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10 <title>Debian Policy Manual</title>
11 <author><ref id="authors"></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
71 This manual also describes Debian policy as it relates to
72 creating Debian packages. It is not a tutorial on how to build
73 packages, nor is it exhaustive where it comes to describing
74 the behavior of the packaging system. Instead, this manual
75 attempts to define the interface to the package management
76 system that the developers have to be conversant with.<footnote>
78 Informally, the criteria used for inclusion is that the
79 material meet one of the following requirements:
80 <taglist compact="compact">
81 <tag>Standard interfaces</tag>
84 The material presented represents an interface to
85 the packaging system that is mandated for use, and
86 is used by, a significant number of packages, and
87 therefore should not be changed without peer
88 review. Package maintainers can then rely on this
89 interfaces not changing, and the package
90 management software authors need to ensure
91 compatibility with these interface
92 definitions. (Control file and changelog file
93 formats are examples.)
96 <tag>Chosen Convention</tag>
99 If there are a number of technically viable choices
100 that can be made, but one needs to select one of
101 these options for inter-operability. The version
102 number format is one example.
106 Please note that these are not mutually exclusive;
107 selected conventions often become parts of standard
114 The footnotes present in this manual are
115 merely informative, and are not part of Debian policy itself.
119 In this manual, the words <em>must</em>, <em>should</em> and
120 <em>may</em>, and the adjectives <em>required</em>,
121 <em>recommended</em> and <em>optional</em>, are used to
122 distinguish the significance of the various guidelines in
123 this policy document. Packages that do not conform to the
124 guidelines denoted by <em>must</em> (or <em>required</em>)
125 will generally not be considered acceptable for the Debian
126 distribution. Non-conformance with guidelines denoted by
127 <em>should</em> (or <em>recommended</em>) will generally be
128 considered a bug, but will not necessarily render a package
129 unsuitable for distribution. Guidelines denoted by
130 <em>may</em> (or <em>optional</em>) are truly optional and
131 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
141 <p>Compare RFC 2119. Note, however, that these words are
142 used in a different way in this document.</p>
146 Much of the information presented in this manual will be
147 useful even when building a package which is to be
148 distributed in some other way or is intended for local use
154 <heading>New versions of this document</heading>
156 The current version of this document is always accessible
157 from the Debian FTP server <ftpsite>ftp.debian.org</ftpsite>
159 <ftppath>/debian/doc/package-developer/policy.txt.gz</ftppath>
160 (also available from the same directory are several other
161 formats: <file>policy.html.tar.gz</file>, <file>policy.pdf.gz</file>
162 and <file>policy.ps.gz</file>) or from the <url
163 id="http://www.debian.org/doc/debian-policy/" name="Debian
164 Policy Manual"> webpage.</p>
167 In addition, this manual is distributed via the Debian package
168 <file>debian-policy</file>.
172 The <tt>debian-policy</tt> package also includes the file
173 <file>upgrading-checklist.txt</file> which indicates policy
174 changes between versions of this document.
179 <heading>Authors and Maintainers</heading>
182 Originally called "Debian GNU/Linux Policy Manual", this
183 manual was initially written in 1996 by Ian Jackson.
184 It was revised on November 27th, 1996 by David A. Morris.
185 Christian Schwarz added new sections on March 15th, 1997,
186 and reworked/restructured it in April-July 1997.
187 Christoph Lameter contributed the "Web Standard".
188 Julian Gilbey largely restructured it in 2001.
192 Since September 1998, the responsibility for the contents of
193 this document lies on the debian-policy mailing list. Proposals
194 are discussed there and inserted into policy after a certain
195 consensus is established.
196 <!-- insert shameless policy-process plug here eventually -->
197 The actual editing is done by a group of maintainers that have
198 no editorial powers. These are the current maintainers:
201 <item>Julian Gilbey</item>
202 <item>Branden Robinson</item>
203 <item>Josip Rodin</item>
204 <item>Manoj Srivastava</item>
209 While the authors of this document have tried hard to avoid
210 typos and other errors, these do still occur. If you discover
211 an error in this manual or if you want to give any
212 comments, suggestions, or criticisms please send an email to
213 the Debian Policy List,
214 <email>debian-policy@lists.debian.org</email>, or submit a
215 bug report against the <tt>debian-policy</tt> package.
219 Please do not try to reach the individual authors or maintainers
220 of the Policy Manual regarding changes to the Policy.
226 <heading>The Debian Archive</heading>
228 The Debian GNU/Linux system is maintained and distributed as a
229 collection of <em>packages</em>. Since there are so many of
230 them (currently well over 6000), they are split into
231 <em>sections</em> and given <em>priorities</em> to simplify
232 the handling of them.
235 The effort of the Debian project is to build a free operating
236 system, but not every package we want to make accessible is
237 <em>free</em> in our sense (see the Debian Free Software
238 Guidelines, below), or may be imported/exported without
239 restrictions. Thus, the archive is split into the sections
240 <em>main</em>, <em>non-free</em>, <em>contrib</em>,
241 <em>non-US/main</em>, <em>non-US/non-free</em>, and
242 <em>non-US/contrib</em>. The sections are explained in detail
247 The <em>main</em> and the <em>non-US/main</em> sections
248 together form the <em>Debian GNU/Linux distribution</em>.
252 Packages in the other sections are not considered to be part
253 of the Debian distribution, although we support their use and
254 provide infrastructure for them (such as our bug-tracking
255 system and mailing lists). This Debian Policy Manual applies
256 to these packages as well.</p>
258 <sect id="pkgcopyright">
259 <heading>Package copyright and sections</heading>
261 The aims of this section are:
263 <list compact="compact">
265 <p>to allow us to make as much software available as we
269 <p>to allow us to encourage everyone to write free
273 <p>to allow us to make it easy for people to produce
274 CD-ROMs of our system without violating any licenses,
275 import/export restrictions, or any other laws.</p>
280 <heading>The Debian Free Software Guidelines</heading>
282 The Debian Free Software Guidelines (DFSG) form our
283 definition of "free software". These are:
285 <tag>Free Redistribution
289 The license of a Debian component may not restrict any
290 party from selling or giving away the software as a
291 component of an aggregate software distribution
292 containing programs from several different
293 sources. The license may not require a royalty or
294 other fee for such sale.
301 The program must include source code, and must allow
302 distribution in source code as well as compiled form.
309 The license must allow modifications and derived
310 works, and must allow them to be distributed under the
311 same terms as the license of the original software.
314 <tag>Integrity of The Author's Source Code
318 The license may restrict source-code from being
319 distributed in modified form <em>only</em> if the
320 license allows the distribution of "patch files"
321 with the source code for the purpose of modifying the
322 program at build time. The license must explicitly
323 permit distribution of software built from modified
324 source code. The license may require derived works to
325 carry a different name or version number from the
326 original software. (This is a compromise. The Debian
327 Project encourages all authors to not restrict any
328 files, source or binary, from being modified.)
331 <tag>No Discrimination Against Persons or Groups
335 The license must not discriminate against any person
339 <tag>No Discrimination Against Fields of Endeavor
343 The license must not restrict anyone from making use
344 of the program in a specific field of endeavor. For
345 example, it may not restrict the program from being
346 used in a business, or from being used for genetic
350 <tag>Distribution of License
354 The rights attached to the program must apply to all
355 to whom the program is redistributed without the need
356 for execution of an additional license by those
360 <tag>License Must Not Be Specific to Debian
364 The rights attached to the program must not depend on
365 the program's being part of a Debian system. If the
366 program is extracted from Debian and used or
367 distributed without Debian but otherwise within the
368 terms of the program's license, all parties to whom
369 the program is redistributed must have the same
370 rights as those that are granted in conjunction with
374 <tag>License Must Not Contaminate Other Software
378 The license must not place restrictions on other
379 software that is distributed along with the licensed
380 software. For example, the license must not insist
381 that all other programs distributed on the same medium
382 must be free software.
385 <tag>Example Licenses
389 The "GPL," "BSD," and "Artistic" licenses are examples of
390 licenses that we consider <em>free</em>.
397 <heading>The main section</heading>
399 Every package in <em>main</em> and <em>non-US/main</em>
400 must comply with the DFSG (Debian Free Software
404 In addition, the packages in <em>main</em>
405 <list compact="compact">
408 must not require a package outside of <em>main</em>
409 for compilation or execution (thus, the package must
410 not declare a "Depends", "Recommends", or
411 "Build-Depends" relationship on a non-<em>main</em>
417 must not be so buggy that we refuse to support them,
423 must meet all policy requirements presented in this
430 Similarly, the packages in <em>non-US/main</em>
431 <list compact="compact">
434 must not require a package outside of <em>main</em>
435 or <em>non-US/main</em> for compilation or
441 must not be so buggy that we refuse to support them,
446 must meet all policy requirements presented in this
454 <heading>The contrib section</heading>
456 Every package in <em>contrib</em> and
457 <em>non-US/contrib</em> must comply with the DFSG.
461 In addition, the packages in <em>contrib</em> and
462 <em>non-US/contrib</em>
463 <list compact="compact">
466 must not be so buggy that we refuse to support them,
472 must meet all policy requirements presented in this
480 Furthermore, packages in <em>contrib</em> must not require
481 a package in a <em>non-US</em> section for compilation or
486 Examples of packages which would be included in
487 <em>contrib</em> or <em>non-US/contrib</em> are:
488 <list compact="compact">
491 free packages which require <em>contrib</em>,
492 <em>non-free</em> packages or packages which are not
493 in our archive at all for compilation or execution,
499 wrapper packages or other sorts of free accessories for
507 <heading>The non-free section</heading>
509 Packages must be placed in <em>non-free</em> or
510 <em>non-US/non-free</em> if they are not compliant with
511 the DFSG or are encumbered by patents or other legal
512 issues that make their distribution problematic.
515 In addition, the packages in <em>non-free</em> and
516 <em>non-US/non-free</em>
517 <list compact="compact">
520 must not be so buggy that we refuse to support them,
526 must meet all policy requirements presented in this
527 manual that it is possible for them to meet.<footnote>
529 It is possible that there are policy
530 requirements which the package is unable to
531 meet, for example, if the source is
532 unavailable. These situations will need to be
533 handled on a case-by-case basis.
543 <heading>The non-US sections</heading>
545 Non-free programs with cryptographic program code need to
546 be stored on the <em>non-us</em> server because of export
547 restrictions of the U.S.
550 Programs which use patented algorithms that have a
551 restrictied license also need to be stored on "non-us",
552 since that is located in a country where it is not allowed
553 to patent algorithms.
556 A package depends on another package which is distributed
557 via the non-us server has to be stored on the non-us
562 <heading>Further copyright considerations</heading>
564 Every package must be accompanied by a verbatim copy of
565 its copyright and distribution license in the file
566 <file>/usr/share/doc/<var>package</var>/copyright</file>
567 (see <ref id="copyrightfile"> for further details).
570 We reserve the right to restrict files from being included
571 anywhere in our archives if
572 <list compact="compact">
575 their use or distribution would break a law,
580 there is an ethical conflict in their distribution or
586 we would have to sign a license for them, or
591 their distribution would conflict with other project
599 Programs whose authors encourage the user to make
600 donations are fine for the main distribution, provided
601 that the authors do not claim that not donating is
602 immoral, unethical, illegal or something similar; in such
603 a case they must go in <em>non-free</em>.</p>
606 Packages whose copyright permission notices (or patent
607 problems) do not even allow redistribution of binaries
608 only, and where no special permission has been obtained,
609 must not be placed on the Debian FTP site and its mirrors
613 Note that under international copyright law (this applies
614 in the United States, too), <em>no</em> distribution or
615 modification of a work is allowed without an explicit
616 notice saying so. Therefore a program without a copyright
617 notice <em>is</em> copyrighted and you may not do anything
618 to it without risking being sued! Likewise if a program
619 has a copyright notice but no statement saying what is
620 permitted then nothing is permitted.</p>
623 Many authors are unaware of the problems that restrictive
624 copyrights (or lack of copyright notices) can cause for
625 the users of their supposedly-free software. It is often
626 worthwhile contacting such authors diplomatically to ask
627 them to modify their license terms. However, this can be a
628 politically difficult thing to do and you should ask for
629 advice on the <tt>debian-legal</tt> mailing list first, as
634 When in doubt about a copyright, send mail to
635 <email>debian-legal@lists.debian.org</email>. Be prepared
636 to provide us with the copyright statement. Software
637 covered by the GPL, public domain software and BSD-like
638 copyrights are safe; be wary of the phrases "commercial
639 use prohibited" and "distribution restricted".
643 <heading>Subsections</heading>
646 The packages in the sections <em>main</em>,
647 <em>contrib</em> and <em>non-free</em> are grouped further
648 into <em>subsections</em> to simplify handling.
652 The section and subsection for each package should be
653 specified in the package's <tt>Section</tt> control
654 record. However, the maintainer of the Debian archive
655 may override this selection to ensure the consistency of
656 the Debian distribution. The <tt>Section</tt> field
657 should be of the form:
658 <list compact="compact">
661 <em>subsection</em> if the package is in the
662 <em>main</em> section,
667 <em>section/subsection</em> if the package is in
668 the <em>contrib</em> or <em>non-free</em> section,
674 <tt>non-US</tt>, <tt>non-US/contrib</tt> or
675 <tt>non-US/non-free</tt> if the package is in
676 <em>non-US/main</em>, <em>non-US/contrib</em> or
677 <em>non-US/non-free</em> respectively.
684 The Debian archive maintainers provide the authoritative
685 list of subsections. At present, they are:
686 <em>admin</em>, <em>base</em>, <em>comm</em>,
687 <em>contrib</em>, <em>devel</em>, <em>doc</em>,
688 <em>editors</em>, <em>electronics</em>, <em>games</em>,
689 <em>graphics</em>, <em>hamradio</em>,
690 <em>interpreters</em>, <em>libs</em>, <em>mail</em>,
691 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
692 <em>non-US</em>, <em>non-free</em>, <em>oldlibs</em>,
693 <em>otherosfs</em>, <em>science</em>, <em>shells</em>,
694 <em>sound</em>, <em>tex</em>, <em>text</em>,
695 <em>utils</em>, <em>web</em>, <em>x11</em>.
699 <heading>Priorities</heading>
702 Each package should have a <em>priority</em> value, which is
703 included in the package's <em>control record</em>. This
704 information is used by the Debian package management tools
705 to separate high-priority packages from less-important
709 The following <em>priority levels</em> are recognised by the
710 Debian package management tools.
712 <tag><tt>required</tt></tag>
715 Packages which are necessary for the proper
716 functioning of the system. You must not remove these
717 packages or your system may become totally broken and
718 you may not even be able to use <prgn>dpkg</prgn> to
719 put things back. Systems with only the
720 <tt>required</tt> packages are probably unusable, but
721 they do have enough functionality to allow the
722 sysadmin to boot and install more software.</p>
724 <tag><tt>important</tt></tag>
727 Important programs, including those which one would
728 expect to find on any Unix-like system. If the
729 expectation is that an experienced Unix person who
730 found it missing would say "What on earth is going on,
731 where is <prgn>foo</prgn>?", it must be an
732 <tt>important</tt> package.<footnote>
734 This is an important criterion because we are
735 trying to produce, amongst other things, a free
739 Other packages without which the system will not run
740 well or be usable must also have priority
741 <tt>important</tt>. This does
742 <em>not</em> include Emacs, the X Window System, TeX
743 or any other large applications. The
744 <tt>important</tt> packages are just a bare minimum of
745 commonly-expected and necessary tools.</p>
747 <tag><tt>standard</tt></tag>
750 These packages provide a reasonably small but not too
751 limited character-mode system. This is what will be
752 installed by default if the user doesn't select anything
753 else. It doesn't include many large applications.</p>
755 <tag><tt>optional</tt></tag>
758 (In a sense everything that isn't required is
759 optional, but that's not what is meant here.) This is
760 all the software that you might reasonably want to
761 install if you didn't know what it was and don't have
762 specialized requirements. This is a much larger system
763 and includes the X Window System, a full TeX
764 distribution, and many applications. Note that
765 optional packages should not conflict with each other.
768 <tag><tt>extra</tt></tag>
771 This contains all packages that conflict with others
772 with required, important, standard or optional
773 priorities, or are only likely to be useful if you
774 already know what they are or have specialised
781 Packages must not depend on packages with lower priority
782 values (excluding build-time dependencies). In order to
783 ensure this, the priorities of one or more packages may need
789 <heading>Binary packages</heading>
792 The Debian GNU/Linux distribution is based on the Debian
793 package management system, called <prgn>dpkg</prgn>. Thus,
794 all packages in the Debian distribution must be provided
795 in the <tt>.deb</tt> file format.</p>
799 <heading>The package name</heading>
802 Every package must have a name that's unique within the Debian
806 Package names must consist of lower case letters
807 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
808 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
809 They must be at least two characters long and must start
810 with an alphanumeric character.
814 The package name is part of the file name of the
815 <tt>.deb</tt> file and is included in the control field
821 <heading>The maintainer of a package</heading>
823 Every package must have a Debian maintainer (the
824 maintainer may be one person or a group of people
825 reachable from a common email address, such as a mailing
826 list). The maintainer is responsible for ensuring that
827 the package is placed in the appropriate distributions.
831 The maintainer must be specified in the
832 <tt>Maintainer</tt> control field with their correct name
833 and a working email address. If one person maintains
834 several packages, he/she should try to avoid having
835 different forms of their name and email address in
836 the <tt>Maintainer</tt> fields of those packages.
840 If the maintainer of a package quits from the Debian
841 project, "Debian QA Group"
842 <email>packages@qa.debian.org</email> takes over the
843 maintainership of the package until someone else
844 volunteers for that task. These packages are called
845 <em>orphaned packages</em>.<footnote>
847 The detailed procedure for doing this gracefully can
848 be found in the Debian Developer's Reference, either
849 in the <tt>developers-reference</tt> package, or on
850 the Debian FTP server
851 <ftpsite>ftp.debian.org</ftpsite> as
852 <ftppath>/debian/doc/package-developer/developers-reference.txt.gz</ftppath>
854 id="http://www.debian.org/doc/packaging-manuals/developers-reference/"
855 name="Debian Developer's Reference"> webpage.
863 <heading>The description of a package</heading>
866 Every Debian package must have an extended description
867 stored in the appropriate field of the control record.</p>
870 The description should be written so that it gives the
871 system administrator enough information to decide whether
872 to install the package. This description should not just
873 be copied verbatim from the program's documentation.
874 Instructions for configuring or using the package should
875 not be included (that is what installation scripts,
876 manual pages, info files, etc., are for). Copyright
877 statements and other administrivia should not be included
878 either (that is what the copyright file is for).
882 Please refer to <ref id="descriptions"> for more information.
889 <heading>Dependencies</heading>
892 Every package must specify the dependency information
893 about other packages that are required for the first to
897 For example, a dependency entry must be provided for any
898 shared libraries required by a dynamically-linked executable
899 binary in a package.</p>
902 Packages are not required to declare any dependencies they
903 have on other packages which are marked <tt>Essential</tt>
904 (see below), and should not do so unless they depend on a
905 particular version of that package.</p>
908 Sometimes, a package requires another package to be installed
909 <em>and</em> configured before it can be installed. In this
910 case, you must specify a <tt>Pre-Depends</tt> entry for
914 You should not specify a <tt>Pre-Depends</tt> entry for a
915 package before this has been discussed on the
916 <tt>debian-devel</tt> mailing list and a consensus about
917 doing that has been reached.</p></sect1>
920 <sect1 id="virtual_pkg_sect">
921 <heading>Virtual packages</heading>
924 Sometimes, there are several packages which offer
925 more-or-less the same functionality. In this case, it's
926 useful to define a <em>virtual package</em> whose name
927 describes that common functionality. (The virtual
928 packages only exist logically, not physically; that's why
929 they are called <em>virtual</em>.) The packages with this
930 particular function will then <em>provide</em> the virtual
931 package. Thus, any other package requiring that function
932 can simply depend on the virtual package without having to
933 specify all possible packages individually.</p>
936 All packages should use virtual package names where
937 appropriate, and arrange to create new ones if necessary.
938 They should not use virtual package names (except privately,
939 amongst a cooperating group of packages) unless they have
940 been agreed upon and appear in the list of virtual package
941 names. (See also <ref id="virtual">)</p>
944 The latest version of the authoritative list of virtual
945 package names can be found on
946 <ftpsite>ftp.debian.org</ftpsite> in
947 <ftppath>/debian/doc/package-developer/virtual-package-names-list.txt</ftppath>
948 or your local mirror. In addition, it is included in the
949 <tt>debian-policy</tt> package. The procedure for updating
950 the list is described at the top of the file.</p></sect1>
954 <heading>Base system</heading>
957 The <tt>base system</tt> is a minimum subset of the Debian
958 GNU/Linux system that is installed before everything else
959 on a new system. Thus, only very few packages are allowed
960 to go into the <tt>base</tt> section to keep the required
961 disk usage very small.</p>
964 Most of these packages will have the priority value
965 <tt>required</tt> or at least <tt>important</tt>, and many
966 of them will be tagged <tt>essential</tt> (see below).</p>
973 <heading>Essential packages</heading>
976 Some packages are tagged <tt>essential</tt>. (They have
977 <tt>Essential: yes</tt> in their package control record.)
978 This flag is used for packages that are <em>essential</em>
982 Since these packages cannot be easily removed (one has to
983 specify an extra <em>force option</em> to
984 <prgn>dpkg</prgn> to do so), this flag must not be used
985 unless absolutely necessary. A shared library package
986 must not be tagged <tt>essential</tt>; dependencies will
987 prevent its premature removal, and we need to be able to
988 remove it when it has been superseded.
992 Since dpkg will not prevent upgrading of other packages
993 while an <tt>essential</tt> package is in an unconfigured
994 state, all <tt>essential</tt> packages must supply all of
995 their core functionality even when unconfigured. If the
996 package cannot satisfy this requirement it must not be
997 tagged as essential, and any packages depending on this
998 package must instead have explicit dependency fields as
1003 You must not tag any packages <tt>essential</tt> before
1004 this has been discussed on the <tt>debian-devel</tt>
1005 mailing list and a consensus about doing that has been
1010 <heading>Tasks</heading>
1013 The Debian install process allows the user to choose from
1014 a number of common tasks which a Debian system can be used to
1015 perform. Selecting a task with <prgn>tasksel</prgn> causes
1016 a set of packages that are useful in performing that task to be
1021 This set of packages is all available packages which have the
1022 name of the selected task in the <tt>Task</tt> field of their
1023 control file. The format of this field is a list of tasks,
1024 separated by commas.
1028 You should not tag any packages as belonging to a task
1029 before this has been discussed on the
1030 <em>debian-devel</em> mailing list and a consensus about
1031 doing that has been reached.
1035 For third parties (and historical reasons), tasksel also
1036 supports constructing tasks based on <em>task
1037 packages</em>. These are packages whose names begin with
1038 <em>task-</em>. Task packages should not be included in the
1043 <sect1 id="maintscripts">
1044 <heading>Maintainer Scripts</heading>
1047 The package installation scripts should avoid producing
1048 output which it is unnecessary for the user to see and
1049 should rely on <prgn>dpkg</prgn> to stave off boredom on
1050 the part of a user installing many packages. This means,
1051 amongst other things, using the <tt>--quiet</tt> option on
1052 <prgn>install-info</prgn>.</p>
1055 Errors which occur during the execution of an installation
1056 script must be checked and the installation must not
1057 continue after an error.
1061 Note that in general <ref id="scripts"> applies to package
1062 maintainer scripts, too.
1066 You should not use <prgn>dpkg-divert</prgn> on a file
1067 belonging to another package without consulting the
1068 maintainer of that package first.
1072 All packages which supply an instance of a common command
1073 name (or, in general, filename) should generally use
1074 <prgn>update-alternatives</prgn>, so that they may be
1075 installed together. If <prgn>update-alternatives</prgn>
1076 is not used, then each package must use
1077 <tt>Conflicts</tt> to ensure that other packages are
1078 de-installed. (In this case, it may be appropriate to
1079 specify a conflict against earlier versions of something
1080 that previously did not use
1081 <prgn>update-alternatives</prgn>; this is an exception to
1082 the usual rule that versioned conflicts should be
1088 <heading>Prompting in maintainer scripts</heading>
1090 Package maintainer scripts may prompt the user if
1091 necessary. Prompting may be accomplished by hand, or by
1092 communicating with a program, such as
1093 <prgn>debconf</prgn>, which conforms to the Debian
1094 Configuration management specification, version 2 or
1095 higher. These are included in the
1096 <file>debconf_specification</file> files in the
1097 <package>debian-policy</package> package.
1098 You may also find this file on the FTP site
1099 <ftpsite>ftp.debian.org</ftpsite> in
1100 <ftppath>/debian/doc/package-developer/debconf_specification.txt.gz</ftppath>
1101 or on your local mirror.<footnote>
1103 4% of Debian packages [see <url
1104 id="http://kitenet.net/programs/debconf/stats/"
1105 name="Debconf stats">] currently use
1106 <package>debconf</package> to prompt the user at
1107 install time, and this number is growing daily. The
1108 benefits of using debconf are briefly explained at
1110 id="http://kitenet.net/doc/debconf-doc/introduction.html"
1111 name="Debconf introduction">; they include
1112 preconfiguration, (mostly) noninteractive
1113 installation, elimination of redundant prompting,
1114 consistency of user interface, etc.
1117 With this increasing number of packages using
1118 <package>debconf</package>, plus the existance of a
1119 nascent second implementation of the Debian
1120 configuration management system
1121 (<package>cdebconf</package>), and the stabilization
1122 of the protocol these things use, the time has
1123 finally come to reflect the use of these things in
1130 Packages which use the Debian Configuration management
1131 specification may contain an additional
1132 <prgn>config</prgn> script and a <tt>templates</tt>
1133 file in their control archive. The <prgn>config</prgn>
1134 script might be run before the <prgn>preinst</prgn>
1135 script, and before the package is unpacked or any of its
1136 dependencies or pre-dependancies are satisfied.
1137 Therefore it must work using only the tools present in
1138 <em>essential</em> packages.<footnote>
1140 <package>Debconf</package> or another tool that
1141 implements the Debian Configuration management
1142 specification will also be installed, and any
1143 versioned dependencies on it will be satisfied
1144 before preconfiguration begins.
1150 Packages should try to minimize the amount of prompting
1151 they need to do, and they should ensure that the user
1152 will only ever be asked each question once. This means
1153 that packages should try to use appropriate shared
1154 configuration files (such as <file>/etc/papersize</file> and
1155 <file>/etc/news/server</file>), and shared
1156 <package>debconf</package> variables rather than each
1157 prompting for their own list of required pieces of
1162 It also means that an upgrade should not ask the same
1163 questions again, unless the user has used <tt>dpkg
1164 --purge</tt> to remove the package's configuration. The
1165 answers to configuration questions should be stored in an
1166 appropriate place in <file>/etc</file> so that the user can
1167 modify them, and how this has been done should be
1171 If a package has a vitally important piece of
1172 information to pass to the user (such as "don't run me
1173 as I am, you must edit the following configuration files
1174 first or you risk your system emitting badly-formatted
1175 messages"), it should display this in the
1176 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1177 prompt the user to hit return to acknowledge the
1178 message. Copyright messages do not count as vitally
1179 important (they belong in
1180 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1181 neither do instructions on how to use a program (these
1182 should be in on-line documentation, where all the users
1186 Any necessary prompting should almost always be confined
1187 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1188 script. If it is done in the <prgn>postinst</prgn>, it
1189 should be protected with a conditional so that
1190 unnecessary prompting doesn't happen if a package's
1191 installation fails and the <prgn>postinst</prgn> is
1192 called with <tt>abort-upgrade</tt>,
1193 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.</p>
1198 <heading>Source packages</heading>
1200 <sect1 id="standardsversion">
1201 <heading>Standards conformance</heading>
1204 In the source package's <tt>Standards-Version</tt> control
1205 field, you should specify the most recent version number
1206 of this policy document with which your package complied
1207 when it was last updated. The current version number is
1212 This information may be used to file bug reports
1213 automatically if your package becomes too much out of
1218 The version number has four components: major and minor
1219 version number and major and minor patch level. When the
1220 standards change in a way that requires every package to
1221 change the major number will be changed. Significant
1222 changes that will require work in many packages will be
1223 signaled by a change to the minor number. The major patch
1224 level will be changed for any change to the meaning of the
1225 standards, however small; the minor patch level will be
1226 changed when only cosmetic, typographical or other edits
1227 are made which neither change the meaning of the document
1228 nor affect the contents of packages.</p>
1231 Thus only the first three components of the policy version
1232 are significant in the <em>Standards-Version</em> control
1233 field, and so either these three components or the all
1234 four components may be specified.<footnote>
1236 In the past, people specified the full version number
1237 in the Standards-Version field, for example "2.3.0.0".
1238 Since minor patch-level changes don"t introduce new
1239 policy, it was thought it would be better to relax
1240 policy and only require the first 3 components to be
1241 specified, in this example "2.3.0". All four
1242 components may still be used if someone wishes to do
1249 You should regularly, and especially if your package has
1250 become out of date, check for the newest Policy Manual
1251 available and update your package, if necessary. When your
1252 package complies with the new standards you should update the
1253 <tt>Standards-Version</tt> source package field and
1254 release it.<footnote>
1256 See the file <file>upgrading-checklist</file> for
1257 information about policy which has changed between
1258 different versions of this document.
1265 <sect1 id="pkg-relations">
1266 <heading>Package relationships</heading>
1269 Source packages should specify which binary packages they
1270 require to be installed or not to be installed in order to
1271 build correctly. For example, if building a package
1272 requires a certain compiler, then the compiler should be
1273 specified as a build-time dependency.
1277 It is not necessary to explicitly specify build-time
1278 relationships on a minimal set of packages that are always
1279 needed to compile, link and put in a Debian package a
1280 standard "Hello World!" program written in C or C++. The
1281 required packages are called <em>build-essential</em>, and
1282 an informational list can be found in
1283 <file>/usr/share/doc/build-essential/list</file> (which is
1284 contained in the <tt>build-essential</tt>
1287 <list compact="compact">
1289 <p>This allows maintaining the list separately
1290 from the policy documents (the list does not
1291 need the kind of control that the policy
1297 Having a separate package allows one to install
1298 the build-essential packages on a machine, as
1299 well as allowing other packages such as tasks to
1300 require installation of the build-essential
1301 packages using the depends relation.
1306 The separate package allows bug reports against
1307 the list to be categorized separately from
1308 the policy management process in the BTS.
1318 When specifying the set of build-time dependencies, one
1319 should list only those packages explicitly required by the
1320 build. It is not necessary to list packages which are
1321 required merely because some other package in the list of
1322 build-time dependencies depends on them.<footnote>
1324 The reason for this is that dependencies change, and
1325 you should list all those packages, and <em>only</em>
1326 those packages that <em>you</em> need directly. What
1327 others need is their business. For example, if you
1328 only link against <file>libimlib</file>, you will need to
1329 build-depend on <package>libimlib2-dev</package> but
1330 not against any <tt>libjpeg*</tt> packages, even
1331 though <tt>libimlib2-dev</tt> currently depends on
1332 them: installation of <package>libimlib2-dev</package>
1333 will automatically ensure that all of its run-time
1334 dependencies are satisfied.
1340 If build-time dependencies are specified, it must be
1341 possible to build the package and produce working binaries
1342 on a system with only essential and build-essential
1343 packages installed and also those required to satisfy the
1344 build-time relationships (including any implied
1345 relationships). In particular, this means that version
1346 clauses should be used rigorously in build-time
1347 relationships so that one cannot produce bad or
1348 inconsistently configured packages when the relationships
1349 are properly satisfied.
1353 <ref id="relationships"> explains the technical details.
1357 <heading>Changes to the upstream sources</heading>
1360 If changes to the source code are made that are not
1361 specific to the needs of the Debian system, they should be
1362 sent to the upstream authors in whatever form they prefer
1363 so as to be included in the upstream version of the
1367 If you need to configure the package differently for
1368 Debian or for Linux, and the upstream source doesn't
1369 provide a way to do so, you should add such configuration
1370 facilities (for example, a new <prgn>autoconf</prgn> test
1371 or <tt>#define</tt>) and send the patch to the upstream
1372 authors, with the default set to the way they originally
1373 had it. You can then easily override the default in your
1374 <file>debian/rules</file> or wherever is appropriate.</p>
1377 You should make sure that the <prgn>configure</prgn> utility
1378 detects the correct architecture specification string
1379 (refer to <ref id="arch-spec"> for details).</p>
1382 If you need to edit a <prgn>Makefile</prgn> where
1383 GNU-style <prgn>configure</prgn> scripts are used, you
1384 should edit the <file>.in</file> files rather than editing the
1385 <prgn>Makefile</prgn> directly. This allows the user to
1386 reconfigure the package if necessary. You should
1387 <em>not</em> configure the package and edit the generated
1388 <prgn>Makefile</prgn>! This makes it impossible for
1389 someone else to later reconfigure the package.</p>
1392 You should document your changes and updates to the source
1393 package properly in the <file>debian/changelog</file> file.
1394 For more information, please see <ref id="changelogs">.
1400 <heading>Error trapping in makefiles</heading>
1403 When <prgn>make</prgn> invokes a command in a makefile
1404 (including your package's upstream makefiles and
1405 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1406 means that <prgn>sh</prgn>'s usual bad error handling
1407 properties apply: if you include a miniature script as one
1408 of the commands in your makefile you'll find that if you
1409 don't do anything about it then errors are not detected
1410 and <prgn>make</prgn> will blithely continue after
1414 Every time you put more than one shell command (this
1415 includes using a loop) in a makefile command you
1416 must make sure that errors are trapped. For
1417 simple compound commands, such as changing directory and
1418 then running a program, using <tt>&&</tt> rather
1419 than semicolon as a command separator is sufficient. For
1420 more complex commands including most loops and
1421 conditionals you should include a separate <tt>set -e</tt>
1422 command at the start of every makefile command that's
1423 actually one of these miniature shell scripts.</p></sect1>
1427 <heading>Obsolete constructs and libraries</heading>
1430 The include file <tt><varargs.h></tt> is
1431 provided to support end-users compiling very old software;
1432 the library <tt>libtermcap</tt> is provided to support the
1433 execution of software which has been linked against it
1434 (either old programs or those such as Netscape which are
1435 only available in binary form).</p>
1438 Debian packages should be patched to use
1439 <tt><stdarg.h></tt> and <tt>ncurses</tt>
1446 <chapt id="controlfields"><heading>Control files and their fields</heading>
1449 Many of the tools in the package management suite manipulate
1450 data represented in a common format, known as <em>control
1451 data</em>. The data is often stored in <em>control
1452 files</em>. Binary and source packages have control files,
1453 and the <file>.changes</file> files which control the installation
1454 of uploaded files are also in control file format.
1455 <prgn>dpkg</prgn>'s internal databases are in a similar
1459 <sect id="controlsyntax"><heading>Syntax of control files</heading>
1462 A control file consists of one or more paragraphs of fields.
1463 The paragraphs are separated by blank lines. Some control
1464 files allow only one paragraph; others allow several, in
1465 which case each paragraph usually refers to a different
1466 package. (For example, in source packages, the first
1467 paragraph refers to the source package, and later paragraphs
1468 refer to binary packages generated from the source.)
1472 Each paragraph consists of a series of data fields; each
1473 field consists of the field name, followed by a colon and
1474 then the data/value associated with that field. It ends at
1475 the end of the line. Horizontal whitespace (spaces and
1476 tabs) may occur immediately before or after the value and is
1477 ignored there; it is conventional to put a single space
1478 after the colon. For example, a field might be:
1479 <example compact="compact">
1482 the field name is <tt>Package</tt> and the field value
1487 Some fields' values may span several lines; in this case
1488 each continuation line <em>must</em> start with a space or
1489 tab. Any trailing spaces or tabs at the end of individual
1490 lines of a field value are ignored.
1494 Except where otherwise stated only a single line of data is
1495 allowed and whitespace is not significant in a field body.
1496 Whitespace must not appear inside names (of packages,
1497 architectures, files or anything else) or version numbers,
1498 or between the characters of multi-character version
1503 Field names are not case-sensitive, but it is usual to
1504 capitalize the field names using mixed case as shown below.
1508 Blank lines, or lines consisting only of spaces and tabs,
1509 are not allowed within field values or between fields - that
1510 would mean a new paragraph.
1515 <sect><heading>List of fields</heading>
1517 This list here is not supposed to be exhaustive. Most fields
1518 are dealt with elsewhere in this document.
1520 <sect1 id="f-Package"><heading><tt>Package</tt>
1524 The name of the binary package. Package names consist of
1525 lower case letters (<tt>a-z</tt>), digits (<tt>0-9</tt>),
1526 plus (<tt>+</tt>) and minus (<tt>-</tt>) signs, and
1527 periods (<tt>.</tt>).
1531 They must be at least two characters long and must start
1532 with an alphanumeric character. The use of lowercase
1533 package names is required unless the package you're
1534 building (or referring to, in other fields) is already
1535 using uppercase characters.</p>
1538 <sect1 id="f-Version"><heading><tt>Version</tt>
1542 This lists the source or binary package's version number -
1543 see <ref id="versions">.
1549 id="f-Standards-Version"><heading><tt>Standards-Version</tt>
1553 The most recent version of the standards (the policy
1554 manual and associated texts) with which the package
1555 complies. This is updated manually when editing the
1556 source package to conform to newer standards; it can
1557 sometimes be used to tell when a package needs attention.
1558 Its format is described above; see
1559 <ref id="standardsversion">.
1564 <sect1 id="f-Distribution"><heading><tt>Distribution</tt>
1568 In a <file>.changes</file> file or parsed changelog output
1569 this contains the (space-separated) name(s) of the
1570 distribution(s) where this version of the package should
1571 be installed. Valid distributions are determined by the
1572 archive maintainers.<footnote>
1573 Current distribution names are:
1574 <taglist compact="compact">
1575 <tag><em>stable</em></tag>
1578 This is the current "released" version of Debian
1579 GNU/Linux. Once the distribution is
1580 <em>stable</em> only security fixes and other
1581 major bug fixes are allowed. When changes are
1582 made to this distribution, the release number is
1583 increased (for example: 2.2r1 becomes 2.2r2 then
1588 <tag><em>unstable</em></tag>
1591 This distribution value refers to the
1592 <em>developmental</em> part of the Debian
1593 distribution tree. New packages, new upstream
1594 versions of packages and bug fixes go into the
1595 <em>unstable</em> directory tree. Download from
1596 this distribution at your own risk.
1600 <tag><em>testing</em></tag>
1603 This distribution value refers to the
1604 <em>testing</em> part of the Debian distribution
1605 tree. It receives its packages from the
1606 unstable distribution after a short time lag to
1607 ensure that there are no major issues with the
1608 unstable packages. It is less prone to breakage
1609 than unstable, but still risky. It is not
1610 possible to upload packages directly to
1615 <tag><em>frozen</em></tag>
1618 From time to time, the <em>testing</em>
1619 distribution enters a state of "code-freeze" in
1620 anticipation of release as a <em>stable</em>
1621 version. During this period of testing only
1622 fixes for existing or newly-discovered bugs will
1623 be allowed. The exact details of this stage are
1624 determined by the Release Manager.
1628 <tag><em>experimental</em></tag>
1631 The packages with this distribution value are
1632 deemed by their maintainers to be high
1633 risk. Oftentimes they represent early beta or
1634 developmental packages from various sources that
1635 the maintainers want people to try, but are not
1636 ready to be a part of the other parts of the
1637 Debian distribution tree. Download at your own
1643 You should list <em>all</em> distributions that the
1644 package should be installed into.
1653 <chapt id="versions"><heading>Version numbering</heading>
1656 Every package has a version number recorded in its
1657 <tt>Version</tt> control file field.
1661 The package management system imposes an ordering on version
1662 numbers, so that it can tell whether packages are being up- or
1663 downgraded and so that package system front end applications
1664 can tell whether a package it finds available is newer than
1665 the one installed on the system. The version number format
1666 has the most significant parts (as far as comparison is
1667 concerned) at the beginning.
1671 The version number format is:
1672 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
1676 The three components here are:
1678 <tag><var>epoch</var></tag>
1681 This is a single (generally small) unsigned integer. It
1682 may be omitted, in which case zero is assumed. If it is
1683 omitted then the <var>upstream_version</var> may not
1688 It is provided to allow mistakes in the version numbers
1689 of older versions of a package, and also a package's
1690 previous version numbering schemes, to be left behind.
1694 <tag><var>upstream_version</var></tag>
1697 This is the main part of the version number. It is
1698 usually the version number of the original ("upstream")
1699 package from which the <file>.deb</file> file has been made,
1700 if this is applicable. Usually this will be in the same
1701 format as that specified by the upstream author(s);
1702 however, it may need to be reformatted to fit into the
1703 package management system's format and comparison
1708 The comparison behavior of the package management system
1709 with respect to the <var>upstream_version</var> is
1710 described below. The <var>upstream_version</var>
1711 portion of the version number is mandatory.
1715 The <var>upstream_version</var> may contain only
1716 alphanumerics<footnote>
1717 <p>Alphanumerics are <tt>A-Za-z0-9</tt> only.</p>
1719 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
1720 <tt>:</tt> (full stop, plus, hyphen, colon) and should
1721 start with a digit. If there is no
1722 <var>debian_revision</var> then hyphens are not allowed;
1723 if there is no <var>epoch</var> then colons are not
1727 <tag><var>debian_revision</var></tag>
1730 This part of the version number specifies the version of
1731 the Debian package based on the upstream version. It
1732 may contain only alphanumerics and the characters
1733 <tt>+</tt> and <tt>.</tt> (plus and full stop) and is
1734 compared in the same way as the
1735 <var>upstream_version</var> is.
1739 It is optional; if it isn't present then the
1740 <var>upstream_version</var> may not contain a hyphen.
1741 This format represents the case where a piece of
1742 software was written specifically to be turned into a
1743 Debian package, and so there is only one "debianization"
1744 of it and therefore no revision indication is required.
1748 It is conventional to restart the
1749 <var>debian_revision</var> at <tt>1</tt> each time the
1750 <var>upstream_version</var> is increased.
1754 The package management system will break the version
1755 number apart at the last hyphen in the string (if there
1756 is one) to determine the <var>upstream_version</var> and
1757 <var>debian_revision</var>. The absence of a
1758 <var>debian_revision</var> compares earlier than the
1759 presence of one (but note that the
1760 <var>debian_revision</var> is the least significant part
1761 of the version number).
1768 The <var>upstream_version</var> and <var>debian_revision</var>
1769 parts are compared by the package management system using the
1774 The strings are compared from left to right.
1778 First the initial part of each string consisting entirely of
1779 non-digit characters is determined. These two parts (one of
1780 which may be empty) are compared lexically. If a difference
1781 is found it is returned. The lexical comparison is a
1782 comparison of ASCII values modified so that all the letters
1783 sort earlier than all the non-letters.
1787 Then the initial part of the remainder of each string which
1788 consists entirely of digit characters is determined. The
1789 numerical values of these two parts are compared, and any
1790 difference found is returned as the result of the comparison.
1791 For these purposes an empty string (which can only occur at
1792 the end of one or both version strings being compared) counts
1797 These two steps (comparing and removing initial non-digit
1798 strings and initial digit strings) are repeated until a
1799 difference is found or both strings are exhausted.
1803 Note that the purpose of epochs is to allow us to leave behind
1804 mistakes in version numbering, and to cope with situations
1805 where the version numbering scheme changes. It is
1806 <em>not</em> intended to cope with version numbers containing
1807 strings of letters which the package management system cannot
1808 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
1809 silly orderings (the author of this manual has heard of a
1810 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
1811 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
1812 <tt>2</tt> and so forth).
1816 If an upstream package has problematic version numbers they
1817 should be converted to a sane form for use in the
1818 <tt>Version</tt> field.
1822 <heading>Version numbers based on dates</heading>
1824 In general, Debian packages should use the same version
1825 numbers as the upstream sources.</p>
1828 However, in some cases where the upstream version number is
1829 based on a date (e.g., a development "snapshot" release) the
1830 package management system cannot handle these version
1831 numbers without epochs. For example, dpkg will consider
1832 "96May01" to be greater than "96Dec24".</p>
1835 To prevent having to use epochs for every new upstream
1836 version, the version number should be changed to the
1837 following format in such cases: "19960501", "19961224". It
1838 is up to the maintainer whether he/she wants to bother the
1839 upstream maintainer to change the version numbers upstream,
1843 Note that other version formats based on dates which are
1844 parsed correctly by the package management system should
1845 <em>not</em> be changed.</p>
1848 Native Debian packages (i.e., packages which have been
1849 written especially for Debian) whose version numbers include
1850 dates should always use the "YYYYMMDD" format.</p>
1854 <chapt id="miscellaneous"><heading>Packaging Considerations</heading>
1856 <sect id="timestamps"><heading>Time Stamps</heading>
1858 Maintainers should preserve the modification times of the
1859 upstream source files in a package, as far as is reasonably
1862 The rationale is that there is some information conveyed
1863 by knowing the age of the file, for example, you could
1864 recognize that some documentation is very old by looking
1865 at the modification time, so it would be nice if the
1866 modification time of the upstream source would be
1873 <sect id="debianrules"><heading><file>debian/rules</file> - the
1874 main building script</heading>
1877 This file must be an executable makefile, and contains the
1878 package-specific recipes for compiling the package and
1879 building binary package(s) from the source.
1883 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1884 so that it can be invoked by saying its name rather than
1885 invoking <prgn>make</prgn> explicitly.
1889 Since an interactive <file>debian/rules</file> script makes it
1890 impossible to auto-compile that package and also makes it
1891 hard for other people to reproduce the same binary
1892 package, all <em>required targets</em> MUST be
1893 non-interactive. At a minimum, required targets are the
1894 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1895 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1896 <em>binary-indep</em>, and <em>build</em>. It also follows
1897 that any target that these targets depend on must also be
1902 The required and optional targets are as follows:
1904 <tag><tt>build</tt>, <tt>build-arch</tt> (optional),
1905 <tt>build-indep</tt> (optional)</tag>
1908 The <tt>build</tt> target should perform all
1909 non-interactive configuration and compilation of the
1910 package. If a package has an interactive pre-build
1911 configuration routine, the Debianized source package
1912 must either be built after this has taken place (so
1913 that the binary package can be built without rerunning
1914 the configuration) or the configuration routine
1915 modified to become non-interactive. (The latter is
1916 preferable if there are architecture-specific features
1917 detected by the configuration routine.)
1921 For some packages, notably ones where the same
1922 source tree is compiled in different ways to produce
1923 two binary packages, the <tt>build</tt> target
1924 does not make much sense. For these packages it is
1925 good enough to provide two (or more) targets
1926 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1927 for each of the ways of building the package, and a
1928 <tt>build</tt> target that does nothing. The
1929 <tt>binary</tt> target will have to build the
1930 package in each of the possible ways and make the
1931 binary package out of each.
1935 The <tt>build</tt> target must not do anything
1936 that might require root privilege.
1940 The <tt>build</tt> target may need to run the
1941 <tt>clean</tt> target first - see below.
1945 When a package has a configuration and build routine
1946 which takes a long time, or when the makefiles are
1947 poorly designed, or when <tt>build</tt> needs to
1948 run <tt>clean</tt> first, it is a good idea to
1949 <tt>touch build</tt> when the build process is
1950 complete. This will ensure that if <tt>debian/rules
1951 build</tt> is run again it will not rebuild the whole
1954 Another common way to do this is for <tt>build</tt>
1955 to depend on <prgn>build-stamp</prgn> and to do
1956 nothing else, and for the <prgn>build-stamp</prgn>
1957 target to do the building and to <tt>touch
1958 build-stamp</tt> on completion. This is
1959 especially useful if the build routine creates a
1960 file or directory called <tt>build</tt>; in such a
1961 case, <tt>build</tt> will need to be listed as
1962 a phony target (i.e., as a dependency of the
1963 <tt>.PHONY</tt> target). See the documentation of
1964 <prgn>make</prgn> for more information on phony
1971 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1972 <tt>binary-indep</tt>
1976 The <tt>binary</tt> target must be all that is
1977 necessary for the user to build the binary package(s)
1978 produced from this source package. All of these
1979 targets are required to be non-interactive. It is
1980 split into two parts: <prgn>binary-arch</prgn> builds
1981 the binary packages which are specific to a particular
1982 architecture, and <tt>binary-indep</tt> builds
1983 those which are not.
1986 <tt>binary</tt> may be (and commonly is) a target with
1987 no commands which simply depends on
1988 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1991 Both <tt>binary-*</tt> targets should depend on the
1992 <tt>build</tt> target, or on the appropriate
1993 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1994 provided, so that the package is built if it has not
1995 been already. It should then create the relevant
1996 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1997 make their control files and <prgn>dpkg-deb</prgn> to
1998 build them and place them in the parent of the top
2003 Both the <tt>binary-arch</tt> and
2004 <tt>binary-indep</tt> targets <em>must</em> exist.
2005 If one of them has nothing to do (which will always be
2006 the case if the source generates only a single binary
2007 package, whether architecture-dependent or not), it
2008 must still exist and must always succeed.
2012 The <tt>binary</tt> targets must be invoked as
2015 The <prgn>fakeroot</prgn> package often allows one
2016 to build a package correctly even without being
2023 <tag><tt>clean</tt></tag>
2026 This must undo any effects that the <tt>build</tt>
2027 and <tt>binary</tt> targets may have had, except
2028 that it should leave alone any output files created in
2029 the parent directory by a run of a <tt>binary</tt>
2030 target. This target must be non-interactive.
2034 If a <tt>build</tt> file is touched at the end of
2035 the <tt>build</tt> target, as suggested above, it
2036 should be removed as the first action that
2037 <tt>clean</tt> performs, so that running
2038 <tt>build</tt> again after an interrupted
2039 <tt>clean</tt> doesn't think that everything is
2044 The <tt>clean</tt> target may need to be
2045 invoked as root if <tt>binary</tt> has been
2046 invoked since the last <tt>clean</tt>, or if
2047 <tt>build</tt> has been invoked as root (since
2048 <tt>build</tt> may create directories, for
2053 <tag><tt>get-orig-source</tt> (optional)</tag>
2056 This target fetches the most recent version of the
2057 original source package from a canonical archive site
2058 (via FTP or WWW, for example), does any necessary
2059 rearrangement to turn it into the original source
2060 tar file format described below, and leaves it in the
2065 This target may be invoked in any directory, and
2066 should take care to clean up any temporary files it
2071 This target is optional, but providing it if
2072 possible is a good idea.
2078 The <tt>build</tt>, <tt>binary</tt> and
2079 <tt>clean</tt> targets must be invoked with the current
2080 directory being the package's top-level directory.
2085 Additional targets may exist in <file>debian/rules</file>,
2086 either as published or undocumented interfaces or for the
2087 package's internal use.
2091 The architectures we build on and build for are determined
2092 by <prgn>make</prgn> variables using the utility
2093 <prgn>dpkg-architecture</prgn>. You can determine the
2094 Debian architecture and the GNU style architecture
2095 specification string for the build machine (the machine type
2096 we are building on) as well as for the host machine (the
2097 machine type we are building for). Here is a list of
2098 supported <prgn>make</prgn> variables:
2099 <list compact="compact">
2101 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
2104 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2105 specification string)</p>
2108 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of
2109 <tt>DEB_*_GNU_TYPE</tt>)</p>
2112 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2113 <tt>DEB_*_GNU_TYPE</tt>)</p>
2115 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2116 the build machine or <tt>HOST</tt> for specification of the
2121 Backward compatibility can be provided in the rules file
2122 by setting the needed variables to suitable default
2123 values; please refer to the documentation of
2124 <prgn>dpkg-architecture</prgn> for details.
2128 It is important to understand that the <tt>DEB_*_ARCH</tt>
2129 string only determines which Debian architecture we are
2130 building on or for. It should not be used to get the CPU
2131 or system information; the GNU style variables should be
2136 <sect id="dpkgchangelog"><heading><file>debian/changelog</file>
2140 This file records the changes to the Debian-specific parts of the
2143 Though there is nothing stopping an author who is also
2144 the Debian maintainer from using it for all their
2145 changes, it will have to be renamed if the Debian and
2146 upstream maintainers become different people. In such a
2147 case, however, it might be better to maintain the
2148 package as a non-native package.
2154 It has a special format which allows the package building
2155 tools to discover which version of the package is being
2156 built and find out other release-specific information.
2160 That format is a series of entries like this:
2161 <example compact="compact">
2162 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
2164 <p>[optional blank line(s), stripped]</p>
2166 * <var>change details</var>
2167 <var>more change details</var>
2169 <p>[blank line(s), included in output of dpkg-parsechangelog]</p>
2171 * <var>even more change details</var>
2173 <p>[optional blank line(s), stripped]</p>
2175 -- <var>maintainer name</var> <<var>email
2176 address</var>><var>[two spaces]</var> <var>date</var>
2181 <var>package</var> and <var>version</var> are the source
2182 package name and version number.
2186 <var>distribution(s)</var> lists the distributions where
2187 this version should be installed when it is uploaded - it
2188 is copied to the <tt>Distribution</tt> field in the
2189 <file>.changes</file> file. See <ref id="f-Distribution">.
2193 <var>urgency</var> is the value for the <tt>Urgency</tt>
2194 field in the <file>.changes</file> file for the upload. It is
2195 not possible to specify an urgency containing commas; commas
2196 are used to separate
2197 <tt><var>keyword</var>=<var>value</var></tt> settings in the
2198 <prgn>dpkg</prgn> changelog format (though there is
2199 currently only one useful <var>keyword</var>,
2200 <tt>urgency</tt>).<footnote>
2202 Recognised urgency values are <tt>low</tt>,
2203 <tt>medium</tt>, <tt>high</tt> and <tt>emergency</tt>.
2204 They have an effect on how quickly a package will be
2205 considered for inclusion into the <tt>testing</tt>
2206 distribution, and give an indication of the importance
2207 of any fixes included in this upload.
2213 The change details may in fact be any series of lines
2214 starting with at least two spaces, but conventionally each
2215 change starts with an asterisk and a separating space and
2216 continuation lines are indented so as to bring them in
2217 line with the start of the text above. Blank lines may be
2218 used here to separate groups of changes, if desired.
2222 If this upload resolves bugs recorded in the Bug Tracking
2223 System (BTS), they may be automatically closed on the
2224 inclusion of this package into the Debian archive by
2225 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
2226 in the change details.<footnote>
2228 To be precise, the string should match the following
2229 Perl regular expression:
2231 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
2233 Then all of the bug numbers listed will be closed by the
2234 archive maintenance script (<prgn>katie</prgn>), or in
2235 the case of an NMU, marked as fixed.
2241 The maintainer name and email address used in the changelog
2242 should be the details of the person uploading <em>this</em>
2243 version. They are <em>not</em> necessarily those of the
2244 usual package maintainer. The information here will be
2245 copied to the <tt>Changed-By</tt> field in the
2246 <tt>.changes</tt> file, and then later used to send an
2247 acknowledgement when the upload has been installed.
2251 The <var>date</var> should be in RFC822 format<footnote>
2253 This is generated by the <prgn>822-date</prgn>
2256 </footnote>; it should include the time zone specified
2257 numerically, with the time zone name or abbreviation
2258 optionally present as a comment in parentheses.
2262 The first "title" line with the package name should start
2263 at the left hand margin; the "trailer" line with the
2264 maintainer and date details should be preceded by exactly
2265 one space. The maintainer details and the date must be
2266 separated by exactly two spaces.
2269 <sect1><heading>Defining alternative changelog formats</heading>
2272 It is possible to use a different format to the standard
2273 one, by providing a parser for the format you wish to
2277 A changelog parser must not interact with the user at
2283 <!-- FIXME: section pkg-srcsubstvars is the same as srcsubstvars -->
2285 <sect id="srcsubstvars"><heading><file>debian/substvars</file>
2286 and variable substitutions </heading>
2289 When <prgn>dpkg-gencontrol</prgn>,
2290 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2291 generate control files they perform variable substitutions
2292 on their output just before writing it. Variable
2293 substitutions have the form <tt>${<var>variable</var>}</tt>.
2294 The optional file <file>debian/substvars</file> contains
2295 variable substitutions to be used; variables can also be set
2296 directly from <file>debian/rules</file> using the <tt>-V</tt>
2297 option to the source packaging commands, and certain
2298 predefined variables are also available.
2302 The <file>debian/substvars</file> file is usually generated and
2303 modified dynamically by <file>debian/rules</file> targets, in
2304 which case it must be removed by the <tt>clean</tt> target.
2308 See <manref name="dpkg-source" section="1"> for full
2309 details about source variable substitutions, including the
2310 format of <file>debian/substvars</file>.</p>
2313 <sect id="debianfiles"><heading><file>debian/files</file>
2317 This file is not a permanent part of the source tree; it
2318 is used while building packages to record which files are
2319 being generated. <prgn>dpkg-genchanges</prgn> uses it
2320 when it generates a <file>.changes</file> file.
2324 It should not exist in a shipped source package, and so it
2325 (and any backup files or temporary files such as
2326 <file>files.new</file><footnote>
2328 <file>files.new</file> is used as a temporary file by
2329 <prgn>dpkg-gencontrol</prgn> and
2330 <prgn>dpkg-distaddfile</prgn> - they write a new
2331 version of <tt>files</tt> here before renaming it,
2332 to avoid leaving a corrupted copy if an error
2335 </footnote>) should be removed by the
2336 <tt>clean</tt> target. It may also be wise to
2337 ensure a fresh start by emptying or removing it at the
2338 start of the <tt>binary</tt> target.
2342 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2343 package, it adds an entry to <file>debian/files</file> for the
2344 <file>.deb</file> file that will be created when <tt>dpkg-deb
2345 --build</tt> is run for that binary package. So for most
2346 packages all that needs to be done with this file is to
2347 delete it in the <tt>clean</tt> target.
2351 If a package upload includes files besides the source
2352 package and any binary packages whose control files were
2353 made with <prgn>dpkg-gencontrol</prgn> then they should be
2354 placed in the parent of the package's top-level directory
2355 and <prgn>dpkg-distaddfile</prgn> should be called to add
2356 the file to the list in <file>debian/files</file>.</p>
2359 <sect id="restrictions"><heading>Restrictions on objects in source packages
2363 The source package may not contain any hard links<footnote>
2365 This is not currently detected when building source
2366 packages, but only when extracting
2370 Hard links may be permitted at some point in the
2371 future, but would require a fair amount of
2374 </footnote>, device special files, sockets or setuid or
2375 setgid files.<footnote>
2377 Setgid directories are allowed.
2383 <sect id="descriptions"><heading>Descriptions of packages - the
2384 <tt>Description</tt> field</heading>
2387 The "Description" control file field consists of two parts,
2388 the synopsis or the short description, and the long description.
2389 The field's format is as follows:
2393 Description: <single line synopsis>
2394 <extended description over several lines>
2398 The description is intended to describe the program to a user
2399 who has never met it before so that they know whether they
2400 want to install it. It should also give information about the
2401 significant dependencies and conflicts between this package
2402 and others, so that the user knows why these dependencies and
2403 conflicts have been declared.
2407 Put important information first, both in the synopsis and
2408 extended description. Sometimes only the first part of the
2409 synopsis or of the description will be displayed. You can
2410 assume that there will usually be a way to see the whole
2411 extended description.
2414 <sect1 id="synopsis"><heading>The single line synopsis</heading>
2417 The single line synopsis should be kept brief - certainly
2418 under 80 characters.
2422 Do not include the package name in the synopsis line. The
2423 display software knows how to display this already, and you
2424 do not need to state it. Remember that in many situations
2425 the user may only see the synopsis line - make it as
2426 informative as you can.
2431 <sect1 id="extendeddesc"><heading>The extended description</heading>
2434 Do not try to continue the single line synopsis into the
2435 extended description. This will not work correctly when
2436 the full description is displayed, and makes no sense
2437 where only the summary (the single line synopsis) is
2442 The extended description should describe what the package
2443 does and how it relates to the rest of the system (in terms
2444 of, for example, which subsystem it is which part of).
2448 The description field needs to make sense to anyone, even
2449 people who have no idea about any of the things the
2450 package deals with.<footnote>
2451 The blurb that comes with a program in its
2452 announcements and/or <prgn>README</prgn> files is
2453 rarely suitable for use in a description. It is
2454 usually aimed at people who are already in the
2455 community where the package is used.
2460 The lines in the extended description can have these formats:
2466 Those starting with a single space are part of a paragraph.
2467 Successive lines of this form will be word-wrapped when
2468 displayed. The leading space will usually be stripped off.
2472 Those starting with two or more spaces. These will be
2473 displayed verbatim. If the display cannot be panned
2474 horizontally, the displaying program will linewrap them "hard"
2475 (i.e., without taking account of word breaks). If it can they
2476 will be allowed to trail off to the right. None, one or two
2477 initial spaces may be deleted, but the number of spaces
2478 deleted from each line will be the same (so that you can have
2479 indenting work correctly, for example).
2483 Those containing a single space followed by a single full stop
2484 character. These are rendered as blank lines. This is the
2485 <em>only</em> way to get a blank line<footnote>
2486 Completely empty lines will not be rendered as blank lines.
2487 Instead, they will cause the parser to think you're starting
2488 a whole new record in the control file, and will therefore
2489 likely abort with an error.
2494 Those containing a space, a full stop and some more characters.
2495 These are for future expansion. Do not use them.
2501 Do not use tab characters. Their effect is not predictable.
2511 <chapt id="maintainerscripts"><heading>Package maintainer scripts
2512 and installation procedure
2515 <sect><heading>Introduction to package maintainer scripts
2519 It is possible to supply scripts as part of a package which
2520 the package management system will run for you when your
2521 package is installed, upgraded or removed.
2525 These scripts are the files <prgn>preinst</prgn>,
2526 <prgn>postinst</prgn>, <prgn>prerm</prgn> and <prgn>postrm</prgn> in the
2527 control area of the package. They must be proper executable
2528 files; if they are scripts (which is recommended), they must
2529 start with the usual <tt>#!</tt> convention. They should be
2530 readable and executable by anyone, and not world-writable.
2534 The package management system looks at the exit status from
2535 these scripts. It is important that they exit with a
2536 non-zero status if there is an error, so that the package
2537 management system can stop its processing. For shell
2538 scripts this means that you <em>almost always</em> need to
2539 use <tt>set -e</tt> (this is usually true when writing shell
2540 scripts, in fact). It is also important, of course, that
2541 they don't exit with a non-zero status if everything went
2546 When a package is upgraded a combination of the scripts from
2547 the old and new packages is called during the upgrade
2548 procedure. If your scripts are going to be at all
2549 complicated you need to be aware of this, and may need to
2550 check the arguments to your scripts.
2554 Broadly speaking the <prgn>preinst</prgn> is called before
2555 (a particular version of) a package is installed, and the
2556 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
2557 before (a version of) a package is removed and the
2558 <prgn>postrm</prgn> afterwards.
2562 Programs called from maintainer scripts should not normally
2563 have a path prepended to them. Before installation is
2564 started, the package management system checks to see if the
2565 programs <prgn>ldconfig</prgn>,
2566 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
2567 and <prgn>update-rc.d</prgn> can be found via the
2568 <tt>PATH</tt> environment variable. Those programs, and any
2569 other program that one would expect to be on the
2570 <tt>PATH</tt>, should thus be invoked without an absolute
2571 pathname. Maintainer scripts should also not reset the
2572 <tt>PATH</tt>, though they might choose to modify it by
2573 prepending or appending package-specific directories. These
2574 considerations really apply to all shell scripts.</p>
2578 <heading>Maintainer scripts Idempotency</heading>
2581 It is necessary for the error recovery procedures that the
2582 scripts be idempotent. This means that if it is run
2583 successfully, and then it is called again, it doesn't bomb
2584 out or cause any harm, but just ensures that everything is
2585 the way it ought to be. If the first call failed, or
2586 aborted half way through for some reason, the second call
2587 should merely do the things that were left undone the first
2588 time, if any, and exit with a success status if everything
2591 This is so that if an error occurs, the user interrupts
2592 <prgn>dpkg</prgn> or some other unforeseen circumstance
2593 happens you don't leave the user with a badly-broken
2594 package when <prgn>dpkg</prgn> attempts to repeat the
2602 <heading>Controlling terminal for maintainer scripts</heading>
2605 The maintainer scripts are guaranteed to run with a
2606 controlling terminal and can interact with the user.
2607 If they need to prompt for passwords, do full-screen
2608 interaction or something similar you should do these
2609 things to and from <file>/dev/tty</file>, since
2610 <prgn>dpkg</prgn> will at some point redirect scripts'
2611 standard input and output so that it can log the
2612 installation process. Likewise, because these scripts
2613 may be executed with standard output redirected into a
2614 pipe for logging purposes, Perl scripts should set
2615 unbuffered output by setting <tt>$|=1</tt> so that the
2616 output is printed immediately rather than being
2621 Each script should return a zero exit status for
2622 success, or a nonzero one for failure.
2626 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
2631 <list compact="compact">
2633 <p><var>new-preinst</var> <tt>install</tt></p>
2636 <p><var>new-preinst</var> <tt>install</tt>
2637 <var>old-version</var></p>
2640 <p><var>new-preinst</var> <tt>upgrade</tt>
2641 <var>old-version</var></p>
2644 <p><var>old-preinst</var> <tt>abort-upgrade</tt>
2645 <var>new-version</var>
2651 <list compact="compact">
2653 <p><var>postinst</var> <tt>configure</tt>
2654 <var>most-recently-configured-version</var></p>
2657 <p><var>old-postinst</var> <tt>abort-upgrade</tt>
2658 <var>new-version</var></p>
2661 <p><var>conflictor's-postinst</var> <tt>abort-remove</tt>
2662 <tt>in-favour</tt> <var>package</var>
2663 <var>new-version</var></p>
2667 <var>deconfigured's-postinst</var>
2668 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
2669 <var>failed-install-package</var> <var>version</var>
2670 <tt>removing</tt> <var>conflicting-package</var>
2677 <list compact="compact">
2679 <p><var>prerm</var> <tt>remove</tt></p>
2682 <p><var>old-prerm</var> <tt>upgrade</tt>
2683 <var>new-version</var></p>
2686 <p><var>new-prerm</var> <tt>failed-upgrade</tt>
2687 <var>old-version</var></p>
2690 <p><var>conflictor's-prerm</var> <tt>remove</tt>
2691 <tt>in-favour</tt> <var>package</var>
2692 <var>new-version</var></p>
2696 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
2697 <tt>in-favour</tt> <var>package-being-installed</var>
2698 <var>version</var> <tt>removing</tt>
2699 <var>conflicting-package</var>
2706 <list compact="compact">
2708 <p><var>postrm</var> <tt>remove</tt></p>
2711 <p><var>postrm</var> <tt>purge</tt></p>
2715 <var>old-postrm</var> <tt>upgrade</tt>
2716 <var>new-version</var></p>
2719 <p><var>new-postrm</var> <tt>failed-upgrade</tt>
2720 <var>old-version</var></p>
2723 <p><var>new-postrm</var> <tt>abort-install</tt></p>
2726 <p><var>new-postrm</var> <tt>abort-install</tt>
2727 <var>old-version</var></p>
2730 <p><var>new-postrm</var> <tt>abort-upgrade</tt>
2731 <var>old-version</var></p>
2735 <var>disappearer's-postrm</var> <tt>disappear</tt>
2736 <var>overwriter</var>
2737 <var>overwriter-version</var></p></item>
2742 <sect id="unpackphase"><heading>Details of unpack phase of
2743 installation or upgrade
2747 The procedure on installation/upgrade/overwrite/disappear
2748 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
2749 stage of <tt>dpkg --install</tt>) is as follows. In each
2750 case, if a major error occurs (unless listed below) the
2751 actions are, in general, run backwards - this means that the
2752 maintainer scripts are run with different arguments in
2753 reverse order. These are the "error unwind" calls listed
2761 <p>If a version of the package is already
2763 <example compact="compact">
2764 <var>old-prerm</var> upgrade <var>new-version</var>
2769 If the script runs but exits with a non-zero
2770 exit status, <prgn>dpkg</prgn> will attempt:
2771 <example compact="compact">
2772 <var>new-prerm</var> failed-upgrade <var>old-version</var>
2774 Error unwind, for both the above cases:
2775 <example compact="compact">
2776 <var>old-postinst</var> abort-upgrade <var>new-version</var>
2784 <p>If a "conflicting" package is being removed at the same time:
2788 If any packages depended on that conflicting
2789 package and <tt>--auto-deconfigure</tt> is
2790 specified, call, for each such package:
2791 <example compact="compact">
2792 <var>deconfigured's-prerm</var> deconfigure \
2793 in-favour <var>package-being-installed</var> <var>version</var> \
2794 removing <var>conflicting-package</var> <var>version</var>
2797 <example compact="compact">
2798 <var>deconfigured's-postinst</var> abort-deconfigure \
2799 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
2800 removing <var>conflicting-package</var> <var>version</var>
2802 The deconfigured packages are marked as
2803 requiring configuration, so that if
2804 <tt>--install</tt> is used they will be
2805 configured again if possible.</p>
2808 <p>To prepare for removal of the conflicting package, call:
2809 <example compact="compact">
2810 <var>conflictor's-prerm</var> remove \
2811 in-favour <var>package</var> <var>new-version</var>
2814 <example compact="compact">
2815 <var>conflictor's-postinst</var> abort-remove \
2816 in-favour <var>package</var> <var>new-version</var>
2827 <p>If the package is being upgraded, call:
2828 <example compact="compact">
2829 <var>new-preinst</var> upgrade <var>old-version</var>
2834 Otherwise, if the package had some configuration
2835 files from a previous version installed (i.e., it
2836 is in the "configuration files only" state):
2837 <example compact="compact">
2838 <var>new-preinst</var> install <var>old-version</var>
2842 <p>Otherwise (i.e., the package was completely purged):
2843 <example compact="compact">
2844 <var>new-preinst</var> install
2846 Error unwind actions, respectively:
2847 <example compact="compact">
2848 <var>new-postrm</var> abort-upgrade <var>old-version</var>
2849 <var>new-postrm</var> abort-install <var>old-version</var>
2850 <var>new-postrm</var> abort-install
2859 The new package's files are unpacked, overwriting any
2860 that may be on the system already, for example any
2861 from the old version of the same package or from
2862 another package. Backups of the old files are kept
2863 temporarily, and if anything goes wrong the package
2864 management system will attempt to put them back as
2865 part of the error unwind.
2869 It is an error for a package to contains files which
2870 are on the system in another package, unless
2871 <tt>Replaces</tt> is used (see <ref id="replaces">).
2873 The following paragraph is not currently the case:
2874 Currently the <tt>- - force-overwrite</tt> flag is
2875 enabled, downgrading it to a warning, but this may not
2881 It is a more serious error for a package to contain a
2882 plain file or other kind of non-directory where another
2883 package has a directory (again, unless
2884 <tt>Replaces</tt> is used). This error can be
2885 overridden if desired using
2886 <tt>--force-overwrite-dir</tt>, but this is not
2891 Packages which overwrite each other's files produce
2892 behavior which, though deterministic, is hard for the
2893 system administrator to understand. It can easily
2894 lead to "missing" programs if, for example, a package
2895 is installed which overwrites a file from another
2896 package, and is then removed again.<footnote>
2898 Part of the problem is due to what is arguably a
2899 bug in <prgn>dpkg</prgn>.
2905 A directory will never be replaced by a symbolic link
2906 to a directory or vice versa; instead, the existing
2907 state (symlink or not) will be left alone and
2908 <prgn>dpkg</prgn> will follow the symlink if there is
2916 <p>If the package is being upgraded, call
2917 <example compact="compact">
2918 <var>old-postrm</var> upgrade <var>new-version</var>
2923 <p>If this fails, <prgn>dpkg</prgn> will attempt:
2924 <example compact="compact">
2925 <var>new-postrm</var> failed-upgrade <var>old-version</var>
2927 Error unwind, for both cases:
2928 <example compact="compact">
2929 <var>old-preinst</var> abort-upgrade <var>new-version</var>
2936 This is the point of no return - if
2937 <prgn>dpkg</prgn> gets this far, it won't back off
2938 past this point if an error occurs. This will
2939 leave the package in a fairly bad state, which
2940 will require a successful re-installation to clear
2941 up, but it's when <prgn>dpkg</prgn> starts doing
2942 things that are irreversible.
2947 Any files which were in the old version of the package
2948 but not in the new are removed.</p>
2951 <p>The new file list replaces the old.</p>
2954 <p>The new maintainer scripts replace the old.</p>
2958 <p>Any packages all of whose files have been overwritten during the
2959 installation, and which aren't required for
2960 dependencies, are considered to have been removed.
2961 For each such package
2964 <p><prgn>dpkg</prgn> calls:
2965 <example compact="compact">
2966 <var>disappearer's-postrm</var> disappear \
2967 <var>overwriter</var> <var>overwriter-version</var>
2972 <p>The package's maintainer scripts are removed.
2977 It is noted in the status database as being in a
2978 sane state, namely not installed (any conffiles
2979 it may have are ignored, rather than being
2980 removed by <prgn>dpkg</prgn>). Note that
2981 disappearing packages do not have their prerm
2982 called, because <prgn>dpkg</prgn> doesn't know
2983 in advance that the package is going to
2992 Any files in the package we're unpacking that are also
2993 listed in the file lists of other packages are removed
2994 from those lists. (This will lobotomize the file list
2995 of the "conflicting" package if there is one.)
3000 The backup files made during installation, above, are
3007 The new package's status is now sane, and recorded as
3012 Here is another point of no return - if the
3013 conflicting package's removal fails we do not unwind
3014 the rest of the installation; the conflicting package
3015 is left in a half-removed limbo.
3021 If there was a conflicting package we go and do the
3022 removal actions (described below), starting with the
3023 removal of the conflicting package's files (any that
3024 are also in the package being installed have already
3025 been removed from the conflicting package's file list,
3026 and so do not get removed now).
3033 <sect id="configdetails"><heading>Details of configuration</heading>
3036 When we configure a package (this happens with <tt>dpkg
3037 --install</tt> and <tt>dpkg --configure</tt>), we first
3038 update any <tt>conffile</tt>s and then call:
3039 <example compact="compact">
3040 <var>postinst</var> configure <var>most-recently-configured-version</var>
3045 No attempt is made to unwind after errors during
3050 If there is no most recently configured version
3051 <prgn>dpkg</prgn> will pass a null argument; older versions
3052 of dpkg may pass <tt><unknown></tt> (including the
3053 angle brackets) in this case. Even older ones do not pass a
3054 second argument at all, under any circumstances.
3058 <sect id="removedetails"><heading>Details of removal and/or
3059 configuration purging</heading>
3065 <example compact="compact">
3066 <var>prerm</var> remove
3072 The package's files are removed (except <tt>conffile</tt>s).
3077 <example compact="compact">
3078 <var>postrm</var> remove
3084 All the maintainer scripts except the <prgn>postrm</prgn>
3089 If we aren't purging the package we stop here. Note
3090 that packages which have no <prgn>postrm</prgn> and no
3091 <tt>conffile</tt>s are automatically purged when
3092 removed, as there is no difference except for the
3093 <prgn>dpkg</prgn> status.</p>
3097 The <tt>conffile</tt>s and any backup files
3098 (<tt>~</tt>-files, <tt>#*#</tt> files,
3099 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3104 <example compact="compact">
3105 <var>postrm</var> purge
3110 <p>The package's file list is removed.</p>
3113 No attempt is made to unwind after errors during
3120 <chapt id="relationships"><heading>Declaring relationships between
3123 <sect id="depsyntax"><heading>Syntax of relationship fields
3127 These fields all have a uniform syntax. They are a list of
3128 package names separated by commas.
3132 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3133 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3134 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3135 control file fields of the package, which declare
3136 dependencies on other packages, the package names listed may
3137 also include lists of alternative package names, separated
3138 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3139 if any one of the alternative packages is installed, that
3140 part of the dependency is considered to be satisfied.
3144 All of the fields except for <tt>Provides</tt> may restrict
3145 their applicability to particular versions of each named
3146 package. This is done in parentheses after each individual
3147 package name; the parentheses should contain a relation from
3148 the list below followed by a version number, in the format
3149 described in <ref id="versions">.
3153 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3154 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3155 strictly earlier, earlier or equal, exactly equal, later or
3156 equal and strictly later, respectively. The deprecated
3157 forms <tt><</tt> and <tt>></tt> were used to mean
3158 earlier/later or equal, rather than strictly earlier/later,
3159 so they should not appear in new packages (though
3160 <prgn>dpkg</prgn> still supports them).
3164 Whitespace may appear at any point in the version
3165 specification subject to the rules in <ref
3166 id="controlsyntax">, and must appear where it's necessary to
3167 disambiguate; it is not otherwise significant. For
3168 consistency and in case of future changes to
3169 <prgn>dpkg</prgn> it is recommended that a single space be
3170 used after a version relationship and before a version
3171 number; it is also conventional to put a single space after
3172 each comma, on either side of each vertical bar, and before
3173 each open parenthesis.
3177 For example, a list of dependencies might appear as:
3178 <example compact="compact">
3181 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3186 All fields that specify build-time relationships
3187 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3188 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3189 may be restricted to a certain set of architectures. This
3190 is indicated in brackets after each individual package name and
3191 the optional version specification. The brackets enclose a
3192 list of Debian architecture names separated by whitespace.
3193 Exclamation marks may be prepended to each of the names.
3194 (It is not permitted for some names to be prepended with
3195 exclamation marks and others not.) If the current Debian
3196 host architecture is not in this list and there are no
3197 exclamation marks in the list, or it is in the list with a
3198 prepended exclamation mark, the package name and the
3199 associated version specification are ignored completely for
3200 the purposes of defining the relationships.
3205 <example compact="compact">
3207 Build-Depends-Indep: texinfo
3208 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3209 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3214 Note that the binary package relationship fields such as
3215 <tt>Depends</tt> appear in one of the binary package
3216 sections of the control file, whereas the build-time
3217 relationships such as <tt>Build-Depends</tt> appear in the
3218 source package section of the control file (which is the
3224 <heading>Binary Dependencies - <tt>Depends</tt>,
3225 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3226 <tt>Pre-Depends</tt>
3230 Packages can declare in their control file that they have
3231 certain relationships to other packages - for example, that
3232 they may not be installed at the same time as certain other
3233 packages, and/or that they depend on the presence of others.
3237 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3238 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3239 <tt>Conflicts</tt> control file fields.
3243 These five fields are used to declare a dependency
3244 relationship by one package on another. Except for
3245 <tt>Enhances</tt>, they appear in the depending (binary)
3246 package's control file. (<tt>Enhances</tt> appears in the
3247 recommending package's control file.)
3251 A <tt>Depends</tt> field takes effect <em>only</em> when a
3252 package is to be configured. It does not prevent a package
3253 being on the system in an unconfigured state while its
3254 dependencies are unsatisfied, and it is possible to replace
3255 a package whose dependencies are satisfied and which is
3256 properly installed with a different version whose
3257 dependencies are not and cannot be satisfied; when this is
3258 done the depending package will be left unconfigured (since
3259 attempts to configure it will give errors) and will not
3260 function properly. If it is necessary, a
3261 <tt>Pre-Depends</tt> field can be used, which has a partial
3262 effect even when a package is being unpacked, as explained
3263 in detail below. (The other three dependency fields,
3264 <tt>Recommends</tt>, <tt>Suggests</tt> and
3265 <tt>Enhances</tt>, are only used by the various front-ends
3266 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3270 For this reason packages in an installation run are usually
3271 all unpacked first and all configured later; this gives
3272 later versions of packages with dependencies on later
3273 versions of other packages the opportunity to have their
3274 dependencies satisfied.
3278 The <tt>Depends</tt> field thus allows package maintainers
3279 to impose an order in which packages should be configured.
3283 The meaning of the five dependency fields is as follows:
3285 <tag><tt>Depends</tt></tag>
3288 This declares an absolute dependency. A package will
3289 not be configured unless all of the packages listed in
3290 its <tt>Depends</tt> field have been correctly
3295 The <tt>Depends</tt> field should be used if the
3296 depended-on package is required for the depending
3297 package to provide a significant amount of
3301 The <tt>Depends</tt> field should also be used if the
3302 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
3303 <prgn>postrm</prgn> scripts require the package to be
3304 present in order to run. Note, however, that the
3305 <prgn>postrm</prgn> cannot rely on any non-essential
3306 packages to be present during the <tt>purge</tt>
3310 <tag><tt>Recommends</tt></tag>
3312 <p>This declares a strong, but not absolute, dependency.
3316 The <tt>Recommends</tt> field should list packages
3317 that would be found together with this one in all but
3318 unusual installations.</p>
3321 <tag><tt>Suggests</tt></tag>
3324 This is used to declare that one package may be more
3325 useful with one or more others. Using this field
3326 tells the packaging system and the user that the
3327 listed packages are related to this one and can
3328 perhaps enhance its usefulness, but that installing
3329 this one without them is perfectly reasonable.
3333 <tag><tt>Enhances</tt></tag>
3336 This field is similar to Suggests but works in the
3337 opposite direction. It is used to declare that a
3338 package can enhance the functionality of another
3343 <tag><tt>Pre-Depends</tt></tag>
3346 This field is like <tt>Depends</tt>, except that it
3347 also forces <prgn>dpkg</prgn> to complete installation
3348 of the packages named before even starting the
3349 installation of the package which declares the
3350 pre-dependency, as follows:
3354 When a package declaring a pre-dependency is about to
3355 be <em>unpacked</em> the pre-dependency can be
3356 satisfied if the depended-on package is either fully
3357 configured, <em>or even if</em> the depended-on
3358 package(s) are only unpacked or half-configured,
3359 provided that they have been configured correctly at
3360 some point in the past (and not removed or partially
3361 removed since). In this case, both the
3362 previously-configured and currently unpacked or
3363 half-configured versions must satisfy any version
3364 clause in the <tt>Pre-Depends</tt> field.
3368 When the package declaring a pre-dependency is about
3369 to be <em>configured</em>, the pre-dependency will be
3370 treated as a normal <tt>Depends</tt>, that is, it will
3371 be considered satisfied only if the depended-on
3372 package has been correctly configured.
3376 <tt>Pre-Depends</tt> should be used sparingly,
3377 preferably only by packages whose premature upgrade or
3378 installation would hamper the ability of the system to
3379 continue with any upgrade that might be in progress.
3383 <tt>Pre-Depends</tt> are also required if the
3384 <prgn>preinst</prgn> script depends on the named
3385 package. It is best to avoid this situation if
3391 When selecting which level of dependency to use you should
3392 consider how important the depended-on package is to the
3393 functionality of the one declaring the dependency. Some
3394 packages are composed of components of varying degrees of
3395 importance. Such a package should list using
3396 <tt>Depends</tt> the package(s) which are required by the
3397 more important components. The other components'
3398 requirements may be mentioned as Suggestions or
3399 Recommendations, as appropriate to the components' relative
3404 <sect id="conflicts"><heading>Conflicting binary packages -
3405 <tt>Conflicts</tt></heading>
3408 When one binary package declares a conflict with another
3409 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
3410 refuse to allow them to be installed on the system at the
3415 If one package is to be installed, the other must be removed
3416 first - if the package being installed is marked as
3417 replacing (see <ref id="replaces">) the one on the system,
3418 or the one on the system is marked as deselected, or both
3419 packages are marked <tt>Essential</tt>, then
3420 <prgn>dpkg</prgn> will automatically remove the package
3421 which is causing the conflict, otherwise it will halt the
3422 installation of the new package with an error. This
3423 mechanism is specifically designed to produce an error when
3424 the installed package is <tt>Essential</tt>, but the new
3429 A package will not cause a conflict merely because its
3430 configuration files are still installed; it must be at least
3435 A special exception is made for packages which declare a
3436 conflict with their own package name, or with a virtual
3437 package which they provide (see below): this does not
3438 prevent their installation, and allows a package to conflict
3439 with others providing a replacement for it. You use this
3440 feature when you want the package in question to be the only
3441 package providing some feature.
3445 A <tt>Conflicts</tt> entry should almost never have an
3446 "earlier than" version clause. This would prevent
3447 <prgn>dpkg</prgn> from upgrading or installing the package
3448 which declared such a conflict until the upgrade or removal
3449 of the conflicted-with package had been completed.
3453 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
3457 As well as the names of actual ("concrete") packages, the
3458 package relationship fields <tt>Depends</tt>,
3459 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3460 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
3461 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3462 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
3463 may mention "virtual packages".
3467 A <em>virtual package</em> is one which appears in the
3468 <tt>Provides</tt> control file field of another package.
3469 The effect is as if the package(s) which provide a
3470 particular virtual package name had been listed by name
3471 everywhere the virtual package name appears. (See also <ref
3472 id="virtual_pkg_sect">)
3476 If there are both concrete and virtual packages of the same
3477 name, then the dependency may be satisfied (or the conflict
3478 caused) by either the concrete package with the name in
3479 question or any other concrete package which provides the
3480 virtual package with the name in question. This is so that,
3481 for example, supposing we have
3482 <example compact="compact">
3486 and someone else releases an enhanced version of the
3487 <tt>bar</tt> package (for example, a non-US variant), they
3489 <example compact="compact">
3493 and the <tt>bar-plus</tt> package will now also satisfy the
3494 dependency for the <tt>foo</tt> package.
3498 If a dependency or a conflict has a version number attached
3499 then only real packages will be considered to see whether
3500 the relationship is satisfied (or the prohibition violated,
3501 for a conflict) - it is assumed that a real package which
3502 provides the virtual package is not of the "right" version.
3503 So, a <tt>Provides</tt> field may not contain version
3504 numbers, and the version number of the concrete package
3505 which provides a particular virtual package will not be
3506 looked at when considering a dependency on or conflict with
3507 the virtual package name.
3511 It is likely that the ability will be added in a future
3512 release of <prgn>dpkg</prgn> to specify a version number for
3513 each virtual package it provides. This feature is not yet
3514 present, however, and is expected to be used only
3519 If you want to specify which of a set of real packages
3520 should be the default to satisfy a particular dependency on
3521 a virtual package, you should list the real package as an
3522 alternative before the virtual one.
3527 <sect id="replaces"><heading>Overwriting files and replacing
3528 packages - <tt>Replaces</tt></heading>
3531 Packages can declare in their control file that they should
3532 overwrite files in certain other packages, or completely
3533 replace other packages. The <tt>Replaces</tt> control file
3534 field has these two distinct purposes.
3537 <sect1><heading>Overwriting files in other packages</heading>
3540 Firstly, as mentioned before, it is usually an error for a
3541 package to contain files which are on the system in
3546 However, if the overwriting package declares that it
3547 <tt>Replaces</tt> the one containing the file being
3548 overwritten, then <prgn>dpkg</prgn> will replace the file
3549 from the old package with that from the new. The file
3550 will no longer be listed as "owned" by the old package.
3554 If a package is completely replaced in this way, so that
3555 <prgn>dpkg</prgn> does not know of any files it still
3556 contains, it is considered to have "disappeared". It will
3557 be marked as not wanted on the system (selected for
3558 removal) and not installed. Any <tt>conffile</tt>s
3559 details noted for the package will be ignored, as they
3560 will have been taken over by the overwriting package. The
3561 package's <prgn>postrm</prgn> script will be run with a
3562 special argument to allow the package to do any final
3563 cleanup required. See <ref id="mscriptsinstact">.
3567 If an installed package, <tt>foo</tt> say, declares that
3568 it replaces another, <tt>bar</tt>, and an attempt is made
3569 to install <tt>bar</tt>, <prgn>dpkg</prgn> will discard
3570 files in the <tt>bar</tt> package which would overwrite
3571 those already present in <tt>foo</tt>. This is so that
3572 you can install an older version of a package without
3577 For this usage of <tt>Replaces</tt>, virtual packages (see
3578 <ref id="virtual">) are not considered when looking at a
3579 <tt>Replaces</tt> field - the packages declared as being
3580 replaced must be mentioned by their real names.
3584 Furthermore, this usage of <tt>Replaces</tt> only takes
3585 effect when both packages are at least partially on the
3586 system at once, so that it can only happen if they do not
3587 conflict or if the conflict has been overridden.
3592 <sect1><heading>Replacing whole packages, forcing their
3596 Secondly, <tt>Replaces</tt> allows the packaging system to
3597 resolve which package should be removed when there is a
3598 conflict - see <ref id="conflicts">. This usage only
3599 takes effect when the two packages <em>do</em> conflict,
3600 so that the two usages of this field do not interfere with
3605 In this situation, the package declared as being replaced
3606 can be a virtual package, so for example, all mail
3607 transport agents (MTAs) would have the following fields in
3608 their control files:
3609 <example compact="compact">
3610 Provides: mail-transport-agent
3611 Conflicts: mail-transport-agent
3612 Replaces: mail-transport-agent
3614 ensuring that only one MTA can be installed at any one
3619 <sect><heading>Relationships between source and binary packages -
3620 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3621 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
3625 Source packages that require certain binary packages to be
3626 installed or absent at the time of building the package
3627 can declare relationships to those binary packages.
3631 This is done using the <tt>Build-Depends</tt>,
3632 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
3633 <tt>Build-Conflicts-Indep</tt> control file fields.
3637 Build-dependencies on "build-essential" binary packages can be
3638 omitted. Please see <ref id="pkg-relations"> for more information.
3642 The dependencies and conflicts they define must be satisfied
3643 (as defined earlier for binary packages) in order to invoke
3644 the targets in <tt>debian/rules</tt>, as follows:<footnote>
3646 If you make "build-arch" or "binary-arch", you need
3647 Build-Depends. If you make "build-indep" or
3648 "binary-indep", you need Build-Depends and
3649 Build-Depends-Indep. If you make "build" or "binary",
3653 There is no Build-Depends-Arch; the autobuilders will
3654 only need the Build-Depends if they know how to build
3655 only build-arch and binary-arch. Anyone building the
3656 build-indep/binary-indep targets is basically assumed to
3657 be building the whole package and so installs all build
3661 The purpose of the original split, I recall, was so that
3662 the autobuilders wouldn't need to install extra packages
3663 needed only for the binary-indep targets. But without a
3664 build-arch/build-indep split, this didn't work, since
3665 most of the work is done in the build target, not in the
3671 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
3674 The <tt>Build-Depends</tt> and
3675 <tt>Build-Conflicts</tt> fields must be satisfied when
3676 any of the following targets is invoked:
3677 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
3678 <tt>binary-arch</tt>, <tt>build-arch</tt>,
3679 <tt>build-indep</tt> and <tt>binary-indep</tt>.
3682 <tag><tt>Build-Depends-Indep</tt>,
3683 <tt>Build-Conflicts-Indep</tt></tag>
3686 The <tt>Build-Depends-Indep</tt> and
3687 <tt>Build-Conflicts-Indep</tt> fields must be
3688 satisfied when any of the following targets is
3689 invoked: <tt>build</tt>, <tt>clean</tt>,
3690 <tt>build-indep</tt>, <tt>binary</tt> and
3691 <tt>binary-indep</tt>.
3702 <chapt id="conffiles"><heading>Configuration file handling
3706 This chapter has been superseded by <ref id="config-files">.
3710 <chapt id="sharedlibs"><heading>Shared libraries</heading>
3713 Packages containing shared libraries must be constructed with
3714 a little care to make sure that the shared library is always
3715 available. This is especially important for packages whose
3716 shared libraries are vitally important, such as the C library
3717 (currently <tt>libc6</tt>).
3721 Firstly, the package should install the shared libraries under
3722 their normal names. For example, the <tt>libgdbmg1</tt>
3723 package should install <tt>libgdbm.so.1.7.3</tt> as
3724 <file>/usr/lib/libgdbm.so.1.7.3</file>. The files should not be
3725 renamed or re-linked by any <prgn>prerm</prgn> or
3726 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
3727 of renaming things safely without affecting running programs,
3728 and attempts to interfere with this are likely to lead to
3733 Secondly, the package should include the symbolic link that
3734 <prgn>ldconfig</prgn> would create for the shared libraries.
3735 For example, the <prgn>libgdbmg1</prgn> package should include
3736 a symbolic link from <file>/usr/lib/libgdbm.so.1</file> to
3737 <file>libgdbm.so.1.7.3</file>. This is needed so that the dynamic
3738 linker (for example <prgn>ld.so</prgn> or
3739 <prgn>ld-linux.so.*</prgn>) can find the library between the
3740 time that <prgn>dpkg</prgn> installs it and the time that
3741 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
3744 The package management system requires the library to be
3745 placed before the symbolic link pointing to it in the
3746 <file>.deb</file> file. This is so that when
3747 <prgn>dpkg</prgn> comes to install the symlink
3748 (overwriting the previous symlink pointing at an older
3749 version of the library), the new shared library is already
3750 in place. In the past, this was achieved by creating the
3751 library in the temporary packaging directory before
3752 creating the symlink. Unfortunately, this was not always
3753 effective, since the building of the tar file in the
3754 <file>.deb</file> depended on the behavior of the underlying
3755 file system. Some file systems (such as reiserfs) reorder
3756 the files so that the order of creation is forgotten.
3757 Starting with release <tt>1.7.0</tt>, <prgn>dpkg</prgn>
3758 will reorder the files itself as necessary when building a
3759 package. Thus it is no longer important to concern
3760 oneself with the order of file creation.
3766 Thirdly, the associated development package should contain a
3767 symlink for the shared library without a version number. For
3768 example, the <tt>libgdbmg1-dev</tt> package should include a
3769 symlink from <tt>/usr/lib/libgdbm.so</tt> to
3770 <file>libgdbm.so.1.7.3</file>. This symlink is needed by the
3771 linker (<prgn>ld</prgn>) when compiling packages, as it will
3772 only look for <file>libgdbm.so</file> when compiling dynamically.
3776 Any package installing shared libraries in one of the default
3777 library directories of the dynamic linker (which are currently
3778 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
3779 listed in <file>/etc/ld.so.conf</file><footnote>
3782 <list compact="compact">
3783 <item><p>/usr/X11R6/lib/Xaw3d</p></item>
3784 <item><p>/usr/local/lib</p></item>
3785 <item><p>/usr/lib/libc5-compat</p></item>
3786 <item><p>/lib/libc5-compat</p></item>
3787 <item><p>/usr/X11R6/lib</p></item>
3791 must use <prgn>ldconfig</prgn> to update the shared library
3792 system. The package must call <prgn>ldconfig</prgn> in the
3793 <prgn>postinst</prgn> script if the first argument is
3794 <tt>configure</tt>; the <prgn>postinst</prgn> script may
3795 optionally invoke <prgn>ldconfig</prgn> at other times. The
3796 package should call <prgn>ldconfig</prgn> in the
3797 <prgn>postrm</prgn> script if the first argument is
3798 <tt>remove</tt>. The maintainer scripts must not invoke
3799 <prgn>ldconfig</prgn> under any circumstances other than those
3800 described in this paragraph.<footnote>
3801 <p>During install or upgrade, the preinst is called before
3802 the new files are installed, so calling "ldconfig" is
3803 pointless. The preinst of an existing package can also be
3804 called if an upgrade fails. However, this happens during
3805 the critical time when a shared libs may exist on-disk
3806 under a temporary name. Thus, it is dangerous and
3807 forbidden by current policy to call "ldconfig" at this
3810 <p>When a package is installed or upgraded, "postinst
3811 configure" runs after the new files are safely on-disk.
3812 Since it is perfectly safe to invoke ldconfig
3813 unconditionally in a postinst, it is OK for a package to
3814 simply put ldconfig in its postinst without checking the
3815 argument. The postinst can also be called to recover from
3816 a failed upgrade. This happens before any new files are
3817 unpacked, so there is no reason to call "ldconfig" at this
3820 <p>For a package that is being removed, prerm is
3821 called with all the files intact, so calling ldconfig is
3822 useless. The other calls to "prerm" happen in the case of
3823 upgrade at a time when all the files of the old package
3824 are on-disk, so again calling "ldconfig" is pointless.
3826 <p>postrm, on the other hand, is called with the "remove"
3827 argument just after the files are removed, so this is the
3828 proper time to call "ldconfig" to notify the system of the
3829 fact shared libraries from the package are removed.
3830 The postrm can be called at several other times. At the
3831 time of "postrm purge", "postrm abort-install", or "postrm
3832 abort-upgrade", calling "ldconfig" is useless because the
3833 shared lib files are not on-disk. However, when "postrm"
3834 is invoked with arguments "upgrade", "failed-upgrade", or
3835 "disappear", a shared lib may exist on-disk under a
3842 <heading>Handling shared library dependencies - the
3843 <tt>shlibs</tt> system</heading>
3846 If a package contains a binary or library which links to a
3847 shared library, we must ensure that when the package is
3848 installed on the system, all of the libraries needed are
3849 also installed. This requirement led to the creation of the
3850 <tt>shlibs</tt> system, which is very simple in its design:
3851 any package which <em>provides</em> a shared library also
3852 provides information on the package dependencies required to
3853 ensure the presence of this library, and any package which
3854 <em>uses</em> a shared library uses this information to
3855 determine the dependencies it requires. The files which
3856 contain the mapping from shared libraries to the necessary
3857 dependency information are called <file>shlibs</file> files.
3861 Thus, when a package is built which contains any shared
3862 libraries, it must provide a <file>shlibs</file> file for other
3863 packages to use, and when a package is built which contains
3864 any shared libraries or compiled binaries, it must run
3865 <prgn>dpkg-shlibdeps</prgn> on these to determine the
3866 libraries used and hence the dependencies needed by this
3869 In the past, the shared libraries linked to were
3870 determined by calling <prgn>ldd</prgn>, but now
3871 <prgn>objdump</prgn> is used to do this. The only
3872 change this makes to package building is that
3873 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
3874 libraries, whereas in the past this was unnecessary.
3875 The rest of this footnote explains the advantage that
3880 We say that a binary <tt>foo</tt> <em>directly</em> uses
3881 a library <tt>libbar</tt> if it is explicitly linked
3882 with that library (that is, it uses the flag
3883 <tt>-lbar</tt> during the linking stage). Other
3884 libraries that are needed by <tt>libbar</tt> are linked
3885 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
3886 linker will load them automatically when it loads
3887 <tt>libbar</tt>. A package should depend on
3888 the libraries it directly uses, and the dependencies for
3889 those libraries should automatically pull in the other
3894 Unfortunately, the <prgn>ldd</prgn> program shows both
3895 the directly and indirectly used libraries, meaning that
3896 the dependencies determined included both direct and
3897 indirect dependencies. The use of <prgn>objdump</prgn>
3898 avoids this problem by determining only the directly
3903 A good example of where this helps is the following. We
3904 could update <tt>libimlib</tt> with a new version that
3905 supports a new graphics format called dgf (but retaining
3906 the same major version number). If we used the old
3907 <prgn>ldd</prgn> method, every package that uses
3908 <tt>libimlib</tt> would need to be recompiled so it
3909 would also depend on <tt>libdgf</tt> or it wouldn't run
3910 due to missing symbols. However with the new system,
3911 packages using <tt>libimlib</tt> can rely on
3912 <tt>libimlib</tt> itself having the dependency on
3913 <tt>libdgf</tt> and so they would not need rebuilding.
3919 In the following sections, we will first describe where the
3920 various <tt>shlibs</tt> files are to be found, then how to
3921 use <prgn>dpkg-shlibdeps</prgn>, and finally the
3922 <tt>shlibs</tt> file format and how to create them if your
3923 package contains a shared library.
3927 <sect><heading>The <tt>shlibs</tt> files present on the system
3931 There are several places where <tt>shlibs</tt> files are
3932 found. The following list gives them in the order in which
3933 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
3934 one which gives the required information is used.)
3940 <p><file>debian/shlibs.local</file></p>
3942 This lists overrides for this package. Its use is
3943 described below (see <ref id="shlibslocal">).
3948 <p><file>/etc/dpkg/shlibs.override</file></p>
3950 This lists global overrides. This list is normally
3951 empty. It is maintained by the local system
3957 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
3959 When packages are being built, any
3960 <file>debian/shlibs</file> files are copied into the
3961 control file area of the temporary build directory and
3962 given the name <file>shlibs</file>. These files give
3963 details of any shared libraries included in the
3966 An example may help here. Let us say that the
3967 source package <tt>foo</tt> generates two binary
3968 packages, <tt>libfoo2</tt> and
3969 <tt>foo-runtime</tt>. When building the binary
3970 packages, the two packages are created in the
3971 directories <file>debian/libfoo2</file> and
3972 <file>debian/foo-runtime</file> respectively.
3973 (<file>debian/tmp</file> could be used instead of one
3974 of these.) Since <tt>libfoo2</tt> provides the
3975 <tt>libfoo</tt> shared library, it will require a
3976 <tt>shlibs</tt> file, which will be installed in
3977 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
3979 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
3980 when <prgn>dpkg-shlibdeps</prgn> is run on the
3982 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
3984 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
3985 determine whether <tt>foo-prog</tt>'s library
3986 dependencies are satisfied by any of the libraries
3987 provided by <tt>libfoo2</tt>. For this reason,
3988 <prgn>dpkg-shlibdeps</prgn> must only be run once
3989 all of the individual binary packages'
3990 <tt>shlibs</tt> files have been installed into the
3998 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4000 These are the <file>shlibs</file> files corresponding to
4001 all of the packages installed on the system, and are
4002 maintained by the relevant package maintainers.
4007 <p><file>/etc/dpkg/shlibs.default</file></p>
4009 This file lists any shared libraries whose packages
4010 have failed to provide correct <file>shlibs</file> files.
4011 It was used when the <file>shlibs</file> setup was first
4012 introduced, but it is now normally empty. It is
4013 maintained by the <tt>dpkg</tt> maintainer.
4021 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4022 <file>shlibs</file> files</heading>
4025 Put a call to <prgn>dpkg-shlibdeps</prgn> into your
4026 <file>debian/rules</file> file. If your package contains only
4027 compiled binaries and libraries (but no scripts), you can
4028 use a command such as:
4029 <example compact="compact">
4030 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4031 debian/tmp/usr/lib/*
4033 Otherwise, you will need to explicitly list the compiled
4034 binaries and libraries.<footnote>
4036 If you are using <tt>debhelper</tt>, the
4037 <prgn>dh_shlibdeps</prgn> program will do this work for
4038 you. It will also correctly handle multi-binary
4045 This command puts the dependency information into the
4046 <file>debian/substvars</file> file, which is then used by
4047 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4048 <tt>${shlib:Depends}</tt> variable in the <tt>Depends</tt>
4049 field in the control file for this to work.
4053 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4054 done. If it does complain you might need to create your own
4055 <file>debian/shlibs.local</file> file, as explained below (see
4056 <ref id="shlibslocal">).
4060 If you have multiple binary packages, you will need to call
4061 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4062 compiled libraries or binaries. In such a case, you will
4063 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4064 utilities to specify a different <file>substvars</file> file.
4065 For more details on this and other options, see <manref
4066 name="dpkg-shlibdeps" section="1">.
4070 <sect id="shlibs"><heading>The <file>shlibs</file> File Format
4074 Each <file>shlibs</file> file has the same format. Lines
4075 beginning with <tt>#</tt> are considered to be comments and
4076 are ignored. Each line is of the form:
4077 <example compact="compact">
4078 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4083 We will explain this by reference to the example of the
4084 <tt>zlib1g</tt> package, which (at the time of writing)
4085 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4089 <var>library-name</var> is the name of the shared library,
4090 in this case <tt>libz</tt>. (This must match the name part
4091 of the soname, see below.)
4095 <var>soname-version-number</var> is the version part of the
4096 soname of the library. The soname is the thing that must
4097 exactly match for the library to be recognized by the
4098 dynamic linker, and is usually of the form
4099 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4100 example, <tt>libz.so.1</tt>.<footnote>
4102 This can be determined using the command
4103 <example compact="compact">
4104 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
4108 The version part is the part which comes after
4109 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
4113 <var>dependencies</var> has the same syntax as a dependency
4114 field in a binary package control file. It should give
4115 details of which packages are required to satisfy a binary
4116 built against the version of the library contained in the
4117 package. See <ref id="depsyntax"> for details.
4121 In our example, if the first version of the <tt>zlib1g</tt>
4122 package which contained a minor number of at least
4123 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
4124 <tt>shlibs</tt> entry for this library could say:
4125 <example compact="compact">
4126 libz 1 zlib1g (>= 1:1.1.3)
4128 The version-specific dependency is to avoid warnings from
4129 the dynamic linker about using older shared libraries with
4135 <heading>Providing a <file>shlibs</file> file</heading>
4138 If your package provides a shared library, you should create
4139 a <file>shlibs</file> file following the format described above.
4140 It is usual to call this file <file>debian/shlibs</file> (but if
4141 you have multiple binary packages, you might want to call it
4142 <file>debian/shlibs.<var>package</var></file> instead). Then
4143 let <file>debian/rules</file> install it in the control area:
4144 <example compact="compact">
4145 install -m644 debian/shlibs debian/tmp/DEBIAN
4147 or, in the case of a multi-binary package:
4148 <example compact="compact">
4149 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
4151 An alternative way of doing this is to create the
4152 <file>shlibs</file> file in the control area directly from
4153 <file>debian/rules</file> without using a <file>debian/shlibs</file>
4154 file at all,<footnote>
4156 This is what <prgn>dh_makeshlibs</prgn> in the
4157 <tt>debhelper</tt> suite does.
4160 since the <file>debian/shlibs</file> file itself is ignored by
4161 <prgn>dpkg-shlibdeps</prgn>.
4165 As <prgn>dpkg-shlibdeps</prgn> reads the
4166 <file>DEBIAN/shlibs</file> files in all of the binary packages
4167 being built from this source package, all of the
4168 <file>DEBIAN/shlibs</file> files should be installed before
4169 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
4174 <sect id="shlibslocal">
4175 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
4178 This file is intended only as a <em>temporary</em> fix if
4179 your binaries or libraries depend on a library whose package
4180 does not yet provide a correct <file>shlibs</file> file.
4184 We will assume that you are trying to package a binary
4185 <tt>foo</tt>. When you try running
4186 <prgn>dpkg-shlibdeps</prgn> you get the following error
4187 message (<tt>-O</tt> displays the dependency information on
4188 <tt>stdout</tt> instead of writing it to
4189 <tt>debian/substvars</tt>, and the lines have been wrapped
4190 for ease of reading):
4191 <example compact="compact">
4192 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
4193 dpkg-shlibdeps: warning: unable to find dependency
4194 information for shared library libbar (soname 1,
4195 path /usr/lib/libbar.so.1, dependency field Depends)
4196 shlibs:Depends=libc6 (>= 2.2.2-2)
4198 You can then run <prgn>ldd</prgn> on the binary to find the
4199 full location of the library concerned:
4200 <example compact="compact">
4202 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
4203 libc.so.6 => /lib/libc.so.6 (0x40032000)
4204 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
4206 So the <prgn>foo</prgn> binary depends on the
4207 <prgn>libbar</prgn> shared library, but no package seems to
4208 provide a <file>*.shlibs</file> file handling
4209 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
4210 determine the package responsible:
4211 <example compact="compact">
4212 $ dpkg -S /usr/lib/libbar.so.1
4213 bar1: /usr/lib/libbar.so.1
4214 $ dpkg -s bar1 | grep Version
4217 This tells us that the <tt>bar1</tt> package, version 1.0-1,
4218 is the one we are using. Now we can file a bug against the
4219 <tt>bar1</tt> package and create our own
4220 <file>debian/shlibs.local</file> to locally fix the problem.
4221 Including the following line into your
4222 <file>debian/shlibs.local</file> file:
4223 <example compact="compact">
4224 libbar 1 bar1 (>= 1.0-1)
4226 should allow the package build to work.
4230 As soon as the maintainer of <tt>bar1</tt> provides a
4231 correct <file>shlibs</file> file, you should remove this line
4232 from your <file>debian/shlibs.local</file> file. (You should
4233 probably also then have a versioned <tt>Build-Depends</tt>
4234 on <tt>bar1</tt> to help ensure that others do not have the
4235 same problem building your package.)
4240 <chapt id="opersys"><heading>The Operating System</heading>
4243 <heading>Filesystem hierarchy</heading>
4247 <heading>Filesystem Structure</heading>
4250 The location of all installed files and directories must
4251 comply with the Filesystem Hierarchy Standard (FHS),
4252 version 2.1, except where doing so would violate other
4253 terms of Debian Policy. The version of this document
4254 referred here can be found in the <tt>debian-policy</tt>
4256 <url id="http://www.debian.org/doc/packaging-manuals/fhs/"
4257 name="FHS (Debian copy)"> alongside this manual (or, if
4258 you have the <package>debian-policy</package> installed,
4260 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
4261 (local copy)">). The
4262 latest version, which may be a more recent version, may
4264 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
4265 Specific questions about following the standard may be
4266 asked on the <tt>debian-devel</tt> mailing list, or
4267 referred to the FHS mailing list (see the
4268 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
4274 <heading>Site-specific programs</heading>
4277 As mandated by the FHS, packages must not place any
4278 files in <file>/usr/local</file>, either by putting them in
4279 the file system archive to be unpacked by <prgn>dpkg</prgn>
4280 or by manipulating them in their maintainer scripts.
4284 However, the package may create empty directories below
4285 <file>/usr/local</file> so that the system administrator knows
4286 where to place site-specific files. These directories
4287 should be removed on package removal if they are
4292 Note, that this applies only to directories <em>below</em>
4293 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
4294 Packages must not create sub-directories in the directory
4295 <file>/usr/local</file> itself, except those listed in FHS,
4296 section 4.5. However, you may create directories below
4297 them as you wish. You must not remove any of the
4298 directories listed in 4.5, even if you created them.
4302 Since <file>/usr/local</file> can be mounted read-only from a
4303 remote server, these directories must be created and
4304 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
4305 maintainer scripts and not be included in the
4306 <file>.deb</file> archive. These scripts must not fail if
4307 either of these operations fail.
4311 For example, the <tt>emacsen-common</tt> package could
4312 contain something like
4313 <example compact="compact">
4314 if [ ! -e /usr/local/share/emacs ]
4316 if mkdir /usr/local/share/emacs 2>/dev/null
4318 chown root:staff /usr/local/share/emacs
4319 chmod 2775 /usr/local/share/emacs
4323 in its <prgn>postinst</prgn> script, and
4324 <example compact="compact">
4325 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
4326 rmdir /usr/local/share/emacs 2>/dev/null || true
4328 in the <prgn>prerm</prgn> script. (Note that this form is
4329 used to ensure that if the script is interrupted, the
4330 directory <file>/usr/local/share/emacs</file> will still be
4335 If you do create a directory in <file>/usr/local</file> for
4336 local additions to a package, you should ensure that
4337 settings in <file>/usr/local</file> take precedence over the
4338 equivalents in <file>/usr</file>.
4342 However, because <file>/usr/local</file> and its contents are
4343 for exclusive use of the local administrator, a package
4344 must not rely on the presence or absence of files or
4345 directories in <file>/usr/local</file> for normal operation.
4349 The <file>/usr/local</file> directory itself and all the
4350 subdirectories created by the package should (by default) have
4351 permissions 2775 (group-writable and set-group-id) and be
4352 owned by <tt>root.staff</tt>.
4357 <heading>The system-wide mail directory</heading>
4359 The system-wide mail directory is <file>/var/mail</file>. This
4360 directory is part of the base system and should not owned
4361 by any particular mail agents. The use of the old
4362 location <file>/var/spool/mail</file> is deprecated, even
4363 though the spool may still be physically located there.
4364 To maintain partial upgrade compatibility for systems
4365 which have <file>/var/spool/mail</file> as their physical mail
4366 spool, packages using <file>/var/mail</file> must depend on
4367 either <package>libc6</package> (>= 2.1.3-13), or on
4368 <package>base-files</package> (>= 2.2.0), or on later
4369 versions of either one of these packages.
4375 <heading>Users and groups</heading>
4378 <heading>Introduction</heading>
4380 The Debian system can be configured to use either plain or
4385 Some user ids (UIDs) and group ids (GIDs) are reserved
4386 globally for use by certain packages. Because some
4387 packages need to include files which are owned by these
4388 users or groups, or need the ids compiled into binaries,
4389 these ids must be used on any Debian system only for the
4390 purpose for which they are allocated. This is a serious
4391 restriction, and we should avoid getting in the way of
4392 local administration policies. In particular, many sites
4393 allocate users and/or local system groups starting at 100.
4397 Apart from this we should have dynamically allocated ids,
4398 which should by default be arranged in some sensible
4399 order, but the behavior should be configurable.
4403 Packages other than <tt>base-passwd</tt> must not modify
4404 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
4405 <file>/etc/group</file> or <file>/etc/gshadow</file>.
4410 <heading>UID and GID classes</heading>
4412 The UID and GID numbers are divided into classes as
4418 Globally allocated by the Debian project, the same
4419 on every Debian system. These ids will appear in
4420 the <file>passwd</file> and <file>group</file> files of all
4421 Debian systems, new ids in this range being added
4422 automatically as the <tt>base-passwd</tt> package is
4427 Packages which need a single statically allocated
4428 uid or gid should use one of these; their
4429 maintainers should ask the <tt>base-passwd</tt>
4437 Dynamically allocated system users and groups.
4438 Packages which need a user or group, but can have
4439 this user or group allocated dynamically and
4440 differently on each system, should use <tt>adduser
4441 --system</tt> to create the group and/or user.
4442 <prgn>adduser</prgn> will check for the existence of
4443 the user or group, and if necessary choose an unused
4444 id based on the ranges specified in
4445 <file>adduser.conf</file>.
4449 <tag>1000-29999:</tag>
4452 Dynamically allocated user accounts. By default
4453 <prgn>adduser</prgn> will choose UIDs and GIDs for
4454 user accounts in this range, though
4455 <file>adduser.conf</file> may be used to modify this
4460 <tag>30000-59999:</tag>
4465 <tag>60000-64999:</tag>
4468 Globally allocated by the Debian project, but only
4469 created on demand. The ids are allocated centrally
4470 and statically, but the actual accounts are only
4471 created on users' systems on demand.
4475 These ids are for packages which are obscure or
4476 which require many statically-allocated ids. These
4477 packages should check for and create the accounts in
4478 <file>/etc/passwd</file> or <file>/etc/group</file> (using
4479 <prgn>adduser</prgn> if it has this facility) if
4480 necessary. Packages which are likely to require
4481 further allocations should have a "hole" left after
4482 them in the allocation, to give them room to
4487 <tag>65000-65533:</tag>
4495 User <tt>nobody</tt>. The corresponding gid refers
4496 to the group <tt>nogroup</tt>.
4503 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
4504 not</em> be used, because it is the error return
4513 <sect id="sysvinit">
4514 <heading>System run levels and <file>init.d</file> scripts</heading>
4516 <sect1 id="/etc/init.d">
4517 <heading>Introduction</heading>
4520 The <file>/etc/init.d</file> directory contains the scripts
4521 executed by <prgn>init</prgn> at boot time and when the
4522 init state (or "runlevel") is changed (see <manref
4523 name="init" section="8">).
4527 There are at least two different, yet functionally
4528 equivalent, ways of handling these scripts. For the sake
4529 of simplicity, this document describes only the symbolic
4530 link method. However, it must not be assumed by maintainer
4531 scripts that this method is being used, and any automated
4532 manipulation of the various runlevel behaviours by
4533 maintainer scripts must be performed using
4534 <prgn>update-rc.d</prgn> as described below and not by
4535 manually installing or removing symlinks. For information
4536 on the implementation details of the other method,
4537 implemented in the <tt>file-rc</tt> package, please refer
4538 to the documentation of that package.
4542 These scripts are referenced by symbolic links in the
4543 <file>/etc/rc<var>n</var>.d</file> directories. When changing
4544 runlevels, <prgn>init</prgn> looks in the directory
4545 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
4546 execute, where <tt><var>n</var></tt> is the runlevel that
4547 is being changed to, or <tt>S</tt> for the boot-up
4552 The names of the links all have the form
4553 <file>S<var>mm</var><var>script</var></file> or
4554 <file>K<var>mm</var><var>script</var></file> where
4555 <var>mm</var> is a two-digit number and <var>script</var>
4556 is the name of the script (this should be the same as the
4557 name of the actual script in <file>/etc/init.d</file>).
4561 When <prgn>init</prgn> changes runlevel first the targets
4562 of the links whose names start with a <tt>K</tt> are
4563 executed, each with the single argument <tt>stop</tt>,
4564 followed by the scripts prefixed with an <tt>S</tt>, each
4565 with the single argument <tt>start</tt>. (The links are
4566 those in the <file>/etc/rc<var>n</var>.d</file> directory
4567 corresponding to the new runlevel.) The <tt>K</tt> links
4568 are responsible for killing services and the <tt>S</tt>
4569 link for starting services upon entering the runlevel.
4573 For example, if we are changing from runlevel 2 to
4574 runlevel 3, init will first execute all of the <tt>K</tt>
4575 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
4576 all of the <tt>S</tt> prefixed scripts in that directory.
4577 The links starting with <tt>K</tt> will cause the
4578 referred-to file to be executed with an argument of
4579 <tt>stop</tt>, and the <tt>S</tt> links with an argument
4584 The two-digit number <var>mm</var> is used to determine
4585 the order in which to run the scripts: low-numbered links
4586 have their scripts run first. For example, the
4587 <tt>K20</tt> scripts will be executed before the
4588 <tt>K30</tt> scripts. This is used when a certain service
4589 must be started before another. For example, the name
4590 server <prgn>bind</prgn> might need to be started before
4591 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
4592 can set up its access lists. In this case, the script
4593 that starts <prgn>bind</prgn> would have a lower number
4594 than the script that starts <prgn>inn</prgn> so that it
4596 <example compact="compact">
4603 The two runlevels 0 (halt) and 6 (reboot) are slightly
4604 different. In these runlevels, the links with an
4605 <tt>S</tt> prefix are still called after those with a
4606 <tt>K</tt> prefix, but they too are called with the single
4607 argument <tt>stop</tt>.
4611 Also, if the script name ends <tt>.sh</tt>, the script
4612 will be sourced in runlevel <tt>S</tt> rather that being
4613 run in a forked subprocess, but will be explicitly run by
4614 <prgn>sh</prgn> in all other runlevels.
4619 <heading>Writing the scripts</heading>
4622 Packages that include daemons for system services should
4623 place scripts in <file>/etc/init.d</file> to start or stop
4624 services at boot time or during a change of runlevel.
4625 These scripts should be named
4626 <file>/etc/init.d/<var>package</var></file>, and they should
4627 accept one argument, saying what to do:
4630 <tag><tt>start</tt></tag>
4631 <item><p>start the service,</p></item>
4633 <tag><tt>stop</tt></tag>
4634 <item><p>stop the service,</p></item>
4636 <tag><tt>restart</tt></tag>
4637 <item><p>stop and restart the service,</p></item>
4639 <tag><tt>reload</tt></tag>
4640 <item><p>cause the configuration of the service to be
4641 reloaded without actually stopping and restarting
4642 the service,</p></item>
4644 <tag><tt>force-reload</tt></tag>
4645 <item><p>cause the configuration to be reloaded if the
4646 service supports this, otherwise restart the
4650 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
4651 <tt>force-reload</tt> options should be supported by all
4652 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
4653 option is optional.</p>
4656 The <file>init.d</file> scripts should ensure that they will
4657 behave sensibly if invoked with <tt>start</tt> when the
4658 service is already running, or with <tt>stop</tt> when it
4659 isn't, and that they don't kill unfortunately-named user
4660 processes. The best way to achieve this is usually to use
4661 <prgn>start-stop-daemon</prgn>.</p>
4664 If a service reloads its configuration automatically (as
4665 in the case of <prgn>cron</prgn>, for example), the
4666 <tt>reload</tt> option of the <file>init.d</file> script
4667 should behave as if the configuration has been reloaded
4671 The <file>/etc/init.d</file> scripts must be treated as
4672 configuration files, either (if they are present in the
4673 package, that is, in the .deb file) by marking them as
4674 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
4675 by managing them correctly in the maintainer scripts (see
4676 <ref id="config-files">). This is important since we want
4677 to give the local system administrator the chance to adapt
4678 the scripts to the local system, e.g., to disable a
4679 service without de-installing the package, or to specify
4680 some special command line options when starting a service,
4681 while making sure her changes aren't lost during the next
4686 These scripts should not fail obscurely when the
4687 configuration files remain but the package has been
4688 removed, as configuration files remain on the system after
4689 the package has been removed. Only when <prgn>dpkg</prgn>
4690 is executed with the <tt>--purge</tt> option will
4691 configuration files be removed. In particular, as the
4692 <file>/etc/init.d/<var>package</var></file> script itself is
4693 usually a <tt>conffile</tt>, it will remain on the system
4694 if the package is removed but not purged. Therefore, you
4695 should include a <tt>test</tt> statement at the top of the
4697 <example compact="compact">
4698 test -f <var>program-executed-later-in-script</var> || exit 0
4703 Often there are some variables in the <file>init.d</file>
4704 scripts whose values control the behaviour of the scripts,
4705 and which a system administrator is likely to want to
4706 change. As the scripts themselves are frequently
4707 <tt>conffile</tt>s, modifying them requires that the
4708 administrator merge in their changes each time the package
4709 is upgraded and the <tt>conffile</tt> changes. To ease
4710 the burden on the system administrator, such configurable
4711 values should not be placed directly in the script.
4712 Instead, they should be placed in a file in
4713 <file>/etc/default</file>, which typically will have the same
4714 base name as the <file>init.d</file> script. This extra file
4715 should be sourced by the script when the script runs. It
4716 must contain only variable settings and comments in POSIX
4717 <prgn>sh</prgn> format. It may either be a
4718 <tt>conffile</tt> or a configuration file maintained by
4719 the package maintainer scripts. See <ref id="config-files">
4724 To ensure that vital configurable values are always
4725 available, the <file>init.d</file> script should set default
4726 values for each of the shell variables it uses, either
4727 before sourcing the <file>/etc/default/</file> file or
4728 afterwards using something like the <tt>:
4729 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
4730 script must behave sensibly and not fail if the
4731 <file>/etc/default</file> file is deleted.
4736 <heading>Interfacing with the initscript system</heading>
4739 Maintainers should use the abstraction layer provided by
4740 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
4741 programs to deal with initscripts in their packages'
4742 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
4743 and <prgn>postrm</prgn>.
4746 Directly managing the /etc/rc?.d links and directly
4747 invoking the <file>/etc/init.d/</file> initscripts should
4748 be done only by packages providing the initscript
4749 subsystem (such as <prgn>sysvinit</prgn> and
4750 <prgn>file-rc</prgn>).
4755 <heading>Managing the links</heading>
4758 The program <prgn>update-rc.d</prgn> is provided for
4759 package maintainers to arrange for the proper creation and
4760 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
4761 or their functional equivalent if another method is being
4762 used. This may be used by maintainers in their packages'
4763 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.</p>
4766 You must not include any <file>/etc/rc<var>n</var>.d</file>
4767 symbolic links in the actual archive or manually create or
4768 remove the symbolic links in maintainer scripts; you must
4769 use the <prgn>update-rc.d</prgn> program instead. (The
4770 former will fail if an alternative method of maintaining
4771 runlevel information is being used.) You must not include
4772 the <file>/etc/rc<var>n</var>.d</file> directories themselves
4773 in the archive either. (Only the <tt>sysvinit</tt>
4778 By default <prgn>update-rc.d</prgn> will start services in
4779 each of the multi-user state runlevels (2, 3, 4, and 5)
4780 and stop them in the halt runlevel (0), the single-user
4781 runlevel (1) and the reboot runlevel (6). The system
4782 administrator will have the opportunity to customize
4783 runlevels by simply adding, moving, or removing the
4784 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
4785 symbolic links are being used, or by modifying
4786 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
4791 To get the default behavior for your package, put in your
4792 <prgn>postinst</prgn> script
4793 <example compact="compact">
4794 update-rc.d <var>package</var> defaults
4796 and in your <prgn>postrm</prgn>
4797 <example compact="compact">
4798 if [ "$1" = purge ]; then
4799 update-rc.d <var>package</var> remove
4801 </example>. Note that if your package changes runlevels
4802 or priority, you may have to remove and recreate the links,
4803 since otherwise the old links may persist. Refer to the
4804 documentation of <prgn>update-rc.d</prgn></p>
4807 This will use a default sequence number of 20. If it does
4808 not matter when or in which order the <file>init.d</file>
4809 script is run, use this default. If it does, then you
4810 should talk to the maintainer of the <prgn>sysvinit</prgn>
4811 package or post to <tt>debian-devel</tt>, and they will
4812 help you choose a number.
4816 For more information about using <tt>update-rc.d</tt>,
4817 please consult its manpage <manref name="update-rc.d"
4823 <heading>Running initscripts</heading>
4825 The program <prgn>invoke-rc.d</prgn> is provided to make
4826 it easier for package maintainers to properly invoke an
4827 initscript, obeying runlevel and other locally-defined
4828 constraints that might limit a package's right to start,
4829 stop and otherwise manage services. This program may be
4830 used by maintainers in their packages' scripts.
4833 The use of <prgn>invoke-rc.d</prgn> to invoke the
4834 <file>/etc/init.d/*</file> initscripts is strongly
4835 recommended<footnote>
4837 In the future, the use of invoke-rc.d to invoke
4838 initscripts shall be made mandatory. Maintainers are
4839 advised to switch to invoke-rc.d as soon as
4841 </footnote>, instead of calling them directly.
4845 By default, <prgn>invoke-rc.d</prgn> will pass any
4846 action requests (start, stop, reload, restart...) to the
4847 <file>/etc/init.d</file> script, filtering out requests
4848 to start or restart a service out of its intended
4852 Most packages will simply need to change:
4853 <example compact="compact">/etc/init.d/<package>
4854 <action></example> in their <prgn>postinst</prgn>
4855 and <prgn>prerm</prgn> scripts to:
4856 <example compact="compact">
4857 if [ -x /usr/sbin/invoke-rc.d ] ; then
4858 invoke-rc.d <var>package</var> <action>
4860 /etc/init.d/<var>package</var> <action>
4864 A package should register its initscript services using
4865 <prgn>update-rc.d</prgn> before it tries to invoke them
4866 using <prgn>invoke-rc.d</prgn>. Invocation of
4867 unregistered services may fail.
4870 For more information about using
4871 <prgn>invoke-rc.d</prgn>, please consult its manpage
4872 <manref name="invoke-rc.d" section="8">.
4879 <heading>Boot-time initialization</heading>
4882 There used to be another directory, <file>/etc/rc.boot</file>,
4883 which contained scripts which were run once per machine
4884 boot. This has been deprecated in favour of links from
4885 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
4886 described in <ref id="/etc/init.d">. Packages must not
4887 place files in <file>/etc/rc.boot</file>.</p>
4890 <heading>Example</heading>
4893 The <prgn>bind</prgn> DNS (nameserver) package wants to
4894 make sure that the nameserver is running in multiuser
4895 runlevels, and is properly shut down with the system. It
4896 puts a script in <file>/etc/init.d</file>, naming the script
4897 appropriately <tt>bind</tt>. As you can see, the script
4898 interprets the argument <tt>reload</tt> to send the
4899 nameserver a <tt>HUP</tt> signal (causing it to reload its
4900 configuration); this way the system administrator can say
4901 <tt>/etc/init.d/bind reload</tt> to reload the name
4902 server. The script has one configurable value, which can
4903 be used to pass parameters to the named program at
4904 startup; this value is read from
4905 <file>/etc/default/bind</file> (see below).
4909 <example compact="compact">
4912 # Original version by Robert Leslie
4913 # <rob@mars.org>, edited by iwj and cs
4915 test -x /usr/sbin/named || exit 0
4917 # Source defaults file.
4919 if [ -f /etc/default/bind ]; then
4926 echo -n "Starting domain name service: named"
4927 start-stop-daemon --start --quiet --exec /usr/sbin/named \
4932 echo -n "Stopping domain name service: named"
4933 start-stop-daemon --stop --quiet \
4934 --pidfile /var/run/named.pid --exec /usr/sbin/named
4938 echo -n "Restarting domain name service: named"
4939 start-stop-daemon --stop --quiet \
4940 --pidfile /var/run/named.pid --exec /usr/sbin/named
4941 start-stop-daemon --start --verbose --exec /usr/sbin/named \
4945 force-reload|reload)
4946 echo -n "Reloading configuration of domain name service: named"
4947 start-stop-daemon --stop --signal 1 --quiet \
4948 --pidfile /var/run/named.pid --exec /usr/sbin/named
4952 echo "Usage: /etc/init.d/bind " \
4953 " {start|stop|restart|reload|force-reload}" >&2
4963 Complementing the above init script is a configuration
4964 file <file>/etc/default/bind</file>, which contains
4965 configurable parameters used by the script. This would be
4966 created by the <prgn>postinst</prgn> script if it was not
4967 already present, and removed on purge by the
4968 <prgn>postrm</prgn> script.
4969 <example compact="compact">
4970 # Specified parameters to pass to named. See named(8).
4971 # You may uncomment the following line, and edit to taste.
4977 Another example on which you can base your
4978 <file>/etc/init.d</file> scripts is found in
4979 <file>/etc/init.d/skeleton</file>.
4983 If this package is happy with the default setup from
4984 <prgn>update-rc.d</prgn>, namely an ordering number of 20
4985 and having named running in all runlevels, it can say in
4986 its <prgn>postinst</prgn>:
4987 <example compact="compact">
4988 update-rc.d bind defaults >/dev/null
4990 And in its <prgn>postrm</prgn>, to remove the links when the
4992 <example compact="compact">
4993 if [ "$1" = purge ]; then
4994 update-rc.d bind remove >/dev/null
5002 <heading>Console messages from <file>init.d</file> scripts</heading>
5005 This section describes the formats to be used for messages
5006 written to standard output by the <file>/etc/init.d</file>
5007 scripts. The intent is to improve the consistency of
5008 Debian's startup and shutdown look and feel. For this
5009 reason, please look very carefully at the details. We want
5010 the messages to have the same format in terms of wording,
5011 spaces, punctuation and case of letters.
5015 Here is a list of overall rules that you should use when you
5016 create output messages. They can be useful if you have a
5017 non-standard message that is not covered specifically in the
5025 Every message should fit in one line (fewer than 80
5026 characters), start with a capital letter and end with
5027 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5033 If you want to express that the computer is working on
5034 something (that is, performing a specific task, not
5035 starting or stopping a program), we use an "ellipsis"
5036 (three dots: <tt>...</tt>). Note that we don't insert
5037 spaces before or after the dots. If the task has been
5038 completed we write <tt>done.</tt> and a line feed.
5044 Design your messages as if the computer is telling you
5045 what he is doing (let him be polite :-), but don't
5046 mention "him" directly. For example, if you think of
5048 <example compact="compact">
5049 I'm starting network daemons: nfsd mountd.
5052 <example compact="compact">
5053 Starting network daemons: nfsd mountd.
5061 There are standard message formats for the following
5062 situations. They should be used by the <tt>init.d</tt>
5069 <p>When daemons are started</p>
5072 If your script starts one or more daemons, the output
5073 should look like this (a single line, no leading
5075 <example compact="compact">
5076 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5078 The <var>description</var> should describe the
5079 subsystem the daemon or set of daemons are part of,
5080 while <var>daemon-1</var> up to <var>daemon-n</var>
5081 denote each daemon's name (typically the file name of
5086 For example, the output of <file>/etc/init.d/lpd</file>
5088 <example compact="compact">
5089 Starting printer spooler: lpd.
5094 This can be achieved by saying
5095 <example compact="compact">
5096 echo -n "Starting printer spooler: lpd"
5097 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5100 in the script. If you have more than one daemon to
5101 start, you should do the following:
5102 <example compact="compact">
5103 echo -n "Starting remote file system services:"
5104 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5105 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5106 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5109 This makes it possible for the user to see what takes
5110 so long and when the final daemon has been started.
5111 You should be careful where to put spaces: in the
5112 example above the system administrator can easily
5113 comment out a line if he don't wants to start a
5114 specific daemon, while the displayed message still
5120 <p>When a system parameter is being set</p>
5123 If you have to set up different system parameters
5124 during the system boot, you should use this format:
5125 <example compact="compact">
5126 Setting <var>parameter</var> to "<var>value</var>".
5131 You can use a statement such as the following to get
5133 <example compact="compact">
5134 echo "Setting DNS domainname to \"$domainname\"."
5139 Note that the same symbol (<tt>"</tt>) is used for the left
5140 and right quotation marks. A grave accent (<tt>`</tt>) is
5141 not a quote character; neither is an apostrophe
5147 <p>When a daemon is stopped or restarted</p>
5150 When you stop or restart a daemon, you should issue a
5151 message identical to the startup message, except that
5152 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5153 or <tt>Restarting</tt> respectively.
5157 For example, stopping the printer daemon will like
5159 <example compact="compact">
5160 Stopping printer spooler: lpd.
5166 <p>When something is executed</p>
5169 There are several examples where you have to run a
5170 program at system startup or shutdown to perform a
5171 specific task, for example, setting the system's clock
5172 using <prgn>netdate</prgn> or killing all processes
5173 when the system shuts down. Your message should look
5175 <example compact="compact">
5176 Doing something very useful...done.
5178 You should print the <tt>done.</tt> immediately after
5179 the job has been completed, so that the user is
5180 informed why she has to wait. You can get this
5182 <example compact="compact">
5183 echo -n "Doing something very useful..."
5192 <p>When the configuration is reloaded</p>
5195 When a daemon is forced to reload its configuration
5196 files you should use the following format:
5197 <example compact="compact">
5198 Reloading <var>description</var> configuration...done.
5200 where <var>description</var> is the same as in the
5201 daemon starting message.
5209 <heading>Cron jobs</heading>
5212 Packages must not modify the configuration file
5213 <file>/etc/crontab</file>, and they must not modify the files in
5214 <file>/var/spool/cron/crontabs</file>.</p>
5217 If a package wants to install a job that has to be executed
5218 via cron, it should place a file with the name of the
5219 package in one or more of the following directories:
5220 <example compact="compact">
5225 As these directory names imply, the files within them are
5226 executed on a daily, weekly, or monthly basis,
5227 respectively. The exact times are listed in
5228 <file>/etc/crontab</file>.</p>
5231 All files installed in any of these directories must be
5232 scripts (e.g., shell scripts or Perl scripts) so that they
5233 can easily be modified by the local system administrator.
5234 In addition, they should be treated as configuration
5239 If a certain job has to be executed more frequently than
5240 daily, the package should install a file
5241 <file>/etc/cron.d/<var>package</var></file>. This file uses the
5242 same syntax as <file>/etc/crontab</file> and is processed by
5243 <prgn>cron</prgn> automatically. The file must also be
5244 treated as a configuration file. (Note that entries in the
5245 <file>/etc/cron.d</file> directory are not handled by
5246 <prgn>anacron</prgn>. Thus, you should only use this
5247 directory for jobs which may be skipped if the system is not
5251 The scripts or crontab entries in these directories should
5252 check if all necessary programs are installed before they
5253 try to execute them. Otherwise, problems will arise when a
5254 package was removed but not purged since configuration files
5255 are kept on the system in this situation.</p>
5259 <heading>Menus</heading>
5262 Menu entries should follow the current menu policy found in
5263 the <tt>menu-policy</tt> files in the <tt>debian-policy</tt>
5264 package. It may also be found on the Debian FTP site
5265 <ftpsite>ftp.debian.org</ftpsite> as the file
5266 <ftppath>/debian/doc/package-developer/menu-policy.txt.gz</ftppath>,
5267 or in the equivalent location on your local mirror.
5271 The Debian <tt>menu</tt> package provides a standard
5272 interface between packages providing applications and
5273 documents, and <em>menu programs</em> (either X window
5274 managers or text-based menu programs such as
5275 <prgn>pdmenu</prgn>).
5279 All packages that provide applications that need not be
5280 passed any special command line arguments for normal
5281 operation should register a menu entry for those
5282 applications, so that users of the <tt>menu</tt> package
5283 will automatically get menu entries in their window
5284 managers, as well in shells like <tt>pdmenu</tt>.</p>
5287 Please also refer to the <em>Debian Menu System</em>
5288 documentation that comes with the <tt>menu</tt> package for
5289 information about how to register your applications and web
5295 <heading>Multimedia handlers</heading>
5298 Packages which provide the ability to view/show/play,
5299 compose, edit or print MIME types should register themselves
5300 as such following the current MIME support policy found in
5301 the <tt>mime-policy</tt> files in the <tt>debian-policy</tt>
5302 package. It may also be found on the Debian FTP site
5303 <ftpsite>ftp.debian.org</ftpsite> as the file
5304 <ftppath>/debian/doc/package-developer/mime-policy.txt.gz</ftppath>,
5305 or in the equivalent location on your local mirror.
5309 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
5310 is a mechanism for encoding files and data streams and
5311 providing meta-information about them, in particular their
5312 type (e.g. audio or video) and format (e.g. PNG, HTML,
5317 Registration of MIME type handlers allows programs like mail
5318 user agents and web browsers to to invoke these handlers to
5319 view, edit or display MIME types they don't support
5325 <heading>Keyboard configuration</heading>
5328 To achieve a consistent keyboard configuration so that all
5329 applications interpret a keyboard event the same way, all
5330 programs in the Debian distribution must be configured to
5331 comply with the following guidelines.
5335 The following keys must have the specified interpretations:
5338 <tag><tt><--</tt></tag>
5339 <item><p>delete the character to the left of the cursor</p></item>
5341 <tag><tt>Delete</tt></tag>
5342 <item><p>delete the character to the right of the cursor</p></item>
5344 <tag><tt>Control+H</tt></tag>
5345 <item><p>emacs: the help prefix</p></item>
5348 The interpretation of any keyboard events should be
5349 independent of the terminal that is used, be it a virtual
5350 console, an X terminal emulator, an rlogin/telnet session,
5355 The following list explains how the different programs
5356 should be set up to achieve this:
5361 <item><p><tt><--</tt> generates <tt>KB_BackSpace</tt>
5364 <item><p><tt>Delete</tt> generates <tt>KB_Delete</tt> in
5369 X translations are set up to make
5370 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
5371 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
5372 is the vt220 escape code for the "delete character"
5373 key). This must be done by loading the X resources
5374 using <prgn>xrdb</prgn> on all local X displays, not
5375 using the application defaults, so that the
5376 translation resources used correspond to the
5377 <prgn>xmodmap</prgn> settings.</p></item>
5381 The Linux console is configured to make
5382 <tt><--</tt> generate DEL, and <tt>Delete</tt>
5383 generate <tt>ESC [ 3 ~</tt>.</p></item>
5387 X applications are configured so that <tt><</tt>
5388 deletes left, and <tt>Delete</tt> deletes right. Motif
5389 applications already work like this.</p></item>
5391 <item><p>Terminals should have <tt>stty erase ^?</tt> .</p></item>
5395 The <tt>xterm</tt> terminfo entry should have <tt>ESC
5396 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
5397 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.</p></item>
5401 Emacs is programmed to map <tt>KB_Backspace</tt> or
5402 the <tt>stty erase</tt> character to
5403 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
5404 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
5405 <tt>^H</tt> to <tt>help</tt> as always.</p></item>
5409 Other applications use the <tt>stty erase</tt>
5410 character and <tt>kdch1</tt> for the two delete keys,
5411 with ASCII DEL being "delete previous character" and
5412 <tt>kdch1</tt> being "delete character under
5419 This will solve the problem except for the following
5427 Some terminals have a <tt><--</tt> key that cannot
5428 be made to produce anything except <tt>^H</tt>. On
5429 these terminals Emacs help will be unavailable on
5430 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
5431 character takes precedence in Emacs, and has been set
5432 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
5433 available) can be used instead.</p></item>
5437 Some operating systems use <tt>^H</tt> for <tt>stty
5438 erase</tt>. However, modern telnet versions and all
5439 rlogin versions propagate <tt>stty</tt> settings, and
5440 almost all UNIX versions honour <tt>stty erase</tt>.
5441 Where the <tt>stty</tt> settings are not propagated
5442 correctly, things can be made to work by using
5443 <tt>stty</tt> manually.</p></item>
5447 Some systems (including previous Debian versions) use
5448 <prgn>xmodmap</prgn> to arrange for both
5449 <tt><--</tt> and <tt>Delete</tt> to generate
5450 <tt>KB_Delete</tt>. We can change the behavior of
5451 their X clients using the same X resources that we use
5452 to do it for our own clients, or configure our clients
5453 using their resources when things are the other way
5454 around. On displays configured like this
5455 <tt>Delete</tt> will not work, but <tt><--</tt>
5460 Some operating systems have different <tt>kdch1</tt>
5461 settings in their <tt>terminfo</tt> database for
5462 <tt>xterm</tt> and others. On these systems the
5463 <tt>Delete</tt> key will not work correctly when you
5464 log in from a system conforming to our policy, but
5465 <tt><--</tt> will.</p></item>
5471 <heading>Environment variables</heading>
5474 A program must not depend on environment variables to get
5475 reasonable defaults. (That's because these environment
5476 variables would have to be set in a system-wide
5477 configuration file like <file>/etc/profile</file>, which is not
5478 supported by all shells.)</p>
5481 If a program usually depends on environment variables for its
5482 configuration, the program should be changed to fall back to
5483 a reasonable default configuration if these environment
5484 variables are not present. If this cannot be done easily
5485 (e.g., if the source code of a non-free program is not
5486 available), the program must be replaced by a small
5487 "wrapper" shell script which sets the environment variables
5488 if they are not already defined, and calls the original program.</p>
5491 Here is an example of a wrapper script for this purpose:
5493 <example compact="compact">
5495 BAR=${BAR:-/var/lib/fubar}
5497 exec /usr/lib/foo/foo "$@"
5502 Furthermore, as <file>/etc/profile</file> is a configuration
5503 file of the <prgn>base-files</prgn> package, other packages must not
5504 put any environment variables or other commands into that
5510 <heading>Files</heading>
5513 <heading>Binaries</heading>
5516 Two different packages must not install programs with
5517 different functionality but with the same filenames. (The
5518 case of two programs having the same functionality but
5519 different implementations is handled via "alternatives" or
5520 the "Conflicts" mechanism. See <ref id="maintscripts"> and
5521 <ref id="conflicts"> respectively.) If this case happens,
5522 one of the programs must be renamed. The maintainers should
5523 report this to the <tt>debian-devel</tt> mailing list and
5524 try to find a consensus about which program will have to be
5525 renamed. If a consensus cannot be reached, <em>both</em>
5526 programs must be renamed.
5530 By default, when a package is being built, any binaries
5531 created should include debugging information, as well as
5532 being compiled with optimization. You should also turn on
5533 as many reasonable compilation warnings as possible; this
5534 makes life easier for porters, who can then look at build
5535 logs for possible problems. For the C programming language,
5536 this means the following compilation parameters should be
5538 <example compact="compact">
5540 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
5542 install -s # (or use strip on the files in debian/tmp)
5547 Note that by default all installed binaries should be stripped,
5548 either by using the <tt>-s</tt> flag to
5549 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
5550 the binaries after they have been copied into
5551 <file>debian/tmp</file> but before the tree is made into a
5555 Although binaries in the build tree should be compiled with
5556 debugging information by default, it can often be difficult
5557 to debug programs if they are also subjected to compiler
5558 optimization. For this reason, it is recommended to support
5559 the standardized environment
5560 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
5561 contain several flags to change how a package is compiled
5569 The presence of this string means that the package
5570 should be complied with a minimum of optimization.
5571 For C programs, it is best to add <tt>-O0</tt>
5572 to <tt>CFLAGS</tt> (although this is usually the
5573 default). Some programs might fail to build or run at
5574 this level of optimization; it may be necessary to
5575 use <tt>-O1</tt>, for example.
5581 This string means that the debugging symbols should
5582 not be stripped from the binary during installation,
5583 so that debugging information may be included in the package.
5589 The following makefile snippet is an example of how one may
5590 implement the build options; you will probably have to
5591 massage this example in order to make it work for your
5593 <example compact="compact">
5596 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
5597 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
5598 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
5599 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
5601 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
5606 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
5607 INSTALL_PROGRAM += -s
5613 It is up to the package maintainer to decide what
5614 compilation options are best for the package. Certain
5615 binaries (such as computationally-intensive programs) will
5616 function better with certain flags (<tt>-O3</tt>, for
5617 example); feel free to use them. Please use good judgment
5618 here. Don't use flags for the sake of it; only use them
5619 if there is good reason to do so. Feel free to override
5620 the upstream author's ideas about which compilation
5621 options are best: they are often inappropriate for our
5628 <heading>Libraries</heading>
5631 In general, libraries must have a shared version in the
5632 library package (<package>lib*</package>) and a static
5633 version in the development package (<package>lib*-dev</package>).
5634 The shared version must be compiled with <tt>-fPIC</tt>,
5635 and the static version must not be. In other words, each source
5636 unit (<tt>*.c</tt>, for example, for C files) will need to be
5641 In some cases, it is acceptable for a library to be
5642 available in static form only; these cases include:
5645 <p>libraries for languages whose shared library support
5646 is immature or unstable</p>
5650 libraries whose interfaces are in flux or under
5651 development (commonly the case when the library's
5652 major version number is zero, or where the ABI breaks
5658 libraries which are explicitly intended to be
5659 available only in static form by their upstream
5663 If a library is available only in static form, then it must follow
5664 the conventions for a development package.
5668 You must specify the gcc option <tt>-D_REENTRANT</tt>
5669 when building a library (either static or shared) to make
5670 the library compatible with LinuxThreads.
5674 Note that all installed shared libraries should be
5676 <example compact="compact">
5677 strip --strip-unneeded <var>your-lib</var>
5679 (The option <tt>--strip-unneeded</tt> makes
5680 <prgn>strip</prgn> remove only the symbols which aren't
5681 needed for relocation processing.) Shared libraries can
5682 function perfectly well when stripped, since the symbols for
5683 dynamic linking are in a separate part of the ELF object
5686 You might also want to use the options
5687 <tt>--remove-section=.comment</tt> and
5688 <tt>--remove-section=.note</tt> on both shared libraries
5689 and executables, and <tt>--strip-debug</tt> on static
5696 Note that under some circumstances it may be useful to
5697 install a shared library unstripped, for example when
5698 building a separate package to support debugging.
5702 Shared object files (often <file>.so</file> files) that are not
5703 public libraries, that is, they are not meant to be linked
5704 to by third party executables (binaries of other packages),
5705 should be installed in subdirectories of the
5706 <file>/usr/lib</file> directory. Such files are exempt from the
5707 rules that govern ordinary shared libraries, except that
5708 they must not be installed executable and should be
5711 A common example are the so-called "plug-ins",
5712 internal shared objects that are dynamically loaded by
5713 programs using <manref name="dlopen" section="3">.
5719 Packages containing shared libraries that may be linked to
5720 by other packages' binaries, but which for some
5721 <em>compelling</em> reason can not be installed in
5722 <file>/usr/lib</file> directory, may install the shared library
5723 files in subdirectories of the <file>/usr/lib</file> directory,
5724 in which case they should arrange to add that directory in
5725 <file>/etc/ld.so.conf</file> in the package's post-installation
5726 script, and remove it in the package's post-removal script.
5730 An ever increasing number of packages are using
5731 <prgn>libtool</prgn> to do their linking. The latest GNU
5732 libtools (>= 1.3a) can take advantage of the metadata in the
5733 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
5734 files). The main advantage of <prgn>libtool</prgn>'s
5735 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
5736 store and subsequently access metadata with respect to the
5737 libraries it builds. <prgn>libtool</prgn> will search for
5738 those files, which contain a lot of useful information about
5739 a library (such as library dependency information for static
5740 linking). Also, they're <em>essential</em> for programs
5741 using <tt>libltdl</tt>.<footnote>
5743 Although <prgn>libtool</prgn> is fully capable of
5744 linking against shared libraries which don't have
5745 <tt>.la</tt> files, as it is a mere shell script it can
5746 add considerably to the build time of a
5747 <prgn>libtool</prgn>-using package if that shell script
5748 has to derive all this information from first principles
5749 for each library every time it is linked. With the
5750 advent of <prgn>libtool</prgn> version 1.4 (and to a
5751 lesser extent <prgn>libtool</prgn> version 1.3), the
5752 <file>.la</file> files also store information about
5753 inter-library dependencies which cannot necessarily be
5754 derived after the <file>.la</file> file is deleted.
5760 Packages that use <prgn>libtool</prgn> to create shared
5761 libraries should include the <file>.la</file> files in the
5762 <tt>-dev</tt> package, unless the package relies on
5763 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
5764 the <tt>.la</tt> files must go in the run-time library
5769 You must make sure that you use only released versions of
5770 shared libraries to build your packages; otherwise other
5771 users will not be able to run your binaries
5772 properly. Producing source packages that depend on
5773 unreleased compilers is also usually a bad
5779 <heading>Shared libraries</heading>
5782 Packages involving shared libraries should be split up
5783 into several binary packages.</p>
5786 For a straightforward library which has a development
5787 environment and a runtime kit including just shared
5788 libraries you need to create two packages:
5789 <file><var>libraryname</var><var>soversion</var></file>, where
5790 <file><var>soversion</var></file> is the version number in the
5791 soname of the shared library<footnote>
5793 The soname is the shared object name: it's the thing
5794 that has to match exactly between building an executable
5795 and running it for the dynamic linker to be able run the
5796 program. For example, if the soname of the library is
5797 <file>libfoo.so.6</file>, the library package would be
5798 called <file>libfoo6</file>.
5801 and <tt><var>libraryname</var><var>soversion</var>-dev</tt>.
5802 Alternatively, if it would be confusing to directly append
5803 <var>soversion</var> to <var>libraryname</var> (e.g. because
5804 <var>libraryname</var> itself ends in a number), you may use
5805 <tt><var>libraryname</var>-<var>soversion</var></tt> and
5806 <tt><var>libraryname</var>-<var>soversion</var>-dev</tt>
5811 If you prefer only to support one development version at a
5812 time you may name the development package
5813 <file><var>libraryname</var>-dev</file>; otherwise you may need
5814 to use <prgn>dpkg</prgn>'s Conflicts mechanism (see <ref
5815 id="conflicts">) to ensure that the user only installs one
5816 development version at a time (as different development
5817 versions are likely to have the same header files in them,
5818 which would cause a filename clash if both were installed).
5819 Typically the development version should also have an exact
5820 version dependency on the runtime library, to make sure that
5821 compilation and linking happens correctly. The
5822 <tt>${Source-Version}</tt> substitution variable can be
5823 useful for this purpose.
5827 Packages which use the shared library should have a
5828 dependency on the name of the shared library package,
5829 <file><var>libraryname</var><var>soversion</var></file>. When
5830 the soname changes you can have both versions of the library
5831 installed while migrating from the old library to the new.
5835 If your package has some run-time support programs which use
5836 the shared library you must not put them in the shared
5837 library package. If you do that then you won't be able to
5838 install several versions of the shared library without
5839 getting filename clashes. Instead, either create a third
5840 package for the runtime binaries (this package might
5841 typically be named <tt><var>libraryname</var>-runtime</tt>;
5842 note the absence of the <var>soversion</var> in the package
5843 name), or if the development package is small you may
5844 include them in there.
5848 If you have several shared libraries built from the same
5849 source tree you may lump them all together into a single
5850 shared library package, provided that you change all of
5851 their sonames at once (so that you don't get filename
5852 clashes if you try to install different versions of the
5853 combined shared libraries package).
5857 Shared libraries should not be installed executable, since
5858 the dynamic linker does not require this and trying to
5859 execute a shared library usually results in a core dump.
5864 <heading>Scripts</heading>
5867 All command scripts, including the package maintainer
5868 scripts inside the package and used by <prgn>dpkg</prgn>,
5869 should have a <tt>#!</tt> line naming the shell to be used
5870 to interpret them.</p>
5873 In the case of Perl scripts this should be
5874 <tt>#!/usr/bin/perl</tt>.</p>
5877 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
5878 should almost certainly start with <tt>set -e</tt> so that
5879 errors are detected. Every script should use
5880 <tt>set -e</tt> or check the exit status of <em>every</em>
5884 The standard shell interpreter <file>/bin/sh</file> can be a
5885 symbolic link to any POSIX compatible shell, if <tt>echo
5886 -n</tt> does not generate a newline.<footnote>
5888 Debian policy specifies POSIX behavior for
5889 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
5890 use in the Linux community (in particular including this
5891 policy, the Linux kernel source, many Debian scripts,
5892 etc.). This <tt>echo -n</tt> mechanism is valid but not
5893 required under POSIX, hence this explicit addition.
5894 Also, rumour has it that this shall be mandated under
5898 Thus, shell scripts specifying <file>/bin/sh</file> as
5899 interpreter should only use POSIX features. If a script
5900 requires non-POSIX features from the shell interpreter, the
5901 appropriate shell must be specified in the first line of the
5902 script (e.g., <tt>#!/bin/bash</tt>) and the package must
5903 depend on the package providing the shell (unless the shell
5904 package is marked "Essential", as in the case of
5909 You may wish to restrict your script to POSIX features when
5910 possible so that it may use <file>/bin/sh</file> as its
5911 interpreter. If your script works with <prgn>dash</prgn>
5912 (originally called <prgn>ash</prgn>), it's probably POSIX
5913 compliant, but if you are in doubt, use
5914 <file>/bin/bash</file>.
5918 Perl scripts should check for errors when making any
5919 system calls, including <tt>open</tt>, <tt>print</tt>,
5920 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
5924 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
5925 scripting languages. See <em>Csh Programming Considered
5926 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
5927 can be found at <url
5928 id="http://language.perl.com/versus/csh.whynot">.<footnote>
5930 It can also be found on
5931 <url id="http://www.cpan.org/doc/FMTEYEWTK/versus/csh.whynot">
5932 or on the ftp site <ftpsite>ftp.cpan.org</ftpsite> as
5933 <ftppath>/pub/perl/CPAN/doc/FMTEYEWTK/versus/csh.whynot</ftppath>.
5936 If an upstream package comes with <prgn>csh</prgn> scripts
5937 then you must make sure that they start with
5938 <tt>#!/bin/csh</tt> and make your package depend on the
5939 <prgn>c-shell</prgn> virtual package.
5943 Any scripts which create files in world-writeable
5944 directories (e.g., in <file>/tmp</file>) must use a
5945 mechanism which will fail if a file with the same name
5949 The Debian base system provides the <prgn>tempfile</prgn>
5950 and <prgn>mktemp</prgn> utilities for use by scripts for
5951 this purpose.</p></sect>
5955 <heading>Symbolic links</heading>
5958 In general, symbolic links within a top-level directory
5959 should be relative, and symbolic links pointing from one
5960 top-level directory into another should be absolute. (A
5961 top-level directory is a sub-directory of the root
5962 directory <file>/</file>.)</p>
5965 In addition, symbolic links should be specified as short as
5966 possible, i.e., link targets like <file>foo/../bar</file> are
5970 Note that when creating a relative link using
5971 <prgn>ln</prgn> it is not necessary for the target of the
5972 link to exist relative to the working directory you're
5973 running <prgn>ln</prgn> from, nor is it necessary to change
5974 directory to the directory where the link is to be made.
5975 Simply include the string that should appear as the target
5976 of the link (this will be a pathname relative to the
5977 directory in which the link resides) as the first argument
5978 to <prgn>ln</prgn>.</p>
5981 For example, in your <prgn>Makefile</prgn> or
5982 <file>debian/rules</file>, you can do things like:
5983 <example compact="compact">
5984 ln -fs gcc $(prefix)/bin/cc
5985 ln -fs gcc debian/tmp/usr/bin/cc
5986 ln -fs ../sbin/sendmail $(prefix)/bin/runq
5987 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
5991 A symbolic link pointing to a compressed file should always
5992 have the same file extension as the referenced file. (For
5993 example, if a file <file>foo.gz</file> is referenced by a
5994 symbolic link, the filename of the link has to end with
5995 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6000 <heading>Device files</heading>
6003 Packages must not include device files in the package file
6007 If a package needs any special device files that are not
6008 included in the base system, it must call
6009 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6010 after notifying the user<footnote>
6012 This notification could be done via a (low-priority)
6013 debconf message, or an echo (printf) statement.
6019 Packages must not remove any device files in the
6020 <prgn>postrm</prgn> or any other script. This is left to the
6021 system administrator.</p>
6024 Debian uses the serial devices
6025 <file>/dev/ttyS*</file>. Programs using the old
6026 <file>/dev/cu*</file> devices should be changed to use
6027 <file>/dev/ttyS*</file>.</p>
6030 <sect id="config-files">
6031 <heading>Configuration files</heading>
6033 <heading>Definitions</heading>
6036 <tag>configuration file</tag>
6039 A file that affects the operation of a program, or
6040 provides site- or host-specific information, or
6041 otherwise customizes the behavior of a program.
6042 Typically, configuration files are intended to be
6043 modified by the system administrator (if needed or
6044 desired) to conform to local policy or to provide
6045 more useful site-specific behavior.
6049 <tag><tt>conffile</tt></tag>
6052 A file listed in a package's <tt>conffiles</tt>
6053 file, and is treated specially by <prgn>dpkg</prgn>
6054 (see <ref id="configdetails">).
6061 The distinction between these two is important; they are
6062 not interchangeable concepts. Almost all
6063 <tt>conffile</tt>s are configuration files, but many
6064 configuration files are not <tt>conffiles</tt>.
6068 Note that a script that embeds configuration information
6069 (such as most of the files in <file>/etc/default</file> and
6070 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6071 configuration file and should be treated as such.
6076 <heading>Location</heading>
6078 Any configuration files created or used by your package
6079 must reside in <file>/etc</file>. If there are several you
6080 should consider creating a subdirectory of <file>/etc</file>
6081 named after your package.</p>
6084 If your package creates or uses configuration files
6085 outside of <file>/etc</file>, and it is not feasible to modify
6086 the package to use the <file>/etc</file>, you should still put
6087 the files in <file>/etc</file> and create symbolic links to
6088 those files from the location that the package
6093 <heading>Behavior</heading>
6095 Configuration file handling must conform to the following
6097 <list compact="compact">
6100 local changes must be preserved during a package
6106 configuration files must be preserved when the
6107 package is removed, and only deleted when the
6115 The easy way to achieve this behavior is to make the
6116 configuration file a <tt>conffile</tt>. This is
6117 appropriate only if it is possible to distribute a default
6118 version that will work for most installations, although
6119 some system administrators may choose to modify it. This
6120 implies that the default version will be part of the
6121 package distribution, and must not be modified by the
6122 maintainer scripts during installation (or at any other
6127 In order to ensure that local changes are preserved
6128 correctly, no package may contain or make hard links to
6129 conffiles.<footnote>
6131 Rationale: There are two problems with hard links.
6132 The first is that some editors break the link while
6133 editing one of the files, so that the two files may
6134 unwittingly become unlinked and different. The second
6135 is that <prgn>dpkg</prgn> might break the hard link
6136 while upgrading <tt>conffile</tt>s.
6142 The other way to do it is via the maintainer scripts. In
6143 this case, the configuration file must not be listed as a
6144 <tt>conffile</tt> and must not be part of the package
6145 distribution. If the existence of a file is required for
6146 the package to be sensibly configured it is the
6147 responsibility of the package maintainer to provide
6148 maintainer scripts which correctly create, update and
6149 maintain the file and remove it on purge. (See <ref
6150 id="maintainerscripts"> for more information.) These
6151 scripts must be idempotent (i.e., must work correctly if
6152 <prgn>dpkg</prgn> needs to re-run them due to errors
6153 during installation or removal), must cope with all the
6154 variety of ways <prgn>dpkg</prgn> can call maintainer
6155 scripts, must not overwrite or otherwise mangle the user's
6156 configuration without asking, must not ask unnecessary
6157 questions (particularly during upgrades), and otherwise be
6162 The scripts are not required to configure every possible
6163 option for the package, but only those necessary to get
6164 the package running on a given system. Ideally the
6165 sysadmin should not have to do any configuration other
6166 than that done (semi-)automatically by the
6167 <prgn>postinst</prgn> script.
6171 A common practice is to create a script called
6172 <file><var>package</var>-configure</file> and have the
6173 package's <prgn>postinst</prgn> call it if and only if the
6174 configuration file does not already exist. In certain
6175 cases it is useful for there to be an example or template
6176 file which the maintainer scripts use. Such files should
6177 be in <file>/usr/share/<var>package</var></file> or
6178 <file>/usr/lib/<var>package</var></file> (depending on whether
6179 they are architecture-independent or not). There should
6180 be symbolic links to them from
6181 <file>/usr/share/doc/<var>package</var>/examples</file> if
6182 they are examples, and should be perfectly ordinary
6183 <prgn>dpkg</prgn>-handled files (<em>not</em>
6184 configuration files).
6188 These two styles of configuration file handling must
6189 not be mixed, for that way lies madness:
6190 <prgn>dpkg</prgn> will ask about overwriting the file
6191 every time the package is upgraded.
6196 <heading>Sharing configuration files</heading>
6198 Packages which specify the same file as a
6199 <tt>conffile</tt> must be tagged as <em>conflicting</em>
6200 with each other. (This is an instance of the general rule
6201 about not sharing files. Note that neither alternatives
6202 nor diversions are likely to be appropriate in this case;
6203 in particular, <prgn>dpkg</prgn> does not handle diverted
6204 <tt>conffile</tt>s well.)
6208 The maintainer scripts must not alter a <tt>conffile</tt>
6209 of <em>any</em> package, including the one the scripts
6214 If two or more packages use the same configuration file
6215 and it is reasonable for both to be installed at the same
6216 time, one of these packages must be defined as
6217 <em>owner</em> of the configuration file, i.e., it will be
6218 the package which handles that file as a configuration
6219 file. Other packages that use the configuration file must
6220 depend on the owning package if they require the
6221 configuration file to operate. If the other package will
6222 use the configuration file if present, but is capable of
6223 operating without it, no dependency need be declared.</p>
6226 If it is desirable for two or more related packages to
6227 share a configuration file <em>and</em> for all of the
6228 related packages to be able to modify that configuration
6229 file, then the following should be done:
6230 <enumlist compact="compact">
6233 One of the related packages (the "owning" package)
6234 will manage the configuration file with maintainer
6235 scripts as described in the previous section.
6240 The owning package should also provide a program
6241 that the other packages may use to modify the
6247 The related packages must use the provided program
6248 to make any desired modifications to the
6249 configuration file. They should either depend on
6250 the core package to guarantee that the configuration
6251 modifier program is available or accept gracefully
6252 that they cannot modify the configuration file if it
6253 is not. (This is in addition to the fact that the
6254 configuration file may not even be present in the
6262 Sometimes it's appropriate to create a new package which
6263 provides the basic infrastructure for the other packages
6264 and which manages the shared configuration files. (The
6265 <tt>sgml-base</tt> package is a good example.)
6270 <heading>User configuration files ("dotfiles")</heading>
6273 The files in <file>/etc/skel</file> will automatically be
6274 copied into new user accounts by <prgn>adduser</prgn>.
6275 No other program should reference the files in
6276 <file>/etc/skel</file>.
6280 Therefore, if a program needs a dotfile to exist in
6281 advance in <file>$HOME</file> to work sensibly, that dotfile
6282 should be installed in <file>/etc/skel</file> and treated as a
6287 However, programs that require dotfiles in order to
6288 operate sensibly are a bad thing, unless they do create
6289 the dotfiles themselves automatically.
6293 Furthermore, programs should be configured by the Debian
6294 default installation to behave as closely to the upstream
6295 default behaviour as possible.
6299 Therefore, if a program in a Debian package needs to be
6300 configured in some way in order to operate sensibly, that
6301 should be done using a site-wide configuration file placed
6302 in <file>/etc</file>. Only if the program doesn't support a
6303 site-wide default configuration and the package maintainer
6304 doesn't have time to add it may a default per-user file be
6305 placed in <file>/etc/skel</file>.
6309 <file>/etc/skel</file> should be as empty as we can make it.
6310 This is particularly true because there is no easy (or
6311 necessarily desirable) mechanism for ensuring that the
6312 appropriate dotfiles are copied into the accounts of
6313 existing users when a package is installed.
6319 <heading>Log files</heading>
6321 Log files should usually be named
6322 <file>/var/log/<var>package</var>.log</file>. If you have many
6323 log files, or need a separate directory for permission
6324 reasons (<file>/var/log</file> is writable only by
6325 <file>root</file>), you should usually create a directory named
6326 <file>/var/log/<var>package</var></file> and place your log
6331 Log files must be rotated occasionally so that they don't
6332 grow indefinitely; the best way to do this is to drop a log
6333 rotation configuration file into the directory
6334 <file>/etc/logrotate.d</file> and use the facilities provided by
6335 logrotate.<footnote>
6337 The traditional approach to log files has been to set up
6338 <em>ad hoc</em> log rotation schemes using simple shell
6339 scripts and cron. While this approach is highly
6340 customizable, it requires quite a lot of sysadmin work.
6341 Even though the original Debian system helped a little
6342 by automatically installing a system which can be used
6343 as a template, this was deemed not enough.
6347 The use of <prgn>logrotate</prgn>, a program developed
6348 by Red Hat, is better, as it centralizes log management.
6349 It has both a configuration file
6350 (<file>/etc/logrotate.conf</file>) and a directory where
6351 packages can drop their individual log rotation
6352 configurations (<file>/etc/logrotate.d</file>).
6355 Here is a good example for a logrotate config
6356 file (for more information see <manref name="logrotate"
6358 <example compact="compact">
6364 /etc/init.d/foo force-reload
6368 This rotates all files under <file>/var/log/foo</file>, saves 12
6369 compressed generations, and forces the daemon to reload its
6370 configuration information after the log rotation.
6374 Log files should be removed when the package is
6375 purged (but not when it is only removed). This should be
6376 done by the <prgn>postrm</prgn> script when it is called
6377 with the argument <tt>purge</tt> (see <ref
6378 id="removedetails">).
6383 <heading>Permissions and owners</heading>
6386 The rules in this section are guidelines for general use.
6387 If necessary you may deviate from the details below.
6388 However, if you do so you must make sure that what is done
6389 is secure and you should try to be as consistent as possible
6390 with the rest of the system. You should probably also
6391 discuss it on <prgn>debian-devel</prgn> first.
6395 Files should be owned by <tt>root.root</tt>, and made
6396 writable only by the owner and universally readable (and
6397 executable, if appropriate), that is mode 644 or 755.
6401 Directories should be mode 755 or (for group-writability)
6402 mode 2775. The ownership of the directory should be
6403 consistent with its mode: if a directory is mode 2775, it
6404 should be owned by the group that needs write access to
6409 Setuid and setgid executables should be mode 4755 or 2755
6410 respectively, and owned by the appropriate user or group.
6411 They should not be made unreadable (modes like 4711 or
6412 2711 or even 4111); doing so achieves no extra security,
6413 because anyone can find the binary in the freely available
6414 Debian package; it is merely inconvenient. For the same
6415 reason you should not restrict read or execute permissions
6416 on non-set-id executables.
6420 Some setuid programs need to be restricted to particular
6421 sets of users, using file permissions. In this case they
6422 should be owned by the uid to which they are set-id, and by
6423 the group which should be allowed to execute them. They
6424 should have mode 4754; again there is no point in making
6425 them unreadable to those users who must not be allowed to
6430 It is possible to arrange that the system administrator can
6431 reconfigure the package to correspond to their local
6432 security policy by changing the permissions on a binary:
6433 they can do this by using <prgn>dpkg-statoverride</prgn>, as
6434 described below.<footnote>
6436 Ordinary files installed by <prgn>dpkg</prgn> (as
6437 opposed to <tt>conffile</tt>s and other similar objects)
6438 normally have their permissions reset to the distributed
6439 permissions when the package is reinstalled. However,
6440 the use of <prgn>dpkg-statoverride</prgn> overrides this
6441 default behaviour. If you use this method, you should
6442 remember to describe <prgn>dpkg-statoverride</prgn> in
6443 the package documentation; being a relatively new
6444 addition to Debian, it is probably not yet well-known.
6447 Another method you should consider is to create a group for
6448 people allowed to use the program(s) and make any setuid
6449 executables executable only by that group.
6453 If you need to create a new user or group for your package
6454 there are two possibilities. Firstly, you may need to
6455 make some files in the binary package be owned by this
6456 user or group, or you may need to compile the user or
6457 group id (rather than just the name) into the binary
6458 (though this latter should be avoided if possible, as in
6459 this case you need a statically allocated id).</p>
6462 If you need a statically allocated id, you must ask for a
6463 user or group id from the <tt>base-passwd</tt> maintainer,
6464 and must not release the package until you have been
6465 allocated one. Once you have been allocated one you must
6466 either make the package depend on a version of the
6467 <tt>base-passwd</tt> package with the id present in
6468 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
6469 your package to create the user or group itself with the
6470 correct id (using <tt>adduser</tt>) in its
6471 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
6472 the <prgn>postinst</prgn> is to be preferred if it is
6473 possible, otherwise a pre-dependency will be needed on the
6474 <tt>adduser</tt> package.)
6478 On the other hand, the program might be able to determine
6479 the uid or gid from the user or group name at runtime, so
6480 that a dynamically allocated id can be used. In this case
6481 you should choose an appropriate user or group name,
6482 discussing this on <prgn>debian-devel</prgn> and checking
6483 with the <package/base-passwd/ maintainer that it is unique and that
6484 they do not wish you to use a statically allocated id
6485 instead. When this has been checked you must arrange for
6486 your package to create the user or group if necessary using
6487 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
6488 <prgn>postinst</prgn> script (again, the latter is to be
6489 preferred if it is possible).
6493 Note that changing the numeric value of an id associated
6494 with a name is very difficult, and involves searching the
6495 file system for all appropriate files. You need to think
6496 carefully whether a static or dynamic id is required, since
6497 changing your mind later will cause problems.
6500 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
6502 This section is not intended as policy, but as a
6503 description of the use of <prgn>dpkg-statoverride</prgn>.
6507 <prgn>dpkg-statoverride</prgn> is a replacement for the
6508 deprecated <tt>suidmanager</tt> package. Packages which
6509 previously used <tt>suidmanager</tt> should have a
6510 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
6511 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
6512 and <tt>suidunregister</tt> should now be simply removed
6513 from the maintainer scripts.
6517 If a system administrator wishes to have a file (or
6518 directory or other such thing) installed with owner and
6519 permissions different from those in the distributed Debian
6520 package, he can use the <prgn>dpkg-statoverride</prgn>
6521 program to instruct <prgn>dpkg</prgn> to use the different
6522 settings every time the file is installed. Thus the
6523 package maintainer should distribute the files with their
6524 normal permissions, and leave it for the system
6525 administrator to make any desired changes. For example, a
6526 daemon which is normally required to be setuid root, but
6527 in certain situations could be used without being setuid,
6528 should be installed setuid in the <tt>.deb</tt>. Then the
6529 local system administrator can change this if they wish.
6530 If there are two standard ways of doing it, the package
6531 maintainer can use <tt>debconf</tt> to find out the
6532 preference, and call <prgn>dpkg-statoverride</prgn> in the
6533 maintainer script if necessary to accommodate the system
6534 administrator's choice.
6538 Given the above, <prgn>dpkg-statoverride</prgn> is
6539 essentially a tool for system administrators and would not
6540 normally be needed in the maintainer scripts. There is
6541 one type of situation, though, where calls to
6542 <prgn>dpkg-statoverride</prgn> would be needed in the
6543 maintainer scripts, and that involves packages which use
6544 dynamically allocated user or group ids. In such a
6545 situation, something like the following idiom can be very
6546 helpful in the package's <prgn>postinst</prgn>, where
6547 <tt>sysuser</tt> is a dynamically allocated id:
6549 for i in /usr/bin/foo /usr/sbin/bar
6551 if ! dpkg-statoverride --list $i >/dev/null
6553 dpkg-statoverride --update --add sysuser root 4755 $i
6557 The corresponding <tt>dpkg-statoverride --remove</tt>
6558 calls can then be made unconditionally when the package is
6565 <chapt id="customized-programs">
6566 <heading>Customized programs</heading>
6568 <sect id="arch-spec">
6569 <heading>Architecture specification strings</heading>
6572 If a program needs to specify an <em>architecture specification
6573 string</em> in some place, the following format should be
6574 used: <var>arch</var>-<var>os</var><footnote>
6576 The following architectures and operating systems are
6577 currently recognised by <prgn>dpkg-archictecture</prgn>.
6578 The architecture, <tt><var>arch</var></tt>, is one of
6579 the following: <tt>alpha</tt>, <tt>arm</tt>,
6580 <tt>hppa</tt>, <tt>i386</tt>, <tt>ia64</tt>,
6581 <tt>m68k</tt>, <tt>mips</tt>, <tt>mipsel</tt>,
6582 <tt>powerpc</tt>, <tt>s390</tt>, <tt>sh</tt>,
6583 <tt>sheb</tt>, <tt>sparc</tt> and <tt>sparc64</tt>. The
6584 operating system, <tt><var>os</var></tt>, is one of:
6585 <tt>linux</tt>, <tt>gnu</tt>, <tt>freebsd</tt> and
6586 <tt>openbsd</tt>. Use of <tt>gnu</tt> in this string is
6587 reserved for the GNU/Hurd operating system.
6593 Note that we don't want to use
6594 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
6595 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
6596 since this would make our programs incompatible with other
6597 Linux distributions. We also don't use something like
6598 <tt><var>arch</var>-unknown-linux</tt>, since the
6599 <tt>unknown</tt> does not look very good.
6604 <heading>Daemons</heading>
6607 The configuration files <file>/etc/services</file>,
6608 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
6609 by the <prgn>netbase</prgn> package and must not be modified
6614 If a package requires a new entry in one of these files, the
6615 maintainer should get in contact with the
6616 <prgn>netbase</prgn> maintainer, who will add the entries
6617 and release a new version of the <prgn>netbase</prgn>
6622 The configuration file <file>/etc/inetd.conf</file> must not be
6623 modified by the package's scripts except via the
6624 <prgn>update-inetd</prgn> script or the
6625 <file>DebianNet.pm</file> Perl module. See their documentation
6626 for details on how to add entries.
6630 If a package wants to install an example entry into
6631 <file>/etc/inetd.conf</file>, the entry must be preceded with
6632 exactly one hash character (<tt>#</tt>). Such lines are
6633 treated as "commented out by user" by the
6634 <prgn>update-inetd</prgn> script and are not changed or
6635 activated during package updates.
6640 <heading>Using pseudo-ttys and modifying wtmp, utmp and
6644 Some programs need to create pseudo-ttys. This should be done
6645 using Unix98 ptys if the C library supports it. The resulting
6646 program must not be installed setuid root, unless that
6647 is required for other functionality.
6651 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
6652 <file>/var/log/lastlog</file> must be installed writeable by
6653 group <tt>utmp</tt>. Programs which need to modify those
6654 files must be installed setgid <tt>utmp</tt>.
6659 <heading>Editors and pagers</heading>
6662 Some programs have the ability to launch an editor or pager
6663 program to edit or display a text document. Since there are
6664 lots of different editors and pagers available in the Debian
6665 distribution, the system administrator and each user should
6666 have the possibility to choose his/her preferred editor and
6671 In addition, every program should choose a good default
6672 editor/pager if none is selected by the user or system
6677 Thus, every program that launches an editor or pager must
6678 use the EDITOR or PAGER environment variable to determine
6679 the editor or pager the user wishes to use. If these
6680 variables are not set, the programs <file>/usr/bin/editor</file>
6681 and <file>/usr/bin/pager</file> should be used, respectively.
6685 These two files are managed through the <prgn>dpkg</prgn>
6686 "alternatives" mechanism. Thus every package providing an
6687 editor or pager must call the
6688 <prgn>update-alternatives</prgn> script to register these
6693 If it is very hard to adapt a program to make use of the
6694 EDITOR or PAGER variables, that program may be configured to
6695 use <file>/usr/bin/sensible-editor</file> and
6696 <file>/usr/bin/sensible-pager</file> as the editor or pager
6697 program respectively. These are two scripts provided in the
6698 Debian base system that check the EDITOR and PAGER variables
6699 and launch the appropriate program, and fall back to
6700 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
6701 variable is not set.
6705 A program may also use the VISUAL environment variable to
6706 determine the user's choice of editor. If it exists, it
6707 should take precedence over EDITOR. This is in fact what
6708 <file>/usr/bin/sensible-editor</file> does.
6712 It is not required for a package to depend on
6713 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
6714 package to provide such virtual packages.<footnote>
6716 The Debian base system already provides an editor and a
6723 <sect id="web-appl">
6724 <heading>Web servers and applications</heading>
6727 This section describes the locations and URLs that should
6728 be used by all web servers and web applications in the
6736 Cgi-bin executable files are installed in the
6738 <example compact="compact">
6739 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
6741 and should be referred to as
6742 <example compact="compact">
6743 http://localhost/cgi-bin/<var>cgi-bin-name</var>
6748 <item><p>Access to HTML documents</p>
6751 HTML documents for a package are stored in
6752 <file>/usr/share/doc/<var>package</var></file>
6753 and can be referred to as
6754 <example compact="compact">
6755 http://localhost/doc/<var>package</var>/<var>filename</var>
6759 The web server should restrict access to the document
6760 tree so that only clients on the same host can read
6761 the documents. If the web server does not support such
6762 access controls, then it should not provide access at
6763 all, or ask about providing access during installation.
6767 <item><p>Web Document Root</p>
6770 Web Applications should try to avoid storing files in
6771 the Web Document Root. Instead they should use the
6772 /usr/share/doc/<var>package</var> directory for
6773 documents and register the Web Application via the
6774 menu package. If access to the web document root is
6775 unavoidable then use
6776 <example compact="compact">
6779 as the Document Root. This might be just a symbolic
6780 link to the location where the system administrator
6781 has put the real document root.
6785 </enumlist></p></sect>
6788 <sect id="mail-transport-agents">
6789 <heading>Mail transport, delivery and user agents</heading>
6792 Debian packages which process electronic mail, whether mail
6793 user agents (MUAs) or mail transport agents (MTAs), must
6794 ensure that they are compatible with the configuration
6795 decisions below. Failure to do this may result in lost
6796 mail, broken <tt>From:</tt> lines, and other serious brain
6801 The mail spool is <file>/var/mail</file> and the interface to
6802 send a mail message is <file>/usr/sbin/sendmail</file> (as per
6803 the FHS). On older systems, the mail spool may be
6804 physically located in <file>/var/spool/mail</file>, but all
6805 access to the mail spool should be via the
6806 <file>/var/mail</file> symlink. The mail spool is part of the
6807 base system and not part of the MTA package.
6811 All Debian MUAs, MTAs, MDAs and other mailbox accessing
6812 programs (such as IMAP daemons) must lock the mailbox in an
6813 NFS-safe way. This means that <tt>fcntl()</tt> locking must
6814 be combined with dot locking. To avoid deadlocks, a program
6815 should use <tt>fcntl()</tt> first and dot locking after
6816 this, or alternatively implement the two locking methods in
6817 a non blocking way<footnote>
6819 If it is not possible to establish both locks, the
6820 system shouldn't wait for the second lock to be
6821 established, but remove the first lock, wait a (random)
6822 time, and start over locking again.
6824 </footnote>. Using the functions <tt>maillock</tt> and
6825 <tt>mailunlock</tt> provided by the
6826 <tt>liblockfile*</tt><footnote>
6828 You will need to depend on <tt>liblockfile1
6829 (>>1.01)</tt> to use these functions.
6831 </footnote> packages is the recommended way to realize this.
6835 Mailboxes are generally mode 660
6836 <tt><var>user</var>.mail</tt> unless the system
6837 administrator has chosen otherwise. A MUA may remove a
6838 mailbox (unless it has nonstandard permissions) in which
6839 case the MTA or another MUA must recreate it if needed.
6840 Mailboxes must be writable by group mail.
6844 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
6845 be setgid mail to do the locking mentioned above (and
6846 must obviously avoid accessing other users' mailboxes
6847 using this privilege).</p>
6850 <file>/etc/aliases</file> is the source file for the system mail
6851 aliases (e.g., postmaster, usenet, etc.), it is the one
6852 which the sysadmin and <prgn>postinst</prgn> scripts may
6853 edit. After <file>/etc/aliases</file> is edited the program or
6854 human editing it must call <prgn>newaliases</prgn>. All MTA
6855 packages must come with a <prgn>newaliases</prgn> program,
6856 even if it does nothing, but older MTA packages did not do
6857 this so programs should not fail if <prgn>newaliases</prgn>
6858 cannot be found. Note that because of this, all MTA
6859 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
6860 <tt>Replaces: mail-transport-agent</tt> control file
6865 The convention of writing <tt>forward to
6866 <var>address</var></tt> in the mailbox itself is not
6867 supported. Use a <tt>.forward</tt> file instead.</p>
6870 The <prgn>rmail</prgn> program used by UUCP
6871 for incoming mail should be <file>/usr/sbin/rmail</file>.
6872 Likewise, <prgn>rsmtp</prgn>, for receiving
6873 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
6877 If your package needs to know what hostname to use on (for
6878 example) outgoing news and mail messages which are generated
6879 locally, you should use the file <file>/etc/mailname</file>. It
6880 will contain the portion after the username and <tt>@</tt>
6881 (at) sign for email addresses of users on the machine
6882 (followed by a newline).
6886 Such package should check for the existence of this file
6887 when it is being configured. If it exists, it should be
6888 used without comment, although an MTA's configuration script
6889 may wish to prompt the user even if it finds that this file
6890 exists. If the file does not exist, the package should
6891 prompt the user for the value (preferably using
6892 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
6893 as well as using it in the package's configuration. The
6894 prompt should make it clear that the name will not just be
6895 used by that package. For example, in this situation the
6896 <tt>inn</tt> package could say something like:
6897 <example compact="compact">
6898 Please enter the "mail name" of your system. This is the
6899 hostname portion of the address to be shown on outgoing
6900 news and mail messages. The default is
6901 <var>syshostname</var>, your system's host name. Mail
6902 name ["<var>syshostname</var>"]:
6904 where <var>syshostname</var> is the output of <tt>hostname
6910 <heading>News system configuration</heading>
6913 All the configuration files related to the NNTP (news)
6914 servers and clients should be located under
6915 <file>/etc/news</file>.</p>
6918 There are some configuration issues that apply to a number
6919 of news clients and server packages on the machine. These
6923 <tag><file>/etc/news/organization</file></tag>
6924 <item><p>A string which should appear as the
6925 organization header for all messages posted
6926 by NNTP clients on the machine</p></item>
6928 <tag><file>/etc/news/server</file></tag>
6929 <item><p>Contains the FQDN of the upstream NNTP
6930 server, or localhost if the local machine is
6931 an NNTP server.</p></item>
6934 Other global files may be added as required for cross-package news
6935 configuration.</p></sect>
6939 <heading>Programs for the X Window System</heading>
6942 <heading>Providing X support and package priorities</heading>
6945 Programs that can be configured with support for the X
6946 Window System must be configured to do so and must declare
6947 any package dependencies necessary to satisfy their
6948 runtime requirements when using the X Window System. If
6949 such a package is of higher priority than the X packages
6950 on which it depends, it is required that either the
6951 X-specific components be split into a separate package, or
6952 that an alternative version of the package, which includes
6953 X support, be provided, or that the package's priority be
6959 <heading>Packages providing an X server</heading>
6962 Packages that provide an X server that, directly or
6963 indirectly, communicates with real input and display
6964 hardware should declare in their control data that they
6965 provide the virtual package <tt>xserver</tt>.<footnote>
6967 This implements current practice, and provides an
6968 actual policy for usage of the <tt>xserver</tt>
6969 virtual package which appears in the virtual packages
6970 list. In a nutshell, X servers that interface
6971 directly with the display and input hardware or via
6972 another subsystem (e.g., GGI) should provide
6973 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
6974 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
6981 <heading>Packages providing a terminal emulator</heading>
6984 Packages that provide a terminal emulator for the X Window
6985 System which meet the criteria listed below should declare
6986 in their control data that they provide the virtual
6987 package <tt>x-terminal-emulator</tt>. They should also
6988 register themselves as an alternative for
6989 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
6994 To be an <tt>x-terminal-emulator</tt>, a program must:
6995 <list compact="compact">
6997 Be able to emulate a DEC VT100 terminal, or a
6998 compatible terminal.
7002 Support the command-line option <tt>-e
7003 <var>command</var></tt>, which creates a new
7004 terminal window<footnote>
7006 "New terminal window" does not necessarily mean
7007 a new top-level X window directly parented by
7008 the window manager; it could, if the terminal
7009 emulator application were so coded, be a new
7010 "view" in a multiple-document interface (MDI).
7013 and runs the specified <var>command</var>.
7017 Support the command-line option <tt>-T
7018 <var>title</var></tt>, which creates a new terminal
7019 window with the window title <var>title</var>.
7026 <heading>Packages providing a window manager</heading>
7029 Packages that provide a window manager should declare in
7030 their control data that they provide the virtual package
7031 <tt>x-window-manager</tt>. They should also register
7032 themselves as an alternative for
7033 <file>/usr/bin/x-window-manager</file>, with a priority
7034 calculated as follows:
7035 <list compact="compact">
7036 <item><p>Start with a priority of 20.</p></item>
7040 If the window manager supports the Debian menu
7041 system, add 20 points if this support is available
7042 in the package's default configuration (i.e., no
7043 configuration files belonging to the system or user
7044 have to be edited to activate the feature); if
7045 configuration files must be modified, add only 10
7051 If the window manager complies with <url
7052 id="http://www.freedesktop.org/standards/wm-spec.html"
7053 name="The Window Manager Specification Project">,
7054 written by the <url id="http://www.freedesktop.org"
7055 name="Free Desktop Group">, add 20 points.
7061 If the window manager permits the X session to be
7062 restarted using a <em>different</em> window manager
7063 (without killing the X server) in its default
7064 configuration, add 10 points; otherwise add none.
7072 <heading>Packages providing fonts</heading>
7075 Packages that provide fonts for the X Window
7078 For the purposes of Debian Policy, a "font for the X
7079 Window System" is one which is accessed via X protocol
7080 requests. Fonts for the Linux console, for PostScript
7081 renderers, or any other purpose, do not fit this
7082 definition. Any tool which makes such fonts available
7083 to the X Window System, however, must abide by this
7087 must do a number of things to ensure that they are both
7088 available without modification of the X or font server
7089 configuration, and that they do not corrupt files used by
7090 other font packages to register information about
7095 Fonts of any type supported by the X Window System
7096 must be in a separate binary package from any
7097 executables, libraries, or documentation (except
7098 that specific to the fonts shipped, such as their
7099 license information). If one or more of the fonts
7100 so packaged are necessary for proper operation of
7101 the package with which they are associated the font
7102 package may be Recommended; if the fonts merely
7103 provide an enhancement, a Suggests relationship may
7104 be used. Packages must not Depend on font
7107 This is because the X server may retrieve fonts
7108 from the local filesystem or over the network
7109 from an X font server; the Debian package system
7110 is empowered to deal only with the local
7119 BDF fonts must be converted to PCF fonts with the
7120 <prgn>bdftopcf</prgn> utility (available in the
7121 <tt>xutils</tt> package, <prgn>gzip</prgn>ped, and
7122 placed in a directory that corresponds to their
7124 <list compact="compact">
7126 100 dpi fonts must be placed in
7127 <file>/usr/X11R6/lib/X11/fonts/100dpi/</file>.
7131 75 dpi fonts must be placed in
7132 <file>/usr/X11R6/lib/X11/fonts/75dpi/</file>.
7136 Character-cell fonts, cursor fonts, and other
7137 low-resolution fonts must be placed in
7138 <file>/usr/X11R6/lib/X11/fonts/misc/</file>.
7145 Speedo fonts must be placed in
7146 <file>/usr/X11R6/lib/X11/fonts/Speedo/</file>.
7150 Type 1 fonts must be placed in
7151 <file>/usr/X11R6/lib/X11/fonts/Type1/</file>. If font
7152 metric files are available, they must be placed here
7158 Subdirectories of <file>/usr/X11R6/lib/X11/fonts/</file>
7159 other than those listed above must be neither
7160 created nor used. (The <file>PEX</file>, <file>CID</file>,
7161 and <file>cyrillic</file> directories are excepted for
7162 historical reasons, but installation of files into
7163 these directories remains discouraged.)
7169 Font packages may, instead of placing files directly
7170 in the X font directories listed above, provide
7171 symbolic links in that font directory pointing to
7172 the files' actual location in the filesystem. Such
7173 a location must comply with the FHS.
7179 Font packages should not contain both 75dpi and
7180 100dpi versions of a font. If both are available,
7181 they should be provided in separate binary packages
7182 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
7183 the names of the packages containing the
7184 corresponding fonts.
7190 Fonts destined for the <file>misc</file> subdirectory
7191 should not be included in the same package as 75dpi
7192 or 100dpi fonts; instead, they should be provided in
7193 a separate package with <tt>-misc</tt> appended to
7200 Font packages must not provide the files
7201 <file>fonts.dir</file>, <file>fonts.alias</file>, or
7202 <file>fonts.scale</file> in a font directory:
7205 <file>fonts.dir</file> files must not be provided at all.
7210 <file>fonts.alias</file> and <file>fonts.scale</file>
7211 files, if needed, should be provided in the
7213 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
7214 where <var>fontdir</var> is the name of the
7216 <file>/usr/X11R6/lib/X11/fonts/</file> where the
7217 package's corresponding fonts are stored
7218 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
7219 <var>package</var> is the name of the package
7220 that provides these fonts, and
7221 <var>extension</var> is either <tt>scale</tt>
7222 or <tt>alias</tt>, whichever corresponds to
7232 Font packages must declare a dependency on
7233 <tt>xutils (>> 4.0.3)</tt> in their control
7240 Font packages that provide one or more
7241 <file>fonts.scale</file> files as described above must
7242 invoke <prgn>update-fonts-scale</prgn> on each
7243 directory into which they installed fonts
7244 <em>before</em> invoking
7245 <prgn>update-fonts-dir</prgn> on that directory.
7246 This invocation must occur in both the
7247 <prgn>postinst</prgn> (for all arguments) and
7248 <prgn>postrm</prgn> (for all arguments except
7249 <tt>upgrade</tt>) scripts.
7255 Font packages that provide one or more
7256 <file>fonts.alias</file> files as described above must
7257 invoke <prgn>update-fonts-alias</prgn> on each
7258 directory into which they installed fonts. This
7259 invocation must occur in both the
7260 <prgn>postinst</prgn> (for all arguments) and
7261 <prgn>postrm</prgn> (for all arguments except
7262 <tt>upgrade</tt>) scripts.
7268 Font packages must invoke
7269 <prgn>update-fonts-dir</prgn> on each directory into
7270 which they installed fonts. This invocation must
7271 occur in both the <prgn>postinst</prgn> (for all
7272 arguments) and <prgn>postrm</prgn> (for all
7273 arguments except <tt>upgrade</tt>) scripts.
7279 Font packages must not provide alias names for the
7280 fonts they include which collide with alias names
7281 already in use by fonts already packaged.
7287 Font packages must not provide fonts with the same
7288 XLFD registry name as another font already packaged.
7296 <heading>Application defaults files</heading>
7299 Application defaults files must be installed in the
7300 directory <file>/etc/X11/app-defaults/</file> (use of a
7301 localized subdirectory of <file>/etc/X11/</file> as described
7302 in the <em>X Toolkit Intrinsics - C Language
7303 Interface</em> manual is also permitted). They must be
7304 registered as <tt>conffile</tt>s or handled as
7305 configuration files. Packages must not provide the
7306 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
7310 Customization of programs' X resources may also be
7311 supported with the provision of a file with the same name
7312 as that of the package placed in the
7313 <file>/etc/X11/Xresources/</file> directory, which must
7314 registered as a <tt>conffile</tt> or handled as a
7315 configuration file.<footnote>
7317 Note that this mechanism is not the same as using
7318 app-defaults; app-defaults are tied to the client
7319 binary on the local filesystem, whereas X resources
7320 are stored in the X server and affect all connecting
7324 <em>Important:</em> packages that install files into the
7325 <file>/etc/X11/Xresources/</file> directory must conflict with
7326 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
7327 it is possible for the installing package to destroy a
7328 previously-existing <file>/etc/X11/Xresources</file> file
7329 which had been customized by the system administrator.
7334 <heading>Installation directory issues</heading>
7337 Packages using the X Window System should not be
7338 configured to install files under the <file>/usr/X11R6/</file>
7339 directory unless they use <prgn>imake</prgn>. The
7340 <file>/usr/X11R6/</file> directory hierarchy should be
7341 regarded as deprecated for all packages except the X
7342 Window System itself, and those which use the
7343 <prgn>imake</prgn> program it provides, in which case the
7344 packages may transition out of the <file>/usr/X11R6/</file>
7345 directory at the maintainer's discretion.<footnote>
7347 <prgn>Imake</prgn>-using programs are exempt because,
7348 as long as they are written correctly, the pathnames
7349 they use to locate resources and install themselves
7350 are derived wholly from the X Window System
7351 configuration. Thus, in the event that the X Window
7352 System moves to <file>/usr/X11R7/</file>,
7353 <file>/usr/X12/</file>, or just plain <file>/usr/</file>, all
7354 that is required for these programs is a recompile
7355 against the corresponding X Window System library
7356 development packages.
7359 Programs that use GNU <prgn>autoconf</prgn> and
7360 <prgn>automake</prgn> are usually easily configured at
7361 compile time to use <file>/usr/</file> instead of
7362 <file>/usr/X11R6/</file>, and this should be done whenever
7363 possible. Configuration files for window managers and
7364 display managers should be placed in a subdirectory of
7365 <file>/etc/X11/</file> corresponding to the package name due
7366 to these programs' tight integration with the mechanisms
7367 of the X Window System. Application-level programs should
7368 use the <file>/etc/</file> directory unless otherwise mandated
7369 by policy. The installation of files into subdirectories
7370 of <file>/usr/X11R6/include/X11/</file> and
7371 <file>/usr/X11R6/lib/X11/</file> is permitted but discouraged;
7372 package maintainers should determine if subdirectories of
7373 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
7374 instead. (The use of symbolic links from the
7375 <file>X11R6</file> directories to other FHS-compliant
7376 locations is encouraged if the program is not easily
7377 configured to look elsewhere for its files.) Packages
7378 must not provide or install files into the directories
7379 <file>/usr/bin/X11/</file>, <file>/usr/include/X11/</file> or
7380 <file>/usr/lib/X11/</file>. Files within a package should,
7381 however, make reference to these directories, rather than
7382 their <tt>X11R6</tt>-named counterparts
7383 <file>/usr/X11R6/bin/</file>, <file>/usr/X11R6/include/X11/</file>
7384 and <file>/usr/X11R6/lib/X11/</file>, if the resources being
7385 referred to have not been moved to other FHS-compliant
7391 <heading>The OSF/Motif and OpenMotif libraries</heading>
7394 <em>Programs that require the non-DFSG-compliant OSF/Motif or
7395 OpenMotif libraries</em><footnote>
7397 OSF/Motif and OpenMotif are collectively referred to as
7398 "Motif" in this policy document.
7401 should be compiled against and tested with LessTif (a free
7402 re-implementation of Motif) instead. If the maintainer
7403 judges that the program or programs do not work
7404 sufficiently well with LessTif to be distributed and
7405 supported, but do so when compiled against Motif, then two
7406 versions of the package should be created; one linked
7407 statically against Motif and with <tt>-smotif</tt>
7408 appended to the package name, and one linked dynamically
7409 against Motif and with <tt>-dmotif</tt> appended to the
7410 package name. Both Motif-linked versions are dependent
7411 upon non-DFSG-compliant software and thus cannot be
7412 uploaded to the <em>main</em> distribution; if the
7413 software is itself DFSG-compliant it may be uploaded to
7414 the <em>contrib</em> distribution. While known existing
7415 versions of Motif permit unlimited redistribution of
7416 binaries linked against the library (whether statically or
7417 dynamically), it is the package maintainer's
7418 responsibility to determine whether this is permitted by
7419 the license of the copy of Motif in his or her possession.
7425 <heading>Perl programs and modules</heading>
7427 Perl programs and modules should follow the current Perl
7428 policy as defined in the file found on
7429 <ftpsite>ftp.debian.org</ftpsite> in
7430 <ftppath>/debian/doc/package-developer/perl-policy.txt.gz</ftppath>
7431 or your local mirror. In addition, it is included in the
7432 <tt>debian-policy</tt> package.
7437 <heading>Emacs lisp programs</heading>
7440 Please refer to the "Debian Emacs Policy" (documented in
7441 <file>debian-emacs-policy.gz</file> of the
7442 <prgn>emacsen-common</prgn> package) for details of how to
7443 package emacs lisp programs.
7448 <heading>Games</heading>
7451 The permissions on <file>/var/games</file> are mode 755, owner
7452 <tt>root</tt> and group <tt>root</tt>.
7456 Each game decides on its own security policy.</p>
7459 Games which require protected, privileged access to
7460 high-score files, savegames, etc., may be made
7461 set-<em>group</em>-id (mode 2755) and owned by
7462 <tt>root.games</tt>, and use files and directories with
7463 appropriate permissions (770 <tt>root.games</tt>, for
7464 example). They must not be made
7465 set-<em>user</em>-id, as this causes security problems. (If
7466 an attacker can subvert any set-user-id game they can
7467 overwrite the executable of any other, causing other players
7468 of these games to run a Trojan horse program. With a
7469 set-group-id game the attacker only gets access to less
7470 important game data, and if they can get at the other
7471 players' accounts at all it will take considerably more
7475 Some packages, for example some fortune cookie programs, are
7476 configured by the upstream authors to install with their
7477 data files or other static information made unreadable so
7478 that they can only be accessed through set-id programs
7479 provided. You should not do this in a Debian package: anyone can
7480 download the <file>.deb</file> file and read the data from it,
7481 so there is no point making the files unreadable. Not
7482 making the files unreadable also means that you don't have
7483 to make so many programs set-id, which reduces the risk of a
7487 As described in the FHS, binaries of games should be
7488 installed in the directory <file>/usr/games</file>. This also
7489 applies to games that use the X Window System. Manual pages
7490 for games (X and non-X games) should be installed in
7491 <file>/usr/share/man/man6</file>.</p>
7495 <chapt id="docs"><heading>Documentation</heading>
7499 <heading>Manual pages</heading>
7502 You should install manual pages in <prgn>nroff</prgn> source
7503 form, in appropriate places under <file>/usr/share/man</file>.
7504 You should only use sections 1 to 9 (see the FHS for more
7505 details). You must not install a preformatted "cat page".
7509 Each program, utility, and function should have an
7510 associated manual page included in the same package. It is
7511 suggested that all configuration files also have a manual
7512 page included as well. Manual pages for protocols and other
7513 auxiliary things are optional.
7517 If no manual page is available, this is considered as a bug
7518 and should be reported to the Debian Bug Tracking System (the
7519 maintainer of the package is allowed to write this bug report
7520 themselves, if they so desire). Do not close the bug report
7521 until a proper manpage is available.<footnote>
7523 It is not very hard to write a man page. See the
7524 <url id="http://www.schweikhardt.net/man_page_howto.html"
7525 name="Man-Page-HOWTO">,
7526 <manref name="man" section="7">, the examples
7527 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
7528 the helper programs <prgn>help2man</prgn>, or the
7529 directory <file>/usr/share/doc/man-db/examples</file>.
7535 You may forward a complaint about a missing manpage to the
7536 upstream authors, and mark the bug as forwarded in the
7537 Debian bug tracking system. Even though the GNU Project do
7538 not in general consider the lack of a manpage to be a bug,
7539 we do; if they tell you that they don't consider it a bug
7540 you should leave the bug in our bug tracking system open
7545 Manual pages should be installed compressed using <tt>gzip -9</tt>.
7549 If one manpage needs to be accessible via several names it
7550 is better to use a symbolic link than the <file>.so</file>
7551 feature, but there is no need to fiddle with the relevant
7552 parts of the upstream source to change from <file>.so</file> to
7553 symlinks: don't do it unless it's easy. You should not
7554 create hard links in the manual page directories, nor put
7555 absolute filenames in <file>.so</file> directives. The filename
7556 in a <file>.so</file> in a manpage should be relative to the
7557 base of the manpage tree (usually
7558 <file>/usr/share/man</file>). If you do not create any links
7559 (whether symlinks, hard links, or <tt>.so</tt> directives)
7560 in the filesystem to the alternate names of the manpage,
7561 then you should not rely on <prgn>man</prgn> finding your
7562 manpage under those names based solely on the information in
7563 the manpage's header.<footnote>
7565 Supporting this in <prgn>man</prgn> often requires
7566 unreasonable processing time to find a manual page or to
7567 report that none exists, and moves knowledge into man's
7568 database that would be better left in the filesystem.
7569 This support is therefore deprecated and will cease to
7570 be present in the future.
7577 <heading>Info documents</heading>
7580 Info documents should be installed in <file>/usr/share/info</file>.
7581 They should be compressed with <tt>gzip -9</tt>.
7585 Your package should call <prgn>install-info</prgn> to update
7586 the Info <file>dir</file> file in its <prgn>postinst</prgn>
7587 script when called with a <tt>configure</tt> argument, for
7589 <example compact="compact">
7590 install-info --quiet --section Development Development \
7591 /usr/share/info/foobar.info
7595 It is a good idea to specify a section for the location of
7596 your program; this is done with the <tt>--section</tt>
7597 switch. To determine which section to use, you should look
7598 at <file>/usr/share/info/dir</file> on your system and choose the most
7599 relevant (or create a new section if none of the current
7600 sections are relevant). Note that the <tt>--section</tt>
7601 flag takes two arguments; the first is a regular expression
7602 to match (case-insensitively) against an existing section,
7603 the second is used when creating a new one.</p>
7606 You should remove the entries in the <prgn>prerm</prgn>
7607 script when called with a <tt>remove</tt> argument:
7608 <example compact="compact">
7609 install-info --quiet --remove /usr/share/info/foobar.info
7613 If <prgn>install-info</prgn> cannot find a description entry
7614 in the Info file you must supply one. See <manref
7615 name="install-info" section="8"> for details.</p>
7619 <heading>Additional documentation</heading>
7622 Any additional documentation that comes with the package may
7623 be installed at the discretion of the package maintainer.
7624 Text documentation should be installed in the directory
7625 <file>/usr/share/doc/<var>package</var></file>, where
7626 <var>package</var> is the name of the package, and
7627 compressed with <tt>gzip -9</tt> unless it is small.
7631 If a package comes with large amounts of documentation which
7632 many users of the package will not require you should create
7633 a separate binary package to contain it, so that it does not
7634 take up disk space on the machines of users who do not need
7635 or want it installed.</p>
7638 It is often a good idea to put text information files
7639 (<file>README</file>s, changelogs, and so forth) that come with
7640 the source package in <file>/usr/share/doc/<var>package</var></file>
7641 in the binary package. However, you don't need to install
7642 the instructions for building and installing the package, of
7646 Packages must not require the existance of any files in
7647 <file>/usr/share/doc/</file> in order to function
7650 The system administrator should be able to
7651 delete files in <file>/usr/share/doc/</file> without causing
7652 any programs to break.
7655 Any files that are referenced by programs but are also
7656 useful as standalone documentation should be installed under
7657 <file>/usr/share/<var>package</var>/</file> with symbolic links from
7658 <file>/usr/share/doc/<var>package</var></file>.
7662 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7663 link to another directory in <file>/usr/share/doc</file> only if
7664 the two packages both come from the same source and the
7665 first package Depends on the second.
7669 Former Debian releases placed all additional documentation
7670 in <file>/usr/doc/<var>package</var></file>. This has been
7671 changed to <file>/usr/share/doc/<var>package</var></file>,
7672 and packages must not put documentation in the directory
7673 <file>/usr/doc/<var>package</var></file>. <footnote>
7674 <p>At this phase of the transition, we no longer require a
7675 symbolic link in <file>/usr/doc/</file>. At a later point,
7676 policy shall change to make the symbolic links a bug.</p>
7682 <heading>Preferred documentation formats</heading>
7685 The unification of Debian documentation is being carried out
7689 If your package comes with extensive documentation in a
7690 markup format that can be converted to various other formats
7691 you should if possible ship HTML versions in a binary
7692 package, in the directory
7693 <file>/usr/share/doc/<var>appropriate-package</var></file> or
7694 its subdirectories.<footnote>
7696 The rationale: The important thing here is that HTML
7697 docs should be available in <em>some</em> package, not
7698 necessarily in the main binary package.
7704 Other formats such as PostScript may be provided at the
7705 package maintainer's discretion.
7709 <sect id="copyrightfile">
7710 <heading>Copyright information</heading>
7713 Every package must be accompanied by a verbatim copy of its
7714 copyright and distribution license in the file
7715 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
7716 file must neither be compressed nor be a symbolic link.
7720 In addition, the copyright file must say where the upstream
7721 sources (if any) were obtained. It should name the original
7722 authors of the package and the Debian maintainer(s) who were
7723 involved with its creation.</p>
7726 A copy of the file which will be installed in
7727 <file>/usr/share/doc/<var>package</var>/copyright</file> should
7728 be in <file>debian/copyright</file> in the source package.
7732 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7733 link to another directory in <file>/usr/share/doc</file> only if
7734 the two packages both come from the same source and the
7735 first package Depends on the second. These rules are
7736 important because copyrights must be extractable by
7741 Packages distributed under the UCB BSD license, the Artistic
7742 license, the GNU GPL, and the GNU LGPL should refer to the
7743 files <file>/usr/share/common-licenses/BSD</file>,
7744 <file>/usr/share/common-licenses/Artistic</file>,
7745 <file>/usr/share/common-licenses/GPL</file>, and
7746 <file>/usr/share/common-licenses/LGPL</file> respectively,
7747 rather than quoting them in the copyright file.
7751 You should not use the copyright file as a general <file>README</file>
7752 file. If your package has such a file it should be
7753 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
7754 <file>README.Debian</file> or some other appropriate place.</p>
7758 <heading>Examples</heading>
7761 Any examples (configurations, source files, whatever),
7762 should be installed in a directory
7763 <file>/usr/share/doc/<var>package</var>/examples</file>. These
7764 files should not be referenced by any program: they're there
7765 for the benefit of the system administrator and users as
7766 documentation only. Architecture-specific example files
7767 should be installed in a directory
7768 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
7770 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
7771 latter directory itself may be a symbolic link to the
7776 <sect id="changelogs">
7777 <heading>Changelog files</heading>
7780 The Debian changelog file (<file>debian/changelog</file>) should
7781 explain briefly what modifications were made in the Debian version
7782 of the package compared to the upstream one. Other changes and
7783 updates to the package should also be documented in this file.
7787 Mistakes in changelogs are usually best rectified by
7788 making a new changelog entry rather than "rewriting history"
7789 by editing old changelog entries.
7793 The format of the <file>debian/changelog</file> file is described
7794 in <ref id="dpkgchangelog">. In non-experimental packages you must
7795 use a format for <file>debian/changelog</file> which is supported
7796 by the most recent released version of <prgn>dpkg</prgn>.<footnote>
7798 If you wish to use an alternative format, you may do so as
7799 long as you include a parser for it in your source package.
7800 The parser must have an API compatible with that expected by
7801 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-gencontrol</prgn>.
7802 If there is general interest in the new format, you should
7803 contact the <package>dpkg</package> maintainer to have the
7804 parser script for it included in the <prgn>dpkg</prgn>
7805 package. (You will need to agree that the parser and its
7806 manpage may be distributed under the GNU GPL, just as the rest
7807 of <prgn>dpkg</prgn> is.)
7813 Packages that are not Debian-native must contain a
7814 compressed copy of the <file>debian/changelog</file> file from
7815 the Debian source tree in
7816 <file>/usr/share/doc/<var>package</var></file> with the name
7817 <file>changelog.Debian.gz</file>.
7821 If an upstream changelog is available, it should be accessible as
7822 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
7823 plain text. If the upstream changelog is distributed in
7824 HTML, it should be made available in that form as
7825 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
7826 and a plain text <file>changelog.gz</file> should be generated
7827 from it using, for example, <tt>lynx -dump -nolist</tt>. If
7828 the upstream changelog files do not already conform to this
7829 naming convention, then this may be achieved either by
7830 renaming the files, or by adding a symbolic link, at the
7831 maintainer's discretion.<footnote>
7833 Rationale: People should not have to look in places for
7834 upstream changelogs merely because they are given
7835 different names or are distributed in HTML format.
7841 All of these files should be installed compressed using
7842 <tt>gzip -9</tt>, as they will become large with time even
7843 if they start out small.
7847 If the package has only one changelog which is used both as
7848 the Debian changelog and the upstream one because there is
7849 no separate upstream maintainer then that changelog should
7850 usually be installed as
7851 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
7852 there is a separate upstream maintainer, but no upstream
7853 changelog, then the Debian changelog should still be called
7854 <file>changelog.Debian.gz</file>.</p>
7859 <appendix id="pkg-scope">
7860 <heading>Introduction and scope of these appendices</heading>
7863 These appendices are taken essentially verbatim from the
7864 now-deprecated Packaging Manual, version 3.2.1.0. They are
7865 the chapters which are likely to be of use to package
7866 maintainers and which have not already been included in the
7867 policy document itself. Most of these sections are very likely
7868 not relevant to policy; they should be treated as
7869 documentation for the packaging system. Please note that these
7870 appendices are included for convenience, and for historical
7871 reasons: they used to be part of policy package, and they have
7872 not yet been incorporated into dpkg documentation. However,
7873 they still have value, and hence they are presented here.
7876 They have not yet been checked to ensure that they are
7877 compatible with the contents of policy, and if there are any
7878 contradictions, the version in the main policy document takes
7879 precedence. The remaining chapters of the old Packaging
7880 Manual have also not been read in detail to ensure that there
7881 are not parts which have been left out. Both of these will be
7886 <prgn>dpkg</prgn> is a suite of programs for creating binary
7887 package files and installing and removing them on Unix
7890 <prgn>dpkg</prgn> is targetted primarily at Debian
7891 GNU/Linux, but may work on or be ported to other
7898 The binary packages are designed for the management of
7899 installed executable programs (usually compiled binaries) and
7900 their associated data, though source code examples and
7901 documentation are provided as part of some packages.</p>
7904 This manual describes the technical aspects of creating Debian
7905 binary packages (<file>.deb</file> files). It documents the
7906 behaviour of the package management programs
7907 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
7908 they interact with packages.</p>
7911 It also documents the interaction between
7912 <prgn>dselect</prgn>'s core and the access method scripts it
7913 uses to actually install the selected packages, and describes
7914 how to create a new access method.</p>
7917 This manual does not go into detail about the options and
7918 usage of the package building and installation tools. It
7919 should therefore be read in conjuction with those programs'
7924 The utility programs which are provided with <prgn>dpkg</prgn>
7925 for managing various system configuration and similar issues,
7926 such as <prgn>update-rc.d</prgn> and
7927 <prgn>install-info</prgn>, are not described in detail here -
7928 please see their manpages.
7932 It does <em>not</em> describe the policy requirements imposed
7933 on Debian packages, such as the permissions on files and
7934 directories, documentation requirements, upload procedure, and
7935 so on. You should see the Debian packaging policy manual for
7936 these details. (Many of them will probably turn out to be
7937 helpful even if you don't plan to upload your package and make
7938 it available as part of the distribution.)
7942 It is assumed that the reader is reasonably familiar with the
7943 <prgn>dpkg</prgn> System Administrators' manual.
7944 Unfortunately this manual does not yet exist.
7948 The Debian version of the FSF's GNU hello program is provided
7949 as an example for people wishing to create Debian
7950 packages. The Debian <prgn>debmake</prgn> package is
7951 recommended as a very helpful tool in creating and maintaining
7952 Debian packages. However, while the tools and examples are
7953 helpful, they do not replace the need to read and follow the
7954 Policy and Programmer's Manual.</p>
7957 <appendix id="pkg-binarypkg"><heading>Binary packages (from old
7962 The binary package has two main sections. The first part
7963 consists of various control information files and scripts used
7964 by <prgn>dpkg</prgn> when installing and removing. See <ref
7965 id="pkg-controlarea">.
7969 The second part is an archive containing the files and
7970 directories to be installed.
7974 In the future binary packages may also contain other
7975 components, such as checksums and digital signatures. The
7976 format for the archive is described in full in the
7977 <file>deb(5)</file> manpage.
7981 <sect id="pkg-bincreating"><heading>Creating package files -
7982 <prgn>dpkg-deb</prgn>
7986 All manipulation of binary package files is done by
7987 <prgn>dpkg-deb</prgn>; it's the only program that has
7988 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
7989 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
7990 will spot that the options requested are appropriate to
7991 <prgn>dpkg-deb</prgn> and invoke that instead with the same
7996 In order to create a binary package you must make a
7997 directory tree which contains all the files and directories
7998 you want to have in the filesystem data part of the package.
7999 In Debian-format source packages this directory is usually
8000 <file>debian/tmp</file>, relative to the top of the package's
8005 They should have the locations (relative to the root of the
8006 directory tree you're constructing) ownerships and
8007 permissions which you want them to have on the system when
8012 With current versions of <prgn>dpkg</prgn> the uid/username
8013 and gid/groupname mappings for the users and groups being
8014 used should be the same on the system where the package is
8015 built and the one where it is installed.
8019 You need to add one special directory to the root of the
8020 miniature filesystem tree you're creating:
8021 <prgn>DEBIAN</prgn>. It should contain the control
8022 information files, notably the binary package control file
8023 (see <ref id="pkg-controlfile">).
8027 The <prgn>DEBIAN</prgn> directory will not appear in the
8028 filesystem archive of the package, and so won't be installed
8029 by <prgn>dpkg</prgn> when the package is installed.
8033 When you've prepared the package, you should invoke:
8035 dpkg --build <var>directory</var>
8040 This will build the package in
8041 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8042 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8043 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8048 See the manpage <manref name="dpkg-deb" section="8"> for details of how
8049 to examine the contents of this newly-created file. You may find the
8050 output of following commands enlightening:
8052 dpkg-deb --info <var>filename</var>.deb
8053 dpkg-deb --contents <var>filename</var>.deb
8054 dpkg --contents <var>filename</var>.deb
8056 To view the copyright file for a package you could use this command:
8058 dpkg --fsys-tarfile <var>filename</var>.deb | tar xof usr/share/doc/<var>\*</var>copyright | less
8063 <sect id="pkg-controlarea">
8065 Package control information files
8069 The control information portion of a binary package is a
8070 collection of files with names known to <prgn>dpkg</prgn>.
8071 It will treat the contents of these files specially - some
8072 of them contain information used by <prgn>dpkg</prgn> when
8073 installing or removing the package; others are scripts which
8074 the package maintainer wants <prgn>dpkg</prgn> to run.
8078 It is possible to put other files in the package control
8079 area, but this is not generally a good idea (though they
8080 will largely be ignored).
8084 Here is a brief list of the control info files supported by
8085 <prgn>dpkg</prgn> and a summary of what they're used for.
8090 <tag><tt>control</tt>
8094 This is the key description file used by
8095 <prgn>dpkg</prgn>. It specifies the package's name
8096 and version, gives its description for the user,
8097 states its relationships with other packages, and so
8098 forth. See <ref id="pkg-controlfile">.
8102 It is usually generated automatically from information
8103 in the source package by the
8104 <prgn>dpkg-gencontrol</prgn> program, and with
8105 assistance from <prgn>dpkg-shlibdeps</prgn>. See <ref
8106 id="pkg-sourcetools">.</p>
8109 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8115 These are exectuable files (usually scripts) which
8116 <prgn>dpkg</prgn> runs during installation, upgrade
8117 and removal of packages. They allow the package to
8118 deal with matters which are particular to that package
8119 or require more complicated processing than that
8120 provided by <prgn>dpkg</prgn>. Details of when and
8121 how they are called are in <ref
8122 id="maintainerscripts">.
8126 It is very important to make these scripts
8130 That means that if it runs successfully or fails
8131 and then you call it again it doesn't bomb out,
8132 but just ensures that everything is the way it
8135 </footnote> This is so that if an error occurs, the
8136 user interrupts <prgn>dpkg</prgn> or some other
8137 unforeseen circumstance happens you don't leave the
8138 user with a badly-broken package.
8142 The maintainer scripts are guaranteed to run with a
8143 controlling terminal and can interact with the user.
8144 If they need to prompt for passwords, do full-screen
8145 interaction or something similar you should do these
8146 things to and from <file>/dev/tty</file>, since
8147 <prgn>dpkg</prgn> will at some point redirect scripts'
8148 standard input and output so that it can log the
8149 installation process. Likewise, because these scripts
8150 may be executed with standard output redirected into a
8151 pipe for logging purposes, Perl scripts should set
8152 unbuffered output by setting <tt>$|=1</tt> so that the
8153 output is printed immediately rather than being
8158 Each script should return a zero exit status for
8159 success, or a nonzero one for failure.</p>
8162 <tag><tt>conffiles</tt>
8167 This file contains a list of configuration files which
8168 are to be handled automatically by <prgn>dpkg</prgn>
8169 (see <ref id="pkg-conffiles">). Note that not necessarily
8170 every configuration file should be listed here.</p>
8173 <tag><tt>shlibs</tt>
8178 This file contains a list of the shared libraries
8179 supplied by the package, with dependency details for
8180 each. This is used by <prgn>dpkg-shlibdeps</prgn>
8181 when it determines what dependencies are required in a
8182 package control file. The <tt>shlibs</tt> file format
8183 is described on <ref id="shlibs">.
8189 <sect id="pkg-controlfile">
8191 The main control information file: <tt>control</tt>
8194 The most important control information file used by
8195 <prgn>dpkg</prgn> when it installs a package is
8196 <tt>control</tt>. It contains all the package"s "vital
8201 The binary package control files of packages built from
8202 Debian sources are made by a special tool,
8203 <prgn>dpkg-gencontrol</prgn>, which reads
8204 <file>debian/control</file> and <file>debian/changelog</file> to
8205 find the information it needs. See <ref id="pkg-sourcepkg"> for
8210 The fields in binary package control files are:
8211 <list compact="compact">
8213 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8216 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
8218 <item><p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8222 This field should appear in all packages, though
8223 <prgn>dpkg</prgn> doesn't require it yet so that
8224 old packages can still be installed.
8230 <p><qref id="relationships"><tt>Depends</tt>,
8231 <tt>Provides</tt> et al.</qref></p>
8234 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8237 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8240 <p><qref id="pkg-f-classification"><tt>Section</tt>,
8241 <tt>Priority</tt></qref></p>
8244 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
8247 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8251 <qref id="pkg-f-Installed-Size"><tt>Installed-Size</tt></qref>
8257 A description of the syntax of control files and the purpose
8258 of these fields is available in <ref id="pkg-controlfields">.
8263 <heading>Time Stamps</heading>
8265 Maintainers are encouraged to preserve the modification
8266 times of the upstream source files in a package, as far as
8267 is reasonably possible.
8270 The rationale is that there is some information conveyed
8271 by knowing the age of the file, for example, you could
8272 recognize that some documentation is very old by looking
8273 at the modification time, so it would be nice if the
8274 modification time of the upstream source would be
8282 <appendix id="pkg-sourcepkg">
8283 <heading>Source packages (from old Packaging Manual) </heading>
8286 The Debian binary packages in the distribution are generated
8287 from Debian sources, which are in a special format to assist
8288 the easy and automatic building of binaries.
8292 There was a previous version of the Debian source format,
8293 which is now being phased out. Instructions for converting an
8294 old-style package are given in the Debian policy manual.
8297 <sect id="pkg-sourcetools">
8298 <heading>Tools for processing source packages</heading>
8301 Various tools are provided for manipulating source packages;
8302 they pack and unpack sources and help build of binary
8303 packages and help manage the distribution of new versions.
8307 They are introduced and typical uses described here; see
8308 <manref name="dpkg-source" section="1"> for full
8309 documentation about their arguments and operation.
8313 For examples of how to construct a Debian source package,
8314 and how to use those utilities that are used by Debian
8315 source packages, please see the <prgn>hello</prgn> example
8321 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
8326 This program is frequently used by hand, and is also
8327 called from package-independent automated building scripts
8328 such as <prgn>dpkg-buildpackage</prgn>.
8332 To unpack a package it is typically invoked with
8334 dpkg-source -x <var>.../path/to/filename</var>.dsc
8339 with the <file><var>filename</var>.tar.gz</file> and
8340 <file><var>filename</var>.diff.gz</file> (if applicable) in
8341 the same directory. It unpacks into
8342 <file><var>package</var>-<var>version</var></file>, and if
8344 <file><var>package</var>-<var>version</var>.orig</file>, in
8345 the current directory.
8349 To create a packed source archive it is typically invoked:
8351 dpkg-source -b <var>package</var>-<var>version</var>
8356 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
8357 <file>.diff.gz</file> (if appropriate) in the current
8358 directory. <prgn>dpkg-source</prgn> does not clean the
8359 source tree first - this must be done separately if it is
8364 See also <ref id="pkg-sourcearchives">.</p>
8370 <prgn>dpkg-buildpackage</prgn> - overall package-building
8375 <prgn>dpkg-buildpackage</prgn> is a script which invokes
8376 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
8377 targets <tt>clean</tt>, <tt>build</tt> and
8378 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
8379 <prgn>pgp</prgn> to build a signed source and binary
8384 It is usually invoked by hand from the top level of the
8385 built or unbuilt source directory. It may be invoked with
8386 no arguments; useful arguments include:
8387 <taglist compact="compact">
8388 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
8391 Do not PGP-sign the <tt>.changes</tt> file or the
8392 source package <tt>.dsc</tt> file, respectively.</p>
8394 <tag><tt>-p<var>pgp-command</var></tt></tag>
8397 Invoke <var>pgp-command</var> instead of finding
8398 <tt>pgp</tt> on the <prgn>PATH</prgn>.
8399 <var>pgp-command</var> must behave just like
8400 <prgn>pgp</prgn>.</p>
8402 <tag><tt>-r<var>root-command</var></tt></tag>
8405 When root privilege is required, invoke the command
8406 <var>root-command</var>. <var>root-command</var>
8407 should invoke its first argument as a command, from
8408 the <prgn>PATH</prgn> if necessary, and pass its
8409 second and subsequent arguments to the command it
8410 calls. If no <var>root-command</var> is supplied
8411 then <var>dpkg-buildpackage</var> will take no
8412 special action to gain root privilege, so that for
8413 most packages it will have to be invoked as root to
8416 <tag><tt>-b</tt>, <tt>-B</tt></tag>
8419 Two types of binary-only build and upload - see
8420 <manref name="dpkg-source" section="1">.
8429 <prgn>dpkg-gencontrol</prgn> - generates binary package
8434 This program is usually called from <file>debian/rules</file>
8435 (see <ref id="pkg-sourcetree">) in the top level of the source
8440 This is usually done just before the files and directories in the
8441 temporary directory tree where the package is being built have their
8442 permissions and ownerships set and the package is constructed using
8443 <prgn>dpkg-deb/</prgn>
8446 This is so that the control file which is produced has
8447 the right permissions
8453 <prgn>dpkg-gencontrol</prgn> must be called after all the
8454 files which are to go into the package have been placed in
8455 the temporary build directory, so that its calculation of
8456 the installed size of a package is correct.
8460 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
8461 be run after <prgn>dpkg-shlibdeps</prgn> so that the
8462 variable substitutions created by
8463 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
8468 For a package which generates only one binary package, and
8469 which builds it in <file>debian/tmp</file> relative to the top
8470 of the source package, it is usually sufficient to call
8471 <prgn>dpkg-gencontrol</prgn>.
8475 Sources which build several binaries will typically need
8478 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
8479 </example> The <tt>-P</tt> tells
8480 <prgn>dpkg-gencontrol</prgn> that the package is being
8481 built in a non-default directory, and the <tt>-p</tt>
8482 tells it which package's control file should be generated.
8486 <prgn>dpkg-gencontrol</prgn> also adds information to the
8487 list of files in <file>debian/files</file>, for the benefit of
8488 (for example) a future invocation of
8489 <prgn>dpkg-genchanges</prgn>.</p>
8494 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
8499 This program is usually called from <file>debian/rules</file>
8500 just before <prgn>dpkg-gencontrol</prgn> (see <ref
8501 id="pkg-sourcetree">), in the top level of the source tree.
8505 Its arguments are executables.
8508 In a forthcoming dpkg version,
8509 <prgn>dpkg-shlibdeps</prgn> would be required to be
8510 called on shared libraries as well.
8513 They may be specified either in the locations in the
8514 source tree where they are created or in the locations
8515 in the temporary build tree where they are installed
8516 prior to binary package creation.
8518 </footnote> for which shared library dependencies should
8519 be included in the binary package's control file.
8523 If some of the found shared libraries should only
8524 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
8525 some warrant a <tt>Pre-Depends</tt>, this can be achieved
8526 by using the <tt>-d<var>dependency-field</var></tt> option
8527 before those executable(s). (Each <tt>-d</tt> option
8528 takes effect until the next <tt>-d</tt>.)
8532 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
8533 output control file to be modified. Instead by default it
8534 adds to the <file>debian/substvars</file> file variable
8535 settings like <tt>shlibs:Depends</tt>. These variable
8536 settings must be referenced in dependency fields in the
8537 appropriate per-binary-package sections of the source
8542 For example, the <prgn>procps</prgn> package generates two
8543 kinds of binaries, simple C binaries like <prgn>ps</prgn>
8544 which require a predependency and full-screen ncurses
8545 binaries like <prgn>top</prgn> which require only a
8546 recommendation. It can say in its <file>debian/rules</file>:
8548 dpkg-shlibdeps -dPre-Depends ps -dRecommends top
8550 and then in its main control file <file>debian/control</file>:
8554 Pre-Depends: ${shlibs:Pre-Depends}
8555 Recommends: ${shlibs:Recommends}
8561 Sources which produce several binary packages with
8562 different shared library dependency requirements can use
8563 the <tt>-p<var>varnameprefix</var></tt> option to override
8564 the default <tt>shlibs:</tt> prefix (one invocation of
8565 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
8566 They can thus produce several sets of dependency
8567 variables, each of the form
8568 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
8569 which can be referred to in the appropriate parts of the
8570 binary package control files.
8577 <prgn>dpkg-distaddfile</prgn> - adds a file to
8578 <file>debian/files</file>
8582 Some packages' uploads need to include files other than
8583 the source and binary package files.
8587 <prgn>dpkg-distaddfile</prgn> adds a file to the
8588 <file>debian/files</file> file so that it will be included in
8589 the <file>.changes</file> file when
8590 <prgn>dpkg-genchanges</prgn> is run.
8594 It is usually invoked from the <tt>binary</tt> target of
8595 <file>debian/rules</file>:
8597 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
8599 The <var>filename</var> is relative to the directory where
8600 <prgn>dpkg-genchanges</prgn> will expect to find it - this
8601 is usually the directory above the top level of the source
8602 tree. The <file>debian/rules</file> target should put the
8603 file there just before or just after calling
8604 <prgn>dpkg-distaddfile</prgn>.
8608 The <var>section</var> and <var>priority</var> are passed
8609 unchanged into the resulting <file>.changes</file> file. See
8610 <ref id="pkg-f-classification">.
8615 <sect1><heading><prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file> upload
8620 This program is usually called by package-independent
8621 automatic building scripts such as
8622 <prgn>dpkg-buildpackage</prgn>, but it may also be called
8627 It is usually called in the top level of a built source
8628 tree, and when invoked with no arguments will print out a
8629 straightforward <file>.changes</file> file based on the
8630 information in the source package's changelog and control
8631 file and the binary and source packages which should have
8637 <sect1><heading><prgn>dpkg-parsechangelog</prgn> - produces parsed representation of
8642 This program is used internally by
8643 <prgn>dpkg-source</prgn> et al. It may also occasionally
8644 be useful in <file>debian/rules</file> and elsewhere. It
8645 parses a changelog, <file>debian/changelog</file> by default,
8646 and prints a control-file format representation of the
8647 information in it to standard output.
8651 <sect1 id="pkg-dpkgarch"><heading><prgn>dpkg-architecture</prgn> -
8652 information about the build and host system
8656 This program can be used manually, but is also invoked by
8657 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
8658 to set environment or make variables which specify the build and
8659 host architecture for the package building process.
8664 <sect id="pkg-sourcetree"><heading>The Debianised source tree
8668 The source archive scheme described later is intended to
8669 allow a Debianised source tree with some associated control
8670 information to be reproduced and transported easily. The
8671 Debianised source tree is a version of the original program
8672 with certain files added for the benefit of the
8673 Debianisation process, and with any other changes required
8674 made to the rest of the source code and installation
8679 The extra files created for Debian are in the subdirectory
8680 <file>debian</file> of the top level of the Debianised source
8681 tree. They are described below.
8684 <sect1 id="pkg-debianrules"><heading><file>debian/rules</file> - the main building
8689 This file is an executable makefile, and contains the
8690 package-specific recipies for compiling the package and
8691 building binary package(s) out of the source.
8695 It must start with the line <tt>#!/usr/bin/make -f</tt>,
8696 so that it can be invoked by saying its name rather than
8697 invoking <prgn>make</prgn> explicitly.
8701 Since an interactive <file>debian/rules</file> script makes it
8702 impossible to autocompile that package and also makes it
8703 hard for other people to reproduce the same binary
8704 package, all <strong>required targets</strong> have to be
8705 non-interactive. At a minimul, required targets are the
8706 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
8707 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>, and
8708 <em>build</em>. It also follows that any target that these
8709 targets depend on must also be non-interactive.
8713 The targets which are required to be present are:
8715 <tag><tt>build</tt></tag>
8718 This should perform all non-interactive
8719 configuration and compilation of the package. If a
8720 package has an interactive pre-build configuration
8721 routine, the Debianised source package should be
8722 built after this has taken place, so that it can be
8723 built without rerunning the configuration.
8727 A package may also provide both of the targets
8728 <tt>build-arch</tt> and <tt>build-indep</tt>. The
8729 <tt>build-arch</tt> target, if provided, should
8730 perform all non-interactive configuration and
8731 compilation required for producing all
8732 architecture-dependant binary packages (those packages
8733 for which the body of the <tt>Architecture</tt> field
8734 in <tt>debian/control</tt> is not <tt>all</tt>).
8735 Similarly, the <tt>build-indep</tt> target, if
8736 provided, should perform all non-interactive
8737 configuration and compilation required for producing
8738 all architecture-independent binary packages (those
8739 packages for which the body of the
8740 <tt>Architecture</tt> field in <tt>debian/control</tt>
8741 is <tt>all</tt>). The <tt>build</tt> target should
8742 depend on those of the targets <tt>build-arch</tt> and
8743 <tt>build-indep</tt> that are provided in the rules
8748 If one or both of the targets <tt>build-arch</tt> and
8749 <tt>build-indep</tt> are not provided, then invoking
8750 <file>debian/rules</file> with one of the not-provided
8751 targets as arguments should produce a exit status code
8752 of 2. Usually this is provided automatically by make
8753 if the target is missing.
8757 For some packages, notably ones where the same
8758 source tree is compiled in different ways to produce
8759 two binary packages, the <tt>build</tt> target does
8760 not make much sense. For these packages it is good
8761 enough to provide two (or more) targets
8762 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
8763 for each of the ways of building the package, and a
8764 <tt>build</tt> target that does nothing. The
8765 <tt>binary</tt> target will have to build the
8766 package in each of the possible ways and make the
8767 binary package out of each.
8771 The targets <tt>build</tt>, <tt>build-arch</tt>
8772 and <tt>build-indep</tt> target must not do
8773 anything that might require root privilege.
8777 The <tt>build</tt> target may need to run
8778 <tt>clean</tt> first - see below.
8782 When a package has a configuration routine that takes
8783 a long time, or when the makefiles are poorly
8784 designed, or when <tt>build</tt> needs to run
8785 <tt>clean</tt> first, it is a good idea to <tt>touch
8786 build</tt> when the build process is complete. This
8787 will ensure that if <tt>debian/rules build</tt> is run
8788 again it will not rebuild the whole program.
8792 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
8793 <tt>binary-indep</tt>
8797 The <tt>binary</tt> target should be all that is
8798 necessary for the user to build the binary
8799 package. All these targets are required to be
8800 non-interactive. It is split into two parts:
8801 <tt>binary-arch</tt> builds the packages' output
8802 files which are specific to a particular
8803 architecture, and <tt>binary-indep</tt> builds
8804 those which are not.
8808 <tt>binary</tt> should usually be a target with
8809 no commands which simply depends on
8810 <prgn>binary-arch</prgn> and
8811 <prgn>binary-indep</prgn>.
8815 Both <prgn>binary-*</prgn> targets should depend on
8816 the <tt>build</tt> target, above, so that the
8817 package is built if it has not been already. It
8818 should then create the relevant binary package(s),
8819 using <prgn>dpkg-gencontrol</prgn> to make their
8820 control files and <prgn>dpkg-deb</prgn> to build
8821 them and place them in the parent of the top level
8826 If one of the <prgn>binary-*</prgn> targets has
8827 nothing to do (this will be always be the case if
8828 the source generates only a single binary package,
8829 whether architecture-dependent or not) it
8830 <em>must</em> still exist, but should always
8835 <ref id="pkg-binarypkg"> describes how to construct
8840 The <tt>binary</tt> targets must be invoked as
8845 <tag><tt>clean</tt></tag>
8849 This should undo any effects that the
8850 <tt>build</tt> and <tt>binary</tt> targets
8851 may have had, except that it should leave alone any
8852 output files created in the parent directory by a
8853 run of <tt>binary</tt>. This target is required
8854 to be non-interactive.
8858 If a <tt>build</tt> file is touched at the end
8859 of the <tt>build</tt> target, as suggested
8860 above, it must be removed as the first thing that
8861 <tt>clean</tt> does, so that running
8862 <tt>build</tt> again after an interrupted
8863 <tt>clean</tt> doesn't think that everything is
8868 The <tt>clean</tt> target must be invoked as
8869 root if <tt>binary</tt> has been invoked since
8870 the last <tt>clean</tt>, or if
8871 <tt>build</tt> has been invoked as root (since
8872 <tt>build</tt> may create directories, for
8877 <tag><tt>get-orig-source</tt> (optional)</tag>
8881 This target fetches the most recent version of the
8882 original source package from a canonical archive
8883 site (via FTP or WWW, for example), does any
8884 necessary rearrangement to turn it into the original
8885 source tarfile format described below, and leaves it
8886 in the current directory.
8890 This target may be invoked in any directory, and
8891 should take care to clean up any temporary files it
8896 This target is optional, but providing it if
8897 possible is a good idea.
8903 The <tt>build</tt>, <tt>binary</tt> and
8904 <tt>clean</tt> targets must be invoked with a current
8905 directory of the package's top-level directory.
8910 Additional targets may exist in <file>debian/rules</file>,
8911 either as published or undocumented interfaces or for the
8912 package's internal use.
8916 The architecture we build on and build for is determined by make
8917 variables via dpkg-architecture (see <ref id="pkg-dpkgarch">). You can
8918 get the Debian architecture and the GNU style architecture
8919 specification string for the build machine as well as the host
8920 machine. Here is a list of supported make variables:
8921 <list compact="compact">
8923 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
8926 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
8927 specification string)</p>
8930 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of DEB_*_GNU_TYPE)</p>
8933 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
8939 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
8940 the build machine or <tt>HOST</tt> for specification of the machine
8945 Backward compatibility can be provided in the rules file
8946 by setting the needed variables to suitable default
8947 values, please refer to the documentation of
8948 dpkg-architecture for details.
8952 It is important to understand that the <tt>DEB_*_ARCH</tt>
8953 string does only determine which Debian architecture we
8954 build on resp. for. It should not be used to get the CPU
8955 or System information, the GNU style variables should be
8961 <sect1><heading><file>debian/control</file>
8965 This file contains version-independent details about the
8966 source package and about the binary packages it creates.
8970 It is a series of sets of control fields, each
8971 syntactically similar to a binary package control file.
8972 The sets are separated by one or more blank lines. The
8973 first set is information about the source package in
8974 general; each subsequent set describes one binary package
8975 that the source tree builds.
8979 The syntax and semantics of the fields are described below
8980 in <ref id="pkg-controlfields">.
8984 The general (binary-package-independent) fields are:
8985 <list compact="compact">
8987 <p><qref id="pkg-f-Source"><tt>Source</tt></qref> (mandatory)</p>
8990 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8994 <qref id="pkg-f-classification"><tt>Section</tt> and
8995 <tt>Priority</tt></qref>
8996 (classification, mandatory)
9001 <qref id="relationships"><tt>Build-Depends</tt> et
9002 al.</qref> (source package interrelationships)
9007 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref>
9013 The per-binary-package fields are:
9014 <list compact="compact">
9016 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
9020 <qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
9024 <p><qref id="descriptions"><tt>Description</tt></qref></p>
9028 <qref id="pkg-f-classification"><tt>Section</tt> and
9029 <tt>Priority</tt></qref> (classification)</p>
9032 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
9036 <qref id="relationships"><tt>Depends</tt> et
9037 al.</qref> (binary package interrelationships)
9043 These fields are used by <prgn>dpkg-gencontrol</prgn> to
9044 generate control files for binary packages (see below), by
9045 <prgn>dpkg-genchanges</prgn> to generate the
9046 <tt>.changes</tt> file to accompany the upload, and by
9047 <prgn>dpkg-source</prgn> when it creates the <file>.dsc</file>
9048 source control file as part of a source archive.
9052 The fields here may contain variable references - their
9053 values will be substituted by
9054 <prgn>dpkg-gencontrol</prgn>, <prgn>dpkg-genchanges</prgn>
9055 or <prgn>dpkg-source</prgn> when they generate output
9056 control files. See <ref id="pkg-srcsubstvars"> for details.
9059 <p> <sect2><heading>User-defined fields
9063 Additional user-defined fields may be added to the
9064 source package control file. Such fields will be
9065 ignored, and not copied to (for example) binary or
9066 source package control files or upload control files.
9070 If you wish to add additional unsupported fields to
9071 these output files you should use the mechanism
9076 Fields in the main source control information file with
9077 names starting <tt>X</tt>, followed by one or more of
9078 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
9079 be copied to the output files. Only the part of the
9080 field name after the hyphen will be used in the output
9081 file. Where the letter <tt>B</tt> is used the field
9082 will appear in binary package control files, where the
9083 letter <tt>S</tt> is used in source package control
9084 files and where <tt>C</tt> is used in upload control
9085 (<tt>.changes</tt>) files.
9089 For example, if the main source information control file
9092 XBS-Comment: I stand between the candle and the star.
9094 then the binary and source package control files will contain the
9097 Comment: I stand between the candle and the star.
9104 <sect1 id="pkg-dpkgchangelog"><heading><file>debian/changelog</file>
9108 This file records the changes to the Debian-specific parts of the
9112 Though there is nothing stopping an author who is also
9113 the Debian maintainer from using it for all their
9114 changes, it will have to be renamed if the Debian and
9115 upstream maintainers become different
9122 It has a special format which allows the package building
9123 tools to discover which version of the package is being
9124 built and find out other release-specific information.
9128 That format is a series of entries like this:
9130 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
9132 * <var>change details</var>
9133 <var>more change details</var>
9134 * <var>even more change details</var>
9136 -- <var>maintainer name and email address</var> <var>date</var>
9141 <var>package</var> and <var>version</var> are the source
9142 package name and version number.
9146 <var>distribution(s)</var> lists the distributions where
9147 this version should be installed when it is uploaded - it
9148 is copied to the <tt>Distribution</tt> field in the
9149 <tt>.changes</tt> file. See <ref id="pkg-f-Distribution">.
9153 <var>urgency</var> is the value for the <tt>Urgency</tt>
9154 field in the <file>.changes</file> file for the upload. See
9155 <ref id="pkg-f-Urgency">. It is not possible to specify an
9156 urgency containing commas; commas are used to separate
9157 <tt><var>keyword</var>=<var>value</var></tt> settings in
9158 the <prgn>dpkg</prgn> changelog format (though there is
9159 currently only one useful <var>keyword</var>,
9164 The change details may in fact be any series of lines
9165 starting with at least two spaces, but conventionally each
9166 change starts with an asterisk and a separating space and
9167 continuation lines are indented so as to bring them in
9168 line with the start of the text above. Blank lines may be
9169 used here to separate groups of changes, if desired.
9173 The maintainer name and email address should <em>not</em>
9174 necessarily be those of the usual package maintainer.
9175 They should be the details of the person doing
9176 <em>this</em> version. The information here will be
9177 copied to the <file>.changes</file> file, and then later used
9178 to send an acknowledgement when the upload has been
9183 The <var>date</var> should be in RFC822 format
9186 This is generated by the <prgn>822-date</prgn>
9189 </footnote>; it should include the timezone specified
9190 numerically, with the timezone name or abbreviation
9191 optionally present as a comment.
9195 The first "title" line with the package name should start
9196 at the left hand margin; the "trailer" line with the
9197 maintainer and date details should be preceded by exactly
9198 one space. The maintainer details and the date must be
9199 separated by exactly two spaces.
9203 An Emacs mode for editing this format is available: it is
9204 called <tt>debian-changelog-mode</tt>. You can have this
9205 mode selected automatically when you edit a Debian
9206 changelog by adding a local variables clause to the end of
9210 <sect2><heading>Defining alternative changelog formats
9214 It is possible to use a different format to the standard
9215 one, by providing a parser for the format you wish to
9220 In order to have <tt>dpkg-parsechangelog</tt> run your
9221 parser, you must include a line within the last 40 lines
9222 of your file matching the Perl regular expression:
9223 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9224 parentheses should be the name of the format. For
9225 example, you might say:
9227 @@@ changelog-format: joebloggs @@@
9229 Changelog format names are non-empty strings of alphanumerics.
9233 If such a line exists then <tt>dpkg-parsechangelog</tt>
9234 will look for the parser as
9235 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9237 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9238 it is an error for it not to find it, or for it not to
9239 be an executable program. The default changelog format
9240 is <tt>dpkg</tt>, and a parser for it is provided with
9241 the <tt>dpkg</tt> package.
9245 The parser will be invoked with the changelog open on
9246 standard input at the start of the file. It should read
9247 the file (it may seek if it wishes) to determine the
9248 information required and return the parsed information
9249 to standard output in the form of a series of control
9250 fields in the standard format. By default it should
9251 return information about only the most recent version in
9252 the changelog; it should accept a
9253 <tt>-v<var>version</var></tt> option to return changes
9254 information from all versions present <em>strictly
9255 after</em> <var>version</var>, and it should then be an
9256 error for <var>version</var> not to be present in the
9262 <list compact="compact">
9264 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9267 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
9271 <qref id="pkg-f-Distribution"><tt>Distribution</tt></qref>
9276 <p><qref id="pkg-f-Urgency"><tt>Urgency</tt></qref> (mandatory)</p>
9280 <qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref>
9285 <p><qref id="pkg-f-Date"><tt>Date</tt></qref></p>
9289 <qref id="pkg-f-Changes"><tt>Changes</tt></qref>
9296 If several versions are being returned (due to the use
9297 of <tt>-v</tt>), the urgency value should be of the
9298 highest urgency code listed at the start of any of the
9299 versions requested followed by the concatenated
9300 (space-separated) comments from all the versions
9301 requested; the maintainer, version, distribution and
9302 date should always be from the most recent version.
9306 For the format of the <tt>Changes</tt> field see <ref
9307 id="pkg-f-Changes">.
9311 If the changelog format which is being parsed always or
9312 almost always leaves a blank line between individual
9313 change notes these blank lines should be stripped out,
9314 so as to make the resulting output compact.
9318 If the changelog format does not contain date or package
9319 name information this information should be omitted from
9320 the output. The parser should not attempt to synthesise
9321 it or find it from other sources.
9325 If the changelog does not have the expected format the
9326 parser should exit with a nonzero exit status, rather
9327 than trying to muddle through and possibly generating
9332 A changelog parser may not interact with the user at
9336 <!-- FIXME: section pkg-srcsubstvars is the same as srcsubstvars -->
9338 <sect1 id="pkg-srcsubstvars"><heading><file>debian/substvars</file>
9339 and variable substitutions
9343 When <prgn>dpkg-gencontrol</prgn>,
9344 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
9345 generate control files they do variable substitutions on
9346 their output just before writing it. Variable
9347 substitutions have the form
9348 <tt>${<var>variable-name</var>}</tt>. The optional file
9349 <file>debian/substvars</file> contains variable substitutions
9350 to be used; variables can also be set directly from
9351 <file>debian/rules</file> using the <tt>-V</tt> option to the
9352 source packaging commands, and certain predefined
9353 variables are available.
9357 This file is usually generated and modified dynamically by
9358 <file>debian/rules</file> targets, in which case it must be
9359 removed by the <tt>clean</tt> target.
9363 See <manref name="dpkg-source" section="1"> for full
9364 details about source variable substitutions, including the
9365 format of <file>debian/substvars</file>.</p>
9368 <sect1><heading><file>debian/files</file>
9372 This file is not a permanent part of the source tree; it
9373 is used while building packages to record which files are
9374 being generated. <prgn>dpkg-genchanges</prgn> uses it
9375 when it generates a <file>.changes</file> file.
9379 It should not exist in a shipped source package, and so it
9380 (and any backup files or temporary files such as
9381 <file>files.new</file>
9384 <file>files.new</file> is used as a temporary file by
9385 <prgn>dpkg-gencontrol</prgn> and
9386 <prgn>dpkg-distaddfile</prgn> - they write a new
9387 version of <file>files</file> here before renaming it,
9388 to avoid leaving a corrupted copy if an error
9391 </footnote>) should be removed by the
9392 <tt>clean</tt> target. It may also be wise to
9393 ensure a fresh start by emptying or removing it at the
9394 start of the <tt>binary</tt> target.
9398 <prgn>dpkg-gencontrol</prgn> adds an entry to this file
9399 for the <file>.deb</file> file that will be created by
9400 <prgn>dpkg-deb</prgn> from the control file that it
9401 generates, so for most packages all that needs to be done
9402 with this file is to delete it in <tt>clean</tt>.
9406 If a package upload includes files besides the source
9407 package and any binary packages whose control files were
9408 made with <prgn>dpkg-gencontrol</prgn> then they should be
9409 placed in the parent of the package's top-level directory
9410 and <prgn>dpkg-distaddfile</prgn> should be called to add
9411 the file to the list in <file>debian/files</file>.</p>
9414 <sect1><heading><file>debian/tmp</file>
9418 This is the canonical temporary location for the
9419 construction of binary packages by the <tt>binary</tt>
9420 target. The directory <file>tmp</file> serves as the root of
9421 the filesystem tree as it is being constructed (for
9422 example, by using the package's upstream makefiles install
9423 targets and redirecting the output there), and it also
9424 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9425 id="pkg-bincreating">.
9429 If several binary packages are generated from the same
9430 source tree it is usual to use several
9431 <file>debian/tmp<var>something</var></file> directories, for
9432 example <file>tmp-a</file> or <file>tmp-doc</file>.
9436 Whatever <file>tmp</file> directories are created and used by
9437 <tt>binary</tt> must of course be removed by the
9438 <tt>clean</tt> target.</p></sect1>
9442 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9446 As it exists on the FTP site, a Debian source package
9447 consists of three related files. You must have the right
9448 versions of all three to be able to use them.
9453 <tag>Debian source control file - <tt>.dsc</tt></tag>
9457 This file contains a series of fields, identified and
9458 separated just like the fields in the control file of
9459 a binary package. The fields are listed below; their
9460 syntax is described above, in <ref id="pkg-controlfields">.
9461 <list compact="compact">
9463 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9466 <p><qref id="versions"><tt>Version</tt></qref></p>
9469 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
9472 <p><qref id="pkg-f-Binary"><tt>Binary</tt></qref></p>
9475 <p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref></p>
9479 <qref id="relationships"><tt>Build-Depends</tt> et
9480 al.</qref> (source package interrelationships)
9485 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref></p>
9488 <p><qref id="pkg-f-Files"><tt>Files</tt></qref></p>
9493 The source package control file is generated by
9494 <prgn>dpkg-source</prgn> when it builds the source
9495 archive, from other files in the source package,
9496 described above. When unpacking it is checked against
9497 the files and directories in the other parts of the
9498 source package, as described below.</p>
9502 Original source archive -
9504 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9511 This is a compressed (with <tt>gzip -9</tt>)
9512 <prgn>tar</prgn> file containing the source code from
9513 the upstream authors of the program. The tarfile
9514 unpacks into a directory
9515 <file><var>package</var>-<var>upstream-version</var>.orig</file>,
9516 and does not contain files anywhere other than in
9517 there or in its subdirectories.</p>
9521 Debianisation diff -
9523 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9529 This is a unified context diff (<tt>diff -u</tt>)
9530 giving the changes which are required to turn the
9531 original source into the Debian source. These changes
9532 may only include editing and creating plain files.
9533 The permissions of files, the targets of symbolic
9534 links and the characteristics of special files or
9535 pipes may not be changed and no files may be removed
9540 All the directories in the diff must exist, except the
9541 <file>debian</file> subdirectory of the top of the source
9542 tree, which will be created by
9543 <prgn>dpkg-source</prgn> if necessary when unpacking.
9547 The <prgn>dpkg-source</prgn> program will
9548 automatically make the <file>debian/rules</file> file
9549 executable (see below).</p></item>
9554 If there is no original source code - for example, if the
9555 package is specially prepared for Debian or the Debian
9556 maintainer is the same as the upstream maintainer - the
9557 format is slightly different: then there is no diff, and the
9559 <file><var>package</var>_<var>version</var>.tar.gz</file> and
9560 contains a directory
9561 <file><var>package</var>-<var>version</var></file>.
9565 <sect><heading>Unpacking a Debian source package without
9566 <prgn>dpkg-source</prgn>
9570 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9571 Debian source package. However, if it is not available it
9572 is possible to unpack a Debian source archive as follows:
9573 <enumlist compact="compact">
9576 Untar the tarfile, which will create a <file>.orig</file>
9580 <p>Rename the <file>.orig</file> directory to
9581 <file><var>package</var>-<var>version</var></file>.</p>
9585 Create the subdirectory <file>debian</file> at the top of
9586 the source tree.</p>
9588 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9590 <item><p>Untar the tarfile again if you want a copy of the original
9591 source code alongside the Debianised version.</p>
9596 It is not possible to generate a valid Debian source archive
9597 without using <prgn>dpkg-source</prgn>. In particular,
9598 attempting to use <prgn>diff</prgn> directly to generate the
9599 <file>.diff.gz</file> file will not work.
9602 <sect1><heading>Restrictions on objects in source packages
9606 The source package may not contain any hard links
9609 This is not currently detected when building source
9610 packages, but only when extracting
9616 Hard links may be permitted at some point in the
9617 future, but would require a fair amount of
9620 </footnote>, device special files, sockets or setuid or
9624 Setgid directories are allowed.
9630 The source packaging tools manage the changes between the
9631 original and Debianised source using <prgn>diff</prgn> and
9632 <prgn>patch</prgn>. Turning the original source tree as
9633 included in the <file>.orig.tar.gz</file> into the debianised
9634 source must not involve any changes which cannot be
9635 handled by these tools. Problematic changes which cause
9636 <prgn>dpkg-source</prgn> to halt with an error when
9637 building the source package are:
9638 <list compact="compact">
9639 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9641 <item><p>Changing the targets of symbolic links.</p>
9643 <item><p>Creating directories, other than <file>debian</file>.</p>
9645 <item><p>Changes to the contents of binary files.</p></item>
9646 </list> Changes which cause <prgn>dpkg-source</prgn> to
9647 print a warning but continue anyway are:
9648 <list compact="compact">
9651 Removing files, directories or symlinks.
9654 Renaming a file is not treated specially - it is
9655 seen as the removal of the old file (which
9656 generates a warning, but is otherwise ignored),
9657 and the creation of the new
9664 Changed text files which are missing the usual final
9665 newline (either in the original or the modified
9670 Changes which are not represented, but which are not detected by
9671 <prgn>dpkg-source</prgn>, are:
9672 <list compact="compact">
9673 <item><p>Changing the permissions of files (other than
9674 <file>debian/rules</file>) and directories.</p></item>
9679 The <file>debian</file> directory and <file>debian/rules</file>
9680 are handled specially by <prgn>dpkg-source</prgn> - before
9681 applying the changes it will create the <file>debian</file>
9682 directory, and afterwards it will make
9683 <file>debian/rules</file> world-exectuable.
9689 <appendix id="pkg-controlfields"><heading>Control files and their
9690 fields (from old Packaging Manual)
9694 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9695 data in a common format, known as control files. Binary and
9696 source packages have control data as do the <file>.changes</file>
9697 files which control the installation of uploaded files, and
9698 <prgn>dpkg</prgn>'s internal databases are in a similar
9702 <sect><heading>Syntax of control files
9706 A file consists of one or more paragraphs of fields. The
9707 paragraphs are separated by blank lines. Some control files
9708 only allow one paragraph; others allow several, in which
9709 case each paragraph often refers to a different package.
9713 Each paragraph is a series of fields and values; each field
9714 consists of a name, followed by a colon and the value. It
9715 ends at the end of the line. Horizontal whitespace (spaces
9716 and tabs) may occur before or after the value and is ignored
9717 there; it is conventional to put a single space after the
9722 Some fields' values may span several lines; in this case
9723 each continuation line <em>must</em> start with a space or
9724 tab. Any trailing spaces or tabs at the end of individual
9725 lines of a field value are ignored.
9729 Except where otherwise stated only a single line of data is
9730 allowed and whitespace is not significant in a field body.
9731 Whitespace may never appear inside names (of packages,
9732 architectures, files or anything else), version numbers or
9733 in between the characters of multi-character version
9738 Field names are not case-sensitive, but it is usual to
9739 capitalise the field names using mixed case as shown below.
9743 Blank lines, or lines consisting only of spaces and tabs,
9744 are not allowed within field values or between fields - that
9745 would mean a new paragraph.
9749 It is important to note that there are several fields which
9750 are optional as far as <prgn>dpkg</prgn> and the related
9751 tools are concerned, but which must appear in every Debian
9752 package, or whose omission may cause problems. When writing
9753 the control files for Debian packages you <em>must</em> read
9754 the Debian policy manual in conjuction with the details
9755 below and the list of fields for the particular file.</p>
9758 <sect><heading>List of fields
9761 <sect1 id="pkg-f-Package"><heading><tt>Package</tt>
9765 The name of the binary package. Package names consist of
9766 the alphanumerics and <tt>+</tt> <tt>-</tt> <tt>.</tt>
9767 (plus, minus and full stop).
9770 The characters <tt>@</tt> <tt>:</tt> <tt>=</tt>
9771 <tt>%</tt> <tt>_</tt> (at, colon, equals, percent
9772 and underscore) used to be legal and are still
9773 accepted when found in a package file, but may not be
9774 used in new packages
9780 They must be at least two characters and must start with
9781 an alphanumeric. In current versions of dpkg they are
9782 sort of case-sensitive<footnote><p>This is a
9783 bug.</p></footnote>; use lowercase package names unless
9784 the package you're building (or referring to, in other
9785 fields) is already using uppercase.</p>
9788 <sect1 id="pkg-f-Version"><heading><tt>Version</tt>
9792 This lists the source or binary package's version number -
9793 see <ref id="versions">.
9798 <sect1 id="pkg-f-Architecture"><heading><tt>Architecture</tt>
9802 This is the architecture string; it is a single word for
9803 the Debian architecture.
9807 <prgn>dpkg</prgn> will check the declared architecture of
9808 a binary package against its own compiled-in value before
9813 The special value <tt>all</tt> indicates that the package
9814 is architecture-independent.
9818 In the main <file>debian/control</file> file in the source
9819 package, or in the source package control file
9820 <file>.dsc</file>, a list of architectures (separated by
9821 spaces) is also allowed, as is the special value
9822 <tt>any</tt>. A list indicates that the source will build
9823 an architecture-dependent package, and will only work
9824 correctly on the listed architectures. <tt>any</tt>
9825 indicates that though the source package isn't dependent
9826 on any particular architecture and should compile fine on
9827 any one, the binary package(s) produced are not
9828 architecture-independent but will instead be specific to
9829 whatever the current build architecture is.
9833 In a <file>.changes</file> file the <tt>Architecture</tt>
9834 field lists the architecture(s) of the package(s)
9835 currently being uploaded. This will be a list; if the
9836 source for the package is being uploaded too the special
9837 entry <tt>source</tt> is also present.
9841 See <ref id="pkg-debianrules"> for information how to get the
9842 architecture for the build process.
9846 <sect1 id="pkg-f-Maintainer"><heading><tt>Maintainer</tt>
9850 The package maintainer's name and email address. The name
9851 should come first, then the email address inside angle
9852 brackets <tt><></tt> (in RFC822 format).
9856 If the maintainer's name contains a full stop then the
9857 whole field will not work directly as an email address due
9858 to a misfeature in the syntax specified in RFC822; a
9859 program using this field as an address must check for this
9860 and correct the problem if necessary (for example by
9861 putting the name in round brackets and moving it to the
9862 end, and bringing the email address forward).
9866 In a <file>.changes</file> file or parsed changelog data this
9867 contains the name and email address of the person
9868 responsible for the particular version in question - this
9869 may not be the package's usual maintainer.
9873 This field is usually optional in as far as the
9874 <prgn>dpkg</prgn> are concerned, but its absence when
9875 building packages usually generates a warning.</p>
9878 <sect1 id="pkg-f-Source"><heading><tt>Source</tt>
9882 This field identifies the source package name.
9886 In a main source control information or a
9887 <file>.changes</file> or <file>.dsc</file> file or parsed
9888 changelog data this may contain only the name of the
9893 In the control file of a binary package (or in a
9894 <file>Packages</file> file) it may be followed by a version
9895 number in parentheses.
9898 It is usual to leave a space after the package name if
9899 a version number is specified.
9901 </footnote> This version number may be omitted (and is, by
9902 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
9903 the <tt>Version</tt> field of the binary package in
9904 question. The field itself may be omitted from a binary
9905 package control file when the source package has the same
9906 name and version as the binary package.
9910 <sect1><heading>Package interrelationship fields:
9911 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
9912 <tt>Recommends</tt> <tt>Suggests</tt>, <tt>Conflicts</tt>,
9913 <tt>Provides</tt>, <tt>Replaces</tt>
9917 These fields describe the package's relationships with
9918 other packages. Their syntax and semantics are described
9919 in <ref id="relationships">.</p>
9922 <sect1 id="pkg-f-Description"><heading><tt>Description</tt>
9926 In a binary package <tt>Packages</tt> file or main source
9927 control file this field contains a description of the
9928 binary package, in a special format. See <ref
9929 id="descriptions"> for details.
9933 In a <file>.changes</file> file it contains a summary of the
9934 descriptions for the packages being uploaded. The part of
9935 the field before the first newline is empty; thereafter
9936 each line has the name of a binary package and the summary
9937 description line from that binary package. Each line is
9938 indented by one space.</p>
9941 <sect1 id="pkg-f-Essential"><heading><tt>Essential</tt>
9945 This is a boolean field which may occur only in the
9946 control file of a binary package (or in the
9947 <file>Packages</file> file) or in a per-package fields
9948 paragraph of a main source control data file.
9952 If set to <tt>yes</tt> then <prgn>dpkg</prgn> and
9953 <prgn>dselect</prgn> will refuse to remove the package
9954 (though it can be upgraded and/or replaced). The other
9955 possible value is <tt>no</tt>, which is the same as not
9956 having the field at all.</p>
9959 <sect1 id="pkg-f-classification"><heading><tt>Section</tt> and
9964 These two fields classify the package. The
9965 <tt>Priority</tt> represents how important that it is that
9966 the user have it installed; the <tt>Section</tt>
9967 represents an application area into which the package has
9972 When they appear in the <file>debian/control</file> file these
9973 fields give values for the section and priority subfields
9974 of the <tt>Files</tt> field of the <file>.changes</file> file,
9975 and give defaults for the section and priority of the
9980 The section and priority are represented, though not as
9981 separate fields, in the information for each file in the
9982 <qref id="pkg-f-Files"><tt>-File</tt></qref>field of a
9983 <file>.changes</file> file. The section value in a
9984 <file>.changes</file> file is used to decide where to install
9985 a package in the FTP archive.
9989 These fields are not used by by <prgn>dpkg</prgn> proper,
9990 but by <prgn>dselect</prgn> when it sorts packages and
9991 selects defaults. See the Debian policy manual for the
9992 priorities in use and the criteria for selecting the
9993 priority for a Debian package, and look at the Debian FTP
9994 archive for a list of currently in-use priorities.
9998 These fields may appear in binary package control files,
9999 in which case they provide a default value in case the
10000 <file>Packages</file> files are missing the information.
10001 <prgn>dpkg</prgn> and <prgn>dselect</prgn> will only use
10002 the value from a <file>.deb</file> file if they have no other
10003 information; a value listed in a <file>Packages</file> file
10004 will always take precedence. By default
10005 <prgn>dpkg-gencontrol</prgn> does not include the section
10006 and priority in the control file of a binary package - use
10007 the <tt>-isp</tt>, <tt>-is</tt> or <tt>-ip</tt> options to
10008 achieve this effect.</p>
10011 <sect1 id="pkg-f-Binary"><heading><tt>Binary</tt>
10015 This field is a list of binary packages.
10019 When it appears in the <file>.dsc</file> file it is the list
10020 of binary packages which a source package can produce. It
10021 does not necessarily produce all of these binary packages
10022 for every architecture. The source control file doesn't
10023 contain details of which architectures are appropriate for
10024 which of the binary packages.
10028 When it appears in a <file>.changes</file> file it lists the
10029 names of the binary packages actually being uploaded.
10033 The syntax is a list of binary packages separated by
10037 A space after each comma is conventional.
10039 </footnote> Currently the packages must be separated using
10040 only spaces in the <file>.changes</file> file.</p>
10043 <sect1 id="pkg-f-Installed-Size"><heading><tt>Installed-Size</tt>
10047 This field appears in the control files of binary
10048 packages, and in the <file>Packages</file> files. It gives
10049 the total amount of disk space required to install the
10054 The disk space is represented in kilobytes as a simple
10055 decimal number.</p>
10058 <sect1 id="pkg-f-Files"><heading><tt>Files</tt>
10062 This field contains a list of files with information about
10063 each one. The exact information and syntax varies with
10064 the context. In all cases the part of the field
10065 contents on the same line as the field name is empty. The
10066 remainder of the field is one line per file, each line
10067 being indented by one space and containing a number of
10068 sub-fields separated by spaces.
10072 In the <file>.dsc</file> (Debian source control) file each
10073 line contains the MD5 checksum, size and filename of the
10074 tarfile and (if applicable) diff file which make up the
10075 remainder of the source package.
10078 That is, the parts which are not the
10081 </footnote> The exact forms of the filenames are described
10082 in <ref id="pkg-sourcearchives">.
10086 In the <file>.changes</file> file this contains one line per
10087 file being uploaded. Each line contains the MD5 checksum,
10088 size, section and priority and the filename. The section
10089 and priority are the values of the corresponding fields in
10090 the main source control file - see <ref
10091 id="pkg-f-classification">. If no section or priority is
10092 specified then <tt>-</tt> should be used, though section
10093 and priority values must be specified for new packages to
10094 be installed properly.
10098 The special value <tt>byhand</tt> for the section in a
10099 <tt>.changes</tt> file indicates that the file in question
10100 is not an ordinary package file and must by installed by
10101 hand by the distribution maintainers. If the section is
10102 <tt>byhand</tt> the priority should be <tt>-</tt>.
10106 If a new Debian revision of a package is being shipped and
10107 no new original source archive is being distributed the
10108 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
10109 entry for the original source archive
10110 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
10111 but the <file>.changes</file> file should leave it out. In
10112 this case the original source archive on the distribution
10113 site must match exactly, byte-for-byte, the original
10114 source archive which was used to generate the
10115 <file>.dsc</file> file and diff which are being uploaded.</p>
10120 id="pkg-f-Standards-Version"><heading><tt>Standards-Version</tt>
10124 The most recent version of the standards (the
10125 <prgn>dpkg</prgn> programmers' and policy manuals and
10126 associated texts) with which the package complies. This
10127 is updated manually when editing the source package to
10128 conform to newer standards; it can sometimes be used to
10129 tell when a package needs attention.
10133 Its format is the same as that of a version number except
10134 that no epoch or Debian revision is allowed - see <ref
10135 id="versions">.</p>
10139 <sect1 id="pkg-f-Distribution"><heading><tt>Distribution</tt>
10143 In a <file>.changes</file> file or parsed changelog output
10144 this contains the (space-separated) name(s) of the
10145 distribution(s) where this version of the package should
10146 be or was installed. Distribution names follow the rules
10147 for package names. (See <ref id="pkg-f-Package">).
10151 Current distribution values are:
10153 <tag><em>stable</em></tag>
10156 This is the current "released" version of Debian
10157 GNU/Linux. A new version is released approximately
10158 every 3 months after the <em>development</em> code has
10159 been <em>frozen</em> for a month of testing. Once the
10160 distribution is <em>stable</em> only major bug fixes
10161 are allowed. When changes are made to this
10162 distribution, the release number is increased
10163 (for example: 1.2r1 becomes 1.2r2 then 1.2r3, etc).
10167 <tag><em>unstable</em></tag>
10170 This distribution value refers to the
10171 <em>developmental</em> part of the Debian distribution
10172 tree. New packages, new upstream versions of packages
10173 and bug fixes go into the <em>unstable</em> directory
10174 tree. Download from this distribution at your own
10178 <tag><em>contrib</em></tag>
10181 The packages with this distribution value do not meet
10182 the criteria for inclusion in the main Debian
10183 distribution as defined by the Policy Manual, but meet
10184 the criteria for the <em>contrib</em>
10185 Distribution. There is currently no distinction
10186 between stable and unstable packages in the
10187 <em>contrib</em> or <em>non-free</em>
10188 distributions. Use your best judgement in downloading
10189 from this Distribution.</p>
10192 <tag><em>non-free</em></tag>
10195 Like the packages in the <em>contrib</em> seciton,
10196 the packages in <em>non-free</em> do not meet the
10197 criteria for inclusion in the main Debian distribution
10198 as defined by the Policy Manual. Again, use your best
10199 judgement in downloading from this Distribution.</p>
10201 <tag><em>experimental</em></tag>
10204 The packages with this distribution value are deemed
10205 by their maintainers to be high risk. Oftentimes they
10206 represent early beta or developmental packages from
10207 various sources that the maintainers want people to
10208 try, but are not ready to be a part of the other parts
10209 of the Debian distribution tree. Download at your own
10213 <tag><em>frozen</em></tag>
10216 From time to time, (currently, every 3 months) the
10217 <em>unstable</em> distribution enters a state of
10218 "code-freeze" in anticipation of release as a
10219 <em>stable</em> version. During this period of testing
10220 (usually 4 weeks) only fixes for existing or
10221 newly-discovered bugs will be allowed.
10224 </taglist> You should list <em>all</em> distributions that
10225 the package should be installed into. Except in unusual
10226 circumstances, installations to <em>stable</em> should also
10227 go into <em>frozen</em> (if it exists) and
10228 <em>unstable</em>. Likewise, installations into
10229 <em>frozen</em> should also go into <em>unstable</em>.</p>
10232 <sect1 id="pkg-f-Urgency"><heading><tt>Urgency</tt>
10236 This is a description of how important it is to upgrade to
10237 this version from previous ones. It consists of a single
10238 keyword usually taking one of the values <tt>LOW</tt>,
10239 <tt>MEDIUM</tt> or <tt>HIGH</tt>) followed by an optional
10240 commentary (separated by a space) which is usually in
10241 parentheses. For example:
10243 Urgency: LOW (HIGH for diversions users)
10248 This field appears in the <file>.changes</file> file and in
10249 parsed changelogs; its value appears as the value of the
10250 <tt>urgency</tt> attribute in a <prgn>dpkg</prgn>-style
10251 changelog (see <ref id="pkg-dpkgchangelog">).
10255 Urgency keywords are not case-sensitive.</p>
10258 <sect1 id="pkg-f-Date"><heading><tt>Date</tt>
10262 In <tt>.changes</tt> files and parsed changelogs, this
10263 gives the date the package was built or last edited.</p>
10266 <sect1 id="pkg-f-Format"><heading><tt>Format</tt>
10270 This field occurs in <file>.changes</file> files, and
10271 specifies a format revision for the file. The format
10272 described here is version <tt>1.5</tt>. The syntax of the
10273 format value is the same as that of a package version
10274 number except that no epoch or Debian revision is allowed
10275 - see <ref id="versions">.</p>
10278 <sect1 id="pkg-f-Changes"><heading><tt>Changes</tt>
10282 In a <file>.changes</file> file or parsed changelog this field
10283 contains the human-readable changes data, describing the
10284 differences between the last version and the current one.
10288 There should be nothing in this field before the first
10289 newline; all the subsequent lines must be indented by at
10290 least one space; blank lines must be represented by a line
10291 consiting only of a space and a full stop.
10295 Each version's change information should be preceded by a
10296 "title" line giving at least the version, distribution(s)
10297 and urgency, in a human-readable way.
10301 If data from several versions is being returned the entry
10302 for the most recent version should be returned first, and
10303 entries should be separated by the representation of a
10304 blank line (the "title" line may also be followed by the
10305 representation of blank line).</p>
10308 <sect1 id="pkg-f-Filename"><heading><tt>Filename</tt> and
10309 <tt>MSDOS-Filename</tt>
10313 These fields in <tt>Packages</tt> files give the
10314 filename(s) of (the parts of) a package in the
10315 distribution directories, relative to the root of the
10316 Debian hierarchy. If the package has been split into
10317 several parts the parts are all listed in order, separated
10321 <sect1 id="pkg-f-Size"><heading><tt>Size</tt> and <tt>MD5sum</tt>
10325 These fields in <file>Packages</file> files give the size (in
10326 bytes, expressed in decimal) and MD5 checksum of the
10327 file(s) which make(s) up a binary package in the
10328 distribution. If the package is split into several parts
10329 the values for the parts are listed in order, separated by
10333 <sect1 id="pkg-f-Status"><heading><tt>Status</tt>
10337 This field in <prgn>dpkg</prgn>'s status file records
10338 whether the user wants a package installed, removed or
10339 left alone, whether it is broken (requiring
10340 reinstallation) or not and what its current state on the
10341 system is. Each of these pieces of information is a
10345 <sect1 id="pkg-f-Config-Version"><heading><tt>Config-Version</tt>
10349 If a package is not installed or not configured, this
10350 field in <prgn>dpkg</prgn>'s status file records the last
10351 version of the package which was successfully
10355 <sect1 id="pkg-f-Conffiles"><heading><tt>Conffiles</tt>
10359 This field in <prgn>dpkg</prgn>'s status file contains
10360 information about the automatically-managed configuration
10361 files held by a package. This field should <em>not</em>
10362 appear anywhere in a package!</p>
10365 <sect1><heading>Obsolete fields
10369 These are still recognised by <prgn>dpkg</prgn> but should
10370 not appear anywhere any more.
10371 <taglist compact="compact">
10373 <tag><tt>Revision</tt></tag>
10374 <tag><tt>Package-Revision</tt></tag>
10375 <tag><tt>Package_Revision</tt></tag>
10378 The Debian revision part of the package version was
10379 at one point in a separate control file field. This
10380 field went through several names.</p>
10383 <tag><tt>Recommended</tt></tag>
10384 <item><p>Old name for <tt>Recommends</tt></p>
10387 <tag><tt>Optional</tt></tag>
10388 <item><p>Old name for <tt>Suggests</tt>.</p>
10390 <tag><tt>Class</tt></tag>
10391 <item><p>Old name for <tt>Priority</tt>.</p>
10399 <appendix id="pkg-conffiles"><heading>Configuration file handling
10400 (from old Packaging Manual)
10404 <prgn>dpkg</prgn> can do a certain amount of automatic
10405 handling of package configuration files.
10409 Whether this mechanism is appropriate depends on a number of
10410 factors, but basically there are two approaches to any
10411 particular configuration file.
10415 The easy method is to ship a best-effort configuration in the
10416 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10417 handle updates. If the user is unlikely to want to edit the
10418 file, but you need them to be able to without losing their
10419 changes, and a new package with a changed version of the file
10420 is only released infrequently, this is a good approach.
10424 The hard method is to build the configuration file from
10425 scratch in the <prgn>postinst</prgn> script, and to take the
10426 responsibility for fixing any mistakes made in earlier
10427 versions of the package automatically. This will be
10428 appropriate if the file is likely to need to be different on
10432 <sect><heading>Automatic handling of configuration files by
10437 A package may contain a control area file called
10438 <tt>conffiles</tt>. This file should be a list of filenames
10439 of configuration files needing automatic handling, separated
10440 by newlines. The filenames should be absolute pathnames,
10441 and the files referred to should actually exist in the
10446 When a package is upgraded <prgn>dpkg</prgn> will process
10447 the configuration files during the configuration stage,
10448 shortly before it runs the package's <prgn>postinst</prgn>
10453 For each file it checks to see whether the version of the
10454 file included in the package is the same as the one that was
10455 included in the last version of the package (the one that is
10456 being upgraded from); it also compares the version currently
10457 installed on the system with the one shipped with the last
10462 If neither the user nor the package maintainer has changed
10463 the file, it is left alone. If one or the other has changed
10464 their version, then the changed version is preferred - i.e.,
10465 if the user edits their file, but the package maintainer
10466 doesn't ship a different version, the user's changes will
10467 stay, silently, but if the maintainer ships a new version
10468 and the user hasn't edited it the new version will be
10469 installed (with an informative message). If both have
10470 changed their version the user is prompted about the problem
10471 and must resolve the differences themselves.
10475 The comparisons are done by calculating the MD5 message
10476 digests of the files, and storing the MD5 of the file as it
10477 was included in the most recent version of the package.
10481 When a package is installed for the first time
10482 <prgn>dpkg</prgn> will install the file that comes with it,
10483 unless that would mean overwriting a file already on the
10488 However, note that <prgn>dpkg</prgn> will <em>not</em>
10489 replace a conffile that was removed by the user (or by a
10490 script). This is necessary because with some programs a
10491 missing file produces an effect hard or impossible to
10492 achieve in another way, so that a missing file needs to be
10493 kept that way if the user did it.
10497 Note that a package should <em>not</em> modify a
10498 <prgn>dpkg</prgn>-handled conffile in its maintainer
10499 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10500 the user confusing and possibly dangerous options for
10501 conffile update when the package is upgraded.</p>
10504 <sect><heading>Fully-featured maintainer script configuration
10509 For files which contain site-specific information such as
10510 the hostname and networking details and so forth, it is
10511 better to create the file in the package's
10512 <prgn>postinst</prgn> script.
10516 This will typically involve examining the state of the rest
10517 of the system to determine values and other information, and
10518 may involve prompting the user for some information which
10519 can't be obtained some other way.
10523 When using this method there are a couple of important
10524 issues which should be considered:
10528 If you discover a bug in the program which generates the
10529 configuration file, or if the format of the file changes
10530 from one version to the next, you will have to arrange for
10531 the postinst script to do something sensible - usually this
10532 will mean editing the installed configuration file to remove
10533 the problem or change the syntax. You will have to do this
10534 very carefully, since the user may have changed the file,
10535 perhaps to fix the very problem that your script is trying
10536 to deal with - you will have to detect these situations and
10537 deal with them correctly.
10541 If you do go down this route it's probably a good idea to
10542 make the program that generates the configuration file(s) a
10543 separate program in <file>/usr/sbin</file>, by convention called
10544 <file><var>package</var>config</file> and then run that if
10545 appropriate from the post-installation script. The
10546 <tt><var>package</var>config</tt> program should not
10547 unquestioningly overwrite an existing configuration - if its
10548 mode of operation is geared towards setting up a package for
10549 the first time (rather than any arbitrary reconfiguration
10550 later) you should have it check whether the configuration
10551 already exists, and require a <tt>--force</tt> flag to
10552 overwrite it.</p></sect>
10555 <appendix id="pkg-alternatives"><heading>Alternative versions of
10556 an interface - <prgn>update-alternatives</prgn> (from old
10561 When several packages all provide different versions of the
10562 same program or file it is useful to have the system select a
10563 default, but to allow the system administrator to change it
10564 and have their decisions respected.
10568 For example, there are several versions of the <prgn>vi</prgn>
10569 editor, and there is no reason to prevent all of them from
10570 being installed at once, each under their own name
10571 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10572 Nevertheless it is desirable to have the name <tt>vi</tt>
10573 refer to something, at least by default.
10577 If all the packages involved cooperate, this can be done with
10578 <prgn>update-alternatives</prgn>.
10582 Each package provides its own version under its own name, and
10583 calls <prgn>update-alternatives</prgn> in its postinst to
10584 register its version (and again in its prerm to deregister
10589 See the manpage <manref name="update-alternatives"
10590 section="8"> for details.
10594 If <prgn>update-alternatives</prgn> does not seem appropriate
10595 you may wish to consider using diversions instead.</p>
10598 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10599 package's version of a file (from old Packaging Manual)
10603 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10604 when it reinstalls the package it belongs to, and to have it
10605 put the file from the package somewhere else instead.
10609 This can be used locally to override a package's version of a
10610 file, or by one package to override another's version (or
10611 provide a wrapper for it).
10615 Before deciding to use a diversion, read <ref
10616 id="pkg-alternatives"> to see if you really want a diversion
10617 rather than several alternative versions of a program.
10621 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10622 and updated by a special program <prgn>dpkg-divert</prgn>.
10623 Please see <manref name="dpkg-divert" section="8"> for full
10624 details of its operation.
10628 When a package wishes to divert a file from another, it should
10629 call <prgn>dpkg-divert</prgn> in its preinst to add the
10630 diversion and rename the existing file. For example,
10631 supposing that a <prgn>smailwrapper</prgn> package wishes to
10632 install a wrapper around <file>/usr/sbin/smail</file>:
10634 if [ install = "$1" ]; then
10635 dpkg-divert --package smailwrapper --add --rename \
10636 --divert /usr/sbin/smail.real /usr/sbin/smail
10638 </example> Testing <tt>$1</tt> is necessary so that the script
10639 doesn't try to add the diversion again when
10640 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10641 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10642 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10643 get installed as the true version.
10647 The postrm has to do the reverse:
10649 if [ remove = "$1" ]; then
10650 dpkg-divert --package smailwrapper --remove --rename \
10651 --divert /usr/sbin/smail.real /usr/sbin/smail
10657 Do not attempt to divert a file which is vitally important for
10658 the system's operation - when using <prgn>dpkg-divert</prgn>
10659 there is a time, after it has been diverted but before
10660 <prgn>dpkg</prgn> has installed the new version, when the file
10661 does not exist.</p>
10666 <!-- vim:set ai et sts=2 sw=2 tw=76: -->