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8 Debian GNU/Linux Policy Manual.
9 Copyright (C)1996,1997,1998 Ian Jackson and Christian Schwarz;
10 released under the terms of the GNU
11 General Public License, version 2 or (at your option) any later.
12 Initial version 1996, Ian Jackson, ijackson@gnu.ai.mit.edu
13 Revised November 27, 1996, David A. Morris, bweaver@debian.org
14 New sections March 15, 1997, Christian Schwarz, schwarz@debian.org
15 Reworked/Restructured April-July 1997, Christian Schwarz, schwarz@debian.org
16 Maintainer since 1997, Christian Schwarz, schwarz@debian.org
17 Christoph Lameter contributed the "Web Standard"
18 The debian-policy mailing list has taken responsibility for the
19 contents of this document since September 1998, with the package
20 maintainers responsible for packaging administrivia only.
25 <title>Debian Policy Manual</title>
27 <name>Ian Jackson </name>
28 <email>ijackson@gnu.ai.mit.edu</email>
31 <name>Christian Schwarz</name>
32 <email>schwarz@debian.org</email>
35 <name>revised: David A. Morris</name>
36 <email>bweaver@debian.org</email>
39 <name>The Debian Policy mailing List</name>
40 <email>debian-policy@lists.debian.org</email>
42 <version>version &version;, &date;</version>
45 This manual describes the policy requirements for the Debian
46 GNU/Linux distribution. This includes the structure and
47 contents of the Debian archive and several design issues of
48 the operating system, as well as technical requirements that
49 each package must satisfy to be included in the distribution.
50 The policy package itself is maintained by a group of
51 maintainers that have no editorial powers. The current list
55 <p>Julian Gilbey <email>jdg@debian.org</email></p>
58 <p>Manoj Srivastava <email>srivasta@debian.org</email></p>
66 Copyright ©1996,1997,1998 Ian Jackson
67 and Christian Schwarz.
70 This manual is free software; you may redistribute it and/or
71 modify it under the terms of the GNU General Public License
72 as published by the Free Software Foundation; either version
73 2, or (at your option) any later version.
77 This is distributed in the hope that it will be useful, but
78 <em>without any warranty</em>; without even the implied
79 warranty of merchantability or fitness for a particular
80 purpose. See the GNU General Public License for more
85 A copy of the GNU General Public License is available as
86 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
87 distribution or on the World Wide Web at
88 <url id="http://www.gnu.org/copyleft/gpl.html"
89 name="The GNU General Public Licence">. You can also
90 obtain it by writing to the Free Software Foundation, Inc.,
91 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
99 <heading>About this manual</heading>
101 <heading>Scope</heading>
103 This manual describes the policy requirements for the Debian
104 GNU/Linux distribution. This includes the structure and
105 contents of the Debian archive and several design issues of the
106 operating system, as well as technical requirements that
107 each package must satisfy to be included in the
113 This manual also describes Debian policy as it relates to
114 creating Debian packages. It is not a tutorial on how to build
115 packages, nor is it exhaustive where it comes to describing
116 the behavior of the packaging system. Instead, this manual
117 attempts to define the interface to the package management
118 system that the developers have to be conversant with.<footnote>
120 Informally, the criteria used for inclusion is that the
121 material meet one of the following requirements:
122 <taglist compact="compact">
123 <tag>Standard interfaces</tag>
126 The material presented represents an interface to
127 the packaging system that is mandated for use, and
128 is used by, a significant number of packages, and
129 therefore should not be changed without peer
130 review. Package maintainers can then rely on this
131 interfaces not changing, and the package
132 management software authors need to ensure
133 compatibility with these interface
134 definitions. (Control file and changelog file
135 formats are examples.)
138 <tag>Chosen Convention</tag>
141 If there are a number of technically viable choices
142 that can be made, but one needs to select one of
143 these options for inter-operability. The version
144 number format is one example.
148 Please note that these are not mutually exclusive;
149 selected conventions often become parts of standard
156 The footnotes present in this manual are
157 merely informative, and are not part of Debian policy itself.
162 In this manual, the words <em>must</em>, <em>should</em> and
163 <em>may</em>, and the adjectives <em>required</em>,
164 <em>recommended</em> and <em>optional</em>, are used to
165 distinguish the significance of the various guidelines in
166 this policy document. Packages that do not conform to the
167 guidelines denoted by <em>must</em> (or <em>required</em>)
168 will generally not be considered acceptable for the Debian
169 distribution. Non-conformance with guidelines denoted by
170 <em>should</em> (or <em>recommended</em>) will generally be
171 considered a bug, but will not necessarily render a package
172 unsuitable for distribution. Guidelines denoted by
173 <em>may</em> (or <em>optional</em>) are truly optional and
174 adherence is left to the maintainer's discretion.
177 These classifications are roughly equivalent to the bug
178 severities <em>serious</em> (for <em>must</em> or
179 <em>required</em> directive violations), <em>minor</em>,
180 <em>normal</em> or <em>important</em>
181 (for <em>should</em> or <em>recommended</em> directive
182 violations) and <em>wishlist</em> (for <em>optional</em>
184 <p>Compare RFC 2119. Note, however, that these words are
185 used in a different way in this document.</p>
189 Much of the information presented in this manual will be
190 useful even when building a package which is to be
191 distributed in some other way or is intended for local use
196 <heading>New versions of this document</heading>
198 The current version of this document is always accessible
199 from the Debian FTP server <ftpsite>ftp.debian.org</ftpsite>
201 <ftppath>/debian/doc/package-developer/policy.txt.gz</ftppath>
202 (also available from the same directory are several other
203 formats: <file>policy.html.tar.gz</file>, <file>policy.pdf.gz</file>
204 and <file>policy.ps.gz</file>) or from the <url
205 id="http://www.debian.org/doc/debian-policy/" name="Debian
206 Policy Manual"> webpage.</p>
209 In addition, this manual is distributed via the Debian package
210 <file>debian-policy</file>.
214 The <tt>debian-policy</tt> package also includes the file
215 <file>upgrading-checklist.txt</file> which indicates policy
216 changes between versions of this document.
220 <heading>Feedback</heading>
223 As the Debian GNU/Linux system is continuously evolving this
227 While the authors of this document have tried hard to avoid
228 typos and other errors, these do still occur. If you discover
229 an error in this manual or if you want to give any
230 comments, suggestions, or criticisms please send an email to
231 the Debian Policy List,
232 <email>debian-policy@lists.debian.org</email>, or submit a
233 bug report against the <tt>debian-policy</tt> package.
239 <heading>The Debian Archive</heading>
241 The Debian GNU/Linux system is maintained and distributed as a
242 collection of <em>packages</em>. Since there are so many of
243 them (currently well over 6000), they are split into
244 <em>sections</em> and given <em>priorities</em> to simplify
245 the handling of them.
248 The effort of the Debian project is to build a free operating
249 system, but not every package we want to make accessible is
250 <em>free</em> in our sense (see the Debian Free Software
251 Guidelines, below), or may be imported/exported without
252 restrictions. Thus, the archive is split into the sections
253 <em>main</em>, <em>non-free</em>, <em>contrib</em>,
254 <em>non-US/main</em>, <em>non-US/non-free</em>, and
255 <em>non-US/contrib</em>. The sections are explained in detail
260 The <em>main</em> and the <em>non-US/main</em> sections
261 together form the <em>Debian GNU/Linux distribution</em>.
265 Packages in the other sections are not considered to be part
266 of the Debian distribution, although we support their use and
267 provide infrastructure for them (such as our bug-tracking
268 system and mailing lists). This Debian Policy Manual applies
269 to these packages as well.</p>
271 <sect id="pkgcopyright">
272 <heading>Package copyright and sections</heading>
274 The aims of this section are:
276 <list compact="compact">
278 <p>to allow us to make as much software available as we
282 <p>to allow us to encourage everyone to write free
286 <p>to allow us to make it easy for people to produce
287 CD-ROMs of our system without violating any licenses,
288 import/export restrictions, or any other laws.</p>
293 <heading>The Debian Free Software Guidelines</heading>
295 The Debian Free Software Guidelines (DFSG) form our
296 definition of `free software'. These are:
298 <tag>Free Redistribution
302 The license of a Debian component may not restrict any
303 party from selling or giving away the software as a
304 component of an aggregate software distribution
305 containing programs from several different
306 sources. The license may not require a royalty or
307 other fee for such sale.
314 The program must include source code, and must allow
315 distribution in source code as well as compiled form.
322 The license must allow modifications and derived
323 works, and must allow them to be distributed under the
324 same terms as the license of the original software.
327 <tag>Integrity of The Author's Source Code
331 The license may restrict source-code from being
332 distributed in modified form <em>only</em> if the
333 license allows the distribution of ``patch files''
334 with the source code for the purpose of modifying the
335 program at build time. The license must explicitly
336 permit distribution of software built from modified
337 source code. The license may require derived works to
338 carry a different name or version number from the
339 original software. (This is a compromise. The Debian
340 Project encourages all authors to not restrict any
341 files, source or binary, from being modified.)
344 <tag>No Discrimination Against Persons or Groups
348 The license must not discriminate against any person
352 <tag>No Discrimination Against Fields of Endeavor
356 The license must not restrict anyone from making use
357 of the program in a specific field of endeavor. For
358 example, it may not restrict the program from being
359 used in a business, or from being used for genetic
363 <tag>Distribution of License
367 The rights attached to the program must apply to all
368 to whom the program is redistributed without the need
369 for execution of an additional license by those
373 <tag>License Must Not Be Specific to Debian
377 The rights attached to the program must not depend on
378 the program's being part of a Debian system. If the
379 program is extracted from Debian and used or
380 distributed without Debian but otherwise within the
381 terms of the program's license, all parties to whom
382 the program is redistributed must have the same
383 rights as those that are granted in conjunction with
387 <tag>License Must Not Contaminate Other Software
391 The license must not place restrictions on other
392 software that is distributed along with the licensed
393 software. For example, the license must not insist
394 that all other programs distributed on the same medium
395 must be free software.
398 <tag>Example Licenses
402 The ``GPL,'' ``BSD,'' and ``Artistic'' licenses are
403 examples of licenses that we consider <em>free</em>.
410 <heading>The main section</heading>
412 Every package in <em>main</em> and <em>non-US/main</em>
413 must comply with the DFSG (Debian Free Software
417 In addition, the packages in <em>main</em>
418 <list compact="compact">
421 must not require a package outside of <em>main</em>
422 for compilation or execution (thus, the package must
423 not declare a "Depends", "Recommends", or
424 "Build-Depends" relationship on a non-<em>main</em>
430 must not be so buggy that we refuse to support them,
436 must meet all policy requirements presented in this
443 Similarly, the packages in <em>non-US/main</em>
444 <list compact="compact">
447 must not require a package outside of <em>main</em>
448 or <em>non-US/main</em> for compilation or
454 must not be so buggy that we refuse to support them,
459 must meet all policy requirements presented in this
467 <heading>The contrib section</heading>
469 Every package in <em>contrib</em> and
470 <em>non-US/contrib</em> must comply with the DFSG.
474 In addition, the packages in <em>contrib</em> and
475 <em>non-US/contrib</em>
476 <list compact="compact">
479 must not be so buggy that we refuse to support them,
485 must meet all policy requirements presented in this
493 Furthermore, packages in <em>contrib</em> must not require
494 a package in a <em>non-US</em> section for compilation or
499 Examples of packages which would be included in
500 <em>contrib</em> or <em>non-US/contrib</em> are:
501 <list compact="compact">
504 free packages which require <em>contrib</em>,
505 <em>non-free</em> packages or packages which are not
506 in our archive at all for compilation or execution,
512 wrapper packages or other sorts of free accessories for
520 <heading>The non-free section</heading>
522 Packages must be placed in <em>non-free</em> or
523 <em>non-US/non-free</em> if they are not compliant with
524 the DFSG or are encumbered by patents or other legal
525 issues that make their distribution problematic.
528 In addition, the packages in <em>non-free</em> and
529 <em>non-US/non-free</em>
530 <list compact="compact">
533 must not be so buggy that we refuse to support them,
539 must meet all policy requirements presented in this
540 manual that it is possible for them to meet.<footnote>
542 It is possible that there are policy
543 requirements which the package is unable to
544 meet, for example, if the source is
545 unavailable. These situations will need to be
546 handled on a case-by-case basis.
556 <heading>The non-US sections</heading>
558 Non-free programs with cryptographic program code need to
559 be stored on the <em>non-us</em> server because of export
560 restrictions of the U.S.
563 Programs which use patented algorithms that have a
564 restrictied license also need to be stored on "non-us",
565 since that is located in a country where it is not allowed
566 to patent algorithms.
569 A package depends on another package which is distributed
570 via the non-us server has to be stored on the non-us
575 <heading>Further copyright considerations</heading>
577 Every package must be accompanied by a verbatim copy of
578 its copyright and distribution license in the file
579 <file>/usr/share/doc/<var>package</var>/copyright</file>
580 (see <ref id="copyrightfile"> for further details).
583 We reserve the right to restrict files from being included
584 anywhere in our archives if
585 <list compact="compact">
588 their use or distribution would break a law,
593 there is an ethical conflict in their distribution or
599 we would have to sign a license for them, or
604 their distribution would conflict with other project
612 Programs whose authors encourage the user to make
613 donations are fine for the main distribution, provided
614 that the authors do not claim that not donating is
615 immoral, unethical, illegal or something similar; in such
616 a case they must go in <em>non-free</em>.</p>
619 Packages whose copyright permission notices (or patent
620 problems) do not even allow redistribution of binaries
621 only, and where no special permission has been obtained,
622 must not be placed on the Debian FTP site and its mirrors
626 Note that under international copyright law (this applies
627 in the United States, too), <em>no</em> distribution or
628 modification of a work is allowed without an explicit
629 notice saying so. Therefore a program without a copyright
630 notice <em>is</em> copyrighted and you may not do anything
631 to it without risking being sued! Likewise if a program
632 has a copyright notice but no statement saying what is
633 permitted then nothing is permitted.</p>
636 Many authors are unaware of the problems that restrictive
637 copyrights (or lack of copyright notices) can cause for
638 the users of their supposedly-free software. It is often
639 worthwhile contacting such authors diplomatically to ask
640 them to modify their license terms. However, this can be a
641 politically difficult thing to do and you should ask for
642 advice on the <tt>debian-legal</tt> mailing list first, as
647 When in doubt about a copyright, send mail to
648 <email>debian-legal@lists.debian.org</email>. Be prepared
649 to provide us with the copyright statement. Software
650 covered by the GPL, public domain software and BSD-like
651 copyrights are safe; be wary of the phrases `commercial
652 use prohibited' and `distribution restricted'.
656 <heading>Subsections</heading>
659 The packages in the sections <em>main</em>,
660 <em>contrib</em> and <em>non-free</em> are grouped further
661 into <em>subsections</em> to simplify handling.
665 The section and subsection for each package should be
666 specified in the package's <tt>Section</tt> control
667 record. However, the maintainer of the Debian archive
668 may override this selection to ensure the consistency of
669 the Debian distribution. The <tt>Section</tt> field
670 should be of the form:
671 <list compact="compact">
674 <em>subsection</em> if the package is in the
675 <em>main</em> section,
680 <em>section/subsection</em> if the package is in
681 the <em>contrib</em> or <em>non-free</em> section,
687 <tt>non-US</tt>, <tt>non-US/contrib</tt> or
688 <tt>non-US/non-free</tt> if the package is in
689 <em>non-US/main</em>, <em>non-US/contrib</em> or
690 <em>non-US/non-free</em> respectively.
697 The Debian archive maintainers provide the authoritative
698 list of subsections. At present, they are:
699 <em>admin</em>, <em>base</em>, <em>comm</em>,
700 <em>contrib</em>, <em>devel</em>, <em>doc</em>,
701 <em>editors</em>, <em>electronics</em>, <em>games</em>,
702 <em>graphics</em>, <em>hamradio</em>,
703 <em>interpreters</em>, <em>libs</em>, <em>mail</em>,
704 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
705 <em>non-US</em>, <em>non-free</em>, <em>oldlibs</em>,
706 <em>otherosfs</em>, <em>science</em>, <em>shells</em>,
707 <em>sound</em>, <em>tex</em>, <em>text</em>,
708 <em>utils</em>, <em>web</em>, <em>x11</em>.
712 <heading>Priorities</heading>
715 Each package should have a <em>priority</em> value, which is
716 included in the package's <em>control record</em>. This
717 information is used by the Debian package management tools
718 to separate high-priority packages from less-important
722 The following <em>priority levels</em> are recognised by the
723 Debian package management tools.
725 <tag><tt>required</tt></tag>
728 Packages which are necessary for the proper
729 functioning of the system. You must not remove these
730 packages or your system may become totally broken and
731 you may not even be able to use <prgn>dpkg</prgn> to
732 put things back. Systems with only the
733 <tt>required</tt> packages are probably unusable, but
734 they do have enough functionality to allow the
735 sysadmin to boot and install more software.</p>
737 <tag><tt>important</tt></tag>
740 Important programs, including those which one would
741 expect to find on any Unix-like system. If the
742 expectation is that an experienced Unix person who
743 found it missing would say `What on earth is going on,
744 where is <prgn>foo</prgn>?', it must be an
745 <tt>important</tt> package.<footnote>
747 This is an important criterion because we are
748 trying to produce, amongst other things, a free
752 Other packages without which the system will not run
753 well or be usable must also have priority
754 <tt>important</tt>. This does
755 <em>not</em> include Emacs, the X Window System, TeX
756 or any other large applications. The
757 <tt>important</tt> packages are just a bare minimum of
758 commonly-expected and necessary tools.</p>
760 <tag><tt>standard</tt></tag>
763 These packages provide a reasonably small but not too
764 limited character-mode system. This is what will be
765 installed by default if the user doesn't select anything
766 else. It doesn't include many large applications.</p>
768 <tag><tt>optional</tt></tag>
771 (In a sense everything that isn't required is
772 optional, but that's not what is meant here.) This is
773 all the software that you might reasonably want to
774 install if you didn't know what it was and don't have
775 specialized requirements. This is a much larger system
776 and includes the X Window System, a full TeX
777 distribution, and many applications. Note that
778 optional packages should not conflict with each other.
781 <tag><tt>extra</tt></tag>
784 This contains all packages that conflict with others
785 with required, important, standard or optional
786 priorities, or are only likely to be useful if you
787 already know what they are or have specialised
794 Packages must not depend on packages with lower priority
795 values (excluding build-time dependencies). In order to
796 ensure this, the priorities of one or more packages may need
802 <heading>Binary packages</heading>
805 The Debian GNU/Linux distribution is based on the Debian
806 package management system, called <prgn>dpkg</prgn>. Thus,
807 all packages in the Debian distribution must be provided
808 in the <tt>.deb</tt> file format.</p>
812 <heading>The package name</heading>
815 Every package must have a name that's unique within the Debian
819 Package names must consist of lower case letters
820 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
821 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
822 They must be at least two characters long and must start
823 with an alphanumeric character.
827 The package name is part of the file name of the
828 <tt>.deb</tt> file and is included in the control field
834 <heading>The maintainer of a package</heading>
836 Every package must have a Debian maintainer (the
837 maintainer may be one person or a group of people
838 reachable from a common email address, such as a mailing
839 list). The maintainer is responsible for ensuring that
840 the package is placed in the appropriate distributions.
844 The maintainer must be specified in the
845 <tt>Maintainer</tt> control field with their correct name
846 and a working email address. If one person maintains
847 several packages, he/she should try to avoid having
848 different forms of their name and email address in
849 the <tt>Maintainer</tt> fields of those packages.
853 If the maintainer of a package quits from the Debian
854 project, "Debian QA Group"
855 <email>packages@qa.debian.org</email> takes over the
856 maintainership of the package until someone else
857 volunteers for that task. These packages are called
858 <em>orphaned packages</em>.<footnote>
860 The detailed procedure for doing this gracefully can
861 be found in the Debian Developer's Reference, either
862 in the <tt>developers-reference</tt> package, or on
863 the Debian FTP server
864 <ftpsite>ftp.debian.org</ftpsite> as
865 <ftppath>/debian/doc/package-developer/developers-reference.txt.gz</ftppath>
867 id="http://www.debian.org/doc/packaging-manuals/developers-reference/"
868 name="Debian Developer's Reference"> webpage.
876 <heading>The description of a package</heading>
879 Every Debian package must have an extended description
880 stored in the appropriate field of the control record.</p>
883 The description should be written so that it gives the
884 system administrator enough information to decide whether
885 to install the package. This description should not just
886 be copied verbatim from the program's documentation.
887 Instructions for configuring or using the package should
888 not be included (that is what installation scripts,
889 manual pages, info files, etc., are for). Copyright
890 statements and other administrivia should not be included
891 either (that is what the copyright file is for).
897 <heading>Dependencies</heading>
900 Every package must specify the dependency information
901 about other packages that are required for the first to
905 For example, a dependency entry must be provided for any
906 shared libraries required by a dynamically-linked executable
907 binary in a package.</p>
910 Packages are not required to declare any dependencies they
911 have on other packages which are marked <tt>Essential</tt>
912 (see below), and should not do so unless they depend on a
913 particular version of that package.</p>
916 Sometimes, a package requires another package to be installed
917 <em>and</em> configured before it can be installed. In this
918 case, you must specify a <tt>Pre-Depends</tt> entry for
922 You should not specify a <tt>Pre-Depends</tt> entry for a
923 package before this has been discussed on the
924 <tt>debian-devel</tt> mailing list and a consensus about
925 doing that has been reached.</p></sect1>
928 <sect1 id="virtual_pkg_sect">
929 <heading>Virtual packages</heading>
932 Sometimes, there are several packages which offer
933 more-or-less the same functionality. In this case, it's
934 useful to define a <em>virtual package</em> whose name
935 describes that common functionality. (The virtual
936 packages only exist logically, not physically; that's why
937 they are called <em>virtual</em>.) The packages with this
938 particular function will then <em>provide</em> the virtual
939 package. Thus, any other package requiring that function
940 can simply depend on the virtual package without having to
941 specify all possible packages individually.</p>
944 All packages should use virtual package names where
945 appropriate, and arrange to create new ones if necessary.
946 They should not use virtual package names (except privately,
947 amongst a cooperating group of packages) unless they have
948 been agreed upon and appear in the list of virtual package
949 names. (See also <ref id="virtual">)</p>
952 The latest version of the authoritative list of virtual
953 package names can be found on
954 <ftpsite>ftp.debian.org</ftpsite> in
955 <ftppath>/debian/doc/package-developer/virtual-package-names-list.txt</ftppath>
956 or your local mirror. In addition, it is included in the
957 <tt>debian-policy</tt> package. The procedure for updating
958 the list is described at the top of the file.</p></sect1>
962 <heading>Base packages</heading>
965 The packages included in the <tt>base</tt> section have a
966 special function. They form a minimum subset of the Debian
967 GNU/Linux system that is installed before everything else
968 on a new system. Thus, only very few packages are allowed
969 to go into the <tt>base</tt> section to keep the required
970 disk usage very small.</p>
973 Most of these packages will have the priority value
974 <tt>required</tt> or at least <tt>important</tt>, and many
975 of them will be tagged <tt>essential</tt> (see below).</p>
978 You must not place any packages into the <tt>base</tt>
979 section before this has been discussed on the
980 <tt>debian-devel</tt> mailing list and a consensus about
981 doing that has been reached.</p></sect1>
985 <heading>Essential packages</heading>
988 Some packages are tagged <tt>essential</tt>. (They have
989 <tt>Essential: yes</tt> in their package control record.)
990 This flag is used for packages that are <em>essential</em>
994 Since these packages cannot be easily removed (one has to
995 specify an extra <em>force option</em> to
996 <prgn>dpkg</prgn> to do so), this flag must not be used
997 unless absolutely necessary. A shared library package
998 must not be tagged <tt>essential</tt>; dependencies will
999 prevent its premature removal, and we need to be able to
1000 remove it when it has been superseded.
1004 Since dpkg will not prevent upgrading of other packages
1005 while an <tt>essential</tt> package is in an unconfigured
1006 state, all <tt>essential</tt> packages must supply all of
1007 their core functionality even when unconfigured. If the
1008 package cannot satisfy this requirement it must not be
1009 tagged as essential, and any packages depending on this
1010 package must instead have explicit dependency fields as
1015 You must not tag any packages <tt>essential</tt> before
1016 this has been discussed on the <tt>debian-devel</tt>
1017 mailing list and a consensus about doing that has been
1022 <heading>Tasks</heading>
1025 The Debian install process allows the user to choose from
1026 a number of common tasks which a Debian system can be used to
1027 perform. Selecting a task with <prgn>tasksel</prgn> causes
1028 a set of packages that are useful in performing that task to be
1033 This set of packages is all available packages which have the
1034 name of the selected task in the <tt>Task</tt> field of their
1035 control file. The format of this field is a list of tasks,
1036 separated by commas.
1040 You should not tag any packages as belonging to a task
1041 before this has been discussed on the
1042 <em>debian-devel</em> mailing list and a consensus about
1043 doing that has been reached.
1047 For third parties (and historical reasons), tasksel also
1048 supports constructing tasks based on <em>task
1049 packages</em>. These are packages whose names begin with
1050 <em>task-</em>. Task packages should not be included in the
1055 <sect1 id="maintscripts">
1056 <heading>Maintainer Scripts</heading>
1059 The package installation scripts should avoid producing
1060 output which it is unnecessary for the user to see and
1061 should rely on <prgn>dpkg</prgn> to stave off boredom on
1062 the part of a user installing many packages. This means,
1063 amongst other things, using the <tt>--quiet</tt> option on
1064 <prgn>install-info</prgn>.</p>
1067 Errors which occur during the execution of an installation
1068 script must be checked and the installation must not
1069 continue after an error.
1073 Note that in general <ref id="scripts"> applies to package
1074 maintainer scripts, too.
1078 You should not use <prgn>dpkg-divert</prgn> on a file
1079 belonging to another package without consulting the
1080 maintainer of that package first.
1084 All packages which supply an instance of a common command
1085 name (or, in general, filename) should generally use
1086 <prgn>update-alternatives</prgn>, so that they may be
1087 installed together. If <prgn>update-alternatives</prgn>
1088 is not used, then each package must use
1089 <tt>Conflicts</tt> to ensure that other packages are
1090 de-installed. (In this case, it may be appropriate to
1091 specify a conflict against earlier versions of something
1092 that previously did not use
1093 <prgn>update-alternatives</prgn>; this is an exception to
1094 the usual rule that versioned conflicts should be
1100 <heading>Prompting in maintainer scripts</heading>
1102 Package maintainer scripts may prompt the user if
1103 necessary. Prompting may be accomplished by hand, or by
1104 communicating with a program, such as
1105 <prgn>debconf</prgn>, which conforms to the Debian
1106 Configuration management specification, version 2 or
1107 higher. These are included in the
1108 <file>debconf_specification</file> files in the
1109 <package>debian-policy</package> package.
1110 You may also find this file on the FTP site
1111 <ftpsite>ftp.debian.org</ftpsite> in
1112 <ftppath>/debian/doc/package-developer/debconf_specification.txt.gz</ftppath>
1113 or on your local mirror.<footnote>
1115 4% of Debian packages [see <url
1116 id="http://kitenet.net/programs/debconf/stats/"
1117 name="Debconf stats">] currently use
1118 <package>debconf</package> to prompt the user at
1119 install time, and this number is growing daily. The
1120 benefits of using debconf are briefly explained at
1122 id="http://kitenet.net/doc/debconf-doc/introduction.html"
1123 name="Debconf introduction">; they include
1124 preconfiguration, (mostly) noninteractive
1125 installation, elimination of redundant prompting,
1126 consistency of user interface, etc.
1129 With this increasing number of packages using
1130 <package>debconf</package>, plus the existance of a
1131 nascent second implementation of the Debian
1132 configuration management system
1133 (<package>cdebconf</package>), and the stabilization
1134 of the protocol these things use, the time has
1135 finally come to reflect the use of these things in
1142 Packages which use the Debian Configuration management
1143 specification may contain an additional
1144 <prgn>config</prgn> script and a <tt>templates</tt>
1145 file in their control archive. The <prgn>config</prgn>
1146 script might be run before the <prgn>preinst</prgn>
1147 script, and before the package is unpacked or any of its
1148 dependencies or pre-dependancies are satisfied.
1149 Therefore it must work using only the tools present in
1150 <em>essential</em> packages.<footnote>
1152 <package>Debconf</package> or another tool that
1153 implements the Debian Configuration management
1154 specification will also be installed, and any
1155 versioned dependencies on it will be satisfied
1156 before preconfiguration begins.
1162 Packages should try to minimize the amount of prompting
1163 they need to do, and they should ensure that the user
1164 will only ever be asked each question once. This means
1165 that packages should try to use appropriate shared
1166 configuration files (such as <file>/etc/papersize</file> and
1167 <file>/etc/news/server</file>), and shared
1168 <package>debconf</package> variables rather than each
1169 prompting for their own list of required pieces of
1174 It also means that an upgrade should not ask the same
1175 questions again, unless the user has used <tt>dpkg
1176 --purge</tt> to remove the package's configuration. The
1177 answers to configuration questions should be stored in an
1178 appropriate place in <file>/etc</file> so that the user can
1179 modify them, and how this has been done should be
1183 If a package has a vitally important piece of
1184 information to pass to the user (such as "don't run me
1185 as I am, you must edit the following configuration files
1186 first or you risk your system emitting badly-formatted
1187 messages"), it should display this in the
1188 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1189 prompt the user to hit return to acknowledge the
1190 message. Copyright messages do not count as vitally
1191 important (they belong in
1192 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1193 neither do instructions on how to use a program (these
1194 should be in on-line documentation, where all the users
1198 Any necessary prompting should almost always be confined
1199 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1200 script. If it is done in the <prgn>postinst</prgn>, it
1201 should be protected with a conditional so that
1202 unnecessary prompting doesn't happen if a package's
1203 installation fails and the <prgn>postinst</prgn> is
1204 called with <tt>abort-upgrade</tt>,
1205 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.</p>
1210 <heading>Source packages</heading>
1212 <sect1 id="standardsversion">
1213 <heading>Standards conformance</heading>
1216 In the source package's <tt>Standards-Version</tt> control
1217 field, you should specify the most recent version number
1218 of this policy document with which your package complied
1219 when it was last updated. The current version number is
1224 This information may be used to file bug reports
1225 automatically if your package becomes too much out of
1230 The version number has four components: major and minor
1231 version number and major and minor patch level. When the
1232 standards change in a way that requires every package to
1233 change the major number will be changed. Significant
1234 changes that will require work in many packages will be
1235 signaled by a change to the minor number. The major patch
1236 level will be changed for any change to the meaning of the
1237 standards, however small; the minor patch level will be
1238 changed when only cosmetic, typographical or other edits
1239 are made which neither change the meaning of the document
1240 nor affect the contents of packages.</p>
1243 Thus only the first three components of the policy version
1244 are significant in the <em>Standards-Version</em> control
1245 field, and so either these three components or the all
1246 four components may be specified.<footnote>
1248 In the past, people specified the full version number
1249 in the Standards-Version field, for example `2.3.0.0'.
1250 Since minor patch-level changes don't introduce new
1251 policy, it was thought it would be better to relax
1252 policy and only require the first 3 components to be
1253 specified, in this example `2.3.0'. All four
1254 components may still be used if someone wishes to do
1261 You should regularly, and especially if your package has
1262 become out of date, check for the newest Policy Manual
1263 available and update your package, if necessary. When your
1264 package complies with the new standards you should update the
1265 <tt>Standards-Version</tt> source package field and
1266 release it.<footnote>
1268 See the file <file>upgrading-checklist</file> for
1269 information about policy which has changed between
1270 different versions of this document.
1278 <heading>Package relationships</heading>
1281 Source packages should specify which binary packages they
1282 require to be installed or not to be installed in order to
1283 build correctly. For example, if building a package
1284 requires a certain compiler, then the compiler should be
1285 specified as a build-time dependency.
1289 It is not necessary to explicitly specify build-time
1290 relationships on a minimal set of packages that are always
1291 needed to compile, link and put in a Debian package a
1292 standard "Hello World!" program written in C or C++. The
1293 required packages are called <em>build-essential</em>, and
1294 an informational list can be found in
1295 <file>/usr/share/doc/build-essential/list</file> (which is
1296 contained in the <tt>build-essential</tt>
1299 <list compact="compact">
1301 <p>This allows maintaining the list separately
1302 from the policy documents (the list does not
1303 need the kind of control that the policy
1309 Having a separate package allows one to install
1310 the build-essential packages on a machine, as
1311 well as allowing other packages such as tasks to
1312 require installation of the build-essential
1313 packages using the depends relation.
1318 The separate package allows bug reports against
1319 the list to be categorized separately from
1320 the policy management process in the BTS.
1330 When specifying the set of build-time dependencies, one
1331 should list only those packages explicitly required by the
1332 build. It is not necessary to list packages which are
1333 required merely because some other package in the list of
1334 build-time dependencies depends on them.<footnote>
1336 The reason for this is that dependencies change, and
1337 you should list all those packages, and <em>only</em>
1338 those packages that <em>you</em> need directly. What
1339 others need is their business. For example, if you
1340 only link against <file>libimlib</file>, you will need to
1341 build-depend on <package>libimlib2-dev</package> but
1342 not against any <tt>libjpeg*</tt> packages, even
1343 though <tt>libimlib2-dev</tt> currently depends on
1344 them: installation of <package>libimlib2-dev</package>
1345 will automatically ensure that all of its run-time
1346 dependencies are satisfied.
1352 If build-time dependencies are specified, it must be
1353 possible to build the package and produce working binaries
1354 on a system with only essential and build-essential
1355 packages installed and also those required to satisfy the
1356 build-time relationships (including any implied
1357 relationships). In particular, this means that version
1358 clauses should be used rigorously in build-time
1359 relationships so that one cannot produce bad or
1360 inconsistently configured packages when the relationships
1361 are properly satisfied.
1365 <heading>Changes to the upstream sources</heading>
1368 If changes to the source code are made that are not
1369 specific to the needs of the Debian system, they should be
1370 sent to the upstream authors in whatever form they prefer
1371 so as to be included in the upstream version of the
1375 If you need to configure the package differently for
1376 Debian or for Linux, and the upstream source doesn't
1377 provide a way to do so, you should add such configuration
1378 facilities (for example, a new <prgn>autoconf</prgn> test
1379 or <tt>#define</tt>) and send the patch to the upstream
1380 authors, with the default set to the way they originally
1381 had it. You can then easily override the default in your
1382 <file>debian/rules</file> or wherever is appropriate.</p>
1385 You should make sure that the <prgn>configure</prgn> utility
1386 detects the correct architecture specification string
1387 (refer to <ref id="arch-spec"> for details).</p>
1390 If you need to edit a <prgn>Makefile</prgn> where
1391 GNU-style <prgn>configure</prgn> scripts are used, you
1392 should edit the <file>.in</file> files rather than editing the
1393 <prgn>Makefile</prgn> directly. This allows the user to
1394 reconfigure the package if necessary. You should
1395 <em>not</em> configure the package and edit the generated
1396 <prgn>Makefile</prgn>! This makes it impossible for
1397 someone else to later reconfigure the package.</p></sect1>
1401 <heading>Documenting your changes</heading>
1404 You should document your changes and updates to the source
1405 package properly in the <file>debian/changelog</file> file. (Note
1406 that mistakes in changelogs are usually best rectified by
1407 making a new changelog entry rather than "rewriting history"
1408 by editing old changelog entries.)</p>
1411 In non-experimental packages you must use a format for
1412 <file>debian/changelog</file> which is supported by the most
1413 recent released version of <prgn>dpkg</prgn>.<footnote>
1415 If you wish to use an alternative format, you may do
1416 so as long as you include a parser for it in your
1417 source package. The parser must have an API
1418 compatible with that expected by
1419 <prgn>dpkg-genchanges</prgn> and
1420 <prgn>dpkg-gencontrol</prgn>. If there is general
1421 interest in the new format, you should contact the
1422 <package>dpkg</package> maintainer to have the parser
1423 script for it included in the <prgn>dpkg</prgn>
1424 package. (You will need to agree that the parser and
1425 its manpage may be distributed under the GNU GPL, just
1426 as the rest of `dpkg' is.)
1434 <heading>Error trapping in makefiles</heading>
1437 When <prgn>make</prgn> invokes a command in a makefile
1438 (including your package's upstream makefiles and
1439 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1440 means that <prgn>sh</prgn>'s usual bad error handling
1441 properties apply: if you include a miniature script as one
1442 of the commands in your makefile you'll find that if you
1443 don't do anything about it then errors are not detected
1444 and <prgn>make</prgn> will blithely continue after
1448 Every time you put more than one shell command (this
1449 includes using a loop) in a makefile command you
1450 must make sure that errors are trapped. For
1451 simple compound commands, such as changing directory and
1452 then running a program, using <tt>&&</tt> rather
1453 than semicolon as a command separator is sufficient. For
1454 more complex commands including most loops and
1455 conditionals you should include a separate <tt>set -e</tt>
1456 command at the start of every makefile command that's
1457 actually one of these miniature shell scripts.</p></sect1>
1461 <heading>Obsolete constructs and libraries</heading>
1464 The include file <tt><varargs.h></tt> is
1465 provided to support end-users compiling very old software;
1466 the library <tt>libtermcap</tt> is provided to support the
1467 execution of software which has been linked against it
1468 (either old programs or those such as Netscape which are
1469 only available in binary form).</p>
1472 Debian packages should be patched to use
1473 <tt><stdarg.h></tt> and <tt>ncurses</tt>
1480 <chapt id="controlfields"><heading>Control files and their fields</heading>
1483 Many of the tools in the package management suite manipulate
1484 data represented in a common format, known as <em>control
1485 data</em>. The data is often stored in <em>control
1486 files</em>. Binary and source packages have control files,
1487 and the <file>.changes</file> files which control the installation
1488 of uploaded files are also in control file format.
1489 <prgn>Dpkg</prgn>'s internal databases are in a similar
1493 <sect id="controlsyntax"><heading>Syntax of control files</heading>
1496 A control file consists of one or more paragraphs of fields.
1497 The paragraphs are separated by blank lines. Some control
1498 files allow only one paragraph; others allow several, in
1499 which case each paragraph usually refers to a different
1500 package. (For example, in source packages, the first
1501 paragraph refers to the source package, and later paragraphs
1502 refer to binary packages generated from the source.)
1506 Each paragraph consists of a series of data fields; each
1507 field consists of the field name, followed by a colon and
1508 then the data/value associated with that field. It ends at
1509 the end of the line. Horizontal whitespace (spaces and
1510 tabs) may occur immediately before or after the value and is
1511 ignored there; it is conventional to put a single space
1512 after the colon. For example, a field might be:
1513 <example compact="compact">
1516 the field name is <tt>Package</tt> and the field value
1521 Some fields' values may span several lines; in this case
1522 each continuation line <em>must</em> start with a space or
1523 tab. Any trailing spaces or tabs at the end of individual
1524 lines of a field value are ignored.
1528 Except where otherwise stated only a single line of data is
1529 allowed and whitespace is not significant in a field body.
1530 Whitespace must not appear inside names (of packages,
1531 architectures, files or anything else) or version numbers,
1532 or between the characters of multi-character version
1537 Field names are not case-sensitive, but it is usual to
1538 capitalize the field names using mixed case as shown below.
1542 Blank lines, or lines consisting only of spaces and tabs,
1543 are not allowed within field values or between fields - that
1544 would mean a new paragraph.
1549 <sect><heading>List of fields</heading>
1551 This list here is not supposed to be exhaustive. Most fields
1552 are dealt with elsewhere in this document.
1554 <sect1 id="f-Package"><heading><tt>Package</tt>
1558 The name of the binary package. Package names consist of
1559 lower case letters (<tt>a-z</tt>), digits (<tt>0-9</tt>),
1560 plus (<tt>+</tt>) and minus (<tt>-</tt>) signs, and
1561 periods (<tt>.</tt>).
1565 They must be at least two characters long and must start
1566 with an alphanumeric character. The use of lowercase
1567 package names is required unless the package you're
1568 building (or referring to, in other fields) is already
1569 using uppercase characters.</p>
1572 <sect1 id="f-Version"><heading><tt>Version</tt>
1576 This lists the source or binary package's version number -
1577 see <ref id="versions">.
1583 id="f-Standards-Version"><heading><tt>Standards-Version</tt>
1587 The most recent version of the standards (the policy
1588 manual and associated texts) with which the package
1589 complies. This is updated manually when editing the
1590 source package to conform to newer standards; it can
1591 sometimes be used to tell when a package needs attention.
1592 Its format is described above; see
1593 <ref id="standardsversion">.
1598 <sect1 id="f-Distribution"><heading><tt>Distribution</tt>
1602 In a <file>.changes</file> file or parsed changelog output
1603 this contains the (space-separated) name(s) of the
1604 distribution(s) where this version of the package should
1605 be installed. Valid distributions are determined by the
1606 archive maintainers.<footnote>
1607 Current distribution names are:
1608 <taglist compact="compact">
1609 <tag><em>stable</em></tag>
1612 This is the current `released' version of Debian
1613 GNU/Linux. Once the distribution is
1614 <em>stable</em> only security fixes and other
1615 major bug fixes are allowed. When changes are
1616 made to this distribution, the release number is
1617 increased (for example: 2.2r1 becomes 2.2r2 then
1622 <tag><em>unstable</em></tag>
1625 This distribution value refers to the
1626 <em>developmental</em> part of the Debian
1627 distribution tree. New packages, new upstream
1628 versions of packages and bug fixes go into the
1629 <em>unstable</em> directory tree. Download from
1630 this distribution at your own risk.
1634 <tag><em>testing</em></tag>
1637 This distribution value refers to the
1638 <em>testing</em> part of the Debian distribution
1639 tree. It receives its packages from the
1640 unstable distribution after a short time lag to
1641 ensure that there are no major issues with the
1642 unstable packages. It is less prone to breakage
1643 than unstable, but still risky. It is not
1644 possible to upload packages directly to
1649 <tag><em>frozen</em></tag>
1652 From time to time, the <em>testing</em>
1653 distribution enters a state of `code-freeze' in
1654 anticipation of release as a <em>stable</em>
1655 version. During this period of testing only
1656 fixes for existing or newly-discovered bugs will
1657 be allowed. The exact details of this stage are
1658 determined by the Release Manager.
1662 <tag><em>experimental</em></tag>
1665 The packages with this distribution value are
1666 deemed by their maintainers to be high
1667 risk. Oftentimes they represent early beta or
1668 developmental packages from various sources that
1669 the maintainers want people to try, but are not
1670 ready to be a part of the other parts of the
1671 Debian distribution tree. Download at your own
1677 You should list <em>all</em> distributions that the
1678 package should be installed into.
1687 <chapt id="versions"><heading>Version numbering</heading>
1690 Every package has a version number recorded in its
1691 <tt>Version</tt> control file field.
1695 The package management system imposes an ordering on version
1696 numbers, so that it can tell whether packages are being up- or
1697 downgraded and so that package system front end applications
1698 can tell whether a package it finds available is newer than
1699 the one installed on the system. The version number format
1700 has the most significant parts (as far as comparison is
1701 concerned) at the beginning.
1705 The version number format is:
1706 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
1710 The three components here are:
1712 <tag><var>epoch</var></tag>
1715 This is a single (generally small) unsigned integer. It
1716 may be omitted, in which case zero is assumed. If it is
1717 omitted then the <var>upstream_version</var> may not
1722 It is provided to allow mistakes in the version numbers
1723 of older versions of a package, and also a package's
1724 previous version numbering schemes, to be left behind.
1728 <tag><var>upstream_version</var></tag>
1731 This is the main part of the version number. It is
1732 usually the version number of the original (`upstream')
1733 package from which the <file>.deb</file> file has been made,
1734 if this is applicable. Usually this will be in the same
1735 format as that specified by the upstream author(s);
1736 however, it may need to be reformatted to fit into the
1737 package management system's format and comparison
1742 The comparison behavior of the package management system
1743 with respect to the <var>upstream_version</var> is
1744 described below. The <var>upstream_version</var>
1745 portion of the version number is mandatory.
1749 The <var>upstream_version</var> may contain only
1750 alphanumerics<footnote>
1751 <p>Alphanumerics are <tt>A-Za-z0-9</tt> only.</p>
1753 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
1754 <tt>:</tt> (full stop, plus, hyphen, colon) and should
1755 start with a digit. If there is no
1756 <var>debian_revision</var> then hyphens are not allowed;
1757 if there is no <var>epoch</var> then colons are not
1761 <tag><var>debian_revision</var></tag>
1764 This part of the version number specifies the version of
1765 the Debian package based on the upstream version. It
1766 may contain only alphanumerics and the characters
1767 <tt>+</tt> and <tt>.</tt> (plus and full stop) and is
1768 compared in the same way as the
1769 <var>upstream_version</var> is.
1773 It is optional; if it isn't present then the
1774 <var>upstream_version</var> may not contain a hyphen.
1775 This format represents the case where a piece of
1776 software was written specifically to be turned into a
1777 Debian package, and so there is only one `debianization'
1778 of it and therefore no revision indication is required.
1782 It is conventional to restart the
1783 <var>debian_revision</var> at <tt>1</tt> each time the
1784 <var>upstream_version</var> is increased.
1788 The package management system will break the version
1789 number apart at the last hyphen in the string (if there
1790 is one) to determine the <var>upstream_version</var> and
1791 <var>debian_revision</var>. The absence of a
1792 <var>debian_revision</var> compares earlier than the
1793 presence of one (but note that the
1794 <var>debian_revision</var> is the least significant part
1795 of the version number).
1802 The <var>upstream_version</var> and <var>debian_revision</var>
1803 parts are compared by the package management system using the
1808 The strings are compared from left to right.
1812 First the initial part of each string consisting entirely of
1813 non-digit characters is determined. These two parts (one of
1814 which may be empty) are compared lexically. If a difference
1815 is found it is returned. The lexical comparison is a
1816 comparison of ASCII values modified so that all the letters
1817 sort earlier than all the non-letters.
1821 Then the initial part of the remainder of each string which
1822 consists entirely of digit characters is determined. The
1823 numerical values of these two parts are compared, and any
1824 difference found is returned as the result of the comparison.
1825 For these purposes an empty string (which can only occur at
1826 the end of one or both version strings being compared) counts
1831 These two steps (comparing and removing initial non-digit
1832 strings and initial digit strings) are repeated until a
1833 difference is found or both strings are exhausted.
1837 Note that the purpose of epochs is to allow us to leave behind
1838 mistakes in version numbering, and to cope with situations
1839 where the version numbering scheme changes. It is
1840 <em>not</em> intended to cope with version numbers containing
1841 strings of letters which the package management system cannot
1842 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
1843 silly orderings (the author of this manual has heard of a
1844 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
1845 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
1846 <tt>2</tt> and so forth).
1850 If an upstream package has problematic version numbers they
1851 should be converted to a sane form for use in the
1852 <tt>Version</tt> field.
1856 <heading>Version numbers based on dates</heading>
1858 In general, Debian packages should use the same version
1859 numbers as the upstream sources.</p>
1862 However, in some cases where the upstream version number is
1863 based on a date (e.g., a development `snapshot' release) the
1864 package management system cannot handle these version
1865 numbers without epochs. For example, dpkg will consider
1866 `96May01' to be greater than `96Dec24'.</p>
1869 To prevent having to use epochs for every new upstream
1870 version, the version number should be changed to the
1871 following format in such cases: `19960501', `19961224'. It
1872 is up to the maintainer whether he/she wants to bother the
1873 upstream maintainer to change the version numbers upstream,
1877 Note that other version formats based on dates which are
1878 parsed correctly by the package management system should
1879 <em>not</em> be changed.</p>
1882 Native Debian packages (i.e., packages which have been
1883 written especially for Debian) whose version numbers include
1884 dates should always use the `YYYYMMDD' format.</p>
1888 <chapt id="miscellaneous"><heading>Packaging Considerations</heading>
1890 <sect id="timestamps"><heading>Time Stamps</heading>
1892 Maintainers should preserve the modification times of the
1893 upstream source files in a package, as far as is reasonably
1896 The rationale is that there is some information conveyed
1897 by knowing the age of the file, for example, you could
1898 recognize that some documentation is very old by looking
1899 at the modification time, so it would be nice if the
1900 modification time of the upstream source would be
1907 <sect id="debianrules"><heading><file>debian/rules</file> - the
1908 main building script</heading>
1911 This file must be an executable makefile, and contains the
1912 package-specific recipes for compiling the package and
1913 building binary package(s) from the source.
1917 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1918 so that it can be invoked by saying its name rather than
1919 invoking <prgn>make</prgn> explicitly.
1923 Since an interactive <file>debian/rules</file> script makes it
1924 impossible to auto-compile that package and also makes it
1925 hard for other people to reproduce the same binary
1926 package, all <em>required targets</em> MUST be
1927 non-interactive. At a minimum, required targets are the
1928 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1929 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1930 <em>binary-indep</em>, and <em>build</em>. It also follows
1931 that any target that these targets depend on must also be
1936 The required and optional targets are as follows:
1938 <tag><tt>build</tt>, <tt>build-arch</tt> (optional),
1939 <tt>build-indep</tt> (optional)</tag>
1942 The <tt>build</tt> target should perform all
1943 non-interactive configuration and compilation of the
1944 package. If a package has an interactive pre-build
1945 configuration routine, the Debianized source package
1946 must either be built after this has taken place (so
1947 that the binary package can be built without rerunning
1948 the configuration) or the configuration routine
1949 modified to become non-interactive. (The latter is
1950 preferable if there are architecture-specific features
1951 detected by the configuration routine.)
1955 For some packages, notably ones where the same
1956 source tree is compiled in different ways to produce
1957 two binary packages, the <tt>build</tt> target
1958 does not make much sense. For these packages it is
1959 good enough to provide two (or more) targets
1960 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1961 for each of the ways of building the package, and a
1962 <tt>build</tt> target that does nothing. The
1963 <tt>binary</tt> target will have to build the
1964 package in each of the possible ways and make the
1965 binary package out of each.
1969 The <tt>build</tt> target must not do anything
1970 that might require root privilege.
1974 The <tt>build</tt> target may need to run the
1975 <tt>clean</tt> target first - see below.
1979 When a package has a configuration and build routine
1980 which takes a long time, or when the makefiles are
1981 poorly designed, or when <tt>build</tt> needs to
1982 run <tt>clean</tt> first, it is a good idea to
1983 <tt>touch build</tt> when the build process is
1984 complete. This will ensure that if <tt>debian/rules
1985 build</tt> is run again it will not rebuild the whole
1988 Another common way to do this is for <tt>build</tt>
1989 to depend on <prgn>build-stamp</prgn> and to do
1990 nothing else, and for the <prgn>build-stamp</prgn>
1991 target to do the building and to <tt>touch
1992 build-stamp</tt> on completion. This is
1993 especially useful if the build routine creates a
1994 file or directory called <tt>build</tt>; in such a
1995 case, <tt>build</tt> will need to be listed as
1996 a phony target (i.e., as a dependency of the
1997 <tt>.PHONY</tt> target). See the documentation of
1998 <prgn>make</prgn> for more information on phony
2005 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
2006 <tt>binary-indep</tt>
2010 The <tt>binary</tt> target must be all that is
2011 necessary for the user to build the binary package(s)
2012 produced from this source package. All of these
2013 targets are required to be non-interactive. It is
2014 split into two parts: <prgn>binary-arch</prgn> builds
2015 the binary packages which are specific to a particular
2016 architecture, and <tt>binary-indep</tt> builds
2017 those which are not.
2020 <tt>binary</tt> may be (and commonly is) a target with
2021 no commands which simply depends on
2022 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2025 Both <tt>binary-*</tt> targets should depend on the
2026 <tt>build</tt> target, or on the appropriate
2027 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2028 provided, so that the package is built if it has not
2029 been already. It should then create the relevant
2030 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2031 make their control files and <prgn>dpkg-deb</prgn> to
2032 build them and place them in the parent of the top
2037 Both the <tt>binary-arch</tt> and
2038 <tt>binary-indep</tt> targets <em>must</em> exist.
2039 If one of them has nothing to do (which will always be
2040 the case if the source generates only a single binary
2041 package, whether architecture-dependent or not), it
2042 must still exist and must always succeed.
2046 The <tt>binary</tt> targets must be invoked as
2049 The <prgn>fakeroot</prgn> package often allows one
2050 to build a package correctly even without being
2057 <tag><tt>clean</tt></tag>
2060 This must undo any effects that the <tt>build</tt>
2061 and <tt>binary</tt> targets may have had, except
2062 that it should leave alone any output files created in
2063 the parent directory by a run of a <tt>binary</tt>
2064 target. This target must be non-interactive.
2068 If a <tt>build</tt> file is touched at the end of
2069 the <tt>build</tt> target, as suggested above, it
2070 should be removed as the first action that
2071 <tt>clean</tt> performs, so that running
2072 <tt>build</tt> again after an interrupted
2073 <tt>clean</tt> doesn't think that everything is
2078 The <tt>clean</tt> target may need to be
2079 invoked as root if <tt>binary</tt> has been
2080 invoked since the last <tt>clean</tt>, or if
2081 <tt>build</tt> has been invoked as root (since
2082 <tt>build</tt> may create directories, for
2087 <tag><tt>get-orig-source</tt> (optional)</tag>
2090 This target fetches the most recent version of the
2091 original source package from a canonical archive site
2092 (via FTP or WWW, for example), does any necessary
2093 rearrangement to turn it into the original source
2094 tar file format described below, and leaves it in the
2099 This target may be invoked in any directory, and
2100 should take care to clean up any temporary files it
2105 This target is optional, but providing it if
2106 possible is a good idea.
2112 The <tt>build</tt>, <tt>binary</tt> and
2113 <tt>clean</tt> targets must be invoked with the current
2114 directory being the package's top-level directory.
2119 Additional targets may exist in <file>debian/rules</file>,
2120 either as published or undocumented interfaces or for the
2121 package's internal use.
2125 The architectures we build on and build for are determined
2126 by <prgn>make</prgn> variables using the utility
2127 <prgn>dpkg-architecture</prgn>. You can determine the
2128 Debian architecture and the GNU style architecture
2129 specification string for the build machine (the machine type
2130 we are building on) as well as for the host machine (the
2131 machine type we are building for). Here is a list of
2132 supported <prgn>make</prgn> variables:
2133 <list compact="compact">
2135 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
2138 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2139 specification string)</p>
2142 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of
2143 <tt>DEB_*_GNU_TYPE</tt>)</p>
2146 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2147 <tt>DEB_*_GNU_TYPE</tt>)</p>
2149 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2150 the build machine or <tt>HOST</tt> for specification of the
2155 Backward compatibility can be provided in the rules file
2156 by setting the needed variables to suitable default
2157 values; please refer to the documentation of
2158 <prgn>dpkg-architecture</prgn> for details.
2162 It is important to understand that the <tt>DEB_*_ARCH</tt>
2163 string only determines which Debian architecture we are
2164 building on or for. It should not be used to get the CPU
2165 or system information; the GNU style variables should be
2170 <sect id="dpkgchangelog"><heading><file>debian/changelog</file>
2174 This file records the changes to the Debian-specific parts of the
2177 Though there is nothing stopping an author who is also
2178 the Debian maintainer from using it for all their
2179 changes, it will have to be renamed if the Debian and
2180 upstream maintainers become different people. In such a
2181 case, however, it might be better to maintain the
2182 package as a non-native package.
2188 It has a special format which allows the package building
2189 tools to discover which version of the package is being
2190 built and find out other release-specific information.
2194 That format is a series of entries like this:
2195 <example compact="compact">
2196 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
2198 <p>[optional blank line(s), stripped]</p>
2200 * <var>change details</var>
2201 <var>more change details</var>
2203 <p>[blank line(s), included in output of dpkg-parsechangelog]</p>
2205 * <var>even more change details</var>
2207 <p>[optional blank line(s), stripped]</p>
2209 -- <var>maintainer name</var> <<var>email
2210 address</var>><var>[two spaces]</var> <var>date</var>
2215 <var>package</var> and <var>version</var> are the source
2216 package name and version number.
2220 <var>distribution(s)</var> lists the distributions where
2221 this version should be installed when it is uploaded - it
2222 is copied to the <tt>Distribution</tt> field in the
2223 <file>.changes</file> file. See <ref id="f-Distribution">.
2227 <var>urgency</var> is the value for the <tt>Urgency</tt>
2228 field in the <file>.changes</file> file for the upload. It is
2229 not possible to specify an urgency containing commas; commas
2230 are used to separate
2231 <tt><var>keyword</var>=<var>value</var></tt> settings in the
2232 <prgn>dpkg</prgn> changelog format (though there is
2233 currently only one useful <var>keyword</var>,
2234 <tt>urgency</tt>).<footnote>
2236 Recognised urgency values are <tt>low</tt>,
2237 <tt>medium</tt>, <tt>high</tt> and <tt>emergency</tt>.
2238 They have an effect on how quickly a package will be
2239 considered for inclusion into the <tt>testing</tt>
2240 distribution, and give an indication of the importance
2241 of any fixes included in this upload.
2247 The change details may in fact be any series of lines
2248 starting with at least two spaces, but conventionally each
2249 change starts with an asterisk and a separating space and
2250 continuation lines are indented so as to bring them in
2251 line with the start of the text above. Blank lines may be
2252 used here to separate groups of changes, if desired.
2256 If this upload resolves bugs recorded in the Bug Tracking
2257 System (BTS), they may be automatically closed on the
2258 inclusion of this package into the Debian archive by
2259 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
2260 in the change details.<footnote>
2262 To be precise, the string should match the following
2263 Perl regular expression:
2265 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
2267 Then all of the bug numbers listed will be closed by the
2268 archive maintenance script (<prgn>katie</prgn>), or in
2269 the case of an NMU, marked as fixed.
2275 The maintainer name and email address used in the changelog
2276 should be the details of the person uploading <em>this</em>
2277 version. They are <em>not</em> necessarily those of the
2278 usual package maintainer. The information here will be
2279 copied to the <tt>Changed-By</tt> field in the
2280 <tt>.changes</tt> file, and then later used to send an
2281 acknowledgement when the upload has been installed.
2285 The <var>date</var> should be in RFC822 format<footnote>
2287 This is generated by the <prgn>822-date</prgn>
2290 </footnote>; it should include the time zone specified
2291 numerically, with the time zone name or abbreviation
2292 optionally present as a comment in parentheses.
2296 The first `title' line with the package name should start
2297 at the left hand margin; the `trailer' line with the
2298 maintainer and date details should be preceded by exactly
2299 one space. The maintainer details and the date must be
2300 separated by exactly two spaces.
2303 <sect1><heading>Defining alternative changelog formats</heading>
2306 It is possible to use a different format to the standard
2307 one, by providing a parser for the format you wish to
2311 A changelog parser must not interact with the user at
2317 <sect id="srcsubstvars"><heading><file>debian/substvars</file>
2318 and variable substitutions </heading>
2321 When <prgn>dpkg-gencontrol</prgn>,
2322 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2323 generate control files they perform variable substitutions
2324 on their output just before writing it. Variable
2325 substitutions have the form <tt>${<var>variable</var>}</tt>.
2326 The optional file <file>debian/substvars</file> contains
2327 variable substitutions to be used; variables can also be set
2328 directly from <file>debian/rules</file> using the <tt>-V</tt>
2329 option to the source packaging commands, and certain
2330 predefined variables are also available.
2334 The <file>debian/substvars</file> file is usually generated and
2335 modified dynamically by <file>debian/rules</file> targets; in
2336 this case it must be removed by the <tt>clean</tt>
2341 See <manref name="dpkg-source" section="1"> for full
2342 details about source variable substitutions, including the
2343 format of <file>debian/substvars</file>.</p>
2346 <sect id="debianfiles"><heading><file>debian/files</file>
2350 This file is not a permanent part of the source tree; it
2351 is used while building packages to record which files are
2352 being generated. <prgn>dpkg-genchanges</prgn> uses it
2353 when it generates a <file>.changes</file> file.
2357 It should not exist in a shipped source package, and so it
2358 (and any backup files or temporary files such as
2359 <file>files.new</file><footnote>
2361 <file>files.new</file> is used as a temporary file by
2362 <prgn>dpkg-gencontrol</prgn> and
2363 <prgn>dpkg-distaddfile</prgn> - they write a new
2364 version of <tt>files</tt> here before renaming it,
2365 to avoid leaving a corrupted copy if an error
2368 </footnote>) should be removed by the
2369 <tt>clean</tt> target. It may also be wise to
2370 ensure a fresh start by emptying or removing it at the
2371 start of the <tt>binary</tt> target.
2375 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2376 package, it adds an entry to <file>debian/files</file> for the
2377 <file>.deb</file> file that will be created when <tt>dpkg-deb
2378 --build</tt> is run for that binary package. So for most
2379 packages all that needs to be done with this file is to
2380 delete it in the <tt>clean</tt> target.
2384 If a package upload includes files besides the source
2385 package and any binary packages whose control files were
2386 made with <prgn>dpkg-gencontrol</prgn> then they should be
2387 placed in the parent of the package's top-level directory
2388 and <prgn>dpkg-distaddfile</prgn> should be called to add
2389 the file to the list in <file>debian/files</file>.</p>
2392 <sect id="restrictions"><heading>Restrictions on objects in source packages
2396 The source package may not contain any hard links<footnote>
2398 This is not currently detected when building source
2399 packages, but only when extracting
2403 Hard links may be permitted at some point in the
2404 future, but would require a fair amount of
2407 </footnote>, device special files, sockets or setuid or
2408 setgid files.<footnote>
2410 Setgid directories are allowed.
2415 <sect id="descriptions"><heading>Descriptions of packages - the
2416 <tt>Description</tt> field </heading>
2419 The description is intended to describe the program to a user
2420 who has never met it before so that they know whether they
2421 want to install it. It should also give information about the
2422 significant dependencies and conflicts between this package
2423 and others, so that the user knows why these dependencies and
2424 conflicts have been declared.
2427 <sect1><heading>Notes about writing descriptions
2431 The single line synopsis should be kept brief - certainly
2432 under 80 characters.
2436 Do not include the package name in the synopsis line. The
2437 display software knows how to display this already, and you
2438 do not need to state it. Remember that in many situations
2439 the user may only see the synopsis line - make it as
2440 informative as you can.
2444 Do not try to continue the single line synopsis into the
2445 extended description. This will not work correctly when
2446 the full description is displayed, and makes no sense
2447 where only the summary (the single line synopsis) is
2452 The extended description should describe what the package
2453 does and how it relates to the rest of the system (in terms
2454 of, for example, which subsystem it is which part of).
2458 The description field needs to make sense to anyone, even
2459 people who have no idea about any of the things the
2460 package deals with.<footnote>
2462 The blurb that comes with a program in its
2463 announcements and/or <prgn>README</prgn> files is
2464 rarely suitable for use in a description. It is
2465 usually aimed at people who are already in the
2466 community where the package is used.
2472 Put important information first, both in the synopsis and
2473 extended description. Sometimes only the first part of the
2474 synopsis or of the description will be displayed. You can
2475 assume that there will usually be a way to see the whole
2476 extended description.
2480 You may include information about dependencies and so forth
2481 in the extended description, if you wish.
2485 Do not use tab characters. Their effect is not predictable.
2493 <chapt id="maintainerscripts"><heading>Package maintainer scripts
2494 and installation procedure
2497 <sect><heading>Introduction to package maintainer scripts
2501 It is possible to supply scripts as part of a package which
2502 the package management system will run for you when your
2503 package is installed, upgraded or removed.
2507 These scripts are the files <prgn>preinst</prgn>,
2508 <prgn>postinst</prgn>, <prgn>prerm</prgn> and <prgn>postrm</prgn> in the
2509 control area of the package. They must be proper executable
2510 files; if they are scripts (which is recommended), they must
2511 start with the usual <tt>#!</tt> convention. They should be
2512 readable and executable by anyone, and not world-writable.
2516 The package management system looks at the exit status from
2517 these scripts. It is important that they exit with a
2518 non-zero status if there is an error, so that the package
2519 management system can stop its processing. For shell
2520 scripts this means that you <em>almost always</em> need to
2521 use <tt>set -e</tt> (this is usually true when writing shell
2522 scripts, in fact). It is also important, of course, that
2523 they don't exit with a non-zero status if everything went
2528 When a package is upgraded a combination of the scripts from
2529 the old and new packages is called during the upgrade
2530 procedure. If your scripts are going to be at all
2531 complicated you need to be aware of this, and may need to
2532 check the arguments to your scripts.
2536 Broadly speaking the <prgn>preinst</prgn> is called before
2537 (a particular version of) a package is installed, and the
2538 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
2539 before (a version of) a package is removed and the
2540 <prgn>postrm</prgn> afterwards.
2544 Programs called from maintainer scripts should not normally
2545 have a path prepended to them. Before installation is
2546 started, the package management system checks to see if the
2547 programs <prgn>ldconfig</prgn>,
2548 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
2549 and <prgn>update-rc.d</prgn> can be found via the
2550 <tt>PATH</tt> environment variable. Those programs, and any
2551 other program that one would expect to be on the
2552 <tt>PATH</tt>, should thus be invoked without an absolute
2553 pathname. Maintainer scripts should also not reset the
2554 <tt>PATH</tt>, though they might choose to modify it by
2555 prepending or appending package-specific directories. These
2556 considerations really apply to all shell scripts.</p>
2560 <heading>Maintainer scripts Idempotency</heading>
2563 It is necessary for the error recovery procedures that the
2564 scripts be idempotent. This means that if it is run
2565 successfully, and then it is called again, it doesn't bomb
2566 out or cause any harm, but just ensures that everything is
2567 the way it ought to be. If the first call failed, or
2568 aborted half way through for some reason, the second call
2569 should merely do the things that were left undone the first
2570 time, if any, and exit with a success status if everything
2573 This is so that if an error occurs, the user interrupts
2574 <prgn>dpkg</prgn> or some other unforeseen circumstance
2575 happens you don't leave the user with a badly-broken
2576 package when <prgn>dpkg</prgn> attempts to repeat the
2584 <heading>Controlling terminal for maintainer scripts</heading>
2587 The maintainer scripts are guaranteed to run with a
2588 controlling terminal and can interact with the user.
2589 If they need to prompt for passwords, do full-screen
2590 interaction or something similar you should do these
2591 things to and from <file>/dev/tty</file>, since
2592 <prgn>dpkg</prgn> will at some point redirect scripts'
2593 standard input and output so that it can log the
2594 installation process. Likewise, because these scripts
2595 may be executed with standard output redirected into a
2596 pipe for logging purposes, Perl scripts should set
2597 unbuffered output by setting <tt>$|=1</tt> so that the
2598 output is printed immediately rather than being
2603 Each script should return a zero exit status for
2604 success, or a nonzero one for failure.
2608 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
2613 <list compact="compact">
2615 <p><var>new-preinst</var> <tt>install</tt></p>
2618 <p><var>new-preinst</var> <tt>install</tt>
2619 <var>old-version</var></p>
2622 <p><var>new-preinst</var> <tt>upgrade</tt>
2623 <var>old-version</var></p>
2626 <p><var>old-preinst</var> <tt>abort-upgrade</tt>
2627 <var>new-version</var>
2633 <list compact="compact">
2635 <p><var>postinst</var> <tt>configure</tt>
2636 <var>most-recently-configured-version</var></p>
2639 <p><var>old-postinst</var> <tt>abort-upgrade</tt>
2640 <var>new-version</var></p>
2643 <p><var>conflictor's-postinst</var> <tt>abort-remove</tt>
2644 <tt>in-favour</tt> <var>package</var>
2645 <var>new-version</var></p>
2649 <var>deconfigured's-postinst</var>
2650 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
2651 <var>failed-install-package</var> <var>version</var>
2652 <tt>removing</tt> <var>conflicting-package</var>
2659 <list compact="compact">
2661 <p><var>prerm</var> <tt>remove</tt></p>
2664 <p><var>old-prerm</var> <tt>upgrade</tt>
2665 <var>new-version</var></p>
2668 <p><var>new-prerm</var> <tt>failed-upgrade</tt>
2669 <var>old-version</var></p>
2672 <p><var>conflictor's-prerm</var> <tt>remove</tt>
2673 <tt>in-favour</tt> <var>package</var>
2674 <var>new-version</var></p>
2678 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
2679 <tt>in-favour</tt> <var>package-being-installed</var>
2680 <var>version</var> <tt>removing</tt>
2681 <var>conflicting-package</var>
2688 <list compact="compact">
2690 <p><var>postrm</var> <tt>remove</tt></p>
2693 <p><var>postrm</var> <tt>purge</tt></p>
2697 <var>old-postrm</var> <tt>upgrade</tt>
2698 <var>new-version</var></p>
2701 <p><var>new-postrm</var> <tt>failed-upgrade</tt>
2702 <var>old-version</var></p>
2705 <p><var>new-postrm</var> <tt>abort-install</tt></p>
2708 <p><var>new-postrm</var> <tt>abort-install</tt>
2709 <var>old-version</var></p>
2712 <p><var>new-postrm</var> <tt>abort-upgrade</tt>
2713 <var>old-version</var></p>
2717 <var>disappearer's-postrm</var> <tt>disappear</tt>
2718 <var>overwriter</var>
2719 <var>overwriter-version</var></p></item>
2724 <sect id="unpackphase"><heading>Details of unpack phase of
2725 installation or upgrade
2729 The procedure on installation/upgrade/overwrite/disappear
2730 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
2731 stage of <tt>dpkg --install</tt>) is as follows. In each
2732 case, if a major error occurs (unless listed below) the
2733 actions are, in general, run backwards - this means that the
2734 maintainer scripts are run with different arguments in
2735 reverse order. These are the `error unwind' calls listed
2743 <p>If a version of the package is already
2745 <example compact="compact">
2746 <var>old-prerm</var> upgrade <var>new-version</var>
2751 If the script runs but exits with a non-zero
2752 exit status, <prgn>dpkg</prgn> will attempt:
2753 <example compact="compact">
2754 <var>new-prerm</var> failed-upgrade <var>old-version</var>
2756 Error unwind, for both the above cases:
2757 <example compact="compact">
2758 <var>old-postinst</var> abort-upgrade <var>new-version</var>
2766 <p>If a `conflicting' package is being removed at the same time:
2770 If any packages depended on that conflicting
2771 package and <tt>--auto-deconfigure</tt> is
2772 specified, call, for each such package:
2773 <example compact="compact">
2774 <var>deconfigured's-prerm</var> deconfigure \
2775 in-favour <var>package-being-installed</var> <var>version</var> \
2776 removing <var>conflicting-package</var> <var>version</var>
2779 <example compact="compact">
2780 <var>deconfigured's-postinst</var> abort-deconfigure \
2781 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
2782 removing <var>conflicting-package</var> <var>version</var>
2784 The deconfigured packages are marked as
2785 requiring configuration, so that if
2786 <tt>--install</tt> is used they will be
2787 configured again if possible.</p>
2790 <p>To prepare for removal of the conflicting package, call:
2791 <example compact="compact">
2792 <var>conflictor's-prerm</var> remove \
2793 in-favour <var>package</var> <var>new-version</var>
2796 <example compact="compact">
2797 <var>conflictor's-postinst</var> abort-remove \
2798 in-favour <var>package</var> <var>new-version</var>
2809 <p>If the package is being upgraded, call:
2810 <example compact="compact">
2811 <var>new-preinst</var> upgrade <var>old-version</var>
2816 Otherwise, if the package had some configuration
2817 files from a previous version installed (i.e., it
2818 is in the `configuration files only' state):
2819 <example compact="compact">
2820 <var>new-preinst</var> install <var>old-version</var>
2824 <p>Otherwise (i.e., the package was completely purged):
2825 <example compact="compact">
2826 <var>new-preinst</var> install
2828 Error unwind actions, respectively:
2829 <example compact="compact">
2830 <var>new-postrm</var> abort-upgrade <var>old-version</var>
2831 <var>new-postrm</var> abort-install <var>old-version</var>
2832 <var>new-postrm</var> abort-install
2841 The new package's files are unpacked, overwriting any
2842 that may be on the system already, for example any
2843 from the old version of the same package or from
2844 another package. Backups of the old files are kept
2845 temporarily, and if anything goes wrong the package
2846 management system will attempt to put them back as
2847 part of the error unwind.
2851 It is an error for a package to contains files which
2852 are on the system in another package, unless
2853 <tt>Replaces</tt> is used (see <ref id="replaces">).
2855 The following paragraph is not currently the case:
2856 Currently the <tt>- - force-overwrite</tt> flag is
2857 enabled, downgrading it to a warning, but this may not
2863 It is a more serious error for a package to contain a
2864 plain file or other kind of non-directory where another
2865 package has a directory (again, unless
2866 <tt>Replaces</tt> is used). This error can be
2867 overridden if desired using
2868 <tt>--force-overwrite-dir</tt>, but this is not
2873 Packages which overwrite each other's files produce
2874 behavior which, though deterministic, is hard for the
2875 system administrator to understand. It can easily
2876 lead to `missing' programs if, for example, a package
2877 is installed which overwrites a file from another
2878 package, and is then removed again.<footnote>
2880 Part of the problem is due to what is arguably a
2881 bug in <prgn>dpkg</prgn>.
2887 A directory will never be replaced by a symbolic link
2888 to a directory or vice versa; instead, the existing
2889 state (symlink or not) will be left alone and
2890 <prgn>dpkg</prgn> will follow the symlink if there is
2898 <p>If the package is being upgraded, call
2899 <example compact="compact">
2900 <var>old-postrm</var> upgrade <var>new-version</var>
2905 <p>If this fails, <prgn>dpkg</prgn> will attempt:
2906 <example compact="compact">
2907 <var>new-postrm</var> failed-upgrade <var>old-version</var>
2909 Error unwind, for both cases:
2910 <example compact="compact">
2911 <var>old-preinst</var> abort-upgrade <var>new-version</var>
2918 This is the point of no return - if
2919 <prgn>dpkg</prgn> gets this far, it won't back off
2920 past this point if an error occurs. This will
2921 leave the package in a fairly bad state, which
2922 will require a successful re-installation to clear
2923 up, but it's when <prgn>dpkg</prgn> starts doing
2924 things that are irreversible.
2929 Any files which were in the old version of the package
2930 but not in the new are removed.</p>
2933 <p>The new file list replaces the old.</p>
2936 <p>The new maintainer scripts replace the old.</p>
2940 <p>Any packages all of whose files have been overwritten during the
2941 installation, and which aren't required for
2942 dependencies, are considered to have been removed.
2943 For each such package
2946 <p><prgn>dpkg</prgn> calls:
2947 <example compact="compact">
2948 <var>disappearer's-postrm</var> disappear \
2949 <var>overwriter</var> <var>overwriter-version</var>
2954 <p>The package's maintainer scripts are removed.
2959 It is noted in the status database as being in a
2960 sane state, namely not installed (any conffiles
2961 it may have are ignored, rather than being
2962 removed by <prgn>dpkg</prgn>). Note that
2963 disappearing packages do not have their prerm
2964 called, because <prgn>dpkg</prgn> doesn't know
2965 in advance that the package is going to
2974 Any files in the package we're unpacking that are also
2975 listed in the file lists of other packages are removed
2976 from those lists. (This will lobotomize the file list
2977 of the `conflicting' package if there is one.)
2982 The backup files made during installation, above, are
2989 The new package's status is now sane, and recorded as
2994 Here is another point of no return - if the
2995 conflicting package's removal fails we do not unwind
2996 the rest of the installation; the conflicting package
2997 is left in a half-removed limbo.
3003 If there was a conflicting package we go and do the
3004 removal actions (described below), starting with the
3005 removal of the conflicting package's files (any that
3006 are also in the package being installed have already
3007 been removed from the conflicting package's file list,
3008 and so do not get removed now).
3015 <sect id="configdetails"><heading>Details of configuration</heading>
3018 When we configure a package (this happens with <tt>dpkg
3019 --install</tt> and <tt>dpkg --configure</tt>), we first
3020 update any <tt>conffile</tt>s and then call:
3021 <example compact="compact">
3022 <var>postinst</var> configure <var>most-recently-configured-version</var>
3027 No attempt is made to unwind after errors during
3032 If there is no most recently configured version
3033 <prgn>dpkg</prgn> will pass a null argument; older versions
3034 of dpkg may pass <tt><unknown></tt> (including the
3035 angle brackets) in this case. Even older ones do not pass a
3036 second argument at all, under any circumstances.
3040 <sect id="removedetails"><heading>Details of removal and/or
3041 configuration purging</heading>
3047 <example compact="compact">
3048 <var>prerm</var> remove
3054 The package's files are removed (except <tt>conffile</tt>s).
3059 <example compact="compact">
3060 <var>postrm</var> remove
3066 All the maintainer scripts except the <prgn>postrm</prgn>
3071 If we aren't purging the package we stop here. Note
3072 that packages which have no <prgn>postrm</prgn> and no
3073 <tt>conffile</tt>s are automatically purged when
3074 removed, as there is no difference except for the
3075 <prgn>dpkg</prgn> status.</p>
3079 The <tt>conffile</tt>s and any backup files
3080 (<tt>~</tt>-files, <tt>#*#</tt> files,
3081 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3086 <example compact="compact">
3087 <var>postrm</var> purge
3092 <p>The package's file list is removed.</p>
3095 No attempt is made to unwind after errors during
3102 <chapt id="relationships"><heading>Declaring relationships between
3106 Packages can declare in their control file that they have
3107 certain relationships to other packages - for example, that
3108 they may not be installed at the same time as certain other
3109 packages, and/or that they depend on the presence of others,
3110 or that they should overwrite files in certain other packages
3115 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3116 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3117 <tt>Conflicts</tt>, <tt>Provides</tt> and <tt>Replaces</tt>
3118 control file fields.
3122 Source packages may declare relationships to binary packages,
3123 saying that they require certain binary packages to be
3124 installed or absent at the time of building the package.
3128 This is done using the <tt>Build-Depends</tt>,
3129 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
3130 <tt>Build-Conflicts-Indep</tt> control file fields.
3133 <sect id="depsyntax"><heading>Syntax of relationship fields
3137 These fields all have a uniform syntax. They are a list of
3138 package names separated by commas.
3142 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3143 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3144 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3145 control file fields of the package, which declare
3146 dependencies on other packages, the package names listed may
3147 also include lists of alternative package names, separated
3148 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3149 if any one of the alternative packages is installed, that
3150 part of the dependency is considered to be satisfied.
3154 All of the fields except for <tt>Provides</tt> may restrict
3155 their applicability to particular versions of each named
3156 package. This is done in parentheses after each individual
3157 package name; the parentheses should contain a relation from
3158 the list below followed by a version number, in the format
3159 described in <ref id="versions">.
3163 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3164 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3165 strictly earlier, earlier or equal, exactly equal, later or
3166 equal and strictly later, respectively. The deprecated
3167 forms <tt><</tt> and <tt>></tt> were used to mean
3168 earlier/later or equal, rather than strictly earlier/later,
3169 so they should not appear in new packages (though
3170 <prgn>dpkg</prgn> still supports them).
3174 Whitespace may appear at any point in the version
3175 specification subject to the rules in <ref
3176 id="controlsyntax">, and must appear where it's necessary to
3177 disambiguate; it is not otherwise significant. For
3178 consistency and in case of future changes to
3179 <prgn>dpkg</prgn> it is recommended that a single space be
3180 used after a version relationship and before a version
3181 number; it is also conventional to put a single space after
3182 each comma, on either side of each vertical bar, and before
3183 each open parenthesis.
3187 For example, a list of dependencies might appear as:
3188 <example compact="compact">
3191 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3196 All fields that specify build-time relationships
3197 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3198 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3199 may be restricted to a certain set of architectures. This
3200 is indicated in brackets after each individual package name and
3201 the optional version specification. The brackets enclose a
3202 list of Debian architecture names separated by whitespace.
3203 Exclamation marks may be prepended to each of the names.
3204 (It is not permitted for some names to be prepended with
3205 exclamation marks and others not.) If the current Debian
3206 host architecture is not in this list and there are no
3207 exclamation marks in the list, or it is in the list with a
3208 prepended exclamation mark, the package name and the
3209 associated version specification are ignored completely for
3210 the purposes of defining the relationships.
3215 <example compact="compact">
3217 Build-Depends-Indep: texinfo
3218 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3219 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3224 Note that the binary package relationship fields such as
3225 <tt>Depends</tt> appear in one of the binary package
3226 sections of the control file, whereas the build-time
3227 relationships such as <tt>Build-Depends</tt> appear in the
3228 source package section of the control file (which is the
3234 <heading>Binary Dependencies - <tt>Depends</tt>,
3235 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3236 <tt>Pre-Depends</tt>
3240 These five fields are used to declare a dependency
3241 relationship by one package on another. Except for
3242 <tt>Enhances</tt>, they appear in the depending (binary)
3243 package's control file. (<tt>Enhances</tt> appears in the
3244 recommending package's control file.)
3248 A <tt>Depends</tt> field takes effect <em>only</em> when a
3249 package is to be configured. It does not prevent a package
3250 being on the system in an unconfigured state while its
3251 dependencies are unsatisfied, and it is possible to replace
3252 a package whose dependencies are satisfied and which is
3253 properly installed with a different version whose
3254 dependencies are not and cannot be satisfied; when this is
3255 done the depending package will be left unconfigured (since
3256 attempts to configure it will give errors) and will not
3257 function properly. If it is necessary, a
3258 <tt>Pre-Depends</tt> field can be used, which has a partial
3259 effect even when a package is being unpacked, as explained
3260 in detail below. (The other three dependency fields,
3261 <tt>Recommends</tt>, <tt>Suggests</tt> and
3262 <tt>Enhances</tt>, are only used by the various front-ends
3263 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3267 For this reason packages in an installation run are usually
3268 all unpacked first and all configured later; this gives
3269 later versions of packages with dependencies on later
3270 versions of other packages the opportunity to have their
3271 dependencies satisfied.
3275 The <tt>Depends</tt> field thus allows package maintainers
3276 to impose an order in which packages should be configured.
3280 The meaning of the five dependency fields is as follows:
3282 <tag><tt>Depends</tt></tag>
3285 This declares an absolute dependency. A package will
3286 not be configured unless all of the packages listed in
3287 its <tt>Depends</tt> field have been correctly
3292 The <tt>Depends</tt> field should be used if the
3293 depended-on package is required for the depending
3294 package to provide a significant amount of
3298 The <tt>Depends</tt> field should also be used if the
3299 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
3300 <prgn>postrm</prgn> scripts require the package to be
3301 present in order to run. Note, however, that the
3302 <prgn>postrm</prgn> cannot rely on any non-essential
3303 packages to be present during the <tt>purge</tt>
3307 <tag><tt>Recommends</tt></tag>
3309 <p>This declares a strong, but not absolute, dependency.
3313 The <tt>Recommends</tt> field should list packages
3314 that would be found together with this one in all but
3315 unusual installations.</p>
3318 <tag><tt>Suggests</tt></tag>
3321 This is used to declare that one package may be more
3322 useful with one or more others. Using this field
3323 tells the packaging system and the user that the
3324 listed packages are related to this one and can
3325 perhaps enhance its usefulness, but that installing
3326 this one without them is perfectly reasonable.
3330 <tag><tt>Enhances</tt></tag>
3333 This field is similar to Suggests but works in the
3334 opposite direction. It is used to declare that a
3335 package can enhance the functionality of another
3340 <tag><tt>Pre-Depends</tt></tag>
3343 This field is like <tt>Depends</tt>, except that it
3344 also forces <prgn>dpkg</prgn> to complete installation
3345 of the packages named before even starting the
3346 installation of the package which declares the
3347 pre-dependency, as follows:
3351 When a package declaring a pre-dependency is about to
3352 be <em>unpacked</em> the pre-dependency can be
3353 satisfied if the depended-on package is either fully
3354 configured, <em>or even if</em> the depended-on
3355 package(s) are only unpacked or half-configured,
3356 provided that they have been configured correctly at
3357 some point in the past (and not removed or partially
3358 removed since). In this case, both the
3359 previously-configured and currently unpacked or
3360 half-configured versions must satisfy any version
3361 clause in the <tt>Pre-Depends</tt> field.
3365 When the package declaring a pre-dependency is about
3366 to be <em>configured</em>, the pre-dependency will be
3367 treated as a normal <tt>Depends</tt>, that is, it will
3368 be considered satisfied only if the depended-on
3369 package has been correctly configured.
3373 <tt>Pre-Depends</tt> should be used sparingly,
3374 preferably only by packages whose premature upgrade or
3375 installation would hamper the ability of the system to
3376 continue with any upgrade that might be in progress.
3380 <tt>Pre-Depends</tt> are also required if the
3381 <prgn>preinst</prgn> script depends on the named
3382 package. It is best to avoid this situation if
3388 When selecting which level of dependency to use you should
3389 consider how important the depended-on package is to the
3390 functionality of the one declaring the dependency. Some
3391 packages are composed of components of varying degrees of
3392 importance. Such a package should list using
3393 <tt>Depends</tt> the package(s) which are required by the
3394 more important components. The other components'
3395 requirements may be mentioned as Suggestions or
3396 Recommendations, as appropriate to the components' relative
3401 <sect id="conflicts"><heading>Conflicting binary packages -
3402 <tt>Conflicts</tt></heading>
3405 When one binary package declares a conflict with another
3406 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
3407 refuse to allow them to be installed on the system at the
3412 If one package is to be installed, the other must be removed
3413 first - if the package being installed is marked as
3414 replacing (see <ref id="replaces">) the one on the system,
3415 or the one on the system is marked as deselected, or both
3416 packages are marked <tt>Essential</tt>, then
3417 <prgn>dpkg</prgn> will automatically remove the package
3418 which is causing the conflict, otherwise it will halt the
3419 installation of the new package with an error. This
3420 mechanism is specifically designed to produce an error when
3421 the installed package is <tt>Essential</tt>, but the new
3426 A package will not cause a conflict merely because its
3427 configuration files are still installed; it must be at least
3432 A special exception is made for packages which declare a
3433 conflict with their own package name, or with a virtual
3434 package which they provide (see below): this does not
3435 prevent their installation, and allows a package to conflict
3436 with others providing a replacement for it. You use this
3437 feature when you want the package in question to be the only
3438 package providing some feature.
3442 A <tt>Conflicts</tt> entry should almost never have an
3443 `earlier than' version clause. This would prevent
3444 <prgn>dpkg</prgn> from upgrading or installing the package
3445 which declared such a conflict until the upgrade or removal
3446 of the conflicted-with package had been completed.
3450 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
3454 As well as the names of actual (`concrete') packages, the
3455 package relationship fields <tt>Depends</tt>,
3456 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3457 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
3458 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3459 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
3460 may mention `virtual packages'.
3464 A <em>virtual package</em> is one which appears in the
3465 <tt>Provides</tt> control file field of another package.
3466 The effect is as if the package(s) which provide a
3467 particular virtual package name had been listed by name
3468 everywhere the virtual package name appears. (See also <ref
3469 id="virtual_pkg_sect">)
3473 If there are both concrete and virtual packages of the same
3474 name, then the dependency may be satisfied (or the conflict
3475 caused) by either the concrete package with the name in
3476 question or any other concrete package which provides the
3477 virtual package with the name in question. This is so that,
3478 for example, supposing we have
3479 <example compact="compact">
3483 and someone else releases an enhanced version of the
3484 <tt>bar</tt> package (for example, a non-US variant), they
3486 <example compact="compact">
3490 and the <tt>bar-plus</tt> package will now also satisfy the
3491 dependency for the <tt>foo</tt> package.
3495 If a dependency or a conflict has a version number attached
3496 then only real packages will be considered to see whether
3497 the relationship is satisfied (or the prohibition violated,
3498 for a conflict) - it is assumed that a real package which
3499 provides the virtual package is not of the `right' version.
3500 So, a <tt>Provides</tt> field may not contain version
3501 numbers, and the version number of the concrete package
3502 which provides a particular virtual package will not be
3503 looked at when considering a dependency on or conflict with
3504 the virtual package name.
3508 It is likely that the ability will be added in a future
3509 release of <prgn>dpkg</prgn> to specify a version number for
3510 each virtual package it provides. This feature is not yet
3511 present, however, and is expected to be used only
3516 If you want to specify which of a set of real packages
3517 should be the default to satisfy a particular dependency on
3518 a virtual package, you should list the real package as an
3519 alternative before the virtual one.
3524 <sect id="replaces"><heading>Overwriting files and replacing
3525 packages - <tt>Replaces</tt></heading>
3528 The <tt>Replaces</tt> control file field has two distinct
3529 purposes, which come into play in different situations.
3532 <sect1><heading>Overwriting files in other packages</heading>
3535 Firstly, as mentioned before, it is usually an error for a
3536 package to contain files which are on the system in
3541 However, if the overwriting package declares that it
3542 <tt>Replaces</tt> the one containing the file being
3543 overwritten, then <prgn>dpkg</prgn> will replace the file
3544 from the old package with that from the new. The file
3545 will no longer be listed as `owned' by the old package.
3549 If a package is completely replaced in this way, so that
3550 <prgn>dpkg</prgn> does not know of any files it still
3551 contains, it is considered to have `disappeared'. It will
3552 be marked as not wanted on the system (selected for
3553 removal) and not installed. Any <tt>conffile</tt>s
3554 details noted for the package will be ignored, as they
3555 will have been taken over by the overwriting package. The
3556 package's <prgn>postrm</prgn> script will be run with a
3557 special argument to allow the package to do any final
3558 cleanup required. See <ref id="mscriptsinstact">.
3562 If an installed package, <tt>foo</tt> say, declares that
3563 it replaces another, <tt>bar</tt>, and an attempt is made
3564 to install <tt>bar</tt>, <prgn>dpkg</prgn> will discard
3565 files in the <tt>bar</tt> package which would overwrite
3566 those already present in <tt>foo</tt>. This is so that
3567 you can install an older version of a package without
3572 For this usage of <tt>Replaces</tt>, virtual packages (see
3573 <ref id="virtual">) are not considered when looking at a
3574 <tt>Replaces</tt> field - the packages declared as being
3575 replaced must be mentioned by their real names.
3579 Furthermore, this usage of <tt>Replaces</tt> only takes
3580 effect when both packages are at least partially on the
3581 system at once, so that it can only happen if they do not
3582 conflict or if the conflict has been overridden.
3587 <sect1><heading>Replacing whole packages, forcing their
3591 Secondly, <tt>Replaces</tt> allows the packaging system to
3592 resolve which package should be removed when there is a
3593 conflict - see <ref id="conflicts">. This usage only
3594 takes effect when the two packages <em>do</em> conflict,
3595 so that the two usages of this field do not interfere with
3600 In this situation, the package declared as being replaced
3601 can be a virtual package, so for example, all mail
3602 transport agents (MTAs) would have the following fields in
3603 their control files:
3604 <example compact="compact">
3605 Provides: mail-transport-agent
3606 Conflicts: mail-transport-agent
3607 Replaces: mail-transport-agent
3609 ensuring that only one MTA can be installed at any one
3614 <sect><heading>Relationships between source and binary packages -
3615 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3616 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
3620 A source package may declare a dependency or a conflict on a
3621 binary package, indicating which packages are required to be
3622 present on the system in order to build the binary packages
3623 from the source package. This is done with the control file
3624 fields <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3625 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>.
3626 The dependencies and conflicts they define must be satisfied
3627 (as defined earlier for binary packages) in order to invoke
3628 the targets in <tt>debian/rules</tt>, as follows:<footnote>
3630 If you make "build-arch" or "binary-arch", you need
3631 Build-Depends. If you make "build-indep" or
3632 "binary-indep", you need Build-Depends and
3633 Build-Depends-Indep. If you make "build" or "binary",
3637 There is no Build-Depends-Arch; the autobuilders will
3638 only need the Build-Depends if they know how to build
3639 only build-arch and binary-arch. Anyone building the
3640 build-indep/binary-indep targets is basically assumed to
3641 be building the whole package and so installs all build
3645 The purpose of the original split, I recall, was so that
3646 the autobuilders wouldn't need to install extra packages
3647 needed only for the binary-indep targets. But without a
3648 build-arch/build-indep split, this didn't work, since
3649 most of the work is done in the build target, not in the
3655 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
3658 The <tt>Build-Depends</tt> and
3659 <tt>Build-Conflicts</tt> fields must be satisfied when
3660 any of the following targets is invoked:
3661 <tt>build</tt>, <tt>binary</tt>, <tt>binary-arch</tt>,
3662 <tt>build-arch</tt>, <tt>build-indep</tt>
3663 and <tt>binary-indep</tt>.
3666 <tag><tt>Build-Depends-Indep</tt>,
3667 <tt>Build-Conflicts-Indep</tt></tag>
3670 The <tt>Build-Depends-Indep</tt> and
3671 <tt>Build-Conflicts-Indep</tt> fields must be
3672 satisfied when any of the following targets is
3673 invoked: <tt>build</tt>, <tt>build-indep</tt>,
3674 <tt>binary</tt> and <tt>binary-indep</tt>.
3685 <chapt id="conffiles"><heading>Configuration file handling
3689 This chapter has been superseded by <ref id="config-files">.
3693 <chapt id="sharedlibs"><heading>Shared libraries</heading>
3696 Packages containing shared libraries must be constructed with
3697 a little care to make sure that the shared library is always
3698 available. This is especially important for packages whose
3699 shared libraries are vitally important, such as the C library
3700 (currently <tt>libc6</tt>).
3704 Firstly, the package should install the shared libraries under
3705 their normal names. For example, the <tt>libgdbmg1</tt>
3706 package should install <tt>libgdbm.so.1.7.3</tt> as
3707 <file>/usr/lib/libgdbm.so.1.7.3</file>. The files should not be
3708 renamed or re-linked by any <prgn>prerm</prgn> or
3709 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
3710 of renaming things safely without affecting running programs,
3711 and attempts to interfere with this are likely to lead to
3716 Secondly, the package should include the symbolic link that
3717 <prgn>ldconfig</prgn> would create for the shared libraries.
3718 For example, the <prgn>libgdbmg1</prgn> package should include
3719 a symbolic link from <file>/usr/lib/libgdbm.so.1</file> to
3720 <file>libgdbm.so.1.7.3</file>. This is needed so that the dynamic
3721 linker (for example <prgn>ld.so</prgn> or
3722 <prgn>ld-linux.so.*</prgn>) can find the library between the
3723 time that <prgn>dpkg</prgn> installs it and the time that
3724 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
3727 The package management system requires the library to be
3728 placed before the symbolic link pointing to it in the
3729 <file>.deb</file> file. This is so that when
3730 <prgn>dpkg</prgn> comes to install the symlink
3731 (overwriting the previous symlink pointing at an older
3732 version of the library), the new shared library is already
3733 in place. In the past, this was achieved by creating the
3734 library in the temporary packaging directory before
3735 creating the symlink. Unfortunately, this was not always
3736 effective, since the building of the tar file in the
3737 <file>.deb</file> depended on the behavior of the underlying
3738 file system. Some file systems (such as reiserfs) reorder
3739 the files so that the order of creation is forgotten.
3740 Starting with release <tt>1.7.0</tt>, <prgn>dpkg</prgn>
3741 will reorder the files itself as necessary when building a
3742 package. Thus it is no longer important to concern
3743 oneself with the order of file creation.
3749 Thirdly, the associated development package should contain a
3750 symlink for the shared library without a version number. For
3751 example, the <tt>libgdbmg1-dev</tt> package should include a
3752 symlink from <tt>/usr/lib/libgdbm.so</tt> to
3753 <file>libgdbm.so.1.7.3</file>. This symlink is needed by the
3754 linker (<prgn>ld</prgn>) when compiling packages, as it will
3755 only look for <file>libgdbm.so</file> when compiling dynamically.
3759 Any package installing shared libraries in one of the default
3760 library directories of the dynamic linker (which are currently
3761 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
3762 listed in <file>/etc/ld.so.conf</file><footnote>
3765 <list compact="compact">
3766 <item><p>/usr/X11R6/lib/Xaw3d</p></item>
3767 <item><p>/usr/local/lib</p></item>
3768 <item><p>/usr/lib/libc5-compat</p></item>
3769 <item><p>/lib/libc5-compat</p></item>
3770 <item><p>/usr/X11R6/lib</p></item>
3774 must use <prgn>ldconfig</prgn> to update the shared library
3775 system. The package must call <prgn>ldconfig</prgn> in the
3776 <prgn>postinst</prgn> script if the first argument is
3777 <tt>configure</tt>; the <prgn>postinst</prgn> script may
3778 optionally invoke <prgn>ldconfig</prgn> at other times. The
3779 package should call <prgn>ldconfig</prgn> in the
3780 <prgn>postrm</prgn> script if the first argument is
3781 <tt>remove</tt>. The maintainer scripts must not invoke
3782 <prgn>ldconfig</prgn> under any circumstances other than those
3783 described in this paragraph.<footnote>
3784 <p>During install or upgrade, the preinst is called before
3785 the new files are installed, so calling "ldconfig" is
3786 pointless. The preinst of an existing package can also be
3787 called if an upgrade fails. However, this happens during
3788 the critical time when a shared libs may exist on-disk
3789 under a temporary name. Thus, it is dangerous and
3790 forbidden by current policy to call "ldconfig" at this
3791 time. When a package is installed or upgraded, "postinst
3792 configure" runs after the new files are safely on-disk.
3793 The postinst can also be called to recover from a failed
3794 upgrade. This happens before any new files are unpacked,
3795 so there is no reason to call "ldconfig" at this point.
3796 For a package that is being removed, prerm is called with
3797 all the files intact, so calling ldconfig is useless. The
3798 other calls to "prerm" happen in the case of upgrade at a
3799 time when all the files of the old package are on-disk, so
3800 again calling "ldconfig" is pointless. If An installed
3801 shared lib has been removed from the system just before
3802 "postrm remove" is run. This is the proper time to call
3803 "ldconfig" to notify the system of that fact. The postrm
3804 can be called at several other times. At the time of
3805 "postrm purge", "postrm abort-install", or "postrm
3806 abort-upgrade", calling "ldconfig" is useless because the
3807 shared lib files are not on-disk. However, when "postrm"
3808 is invoked with arguments "upgrade", "failed-upgrade", or
3809 "disappear", a shared lib may exist on-disk under a
3816 <heading>Handling shared library dependencies - the
3817 <tt>shlibs</tt> system</heading>
3820 If a package contains a binary or library which links to a
3821 shared library, we must ensure that when the package is
3822 installed on the system, all of the libraries needed are
3823 also installed. This requirement led to the creation of the
3824 <tt>shlibs</tt> system, which is very simple in its design:
3825 any package which <em>provides</em> a shared library also
3826 provides information on the package dependencies required to
3827 ensure the presence of this library, and any package which
3828 <em>uses</em> a shared library uses this information to
3829 determine the dependencies it requires. The files which
3830 contain the mapping from shared libraries to the necessary
3831 dependency information are called <file>shlibs</file> files.
3835 Thus, when a package is built which contains any shared
3836 libraries, it must provide a <file>shlibs</file> file for other
3837 packages to use, and when a package is built which contains
3838 any shared libraries or compiled binaries, it must run
3839 <prgn>dpkg-shlibdeps</prgn> on these to determine the
3840 libraries used and hence the dependencies needed by this
3843 In the past, the shared libraries linked to were
3844 determined by calling <prgn>ldd</prgn>, but now
3845 <prgn>objdump</prgn> is used to do this. The only
3846 change this makes to package building is that
3847 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
3848 libraries, whereas in the past this was unnecessary.
3849 The rest of this footnote explains the advantage that
3854 We say that a binary <tt>foo</tt> <em>directly</em> uses
3855 a library <tt>libbar</tt> if it is explicitly linked
3856 with that library (that is, it uses the flag
3857 <tt>-lbar</tt> during the linking stage). Other
3858 libraries that are needed by <tt>libbar</tt> are linked
3859 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
3860 linker will load them automatically when it loads
3861 <tt>libbar</tt>. A package should depend on
3862 the libraries it directly uses, and the dependencies for
3863 those libraries should automatically pull in the other
3868 Unfortunately, the <prgn>ldd</prgn> program shows both
3869 the directly and indirectly used libraries, meaning that
3870 the dependencies determined included both direct and
3871 indirect dependencies. The use of <prgn>objdump</prgn>
3872 avoids this problem by determining only the directly
3877 A good example of where this helps is the following. We
3878 could update <tt>libimlib</tt> with a new version that
3879 supports a new graphics format called dgf (but retaining
3880 the same major version number). If we used the old
3881 <prgn>ldd</prgn> method, every package that uses
3882 <tt>libimlib</tt> would need to be recompiled so it
3883 would also depend on <tt>libdgf</tt> or it wouldn't run
3884 due to missing symbols. However with the new system,
3885 packages using <tt>libimlib</tt> can rely on
3886 <tt>libimlib</tt> itself having the dependency on
3887 <tt>libdgf</tt> and so they would not need rebuilding.
3893 In the following sections, we will first describe where the
3894 various <tt>shlibs</tt> files are to be found, then how to
3895 use <prgn>dpkg-shlibdeps</prgn>, and finally the
3896 <tt>shlibs</tt> file format and how to create them if your
3897 package contains a shared library.
3901 <sect><heading>The <tt>shlibs</tt> files present on the system
3905 There are several places where <tt>shlibs</tt> files are
3906 found. The following list gives them in the order in which
3907 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
3908 one which gives the required information is used.)
3914 <p><file>debian/shlibs.local</file></p>
3916 This lists overrides for this package. Its use is
3917 described below (see <ref id="shlibslocal">).
3922 <p><file>/etc/dpkg/shlibs.override</file></p>
3924 This lists global overrides. This list is normally
3925 empty. It is maintained by the local system
3931 <p><file>DEBIAN/shlibs</file> files in the `build directory'</p>
3933 When packages are being built, any
3934 <file>debian/shlibs</file> files are copied into the
3935 control file area of the temporary build directory and
3936 given the name <file>shlibs</file>. These files give
3937 details of any shared libraries included in the
3940 An example may help here. Let us say that the
3941 source package <tt>foo</tt> generates two binary
3942 packages, <tt>libfoo2</tt> and
3943 <tt>foo-runtime</tt>. When building the binary
3944 packages, the two packages are created in the
3945 directories <file>debian/libfoo2</file> and
3946 <file>debian/foo-runtime</file> respectively.
3947 (<file>debian/tmp</file> could be used instead of one
3948 of these.) Since <tt>libfoo2</tt> provides the
3949 <tt>libfoo</tt> shared library, it will require a
3950 <tt>shlibs</tt> file, which will be installed in
3951 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
3953 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
3954 when <prgn>dpkg-shlibdeps</prgn> is run on the
3956 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
3958 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
3959 determine whether <tt>foo-prog</tt>'s library
3960 dependencies are satisfied by any of the libraries
3961 provided by <tt>libfoo2</tt>. For this reason,
3962 <prgn>dpkg-shlibdeps</prgn> must only be run once
3963 all of the individual binary packages'
3964 <tt>shlibs</tt> files have been installed into the
3972 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
3974 These are the <file>shlibs</file> files corresponding to
3975 all of the packages installed on the system, and are
3976 maintained by the relevant package maintainers.
3981 <p><file>/etc/dpkg/shlibs.default</file></p>
3983 This file lists any shared libraries whose packages
3984 have failed to provide correct <file>shlibs</file> files.
3985 It was used when the <file>shlibs</file> setup was first
3986 introduced, but it is now normally empty. It is
3987 maintained by the <tt>dpkg</tt> maintainer.
3995 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
3996 <file>shlibs</file> files</heading>
3999 Put a call to <prgn>dpkg-shlibdeps</prgn> into your
4000 <file>debian/rules</file> file. If your package contains only
4001 compiled binaries and libraries (but no scripts), you can
4002 use a command such as:
4003 <example compact="compact">
4004 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4005 debian/tmp/usr/lib/*
4007 Otherwise, you will need to explicitly list the compiled
4008 binaries and libraries.<footnote>
4010 If you are using <tt>debhelper</tt>, the
4011 <prgn>dh_shlibdeps</prgn> program will do this work for
4012 you. It will also correctly handle multi-binary
4019 This command puts the dependency information into the
4020 <file>debian/substvars</file> file, which is then used by
4021 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4022 <tt>${shlib:Depends}</tt> variable in the <tt>Depends</tt>
4023 field in the control file for this to work.
4027 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4028 done. If it does complain you might need to create your own
4029 <file>debian/shlibs.local</file> file, as explained below (see
4030 <ref id="shlibslocal">).
4034 If you have multiple binary packages, you will need to call
4035 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4036 compiled libraries or binaries. In such a case, you will
4037 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4038 utilities to specify a different <file>substvars</file> file.
4039 For more details on this and other options, see <manref
4040 name="dpkg-shlibdeps" section="1">.
4044 <sect id="shlibs"><heading>The <file>shlibs</file> File Format
4048 Each <file>shlibs</file> file has the same format. Lines
4049 beginning with <tt>#</tt> are considered to be comments and
4050 are ignored. Each line is of the form:
4051 <example compact="compact">
4052 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4057 We will explain this by reference to the example of the
4058 <tt>zlib1g</tt> package, which (at the time of writing)
4059 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4063 <var>library-name</var> is the name of the shared library,
4064 in this case <tt>libz</tt>. (This must match the name part
4065 of the soname, see below.)
4069 <var>soname-version-number</var> is the version part of the
4070 soname of the library. The soname is the thing that must
4071 exactly match for the library to be recognized by the
4072 dynamic linker, and is usually of the form
4073 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4074 example, <tt>libz.so.1</tt>.<footnote>
4076 This can be determined using the command
4077 <example compact="compact">
4078 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
4082 The version part is the part which comes after
4083 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
4087 <var>dependencies</var> has the same syntax as a dependency
4088 field in a binary package control file. It should give
4089 details of which packages are required to satisfy a binary
4090 built against the version of the library contained in the
4091 package. See <ref id="depsyntax"> for details.
4095 In our example, if the first version of the <tt>zlib1g</tt>
4096 package which contained a minor number of at least
4097 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
4098 <tt>shlibs</tt> entry for this library could say:
4099 <example compact="compact">
4100 libz 1 zlib1g (>= 1:1.1.3)
4102 The version-specific dependency is to avoid warnings from
4103 the dynamic linker about using older shared libraries with
4109 <heading>Providing a <file>shlibs</file> file</heading>
4112 If your package provides a shared library, you should create
4113 a <file>shlibs</file> file following the format described above.
4114 It is usual to call this file <file>debian/shlibs</file> (but if
4115 you have multiple binary packages, you might want to call it
4116 <file>debian/shlibs.<var>package</var></file> instead). Then
4117 let <file>debian/rules</file> install it in the control area:
4118 <example compact="compact">
4119 install -m644 debian/shlibs debian/tmp/DEBIAN
4121 or, in the case of a multi-binary package:
4122 <example compact="compact">
4123 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
4125 An alternative way of doing this is to create the
4126 <file>shlibs</file> file in the control area directly from
4127 <file>debian/rules</file> without using a <file>debian/shlibs</file>
4128 file at all,<footnote>
4130 This is what <prgn>dh_makeshlibs</prgn> in the
4131 <tt>debhelper</tt> suite does.
4134 since the <file>debian/shlibs</file> file itself is ignored by
4135 <prgn>dpkg-shlibdeps</prgn>.
4139 As <prgn>dpkg-shlibdeps</prgn> reads the
4140 <file>DEBIAN/shlibs</file> files in all of the binary packages
4141 being built from this source package, all of the
4142 <file>DEBIAN/shlibs</file> files should be installed before
4143 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
4148 <sect id="shlibslocal">
4149 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
4152 This file is intended only as a <em>temporary</em> fix if
4153 your binaries or libraries depend on a library whose package
4154 does not yet provide a correct <file>shlibs</file> file.
4158 We will assume that you are trying to package a binary
4159 <tt>foo</tt>. When you try running
4160 <prgn>dpkg-shlibdeps</prgn> you get the following error
4161 message (<tt>-O</tt> displays the dependency information on
4162 <tt>stdout</tt> instead of writing it to
4163 <tt>debian/substvars</tt>, and the lines have been wrapped
4164 for ease of reading):
4165 <example compact="compact">
4166 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
4167 dpkg-shlibdeps: warning: unable to find dependency
4168 information for shared library libbar (soname 1,
4169 path /usr/lib/libbar.so.1, dependency field Depends)
4170 shlibs:Depends=libc6 (>= 2.2.2-2)
4172 You can then run <prgn>ldd</prgn> on the binary to find the
4173 full location of the library concerned:
4174 <example compact="compact">
4176 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
4177 libc.so.6 => /lib/libc.so.6 (0x40032000)
4178 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
4180 So the <prgn>foo</prgn> binary depends on the
4181 <prgn>libbar</prgn> shared library, but no package seems to
4182 provide a <file>*.shlibs</file> file handling
4183 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
4184 determine the package responsible:
4185 <example compact="compact">
4186 $ dpkg -S /usr/lib/libbar.so.1
4187 bar1: /usr/lib/libbar.so.1
4188 $ dpkg -s bar1 | grep Version
4191 This tells us that the <tt>bar1</tt> package, version 1.0-1,
4192 is the one we are using. Now we can file a bug against the
4193 <tt>bar1</tt> package and create our own
4194 <file>debian/shlibs.local</file> to locally fix the problem.
4195 Including the following line into your
4196 <file>debian/shlibs.local</file> file:
4197 <example compact="compact">
4198 libbar 1 bar1 (>= 1.0-1)
4200 should allow the package build to work.
4204 As soon as the maintainer of <tt>bar1</tt> provides a
4205 correct <file>shlibs</file> file, you should remove this line
4206 from your <file>debian/shlibs.local</file> file. (You should
4207 probably also then have a versioned <tt>Build-Depends</tt>
4208 on <tt>bar1</tt> to help ensure that others do not have the
4209 same problem building your package.)
4214 <chapt id="opersys"><heading>The Operating System</heading>
4217 <heading>Filesystem hierarchy</heading>
4221 <heading>Filesystem Structure</heading>
4224 The location of all installed files and directories must
4225 comply with the Filesystem Hierarchy Standard (FHS),
4226 version 2.1, except where doing so would violate other
4227 terms of Debian Policy. The version of this document
4228 referred here can be found in the <tt>debian-policy</tt>
4230 <url id="http://www.debian.org/doc/packaging-manuals/fhs/"
4231 name="FHS (Debian copy)"> alongside this manual. The
4232 latest version, which may be a more recent version, may
4234 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
4235 Specific questions about following the standard may be
4236 asked on the <tt>debian-devel</tt> mailing list, or
4237 referred to the FHS mailing list (see the
4238 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
4244 <heading>Site-specific programs</heading>
4247 As mandated by the FHS, packages must not place any
4248 files in <file>/usr/local</file>, either by putting them in
4249 the file system archive to be unpacked by <prgn>dpkg</prgn>
4250 or by manipulating them in their maintainer scripts.
4254 However, the package may create empty directories below
4255 <file>/usr/local</file> so that the system administrator knows
4256 where to place site-specific files. These directories
4257 should be removed on package removal if they are
4262 Note, that this applies only to directories <em>below</em>
4263 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
4264 Packages must not create sub-directories in the directory
4265 <file>/usr/local</file> itself, except those listed in FHS,
4266 section 4.5. However, you may create directories below
4267 them as you wish. You must not remove any of the
4268 directories listed in 4.5, even if you created them.
4272 Since <file>/usr/local</file> can be mounted read-only from a
4273 remote server, these directories must be created and
4274 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
4275 maintainer scripts and not be included in the
4276 <file>.deb</file> archive. These scripts must not fail if
4277 either of these operations fail.
4281 For example, the <tt>emacsen-common</tt> package could
4282 contain something like
4283 <example compact="compact">
4284 if [ ! -e /usr/local/share/emacs ]
4286 if mkdir /usr/local/share/emacs 2>/dev/null
4288 chown root:staff /usr/local/share/emacs
4289 chmod 2775 /usr/local/share/emacs
4293 in its <prgn>postinst</prgn> script, and
4294 <example compact="compact">
4295 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
4296 rmdir /usr/local/share/emacs 2>/dev/null || true
4298 in the <prgn>prerm</prgn> script. (Note that this form is
4299 used to ensure that if the script is interrupted, the
4300 directory <file>/usr/local/share/emacs</file> will still be
4305 If you do create a directory in <file>/usr/local</file> for
4306 local additions to a package, you should ensure that
4307 settings in <file>/usr/local</file> take precedence over the
4308 equivalents in <file>/usr</file>.
4312 However, because <file>/usr/local</file> and its contents are
4313 for exclusive use of the local administrator, a package
4314 must not rely on the presence or absence of files or
4315 directories in <file>/usr/local</file> for normal operation.
4319 The <file>/usr/local</file> directory itself and all the
4320 subdirectories created by the package should (by default) have
4321 permissions 2775 (group-writable and set-group-id) and be
4322 owned by <tt>root.staff</tt>.
4327 <heading>The system-wide mail directory</heading>
4329 The system-wide mail directory is <file>/var/mail</file>. This
4330 directory is part of the base system and should not owned
4331 by any particular mail agents. The use of the old
4332 location <file>/var/spool/mail</file> is deprecated, even
4333 though the spool may still be physically located there.
4334 To maintain partial upgrade compatibility for systems
4335 which have <file>/var/spool/mail</file> as their physical mail
4336 spool, packages using <file>/var/mail</file> must depend on
4337 either <package>libc6</package> (>= 2.1.3-13), or on
4338 <package>base-files</package> (>= 2.2.0), or on later
4339 versions of either one of these packages.
4345 <heading>Users and groups</heading>
4348 <heading>Introduction</heading>
4350 The Debian system can be configured to use either plain or
4355 Some user ids (UIDs) and group ids (GIDs) are reserved
4356 globally for use by certain packages. Because some
4357 packages need to include files which are owned by these
4358 users or groups, or need the ids compiled into binaries,
4359 these ids must be used on any Debian system only for the
4360 purpose for which they are allocated. This is a serious
4361 restriction, and we should avoid getting in the way of
4362 local administration policies. In particular, many sites
4363 allocate users and/or local system groups starting at 100.
4367 Apart from this we should have dynamically allocated ids,
4368 which should by default be arranged in some sensible
4369 order, but the behavior should be configurable.
4373 Packages other than <tt>base-passwd</tt> must not modify
4374 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
4375 <file>/etc/group</file> or <file>/etc/gshadow</file>.
4380 <heading>UID and GID classes</heading>
4382 The UID and GID numbers are divided into classes as
4388 Globally allocated by the Debian project, the same
4389 on every Debian system. These ids will appear in
4390 the <file>passwd</file> and <file>group</file> files of all
4391 Debian systems, new ids in this range being added
4392 automatically as the <tt>base-passwd</tt> package is
4397 Packages which need a single statically allocated
4398 uid or gid should use one of these; their
4399 maintainers should ask the <tt>base-passwd</tt>
4407 Dynamically allocated system users and groups.
4408 Packages which need a user or group, but can have
4409 this user or group allocated dynamically and
4410 differently on each system, should use <tt>adduser
4411 --system</tt> to create the group and/or user.
4412 <prgn>adduser</prgn> will check for the existence of
4413 the user or group, and if necessary choose an unused
4414 id based on the ranges specified in
4415 <file>adduser.conf</file>.
4419 <tag>1000-29999:</tag>
4422 Dynamically allocated user accounts. By default
4423 <prgn>adduser</prgn> will choose UIDs and GIDs for
4424 user accounts in this range, though
4425 <file>adduser.conf</file> may be used to modify this
4430 <tag>30000-59999:</tag>
4435 <tag>60000-64999:</tag>
4438 Globally allocated by the Debian project, but only
4439 created on demand. The ids are allocated centrally
4440 and statically, but the actual accounts are only
4441 created on users' systems on demand.
4445 These ids are for packages which are obscure or
4446 which require many statically-allocated ids. These
4447 packages should check for and create the accounts in
4448 <file>/etc/passwd</file> or <file>/etc/group</file> (using
4449 <prgn>adduser</prgn> if it has this facility) if
4450 necessary. Packages which are likely to require
4451 further allocations should have a `hole' left after
4452 them in the allocation, to give them room to
4457 <tag>65000-65533:</tag>
4465 User <tt>nobody</tt>. The corresponding gid refers
4466 to the group <tt>nogroup</tt>.
4473 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
4474 not</em> be used, because it is the error return
4483 <sect id="sysvinit">
4484 <heading>System run levels and <file>init.d</file> scripts</heading>
4486 <sect1 id="/etc/init.d">
4487 <heading>Introduction</heading>
4490 The <file>/etc/init.d</file> directory contains the scripts
4491 executed by <prgn>init</prgn> at boot time and when the
4492 init state (or `runlevel') is changed (see <manref
4493 name="init" section="8">).
4497 There are at least two different, yet functionally
4498 equivalent, ways of handling these scripts. For the sake
4499 of simplicity, this document describes only the symbolic
4500 link method. However, it must not be assumed by maintainer
4501 scripts that this method is being used, and any automated
4502 manipulation of the various runlevel behaviours by
4503 maintainer scripts must be performed using
4504 <prgn>update-rc.d</prgn> as described below and not by
4505 manually installing or removing symlinks. For information
4506 on the implementation details of the other method,
4507 implemented in the <tt>file-rc</tt> package, please refer
4508 to the documentation of that package.
4512 These scripts are referenced by symbolic links in the
4513 <file>/etc/rc<var>n</var>.d</file> directories. When changing
4514 runlevels, <prgn>init</prgn> looks in the directory
4515 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
4516 execute, where <tt><var>n</var></tt> is the runlevel that
4517 is being changed to, or <tt>S</tt> for the boot-up
4522 The names of the links all have the form
4523 <file>S<var>mm</var><var>script</var></file> or
4524 <file>K<var>mm</var><var>script</var></file> where
4525 <var>mm</var> is a two-digit number and <var>script</var>
4526 is the name of the script (this should be the same as the
4527 name of the actual script in <file>/etc/init.d</file>).
4531 When <prgn>init</prgn> changes runlevel first the targets
4532 of the links whose names start with a <tt>K</tt> are
4533 executed, each with the single argument <tt>stop</tt>,
4534 followed by the scripts prefixed with an <tt>S</tt>, each
4535 with the single argument <tt>start</tt>. (The links are
4536 those in the <file>/etc/rc<var>n</var>.d</file> directory
4537 corresponding to the new runlevel.) The <tt>K</tt> links
4538 are responsible for killing services and the <tt>S</tt>
4539 link for starting services upon entering the runlevel.
4543 For example, if we are changing from runlevel 2 to
4544 runlevel 3, init will first execute all of the <tt>K</tt>
4545 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
4546 all of the <tt>S</tt> prefixed scripts in that directory.
4547 The links starting with <tt>K</tt> will cause the
4548 referred-to file to be executed with an argument of
4549 <tt>stop</tt>, and the <tt>S</tt> links with an argument
4554 The two-digit number <var>mm</var> is used to determine
4555 the order in which to run the scripts: low-numbered links
4556 have their scripts run first. For example, the
4557 <tt>K20</tt> scripts will be executed before the
4558 <tt>K30</tt> scripts. This is used when a certain service
4559 must be started before another. For example, the name
4560 server <prgn>bind</prgn> might need to be started before
4561 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
4562 can set up its access lists. In this case, the script
4563 that starts <prgn>bind</prgn> would have a lower number
4564 than the script that starts <prgn>inn</prgn> so that it
4566 <example compact="compact">
4573 The two runlevels 0 (halt) and 6 (reboot) are slightly
4574 different. In these runlevels, the links with an
4575 <tt>S</tt> prefix are still called after those with a
4576 <tt>K</tt> prefix, but they too are called with the single
4577 argument <tt>stop</tt>.
4581 Also, if the script name ends <tt>.sh</tt>, the script
4582 will be sourced in runlevel <tt>S</tt> rather that being
4583 run in a forked subprocess, but will be explicitly run by
4584 <prgn>sh</prgn> in all other runlevels.
4589 <heading>Writing the scripts</heading>
4592 Packages that include daemons for system services should
4593 place scripts in <file>/etc/init.d</file> to start or stop
4594 services at boot time or during a change of runlevel.
4595 These scripts should be named
4596 <file>/etc/init.d/<var>package</var></file>, and they should
4597 accept one argument, saying what to do:
4600 <tag><tt>start</tt></tag>
4601 <item><p>start the service,</p></item>
4603 <tag><tt>stop</tt></tag>
4604 <item><p>stop the service,</p></item>
4606 <tag><tt>restart</tt></tag>
4607 <item><p>stop and restart the service,</p></item>
4609 <tag><tt>reload</tt></tag>
4610 <item><p>cause the configuration of the service to be
4611 reloaded without actually stopping and restarting
4612 the service,</p></item>
4614 <tag><tt>force-reload</tt></tag>
4615 <item><p>cause the configuration to be reloaded if the
4616 service supports this, otherwise restart the
4620 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
4621 <tt>force-reload</tt> options should be supported by all
4622 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
4623 option is optional.</p>
4626 The <file>init.d</file> scripts should ensure that they will
4627 behave sensibly if invoked with <tt>start</tt> when the
4628 service is already running, or with <tt>stop</tt> when it
4629 isn't, and that they don't kill unfortunately-named user
4630 processes. The best way to achieve this is usually to use
4631 <prgn>start-stop-daemon</prgn>.</p>
4634 If a service reloads its configuration automatically (as
4635 in the case of <prgn>cron</prgn>, for example), the
4636 <tt>reload</tt> option of the <file>init.d</file> script
4637 should behave as if the configuration has been reloaded
4641 The <file>/etc/init.d</file> scripts must be treated as
4642 configuration files, either (if they are present in the
4643 package, that is, in the .deb file) by marking them as
4644 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
4645 by managing them correctly in the maintainer scripts (see
4646 <ref id="config-files">). This is important since we want
4647 to give the local system administrator the chance to adapt
4648 the scripts to the local system, e.g., to disable a
4649 service without de-installing the package, or to specify
4650 some special command line options when starting a service,
4651 while making sure her changes aren't lost during the next
4656 These scripts should not fail obscurely when the
4657 configuration files remain but the package has been
4658 removed, as configuration files remain on the system after
4659 the package has been removed. Only when <prgn>dpkg</prgn>
4660 is executed with the <tt>--purge</tt> option will
4661 configuration files be removed. In particular, as the
4662 <file>/etc/init.d/<var>package</var></file> script itself is
4663 usually a <tt>conffile</tt>, it will remain on the system
4664 if the package is removed but not purged. Therefore, you
4665 should include a <tt>test</tt> statement at the top of the
4667 <example compact="compact">
4668 test -f <var>program-executed-later-in-script</var> || exit 0
4673 Often there are some variables in the <file>init.d</file>
4674 scripts whose values control the behaviour of the scripts,
4675 and which a system administrator is likely to want to
4676 change. As the scripts themselves are frequently
4677 <tt>conffile</tt>s, modifying them requires that the
4678 administrator merge in their changes each time the package
4679 is upgraded and the <tt>conffile</tt> changes. To ease
4680 the burden on the system administrator, such configurable
4681 values should not be placed directly in the script.
4682 Instead, they should be placed in a file in
4683 <file>/etc/default</file>, which typically will have the same
4684 base name as the <file>init.d</file> script. This extra file
4685 should be sourced by the script when the script runs. It
4686 must contain only variable settings and comments in POSIX
4687 <prgn>sh</prgn> format. It may either be a
4688 <tt>conffile</tt> or a configuration file maintained by
4689 the package maintainer scripts. See <ref id="config-files">
4694 To ensure that vital configurable values are always
4695 available, the <file>init.d</file> script should set default
4696 values for each of the shell variables it uses, either
4697 before sourcing the <file>/etc/default/</file> file or
4698 afterwards using something like the <tt>:
4699 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
4700 script must behave sensibly and not fail if the
4701 <file>/etc/default</file> file is deleted.
4706 <heading>Interfacing with the initscript system</heading>
4709 Maintainers should use the abstraction layer provided by
4710 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
4711 programs to deal with initscripts in their packages'
4712 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
4713 and <prgn>postrm</prgn>.
4716 Directly managing the /etc/rc?.d links and directly
4717 invoking the <file>/etc/init.d/</file> initscripts should
4718 be done only by packages providing the initscript
4719 subsystem (such as <prgn>sysvinit</prgn> and
4720 <prgn>file-rc</prgn>).
4725 <heading>Managing the links</heading>
4728 The program <prgn>update-rc.d</prgn> is provided for
4729 package maintainers to arrange for the proper creation and
4730 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
4731 or their functional equivalent if another method is being
4732 used. This may be used by maintainers in their packages'
4733 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.</p>
4736 You must not include any <file>/etc/rc<var>n</var>.d</file>
4737 symbolic links in the actual archive or manually create or
4738 remove the symbolic links in maintainer scripts; you must
4739 use the <prgn>update-rc.d</prgn> program instead. (The
4740 former will fail if an alternative method of maintaining
4741 runlevel information is being used.) You must not include
4742 the <file>/etc/rc<var>n</var>.d</file> directories themselves
4743 in the archive either. (Only the <tt>sysvinit</tt>
4748 By default <prgn>update-rc.d</prgn> will start services in
4749 each of the multi-user state runlevels (2, 3, 4, and 5)
4750 and stop them in the halt runlevel (0), the single-user
4751 runlevel (1) and the reboot runlevel (6). The system
4752 administrator will have the opportunity to customize
4753 runlevels by simply adding, moving, or removing the
4754 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
4755 symbolic links are being used, or by modifying
4756 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
4761 To get the default behavior for your package, put in your
4762 <prgn>postinst</prgn> script
4763 <example compact="compact">
4764 update-rc.d <var>package</var> defaults
4766 and in your <prgn>postrm</prgn>
4767 <example compact="compact">
4768 if [ "$1" = purge ]; then
4769 update-rc.d <var>package</var> remove
4771 </example>. Note that is your package changes runlevels
4772 or priority, you may have to remove and recreate the
4773 links, since otherwise the old links may
4774 persist. Refer to the documentation of
4775 <prgn>update-rc.d</prgn></p>
4778 This will use a default sequence number of 20. If it does
4779 not matter when or in which order the <file>init.d</file>
4780 script is run, use this default. If it does, then you
4781 should talk to the maintainer of the <prgn>sysvinit</prgn>
4782 package or post to <tt>debian-devel</tt>, and they will
4783 help you choose a number.
4787 For more information about using <tt>update-rc.d</tt>,
4788 please consult its manpage <manref name="update-rc.d"
4794 <heading>Running initscripts</heading>
4796 The program <prgn>invoke-rc.d</prgn> is provided to make
4797 it easier for package maintainers to properly invoke an
4798 initscript, obeying runlevel and other locally-defined
4799 constraints that might limit a package's right to start,
4800 stop and otherwise manage services. This program may be
4801 used by maintainers in their packages' scripts.
4804 The use of <prgn>invoke-rc.d</prgn> to invoke the
4805 <file>/etc/init.d/*</file> initscripts is strongly
4806 recommended<footnote>
4808 In the future, the use of invoke-rc.d to invoke
4809 initscripts shall be made mandatory. Maintainers are
4810 advised to switch to invoke-rc.d as soon as
4812 </footnote>, instead of calling them directly.
4816 By default, <prgn>invoke-rc.d</prgn> will pass any
4817 action requests (start, stop, reload, restart...) to the
4818 <file>/etc/init.d</file> script, filtering out requests
4819 to start or restart a service out of its intended
4823 Most packages will simply need to change:
4824 <example compact="compact">/etc/init.d/<package>
4825 <action></example> in their <prgn>postinst</prgn>
4826 and <prgn>prerm</prgn> scripts to:
4827 <example compact="compact">
4828 if [ -x /usr/sbin/invoke-rc.d ] ; then
4829 invoke-rc.d <var>package</var> <action>
4831 /etc/init.d/<var>package</var> <action>
4835 A package should register its initscript services using
4836 <prgn>update-rc.d</prgn> before it tries to invoke them
4837 using <prgn>invoke-rc.d</prgn>. Invocation of
4838 unregistered services may fail.
4841 For more information about using
4842 <prgn>invoke-rc.d</prgn>, please consult its manpage
4843 <manref name="invoke-rc.d" section="8">.
4850 <heading>Boot-time initialization</heading>
4853 There used to be another directory, <file>/etc/rc.boot</file>,
4854 which contained scripts which were run once per machine
4855 boot. This has been deprecated in favour of links from
4856 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
4857 described in <ref id="/etc/init.d">. Packages must not
4858 place files in <file>/etc/rc.boot</file>.</p>
4861 <heading>Example</heading>
4864 The <prgn>bind</prgn> DNS (nameserver) package wants to
4865 make sure that the nameserver is running in multiuser
4866 runlevels, and is properly shut down with the system. It
4867 puts a script in <file>/etc/init.d</file>, naming the script
4868 appropriately <tt>bind</tt>. As you can see, the script
4869 interprets the argument <tt>reload</tt> to send the
4870 nameserver a <tt>HUP</tt> signal (causing it to reload its
4871 configuration); this way the system administrator can say
4872 <file>/etc/init.d/bind reload</file> to reload the name
4873 server. The script has one configurable value, which can
4874 be used to pass parameters to the named program at
4875 startup; this value is read from
4876 <file>/etc/default/bind</file> (see below).
4880 <example compact="compact">
4883 # Original version by Robert Leslie
4884 # <rob@mars.org>, edited by iwj and cs
4886 test -x /usr/sbin/named || exit 0
4888 # Source defaults file.
4890 if [ -f /etc/default/bind ]; then
4897 echo -n "Starting domain name service: named"
4898 start-stop-daemon --start --quiet --exec /usr/sbin/named \
4903 echo -n "Stopping domain name service: named"
4904 start-stop-daemon --stop --quiet \
4905 --pidfile /var/run/named.pid --exec /usr/sbin/named
4909 echo -n "Restarting domain name service: named"
4910 start-stop-daemon --stop --quiet \
4911 --pidfile /var/run/named.pid --exec /usr/sbin/named
4912 start-stop-daemon --start --verbose --exec /usr/sbin/named \
4916 force-reload|reload)
4917 echo -n "Reloading configuration of domain name service: named"
4918 start-stop-daemon --stop --signal 1 --quiet \
4919 --pidfile /var/run/named.pid --exec /usr/sbin/named
4923 echo "Usage: /etc/init.d/bind " \
4924 " {start|stop|restart|reload|force-reload}" >&2
4934 Complementing the above init script is a configuration
4935 file <file>/etc/default/bind</file>, which contains
4936 configurable parameters used by the script. This would be
4937 created by the <prgn>postinst</prgn> script if it was not
4938 already present, and removed on purge by the
4939 <prgn>postrm</prgn> script.
4940 <example compact="compact">
4941 # Specified parameters to pass to named. See named(8).
4942 # You may uncomment the following line, and edit to taste.
4948 Another example on which you can base your
4949 <file>/etc/init.d</file> scripts is found in
4950 <file>/etc/init.d/skeleton</file>.
4954 If this package is happy with the default setup from
4955 <prgn>update-rc.d</prgn>, namely an ordering number of 20
4956 and having named running in all runlevels, it can say in
4957 its <prgn>postinst</prgn>:
4958 <example compact="compact">
4959 update-rc.d bind defaults >/dev/null
4961 And in its <prgn>postrm</prgn>, to remove the links when the
4963 <example compact="compact">
4964 if [ "$1" = purge ]; then
4965 update-rc.d bind remove >/dev/null
4973 <heading>Console messages from <file>init.d</file> scripts</heading>
4976 This section describes the formats to be used for messages
4977 written to standard output by the <file>/etc/init.d</file>
4978 scripts. The intent is to improve the consistency of
4979 Debian's startup and shutdown look and feel. For this
4980 reason, please look very carefully at the details. We want
4981 the messages to have the same format in terms of wording,
4982 spaces, punctuation and case of letters.
4986 Here is a list of overall rules that you should use when you
4987 create output messages. They can be useful if you have a
4988 non-standard message that is not covered specifically in the
4996 Every message should fit in one line (fewer than 80
4997 characters), start with a capital letter and end with
4998 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5004 If you want to express that the computer is working on
5005 something (that is, performing a specific task, not
5006 starting or stopping a program), we use an "ellipsis"
5007 (three dots: <tt>...</tt>). Note that we don't insert
5008 spaces before or after the dots. If the task has been
5009 completed we write <tt>done.</tt> and a line feed.
5015 Design your messages as if the computer is telling you
5016 what he is doing (let him be polite :-), but don't
5017 mention "him" directly. For example, if you think of
5019 <example compact="compact">
5020 I'm starting network daemons: nfsd mountd.
5023 <example compact="compact">
5024 Starting network daemons: nfsd mountd.
5032 There are standard message formats for the following
5033 situations. They should be used by the <tt>init.d</tt>
5040 <p>When daemons are started</p>
5043 If your script starts one or more daemons, the output
5044 should look like this (a single line, no leading
5046 <example compact="compact">
5047 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5049 The <var>description</var> should describe the
5050 subsystem the daemon or set of daemons are part of,
5051 while <var>daemon-1</var> up to <var>daemon-n</var>
5052 denote each daemon's name (typically the file name of
5057 For example, the output of <file>/etc/init.d/lpd</file>
5059 <example compact="compact">
5060 Starting printer spooler: lpd.
5065 This can be achieved by saying
5066 <example compact="compact">
5067 echo -n "Starting printer spooler: lpd"
5068 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5071 in the script. If you have more than one daemon to
5072 start, you should do the following:
5073 <example compact="compact">
5074 echo -n "Starting remote file system services:"
5075 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5076 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5077 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5080 This makes it possible for the user to see what takes
5081 so long and when the final daemon has been started.
5082 You should be careful where to put spaces: in the
5083 example above the system administrator can easily
5084 comment out a line if he don't wants to start a
5085 specific daemon, while the displayed message still
5091 <p>When a system parameter is being set</p>
5094 If you have to set up different system parameters
5095 during the system boot, you should use this format:
5096 <example compact="compact">
5097 Setting <var>parameter</var> to `<var>value</var>'.
5102 You can use a statement such as the following to get
5104 <example compact="compact">
5105 echo "Setting DNS domainname to \`$domainname'."
5110 Note that the left quotation mark (<tt>`</tt>) is
5111 different from the right one (<tt>'</tt>).
5116 <p>When a daemon is stopped or restarted</p>
5119 When you stop or restart a daemon, you should issue a
5120 message identical to the startup message, except that
5121 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5122 or <tt>Restarting</tt> respectively.
5126 For example, stopping the printer daemon will like
5128 <example compact="compact">
5129 Stopping printer spooler: lpd.
5135 <p>When something is executed</p>
5138 There are several examples where you have to run a
5139 program at system startup or shutdown to perform a
5140 specific task, for example, setting the system's clock
5141 using <prgn>netdate</prgn> or killing all processes
5142 when the system shuts down. Your message should look
5144 <example compact="compact">
5145 Doing something very useful...done.
5147 You should print the <tt>done.</tt> immediately after
5148 the job has been completed, so that the user is
5149 informed why she has to wait. You can get this
5151 <example compact="compact">
5152 echo -n "Doing something very useful..."
5161 <p>When the configuration is reloaded</p>
5164 When a daemon is forced to reload its configuration
5165 files you should use the following format:
5166 <example compact="compact">
5167 Reloading <var>description</var> configuration...done.
5169 where <var>description</var> is the same as in the
5170 daemon starting message.
5178 <heading>Cron jobs</heading>
5181 Packages must not modify the configuration file
5182 <file>/etc/crontab</file>, and they must not modify the files in
5183 <file>/var/spool/cron/crontabs</file>.</p>
5186 If a package wants to install a job that has to be executed
5187 via cron, it should place a file with the name of the
5188 package in one or more of the following directories:
5189 <example compact="compact">
5194 As these directory names imply, the files within them are
5195 executed on a daily, weekly, or monthly basis,
5196 respectively. The exact times are listed in
5197 <file>/etc/crontab</file>.</p>
5200 All files installed in any of these directories must be
5201 scripts (e.g., shell scripts or Perl scripts) so that they
5202 can easily be modified by the local system administrator.
5203 In addition, they should be treated as configuration
5208 If a certain job has to be executed more frequently than
5209 daily, the package should install a file
5210 <file>/etc/cron.d/<var>package</var></file>. This file uses the
5211 same syntax as <file>/etc/crontab</file> and is processed by
5212 <prgn>cron</prgn> automatically. The file must also be
5213 treated as a configuration file. (Note that entries in the
5214 <file>/etc/cron.d</file> directory are not handled by
5215 <prgn>anacron</prgn>. Thus, you should only use this
5216 directory for jobs which may be skipped if the system is not
5220 The scripts or crontab entries in these directories should
5221 check if all necessary programs are installed before they
5222 try to execute them. Otherwise, problems will arise when a
5223 package was removed but not purged since configuration files
5224 are kept on the system in this situation.</p>
5228 <heading>Menus</heading>
5231 Menu entries should follow the current menu policy found in
5232 the <tt>menu-policy</tt> files in the <tt>debian-policy</tt>
5233 package. It may also be found on the Debian FTP site
5234 <ftpsite>ftp.debian.org</ftpsite> as the file
5235 <ftppath>/debian/doc/package-developer/menu-policy.txt.gz</ftppath>,
5236 or in the equivalent location on your local mirror.
5240 The Debian <tt>menu</tt> package provides a standard
5241 interface between packages providing applications and
5242 documents, and <em>menu programs</em> (either X window
5243 managers or text-based menu programs such as
5244 <prgn>pdmenu</prgn>).
5248 All packages that provide applications that need not be
5249 passed any special command line arguments for normal
5250 operation should register a menu entry for those
5251 applications, so that users of the <tt>menu</tt> package
5252 will automatically get menu entries in their window
5253 managers, as well in shells like <tt>pdmenu</tt>.</p>
5256 Please also refer to the <em>Debian Menu System</em>
5257 documentation that comes with the <tt>menu</tt> package for
5258 information about how to register your applications and web
5264 <heading>Multimedia handlers</heading>
5267 Packages which provide the ability to view/show/play,
5268 compose, edit or print MIME types should register themselves
5269 as such following the current MIME support policy found in
5270 the <tt>mime-policy</tt> files in the <tt>debian-policy</tt>
5271 package. It may also be found on the Debian FTP site
5272 <ftpsite>ftp.debian.org</ftpsite> as the file
5273 <ftppath>/debian/doc/package-developer/mime-policy.txt.gz</ftppath>,
5274 or in the equivalent location on your local mirror.
5278 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
5279 is a mechanism for encoding files and data streams and
5280 providing meta-information about them, in particular their
5281 type (e.g. audio or video) and format (e.g. PNG, HTML,
5286 Registration of MIME type handlers allows programs like mail
5287 user agents and web browsers to to invoke these handlers to
5288 view, edit or display MIME types they don't support
5294 <heading>Keyboard configuration</heading>
5297 To achieve a consistent keyboard configuration so that all
5298 applications interpret a keyboard event the same way, all
5299 programs in the Debian distribution must be configured to
5300 comply with the following guidelines.
5304 The following keys must have the specified interpretations:
5307 <tag><tt><--</tt></tag>
5308 <item><p>delete the character to the left of the cursor</p></item>
5310 <tag><tt>Delete</tt></tag>
5311 <item><p>delete the character to the right of the cursor</p></item>
5313 <tag><tt>Control+H</tt></tag>
5314 <item><p>emacs: the help prefix</p></item>
5317 The interpretation of any keyboard events should be
5318 independent of the terminal that is used, be it a virtual
5319 console, an X terminal emulator, an rlogin/telnet session,
5324 The following list explains how the different programs
5325 should be set up to achieve this:
5330 <item><p><tt><--</tt> generates <tt>KB_Backspace</tt>
5333 <item><p><tt>Delete</tt> generates <tt>KB_Delete</tt> in
5338 X translations are set up to make
5339 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
5340 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
5341 is the vt220 escape code for the `delete character'
5342 key). This must be done by loading the X resources
5343 using <prgn>xrdb</prgn> on all local X displays, not
5344 using the application defaults, so that the
5345 translation resources used correspond to the
5346 <prgn>xmodmap</prgn> settings.</p></item>
5350 The Linux console is configured to make
5351 <tt><--</tt> generate DEL, and <tt>Delete</tt>
5352 generate <tt>ESC [ 3 ~</tt>.</p></item>
5356 X applications are configured so that <tt><</tt>
5357 deletes left, and <tt>Delete</tt> deletes right. Motif
5358 applications already work like this.</p></item>
5360 <item><p>Terminals should have <tt>stty erase ^?</tt> .</p></item>
5364 The <tt>xterm</tt> terminfo entry should have <tt>ESC
5365 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
5366 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.</p></item>
5370 Emacs is programmed to map <tt>KB_Backspace</tt> or
5371 the <tt>stty erase</tt> character to
5372 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
5373 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
5374 <tt>^H</tt> to <tt>help</tt> as always.</p></item>
5378 Other applications use the <tt>stty erase</tt>
5379 character and <tt>kdch1</tt> for the two delete keys,
5380 with ASCII DEL being `delete previous character' and
5381 <tt>kdch1</tt> being `delete character under
5388 This will solve the problem except for the following
5396 Some terminals have a <tt><--</tt> key that cannot
5397 be made to produce anything except <tt>^H</tt>. On
5398 these terminals Emacs help will be unavailable on
5399 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
5400 character takes precedence in Emacs, and has been set
5401 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
5402 available) can be used instead.</p></item>
5406 Some operating systems use <tt>^H</tt> for <tt>stty
5407 erase</tt>. However, modern telnet versions and all
5408 rlogin versions propagate <tt>stty</tt> settings, and
5409 almost all UNIX versions honour <tt>stty erase</tt>.
5410 Where the <tt>stty</tt> settings are not propagated
5411 correctly, things can be made to work by using
5412 <tt>stty</tt> manually.</p></item>
5416 Some systems (including previous Debian versions) use
5417 <prgn>xmodmap</prgn> to arrange for both
5418 <tt><--</tt> and <tt>Delete</tt> to generate
5419 <tt>KB_Delete</tt>. We can change the behavior of
5420 their X clients using the same X resources that we use
5421 to do it for our own clients, or configure our clients
5422 using their resources when things are the other way
5423 around. On displays configured like this
5424 <tt>Delete</tt> will not work, but <tt><--</tt>
5429 Some operating systems have different <tt>kdch1</tt>
5430 settings in their <tt>terminfo</tt> database for
5431 <tt>xterm</tt> and others. On these systems the
5432 <tt>Delete</tt> key will not work correctly when you
5433 log in from a system conforming to our policy, but
5434 <tt><--</tt> will.</p></item>
5440 <heading>Environment variables</heading>
5443 A program must not depend on environment variables to get
5444 reasonable defaults. (That's because these environment
5445 variables would have to be set in a system-wide
5446 configuration file like <file>/etc/profile</file>, which is not
5447 supported by all shells.)</p>
5450 If a program usually depends on environment variables for its
5451 configuration, the program should be changed to fall back to
5452 a reasonable default configuration if these environment
5453 variables are not present. If this cannot be done easily
5454 (e.g., if the source code of a non-free program is not
5455 available), the program must be replaced by a small
5456 `wrapper' shell script which sets the environment variables
5457 if they are not already defined, and calls the original program.</p>
5460 Here is an example of a wrapper script for this purpose:
5462 <example compact="compact">
5464 BAR=${BAR:-/var/lib/fubar}
5466 exec /usr/lib/foo/foo "$@"
5471 Furthermore, as <file>/etc/profile</file> is a configuration
5472 file of the <prgn>base-files</prgn> package, other packages must not
5473 put any environment variables or other commands into that
5479 <heading>Files</heading>
5482 <heading>Binaries</heading>
5485 Two different packages must not install programs with
5486 different functionality but with the same filenames. (The
5487 case of two programs having the same functionality but
5488 different implementations is handled via `alternatives' or
5489 the `Conflicts' mechanism. See <ref id="maintscripts"> and
5490 <ref id="conflicts"> respectively.) If this case happens,
5491 one of the programs must be renamed. The maintainers should
5492 report this to the <tt>debian-devel</tt> mailing list and
5493 try to find a consensus about which program will have to be
5494 renamed. If a consensus cannot be reached, <em>both</em>
5495 programs must be renamed.
5499 By default, when a package is being built, any binaries
5500 created should include debugging information, as well as
5501 being compiled with optimization. You should also turn on
5502 as many reasonable compilation warnings as possible; this
5503 makes life easier for porters, who can then look at build
5504 logs for possible problems. For the C programming language,
5505 this means the following compilation parameters should be
5507 <example compact="compact">
5509 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
5511 install -s # (or use strip on the files in debian/tmp)
5516 Note that by default all installed binaries should be stripped,
5517 either by using the <tt>-s</tt> flag to
5518 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
5519 the binaries after they have been copied into
5520 <file>debian/tmp</file> but before the tree is made into a
5524 Although binaries in the build tree should be compiled with
5525 debugging information by default, it can often be difficult
5526 to debug programs if they are also subjected to compiler
5527 optimization. For this reason, it is recommended to support
5528 the standardized environment
5529 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
5530 contain several flags to change how a package is compiled
5538 The presence of this string means that the package
5539 should be complied with a minimum of optimization.
5540 For C programs, it is best to add <tt>-O0</tt>
5541 to <tt>CFLAGS</tt> (although this is usually the
5542 default). Some programs might fail to build or run at
5543 this level of optimization; it may be necessary to
5544 use <tt>-O1</tt>, for example.
5550 This string means that the debugging symbols should
5551 not be stripped from the binary during installation,
5552 so that debugging information may be included in the + package.
5558 The following makefile snippet is an example of how one may
5559 implement the build options; you will probably have to
5560 massage this example in order to make it work for your
5562 <example compact="compact">
5565 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
5566 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
5567 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
5568 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
5570 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
5575 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
5576 INSTALL_PROGRAM += -s
5582 It is up to the package maintainer to decide what
5583 compilation options are best for the package. Certain
5584 binaries (such as computationally-intensive programs) will
5585 function better with certain flags (<tt>-O3</tt>, for
5586 example); feel free to use them. Please use good judgment
5587 here. Don't use flags for the sake of it; only use them
5588 if there is good reason to do so. Feel free to override
5589 the upstream author's ideas about which compilation
5590 options are best: they are often inappropriate for our
5597 <heading>Libraries</heading>
5599 In general, libraries must have a shared version in the
5600 library package and a static version in the development
5601 package. The shared version must be compiled with
5602 <tt>-fPIC</tt>, and the static version must not be. In
5603 other words, each source unit ( <tt>*.c</tt>, for example,
5604 for C files) will need to be compiled twice.
5607 In some cases, it is acceptable for a library to be
5608 available in static form only; these cases include:
5611 <p>libraries for languages whose shared library support
5612 is immature or unstable</p>
5616 libraries whose interfaces are in flux or under
5617 development (commonly the case when the library's
5618 major version number is zero, or where the ABI breaks
5624 libraries which are explicitly intended to be
5625 available only in static form by their upstream
5629 If a library is available only in static form, then it must follow
5630 the conventions for a development package.
5633 All libraries must have a shared version in the
5634 <tt>lib*</tt> package and a static version in the
5635 <tt>lib*-dev</tt> package. The shared version must be
5636 compiled with <tt>-fPIC</tt>, and the static version must
5637 not be. In other words, each <tt>*.c</tt> file will need to
5638 be compiled twice.</p>
5641 You must specify the gcc option <tt>-D_REENTRANT</tt>
5642 when building a library (either static or shared) to make
5643 the library compatible with LinuxThreads.</p>
5646 Note that all installed shared libraries should be
5648 <example compact="compact">
5649 strip --strip-unneeded <var>your-lib</var>
5651 (The option <tt>--strip-unneeded</tt> makes
5652 <prgn>strip</prgn> remove only the symbols which aren't
5653 needed for relocation processing.) Shared libraries can
5654 function perfectly well when stripped, since the symbols for
5655 dynamic linking are in a separate part of the ELF object
5658 You might also want to use the options
5659 <tt>--remove-section=.comment</tt> and
5660 <tt>--remove-section=.note</tt> on both shared libraries
5661 and executables, and <tt>--strip-debug</tt> on static
5668 Note that under some circumstances it may be useful to
5669 install a shared library unstripped, for example when
5670 building a separate package to support debugging.
5674 Shared object files (often <file>.so</file> files) that are not
5675 public libraries, that is, they are not meant to be linked
5676 to by third party executables (binaries of other packages),
5677 should be installed in subdirectories of the
5678 <file>/usr/lib</file> directory. Such files are exempt from the
5679 rules that govern ordinary shared libraries, except that
5680 they must not be installed executable and should be
5683 A common example are the so-called ``plug-ins'',
5684 internal shared objects that are dynamically loaded by
5685 programs using <manref name="dlopen" section="3">.
5691 Packages containing shared libraries that may be linked to
5692 by other packages' binaries, but which for some
5693 <em>compelling</em> reason can not be installed in
5694 <file>/usr/lib</file> directory, may install the shared library
5695 files in subdirectories of the <file>/usr/lib</file> directory,
5696 in which case they should arrange to add that directory in
5697 <file>/etc/ld.so.conf</file> in the package's post-installation
5698 script, and remove it in the package's post-removal script.
5702 An ever increasing number of packages are using
5703 <prgn>libtool</prgn> to do their linking. The latest GNU
5704 libtools (>= 1.3a) can take advantage of the metadata in the
5705 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
5706 files). The main advantage of <prgn>libtool</prgn>'s
5707 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
5708 store and subsequently access metadata with respect to the
5709 libraries it builds. <prgn>libtool</prgn> will search for
5710 those files, which contain a lot of useful information about
5711 a library (such as library dependency information for static
5712 linking). Also, they're <em>essential</em> for programs
5713 using <tt>libltdl</tt>.<footnote>
5715 Although <prgn>libtool</prgn> is fully capable of
5716 linking against shared libraries which don't have
5717 <tt>.la</tt> files, as it is a mere shell script it can
5718 add considerably to the build time of a
5719 <prgn>libtool</prgn>-using package if that shell script
5720 has to derive all this information from first principles
5721 for each library every time it is linked. With the
5722 advent of <prgn>libtool</prgn> version 1.4 (and to a
5723 lesser extent <prgn>libtool</prgn> version 1.3), the
5724 <file>.la</file> files also store information about
5725 inter-library dependencies which cannot necessarily be
5726 derived after the <file>.la</file> file is deleted.
5732 Packages that use <prgn>libtool</prgn> to create shared
5733 libraries should include the <file>.la</file> files in the
5734 <tt>-dev</tt> package, unless the package relies on
5735 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
5736 the <tt>.la</tt> files must go in the run-time library
5741 You must make sure that you use only released versions of
5742 shared libraries to build your packages; otherwise other
5743 users will not be able to run your binaries
5744 properly. Producing source packages that depend on
5745 unreleased compilers is also usually a bad
5751 <heading>Shared libraries</heading>
5754 Packages involving shared libraries should be split up
5755 into several binary packages.</p>
5758 For a straightforward library which has a development
5759 environment and a runtime kit including just shared
5760 libraries you need to create two packages:
5761 <file><var>libraryname</var><var>soversion</var></file>, where
5762 <file><var>soversion</var></file> is the version number in the
5763 soname of the shared library<footnote>
5765 The soname is the shared object name: it's the thing
5766 that has to match exactly between building an executable
5767 and running it for the dynamic linker to be able run the
5768 program. For example, if the soname of the library is
5769 <file>libfoo.so.6</file>, the library package would be
5770 called <file>libfoo6</file>.
5773 and <tt><var>libraryname</var><var>soversion</var>-dev</tt>.
5774 Alternatively, if it would be confusing to directly append
5775 <var>soversion</var> to <var>libraryname</var> (e.g. because
5776 <var>libraryname</var> itself ends in a number), you may use
5777 <tt><var>libraryname</var>-<var>soversion</var></tt> and
5778 <tt><var>libraryname</var>-<var>soversion</var>-dev</tt>
5783 If you prefer only to support one development version at a
5784 time you may name the development package
5785 <file><var>libraryname</var>-dev</file>; otherwise you may need
5786 to use <prgn>dpkg</prgn>'s Conflicts mechanism (see <ref
5787 id="conflicts">) to ensure that the user only installs one
5788 development version at a time (as different development
5789 versions are likely to have the same header files in them,
5790 which would cause a filename clash if both were installed).
5791 Typically the development version should also have an exact
5792 version dependency on the runtime library, to make sure that
5793 compilation and linking happens correctly. The
5794 <tt>${Source-Version}</tt> substitution variable can be
5795 useful for this purpose.
5799 Packages which use the shared library should have a
5800 dependency on the name of the shared library package,
5801 <file><var>libraryname</var><var>soversion</var></file>. When
5802 the soname changes you can have both versions of the library
5803 installed while migrating from the old library to the new.
5807 If your package has some run-time support programs which use
5808 the shared library you must not put them in the shared
5809 library package. If you do that then you won't be able to
5810 install several versions of the shared library without
5811 getting filename clashes. Instead, either create a third
5812 package for the runtime binaries (this package might
5813 typically be named <tt><var>libraryname</var>-runtime</tt>;
5814 note the absence of the <var>soversion</var> in the package
5815 name), or if the development package is small you may
5816 include them in there.
5820 If you have several shared libraries built from the same
5821 source tree you may lump them all together into a single
5822 shared library package, provided that you change all of
5823 their sonames at once (so that you don't get filename
5824 clashes if you try to install different versions of the
5825 combined shared libraries package).
5829 Shared libraries should not be installed executable, since
5830 the dynamic linker does not require this and trying to
5831 execute a shared library usually results in a core dump.
5836 <heading>Scripts</heading>
5839 All command scripts, including the package maintainer
5840 scripts inside the package and used by <prgn>dpkg</prgn>,
5841 should have a <tt>#!</tt> line naming the shell to be used
5842 to interpret them.</p>
5845 In the case of Perl scripts this should be
5846 <tt>#!/usr/bin/perl</tt>.</p>
5849 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
5850 should almost certainly start with <tt>set -e</tt> so that
5851 errors are detected. Every script should use
5852 <tt>set -e</tt> or check the exit status of <em>every</em>
5856 The standard shell interpreter <file>/bin/sh</file> can be a
5857 symbolic link to any POSIX compatible shell, if <tt>echo
5858 -n</tt> does not generate a newline.<footnote>
5860 Debian policy specifies POSIX behavior for
5861 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
5862 use in the Linux community (in particular including this
5863 policy, the Linux kernel source, many Debian scripts,
5864 etc.). This <tt>echo -n</tt> mechanism is valid but not
5865 required under POSIX, hence this explicit addition.
5866 Also, rumour has it that this shall be mandated under
5870 Thus, shell scripts specifying <file>/bin/sh</file> as
5871 interpreter should only use POSIX features. If a script
5872 requires non-POSIX features from the shell interpreter, the
5873 appropriate shell must be specified in the first line of the
5874 script (e.g., <tt>#!/bin/bash</tt>) and the package must
5875 depend on the package providing the shell (unless the shell
5876 package is marked `Essential', as in the case of
5881 You may wish to restrict your script to POSIX features when
5882 possible so that it may use <file>/bin/sh</file> as its
5883 interpreter. If your script works with <prgn>ash</prgn>,
5884 it's probably POSIX compliant, but if you are in doubt, use
5885 <file>/bin/bash</file>.
5889 Perl scripts should check for errors when making any
5890 system calls, including <tt>open</tt>, <tt>print</tt>,
5891 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
5895 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
5896 scripting languages. See <em>Csh Programming Considered
5897 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
5898 can be found at <url
5899 id="http://language.perl.com/versus/csh.whynot">.<footnote>
5901 It can also be found on
5902 <url id="http://www.cpan.org/doc/FMTEYEWTK/versus/csh.whynot">
5903 or on the ftp site <ftpsite>ftp.cpan.org</ftpsite> as
5904 <ftppath>/pub/perl/CPAN/doc/FMTEYEWTK/versus/csh.whynot</ftppath>.
5907 If an upstream package comes with <prgn>csh</prgn> scripts
5908 then you must make sure that they start with
5909 <tt>#!/bin/csh</tt> and make your package depend on the
5910 <prgn>c-shell</prgn> virtual package.
5914 Any scripts which create files in world-writeable
5915 directories (e.g., in <file>/tmp</file>) must use a
5916 mechanism which will fail if a file with the same name
5920 The Debian base system provides the <prgn>tempfile</prgn>
5921 and <prgn>mktemp</prgn> utilities for use by scripts for
5922 this purpose.</p></sect>
5926 <heading>Symbolic links</heading>
5929 In general, symbolic links within a top-level directory
5930 should be relative, and symbolic links pointing from one
5931 top-level directory into another should be absolute. (A
5932 top-level directory is a sub-directory of the root
5933 directory <file>/</file>.)</p>
5936 In addition, symbolic links should be specified as short as
5937 possible, i.e., link targets like <file>foo/../bar</file> are
5941 Note that when creating a relative link using
5942 <prgn>ln</prgn> it is not necessary for the target of the
5943 link to exist relative to the working directory you're
5944 running <prgn>ln</prgn> from, nor is it necessary to change
5945 directory to the directory where the link is to be made.
5946 Simply include the string that should appear as the target
5947 of the link (this will be a pathname relative to the
5948 directory in which the link resides) as the first argument
5949 to <prgn>ln</prgn>.</p>
5952 For example, in your <prgn>Makefile</prgn> or
5953 <file>debian/rules</file>, you can do things like:
5954 <example compact="compact">
5955 ln -fs gcc $(prefix)/bin/cc
5956 ln -fs gcc debian/tmp/usr/bin/cc
5957 ln -fs ../sbin/sendmail $(prefix)/bin/runq
5958 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
5962 A symbolic link pointing to a compressed file should always
5963 have the same file extension as the referenced file. (For
5964 example, if a file <file>foo.gz</file> is referenced by a
5965 symbolic link, the filename of the link has to end with
5966 `<file>.gz</file>' too, as in <file>bar.gz</file>.)
5971 <heading>Device files</heading>
5974 Packages must not include device files in the package file
5978 If a package needs any special device files that are not
5979 included in the base system, it must call
5980 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
5981 after notifying the user<footnote>
5983 This notification could be done via a (low-priority)
5984 debconf message, or an echo (printf) statement.
5990 Packages must not remove any device files in the
5991 <prgn>postrm</prgn> or any other script. This is left to the
5992 system administrator.</p>
5995 Debian uses the serial devices
5996 <file>/dev/ttyS*</file>. Programs using the old
5997 <file>/dev/cu*</file> devices should be changed to use
5998 <file>/dev/ttyS*</file>.</p>
6001 <sect id="config-files">
6002 <heading>Configuration files</heading>
6004 <heading>Definitions</heading>
6007 <tag>configuration file</tag>
6010 A file that affects the operation of a program, or
6011 provides site- or host-specific information, or
6012 otherwise customizes the behavior of a program.
6013 Typically, configuration files are intended to be
6014 modified by the system administrator (if needed or
6015 desired) to conform to local policy or to provide
6016 more useful site-specific behavior.
6020 <tag><tt>conffile</tt></tag>
6023 A file listed in a package's <tt>conffiles</tt>
6024 file, and is treated specially by <prgn>dpkg</prgn>
6025 (see <ref id="configdetails">).
6032 The distinction between these two is important; they are
6033 not interchangeable concepts. Almost all
6034 <tt>conffile</tt>s are configuration files, but many
6035 configuration files are not <tt>conffiles</tt>.
6039 Note that a script that embeds configuration information
6040 (such as most of the files in <file>/etc/default</file> and
6041 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6042 configuration file and should be treated as such.
6047 <heading>Location</heading>
6049 Any configuration files created or used by your package
6050 must reside in <file>/etc</file>. If there are several you
6051 should consider creating a subdirectory of <file>/etc</file>
6052 named after your package.</p>
6055 If your package creates or uses configuration files
6056 outside of <file>/etc</file>, and it is not feasible to modify
6057 the package to use the <file>/etc</file>, you should still put
6058 the files in <file>/etc</file> and create symbolic links to
6059 those files from the location that the package
6064 <heading>Behavior</heading>
6066 Configuration file handling must conform to the following
6068 <list compact="compact">
6071 local changes must be preserved during a package
6077 configuration files must be preserved when the
6078 package is removed, and only deleted when the
6086 The easy way to achieve this behavior is to make the
6087 configuration file a <tt>conffile</tt>. This is
6088 appropriate only if it is possible to distribute a default
6089 version that will work for most installations, although
6090 some system administrators may choose to modify it. This
6091 implies that the default version will be part of the
6092 package distribution, and must not be modified by the
6093 maintainer scripts during installation (or at any other
6098 In order to ensure that local changes are preserved
6099 correctly, no package may contain or make hard links to
6100 conffiles.<footnote>
6102 Rationale: There are two problems with hard links.
6103 The first is that some editors break the link while
6104 editing one of the files, so that the two files may
6105 unwittingly become unlinked and different. The second
6106 is that <prgn>dpkg</prgn> might break the hard link
6107 while upgrading <tt>conffile</tt>s.
6113 The other way to do it is via the maintainer scripts. In
6114 this case, the configuration file must not be listed as a
6115 <tt>conffile</tt> and must not be part of the package
6116 distribution. If the existence of a file is required for
6117 the package to be sensibly configured it is the
6118 responsibility of the package maintainer to provide
6119 maintainer scripts which correctly create, update and
6120 maintain the file and remove it on purge. (See <ref
6121 id="maintainerscripts"> for more information.) These
6122 scripts must be idempotent (i.e., must work correctly if
6123 <prgn>dpkg</prgn> needs to re-run them due to errors
6124 during installation or removal), must cope with all the
6125 variety of ways <prgn>dpkg</prgn> can call maintainer
6126 scripts, must not overwrite or otherwise mangle the user's
6127 configuration without asking, must not ask unnecessary
6128 questions (particularly during upgrades), and otherwise be
6133 The scripts are not required to configure every possible
6134 option for the package, but only those necessary to get
6135 the package running on a given system. Ideally the
6136 sysadmin should not have to do any configuration other
6137 than that done (semi-)automatically by the
6138 <prgn>postinst</prgn> script.
6142 A common practice is to create a script called
6143 <file><var>package</var>-configure</file> and have the
6144 package's <prgn>postinst</prgn> call it if and only if the
6145 configuration file does not already exist. In certain
6146 cases it is useful for there to be an example or template
6147 file which the maintainer scripts use. Such files should
6148 be in <file>/usr/share/<var>package</var></file> or
6149 <file>/usr/lib/<var>package</var></file> (depending on whether
6150 they are architecture-independent or not). There should
6151 be symbolic links to them from
6152 <file>/usr/share/doc/<var>package</var>/examples</file> if
6153 they are examples, and should be perfectly ordinary
6154 <prgn>dpkg</prgn>-handled files (<em>not</em>
6155 configuration files).
6159 These two styles of configuration file handling must
6160 not be mixed, for that way lies madness:
6161 <prgn>dpkg</prgn> will ask about overwriting the file
6162 every time the package is upgraded.
6167 <heading>Sharing configuration files</heading>
6169 Packages which specify the same file as a
6170 <tt>conffile</tt> must be tagged as <em>conflicting</em>
6171 with each other. (This is an instance of the general rule
6172 about not sharing files. Note that neither alternatives
6173 nor diversions are likely to be appropriate in this case;
6174 in particular, <prgn>dpkg</prgn> does not handle diverted
6175 <tt>conffile</tt>s well.)
6179 The maintainer scripts must not alter a <tt>conffile</tt>
6180 of <em>any</em> package, including the one the scripts
6185 If two or more packages use the same configuration file
6186 and it is reasonable for both to be installed at the same
6187 time, one of these packages must be defined as
6188 <em>owner</em> of the configuration file, i.e., it will be
6189 the package which handles that file as a configuration
6190 file. Other packages that use the configuration file must
6191 depend on the owning package if they require the
6192 configuration file to operate. If the other package will
6193 use the configuration file if present, but is capable of
6194 operating without it, no dependency need be declared.</p>
6197 If it is desirable for two or more related packages to
6198 share a configuration file <em>and</em> for all of the
6199 related packages to be able to modify that configuration
6200 file, then the following should be done:
6201 <enumlist compact="compact">
6204 One of the related packages (the "owning" package)
6205 will manage the configuration file with maintainer
6206 scripts as described in the previous section.
6211 The owning package should also provide a program
6212 that the other packages may use to modify the
6218 The related packages must use the provided program
6219 to make any desired modifications to the
6220 configuration file. They should either depend on
6221 the core package to guarantee that the configuration
6222 modifier program is available or accept gracefully
6223 that they cannot modify the configuration file if it
6224 is not. (This is in addition to the fact that the
6225 configuration file may not even be present in the
6233 Sometimes it's appropriate to create a new package which
6234 provides the basic infrastructure for the other packages
6235 and which manages the shared configuration files. (The
6236 <tt>sgml-base</tt> package is a good example.)
6241 <heading>User configuration files ("dotfiles")</heading>
6244 The files in <file>/etc/skel</file> will automatically be
6245 copied into new user accounts by <prgn>adduser</prgn>.
6246 No other program should reference the files in
6247 <file>/etc/skel</file>.
6251 Therefore, if a program needs a dotfile to exist in
6252 advance in <file>$HOME</file> to work sensibly, that dotfile
6253 should be installed in <file>/etc/skel</file> and treated as a
6258 However, programs that require dotfiles in order to
6259 operate sensibly (dotfiles that they do not create
6260 themselves automatically, that is) are a bad thing.
6261 Furthermore, programs should be configured by the Debian
6262 default installation to behave as closely to the upstream
6263 default behaviour as possible.
6267 Therefore, if a program in a Debian package needs to be
6268 configured in some way in order to operate sensibly, that
6269 should be done using a site-wide configuration file placed
6270 in <file>/etc</file>. Only if the program doesn't support a
6271 site-wide default configuration and the package maintainer
6272 doesn't have time to add it may a default per-user file be
6273 placed in <file>/etc/skel</file>.
6277 <file>/etc/skel</file> should be as empty as we can make it.
6278 This is particularly true because there is no easy (or
6279 necessarily desirable) mechanism for ensuring that the
6280 appropriate dotfiles are copied into the accounts of
6281 existing users when a package is installed.
6287 <heading>Log files</heading>
6289 Log files should usually be named
6290 <file>/var/log/<var>package</var>.log</file>. If you have many
6291 log files, or need a separate directory for permission
6292 reasons (<file>/var/log</file> is writable only by
6293 <file>root</file>), you should usually create a directory named
6294 <file>/var/log/<var>package</var></file> and place your log
6299 Log files must be rotated occasionally so that they don't
6300 grow indefinitely; the best way to do this is to drop a log
6301 rotation configuration file into the directory
6302 <file>/etc/logrotate.d</file> and use the facilities provided by
6303 logrotate.<footnote>
6305 The traditional approach to log files has been to set up
6306 <em>ad hoc</em> log rotation schemes using simple shell
6307 scripts and cron. While this approach is highly
6308 customizable, it requires quite a lot of sysadmin work.
6309 Even though the original Debian system helped a little
6310 by automatically installing a system which can be used
6311 as a template, this was deemed not enough.
6315 The use of <prgn>logrotate</prgn>, a program developed
6316 by Red Hat, is better, as it centralizes log management.
6317 It has both a configuration file
6318 (<file>/etc/logrotate.conf</file>) and a directory where
6319 packages can drop their individual log rotation
6320 configurations (<file>/etc/logrotate.d</file>).
6323 Here is a good example for a logrotate config
6324 file (for more information see <manref name="logrotate"
6326 <example compact="compact">
6332 /etc/init.d/foo force-reload
6336 This rotates all files under <file>/var/log/foo</file>, saves 12
6337 compressed generations, and forces the daemon to reload its
6338 configuration information after the log rotation.
6342 Log files should be removed when the package is
6343 purged (but not when it is only removed). This should be
6344 done by the <prgn>postrm</prgn> script when it is called
6345 with the argument <tt>purge</tt> (see <ref
6346 id="removedetails">).
6351 <heading>Permissions and owners</heading>
6354 The rules in this section are guidelines for general use.
6355 If necessary you may deviate from the details below.
6356 However, if you do so you must make sure that what is done
6357 is secure and you should try to be as consistent as possible
6358 with the rest of the system. You should probably also
6359 discuss it on <prgn>debian-devel</prgn> first.
6363 Files should be owned by <tt>root.root</tt>, and made
6364 writable only by the owner and universally readable (and
6365 executable, if appropriate), that is mode 644 or 755.
6369 Directories should be mode 755 or (for group-writability)
6370 mode 2775. The ownership of the directory should be
6371 consistent with its mode: if a directory is mode 2775, it
6372 should be owned by the group that needs write access to
6377 Setuid and setgid executables should be mode 4755 or 2755
6378 respectively, and owned by the appropriate user or group.
6379 They should not be made unreadable (modes like 4711 or
6380 2711 or even 4111); doing so achieves no extra security,
6381 because anyone can find the binary in the freely available
6382 Debian package; it is merely inconvenient. For the same
6383 reason you should not restrict read or execute permissions
6384 on non-set-id executables.
6388 Some setuid programs need to be restricted to particular
6389 sets of users, using file permissions. In this case they
6390 should be owned by the uid to which they are set-id, and by
6391 the group which should be allowed to execute them. They
6392 should have mode 4754; again there is no point in making
6393 them unreadable to those users who must not be allowed to
6398 It is possible to arrange that the system administrator can
6399 reconfigure the package to correspond to their local
6400 security policy by changing the permissions on a binary:
6401 they can do this by using <prgn>dpkg-statoverride</prgn>, as
6402 described below.<footnote>
6404 Ordinary files installed by <prgn>dpkg</prgn> (as
6405 opposed to <tt>conffile</tt>s and other similar objects)
6406 normally have their permissions reset to the distributed
6407 permissions when the package is reinstalled. However,
6408 the use of <prgn>dpkg-statoverride</prgn> overrides this
6409 default behaviour. If you use this method, you should
6410 remember to describe <prgn>dpkg-statoverride</prgn> in
6411 the package documentation; being a relatively new
6412 addition to Debian, it is probably not yet well-known.
6415 Another method you should consider is to create a group for
6416 people allowed to use the program(s) and make any setuid
6417 executables executable only by that group.
6421 If you need to create a new user or group for your package
6422 there are two possibilities. Firstly, you may need to
6423 make some files in the binary package be owned by this
6424 user or group, or you may need to compile the user or
6425 group id (rather than just the name) into the binary
6426 (though this latter should be avoided if possible, as in
6427 this case you need a statically allocated id).</p>
6430 If you need a statically allocated id, you must ask for a
6431 user or group id from the <tt>base-passwd</tt> maintainer,
6432 and must not release the package until you have been
6433 allocated one. Once you have been allocated one you must
6434 either make the package depend on a version of the
6435 <tt>base-passwd</tt> package with the id present in
6436 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
6437 your package to create the user or group itself with the
6438 correct id (using <tt>adduser</tt>) in its
6439 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
6440 the <prgn>postinst</prgn> is to be preferred if it is
6441 possible, otherwise a pre-dependency will be needed on the
6442 <tt>adduser</tt> package.)
6446 On the other hand, the program might be able to determine
6447 the uid or gid from the user or group name at runtime, so
6448 that a dynamically allocated id can be used. In this case
6449 you should choose an appropriate user or group name,
6450 discussing this on <prgn>debian-devel</prgn> and checking
6451 with the base system maintainer that it is unique and that
6452 they do not wish you to use a statically allocated id
6453 instead. When this has been checked you must arrange for
6454 your package to create the user or group if necessary using
6455 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
6456 <prgn>postinst</prgn> script (again, the latter is to be
6457 preferred if it is possible).
6461 Note that changing the numeric value of an id associated
6462 with a name is very difficult, and involves searching the
6463 file system for all appropriate files. You need to think
6464 carefully whether a static or dynamic id is required, since
6465 changing your mind later will cause problems.
6468 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
6470 This section is not intended as policy, but as a
6471 description of the use of <prgn>dpkg-statoverride</prgn>.
6475 <prgn>dpkg-statoverride</prgn> is a replacement for the
6476 deprecated <tt>suidmanager</tt> package. Packages which
6477 previously used <tt>suidmanager</tt> should have a
6478 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
6479 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
6480 and <tt>suidunregister</tt> should now be simply removed
6481 from the maintainer scripts.
6485 If a system administrator wishes to have a file (or
6486 directory or other such thing) installed with owner and
6487 permissions different from those in the distributed Debian
6488 package, he can use the <prgn>dpkg-statoverride</prgn>
6489 program to instruct <prgn>dpkg</prgn> to use the different
6490 settings every time the file is installed. Thus the
6491 package maintainer should distribute the files with their
6492 normal permissions, and leave it for the system
6493 administrator to make any desired changes. For example, a
6494 daemon which is normally required to be setuid root, but
6495 in certain situations could be used without being setuid,
6496 should be installed setuid in the <tt>.deb</tt>. Then the
6497 local system administrator can change this if they wish.
6498 If there are two standard ways of doing it, the package
6499 maintainer can use <tt>debconf</tt> to find out the
6500 preference, and call <prgn>dpkg-statoverride</prgn> in the
6501 maintainer script if necessary to accommodate the system
6502 administrator's choice.
6506 Given the above, <prgn>dpkg-statoverride</prgn> is
6507 essentially a tool for system administrators and would not
6508 normally be needed in the maintainer scripts. There is
6509 one type of situation, though, where calls to
6510 <prgn>dpkg-statoverride</prgn> would be needed in the
6511 maintainer scripts, and that involves packages which use
6512 dynamically allocated user or group ids. In such a
6513 situation, something like the following idiom can be very
6514 helpful in the package's <prgn>postinst</prgn>, where
6515 <tt>sysuser</tt> is a dynamically allocated id:
6517 for i in /usr/bin/foo /usr/sbin/bar
6519 if ! dpkg-statoverride --list $i >/dev/null
6521 dpkg-statoverride --update --add sysuser root 4755 $i
6525 The corresponding <tt>dpkg-statoverride --remove</tt>
6526 calls can then be made unconditionally when the package is
6533 <chapt id="customized-programs">
6534 <heading>Customized programs</heading>
6536 <sect id="arch-spec">
6537 <heading>Architecture specification strings</heading>
6540 If a program needs to specify an <em>architecture specification
6541 string</em> in some place, the following format should be
6542 used: <var>arch</var>-<var>os</var><footnote>
6544 The following architectures and operating systems are
6545 currently recognised by <prgn>dpkg-archictecture</prgn>.
6546 The architecture, <tt><var>arch</var></tt>, is one of
6547 the following: <tt>alpha</tt>, <tt>arm</tt>,
6548 <tt>hppa</tt>, <tt>i386</tt>, <tt>ia64</tt>,
6549 <tt>m68k</tt>, <tt>mips</tt>, <tt>mipsel</tt>,
6550 <tt>powerpc</tt>, <tt>s390</tt>, <tt>sh</tt>,
6551 <tt>sheb</tt>, <tt>sparc</tt> and <tt>sparc64</tt>. The
6552 operating system, <tt><var>os</var></tt>, is one of:
6553 <tt>linux</tt>, <tt>gnu</tt>, <tt>freebsd</tt> and
6554 <tt>openbsd</tt>. Use of <tt>gnu</tt> in this string is
6555 reserved for the GNU/Hurd operating system.
6561 Note that we don't want to use
6562 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
6563 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
6564 since this would make our programs incompatible with other
6565 Linux distributions. We also don't use something like
6566 <tt><var>arch</var>-unknown-linux</tt>, since the
6567 <tt>unknown</tt> does not look very good.
6572 <heading>Daemons</heading>
6575 The configuration files <file>/etc/services</file>,
6576 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
6577 by the <prgn>netbase</prgn> package and must not be modified
6582 If a package requires a new entry in one of these files, the
6583 maintainer should get in contact with the
6584 <prgn>netbase</prgn> maintainer, who will add the entries
6585 and release a new version of the <prgn>netbase</prgn>
6590 The configuration file <file>/etc/inetd.conf</file> must not be
6591 modified by the package's scripts except via the
6592 <prgn>update-inetd</prgn> script or the
6593 <file>DebianNet.pm</file> Perl module. See their documentation
6594 for details on how to add entries.
6598 If a package wants to install an example entry into
6599 <file>/etc/inetd.conf</file>, the entry must be preceded with
6600 exactly one hash character (<tt>#</tt>). Such lines are
6601 treated as `commented out by user' by the
6602 <prgn>update-inetd</prgn> script and are not changed or
6603 activated during package updates.
6608 <heading>Using pseudo-ttys and modifying wtmp, utmp and
6612 Some programs need to create pseudo-ttys. This should be done
6613 using Unix98 ptys if the C library supports it. The resulting
6614 program must not be installed setuid root, unless that
6615 is required for other functionality.
6619 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
6620 <file>/var/log/lastlog</file> must be installed writeable by
6621 group <tt>utmp</tt>. Programs which need to modify those
6622 files must be installed setgid <tt>utmp</tt>.
6627 <heading>Editors and pagers</heading>
6630 Some programs have the ability to launch an editor or pager
6631 program to edit or display a text document. Since there are
6632 lots of different editors and pagers available in the Debian
6633 distribution, the system administrator and each user should
6634 have the possibility to choose his/her preferred editor and
6639 In addition, every program should choose a good default
6640 editor/pager if none is selected by the user or system
6645 Thus, every program that launches an editor or pager must
6646 use the EDITOR or PAGER environment variable to determine
6647 the editor or pager the user wishes to use. If these
6648 variables are not set, the programs <file>/usr/bin/editor</file>
6649 and <file>/usr/bin/pager</file> should be used, respectively.
6653 These two files are managed through the <prgn>dpkg</prgn>
6654 `alternatives' mechanism. Thus every package providing an
6655 editor or pager must call the
6656 <prgn>update-alternatives</prgn> script to register these
6661 If it is very hard to adapt a program to make use of the
6662 EDITOR or PAGER variables, that program may be configured to
6663 use <file>/usr/bin/sensible-editor</file> and
6664 <file>/usr/bin/sensible-pager</file> as the editor or pager
6665 program respectively. These are two scripts provided in the
6666 Debian base system that check the EDITOR and PAGER variables
6667 and launch the appropriate program, and fall back to
6668 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
6669 variable is not set.
6673 A program may also use the VISUAL environment variable to
6674 determine the user's choice of editor. If it exists, it
6675 should take precedence over EDITOR. This is in fact what
6676 <file>/usr/bin/sensible-editor</file> does.
6680 It is not required for a package to depend on
6681 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
6682 package to provide such virtual packages.<footnote>
6684 The Debian base system already provides an editor and a
6691 <sect id="web-appl">
6692 <heading>Web servers and applications</heading>
6695 This section describes the locations and URLs that should
6696 be used by all web servers and web applications in the
6704 Cgi-bin executable files are installed in the
6706 <example compact="compact">
6707 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
6709 and should be referred to as
6710 <example compact="compact">
6711 http://localhost/cgi-bin/<var>cgi-bin-name</var>
6716 <item><p>Access to HTML documents</p>
6719 HTML documents for a package are stored in
6720 <file>/usr/share/doc/<var>package</var></file>
6721 and can be referred to as
6722 <example compact="compact">
6723 http://localhost/doc/<var>package</var>/<var>filename</var>
6727 The web server should restrict access to the document
6728 tree so that only clients on the same host can read
6729 the documents. If the web server does not support such
6730 access controls, then it should not provide access at
6731 all, or ask about providing access during installation.
6735 <item><p>Web Document Root</p>
6738 Web Applications should try to avoid storing files in
6739 the Web Document Root. Instead they should use the
6740 /usr/share/doc/<var>package</var> directory for
6741 documents and register the Web Application via the
6742 menu package. If access to the web document root is
6743 unavoidable then use
6744 <example compact="compact">
6747 as the Document Root. This might be just a symbolic
6748 link to the location where the system administrator
6749 has put the real document root.
6753 </enumlist></p></sect>
6756 <sect id="mail-transport-agents">
6757 <heading>Mail transport, delivery and user agents</heading>
6760 Debian packages which process electronic mail, whether mail
6761 user agents (MUAs) or mail transport agents (MTAs), must
6762 ensure that they are compatible with the configuration
6763 decisions below. Failure to do this may result in lost
6764 mail, broken <tt>From:</tt> lines, and other serious brain
6769 The mail spool is <file>/var/mail</file> and the interface to
6770 send a mail message is <file>/usr/sbin/sendmail</file> (as per
6771 the FHS). On older systems, the mail spool may be
6772 physically located in <file>/var/spool/mail</file>, but all
6773 access to the mail spool should be via the
6774 <file>/var/mail</file> symlink. The mail spool is part of the
6775 base system and not part of the MTA package.
6779 All Debian MUAs, MTAs, MDAs and other mailbox accessing
6780 programs (such as IMAP daemons) must lock the mailbox in an
6781 NFS-safe way. This means that <tt>fcntl()</tt> locking must
6782 be combined with dot locking. To avoid deadlocks, a program
6783 should use <tt>fcntl()</tt> first and dot locking after
6784 this, or alternatively implement the two locking methods in
6785 a non blocking way<footnote>
6787 If it is not possible to establish both locks, the
6788 system shouldn't wait for the second lock to be
6789 established, but remove the first lock, wait a (random)
6790 time, and start over locking again.
6792 </footnote>. Using the functions <tt>maillock</tt> and
6793 <tt>mailunlock</tt> provided by the
6794 <tt>liblockfile*</tt><footnote>
6796 You will need to depend on <tt>liblockfile1
6797 (>>1.01)</tt> to use these functions.
6799 </footnote> packages is the recommended way to realize this.
6803 Mailboxes are generally mode 660
6804 <tt><var>user</var>.mail</tt> unless the system
6805 administrator has chosen otherwise. A MUA may remove a
6806 mailbox (unless it has nonstandard permissions) in which
6807 case the MTA or another MUA must recreate it if needed.
6808 Mailboxes must be writable by group mail.
6812 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
6813 be setgid mail to do the locking mentioned above (and
6814 must obviously avoid accessing other users' mailboxes
6815 using this privilege).</p>
6818 <file>/etc/aliases</file> is the source file for the system mail
6819 aliases (e.g., postmaster, usenet, etc.), it is the one
6820 which the sysadmin and <prgn>postinst</prgn> scripts may
6821 edit. After <file>/etc/aliases</file> is edited the program or
6822 human editing it must call <prgn>newaliases</prgn>. All MTA
6823 packages must come with a <prgn>newaliases</prgn> program,
6824 even if it does nothing, but older MTA packages did not do
6825 this so programs should not fail if <prgn>newaliases</prgn>
6826 cannot be found. Note that because of this, all MTA
6827 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
6828 <tt>Replaces: mail-transport-agent</tt> control file
6833 The convention of writing <tt>forward to
6834 <var>address</var></tt> in the mailbox itself is not
6835 supported. Use a <tt>.forward</tt> file instead.</p>
6838 The <prgn>rmail</prgn> program used by UUCP
6839 for incoming mail should be <file>/usr/sbin/rmail</file>.
6840 Likewise, <prgn>rsmtp</prgn>, for receiving
6841 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
6845 If your package needs to know what hostname to use on (for
6846 example) outgoing news and mail messages which are generated
6847 locally, you should use the file <file>/etc/mailname</file>. It
6848 will contain the portion after the username and <tt>@</tt>
6849 (at) sign for email addresses of users on the machine
6850 (followed by a newline).
6854 Such package should check for the existence of this file
6855 when it is being configured. If it exists, it should be
6856 used without comment, although an MTA's configuration script
6857 may wish to prompt the user even if it finds that this file
6858 exists. If the file does not exist, the package should
6859 prompt the user for the value (preferably using
6860 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
6861 as well as using it in the package's configuration. The
6862 prompt should make it clear that the name will not just be
6863 used by that package. For example, in this situation the
6864 <tt>inn</tt> package could say something like:
6865 <example compact="compact">
6866 Please enter the `mail name' of your system. This is the
6867 hostname portion of the address to be shown on outgoing
6868 news and mail messages. The default is
6869 <var>syshostname</var>, your system's host name. Mail
6870 name [`<var>syshostname</var>']:
6872 where <var>syshostname</var> is the output of <tt>hostname
6878 <heading>News system configuration</heading>
6881 All the configuration files related to the NNTP (news)
6882 servers and clients should be located under
6883 <file>/etc/news</file>.</p>
6886 There are some configuration issues that apply to a number
6887 of news clients and server packages on the machine. These
6891 <tag><file>/etc/news/organization</file></tag>
6892 <item><p>A string which should appear as the
6893 organization header for all messages posted
6894 by NNTP clients on the machine</p></item>
6896 <tag><file>/etc/news/server</file></tag>
6897 <item><p>Contains the FQDN of the upstream NNTP
6898 server, or localhost if the local machine is
6899 an NNTP server.</p></item>
6902 Other global files may be added as required for cross-package news
6903 configuration.</p></sect>
6907 <heading>Programs for the X Window System</heading>
6910 <heading>Providing X support and package priorities</heading>
6913 Programs that can be configured with support for the X
6914 Window System must be configured to do so and must declare
6915 any package dependencies necessary to satisfy their
6916 runtime requirements when using the X Window System. If
6917 such a package is of higher priority than the X packages
6918 on which it depends, it is required that either the
6919 X-specific components be split into a separate package, or
6920 that an alternative version of the package, which includes
6921 X support, be provided, or that the package's priority be
6927 <heading>Packages providing an X server</heading>
6930 Packages that provide an X server that, directly or
6931 indirectly, communicates with real input and display
6932 hardware should declare in their control data that they
6933 provide the virtual package <tt>xserver</tt>.<footnote>
6935 This implements current practice, and provides an
6936 actual policy for usage of the <tt>xserver</tt>
6937 virtual package which appears in the virtual packages
6938 list. In a nutshell, X servers that interface
6939 directly with the display and input hardware or via
6940 another subsystem (e.g., GGI) should provide
6941 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
6942 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
6949 <heading>Packages providing a terminal emulator</heading>
6952 Packages that provide a terminal emulator for the X Window
6953 System which meet the criteria listed below should declare
6954 in their control data that they provide the virtual
6955 package <tt>x-terminal-emulator</tt>. They should also
6956 register themselves as an alternative for
6957 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
6962 To be an <tt>x-terminal-emulator</tt>, a program must:
6963 <list compact="compact">
6965 Be able to emulate a DEC VT100 terminal, or a
6966 compatible terminal.
6970 Support the command-line option <tt>-e
6971 <var>command</var></tt>, which creates a new
6972 terminal window<footnote>
6974 "New terminal window" does not necessarily mean
6975 a new top-level X window directly parented by
6976 the window manager; it could, if the terminal
6977 emulator application were so coded, be a new
6978 "view" in a multiple-document interface (MDI).
6981 and runs the specified <var>command</var>.
6985 Support the command-line option <tt>-T
6986 <var>title</var></tt>, which creates a new terminal
6987 window with the window title <var>title</var>.
6994 <heading>Packages providing a window manager</heading>
6997 Packages that provide a window manager should declare in
6998 their control data that they provide the virtual package
6999 <tt>x-window-manager</tt>. They should also register
7000 themselves as an alternative for
7001 <file>/usr/bin/x-window-manager</file>, with a priority
7002 calculated as follows:
7003 <list compact="compact">
7004 <item><p>Start with a priority of 20.</p></item>
7008 If the window manager supports the Debian menu
7009 system, add 20 points if this support is available
7010 in the package's default configuration (i.e., no
7011 configuration files belonging to the system or user
7012 have to be edited to activate the feature); if
7013 configuration files must be modified, add only 10
7019 If the window manager complies with <url
7020 id="http://www.freedesktop.org/standards/wm-spec.html"
7021 name="The Window Manager Specification Project">,
7022 written by the <url id="http://www.freedesktop.org"
7023 name="Free Desktop Group">, add 20 points.
7029 If the window manager permits the X session to be
7030 restarted using a <em>different</em> window manager
7031 (without killing the X server) in its default
7032 configuration, add 10 points; otherwise add none.
7040 <heading>Packages providing fonts</heading>
7043 Packages that provide fonts for the X Window
7046 For the purposes of Debian Policy, a "font for the X
7047 Window System" is one which is accessed via X protocol
7048 requests. Fonts for the Linux console, for PostScript
7049 renderers, or any other purpose, do not fit this
7050 definition. Any tool which makes such fonts available
7051 to the X Window System, however, must abide by this
7055 must do a number of things to ensure that they are both
7056 available without modification of the X or font server
7057 configuration, and that they do not corrupt files used by
7058 other font packages to register information about
7063 Fonts of any type supported by the X Window System
7064 must be in a separate binary package from any
7065 executables, libraries, or documentation (except
7066 that specific to the fonts shipped, such as their
7067 license information). If one or more of the fonts
7068 so packaged are necessary for proper operation of
7069 the package with which they are associated the font
7070 package may be Recommended; if the fonts merely
7071 provide an enhancement, a Suggests relationship may
7072 be used. Packages must not Depend on font
7075 This is because the X server may retrieve fonts
7076 from the local filesystem or over the network
7077 from an X font server; the Debian package system
7078 is empowered to deal only with the local
7087 BDF fonts must be converted to PCF fonts with the
7088 <prgn>bdftopcf</prgn> utility (available in the
7089 <tt>xutils</tt> package, <tt>gzip</tt>ped, and
7090 placed in a directory that corresponds to their
7092 <list compact="compact">
7094 100 dpi fonts must be placed in
7095 <file>/usr/X11R6/lib/X11/fonts/100dpi/</file>.
7099 75 dpi fonts must be placed in
7100 <file>/usr/X11R6/lib/X11/fonts/75dpi/</file>.
7104 Character-cell fonts, cursor fonts, and other
7105 low-resolution fonts must be placed in
7106 <file>/usr/X11R6/lib/X11/fonts/misc/</file>.
7113 Speedo fonts must be placed in
7114 <file>/usr/X11R6/lib/X11/fonts/Speedo/</file>.
7118 Type 1 fonts must be placed in
7119 <file>/usr/X11R6/lib/X11/fonts/Type1/</file>. If font
7120 metric files are available, they must be placed here
7126 Subdirectories of <file>/usr/X11R6/lib/X11/fonts/</file>
7127 other than those listed above must be neither
7128 created nor used. (The <file>PEX</file>, <file>CID</file>,
7129 and <file>cyrillic</file> directories are excepted for
7130 historical reasons, but installation of files into
7131 these directories remains discouraged.)
7137 Font packages may, instead of placing files directly
7138 in the X font directories listed above, provide
7139 symbolic links in that font directory pointing to
7140 the files' actual location in the filesystem. Such
7141 a location must comply with the FHS.
7147 Font packages should not contain both 75dpi and
7148 100dpi versions of a font. If both are available,
7149 they should be provided in separate binary packages
7150 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
7151 the names of the packages containing the
7152 corresponding fonts.
7158 Fonts destined for the <file>misc</file> subdirectory
7159 should not be included in the same package as 75dpi
7160 or 100dpi fonts; instead, they should be provided in
7161 a separate package with <tt>-misc</tt> appended to
7168 Font packages must not provide the files
7169 <file>fonts.dir</file>, <file>fonts.alias</file>, or
7170 <file>fonts.scale</file> in a font directory:
7173 <file>fonts.dir</file> files must not be provided at all.
7178 <file>fonts.alias</file> and <file>fonts.scale</file>
7179 files, if needed, should be provided in the
7181 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
7182 where <var>fontdir</var> is the name of the
7184 <file>/usr/X11R6/lib/X11/fonts/</file> where the
7185 package's corresponding fonts are stored
7186 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
7187 <var>package</var> is the name of the package
7188 that provides these fonts, and
7189 <var>extension</var> is either <tt>scale</tt>
7190 or <tt>alias</tt>, whichever corresponds to
7200 Font packages must declare a dependency on
7201 <tt>xutils (>> 4.0.3)</tt> in their control
7208 Font packages that provide one or more
7209 <file>fonts.scale</file> files as described above must
7210 invoke <prgn>update-fonts-scale</prgn> on each
7211 directory into which they installed fonts
7212 <em>before</em> invoking
7213 <prgn>update-fonts-dir</prgn> on that directory.
7214 This invocation must occur in both the
7215 <prgn>postinst</prgn> (for all arguments) and
7216 <prgn>postrm</prgn> (for all arguments except
7217 <tt>upgrade</tt>) scripts.
7223 Font packages that provide one or more
7224 <file>fonts.alias</file> files as described above must
7225 invoke <prgn>update-fonts-alias</prgn> on each
7226 directory into which they installed fonts. This
7227 invocation must occur in both the
7228 <prgn>postinst</prgn> (for all arguments) and
7229 <prgn>postrm</prgn> (for all arguments except
7230 <tt>upgrade</tt>) scripts.
7236 Font packages must invoke
7237 <prgn>update-fonts-dir</prgn> on each directory into
7238 which they installed fonts. This invocation must
7239 occur in both the <prgn>postinst</prgn> (for all
7240 arguments) and <prgn>postrm</prgn> (for all
7241 arguments except <tt>upgrade</tt>) scripts.
7247 Font packages must not provide alias names for the
7248 fonts they include which collide with alias names
7249 already in use by fonts already packaged.
7255 Font packages must not provide fonts with the same
7256 XLFD registry name as another font already packaged.
7264 <heading>Application defaults files</heading>
7267 Application defaults files must be installed in the
7268 directory <file>/etc/X11/app-defaults/</file> (use of a
7269 localized subdirectory of <file>/etc/X11/</file> as described
7270 in the <em>X Toolkit Intrinsics - C Language
7271 Interface</em> manual is also permitted). They must be
7272 registered as <tt>conffile</tt>s or handled as
7273 configuration files. Packages must not provide the
7274 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
7278 Customization of programs' X resources may also be
7279 supported with the provision of a file with the same name
7280 as that of the package placed in the
7281 <file>/etc/X11/Xresources/</file> directory, which must
7282 registered as a <tt>conffile</tt> or handled as a
7283 configuration file.<footnote>
7285 Note that this mechanism is not the same as using
7286 app-defaults; app-defaults are tied to the client
7287 binary on the local filesystem, whereas X resources
7288 are stored in the X server and affect all connecting
7292 <em>Important:</em> packages that install files into the
7293 <file>/etc/X11/Xresources/</file> directory must conflict with
7294 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
7295 it is possible for the installing package to destroy a
7296 previously-existing <file>/etc/X11/Xresources</file> file
7297 which had been customized by the system administrator.
7302 <heading>Installation directory issues</heading>
7305 Packages using the X Window System should not be
7306 configured to install files under the <file>/usr/X11R6/</file>
7307 directory unless they use <prgn>imake</prgn>. The
7308 <file>/usr/X11R6/</file> directory hierarchy should be
7309 regarded as deprecated for all packages except the X
7310 Window System itself, and those which use the
7311 <prgn>imake</prgn> program it provides, in which case the
7312 packages may transition out of the <file>/usr/X11R6/</file>
7313 directory at the maintainer's discretion.<footnote>
7315 <prgn>Imake</prgn>-using programs are exempt because,
7316 as long as they are written correctly, the pathnames
7317 they use to locate resources and install themselves
7318 are derived wholly from the X Window System
7319 configuration. Thus, in the event that the X Window
7320 System moves to <file>/usr/X11R7/</file>,
7321 <file>/usr/X12/</file>, or just plain <file>/usr/</file>, all
7322 that is required for these programs is a recompile
7323 against the corresponding X Window System library
7324 development packages.
7327 Programs that use GNU <prgn>autoconf</prgn> and
7328 <prgn>automake</prgn> are usually easily configured at
7329 compile time to use <file>/usr/</file> instead of
7330 <file>/usr/X11R6/</file>, and this should be done whenever
7331 possible. Configuration files for window managers and
7332 display managers should be placed in a subdirectory of
7333 <file>/etc/X11/</file> corresponding to the package name due
7334 to these programs' tight integration with the mechanisms
7335 of the X Window System. Application-level programs should
7336 use the <file>/etc/</file> directory unless otherwise mandated
7337 by policy. The installation of files into subdirectories
7338 of <file>/usr/X11R6/include/X11/</file> and
7339 <file>/usr/X11R6/lib/X11/</file> is permitted but discouraged;
7340 package maintainers should determine if subdirectories of
7341 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
7342 instead. (The use of symbolic links from the
7343 <file>X11R6</file> directories to other FHS-compliant
7344 locations is encouraged if the program is not easily
7345 configured to look elsewhere for its files.) Packages
7346 must not provide or install files into the directories
7347 <file>/usr/bin/X11/</file>, <file>/usr/include/X11/</file> or
7348 <file>/usr/lib/X11/</file>. Files within a package should,
7349 however, make reference to these directories, rather than
7350 their <tt>X11R6</tt>-named counterparts
7351 <file>/usr/X11R6/bin/</file>, <file>/usr/X11R6/include/X11/</file>
7352 and <file>/usr/X11R6/lib/X11/</file>, if the resources being
7353 referred to have not been moved to other FHS-compliant
7359 <heading>The OSF/Motif and OpenMotif libraries</heading>
7362 <em>Programs that require the non-DFSG-compliant OSF/Motif or
7363 OpenMotif libraries</em><footnote>
7365 OSF/Motif and OpenMotif are collectively referred to as
7366 "Motif" in this policy document.
7369 should be compiled against and tested with LessTif (a free
7370 re-implementation of Motif) instead. If the maintainer
7371 judges that the program or programs do not work
7372 sufficiently well with LessTif to be distributed and
7373 supported, but do so when compiled against Motif, then two
7374 versions of the package should be created; one linked
7375 statically against Motif and with <tt>-smotif</tt>
7376 appended to the package name, and one linked dynamically
7377 against Motif and with <tt>-dmotif</tt> appended to the
7378 package name. Both Motif-linked versions are dependent
7379 upon non-DFSG-compliant software and thus cannot be
7380 uploaded to the <em>main</em> distribution; if the
7381 software is itself DFSG-compliant it may be uploaded to
7382 the <em>contrib</em> distribution. While known existing
7383 versions of Motif permit unlimited redistribution of
7384 binaries linked against the library (whether statically or
7385 dynamically), it is the package maintainer's
7386 responsibility to determine whether this is permitted by
7387 the license of the copy of Motif in his or her possession.
7393 <heading>Perl programs and modules</heading>
7395 Perl programs and modules should follow the current Perl
7396 policy as defined in the file found on
7397 <ftpsite>ftp.debian.org</ftpsite> in
7398 <ftppath>/debian/doc/package-developer/perl-policy.txt.gz</ftppath>
7399 or your local mirror. In addition, it is included in the
7400 <tt>debian-policy</tt> package.
7405 <heading>Emacs lisp programs</heading>
7408 Please refer to the `Debian Emacs Policy' (documented in
7409 <file>debian-emacs-policy.gz</file> of the
7410 <prgn>emacsen-common</prgn> package) for details of how to
7411 package emacs lisp programs.
7416 <heading>Games</heading>
7419 The permissions on <file>/var/games</file> are mode 755, owner
7420 <tt>root</tt> and group <tt>root</tt>.
7424 Each game decides on its own security policy.</p>
7427 Games which require protected, privileged access to
7428 high-score files, savegames, etc., may be made
7429 set-<em>group</em>-id (mode 2755) and owned by
7430 <tt>root.games</tt>, and use files and directories with
7431 appropriate permissions (770 <tt>root.games</tt>, for
7432 example). They must not be made
7433 set-<em>user</em>-id, as this causes security problems. (If
7434 an attacker can subvert any set-user-id game they can
7435 overwrite the executable of any other, causing other players
7436 of these games to run a Trojan horse program. With a
7437 set-group-id game the attacker only gets access to less
7438 important game data, and if they can get at the other
7439 players' accounts at all it will take considerably more
7443 Some packages, for example some fortune cookie programs, are
7444 configured by the upstream authors to install with their
7445 data files or other static information made unreadable so
7446 that they can only be accessed through set-id programs
7447 provided. You should not do this in a Debian package: anyone can
7448 download the <file>.deb</file> file and read the data from it,
7449 so there is no point making the files unreadable. Not
7450 making the files unreadable also means that you don't have
7451 to make so many programs set-id, which reduces the risk of a
7455 As described in the FHS, binaries of games should be
7456 installed in the directory <file>/usr/games</file>. This also
7457 applies to games that use the X Window System. Manual pages
7458 for games (X and non-X games) should be installed in
7459 <file>/usr/share/man/man6</file>.</p>
7463 <chapt id="docs"><heading>Documentation</heading>
7467 <heading>Manual pages</heading>
7470 You should install manual pages in <prgn>nroff</prgn> source
7471 form, in appropriate places under <file>/usr/share/man</file>. You
7472 should only use sections 1 to 9 (see the FHS for more
7473 details). You must not install a preformatted `cat
7477 Each program, utility, and function should have an
7478 associated manpage included in the same package. It is
7479 suggested that all configuration files also have a manual
7480 page included as well.
7484 If no manual page is available for a particular program,
7485 utility, function or configuration file and this is reported
7486 as a bug to the Debian Bug Tracking System, a symbolic link
7487 from the requested manual page to the <manref
7488 name="undocumented" section="7"> manual page may be
7489 provided. This symbolic link can be created from
7490 <file>debian/rules</file> like this:
7491 <example compact="compact">
7492 ln -s ../man7/undocumented.7.gz \
7493 debian/tmp/usr/share/man/man[1-9]/<var>requested_manpage</var>.[1-9].gz
7495 This manpage claims that the lack of a manpage has been
7496 reported as a bug, so you may only do this if it really has
7497 (you can report it yourself, if you like). Do not close the
7498 bug report until a proper manpage is available.</p>
7501 You may forward a complaint about a missing manpage to the
7502 upstream authors, and mark the bug as forwarded in the
7503 Debian bug tracking system. Even though the GNU Project do
7504 not in general consider the lack of a manpage to be a bug,
7505 we do; if they tell you that they don't consider it a bug
7506 you should leave the bug in our bug tracking system open
7510 Manual pages should be installed compressed using <tt>gzip
7514 If one manpage needs to be accessible via several names it
7515 is better to use a symbolic link than the <file>.so</file>
7516 feature, but there is no need to fiddle with the relevant
7517 parts of the upstream source to change from <file>.so</file> to
7518 symlinks: don't do it unless it's easy. You should not
7519 create hard links in the manual page directories, nor put
7520 absolute filenames in <file>.so</file> directives. The filename
7521 in a <file>.so</file> in a manpage should be relative to the
7522 base of the manpage tree (usually
7523 <file>/usr/share/man</file>). If you do not create any links
7524 (whether symlinks, hard links, or <tt>.so</tt> directives)
7525 in the filesystem to the alternate names of the manpage,
7526 then you should not rely on <prgn>man</prgn> finding your
7527 manpage under those names based solely on the information in
7528 the manpage's header.<footnote>
7530 Supporting this in <prgn>man</prgn> often requires
7531 unreasonable processing time to find a manual page or to
7532 report that none exists, and moves knowledge into man's
7533 database that would be better left in the filesystem.
7534 This support is therefore deprecated and will cease to
7535 be present in the future.
7542 <heading>Info documents</heading>
7545 Info documents should be installed in <file>/usr/share/info</file>.
7546 They should be compressed with <tt>gzip -9</tt>.</p>
7549 Your package should call <prgn>install-info</prgn> to update
7550 the Info <file>dir</file> file in its <prgn>postinst</prgn>
7551 script when called with a <tt>configure</tt> argument, for
7553 <example compact="compact">
7554 install-info --quiet --section Development Development \
7555 /usr/share/info/foobar.info
7559 It is a good idea to specify a section for the location of
7560 your program; this is done with the <tt>--section</tt>
7561 switch. To determine which section to use, you should look
7562 at <file>/usr/share/info/dir</file> on your system and choose the most
7563 relevant (or create a new section if none of the current
7564 sections are relevant). Note that the <tt>--section</tt>
7565 flag takes two arguments; the first is a regular expression
7566 to match (case-insensitively) against an existing section,
7567 the second is used when creating a new one.</p>
7570 You should remove the entries in the <prgn>prerm</prgn>
7571 script when called with a <tt>remove</tt> argument:
7572 <example compact="compact">
7573 install-info --quiet --remove /usr/share/info/foobar.info
7577 If <prgn>install-info</prgn> cannot find a description entry
7578 in the Info file you must supply one. See <manref
7579 name="install-info" section="8"> for details.</p>
7583 <heading>Additional documentation</heading>
7586 Any additional documentation that comes with the package may
7587 be installed at the discretion of the package maintainer.
7588 Text documentation should be installed in the directory
7589 <file>/usr/share/doc/<var>package</var></file>, where
7590 <var>package</var> is the name of the package, and
7591 compressed with <tt>gzip -9</tt> unless it is small.</p>
7594 If a package comes with large amounts of documentation which
7595 many users of the package will not require you should create
7596 a separate binary package to contain it, so that it does not
7597 take up disk space on the machines of users who do not need
7598 or want it installed.</p>
7601 It is often a good idea to put text information files
7602 (<file>README</file>s, changelogs, and so forth) that come with
7603 the source package in <file>/usr/share/doc/<var>package</var></file>
7604 in the binary package. However, you don't need to install
7605 the instructions for building and installing the package, of
7609 Files in <file>/usr/share/doc</file> should not be referenced by
7610 any program, and the system administrator should be able to
7611 delete them without causing any programs to break. Any files
7612 that are referenced by programs but are also useful as
7613 standalone documentation should be installed under
7614 <file>/usr/share/<var>package</var>/</file> with symbolic links
7615 from <file>/usr/share/doc/<var>package</var>/</file>.
7621 <heading>Accessing the documentation</heading>
7624 Former Debian releases placed all additional documentation
7625 in <file>/usr/doc/<var>package</var></file>. This has now
7626 changed to <file>/usr/share/doc/<var>package</var></file>,
7627 and packages must not put documentation in the directory
7628 <file>/usr/doc/<var>package</var></file>. <footnote>
7629 <p>At this phase of the transition, we no longer require a
7630 symbolic link in <file>/usr/doc/</file>. At a later point,
7631 policy shall change to make the symbolic links a bug.</p>
7637 <heading>Preferred documentation formats</heading>
7640 The unification of Debian documentation is being carried out
7644 If your package comes with extensive documentation in a
7645 markup format that can be converted to various other formats
7646 you should if possible ship HTML versions in a binary
7647 package, in the directory
7648 <file>/usr/share/doc/<var>appropriate-package</var></file> or
7649 its subdirectories.<footnote>
7651 The rationale: The important thing here is that HTML
7652 docs should be available in <em>some</em> package, not
7653 necessarily in the main binary package.
7659 Other formats such as PostScript may be provided at the
7660 package maintainer's discretion.
7664 <sect id="copyrightfile">
7665 <heading>Copyright information</heading>
7668 Every package must be accompanied by a verbatim copy of its
7669 copyright and distribution license in the file
7670 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
7671 file must neither be compressed nor be a symbolic link.
7675 In addition, the copyright file must say where the upstream
7676 sources (if any) were obtained, and should explain briefly what
7677 modifications were made in the Debian version of the package
7678 compared to the upstream one. It should name the original
7679 authors of the package and the Debian maintainer(s) who were
7680 involved with its creation.</p>
7683 A copy of the file which will be installed in
7684 <file>/usr/share/doc/<var>package</var>/copyright</file> should
7685 be in <file>debian/copyright</file> in the source package.
7689 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7690 link to another directory in <file>/usr/share/doc</file> only if
7691 the two packages both come from the same source and the
7692 first package Depends on the second. These rules are
7693 important because copyrights must be extractable by
7698 Packages distributed under the UCB BSD license, the Artistic
7699 license, the GNU GPL, and the GNU LGPL should refer to the
7700 files <file>/usr/share/common-licenses/BSD</file>,
7701 <file>/usr/share/common-licenses/Artistic</file>,
7702 <file>/usr/share/common-licenses/GPL</file>, and
7703 <file>/usr/share/common-licenses/LGPL</file> respectively,
7704 rather than quoting them in the copyright file.
7708 You should not use the copyright file as a general <file>README</file>
7709 file. If your package has such a file it should be
7710 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
7711 <file>README.Debian</file> or some other appropriate place.</p>
7715 <heading>Examples</heading>
7718 Any examples (configurations, source files, whatever),
7719 should be installed in a directory
7720 <file>/usr/share/doc/<var>package</var>/examples</file>. These
7721 files should not be referenced by any program: they're there
7722 for the benefit of the system administrator and users as
7723 documentation only. Architecture-specific example files
7724 should be installed in a directory
7725 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
7727 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
7728 latter directory itself may be a symbolic link to the
7733 <sect id="instchangelog">
7734 <heading>Changelog files</heading>
7737 Packages that are not Debian-native must contain a
7738 compressed copy of the <file>debian/changelog</file> file from
7739 the Debian source tree in
7740 <file>/usr/share/doc/<var>package</var></file> with the name
7741 <file>changelog.Debian.gz</file>. If an upstream changelog is
7742 available, it should be accessible as
7743 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
7744 plain text. If the upstream changelog is distributed in
7745 HTML, it should be made available in that form as
7746 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
7747 and a plain text <file>changelog.gz</file> should be generated
7748 from it using, for example, <tt>lynx -dump -nolist</tt>. If
7749 the upstream changelog files do not already conform to this
7750 naming convention, then this may be achieved either by
7751 renaming the files, or by adding a symbolic link, at the
7752 maintainer's discretion.<footnote>
7754 Rationale: People should not have to look in places for
7755 upstream changelogs merely because they are given
7756 different names or are distributed in HTML format.
7762 All of these files should be installed compressed using
7763 <tt>gzip -9</tt>, as they will become large with time even
7764 if they start out small.
7768 If the package has only one changelog which is used both as
7769 the Debian changelog and the upstream one because there is
7770 no separate upstream maintainer then that changelog should
7771 usually be installed as
7772 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
7773 there is a separate upstream maintainer, but no upstream
7774 changelog, then the Debian changelog should still be called
7775 <file>changelog.Debian.gz</file>.</p>
7779 <appendix id="pkg-scope">
7780 <heading>Introduction and scope of these appendices</heading>
7783 These appendices are taken essentially verbatim from the
7784 now-deprecated Packaging Manual, version 3.2.1.0. They are
7785 the chapters which are likely to be of use to package
7786 maintainers and which have not already been included in the
7787 policy document itself. Most of these sections are very likely
7788 not relevant to policy; they should be treated as
7789 documentation for the packaging system. Please note that these
7790 appendices are included for convenience, and for historical
7791 reasons: they used to be part of policy package, and they have
7792 not yet been incorporated into dpkg documentation. However,
7793 they still have value, and hence they are presented here.
7796 They have not yet been checked to ensure that they are
7797 compatible with the contents of policy, and if there are any
7798 contradictions, the version in the main policy document takes
7799 precedence. The remaining chapters of the old Packaging
7800 Manual have also not been read in detail to ensure that there
7801 are not parts which have been left out. Both of these will be
7806 <prgn>dpkg</prgn> is a suite of programs for creating binary
7807 package files and installing and removing them on Unix
7810 <prgn>dpkg</prgn> is targetted primarily at Debian
7811 GNU/Linux, but may work on or be ported to other
7818 The binary packages are designed for the management of
7819 installed executable programs (usually compiled binaries) and
7820 their associated data, though source code examples and
7821 documentation are provided as part of some packages.</p>
7824 This manual describes the technical aspects of creating Debian
7825 binary packages (<file>.deb</file> files). It documents the
7826 behaviour of the package management programs
7827 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
7828 they interact with packages.</p>
7831 It also documents the interaction between
7832 <prgn>dselect</prgn>'s core and the access method scripts it
7833 uses to actually install the selected packages, and describes
7834 how to create a new access method.</p>
7837 This manual does not go into detail about the options and
7838 usage of the package building and installation tools. It
7839 should therefore be read in conjuction with those programs'
7844 The utility programs which are provided with <prgn>dpkg</prgn>
7845 for managing various system configuration and similar issues,
7846 such as <prgn>update-rc.d</prgn> and
7847 <prgn>install-info</prgn>, are not described in detail here -
7848 please see their manpages.
7852 It does <em>not</em> describe the policy requirements imposed
7853 on Debian packages, such as the permissions on files and
7854 directories, documentation requirements, upload procedure, and
7855 so on. You should see the Debian packaging policy manual for
7856 these details. (Many of them will probably turn out to be
7857 helpful even if you don't plan to upload your package and make
7858 it available as part of the distribution.)
7862 It is assumed that the reader is reasonably familiar with the
7863 <prgn>dpkg</prgn> System Administrators' manual.
7864 Unfortunately this manual does not yet exist.
7868 The Debian version of the FSF's GNU hello program is provided
7869 as an example for people wishing to create Debian
7870 packages. The Debian <prgn>debmake</prgn> package is
7871 recommended as a very helpful tool in creating and maintaining
7872 Debian packages. However, while the tools and examples are
7873 helpful, they do not replace the need to read and follow the
7874 Policy and Programmer's Manual.</p>
7877 <appendix id="pkg-binarypkg"><heading>Binary packages (from old
7882 The binary package has two main sections. The first part
7883 consists of various control information files and scripts used
7884 by <prgn>dpkg</prgn> when installing and removing. See <ref
7885 id="pkg-controlarea">.
7889 The second part is an archive containing the files and
7890 directories to be installed.
7894 In the future binary packages may also contain other
7895 components, such as checksums and digital signatures. The
7896 format for the archive is described in full in the
7897 <file>deb(5)</file> manpage.
7901 <sect id="pkg-bincreating"><heading>Creating package files -
7902 <prgn>dpkg-deb</prgn>
7906 All manipulation of binary package files is done by
7907 <prgn>dpkg-deb</prgn>; it's the only program that has
7908 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
7909 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
7910 will spot that the options requested are appropriate to
7911 <prgn>dpkg-deb</prgn> and invoke that instead with the same
7916 In order to create a binary package you must make a
7917 directory tree which contains all the files and directories
7918 you want to have in the filesystem data part of the package.
7919 In Debian-format source packages this directory is usually
7920 <file>debian/tmp</file>, relative to the top of the package's
7925 They should have the locations (relative to the root of the
7926 directory tree you're constructing) ownerships and
7927 permissions which you want them to have on the system when
7932 With current versions of <prgn>dpkg</prgn> the uid/username
7933 and gid/groupname mappings for the users and groups being
7934 used should be the same on the system where the package is
7935 built and the one where it is installed.
7939 You need to add one special directory to the root of the
7940 miniature filesystem tree you're creating:
7941 <prgn>DEBIAN</prgn>. It should contain the control
7942 information files, notably the binary package control file
7943 (see <ref id="pkg-controlfile">).
7947 The <prgn>DEBIAN</prgn> directory will not appear in the
7948 filesystem archive of the package, and so won't be installed
7949 by <prgn>dpkg</prgn> when the package is installed.
7953 When you've prepared the package, you should invoke:
7955 dpkg --build <var>directory</var>
7960 This will build the package in
7961 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
7962 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
7963 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
7968 See the manpage <manref name="dpkg-deb" section="8"> for details of how
7969 to examine the contents of this newly-created file. You may find the
7970 output of following commands enlightening:
7972 dpkg-deb --info <var>filename</var>.deb
7973 dpkg-deb --contents <var>filename</var>.deb
7974 dpkg --contents <var>filename</var>.deb
7976 To view the copyright file for a package you could use this command:
7978 dpkg --fsys-tarfile <var>filename</var>.deb | tar xof usr/share/doc/<var>\*</var>copyright | less
7983 <sect id="pkg-controlarea">
7985 Package control information files
7989 The control information portion of a binary package is a
7990 collection of files with names known to <prgn>dpkg</prgn>.
7991 It will treat the contents of these files specially - some
7992 of them contain information used by <prgn>dpkg</prgn> when
7993 installing or removing the package; others are scripts which
7994 the package maintainer wants <prgn>dpkg</prgn> to run.
7998 It is possible to put other files in the package control
7999 area, but this is not generally a good idea (though they
8000 will largely be ignored).
8004 Here is a brief list of the control info files supported by
8005 <prgn>dpkg</prgn> and a summary of what they're used for.
8010 <tag><tt>control</tt>
8014 This is the key description file used by
8015 <prgn>dpkg</prgn>. It specifies the package's name
8016 and version, gives its description for the user,
8017 states its relationships with other packages, and so
8018 forth. See <ref id="pkg-controlfile">.
8022 It is usually generated automatically from information
8023 in the source package by the
8024 <prgn>dpkg-gencontrol</prgn> program, and with
8025 assistance from <prgn>dpkg-shlibdeps</prgn>. See <ref
8026 id="pkg-sourcetools">.</p>
8029 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8035 These are exectuable files (usually scripts) which
8036 <prgn>dpkg</prgn> runs during installation, upgrade
8037 and removal of packages. They allow the package to
8038 deal with matters which are particular to that package
8039 or require more complicated processing than that
8040 provided by <prgn>dpkg</prgn>. Details of when and
8041 how they are called are in <ref
8042 id="maintainerscripts">.
8046 It is very important to make these scripts
8050 That means that if it runs successfully or fails
8051 and then you call it again it doesn't bomb out,
8052 but just ensures that everything is the way it
8055 </footnote> This is so that if an error occurs, the
8056 user interrupts <prgn>dpkg</prgn> or some other
8057 unforeseen circumstance happens you don't leave the
8058 user with a badly-broken package.
8062 The maintainer scripts are guaranteed to run with a
8063 controlling terminal and can interact with the user.
8064 If they need to prompt for passwords, do full-screen
8065 interaction or something similar you should do these
8066 things to and from <file>/dev/tty</file>, since
8067 <prgn>dpkg</prgn> will at some point redirect scripts'
8068 standard input and output so that it can log the
8069 installation process. Likewise, because these scripts
8070 may be executed with standard output redirected into a
8071 pipe for logging purposes, Perl scripts should set
8072 unbuffered output by setting <tt>$|=1</tt> so that the
8073 output is printed immediately rather than being
8078 Each script should return a zero exit status for
8079 success, or a nonzero one for failure.</p>
8082 <tag><tt>conffiles</tt>
8087 This file contains a list of configuration files which
8088 are to be handled automatically by <prgn>dpkg</prgn>
8089 (see <ref id="pkg-conffiles">). Note that not necessarily
8090 every configuration file should be listed here.</p>
8093 <tag><tt>shlibs</tt>
8098 This file contains a list of the shared libraries
8099 supplied by the package, with dependency details for
8100 each. This is used by <prgn>dpkg-shlibdeps</prgn>
8101 when it determines what dependencies are required in a
8102 package control file. The <tt>shlibs</tt> file format
8103 is described on <ref id="shlibs">.
8109 <sect id="pkg-controlfile">
8111 The main control information file: <tt>control</tt>
8114 The most important control information file used by
8115 <prgn>dpkg</prgn> when it installs a package is
8116 <tt>control</tt>. It contains all the package's `vital
8121 The binary package control files of packages built from
8122 Debian sources are made by a special tool,
8123 <prgn>dpkg-gencontrol</prgn>, which reads
8124 <file>debian/control</file> and <file>debian/changelog</file> to
8125 find the information it needs. See <ref id="pkg-sourcepkg"> for
8130 The fields in binary package control files are:
8131 <list compact="compact">
8133 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8136 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
8138 <item><p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8142 This field should appear in all packages, though
8143 <prgn>dpkg</prgn> doesn't require it yet so that
8144 old packages can still be installed.
8150 <p><qref id="relationships"><tt>Depends</tt>,
8151 <tt>Provides</tt> et al.</qref></p>
8154 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8157 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8160 <p><qref id="pkg-f-classification"><tt>Section</tt>,
8161 <tt>Priority</tt></qref></p>
8164 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
8167 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8171 <qref id="pkg-f-Installed-Size"><tt>Installed-Size</tt></qref>
8177 A description of the syntax of control files and the purpose
8178 of these fields is available in <ref id="pkg-controlfields">.
8183 <heading>Time Stamps</heading>
8185 Maintainers are encouraged to preserve the modification
8186 times of the upstream source files in a package, as far as
8187 is reasonably possible.
8190 The rationale is that there is some information conveyed
8191 by knowing the age of the file, for example, you could
8192 recognize that some documentation is very old by looking
8193 at the modification time, so it would be nice if the
8194 modification time of the upstream source would be
8202 <appendix id="pkg-sourcepkg">
8203 <heading>Source packages (from old Packaging Manual) </heading>
8206 The Debian binary packages in the distribution are generated
8207 from Debian sources, which are in a special format to assist
8208 the easy and automatic building of binaries.
8212 There was a previous version of the Debian source format,
8213 which is now being phased out. Instructions for converting an
8214 old-style package are given in the Debian policy manual.
8217 <sect id="pkg-sourcetools">
8218 <heading>Tools for processing source packages</heading>
8221 Various tools are provided for manipulating source packages;
8222 they pack and unpack sources and help build of binary
8223 packages and help manage the distribution of new versions.
8227 They are introduced and typical uses described here; see
8228 <manref name="dpkg-source" section="1"> for full
8229 documentation about their arguments and operation.
8233 For examples of how to construct a Debian source package,
8234 and how to use those utilities that are used by Debian
8235 source packages, please see the <prgn>hello</prgn> example
8241 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
8246 This program is frequently used by hand, and is also
8247 called from package-independent automated building scripts
8248 such as <prgn>dpkg-buildpackage</prgn>.
8252 To unpack a package it is typically invoked with
8254 dpkg-source -x <var>.../path/to/filename</var>.dsc
8259 with the <file><var>filename</var>.tar.gz</file> and
8260 <file><var>filename</var>.diff.gz</file> (if applicable) in
8261 the same directory. It unpacks into
8262 <file><var>package</var>-<var>version</var></file>, and if
8264 <file><var>package</var>-<var>version</var>.orig</file>, in
8265 the current directory.
8269 To create a packed source archive it is typically invoked:
8271 dpkg-source -b <var>package</var>-<var>version</var>
8276 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
8277 <file>.diff.gz</file> (if appropriate) in the current
8278 directory. <prgn>dpkg-source</prgn> does not clean the
8279 source tree first - this must be done separately if it is
8284 See also <ref id="pkg-sourcearchives">.</p>
8290 <prgn>dpkg-buildpackage</prgn> - overall package-building
8295 <prgn>dpkg-buildpackage</prgn> is a script which invokes
8296 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
8297 targets <tt>clean</tt>, <tt>build</tt> and
8298 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
8299 <prgn>pgp</prgn> to build a signed source and binary
8304 It is usually invoked by hand from the top level of the
8305 built or unbuilt source directory. It may be invoked with
8306 no arguments; useful arguments include:
8307 <taglist compact="compact">
8308 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
8311 Do not PGP-sign the <tt>.changes</tt> file or the
8312 source package <tt>.dsc</tt> file, respectively.</p>
8314 <tag><tt>-p<var>pgp-command</var></tt></tag>
8317 Invoke <var>pgp-command</var> instead of finding
8318 <tt>pgp</tt> on the <prgn>PATH</prgn>.
8319 <var>pgp-command</var> must behave just like
8320 <prgn>pgp</prgn>.</p>
8322 <tag><tt>-r<var>root-command</var></tt></tag>
8325 When root privilege is required, invoke the command
8326 <var>root-command</var>. <var>root-command</var>
8327 should invoke its first argument as a command, from
8328 the <prgn>PATH</prgn> if necessary, and pass its
8329 second and subsequent arguments to the command it
8330 calls. If no <var>root-command</var> is supplied
8331 then <var>dpkg-buildpackage</var> will take no
8332 special action to gain root privilege, so that for
8333 most packages it will have to be invoked as root to
8336 <tag><tt>-b</tt>, <tt>-B</tt></tag>
8339 Two types of binary-only build and upload - see
8340 <manref name="dpkg-source" section="1">.
8349 <prgn>dpkg-gencontrol</prgn> - generates binary package
8354 This program is usually called from <file>debian/rules</file>
8355 (see <ref id="pkg-sourcetree">) in the top level of the source
8360 This is usually done just before the files and directories in the
8361 temporary directory tree where the package is being built have their
8362 permissions and ownerships set and the package is constructed using
8363 <prgn>dpkg-deb/</prgn>
8366 This is so that the control file which is produced has
8367 the right permissions
8373 <prgn>dpkg-gencontrol</prgn> must be called after all the
8374 files which are to go into the package have been placed in
8375 the temporary build directory, so that its calculation of
8376 the installed size of a package is correct.
8380 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
8381 be run after <prgn>dpkg-shlibdeps</prgn> so that the
8382 variable substitutions created by
8383 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
8388 For a package which generates only one binary package, and
8389 which builds it in <file>debian/tmp</file> relative to the top
8390 of the source package, it is usually sufficient to call
8391 <prgn>dpkg-gencontrol</prgn>.
8395 Sources which build several binaries will typically need
8398 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
8399 </example> The <tt>-P</tt> tells
8400 <prgn>dpkg-gencontrol</prgn> that the package is being
8401 built in a non-default directory, and the <tt>-p</tt>
8402 tells it which package's control file should be generated.
8406 <prgn>dpkg-gencontrol</prgn> also adds information to the
8407 list of files in <file>debian/files</file>, for the benefit of
8408 (for example) a future invocation of
8409 <prgn>dpkg-genchanges</prgn>.</p>
8414 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
8419 This program is usually called from <file>debian/rules</file>
8420 just before <prgn>dpkg-gencontrol</prgn> (see <ref
8421 id="pkg-sourcetree">), in the top level of the source tree.
8425 Its arguments are executables.
8428 In a forthcoming dpkg version,
8429 <prgn>dpkg-shlibdeps</prgn> would be required to be
8430 called on shared libraries as well.
8433 They may be specified either in the locations in the
8434 source tree where they are created or in the locations
8435 in the temporary build tree where they are installed
8436 prior to binary package creation.
8438 </footnote> for which shared library dependencies should
8439 be included in the binary package's control file.
8443 If some of the found shared libraries should only
8444 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
8445 some warrant a <tt>Pre-Depends</tt>, this can be achieved
8446 by using the <tt>-d<var>dependency-field</var></tt> option
8447 before those executable(s). (Each <tt>-d</tt> option
8448 takes effect until the next <tt>-d</tt>.)
8452 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
8453 output control file to be modified. Instead by default it
8454 adds to the <file>debian/substvars</file> file variable
8455 settings like <tt>shlibs:Depends</tt>. These variable
8456 settings must be referenced in dependency fields in the
8457 appropriate per-binary-package sections of the source
8462 For example, the <prgn>procps</prgn> package generates two
8463 kinds of binaries, simple C binaries like <prgn>ps</prgn>
8464 which require a predependency and full-screen ncurses
8465 binaries like <prgn>top</prgn> which require only a
8466 recommendation. It can say in its <file>debian/rules</file>:
8468 dpkg-shlibdeps -dPre-Depends ps -dRecommends top
8470 and then in its main control file <file>debian/control</file>:
8474 Pre-Depends: ${shlibs:Pre-Depends}
8475 Recommends: ${shlibs:Recommends}
8481 Sources which produce several binary packages with
8482 different shared library dependency requirements can use
8483 the <tt>-p<var>varnameprefix</var></tt> option to override
8484 the default <tt>shlibs:</tt> prefix (one invocation of
8485 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
8486 They can thus produce several sets of dependency
8487 variables, each of the form
8488 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
8489 which can be referred to in the appropriate parts of the
8490 binary package control files.
8497 <prgn>dpkg-distaddfile</prgn> - adds a file to
8498 <file>debian/files</file>
8502 Some packages' uploads need to include files other than
8503 the source and binary package files.
8507 <prgn>dpkg-distaddfile</prgn> adds a file to the
8508 <file>debian/files</file> file so that it will be included in
8509 the <file>.changes</file> file when
8510 <prgn>dpkg-genchanges</prgn> is run.
8514 It is usually invoked from the <tt>binary</tt> target of
8515 <file>debian/rules</file>:
8517 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
8519 The <var>filename</var> is relative to the directory where
8520 <prgn>dpkg-genchanges</prgn> will expect to find it - this
8521 is usually the directory above the top level of the source
8522 tree. The <file>debian/rules</file> target should put the
8523 file there just before or just after calling
8524 <prgn>dpkg-distaddfile</prgn>.
8528 The <var>section</var> and <var>priority</var> are passed
8529 unchanged into the resulting <file>.changes</file> file. See
8530 <ref id="pkg-f-classification">.
8535 <sect1><heading><prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file> upload
8540 This program is usually called by package-independent
8541 automatic building scripts such as
8542 <prgn>dpkg-buildpackage</prgn>, but it may also be called
8547 It is usually called in the top level of a built source
8548 tree, and when invoked with no arguments will print out a
8549 straightforward <file>.changes</file> file based on the
8550 information in the source package's changelog and control
8551 file and the binary and source packages which should have
8557 <sect1><heading><prgn>dpkg-parsechangelog</prgn> - produces parsed representation of
8562 This program is used internally by
8563 <prgn>dpkg-source</prgn> et al. It may also occasionally
8564 be useful in <file>debian/rules</file> and elsewhere. It
8565 parses a changelog, <file>debian/changelog</file> by default,
8566 and prints a control-file format representation of the
8567 information in it to standard output.
8571 <sect1 id="pkg-dpkgarch"><heading><prgn>dpkg-architecture</prgn> -
8572 information about the build and host system
8576 This program can be used manually, but is also invoked by
8577 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
8578 to set environment or make variables which specify the build and
8579 host architecture for the package building process.
8584 <sect id="pkg-sourcetree"><heading>The Debianised source tree
8588 The source archive scheme described later is intended to
8589 allow a Debianised source tree with some associated control
8590 information to be reproduced and transported easily. The
8591 Debianised source tree is a version of the original program
8592 with certain files added for the benefit of the
8593 Debianisation process, and with any other changes required
8594 made to the rest of the source code and installation
8599 The extra files created for Debian are in the subdirectory
8600 <file>debian</file> of the top level of the Debianised source
8601 tree. They are described below.
8604 <sect1 id="pkg-debianrules"><heading><file>debian/rules</file> - the main building
8609 This file is an executable makefile, and contains the
8610 package-specific recipies for compiling the package and
8611 building binary package(s) out of the source.
8615 It must start with the line <tt>#!/usr/bin/make -f</tt>,
8616 so that it can be invoked by saying its name rather than
8617 invoking <prgn>make</prgn> explicitly.
8621 Since an interactive <file>debian/rules</file> script makes it
8622 impossible to autocompile that package and also makes it
8623 hard for other people to reproduce the same binary
8624 package, all <strong>required targets</strong> have to be
8625 non-interactive. At a minimul, required targets are the
8626 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
8627 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>, and
8628 <em>build</em>. It also follows that any target that these
8629 targets depend on must also be non-interactive.
8633 The targets which are required to be present are:
8635 <tag><tt>build</tt></tag>
8638 This should perform all non-interactive
8639 configuration and compilation of the package. If a
8640 package has an interactive pre-build configuration
8641 routine, the Debianised source package should be
8642 built after this has taken place, so that it can be
8643 built without rerunning the configuration.
8647 A package may also provide both of the targets
8648 <tt>build-arch</tt> and <tt>build-indep</tt>. The
8649 <tt>build-arch</tt> target, if provided, should
8650 perform all non-interactive configuration and
8651 compilation required for producing all
8652 architecture-dependant binary packages (those packages
8653 for which the body of the <tt>Architecture</tt> field
8654 in <tt>debian/control</tt> is not <tt>all</tt>).
8655 Similarly, the <tt>build-indep</tt> target, if
8656 provided, should perform all non-interactive
8657 configuration and compilation required for producing
8658 all architecture-independent binary packages (those
8659 packages for which the body of the
8660 <tt>Architecture</tt> field in <tt>debian/control</tt>
8661 is <tt>all</tt>). The <tt>build</tt> target should
8662 depend on those of the targets <tt>build-arch</tt> and
8663 <tt>build-indep</tt> that are provided in the rules
8668 If one or both of the targets <tt>build-arch</tt> and
8669 <tt>build-indep</tt> are not provided, then invoking
8670 <file>debian/rules</file> with one of the not-provided
8671 targets as arguments should produce a exit status code
8672 of 2. Usually this is provided automatically by make
8673 if the target is missing.
8677 For some packages, notably ones where the same
8678 source tree is compiled in different ways to produce
8679 two binary packages, the <tt>build</tt> target does
8680 not make much sense. For these packages it is good
8681 enough to provide two (or more) targets
8682 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
8683 for each of the ways of building the package, and a
8684 <tt>build</tt> target that does nothing. The
8685 <tt>binary</tt> target will have to build the
8686 package in each of the possible ways and make the
8687 binary package out of each.
8691 The targets <tt>build</tt>, <tt>build-arch</tt>
8692 and <tt>build-indep</tt> target must not do
8693 anything that might require root privilege.
8697 The <tt>build</tt> target may need to run
8698 <tt>clean</tt> first - see below.
8702 When a package has a configuration routine that takes
8703 a long time, or when the makefiles are poorly
8704 designed, or when <tt>build</tt> needs to run
8705 <tt>clean</tt> first, it is a good idea to <tt>touch
8706 build</tt> when the build process is complete. This
8707 will ensure that if <tt>debian/rules build</tt> is run
8708 again it will not rebuild the whole program.
8712 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
8713 <tt>binary-indep</tt>
8717 The <tt>binary</tt> target should be all that is
8718 necessary for the user to build the binary
8719 package. All these targets are required to be
8720 non-interactive. It is split into two parts:
8721 <tt>binary-arch</tt> builds the packages' output
8722 files which are specific to a particular
8723 architecture, and <tt>binary-indep</tt> builds
8724 those which are not.
8728 <tt>binary</tt> should usually be a target with
8729 no commands which simply depends on
8730 <prgn>binary-arch</prgn> and
8731 <prgn>binary-indep</prgn>.
8735 Both <prgn>binary-*</prgn> targets should depend on
8736 the <tt>build</tt> target, above, so that the
8737 package is built if it has not been already. It
8738 should then create the relevant binary package(s),
8739 using <prgn>dpkg-gencontrol</prgn> to make their
8740 control files and <prgn>dpkg-deb</prgn> to build
8741 them and place them in the parent of the top level
8746 If one of the <prgn>binary-*</prgn> targets has
8747 nothing to do (this will be always be the case if
8748 the source generates only a single binary package,
8749 whether architecture-dependent or not) it
8750 <em>must</em> still exist, but should always
8755 <ref id="pkg-binarypkg"> describes how to construct
8760 The <tt>binary</tt> targets must be invoked as
8765 <tag><tt>clean</tt></tag>
8769 This should undo any effects that the
8770 <tt>build</tt> and <tt>binary</tt> targets
8771 may have had, except that it should leave alone any
8772 output files created in the parent directory by a
8773 run of <tt>binary</tt>. This target is required
8774 to be non-interactive.
8778 If a <tt>build</tt> file is touched at the end
8779 of the <tt>build</tt> target, as suggested
8780 above, it must be removed as the first thing that
8781 <tt>clean</tt> does, so that running
8782 <tt>build</tt> again after an interrupted
8783 <tt>clean</tt> doesn't think that everything is
8788 The <tt>clean</tt> target must be invoked as
8789 root if <tt>binary</tt> has been invoked since
8790 the last <tt>clean</tt>, or if
8791 <tt>build</tt> has been invoked as root (since
8792 <tt>build</tt> may create directories, for
8797 <tag><tt>get-orig-source</tt> (optional)</tag>
8801 This target fetches the most recent version of the
8802 original source package from a canonical archive
8803 site (via FTP or WWW, for example), does any
8804 necessary rearrangement to turn it into the original
8805 source tarfile format described below, and leaves it
8806 in the current directory.
8810 This target may be invoked in any directory, and
8811 should take care to clean up any temporary files it
8816 This target is optional, but providing it if
8817 possible is a good idea.
8823 The <tt>build</tt>, <tt>binary</tt> and
8824 <tt>clean</tt> targets must be invoked with a current
8825 directory of the package's top-level directory.
8830 Additional targets may exist in <file>debian/rules</file>,
8831 either as published or undocumented interfaces or for the
8832 package's internal use.
8836 The architecture we build on and build for is determined by make
8837 variables via dpkg-architecture (see <ref id="pkg-dpkgarch">). You can
8838 get the Debian architecture and the GNU style architecture
8839 specification string for the build machine as well as the host
8840 machine. Here is a list of supported make variables:
8841 <list compact="compact">
8843 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
8846 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
8847 specification string)</p>
8850 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of DEB_*_GNU_TYPE)</p>
8853 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
8859 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
8860 the build machine or <tt>HOST</tt> for specification of the machine
8865 Backward compatibility can be provided in the rules file
8866 by setting the needed variables to suitable default
8867 values, please refer to the documentation of
8868 dpkg-architecture for details.
8872 It is important to understand that the <tt>DEB_*_ARCH</tt>
8873 string does only determine which Debian architecture we
8874 build on resp. for. It should not be used to get the CPU
8875 or System information, the GNU style variables should be
8881 <sect1><heading><file>debian/control</file>
8885 This file contains version-independent details about the
8886 source package and about the binary packages it creates.
8890 It is a series of sets of control fields, each
8891 syntactically similar to a binary package control file.
8892 The sets are separated by one or more blank lines. The
8893 first set is information about the source package in
8894 general; each subsequent set describes one binary package
8895 that the source tree builds.
8899 The syntax and semantics of the fields are described below
8900 in <ref id="pkg-controlfields">.
8904 The general (binary-package-independent) fields are:
8905 <list compact="compact">
8907 <p><qref id="pkg-f-Source"><tt>Source</tt></qref> (mandatory)</p>
8910 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8914 <qref id="pkg-f-classification"><tt>Section</tt> and
8915 <tt>Priority</tt></qref>
8916 (classification, mandatory)
8921 <qref id="relationships"><tt>Build-Depends</tt> et
8922 al.</qref> (source package interrelationships)
8927 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref>
8933 The per-binary-package fields are:
8934 <list compact="compact">
8936 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8940 <qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8944 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8948 <qref id="pkg-f-classification"><tt>Section</tt> and
8949 <tt>Priority</tt></qref> (classification)</p>
8952 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8956 <qref id="relationships"><tt>Depends</tt> et
8957 al.</qref> (binary package interrelationships)
8963 These fields are used by <prgn>dpkg-gencontrol</prgn> to
8964 generate control files for binary packages (see below), by
8965 <prgn>dpkg-genchanges</prgn> to generate the
8966 <tt>.changes</tt> file to accompany the upload, and by
8967 <prgn>dpkg-source</prgn> when it creates the <file>.dsc</file>
8968 source control file as part of a source archive.
8972 The fields here may contain variable references - their
8973 values will be substituted by
8974 <prgn>dpkg-gencontrol</prgn>, <prgn>dpkg-genchanges</prgn>
8975 or <prgn>dpkg-source</prgn> when they generate output
8976 control files. See <ref id="pkg-srcsubstvars"> for details.
8979 <p> <sect2><heading>User-defined fields
8983 Additional user-defined fields may be added to the
8984 source package control file. Such fields will be
8985 ignored, and not copied to (for example) binary or
8986 source package control files or upload control files.
8990 If you wish to add additional unsupported fields to
8991 these output files you should use the mechanism
8996 Fields in the main source control information file with
8997 names starting <tt>X</tt>, followed by one or more of
8998 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
8999 be copied to the output files. Only the part of the
9000 field name after the hyphen will be used in the output
9001 file. Where the letter <tt>B</tt> is used the field
9002 will appear in binary package control files, where the
9003 letter <tt>S</tt> is used in source package control
9004 files and where <tt>C</tt> is used in upload control
9005 (<tt>.changes</tt>) files.
9009 For example, if the main source information control file
9012 XBS-Comment: I stand between the candle and the star.
9014 then the binary and source package control files will contain the
9017 Comment: I stand between the candle and the star.
9024 <sect1 id="pkg-dpkgchangelog"><heading><file>debian/changelog</file>
9028 This file records the changes to the Debian-specific parts of the
9032 Though there is nothing stopping an author who is also
9033 the Debian maintainer from using it for all their
9034 changes, it will have to be renamed if the Debian and
9035 upstream maintainers become different
9042 It has a special format which allows the package building
9043 tools to discover which version of the package is being
9044 built and find out other release-specific information.
9048 That format is a series of entries like this:
9050 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
9052 * <var>change details</var>
9053 <var>more change details</var>
9054 * <var>even more change details</var>
9056 -- <var>maintainer name and email address</var> <var>date</var>
9061 <var>package</var> and <var>version</var> are the source
9062 package name and version number.
9066 <var>distribution(s)</var> lists the distributions where
9067 this version should be installed when it is uploaded - it
9068 is copied to the <tt>Distribution</tt> field in the
9069 <tt>.changes</tt> file. See <ref id="pkg-f-Distribution">.
9073 <var>urgency</var> is the value for the <tt>Urgency</tt>
9074 field in the <file>.changes</file> file for the upload. See
9075 <ref id="pkg-f-Urgency">. It is not possible to specify an
9076 urgency containing commas; commas are used to separate
9077 <tt><var>keyword</var>=<var>value</var></tt> settings in
9078 the <prgn>dpkg</prgn> changelog format (though there is
9079 currently only one useful <var>keyword</var>,
9084 The change details may in fact be any series of lines
9085 starting with at least two spaces, but conventionally each
9086 change starts with an asterisk and a separating space and
9087 continuation lines are indented so as to bring them in
9088 line with the start of the text above. Blank lines may be
9089 used here to separate groups of changes, if desired.
9093 The maintainer name and email address should <em>not</em>
9094 necessarily be those of the usual package maintainer.
9095 They should be the details of the person doing
9096 <em>this</em> version. The information here will be
9097 copied to the <file>.changes</file> file, and then later used
9098 to send an acknowledgement when the upload has been
9103 The <var>date</var> should be in RFC822 format
9106 This is generated by the <prgn>822-date</prgn>
9109 </footnote>; it should include the timezone specified
9110 numerically, with the timezone name or abbreviation
9111 optionally present as a comment.
9115 The first `title' line with the package name should start
9116 at the left hand margin; the `trailer' line with the
9117 maintainer and date details should be preceded by exactly
9118 one space. The maintainer details and the date must be
9119 separated by exactly two spaces.
9123 An Emacs mode for editing this format is available: it is
9124 called <tt>debian-changelog-mode</tt>. You can have this
9125 mode selected automatically when you edit a Debian
9126 changelog by adding a local variables clause to the end of
9130 <sect2><heading>Defining alternative changelog formats
9134 It is possible to use a different format to the standard
9135 one, by providing a parser for the format you wish to
9140 In order to have <tt>dpkg-parsechangelog</tt> run your
9141 parser, you must include a line within the last 40 lines
9142 of your file matching the Perl regular expression:
9143 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9144 parentheses should be the name of the format. For
9145 example, you might say:
9147 @@@ changelog-format: joebloggs @@@
9149 Changelog format names are non-empty strings of alphanumerics.
9153 If such a line exists then <tt>dpkg-parsechangelog</tt>
9154 will look for the parser as
9155 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9157 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9158 it is an error for it not to find it, or for it not to
9159 be an executable program. The default changelog format
9160 is <tt>dpkg</tt>, and a parser for it is provided with
9161 the <tt>dpkg</tt> package.
9165 The parser will be invoked with the changelog open on
9166 standard input at the start of the file. It should read
9167 the file (it may seek if it wishes) to determine the
9168 information required and return the parsed information
9169 to standard output in the form of a series of control
9170 fields in the standard format. By default it should
9171 return information about only the most recent version in
9172 the changelog; it should accept a
9173 <tt>-v<var>version</var></tt> option to return changes
9174 information from all versions present <em>strictly
9175 after</em> <var>version</var>, and it should then be an
9176 error for <var>version</var> not to be present in the
9182 <list compact="compact">
9184 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9187 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
9191 <qref id="pkg-f-Distribution"><tt>Distribution</tt></qref>
9196 <p><qref id="pkg-f-Urgency"><tt>Urgency</tt></qref> (mandatory)</p>
9200 <qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref>
9205 <p><qref id="pkg-f-Date"><tt>Date</tt></qref></p>
9209 <qref id="pkg-f-Changes"><tt>Changes</tt></qref>
9216 If several versions are being returned (due to the use
9217 of <tt>-v</tt>), the urgency value should be of the
9218 highest urgency code listed at the start of any of the
9219 versions requested followed by the concatenated
9220 (space-separated) comments from all the versions
9221 requested; the maintainer, version, distribution and
9222 date should always be from the most recent version.
9226 For the format of the <tt>Changes</tt> field see <ref
9227 id="pkg-f-Changes">.
9231 If the changelog format which is being parsed always or
9232 almost always leaves a blank line between individual
9233 change notes these blank lines should be stripped out,
9234 so as to make the resulting output compact.
9238 If the changelog format does not contain date or package
9239 name information this information should be omitted from
9240 the output. The parser should not attempt to synthesise
9241 it or find it from other sources.
9245 If the changelog does not have the expected format the
9246 parser should exit with a nonzero exit status, rather
9247 than trying to muddle through and possibly generating
9252 A changelog parser may not interact with the user at
9256 <sect1 id="pkg-srcsubstvars"><heading><file>debian/substvars</file>
9257 and variable substitutions
9261 When <prgn>dpkg-gencontrol</prgn>,
9262 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
9263 generate control files they do variable substitutions on
9264 their output just before writing it. Variable
9265 substitutions have the form
9266 <tt>${<var>variable-name</var>}</tt>. The optional file
9267 <file>debian/substvars</file> contains variable substitutions
9268 to be used; variables can also be set directly from
9269 <file>debian/rules</file> using the <tt>-V</tt> option to the
9270 source packaging commands, and certain predefined
9271 variables are available.
9275 The is usually generated and modified dynamically by
9276 <file>debian/rules</file> targets; in this case it must be
9277 removed by the <tt>clean</tt> target.
9281 See <manref name="dpkg-source" section="1"> for full
9282 details about source variable substitutions, including the
9283 format of <file>debian/substvars</file>.</p>
9286 <sect1><heading><file>debian/files</file>
9290 This file is not a permanent part of the source tree; it
9291 is used while building packages to record which files are
9292 being generated. <prgn>dpkg-genchanges</prgn> uses it
9293 when it generates a <file>.changes</file> file.
9297 It should not exist in a shipped source package, and so it
9298 (and any backup files or temporary files such as
9299 <file>files.new</file>
9302 <file>files.new</file> is used as a temporary file by
9303 <prgn>dpkg-gencontrol</prgn> and
9304 <prgn>dpkg-distaddfile</prgn> - they write a new
9305 version of <file>files</file> here before renaming it,
9306 to avoid leaving a corrupted copy if an error
9309 </footnote>) should be removed by the
9310 <tt>clean</tt> target. It may also be wise to
9311 ensure a fresh start by emptying or removing it at the
9312 start of the <tt>binary</tt> target.
9316 <prgn>dpkg-gencontrol</prgn> adds an entry to this file
9317 for the <file>.deb</file> file that will be created by
9318 <prgn>dpkg-deb</prgn> from the control file that it
9319 generates, so for most packages all that needs to be done
9320 with this file is to delete it in <tt>clean</tt>.
9324 If a package upload includes files besides the source
9325 package and any binary packages whose control files were
9326 made with <prgn>dpkg-gencontrol</prgn> then they should be
9327 placed in the parent of the package's top-level directory
9328 and <prgn>dpkg-distaddfile</prgn> should be called to add
9329 the file to the list in <file>debian/files</file>.</p>
9332 <sect1><heading><file>debian/tmp</file>
9336 This is the canonical temporary location for the
9337 construction of binary packages by the <tt>binary</tt>
9338 target. The directory <file>tmp</file> serves as the root of
9339 the filesystem tree as it is being constructed (for
9340 example, by using the package's upstream makefiles install
9341 targets and redirecting the output there), and it also
9342 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9343 id="pkg-bincreating">.
9347 If several binary packages are generated from the same
9348 source tree it is usual to use several
9349 <file>debian/tmp<var>something</var></file> directories, for
9350 example <file>tmp-a</file> or <file>tmp-doc</file>.
9354 Whatever <file>tmp</file> directories are created and used by
9355 <tt>binary</tt> must of course be removed by the
9356 <tt>clean</tt> target.</p></sect1>
9360 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9364 As it exists on the FTP site, a Debian source package
9365 consists of three related files. You must have the right
9366 versions of all three to be able to use them.
9371 <tag>Debian source control file - <tt>.dsc</tt></tag>
9375 This file contains a series of fields, identified and
9376 separated just like the fields in the control file of
9377 a binary package. The fields are listed below; their
9378 syntax is described above, in <ref id="pkg-controlfields">.
9379 <list compact="compact">
9381 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9384 <p><qref id="versions"><tt>Version</tt></qref></p>
9387 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
9390 <p><qref id="pkg-f-Binary"><tt>Binary</tt></qref></p>
9393 <p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref></p>
9397 <qref id="relationships"><tt>Build-Depends</tt> et
9398 al.</qref> (source package interrelationships)
9403 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref></p>
9406 <p><qref id="pkg-f-Files"><tt>Files</tt></qref></p>
9411 The source package control file is generated by
9412 <prgn>dpkg-source</prgn> when it builds the source
9413 archive, from other files in the source package,
9414 described above. When unpacking it is checked against
9415 the files and directories in the other parts of the
9416 source package, as described below.</p>
9420 Original source archive -
9422 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9429 This is a compressed (with <tt>gzip -9</tt>)
9430 <prgn>tar</prgn> file containing the source code from
9431 the upstream authors of the program. The tarfile
9432 unpacks into a directory
9433 <file><var>package</var>-<var>upstream-version</var>.orig</file>,
9434 and does not contain files anywhere other than in
9435 there or in its subdirectories.</p>
9439 Debianisation diff -
9441 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9447 This is a unified context diff (<tt>diff -u</tt>)
9448 giving the changes which are required to turn the
9449 original source into the Debian source. These changes
9450 may only include editing and creating plain files.
9451 The permissions of files, the targets of symbolic
9452 links and the characteristics of special files or
9453 pipes may not be changed and no files may be removed
9458 All the directories in the diff must exist, except the
9459 <file>debian</file> subdirectory of the top of the source
9460 tree, which will be created by
9461 <prgn>dpkg-source</prgn> if necessary when unpacking.
9465 The <prgn>dpkg-source</prgn> program will
9466 automatically make the <file>debian/rules</file> file
9467 executable (see below).</p></item>
9472 If there is no original source code - for example, if the
9473 package is specially prepared for Debian or the Debian
9474 maintainer is the same as the upstream maintainer - the
9475 format is slightly different: then there is no diff, and the
9477 <file><var>package</var>_<var>version</var>.tar.gz</file> and
9478 contains a directory
9479 <file><var>package</var>-<var>version</var></file>.
9483 <sect><heading>Unpacking a Debian source package without
9484 <prgn>dpkg-source</prgn>
9488 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9489 Debian source package. However, if it is not available it
9490 is possible to unpack a Debian source archive as follows:
9491 <enumlist compact="compact">
9494 Untar the tarfile, which will create a <file>.orig</file>
9498 <p>Rename the <file>.orig</file> directory to
9499 <file><var>package</var>-<var>version</var></file>.</p>
9503 Create the subdirectory <file>debian</file> at the top of
9504 the source tree.</p>
9506 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9508 <item><p>Untar the tarfile again if you want a copy of the original
9509 source code alongside the Debianised version.</p>
9514 It is not possible to generate a valid Debian source archive
9515 without using <prgn>dpkg-source</prgn>. In particular,
9516 attempting to use <prgn>diff</prgn> directly to generate the
9517 <file>.diff.gz</file> file will not work.
9520 <sect1><heading>Restrictions on objects in source packages
9524 The source package may not contain any hard links
9527 This is not currently detected when building source
9528 packages, but only when extracting
9534 Hard links may be permitted at some point in the
9535 future, but would require a fair amount of
9538 </footnote>, device special files, sockets or setuid or
9542 Setgid directories are allowed.
9548 The source packaging tools manage the changes between the
9549 original and Debianised source using <prgn>diff</prgn> and
9550 <prgn>patch</prgn>. Turning the original source tree as
9551 included in the <file>.orig.tar.gz</file> into the debianised
9552 source must not involve any changes which cannot be
9553 handled by these tools. Problematic changes which cause
9554 <prgn>dpkg-source</prgn> to halt with an error when
9555 building the source package are:
9556 <list compact="compact">
9557 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9559 <item><p>Changing the targets of symbolic links.</p>
9561 <item><p>Creating directories, other than <file>debian</file>.</p>
9563 <item><p>Changes to the contents of binary files.</p></item>
9564 </list> Changes which cause <prgn>dpkg-source</prgn> to
9565 print a warning but continue anyway are:
9566 <list compact="compact">
9569 Removing files, directories or symlinks.
9572 Renaming a file is not treated specially - it is
9573 seen as the removal of the old file (which
9574 generates a warning, but is otherwise ignored),
9575 and the creation of the new
9582 Changed text files which are missing the usual final
9583 newline (either in the original or the modified
9588 Changes which are not represented, but which are not detected by
9589 <prgn>dpkg-source</prgn>, are:
9590 <list compact="compact">
9591 <item><p>Changing the permissions of files (other than
9592 <file>debian/rules</file>) and directories.</p></item>
9597 The <file>debian</file> directory and <file>debian/rules</file>
9598 are handled specially by <prgn>dpkg-source</prgn> - before
9599 applying the changes it will create the <file>debian</file>
9600 directory, and afterwards it will make
9601 <file>debian/rules</file> world-exectuable.
9607 <appendix id="pkg-controlfields"><heading>Control files and their
9608 fields (from old Packaging Manual)
9612 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9613 data in a common format, known as control files. Binary and
9614 source packages have control data as do the <file>.changes</file>
9615 files which control the installation of uploaded files, and
9616 <prgn>dpkg</prgn>'s internal databases are in a similar
9620 <sect><heading>Syntax of control files
9624 A file consists of one or more paragraphs of fields. The
9625 paragraphs are separated by blank lines. Some control files
9626 only allow one paragraph; others allow several, in which
9627 case each paragraph often refers to a different package.
9631 Each paragraph is a series of fields and values; each field
9632 consists of a name, followed by a colon and the value. It
9633 ends at the end of the line. Horizontal whitespace (spaces
9634 and tabs) may occur before or after the value and is ignored
9635 there; it is conventional to put a single space after the
9640 Some fields' values may span several lines; in this case
9641 each continuation line <em>must</em> start with a space or
9642 tab. Any trailing spaces or tabs at the end of individual
9643 lines of a field value are ignored.
9647 Except where otherwise stated only a single line of data is
9648 allowed and whitespace is not significant in a field body.
9649 Whitespace may never appear inside names (of packages,
9650 architectures, files or anything else), version numbers or
9651 in between the characters of multi-character version
9656 Field names are not case-sensitive, but it is usual to
9657 capitalise the field names using mixed case as shown below.
9661 Blank lines, or lines consisting only of spaces and tabs,
9662 are not allowed within field values or between fields - that
9663 would mean a new paragraph.
9667 It is important to note that there are several fields which
9668 are optional as far as <prgn>dpkg</prgn> and the related
9669 tools are concerned, but which must appear in every Debian
9670 package, or whose omission may cause problems. When writing
9671 the control files for Debian packages you <em>must</em> read
9672 the Debian policy manual in conjuction with the details
9673 below and the list of fields for the particular file.</p>
9676 <sect><heading>List of fields
9679 <sect1 id="pkg-f-Package"><heading><tt>Package</tt>
9683 The name of the binary package. Package names consist of
9684 the alphanumerics and <tt>+</tt> <tt>-</tt> <tt>.</tt>
9685 (plus, minus and full stop).
9688 The characters <tt>@</tt> <tt>:</tt> <tt>=</tt>
9689 <tt>%</tt> <tt>_</tt> (at, colon, equals, percent
9690 and underscore) used to be legal and are still
9691 accepted when found in a package file, but may not be
9692 used in new packages
9698 They must be at least two characters and must start with
9699 an alphanumeric. In current versions of dpkg they are
9700 sort of case-sensitive<footnote><p>This is a
9701 bug.</p></footnote>; use lowercase package names unless
9702 the package you're building (or referring to, in other
9703 fields) is already using uppercase.</p>
9706 <sect1 id="pkg-f-Version"><heading><tt>Version</tt>
9710 This lists the source or binary package's version number -
9711 see <ref id="versions">.
9716 <sect1 id="pkg-f-Architecture"><heading><tt>Architecture</tt>
9720 This is the architecture string; it is a single word for
9721 the Debian architecture.
9725 <prgn>dpkg</prgn> will check the declared architecture of
9726 a binary package against its own compiled-in value before
9731 The special value <tt>all</tt> indicates that the package
9732 is architecture-independent.
9736 In the main <file>debian/control</file> file in the source
9737 package, or in the source package control file
9738 <file>.dsc</file>, a list of architectures (separated by
9739 spaces) is also allowed, as is the special value
9740 <tt>any</tt>. A list indicates that the source will build
9741 an architecture-dependent package, and will only work
9742 correctly on the listed architectures. <tt>any</tt>
9743 indicates that though the source package isn't dependent
9744 on any particular architecture and should compile fine on
9745 any one, the binary package(s) produced are not
9746 architecture-independent but will instead be specific to
9747 whatever the current build architecture is.
9751 In a <file>.changes</file> file the <tt>Architecture</tt>
9752 field lists the architecture(s) of the package(s)
9753 currently being uploaded. This will be a list; if the
9754 source for the package is being uploaded too the special
9755 entry <tt>source</tt> is also present.
9759 See <ref id="pkg-debianrules"> for information how to get the
9760 architecture for the build process.
9764 <sect1 id="pkg-f-Maintainer"><heading><tt>Maintainer</tt>
9768 The package maintainer's name and email address. The name
9769 should come first, then the email address inside angle
9770 brackets <tt><></tt> (in RFC822 format).
9774 If the maintainer's name contains a full stop then the
9775 whole field will not work directly as an email address due
9776 to a misfeature in the syntax specified in RFC822; a
9777 program using this field as an address must check for this
9778 and correct the problem if necessary (for example by
9779 putting the name in round brackets and moving it to the
9780 end, and bringing the email address forward).
9784 In a <file>.changes</file> file or parsed changelog data this
9785 contains the name and email address of the person
9786 responsible for the particular version in question - this
9787 may not be the package's usual maintainer.
9791 This field is usually optional in as far as the
9792 <prgn>dpkg</prgn> are concerned, but its absence when
9793 building packages usually generates a warning.</p>
9796 <sect1 id="pkg-f-Source"><heading><tt>Source</tt>
9800 This field identifies the source package name.
9804 In a main source control information or a
9805 <file>.changes</file> or <file>.dsc</file> file or parsed
9806 changelog data this may contain only the name of the
9811 In the control file of a binary package (or in a
9812 <file>Packages</file> file) it may be followed by a version
9813 number in parentheses.
9816 It is usual to leave a space after the package name if
9817 a version number is specified.
9819 </footnote> This version number may be omitted (and is, by
9820 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
9821 the <tt>Version</tt> field of the binary package in
9822 question. The field itself may be omitted from a binary
9823 package control file when the source package has the same
9824 name and version as the binary package.
9828 <sect1><heading>Package interrelationship fields:
9829 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
9830 <tt>Recommends</tt> <tt>Suggests</tt>, <tt>Conflicts</tt>,
9831 <tt>Provides</tt>, <tt>Replaces</tt>
9835 These fields describe the package's relationships with
9836 other packages. Their syntax and semantics are described
9837 in <ref id="relationships">.</p>
9840 <sect1 id="pkg-f-Description"><heading><tt>Description</tt>
9844 In a binary package <tt>Packages</tt> file or main source
9845 control file this field contains a description of the
9846 binary package, in a special format. See <ref
9847 id="descriptions"> for details.
9851 In a <file>.changes</file> file it contains a summary of the
9852 descriptions for the packages being uploaded. The part of
9853 the field before the first newline is empty; thereafter
9854 each line has the name of a binary package and the summary
9855 description line from that binary package. Each line is
9856 indented by one space.</p>
9859 <sect1 id="pkg-f-Essential"><heading><tt>Essential</tt>
9863 This is a boolean field which may occur only in the
9864 control file of a binary package (or in the
9865 <file>Packages</file> file) or in a per-package fields
9866 paragraph of a main source control data file.
9870 If set to <tt>yes</tt> then <prgn>dpkg</prgn> and
9871 <prgn>dselect</prgn> will refuse to remove the package
9872 (though it can be upgraded and/or replaced). The other
9873 possible value is <tt>no</tt>, which is the same as not
9874 having the field at all.</p>
9877 <sect1 id="pkg-f-classification"><heading><tt>Section</tt> and
9882 These two fields classify the package. The
9883 <tt>Priority</tt> represents how important that it is that
9884 the user have it installed; the <tt>Section</tt>
9885 represents an application area into which the package has
9890 When they appear in the <file>debian/control</file> file these
9891 fields give values for the section and priority subfields
9892 of the <tt>Files</tt> field of the <file>.changes</file> file,
9893 and give defaults for the section and priority of the
9898 The section and priority are represented, though not as
9899 separate fields, in the information for each file in the
9900 <qref id="pkg-f-Files"><tt>-File</tt></qref>field of a
9901 <file>.changes</file> file. The section value in a
9902 <file>.changes</file> file is used to decide where to install
9903 a package in the FTP archive.
9907 These fields are not used by by <prgn>dpkg</prgn> proper,
9908 but by <prgn>dselect</prgn> when it sorts packages and
9909 selects defaults. See the Debian policy manual for the
9910 priorities in use and the criteria for selecting the
9911 priority for a Debian package, and look at the Debian FTP
9912 archive for a list of currently in-use priorities.
9916 These fields may appear in binary package control files,
9917 in which case they provide a default value in case the
9918 <file>Packages</file> files are missing the information.
9919 <prgn>dpkg</prgn> and <prgn>dselect</prgn> will only use
9920 the value from a <file>.deb</file> file if they have no other
9921 information; a value listed in a <file>Packages</file> file
9922 will always take precedence. By default
9923 <prgn>dpkg-gencontrol</prgn> does not include the section
9924 and priority in the control file of a binary package - use
9925 the <tt>-isp</tt>, <tt>-is</tt> or <tt>-ip</tt> options to
9926 achieve this effect.</p>
9929 <sect1 id="pkg-f-Binary"><heading><tt>Binary</tt>
9933 This field is a list of binary packages.
9937 When it appears in the <file>.dsc</file> file it is the list
9938 of binary packages which a source package can produce. It
9939 does not necessarily produce all of these binary packages
9940 for every architecture. The source control file doesn't
9941 contain details of which architectures are appropriate for
9942 which of the binary packages.
9946 When it appears in a <file>.changes</file> file it lists the
9947 names of the binary packages actually being uploaded.
9951 The syntax is a list of binary packages separated by
9955 A space after each comma is conventional.
9957 </footnote> Currently the packages must be separated using
9958 only spaces in the <file>.changes</file> file.</p>
9961 <sect1 id="pkg-f-Installed-Size"><heading><tt>Installed-Size</tt>
9965 This field appears in the control files of binary
9966 packages, and in the <file>Packages</file> files. It gives
9967 the total amount of disk space required to install the
9972 The disk space is represented in kilobytes as a simple
9976 <sect1 id="pkg-f-Files"><heading><tt>Files</tt>
9980 This field contains a list of files with information about
9981 each one. The exact information and syntax varies with
9982 the context. In all cases the the part of the field
9983 contents on the same line as the field name is empty. The
9984 remainder of the field is one line per file, each line
9985 being indented by one space and containing a number of
9986 sub-fields separated by spaces.
9990 In the <file>.dsc</file> (Debian source control) file each
9991 line contains the MD5 checksum, size and filename of the
9992 tarfile and (if applicable) diff file which make up the
9993 remainder of the source package.
9996 That is, the parts which are not the
9999 </footnote> The exact forms of the filenames are described
10000 in <ref id="pkg-sourcearchives">.
10004 In the <file>.changes</file> file this contains one line per
10005 file being uploaded. Each line contains the MD5 checksum,
10006 size, section and priority and the filename. The section
10007 and priority are the values of the corresponding fields in
10008 the main source control file - see <ref
10009 id="pkg-f-classification">. If no section or priority is
10010 specified then <tt>-</tt> should be used, though section
10011 and priority values must be specified for new packages to
10012 be installed properly.
10016 The special value <tt>byhand</tt> for the section in a
10017 <tt>.changes</tt> file indicates that the file in question
10018 is not an ordinary package file and must by installed by
10019 hand by the distribution maintainers. If the section is
10020 <tt>byhand</tt> the priority should be <tt>-</tt>.
10024 If a new Debian revision of a package is being shipped and
10025 no new original source archive is being distributed the
10026 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
10027 entry for the original source archive
10028 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
10029 but the <file>.changes</file> file should leave it out. In
10030 this case the original source archive on the distribution
10031 site must match exactly, byte-for-byte, the original
10032 source archive which was used to generate the
10033 <file>.dsc</file> file and diff which are being uploaded.</p>
10038 id="pkg-f-Standards-Version"><heading><tt>Standards-Version</tt>
10042 The most recent version of the standards (the
10043 <prgn>dpkg</prgn> programmers' and policy manuals and
10044 associated texts) with which the package complies. This
10045 is updated manually when editing the source package to
10046 conform to newer standards; it can sometimes be used to
10047 tell when a package needs attention.
10051 Its format is the same as that of a version number except
10052 that no epoch or Debian revision is allowed - see <ref
10053 id="versions">.</p>
10057 <sect1 id="pkg-f-Distribution"><heading><tt>Distribution</tt>
10061 In a <file>.changes</file> file or parsed changelog output
10062 this contains the (space-separated) name(s) of the
10063 distribution(s) where this version of the package should
10064 be or was installed. Distribution names follow the rules
10065 for package names. (See <ref id="pkg-f-Package">).
10069 Current distribution values are:
10071 <tag><em>stable</em></tag>
10074 This is the current `released' version of Debian
10075 GNU/Linux. A new version is released approximately
10076 every 3 months after the <em>development</em> code has
10077 been <em>frozen</em> for a month of testing. Once the
10078 distribution is <em>stable</em> only major bug fixes
10079 are allowed. When changes are made to this
10080 distribution, the release number is increased
10081 (for example: 1.2r1 becomes 1.2r2 then 1.2r3, etc).
10085 <tag><em>unstable</em></tag>
10088 This distribution value refers to the
10089 <em>developmental</em> part of the Debian distribution
10090 tree. New packages, new upstream versions of packages
10091 and bug fixes go into the <em>unstable</em> directory
10092 tree. Download from this distribution at your own
10096 <tag><em>contrib</em></tag>
10099 The packages with this distribution value do not meet
10100 the criteria for inclusion in the main Debian
10101 distribution as defined by the Policy Manual, but meet
10102 the criteria for the <em>contrib</em>
10103 Distribution. There is currently no distinction
10104 between stable and unstable packages in the
10105 <em>contrib</em> or <em>non-free</em>
10106 distributions. Use your best judgement in downloading
10107 from this Distribution.</p>
10110 <tag><em>non-free</em></tag>
10113 Like the packages in the <em>contrib</em> seciton,
10114 the packages in <em>non-free</em> do not meet the
10115 criteria for inclusion in the main Debian distribution
10116 as defined by the Policy Manual. Again, use your best
10117 judgement in downloading from this Distribution.</p>
10119 <tag><em>experimental</em></tag>
10122 The packages with this distribution value are deemed
10123 by their maintainers to be high risk. Oftentimes they
10124 represent early beta or developmental packages from
10125 various sources that the maintainers want people to
10126 try, but are not ready to be a part of the other parts
10127 of the Debian distribution tree. Download at your own
10131 <tag><em>frozen</em></tag>
10134 From time to time, (currently, every 3 months) the
10135 <em>unstable</em> distribution enters a state of
10136 `code-freeze' in anticipation of release as a
10137 <em>stable</em> version. During this period of testing
10138 (usually 4 weeks) only fixes for existing or
10139 newly-discovered bugs will be allowed.
10142 </taglist> You should list <em>all</em> distributions that
10143 the package should be installed into. Except in unusual
10144 circumstances, installations to <em>stable</em> should also
10145 go into <em>frozen</em> (if it exists) and
10146 <em>unstable</em>. Likewise, installations into
10147 <em>frozen</em> should also go into <em>unstable</em>.</p>
10150 <sect1 id="pkg-f-Urgency"><heading><tt>Urgency</tt>
10154 This is a description of how important it is to upgrade to
10155 this version from previous ones. It consists of a single
10156 keyword usually taking one of the values <tt>LOW</tt>,
10157 <tt>MEDIUM</tt> or <tt>HIGH</tt>) followed by an optional
10158 commentary (separated by a space) which is usually in
10159 parentheses. For example:
10161 Urgency: LOW (HIGH for diversions users)
10166 This field appears in the <file>.changes</file> file and in
10167 parsed changelogs; its value appears as the value of the
10168 <tt>urgency</tt> attribute in a <prgn>dpkg</prgn>-style
10169 changelog (see <ref id="pkg-dpkgchangelog">).
10173 Urgency keywords are not case-sensitive.</p>
10176 <sect1 id="pkg-f-Date"><heading><tt>Date</tt>
10180 In <tt>.changes</tt> files and parsed changelogs, this
10181 gives the date the package was built or last edited.</p>
10184 <sect1 id="pkg-f-Format"><heading><tt>Format</tt>
10188 This field occurs in <file>.changes</file> files, and
10189 specifies a format revision for the file. The format
10190 described here is version <tt>1.5</tt>. The syntax of the
10191 format value is the same as that of a package version
10192 number except that no epoch or Debian revision is allowed
10193 - see <ref id="versions">.</p>
10196 <sect1 id="pkg-f-Changes"><heading><tt>Changes</tt>
10200 In a <file>.changes</file> file or parsed changelog this field
10201 contains the human-readable changes data, describing the
10202 differences between the last version and the current one.
10206 There should be nothing in this field before the first
10207 newline; all the subsequent lines must be indented by at
10208 least one space; blank lines must be represented by a line
10209 consiting only of a space and a full stop.
10213 Each version's change information should be preceded by a
10214 `title' line giving at least the version, distribution(s)
10215 and urgency, in a human-readable way.
10219 If data from several versions is being returned the entry
10220 for the most recent version should be returned first, and
10221 entries should be separated by the representation of a
10222 blank line (the `title' line may also be followed by the
10223 representation of blank line).</p>
10226 <sect1 id="pkg-f-Filename"><heading><tt>Filename</tt> and
10227 <tt>MSDOS-Filename</tt>
10231 These fields in <tt>Packages</tt> files give the
10232 filename(s) of (the parts of) a package in the
10233 distribution directories, relative to the root of the
10234 Debian hierarchy. If the package has been split into
10235 several parts the parts are all listed in order, separated
10239 <sect1 id="pkg-f-Size"><heading><tt>Size</tt> and <tt>MD5sum</tt>
10243 These fields in <file>Packages</file> files give the size (in
10244 bytes, expressed in decimal) and MD5 checksum of the
10245 file(s) which make(s) up a binary package in the
10246 distribution. If the package is split into several parts
10247 the values for the parts are listed in order, separated by
10251 <sect1 id="pkg-f-Status"><heading><tt>Status</tt>
10255 This field in <prgn>dpkg</prgn>'s status file records
10256 whether the user wants a package installed, removed or
10257 left alone, whether it is broken (requiring
10258 reinstallation) or not and what its current state on the
10259 system is. Each of these pieces of information is a
10263 <sect1 id="pkg-f-Config-Version"><heading><tt>Config-Version</tt>
10267 If a package is not installed or not configured, this
10268 field in <prgn>dpkg</prgn>'s status file records the last
10269 version of the package which was successfully
10273 <sect1 id="pkg-f-Conffiles"><heading><tt>Conffiles</tt>
10277 This field in <prgn>dpkg</prgn>'s status file contains
10278 information about the automatically-managed configuration
10279 files held by a package. This field should <em>not</em>
10280 appear anywhere in a package!</p>
10283 <sect1><heading>Obsolete fields
10287 These are still recognised by <prgn>dpkg</prgn> but should
10288 not appear anywhere any more.
10289 <taglist compact="compact">
10291 <tag><tt>Revision</tt></tag>
10292 <tag><tt>Package-Revision</tt></tag>
10293 <tag><tt>Package_Revision</tt></tag>
10296 The Debian revision part of the package version was
10297 at one point in a separate control file field. This
10298 field went through several names.</p>
10301 <tag><tt>Recommended</tt></tag>
10302 <item><p>Old name for <tt>Recommends</tt></p>
10305 <tag><tt>Optional</tt></tag>
10306 <item><p>Old name for <tt>Suggests</tt>.</p>
10308 <tag><tt>Class</tt></tag>
10309 <item><p>Old name for <tt>Priority</tt>.</p>
10317 <appendix id="pkg-conffiles"><heading>Configuration file handling
10318 (from old Packaging Manual)
10322 <prgn>dpkg</prgn> can do a certain amount of automatic
10323 handling of package configuration files.
10327 Whether this mechanism is appropriate depends on a number of
10328 factors, but basically there are two approaches to any
10329 particular configuration file.
10333 The easy method is to ship a best-effort configuration in the
10334 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10335 handle updates. If the user is unlikely to want to edit the
10336 file, but you need them to be able to without losing their
10337 changes, and a new package with a changed version of the file
10338 is only released infrequently, this is a good approach.
10342 The hard method is to build the configuration file from
10343 scratch in the <prgn>postinst</prgn> script, and to take the
10344 responsibility for fixing any mistakes made in earlier
10345 versions of the package automatically. This will be
10346 appropriate if the file is likely to need to be different on
10350 <sect><heading>Automatic handling of configuration files by
10355 A package may contain a control area file called
10356 <tt>conffiles</tt>. This file should be a list of filenames
10357 of configuration files needing automatic handling, separated
10358 by newlines. The filenames should be absolute pathnames,
10359 and the files referred to should actually exist in the
10364 When a package is upgraded <prgn>dpkg</prgn> will process
10365 the configuration files during the configuration stage,
10366 shortly before it runs the package's <prgn>postinst</prgn>
10371 For each file it checks to see whether the version of the
10372 file included in the package is the same as the one that was
10373 included in the last version of the package (the one that is
10374 being upgraded from); it also compares the version currently
10375 installed on the system with the one shipped with the last
10380 If neither the user nor the package maintainer has changed
10381 the file, it is left alone. If one or the other has changed
10382 their version, then the changed version is preferred - i.e.,
10383 if the user edits their file, but the package maintainer
10384 doesn't ship a different version, the user's changes will
10385 stay, silently, but if the maintainer ships a new version
10386 and the user hasn't edited it the new version will be
10387 installed (with an informative message). If both have
10388 changed their version the user is prompted about the problem
10389 and must resolve the differences themselves.
10393 The comparisons are done by calculating the MD5 message
10394 digests of the files, and storing the MD5 of the file as it
10395 was included in the most recent version of the package.
10399 When a package is installed for the first time
10400 <prgn>dpkg</prgn> will install the file that comes with it,
10401 unless that would mean overwriting a file already on the
10406 However, note that <prgn>dpkg</prgn> will <em>not</em>
10407 replace a conffile that was removed by the user (or by a
10408 script). This is necessary because with some programs a
10409 missing file produces an effect hard or impossible to
10410 achieve in another way, so that a missing file needs to be
10411 kept that way if the user did it.
10415 Note that a package should <em>not</em> modify a
10416 <prgn>dpkg</prgn>-handled conffile in its maintainer
10417 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10418 the user confusing and possibly dangerous options for
10419 conffile update when the package is upgraded.</p>
10422 <sect><heading>Fully-featured maintainer script configuration
10427 For files which contain site-specific information such as
10428 the hostname and networking details and so forth, it is
10429 better to create the file in the package's
10430 <prgn>postinst</prgn> script.
10434 This will typically involve examining the state of the rest
10435 of the system to determine values and other information, and
10436 may involve prompting the user for some information which
10437 can't be obtained some other way.
10441 When using this method there are a couple of important
10442 issues which should be considered:
10446 If you discover a bug in the program which generates the
10447 configuration file, or if the format of the file changes
10448 from one version to the next, you will have to arrange for
10449 the postinst script to do something sensible - usually this
10450 will mean editing the installed configuration file to remove
10451 the problem or change the syntax. You will have to do this
10452 very carefully, since the user may have changed the file,
10453 perhaps to fix the very problem that your script is trying
10454 to deal with - you will have to detect these situations and
10455 deal with them correctly.
10459 If you do go down this route it's probably a good idea to
10460 make the program that generates the configuration file(s) a
10461 separate program in <file>/usr/sbin</file>, by convention called
10462 <file><var>package</var>config</file> and then run that if
10463 appropriate from the post-installation script. The
10464 <tt><var>package</var>config</tt> program should not
10465 unquestioningly overwrite an existing configuration - if its
10466 mode of operation is geared towards setting up a package for
10467 the first time (rather than any arbitrary reconfiguration
10468 later) you should have it check whether the configuration
10469 already exists, and require a <tt>--force</tt> flag to
10470 overwrite it.</p></sect>
10473 <appendix id="pkg-alternatives"><heading>Alternative versions of
10474 an interface - <prgn>update-alternatives</prgn> (from old
10479 When several packages all provide different versions of the
10480 same program or file it is useful to have the system select a
10481 default, but to allow the system administrator to change it
10482 and have their decisions respected.
10486 For example, there are several versions of the <prgn>vi</prgn>
10487 editor, and there is no reason to prevent all of them from
10488 being installed at once, each under their own name
10489 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10490 Nevertheless it is desirable to have the name <tt>vi</tt>
10491 refer to something, at least by default.
10495 If all the packages involved cooperate, this can be done with
10496 <prgn>update-alternatives</prgn>.
10500 Each package provides its own version under its own name, and
10501 calls <prgn>update-alternatives</prgn> in its postinst to
10502 register its version (and again in its prerm to deregister
10507 See the manpage <manref name="update-alternatives"
10508 section="8"> for details.
10512 If <prgn>update-alternatives</prgn> does not seem appropriate
10513 you may wish to consider using diversions instead.</p>
10516 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10517 package's version of a file (from old Packaging Manual)
10521 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10522 when it reinstalls the package it belongs to, and to have it
10523 put the file from the package somewhere else instead.
10527 This can be used locally to override a package's version of a
10528 file, or by one package to override another's version (or
10529 provide a wrapper for it).
10533 Before deciding to use a diversion, read <ref
10534 id="pkg-alternatives"> to see if you really want a diversion
10535 rather than several alternative versions of a program.
10539 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10540 and updated by a special program <prgn>dpkg-divert</prgn>.
10541 Please see <manref name="dpkg-divert" section="8"> for full
10542 details of its operation.
10546 When a package wishes to divert a file from another, it should
10547 call <prgn>dpkg-divert</prgn> in its preinst to add the
10548 diversion and rename the existing file. For example,
10549 supposing that a <prgn>smailwrapper</prgn> package wishes to
10550 install a wrapper around <file>/usr/sbin/smail</file>:
10552 if [ install = "$1" ]; then
10553 dpkg-divert --package smailwrapper --add --rename \
10554 --divert /usr/sbin/smail.real /usr/sbin/smail
10556 </example> Testing <tt>$1</tt> is necessary so that the script
10557 doesn't try to add the diversion again when
10558 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10559 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10560 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10561 get installed as the true version.
10565 The postrm has to do the reverse:
10567 if [ remove = "$1" ]; then
10568 dpkg-divert --package smailwrapper --remove --rename \
10569 --divert /usr/sbin/smail.real /usr/sbin/smail
10575 Do not attempt to divert a file which is vitally important for
10576 the system's operation - when using <prgn>dpkg-divert</prgn>
10577 there is a time, after it has been diverted but before
10578 <prgn>dpkg</prgn> has installed the new version, when the file
10579 does not exist.</p>