tt>debian/substvars</tt>, and the lines have been wrapped
5147 for ease of reading):
5148 <example compact="compact">
5149 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5150 dpkg-shlibdeps: warning: unable to find dependency
5151 information for shared library libbar (soname 1,
5152 path /usr/lib/libbar.so.1, dependency field Depends)
5153 shlibs:Depends=libc6 (>= 2.2.2-2)
5155 You can then run <prgn>ldd</prgn> on the binary to find the
5156 full location of the library concerned:
5157 <example compact="compact">
5159 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5160 libc.so.6 => /lib/libc.so.6 (0x40032000)
5161 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5163 So the <prgn>foo</prgn> binary depends on the
5164 <prgn>libbar</prgn> shared library, but no package seems to
5165 provide a <file>*.shlibs</file> file handling
5166 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5167 determine the package responsible:
5168 <example compact="compact">
5169 $ dpkg -S /usr/lib/libbar.so.1
5170 bar1: /usr/lib/libbar.so.1
5171 $ dpkg -s bar1 | grep Version
5174 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5175 is the one we are using. Now we can file a bug against the
5176 <tt>bar1</tt> package and create our own
5177 <file>debian/shlibs.local</file> to locally fix the problem.
5178 Including the following line into your
5179 <file>debian/shlibs.local</file> file:
5180 <example compact="compact">
5181 libbar 1 bar1 (>= 1.0-1)
5183 should allow the package build to work.
5187 As soon as the maintainer of <tt>bar1</tt> provides a
5188 correct <file>shlibs</file> file, you should remove this line
5189 from your <file>debian/shlibs.local</file> file. (You should
5190 probably also then have a versioned <tt>Build-Depends</tt>
5191 on <tt>bar1</tt> to help ensure that others do not have the
5192 same problem building your package.)
5201 <chapt id="opersys"><heading>The Operating System</heading>
5204 <heading>File system hierarchy</heading>
5208 <heading>File system Structure</heading>
5211 The location of all installed files and directories must
5212 comply with the File system Hierarchy Standard (FHS),
5213 version 2.3, with the exceptions noted below, and except
5214 where doing so would violate other terms of Debian
5215 Policy. The following exceptions to the FHS apply:
5220 Legacy XFree86 servers are permitted to retain the
5221 configuration file location
5222 <file>/etc/X11/XF86Config-4</file>.
5227 The optional rules related to user specific
5228 configuration files for applications are stored in
5229 the user's home directory are relaxed. It is
5230 recommended that such files start with the
5231 '<tt>.</tt>' character (a "dot file"), and if an
5232 application needs to create more than one dot file
5233 then the preferred placement is in a subdirectory
5234 with a name starting with a '.' character, (a "dot
5235 directory"). In this case it is recommended the
5236 configuration files not start with the '.'
5242 The requirement for amd64 to use <file>/lib64</file>
5243 for 64 bit binaries is removed.
5248 The requirement that
5249 <file>/usr/local/share/man</file> be "synonymous"
5250 with <file>/usr/local/man</file> is relaxed to a
5255 The requirement that windowmanagers with a single
5256 configuration file call it <file>system.*wmrc</file>
5257 is removed, as is the restriction that the window
5258 manager subdirectory be named identically to the
5259 window manager name itself.
5264 The requirement that boot manager configuration
5265 files live in <file>/etc</file>, or at least are
5266 symlinked there, is relaxed to a recommendation.
5273 The version of this document referred here can be
5274 found in the <tt>debian-policy</tt> package or on <url
5275 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5276 name="FHS (Debian copy)"> alongside this manual (or, if
5277 you have the <package>debian-policy</package> installed,
5279 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5280 (local copy)">). The
5281 latest version, which may be a more recent version, may
5283 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5284 Specific questions about following the standard may be
5285 asked on the <tt>debian-devel</tt> mailing list, or
5286 referred to the FHS mailing list (see the
5287 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5293 <heading>Site-specific programs</heading>
5296 As mandated by the FHS, packages must not place any
5297 files in <file>/usr/local</file>, either by putting them in
5298 the file system archive to be unpacked by <prgn>dpkg</prgn>
5299 or by manipulating them in their maintainer scripts.
5303 However, the package may create empty directories below
5304 <file>/usr/local</file> so that the system administrator knows
5305 where to place site-specific files. These are not
5306 directories <em>in</em> <file>/usr/local</file>, but are
5307 children of directories in <file>/usr/local</file>. These
5308 directories (<file>/usr/local/*/dir/</file>)
5309 should be removed on package removal if they are
5314 Note, that this applies only to directories <em>below</em>
5315 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5316 Packages must not create sub-directories in the directory
5317 <file>/usr/local</file> itself, except those listed in FHS,
5318 section 4.5. However, you may create directories below
5319 them as you wish. You must not remove any of the
5320 directories listed in 4.5, even if you created them.
5324 Since <file>/usr/local</file> can be mounted read-only from a
5325 remote server, these directories must be created and
5326 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5327 maintainer scripts and not be included in the
5328 <file>.deb</file> archive. These scripts must not fail if
5329 either of these operations fail.
5333 For example, the <tt>emacsen-common</tt> package could
5334 contain something like
5335 <example compact="compact">
5336 if [ ! -e /usr/local/share/emacs ]
5338 if mkdir /usr/local/share/emacs 2>/dev/null
5340 chown root:staff /usr/local/share/emacs
5341 chmod 2775 /usr/local/share/emacs
5345 in its <prgn>postinst</prgn> script, and
5346 <example compact="compact">
5347 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5348 rmdir /usr/local/share/emacs 2>/dev/null || true
5350 in the <prgn>prerm</prgn> script. (Note that this form is
5351 used to ensure that if the script is interrupted, the
5352 directory <file>/usr/local/share/emacs</file> will still be
5357 If you do create a directory in <file>/usr/local</file> for
5358 local additions to a package, you should ensure that
5359 settings in <file>/usr/local</file> take precedence over the
5360 equivalents in <file>/usr</file>.
5364 However, because <file>/usr/local</file> and its contents are
5365 for exclusive use of the local administrator, a package
5366 must not rely on the presence or absence of files or
5367 directories in <file>/usr/local</file> for normal operation.
5371 The <file>/usr/local</file> directory itself and all the
5372 subdirectories created by the package should (by default) have
5373 permissions 2775 (group-writable and set-group-id) and be
5374 owned by <tt>root.staff</tt>.
5379 <heading>The system-wide mail directory</heading>
5381 The system-wide mail directory is <file>/var/mail</file>. This
5382 directory is part of the base system and should not owned
5383 by any particular mail agents. The use of the old
5384 location <file>/var/spool/mail</file> is deprecated, even
5385 though the spool may still be physically located there.
5386 To maintain partial upgrade compatibility for systems
5387 which have <file>/var/spool/mail</file> as their physical mail
5388 spool, packages using <file>/var/mail</file> must depend on
5389 either <package>libc6</package> (>= 2.1.3-13), or on
5390 <package>base-files</package> (>= 2.2.0), or on later
5391 versions of either one of these packages.
5397 <heading>Users and groups</heading>
5400 <heading>Introduction</heading>
5402 The Debian system can be configured to use either plain or
5407 Some user ids (UIDs) and group ids (GIDs) are reserved
5408 globally for use by certain packages. Because some
5409 packages need to include files which are owned by these
5410 users or groups, or need the ids compiled into binaries,
5411 these ids must be used on any Debian system only for the
5412 purpose for which they are allocated. This is a serious
5413 restriction, and we should avoid getting in the way of
5414 local administration policies. In particular, many sites
5415 allocate users and/or local system groups starting at 100.
5419 Apart from this we should have dynamically allocated ids,
5420 which should by default be arranged in some sensible
5421 order, but the behavior should be configurable.
5425 Packages other than <tt>base-passwd</tt> must not modify
5426 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5427 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5432 <heading>UID and GID classes</heading>
5434 The UID and GID numbers are divided into classes as
5440 Globally allocated by the Debian project, the same
5441 on every Debian system. These ids will appear in
5442 the <file>passwd</file> and <file>group</file> files of all
5443 Debian systems, new ids in this range being added
5444 automatically as the <tt>base-passwd</tt> package is
5449 Packages which need a single statically allocated
5450 uid or gid should use one of these; their
5451 maintainers should ask the <tt>base-passwd</tt>
5459 Dynamically allocated system users and groups.
5460 Packages which need a user or group, but can have
5461 this user or group allocated dynamically and
5462 differently on each system, should use <tt>adduser
5463 --system</tt> to create the group and/or user.
5464 <prgn>adduser</prgn> will check for the existence of
5465 the user or group, and if necessary choose an unused
5466 id based on the ranges specified in
5467 <file>adduser.conf</file>.
5471 <tag>1000-29999:</tag>
5474 Dynamically allocated user accounts. By default
5475 <prgn>adduser</prgn> will choose UIDs and GIDs for
5476 user accounts in this range, though
5477 <file>adduser.conf</file> may be used to modify this
5482 <tag>30000-59999:</tag>
5487 <tag>60000-64999:</tag>
5490 Globally allocated by the Debian project, but only
5491 created on demand. The ids are allocated centrally
5492 and statically, but the actual accounts are only
5493 created on users' systems on demand.
5497 These ids are for packages which are obscure or
5498 which require many statically-allocated ids. These
5499 packages should check for and create the accounts in
5500 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5501 <prgn>adduser</prgn> if it has this facility) if
5502 necessary. Packages which are likely to require
5503 further allocations should have a "hole" left after
5504 them in the allocation, to give them room to
5509 <tag>65000-65533:</tag>
5517 User <tt>nobody</tt>. The corresponding gid refers
5518 to the group <tt>nogroup</tt>.
5525 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5526 not</em> be used, because it is the error return
5535 <sect id="sysvinit">
5536 <heading>System run levels and <file>init.d</file> scripts</heading>
5538 <sect1 id="/etc/init.d">
5539 <heading>Introduction</heading>
5542 The <file>/etc/init.d</file> directory contains the scripts
5543 executed by <prgn>init</prgn> at boot time and when the
5544 init state (or "runlevel") is changed (see <manref
5545 name="init" section="8">).
5549 There are at least two different, yet functionally
5550 equivalent, ways of handling these scripts. For the sake
5551 of simplicity, this document describes only the symbolic
5552 link method. However, it must not be assumed by maintainer
5553 scripts that this method is being used, and any automated
5554 manipulation of the various runlevel behaviors by
5555 maintainer scripts must be performed using
5556 <prgn>update-rc.d</prgn> as described below and not by
5557 manually installing or removing symlinks. For information
5558 on the implementation details of the other method,
5559 implemented in the <tt>file-rc</tt> package, please refer
5560 to the documentation of that package.
5564 These scripts are referenced by symbolic links in the
5565 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5566 runlevels, <prgn>init</prgn> looks in the directory
5567 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5568 execute, where <tt><var>n</var></tt> is the runlevel that
5569 is being changed to, or <tt>S</tt> for the boot-up
5574 The names of the links all have the form
5575 <file>S<var>mm</var><var>script</var></file> or
5576 <file>K<var>mm</var><var>script</var></file> where
5577 <var>mm</var> is a two-digit number and <var>script</var>
5578 is the name of the script (this should be the same as the
5579 name of the actual script in <file>/etc/init.d</file>).
5583 When <prgn>init</prgn> changes runlevel first the targets
5584 of the links whose names start with a <tt>K</tt> are
5585 executed, each with the single argument <tt>stop</tt>,
5586 followed by the scripts prefixed with an <tt>S</tt>, each
5587 with the single argument <tt>start</tt>. (The links are
5588 those in the <file>/etc/rc<var>n</var>.d</file> directory
5589 corresponding to the new runlevel.) The <tt>K</tt> links
5590 are responsible for killing services and the <tt>S</tt>
5591 link for starting services upon entering the runlevel.
5595 For example, if we are changing from runlevel 2 to
5596 runlevel 3, init will first execute all of the <tt>K</tt>
5597 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5598 all of the <tt>S</tt> prefixed scripts in that directory.
5599 The links starting with <tt>K</tt> will cause the
5600 referred-to file to be executed with an argument of
5601 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5606 The two-digit number <var>mm</var> is used to determine
5607 the order in which to run the scripts: low-numbered links
5608 have their scripts run first. For example, the
5609 <tt>K20</tt> scripts will be executed before the
5610 <tt>K30</tt> scripts. This is used when a certain service
5611 must be started before another. For example, the name
5612 server <prgn>bind</prgn> might need to be started before
5613 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5614 can set up its access lists. In this case, the script
5615 that starts <prgn>bind</prgn> would have a lower number
5616 than the script that starts <prgn>inn</prgn> so that it
5618 <example compact="compact">
5625 The two runlevels 0 (halt) and 6 (reboot) are slightly
5626 different. In these runlevels, the links with an
5627 <tt>S</tt> prefix are still called after those with a
5628 <tt>K</tt> prefix, but they too are called with the single
5629 argument <tt>stop</tt>.
5633 Also, if the script name ends in <tt>.sh</tt>, the script
5634 will be sourced in runlevel <tt>S</tt> rather than being
5635 run in a forked subprocess, but will be explicitly run by
5636 <prgn>sh</prgn> in all other runlevels.
5641 <heading>Writing the scripts</heading>
5644 Packages that include daemons for system services should
5645 place scripts in <file>/etc/init.d</file> to start or stop
5646 services at boot time or during a change of runlevel.
5647 These scripts should be named
5648 <file>/etc/init.d/<var>package</var></file>, and they should
5649 accept one argument, saying what to do:
5652 <tag><tt>start</tt></tag>
5653 <item>start the service,</item>
5655 <tag><tt>stop</tt></tag>
5656 <item>stop the service,</item>
5658 <tag><tt>restart</tt></tag>
5659 <item>stop and restart the service if it's already running,
5660 otherwise start the service</item>
5662 <tag><tt>reload</tt></tag>
5663 <item><p>cause the configuration of the service to be
5664 reloaded without actually stopping and restarting
5667 <tag><tt>force-reload</tt></tag>
5668 <item>cause the configuration to be reloaded if the
5669 service supports this, otherwise restart the
5673 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5674 <tt>force-reload</tt> options should be supported by all
5675 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5680 The <file>init.d</file> scripts must ensure that they will
5681 behave sensibly if invoked with <tt>start</tt> when the
5682 service is already running, or with <tt>stop</tt> when it
5683 isn't, and that they don't kill unfortunately-named user
5684 processes. The best way to achieve this is usually to use
5685 <prgn>start-stop-daemon</prgn>.
5689 If a service reloads its configuration automatically (as
5690 in the case of <prgn>cron</prgn>, for example), the
5691 <tt>reload</tt> option of the <file>init.d</file> script
5692 should behave as if the configuration has been reloaded
5697 The <file>/etc/init.d</file> scripts must be treated as
5698 configuration files, either (if they are present in the
5699 package, that is, in the .deb file) by marking them as
5700 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5701 by managing them correctly in the maintainer scripts (see
5702 <ref id="config-files">). This is important since we want
5703 to give the local system administrator the chance to adapt
5704 the scripts to the local system, e.g., to disable a
5705 service without de-installing the package, or to specify
5706 some special command line options when starting a service,
5707 while making sure their changes aren't lost during the next
5712 These scripts should not fail obscurely when the
5713 configuration files remain but the package has been
5714 removed, as configuration files remain on the system after
5715 the package has been removed. Only when <prgn>dpkg</prgn>
5716 is executed with the <tt>--purge</tt> option will
5717 configuration files be removed. In particular, as the
5718 <file>/etc/init.d/<var>package</var></file> script itself is
5719 usually a <tt>conffile</tt>, it will remain on the system
5720 if the package is removed but not purged. Therefore, you
5721 should include a <tt>test</tt> statement at the top of the
5723 <example compact="compact">
5724 test -f <var>program-executed-later-in-script</var> || exit 0
5729 Often there are some variables in the <file>init.d</file>
5730 scripts whose values control the behavior of the scripts,
5731 and which a system administrator is likely to want to
5732 change. As the scripts themselves are frequently
5733 <tt>conffile</tt>s, modifying them requires that the
5734 administrator merge in their changes each time the package
5735 is upgraded and the <tt>conffile</tt> changes. To ease
5736 the burden on the system administrator, such configurable
5737 values should not be placed directly in the script.
5738 Instead, they should be placed in a file in
5739 <file>/etc/default</file>, which typically will have the same
5740 base name as the <file>init.d</file> script. This extra file
5741 should be sourced by the script when the script runs. It
5742 must contain only variable settings and comments in SUSv3
5743 <prgn>sh</prgn> format. It may either be a
5744 <tt>conffile</tt> or a configuration file maintained by
5745 the package maintainer scripts. See <ref id="config-files">
5750 To ensure that vital configurable values are always
5751 available, the <file>init.d</file> script should set default
5752 values for each of the shell variables it uses, either
5753 before sourcing the <file>/etc/default/</file> file or
5754 afterwards using something like the <tt>:
5755 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5756 script must behave sensibly and not fail if the
5757 <file>/etc/default</file> file is deleted.
5762 <heading>Interfacing with the initscript system</heading>
5765 Maintainers should use the abstraction layer provided by
5766 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5767 programs to deal with initscripts in their packages'
5768 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5769 and <prgn>postrm</prgn>.
5773 Directly managing the /etc/rc?.d links and directly
5774 invoking the <file>/etc/init.d/</file> initscripts should
5775 be done only by packages providing the initscript
5776 subsystem (such as <prgn>sysv-rc</prgn> and
5777 <prgn>file-rc</prgn>).
5781 <heading>Managing the links</heading>
5784 The program <prgn>update-rc.d</prgn> is provided for
5785 package maintainers to arrange for the proper creation and
5786 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5787 or their functional equivalent if another method is being
5788 used. This may be used by maintainers in their packages'
5789 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5793 You must not include any <file>/etc/rc<var>n</var>.d</file>
5794 symbolic links in the actual archive or manually create or
5795 remove the symbolic links in maintainer scripts; you must
5796 use the <prgn>update-rc.d</prgn> program instead. (The
5797 former will fail if an alternative method of maintaining
5798 runlevel information is being used.) You must not include
5799 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5800 in the archive either. (Only the <tt>sysvinit</tt>
5805 By default <prgn>update-rc.d</prgn> will start services in
5806 each of the multi-user state runlevels (2, 3, 4, and 5)
5807 and stop them in the halt runlevel (0), the single-user
5808 runlevel (1) and the reboot runlevel (6). The system
5809 administrator will have the opportunity to customize
5810 runlevels by simply adding, moving, or removing the
5811 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5812 symbolic links are being used, or by modifying
5813 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5818 To get the default behavior for your package, put in your
5819 <prgn>postinst</prgn> script
5820 <example compact="compact">
5821 update-rc.d <var>package</var> defaults
5823 and in your <prgn>postrm</prgn>
5824 <example compact="compact">
5825 if [ "$1" = purge ]; then
5826 update-rc.d <var>package</var> remove
5828 </example>. Note that if your package changes runlevels
5829 or priority, you may have to remove and recreate the links,
5830 since otherwise the old links may persist. Refer to the
5831 documentation of <prgn>update-rc.d</prgn>.
5835 This will use a default sequence number of 20. If it does
5836 not matter when or in which order the <file>init.d</file>
5837 script is run, use this default. If it does, then you
5838 should talk to the maintainer of the <prgn>sysvinit</prgn>
5839 package or post to <tt>debian-devel</tt>, and they will
5840 help you choose a number.
5844 For more information about using <tt>update-rc.d</tt>,
5845 please consult its man page <manref name="update-rc.d"
5851 <heading>Running initscripts</heading>
5853 The program <prgn>invoke-rc.d</prgn> is provided to make
5854 it easier for package maintainers to properly invoke an
5855 initscript, obeying runlevel and other locally-defined
5856 constraints that might limit a package's right to start,
5857 stop and otherwise manage services. This program may be
5858 used by maintainers in their packages' scripts.
5862 The package maintainer scripts must use
5863 <prgn>invoke-rc.d</prgn> to invoke the
5864 <file>/etc/init.d/*</file> initscripts, instead of
5865 calling them directly.
5869 By default, <prgn>invoke-rc.d</prgn> will pass any
5870 action requests (start, stop, reload, restart...) to the
5871 <file>/etc/init.d</file> script, filtering out requests
5872 to start or restart a service out of its intended
5877 Most packages will simply need to change:
5878 <example compact="compact">/etc/init.d/<package>
5879 <action></example> in their <prgn>postinst</prgn>
5880 and <prgn>prerm</prgn> scripts to:
5881 <example compact="compact">
5882 if which invoke-rc.d >/dev/null 2>&1; then
5883 invoke-rc.d <var>package</var> <action>
5885 /etc/init.d/<var>package</var> <action>
5891 A package should register its initscript services using
5892 <prgn>update-rc.d</prgn> before it tries to invoke them
5893 using <prgn>invoke-rc.d</prgn>. Invocation of
5894 unregistered services may fail.
5898 For more information about using
5899 <prgn>invoke-rc.d</prgn>, please consult its man page
5900 <manref name="invoke-rc.d" section="8">.
5906 <heading>Boot-time initialization</heading>
5909 There used to be another directory, <file>/etc/rc.boot</file>,
5910 which contained scripts which were run once per machine
5911 boot. This has been deprecated in favour of links from
5912 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5913 described in <ref id="/etc/init.d">. Packages must not
5914 place files in <file>/etc/rc.boot</file>.
5919 <heading>Example</heading>
5922 An example on which you can base your
5923 <file>/etc/init.d</file> scripts is found in
5924 <file>/etc/init.d/skeleton</file>.
5931 <heading>Console messages from <file>init.d</file> scripts</heading>
5934 This section describes the formats to be used for messages
5935 written to standard output by the <file>/etc/init.d</file>
5936 scripts. The intent is to improve the consistency of
5937 Debian's startup and shutdown look and feel. For this
5938 reason, please look very carefully at the details. We want
5939 the messages to have the same format in terms of wording,
5940 spaces, punctuation and case of letters.
5944 Here is a list of overall rules that should be used for
5945 messages generated by <file>/etc/init.d</file> scripts.
5951 The message should fit in one line (fewer than 80
5952 characters), start with a capital letter and end with
5953 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5957 If the script is performing some time consuming task in
5958 the background (not merely starting or stopping a
5959 program, for instance), an ellipsis (three dots:
5960 <tt>...</tt>) should be output to the screen, with no
5961 leading or tailing whitespace or line feeds.
5965 The messages should appear as if the computer is telling
5966 the user what it is doing (politely :-), but should not
5967 mention "it" directly. For example, instead of:
5968 <example compact="compact">
5969 I'm starting network daemons: nfsd mountd.
5971 the message should say
5972 <example compact="compact">
5973 Starting network daemons: nfsd mountd.
5980 <tt>init.d</tt> script should use the following standard
5981 message formats for the situations enumerated below.
5987 <p>When daemons are started</p>
5990 If the script starts one or more daemons, the output
5991 should look like this (a single line, no leading
5993 <example compact="compact">
5994 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5996 The <var>description</var> should describe the
5997 subsystem the daemon or set of daemons are part of,
5998 while <var>daemon-1</var> up to <var>daemon-n</var>
5999 denote each daemon's name (typically the file name of
6004 For example, the output of <file>/etc/init.d/lpd</file>
6006 <example compact="compact">
6007 Starting printer spooler: lpd.
6012 This can be achieved by saying
6013 <example compact="compact">
6014 echo -n "Starting printer spooler: lpd"
6015 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6018 in the script. If there are more than one daemon to
6019 start, the output should look like this:
6020 <example compact="compact">
6021 echo -n "Starting remote file system services:"
6022 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6023 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6024 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6027 This makes it possible for the user to see what is
6028 happening and when the final daemon has been started.
6029 Care should be taken in the placement of white spaces:
6030 in the example above the system administrators can
6031 easily comment out a line if they don't want to start
6032 a specific daemon, while the displayed message still
6038 <p>When a system parameter is being set</p>
6041 If you have to set up different system parameters
6042 during the system boot, you should use this format:
6043 <example compact="compact">
6044 Setting <var>parameter</var> to "<var>value</var>".
6049 You can use a statement such as the following to get
6051 <example compact="compact">
6052 echo "Setting DNS domainname to \"$domainname\"."
6057 Note that the same symbol (<tt>"</tt>) is used for the left
6058 and right quotation marks. A grave accent (<tt>`</tt>) is
6059 not a quote character; neither is an apostrophe
6065 <p>When a daemon is stopped or restarted</p>
6068 When you stop or restart a daemon, you should issue a
6069 message identical to the startup message, except that
6070 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6071 or <tt>Restarting</tt> respectively.
6075 For example, stopping the printer daemon will look like
6077 <example compact="compact">
6078 Stopping printer spooler: lpd.
6084 <p>When something is executed</p>
6087 There are several examples where you have to run a
6088 program at system startup or shutdown to perform a
6089 specific task, for example, setting the system's clock
6090 using <prgn>netdate</prgn> or killing all processes
6091 when the system shuts down. Your message should look
6093 <example compact="compact">
6094 Doing something very useful...done.
6096 You should print the <tt>done.</tt> immediately after
6097 the job has been completed, so that the user is
6098 informed why they have to wait. You can get this
6100 <example compact="compact">
6101 echo -n "Doing something very useful..."
6110 <p>When the configuration is reloaded</p>
6113 When a daemon is forced to reload its configuration
6114 files you should use the following format:
6115 <example compact="compact">
6116 Reloading <var>description</var> configuration...done.
6118 where <var>description</var> is the same as in the
6119 daemon starting message.
6127 <heading>Cron jobs</heading>
6130 Packages must not modify the configuration file
6131 <file>/etc/crontab</file>, and they must not modify the files in
6132 <file>/var/spool/cron/crontabs</file>.</p>
6135 If a package wants to install a job that has to be executed
6136 via cron, it should place a file with the name of the
6137 package in one or more of the following directories:
6138 <example compact="compact">
6143 As these directory names imply, the files within them are
6144 executed on a daily, weekly, or monthly basis,
6145 respectively. The exact times are listed in
6146 <file>/etc/crontab</file>.</p>
6149 All files installed in any of these directories must be
6150 scripts (e.g., shell scripts or Perl scripts) so that they
6151 can easily be modified by the local system administrator.
6152 In addition, they should be treated as configuration
6157 If a certain job has to be executed more frequently than
6158 daily, the package should install a file
6159 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6160 same syntax as <file>/etc/crontab</file> and is processed by
6161 <prgn>cron</prgn> automatically. The file must also be
6162 treated as a configuration file. (Note that entries in the
6163 <file>/etc/cron.d</file> directory are not handled by
6164 <prgn>anacron</prgn>. Thus, you should only use this
6165 directory for jobs which may be skipped if the system is not
6169 The scripts or crontab entries in these directories should
6170 check if all necessary programs are installed before they
6171 try to execute them. Otherwise, problems will arise when a
6172 package was removed but not purged since configuration files
6173 are kept on the system in this situation.</p>
6177 <heading>Menus</heading>
6180 The Debian <tt>menu</tt> package provides a standard
6181 interface between packages providing applications and
6182 <em>menu programs</em> (either X window managers or
6183 text-based menu programs such as <prgn>pdmenu</prgn>).
6187 All packages that provide applications that need not be
6188 passed any special command line arguments for normal
6189 operation should register a menu entry for those
6190 applications, so that users of the <tt>menu</tt> package
6191 will automatically get menu entries in their window
6192 managers, as well in shells like <tt>pdmenu</tt>.
6196 Menu entries should follow the current menu policy.
6200 The menu policy can be found in the <tt>menu-policy</tt>
6201 files in the <tt>debian-policy</tt> package.
6202 It is also available from the Debian web mirrors at
6203 <tt><url name="/doc/packaging-manuals/menu-policy/"
6204 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6208 Please also refer to the <em>Debian Menu System</em>
6209 documentation that comes with the <package>menu</package>
6210 package for information about how to register your
6216 <heading>Multimedia handlers</heading>
6219 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6220 is a mechanism for encoding files and data streams and
6221 providing meta-information about them, in particular their
6222 type (e.g. audio or video) and format (e.g. PNG, HTML,
6227 Registration of MIME type handlers allows programs like mail
6228 user agents and web browsers to invoke these handlers to
6229 view, edit or display MIME types they don't support directly.
6233 Packages which provide the ability to view/show/play,
6234 compose, edit or print MIME types should register themselves
6235 as such following the current MIME support policy.
6239 The MIME support policy can be found in the <tt>mime-policy</tt>
6240 files in the <tt>debian-policy</tt> package.
6241 It is also available from the Debian web mirrors at
6242 <tt><url name="/doc/packaging-manuals/mime-policy/"
6243 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6249 <heading>Keyboard configuration</heading>
6252 To achieve a consistent keyboard configuration so that all
6253 applications interpret a keyboard event the same way, all
6254 programs in the Debian distribution must be configured to
6255 comply with the following guidelines.
6259 The following keys must have the specified interpretations:
6262 <tag><tt><--</tt></tag>
6263 <item>delete the character to the left of the cursor</item>
6265 <tag><tt>Delete</tt></tag>
6266 <item>delete the character to the right of the cursor</item>
6268 <tag><tt>Control+H</tt></tag>
6269 <item>emacs: the help prefix</item>
6272 The interpretation of any keyboard events should be
6273 independent of the terminal that is used, be it a virtual
6274 console, an X terminal emulator, an rlogin/telnet session,
6279 The following list explains how the different programs
6280 should be set up to achieve this:
6286 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6290 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6294 X translations are set up to make
6295 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6296 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6297 is the vt220 escape code for the "delete character"
6298 key). This must be done by loading the X resources
6299 using <prgn>xrdb</prgn> on all local X displays, not
6300 using the application defaults, so that the
6301 translation resources used correspond to the
6302 <prgn>xmodmap</prgn> settings.
6306 The Linux console is configured to make
6307 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6308 generate <tt>ESC [ 3 ~</tt>.
6312 X applications are configured so that <tt><</tt>
6313 deletes left, and <tt>Delete</tt> deletes right. Motif
6314 applications already work like this.
6318 Terminals should have <tt>stty erase ^?</tt> .
6322 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6323 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6324 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6328 Emacs is programmed to map <tt>KB_Backspace</tt> or
6329 the <tt>stty erase</tt> character to
6330 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6331 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6332 <tt>^H</tt> to <tt>help</tt> as always.
6336 Other applications use the <tt>stty erase</tt>
6337 character and <tt>kdch1</tt> for the two delete keys,
6338 with ASCII DEL being "delete previous character" and
6339 <tt>kdch1</tt> being "delete character under
6347 This will solve the problem except for the following
6354 Some terminals have a <tt><--</tt> key that cannot
6355 be made to produce anything except <tt>^H</tt>. On
6356 these terminals Emacs help will be unavailable on
6357 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6358 character takes precedence in Emacs, and has been set
6359 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6360 available) can be used instead.
6364 Some operating systems use <tt>^H</tt> for <tt>stty
6365 erase</tt>. However, modern telnet versions and all
6366 rlogin versions propagate <tt>stty</tt> settings, and
6367 almost all UNIX versions honour <tt>stty erase</tt>.
6368 Where the <tt>stty</tt> settings are not propagated
6369 correctly, things can be made to work by using
6370 <tt>stty</tt> manually.
6374 Some systems (including previous Debian versions) use
6375 <prgn>xmodmap</prgn> to arrange for both
6376 <tt><--</tt> and <tt>Delete</tt> to generate
6377 <tt>KB_Delete</tt>. We can change the behavior of
6378 their X clients using the same X resources that we use
6379 to do it for our own clients, or configure our clients
6380 using their resources when things are the other way
6381 around. On displays configured like this
6382 <tt>Delete</tt> will not work, but <tt><--</tt>
6387 Some operating systems have different <tt>kdch1</tt>
6388 settings in their <tt>terminfo</tt> database for
6389 <tt>xterm</tt> and others. On these systems the
6390 <tt>Delete</tt> key will not work correctly when you
6391 log in from a system conforming to our policy, but
6392 <tt><--</tt> will.
6399 <heading>Environment variables</heading>
6402 A program must not depend on environment variables to get
6403 reasonable defaults. (That's because these environment
6404 variables would have to be set in a system-wide
6405 configuration file like <file>/etc/profile</file>, which is not
6406 supported by all shells.)
6410 If a program usually depends on environment variables for its
6411 configuration, the program should be changed to fall back to
6412 a reasonable default configuration if these environment
6413 variables are not present. If this cannot be done easily
6414 (e.g., if the source code of a non-free program is not
6415 available), the program must be replaced by a small
6416 "wrapper" shell script which sets the environment variables
6417 if they are not already defined, and calls the original program.
6421 Here is an example of a wrapper script for this purpose:
6423 <example compact="compact">
6425 BAR=${BAR:-/var/lib/fubar}
6427 exec /usr/lib/foo/foo "$@"
6432 Furthermore, as <file>/etc/profile</file> is a configuration
6433 file of the <prgn>base-files</prgn> package, other packages must
6434 not put any environment variables or other commands into that
6439 <sect id="doc-base">
6440 <heading>Registering Documents using doc-base</heading>
6443 The <package>doc-base</package> package implements a
6444 flexible mechanism for handling and presenting
6445 documentation. The recommended practice is for every Debian
6446 package that provides online documentation (other than just
6447 manual pages) to register these documents with
6448 <package>doc-base</package> by installing a
6449 <package>doc-base</package> control file via the
6450 <prgn/install-docs/ script at installation time and
6451 de-register the manuals again when the package is removed.
6454 Please refer to the documentation that comes with the
6455 <package>doc-base</package> package for information and
6464 <heading>Files</heading>
6467 <heading>Binaries</heading>
6470 Two different packages must not install programs with
6471 different functionality but with the same filenames. (The
6472 case of two programs having the same functionality but
6473 different implementations is handled via "alternatives" or
6474 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6475 <ref id="conflicts"> respectively.) If this case happens,
6476 one of the programs must be renamed. The maintainers should
6477 report this to the <tt>debian-devel</tt> mailing list and
6478 try to find a consensus about which program will have to be
6479 renamed. If a consensus cannot be reached, <em>both</em>
6480 programs must be renamed.
6484 By default, when a package is being built, any binaries
6485 created should include debugging information, as well as
6486 being compiled with optimization. You should also turn on
6487 as many reasonable compilation warnings as possible; this
6488 makes life easier for porters, who can then look at build
6489 logs for possible problems. For the C programming language,
6490 this means the following compilation parameters should be
6492 <example compact="compact">
6494 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6496 INSTALL = install -s # (or use strip on the files in debian/tmp)
6501 Note that by default all installed binaries should be stripped,
6502 either by using the <tt>-s</tt> flag to
6503 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6504 the binaries after they have been copied into
6505 <file>debian/tmp</file> but before the tree is made into a
6510 Although binaries in the build tree should be compiled with
6511 debugging information by default, it can often be difficult
6512 to debug programs if they are also subjected to compiler
6513 optimization. For this reason, it is recommended to support
6514 the standardized environment
6515 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6516 contain several flags to change how a package is compiled
6524 The presence of this string means that the package
6525 should be compiled with a minimum of optimization.
6526 For C programs, it is best to add <tt>-O0</tt>
6527 to <tt>CFLAGS</tt> (although this is usually the
6528 default). Some programs might fail to build or run at
6529 this level of optimization; it may be necessary to
6530 use <tt>-O1</tt>, for example.
6534 This string means that the debugging symbols should
6535 not be stripped from the binary during installation,
6536 so that debugging information may be included in the package.
6542 The following makefile snippet is an example of how one may
6543 implement the build options; you will probably have to
6544 massage this example in order to make it work for your
6546 <example compact="compact">
6549 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6550 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6551 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6552 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6554 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6559 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6560 INSTALL_PROGRAM += -s
6566 It is up to the package maintainer to decide what
6567 compilation options are best for the package. Certain
6568 binaries (such as computationally-intensive programs) will
6569 function better with certain flags (<tt>-O3</tt>, for
6570 example); feel free to use them. Please use good judgment
6571 here. Don't use flags for the sake of it; only use them
6572 if there is good reason to do so. Feel free to override
6573 the upstream author's ideas about which compilation
6574 options are best: they are often inappropriate for our
6580 <sect id="libraries">
6581 <heading>Libraries</heading>
6584 If the package is <strong>architecture: any</strong>, then
6585 the shared library compilation and linking flags must have
6586 <tt>-fPIC</tt>, or the package shall not build on some of
6587 the supported architectures<footnote>
6589 If you are using GCC, <tt>-fPIC</tt> produces code with
6590 relocatable position independent code, which is required for
6591 most architectures to create a shared library, with i386 and
6592 perhaps some others where non position independent code is
6593 permitted in a shared library.
6596 Position independent code may have a performance penalty,
6597 especially on <tt>i386</tt>. However, in most cases the
6598 speed penalty must be measured against the memory wasted on
6599 the few architectures where non position independent code is
6602 </footnote>. Any exception to this rule must be discussed on
6603 the mailing list <em>debian-devel@lists.debian.org</em>, and
6604 a rough consensus obtained. The reasons for not compiling
6605 with <tt>-fPIC</tt> flag must be recorded in the file
6606 <tt>README.Debian</tt>, and care must be taken to either
6607 restrict the architecture or arrange for <tt>-fPIC</tt> to
6608 be used on architectures where it is required.<footnote>
6610 Some of the reasons why this might be required is if the
6611 library contains hand crafted assembly code that is not
6612 relocatable, the speed penalty is excessive for compute
6613 intensive libs, and similar reasons.
6618 As to the static libraries, the common case is not to have
6619 relocatable code, since there is no benefit, unless in specific
6620 cases; therefore the static version must not be compiled
6621 with the <tt>-fPIC</tt> flag. Any exception to this rule
6622 should be discussed on the mailing list
6623 <em>debian-devel@lists.debian.org</em>, and the reasons for
6624 compiling with the <tt>-fPIC</tt> flag must be recorded in
6625 the file <tt>README.Debian</tt>. <footnote>
6627 Some of the reasons for linking static libraries with
6628 the <tt>-fPIC</tt> flag are if, for example, one needs a
6629 Perl API for a library that is under rapid development,
6630 and has an unstable API, so shared libraries are
6631 pointless at this phase of the library's development. In
6632 that case, since Perl needs a library with relocatable
6633 code, it may make sense to create a static library with
6634 relocatable code. Another reason cited is if you are
6635 distilling various libraries into a common shared
6636 library, like <tt>mklibs</tt> does in the Debian
6642 In other words, if both a shared and a static library is
6643 being built, each source unit (<tt>*.c</tt>, for example,
6644 for C files) will need to be compiled twice, for the normal
6648 You must specify the gcc option <tt>-D_REENTRANT</tt>
6649 when building a library (either static or shared) to make
6650 the library compatible with LinuxThreads.
6654 Although not enforced by the build tools, shared libraries
6655 must be linked against all libraries that they use symbols from
6656 in the same way that binaries are. This ensures the correct
6657 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6658 system and guarantees that all libraries can be safely opened
6659 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6660 option <tt>-Wl,-z,defs</tt> when building a shared library.
6661 Since this option enforces symbol resolution at build time,
6662 a missing library reference will be caught early as a fatal
6667 All installed shared libraries should be stripped with
6668 <example compact="compact">
6669 strip --strip-unneeded <var>your-lib</var>
6671 (The option <tt>--strip-unneeded</tt> makes
6672 <prgn>strip</prgn> remove only the symbols which aren't
6673 needed for relocation processing.) Shared libraries can
6674 function perfectly well when stripped, since the symbols for
6675 dynamic linking are in a separate part of the ELF object
6677 You might also want to use the options
6678 <tt>--remove-section=.comment</tt> and
6679 <tt>--remove-section=.note</tt> on both shared libraries
6680 and executables, and <tt>--strip-debug</tt> on static
6686 Note that under some circumstances it may be useful to
6687 install a shared library unstripped, for example when
6688 building a separate package to support debugging.
6692 Shared object files (often <file>.so</file> files) that are not
6693 public libraries, that is, they are not meant to be linked
6694 to by third party executables (binaries of other packages),
6695 should be installed in subdirectories of the
6696 <file>/usr/lib</file> directory. Such files are exempt from the
6697 rules that govern ordinary shared libraries, except that
6698 they must not be installed executable and should be
6700 A common example are the so-called "plug-ins",
6701 internal shared objects that are dynamically loaded by
6702 programs using <manref name="dlopen" section="3">.
6707 Packages containing shared libraries that may be linked to
6708 by other packages' binaries, but which for some
6709 <em>compelling</em> reason can not be installed in
6710 <file>/usr/lib</file> directory, may install the shared library
6711 files in subdirectories of the <file>/usr/lib</file> directory,
6712 in which case they should arrange to add that directory in
6713 <file>/etc/ld.so.conf</file> in the package's post-installation
6714 script, and remove it in the package's post-removal script.
6718 An ever increasing number of packages are using
6719 <prgn>libtool</prgn> to do their linking. The latest GNU
6720 libtools (>= 1.3a) can take advantage of the metadata in the
6721 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6722 files). The main advantage of <prgn>libtool</prgn>'s
6723 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6724 store and subsequently access metadata with respect to the
6725 libraries it builds. <prgn>libtool</prgn> will search for
6726 those files, which contain a lot of useful information about
6727 a library (such as library dependency information for static
6728 linking). Also, they're <em>essential</em> for programs
6729 using <tt>libltdl</tt>.<footnote>
6730 Although <prgn>libtool</prgn> is fully capable of
6731 linking against shared libraries which don't have
6732 <tt>.la</tt> files, as it is a mere shell script it can
6733 add considerably to the build time of a
6734 <prgn>libtool</prgn>-using package if that shell script
6735 has to derive all this information from first principles
6736 for each library every time it is linked. With the
6737 advent of <prgn>libtool</prgn> version 1.4 (and to a
6738 lesser extent <prgn>libtool</prgn> version 1.3), the
6739 <file>.la</file> files also store information about
6740 inter-library dependencies which cannot necessarily be
6741 derived after the <file>.la</file> file is deleted.
6746 Packages that use <prgn>libtool</prgn> to create shared
6747 libraries should include the <file>.la</file> files in the
6748 <tt>-dev</tt> package, unless the package relies on
6749 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6750 the <tt>.la</tt> files must go in the run-time library
6755 You must make sure that you use only released versions of
6756 shared libraries to build your packages; otherwise other
6757 users will not be able to run your binaries
6758 properly. Producing source packages that depend on
6759 unreleased compilers is also usually a bad
6766 <heading>Shared libraries</heading>
6768 This section has moved to <ref id="sharedlibs">.
6774 <heading>Scripts</heading>
6777 All command scripts, including the package maintainer
6778 scripts inside the package and used by <prgn>dpkg</prgn>,
6779 should have a <tt>#!</tt> line naming the shell to be used
6784 In the case of Perl scripts this should be
6785 <tt>#!/usr/bin/perl</tt>.
6789 When scripts are installed into a directory in the system
6790 PATH, the script name should not include an extension such
6791 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6792 language currently used to implement it.
6795 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6796 should almost certainly start with <tt>set -e</tt> so that
6797 errors are detected. Every script should use
6798 <tt>set -e</tt> or check the exit status of <em>every</em>
6803 Scripts may assume that <file>/bin/sh</file> implements the
6804 SUSv3 Shell Command Language<footnote>
6805 Single UNIX Specification, version 3, which is also IEEE
6806 1003.1-2004 (POSIX), and is available on the World Wide Web
6807 from <url id="http://www.unix.org/version3/online.html"
6808 name="The Open Group"> after free
6809 registration.</footnote>
6810 plus the following additional features not mandated by
6812 These features are in widespread use in the Linux community
6813 and are implemented in all of bash, dash, and ksh, the most
6814 common shells users may wish to use as <file>/bin/sh</file>.
6817 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6818 must not generate a newline.</item>
6819 <item><tt>test</tt>, if implemented as a shell built-in, must
6820 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6822 <item><tt>local</tt> to create a scoped variable must be
6823 supported; however, <tt>local</tt> may or may not preserve
6824 the variable value from an outer scope and may or may not
6825 support arguments more complex than simple variables. Only
6837 If a shell script requires non-SUSv3 features from the shell
6838 interpreter other than those listed above, the appropriate shell
6839 must be specified in the first line of the script (e.g.,
6840 <tt>#!/bin/bash</tt>) and the package must depend on the package
6841 providing the shell (unless the shell package is marked
6842 "Essential", as in the case of <prgn>bash</prgn>).
6846 You may wish to restrict your script to SUSv3 features plus the
6847 above set when possible so that it may use <file>/bin/sh</file>
6848 as its interpreter. If your script works with <prgn>dash</prgn>
6849 (originally called <prgn>ash</prgn>), it probably complies with
6850 the above requirements, but if you are in doubt, use
6851 <file>/bin/bash</file>.
6855 Perl scripts should check for errors when making any
6856 system calls, including <tt>open</tt>, <tt>print</tt>,
6857 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6861 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6862 scripting languages. See <em>Csh Programming Considered
6863 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6864 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6865 If an upstream package comes with <prgn>csh</prgn> scripts
6866 then you must make sure that they start with
6867 <tt>#!/bin/csh</tt> and make your package depend on the
6868 <prgn>c-shell</prgn> virtual package.
6872 Any scripts which create files in world-writeable
6873 directories (e.g., in <file>/tmp</file>) must use a
6874 mechanism which will fail atomically if a file with the same
6875 name already exists.
6879 The Debian base system provides the <prgn>tempfile</prgn>
6880 and <prgn>mktemp</prgn> utilities for use by scripts for
6887 <heading>Symbolic links</heading>
6890 In general, symbolic links within a top-level directory
6891 should be relative, and symbolic links pointing from one
6892 top-level directory into another should be absolute. (A
6893 top-level directory is a sub-directory of the root
6894 directory <file>/</file>.)
6898 In addition, symbolic links should be specified as short as
6899 possible, i.e., link targets like <file>foo/../bar</file> are
6904 Note that when creating a relative link using
6905 <prgn>ln</prgn> it is not necessary for the target of the
6906 link to exist relative to the working directory you're
6907 running <prgn>ln</prgn> from, nor is it necessary to change
6908 directory to the directory where the link is to be made.
6909 Simply include the string that should appear as the target
6910 of the link (this will be a pathname relative to the
6911 directory in which the link resides) as the first argument
6916 For example, in your <prgn>Makefile</prgn> or
6917 <file>debian/rules</file>, you can do things like:
6918 <example compact="compact">
6919 ln -fs gcc $(prefix)/bin/cc
6920 ln -fs gcc debian/tmp/usr/bin/cc
6921 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6922 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6927 A symbolic link pointing to a compressed file should always
6928 have the same file extension as the referenced file. (For
6929 example, if a file <file>foo.gz</file> is referenced by a
6930 symbolic link, the filename of the link has to end with
6931 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6936 <heading>Device files</heading>
6939 Packages must not include device files in the package file
6944 If a package needs any special device files that are not
6945 included in the base system, it must call
6946 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6947 after notifying the user<footnote>
6948 This notification could be done via a (low-priority)
6949 debconf message, or an echo (printf) statement.
6954 Packages must not remove any device files in the
6955 <prgn>postrm</prgn> or any other script. This is left to the
6956 system administrator.
6960 Debian uses the serial devices
6961 <file>/dev/ttyS*</file>. Programs using the old
6962 <file>/dev/cu*</file> devices should be changed to use
6963 <file>/dev/ttyS*</file>.
6967 <sect id="config-files">
6968 <heading>Configuration files</heading>
6971 <heading>Definitions</heading>
6975 <tag>configuration file</tag>
6977 A file that affects the operation of a program, or
6978 provides site- or host-specific information, or
6979 otherwise customizes the behavior of a program.
6980 Typically, configuration files are intended to be
6981 modified by the system administrator (if needed or
6982 desired) to conform to local policy or to provide
6983 more useful site-specific behavior.
6986 <tag><tt>conffile</tt></tag>
6988 A file listed in a package's <tt>conffiles</tt>
6989 file, and is treated specially by <prgn>dpkg</prgn>
6990 (see <ref id="configdetails">).
6996 The distinction between these two is important; they are
6997 not interchangeable concepts. Almost all
6998 <tt>conffile</tt>s are configuration files, but many
6999 configuration files are not <tt>conffiles</tt>.
7003 Note that a script that embeds configuration information
7004 (such as most of the files in <file>/etc/default</file> and
7005 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
7006 configuration file and should be treated as such.
7011 <heading>Location</heading>
7014 Any configuration files created or used by your package
7015 must reside in <file>/etc</file>. If there are several,
7016 consider creating a subdirectory of <file>/etc</file>
7017 named after your package.
7021 If your package creates or uses configuration files
7022 outside of <file>/etc</file>, and it is not feasible to modify
7023 the package to use <file>/etc</file> directly, put the files
7024 in <file>/etc</file> and create symbolic links to those files
7025 from the location that the package requires.
7030 <heading>Behavior</heading>
7033 Configuration file handling must conform to the following
7035 <list compact="compact">
7037 local changes must be preserved during a package
7041 configuration files must be preserved when the
7042 package is removed, and only deleted when the
7049 The easy way to achieve this behavior is to make the
7050 configuration file a <tt>conffile</tt>. This is
7051 appropriate only if it is possible to distribute a default
7052 version that will work for most installations, although
7053 some system administrators may choose to modify it. This
7054 implies that the default version will be part of the
7055 package distribution, and must not be modified by the
7056 maintainer scripts during installation (or at any other
7061 In order to ensure that local changes are preserved
7062 correctly, no package may contain or make hard links to
7063 conffiles.<footnote>
7064 Rationale: There are two problems with hard links.
7065 The first is that some editors break the link while
7066 editing one of the files, so that the two files may
7067 unwittingly become unlinked and different. The second
7068 is that <prgn>dpkg</prgn> might break the hard link
7069 while upgrading <tt>conffile</tt>s.
7074 The other way to do it is via the maintainer scripts. In
7075 this case, the configuration file must not be listed as a
7076 <tt>conffile</tt> and must not be part of the package
7077 distribution. If the existence of a file is required for
7078 the package to be sensibly configured it is the
7079 responsibility of the package maintainer to provide
7080 maintainer scripts which correctly create, update and
7081 maintain the file and remove it on purge. (See <ref
7082 id="maintainerscripts"> for more information.) These
7083 scripts must be idempotent (i.e., must work correctly if
7084 <prgn>dpkg</prgn> needs to re-run them due to errors
7085 during installation or removal), must cope with all the
7086 variety of ways <prgn>dpkg</prgn> can call maintainer
7087 scripts, must not overwrite or otherwise mangle the user's
7088 configuration without asking, must not ask unnecessary
7089 questions (particularly during upgrades), and must
7090 otherwise be good citizens.
7094 The scripts are not required to configure every possible
7095 option for the package, but only those necessary to get
7096 the package running on a given system. Ideally the
7097 sysadmin should not have to do any configuration other
7098 than that done (semi-)automatically by the
7099 <prgn>postinst</prgn> script.
7103 A common practice is to create a script called
7104 <file><var>package</var>-configure</file> and have the
7105 package's <prgn>postinst</prgn> call it if and only if the
7106 configuration file does not already exist. In certain
7107 cases it is useful for there to be an example or template
7108 file which the maintainer scripts use. Such files should
7109 be in <file>/usr/share/<var>package</var></file> or
7110 <file>/usr/lib/<var>package</var></file> (depending on whether
7111 they are architecture-independent or not). There should
7112 be symbolic links to them from
7113 <file>/usr/share/doc/<var>package</var>/examples</file> if
7114 they are examples, and should be perfectly ordinary
7115 <prgn>dpkg</prgn>-handled files (<em>not</em>
7116 configuration files).
7120 These two styles of configuration file handling must
7121 not be mixed, for that way lies madness:
7122 <prgn>dpkg</prgn> will ask about overwriting the file
7123 every time the package is upgraded.
7128 <heading>Sharing configuration files</heading>
7131 Packages which specify the same file as a
7132 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7133 with each other. (This is an instance of the general rule
7134 about not sharing files. Note that neither alternatives
7135 nor diversions are likely to be appropriate in this case;
7136 in particular, <prgn>dpkg</prgn> does not handle diverted
7137 <tt>conffile</tt>s well.)
7141 The maintainer scripts must not alter a <tt>conffile</tt>
7142 of <em>any</em> package, including the one the scripts
7147 If two or more packages use the same configuration file
7148 and it is reasonable for both to be installed at the same
7149 time, one of these packages must be defined as
7150 <em>owner</em> of the configuration file, i.e., it will be
7151 the package which handles that file as a configuration
7152 file. Other packages that use the configuration file must
7153 depend on the owning package if they require the
7154 configuration file to operate. If the other package will
7155 use the configuration file if present, but is capable of
7156 operating without it, no dependency need be declared.
7160 If it is desirable for two or more related packages to
7161 share a configuration file <em>and</em> for all of the
7162 related packages to be able to modify that configuration
7163 file, then the following should be done:
7164 <enumlist compact="compact">
7166 One of the related packages (the "owning" package)
7167 will manage the configuration file with maintainer
7168 scripts as described in the previous section.
7171 The owning package should also provide a program
7172 that the other packages may use to modify the
7176 The related packages must use the provided program
7177 to make any desired modifications to the
7178 configuration file. They should either depend on
7179 the core package to guarantee that the configuration
7180 modifier program is available or accept gracefully
7181 that they cannot modify the configuration file if it
7182 is not. (This is in addition to the fact that the
7183 configuration file may not even be present in the
7190 Sometimes it's appropriate to create a new package which
7191 provides the basic infrastructure for the other packages
7192 and which manages the shared configuration files. (The
7193 <tt>sgml-base</tt> package is a good example.)
7198 <heading>User configuration files ("dotfiles")</heading>
7201 The files in <file>/etc/skel</file> will automatically be
7202 copied into new user accounts by <prgn>adduser</prgn>.
7203 No other program should reference the files in
7204 <file>/etc/skel</file>.
7208 Therefore, if a program needs a dotfile to exist in
7209 advance in <file>$HOME</file> to work sensibly, that dotfile
7210 should be installed in <file>/etc/skel</file> and treated as a
7215 However, programs that require dotfiles in order to
7216 operate sensibly are a bad thing, unless they do create
7217 the dotfiles themselves automatically.
7221 Furthermore, programs should be configured by the Debian
7222 default installation to behave as closely to the upstream
7223 default behavior as possible.
7227 Therefore, if a program in a Debian package needs to be
7228 configured in some way in order to operate sensibly, that
7229 should be done using a site-wide configuration file placed
7230 in <file>/etc</file>. Only if the program doesn't support a
7231 site-wide default configuration and the package maintainer
7232 doesn't have time to add it may a default per-user file be
7233 placed in <file>/etc/skel</file>.
7237 <file>/etc/skel</file> should be as empty as we can make it.
7238 This is particularly true because there is no easy (or
7239 necessarily desirable) mechanism for ensuring that the
7240 appropriate dotfiles are copied into the accounts of
7241 existing users when a package is installed.
7247 <heading>Log files</heading>
7249 Log files should usually be named
7250 <file>/var/log/<var>package</var>.log</file>. If you have many
7251 log files, or need a separate directory for permission
7252 reasons (<file>/var/log</file> is writable only by
7253 <file>root</file>), you should usually create a directory named
7254 <file>/var/log/<var>package</var></file> and place your log
7259 Log files must be rotated occasionally so that they don't
7260 grow indefinitely; the best way to do this is to drop a log
7261 rotation configuration file into the directory
7262 <file>/etc/logrotate.d</file> and use the facilities provided by
7263 logrotate.<footnote>
7265 The traditional approach to log files has been to set up
7266 <em>ad hoc</em> log rotation schemes using simple shell
7267 scripts and cron. While this approach is highly
7268 customizable, it requires quite a lot of sysadmin work.
7269 Even though the original Debian system helped a little
7270 by automatically installing a system which can be used
7271 as a template, this was deemed not enough.
7275 The use of <prgn>logrotate</prgn>, a program developed
7276 by Red Hat, is better, as it centralizes log management.
7277 It has both a configuration file
7278 (<file>/etc/logrotate.conf</file>) and a directory where
7279 packages can drop their individual log rotation
7280 configurations (<file>/etc/logrotate.d</file>).
7283 Here is a good example for a logrotate config
7284 file (for more information see <manref name="logrotate"
7286 <example compact="compact">
7287 /var/log/foo/*.log {
7292 /etc/init.d/foo force-reload
7296 This rotates all files under <file>/var/log/foo</file>, saves 12
7297 compressed generations, and forces the daemon to reload its
7298 configuration information after the log rotation.
7302 Log files should be removed when the package is
7303 purged (but not when it is only removed). This should be
7304 done by the <prgn>postrm</prgn> script when it is called
7305 with the argument <tt>purge</tt> (see <ref
7306 id="removedetails">).
7311 <heading>Permissions and owners</heading>
7314 The rules in this section are guidelines for general use.
7315 If necessary you may deviate from the details below.
7316 However, if you do so you must make sure that what is done
7317 is secure and you should try to be as consistent as possible
7318 with the rest of the system. You should probably also
7319 discuss it on <prgn>debian-devel</prgn> first.
7323 Files should be owned by <tt>root.root</tt>, and made
7324 writable only by the owner and universally readable (and
7325 executable, if appropriate), that is mode 644 or 755.
7329 Directories should be mode 755 or (for group-writability)
7330 mode 2775. The ownership of the directory should be
7331 consistent with its mode: if a directory is mode 2775, it
7332 should be owned by the group that needs write access to
7335 When a package is upgraded, and the owner or permissions
7336 of a file included in the package has changed, dpkg
7337 arranges for the ownership and permissions to be
7338 correctly set upon installation. However, this does not
7339 extend to directories; the permissions and ownership of
7340 directories already on the system does not change on
7341 install or upgrade of packages. This makes sense, since
7342 otherwise common directories like <tt>/usr</tt> would
7343 always be in flux. To correctly change permissions of a
7344 directory the package owns, explicit action is required,
7345 usually in the <tt>postinst</tt> script. Care must be
7346 taken to handle downgrades as well, in that case.
7353 Setuid and setgid executables should be mode 4755 or 2755
7354 respectively, and owned by the appropriate user or group.
7355 They should not be made unreadable (modes like 4711 or
7356 2711 or even 4111); doing so achieves no extra security,
7357 because anyone can find the binary in the freely available
7358 Debian package; it is merely inconvenient. For the same
7359 reason you should not restrict read or execute permissions
7360 on non-set-id executables.
7364 Some setuid programs need to be restricted to particular
7365 sets of users, using file permissions. In this case they
7366 should be owned by the uid to which they are set-id, and by
7367 the group which should be allowed to execute them. They
7368 should have mode 4754; again there is no point in making
7369 them unreadable to those users who must not be allowed to
7374 It is possible to arrange that the system administrator can
7375 reconfigure the package to correspond to their local
7376 security policy by changing the permissions on a binary:
7377 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7378 described below.<footnote>
7379 Ordinary files installed by <prgn>dpkg</prgn> (as
7380 opposed to <tt>conffile</tt>s and other similar objects)
7381 normally have their permissions reset to the distributed
7382 permissions when the package is reinstalled. However,
7383 the use of <prgn>dpkg-statoverride</prgn> overrides this
7384 default behavior. If you use this method, you should
7385 remember to describe <prgn>dpkg-statoverride</prgn> in
7386 the package documentation; being a relatively new
7387 addition to Debian, it is probably not yet well-known.
7389 Another method you should consider is to create a group for
7390 people allowed to use the program(s) and make any setuid
7391 executables executable only by that group.
7395 If you need to create a new user or group for your package
7396 there are two possibilities. Firstly, you may need to
7397 make some files in the binary package be owned by this
7398 user or group, or you may need to compile the user or
7399 group id (rather than just the name) into the binary
7400 (though this latter should be avoided if possible, as in
7401 this case you need a statically allocated id).</p>
7404 If you need a statically allocated id, you must ask for a
7405 user or group id from the <tt>base-passwd</tt> maintainer,
7406 and must not release the package until you have been
7407 allocated one. Once you have been allocated one you must
7408 either make the package depend on a version of the
7409 <tt>base-passwd</tt> package with the id present in
7410 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7411 your package to create the user or group itself with the
7412 correct id (using <tt>adduser</tt>) in its
7413 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7414 the <prgn>postinst</prgn> is to be preferred if it is
7415 possible, otherwise a pre-dependency will be needed on the
7416 <tt>adduser</tt> package.)
7420 On the other hand, the program might be able to determine
7421 the uid or gid from the user or group name at runtime, so
7422 that a dynamically allocated id can be used. In this case
7423 you should choose an appropriate user or group name,
7424 discussing this on <prgn>debian-devel</prgn> and checking
7425 with the <package/base-passwd/ maintainer that it is unique and that
7426 they do not wish you to use a statically allocated id
7427 instead. When this has been checked you must arrange for
7428 your package to create the user or group if necessary using
7429 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7430 <prgn>postinst</prgn> script (again, the latter is to be
7431 preferred if it is possible).
7435 Note that changing the numeric value of an id associated
7436 with a name is very difficult, and involves searching the
7437 file system for all appropriate files. You need to think
7438 carefully whether a static or dynamic id is required, since
7439 changing your mind later will cause problems.
7442 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7444 This section is not intended as policy, but as a
7445 description of the use of <prgn>dpkg-statoverride</prgn>.
7449 <prgn>dpkg-statoverride</prgn> is a replacement for the
7450 deprecated <tt>suidmanager</tt> package. Packages which
7451 previously used <tt>suidmanager</tt> should have a
7452 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7453 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7454 and <tt>suidunregister</tt> should now be simply removed
7455 from the maintainer scripts.
7459 If a system administrator wishes to have a file (or
7460 directory or other such thing) installed with owner and
7461 permissions different from those in the distributed Debian
7462 package, they can use the <prgn>dpkg-statoverride</prgn>
7463 program to instruct <prgn>dpkg</prgn> to use the different
7464 settings every time the file is installed. Thus the
7465 package maintainer should distribute the files with their
7466 normal permissions, and leave it for the system
7467 administrator to make any desired changes. For example, a
7468 daemon which is normally required to be setuid root, but
7469 in certain situations could be used without being setuid,
7470 should be installed setuid in the <tt>.deb</tt>. Then the
7471 local system administrator can change this if they wish.
7472 If there are two standard ways of doing it, the package
7473 maintainer can use <tt>debconf</tt> to find out the
7474 preference, and call <prgn>dpkg-statoverride</prgn> in the
7475 maintainer script if necessary to accommodate the system
7476 administrator's choice. Care must be taken during
7477 upgrades to not override an existing setting.
7481 Given the above, <prgn>dpkg-statoverride</prgn> is
7482 essentially a tool for system administrators and would not
7483 normally be needed in the maintainer scripts. There is
7484 one type of situation, though, where calls to
7485 <prgn>dpkg-statoverride</prgn> would be needed in the
7486 maintainer scripts, and that involves packages which use
7487 dynamically allocated user or group ids. In such a
7488 situation, something like the following idiom can be very
7489 helpful in the package's <prgn>postinst</prgn>, where
7490 <tt>sysuser</tt> is a dynamically allocated id:
7492 for i in /usr/bin/foo /usr/sbin/bar
7494 # only do something when no setting exists
7495 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7497 #include: debconf processing, question about foo and bar
7498 if [ "$RET" = "true" ] ; then
7499 dpkg-statoverride --update --add sysuser root 4755 $i
7504 The corresponding <tt>dpkg-statoverride --remove</tt>
7505 calls can then be made unconditionally when the package is
7513 <chapt id="customized-programs">
7514 <heading>Customized programs</heading>
7516 <sect id="arch-spec">
7517 <heading>Architecture specification strings</heading>
7520 If a program needs to specify an <em>architecture specification
7521 string</em> in some place, it should select one of the
7522 strings provided by <tt>dpkg-architecture -L</tt>. The
7523 strings are in the format
7524 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7525 is sometimes elided, as when the OS is Linux.<footnote>
7526 <p>Currently, the strings are:
7527 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7528 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7529 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7530 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7531 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7532 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7533 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7534 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7535 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7536 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7537 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7538 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7539 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7540 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7541 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7542 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7543 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7544 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7545 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7546 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7547 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7548 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7549 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7550 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7551 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7552 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7553 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7554 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7555 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7556 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7557 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7558 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7559 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7560 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7561 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7562 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7563 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7569 Note that we don't want to use
7570 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7571 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7572 since this would make our programs incompatible with other
7573 Linux distributions. We also don't use something like
7574 <tt><var>arch</var>-unknown-linux</tt>, since the
7575 <tt>unknown</tt> does not look very good.
7580 <heading>Daemons</heading>
7583 The configuration files <file>/etc/services</file>,
7584 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7585 by the <prgn>netbase</prgn> package and must not be modified
7590 If a package requires a new entry in one of these files, the
7591 maintainer should get in contact with the
7592 <prgn>netbase</prgn> maintainer, who will add the entries
7593 and release a new version of the <prgn>netbase</prgn>
7598 The configuration file <file>/etc/inetd.conf</file> must not be
7599 modified by the package's scripts except via the
7600 <prgn>update-inetd</prgn> script or the
7601 <file>DebianNet.pm</file> Perl module. See their documentation
7602 for details on how to add entries.
7606 If a package wants to install an example entry into
7607 <file>/etc/inetd.conf</file>, the entry must be preceded with
7608 exactly one hash character (<tt>#</tt>). Such lines are
7609 treated as "commented out by user" by the
7610 <prgn>update-inetd</prgn> script and are not changed or
7611 activated during package updates.
7616 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7620 Some programs need to create pseudo-ttys. This should be done
7621 using Unix98 ptys if the C library supports it. The resulting
7622 program must not be installed setuid root, unless that
7623 is required for other functionality.
7627 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7628 <file>/var/log/lastlog</file> must be installed writable by
7629 group <tt>utmp</tt>. Programs which need to modify those
7630 files must be installed setgid <tt>utmp</tt>.
7635 <heading>Editors and pagers</heading>
7638 Some programs have the ability to launch an editor or pager
7639 program to edit or display a text document. Since there are
7640 lots of different editors and pagers available in the Debian
7641 distribution, the system administrator and each user should
7642 have the possibility to choose their preferred editor and
7647 In addition, every program should choose a good default
7648 editor/pager if none is selected by the user or system
7653 Thus, every program that launches an editor or pager must
7654 use the EDITOR or PAGER environment variable to determine
7655 the editor or pager the user wishes to use. If these
7656 variables are not set, the programs <file>/usr/bin/editor</file>
7657 and <file>/usr/bin/pager</file> should be used, respectively.
7661 These two files are managed through the <prgn>dpkg</prgn>
7662 "alternatives" mechanism. Thus every package providing an
7663 editor or pager must call the
7664 <prgn>update-alternatives</prgn> script to register these
7669 If it is very hard to adapt a program to make use of the
7670 EDITOR or PAGER variables, that program may be configured to
7671 use <file>/usr/bin/sensible-editor</file> and
7672 <file>/usr/bin/sensible-pager</file> as the editor or pager
7673 program respectively. These are two scripts provided in the
7674 Debian base system that check the EDITOR and PAGER variables
7675 and launch the appropriate program, and fall back to
7676 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7677 variable is not set.
7681 A program may also use the VISUAL environment variable to
7682 determine the user's choice of editor. If it exists, it
7683 should take precedence over EDITOR. This is in fact what
7684 <file>/usr/bin/sensible-editor</file> does.
7688 It is not required for a package to depend on
7689 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7690 package to provide such virtual packages.<footnote>
7691 The Debian base system already provides an editor and a
7697 <sect id="web-appl">
7698 <heading>Web servers and applications</heading>
7701 This section describes the locations and URLs that should
7702 be used by all web servers and web applications in the
7709 Cgi-bin executable files are installed in the
7711 <example compact="compact">
7712 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7714 and should be referred to as
7715 <example compact="compact">
7716 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7722 <p>Access to HTML documents</p>
7725 HTML documents for a package are stored in
7726 <file>/usr/share/doc/<var>package</var></file>
7727 and can be referred to as
7728 <example compact="compact">
7729 http://localhost/doc/<var>package</var>/<var>filename</var>
7734 The web server should restrict access to the document
7735 tree so that only clients on the same host can read
7736 the documents. If the web server does not support such
7737 access controls, then it should not provide access at
7738 all, or ask about providing access during installation.
7743 <p>Access to images</p>
7745 It is recommended that images for a package be stored
7746 in <tt>/usr/share/images/<var>package</var></tt> and
7747 may be referred to through an alias <tt>/images/</tt>
7750 http://localhost/images/<package>/<filename>
7757 <p>Web Document Root</p>
7760 Web Applications should try to avoid storing files in
7761 the Web Document Root. Instead they should use the
7762 /usr/share/doc/<var>package</var> directory for
7763 documents and register the Web Application via the
7764 <package>doc-base</package> package. If access to the
7765 web document root is unavoidable then use
7766 <example compact="compact">
7769 as the Document Root. This might be just a symbolic
7770 link to the location where the system administrator
7771 has put the real document root.
7774 <item><p>Providing httpd and/or httpd-cgi</p>
7776 All web servers should provide the virtual package
7777 <tt>httpd</tt>. If a web server has CGI support it should
7778 provide <tt>httpd-cgi</tt> additionally.
7781 All web applications which do not contain CGI scripts should
7782 depend on <tt>httpd</tt>, all those web applications which
7783 <tt>do</tt> contain CGI scripts, should depend on
7791 <sect id="mail-transport-agents">
7792 <heading>Mail transport, delivery and user agents</heading>
7795 Debian packages which process electronic mail, whether mail
7796 user agents (MUAs) or mail transport agents (MTAs), must
7797 ensure that they are compatible with the configuration
7798 decisions below. Failure to do this may result in lost
7799 mail, broken <tt>From:</tt> lines, and other serious brain
7804 The mail spool is <file>/var/mail</file> and the interface to
7805 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7806 the FHS). On older systems, the mail spool may be
7807 physically located in <file>/var/spool/mail</file>, but all
7808 access to the mail spool should be via the
7809 <file>/var/mail</file> symlink. The mail spool is part of the
7810 base system and not part of the MTA package.
7814 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7815 programs (such as IMAP daemons) must lock the mailbox in an
7816 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7817 be combined with dot locking. To avoid deadlocks, a program
7818 should use <tt>fcntl()</tt> first and dot locking after
7819 this, or alternatively implement the two locking methods in
7820 a non blocking way<footnote>
7821 If it is not possible to establish both locks, the
7822 system shouldn't wait for the second lock to be
7823 established, but remove the first lock, wait a (random)
7824 time, and start over locking again.
7825 </footnote>. Using the functions <tt>maillock</tt> and
7826 <tt>mailunlock</tt> provided by the
7827 <tt>liblockfile*</tt><footnote>
7828 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7829 to use these functions.
7830 </footnote> packages is the recommended way to realize this.
7834 Mailboxes are generally mode 660
7835 <tt><var>user</var>.mail</tt> unless the system
7836 administrator has chosen otherwise. A MUA may remove a
7837 mailbox (unless it has nonstandard permissions) in which
7838 case the MTA or another MUA must recreate it if needed.
7839 Mailboxes must be writable by group mail.
7843 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7844 be setgid mail to do the locking mentioned above (and
7845 must obviously avoid accessing other users' mailboxes
7846 using this privilege).</p>
7849 <file>/etc/aliases</file> is the source file for the system mail
7850 aliases (e.g., postmaster, usenet, etc.), it is the one
7851 which the sysadmin and <prgn>postinst</prgn> scripts may
7852 edit. After <file>/etc/aliases</file> is edited the program or
7853 human editing it must call <prgn>newaliases</prgn>. All MTA
7854 packages must come with a <prgn>newaliases</prgn> program,
7855 even if it does nothing, but older MTA packages did not do
7856 this so programs should not fail if <prgn>newaliases</prgn>
7857 cannot be found. Note that because of this, all MTA
7858 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7859 <tt>Replaces: mail-transport-agent</tt> control file
7864 The convention of writing <tt>forward to
7865 <var>address</var></tt> in the mailbox itself is not
7866 supported. Use a <tt>.forward</tt> file instead.</p>
7869 The <prgn>rmail</prgn> program used by UUCP
7870 for incoming mail should be <file>/usr/sbin/rmail</file>.
7871 Likewise, <prgn>rsmtp</prgn>, for receiving
7872 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7876 If your package needs to know what hostname to use on (for
7877 example) outgoing news and mail messages which are generated
7878 locally, you should use the file <file>/etc/mailname</file>. It
7879 will contain the portion after the username and <tt>@</tt>
7880 (at) sign for email addresses of users on the machine
7881 (followed by a newline).
7885 Such a package should check for the existence of this file
7886 when it is being configured. If it exists, it should be
7887 used without comment, although an MTA's configuration script
7888 may wish to prompt the user even if it finds that this file
7889 exists. If the file does not exist, the package should
7890 prompt the user for the value (preferably using
7891 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7892 as well as using it in the package's configuration. The
7893 prompt should make it clear that the name will not just be
7894 used by that package. For example, in this situation the
7895 <tt>inn</tt> package could say something like:
7896 <example compact="compact">
7897 Please enter the "mail name" of your system. This is the
7898 hostname portion of the address to be shown on outgoing
7899 news and mail messages. The default is
7900 <var>syshostname</var>, your system's host name. Mail
7901 name ["<var>syshostname</var>"]:
7903 where <var>syshostname</var> is the output of <tt>hostname
7909 <heading>News system configuration</heading>
7912 All the configuration files related to the NNTP (news)
7913 servers and clients should be located under
7914 <file>/etc/news</file>.</p>
7917 There are some configuration issues that apply to a number
7918 of news clients and server packages on the machine. These
7922 <tag><file>/etc/news/organization</file></tag>
7924 A string which should appear as the
7925 organization header for all messages posted
7926 by NNTP clients on the machine
7929 <tag><file>/etc/news/server</file></tag>
7931 Contains the FQDN of the upstream NNTP
7932 server, or localhost if the local machine is
7937 Other global files may be added as required for cross-package news
7944 <heading>Programs for the X Window System</heading>
7947 <heading>Providing X support and package priorities</heading>
7950 Programs that can be configured with support for the X
7951 Window System must be configured to do so and must declare
7952 any package dependencies necessary to satisfy their
7953 runtime requirements when using the X Window System. If
7954 such a package is of higher priority than the X packages
7955 on which it depends, it is required that either the
7956 X-specific components be split into a separate package, or
7957 that an alternative version of the package, which includes
7958 X support, be provided, or that the package's priority be
7964 <heading>Packages providing an X server</heading>
7967 Packages that provide an X server that, directly or
7968 indirectly, communicates with real input and display
7969 hardware should declare in their control data that they
7970 provide the virtual package <tt>xserver</tt>.<footnote>
7971 This implements current practice, and provides an
7972 actual policy for usage of the <tt>xserver</tt>
7973 virtual package which appears in the virtual packages
7974 list. In a nutshell, X servers that interface
7975 directly with the display and input hardware or via
7976 another subsystem (e.g., GGI) should provide
7977 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7978 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7984 <heading>Packages providing a terminal emulator</heading>
7987 Packages that provide a terminal emulator for the X Window
7988 System which meet the criteria listed below should declare
7989 in their control data that they provide the virtual
7990 package <tt>x-terminal-emulator</tt>. They should also
7991 register themselves as an alternative for
7992 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7997 To be an <tt>x-terminal-emulator</tt>, a program must:
7998 <list compact="compact">
8000 Be able to emulate a DEC VT100 terminal, or a
8001 compatible terminal.
8005 Support the command-line option <tt>-e
8006 <var>command</var></tt>, which creates a new
8007 terminal window<footnote>
8008 "New terminal window" does not necessarily mean
8009 a new top-level X window directly parented by
8010 the window manager; it could, if the terminal
8011 emulator application were so coded, be a new
8012 "view" in a multiple-document interface (MDI).
8014 and runs the specified <var>command</var>,
8015 interpreting the entirety of the rest of the command
8016 line as a command to pass straight to exec, in the
8017 manner that <tt>xterm</tt> does.
8021 Support the command-line option <tt>-T
8022 <var>title</var></tt>, which creates a new terminal
8023 window with the window title <var>title</var>.
8030 <heading>Packages providing a window manager</heading>
8033 Packages that provide a window manager should declare in
8034 their control data that they provide the virtual package
8035 <tt>x-window-manager</tt>. They should also register
8036 themselves as an alternative for
8037 <file>/usr/bin/x-window-manager</file>, with a priority
8038 calculated as follows:
8039 <list compact="compact">
8041 Start with a priority of 20.
8045 If the window manager supports the Debian menu
8046 system, add 20 points if this support is available
8047 in the package's default configuration (i.e., no
8048 configuration files belonging to the system or user
8049 have to be edited to activate the feature); if
8050 configuration files must be modified, add only 10
8056 If the window manager complies with <url
8057 id="http://www.freedesktop.org/Standards/wm-spec"
8058 name="The Window Manager Specification Project">,
8059 written by the <url id="http://www.freedesktop.org/"
8060 name="Free Desktop Group">, add 40 points.
8064 If the window manager permits the X session to be
8065 restarted using a <em>different</em> window manager
8066 (without killing the X server) in its default
8067 configuration, add 10 points; otherwise add none.
8074 <heading>Packages providing fonts</heading>
8077 Packages that provide fonts for the X Window
8079 For the purposes of Debian Policy, a "font for the X
8080 Window System" is one which is accessed via X protocol
8081 requests. Fonts for the Linux console, for PostScript
8082 renderer, or any other purpose, do not fit this
8083 definition. Any tool which makes such fonts available
8084 to the X Window System, however, must abide by this
8087 must do a number of things to ensure that they are both
8088 available without modification of the X or font server
8089 configuration, and that they do not corrupt files used by
8090 other font packages to register information about
8094 Fonts of any type supported by the X Window System
8095 must be in a separate binary package from any
8096 executables, libraries, or documentation (except
8097 that specific to the fonts shipped, such as their
8098 license information). If one or more of the fonts
8099 so packaged are necessary for proper operation of
8100 the package with which they are associated the font
8101 package may be Recommended; if the fonts merely
8102 provide an enhancement, a Suggests relationship may
8103 be used. Packages must not Depend on font
8105 This is because the X server may retrieve fonts
8106 from the local file system or over the network
8107 from an X font server; the Debian package system
8108 is empowered to deal only with the local
8114 BDF fonts must be converted to PCF fonts with the
8115 <prgn>bdftopcf</prgn> utility (available in the
8116 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8117 placed in a directory that corresponds to their
8119 <list compact="compact">
8121 100 dpi fonts must be placed in
8122 <file>/usr/share/fonts/X11/100dpi/</file>.
8126 75 dpi fonts must be placed in
8127 <file>/usr/share/fonts/X11/75dpi/</file>.
8131 Character-cell fonts, cursor fonts, and other
8132 low-resolution fonts must be placed in
8133 <file>/usr/share/fonts/X11/misc/</file>.
8139 Speedo fonts must be placed in
8140 <file>/usr/share/fonts/X11/Speedo/</file>.
8144 Type 1 fonts must be placed in
8145 <file>/usr/share/fonts/X11/Type1/</file>. If font
8146 metric files are available, they must be placed here
8151 Subdirectories of <file>/usr/share/fonts/X11/</file>
8152 other than those listed above must be neither
8153 created nor used. (The <file>PEX</file>, <file>CID</file>,
8154 and <file>cyrillic</file> directories are excepted for
8155 historical reasons, but installation of files into
8156 these directories remains discouraged.)
8160 Font packages may, instead of placing files directly
8161 in the X font directories listed above, provide
8162 symbolic links in that font directory pointing to
8163 the files' actual location in the filesystem. Such
8164 a location must comply with the FHS.
8168 Font packages should not contain both 75dpi and
8169 100dpi versions of a font. If both are available,
8170 they should be provided in separate binary packages
8171 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8172 the names of the packages containing the
8173 corresponding fonts.
8177 Fonts destined for the <file>misc</file> subdirectory
8178 should not be included in the same package as 75dpi
8179 or 100dpi fonts; instead, they should be provided in
8180 a separate package with <tt>-misc</tt> appended to
8185 Font packages must not provide the files
8186 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8187 <file>fonts.scale</file> in a font directory:
8190 <file>fonts.dir</file> files must not be provided at all.
8194 <file>fonts.alias</file> and <file>fonts.scale</file>
8195 files, if needed, should be provided in the
8197 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8198 where <var>fontdir</var> is the name of the
8200 <file>/usr/share/fonts/X11/</file> where the
8201 package's corresponding fonts are stored
8202 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8203 <var>package</var> is the name of the package
8204 that provides these fonts, and
8205 <var>extension</var> is either <tt>scale</tt>
8206 or <tt>alias</tt>, whichever corresponds to
8213 Font packages must declare a dependency on
8214 <tt>xfonts-utils</tt> in their control
8219 Font packages that provide one or more
8220 <file>fonts.scale</file> files as described above must
8221 invoke <prgn>update-fonts-scale</prgn> on each
8222 directory into which they installed fonts
8223 <em>before</em> invoking
8224 <prgn>update-fonts-dir</prgn> on that directory.
8225 This invocation must occur in both the
8226 <prgn>postinst</prgn> (for all arguments) and
8227 <prgn>postrm</prgn> (for all arguments except
8228 <tt>upgrade</tt>) scripts.
8232 Font packages that provide one or more
8233 <file>fonts.alias</file> files as described above must
8234 invoke <prgn>update-fonts-alias</prgn> on each
8235 directory into which they installed fonts. This
8236 invocation must occur in both the
8237 <prgn>postinst</prgn> (for all arguments) and
8238 <prgn>postrm</prgn> (for all arguments except
8239 <tt>upgrade</tt>) scripts.
8243 Font packages must invoke
8244 <prgn>update-fonts-dir</prgn> on each directory into
8245 which they installed fonts. This invocation must
8246 occur in both the <prgn>postinst</prgn> (for all
8247 arguments) and <prgn>postrm</prgn> (for all
8248 arguments except <tt>upgrade</tt>) scripts.
8252 Font packages must not provide alias names for the
8253 fonts they include which collide with alias names
8254 already in use by fonts already packaged.
8258 Font packages must not provide fonts with the same
8259 XLFD registry name as another font already packaged.
8266 <heading>Application defaults files</heading>
8269 Application defaults files must be installed in the
8270 directory <file>/etc/X11/app-defaults/</file> (use of a
8271 localized subdirectory of <file>/etc/X11/</file> as described
8272 in the <em>X Toolkit Intrinsics - C Language
8273 Interface</em> manual is also permitted). They must be
8274 registered as <tt>conffile</tt>s or handled as
8275 configuration files. Packages must not provide the
8276 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8280 Customization of programs' X resources may also be
8281 supported with the provision of a file with the same name
8282 as that of the package placed in the
8283 <file>/etc/X11/Xresources/</file> directory, which must
8284 registered as a <tt>conffile</tt> or handled as a
8285 configuration file.<footnote>
8286 Note that this mechanism is not the same as using
8287 app-defaults; app-defaults are tied to the client
8288 binary on the local file system, whereas X resources
8289 are stored in the X server and affect all connecting
8292 <em>Important:</em> packages that install files into the
8293 <file>/etc/X11/Xresources/</file> directory must conflict with
8294 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8295 it is possible for the installing package to destroy a
8296 previously-existing <file>/etc/X11/Xresources</file> file
8297 which had been customized by the system administrator.
8302 <heading>Installation directory issues</heading>
8305 Packages using the X Window System should not be
8306 configured to install files under the
8307 <file>/usr/X11R6/</file> directory. The
8308 <file>/usr/X11R6/</file> directory hierarchy should be
8309 regarded as obsolete.
8313 Programs that use GNU <prgn>autoconf</prgn> and
8314 <prgn>automake</prgn> are usually easily configured at
8315 compile time to use <file>/usr/</file> instead of
8316 <file>/usr/X11R6/</file>, and this should be done whenever
8317 possible. Configuration files for window managers and
8318 display managers should be placed in a subdirectory of
8319 <file>/etc/X11/</file> corresponding to the package name due
8320 to these programs' tight integration with the mechanisms
8321 of the X Window System. Application-level programs should
8322 use the <file>/etc/</file> directory unless otherwise mandated
8327 The installation of files into subdirectories
8328 of <file>/usr/X11R6/include/X11/</file> and
8329 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8330 package maintainers should determine if subdirectories of
8331 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8336 Packages should install any relevant files into the
8337 directories <file>/usr/include/X11/</file> and
8338 <file>/usr/lib/X11/</file>, but if they do so, they must
8339 pre-depend on <tt>x11-common (>=
8340 1:7.0.0)</tt><footnote>
8342 These libraries used to be all symbolic
8343 links. However, with <tt>X11R7</tt>,
8344 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8345 are now real directories, and packages
8346 <strong>should</strong> ship their files here instead
8347 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8348 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8349 responsible for converting these symlinks into
8357 <heading>The OSF/Motif and OpenMotif libraries</heading>
8360 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8361 OpenMotif libraries</em><footnote>
8362 OSF/Motif and OpenMotif are collectively referred to as
8363 "Motif" in this policy document.
8365 should be compiled against and tested with LessTif (a free
8366 re-implementation of Motif) instead. If the maintainer
8367 judges that the program or programs do not work
8368 sufficiently well with LessTif to be distributed and
8369 supported, but do so when compiled against Motif, then two
8370 versions of the package should be created; one linked
8371 statically against Motif and with <tt>-smotif</tt>
8372 appended to the package name, and one linked dynamically
8373 against Motif and with <tt>-dmotif</tt> appended to the
8378 Both Motif-linked versions are dependent
8379 upon non-DFSG-compliant software and thus cannot be
8380 uploaded to the <em>main</em> distribution; if the
8381 software is itself DFSG-compliant it may be uploaded to
8382 the <em>contrib</em> distribution. While known existing
8383 versions of Motif permit unlimited redistribution of
8384 binaries linked against the library (whether statically or
8385 dynamically), it is the package maintainer's
8386 responsibility to determine whether this is permitted by
8387 the license of the copy of Motif in their possession.
8393 <heading>Perl programs and modules</heading>
8396 Perl programs and modules should follow the current Perl policy.
8400 The Perl policy can be found in the <tt>perl-policy</tt>
8401 files in the <tt>debian-policy</tt> package.
8402 It is also available from the Debian web mirrors at
8403 <tt><url name="/doc/packaging-manuals/perl-policy/"
8404 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8409 <heading>Emacs lisp programs</heading>
8412 Please refer to the "Debian Emacs Policy" for details of how to
8413 package emacs lisp programs.
8417 The Emacs policy is available in
8418 <file>debian-emacs-policy.gz</file> of the
8419 <package>emacsen-common</package> package.
8420 It is also available from the Debian web mirrors at
8421 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8422 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8427 <heading>Games</heading>
8430 The permissions on <file>/var/games</file> are mode 755, owner
8431 <tt>root</tt> and group <tt>root</tt>.
8435 Each game decides on its own security policy.</p>
8438 Games which require protected, privileged access to
8439 high-score files, saved games, etc., may be made
8440 set-<em>group</em>-id (mode 2755) and owned by
8441 <tt>root.games</tt>, and use files and directories with
8442 appropriate permissions (770 <tt>root.games</tt>, for
8443 example). They must not be made
8444 set-<em>user</em>-id, as this causes security problems. (If
8445 an attacker can subvert any set-user-id game they can
8446 overwrite the executable of any other, causing other players
8447 of these games to run a Trojan horse program. With a
8448 set-group-id game the attacker only gets access to less
8449 important game data, and if they can get at the other
8450 players' accounts at all it will take considerably more
8454 Some packages, for example some fortune cookie programs, are
8455 configured by the upstream authors to install with their
8456 data files or other static information made unreadable so
8457 that they can only be accessed through set-id programs
8458 provided. You should not do this in a Debian package: anyone can
8459 download the <file>.deb</file> file and read the data from it,
8460 so there is no point making the files unreadable. Not
8461 making the files unreadable also means that you don't have
8462 to make so many programs set-id, which reduces the risk of a
8466 As described in the FHS, binaries of games should be
8467 installed in the directory <file>/usr/games</file>. This also
8468 applies to games that use the X Window System. Manual pages
8469 for games (X and non-X games) should be installed in
8470 <file>/usr/share/man/man6</file>.</p>
8476 <heading>Documentation</heading>
8479 <heading>Manual pages</heading>
8482 You should install manual pages in <prgn>nroff</prgn> source
8483 form, in appropriate places under <file>/usr/share/man</file>.
8484 You should only use sections 1 to 9 (see the FHS for more
8485 details). You must not install a pre-formatted "cat page".
8489 Each program, utility, and function should have an
8490 associated manual page included in the same package. It is
8491 suggested that all configuration files also have a manual
8492 page included as well. Manual pages for protocols and other
8493 auxiliary things are optional.
8497 If no manual page is available, this is considered as a bug
8498 and should be reported to the Debian Bug Tracking System (the
8499 maintainer of the package is allowed to write this bug report
8500 themselves, if they so desire). Do not close the bug report
8501 until a proper man page is available.<footnote>
8502 It is not very hard to write a man page. See the
8503 <url id="http://www.schweikhardt.net/man_page_howto.html"
8504 name="Man-Page-HOWTO">,
8505 <manref name="man" section="7">, the examples
8506 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8507 the helper programs <prgn>help2man</prgn>, or the
8508 directory <file>/usr/share/doc/man-db/examples</file>.
8513 You may forward a complaint about a missing man page to the
8514 upstream authors, and mark the bug as forwarded in the
8515 Debian bug tracking system. Even though the GNU Project do
8516 not in general consider the lack of a man page to be a bug,
8517 we do; if they tell you that they don't consider it a bug
8518 you should leave the bug in our bug tracking system open
8523 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8527 If one man page needs to be accessible via several names it
8528 is better to use a symbolic link than the <file>.so</file>
8529 feature, but there is no need to fiddle with the relevant
8530 parts of the upstream source to change from <file>.so</file> to
8531 symlinks: don't do it unless it's easy. You should not
8532 create hard links in the manual page directories, nor put
8533 absolute filenames in <file>.so</file> directives. The filename
8534 in a <file>.so</file> in a man page should be relative to the
8535 base of the man page tree (usually
8536 <file>/usr/share/man</file>). If you do not create any links
8537 (whether symlinks, hard links, or <tt>.so</tt> directives)
8538 in the file system to the alternate names of the man page,
8539 then you should not rely on <prgn>man</prgn> finding your
8540 man page under those names based solely on the information in
8541 the man page's header.<footnote>
8542 Supporting this in <prgn>man</prgn> often requires
8543 unreasonable processing time to find a manual page or to
8544 report that none exists, and moves knowledge into man's
8545 database that would be better left in the file system.
8546 This support is therefore deprecated and will cease to
8547 be present in the future.
8552 Manual pages in locale-specific subdirectories of
8553 <file>/usr/share/man</file> should use either UTF-8 or the usual
8554 legacy encoding for that language (normally the one corresponding
8555 to the shortest relevant locale name in
8556 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8557 <file>/usr/share/man/fr</file> should use either UTF-8 or
8558 ISO-8859-1.<footnote>
8559 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8560 use. In future, all manual pages will be required to use
8566 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8567 included in the subdirectory name unless it indicates a
8568 significant difference in the language, as this excludes
8569 speakers of the language in other countries.<footnote>
8570 At the time of writing, Chinese and Portuguese are the main
8571 languages with such differences, so <file>pt_BR</file>,
8572 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8577 Due to limitations in current implementations, all characters
8578 in the manual page source should be representable in the usual
8579 legacy encoding for that language, even if the file is
8580 actually encoded in UTF-8. Safe alternative ways to write many
8581 characters outside that range may be found in
8582 <manref name="groff_char" section="7">.
8587 <heading>Info documents</heading>
8590 Info documents should be installed in <file>/usr/share/info</file>.
8591 They should be compressed with <tt>gzip -9</tt>.
8595 Your package should call <prgn>install-info</prgn> to update
8596 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8597 script when called with a <tt>configure</tt> argument, for
8599 <example compact="compact">
8600 install-info --quiet --section Development Development \
8601 /usr/share/info/foobar.info
8605 It is a good idea to specify a section for the location of
8606 your program; this is done with the <tt>--section</tt>
8607 switch. To determine which section to use, you should look
8608 at <file>/usr/share/info/dir</file> on your system and choose the most
8609 relevant (or create a new section if none of the current
8610 sections are relevant). Note that the <tt>--section</tt>
8611 flag takes two arguments; the first is a regular expression
8612 to match (case-insensitively) against an existing section,
8613 the second is used when creating a new one.</p>
8616 You should remove the entries in the <prgn>prerm</prgn>
8617 script when called with a <tt>remove</tt> argument:
8618 <example compact="compact">
8619 install-info --quiet --remove /usr/share/info/foobar.info
8623 If <prgn>install-info</prgn> cannot find a description entry
8624 in the Info file you must supply one. See <manref
8625 name="install-info" section="8"> for details.</p>
8629 <heading>Additional documentation</heading>
8632 Any additional documentation that comes with the package may
8633 be installed at the discretion of the package maintainer.
8634 Plain text documentation should be installed in the directory
8635 <file>/usr/share/doc/<var>package</var></file>, where
8636 <var>package</var> is the name of the package, and
8637 compressed with <tt>gzip -9</tt> unless it is small.
8641 If a package comes with large amounts of documentation which
8642 many users of the package will not require you should create
8643 a separate binary package to contain it, so that it does not
8644 take up disk space on the machines of users who do not need
8645 or want it installed.</p>
8648 It is often a good idea to put text information files
8649 (<file>README</file>s, changelogs, and so forth) that come with
8650 the source package in <file>/usr/share/doc/<var>package</var></file>
8651 in the binary package. However, you don't need to install
8652 the instructions for building and installing the package, of
8656 Packages must not require the existence of any files in
8657 <file>/usr/share/doc/</file> in order to function
8659 The system administrator should be able to
8660 delete files in <file>/usr/share/doc/</file> without causing
8661 any programs to break.
8663 Any files that are referenced by programs but are also
8664 useful as stand alone documentation should be installed under
8665 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8666 <file>/usr/share/doc/<var>package</var></file>.
8670 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8671 link to another directory in <file>/usr/share/doc</file> only if
8672 the two packages both come from the same source and the
8673 first package Depends on the second.<footnote>
8675 Please note that this does not override the section on
8676 changelog files below, so the file
8677 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8678 must refer to the changelog for the current version of
8679 <var>package</var> in question. In practice, this means
8680 that the sources of the target and the destination of the
8681 symlink must be the same (same source package and
8688 Former Debian releases placed all additional documentation
8689 in <file>/usr/doc/<var>package</var></file>. This has been
8690 changed to <file>/usr/share/doc/<var>package</var></file>,
8691 and packages must not put documentation in the directory
8692 <file>/usr/doc/<var>package</var></file>. <footnote>
8693 At this phase of the transition, we no longer require a
8694 symbolic link in <file>/usr/doc/</file>. At a later point,
8695 policy shall change to make the symbolic links a bug.
8701 <heading>Preferred documentation formats</heading>
8704 The unification of Debian documentation is being carried out
8708 If your package comes with extensive documentation in a
8709 markup format that can be converted to various other formats
8710 you should if possible ship HTML versions in a binary
8711 package, in the directory
8712 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8713 its subdirectories.<footnote>
8714 The rationale: The important thing here is that HTML
8715 docs should be available in <em>some</em> package, not
8716 necessarily in the main binary package.
8721 Other formats such as PostScript may be provided at the
8722 package maintainer's discretion.
8726 <sect id="copyrightfile">
8727 <heading>Copyright information</heading>
8730 Every package must be accompanied by a verbatim copy of its
8731 copyright and distribution license in the file
8732 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8733 file must neither be compressed nor be a symbolic link.
8737 In addition, the copyright file must say where the upstream
8738 sources (if any) were obtained. It should name the original
8739 authors of the package and the Debian maintainer(s) who were
8740 involved with its creation.</p>
8743 A copy of the file which will be installed in
8744 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8745 be in <file>debian/copyright</file> in the source package.
8749 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8750 link to another directory in <file>/usr/share/doc</file> only if
8751 the two packages both come from the same source and the
8752 first package Depends on the second. These rules are
8753 important because copyrights must be extractable by
8758 Packages distributed under the UCB BSD license, the Artistic
8759 license, the GNU GPL (version 2 or 3), the GNU LGPL (versions
8760 2, 2.1, or 3), and the GNU FDL (version 1.2) should refer to
8761 the corresponding files under
8762 <file>/usr/share/common-licenses</file>,<footnote>
8765 <file>/usr/share/common-licenses/BSD</file>,
8766 <file>/usr/share/common-licenses/Artistic</file>,
8767 <file>/usr/share/common-licenses/GPL-2</file>,
8768 <file>/usr/share/common-licenses/GPL-3</file>,
8769 <file>/usr/share/common-licenses/LGPL-2</file>,
8770 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8771 <file>/usr/share/common-licenses/LGPL-3</file>, and
8772 <file>/usr/share/common-licenses/GFDL-1.2</file>,
8775 </footnote> rather than quoting them in the copyright
8780 You should not use the copyright file as a general <file>README</file>
8781 file. If your package has such a file it should be
8782 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8783 <file>README.Debian</file> or some other appropriate place.</p>
8787 <heading>Examples</heading>
8790 Any examples (configurations, source files, whatever),
8791 should be installed in a directory
8792 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8793 files should not be referenced by any program: they're there
8794 for the benefit of the system administrator and users as
8795 documentation only. Architecture-specific example files
8796 should be installed in a directory
8797 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8799 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8800 latter directory itself may be a symbolic link to the
8805 If the purpose of a package is to provide examples, then the
8806 example files may be installed into
8807 <file>/usr/share/doc/<var>package</var></file>.
8811 <sect id="changelogs">
8812 <heading>Changelog files</heading>
8815 Packages that are not Debian-native must contain a
8816 compressed copy of the <file>debian/changelog</file> file from
8817 the Debian source tree in
8818 <file>/usr/share/doc/<var>package</var></file> with the name
8819 <file>changelog.Debian.gz</file>.
8823 If an upstream changelog is available, it should be accessible as
8824 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8825 plain text. If the upstream changelog is distributed in
8826 HTML, it should be made available in that form as
8827 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8828 and a plain text <file>changelog.gz</file> should be generated
8829 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8830 the upstream changelog files do not already conform to this
8831 naming convention, then this may be achieved either by
8832 renaming the files, or by adding a symbolic link, at the
8833 maintainer's discretion.<footnote>
8834 Rationale: People should not have to look in places for
8835 upstream changelogs merely because they are given
8836 different names or are distributed in HTML format.
8841 All of these files should be installed compressed using
8842 <tt>gzip -9</tt>, as they will become large with time even
8843 if they start out small.
8847 If the package has only one changelog which is used both as
8848 the Debian changelog and the upstream one because there is
8849 no separate upstream maintainer then that changelog should
8850 usually be installed as
8851 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8852 there is a separate upstream maintainer, but no upstream
8853 changelog, then the Debian changelog should still be called
8854 <file>changelog.Debian.gz</file>.
8858 For details about the format and contents of the Debian
8859 changelog file, please see <ref id="dpkgchangelog">.
8864 <appendix id="pkg-scope">
8865 <heading>Introduction and scope of these appendices</heading>
8868 These appendices are taken essentially verbatim from the
8869 now-deprecated Packaging Manual, version 3.2.1.0. They are
8870 the chapters which are likely to be of use to package
8871 maintainers and which have not already been included in the
8872 policy document itself. Most of these sections are very likely
8873 not relevant to policy; they should be treated as
8874 documentation for the packaging system. Please note that these
8875 appendices are included for convenience, and for historical
8876 reasons: they used to be part of policy package, and they have
8877 not yet been incorporated into dpkg documentation. However,
8878 they still have value, and hence they are presented here.
8882 They have not yet been checked to ensure that they are
8883 compatible with the contents of policy, and if there are any
8884 contradictions, the version in the main policy document takes
8885 precedence. The remaining chapters of the old Packaging
8886 Manual have also not been read in detail to ensure that there
8887 are not parts which have been left out. Both of these will be
8892 Certain parts of the Packaging manual were integrated into the
8893 Policy Manual proper, and removed from the appendices. Links
8894 have been placed from the old locations to the new ones.
8898 <prgn>dpkg</prgn> is a suite of programs for creating binary
8899 package files and installing and removing them on Unix
8901 <prgn>dpkg</prgn> is targeted primarily at Debian
8902 GNU/Linux, but may work on or be ported to other
8908 The binary packages are designed for the management of
8909 installed executable programs (usually compiled binaries) and
8910 their associated data, though source code examples and
8911 documentation are provided as part of some packages.</p>
8914 This manual describes the technical aspects of creating Debian
8915 binary packages (<file>.deb</file> files). It documents the
8916 behavior of the package management programs
8917 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8918 they interact with packages.</p>
8921 It also documents the interaction between
8922 <prgn>dselect</prgn>'s core and the access method scripts it
8923 uses to actually install the selected packages, and describes
8924 how to create a new access method.</p>
8927 This manual does not go into detail about the options and
8928 usage of the package building and installation tools. It
8929 should therefore be read in conjunction with those programs'
8934 The utility programs which are provided with <prgn>dpkg</prgn>
8935 for managing various system configuration and similar issues,
8936 such as <prgn>update-rc.d</prgn> and
8937 <prgn>install-info</prgn>, are not described in detail here -
8938 please see their man pages.
8942 It is assumed that the reader is reasonably familiar with the
8943 <prgn>dpkg</prgn> System Administrators' manual.
8944 Unfortunately this manual does not yet exist.
8948 The Debian version of the FSF's GNU hello program is provided
8949 as an example for people wishing to create Debian
8950 packages. The Debian <prgn>debmake</prgn> package is
8951 recommended as a very helpful tool in creating and maintaining
8952 Debian packages. However, while the tools and examples are
8953 helpful, they do not replace the need to read and follow the
8954 Policy and Programmer's Manual.</p>
8957 <appendix id="pkg-binarypkg">
8958 <heading>Binary packages (from old Packaging Manual)</heading>
8961 The binary package has two main sections. The first part
8962 consists of various control information files and scripts used
8963 by <prgn>dpkg</prgn> when installing and removing. See <ref
8964 id="pkg-controlarea">.
8968 The second part is an archive containing the files and
8969 directories to be installed.
8973 In the future binary packages may also contain other
8974 components, such as checksums and digital signatures. The
8975 format for the archive is described in full in the
8976 <file>deb(5)</file> man page.
8980 <sect id="pkg-bincreating"><heading>Creating package files -
8981 <prgn>dpkg-deb</prgn>
8985 All manipulation of binary package files is done by
8986 <prgn>dpkg-deb</prgn>; it's the only program that has
8987 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8988 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8989 will spot that the options requested are appropriate to
8990 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8995 In order to create a binary package you must make a
8996 directory tree which contains all the files and directories
8997 you want to have in the file system data part of the package.
8998 In Debian-format source packages this directory is usually
8999 <file>debian/tmp</file>, relative to the top of the package's
9004 They should have the locations (relative to the root of the
9005 directory tree you're constructing) ownerships and
9006 permissions which you want them to have on the system when
9011 With current versions of <prgn>dpkg</prgn> the uid/username
9012 and gid/groupname mappings for the users and groups being
9013 used should be the same on the system where the package is
9014 built and the one where it is installed.
9018 You need to add one special directory to the root of the
9019 miniature file system tree you're creating:
9020 <prgn>DEBIAN</prgn>. It should contain the control
9021 information files, notably the binary package control file
9022 (see <ref id="pkg-controlfile">).
9026 The <prgn>DEBIAN</prgn> directory will not appear in the
9027 file system archive of the package, and so won't be installed
9028 by <prgn>dpkg</prgn> when the package is installed.
9032 When you've prepared the package, you should invoke:
9034 dpkg --build <var>directory</var>
9039 This will build the package in
9040 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9041 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9042 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9047 See the man page <manref name="dpkg-deb" section="8"> for details of how
9048 to examine the contents of this newly-created file. You may find the
9049 output of following commands enlightening:
9051 dpkg-deb --info <var>filename</var>.deb
9052 dpkg-deb --contents <var>filename</var>.deb
9053 dpkg --contents <var>filename</var>.deb
9055 To view the copyright file for a package you could use this command:
9057 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9062 <sect id="pkg-controlarea">
9063 <heading>Package control information files</heading>
9066 The control information portion of a binary package is a
9067 collection of files with names known to <prgn>dpkg</prgn>.
9068 It will treat the contents of these files specially - some
9069 of them contain information used by <prgn>dpkg</prgn> when
9070 installing or removing the package; others are scripts which
9071 the package maintainer wants <prgn>dpkg</prgn> to run.
9075 It is possible to put other files in the package control
9076 area, but this is not generally a good idea (though they
9077 will largely be ignored).
9081 Here is a brief list of the control info files supported by
9082 <prgn>dpkg</prgn> and a summary of what they're used for.
9087 <tag><tt>control</tt>
9090 This is the key description file used by
9091 <prgn>dpkg</prgn>. It specifies the package's name
9092 and version, gives its description for the user,
9093 states its relationships with other packages, and so
9094 forth. See <ref id="sourcecontrolfiles"> and
9095 <ref id="binarycontrolfiles">.
9099 It is usually generated automatically from information
9100 in the source package by the
9101 <prgn>dpkg-gencontrol</prgn> program, and with
9102 assistance from <prgn>dpkg-shlibdeps</prgn>.
9103 See <ref id="pkg-sourcetools">.
9107 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9112 These are executable files (usually scripts) which
9113 <prgn>dpkg</prgn> runs during installation, upgrade
9114 and removal of packages. They allow the package to
9115 deal with matters which are particular to that package
9116 or require more complicated processing than that
9117 provided by <prgn>dpkg</prgn>. Details of when and
9118 how they are called are in <ref id="maintainerscripts">.
9122 It is very important to make these scripts idempotent.
9123 See <ref id="idempotency">.
9127 The maintainer scripts are guaranteed to run with a
9128 controlling terminal and can interact with the user.
9129 See <ref id="controllingterminal">.
9133 <tag><tt>conffiles</tt>
9136 This file contains a list of configuration files which
9137 are to be handled automatically by <prgn>dpkg</prgn>
9138 (see <ref id="pkg-conffiles">). Note that not necessarily
9139 every configuration file should be listed here.
9142 <tag><tt>shlibs</tt>
9145 This file contains a list of the shared libraries
9146 supplied by the package, with dependency details for
9147 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9148 when it determines what dependencies are required in a
9149 package control file. The <tt>shlibs</tt> file format
9150 is described on <ref id="shlibs">.
9155 <sect id="pkg-controlfile">
9156 <heading>The main control information file: <tt>control</tt></heading>
9159 The most important control information file used by
9160 <prgn>dpkg</prgn> when it installs a package is
9161 <tt>control</tt>. It contains all the package's "vital
9166 The binary package control files of packages built from
9167 Debian sources are made by a special tool,
9168 <prgn>dpkg-gencontrol</prgn>, which reads
9169 <file>debian/control</file> and <file>debian/changelog</file> to
9170 find the information it needs. See <ref id="pkg-sourcepkg"> for
9175 The fields in binary package control files are listed in
9176 <ref id="binarycontrolfiles">.
9180 A description of the syntax of control files and the purpose
9181 of the fields is available in <ref id="controlfields">.
9186 <heading>Time Stamps</heading>
9189 See <ref id="timestamps">.
9194 <appendix id="pkg-sourcepkg">
9195 <heading>Source packages (from old Packaging Manual) </heading>
9198 The Debian binary packages in the distribution are generated
9199 from Debian sources, which are in a special format to assist
9200 the easy and automatic building of binaries.
9203 <sect id="pkg-sourcetools">
9204 <heading>Tools for processing source packages</heading>
9207 Various tools are provided for manipulating source packages;
9208 they pack and unpack sources and help build of binary
9209 packages and help manage the distribution of new versions.
9213 They are introduced and typical uses described here; see
9214 <manref name="dpkg-source" section="1"> for full
9215 documentation about their arguments and operation.
9219 For examples of how to construct a Debian source package,
9220 and how to use those utilities that are used by Debian
9221 source packages, please see the <prgn>hello</prgn> example
9225 <sect1 id="pkg-dpkg-source">
9227 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9232 This program is frequently used by hand, and is also
9233 called from package-independent automated building scripts
9234 such as <prgn>dpkg-buildpackage</prgn>.
9238 To unpack a package it is typically invoked with
9240 dpkg-source -x <var>.../path/to/filename</var>.dsc
9245 with the <file><var>filename</var>.tar.gz</file> and
9246 <file><var>filename</var>.diff.gz</file> (if applicable) in
9247 the same directory. It unpacks into
9248 <file><var>package</var>-<var>version</var></file>, and if
9250 <file><var>package</var>-<var>version</var>.orig</file>, in
9251 the current directory.
9255 To create a packed source archive it is typically invoked:
9257 dpkg-source -b <var>package</var>-<var>version</var>
9262 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9263 <file>.diff.gz</file> (if appropriate) in the current
9264 directory. <prgn>dpkg-source</prgn> does not clean the
9265 source tree first - this must be done separately if it is
9270 See also <ref id="pkg-sourcearchives">.</p>
9274 <sect1 id="pkg-dpkg-buildpackage">
9276 <prgn>dpkg-buildpackage</prgn> - overall package-building
9281 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9282 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9283 targets <tt>clean</tt>, <tt>build</tt> and
9284 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9285 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9286 source and binary package upload.
9290 It is usually invoked by hand from the top level of the
9291 built or unbuilt source directory. It may be invoked with
9292 no arguments; useful arguments include:
9293 <taglist compact="compact">
9294 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9297 Do not sign the <tt>.changes</tt> file or the
9298 source package <tt>.dsc</tt> file, respectively.</p>
9300 <tag><tt>-p<var>sign-command</var></tt></tag>
9303 Invoke <var>sign-command</var> instead of finding
9304 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9305 <var>sign-command</var> must behave just like
9306 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9308 <tag><tt>-r<var>root-command</var></tt></tag>
9311 When root privilege is required, invoke the command
9312 <var>root-command</var>. <var>root-command</var>
9313 should invoke its first argument as a command, from
9314 the <prgn>PATH</prgn> if necessary, and pass its
9315 second and subsequent arguments to the command it
9316 calls. If no <var>root-command</var> is supplied
9317 then <var>dpkg-buildpackage</var> will take no
9318 special action to gain root privilege, so that for
9319 most packages it will have to be invoked as root to
9322 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9325 Two types of binary-only build and upload - see
9326 <manref name="dpkg-source" section="1">.
9333 <sect1 id="pkg-dpkg-gencontrol">
9335 <prgn>dpkg-gencontrol</prgn> - generates binary package
9340 This program is usually called from <file>debian/rules</file>
9341 (see <ref id="pkg-sourcetree">) in the top level of the source
9346 This is usually done just before the files and directories in the
9347 temporary directory tree where the package is being built have their
9348 permissions and ownerships set and the package is constructed using
9349 <prgn>dpkg-deb/</prgn>
9351 This is so that the control file which is produced has
9352 the right permissions
9357 <prgn>dpkg-gencontrol</prgn> must be called after all the
9358 files which are to go into the package have been placed in
9359 the temporary build directory, so that its calculation of
9360 the installed size of a package is correct.
9364 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9365 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9366 variable substitutions created by
9367 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9372 For a package which generates only one binary package, and
9373 which builds it in <file>debian/tmp</file> relative to the top
9374 of the source package, it is usually sufficient to call
9375 <prgn>dpkg-gencontrol</prgn>.
9379 Sources which build several binaries will typically need
9382 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9383 </example> The <tt>-P</tt> tells
9384 <prgn>dpkg-gencontrol</prgn> that the package is being
9385 built in a non-default directory, and the <tt>-p</tt>
9386 tells it which package's control file should be generated.
9390 <prgn>dpkg-gencontrol</prgn> also adds information to the
9391 list of files in <file>debian/files</file>, for the benefit of
9392 (for example) a future invocation of
9393 <prgn>dpkg-genchanges</prgn>.</p>
9396 <sect1 id="pkg-dpkg-shlibdeps">
9398 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9403 This program is usually called from <file>debian/rules</file>
9404 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9405 id="pkg-sourcetree">), in the top level of the source tree.
9409 Its arguments are executables.
9412 In a forthcoming dpkg version,
9413 <prgn>dpkg-shlibdeps</prgn> would be required to be
9414 called on shared libraries as well.
9417 They may be specified either in the locations in the
9418 source tree where they are created or in the locations
9419 in the temporary build tree where they are installed
9420 prior to binary package creation.
9422 </footnote> for which shared library dependencies should
9423 be included in the binary package's control file.
9427 If some of the found shared libraries should only
9428 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9429 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9430 by using the <tt>-d<var>dependency-field</var></tt> option
9431 before those executable(s). (Each <tt>-d</tt> option
9432 takes effect until the next <tt>-d</tt>.)
9436 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9437 output control file to be modified. Instead by default it
9438 adds to the <file>debian/substvars</file> file variable
9439 settings like <tt>shlibs:Depends</tt>. These variable
9440 settings must be referenced in dependency fields in the
9441 appropriate per-binary-package sections of the source
9446 For example, a package that generates an essential part
9447 which requires dependencies, and optional parts that
9448 which only require a recommendation, would separate those
9449 two sets of dependencies into two different fields.<footnote>
9450 At the time of writing, an example for this was the
9451 <package/xmms/ package, with Depends used for the xmms
9452 executable, Recommends for the plug-ins and Suggests for
9453 even more optional features provided by unzip.
9455 It can say in its <file>debian/rules</file>:
9457 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9458 -dRecommends <var>optionalpart anotheroptionalpart</var>
9460 and then in its main control file <file>debian/control</file>:
9463 Depends: ${shlibs:Pre-Depends}
9464 Recommends: ${shlibs:Recommends}
9470 Sources which produce several binary packages with
9471 different shared library dependency requirements can use
9472 the <tt>-p<var>varnameprefix</var></tt> option to override
9473 the default <tt>shlibs:</tt> prefix (one invocation of
9474 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9475 They can thus produce several sets of dependency
9476 variables, each of the form
9477 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9478 which can be referred to in the appropriate parts of the
9479 binary package control files.
9484 <sect1 id="pkg-dpkg-distaddfile">
9486 <prgn>dpkg-distaddfile</prgn> - adds a file to
9487 <file>debian/files</file>
9491 Some packages' uploads need to include files other than
9492 the source and binary package files.
9496 <prgn>dpkg-distaddfile</prgn> adds a file to the
9497 <file>debian/files</file> file so that it will be included in
9498 the <file>.changes</file> file when
9499 <prgn>dpkg-genchanges</prgn> is run.
9503 It is usually invoked from the <tt>binary</tt> target of
9504 <file>debian/rules</file>:
9506 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9508 The <var>filename</var> is relative to the directory where
9509 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9510 is usually the directory above the top level of the source
9511 tree. The <file>debian/rules</file> target should put the
9512 file there just before or just after calling
9513 <prgn>dpkg-distaddfile</prgn>.
9517 The <var>section</var> and <var>priority</var> are passed
9518 unchanged into the resulting <file>.changes</file> file.
9523 <sect1 id="pkg-dpkg-genchanges">
9525 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9530 This program is usually called by package-independent
9531 automatic building scripts such as
9532 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9537 It is usually called in the top level of a built source
9538 tree, and when invoked with no arguments will print out a
9539 straightforward <file>.changes</file> file based on the
9540 information in the source package's changelog and control
9541 file and the binary and source packages which should have
9547 <sect1 id="pkg-dpkg-parsechangelog">
9549 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9550 representation of a changelog
9554 This program is used internally by
9555 <prgn>dpkg-source</prgn> et al. It may also occasionally
9556 be useful in <file>debian/rules</file> and elsewhere. It
9557 parses a changelog, <file>debian/changelog</file> by default,
9558 and prints a control-file format representation of the
9559 information in it to standard output.
9563 <sect1 id="pkg-dpkg-architecture">
9565 <prgn>dpkg-architecture</prgn> - information about the build and
9570 This program can be used manually, but is also invoked by
9571 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9572 to set environment or make variables which specify the build and
9573 host architecture for the package building process.
9578 <sect id="pkg-sourcetree">
9579 <heading>The Debianised source tree</heading>
9582 The source archive scheme described later is intended to
9583 allow a Debianised source tree with some associated control
9584 information to be reproduced and transported easily. The
9585 Debianised source tree is a version of the original program
9586 with certain files added for the benefit of the
9587 Debianisation process, and with any other changes required
9588 made to the rest of the source code and installation
9593 The extra files created for Debian are in the subdirectory
9594 <file>debian</file> of the top level of the Debianised source
9595 tree. They are described below.
9598 <sect1 id="pkg-debianrules">
9599 <heading><file>debian/rules</file> - the main building script</heading>
9602 See <ref id="debianrules">.
9607 <sect1 id="pkg-dpkgchangelog">
9608 <heading><file>debian/changelog</file></heading>
9611 See <ref id="dpkgchangelog">.
9615 It is recommended that the entire changelog be encoded in the
9616 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9618 <url id="http://www.unicode.org/"
9619 name="Unicode">.<footnote>
9621 I think it is fairly obvious that we need to
9622 eventually transition to UTF-8 for our package
9623 infrastructure; it is really the only sane char-set in
9624 an international environment. Now, we can't switch to
9625 using UTF-8 for package control fields and the like
9626 until dpkg has better support, but one thing we can
9627 start doing today is requesting that Debian changelogs
9628 are UTF-8 encoded. At some point in time, we can start
9629 requiring them to do so.
9632 Checking for non-UTF8 characters in a changelog is
9633 trivial. Dump the file through
9634 <example>iconv -f utf-8 -t ucs-4</example>
9635 discard the output, and check the return
9636 value. If there are any characters in the stream
9637 which are invalid UTF-8 sequences, iconv will exit
9638 with an error code; and this will be the case for the
9639 vast majority of other character sets.
9644 <sect2><heading>Defining alternative changelog formats
9648 It is possible to use a different format to the standard
9649 one, by providing a parser for the format you wish to
9654 In order to have <tt>dpkg-parsechangelog</tt> run your
9655 parser, you must include a line within the last 40 lines
9656 of your file matching the Perl regular expression:
9657 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9658 parentheses should be the name of the format. For
9659 example, you might say:
9661 @@@ changelog-format: joebloggs @@@
9663 Changelog format names are non-empty strings of alphanumerics.
9667 If such a line exists then <tt>dpkg-parsechangelog</tt>
9668 will look for the parser as
9669 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9671 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9672 it is an error for it not to find it, or for it not to
9673 be an executable program. The default changelog format
9674 is <tt>dpkg</tt>, and a parser for it is provided with
9675 the <tt>dpkg</tt> package.
9679 The parser will be invoked with the changelog open on
9680 standard input at the start of the file. It should read
9681 the file (it may seek if it wishes) to determine the
9682 information required and return the parsed information
9683 to standard output in the form of a series of control
9684 fields in the standard format. By default it should
9685 return information about only the most recent version in
9686 the changelog; it should accept a
9687 <tt>-v<var>version</var></tt> option to return changes
9688 information from all versions present <em>strictly
9689 after</em> <var>version</var>, and it should then be an
9690 error for <var>version</var> not to be present in the
9696 <list compact="compact">
9697 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9698 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9699 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9700 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9701 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9702 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9703 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9708 If several versions are being returned (due to the use
9709 of <tt>-v</tt>), the urgency value should be of the
9710 highest urgency code listed at the start of any of the
9711 versions requested followed by the concatenated
9712 (space-separated) comments from all the versions
9713 requested; the maintainer, version, distribution and
9714 date should always be from the most recent version.
9718 For the format of the <tt>Changes</tt> field see
9719 <ref id="f-Changes">.
9723 If the changelog format which is being parsed always or
9724 almost always leaves a blank line between individual
9725 change notes these blank lines should be stripped out,
9726 so as to make the resulting output compact.
9730 If the changelog format does not contain date or package
9731 name information this information should be omitted from
9732 the output. The parser should not attempt to synthesize
9733 it or find it from other sources.
9737 If the changelog does not have the expected format the
9738 parser should exit with a nonzero exit status, rather
9739 than trying to muddle through and possibly generating
9744 A changelog parser may not interact with the user at
9750 <sect1 id="pkg-srcsubstvars">
9751 <heading><file>debian/substvars</file> and variable substitutions</heading>
9754 See <ref id="substvars">.
9760 <heading><file>debian/files</file></heading>
9763 See <ref id="debianfiles">.
9767 <sect1><heading><file>debian/tmp</file>
9771 This is the canonical temporary location for the
9772 construction of binary packages by the <tt>binary</tt>
9773 target. The directory <file>tmp</file> serves as the root of
9774 the file system tree as it is being constructed (for
9775 example, by using the package's upstream makefiles install
9776 targets and redirecting the output there), and it also
9777 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9778 id="pkg-bincreating">.
9782 If several binary packages are generated from the same
9783 source tree it is usual to use several
9784 <file>debian/tmp<var>something</var></file> directories, for
9785 example <file>tmp-a</file> or <file>tmp-doc</file>.
9789 Whatever <file>tmp</file> directories are created and used by
9790 <tt>binary</tt> must of course be removed by the
9791 <tt>clean</tt> target.</p></sect1>
9795 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9799 As it exists on the FTP site, a Debian source package
9800 consists of three related files. You must have the right
9801 versions of all three to be able to use them.
9806 <tag>Debian source control file - <tt>.dsc</tt></tag>
9808 This file is a control file used by <prgn>dpkg-source</prgn>
9809 to extract a source package.
9810 See <ref id="debiansourcecontrolfiles">.
9814 Original source archive -
9816 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9822 This is a compressed (with <tt>gzip -9</tt>)
9823 <prgn>tar</prgn> file containing the source code from
9824 the upstream authors of the program.
9829 Debianisation diff -
9831 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9837 This is a unified context diff (<tt>diff -u</tt>)
9838 giving the changes which are required to turn the
9839 original source into the Debian source. These changes
9840 may only include editing and creating plain files.
9841 The permissions of files, the targets of symbolic
9842 links and the characteristics of special files or
9843 pipes may not be changed and no files may be removed
9848 All the directories in the diff must exist, except the
9849 <file>debian</file> subdirectory of the top of the source
9850 tree, which will be created by
9851 <prgn>dpkg-source</prgn> if necessary when unpacking.
9855 The <prgn>dpkg-source</prgn> program will
9856 automatically make the <file>debian/rules</file> file
9857 executable (see below).</p></item>
9862 If there is no original source code - for example, if the
9863 package is specially prepared for Debian or the Debian
9864 maintainer is the same as the upstream maintainer - the
9865 format is slightly different: then there is no diff, and the
9867 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9868 and preferably contains a directory named
9869 <file><var>package</var>-<var>version</var></file>.
9874 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9877 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9878 Debian source package. However, if it is not available it
9879 is possible to unpack a Debian source archive as follows:
9880 <enumlist compact="compact">
9883 Untar the tarfile, which will create a <file>.orig</file>
9887 <p>Rename the <file>.orig</file> directory to
9888 <file><var>package</var>-<var>version</var></file>.</p>
9892 Create the subdirectory <file>debian</file> at the top of
9893 the source tree.</p>
9895 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9897 <item><p>Untar the tarfile again if you want a copy of the original
9898 source code alongside the Debianised version.</p>
9903 It is not possible to generate a valid Debian source archive
9904 without using <prgn>dpkg-source</prgn>. In particular,
9905 attempting to use <prgn>diff</prgn> directly to generate the
9906 <file>.diff.gz</file> file will not work.
9910 <heading>Restrictions on objects in source packages</heading>
9913 The source package may not contain any hard links
9915 This is not currently detected when building source
9916 packages, but only when extracting
9920 Hard links may be permitted at some point in the
9921 future, but would require a fair amount of
9923 </footnote>, device special files, sockets or setuid or
9926 Setgid directories are allowed.
9931 The source packaging tools manage the changes between the
9932 original and Debianised source using <prgn>diff</prgn> and
9933 <prgn>patch</prgn>. Turning the original source tree as
9934 included in the <file>.orig.tar.gz</file> into the debianised
9935 source must not involve any changes which cannot be
9936 handled by these tools. Problematic changes which cause
9937 <prgn>dpkg-source</prgn> to halt with an error when
9938 building the source package are:
9939 <list compact="compact">
9940 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9942 <item><p>Changing the targets of symbolic links.</p>
9944 <item><p>Creating directories, other than <file>debian</file>.</p>
9946 <item><p>Changes to the contents of binary files.</p></item>
9947 </list> Changes which cause <prgn>dpkg-source</prgn> to
9948 print a warning but continue anyway are:
9949 <list compact="compact">
9952 Removing files, directories or symlinks.
9954 Renaming a file is not treated specially - it is
9955 seen as the removal of the old file (which
9956 generates a warning, but is otherwise ignored),
9957 and the creation of the new one.
9963 Changed text files which are missing the usual final
9964 newline (either in the original or the modified
9969 Changes which are not represented, but which are not detected by
9970 <prgn>dpkg-source</prgn>, are:
9971 <list compact="compact">
9972 <item><p>Changing the permissions of files (other than
9973 <file>debian/rules</file>) and directories.</p></item>
9978 The <file>debian</file> directory and <file>debian/rules</file>
9979 are handled specially by <prgn>dpkg-source</prgn> - before
9980 applying the changes it will create the <file>debian</file>
9981 directory, and afterwards it will make
9982 <file>debian/rules</file> world-executable.
9988 <appendix id="pkg-controlfields">
9989 <heading>Control files and their fields (from old Packaging Manual)</heading>
9992 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9993 data in a common format, known as control files. Binary and
9994 source packages have control data as do the <file>.changes</file>
9995 files which control the installation of uploaded files, and
9996 <prgn>dpkg</prgn>'s internal databases are in a similar
10001 <heading>Syntax of control files</heading>
10004 See <ref id="controlsyntax">.
10008 It is important to note that there are several fields which
10009 are optional as far as <prgn>dpkg</prgn> and the related
10010 tools are concerned, but which must appear in every Debian
10011 package, or whose omission may cause problems.
10016 <heading>List of fields</heading>
10019 See <ref id="controlfieldslist">.
10023 This section now contains only the fields that didn't belong
10024 to the Policy manual.
10027 <sect1 id="pkg-f-Filename">
10028 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10031 These fields in <tt>Packages</tt> files give the
10032 filename(s) of (the parts of) a package in the
10033 distribution directories, relative to the root of the
10034 Debian hierarchy. If the package has been split into
10035 several parts the parts are all listed in order, separated
10040 <sect1 id="pkg-f-Size">
10041 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10044 These fields in <file>Packages</file> files give the size (in
10045 bytes, expressed in decimal) and MD5 checksum of the
10046 file(s) which make(s) up a binary package in the
10047 distribution. If the package is split into several parts
10048 the values for the parts are listed in order, separated by
10053 <sect1 id="pkg-f-Status">
10054 <heading><tt>Status</tt></heading>
10057 This field in <prgn>dpkg</prgn>'s status file records
10058 whether the user wants a package installed, removed or
10059 left alone, whether it is broken (requiring
10060 re-installation) or not and what its current state on the
10061 system is. Each of these pieces of information is a
10066 <sect1 id="pkg-f-Config-Version">
10067 <heading><tt>Config-Version</tt></heading>
10070 If a package is not installed or not configured, this
10071 field in <prgn>dpkg</prgn>'s status file records the last
10072 version of the package which was successfully
10077 <sect1 id="pkg-f-Conffiles">
10078 <heading><tt>Conffiles</tt></heading>
10081 This field in <prgn>dpkg</prgn>'s status file contains
10082 information about the automatically-managed configuration
10083 files held by a package. This field should <em>not</em>
10084 appear anywhere in a package!
10089 <heading>Obsolete fields</heading>
10092 These are still recognized by <prgn>dpkg</prgn> but should
10093 not appear anywhere any more.
10095 <taglist compact="compact">
10097 <tag><tt>Revision</tt></tag>
10098 <tag><tt>Package-Revision</tt></tag>
10099 <tag><tt>Package_Revision</tt></tag>
10101 The Debian revision part of the package version was
10102 at one point in a separate control file field. This
10103 field went through several names.
10106 <tag><tt>Recommended</tt></tag>
10107 <item>Old name for <tt>Recommends</tt>.</item>
10109 <tag><tt>Optional</tt></tag>
10110 <item>Old name for <tt>Suggests</tt>.</item>
10112 <tag><tt>Class</tt></tag>
10113 <item>Old name for <tt>Priority</tt>.</item>
10122 <appendix id="pkg-conffiles">
10123 <heading>Configuration file handling (from old Packaging Manual)</heading>
10126 <prgn>dpkg</prgn> can do a certain amount of automatic
10127 handling of package configuration files.
10131 Whether this mechanism is appropriate depends on a number of
10132 factors, but basically there are two approaches to any
10133 particular configuration file.
10137 The easy method is to ship a best-effort configuration in the
10138 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10139 handle updates. If the user is unlikely to want to edit the
10140 file, but you need them to be able to without losing their
10141 changes, and a new package with a changed version of the file
10142 is only released infrequently, this is a good approach.
10146 The hard method is to build the configuration file from
10147 scratch in the <prgn>postinst</prgn> script, and to take the
10148 responsibility for fixing any mistakes made in earlier
10149 versions of the package automatically. This will be
10150 appropriate if the file is likely to need to be different on
10154 <sect><heading>Automatic handling of configuration files by
10159 A package may contain a control area file called
10160 <tt>conffiles</tt>. This file should be a list of filenames
10161 of configuration files needing automatic handling, separated
10162 by newlines. The filenames should be absolute pathnames,
10163 and the files referred to should actually exist in the
10168 When a package is upgraded <prgn>dpkg</prgn> will process
10169 the configuration files during the configuration stage,
10170 shortly before it runs the package's <prgn>postinst</prgn>
10175 For each file it checks to see whether the version of the
10176 file included in the package is the same as the one that was
10177 included in the last version of the package (the one that is
10178 being upgraded from); it also compares the version currently
10179 installed on the system with the one shipped with the last
10184 If neither the user nor the package maintainer has changed
10185 the file, it is left alone. If one or the other has changed
10186 their version, then the changed version is preferred - i.e.,
10187 if the user edits their file, but the package maintainer
10188 doesn't ship a different version, the user's changes will
10189 stay, silently, but if the maintainer ships a new version
10190 and the user hasn't edited it the new version will be
10191 installed (with an informative message). If both have
10192 changed their version the user is prompted about the problem
10193 and must resolve the differences themselves.
10197 The comparisons are done by calculating the MD5 message
10198 digests of the files, and storing the MD5 of the file as it
10199 was included in the most recent version of the package.
10203 When a package is installed for the first time
10204 <prgn>dpkg</prgn> will install the file that comes with it,
10205 unless that would mean overwriting a file already on the
10210 However, note that <prgn>dpkg</prgn> will <em>not</em>
10211 replace a conffile that was removed by the user (or by a
10212 script). This is necessary because with some programs a
10213 missing file produces an effect hard or impossible to
10214 achieve in another way, so that a missing file needs to be
10215 kept that way if the user did it.
10219 Note that a package should <em>not</em> modify a
10220 <prgn>dpkg</prgn>-handled conffile in its maintainer
10221 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10222 the user confusing and possibly dangerous options for
10223 conffile update when the package is upgraded.</p>
10226 <sect><heading>Fully-featured maintainer script configuration
10231 For files which contain site-specific information such as
10232 the hostname and networking details and so forth, it is
10233 better to create the file in the package's
10234 <prgn>postinst</prgn> script.
10238 This will typically involve examining the state of the rest
10239 of the system to determine values and other information, and
10240 may involve prompting the user for some information which
10241 can't be obtained some other way.
10245 When using this method there are a couple of important
10246 issues which should be considered:
10250 If you discover a bug in the program which generates the
10251 configuration file, or if the format of the file changes
10252 from one version to the next, you will have to arrange for
10253 the postinst script to do something sensible - usually this
10254 will mean editing the installed configuration file to remove
10255 the problem or change the syntax. You will have to do this
10256 very carefully, since the user may have changed the file,
10257 perhaps to fix the very problem that your script is trying
10258 to deal with - you will have to detect these situations and
10259 deal with them correctly.
10263 If you do go down this route it's probably a good idea to
10264 make the program that generates the configuration file(s) a
10265 separate program in <file>/usr/sbin</file>, by convention called
10266 <file><var>package</var>config</file> and then run that if
10267 appropriate from the post-installation script. The
10268 <tt><var>package</var>config</tt> program should not
10269 unquestioningly overwrite an existing configuration - if its
10270 mode of operation is geared towards setting up a package for
10271 the first time (rather than any arbitrary reconfiguration
10272 later) you should have it check whether the configuration
10273 already exists, and require a <tt>--force</tt> flag to
10274 overwrite it.</p></sect>
10277 <appendix id="pkg-alternatives"><heading>Alternative versions of
10278 an interface - <prgn>update-alternatives</prgn> (from old
10283 When several packages all provide different versions of the
10284 same program or file it is useful to have the system select a
10285 default, but to allow the system administrator to change it
10286 and have their decisions respected.
10290 For example, there are several versions of the <prgn>vi</prgn>
10291 editor, and there is no reason to prevent all of them from
10292 being installed at once, each under their own name
10293 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10294 Nevertheless it is desirable to have the name <tt>vi</tt>
10295 refer to something, at least by default.
10299 If all the packages involved cooperate, this can be done with
10300 <prgn>update-alternatives</prgn>.
10304 Each package provides its own version under its own name, and
10305 calls <prgn>update-alternatives</prgn> in its postinst to
10306 register its version (and again in its prerm to deregister
10311 See the man page <manref name="update-alternatives"
10312 section="8"> for details.
10316 If <prgn>update-alternatives</prgn> does not seem appropriate
10317 you may wish to consider using diversions instead.</p>
10320 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10321 package's version of a file (from old Packaging Manual)
10325 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10326 when it reinstalls the package it belongs to, and to have it
10327 put the file from the package somewhere else instead.
10331 This can be used locally to override a package's version of a
10332 file, or by one package to override another's version (or
10333 provide a wrapper for it).
10337 Before deciding to use a diversion, read <ref
10338 id="pkg-alternatives"> to see if you really want a diversion
10339 rather than several alternative versions of a program.
10343 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10344 and updated by a special program <prgn>dpkg-divert</prgn>.
10345 Please see <manref name="dpkg-divert" section="8"> for full
10346 details of its operation.
10350 When a package wishes to divert a file from another, it should
10351 call <prgn>dpkg-divert</prgn> in its preinst to add the
10352 diversion and rename the existing file. For example,
10353 supposing that a <prgn>smailwrapper</prgn> package wishes to
10354 install a wrapper around <file>/usr/sbin/smail</file>:
10356 if [ install = "$1" ]; then
10357 dpkg-divert --package smailwrapper --add --rename \
10358 --divert /usr/sbin/smail.real /usr/sbin/smail
10360 </example> Testing <tt>$1</tt> is necessary so that the script
10361 doesn't try to add the diversion again when
10362 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10363 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10364 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10365 get installed as the true version.
10369 The postrm has to do the reverse:
10371 if [ remove = "$1" ]; then
10372 dpkg-divert --package smailwrapper --remove --rename \
10373 --divert /usr/sbin/smail.real /usr/sbin/smail
10379 Do not attempt to divert a file which is vitally important for
10380 the system's operation - when using <prgn>dpkg-divert</prgn>
10381 there is a time, after it has been diverted but before
10382 <prgn>dpkg</prgn> has installed the new version, when the file
10383 does not exist.</p>
10388 <!-- Local variables: -->
10389 <!-- indent-tabs-mode: t -->
10391 <!-- vim:set ai et sts=2 sw=2 tw=76: -->