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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
3793 <p>When a package is installed or upgraded, "postinst
3794 configure" runs after the new files are safely on-disk.
3795 Since it is perfectly safe to invoke ldconfig
3796 unconditionally in a postinst, it is OK for a package to
3797 simply put ldconfig in its postinst without checking the
3798 argument. The postinst can also be called to recover from
3799 a failed upgrade. This happens before any new files are
3800 unpacked, so there is no reason to call "ldconfig" at this
3803 <p>For a package that is being removed, prerm is
3804 called with all the files intact, so calling ldconfig is
3805 useless. The other calls to "prerm" happen in the case of
3806 upgrade at a time when all the files of the old package
3807 are on-disk, so again calling "ldconfig" is pointless.
3809 <p>postrm, on the other hand, is called with the "remove"
3810 argument just after the files are removed, so this is the
3811 proper time to call "ldconfig" to notify the system of the
3812 fact shared libraries from the package are removed.
3813 The postrm can be called at several other times. At the
3814 time of "postrm purge", "postrm abort-install", or "postrm
3815 abort-upgrade", calling "ldconfig" is useless because the
3816 shared lib files are not on-disk. However, when "postrm"
3817 is invoked with arguments "upgrade", "failed-upgrade", or
3818 "disappear", a shared lib may exist on-disk under a
3825 <heading>Handling shared library dependencies - the
3826 <tt>shlibs</tt> system</heading>
3829 If a package contains a binary or library which links to a
3830 shared library, we must ensure that when the package is
3831 installed on the system, all of the libraries needed are
3832 also installed. This requirement led to the creation of the
3833 <tt>shlibs</tt> system, which is very simple in its design:
3834 any package which <em>provides</em> a shared library also
3835 provides information on the package dependencies required to
3836 ensure the presence of this library, and any package which
3837 <em>uses</em> a shared library uses this information to
3838 determine the dependencies it requires. The files which
3839 contain the mapping from shared libraries to the necessary
3840 dependency information are called <file>shlibs</file> files.
3844 Thus, when a package is built which contains any shared
3845 libraries, it must provide a <file>shlibs</file> file for other
3846 packages to use, and when a package is built which contains
3847 any shared libraries or compiled binaries, it must run
3848 <prgn>dpkg-shlibdeps</prgn> on these to determine the
3849 libraries used and hence the dependencies needed by this
3852 In the past, the shared libraries linked to were
3853 determined by calling <prgn>ldd</prgn>, but now
3854 <prgn>objdump</prgn> is used to do this. The only
3855 change this makes to package building is that
3856 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
3857 libraries, whereas in the past this was unnecessary.
3858 The rest of this footnote explains the advantage that
3863 We say that a binary <tt>foo</tt> <em>directly</em> uses
3864 a library <tt>libbar</tt> if it is explicitly linked
3865 with that library (that is, it uses the flag
3866 <tt>-lbar</tt> during the linking stage). Other
3867 libraries that are needed by <tt>libbar</tt> are linked
3868 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
3869 linker will load them automatically when it loads
3870 <tt>libbar</tt>. A package should depend on
3871 the libraries it directly uses, and the dependencies for
3872 those libraries should automatically pull in the other
3877 Unfortunately, the <prgn>ldd</prgn> program shows both
3878 the directly and indirectly used libraries, meaning that
3879 the dependencies determined included both direct and
3880 indirect dependencies. The use of <prgn>objdump</prgn>
3881 avoids this problem by determining only the directly
3886 A good example of where this helps is the following. We
3887 could update <tt>libimlib</tt> with a new version that
3888 supports a new graphics format called dgf (but retaining
3889 the same major version number). If we used the old
3890 <prgn>ldd</prgn> method, every package that uses
3891 <tt>libimlib</tt> would need to be recompiled so it
3892 would also depend on <tt>libdgf</tt> or it wouldn't run
3893 due to missing symbols. However with the new system,
3894 packages using <tt>libimlib</tt> can rely on
3895 <tt>libimlib</tt> itself having the dependency on
3896 <tt>libdgf</tt> and so they would not need rebuilding.
3902 In the following sections, we will first describe where the
3903 various <tt>shlibs</tt> files are to be found, then how to
3904 use <prgn>dpkg-shlibdeps</prgn>, and finally the
3905 <tt>shlibs</tt> file format and how to create them if your
3906 package contains a shared library.
3910 <sect><heading>The <tt>shlibs</tt> files present on the system
3914 There are several places where <tt>shlibs</tt> files are
3915 found. The following list gives them in the order in which
3916 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
3917 one which gives the required information is used.)
3923 <p><file>debian/shlibs.local</file></p>
3925 This lists overrides for this package. Its use is
3926 described below (see <ref id="shlibslocal">).
3931 <p><file>/etc/dpkg/shlibs.override</file></p>
3933 This lists global overrides. This list is normally
3934 empty. It is maintained by the local system
3940 <p><file>DEBIAN/shlibs</file> files in the `build directory'</p>
3942 When packages are being built, any
3943 <file>debian/shlibs</file> files are copied into the
3944 control file area of the temporary build directory and
3945 given the name <file>shlibs</file>. These files give
3946 details of any shared libraries included in the
3949 An example may help here. Let us say that the
3950 source package <tt>foo</tt> generates two binary
3951 packages, <tt>libfoo2</tt> and
3952 <tt>foo-runtime</tt>. When building the binary
3953 packages, the two packages are created in the
3954 directories <file>debian/libfoo2</file> and
3955 <file>debian/foo-runtime</file> respectively.
3956 (<file>debian/tmp</file> could be used instead of one
3957 of these.) Since <tt>libfoo2</tt> provides the
3958 <tt>libfoo</tt> shared library, it will require a
3959 <tt>shlibs</tt> file, which will be installed in
3960 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
3962 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
3963 when <prgn>dpkg-shlibdeps</prgn> is run on the
3965 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
3967 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
3968 determine whether <tt>foo-prog</tt>'s library
3969 dependencies are satisfied by any of the libraries
3970 provided by <tt>libfoo2</tt>. For this reason,
3971 <prgn>dpkg-shlibdeps</prgn> must only be run once
3972 all of the individual binary packages'
3973 <tt>shlibs</tt> files have been installed into the
3981 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
3983 These are the <file>shlibs</file> files corresponding to
3984 all of the packages installed on the system, and are
3985 maintained by the relevant package maintainers.
3990 <p><file>/etc/dpkg/shlibs.default</file></p>
3992 This file lists any shared libraries whose packages
3993 have failed to provide correct <file>shlibs</file> files.
3994 It was used when the <file>shlibs</file> setup was first
3995 introduced, but it is now normally empty. It is
3996 maintained by the <tt>dpkg</tt> maintainer.
4004 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4005 <file>shlibs</file> files</heading>
4008 Put a call to <prgn>dpkg-shlibdeps</prgn> into your
4009 <file>debian/rules</file> file. If your package contains only
4010 compiled binaries and libraries (but no scripts), you can
4011 use a command such as:
4012 <example compact="compact">
4013 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4014 debian/tmp/usr/lib/*
4016 Otherwise, you will need to explicitly list the compiled
4017 binaries and libraries.<footnote>
4019 If you are using <tt>debhelper</tt>, the
4020 <prgn>dh_shlibdeps</prgn> program will do this work for
4021 you. It will also correctly handle multi-binary
4028 This command puts the dependency information into the
4029 <file>debian/substvars</file> file, which is then used by
4030 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4031 <tt>${shlib:Depends}</tt> variable in the <tt>Depends</tt>
4032 field in the control file for this to work.
4036 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4037 done. If it does complain you might need to create your own
4038 <file>debian/shlibs.local</file> file, as explained below (see
4039 <ref id="shlibslocal">).
4043 If you have multiple binary packages, you will need to call
4044 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4045 compiled libraries or binaries. In such a case, you will
4046 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4047 utilities to specify a different <file>substvars</file> file.
4048 For more details on this and other options, see <manref
4049 name="dpkg-shlibdeps" section="1">.
4053 <sect id="shlibs"><heading>The <file>shlibs</file> File Format
4057 Each <file>shlibs</file> file has the same format. Lines
4058 beginning with <tt>#</tt> are considered to be comments and
4059 are ignored. Each line is of the form:
4060 <example compact="compact">
4061 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4066 We will explain this by reference to the example of the
4067 <tt>zlib1g</tt> package, which (at the time of writing)
4068 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4072 <var>library-name</var> is the name of the shared library,
4073 in this case <tt>libz</tt>. (This must match the name part
4074 of the soname, see below.)
4078 <var>soname-version-number</var> is the version part of the
4079 soname of the library. The soname is the thing that must
4080 exactly match for the library to be recognized by the
4081 dynamic linker, and is usually of the form
4082 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4083 example, <tt>libz.so.1</tt>.<footnote>
4085 This can be determined using the command
4086 <example compact="compact">
4087 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
4091 The version part is the part which comes after
4092 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
4096 <var>dependencies</var> has the same syntax as a dependency
4097 field in a binary package control file. It should give
4098 details of which packages are required to satisfy a binary
4099 built against the version of the library contained in the
4100 package. See <ref id="depsyntax"> for details.
4104 In our example, if the first version of the <tt>zlib1g</tt>
4105 package which contained a minor number of at least
4106 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
4107 <tt>shlibs</tt> entry for this library could say:
4108 <example compact="compact">
4109 libz 1 zlib1g (>= 1:1.1.3)
4111 The version-specific dependency is to avoid warnings from
4112 the dynamic linker about using older shared libraries with
4118 <heading>Providing a <file>shlibs</file> file</heading>
4121 If your package provides a shared library, you should create
4122 a <file>shlibs</file> file following the format described above.
4123 It is usual to call this file <file>debian/shlibs</file> (but if
4124 you have multiple binary packages, you might want to call it
4125 <file>debian/shlibs.<var>package</var></file> instead). Then
4126 let <file>debian/rules</file> install it in the control area:
4127 <example compact="compact">
4128 install -m644 debian/shlibs debian/tmp/DEBIAN
4130 or, in the case of a multi-binary package:
4131 <example compact="compact">
4132 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
4134 An alternative way of doing this is to create the
4135 <file>shlibs</file> file in the control area directly from
4136 <file>debian/rules</file> without using a <file>debian/shlibs</file>
4137 file at all,<footnote>
4139 This is what <prgn>dh_makeshlibs</prgn> in the
4140 <tt>debhelper</tt> suite does.
4143 since the <file>debian/shlibs</file> file itself is ignored by
4144 <prgn>dpkg-shlibdeps</prgn>.
4148 As <prgn>dpkg-shlibdeps</prgn> reads the
4149 <file>DEBIAN/shlibs</file> files in all of the binary packages
4150 being built from this source package, all of the
4151 <file>DEBIAN/shlibs</file> files should be installed before
4152 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
4157 <sect id="shlibslocal">
4158 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
4161 This file is intended only as a <em>temporary</em> fix if
4162 your binaries or libraries depend on a library whose package
4163 does not yet provide a correct <file>shlibs</file> file.
4167 We will assume that you are trying to package a binary
4168 <tt>foo</tt>. When you try running
4169 <prgn>dpkg-shlibdeps</prgn> you get the following error
4170 message (<tt>-O</tt> displays the dependency information on
4171 <tt>stdout</tt> instead of writing it to
4172 <tt>debian/substvars</tt>, and the lines have been wrapped
4173 for ease of reading):
4174 <example compact="compact">
4175 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
4176 dpkg-shlibdeps: warning: unable to find dependency
4177 information for shared library libbar (soname 1,
4178 path /usr/lib/libbar.so.1, dependency field Depends)
4179 shlibs:Depends=libc6 (>= 2.2.2-2)
4181 You can then run <prgn>ldd</prgn> on the binary to find the
4182 full location of the library concerned:
4183 <example compact="compact">
4185 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
4186 libc.so.6 => /lib/libc.so.6 (0x40032000)
4187 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
4189 So the <prgn>foo</prgn> binary depends on the
4190 <prgn>libbar</prgn> shared library, but no package seems to
4191 provide a <file>*.shlibs</file> file handling
4192 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
4193 determine the package responsible:
4194 <example compact="compact">
4195 $ dpkg -S /usr/lib/libbar.so.1
4196 bar1: /usr/lib/libbar.so.1
4197 $ dpkg -s bar1 | grep Version
4200 This tells us that the <tt>bar1</tt> package, version 1.0-1,
4201 is the one we are using. Now we can file a bug against the
4202 <tt>bar1</tt> package and create our own
4203 <file>debian/shlibs.local</file> to locally fix the problem.
4204 Including the following line into your
4205 <file>debian/shlibs.local</file> file:
4206 <example compact="compact">
4207 libbar 1 bar1 (>= 1.0-1)
4209 should allow the package build to work.
4213 As soon as the maintainer of <tt>bar1</tt> provides a
4214 correct <file>shlibs</file> file, you should remove this line
4215 from your <file>debian/shlibs.local</file> file. (You should
4216 probably also then have a versioned <tt>Build-Depends</tt>
4217 on <tt>bar1</tt> to help ensure that others do not have the
4218 same problem building your package.)
4223 <chapt id="opersys"><heading>The Operating System</heading>
4226 <heading>Filesystem hierarchy</heading>
4230 <heading>Filesystem Structure</heading>
4233 The location of all installed files and directories must
4234 comply with the Filesystem Hierarchy Standard (FHS),
4235 version 2.1, except where doing so would violate other
4236 terms of Debian Policy. The version of this document
4237 referred here can be found in the <tt>debian-policy</tt>
4239 <url id="http://www.debian.org/doc/packaging-manuals/fhs/"
4240 name="FHS (Debian copy)"> alongside this manual (or, if
4241 you have the <package>debian-policy</package> installed,
4243 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
4244 (local copy)">). The
4245 latest version, which may be a more recent version, may
4247 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
4248 Specific questions about following the standard may be
4249 asked on the <tt>debian-devel</tt> mailing list, or
4250 referred to the FHS mailing list (see the
4251 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
4257 <heading>Site-specific programs</heading>
4260 As mandated by the FHS, packages must not place any
4261 files in <file>/usr/local</file>, either by putting them in
4262 the file system archive to be unpacked by <prgn>dpkg</prgn>
4263 or by manipulating them in their maintainer scripts.
4267 However, the package may create empty directories below
4268 <file>/usr/local</file> so that the system administrator knows
4269 where to place site-specific files. These directories
4270 should be removed on package removal if they are
4275 Note, that this applies only to directories <em>below</em>
4276 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
4277 Packages must not create sub-directories in the directory
4278 <file>/usr/local</file> itself, except those listed in FHS,
4279 section 4.5. However, you may create directories below
4280 them as you wish. You must not remove any of the
4281 directories listed in 4.5, even if you created them.
4285 Since <file>/usr/local</file> can be mounted read-only from a
4286 remote server, these directories must be created and
4287 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
4288 maintainer scripts and not be included in the
4289 <file>.deb</file> archive. These scripts must not fail if
4290 either of these operations fail.
4294 For example, the <tt>emacsen-common</tt> package could
4295 contain something like
4296 <example compact="compact">
4297 if [ ! -e /usr/local/share/emacs ]
4299 if mkdir /usr/local/share/emacs 2>/dev/null
4301 chown root:staff /usr/local/share/emacs
4302 chmod 2775 /usr/local/share/emacs
4306 in its <prgn>postinst</prgn> script, and
4307 <example compact="compact">
4308 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
4309 rmdir /usr/local/share/emacs 2>/dev/null || true
4311 in the <prgn>prerm</prgn> script. (Note that this form is
4312 used to ensure that if the script is interrupted, the
4313 directory <file>/usr/local/share/emacs</file> will still be
4318 If you do create a directory in <file>/usr/local</file> for
4319 local additions to a package, you should ensure that
4320 settings in <file>/usr/local</file> take precedence over the
4321 equivalents in <file>/usr</file>.
4325 However, because <file>/usr/local</file> and its contents are
4326 for exclusive use of the local administrator, a package
4327 must not rely on the presence or absence of files or
4328 directories in <file>/usr/local</file> for normal operation.
4332 The <file>/usr/local</file> directory itself and all the
4333 subdirectories created by the package should (by default) have
4334 permissions 2775 (group-writable and set-group-id) and be
4335 owned by <tt>root.staff</tt>.
4340 <heading>The system-wide mail directory</heading>
4342 The system-wide mail directory is <file>/var/mail</file>. This
4343 directory is part of the base system and should not owned
4344 by any particular mail agents. The use of the old
4345 location <file>/var/spool/mail</file> is deprecated, even
4346 though the spool may still be physically located there.
4347 To maintain partial upgrade compatibility for systems
4348 which have <file>/var/spool/mail</file> as their physical mail
4349 spool, packages using <file>/var/mail</file> must depend on
4350 either <package>libc6</package> (>= 2.1.3-13), or on
4351 <package>base-files</package> (>= 2.2.0), or on later
4352 versions of either one of these packages.
4358 <heading>Users and groups</heading>
4361 <heading>Introduction</heading>
4363 The Debian system can be configured to use either plain or
4368 Some user ids (UIDs) and group ids (GIDs) are reserved
4369 globally for use by certain packages. Because some
4370 packages need to include files which are owned by these
4371 users or groups, or need the ids compiled into binaries,
4372 these ids must be used on any Debian system only for the
4373 purpose for which they are allocated. This is a serious
4374 restriction, and we should avoid getting in the way of
4375 local administration policies. In particular, many sites
4376 allocate users and/or local system groups starting at 100.
4380 Apart from this we should have dynamically allocated ids,
4381 which should by default be arranged in some sensible
4382 order, but the behavior should be configurable.
4386 Packages other than <tt>base-passwd</tt> must not modify
4387 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
4388 <file>/etc/group</file> or <file>/etc/gshadow</file>.
4393 <heading>UID and GID classes</heading>
4395 The UID and GID numbers are divided into classes as
4401 Globally allocated by the Debian project, the same
4402 on every Debian system. These ids will appear in
4403 the <file>passwd</file> and <file>group</file> files of all
4404 Debian systems, new ids in this range being added
4405 automatically as the <tt>base-passwd</tt> package is
4410 Packages which need a single statically allocated
4411 uid or gid should use one of these; their
4412 maintainers should ask the <tt>base-passwd</tt>
4420 Dynamically allocated system users and groups.
4421 Packages which need a user or group, but can have
4422 this user or group allocated dynamically and
4423 differently on each system, should use <tt>adduser
4424 --system</tt> to create the group and/or user.
4425 <prgn>adduser</prgn> will check for the existence of
4426 the user or group, and if necessary choose an unused
4427 id based on the ranges specified in
4428 <file>adduser.conf</file>.
4432 <tag>1000-29999:</tag>
4435 Dynamically allocated user accounts. By default
4436 <prgn>adduser</prgn> will choose UIDs and GIDs for
4437 user accounts in this range, though
4438 <file>adduser.conf</file> may be used to modify this
4443 <tag>30000-59999:</tag>
4448 <tag>60000-64999:</tag>
4451 Globally allocated by the Debian project, but only
4452 created on demand. The ids are allocated centrally
4453 and statically, but the actual accounts are only
4454 created on users' systems on demand.
4458 These ids are for packages which are obscure or
4459 which require many statically-allocated ids. These
4460 packages should check for and create the accounts in
4461 <file>/etc/passwd</file> or <file>/etc/group</file> (using
4462 <prgn>adduser</prgn> if it has this facility) if
4463 necessary. Packages which are likely to require
4464 further allocations should have a `hole' left after
4465 them in the allocation, to give them room to
4470 <tag>65000-65533:</tag>
4478 User <tt>nobody</tt>. The corresponding gid refers
4479 to the group <tt>nogroup</tt>.
4486 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
4487 not</em> be used, because it is the error return
4496 <sect id="sysvinit">
4497 <heading>System run levels and <file>init.d</file> scripts</heading>
4499 <sect1 id="/etc/init.d">
4500 <heading>Introduction</heading>
4503 The <file>/etc/init.d</file> directory contains the scripts
4504 executed by <prgn>init</prgn> at boot time and when the
4505 init state (or `runlevel') is changed (see <manref
4506 name="init" section="8">).
4510 There are at least two different, yet functionally
4511 equivalent, ways of handling these scripts. For the sake
4512 of simplicity, this document describes only the symbolic
4513 link method. However, it must not be assumed by maintainer
4514 scripts that this method is being used, and any automated
4515 manipulation of the various runlevel behaviours by
4516 maintainer scripts must be performed using
4517 <prgn>update-rc.d</prgn> as described below and not by
4518 manually installing or removing symlinks. For information
4519 on the implementation details of the other method,
4520 implemented in the <tt>file-rc</tt> package, please refer
4521 to the documentation of that package.
4525 These scripts are referenced by symbolic links in the
4526 <file>/etc/rc<var>n</var>.d</file> directories. When changing
4527 runlevels, <prgn>init</prgn> looks in the directory
4528 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
4529 execute, where <tt><var>n</var></tt> is the runlevel that
4530 is being changed to, or <tt>S</tt> for the boot-up
4535 The names of the links all have the form
4536 <file>S<var>mm</var><var>script</var></file> or
4537 <file>K<var>mm</var><var>script</var></file> where
4538 <var>mm</var> is a two-digit number and <var>script</var>
4539 is the name of the script (this should be the same as the
4540 name of the actual script in <file>/etc/init.d</file>).
4544 When <prgn>init</prgn> changes runlevel first the targets
4545 of the links whose names start with a <tt>K</tt> are
4546 executed, each with the single argument <tt>stop</tt>,
4547 followed by the scripts prefixed with an <tt>S</tt>, each
4548 with the single argument <tt>start</tt>. (The links are
4549 those in the <file>/etc/rc<var>n</var>.d</file> directory
4550 corresponding to the new runlevel.) The <tt>K</tt> links
4551 are responsible for killing services and the <tt>S</tt>
4552 link for starting services upon entering the runlevel.
4556 For example, if we are changing from runlevel 2 to
4557 runlevel 3, init will first execute all of the <tt>K</tt>
4558 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
4559 all of the <tt>S</tt> prefixed scripts in that directory.
4560 The links starting with <tt>K</tt> will cause the
4561 referred-to file to be executed with an argument of
4562 <tt>stop</tt>, and the <tt>S</tt> links with an argument
4567 The two-digit number <var>mm</var> is used to determine
4568 the order in which to run the scripts: low-numbered links
4569 have their scripts run first. For example, the
4570 <tt>K20</tt> scripts will be executed before the
4571 <tt>K30</tt> scripts. This is used when a certain service
4572 must be started before another. For example, the name
4573 server <prgn>bind</prgn> might need to be started before
4574 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
4575 can set up its access lists. In this case, the script
4576 that starts <prgn>bind</prgn> would have a lower number
4577 than the script that starts <prgn>inn</prgn> so that it
4579 <example compact="compact">
4586 The two runlevels 0 (halt) and 6 (reboot) are slightly
4587 different. In these runlevels, the links with an
4588 <tt>S</tt> prefix are still called after those with a
4589 <tt>K</tt> prefix, but they too are called with the single
4590 argument <tt>stop</tt>.
4594 Also, if the script name ends <tt>.sh</tt>, the script
4595 will be sourced in runlevel <tt>S</tt> rather that being
4596 run in a forked subprocess, but will be explicitly run by
4597 <prgn>sh</prgn> in all other runlevels.
4602 <heading>Writing the scripts</heading>
4605 Packages that include daemons for system services should
4606 place scripts in <file>/etc/init.d</file> to start or stop
4607 services at boot time or during a change of runlevel.
4608 These scripts should be named
4609 <file>/etc/init.d/<var>package</var></file>, and they should
4610 accept one argument, saying what to do:
4613 <tag><tt>start</tt></tag>
4614 <item><p>start the service,</p></item>
4616 <tag><tt>stop</tt></tag>
4617 <item><p>stop the service,</p></item>
4619 <tag><tt>restart</tt></tag>
4620 <item><p>stop and restart the service,</p></item>
4622 <tag><tt>reload</tt></tag>
4623 <item><p>cause the configuration of the service to be
4624 reloaded without actually stopping and restarting
4625 the service,</p></item>
4627 <tag><tt>force-reload</tt></tag>
4628 <item><p>cause the configuration to be reloaded if the
4629 service supports this, otherwise restart the
4633 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
4634 <tt>force-reload</tt> options should be supported by all
4635 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
4636 option is optional.</p>
4639 The <file>init.d</file> scripts should ensure that they will
4640 behave sensibly if invoked with <tt>start</tt> when the
4641 service is already running, or with <tt>stop</tt> when it
4642 isn't, and that they don't kill unfortunately-named user
4643 processes. The best way to achieve this is usually to use
4644 <prgn>start-stop-daemon</prgn>.</p>
4647 If a service reloads its configuration automatically (as
4648 in the case of <prgn>cron</prgn>, for example), the
4649 <tt>reload</tt> option of the <file>init.d</file> script
4650 should behave as if the configuration has been reloaded
4654 The <file>/etc/init.d</file> scripts must be treated as
4655 configuration files, either (if they are present in the
4656 package, that is, in the .deb file) by marking them as
4657 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
4658 by managing them correctly in the maintainer scripts (see
4659 <ref id="config-files">). This is important since we want
4660 to give the local system administrator the chance to adapt
4661 the scripts to the local system, e.g., to disable a
4662 service without de-installing the package, or to specify
4663 some special command line options when starting a service,
4664 while making sure her changes aren't lost during the next
4669 These scripts should not fail obscurely when the
4670 configuration files remain but the package has been
4671 removed, as configuration files remain on the system after
4672 the package has been removed. Only when <prgn>dpkg</prgn>
4673 is executed with the <tt>--purge</tt> option will
4674 configuration files be removed. In particular, as the
4675 <file>/etc/init.d/<var>package</var></file> script itself is
4676 usually a <tt>conffile</tt>, it will remain on the system
4677 if the package is removed but not purged. Therefore, you
4678 should include a <tt>test</tt> statement at the top of the
4680 <example compact="compact">
4681 test -f <var>program-executed-later-in-script</var> || exit 0
4686 Often there are some variables in the <file>init.d</file>
4687 scripts whose values control the behaviour of the scripts,
4688 and which a system administrator is likely to want to
4689 change. As the scripts themselves are frequently
4690 <tt>conffile</tt>s, modifying them requires that the
4691 administrator merge in their changes each time the package
4692 is upgraded and the <tt>conffile</tt> changes. To ease
4693 the burden on the system administrator, such configurable
4694 values should not be placed directly in the script.
4695 Instead, they should be placed in a file in
4696 <file>/etc/default</file>, which typically will have the same
4697 base name as the <file>init.d</file> script. This extra file
4698 should be sourced by the script when the script runs. It
4699 must contain only variable settings and comments in POSIX
4700 <prgn>sh</prgn> format. It may either be a
4701 <tt>conffile</tt> or a configuration file maintained by
4702 the package maintainer scripts. See <ref id="config-files">
4707 To ensure that vital configurable values are always
4708 available, the <file>init.d</file> script should set default
4709 values for each of the shell variables it uses, either
4710 before sourcing the <file>/etc/default/</file> file or
4711 afterwards using something like the <tt>:
4712 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
4713 script must behave sensibly and not fail if the
4714 <file>/etc/default</file> file is deleted.
4719 <heading>Interfacing with the initscript system</heading>
4722 Maintainers should use the abstraction layer provided by
4723 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
4724 programs to deal with initscripts in their packages'
4725 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
4726 and <prgn>postrm</prgn>.
4729 Directly managing the /etc/rc?.d links and directly
4730 invoking the <file>/etc/init.d/</file> initscripts should
4731 be done only by packages providing the initscript
4732 subsystem (such as <prgn>sysvinit</prgn> and
4733 <prgn>file-rc</prgn>).
4738 <heading>Managing the links</heading>
4741 The program <prgn>update-rc.d</prgn> is provided for
4742 package maintainers to arrange for the proper creation and
4743 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
4744 or their functional equivalent if another method is being
4745 used. This may be used by maintainers in their packages'
4746 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.</p>
4749 You must not include any <file>/etc/rc<var>n</var>.d</file>
4750 symbolic links in the actual archive or manually create or
4751 remove the symbolic links in maintainer scripts; you must
4752 use the <prgn>update-rc.d</prgn> program instead. (The
4753 former will fail if an alternative method of maintaining
4754 runlevel information is being used.) You must not include
4755 the <file>/etc/rc<var>n</var>.d</file> directories themselves
4756 in the archive either. (Only the <tt>sysvinit</tt>
4761 By default <prgn>update-rc.d</prgn> will start services in
4762 each of the multi-user state runlevels (2, 3, 4, and 5)
4763 and stop them in the halt runlevel (0), the single-user
4764 runlevel (1) and the reboot runlevel (6). The system
4765 administrator will have the opportunity to customize
4766 runlevels by simply adding, moving, or removing the
4767 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
4768 symbolic links are being used, or by modifying
4769 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
4774 To get the default behavior for your package, put in your
4775 <prgn>postinst</prgn> script
4776 <example compact="compact">
4777 update-rc.d <var>package</var> defaults
4779 and in your <prgn>postrm</prgn>
4780 <example compact="compact">
4781 if [ "$1" = purge ]; then
4782 update-rc.d <var>package</var> remove
4784 </example>. Note that is your package changes runlevels
4785 or priority, you may have to remove and recreate the
4786 links, since otherwise the old links may
4787 persist. Refer to the documentation of
4788 <prgn>update-rc.d</prgn></p>
4791 This will use a default sequence number of 20. If it does
4792 not matter when or in which order the <file>init.d</file>
4793 script is run, use this default. If it does, then you
4794 should talk to the maintainer of the <prgn>sysvinit</prgn>
4795 package or post to <tt>debian-devel</tt>, and they will
4796 help you choose a number.
4800 For more information about using <tt>update-rc.d</tt>,
4801 please consult its manpage <manref name="update-rc.d"
4807 <heading>Running initscripts</heading>
4809 The program <prgn>invoke-rc.d</prgn> is provided to make
4810 it easier for package maintainers to properly invoke an
4811 initscript, obeying runlevel and other locally-defined
4812 constraints that might limit a package's right to start,
4813 stop and otherwise manage services. This program may be
4814 used by maintainers in their packages' scripts.
4817 The use of <prgn>invoke-rc.d</prgn> to invoke the
4818 <file>/etc/init.d/*</file> initscripts is strongly
4819 recommended<footnote>
4821 In the future, the use of invoke-rc.d to invoke
4822 initscripts shall be made mandatory. Maintainers are
4823 advised to switch to invoke-rc.d as soon as
4825 </footnote>, instead of calling them directly.
4829 By default, <prgn>invoke-rc.d</prgn> will pass any
4830 action requests (start, stop, reload, restart...) to the
4831 <file>/etc/init.d</file> script, filtering out requests
4832 to start or restart a service out of its intended
4836 Most packages will simply need to change:
4837 <example compact="compact">/etc/init.d/<package>
4838 <action></example> in their <prgn>postinst</prgn>
4839 and <prgn>prerm</prgn> scripts to:
4840 <example compact="compact">
4841 if [ -x /usr/sbin/invoke-rc.d ] ; then
4842 invoke-rc.d <var>package</var> <action>
4844 /etc/init.d/<var>package</var> <action>
4848 A package should register its initscript services using
4849 <prgn>update-rc.d</prgn> before it tries to invoke them
4850 using <prgn>invoke-rc.d</prgn>. Invocation of
4851 unregistered services may fail.
4854 For more information about using
4855 <prgn>invoke-rc.d</prgn>, please consult its manpage
4856 <manref name="invoke-rc.d" section="8">.
4863 <heading>Boot-time initialization</heading>
4866 There used to be another directory, <file>/etc/rc.boot</file>,
4867 which contained scripts which were run once per machine
4868 boot. This has been deprecated in favour of links from
4869 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
4870 described in <ref id="/etc/init.d">. Packages must not
4871 place files in <file>/etc/rc.boot</file>.</p>
4874 <heading>Example</heading>
4877 The <prgn>bind</prgn> DNS (nameserver) package wants to
4878 make sure that the nameserver is running in multiuser
4879 runlevels, and is properly shut down with the system. It
4880 puts a script in <file>/etc/init.d</file>, naming the script
4881 appropriately <tt>bind</tt>. As you can see, the script
4882 interprets the argument <tt>reload</tt> to send the
4883 nameserver a <tt>HUP</tt> signal (causing it to reload its
4884 configuration); this way the system administrator can say
4885 <file>/etc/init.d/bind reload</file> to reload the name
4886 server. The script has one configurable value, which can
4887 be used to pass parameters to the named program at
4888 startup; this value is read from
4889 <file>/etc/default/bind</file> (see below).
4893 <example compact="compact">
4896 # Original version by Robert Leslie
4897 # <rob@mars.org>, edited by iwj and cs
4899 test -x /usr/sbin/named || exit 0
4901 # Source defaults file.
4903 if [ -f /etc/default/bind ]; then
4910 echo -n "Starting domain name service: named"
4911 start-stop-daemon --start --quiet --exec /usr/sbin/named \
4916 echo -n "Stopping domain name service: named"
4917 start-stop-daemon --stop --quiet \
4918 --pidfile /var/run/named.pid --exec /usr/sbin/named
4922 echo -n "Restarting domain name service: named"
4923 start-stop-daemon --stop --quiet \
4924 --pidfile /var/run/named.pid --exec /usr/sbin/named
4925 start-stop-daemon --start --verbose --exec /usr/sbin/named \
4929 force-reload|reload)
4930 echo -n "Reloading configuration of domain name service: named"
4931 start-stop-daemon --stop --signal 1 --quiet \
4932 --pidfile /var/run/named.pid --exec /usr/sbin/named
4936 echo "Usage: /etc/init.d/bind " \
4937 " {start|stop|restart|reload|force-reload}" >&2
4947 Complementing the above init script is a configuration
4948 file <file>/etc/default/bind</file>, which contains
4949 configurable parameters used by the script. This would be
4950 created by the <prgn>postinst</prgn> script if it was not
4951 already present, and removed on purge by the
4952 <prgn>postrm</prgn> script.
4953 <example compact="compact">
4954 # Specified parameters to pass to named. See named(8).
4955 # You may uncomment the following line, and edit to taste.
4961 Another example on which you can base your
4962 <file>/etc/init.d</file> scripts is found in
4963 <file>/etc/init.d/skeleton</file>.
4967 If this package is happy with the default setup from
4968 <prgn>update-rc.d</prgn>, namely an ordering number of 20
4969 and having named running in all runlevels, it can say in
4970 its <prgn>postinst</prgn>:
4971 <example compact="compact">
4972 update-rc.d bind defaults >/dev/null
4974 And in its <prgn>postrm</prgn>, to remove the links when the
4976 <example compact="compact">
4977 if [ "$1" = purge ]; then
4978 update-rc.d bind remove >/dev/null
4986 <heading>Console messages from <file>init.d</file> scripts</heading>
4989 This section describes the formats to be used for messages
4990 written to standard output by the <file>/etc/init.d</file>
4991 scripts. The intent is to improve the consistency of
4992 Debian's startup and shutdown look and feel. For this
4993 reason, please look very carefully at the details. We want
4994 the messages to have the same format in terms of wording,
4995 spaces, punctuation and case of letters.
4999 Here is a list of overall rules that you should use when you
5000 create output messages. They can be useful if you have a
5001 non-standard message that is not covered specifically in the
5009 Every message should fit in one line (fewer than 80
5010 characters), start with a capital letter and end with
5011 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5017 If you want to express that the computer is working on
5018 something (that is, performing a specific task, not
5019 starting or stopping a program), we use an "ellipsis"
5020 (three dots: <tt>...</tt>). Note that we don't insert
5021 spaces before or after the dots. If the task has been
5022 completed we write <tt>done.</tt> and a line feed.
5028 Design your messages as if the computer is telling you
5029 what he is doing (let him be polite :-), but don't
5030 mention "him" directly. For example, if you think of
5032 <example compact="compact">
5033 I'm starting network daemons: nfsd mountd.
5036 <example compact="compact">
5037 Starting network daemons: nfsd mountd.
5045 There are standard message formats for the following
5046 situations. They should be used by the <tt>init.d</tt>
5053 <p>When daemons are started</p>
5056 If your script starts one or more daemons, the output
5057 should look like this (a single line, no leading
5059 <example compact="compact">
5060 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5062 The <var>description</var> should describe the
5063 subsystem the daemon or set of daemons are part of,
5064 while <var>daemon-1</var> up to <var>daemon-n</var>
5065 denote each daemon's name (typically the file name of
5070 For example, the output of <file>/etc/init.d/lpd</file>
5072 <example compact="compact">
5073 Starting printer spooler: lpd.
5078 This can be achieved by saying
5079 <example compact="compact">
5080 echo -n "Starting printer spooler: lpd"
5081 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5084 in the script. If you have more than one daemon to
5085 start, you should do the following:
5086 <example compact="compact">
5087 echo -n "Starting remote file system services:"
5088 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5089 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5090 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5093 This makes it possible for the user to see what takes
5094 so long and when the final daemon has been started.
5095 You should be careful where to put spaces: in the
5096 example above the system administrator can easily
5097 comment out a line if he don't wants to start a
5098 specific daemon, while the displayed message still
5104 <p>When a system parameter is being set</p>
5107 If you have to set up different system parameters
5108 during the system boot, you should use this format:
5109 <example compact="compact">
5110 Setting <var>parameter</var> to `<var>value</var>'.
5115 You can use a statement such as the following to get
5117 <example compact="compact">
5118 echo "Setting DNS domainname to \`$domainname'."
5123 Note that the left quotation mark (<tt>`</tt>) is
5124 different from the right one (<tt>'</tt>).
5129 <p>When a daemon is stopped or restarted</p>
5132 When you stop or restart a daemon, you should issue a
5133 message identical to the startup message, except that
5134 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5135 or <tt>Restarting</tt> respectively.
5139 For example, stopping the printer daemon will like
5141 <example compact="compact">
5142 Stopping printer spooler: lpd.
5148 <p>When something is executed</p>
5151 There are several examples where you have to run a
5152 program at system startup or shutdown to perform a
5153 specific task, for example, setting the system's clock
5154 using <prgn>netdate</prgn> or killing all processes
5155 when the system shuts down. Your message should look
5157 <example compact="compact">
5158 Doing something very useful...done.
5160 You should print the <tt>done.</tt> immediately after
5161 the job has been completed, so that the user is
5162 informed why she has to wait. You can get this
5164 <example compact="compact">
5165 echo -n "Doing something very useful..."
5174 <p>When the configuration is reloaded</p>
5177 When a daemon is forced to reload its configuration
5178 files you should use the following format:
5179 <example compact="compact">
5180 Reloading <var>description</var> configuration...done.
5182 where <var>description</var> is the same as in the
5183 daemon starting message.
5191 <heading>Cron jobs</heading>
5194 Packages must not modify the configuration file
5195 <file>/etc/crontab</file>, and they must not modify the files in
5196 <file>/var/spool/cron/crontabs</file>.</p>
5199 If a package wants to install a job that has to be executed
5200 via cron, it should place a file with the name of the
5201 package in one or more of the following directories:
5202 <example compact="compact">
5207 As these directory names imply, the files within them are
5208 executed on a daily, weekly, or monthly basis,
5209 respectively. The exact times are listed in
5210 <file>/etc/crontab</file>.</p>
5213 All files installed in any of these directories must be
5214 scripts (e.g., shell scripts or Perl scripts) so that they
5215 can easily be modified by the local system administrator.
5216 In addition, they should be treated as configuration
5221 If a certain job has to be executed more frequently than
5222 daily, the package should install a file
5223 <file>/etc/cron.d/<var>package</var></file>. This file uses the
5224 same syntax as <file>/etc/crontab</file> and is processed by
5225 <prgn>cron</prgn> automatically. The file must also be
5226 treated as a configuration file. (Note that entries in the
5227 <file>/etc/cron.d</file> directory are not handled by
5228 <prgn>anacron</prgn>. Thus, you should only use this
5229 directory for jobs which may be skipped if the system is not
5233 The scripts or crontab entries in these directories should
5234 check if all necessary programs are installed before they
5235 try to execute them. Otherwise, problems will arise when a
5236 package was removed but not purged since configuration files
5237 are kept on the system in this situation.</p>
5241 <heading>Menus</heading>
5244 Menu entries should follow the current menu policy found in
5245 the <tt>menu-policy</tt> files in the <tt>debian-policy</tt>
5246 package. It may also be found on the Debian FTP site
5247 <ftpsite>ftp.debian.org</ftpsite> as the file
5248 <ftppath>/debian/doc/package-developer/menu-policy.txt.gz</ftppath>,
5249 or in the equivalent location on your local mirror.
5253 The Debian <tt>menu</tt> package provides a standard
5254 interface between packages providing applications and
5255 documents, and <em>menu programs</em> (either X window
5256 managers or text-based menu programs such as
5257 <prgn>pdmenu</prgn>).
5261 All packages that provide applications that need not be
5262 passed any special command line arguments for normal
5263 operation should register a menu entry for those
5264 applications, so that users of the <tt>menu</tt> package
5265 will automatically get menu entries in their window
5266 managers, as well in shells like <tt>pdmenu</tt>.</p>
5269 Please also refer to the <em>Debian Menu System</em>
5270 documentation that comes with the <tt>menu</tt> package for
5271 information about how to register your applications and web
5277 <heading>Multimedia handlers</heading>
5280 Packages which provide the ability to view/show/play,
5281 compose, edit or print MIME types should register themselves
5282 as such following the current MIME support policy found in
5283 the <tt>mime-policy</tt> files in the <tt>debian-policy</tt>
5284 package. It may also be found on the Debian FTP site
5285 <ftpsite>ftp.debian.org</ftpsite> as the file
5286 <ftppath>/debian/doc/package-developer/mime-policy.txt.gz</ftppath>,
5287 or in the equivalent location on your local mirror.
5291 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
5292 is a mechanism for encoding files and data streams and
5293 providing meta-information about them, in particular their
5294 type (e.g. audio or video) and format (e.g. PNG, HTML,
5299 Registration of MIME type handlers allows programs like mail
5300 user agents and web browsers to to invoke these handlers to
5301 view, edit or display MIME types they don't support
5307 <heading>Keyboard configuration</heading>
5310 To achieve a consistent keyboard configuration so that all
5311 applications interpret a keyboard event the same way, all
5312 programs in the Debian distribution must be configured to
5313 comply with the following guidelines.
5317 The following keys must have the specified interpretations:
5320 <tag><tt><--</tt></tag>
5321 <item><p>delete the character to the left of the cursor</p></item>
5323 <tag><tt>Delete</tt></tag>
5324 <item><p>delete the character to the right of the cursor</p></item>
5326 <tag><tt>Control+H</tt></tag>
5327 <item><p>emacs: the help prefix</p></item>
5330 The interpretation of any keyboard events should be
5331 independent of the terminal that is used, be it a virtual
5332 console, an X terminal emulator, an rlogin/telnet session,
5337 The following list explains how the different programs
5338 should be set up to achieve this:
5343 <item><p><tt><--</tt> generates <tt>KB_BackSpace</tt>
5346 <item><p><tt>Delete</tt> generates <tt>KB_Delete</tt> in
5351 X translations are set up to make
5352 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
5353 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
5354 is the vt220 escape code for the `delete character'
5355 key). This must be done by loading the X resources
5356 using <prgn>xrdb</prgn> on all local X displays, not
5357 using the application defaults, so that the
5358 translation resources used correspond to the
5359 <prgn>xmodmap</prgn> settings.</p></item>
5363 The Linux console is configured to make
5364 <tt><--</tt> generate DEL, and <tt>Delete</tt>
5365 generate <tt>ESC [ 3 ~</tt>.</p></item>
5369 X applications are configured so that <tt><</tt>
5370 deletes left, and <tt>Delete</tt> deletes right. Motif
5371 applications already work like this.</p></item>
5373 <item><p>Terminals should have <tt>stty erase ^?</tt> .</p></item>
5377 The <tt>xterm</tt> terminfo entry should have <tt>ESC
5378 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
5379 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.</p></item>
5383 Emacs is programmed to map <tt>KB_Backspace</tt> or
5384 the <tt>stty erase</tt> character to
5385 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
5386 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
5387 <tt>^H</tt> to <tt>help</tt> as always.</p></item>
5391 Other applications use the <tt>stty erase</tt>
5392 character and <tt>kdch1</tt> for the two delete keys,
5393 with ASCII DEL being `delete previous character' and
5394 <tt>kdch1</tt> being `delete character under
5401 This will solve the problem except for the following
5409 Some terminals have a <tt><--</tt> key that cannot
5410 be made to produce anything except <tt>^H</tt>. On
5411 these terminals Emacs help will be unavailable on
5412 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
5413 character takes precedence in Emacs, and has been set
5414 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
5415 available) can be used instead.</p></item>
5419 Some operating systems use <tt>^H</tt> for <tt>stty
5420 erase</tt>. However, modern telnet versions and all
5421 rlogin versions propagate <tt>stty</tt> settings, and
5422 almost all UNIX versions honour <tt>stty erase</tt>.
5423 Where the <tt>stty</tt> settings are not propagated
5424 correctly, things can be made to work by using
5425 <tt>stty</tt> manually.</p></item>
5429 Some systems (including previous Debian versions) use
5430 <prgn>xmodmap</prgn> to arrange for both
5431 <tt><--</tt> and <tt>Delete</tt> to generate
5432 <tt>KB_Delete</tt>. We can change the behavior of
5433 their X clients using the same X resources that we use
5434 to do it for our own clients, or configure our clients
5435 using their resources when things are the other way
5436 around. On displays configured like this
5437 <tt>Delete</tt> will not work, but <tt><--</tt>
5442 Some operating systems have different <tt>kdch1</tt>
5443 settings in their <tt>terminfo</tt> database for
5444 <tt>xterm</tt> and others. On these systems the
5445 <tt>Delete</tt> key will not work correctly when you
5446 log in from a system conforming to our policy, but
5447 <tt><--</tt> will.</p></item>
5453 <heading>Environment variables</heading>
5456 A program must not depend on environment variables to get
5457 reasonable defaults. (That's because these environment
5458 variables would have to be set in a system-wide
5459 configuration file like <file>/etc/profile</file>, which is not
5460 supported by all shells.)</p>
5463 If a program usually depends on environment variables for its
5464 configuration, the program should be changed to fall back to
5465 a reasonable default configuration if these environment
5466 variables are not present. If this cannot be done easily
5467 (e.g., if the source code of a non-free program is not
5468 available), the program must be replaced by a small
5469 `wrapper' shell script which sets the environment variables
5470 if they are not already defined, and calls the original program.</p>
5473 Here is an example of a wrapper script for this purpose:
5475 <example compact="compact">
5477 BAR=${BAR:-/var/lib/fubar}
5479 exec /usr/lib/foo/foo "$@"
5484 Furthermore, as <file>/etc/profile</file> is a configuration
5485 file of the <prgn>base-files</prgn> package, other packages must not
5486 put any environment variables or other commands into that
5492 <heading>Files</heading>
5495 <heading>Binaries</heading>
5498 Two different packages must not install programs with
5499 different functionality but with the same filenames. (The
5500 case of two programs having the same functionality but
5501 different implementations is handled via `alternatives' or
5502 the `Conflicts' mechanism. See <ref id="maintscripts"> and
5503 <ref id="conflicts"> respectively.) If this case happens,
5504 one of the programs must be renamed. The maintainers should
5505 report this to the <tt>debian-devel</tt> mailing list and
5506 try to find a consensus about which program will have to be
5507 renamed. If a consensus cannot be reached, <em>both</em>
5508 programs must be renamed.
5512 By default, when a package is being built, any binaries
5513 created should include debugging information, as well as
5514 being compiled with optimization. You should also turn on
5515 as many reasonable compilation warnings as possible; this
5516 makes life easier for porters, who can then look at build
5517 logs for possible problems. For the C programming language,
5518 this means the following compilation parameters should be
5520 <example compact="compact">
5522 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
5524 install -s # (or use strip on the files in debian/tmp)
5529 Note that by default all installed binaries should be stripped,
5530 either by using the <tt>-s</tt> flag to
5531 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
5532 the binaries after they have been copied into
5533 <file>debian/tmp</file> but before the tree is made into a
5537 Although binaries in the build tree should be compiled with
5538 debugging information by default, it can often be difficult
5539 to debug programs if they are also subjected to compiler
5540 optimization. For this reason, it is recommended to support
5541 the standardized environment
5542 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
5543 contain several flags to change how a package is compiled
5551 The presence of this string means that the package
5552 should be complied with a minimum of optimization.
5553 For C programs, it is best to add <tt>-O0</tt>
5554 to <tt>CFLAGS</tt> (although this is usually the
5555 default). Some programs might fail to build or run at
5556 this level of optimization; it may be necessary to
5557 use <tt>-O1</tt>, for example.
5563 This string means that the debugging symbols should
5564 not be stripped from the binary during installation,
5565 so that debugging information may be included in the package.
5571 The following makefile snippet is an example of how one may
5572 implement the build options; you will probably have to
5573 massage this example in order to make it work for your
5575 <example compact="compact">
5578 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
5579 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
5580 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
5581 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
5583 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
5588 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
5589 INSTALL_PROGRAM += -s
5595 It is up to the package maintainer to decide what
5596 compilation options are best for the package. Certain
5597 binaries (such as computationally-intensive programs) will
5598 function better with certain flags (<tt>-O3</tt>, for
5599 example); feel free to use them. Please use good judgment
5600 here. Don't use flags for the sake of it; only use them
5601 if there is good reason to do so. Feel free to override
5602 the upstream author's ideas about which compilation
5603 options are best: they are often inappropriate for our
5610 <heading>Libraries</heading>
5612 In general, libraries must have a shared version in the
5613 library package and a static version in the development
5614 package. The shared version must be compiled with
5615 <tt>-fPIC</tt>, and the static version must not be. In
5616 other words, each source unit ( <tt>*.c</tt>, for example,
5617 for C files) will need to be compiled twice.
5620 In some cases, it is acceptable for a library to be
5621 available in static form only; these cases include:
5624 <p>libraries for languages whose shared library support
5625 is immature or unstable</p>
5629 libraries whose interfaces are in flux or under
5630 development (commonly the case when the library's
5631 major version number is zero, or where the ABI breaks
5637 libraries which are explicitly intended to be
5638 available only in static form by their upstream
5642 If a library is available only in static form, then it must follow
5643 the conventions for a development package.
5646 All libraries must have a shared version in the
5647 <tt>lib*</tt> package and a static version in the
5648 <tt>lib*-dev</tt> package. The shared version must be
5649 compiled with <tt>-fPIC</tt>, and the static version must
5650 not be. In other words, each <tt>*.c</tt> file will need to
5651 be compiled twice.</p>
5654 You must specify the gcc option <tt>-D_REENTRANT</tt>
5655 when building a library (either static or shared) to make
5656 the library compatible with LinuxThreads.</p>
5659 Note that all installed shared libraries should be
5661 <example compact="compact">
5662 strip --strip-unneeded <var>your-lib</var>
5664 (The option <tt>--strip-unneeded</tt> makes
5665 <prgn>strip</prgn> remove only the symbols which aren't
5666 needed for relocation processing.) Shared libraries can
5667 function perfectly well when stripped, since the symbols for
5668 dynamic linking are in a separate part of the ELF object
5671 You might also want to use the options
5672 <tt>--remove-section=.comment</tt> and
5673 <tt>--remove-section=.note</tt> on both shared libraries
5674 and executables, and <tt>--strip-debug</tt> on static
5681 Note that under some circumstances it may be useful to
5682 install a shared library unstripped, for example when
5683 building a separate package to support debugging.
5687 Shared object files (often <file>.so</file> files) that are not
5688 public libraries, that is, they are not meant to be linked
5689 to by third party executables (binaries of other packages),
5690 should be installed in subdirectories of the
5691 <file>/usr/lib</file> directory. Such files are exempt from the
5692 rules that govern ordinary shared libraries, except that
5693 they must not be installed executable and should be
5696 A common example are the so-called ``plug-ins'',
5697 internal shared objects that are dynamically loaded by
5698 programs using <manref name="dlopen" section="3">.
5704 Packages containing shared libraries that may be linked to
5705 by other packages' binaries, but which for some
5706 <em>compelling</em> reason can not be installed in
5707 <file>/usr/lib</file> directory, may install the shared library
5708 files in subdirectories of the <file>/usr/lib</file> directory,
5709 in which case they should arrange to add that directory in
5710 <file>/etc/ld.so.conf</file> in the package's post-installation
5711 script, and remove it in the package's post-removal script.
5715 An ever increasing number of packages are using
5716 <prgn>libtool</prgn> to do their linking. The latest GNU
5717 libtools (>= 1.3a) can take advantage of the metadata in the
5718 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
5719 files). The main advantage of <prgn>libtool</prgn>'s
5720 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
5721 store and subsequently access metadata with respect to the
5722 libraries it builds. <prgn>libtool</prgn> will search for
5723 those files, which contain a lot of useful information about
5724 a library (such as library dependency information for static
5725 linking). Also, they're <em>essential</em> for programs
5726 using <tt>libltdl</tt>.<footnote>
5728 Although <prgn>libtool</prgn> is fully capable of
5729 linking against shared libraries which don't have
5730 <tt>.la</tt> files, as it is a mere shell script it can
5731 add considerably to the build time of a
5732 <prgn>libtool</prgn>-using package if that shell script
5733 has to derive all this information from first principles
5734 for each library every time it is linked. With the
5735 advent of <prgn>libtool</prgn> version 1.4 (and to a
5736 lesser extent <prgn>libtool</prgn> version 1.3), the
5737 <file>.la</file> files also store information about
5738 inter-library dependencies which cannot necessarily be
5739 derived after the <file>.la</file> file is deleted.
5745 Packages that use <prgn>libtool</prgn> to create shared
5746 libraries should include the <file>.la</file> files in the
5747 <tt>-dev</tt> package, unless the package relies on
5748 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
5749 the <tt>.la</tt> files must go in the run-time library
5754 You must make sure that you use only released versions of
5755 shared libraries to build your packages; otherwise other
5756 users will not be able to run your binaries
5757 properly. Producing source packages that depend on
5758 unreleased compilers is also usually a bad
5764 <heading>Shared libraries</heading>
5767 Packages involving shared libraries should be split up
5768 into several binary packages.</p>
5771 For a straightforward library which has a development
5772 environment and a runtime kit including just shared
5773 libraries you need to create two packages:
5774 <file><var>libraryname</var><var>soversion</var></file>, where
5775 <file><var>soversion</var></file> is the version number in the
5776 soname of the shared library<footnote>
5778 The soname is the shared object name: it's the thing
5779 that has to match exactly between building an executable
5780 and running it for the dynamic linker to be able run the
5781 program. For example, if the soname of the library is
5782 <file>libfoo.so.6</file>, the library package would be
5783 called <file>libfoo6</file>.
5786 and <tt><var>libraryname</var><var>soversion</var>-dev</tt>.
5787 Alternatively, if it would be confusing to directly append
5788 <var>soversion</var> to <var>libraryname</var> (e.g. because
5789 <var>libraryname</var> itself ends in a number), you may use
5790 <tt><var>libraryname</var>-<var>soversion</var></tt> and
5791 <tt><var>libraryname</var>-<var>soversion</var>-dev</tt>
5796 If you prefer only to support one development version at a
5797 time you may name the development package
5798 <file><var>libraryname</var>-dev</file>; otherwise you may need
5799 to use <prgn>dpkg</prgn>'s Conflicts mechanism (see <ref
5800 id="conflicts">) to ensure that the user only installs one
5801 development version at a time (as different development
5802 versions are likely to have the same header files in them,
5803 which would cause a filename clash if both were installed).
5804 Typically the development version should also have an exact
5805 version dependency on the runtime library, to make sure that
5806 compilation and linking happens correctly. The
5807 <tt>${Source-Version}</tt> substitution variable can be
5808 useful for this purpose.
5812 Packages which use the shared library should have a
5813 dependency on the name of the shared library package,
5814 <file><var>libraryname</var><var>soversion</var></file>. When
5815 the soname changes you can have both versions of the library
5816 installed while migrating from the old library to the new.
5820 If your package has some run-time support programs which use
5821 the shared library you must not put them in the shared
5822 library package. If you do that then you won't be able to
5823 install several versions of the shared library without
5824 getting filename clashes. Instead, either create a third
5825 package for the runtime binaries (this package might
5826 typically be named <tt><var>libraryname</var>-runtime</tt>;
5827 note the absence of the <var>soversion</var> in the package
5828 name), or if the development package is small you may
5829 include them in there.
5833 If you have several shared libraries built from the same
5834 source tree you may lump them all together into a single
5835 shared library package, provided that you change all of
5836 their sonames at once (so that you don't get filename
5837 clashes if you try to install different versions of the
5838 combined shared libraries package).
5842 Shared libraries should not be installed executable, since
5843 the dynamic linker does not require this and trying to
5844 execute a shared library usually results in a core dump.
5849 <heading>Scripts</heading>
5852 All command scripts, including the package maintainer
5853 scripts inside the package and used by <prgn>dpkg</prgn>,
5854 should have a <tt>#!</tt> line naming the shell to be used
5855 to interpret them.</p>
5858 In the case of Perl scripts this should be
5859 <tt>#!/usr/bin/perl</tt>.</p>
5862 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
5863 should almost certainly start with <tt>set -e</tt> so that
5864 errors are detected. Every script should use
5865 <tt>set -e</tt> or check the exit status of <em>every</em>
5869 The standard shell interpreter <file>/bin/sh</file> can be a
5870 symbolic link to any POSIX compatible shell, if <tt>echo
5871 -n</tt> does not generate a newline.<footnote>
5873 Debian policy specifies POSIX behavior for
5874 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
5875 use in the Linux community (in particular including this
5876 policy, the Linux kernel source, many Debian scripts,
5877 etc.). This <tt>echo -n</tt> mechanism is valid but not
5878 required under POSIX, hence this explicit addition.
5879 Also, rumour has it that this shall be mandated under
5883 Thus, shell scripts specifying <file>/bin/sh</file> as
5884 interpreter should only use POSIX features. If a script
5885 requires non-POSIX features from the shell interpreter, the
5886 appropriate shell must be specified in the first line of the
5887 script (e.g., <tt>#!/bin/bash</tt>) and the package must
5888 depend on the package providing the shell (unless the shell
5889 package is marked `Essential', as in the case of
5894 You may wish to restrict your script to POSIX features when
5895 possible so that it may use <file>/bin/sh</file> as its
5896 interpreter. If your script works with <prgn>dash</prgn>
5897 (originally called <prgn>ash</prgn>), it's probably POSIX
5898 compliant, but if you are in doubt, use
5899 <file>/bin/bash</file>.
5903 Perl scripts should check for errors when making any
5904 system calls, including <tt>open</tt>, <tt>print</tt>,
5905 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
5909 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
5910 scripting languages. See <em>Csh Programming Considered
5911 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
5912 can be found at <url
5913 id="http://language.perl.com/versus/csh.whynot">.<footnote>
5915 It can also be found on
5916 <url id="http://www.cpan.org/doc/FMTEYEWTK/versus/csh.whynot">
5917 or on the ftp site <ftpsite>ftp.cpan.org</ftpsite> as
5918 <ftppath>/pub/perl/CPAN/doc/FMTEYEWTK/versus/csh.whynot</ftppath>.
5921 If an upstream package comes with <prgn>csh</prgn> scripts
5922 then you must make sure that they start with
5923 <tt>#!/bin/csh</tt> and make your package depend on the
5924 <prgn>c-shell</prgn> virtual package.
5928 Any scripts which create files in world-writeable
5929 directories (e.g., in <file>/tmp</file>) must use a
5930 mechanism which will fail if a file with the same name
5934 The Debian base system provides the <prgn>tempfile</prgn>
5935 and <prgn>mktemp</prgn> utilities for use by scripts for
5936 this purpose.</p></sect>
5940 <heading>Symbolic links</heading>
5943 In general, symbolic links within a top-level directory
5944 should be relative, and symbolic links pointing from one
5945 top-level directory into another should be absolute. (A
5946 top-level directory is a sub-directory of the root
5947 directory <file>/</file>.)</p>
5950 In addition, symbolic links should be specified as short as
5951 possible, i.e., link targets like <file>foo/../bar</file> are
5955 Note that when creating a relative link using
5956 <prgn>ln</prgn> it is not necessary for the target of the
5957 link to exist relative to the working directory you're
5958 running <prgn>ln</prgn> from, nor is it necessary to change
5959 directory to the directory where the link is to be made.
5960 Simply include the string that should appear as the target
5961 of the link (this will be a pathname relative to the
5962 directory in which the link resides) as the first argument
5963 to <prgn>ln</prgn>.</p>
5966 For example, in your <prgn>Makefile</prgn> or
5967 <file>debian/rules</file>, you can do things like:
5968 <example compact="compact">
5969 ln -fs gcc $(prefix)/bin/cc
5970 ln -fs gcc debian/tmp/usr/bin/cc
5971 ln -fs ../sbin/sendmail $(prefix)/bin/runq
5972 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
5976 A symbolic link pointing to a compressed file should always
5977 have the same file extension as the referenced file. (For
5978 example, if a file <file>foo.gz</file> is referenced by a
5979 symbolic link, the filename of the link has to end with
5980 `<file>.gz</file>' too, as in <file>bar.gz</file>.)
5985 <heading>Device files</heading>
5988 Packages must not include device files in the package file
5992 If a package needs any special device files that are not
5993 included in the base system, it must call
5994 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
5995 after notifying the user<footnote>
5997 This notification could be done via a (low-priority)
5998 debconf message, or an echo (printf) statement.
6004 Packages must not remove any device files in the
6005 <prgn>postrm</prgn> or any other script. This is left to the
6006 system administrator.</p>
6009 Debian uses the serial devices
6010 <file>/dev/ttyS*</file>. Programs using the old
6011 <file>/dev/cu*</file> devices should be changed to use
6012 <file>/dev/ttyS*</file>.</p>
6015 <sect id="config-files">
6016 <heading>Configuration files</heading>
6018 <heading>Definitions</heading>
6021 <tag>configuration file</tag>
6024 A file that affects the operation of a program, or
6025 provides site- or host-specific information, or
6026 otherwise customizes the behavior of a program.
6027 Typically, configuration files are intended to be
6028 modified by the system administrator (if needed or
6029 desired) to conform to local policy or to provide
6030 more useful site-specific behavior.
6034 <tag><tt>conffile</tt></tag>
6037 A file listed in a package's <tt>conffiles</tt>
6038 file, and is treated specially by <prgn>dpkg</prgn>
6039 (see <ref id="configdetails">).
6046 The distinction between these two is important; they are
6047 not interchangeable concepts. Almost all
6048 <tt>conffile</tt>s are configuration files, but many
6049 configuration files are not <tt>conffiles</tt>.
6053 Note that a script that embeds configuration information
6054 (such as most of the files in <file>/etc/default</file> and
6055 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6056 configuration file and should be treated as such.
6061 <heading>Location</heading>
6063 Any configuration files created or used by your package
6064 must reside in <file>/etc</file>. If there are several you
6065 should consider creating a subdirectory of <file>/etc</file>
6066 named after your package.</p>
6069 If your package creates or uses configuration files
6070 outside of <file>/etc</file>, and it is not feasible to modify
6071 the package to use the <file>/etc</file>, you should still put
6072 the files in <file>/etc</file> and create symbolic links to
6073 those files from the location that the package
6078 <heading>Behavior</heading>
6080 Configuration file handling must conform to the following
6082 <list compact="compact">
6085 local changes must be preserved during a package
6091 configuration files must be preserved when the
6092 package is removed, and only deleted when the
6100 The easy way to achieve this behavior is to make the
6101 configuration file a <tt>conffile</tt>. This is
6102 appropriate only if it is possible to distribute a default
6103 version that will work for most installations, although
6104 some system administrators may choose to modify it. This
6105 implies that the default version will be part of the
6106 package distribution, and must not be modified by the
6107 maintainer scripts during installation (or at any other
6112 In order to ensure that local changes are preserved
6113 correctly, no package may contain or make hard links to
6114 conffiles.<footnote>
6116 Rationale: There are two problems with hard links.
6117 The first is that some editors break the link while
6118 editing one of the files, so that the two files may
6119 unwittingly become unlinked and different. The second
6120 is that <prgn>dpkg</prgn> might break the hard link
6121 while upgrading <tt>conffile</tt>s.
6127 The other way to do it is via the maintainer scripts. In
6128 this case, the configuration file must not be listed as a
6129 <tt>conffile</tt> and must not be part of the package
6130 distribution. If the existence of a file is required for
6131 the package to be sensibly configured it is the
6132 responsibility of the package maintainer to provide
6133 maintainer scripts which correctly create, update and
6134 maintain the file and remove it on purge. (See <ref
6135 id="maintainerscripts"> for more information.) These
6136 scripts must be idempotent (i.e., must work correctly if
6137 <prgn>dpkg</prgn> needs to re-run them due to errors
6138 during installation or removal), must cope with all the
6139 variety of ways <prgn>dpkg</prgn> can call maintainer
6140 scripts, must not overwrite or otherwise mangle the user's
6141 configuration without asking, must not ask unnecessary
6142 questions (particularly during upgrades), and otherwise be
6147 The scripts are not required to configure every possible
6148 option for the package, but only those necessary to get
6149 the package running on a given system. Ideally the
6150 sysadmin should not have to do any configuration other
6151 than that done (semi-)automatically by the
6152 <prgn>postinst</prgn> script.
6156 A common practice is to create a script called
6157 <file><var>package</var>-configure</file> and have the
6158 package's <prgn>postinst</prgn> call it if and only if the
6159 configuration file does not already exist. In certain
6160 cases it is useful for there to be an example or template
6161 file which the maintainer scripts use. Such files should
6162 be in <file>/usr/share/<var>package</var></file> or
6163 <file>/usr/lib/<var>package</var></file> (depending on whether
6164 they are architecture-independent or not). There should
6165 be symbolic links to them from
6166 <file>/usr/share/doc/<var>package</var>/examples</file> if
6167 they are examples, and should be perfectly ordinary
6168 <prgn>dpkg</prgn>-handled files (<em>not</em>
6169 configuration files).
6173 These two styles of configuration file handling must
6174 not be mixed, for that way lies madness:
6175 <prgn>dpkg</prgn> will ask about overwriting the file
6176 every time the package is upgraded.
6181 <heading>Sharing configuration files</heading>
6183 Packages which specify the same file as a
6184 <tt>conffile</tt> must be tagged as <em>conflicting</em>
6185 with each other. (This is an instance of the general rule
6186 about not sharing files. Note that neither alternatives
6187 nor diversions are likely to be appropriate in this case;
6188 in particular, <prgn>dpkg</prgn> does not handle diverted
6189 <tt>conffile</tt>s well.)
6193 The maintainer scripts must not alter a <tt>conffile</tt>
6194 of <em>any</em> package, including the one the scripts
6199 If two or more packages use the same configuration file
6200 and it is reasonable for both to be installed at the same
6201 time, one of these packages must be defined as
6202 <em>owner</em> of the configuration file, i.e., it will be
6203 the package which handles that file as a configuration
6204 file. Other packages that use the configuration file must
6205 depend on the owning package if they require the
6206 configuration file to operate. If the other package will
6207 use the configuration file if present, but is capable of
6208 operating without it, no dependency need be declared.</p>
6211 If it is desirable for two or more related packages to
6212 share a configuration file <em>and</em> for all of the
6213 related packages to be able to modify that configuration
6214 file, then the following should be done:
6215 <enumlist compact="compact">
6218 One of the related packages (the "owning" package)
6219 will manage the configuration file with maintainer
6220 scripts as described in the previous section.
6225 The owning package should also provide a program
6226 that the other packages may use to modify the
6232 The related packages must use the provided program
6233 to make any desired modifications to the
6234 configuration file. They should either depend on
6235 the core package to guarantee that the configuration
6236 modifier program is available or accept gracefully
6237 that they cannot modify the configuration file if it
6238 is not. (This is in addition to the fact that the
6239 configuration file may not even be present in the
6247 Sometimes it's appropriate to create a new package which
6248 provides the basic infrastructure for the other packages
6249 and which manages the shared configuration files. (The
6250 <tt>sgml-base</tt> package is a good example.)
6255 <heading>User configuration files ("dotfiles")</heading>
6258 The files in <file>/etc/skel</file> will automatically be
6259 copied into new user accounts by <prgn>adduser</prgn>.
6260 No other program should reference the files in
6261 <file>/etc/skel</file>.
6265 Therefore, if a program needs a dotfile to exist in
6266 advance in <file>$HOME</file> to work sensibly, that dotfile
6267 should be installed in <file>/etc/skel</file> and treated as a
6272 However, programs that require dotfiles in order to
6273 operate sensibly (dotfiles that they do not create
6274 themselves automatically, that is) are a bad thing.
6275 Furthermore, programs should be configured by the Debian
6276 default installation to behave as closely to the upstream
6277 default behaviour as possible.
6281 Therefore, if a program in a Debian package needs to be
6282 configured in some way in order to operate sensibly, that
6283 should be done using a site-wide configuration file placed
6284 in <file>/etc</file>. Only if the program doesn't support a
6285 site-wide default configuration and the package maintainer
6286 doesn't have time to add it may a default per-user file be
6287 placed in <file>/etc/skel</file>.
6291 <file>/etc/skel</file> should be as empty as we can make it.
6292 This is particularly true because there is no easy (or
6293 necessarily desirable) mechanism for ensuring that the
6294 appropriate dotfiles are copied into the accounts of
6295 existing users when a package is installed.
6301 <heading>Log files</heading>
6303 Log files should usually be named
6304 <file>/var/log/<var>package</var>.log</file>. If you have many
6305 log files, or need a separate directory for permission
6306 reasons (<file>/var/log</file> is writable only by
6307 <file>root</file>), you should usually create a directory named
6308 <file>/var/log/<var>package</var></file> and place your log
6313 Log files must be rotated occasionally so that they don't
6314 grow indefinitely; the best way to do this is to drop a log
6315 rotation configuration file into the directory
6316 <file>/etc/logrotate.d</file> and use the facilities provided by
6317 logrotate.<footnote>
6319 The traditional approach to log files has been to set up
6320 <em>ad hoc</em> log rotation schemes using simple shell
6321 scripts and cron. While this approach is highly
6322 customizable, it requires quite a lot of sysadmin work.
6323 Even though the original Debian system helped a little
6324 by automatically installing a system which can be used
6325 as a template, this was deemed not enough.
6329 The use of <prgn>logrotate</prgn>, a program developed
6330 by Red Hat, is better, as it centralizes log management.
6331 It has both a configuration file
6332 (<file>/etc/logrotate.conf</file>) and a directory where
6333 packages can drop their individual log rotation
6334 configurations (<file>/etc/logrotate.d</file>).
6337 Here is a good example for a logrotate config
6338 file (for more information see <manref name="logrotate"
6340 <example compact="compact">
6346 /etc/init.d/foo force-reload
6350 This rotates all files under <file>/var/log/foo</file>, saves 12
6351 compressed generations, and forces the daemon to reload its
6352 configuration information after the log rotation.
6356 Log files should be removed when the package is
6357 purged (but not when it is only removed). This should be
6358 done by the <prgn>postrm</prgn> script when it is called
6359 with the argument <tt>purge</tt> (see <ref
6360 id="removedetails">).
6365 <heading>Permissions and owners</heading>
6368 The rules in this section are guidelines for general use.
6369 If necessary you may deviate from the details below.
6370 However, if you do so you must make sure that what is done
6371 is secure and you should try to be as consistent as possible
6372 with the rest of the system. You should probably also
6373 discuss it on <prgn>debian-devel</prgn> first.
6377 Files should be owned by <tt>root.root</tt>, and made
6378 writable only by the owner and universally readable (and
6379 executable, if appropriate), that is mode 644 or 755.
6383 Directories should be mode 755 or (for group-writability)
6384 mode 2775. The ownership of the directory should be
6385 consistent with its mode: if a directory is mode 2775, it
6386 should be owned by the group that needs write access to
6391 Setuid and setgid executables should be mode 4755 or 2755
6392 respectively, and owned by the appropriate user or group.
6393 They should not be made unreadable (modes like 4711 or
6394 2711 or even 4111); doing so achieves no extra security,
6395 because anyone can find the binary in the freely available
6396 Debian package; it is merely inconvenient. For the same
6397 reason you should not restrict read or execute permissions
6398 on non-set-id executables.
6402 Some setuid programs need to be restricted to particular
6403 sets of users, using file permissions. In this case they
6404 should be owned by the uid to which they are set-id, and by
6405 the group which should be allowed to execute them. They
6406 should have mode 4754; again there is no point in making
6407 them unreadable to those users who must not be allowed to
6412 It is possible to arrange that the system administrator can
6413 reconfigure the package to correspond to their local
6414 security policy by changing the permissions on a binary:
6415 they can do this by using <prgn>dpkg-statoverride</prgn>, as
6416 described below.<footnote>
6418 Ordinary files installed by <prgn>dpkg</prgn> (as
6419 opposed to <tt>conffile</tt>s and other similar objects)
6420 normally have their permissions reset to the distributed
6421 permissions when the package is reinstalled. However,
6422 the use of <prgn>dpkg-statoverride</prgn> overrides this
6423 default behaviour. If you use this method, you should
6424 remember to describe <prgn>dpkg-statoverride</prgn> in
6425 the package documentation; being a relatively new
6426 addition to Debian, it is probably not yet well-known.
6429 Another method you should consider is to create a group for
6430 people allowed to use the program(s) and make any setuid
6431 executables executable only by that group.
6435 If you need to create a new user or group for your package
6436 there are two possibilities. Firstly, you may need to
6437 make some files in the binary package be owned by this
6438 user or group, or you may need to compile the user or
6439 group id (rather than just the name) into the binary
6440 (though this latter should be avoided if possible, as in
6441 this case you need a statically allocated id).</p>
6444 If you need a statically allocated id, you must ask for a
6445 user or group id from the <tt>base-passwd</tt> maintainer,
6446 and must not release the package until you have been
6447 allocated one. Once you have been allocated one you must
6448 either make the package depend on a version of the
6449 <tt>base-passwd</tt> package with the id present in
6450 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
6451 your package to create the user or group itself with the
6452 correct id (using <tt>adduser</tt>) in its
6453 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
6454 the <prgn>postinst</prgn> is to be preferred if it is
6455 possible, otherwise a pre-dependency will be needed on the
6456 <tt>adduser</tt> package.)
6460 On the other hand, the program might be able to determine
6461 the uid or gid from the user or group name at runtime, so
6462 that a dynamically allocated id can be used. In this case
6463 you should choose an appropriate user or group name,
6464 discussing this on <prgn>debian-devel</prgn> and checking
6465 with the base system maintainer that it is unique and that
6466 they do not wish you to use a statically allocated id
6467 instead. When this has been checked you must arrange for
6468 your package to create the user or group if necessary using
6469 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
6470 <prgn>postinst</prgn> script (again, the latter is to be
6471 preferred if it is possible).
6475 Note that changing the numeric value of an id associated
6476 with a name is very difficult, and involves searching the
6477 file system for all appropriate files. You need to think
6478 carefully whether a static or dynamic id is required, since
6479 changing your mind later will cause problems.
6482 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
6484 This section is not intended as policy, but as a
6485 description of the use of <prgn>dpkg-statoverride</prgn>.
6489 <prgn>dpkg-statoverride</prgn> is a replacement for the
6490 deprecated <tt>suidmanager</tt> package. Packages which
6491 previously used <tt>suidmanager</tt> should have a
6492 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
6493 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
6494 and <tt>suidunregister</tt> should now be simply removed
6495 from the maintainer scripts.
6499 If a system administrator wishes to have a file (or
6500 directory or other such thing) installed with owner and
6501 permissions different from those in the distributed Debian
6502 package, he can use the <prgn>dpkg-statoverride</prgn>
6503 program to instruct <prgn>dpkg</prgn> to use the different
6504 settings every time the file is installed. Thus the
6505 package maintainer should distribute the files with their
6506 normal permissions, and leave it for the system
6507 administrator to make any desired changes. For example, a
6508 daemon which is normally required to be setuid root, but
6509 in certain situations could be used without being setuid,
6510 should be installed setuid in the <tt>.deb</tt>. Then the
6511 local system administrator can change this if they wish.
6512 If there are two standard ways of doing it, the package
6513 maintainer can use <tt>debconf</tt> to find out the
6514 preference, and call <prgn>dpkg-statoverride</prgn> in the
6515 maintainer script if necessary to accommodate the system
6516 administrator's choice.
6520 Given the above, <prgn>dpkg-statoverride</prgn> is
6521 essentially a tool for system administrators and would not
6522 normally be needed in the maintainer scripts. There is
6523 one type of situation, though, where calls to
6524 <prgn>dpkg-statoverride</prgn> would be needed in the
6525 maintainer scripts, and that involves packages which use
6526 dynamically allocated user or group ids. In such a
6527 situation, something like the following idiom can be very
6528 helpful in the package's <prgn>postinst</prgn>, where
6529 <tt>sysuser</tt> is a dynamically allocated id:
6531 for i in /usr/bin/foo /usr/sbin/bar
6533 if ! dpkg-statoverride --list $i >/dev/null
6535 dpkg-statoverride --update --add sysuser root 4755 $i
6539 The corresponding <tt>dpkg-statoverride --remove</tt>
6540 calls can then be made unconditionally when the package is
6547 <chapt id="customized-programs">
6548 <heading>Customized programs</heading>
6550 <sect id="arch-spec">
6551 <heading>Architecture specification strings</heading>
6554 If a program needs to specify an <em>architecture specification
6555 string</em> in some place, the following format should be
6556 used: <var>arch</var>-<var>os</var><footnote>
6558 The following architectures and operating systems are
6559 currently recognised by <prgn>dpkg-archictecture</prgn>.
6560 The architecture, <tt><var>arch</var></tt>, is one of
6561 the following: <tt>alpha</tt>, <tt>arm</tt>,
6562 <tt>hppa</tt>, <tt>i386</tt>, <tt>ia64</tt>,
6563 <tt>m68k</tt>, <tt>mips</tt>, <tt>mipsel</tt>,
6564 <tt>powerpc</tt>, <tt>s390</tt>, <tt>sh</tt>,
6565 <tt>sheb</tt>, <tt>sparc</tt> and <tt>sparc64</tt>. The
6566 operating system, <tt><var>os</var></tt>, is one of:
6567 <tt>linux</tt>, <tt>gnu</tt>, <tt>freebsd</tt> and
6568 <tt>openbsd</tt>. Use of <tt>gnu</tt> in this string is
6569 reserved for the GNU/Hurd operating system.
6575 Note that we don't want to use
6576 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
6577 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
6578 since this would make our programs incompatible with other
6579 Linux distributions. We also don't use something like
6580 <tt><var>arch</var>-unknown-linux</tt>, since the
6581 <tt>unknown</tt> does not look very good.
6586 <heading>Daemons</heading>
6589 The configuration files <file>/etc/services</file>,
6590 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
6591 by the <prgn>netbase</prgn> package and must not be modified
6596 If a package requires a new entry in one of these files, the
6597 maintainer should get in contact with the
6598 <prgn>netbase</prgn> maintainer, who will add the entries
6599 and release a new version of the <prgn>netbase</prgn>
6604 The configuration file <file>/etc/inetd.conf</file> must not be
6605 modified by the package's scripts except via the
6606 <prgn>update-inetd</prgn> script or the
6607 <file>DebianNet.pm</file> Perl module. See their documentation
6608 for details on how to add entries.
6612 If a package wants to install an example entry into
6613 <file>/etc/inetd.conf</file>, the entry must be preceded with
6614 exactly one hash character (<tt>#</tt>). Such lines are
6615 treated as `commented out by user' by the
6616 <prgn>update-inetd</prgn> script and are not changed or
6617 activated during package updates.
6622 <heading>Using pseudo-ttys and modifying wtmp, utmp and
6626 Some programs need to create pseudo-ttys. This should be done
6627 using Unix98 ptys if the C library supports it. The resulting
6628 program must not be installed setuid root, unless that
6629 is required for other functionality.
6633 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
6634 <file>/var/log/lastlog</file> must be installed writeable by
6635 group <tt>utmp</tt>. Programs which need to modify those
6636 files must be installed setgid <tt>utmp</tt>.
6641 <heading>Editors and pagers</heading>
6644 Some programs have the ability to launch an editor or pager
6645 program to edit or display a text document. Since there are
6646 lots of different editors and pagers available in the Debian
6647 distribution, the system administrator and each user should
6648 have the possibility to choose his/her preferred editor and
6653 In addition, every program should choose a good default
6654 editor/pager if none is selected by the user or system
6659 Thus, every program that launches an editor or pager must
6660 use the EDITOR or PAGER environment variable to determine
6661 the editor or pager the user wishes to use. If these
6662 variables are not set, the programs <file>/usr/bin/editor</file>
6663 and <file>/usr/bin/pager</file> should be used, respectively.
6667 These two files are managed through the <prgn>dpkg</prgn>
6668 `alternatives' mechanism. Thus every package providing an
6669 editor or pager must call the
6670 <prgn>update-alternatives</prgn> script to register these
6675 If it is very hard to adapt a program to make use of the
6676 EDITOR or PAGER variables, that program may be configured to
6677 use <file>/usr/bin/sensible-editor</file> and
6678 <file>/usr/bin/sensible-pager</file> as the editor or pager
6679 program respectively. These are two scripts provided in the
6680 Debian base system that check the EDITOR and PAGER variables
6681 and launch the appropriate program, and fall back to
6682 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
6683 variable is not set.
6687 A program may also use the VISUAL environment variable to
6688 determine the user's choice of editor. If it exists, it
6689 should take precedence over EDITOR. This is in fact what
6690 <file>/usr/bin/sensible-editor</file> does.
6694 It is not required for a package to depend on
6695 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
6696 package to provide such virtual packages.<footnote>
6698 The Debian base system already provides an editor and a
6705 <sect id="web-appl">
6706 <heading>Web servers and applications</heading>
6709 This section describes the locations and URLs that should
6710 be used by all web servers and web applications in the
6718 Cgi-bin executable files are installed in the
6720 <example compact="compact">
6721 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
6723 and should be referred to as
6724 <example compact="compact">
6725 http://localhost/cgi-bin/<var>cgi-bin-name</var>
6730 <item><p>Access to HTML documents</p>
6733 HTML documents for a package are stored in
6734 <file>/usr/share/doc/<var>package</var></file>
6735 and can be referred to as
6736 <example compact="compact">
6737 http://localhost/doc/<var>package</var>/<var>filename</var>
6741 The web server should restrict access to the document
6742 tree so that only clients on the same host can read
6743 the documents. If the web server does not support such
6744 access controls, then it should not provide access at
6745 all, or ask about providing access during installation.
6749 <item><p>Web Document Root</p>
6752 Web Applications should try to avoid storing files in
6753 the Web Document Root. Instead they should use the
6754 /usr/share/doc/<var>package</var> directory for
6755 documents and register the Web Application via the
6756 menu package. If access to the web document root is
6757 unavoidable then use
6758 <example compact="compact">
6761 as the Document Root. This might be just a symbolic
6762 link to the location where the system administrator
6763 has put the real document root.
6767 </enumlist></p></sect>
6770 <sect id="mail-transport-agents">
6771 <heading>Mail transport, delivery and user agents</heading>
6774 Debian packages which process electronic mail, whether mail
6775 user agents (MUAs) or mail transport agents (MTAs), must
6776 ensure that they are compatible with the configuration
6777 decisions below. Failure to do this may result in lost
6778 mail, broken <tt>From:</tt> lines, and other serious brain
6783 The mail spool is <file>/var/mail</file> and the interface to
6784 send a mail message is <file>/usr/sbin/sendmail</file> (as per
6785 the FHS). On older systems, the mail spool may be
6786 physically located in <file>/var/spool/mail</file>, but all
6787 access to the mail spool should be via the
6788 <file>/var/mail</file> symlink. The mail spool is part of the
6789 base system and not part of the MTA package.
6793 All Debian MUAs, MTAs, MDAs and other mailbox accessing
6794 programs (such as IMAP daemons) must lock the mailbox in an
6795 NFS-safe way. This means that <tt>fcntl()</tt> locking must
6796 be combined with dot locking. To avoid deadlocks, a program
6797 should use <tt>fcntl()</tt> first and dot locking after
6798 this, or alternatively implement the two locking methods in
6799 a non blocking way<footnote>
6801 If it is not possible to establish both locks, the
6802 system shouldn't wait for the second lock to be
6803 established, but remove the first lock, wait a (random)
6804 time, and start over locking again.
6806 </footnote>. Using the functions <tt>maillock</tt> and
6807 <tt>mailunlock</tt> provided by the
6808 <tt>liblockfile*</tt><footnote>
6810 You will need to depend on <tt>liblockfile1
6811 (>>1.01)</tt> to use these functions.
6813 </footnote> packages is the recommended way to realize this.
6817 Mailboxes are generally mode 660
6818 <tt><var>user</var>.mail</tt> unless the system
6819 administrator has chosen otherwise. A MUA may remove a
6820 mailbox (unless it has nonstandard permissions) in which
6821 case the MTA or another MUA must recreate it if needed.
6822 Mailboxes must be writable by group mail.
6826 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
6827 be setgid mail to do the locking mentioned above (and
6828 must obviously avoid accessing other users' mailboxes
6829 using this privilege).</p>
6832 <file>/etc/aliases</file> is the source file for the system mail
6833 aliases (e.g., postmaster, usenet, etc.), it is the one
6834 which the sysadmin and <prgn>postinst</prgn> scripts may
6835 edit. After <file>/etc/aliases</file> is edited the program or
6836 human editing it must call <prgn>newaliases</prgn>. All MTA
6837 packages must come with a <prgn>newaliases</prgn> program,
6838 even if it does nothing, but older MTA packages did not do
6839 this so programs should not fail if <prgn>newaliases</prgn>
6840 cannot be found. Note that because of this, all MTA
6841 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
6842 <tt>Replaces: mail-transport-agent</tt> control file
6847 The convention of writing <tt>forward to
6848 <var>address</var></tt> in the mailbox itself is not
6849 supported. Use a <tt>.forward</tt> file instead.</p>
6852 The <prgn>rmail</prgn> program used by UUCP
6853 for incoming mail should be <file>/usr/sbin/rmail</file>.
6854 Likewise, <prgn>rsmtp</prgn>, for receiving
6855 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
6859 If your package needs to know what hostname to use on (for
6860 example) outgoing news and mail messages which are generated
6861 locally, you should use the file <file>/etc/mailname</file>. It
6862 will contain the portion after the username and <tt>@</tt>
6863 (at) sign for email addresses of users on the machine
6864 (followed by a newline).
6868 Such package should check for the existence of this file
6869 when it is being configured. If it exists, it should be
6870 used without comment, although an MTA's configuration script
6871 may wish to prompt the user even if it finds that this file
6872 exists. If the file does not exist, the package should
6873 prompt the user for the value (preferably using
6874 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
6875 as well as using it in the package's configuration. The
6876 prompt should make it clear that the name will not just be
6877 used by that package. For example, in this situation the
6878 <tt>inn</tt> package could say something like:
6879 <example compact="compact">
6880 Please enter the `mail name' of your system. This is the
6881 hostname portion of the address to be shown on outgoing
6882 news and mail messages. The default is
6883 <var>syshostname</var>, your system's host name. Mail
6884 name [`<var>syshostname</var>']:
6886 where <var>syshostname</var> is the output of <tt>hostname
6892 <heading>News system configuration</heading>
6895 All the configuration files related to the NNTP (news)
6896 servers and clients should be located under
6897 <file>/etc/news</file>.</p>
6900 There are some configuration issues that apply to a number
6901 of news clients and server packages on the machine. These
6905 <tag><file>/etc/news/organization</file></tag>
6906 <item><p>A string which should appear as the
6907 organization header for all messages posted
6908 by NNTP clients on the machine</p></item>
6910 <tag><file>/etc/news/server</file></tag>
6911 <item><p>Contains the FQDN of the upstream NNTP
6912 server, or localhost if the local machine is
6913 an NNTP server.</p></item>
6916 Other global files may be added as required for cross-package news
6917 configuration.</p></sect>
6921 <heading>Programs for the X Window System</heading>
6924 <heading>Providing X support and package priorities</heading>
6927 Programs that can be configured with support for the X
6928 Window System must be configured to do so and must declare
6929 any package dependencies necessary to satisfy their
6930 runtime requirements when using the X Window System. If
6931 such a package is of higher priority than the X packages
6932 on which it depends, it is required that either the
6933 X-specific components be split into a separate package, or
6934 that an alternative version of the package, which includes
6935 X support, be provided, or that the package's priority be
6941 <heading>Packages providing an X server</heading>
6944 Packages that provide an X server that, directly or
6945 indirectly, communicates with real input and display
6946 hardware should declare in their control data that they
6947 provide the virtual package <tt>xserver</tt>.<footnote>
6949 This implements current practice, and provides an
6950 actual policy for usage of the <tt>xserver</tt>
6951 virtual package which appears in the virtual packages
6952 list. In a nutshell, X servers that interface
6953 directly with the display and input hardware or via
6954 another subsystem (e.g., GGI) should provide
6955 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
6956 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
6963 <heading>Packages providing a terminal emulator</heading>
6966 Packages that provide a terminal emulator for the X Window
6967 System which meet the criteria listed below should declare
6968 in their control data that they provide the virtual
6969 package <tt>x-terminal-emulator</tt>. They should also
6970 register themselves as an alternative for
6971 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
6976 To be an <tt>x-terminal-emulator</tt>, a program must:
6977 <list compact="compact">
6979 Be able to emulate a DEC VT100 terminal, or a
6980 compatible terminal.
6984 Support the command-line option <tt>-e
6985 <var>command</var></tt>, which creates a new
6986 terminal window<footnote>
6988 "New terminal window" does not necessarily mean
6989 a new top-level X window directly parented by
6990 the window manager; it could, if the terminal
6991 emulator application were so coded, be a new
6992 "view" in a multiple-document interface (MDI).
6995 and runs the specified <var>command</var>.
6999 Support the command-line option <tt>-T
7000 <var>title</var></tt>, which creates a new terminal
7001 window with the window title <var>title</var>.
7008 <heading>Packages providing a window manager</heading>
7011 Packages that provide a window manager should declare in
7012 their control data that they provide the virtual package
7013 <tt>x-window-manager</tt>. They should also register
7014 themselves as an alternative for
7015 <file>/usr/bin/x-window-manager</file>, with a priority
7016 calculated as follows:
7017 <list compact="compact">
7018 <item><p>Start with a priority of 20.</p></item>
7022 If the window manager supports the Debian menu
7023 system, add 20 points if this support is available
7024 in the package's default configuration (i.e., no
7025 configuration files belonging to the system or user
7026 have to be edited to activate the feature); if
7027 configuration files must be modified, add only 10
7033 If the window manager complies with <url
7034 id="http://www.freedesktop.org/standards/wm-spec.html"
7035 name="The Window Manager Specification Project">,
7036 written by the <url id="http://www.freedesktop.org"
7037 name="Free Desktop Group">, add 20 points.
7043 If the window manager permits the X session to be
7044 restarted using a <em>different</em> window manager
7045 (without killing the X server) in its default
7046 configuration, add 10 points; otherwise add none.
7054 <heading>Packages providing fonts</heading>
7057 Packages that provide fonts for the X Window
7060 For the purposes of Debian Policy, a "font for the X
7061 Window System" is one which is accessed via X protocol
7062 requests. Fonts for the Linux console, for PostScript
7063 renderers, or any other purpose, do not fit this
7064 definition. Any tool which makes such fonts available
7065 to the X Window System, however, must abide by this
7069 must do a number of things to ensure that they are both
7070 available without modification of the X or font server
7071 configuration, and that they do not corrupt files used by
7072 other font packages to register information about
7077 Fonts of any type supported by the X Window System
7078 must be in a separate binary package from any
7079 executables, libraries, or documentation (except
7080 that specific to the fonts shipped, such as their
7081 license information). If one or more of the fonts
7082 so packaged are necessary for proper operation of
7083 the package with which they are associated the font
7084 package may be Recommended; if the fonts merely
7085 provide an enhancement, a Suggests relationship may
7086 be used. Packages must not Depend on font
7089 This is because the X server may retrieve fonts
7090 from the local filesystem or over the network
7091 from an X font server; the Debian package system
7092 is empowered to deal only with the local
7101 BDF fonts must be converted to PCF fonts with the
7102 <prgn>bdftopcf</prgn> utility (available in the
7103 <tt>xutils</tt> package, <tt>gzip</tt>ped, and
7104 placed in a directory that corresponds to their
7106 <list compact="compact">
7108 100 dpi fonts must be placed in
7109 <file>/usr/X11R6/lib/X11/fonts/100dpi/</file>.
7113 75 dpi fonts must be placed in
7114 <file>/usr/X11R6/lib/X11/fonts/75dpi/</file>.
7118 Character-cell fonts, cursor fonts, and other
7119 low-resolution fonts must be placed in
7120 <file>/usr/X11R6/lib/X11/fonts/misc/</file>.
7127 Speedo fonts must be placed in
7128 <file>/usr/X11R6/lib/X11/fonts/Speedo/</file>.
7132 Type 1 fonts must be placed in
7133 <file>/usr/X11R6/lib/X11/fonts/Type1/</file>. If font
7134 metric files are available, they must be placed here
7140 Subdirectories of <file>/usr/X11R6/lib/X11/fonts/</file>
7141 other than those listed above must be neither
7142 created nor used. (The <file>PEX</file>, <file>CID</file>,
7143 and <file>cyrillic</file> directories are excepted for
7144 historical reasons, but installation of files into
7145 these directories remains discouraged.)
7151 Font packages may, instead of placing files directly
7152 in the X font directories listed above, provide
7153 symbolic links in that font directory pointing to
7154 the files' actual location in the filesystem. Such
7155 a location must comply with the FHS.
7161 Font packages should not contain both 75dpi and
7162 100dpi versions of a font. If both are available,
7163 they should be provided in separate binary packages
7164 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
7165 the names of the packages containing the
7166 corresponding fonts.
7172 Fonts destined for the <file>misc</file> subdirectory
7173 should not be included in the same package as 75dpi
7174 or 100dpi fonts; instead, they should be provided in
7175 a separate package with <tt>-misc</tt> appended to
7182 Font packages must not provide the files
7183 <file>fonts.dir</file>, <file>fonts.alias</file>, or
7184 <file>fonts.scale</file> in a font directory:
7187 <file>fonts.dir</file> files must not be provided at all.
7192 <file>fonts.alias</file> and <file>fonts.scale</file>
7193 files, if needed, should be provided in the
7195 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
7196 where <var>fontdir</var> is the name of the
7198 <file>/usr/X11R6/lib/X11/fonts/</file> where the
7199 package's corresponding fonts are stored
7200 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
7201 <var>package</var> is the name of the package
7202 that provides these fonts, and
7203 <var>extension</var> is either <tt>scale</tt>
7204 or <tt>alias</tt>, whichever corresponds to
7214 Font packages must declare a dependency on
7215 <tt>xutils (>> 4.0.3)</tt> in their control
7222 Font packages that provide one or more
7223 <file>fonts.scale</file> files as described above must
7224 invoke <prgn>update-fonts-scale</prgn> on each
7225 directory into which they installed fonts
7226 <em>before</em> invoking
7227 <prgn>update-fonts-dir</prgn> on that directory.
7228 This invocation must occur in both the
7229 <prgn>postinst</prgn> (for all arguments) and
7230 <prgn>postrm</prgn> (for all arguments except
7231 <tt>upgrade</tt>) scripts.
7237 Font packages that provide one or more
7238 <file>fonts.alias</file> files as described above must
7239 invoke <prgn>update-fonts-alias</prgn> on each
7240 directory into which they installed fonts. This
7241 invocation must occur in both the
7242 <prgn>postinst</prgn> (for all arguments) and
7243 <prgn>postrm</prgn> (for all arguments except
7244 <tt>upgrade</tt>) scripts.
7250 Font packages must invoke
7251 <prgn>update-fonts-dir</prgn> on each directory into
7252 which they installed fonts. This invocation must
7253 occur in both the <prgn>postinst</prgn> (for all
7254 arguments) and <prgn>postrm</prgn> (for all
7255 arguments except <tt>upgrade</tt>) scripts.
7261 Font packages must not provide alias names for the
7262 fonts they include which collide with alias names
7263 already in use by fonts already packaged.
7269 Font packages must not provide fonts with the same
7270 XLFD registry name as another font already packaged.
7278 <heading>Application defaults files</heading>
7281 Application defaults files must be installed in the
7282 directory <file>/etc/X11/app-defaults/</file> (use of a
7283 localized subdirectory of <file>/etc/X11/</file> as described
7284 in the <em>X Toolkit Intrinsics - C Language
7285 Interface</em> manual is also permitted). They must be
7286 registered as <tt>conffile</tt>s or handled as
7287 configuration files. Packages must not provide the
7288 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
7292 Customization of programs' X resources may also be
7293 supported with the provision of a file with the same name
7294 as that of the package placed in the
7295 <file>/etc/X11/Xresources/</file> directory, which must
7296 registered as a <tt>conffile</tt> or handled as a
7297 configuration file.<footnote>
7299 Note that this mechanism is not the same as using
7300 app-defaults; app-defaults are tied to the client
7301 binary on the local filesystem, whereas X resources
7302 are stored in the X server and affect all connecting
7306 <em>Important:</em> packages that install files into the
7307 <file>/etc/X11/Xresources/</file> directory must conflict with
7308 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
7309 it is possible for the installing package to destroy a
7310 previously-existing <file>/etc/X11/Xresources</file> file
7311 which had been customized by the system administrator.
7316 <heading>Installation directory issues</heading>
7319 Packages using the X Window System should not be
7320 configured to install files under the <file>/usr/X11R6/</file>
7321 directory unless they use <prgn>imake</prgn>. The
7322 <file>/usr/X11R6/</file> directory hierarchy should be
7323 regarded as deprecated for all packages except the X
7324 Window System itself, and those which use the
7325 <prgn>imake</prgn> program it provides, in which case the
7326 packages may transition out of the <file>/usr/X11R6/</file>
7327 directory at the maintainer's discretion.<footnote>
7329 <prgn>Imake</prgn>-using programs are exempt because,
7330 as long as they are written correctly, the pathnames
7331 they use to locate resources and install themselves
7332 are derived wholly from the X Window System
7333 configuration. Thus, in the event that the X Window
7334 System moves to <file>/usr/X11R7/</file>,
7335 <file>/usr/X12/</file>, or just plain <file>/usr/</file>, all
7336 that is required for these programs is a recompile
7337 against the corresponding X Window System library
7338 development packages.
7341 Programs that use GNU <prgn>autoconf</prgn> and
7342 <prgn>automake</prgn> are usually easily configured at
7343 compile time to use <file>/usr/</file> instead of
7344 <file>/usr/X11R6/</file>, and this should be done whenever
7345 possible. Configuration files for window managers and
7346 display managers should be placed in a subdirectory of
7347 <file>/etc/X11/</file> corresponding to the package name due
7348 to these programs' tight integration with the mechanisms
7349 of the X Window System. Application-level programs should
7350 use the <file>/etc/</file> directory unless otherwise mandated
7351 by policy. The installation of files into subdirectories
7352 of <file>/usr/X11R6/include/X11/</file> and
7353 <file>/usr/X11R6/lib/X11/</file> is permitted but discouraged;
7354 package maintainers should determine if subdirectories of
7355 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
7356 instead. (The use of symbolic links from the
7357 <file>X11R6</file> directories to other FHS-compliant
7358 locations is encouraged if the program is not easily
7359 configured to look elsewhere for its files.) Packages
7360 must not provide or install files into the directories
7361 <file>/usr/bin/X11/</file>, <file>/usr/include/X11/</file> or
7362 <file>/usr/lib/X11/</file>. Files within a package should,
7363 however, make reference to these directories, rather than
7364 their <tt>X11R6</tt>-named counterparts
7365 <file>/usr/X11R6/bin/</file>, <file>/usr/X11R6/include/X11/</file>
7366 and <file>/usr/X11R6/lib/X11/</file>, if the resources being
7367 referred to have not been moved to other FHS-compliant
7373 <heading>The OSF/Motif and OpenMotif libraries</heading>
7376 <em>Programs that require the non-DFSG-compliant OSF/Motif or
7377 OpenMotif libraries</em><footnote>
7379 OSF/Motif and OpenMotif are collectively referred to as
7380 "Motif" in this policy document.
7383 should be compiled against and tested with LessTif (a free
7384 re-implementation of Motif) instead. If the maintainer
7385 judges that the program or programs do not work
7386 sufficiently well with LessTif to be distributed and
7387 supported, but do so when compiled against Motif, then two
7388 versions of the package should be created; one linked
7389 statically against Motif and with <tt>-smotif</tt>
7390 appended to the package name, and one linked dynamically
7391 against Motif and with <tt>-dmotif</tt> appended to the
7392 package name. Both Motif-linked versions are dependent
7393 upon non-DFSG-compliant software and thus cannot be
7394 uploaded to the <em>main</em> distribution; if the
7395 software is itself DFSG-compliant it may be uploaded to
7396 the <em>contrib</em> distribution. While known existing
7397 versions of Motif permit unlimited redistribution of
7398 binaries linked against the library (whether statically or
7399 dynamically), it is the package maintainer's
7400 responsibility to determine whether this is permitted by
7401 the license of the copy of Motif in his or her possession.
7407 <heading>Perl programs and modules</heading>
7409 Perl programs and modules should follow the current Perl
7410 policy as defined in the file found on
7411 <ftpsite>ftp.debian.org</ftpsite> in
7412 <ftppath>/debian/doc/package-developer/perl-policy.txt.gz</ftppath>
7413 or your local mirror. In addition, it is included in the
7414 <tt>debian-policy</tt> package.
7419 <heading>Emacs lisp programs</heading>
7422 Please refer to the `Debian Emacs Policy' (documented in
7423 <file>debian-emacs-policy.gz</file> of the
7424 <prgn>emacsen-common</prgn> package) for details of how to
7425 package emacs lisp programs.
7430 <heading>Games</heading>
7433 The permissions on <file>/var/games</file> are mode 755, owner
7434 <tt>root</tt> and group <tt>root</tt>.
7438 Each game decides on its own security policy.</p>
7441 Games which require protected, privileged access to
7442 high-score files, savegames, etc., may be made
7443 set-<em>group</em>-id (mode 2755) and owned by
7444 <tt>root.games</tt>, and use files and directories with
7445 appropriate permissions (770 <tt>root.games</tt>, for
7446 example). They must not be made
7447 set-<em>user</em>-id, as this causes security problems. (If
7448 an attacker can subvert any set-user-id game they can
7449 overwrite the executable of any other, causing other players
7450 of these games to run a Trojan horse program. With a
7451 set-group-id game the attacker only gets access to less
7452 important game data, and if they can get at the other
7453 players' accounts at all it will take considerably more
7457 Some packages, for example some fortune cookie programs, are
7458 configured by the upstream authors to install with their
7459 data files or other static information made unreadable so
7460 that they can only be accessed through set-id programs
7461 provided. You should not do this in a Debian package: anyone can
7462 download the <file>.deb</file> file and read the data from it,
7463 so there is no point making the files unreadable. Not
7464 making the files unreadable also means that you don't have
7465 to make so many programs set-id, which reduces the risk of a
7469 As described in the FHS, binaries of games should be
7470 installed in the directory <file>/usr/games</file>. This also
7471 applies to games that use the X Window System. Manual pages
7472 for games (X and non-X games) should be installed in
7473 <file>/usr/share/man/man6</file>.</p>
7477 <chapt id="docs"><heading>Documentation</heading>
7481 <heading>Manual pages</heading>
7484 You should install manual pages in <prgn>nroff</prgn> source
7485 form, in appropriate places under <file>/usr/share/man</file>. You
7486 should only use sections 1 to 9 (see the FHS for more
7487 details). You must not install a preformatted `cat
7491 Each program, utility, and function should have an
7492 associated manpage included in the same package. It is
7493 suggested that all configuration files also have a manual
7494 page included as well.
7498 If no manual page is available for a particular program,
7499 utility, function or configuration file and this is reported
7500 as a bug to the Debian Bug Tracking System, a symbolic link
7501 from the requested manual page to the <manref
7502 name="undocumented" section="7"> manual page may be
7503 provided. This symbolic link can be created from
7504 <file>debian/rules</file> like this:
7505 <example compact="compact">
7506 ln -s ../man7/undocumented.7.gz \
7507 debian/tmp/usr/share/man/man[1-9]/<var>requested_manpage</var>.[1-9].gz
7509 This manpage claims that the lack of a manpage has been
7510 reported as a bug, so you may only do this if it really has
7511 (you can report it yourself, if you like). Do not close the
7512 bug report until a proper manpage is available.</p>
7515 You may forward a complaint about a missing manpage to the
7516 upstream authors, and mark the bug as forwarded in the
7517 Debian bug tracking system. Even though the GNU Project do
7518 not in general consider the lack of a manpage to be a bug,
7519 we do; if they tell you that they don't consider it a bug
7520 you should leave the bug in our bug tracking system open
7524 Manual pages should be installed compressed using <tt>gzip
7528 If one manpage needs to be accessible via several names it
7529 is better to use a symbolic link than the <file>.so</file>
7530 feature, but there is no need to fiddle with the relevant
7531 parts of the upstream source to change from <file>.so</file> to
7532 symlinks: don't do it unless it's easy. You should not
7533 create hard links in the manual page directories, nor put
7534 absolute filenames in <file>.so</file> directives. The filename
7535 in a <file>.so</file> in a manpage should be relative to the
7536 base of the manpage tree (usually
7537 <file>/usr/share/man</file>). If you do not create any links
7538 (whether symlinks, hard links, or <tt>.so</tt> directives)
7539 in the filesystem to the alternate names of the manpage,
7540 then you should not rely on <prgn>man</prgn> finding your
7541 manpage under those names based solely on the information in
7542 the manpage's header.<footnote>
7544 Supporting this in <prgn>man</prgn> often requires
7545 unreasonable processing time to find a manual page or to
7546 report that none exists, and moves knowledge into man's
7547 database that would be better left in the filesystem.
7548 This support is therefore deprecated and will cease to
7549 be present in the future.
7556 <heading>Info documents</heading>
7559 Info documents should be installed in <file>/usr/share/info</file>.
7560 They should be compressed with <tt>gzip -9</tt>.</p>
7563 Your package should call <prgn>install-info</prgn> to update
7564 the Info <file>dir</file> file in its <prgn>postinst</prgn>
7565 script when called with a <tt>configure</tt> argument, for
7567 <example compact="compact">
7568 install-info --quiet --section Development Development \
7569 /usr/share/info/foobar.info
7573 It is a good idea to specify a section for the location of
7574 your program; this is done with the <tt>--section</tt>
7575 switch. To determine which section to use, you should look
7576 at <file>/usr/share/info/dir</file> on your system and choose the most
7577 relevant (or create a new section if none of the current
7578 sections are relevant). Note that the <tt>--section</tt>
7579 flag takes two arguments; the first is a regular expression
7580 to match (case-insensitively) against an existing section,
7581 the second is used when creating a new one.</p>
7584 You should remove the entries in the <prgn>prerm</prgn>
7585 script when called with a <tt>remove</tt> argument:
7586 <example compact="compact">
7587 install-info --quiet --remove /usr/share/info/foobar.info
7591 If <prgn>install-info</prgn> cannot find a description entry
7592 in the Info file you must supply one. See <manref
7593 name="install-info" section="8"> for details.</p>
7597 <heading>Additional documentation</heading>
7600 Any additional documentation that comes with the package may
7601 be installed at the discretion of the package maintainer.
7602 Text documentation should be installed in the directory
7603 <file>/usr/share/doc/<var>package</var></file>, where
7604 <var>package</var> is the name of the package, and
7605 compressed with <tt>gzip -9</tt> unless it is small.</p>
7608 If a package comes with large amounts of documentation which
7609 many users of the package will not require you should create
7610 a separate binary package to contain it, so that it does not
7611 take up disk space on the machines of users who do not need
7612 or want it installed.</p>
7615 It is often a good idea to put text information files
7616 (<file>README</file>s, changelogs, and so forth) that come with
7617 the source package in <file>/usr/share/doc/<var>package</var></file>
7618 in the binary package. However, you don't need to install
7619 the instructions for building and installing the package, of
7623 Files in <file>/usr/share/doc</file> should not be referenced by
7624 any program, and the system administrator should be able to
7625 delete them without causing any programs to break. Any files
7626 that are referenced by programs but are also useful as
7627 standalone documentation should be installed under
7628 <file>/usr/share/<var>package</var>/</file> with symbolic links
7629 from <file>/usr/share/doc/<var>package</var>/</file>.
7635 <heading>Accessing the documentation</heading>
7638 Former Debian releases placed all additional documentation
7639 in <file>/usr/doc/<var>package</var></file>. This has now
7640 changed to <file>/usr/share/doc/<var>package</var></file>,
7641 and packages must not put documentation in the directory
7642 <file>/usr/doc/<var>package</var></file>. <footnote>
7643 <p>At this phase of the transition, we no longer require a
7644 symbolic link in <file>/usr/doc/</file>. At a later point,
7645 policy shall change to make the symbolic links a bug.</p>
7651 <heading>Preferred documentation formats</heading>
7654 The unification of Debian documentation is being carried out
7658 If your package comes with extensive documentation in a
7659 markup format that can be converted to various other formats
7660 you should if possible ship HTML versions in a binary
7661 package, in the directory
7662 <file>/usr/share/doc/<var>appropriate-package</var></file> or
7663 its subdirectories.<footnote>
7665 The rationale: The important thing here is that HTML
7666 docs should be available in <em>some</em> package, not
7667 necessarily in the main binary package.
7673 Other formats such as PostScript may be provided at the
7674 package maintainer's discretion.
7678 <sect id="copyrightfile">
7679 <heading>Copyright information</heading>
7682 Every package must be accompanied by a verbatim copy of its
7683 copyright and distribution license in the file
7684 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
7685 file must neither be compressed nor be a symbolic link.
7689 In addition, the copyright file must say where the upstream
7690 sources (if any) were obtained, and should explain briefly what
7691 modifications were made in the Debian version of the package
7692 compared to the upstream one. It should name the original
7693 authors of the package and the Debian maintainer(s) who were
7694 involved with its creation.</p>
7697 A copy of the file which will be installed in
7698 <file>/usr/share/doc/<var>package</var>/copyright</file> should
7699 be in <file>debian/copyright</file> in the source package.
7703 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7704 link to another directory in <file>/usr/share/doc</file> only if
7705 the two packages both come from the same source and the
7706 first package Depends on the second. These rules are
7707 important because copyrights must be extractable by
7712 Packages distributed under the UCB BSD license, the Artistic
7713 license, the GNU GPL, and the GNU LGPL should refer to the
7714 files <file>/usr/share/common-licenses/BSD</file>,
7715 <file>/usr/share/common-licenses/Artistic</file>,
7716 <file>/usr/share/common-licenses/GPL</file>, and
7717 <file>/usr/share/common-licenses/LGPL</file> respectively,
7718 rather than quoting them in the copyright file.
7722 You should not use the copyright file as a general <file>README</file>
7723 file. If your package has such a file it should be
7724 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
7725 <file>README.Debian</file> or some other appropriate place.</p>
7729 <heading>Examples</heading>
7732 Any examples (configurations, source files, whatever),
7733 should be installed in a directory
7734 <file>/usr/share/doc/<var>package</var>/examples</file>. These
7735 files should not be referenced by any program: they're there
7736 for the benefit of the system administrator and users as
7737 documentation only. Architecture-specific example files
7738 should be installed in a directory
7739 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
7741 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
7742 latter directory itself may be a symbolic link to the
7747 <sect id="instchangelog">
7748 <heading>Changelog files</heading>
7751 Packages that are not Debian-native must contain a
7752 compressed copy of the <file>debian/changelog</file> file from
7753 the Debian source tree in
7754 <file>/usr/share/doc/<var>package</var></file> with the name
7755 <file>changelog.Debian.gz</file>. If an upstream changelog is
7756 available, it should be accessible as
7757 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
7758 plain text. If the upstream changelog is distributed in
7759 HTML, it should be made available in that form as
7760 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
7761 and a plain text <file>changelog.gz</file> should be generated
7762 from it using, for example, <tt>lynx -dump -nolist</tt>. If
7763 the upstream changelog files do not already conform to this
7764 naming convention, then this may be achieved either by
7765 renaming the files, or by adding a symbolic link, at the
7766 maintainer's discretion.<footnote>
7768 Rationale: People should not have to look in places for
7769 upstream changelogs merely because they are given
7770 different names or are distributed in HTML format.
7776 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7777 link to another directory in <file>/usr/share/doc</file> only if
7778 the two packages both come from the same source and the
7779 first package Depends on the second.
7784 All of these files should be installed compressed using
7785 <tt>gzip -9</tt>, as they will become large with time even
7786 if they start out small.
7790 If the package has only one changelog which is used both as
7791 the Debian changelog and the upstream one because there is
7792 no separate upstream maintainer then that changelog should
7793 usually be installed as
7794 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
7795 there is a separate upstream maintainer, but no upstream
7796 changelog, then the Debian changelog should still be called
7797 <file>changelog.Debian.gz</file>.</p>
7801 <appendix id="pkg-scope">
7802 <heading>Introduction and scope of these appendices</heading>
7805 These appendices are taken essentially verbatim from the
7806 now-deprecated Packaging Manual, version 3.2.1.0. They are
7807 the chapters which are likely to be of use to package
7808 maintainers and which have not already been included in the
7809 policy document itself. Most of these sections are very likely
7810 not relevant to policy; they should be treated as
7811 documentation for the packaging system. Please note that these
7812 appendices are included for convenience, and for historical
7813 reasons: they used to be part of policy package, and they have
7814 not yet been incorporated into dpkg documentation. However,
7815 they still have value, and hence they are presented here.
7818 They have not yet been checked to ensure that they are
7819 compatible with the contents of policy, and if there are any
7820 contradictions, the version in the main policy document takes
7821 precedence. The remaining chapters of the old Packaging
7822 Manual have also not been read in detail to ensure that there
7823 are not parts which have been left out. Both of these will be
7828 <prgn>dpkg</prgn> is a suite of programs for creating binary
7829 package files and installing and removing them on Unix
7832 <prgn>dpkg</prgn> is targetted primarily at Debian
7833 GNU/Linux, but may work on or be ported to other
7840 The binary packages are designed for the management of
7841 installed executable programs (usually compiled binaries) and
7842 their associated data, though source code examples and
7843 documentation are provided as part of some packages.</p>
7846 This manual describes the technical aspects of creating Debian
7847 binary packages (<file>.deb</file> files). It documents the
7848 behaviour of the package management programs
7849 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
7850 they interact with packages.</p>
7853 It also documents the interaction between
7854 <prgn>dselect</prgn>'s core and the access method scripts it
7855 uses to actually install the selected packages, and describes
7856 how to create a new access method.</p>
7859 This manual does not go into detail about the options and
7860 usage of the package building and installation tools. It
7861 should therefore be read in conjuction with those programs'
7866 The utility programs which are provided with <prgn>dpkg</prgn>
7867 for managing various system configuration and similar issues,
7868 such as <prgn>update-rc.d</prgn> and
7869 <prgn>install-info</prgn>, are not described in detail here -
7870 please see their manpages.
7874 It does <em>not</em> describe the policy requirements imposed
7875 on Debian packages, such as the permissions on files and
7876 directories, documentation requirements, upload procedure, and
7877 so on. You should see the Debian packaging policy manual for
7878 these details. (Many of them will probably turn out to be
7879 helpful even if you don't plan to upload your package and make
7880 it available as part of the distribution.)
7884 It is assumed that the reader is reasonably familiar with the
7885 <prgn>dpkg</prgn> System Administrators' manual.
7886 Unfortunately this manual does not yet exist.
7890 The Debian version of the FSF's GNU hello program is provided
7891 as an example for people wishing to create Debian
7892 packages. The Debian <prgn>debmake</prgn> package is
7893 recommended as a very helpful tool in creating and maintaining
7894 Debian packages. However, while the tools and examples are
7895 helpful, they do not replace the need to read and follow the
7896 Policy and Programmer's Manual.</p>
7899 <appendix id="pkg-binarypkg"><heading>Binary packages (from old
7904 The binary package has two main sections. The first part
7905 consists of various control information files and scripts used
7906 by <prgn>dpkg</prgn> when installing and removing. See <ref
7907 id="pkg-controlarea">.
7911 The second part is an archive containing the files and
7912 directories to be installed.
7916 In the future binary packages may also contain other
7917 components, such as checksums and digital signatures. The
7918 format for the archive is described in full in the
7919 <file>deb(5)</file> manpage.
7923 <sect id="pkg-bincreating"><heading>Creating package files -
7924 <prgn>dpkg-deb</prgn>
7928 All manipulation of binary package files is done by
7929 <prgn>dpkg-deb</prgn>; it's the only program that has
7930 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
7931 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
7932 will spot that the options requested are appropriate to
7933 <prgn>dpkg-deb</prgn> and invoke that instead with the same
7938 In order to create a binary package you must make a
7939 directory tree which contains all the files and directories
7940 you want to have in the filesystem data part of the package.
7941 In Debian-format source packages this directory is usually
7942 <file>debian/tmp</file>, relative to the top of the package's
7947 They should have the locations (relative to the root of the
7948 directory tree you're constructing) ownerships and
7949 permissions which you want them to have on the system when
7954 With current versions of <prgn>dpkg</prgn> the uid/username
7955 and gid/groupname mappings for the users and groups being
7956 used should be the same on the system where the package is
7957 built and the one where it is installed.
7961 You need to add one special directory to the root of the
7962 miniature filesystem tree you're creating:
7963 <prgn>DEBIAN</prgn>. It should contain the control
7964 information files, notably the binary package control file
7965 (see <ref id="pkg-controlfile">).
7969 The <prgn>DEBIAN</prgn> directory will not appear in the
7970 filesystem archive of the package, and so won't be installed
7971 by <prgn>dpkg</prgn> when the package is installed.
7975 When you've prepared the package, you should invoke:
7977 dpkg --build <var>directory</var>
7982 This will build the package in
7983 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
7984 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
7985 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
7990 See the manpage <manref name="dpkg-deb" section="8"> for details of how
7991 to examine the contents of this newly-created file. You may find the
7992 output of following commands enlightening:
7994 dpkg-deb --info <var>filename</var>.deb
7995 dpkg-deb --contents <var>filename</var>.deb
7996 dpkg --contents <var>filename</var>.deb
7998 To view the copyright file for a package you could use this command:
8000 dpkg --fsys-tarfile <var>filename</var>.deb | tar xof usr/share/doc/<var>\*</var>copyright | less
8005 <sect id="pkg-controlarea">
8007 Package control information files
8011 The control information portion of a binary package is a
8012 collection of files with names known to <prgn>dpkg</prgn>.
8013 It will treat the contents of these files specially - some
8014 of them contain information used by <prgn>dpkg</prgn> when
8015 installing or removing the package; others are scripts which
8016 the package maintainer wants <prgn>dpkg</prgn> to run.
8020 It is possible to put other files in the package control
8021 area, but this is not generally a good idea (though they
8022 will largely be ignored).
8026 Here is a brief list of the control info files supported by
8027 <prgn>dpkg</prgn> and a summary of what they're used for.
8032 <tag><tt>control</tt>
8036 This is the key description file used by
8037 <prgn>dpkg</prgn>. It specifies the package's name
8038 and version, gives its description for the user,
8039 states its relationships with other packages, and so
8040 forth. See <ref id="pkg-controlfile">.
8044 It is usually generated automatically from information
8045 in the source package by the
8046 <prgn>dpkg-gencontrol</prgn> program, and with
8047 assistance from <prgn>dpkg-shlibdeps</prgn>. See <ref
8048 id="pkg-sourcetools">.</p>
8051 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8057 These are exectuable files (usually scripts) which
8058 <prgn>dpkg</prgn> runs during installation, upgrade
8059 and removal of packages. They allow the package to
8060 deal with matters which are particular to that package
8061 or require more complicated processing than that
8062 provided by <prgn>dpkg</prgn>. Details of when and
8063 how they are called are in <ref
8064 id="maintainerscripts">.
8068 It is very important to make these scripts
8072 That means that if it runs successfully or fails
8073 and then you call it again it doesn't bomb out,
8074 but just ensures that everything is the way it
8077 </footnote> This is so that if an error occurs, the
8078 user interrupts <prgn>dpkg</prgn> or some other
8079 unforeseen circumstance happens you don't leave the
8080 user with a badly-broken package.
8084 The maintainer scripts are guaranteed to run with a
8085 controlling terminal and can interact with the user.
8086 If they need to prompt for passwords, do full-screen
8087 interaction or something similar you should do these
8088 things to and from <file>/dev/tty</file>, since
8089 <prgn>dpkg</prgn> will at some point redirect scripts'
8090 standard input and output so that it can log the
8091 installation process. Likewise, because these scripts
8092 may be executed with standard output redirected into a
8093 pipe for logging purposes, Perl scripts should set
8094 unbuffered output by setting <tt>$|=1</tt> so that the
8095 output is printed immediately rather than being
8100 Each script should return a zero exit status for
8101 success, or a nonzero one for failure.</p>
8104 <tag><tt>conffiles</tt>
8109 This file contains a list of configuration files which
8110 are to be handled automatically by <prgn>dpkg</prgn>
8111 (see <ref id="pkg-conffiles">). Note that not necessarily
8112 every configuration file should be listed here.</p>
8115 <tag><tt>shlibs</tt>
8120 This file contains a list of the shared libraries
8121 supplied by the package, with dependency details for
8122 each. This is used by <prgn>dpkg-shlibdeps</prgn>
8123 when it determines what dependencies are required in a
8124 package control file. The <tt>shlibs</tt> file format
8125 is described on <ref id="shlibs">.
8131 <sect id="pkg-controlfile">
8133 The main control information file: <tt>control</tt>
8136 The most important control information file used by
8137 <prgn>dpkg</prgn> when it installs a package is
8138 <tt>control</tt>. It contains all the package's `vital
8143 The binary package control files of packages built from
8144 Debian sources are made by a special tool,
8145 <prgn>dpkg-gencontrol</prgn>, which reads
8146 <file>debian/control</file> and <file>debian/changelog</file> to
8147 find the information it needs. See <ref id="pkg-sourcepkg"> for
8152 The fields in binary package control files are:
8153 <list compact="compact">
8155 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8158 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
8160 <item><p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8164 This field should appear in all packages, though
8165 <prgn>dpkg</prgn> doesn't require it yet so that
8166 old packages can still be installed.
8172 <p><qref id="relationships"><tt>Depends</tt>,
8173 <tt>Provides</tt> et al.</qref></p>
8176 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8179 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8182 <p><qref id="pkg-f-classification"><tt>Section</tt>,
8183 <tt>Priority</tt></qref></p>
8186 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
8189 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8193 <qref id="pkg-f-Installed-Size"><tt>Installed-Size</tt></qref>
8199 A description of the syntax of control files and the purpose
8200 of these fields is available in <ref id="pkg-controlfields">.
8205 <heading>Time Stamps</heading>
8207 Maintainers are encouraged to preserve the modification
8208 times of the upstream source files in a package, as far as
8209 is reasonably possible.
8212 The rationale is that there is some information conveyed
8213 by knowing the age of the file, for example, you could
8214 recognize that some documentation is very old by looking
8215 at the modification time, so it would be nice if the
8216 modification time of the upstream source would be
8224 <appendix id="pkg-sourcepkg">
8225 <heading>Source packages (from old Packaging Manual) </heading>
8228 The Debian binary packages in the distribution are generated
8229 from Debian sources, which are in a special format to assist
8230 the easy and automatic building of binaries.
8234 There was a previous version of the Debian source format,
8235 which is now being phased out. Instructions for converting an
8236 old-style package are given in the Debian policy manual.
8239 <sect id="pkg-sourcetools">
8240 <heading>Tools for processing source packages</heading>
8243 Various tools are provided for manipulating source packages;
8244 they pack and unpack sources and help build of binary
8245 packages and help manage the distribution of new versions.
8249 They are introduced and typical uses described here; see
8250 <manref name="dpkg-source" section="1"> for full
8251 documentation about their arguments and operation.
8255 For examples of how to construct a Debian source package,
8256 and how to use those utilities that are used by Debian
8257 source packages, please see the <prgn>hello</prgn> example
8263 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
8268 This program is frequently used by hand, and is also
8269 called from package-independent automated building scripts
8270 such as <prgn>dpkg-buildpackage</prgn>.
8274 To unpack a package it is typically invoked with
8276 dpkg-source -x <var>.../path/to/filename</var>.dsc
8281 with the <file><var>filename</var>.tar.gz</file> and
8282 <file><var>filename</var>.diff.gz</file> (if applicable) in
8283 the same directory. It unpacks into
8284 <file><var>package</var>-<var>version</var></file>, and if
8286 <file><var>package</var>-<var>version</var>.orig</file>, in
8287 the current directory.
8291 To create a packed source archive it is typically invoked:
8293 dpkg-source -b <var>package</var>-<var>version</var>
8298 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
8299 <file>.diff.gz</file> (if appropriate) in the current
8300 directory. <prgn>dpkg-source</prgn> does not clean the
8301 source tree first - this must be done separately if it is
8306 See also <ref id="pkg-sourcearchives">.</p>
8312 <prgn>dpkg-buildpackage</prgn> - overall package-building
8317 <prgn>dpkg-buildpackage</prgn> is a script which invokes
8318 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
8319 targets <tt>clean</tt>, <tt>build</tt> and
8320 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
8321 <prgn>pgp</prgn> to build a signed source and binary
8326 It is usually invoked by hand from the top level of the
8327 built or unbuilt source directory. It may be invoked with
8328 no arguments; useful arguments include:
8329 <taglist compact="compact">
8330 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
8333 Do not PGP-sign the <tt>.changes</tt> file or the
8334 source package <tt>.dsc</tt> file, respectively.</p>
8336 <tag><tt>-p<var>pgp-command</var></tt></tag>
8339 Invoke <var>pgp-command</var> instead of finding
8340 <tt>pgp</tt> on the <prgn>PATH</prgn>.
8341 <var>pgp-command</var> must behave just like
8342 <prgn>pgp</prgn>.</p>
8344 <tag><tt>-r<var>root-command</var></tt></tag>
8347 When root privilege is required, invoke the command
8348 <var>root-command</var>. <var>root-command</var>
8349 should invoke its first argument as a command, from
8350 the <prgn>PATH</prgn> if necessary, and pass its
8351 second and subsequent arguments to the command it
8352 calls. If no <var>root-command</var> is supplied
8353 then <var>dpkg-buildpackage</var> will take no
8354 special action to gain root privilege, so that for
8355 most packages it will have to be invoked as root to
8358 <tag><tt>-b</tt>, <tt>-B</tt></tag>
8361 Two types of binary-only build and upload - see
8362 <manref name="dpkg-source" section="1">.
8371 <prgn>dpkg-gencontrol</prgn> - generates binary package
8376 This program is usually called from <file>debian/rules</file>
8377 (see <ref id="pkg-sourcetree">) in the top level of the source
8382 This is usually done just before the files and directories in the
8383 temporary directory tree where the package is being built have their
8384 permissions and ownerships set and the package is constructed using
8385 <prgn>dpkg-deb/</prgn>
8388 This is so that the control file which is produced has
8389 the right permissions
8395 <prgn>dpkg-gencontrol</prgn> must be called after all the
8396 files which are to go into the package have been placed in
8397 the temporary build directory, so that its calculation of
8398 the installed size of a package is correct.
8402 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
8403 be run after <prgn>dpkg-shlibdeps</prgn> so that the
8404 variable substitutions created by
8405 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
8410 For a package which generates only one binary package, and
8411 which builds it in <file>debian/tmp</file> relative to the top
8412 of the source package, it is usually sufficient to call
8413 <prgn>dpkg-gencontrol</prgn>.
8417 Sources which build several binaries will typically need
8420 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
8421 </example> The <tt>-P</tt> tells
8422 <prgn>dpkg-gencontrol</prgn> that the package is being
8423 built in a non-default directory, and the <tt>-p</tt>
8424 tells it which package's control file should be generated.
8428 <prgn>dpkg-gencontrol</prgn> also adds information to the
8429 list of files in <file>debian/files</file>, for the benefit of
8430 (for example) a future invocation of
8431 <prgn>dpkg-genchanges</prgn>.</p>
8436 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
8441 This program is usually called from <file>debian/rules</file>
8442 just before <prgn>dpkg-gencontrol</prgn> (see <ref
8443 id="pkg-sourcetree">), in the top level of the source tree.
8447 Its arguments are executables.
8450 In a forthcoming dpkg version,
8451 <prgn>dpkg-shlibdeps</prgn> would be required to be
8452 called on shared libraries as well.
8455 They may be specified either in the locations in the
8456 source tree where they are created or in the locations
8457 in the temporary build tree where they are installed
8458 prior to binary package creation.
8460 </footnote> for which shared library dependencies should
8461 be included in the binary package's control file.
8465 If some of the found shared libraries should only
8466 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
8467 some warrant a <tt>Pre-Depends</tt>, this can be achieved
8468 by using the <tt>-d<var>dependency-field</var></tt> option
8469 before those executable(s). (Each <tt>-d</tt> option
8470 takes effect until the next <tt>-d</tt>.)
8474 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
8475 output control file to be modified. Instead by default it
8476 adds to the <file>debian/substvars</file> file variable
8477 settings like <tt>shlibs:Depends</tt>. These variable
8478 settings must be referenced in dependency fields in the
8479 appropriate per-binary-package sections of the source
8484 For example, the <prgn>procps</prgn> package generates two
8485 kinds of binaries, simple C binaries like <prgn>ps</prgn>
8486 which require a predependency and full-screen ncurses
8487 binaries like <prgn>top</prgn> which require only a
8488 recommendation. It can say in its <file>debian/rules</file>:
8490 dpkg-shlibdeps -dPre-Depends ps -dRecommends top
8492 and then in its main control file <file>debian/control</file>:
8496 Pre-Depends: ${shlibs:Pre-Depends}
8497 Recommends: ${shlibs:Recommends}
8503 Sources which produce several binary packages with
8504 different shared library dependency requirements can use
8505 the <tt>-p<var>varnameprefix</var></tt> option to override
8506 the default <tt>shlibs:</tt> prefix (one invocation of
8507 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
8508 They can thus produce several sets of dependency
8509 variables, each of the form
8510 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
8511 which can be referred to in the appropriate parts of the
8512 binary package control files.
8519 <prgn>dpkg-distaddfile</prgn> - adds a file to
8520 <file>debian/files</file>
8524 Some packages' uploads need to include files other than
8525 the source and binary package files.
8529 <prgn>dpkg-distaddfile</prgn> adds a file to the
8530 <file>debian/files</file> file so that it will be included in
8531 the <file>.changes</file> file when
8532 <prgn>dpkg-genchanges</prgn> is run.
8536 It is usually invoked from the <tt>binary</tt> target of
8537 <file>debian/rules</file>:
8539 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
8541 The <var>filename</var> is relative to the directory where
8542 <prgn>dpkg-genchanges</prgn> will expect to find it - this
8543 is usually the directory above the top level of the source
8544 tree. The <file>debian/rules</file> target should put the
8545 file there just before or just after calling
8546 <prgn>dpkg-distaddfile</prgn>.
8550 The <var>section</var> and <var>priority</var> are passed
8551 unchanged into the resulting <file>.changes</file> file. See
8552 <ref id="pkg-f-classification">.
8557 <sect1><heading><prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file> upload
8562 This program is usually called by package-independent
8563 automatic building scripts such as
8564 <prgn>dpkg-buildpackage</prgn>, but it may also be called
8569 It is usually called in the top level of a built source
8570 tree, and when invoked with no arguments will print out a
8571 straightforward <file>.changes</file> file based on the
8572 information in the source package's changelog and control
8573 file and the binary and source packages which should have
8579 <sect1><heading><prgn>dpkg-parsechangelog</prgn> - produces parsed representation of
8584 This program is used internally by
8585 <prgn>dpkg-source</prgn> et al. It may also occasionally
8586 be useful in <file>debian/rules</file> and elsewhere. It
8587 parses a changelog, <file>debian/changelog</file> by default,
8588 and prints a control-file format representation of the
8589 information in it to standard output.
8593 <sect1 id="pkg-dpkgarch"><heading><prgn>dpkg-architecture</prgn> -
8594 information about the build and host system
8598 This program can be used manually, but is also invoked by
8599 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
8600 to set environment or make variables which specify the build and
8601 host architecture for the package building process.
8606 <sect id="pkg-sourcetree"><heading>The Debianised source tree
8610 The source archive scheme described later is intended to
8611 allow a Debianised source tree with some associated control
8612 information to be reproduced and transported easily. The
8613 Debianised source tree is a version of the original program
8614 with certain files added for the benefit of the
8615 Debianisation process, and with any other changes required
8616 made to the rest of the source code and installation
8621 The extra files created for Debian are in the subdirectory
8622 <file>debian</file> of the top level of the Debianised source
8623 tree. They are described below.
8626 <sect1 id="pkg-debianrules"><heading><file>debian/rules</file> - the main building
8631 This file is an executable makefile, and contains the
8632 package-specific recipies for compiling the package and
8633 building binary package(s) out of the source.
8637 It must start with the line <tt>#!/usr/bin/make -f</tt>,
8638 so that it can be invoked by saying its name rather than
8639 invoking <prgn>make</prgn> explicitly.
8643 Since an interactive <file>debian/rules</file> script makes it
8644 impossible to autocompile that package and also makes it
8645 hard for other people to reproduce the same binary
8646 package, all <strong>required targets</strong> have to be
8647 non-interactive. At a minimul, required targets are the
8648 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
8649 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>, and
8650 <em>build</em>. It also follows that any target that these
8651 targets depend on must also be non-interactive.
8655 The targets which are required to be present are:
8657 <tag><tt>build</tt></tag>
8660 This should perform all non-interactive
8661 configuration and compilation of the package. If a
8662 package has an interactive pre-build configuration
8663 routine, the Debianised source package should be
8664 built after this has taken place, so that it can be
8665 built without rerunning the configuration.
8669 A package may also provide both of the targets
8670 <tt>build-arch</tt> and <tt>build-indep</tt>. The
8671 <tt>build-arch</tt> target, if provided, should
8672 perform all non-interactive configuration and
8673 compilation required for producing all
8674 architecture-dependant binary packages (those packages
8675 for which the body of the <tt>Architecture</tt> field
8676 in <tt>debian/control</tt> is not <tt>all</tt>).
8677 Similarly, the <tt>build-indep</tt> target, if
8678 provided, should perform all non-interactive
8679 configuration and compilation required for producing
8680 all architecture-independent binary packages (those
8681 packages for which the body of the
8682 <tt>Architecture</tt> field in <tt>debian/control</tt>
8683 is <tt>all</tt>). The <tt>build</tt> target should
8684 depend on those of the targets <tt>build-arch</tt> and
8685 <tt>build-indep</tt> that are provided in the rules
8690 If one or both of the targets <tt>build-arch</tt> and
8691 <tt>build-indep</tt> are not provided, then invoking
8692 <file>debian/rules</file> with one of the not-provided
8693 targets as arguments should produce a exit status code
8694 of 2. Usually this is provided automatically by make
8695 if the target is missing.
8699 For some packages, notably ones where the same
8700 source tree is compiled in different ways to produce
8701 two binary packages, the <tt>build</tt> target does
8702 not make much sense. For these packages it is good
8703 enough to provide two (or more) targets
8704 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
8705 for each of the ways of building the package, and a
8706 <tt>build</tt> target that does nothing. The
8707 <tt>binary</tt> target will have to build the
8708 package in each of the possible ways and make the
8709 binary package out of each.
8713 The targets <tt>build</tt>, <tt>build-arch</tt>
8714 and <tt>build-indep</tt> target must not do
8715 anything that might require root privilege.
8719 The <tt>build</tt> target may need to run
8720 <tt>clean</tt> first - see below.
8724 When a package has a configuration routine that takes
8725 a long time, or when the makefiles are poorly
8726 designed, or when <tt>build</tt> needs to run
8727 <tt>clean</tt> first, it is a good idea to <tt>touch
8728 build</tt> when the build process is complete. This
8729 will ensure that if <tt>debian/rules build</tt> is run
8730 again it will not rebuild the whole program.
8734 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
8735 <tt>binary-indep</tt>
8739 The <tt>binary</tt> target should be all that is
8740 necessary for the user to build the binary
8741 package. All these targets are required to be
8742 non-interactive. It is split into two parts:
8743 <tt>binary-arch</tt> builds the packages' output
8744 files which are specific to a particular
8745 architecture, and <tt>binary-indep</tt> builds
8746 those which are not.
8750 <tt>binary</tt> should usually be a target with
8751 no commands which simply depends on
8752 <prgn>binary-arch</prgn> and
8753 <prgn>binary-indep</prgn>.
8757 Both <prgn>binary-*</prgn> targets should depend on
8758 the <tt>build</tt> target, above, so that the
8759 package is built if it has not been already. It
8760 should then create the relevant binary package(s),
8761 using <prgn>dpkg-gencontrol</prgn> to make their
8762 control files and <prgn>dpkg-deb</prgn> to build
8763 them and place them in the parent of the top level
8768 If one of the <prgn>binary-*</prgn> targets has
8769 nothing to do (this will be always be the case if
8770 the source generates only a single binary package,
8771 whether architecture-dependent or not) it
8772 <em>must</em> still exist, but should always
8777 <ref id="pkg-binarypkg"> describes how to construct
8782 The <tt>binary</tt> targets must be invoked as
8787 <tag><tt>clean</tt></tag>
8791 This should undo any effects that the
8792 <tt>build</tt> and <tt>binary</tt> targets
8793 may have had, except that it should leave alone any
8794 output files created in the parent directory by a
8795 run of <tt>binary</tt>. This target is required
8796 to be non-interactive.
8800 If a <tt>build</tt> file is touched at the end
8801 of the <tt>build</tt> target, as suggested
8802 above, it must be removed as the first thing that
8803 <tt>clean</tt> does, so that running
8804 <tt>build</tt> again after an interrupted
8805 <tt>clean</tt> doesn't think that everything is
8810 The <tt>clean</tt> target must be invoked as
8811 root if <tt>binary</tt> has been invoked since
8812 the last <tt>clean</tt>, or if
8813 <tt>build</tt> has been invoked as root (since
8814 <tt>build</tt> may create directories, for
8819 <tag><tt>get-orig-source</tt> (optional)</tag>
8823 This target fetches the most recent version of the
8824 original source package from a canonical archive
8825 site (via FTP or WWW, for example), does any
8826 necessary rearrangement to turn it into the original
8827 source tarfile format described below, and leaves it
8828 in the current directory.
8832 This target may be invoked in any directory, and
8833 should take care to clean up any temporary files it
8838 This target is optional, but providing it if
8839 possible is a good idea.
8845 The <tt>build</tt>, <tt>binary</tt> and
8846 <tt>clean</tt> targets must be invoked with a current
8847 directory of the package's top-level directory.
8852 Additional targets may exist in <file>debian/rules</file>,
8853 either as published or undocumented interfaces or for the
8854 package's internal use.
8858 The architecture we build on and build for is determined by make
8859 variables via dpkg-architecture (see <ref id="pkg-dpkgarch">). You can
8860 get the Debian architecture and the GNU style architecture
8861 specification string for the build machine as well as the host
8862 machine. Here is a list of supported make variables:
8863 <list compact="compact">
8865 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
8868 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
8869 specification string)</p>
8872 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of DEB_*_GNU_TYPE)</p>
8875 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
8881 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
8882 the build machine or <tt>HOST</tt> for specification of the machine
8887 Backward compatibility can be provided in the rules file
8888 by setting the needed variables to suitable default
8889 values, please refer to the documentation of
8890 dpkg-architecture for details.
8894 It is important to understand that the <tt>DEB_*_ARCH</tt>
8895 string does only determine which Debian architecture we
8896 build on resp. for. It should not be used to get the CPU
8897 or System information, the GNU style variables should be
8903 <sect1><heading><file>debian/control</file>
8907 This file contains version-independent details about the
8908 source package and about the binary packages it creates.
8912 It is a series of sets of control fields, each
8913 syntactically similar to a binary package control file.
8914 The sets are separated by one or more blank lines. The
8915 first set is information about the source package in
8916 general; each subsequent set describes one binary package
8917 that the source tree builds.
8921 The syntax and semantics of the fields are described below
8922 in <ref id="pkg-controlfields">.
8926 The general (binary-package-independent) fields are:
8927 <list compact="compact">
8929 <p><qref id="pkg-f-Source"><tt>Source</tt></qref> (mandatory)</p>
8932 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8936 <qref id="pkg-f-classification"><tt>Section</tt> and
8937 <tt>Priority</tt></qref>
8938 (classification, mandatory)
8943 <qref id="relationships"><tt>Build-Depends</tt> et
8944 al.</qref> (source package interrelationships)
8949 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref>
8955 The per-binary-package fields are:
8956 <list compact="compact">
8958 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8962 <qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8966 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8970 <qref id="pkg-f-classification"><tt>Section</tt> and
8971 <tt>Priority</tt></qref> (classification)</p>
8974 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8978 <qref id="relationships"><tt>Depends</tt> et
8979 al.</qref> (binary package interrelationships)
8985 These fields are used by <prgn>dpkg-gencontrol</prgn> to
8986 generate control files for binary packages (see below), by
8987 <prgn>dpkg-genchanges</prgn> to generate the
8988 <tt>.changes</tt> file to accompany the upload, and by
8989 <prgn>dpkg-source</prgn> when it creates the <file>.dsc</file>
8990 source control file as part of a source archive.
8994 The fields here may contain variable references - their
8995 values will be substituted by
8996 <prgn>dpkg-gencontrol</prgn>, <prgn>dpkg-genchanges</prgn>
8997 or <prgn>dpkg-source</prgn> when they generate output
8998 control files. See <ref id="pkg-srcsubstvars"> for details.
9001 <p> <sect2><heading>User-defined fields
9005 Additional user-defined fields may be added to the
9006 source package control file. Such fields will be
9007 ignored, and not copied to (for example) binary or
9008 source package control files or upload control files.
9012 If you wish to add additional unsupported fields to
9013 these output files you should use the mechanism
9018 Fields in the main source control information file with
9019 names starting <tt>X</tt>, followed by one or more of
9020 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
9021 be copied to the output files. Only the part of the
9022 field name after the hyphen will be used in the output
9023 file. Where the letter <tt>B</tt> is used the field
9024 will appear in binary package control files, where the
9025 letter <tt>S</tt> is used in source package control
9026 files and where <tt>C</tt> is used in upload control
9027 (<tt>.changes</tt>) files.
9031 For example, if the main source information control file
9034 XBS-Comment: I stand between the candle and the star.
9036 then the binary and source package control files will contain the
9039 Comment: I stand between the candle and the star.
9046 <sect1 id="pkg-dpkgchangelog"><heading><file>debian/changelog</file>
9050 This file records the changes to the Debian-specific parts of the
9054 Though there is nothing stopping an author who is also
9055 the Debian maintainer from using it for all their
9056 changes, it will have to be renamed if the Debian and
9057 upstream maintainers become different
9064 It has a special format which allows the package building
9065 tools to discover which version of the package is being
9066 built and find out other release-specific information.
9070 That format is a series of entries like this:
9072 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
9074 * <var>change details</var>
9075 <var>more change details</var>
9076 * <var>even more change details</var>
9078 -- <var>maintainer name and email address</var> <var>date</var>
9083 <var>package</var> and <var>version</var> are the source
9084 package name and version number.
9088 <var>distribution(s)</var> lists the distributions where
9089 this version should be installed when it is uploaded - it
9090 is copied to the <tt>Distribution</tt> field in the
9091 <tt>.changes</tt> file. See <ref id="pkg-f-Distribution">.
9095 <var>urgency</var> is the value for the <tt>Urgency</tt>
9096 field in the <file>.changes</file> file for the upload. See
9097 <ref id="pkg-f-Urgency">. It is not possible to specify an
9098 urgency containing commas; commas are used to separate
9099 <tt><var>keyword</var>=<var>value</var></tt> settings in
9100 the <prgn>dpkg</prgn> changelog format (though there is
9101 currently only one useful <var>keyword</var>,
9106 The change details may in fact be any series of lines
9107 starting with at least two spaces, but conventionally each
9108 change starts with an asterisk and a separating space and
9109 continuation lines are indented so as to bring them in
9110 line with the start of the text above. Blank lines may be
9111 used here to separate groups of changes, if desired.
9115 The maintainer name and email address should <em>not</em>
9116 necessarily be those of the usual package maintainer.
9117 They should be the details of the person doing
9118 <em>this</em> version. The information here will be
9119 copied to the <file>.changes</file> file, and then later used
9120 to send an acknowledgement when the upload has been
9125 The <var>date</var> should be in RFC822 format
9128 This is generated by the <prgn>822-date</prgn>
9131 </footnote>; it should include the timezone specified
9132 numerically, with the timezone name or abbreviation
9133 optionally present as a comment.
9137 The first `title' line with the package name should start
9138 at the left hand margin; the `trailer' line with the
9139 maintainer and date details should be preceded by exactly
9140 one space. The maintainer details and the date must be
9141 separated by exactly two spaces.
9145 An Emacs mode for editing this format is available: it is
9146 called <tt>debian-changelog-mode</tt>. You can have this
9147 mode selected automatically when you edit a Debian
9148 changelog by adding a local variables clause to the end of
9152 <sect2><heading>Defining alternative changelog formats
9156 It is possible to use a different format to the standard
9157 one, by providing a parser for the format you wish to
9162 In order to have <tt>dpkg-parsechangelog</tt> run your
9163 parser, you must include a line within the last 40 lines
9164 of your file matching the Perl regular expression:
9165 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9166 parentheses should be the name of the format. For
9167 example, you might say:
9169 @@@ changelog-format: joebloggs @@@
9171 Changelog format names are non-empty strings of alphanumerics.
9175 If such a line exists then <tt>dpkg-parsechangelog</tt>
9176 will look for the parser as
9177 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9179 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9180 it is an error for it not to find it, or for it not to
9181 be an executable program. The default changelog format
9182 is <tt>dpkg</tt>, and a parser for it is provided with
9183 the <tt>dpkg</tt> package.
9187 The parser will be invoked with the changelog open on
9188 standard input at the start of the file. It should read
9189 the file (it may seek if it wishes) to determine the
9190 information required and return the parsed information
9191 to standard output in the form of a series of control
9192 fields in the standard format. By default it should
9193 return information about only the most recent version in
9194 the changelog; it should accept a
9195 <tt>-v<var>version</var></tt> option to return changes
9196 information from all versions present <em>strictly
9197 after</em> <var>version</var>, and it should then be an
9198 error for <var>version</var> not to be present in the
9204 <list compact="compact">
9206 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9209 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
9213 <qref id="pkg-f-Distribution"><tt>Distribution</tt></qref>
9218 <p><qref id="pkg-f-Urgency"><tt>Urgency</tt></qref> (mandatory)</p>
9222 <qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref>
9227 <p><qref id="pkg-f-Date"><tt>Date</tt></qref></p>
9231 <qref id="pkg-f-Changes"><tt>Changes</tt></qref>
9238 If several versions are being returned (due to the use
9239 of <tt>-v</tt>), the urgency value should be of the
9240 highest urgency code listed at the start of any of the
9241 versions requested followed by the concatenated
9242 (space-separated) comments from all the versions
9243 requested; the maintainer, version, distribution and
9244 date should always be from the most recent version.
9248 For the format of the <tt>Changes</tt> field see <ref
9249 id="pkg-f-Changes">.
9253 If the changelog format which is being parsed always or
9254 almost always leaves a blank line between individual
9255 change notes these blank lines should be stripped out,
9256 so as to make the resulting output compact.
9260 If the changelog format does not contain date or package
9261 name information this information should be omitted from
9262 the output. The parser should not attempt to synthesise
9263 it or find it from other sources.
9267 If the changelog does not have the expected format the
9268 parser should exit with a nonzero exit status, rather
9269 than trying to muddle through and possibly generating
9274 A changelog parser may not interact with the user at
9278 <sect1 id="pkg-srcsubstvars"><heading><file>debian/substvars</file>
9279 and variable substitutions
9283 When <prgn>dpkg-gencontrol</prgn>,
9284 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
9285 generate control files they do variable substitutions on
9286 their output just before writing it. Variable
9287 substitutions have the form
9288 <tt>${<var>variable-name</var>}</tt>. The optional file
9289 <file>debian/substvars</file> contains variable substitutions
9290 to be used; variables can also be set directly from
9291 <file>debian/rules</file> using the <tt>-V</tt> option to the
9292 source packaging commands, and certain predefined
9293 variables are available.
9297 The is usually generated and modified dynamically by
9298 <file>debian/rules</file> targets; in this case it must be
9299 removed by the <tt>clean</tt> target.
9303 See <manref name="dpkg-source" section="1"> for full
9304 details about source variable substitutions, including the
9305 format of <file>debian/substvars</file>.</p>
9308 <sect1><heading><file>debian/files</file>
9312 This file is not a permanent part of the source tree; it
9313 is used while building packages to record which files are
9314 being generated. <prgn>dpkg-genchanges</prgn> uses it
9315 when it generates a <file>.changes</file> file.
9319 It should not exist in a shipped source package, and so it
9320 (and any backup files or temporary files such as
9321 <file>files.new</file>
9324 <file>files.new</file> is used as a temporary file by
9325 <prgn>dpkg-gencontrol</prgn> and
9326 <prgn>dpkg-distaddfile</prgn> - they write a new
9327 version of <file>files</file> here before renaming it,
9328 to avoid leaving a corrupted copy if an error
9331 </footnote>) should be removed by the
9332 <tt>clean</tt> target. It may also be wise to
9333 ensure a fresh start by emptying or removing it at the
9334 start of the <tt>binary</tt> target.
9338 <prgn>dpkg-gencontrol</prgn> adds an entry to this file
9339 for the <file>.deb</file> file that will be created by
9340 <prgn>dpkg-deb</prgn> from the control file that it
9341 generates, so for most packages all that needs to be done
9342 with this file is to delete it in <tt>clean</tt>.
9346 If a package upload includes files besides the source
9347 package and any binary packages whose control files were
9348 made with <prgn>dpkg-gencontrol</prgn> then they should be
9349 placed in the parent of the package's top-level directory
9350 and <prgn>dpkg-distaddfile</prgn> should be called to add
9351 the file to the list in <file>debian/files</file>.</p>
9354 <sect1><heading><file>debian/tmp</file>
9358 This is the canonical temporary location for the
9359 construction of binary packages by the <tt>binary</tt>
9360 target. The directory <file>tmp</file> serves as the root of
9361 the filesystem tree as it is being constructed (for
9362 example, by using the package's upstream makefiles install
9363 targets and redirecting the output there), and it also
9364 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9365 id="pkg-bincreating">.
9369 If several binary packages are generated from the same
9370 source tree it is usual to use several
9371 <file>debian/tmp<var>something</var></file> directories, for
9372 example <file>tmp-a</file> or <file>tmp-doc</file>.
9376 Whatever <file>tmp</file> directories are created and used by
9377 <tt>binary</tt> must of course be removed by the
9378 <tt>clean</tt> target.</p></sect1>
9382 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9386 As it exists on the FTP site, a Debian source package
9387 consists of three related files. You must have the right
9388 versions of all three to be able to use them.
9393 <tag>Debian source control file - <tt>.dsc</tt></tag>
9397 This file contains a series of fields, identified and
9398 separated just like the fields in the control file of
9399 a binary package. The fields are listed below; their
9400 syntax is described above, in <ref id="pkg-controlfields">.
9401 <list compact="compact">
9403 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9406 <p><qref id="versions"><tt>Version</tt></qref></p>
9409 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
9412 <p><qref id="pkg-f-Binary"><tt>Binary</tt></qref></p>
9415 <p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref></p>
9419 <qref id="relationships"><tt>Build-Depends</tt> et
9420 al.</qref> (source package interrelationships)
9425 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref></p>
9428 <p><qref id="pkg-f-Files"><tt>Files</tt></qref></p>
9433 The source package control file is generated by
9434 <prgn>dpkg-source</prgn> when it builds the source
9435 archive, from other files in the source package,
9436 described above. When unpacking it is checked against
9437 the files and directories in the other parts of the
9438 source package, as described below.</p>
9442 Original source archive -
9444 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9451 This is a compressed (with <tt>gzip -9</tt>)
9452 <prgn>tar</prgn> file containing the source code from
9453 the upstream authors of the program. The tarfile
9454 unpacks into a directory
9455 <file><var>package</var>-<var>upstream-version</var>.orig</file>,
9456 and does not contain files anywhere other than in
9457 there or in its subdirectories.</p>
9461 Debianisation diff -
9463 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9469 This is a unified context diff (<tt>diff -u</tt>)
9470 giving the changes which are required to turn the
9471 original source into the Debian source. These changes
9472 may only include editing and creating plain files.
9473 The permissions of files, the targets of symbolic
9474 links and the characteristics of special files or
9475 pipes may not be changed and no files may be removed
9480 All the directories in the diff must exist, except the
9481 <file>debian</file> subdirectory of the top of the source
9482 tree, which will be created by
9483 <prgn>dpkg-source</prgn> if necessary when unpacking.
9487 The <prgn>dpkg-source</prgn> program will
9488 automatically make the <file>debian/rules</file> file
9489 executable (see below).</p></item>
9494 If there is no original source code - for example, if the
9495 package is specially prepared for Debian or the Debian
9496 maintainer is the same as the upstream maintainer - the
9497 format is slightly different: then there is no diff, and the
9499 <file><var>package</var>_<var>version</var>.tar.gz</file> and
9500 contains a directory
9501 <file><var>package</var>-<var>version</var></file>.
9505 <sect><heading>Unpacking a Debian source package without
9506 <prgn>dpkg-source</prgn>
9510 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9511 Debian source package. However, if it is not available it
9512 is possible to unpack a Debian source archive as follows:
9513 <enumlist compact="compact">
9516 Untar the tarfile, which will create a <file>.orig</file>
9520 <p>Rename the <file>.orig</file> directory to
9521 <file><var>package</var>-<var>version</var></file>.</p>
9525 Create the subdirectory <file>debian</file> at the top of
9526 the source tree.</p>
9528 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9530 <item><p>Untar the tarfile again if you want a copy of the original
9531 source code alongside the Debianised version.</p>
9536 It is not possible to generate a valid Debian source archive
9537 without using <prgn>dpkg-source</prgn>. In particular,
9538 attempting to use <prgn>diff</prgn> directly to generate the
9539 <file>.diff.gz</file> file will not work.
9542 <sect1><heading>Restrictions on objects in source packages
9546 The source package may not contain any hard links
9549 This is not currently detected when building source
9550 packages, but only when extracting
9556 Hard links may be permitted at some point in the
9557 future, but would require a fair amount of
9560 </footnote>, device special files, sockets or setuid or
9564 Setgid directories are allowed.
9570 The source packaging tools manage the changes between the
9571 original and Debianised source using <prgn>diff</prgn> and
9572 <prgn>patch</prgn>. Turning the original source tree as
9573 included in the <file>.orig.tar.gz</file> into the debianised
9574 source must not involve any changes which cannot be
9575 handled by these tools. Problematic changes which cause
9576 <prgn>dpkg-source</prgn> to halt with an error when
9577 building the source package are:
9578 <list compact="compact">
9579 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9581 <item><p>Changing the targets of symbolic links.</p>
9583 <item><p>Creating directories, other than <file>debian</file>.</p>
9585 <item><p>Changes to the contents of binary files.</p></item>
9586 </list> Changes which cause <prgn>dpkg-source</prgn> to
9587 print a warning but continue anyway are:
9588 <list compact="compact">
9591 Removing files, directories or symlinks.
9594 Renaming a file is not treated specially - it is
9595 seen as the removal of the old file (which
9596 generates a warning, but is otherwise ignored),
9597 and the creation of the new
9604 Changed text files which are missing the usual final
9605 newline (either in the original or the modified
9610 Changes which are not represented, but which are not detected by
9611 <prgn>dpkg-source</prgn>, are:
9612 <list compact="compact">
9613 <item><p>Changing the permissions of files (other than
9614 <file>debian/rules</file>) and directories.</p></item>
9619 The <file>debian</file> directory and <file>debian/rules</file>
9620 are handled specially by <prgn>dpkg-source</prgn> - before
9621 applying the changes it will create the <file>debian</file>
9622 directory, and afterwards it will make
9623 <file>debian/rules</file> world-exectuable.
9629 <appendix id="pkg-controlfields"><heading>Control files and their
9630 fields (from old Packaging Manual)
9634 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9635 data in a common format, known as control files. Binary and
9636 source packages have control data as do the <file>.changes</file>
9637 files which control the installation of uploaded files, and
9638 <prgn>dpkg</prgn>'s internal databases are in a similar
9642 <sect><heading>Syntax of control files
9646 A file consists of one or more paragraphs of fields. The
9647 paragraphs are separated by blank lines. Some control files
9648 only allow one paragraph; others allow several, in which
9649 case each paragraph often refers to a different package.
9653 Each paragraph is a series of fields and values; each field
9654 consists of a name, followed by a colon and the value. It
9655 ends at the end of the line. Horizontal whitespace (spaces
9656 and tabs) may occur before or after the value and is ignored
9657 there; it is conventional to put a single space after the
9662 Some fields' values may span several lines; in this case
9663 each continuation line <em>must</em> start with a space or
9664 tab. Any trailing spaces or tabs at the end of individual
9665 lines of a field value are ignored.
9669 Except where otherwise stated only a single line of data is
9670 allowed and whitespace is not significant in a field body.
9671 Whitespace may never appear inside names (of packages,
9672 architectures, files or anything else), version numbers or
9673 in between the characters of multi-character version
9678 Field names are not case-sensitive, but it is usual to
9679 capitalise the field names using mixed case as shown below.
9683 Blank lines, or lines consisting only of spaces and tabs,
9684 are not allowed within field values or between fields - that
9685 would mean a new paragraph.
9689 It is important to note that there are several fields which
9690 are optional as far as <prgn>dpkg</prgn> and the related
9691 tools are concerned, but which must appear in every Debian
9692 package, or whose omission may cause problems. When writing
9693 the control files for Debian packages you <em>must</em> read
9694 the Debian policy manual in conjuction with the details
9695 below and the list of fields for the particular file.</p>
9698 <sect><heading>List of fields
9701 <sect1 id="pkg-f-Package"><heading><tt>Package</tt>
9705 The name of the binary package. Package names consist of
9706 the alphanumerics and <tt>+</tt> <tt>-</tt> <tt>.</tt>
9707 (plus, minus and full stop).
9710 The characters <tt>@</tt> <tt>:</tt> <tt>=</tt>
9711 <tt>%</tt> <tt>_</tt> (at, colon, equals, percent
9712 and underscore) used to be legal and are still
9713 accepted when found in a package file, but may not be
9714 used in new packages
9720 They must be at least two characters and must start with
9721 an alphanumeric. In current versions of dpkg they are
9722 sort of case-sensitive<footnote><p>This is a
9723 bug.</p></footnote>; use lowercase package names unless
9724 the package you're building (or referring to, in other
9725 fields) is already using uppercase.</p>
9728 <sect1 id="pkg-f-Version"><heading><tt>Version</tt>
9732 This lists the source or binary package's version number -
9733 see <ref id="versions">.
9738 <sect1 id="pkg-f-Architecture"><heading><tt>Architecture</tt>
9742 This is the architecture string; it is a single word for
9743 the Debian architecture.
9747 <prgn>dpkg</prgn> will check the declared architecture of
9748 a binary package against its own compiled-in value before
9753 The special value <tt>all</tt> indicates that the package
9754 is architecture-independent.
9758 In the main <file>debian/control</file> file in the source
9759 package, or in the source package control file
9760 <file>.dsc</file>, a list of architectures (separated by
9761 spaces) is also allowed, as is the special value
9762 <tt>any</tt>. A list indicates that the source will build
9763 an architecture-dependent package, and will only work
9764 correctly on the listed architectures. <tt>any</tt>
9765 indicates that though the source package isn't dependent
9766 on any particular architecture and should compile fine on
9767 any one, the binary package(s) produced are not
9768 architecture-independent but will instead be specific to
9769 whatever the current build architecture is.
9773 In a <file>.changes</file> file the <tt>Architecture</tt>
9774 field lists the architecture(s) of the package(s)
9775 currently being uploaded. This will be a list; if the
9776 source for the package is being uploaded too the special
9777 entry <tt>source</tt> is also present.
9781 See <ref id="pkg-debianrules"> for information how to get the
9782 architecture for the build process.
9786 <sect1 id="pkg-f-Maintainer"><heading><tt>Maintainer</tt>
9790 The package maintainer's name and email address. The name
9791 should come first, then the email address inside angle
9792 brackets <tt><></tt> (in RFC822 format).
9796 If the maintainer's name contains a full stop then the
9797 whole field will not work directly as an email address due
9798 to a misfeature in the syntax specified in RFC822; a
9799 program using this field as an address must check for this
9800 and correct the problem if necessary (for example by
9801 putting the name in round brackets and moving it to the
9802 end, and bringing the email address forward).
9806 In a <file>.changes</file> file or parsed changelog data this
9807 contains the name and email address of the person
9808 responsible for the particular version in question - this
9809 may not be the package's usual maintainer.
9813 This field is usually optional in as far as the
9814 <prgn>dpkg</prgn> are concerned, but its absence when
9815 building packages usually generates a warning.</p>
9818 <sect1 id="pkg-f-Source"><heading><tt>Source</tt>
9822 This field identifies the source package name.
9826 In a main source control information or a
9827 <file>.changes</file> or <file>.dsc</file> file or parsed
9828 changelog data this may contain only the name of the
9833 In the control file of a binary package (or in a
9834 <file>Packages</file> file) it may be followed by a version
9835 number in parentheses.
9838 It is usual to leave a space after the package name if
9839 a version number is specified.
9841 </footnote> This version number may be omitted (and is, by
9842 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
9843 the <tt>Version</tt> field of the binary package in
9844 question. The field itself may be omitted from a binary
9845 package control file when the source package has the same
9846 name and version as the binary package.
9850 <sect1><heading>Package interrelationship fields:
9851 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
9852 <tt>Recommends</tt> <tt>Suggests</tt>, <tt>Conflicts</tt>,
9853 <tt>Provides</tt>, <tt>Replaces</tt>
9857 These fields describe the package's relationships with
9858 other packages. Their syntax and semantics are described
9859 in <ref id="relationships">.</p>
9862 <sect1 id="pkg-f-Description"><heading><tt>Description</tt>
9866 In a binary package <tt>Packages</tt> file or main source
9867 control file this field contains a description of the
9868 binary package, in a special format. See <ref
9869 id="descriptions"> for details.
9873 In a <file>.changes</file> file it contains a summary of the
9874 descriptions for the packages being uploaded. The part of
9875 the field before the first newline is empty; thereafter
9876 each line has the name of a binary package and the summary
9877 description line from that binary package. Each line is
9878 indented by one space.</p>
9881 <sect1 id="pkg-f-Essential"><heading><tt>Essential</tt>
9885 This is a boolean field which may occur only in the
9886 control file of a binary package (or in the
9887 <file>Packages</file> file) or in a per-package fields
9888 paragraph of a main source control data file.
9892 If set to <tt>yes</tt> then <prgn>dpkg</prgn> and
9893 <prgn>dselect</prgn> will refuse to remove the package
9894 (though it can be upgraded and/or replaced). The other
9895 possible value is <tt>no</tt>, which is the same as not
9896 having the field at all.</p>
9899 <sect1 id="pkg-f-classification"><heading><tt>Section</tt> and
9904 These two fields classify the package. The
9905 <tt>Priority</tt> represents how important that it is that
9906 the user have it installed; the <tt>Section</tt>
9907 represents an application area into which the package has
9912 When they appear in the <file>debian/control</file> file these
9913 fields give values for the section and priority subfields
9914 of the <tt>Files</tt> field of the <file>.changes</file> file,
9915 and give defaults for the section and priority of the
9920 The section and priority are represented, though not as
9921 separate fields, in the information for each file in the
9922 <qref id="pkg-f-Files"><tt>-File</tt></qref>field of a
9923 <file>.changes</file> file. The section value in a
9924 <file>.changes</file> file is used to decide where to install
9925 a package in the FTP archive.
9929 These fields are not used by by <prgn>dpkg</prgn> proper,
9930 but by <prgn>dselect</prgn> when it sorts packages and
9931 selects defaults. See the Debian policy manual for the
9932 priorities in use and the criteria for selecting the
9933 priority for a Debian package, and look at the Debian FTP
9934 archive for a list of currently in-use priorities.
9938 These fields may appear in binary package control files,
9939 in which case they provide a default value in case the
9940 <file>Packages</file> files are missing the information.
9941 <prgn>dpkg</prgn> and <prgn>dselect</prgn> will only use
9942 the value from a <file>.deb</file> file if they have no other
9943 information; a value listed in a <file>Packages</file> file
9944 will always take precedence. By default
9945 <prgn>dpkg-gencontrol</prgn> does not include the section
9946 and priority in the control file of a binary package - use
9947 the <tt>-isp</tt>, <tt>-is</tt> or <tt>-ip</tt> options to
9948 achieve this effect.</p>
9951 <sect1 id="pkg-f-Binary"><heading><tt>Binary</tt>
9955 This field is a list of binary packages.
9959 When it appears in the <file>.dsc</file> file it is the list
9960 of binary packages which a source package can produce. It
9961 does not necessarily produce all of these binary packages
9962 for every architecture. The source control file doesn't
9963 contain details of which architectures are appropriate for
9964 which of the binary packages.
9968 When it appears in a <file>.changes</file> file it lists the
9969 names of the binary packages actually being uploaded.
9973 The syntax is a list of binary packages separated by
9977 A space after each comma is conventional.
9979 </footnote> Currently the packages must be separated using
9980 only spaces in the <file>.changes</file> file.</p>
9983 <sect1 id="pkg-f-Installed-Size"><heading><tt>Installed-Size</tt>
9987 This field appears in the control files of binary
9988 packages, and in the <file>Packages</file> files. It gives
9989 the total amount of disk space required to install the
9994 The disk space is represented in kilobytes as a simple
9998 <sect1 id="pkg-f-Files"><heading><tt>Files</tt>
10002 This field contains a list of files with information about
10003 each one. The exact information and syntax varies with
10004 the context. In all cases the the part of the field
10005 contents on the same line as the field name is empty. The
10006 remainder of the field is one line per file, each line
10007 being indented by one space and containing a number of
10008 sub-fields separated by spaces.
10012 In the <file>.dsc</file> (Debian source control) file each
10013 line contains the MD5 checksum, size and filename of the
10014 tarfile and (if applicable) diff file which make up the
10015 remainder of the source package.
10018 That is, the parts which are not the
10021 </footnote> The exact forms of the filenames are described
10022 in <ref id="pkg-sourcearchives">.
10026 In the <file>.changes</file> file this contains one line per
10027 file being uploaded. Each line contains the MD5 checksum,
10028 size, section and priority and the filename. The section
10029 and priority are the values of the corresponding fields in
10030 the main source control file - see <ref
10031 id="pkg-f-classification">. If no section or priority is
10032 specified then <tt>-</tt> should be used, though section
10033 and priority values must be specified for new packages to
10034 be installed properly.
10038 The special value <tt>byhand</tt> for the section in a
10039 <tt>.changes</tt> file indicates that the file in question
10040 is not an ordinary package file and must by installed by
10041 hand by the distribution maintainers. If the section is
10042 <tt>byhand</tt> the priority should be <tt>-</tt>.
10046 If a new Debian revision of a package is being shipped and
10047 no new original source archive is being distributed the
10048 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
10049 entry for the original source archive
10050 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
10051 but the <file>.changes</file> file should leave it out. In
10052 this case the original source archive on the distribution
10053 site must match exactly, byte-for-byte, the original
10054 source archive which was used to generate the
10055 <file>.dsc</file> file and diff which are being uploaded.</p>
10060 id="pkg-f-Standards-Version"><heading><tt>Standards-Version</tt>
10064 The most recent version of the standards (the
10065 <prgn>dpkg</prgn> programmers' and policy manuals and
10066 associated texts) with which the package complies. This
10067 is updated manually when editing the source package to
10068 conform to newer standards; it can sometimes be used to
10069 tell when a package needs attention.
10073 Its format is the same as that of a version number except
10074 that no epoch or Debian revision is allowed - see <ref
10075 id="versions">.</p>
10079 <sect1 id="pkg-f-Distribution"><heading><tt>Distribution</tt>
10083 In a <file>.changes</file> file or parsed changelog output
10084 this contains the (space-separated) name(s) of the
10085 distribution(s) where this version of the package should
10086 be or was installed. Distribution names follow the rules
10087 for package names. (See <ref id="pkg-f-Package">).
10091 Current distribution values are:
10093 <tag><em>stable</em></tag>
10096 This is the current `released' version of Debian
10097 GNU/Linux. A new version is released approximately
10098 every 3 months after the <em>development</em> code has
10099 been <em>frozen</em> for a month of testing. Once the
10100 distribution is <em>stable</em> only major bug fixes
10101 are allowed. When changes are made to this
10102 distribution, the release number is increased
10103 (for example: 1.2r1 becomes 1.2r2 then 1.2r3, etc).
10107 <tag><em>unstable</em></tag>
10110 This distribution value refers to the
10111 <em>developmental</em> part of the Debian distribution
10112 tree. New packages, new upstream versions of packages
10113 and bug fixes go into the <em>unstable</em> directory
10114 tree. Download from this distribution at your own
10118 <tag><em>contrib</em></tag>
10121 The packages with this distribution value do not meet
10122 the criteria for inclusion in the main Debian
10123 distribution as defined by the Policy Manual, but meet
10124 the criteria for the <em>contrib</em>
10125 Distribution. There is currently no distinction
10126 between stable and unstable packages in the
10127 <em>contrib</em> or <em>non-free</em>
10128 distributions. Use your best judgement in downloading
10129 from this Distribution.</p>
10132 <tag><em>non-free</em></tag>
10135 Like the packages in the <em>contrib</em> seciton,
10136 the packages in <em>non-free</em> do not meet the
10137 criteria for inclusion in the main Debian distribution
10138 as defined by the Policy Manual. Again, use your best
10139 judgement in downloading from this Distribution.</p>
10141 <tag><em>experimental</em></tag>
10144 The packages with this distribution value are deemed
10145 by their maintainers to be high risk. Oftentimes they
10146 represent early beta or developmental packages from
10147 various sources that the maintainers want people to
10148 try, but are not ready to be a part of the other parts
10149 of the Debian distribution tree. Download at your own
10153 <tag><em>frozen</em></tag>
10156 From time to time, (currently, every 3 months) the
10157 <em>unstable</em> distribution enters a state of
10158 `code-freeze' in anticipation of release as a
10159 <em>stable</em> version. During this period of testing
10160 (usually 4 weeks) only fixes for existing or
10161 newly-discovered bugs will be allowed.
10164 </taglist> You should list <em>all</em> distributions that
10165 the package should be installed into. Except in unusual
10166 circumstances, installations to <em>stable</em> should also
10167 go into <em>frozen</em> (if it exists) and
10168 <em>unstable</em>. Likewise, installations into
10169 <em>frozen</em> should also go into <em>unstable</em>.</p>
10172 <sect1 id="pkg-f-Urgency"><heading><tt>Urgency</tt>
10176 This is a description of how important it is to upgrade to
10177 this version from previous ones. It consists of a single
10178 keyword usually taking one of the values <tt>LOW</tt>,
10179 <tt>MEDIUM</tt> or <tt>HIGH</tt>) followed by an optional
10180 commentary (separated by a space) which is usually in
10181 parentheses. For example:
10183 Urgency: LOW (HIGH for diversions users)
10188 This field appears in the <file>.changes</file> file and in
10189 parsed changelogs; its value appears as the value of the
10190 <tt>urgency</tt> attribute in a <prgn>dpkg</prgn>-style
10191 changelog (see <ref id="pkg-dpkgchangelog">).
10195 Urgency keywords are not case-sensitive.</p>
10198 <sect1 id="pkg-f-Date"><heading><tt>Date</tt>
10202 In <tt>.changes</tt> files and parsed changelogs, this
10203 gives the date the package was built or last edited.</p>
10206 <sect1 id="pkg-f-Format"><heading><tt>Format</tt>
10210 This field occurs in <file>.changes</file> files, and
10211 specifies a format revision for the file. The format
10212 described here is version <tt>1.5</tt>. The syntax of the
10213 format value is the same as that of a package version
10214 number except that no epoch or Debian revision is allowed
10215 - see <ref id="versions">.</p>
10218 <sect1 id="pkg-f-Changes"><heading><tt>Changes</tt>
10222 In a <file>.changes</file> file or parsed changelog this field
10223 contains the human-readable changes data, describing the
10224 differences between the last version and the current one.
10228 There should be nothing in this field before the first
10229 newline; all the subsequent lines must be indented by at
10230 least one space; blank lines must be represented by a line
10231 consiting only of a space and a full stop.
10235 Each version's change information should be preceded by a
10236 `title' line giving at least the version, distribution(s)
10237 and urgency, in a human-readable way.
10241 If data from several versions is being returned the entry
10242 for the most recent version should be returned first, and
10243 entries should be separated by the representation of a
10244 blank line (the `title' line may also be followed by the
10245 representation of blank line).</p>
10248 <sect1 id="pkg-f-Filename"><heading><tt>Filename</tt> and
10249 <tt>MSDOS-Filename</tt>
10253 These fields in <tt>Packages</tt> files give the
10254 filename(s) of (the parts of) a package in the
10255 distribution directories, relative to the root of the
10256 Debian hierarchy. If the package has been split into
10257 several parts the parts are all listed in order, separated
10261 <sect1 id="pkg-f-Size"><heading><tt>Size</tt> and <tt>MD5sum</tt>
10265 These fields in <file>Packages</file> files give the size (in
10266 bytes, expressed in decimal) and MD5 checksum of the
10267 file(s) which make(s) up a binary package in the
10268 distribution. If the package is split into several parts
10269 the values for the parts are listed in order, separated by
10273 <sect1 id="pkg-f-Status"><heading><tt>Status</tt>
10277 This field in <prgn>dpkg</prgn>'s status file records
10278 whether the user wants a package installed, removed or
10279 left alone, whether it is broken (requiring
10280 reinstallation) or not and what its current state on the
10281 system is. Each of these pieces of information is a
10285 <sect1 id="pkg-f-Config-Version"><heading><tt>Config-Version</tt>
10289 If a package is not installed or not configured, this
10290 field in <prgn>dpkg</prgn>'s status file records the last
10291 version of the package which was successfully
10295 <sect1 id="pkg-f-Conffiles"><heading><tt>Conffiles</tt>
10299 This field in <prgn>dpkg</prgn>'s status file contains
10300 information about the automatically-managed configuration
10301 files held by a package. This field should <em>not</em>
10302 appear anywhere in a package!</p>
10305 <sect1><heading>Obsolete fields
10309 These are still recognised by <prgn>dpkg</prgn> but should
10310 not appear anywhere any more.
10311 <taglist compact="compact">
10313 <tag><tt>Revision</tt></tag>
10314 <tag><tt>Package-Revision</tt></tag>
10315 <tag><tt>Package_Revision</tt></tag>
10318 The Debian revision part of the package version was
10319 at one point in a separate control file field. This
10320 field went through several names.</p>
10323 <tag><tt>Recommended</tt></tag>
10324 <item><p>Old name for <tt>Recommends</tt></p>
10327 <tag><tt>Optional</tt></tag>
10328 <item><p>Old name for <tt>Suggests</tt>.</p>
10330 <tag><tt>Class</tt></tag>
10331 <item><p>Old name for <tt>Priority</tt>.</p>
10339 <appendix id="pkg-conffiles"><heading>Configuration file handling
10340 (from old Packaging Manual)
10344 <prgn>dpkg</prgn> can do a certain amount of automatic
10345 handling of package configuration files.
10349 Whether this mechanism is appropriate depends on a number of
10350 factors, but basically there are two approaches to any
10351 particular configuration file.
10355 The easy method is to ship a best-effort configuration in the
10356 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10357 handle updates. If the user is unlikely to want to edit the
10358 file, but you need them to be able to without losing their
10359 changes, and a new package with a changed version of the file
10360 is only released infrequently, this is a good approach.
10364 The hard method is to build the configuration file from
10365 scratch in the <prgn>postinst</prgn> script, and to take the
10366 responsibility for fixing any mistakes made in earlier
10367 versions of the package automatically. This will be
10368 appropriate if the file is likely to need to be different on
10372 <sect><heading>Automatic handling of configuration files by
10377 A package may contain a control area file called
10378 <tt>conffiles</tt>. This file should be a list of filenames
10379 of configuration files needing automatic handling, separated
10380 by newlines. The filenames should be absolute pathnames,
10381 and the files referred to should actually exist in the
10386 When a package is upgraded <prgn>dpkg</prgn> will process
10387 the configuration files during the configuration stage,
10388 shortly before it runs the package's <prgn>postinst</prgn>
10393 For each file it checks to see whether the version of the
10394 file included in the package is the same as the one that was
10395 included in the last version of the package (the one that is
10396 being upgraded from); it also compares the version currently
10397 installed on the system with the one shipped with the last
10402 If neither the user nor the package maintainer has changed
10403 the file, it is left alone. If one or the other has changed
10404 their version, then the changed version is preferred - i.e.,
10405 if the user edits their file, but the package maintainer
10406 doesn't ship a different version, the user's changes will
10407 stay, silently, but if the maintainer ships a new version
10408 and the user hasn't edited it the new version will be
10409 installed (with an informative message). If both have
10410 changed their version the user is prompted about the problem
10411 and must resolve the differences themselves.
10415 The comparisons are done by calculating the MD5 message
10416 digests of the files, and storing the MD5 of the file as it
10417 was included in the most recent version of the package.
10421 When a package is installed for the first time
10422 <prgn>dpkg</prgn> will install the file that comes with it,
10423 unless that would mean overwriting a file already on the
10428 However, note that <prgn>dpkg</prgn> will <em>not</em>
10429 replace a conffile that was removed by the user (or by a
10430 script). This is necessary because with some programs a
10431 missing file produces an effect hard or impossible to
10432 achieve in another way, so that a missing file needs to be
10433 kept that way if the user did it.
10437 Note that a package should <em>not</em> modify a
10438 <prgn>dpkg</prgn>-handled conffile in its maintainer
10439 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10440 the user confusing and possibly dangerous options for
10441 conffile update when the package is upgraded.</p>
10444 <sect><heading>Fully-featured maintainer script configuration
10449 For files which contain site-specific information such as
10450 the hostname and networking details and so forth, it is
10451 better to create the file in the package's
10452 <prgn>postinst</prgn> script.
10456 This will typically involve examining the state of the rest
10457 of the system to determine values and other information, and
10458 may involve prompting the user for some information which
10459 can't be obtained some other way.
10463 When using this method there are a couple of important
10464 issues which should be considered:
10468 If you discover a bug in the program which generates the
10469 configuration file, or if the format of the file changes
10470 from one version to the next, you will have to arrange for
10471 the postinst script to do something sensible - usually this
10472 will mean editing the installed configuration file to remove
10473 the problem or change the syntax. You will have to do this
10474 very carefully, since the user may have changed the file,
10475 perhaps to fix the very problem that your script is trying
10476 to deal with - you will have to detect these situations and
10477 deal with them correctly.
10481 If you do go down this route it's probably a good idea to
10482 make the program that generates the configuration file(s) a
10483 separate program in <file>/usr/sbin</file>, by convention called
10484 <file><var>package</var>config</file> and then run that if
10485 appropriate from the post-installation script. The
10486 <tt><var>package</var>config</tt> program should not
10487 unquestioningly overwrite an existing configuration - if its
10488 mode of operation is geared towards setting up a package for
10489 the first time (rather than any arbitrary reconfiguration
10490 later) you should have it check whether the configuration
10491 already exists, and require a <tt>--force</tt> flag to
10492 overwrite it.</p></sect>
10495 <appendix id="pkg-alternatives"><heading>Alternative versions of
10496 an interface - <prgn>update-alternatives</prgn> (from old
10501 When several packages all provide different versions of the
10502 same program or file it is useful to have the system select a
10503 default, but to allow the system administrator to change it
10504 and have their decisions respected.
10508 For example, there are several versions of the <prgn>vi</prgn>
10509 editor, and there is no reason to prevent all of them from
10510 being installed at once, each under their own name
10511 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10512 Nevertheless it is desirable to have the name <tt>vi</tt>
10513 refer to something, at least by default.
10517 If all the packages involved cooperate, this can be done with
10518 <prgn>update-alternatives</prgn>.
10522 Each package provides its own version under its own name, and
10523 calls <prgn>update-alternatives</prgn> in its postinst to
10524 register its version (and again in its prerm to deregister
10529 See the manpage <manref name="update-alternatives"
10530 section="8"> for details.
10534 If <prgn>update-alternatives</prgn> does not seem appropriate
10535 you may wish to consider using diversions instead.</p>
10538 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10539 package's version of a file (from old Packaging Manual)
10543 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10544 when it reinstalls the package it belongs to, and to have it
10545 put the file from the package somewhere else instead.
10549 This can be used locally to override a package's version of a
10550 file, or by one package to override another's version (or
10551 provide a wrapper for it).
10555 Before deciding to use a diversion, read <ref
10556 id="pkg-alternatives"> to see if you really want a diversion
10557 rather than several alternative versions of a program.
10561 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10562 and updated by a special program <prgn>dpkg-divert</prgn>.
10563 Please see <manref name="dpkg-divert" section="8"> for full
10564 details of its operation.
10568 When a package wishes to divert a file from another, it should
10569 call <prgn>dpkg-divert</prgn> in its preinst to add the
10570 diversion and rename the existing file. For example,
10571 supposing that a <prgn>smailwrapper</prgn> package wishes to
10572 install a wrapper around <file>/usr/sbin/smail</file>:
10574 if [ install = "$1" ]; then
10575 dpkg-divert --package smailwrapper --add --rename \
10576 --divert /usr/sbin/smail.real /usr/sbin/smail
10578 </example> Testing <tt>$1</tt> is necessary so that the script
10579 doesn't try to add the diversion again when
10580 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10581 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10582 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10583 get installed as the true version.
10587 The postrm has to do the reverse:
10589 if [ remove = "$1" ]; then
10590 dpkg-divert --package smailwrapper --remove --rename \
10591 --divert /usr/sbin/smail.real /usr/sbin/smail
10597 Do not attempt to divert a file which is vitally important for
10598 the system's operation - when using <prgn>dpkg-divert</prgn>
10599 there is a time, after it has been diverted but before
10600 <prgn>dpkg</prgn> has installed the new version, when the file
10601 does not exist.</p>