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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 if it's already
4638 already running, otherwise start the service</p></item>
4640 <tag><tt>reload</tt></tag>
4641 <item><p>cause the configuration of the service to be
4642 reloaded without actually stopping and restarting
4643 the service,</p></item>
4645 <tag><tt>force-reload</tt></tag>
4646 <item><p>cause the configuration to be reloaded if the
4647 service supports this, otherwise restart the
4651 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
4652 <tt>force-reload</tt> options should be supported by all
4653 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
4654 option is optional.</p>
4657 The <file>init.d</file> scripts should ensure that they will
4658 behave sensibly if invoked with <tt>start</tt> when the
4659 service is already running, or with <tt>stop</tt> when it
4660 isn't, and that they don't kill unfortunately-named user
4661 processes. The best way to achieve this is usually to use
4662 <prgn>start-stop-daemon</prgn>.</p>
4665 If a service reloads its configuration automatically (as
4666 in the case of <prgn>cron</prgn>, for example), the
4667 <tt>reload</tt> option of the <file>init.d</file> script
4668 should behave as if the configuration has been reloaded
4672 The <file>/etc/init.d</file> scripts must be treated as
4673 configuration files, either (if they are present in the
4674 package, that is, in the .deb file) by marking them as
4675 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
4676 by managing them correctly in the maintainer scripts (see
4677 <ref id="config-files">). This is important since we want
4678 to give the local system administrator the chance to adapt
4679 the scripts to the local system, e.g., to disable a
4680 service without de-installing the package, or to specify
4681 some special command line options when starting a service,
4682 while making sure her changes aren't lost during the next
4687 These scripts should not fail obscurely when the
4688 configuration files remain but the package has been
4689 removed, as configuration files remain on the system after
4690 the package has been removed. Only when <prgn>dpkg</prgn>
4691 is executed with the <tt>--purge</tt> option will
4692 configuration files be removed. In particular, as the
4693 <file>/etc/init.d/<var>package</var></file> script itself is
4694 usually a <tt>conffile</tt>, it will remain on the system
4695 if the package is removed but not purged. Therefore, you
4696 should include a <tt>test</tt> statement at the top of the
4698 <example compact="compact">
4699 test -f <var>program-executed-later-in-script</var> || exit 0
4704 Often there are some variables in the <file>init.d</file>
4705 scripts whose values control the behaviour of the scripts,
4706 and which a system administrator is likely to want to
4707 change. As the scripts themselves are frequently
4708 <tt>conffile</tt>s, modifying them requires that the
4709 administrator merge in their changes each time the package
4710 is upgraded and the <tt>conffile</tt> changes. To ease
4711 the burden on the system administrator, such configurable
4712 values should not be placed directly in the script.
4713 Instead, they should be placed in a file in
4714 <file>/etc/default</file>, which typically will have the same
4715 base name as the <file>init.d</file> script. This extra file
4716 should be sourced by the script when the script runs. It
4717 must contain only variable settings and comments in POSIX
4718 <prgn>sh</prgn> format. It may either be a
4719 <tt>conffile</tt> or a configuration file maintained by
4720 the package maintainer scripts. See <ref id="config-files">
4725 To ensure that vital configurable values are always
4726 available, the <file>init.d</file> script should set default
4727 values for each of the shell variables it uses, either
4728 before sourcing the <file>/etc/default/</file> file or
4729 afterwards using something like the <tt>:
4730 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
4731 script must behave sensibly and not fail if the
4732 <file>/etc/default</file> file is deleted.
4737 <heading>Interfacing with the initscript system</heading>
4740 Maintainers should use the abstraction layer provided by
4741 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
4742 programs to deal with initscripts in their packages'
4743 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
4744 and <prgn>postrm</prgn>.
4747 Directly managing the /etc/rc?.d links and directly
4748 invoking the <file>/etc/init.d/</file> initscripts should
4749 be done only by packages providing the initscript
4750 subsystem (such as <prgn>sysvinit</prgn> and
4751 <prgn>file-rc</prgn>).
4756 <heading>Managing the links</heading>
4759 The program <prgn>update-rc.d</prgn> is provided for
4760 package maintainers to arrange for the proper creation and
4761 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
4762 or their functional equivalent if another method is being
4763 used. This may be used by maintainers in their packages'
4764 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.</p>
4767 You must not include any <file>/etc/rc<var>n</var>.d</file>
4768 symbolic links in the actual archive or manually create or
4769 remove the symbolic links in maintainer scripts; you must
4770 use the <prgn>update-rc.d</prgn> program instead. (The
4771 former will fail if an alternative method of maintaining
4772 runlevel information is being used.) You must not include
4773 the <file>/etc/rc<var>n</var>.d</file> directories themselves
4774 in the archive either. (Only the <tt>sysvinit</tt>
4779 By default <prgn>update-rc.d</prgn> will start services in
4780 each of the multi-user state runlevels (2, 3, 4, and 5)
4781 and stop them in the halt runlevel (0), the single-user
4782 runlevel (1) and the reboot runlevel (6). The system
4783 administrator will have the opportunity to customize
4784 runlevels by simply adding, moving, or removing the
4785 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
4786 symbolic links are being used, or by modifying
4787 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
4792 To get the default behavior for your package, put in your
4793 <prgn>postinst</prgn> script
4794 <example compact="compact">
4795 update-rc.d <var>package</var> defaults
4797 and in your <prgn>postrm</prgn>
4798 <example compact="compact">
4799 if [ "$1" = purge ]; then
4800 update-rc.d <var>package</var> remove
4802 </example>. Note that if your package changes runlevels
4803 or priority, you may have to remove and recreate the links,
4804 since otherwise the old links may persist. Refer to the
4805 documentation of <prgn>update-rc.d</prgn></p>
4808 This will use a default sequence number of 20. If it does
4809 not matter when or in which order the <file>init.d</file>
4810 script is run, use this default. If it does, then you
4811 should talk to the maintainer of the <prgn>sysvinit</prgn>
4812 package or post to <tt>debian-devel</tt>, and they will
4813 help you choose a number.
4817 For more information about using <tt>update-rc.d</tt>,
4818 please consult its manpage <manref name="update-rc.d"
4824 <heading>Running initscripts</heading>
4826 The program <prgn>invoke-rc.d</prgn> is provided to make
4827 it easier for package maintainers to properly invoke an
4828 initscript, obeying runlevel and other locally-defined
4829 constraints that might limit a package's right to start,
4830 stop and otherwise manage services. This program may be
4831 used by maintainers in their packages' scripts.
4834 The use of <prgn>invoke-rc.d</prgn> to invoke the
4835 <file>/etc/init.d/*</file> initscripts is strongly
4836 recommended<footnote>
4838 In the future, the use of invoke-rc.d to invoke
4839 initscripts shall be made mandatory. Maintainers are
4840 advised to switch to invoke-rc.d as soon as
4842 </footnote>, instead of calling them directly.
4846 By default, <prgn>invoke-rc.d</prgn> will pass any
4847 action requests (start, stop, reload, restart...) to the
4848 <file>/etc/init.d</file> script, filtering out requests
4849 to start or restart a service out of its intended
4853 Most packages will simply need to change:
4854 <example compact="compact">/etc/init.d/<package>
4855 <action></example> in their <prgn>postinst</prgn>
4856 and <prgn>prerm</prgn> scripts to:
4857 <example compact="compact">
4858 if [ -x /usr/sbin/invoke-rc.d ] ; then
4859 invoke-rc.d <var>package</var> <action>
4861 /etc/init.d/<var>package</var> <action>
4865 A package should register its initscript services using
4866 <prgn>update-rc.d</prgn> before it tries to invoke them
4867 using <prgn>invoke-rc.d</prgn>. Invocation of
4868 unregistered services may fail.
4871 For more information about using
4872 <prgn>invoke-rc.d</prgn>, please consult its manpage
4873 <manref name="invoke-rc.d" section="8">.
4880 <heading>Boot-time initialization</heading>
4883 There used to be another directory, <file>/etc/rc.boot</file>,
4884 which contained scripts which were run once per machine
4885 boot. This has been deprecated in favour of links from
4886 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
4887 described in <ref id="/etc/init.d">. Packages must not
4888 place files in <file>/etc/rc.boot</file>.</p>
4891 <heading>Example</heading>
4894 The <prgn>bind</prgn> DNS (nameserver) package wants to
4895 make sure that the nameserver is running in multiuser
4896 runlevels, and is properly shut down with the system. It
4897 puts a script in <file>/etc/init.d</file>, naming the script
4898 appropriately <tt>bind</tt>. As you can see, the script
4899 interprets the argument <tt>reload</tt> to send the
4900 nameserver a <tt>HUP</tt> signal (causing it to reload its
4901 configuration); this way the system administrator can say
4902 <tt>/etc/init.d/bind reload</tt> to reload the name
4903 server. The script has one configurable value, which can
4904 be used to pass parameters to the named program at
4905 startup; this value is read from
4906 <file>/etc/default/bind</file> (see below).
4910 <example compact="compact">
4913 # Original version by Robert Leslie
4914 # <rob@mars.org>, edited by iwj and cs
4916 test -x /usr/sbin/named || exit 0
4918 # Source defaults file.
4920 if [ -f /etc/default/bind ]; then
4927 echo -n "Starting domain name service: named"
4928 start-stop-daemon --start --quiet --exec /usr/sbin/named \
4933 echo -n "Stopping domain name service: named"
4934 start-stop-daemon --stop --quiet \
4935 --pidfile /var/run/named.pid --exec /usr/sbin/named
4939 echo -n "Restarting domain name service: named"
4940 start-stop-daemon --stop --quiet \
4941 --pidfile /var/run/named.pid --exec /usr/sbin/named
4942 start-stop-daemon --start --verbose --exec /usr/sbin/named \
4946 force-reload|reload)
4947 echo -n "Reloading configuration of domain name service: named"
4948 start-stop-daemon --stop --signal 1 --quiet \
4949 --pidfile /var/run/named.pid --exec /usr/sbin/named
4953 echo "Usage: /etc/init.d/bind " \
4954 " {start|stop|restart|reload|force-reload}" >&2
4964 Complementing the above init script is a configuration
4965 file <file>/etc/default/bind</file>, which contains
4966 configurable parameters used by the script. This would be
4967 created by the <prgn>postinst</prgn> script if it was not
4968 already present, and removed on purge by the
4969 <prgn>postrm</prgn> script.
4970 <example compact="compact">
4971 # Specified parameters to pass to named. See named(8).
4972 # You may uncomment the following line, and edit to taste.
4978 Another example on which you can base your
4979 <file>/etc/init.d</file> scripts is found in
4980 <file>/etc/init.d/skeleton</file>.
4984 If this package is happy with the default setup from
4985 <prgn>update-rc.d</prgn>, namely an ordering number of 20
4986 and having named running in all runlevels, it can say in
4987 its <prgn>postinst</prgn>:
4988 <example compact="compact">
4989 update-rc.d bind defaults >/dev/null
4991 And in its <prgn>postrm</prgn>, to remove the links when the
4993 <example compact="compact">
4994 if [ "$1" = purge ]; then
4995 update-rc.d bind remove >/dev/null
5003 <heading>Console messages from <file>init.d</file> scripts</heading>
5006 This section describes the formats to be used for messages
5007 written to standard output by the <file>/etc/init.d</file>
5008 scripts. The intent is to improve the consistency of
5009 Debian's startup and shutdown look and feel. For this
5010 reason, please look very carefully at the details. We want
5011 the messages to have the same format in terms of wording,
5012 spaces, punctuation and case of letters.
5016 Here is a list of overall rules that you should use when you
5017 create output messages. They can be useful if you have a
5018 non-standard message that is not covered specifically in the
5026 Every message should fit in one line (fewer than 80
5027 characters), start with a capital letter and end with
5028 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5034 If you want to express that the computer is working on
5035 something (that is, performing a specific task, not
5036 starting or stopping a program), we use an "ellipsis"
5037 (three dots: <tt>...</tt>). Note that we don't insert
5038 spaces before or after the dots. If the task has been
5039 completed we write <tt>done.</tt> and a line feed.
5045 Design your messages as if the computer is telling you
5046 what he is doing (let him be polite :-), but don't
5047 mention "him" directly. For example, if you think of
5049 <example compact="compact">
5050 I'm starting network daemons: nfsd mountd.
5053 <example compact="compact">
5054 Starting network daemons: nfsd mountd.
5062 There are standard message formats for the following
5063 situations. They should be used by the <tt>init.d</tt>
5070 <p>When daemons are started</p>
5073 If your script starts one or more daemons, the output
5074 should look like this (a single line, no leading
5076 <example compact="compact">
5077 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5079 The <var>description</var> should describe the
5080 subsystem the daemon or set of daemons are part of,
5081 while <var>daemon-1</var> up to <var>daemon-n</var>
5082 denote each daemon's name (typically the file name of
5087 For example, the output of <file>/etc/init.d/lpd</file>
5089 <example compact="compact">
5090 Starting printer spooler: lpd.
5095 This can be achieved by saying
5096 <example compact="compact">
5097 echo -n "Starting printer spooler: lpd"
5098 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5101 in the script. If you have more than one daemon to
5102 start, you should do the following:
5103 <example compact="compact">
5104 echo -n "Starting remote file system services:"
5105 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5106 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5107 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5110 This makes it possible for the user to see what takes
5111 so long and when the final daemon has been started.
5112 You should be careful where to put spaces: in the
5113 example above the system administrator can easily
5114 comment out a line if he don't wants to start a
5115 specific daemon, while the displayed message still
5121 <p>When a system parameter is being set</p>
5124 If you have to set up different system parameters
5125 during the system boot, you should use this format:
5126 <example compact="compact">
5127 Setting <var>parameter</var> to "<var>value</var>".
5132 You can use a statement such as the following to get
5134 <example compact="compact">
5135 echo "Setting DNS domainname to \"$domainname\"."
5140 Note that the same symbol (<tt>"</tt>) is used for the left
5141 and right quotation marks. A grave accent (<tt>`</tt>) is
5142 not a quote character; neither is an apostrophe
5148 <p>When a daemon is stopped or restarted</p>
5151 When you stop or restart a daemon, you should issue a
5152 message identical to the startup message, except that
5153 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5154 or <tt>Restarting</tt> respectively.
5158 For example, stopping the printer daemon will like
5160 <example compact="compact">
5161 Stopping printer spooler: lpd.
5167 <p>When something is executed</p>
5170 There are several examples where you have to run a
5171 program at system startup or shutdown to perform a
5172 specific task, for example, setting the system's clock
5173 using <prgn>netdate</prgn> or killing all processes
5174 when the system shuts down. Your message should look
5176 <example compact="compact">
5177 Doing something very useful...done.
5179 You should print the <tt>done.</tt> immediately after
5180 the job has been completed, so that the user is
5181 informed why she has to wait. You can get this
5183 <example compact="compact">
5184 echo -n "Doing something very useful..."
5193 <p>When the configuration is reloaded</p>
5196 When a daemon is forced to reload its configuration
5197 files you should use the following format:
5198 <example compact="compact">
5199 Reloading <var>description</var> configuration...done.
5201 where <var>description</var> is the same as in the
5202 daemon starting message.
5210 <heading>Cron jobs</heading>
5213 Packages must not modify the configuration file
5214 <file>/etc/crontab</file>, and they must not modify the files in
5215 <file>/var/spool/cron/crontabs</file>.</p>
5218 If a package wants to install a job that has to be executed
5219 via cron, it should place a file with the name of the
5220 package in one or more of the following directories:
5221 <example compact="compact">
5226 As these directory names imply, the files within them are
5227 executed on a daily, weekly, or monthly basis,
5228 respectively. The exact times are listed in
5229 <file>/etc/crontab</file>.</p>
5232 All files installed in any of these directories must be
5233 scripts (e.g., shell scripts or Perl scripts) so that they
5234 can easily be modified by the local system administrator.
5235 In addition, they should be treated as configuration
5240 If a certain job has to be executed more frequently than
5241 daily, the package should install a file
5242 <file>/etc/cron.d/<var>package</var></file>. This file uses the
5243 same syntax as <file>/etc/crontab</file> and is processed by
5244 <prgn>cron</prgn> automatically. The file must also be
5245 treated as a configuration file. (Note that entries in the
5246 <file>/etc/cron.d</file> directory are not handled by
5247 <prgn>anacron</prgn>. Thus, you should only use this
5248 directory for jobs which may be skipped if the system is not
5252 The scripts or crontab entries in these directories should
5253 check if all necessary programs are installed before they
5254 try to execute them. Otherwise, problems will arise when a
5255 package was removed but not purged since configuration files
5256 are kept on the system in this situation.</p>
5260 <heading>Menus</heading>
5263 Menu entries should follow the current menu policy found in
5264 the <tt>menu-policy</tt> files in the <tt>debian-policy</tt>
5265 package. It may also be found on the Debian FTP site
5266 <ftpsite>ftp.debian.org</ftpsite> as the file
5267 <ftppath>/debian/doc/package-developer/menu-policy.txt.gz</ftppath>,
5268 or in the equivalent location on your local mirror.
5272 The Debian <tt>menu</tt> package provides a standard
5273 interface between packages providing applications and
5274 documents, and <em>menu programs</em> (either X window
5275 managers or text-based menu programs such as
5276 <prgn>pdmenu</prgn>).
5280 All packages that provide applications that need not be
5281 passed any special command line arguments for normal
5282 operation should register a menu entry for those
5283 applications, so that users of the <tt>menu</tt> package
5284 will automatically get menu entries in their window
5285 managers, as well in shells like <tt>pdmenu</tt>.</p>
5288 Please also refer to the <em>Debian Menu System</em>
5289 documentation that comes with the <tt>menu</tt> package for
5290 information about how to register your applications and web
5296 <heading>Multimedia handlers</heading>
5299 Packages which provide the ability to view/show/play,
5300 compose, edit or print MIME types should register themselves
5301 as such following the current MIME support policy found in
5302 the <tt>mime-policy</tt> files in the <tt>debian-policy</tt>
5303 package. It may also be found on the Debian FTP site
5304 <ftpsite>ftp.debian.org</ftpsite> as the file
5305 <ftppath>/debian/doc/package-developer/mime-policy.txt.gz</ftppath>,
5306 or in the equivalent location on your local mirror.
5310 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
5311 is a mechanism for encoding files and data streams and
5312 providing meta-information about them, in particular their
5313 type (e.g. audio or video) and format (e.g. PNG, HTML,
5318 Registration of MIME type handlers allows programs like mail
5319 user agents and web browsers to to invoke these handlers to
5320 view, edit or display MIME types they don't support
5326 <heading>Keyboard configuration</heading>
5329 To achieve a consistent keyboard configuration so that all
5330 applications interpret a keyboard event the same way, all
5331 programs in the Debian distribution must be configured to
5332 comply with the following guidelines.
5336 The following keys must have the specified interpretations:
5339 <tag><tt><--</tt></tag>
5340 <item><p>delete the character to the left of the cursor</p></item>
5342 <tag><tt>Delete</tt></tag>
5343 <item><p>delete the character to the right of the cursor</p></item>
5345 <tag><tt>Control+H</tt></tag>
5346 <item><p>emacs: the help prefix</p></item>
5349 The interpretation of any keyboard events should be
5350 independent of the terminal that is used, be it a virtual
5351 console, an X terminal emulator, an rlogin/telnet session,
5356 The following list explains how the different programs
5357 should be set up to achieve this:
5362 <item><p><tt><--</tt> generates <tt>KB_BackSpace</tt>
5365 <item><p><tt>Delete</tt> generates <tt>KB_Delete</tt> in
5370 X translations are set up to make
5371 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
5372 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
5373 is the vt220 escape code for the "delete character"
5374 key). This must be done by loading the X resources
5375 using <prgn>xrdb</prgn> on all local X displays, not
5376 using the application defaults, so that the
5377 translation resources used correspond to the
5378 <prgn>xmodmap</prgn> settings.</p></item>
5382 The Linux console is configured to make
5383 <tt><--</tt> generate DEL, and <tt>Delete</tt>
5384 generate <tt>ESC [ 3 ~</tt>.</p></item>
5388 X applications are configured so that <tt><</tt>
5389 deletes left, and <tt>Delete</tt> deletes right. Motif
5390 applications already work like this.</p></item>
5392 <item><p>Terminals should have <tt>stty erase ^?</tt> .</p></item>
5396 The <tt>xterm</tt> terminfo entry should have <tt>ESC
5397 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
5398 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.</p></item>
5402 Emacs is programmed to map <tt>KB_Backspace</tt> or
5403 the <tt>stty erase</tt> character to
5404 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
5405 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
5406 <tt>^H</tt> to <tt>help</tt> as always.</p></item>
5410 Other applications use the <tt>stty erase</tt>
5411 character and <tt>kdch1</tt> for the two delete keys,
5412 with ASCII DEL being "delete previous character" and
5413 <tt>kdch1</tt> being "delete character under
5420 This will solve the problem except for the following
5428 Some terminals have a <tt><--</tt> key that cannot
5429 be made to produce anything except <tt>^H</tt>. On
5430 these terminals Emacs help will be unavailable on
5431 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
5432 character takes precedence in Emacs, and has been set
5433 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
5434 available) can be used instead.</p></item>
5438 Some operating systems use <tt>^H</tt> for <tt>stty
5439 erase</tt>. However, modern telnet versions and all
5440 rlogin versions propagate <tt>stty</tt> settings, and
5441 almost all UNIX versions honour <tt>stty erase</tt>.
5442 Where the <tt>stty</tt> settings are not propagated
5443 correctly, things can be made to work by using
5444 <tt>stty</tt> manually.</p></item>
5448 Some systems (including previous Debian versions) use
5449 <prgn>xmodmap</prgn> to arrange for both
5450 <tt><--</tt> and <tt>Delete</tt> to generate
5451 <tt>KB_Delete</tt>. We can change the behavior of
5452 their X clients using the same X resources that we use
5453 to do it for our own clients, or configure our clients
5454 using their resources when things are the other way
5455 around. On displays configured like this
5456 <tt>Delete</tt> will not work, but <tt><--</tt>
5461 Some operating systems have different <tt>kdch1</tt>
5462 settings in their <tt>terminfo</tt> database for
5463 <tt>xterm</tt> and others. On these systems the
5464 <tt>Delete</tt> key will not work correctly when you
5465 log in from a system conforming to our policy, but
5466 <tt><--</tt> will.</p></item>
5472 <heading>Environment variables</heading>
5475 A program must not depend on environment variables to get
5476 reasonable defaults. (That's because these environment
5477 variables would have to be set in a system-wide
5478 configuration file like <file>/etc/profile</file>, which is not
5479 supported by all shells.)</p>
5482 If a program usually depends on environment variables for its
5483 configuration, the program should be changed to fall back to
5484 a reasonable default configuration if these environment
5485 variables are not present. If this cannot be done easily
5486 (e.g., if the source code of a non-free program is not
5487 available), the program must be replaced by a small
5488 "wrapper" shell script which sets the environment variables
5489 if they are not already defined, and calls the original program.</p>
5492 Here is an example of a wrapper script for this purpose:
5494 <example compact="compact">
5496 BAR=${BAR:-/var/lib/fubar}
5498 exec /usr/lib/foo/foo "$@"
5503 Furthermore, as <file>/etc/profile</file> is a configuration
5504 file of the <prgn>base-files</prgn> package, other packages must not
5505 put any environment variables or other commands into that
5511 <heading>Files</heading>
5514 <heading>Binaries</heading>
5517 Two different packages must not install programs with
5518 different functionality but with the same filenames. (The
5519 case of two programs having the same functionality but
5520 different implementations is handled via "alternatives" or
5521 the "Conflicts" mechanism. See <ref id="maintscripts"> and
5522 <ref id="conflicts"> respectively.) If this case happens,
5523 one of the programs must be renamed. The maintainers should
5524 report this to the <tt>debian-devel</tt> mailing list and
5525 try to find a consensus about which program will have to be
5526 renamed. If a consensus cannot be reached, <em>both</em>
5527 programs must be renamed.
5531 By default, when a package is being built, any binaries
5532 created should include debugging information, as well as
5533 being compiled with optimization. You should also turn on
5534 as many reasonable compilation warnings as possible; this
5535 makes life easier for porters, who can then look at build
5536 logs for possible problems. For the C programming language,
5537 this means the following compilation parameters should be
5539 <example compact="compact">
5541 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
5543 install -s # (or use strip on the files in debian/tmp)
5548 Note that by default all installed binaries should be stripped,
5549 either by using the <tt>-s</tt> flag to
5550 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
5551 the binaries after they have been copied into
5552 <file>debian/tmp</file> but before the tree is made into a
5556 Although binaries in the build tree should be compiled with
5557 debugging information by default, it can often be difficult
5558 to debug programs if they are also subjected to compiler
5559 optimization. For this reason, it is recommended to support
5560 the standardized environment
5561 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
5562 contain several flags to change how a package is compiled
5570 The presence of this string means that the package
5571 should be complied with a minimum of optimization.
5572 For C programs, it is best to add <tt>-O0</tt>
5573 to <tt>CFLAGS</tt> (although this is usually the
5574 default). Some programs might fail to build or run at
5575 this level of optimization; it may be necessary to
5576 use <tt>-O1</tt>, for example.
5582 This string means that the debugging symbols should
5583 not be stripped from the binary during installation,
5584 so that debugging information may be included in the package.
5590 The following makefile snippet is an example of how one may
5591 implement the build options; you will probably have to
5592 massage this example in order to make it work for your
5594 <example compact="compact">
5597 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
5598 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
5599 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
5600 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
5602 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
5607 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
5608 INSTALL_PROGRAM += -s
5614 It is up to the package maintainer to decide what
5615 compilation options are best for the package. Certain
5616 binaries (such as computationally-intensive programs) will
5617 function better with certain flags (<tt>-O3</tt>, for
5618 example); feel free to use them. Please use good judgment
5619 here. Don't use flags for the sake of it; only use them
5620 if there is good reason to do so. Feel free to override
5621 the upstream author's ideas about which compilation
5622 options are best: they are often inappropriate for our
5629 <heading>Libraries</heading>
5632 In general, libraries must have a shared version in the
5633 library package (<package>lib*</package>) and a static
5634 version in the development package (<package>lib*-dev</package>).
5635 The shared version must be compiled with <tt>-fPIC</tt>,
5636 and the static version must not be. In other words, each source
5637 unit (<tt>*.c</tt>, for example, for C files) will need to be
5642 In some cases, it is acceptable for a library to be
5643 available in static form only; these cases include:
5646 <p>libraries for languages whose shared library support
5647 is immature or unstable</p>
5651 libraries whose interfaces are in flux or under
5652 development (commonly the case when the library's
5653 major version number is zero, or where the ABI breaks
5659 libraries which are explicitly intended to be
5660 available only in static form by their upstream
5664 If a library is available only in static form, then it must follow
5665 the conventions for a development package.
5669 You must specify the gcc option <tt>-D_REENTRANT</tt>
5670 when building a library (either static or shared) to make
5671 the library compatible with LinuxThreads.
5675 Note that all installed shared libraries should be
5677 <example compact="compact">
5678 strip --strip-unneeded <var>your-lib</var>
5680 (The option <tt>--strip-unneeded</tt> makes
5681 <prgn>strip</prgn> remove only the symbols which aren't
5682 needed for relocation processing.) Shared libraries can
5683 function perfectly well when stripped, since the symbols for
5684 dynamic linking are in a separate part of the ELF object
5687 You might also want to use the options
5688 <tt>--remove-section=.comment</tt> and
5689 <tt>--remove-section=.note</tt> on both shared libraries
5690 and executables, and <tt>--strip-debug</tt> on static
5697 Note that under some circumstances it may be useful to
5698 install a shared library unstripped, for example when
5699 building a separate package to support debugging.
5703 Shared object files (often <file>.so</file> files) that are not
5704 public libraries, that is, they are not meant to be linked
5705 to by third party executables (binaries of other packages),
5706 should be installed in subdirectories of the
5707 <file>/usr/lib</file> directory. Such files are exempt from the
5708 rules that govern ordinary shared libraries, except that
5709 they must not be installed executable and should be
5712 A common example are the so-called "plug-ins",
5713 internal shared objects that are dynamically loaded by
5714 programs using <manref name="dlopen" section="3">.
5720 Packages containing shared libraries that may be linked to
5721 by other packages' binaries, but which for some
5722 <em>compelling</em> reason can not be installed in
5723 <file>/usr/lib</file> directory, may install the shared library
5724 files in subdirectories of the <file>/usr/lib</file> directory,
5725 in which case they should arrange to add that directory in
5726 <file>/etc/ld.so.conf</file> in the package's post-installation
5727 script, and remove it in the package's post-removal script.
5731 An ever increasing number of packages are using
5732 <prgn>libtool</prgn> to do their linking. The latest GNU
5733 libtools (>= 1.3a) can take advantage of the metadata in the
5734 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
5735 files). The main advantage of <prgn>libtool</prgn>'s
5736 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
5737 store and subsequently access metadata with respect to the
5738 libraries it builds. <prgn>libtool</prgn> will search for
5739 those files, which contain a lot of useful information about
5740 a library (such as library dependency information for static
5741 linking). Also, they're <em>essential</em> for programs
5742 using <tt>libltdl</tt>.<footnote>
5744 Although <prgn>libtool</prgn> is fully capable of
5745 linking against shared libraries which don't have
5746 <tt>.la</tt> files, as it is a mere shell script it can
5747 add considerably to the build time of a
5748 <prgn>libtool</prgn>-using package if that shell script
5749 has to derive all this information from first principles
5750 for each library every time it is linked. With the
5751 advent of <prgn>libtool</prgn> version 1.4 (and to a
5752 lesser extent <prgn>libtool</prgn> version 1.3), the
5753 <file>.la</file> files also store information about
5754 inter-library dependencies which cannot necessarily be
5755 derived after the <file>.la</file> file is deleted.
5761 Packages that use <prgn>libtool</prgn> to create shared
5762 libraries should include the <file>.la</file> files in the
5763 <tt>-dev</tt> package, unless the package relies on
5764 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
5765 the <tt>.la</tt> files must go in the run-time library
5770 You must make sure that you use only released versions of
5771 shared libraries to build your packages; otherwise other
5772 users will not be able to run your binaries
5773 properly. Producing source packages that depend on
5774 unreleased compilers is also usually a bad
5780 <heading>Shared libraries</heading>
5783 Packages involving shared libraries should be split up
5784 into several binary packages.</p>
5787 For a straightforward library which has a development
5788 environment and a runtime kit including just shared
5789 libraries you need to create two packages:
5790 <file><var>libraryname</var><var>soversion</var></file>, where
5791 <file><var>soversion</var></file> is the version number in the
5792 soname of the shared library<footnote>
5794 The soname is the shared object name: it's the thing
5795 that has to match exactly between building an executable
5796 and running it for the dynamic linker to be able run the
5797 program. For example, if the soname of the library is
5798 <file>libfoo.so.6</file>, the library package would be
5799 called <file>libfoo6</file>.
5802 and <tt><var>libraryname</var><var>soversion</var>-dev</tt>.
5803 Alternatively, if it would be confusing to directly append
5804 <var>soversion</var> to <var>libraryname</var> (e.g. because
5805 <var>libraryname</var> itself ends in a number), you may use
5806 <tt><var>libraryname</var>-<var>soversion</var></tt> and
5807 <tt><var>libraryname</var>-<var>soversion</var>-dev</tt>
5812 If you prefer only to support one development version at a
5813 time you may name the development package
5814 <file><var>libraryname</var>-dev</file>; otherwise you may need
5815 to use <prgn>dpkg</prgn>'s Conflicts mechanism (see <ref
5816 id="conflicts">) to ensure that the user only installs one
5817 development version at a time (as different development
5818 versions are likely to have the same header files in them,
5819 which would cause a filename clash if both were installed).
5820 Typically the development version should also have an exact
5821 version dependency on the runtime library, to make sure that
5822 compilation and linking happens correctly. The
5823 <tt>${Source-Version}</tt> substitution variable can be
5824 useful for this purpose.
5828 Packages which use the shared library should have a
5829 dependency on the name of the shared library package,
5830 <file><var>libraryname</var><var>soversion</var></file>. When
5831 the soname changes you can have both versions of the library
5832 installed while migrating from the old library to the new.
5836 If your package has some run-time support programs which use
5837 the shared library you must not put them in the shared
5838 library package. If you do that then you won't be able to
5839 install several versions of the shared library without
5840 getting filename clashes. Instead, either create a third
5841 package for the runtime binaries (this package might
5842 typically be named <tt><var>libraryname</var>-runtime</tt>;
5843 note the absence of the <var>soversion</var> in the package
5844 name), or if the development package is small you may
5845 include them in there.
5849 If you have several shared libraries built from the same
5850 source tree you may lump them all together into a single
5851 shared library package, provided that you change all of
5852 their sonames at once (so that you don't get filename
5853 clashes if you try to install different versions of the
5854 combined shared libraries package).
5858 Shared libraries should not be installed executable, since
5859 the dynamic linker does not require this and trying to
5860 execute a shared library usually results in a core dump.
5865 <heading>Scripts</heading>
5868 All command scripts, including the package maintainer
5869 scripts inside the package and used by <prgn>dpkg</prgn>,
5870 should have a <tt>#!</tt> line naming the shell to be used
5871 to interpret them.</p>
5874 In the case of Perl scripts this should be
5875 <tt>#!/usr/bin/perl</tt>.</p>
5878 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
5879 should almost certainly start with <tt>set -e</tt> so that
5880 errors are detected. Every script should use
5881 <tt>set -e</tt> or check the exit status of <em>every</em>
5885 The standard shell interpreter <file>/bin/sh</file> can be a
5886 symbolic link to any POSIX compatible shell, if <tt>echo
5887 -n</tt> does not generate a newline.<footnote>
5889 Debian policy specifies POSIX behavior for
5890 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
5891 use in the Linux community (in particular including this
5892 policy, the Linux kernel source, many Debian scripts,
5893 etc.). This <tt>echo -n</tt> mechanism is valid but not
5894 required under POSIX, hence this explicit addition.
5895 Also, rumour has it that this shall be mandated under
5899 Thus, shell scripts specifying <file>/bin/sh</file> as
5900 interpreter should only use POSIX features. If a script
5901 requires non-POSIX features from the shell interpreter, the
5902 appropriate shell must be specified in the first line of the
5903 script (e.g., <tt>#!/bin/bash</tt>) and the package must
5904 depend on the package providing the shell (unless the shell
5905 package is marked "Essential", as in the case of
5910 You may wish to restrict your script to POSIX features when
5911 possible so that it may use <file>/bin/sh</file> as its
5912 interpreter. If your script works with <prgn>dash</prgn>
5913 (originally called <prgn>ash</prgn>), it's probably POSIX
5914 compliant, but if you are in doubt, use
5915 <file>/bin/bash</file>.
5919 Perl scripts should check for errors when making any
5920 system calls, including <tt>open</tt>, <tt>print</tt>,
5921 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
5925 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
5926 scripting languages. See <em>Csh Programming Considered
5927 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
5928 can be found at <url
5929 id="http://language.perl.com/versus/csh.whynot">.<footnote>
5931 It can also be found on
5932 <url id="http://www.cpan.org/doc/FMTEYEWTK/versus/csh.whynot">
5933 or on the ftp site <ftpsite>ftp.cpan.org</ftpsite> as
5934 <ftppath>/pub/perl/CPAN/doc/FMTEYEWTK/versus/csh.whynot</ftppath>.
5937 If an upstream package comes with <prgn>csh</prgn> scripts
5938 then you must make sure that they start with
5939 <tt>#!/bin/csh</tt> and make your package depend on the
5940 <prgn>c-shell</prgn> virtual package.
5944 Any scripts which create files in world-writeable
5945 directories (e.g., in <file>/tmp</file>) must use a
5946 mechanism which will fail if a file with the same name
5950 The Debian base system provides the <prgn>tempfile</prgn>
5951 and <prgn>mktemp</prgn> utilities for use by scripts for
5952 this purpose.</p></sect>
5956 <heading>Symbolic links</heading>
5959 In general, symbolic links within a top-level directory
5960 should be relative, and symbolic links pointing from one
5961 top-level directory into another should be absolute. (A
5962 top-level directory is a sub-directory of the root
5963 directory <file>/</file>.)</p>
5966 In addition, symbolic links should be specified as short as
5967 possible, i.e., link targets like <file>foo/../bar</file> are
5971 Note that when creating a relative link using
5972 <prgn>ln</prgn> it is not necessary for the target of the
5973 link to exist relative to the working directory you're
5974 running <prgn>ln</prgn> from, nor is it necessary to change
5975 directory to the directory where the link is to be made.
5976 Simply include the string that should appear as the target
5977 of the link (this will be a pathname relative to the
5978 directory in which the link resides) as the first argument
5979 to <prgn>ln</prgn>.</p>
5982 For example, in your <prgn>Makefile</prgn> or
5983 <file>debian/rules</file>, you can do things like:
5984 <example compact="compact">
5985 ln -fs gcc $(prefix)/bin/cc
5986 ln -fs gcc debian/tmp/usr/bin/cc
5987 ln -fs ../sbin/sendmail $(prefix)/bin/runq
5988 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
5992 A symbolic link pointing to a compressed file should always
5993 have the same file extension as the referenced file. (For
5994 example, if a file <file>foo.gz</file> is referenced by a
5995 symbolic link, the filename of the link has to end with
5996 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6001 <heading>Device files</heading>
6004 Packages must not include device files in the package file
6008 If a package needs any special device files that are not
6009 included in the base system, it must call
6010 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6011 after notifying the user<footnote>
6013 This notification could be done via a (low-priority)
6014 debconf message, or an echo (printf) statement.
6020 Packages must not remove any device files in the
6021 <prgn>postrm</prgn> or any other script. This is left to the
6022 system administrator.</p>
6025 Debian uses the serial devices
6026 <file>/dev/ttyS*</file>. Programs using the old
6027 <file>/dev/cu*</file> devices should be changed to use
6028 <file>/dev/ttyS*</file>.</p>
6031 <sect id="config-files">
6032 <heading>Configuration files</heading>
6034 <heading>Definitions</heading>
6037 <tag>configuration file</tag>
6040 A file that affects the operation of a program, or
6041 provides site- or host-specific information, or
6042 otherwise customizes the behavior of a program.
6043 Typically, configuration files are intended to be
6044 modified by the system administrator (if needed or
6045 desired) to conform to local policy or to provide
6046 more useful site-specific behavior.
6050 <tag><tt>conffile</tt></tag>
6053 A file listed in a package's <tt>conffiles</tt>
6054 file, and is treated specially by <prgn>dpkg</prgn>
6055 (see <ref id="configdetails">).
6062 The distinction between these two is important; they are
6063 not interchangeable concepts. Almost all
6064 <tt>conffile</tt>s are configuration files, but many
6065 configuration files are not <tt>conffiles</tt>.
6069 Note that a script that embeds configuration information
6070 (such as most of the files in <file>/etc/default</file> and
6071 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6072 configuration file and should be treated as such.
6077 <heading>Location</heading>
6079 Any configuration files created or used by your package
6080 must reside in <file>/etc</file>. If there are several you
6081 should consider creating a subdirectory of <file>/etc</file>
6082 named after your package.</p>
6085 If your package creates or uses configuration files
6086 outside of <file>/etc</file>, and it is not feasible to modify
6087 the package to use the <file>/etc</file>, you should still put
6088 the files in <file>/etc</file> and create symbolic links to
6089 those files from the location that the package
6094 <heading>Behavior</heading>
6096 Configuration file handling must conform to the following
6098 <list compact="compact">
6101 local changes must be preserved during a package
6107 configuration files must be preserved when the
6108 package is removed, and only deleted when the
6116 The easy way to achieve this behavior is to make the
6117 configuration file a <tt>conffile</tt>. This is
6118 appropriate only if it is possible to distribute a default
6119 version that will work for most installations, although
6120 some system administrators may choose to modify it. This
6121 implies that the default version will be part of the
6122 package distribution, and must not be modified by the
6123 maintainer scripts during installation (or at any other
6128 In order to ensure that local changes are preserved
6129 correctly, no package may contain or make hard links to
6130 conffiles.<footnote>
6132 Rationale: There are two problems with hard links.
6133 The first is that some editors break the link while
6134 editing one of the files, so that the two files may
6135 unwittingly become unlinked and different. The second
6136 is that <prgn>dpkg</prgn> might break the hard link
6137 while upgrading <tt>conffile</tt>s.
6143 The other way to do it is via the maintainer scripts. In
6144 this case, the configuration file must not be listed as a
6145 <tt>conffile</tt> and must not be part of the package
6146 distribution. If the existence of a file is required for
6147 the package to be sensibly configured it is the
6148 responsibility of the package maintainer to provide
6149 maintainer scripts which correctly create, update and
6150 maintain the file and remove it on purge. (See <ref
6151 id="maintainerscripts"> for more information.) These
6152 scripts must be idempotent (i.e., must work correctly if
6153 <prgn>dpkg</prgn> needs to re-run them due to errors
6154 during installation or removal), must cope with all the
6155 variety of ways <prgn>dpkg</prgn> can call maintainer
6156 scripts, must not overwrite or otherwise mangle the user's
6157 configuration without asking, must not ask unnecessary
6158 questions (particularly during upgrades), and otherwise be
6163 The scripts are not required to configure every possible
6164 option for the package, but only those necessary to get
6165 the package running on a given system. Ideally the
6166 sysadmin should not have to do any configuration other
6167 than that done (semi-)automatically by the
6168 <prgn>postinst</prgn> script.
6172 A common practice is to create a script called
6173 <file><var>package</var>-configure</file> and have the
6174 package's <prgn>postinst</prgn> call it if and only if the
6175 configuration file does not already exist. In certain
6176 cases it is useful for there to be an example or template
6177 file which the maintainer scripts use. Such files should
6178 be in <file>/usr/share/<var>package</var></file> or
6179 <file>/usr/lib/<var>package</var></file> (depending on whether
6180 they are architecture-independent or not). There should
6181 be symbolic links to them from
6182 <file>/usr/share/doc/<var>package</var>/examples</file> if
6183 they are examples, and should be perfectly ordinary
6184 <prgn>dpkg</prgn>-handled files (<em>not</em>
6185 configuration files).
6189 These two styles of configuration file handling must
6190 not be mixed, for that way lies madness:
6191 <prgn>dpkg</prgn> will ask about overwriting the file
6192 every time the package is upgraded.
6197 <heading>Sharing configuration files</heading>
6199 Packages which specify the same file as a
6200 <tt>conffile</tt> must be tagged as <em>conflicting</em>
6201 with each other. (This is an instance of the general rule
6202 about not sharing files. Note that neither alternatives
6203 nor diversions are likely to be appropriate in this case;
6204 in particular, <prgn>dpkg</prgn> does not handle diverted
6205 <tt>conffile</tt>s well.)
6209 The maintainer scripts must not alter a <tt>conffile</tt>
6210 of <em>any</em> package, including the one the scripts
6215 If two or more packages use the same configuration file
6216 and it is reasonable for both to be installed at the same
6217 time, one of these packages must be defined as
6218 <em>owner</em> of the configuration file, i.e., it will be
6219 the package which handles that file as a configuration
6220 file. Other packages that use the configuration file must
6221 depend on the owning package if they require the
6222 configuration file to operate. If the other package will
6223 use the configuration file if present, but is capable of
6224 operating without it, no dependency need be declared.</p>
6227 If it is desirable for two or more related packages to
6228 share a configuration file <em>and</em> for all of the
6229 related packages to be able to modify that configuration
6230 file, then the following should be done:
6231 <enumlist compact="compact">
6234 One of the related packages (the "owning" package)
6235 will manage the configuration file with maintainer
6236 scripts as described in the previous section.
6241 The owning package should also provide a program
6242 that the other packages may use to modify the
6248 The related packages must use the provided program
6249 to make any desired modifications to the
6250 configuration file. They should either depend on
6251 the core package to guarantee that the configuration
6252 modifier program is available or accept gracefully
6253 that they cannot modify the configuration file if it
6254 is not. (This is in addition to the fact that the
6255 configuration file may not even be present in the
6263 Sometimes it's appropriate to create a new package which
6264 provides the basic infrastructure for the other packages
6265 and which manages the shared configuration files. (The
6266 <tt>sgml-base</tt> package is a good example.)
6271 <heading>User configuration files ("dotfiles")</heading>
6274 The files in <file>/etc/skel</file> will automatically be
6275 copied into new user accounts by <prgn>adduser</prgn>.
6276 No other program should reference the files in
6277 <file>/etc/skel</file>.
6281 Therefore, if a program needs a dotfile to exist in
6282 advance in <file>$HOME</file> to work sensibly, that dotfile
6283 should be installed in <file>/etc/skel</file> and treated as a
6288 However, programs that require dotfiles in order to
6289 operate sensibly are a bad thing, unless they do create
6290 the dotfiles themselves automatically.
6294 Furthermore, programs should be configured by the Debian
6295 default installation to behave as closely to the upstream
6296 default behaviour as possible.
6300 Therefore, if a program in a Debian package needs to be
6301 configured in some way in order to operate sensibly, that
6302 should be done using a site-wide configuration file placed
6303 in <file>/etc</file>. Only if the program doesn't support a
6304 site-wide default configuration and the package maintainer
6305 doesn't have time to add it may a default per-user file be
6306 placed in <file>/etc/skel</file>.
6310 <file>/etc/skel</file> should be as empty as we can make it.
6311 This is particularly true because there is no easy (or
6312 necessarily desirable) mechanism for ensuring that the
6313 appropriate dotfiles are copied into the accounts of
6314 existing users when a package is installed.
6320 <heading>Log files</heading>
6322 Log files should usually be named
6323 <file>/var/log/<var>package</var>.log</file>. If you have many
6324 log files, or need a separate directory for permission
6325 reasons (<file>/var/log</file> is writable only by
6326 <file>root</file>), you should usually create a directory named
6327 <file>/var/log/<var>package</var></file> and place your log
6332 Log files must be rotated occasionally so that they don't
6333 grow indefinitely; the best way to do this is to drop a log
6334 rotation configuration file into the directory
6335 <file>/etc/logrotate.d</file> and use the facilities provided by
6336 logrotate.<footnote>
6338 The traditional approach to log files has been to set up
6339 <em>ad hoc</em> log rotation schemes using simple shell
6340 scripts and cron. While this approach is highly
6341 customizable, it requires quite a lot of sysadmin work.
6342 Even though the original Debian system helped a little
6343 by automatically installing a system which can be used
6344 as a template, this was deemed not enough.
6348 The use of <prgn>logrotate</prgn>, a program developed
6349 by Red Hat, is better, as it centralizes log management.
6350 It has both a configuration file
6351 (<file>/etc/logrotate.conf</file>) and a directory where
6352 packages can drop their individual log rotation
6353 configurations (<file>/etc/logrotate.d</file>).
6356 Here is a good example for a logrotate config
6357 file (for more information see <manref name="logrotate"
6359 <example compact="compact">
6365 /etc/init.d/foo force-reload
6369 This rotates all files under <file>/var/log/foo</file>, saves 12
6370 compressed generations, and forces the daemon to reload its
6371 configuration information after the log rotation.
6375 Log files should be removed when the package is
6376 purged (but not when it is only removed). This should be
6377 done by the <prgn>postrm</prgn> script when it is called
6378 with the argument <tt>purge</tt> (see <ref
6379 id="removedetails">).
6384 <heading>Permissions and owners</heading>
6387 The rules in this section are guidelines for general use.
6388 If necessary you may deviate from the details below.
6389 However, if you do so you must make sure that what is done
6390 is secure and you should try to be as consistent as possible
6391 with the rest of the system. You should probably also
6392 discuss it on <prgn>debian-devel</prgn> first.
6396 Files should be owned by <tt>root.root</tt>, and made
6397 writable only by the owner and universally readable (and
6398 executable, if appropriate), that is mode 644 or 755.
6402 Directories should be mode 755 or (for group-writability)
6403 mode 2775. The ownership of the directory should be
6404 consistent with its mode: if a directory is mode 2775, it
6405 should be owned by the group that needs write access to
6410 Setuid and setgid executables should be mode 4755 or 2755
6411 respectively, and owned by the appropriate user or group.
6412 They should not be made unreadable (modes like 4711 or
6413 2711 or even 4111); doing so achieves no extra security,
6414 because anyone can find the binary in the freely available
6415 Debian package; it is merely inconvenient. For the same
6416 reason you should not restrict read or execute permissions
6417 on non-set-id executables.
6421 Some setuid programs need to be restricted to particular
6422 sets of users, using file permissions. In this case they
6423 should be owned by the uid to which they are set-id, and by
6424 the group which should be allowed to execute them. They
6425 should have mode 4754; again there is no point in making
6426 them unreadable to those users who must not be allowed to
6431 It is possible to arrange that the system administrator can
6432 reconfigure the package to correspond to their local
6433 security policy by changing the permissions on a binary:
6434 they can do this by using <prgn>dpkg-statoverride</prgn>, as
6435 described below.<footnote>
6437 Ordinary files installed by <prgn>dpkg</prgn> (as
6438 opposed to <tt>conffile</tt>s and other similar objects)
6439 normally have their permissions reset to the distributed
6440 permissions when the package is reinstalled. However,
6441 the use of <prgn>dpkg-statoverride</prgn> overrides this
6442 default behaviour. If you use this method, you should
6443 remember to describe <prgn>dpkg-statoverride</prgn> in
6444 the package documentation; being a relatively new
6445 addition to Debian, it is probably not yet well-known.
6448 Another method you should consider is to create a group for
6449 people allowed to use the program(s) and make any setuid
6450 executables executable only by that group.
6454 If you need to create a new user or group for your package
6455 there are two possibilities. Firstly, you may need to
6456 make some files in the binary package be owned by this
6457 user or group, or you may need to compile the user or
6458 group id (rather than just the name) into the binary
6459 (though this latter should be avoided if possible, as in
6460 this case you need a statically allocated id).</p>
6463 If you need a statically allocated id, you must ask for a
6464 user or group id from the <tt>base-passwd</tt> maintainer,
6465 and must not release the package until you have been
6466 allocated one. Once you have been allocated one you must
6467 either make the package depend on a version of the
6468 <tt>base-passwd</tt> package with the id present in
6469 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
6470 your package to create the user or group itself with the
6471 correct id (using <tt>adduser</tt>) in its
6472 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
6473 the <prgn>postinst</prgn> is to be preferred if it is
6474 possible, otherwise a pre-dependency will be needed on the
6475 <tt>adduser</tt> package.)
6479 On the other hand, the program might be able to determine
6480 the uid or gid from the user or group name at runtime, so
6481 that a dynamically allocated id can be used. In this case
6482 you should choose an appropriate user or group name,
6483 discussing this on <prgn>debian-devel</prgn> and checking
6484 with the <package/base-passwd/ maintainer that it is unique and that
6485 they do not wish you to use a statically allocated id
6486 instead. When this has been checked you must arrange for
6487 your package to create the user or group if necessary using
6488 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
6489 <prgn>postinst</prgn> script (again, the latter is to be
6490 preferred if it is possible).
6494 Note that changing the numeric value of an id associated
6495 with a name is very difficult, and involves searching the
6496 file system for all appropriate files. You need to think
6497 carefully whether a static or dynamic id is required, since
6498 changing your mind later will cause problems.
6501 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
6503 This section is not intended as policy, but as a
6504 description of the use of <prgn>dpkg-statoverride</prgn>.
6508 <prgn>dpkg-statoverride</prgn> is a replacement for the
6509 deprecated <tt>suidmanager</tt> package. Packages which
6510 previously used <tt>suidmanager</tt> should have a
6511 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
6512 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
6513 and <tt>suidunregister</tt> should now be simply removed
6514 from the maintainer scripts.
6518 If a system administrator wishes to have a file (or
6519 directory or other such thing) installed with owner and
6520 permissions different from those in the distributed Debian
6521 package, he can use the <prgn>dpkg-statoverride</prgn>
6522 program to instruct <prgn>dpkg</prgn> to use the different
6523 settings every time the file is installed. Thus the
6524 package maintainer should distribute the files with their
6525 normal permissions, and leave it for the system
6526 administrator to make any desired changes. For example, a
6527 daemon which is normally required to be setuid root, but
6528 in certain situations could be used without being setuid,
6529 should be installed setuid in the <tt>.deb</tt>. Then the
6530 local system administrator can change this if they wish.
6531 If there are two standard ways of doing it, the package
6532 maintainer can use <tt>debconf</tt> to find out the
6533 preference, and call <prgn>dpkg-statoverride</prgn> in the
6534 maintainer script if necessary to accommodate the system
6535 administrator's choice.
6539 Given the above, <prgn>dpkg-statoverride</prgn> is
6540 essentially a tool for system administrators and would not
6541 normally be needed in the maintainer scripts. There is
6542 one type of situation, though, where calls to
6543 <prgn>dpkg-statoverride</prgn> would be needed in the
6544 maintainer scripts, and that involves packages which use
6545 dynamically allocated user or group ids. In such a
6546 situation, something like the following idiom can be very
6547 helpful in the package's <prgn>postinst</prgn>, where
6548 <tt>sysuser</tt> is a dynamically allocated id:
6550 for i in /usr/bin/foo /usr/sbin/bar
6552 if ! dpkg-statoverride --list $i >/dev/null
6554 dpkg-statoverride --update --add sysuser root 4755 $i
6558 The corresponding <tt>dpkg-statoverride --remove</tt>
6559 calls can then be made unconditionally when the package is
6566 <chapt id="customized-programs">
6567 <heading>Customized programs</heading>
6569 <sect id="arch-spec">
6570 <heading>Architecture specification strings</heading>
6573 If a program needs to specify an <em>architecture specification
6574 string</em> in some place, the following format should be
6575 used: <var>arch</var>-<var>os</var><footnote>
6577 The following architectures and operating systems are
6578 currently recognised by <prgn>dpkg-archictecture</prgn>.
6579 The architecture, <tt><var>arch</var></tt>, is one of
6580 the following: <tt>alpha</tt>, <tt>arm</tt>,
6581 <tt>hppa</tt>, <tt>i386</tt>, <tt>ia64</tt>,
6582 <tt>m68k</tt>, <tt>mips</tt>, <tt>mipsel</tt>,
6583 <tt>powerpc</tt>, <tt>s390</tt>, <tt>sh</tt>,
6584 <tt>sheb</tt>, <tt>sparc</tt> and <tt>sparc64</tt>. The
6585 operating system, <tt><var>os</var></tt>, is one of:
6586 <tt>linux</tt>, <tt>gnu</tt>, <tt>freebsd</tt> and
6587 <tt>openbsd</tt>. Use of <tt>gnu</tt> in this string is
6588 reserved for the GNU/Hurd operating system.
6594 Note that we don't want to use
6595 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
6596 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
6597 since this would make our programs incompatible with other
6598 Linux distributions. We also don't use something like
6599 <tt><var>arch</var>-unknown-linux</tt>, since the
6600 <tt>unknown</tt> does not look very good.
6605 <heading>Daemons</heading>
6608 The configuration files <file>/etc/services</file>,
6609 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
6610 by the <prgn>netbase</prgn> package and must not be modified
6615 If a package requires a new entry in one of these files, the
6616 maintainer should get in contact with the
6617 <prgn>netbase</prgn> maintainer, who will add the entries
6618 and release a new version of the <prgn>netbase</prgn>
6623 The configuration file <file>/etc/inetd.conf</file> must not be
6624 modified by the package's scripts except via the
6625 <prgn>update-inetd</prgn> script or the
6626 <file>DebianNet.pm</file> Perl module. See their documentation
6627 for details on how to add entries.
6631 If a package wants to install an example entry into
6632 <file>/etc/inetd.conf</file>, the entry must be preceded with
6633 exactly one hash character (<tt>#</tt>). Such lines are
6634 treated as "commented out by user" by the
6635 <prgn>update-inetd</prgn> script and are not changed or
6636 activated during package updates.
6641 <heading>Using pseudo-ttys and modifying wtmp, utmp and
6645 Some programs need to create pseudo-ttys. This should be done
6646 using Unix98 ptys if the C library supports it. The resulting
6647 program must not be installed setuid root, unless that
6648 is required for other functionality.
6652 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
6653 <file>/var/log/lastlog</file> must be installed writeable by
6654 group <tt>utmp</tt>. Programs which need to modify those
6655 files must be installed setgid <tt>utmp</tt>.
6660 <heading>Editors and pagers</heading>
6663 Some programs have the ability to launch an editor or pager
6664 program to edit or display a text document. Since there are
6665 lots of different editors and pagers available in the Debian
6666 distribution, the system administrator and each user should
6667 have the possibility to choose his/her preferred editor and
6672 In addition, every program should choose a good default
6673 editor/pager if none is selected by the user or system
6678 Thus, every program that launches an editor or pager must
6679 use the EDITOR or PAGER environment variable to determine
6680 the editor or pager the user wishes to use. If these
6681 variables are not set, the programs <file>/usr/bin/editor</file>
6682 and <file>/usr/bin/pager</file> should be used, respectively.
6686 These two files are managed through the <prgn>dpkg</prgn>
6687 "alternatives" mechanism. Thus every package providing an
6688 editor or pager must call the
6689 <prgn>update-alternatives</prgn> script to register these
6694 If it is very hard to adapt a program to make use of the
6695 EDITOR or PAGER variables, that program may be configured to
6696 use <file>/usr/bin/sensible-editor</file> and
6697 <file>/usr/bin/sensible-pager</file> as the editor or pager
6698 program respectively. These are two scripts provided in the
6699 Debian base system that check the EDITOR and PAGER variables
6700 and launch the appropriate program, and fall back to
6701 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
6702 variable is not set.
6706 A program may also use the VISUAL environment variable to
6707 determine the user's choice of editor. If it exists, it
6708 should take precedence over EDITOR. This is in fact what
6709 <file>/usr/bin/sensible-editor</file> does.
6713 It is not required for a package to depend on
6714 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
6715 package to provide such virtual packages.<footnote>
6717 The Debian base system already provides an editor and a
6724 <sect id="web-appl">
6725 <heading>Web servers and applications</heading>
6728 This section describes the locations and URLs that should
6729 be used by all web servers and web applications in the
6737 Cgi-bin executable files are installed in the
6739 <example compact="compact">
6740 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
6742 and should be referred to as
6743 <example compact="compact">
6744 http://localhost/cgi-bin/<var>cgi-bin-name</var>
6749 <item><p>Access to HTML documents</p>
6752 HTML documents for a package are stored in
6753 <file>/usr/share/doc/<var>package</var></file>
6754 and can be referred to as
6755 <example compact="compact">
6756 http://localhost/doc/<var>package</var>/<var>filename</var>
6760 The web server should restrict access to the document
6761 tree so that only clients on the same host can read
6762 the documents. If the web server does not support such
6763 access controls, then it should not provide access at
6764 all, or ask about providing access during installation.
6768 <item><p>Web Document Root</p>
6771 Web Applications should try to avoid storing files in
6772 the Web Document Root. Instead they should use the
6773 /usr/share/doc/<var>package</var> directory for
6774 documents and register the Web Application via the
6775 menu package. If access to the web document root is
6776 unavoidable then use
6777 <example compact="compact">
6780 as the Document Root. This might be just a symbolic
6781 link to the location where the system administrator
6782 has put the real document root.
6786 </enumlist></p></sect>
6789 <sect id="mail-transport-agents">
6790 <heading>Mail transport, delivery and user agents</heading>
6793 Debian packages which process electronic mail, whether mail
6794 user agents (MUAs) or mail transport agents (MTAs), must
6795 ensure that they are compatible with the configuration
6796 decisions below. Failure to do this may result in lost
6797 mail, broken <tt>From:</tt> lines, and other serious brain
6802 The mail spool is <file>/var/mail</file> and the interface to
6803 send a mail message is <file>/usr/sbin/sendmail</file> (as per
6804 the FHS). On older systems, the mail spool may be
6805 physically located in <file>/var/spool/mail</file>, but all
6806 access to the mail spool should be via the
6807 <file>/var/mail</file> symlink. The mail spool is part of the
6808 base system and not part of the MTA package.
6812 All Debian MUAs, MTAs, MDAs and other mailbox accessing
6813 programs (such as IMAP daemons) must lock the mailbox in an
6814 NFS-safe way. This means that <tt>fcntl()</tt> locking must
6815 be combined with dot locking. To avoid deadlocks, a program
6816 should use <tt>fcntl()</tt> first and dot locking after
6817 this, or alternatively implement the two locking methods in
6818 a non blocking way<footnote>
6820 If it is not possible to establish both locks, the
6821 system shouldn't wait for the second lock to be
6822 established, but remove the first lock, wait a (random)
6823 time, and start over locking again.
6825 </footnote>. Using the functions <tt>maillock</tt> and
6826 <tt>mailunlock</tt> provided by the
6827 <tt>liblockfile*</tt><footnote>
6829 You will need to depend on <tt>liblockfile1
6830 (>>1.01)</tt> to use these functions.
6832 </footnote> packages is the recommended way to realize this.
6836 Mailboxes are generally mode 660
6837 <tt><var>user</var>.mail</tt> unless the system
6838 administrator has chosen otherwise. A MUA may remove a
6839 mailbox (unless it has nonstandard permissions) in which
6840 case the MTA or another MUA must recreate it if needed.
6841 Mailboxes must be writable by group mail.
6845 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
6846 be setgid mail to do the locking mentioned above (and
6847 must obviously avoid accessing other users' mailboxes
6848 using this privilege).</p>
6851 <file>/etc/aliases</file> is the source file for the system mail
6852 aliases (e.g., postmaster, usenet, etc.), it is the one
6853 which the sysadmin and <prgn>postinst</prgn> scripts may
6854 edit. After <file>/etc/aliases</file> is edited the program or
6855 human editing it must call <prgn>newaliases</prgn>. All MTA
6856 packages must come with a <prgn>newaliases</prgn> program,
6857 even if it does nothing, but older MTA packages did not do
6858 this so programs should not fail if <prgn>newaliases</prgn>
6859 cannot be found. Note that because of this, all MTA
6860 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
6861 <tt>Replaces: mail-transport-agent</tt> control file
6866 The convention of writing <tt>forward to
6867 <var>address</var></tt> in the mailbox itself is not
6868 supported. Use a <tt>.forward</tt> file instead.</p>
6871 The <prgn>rmail</prgn> program used by UUCP
6872 for incoming mail should be <file>/usr/sbin/rmail</file>.
6873 Likewise, <prgn>rsmtp</prgn>, for receiving
6874 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
6878 If your package needs to know what hostname to use on (for
6879 example) outgoing news and mail messages which are generated
6880 locally, you should use the file <file>/etc/mailname</file>. It
6881 will contain the portion after the username and <tt>@</tt>
6882 (at) sign for email addresses of users on the machine
6883 (followed by a newline).
6887 Such package should check for the existence of this file
6888 when it is being configured. If it exists, it should be
6889 used without comment, although an MTA's configuration script
6890 may wish to prompt the user even if it finds that this file
6891 exists. If the file does not exist, the package should
6892 prompt the user for the value (preferably using
6893 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
6894 as well as using it in the package's configuration. The
6895 prompt should make it clear that the name will not just be
6896 used by that package. For example, in this situation the
6897 <tt>inn</tt> package could say something like:
6898 <example compact="compact">
6899 Please enter the "mail name" of your system. This is the
6900 hostname portion of the address to be shown on outgoing
6901 news and mail messages. The default is
6902 <var>syshostname</var>, your system's host name. Mail
6903 name ["<var>syshostname</var>"]:
6905 where <var>syshostname</var> is the output of <tt>hostname
6911 <heading>News system configuration</heading>
6914 All the configuration files related to the NNTP (news)
6915 servers and clients should be located under
6916 <file>/etc/news</file>.</p>
6919 There are some configuration issues that apply to a number
6920 of news clients and server packages on the machine. These
6924 <tag><file>/etc/news/organization</file></tag>
6925 <item><p>A string which should appear as the
6926 organization header for all messages posted
6927 by NNTP clients on the machine</p></item>
6929 <tag><file>/etc/news/server</file></tag>
6930 <item><p>Contains the FQDN of the upstream NNTP
6931 server, or localhost if the local machine is
6932 an NNTP server.</p></item>
6935 Other global files may be added as required for cross-package news
6936 configuration.</p></sect>
6940 <heading>Programs for the X Window System</heading>
6943 <heading>Providing X support and package priorities</heading>
6946 Programs that can be configured with support for the X
6947 Window System must be configured to do so and must declare
6948 any package dependencies necessary to satisfy their
6949 runtime requirements when using the X Window System. If
6950 such a package is of higher priority than the X packages
6951 on which it depends, it is required that either the
6952 X-specific components be split into a separate package, or
6953 that an alternative version of the package, which includes
6954 X support, be provided, or that the package's priority be
6960 <heading>Packages providing an X server</heading>
6963 Packages that provide an X server that, directly or
6964 indirectly, communicates with real input and display
6965 hardware should declare in their control data that they
6966 provide the virtual package <tt>xserver</tt>.<footnote>
6968 This implements current practice, and provides an
6969 actual policy for usage of the <tt>xserver</tt>
6970 virtual package which appears in the virtual packages
6971 list. In a nutshell, X servers that interface
6972 directly with the display and input hardware or via
6973 another subsystem (e.g., GGI) should provide
6974 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
6975 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
6982 <heading>Packages providing a terminal emulator</heading>
6985 Packages that provide a terminal emulator for the X Window
6986 System which meet the criteria listed below should declare
6987 in their control data that they provide the virtual
6988 package <tt>x-terminal-emulator</tt>. They should also
6989 register themselves as an alternative for
6990 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
6995 To be an <tt>x-terminal-emulator</tt>, a program must:
6996 <list compact="compact">
6998 Be able to emulate a DEC VT100 terminal, or a
6999 compatible terminal.
7003 Support the command-line option <tt>-e
7004 <var>command</var></tt>, which creates a new
7005 terminal window<footnote>
7007 "New terminal window" does not necessarily mean
7008 a new top-level X window directly parented by
7009 the window manager; it could, if the terminal
7010 emulator application were so coded, be a new
7011 "view" in a multiple-document interface (MDI).
7014 and runs the specified <var>command</var>.
7018 Support the command-line option <tt>-T
7019 <var>title</var></tt>, which creates a new terminal
7020 window with the window title <var>title</var>.
7027 <heading>Packages providing a window manager</heading>
7030 Packages that provide a window manager should declare in
7031 their control data that they provide the virtual package
7032 <tt>x-window-manager</tt>. They should also register
7033 themselves as an alternative for
7034 <file>/usr/bin/x-window-manager</file>, with a priority
7035 calculated as follows:
7036 <list compact="compact">
7037 <item><p>Start with a priority of 20.</p></item>
7041 If the window manager supports the Debian menu
7042 system, add 20 points if this support is available
7043 in the package's default configuration (i.e., no
7044 configuration files belonging to the system or user
7045 have to be edited to activate the feature); if
7046 configuration files must be modified, add only 10
7052 If the window manager complies with <url
7053 id="http://www.freedesktop.org/standards/wm-spec.html"
7054 name="The Window Manager Specification Project">,
7055 written by the <url id="http://www.freedesktop.org"
7056 name="Free Desktop Group">, add 20 points.
7062 If the window manager permits the X session to be
7063 restarted using a <em>different</em> window manager
7064 (without killing the X server) in its default
7065 configuration, add 10 points; otherwise add none.
7073 <heading>Packages providing fonts</heading>
7076 Packages that provide fonts for the X Window
7079 For the purposes of Debian Policy, a "font for the X
7080 Window System" is one which is accessed via X protocol
7081 requests. Fonts for the Linux console, for PostScript
7082 renderers, or any other purpose, do not fit this
7083 definition. Any tool which makes such fonts available
7084 to the X Window System, however, must abide by this
7088 must do a number of things to ensure that they are both
7089 available without modification of the X or font server
7090 configuration, and that they do not corrupt files used by
7091 other font packages to register information about
7096 Fonts of any type supported by the X Window System
7097 must be in a separate binary package from any
7098 executables, libraries, or documentation (except
7099 that specific to the fonts shipped, such as their
7100 license information). If one or more of the fonts
7101 so packaged are necessary for proper operation of
7102 the package with which they are associated the font
7103 package may be Recommended; if the fonts merely
7104 provide an enhancement, a Suggests relationship may
7105 be used. Packages must not Depend on font
7108 This is because the X server may retrieve fonts
7109 from the local filesystem or over the network
7110 from an X font server; the Debian package system
7111 is empowered to deal only with the local
7120 BDF fonts must be converted to PCF fonts with the
7121 <prgn>bdftopcf</prgn> utility (available in the
7122 <tt>xutils</tt> package, <prgn>gzip</prgn>ped, and
7123 placed in a directory that corresponds to their
7125 <list compact="compact">
7127 100 dpi fonts must be placed in
7128 <file>/usr/X11R6/lib/X11/fonts/100dpi/</file>.
7132 75 dpi fonts must be placed in
7133 <file>/usr/X11R6/lib/X11/fonts/75dpi/</file>.
7137 Character-cell fonts, cursor fonts, and other
7138 low-resolution fonts must be placed in
7139 <file>/usr/X11R6/lib/X11/fonts/misc/</file>.
7146 Speedo fonts must be placed in
7147 <file>/usr/X11R6/lib/X11/fonts/Speedo/</file>.
7151 Type 1 fonts must be placed in
7152 <file>/usr/X11R6/lib/X11/fonts/Type1/</file>. If font
7153 metric files are available, they must be placed here
7159 Subdirectories of <file>/usr/X11R6/lib/X11/fonts/</file>
7160 other than those listed above must be neither
7161 created nor used. (The <file>PEX</file>, <file>CID</file>,
7162 and <file>cyrillic</file> directories are excepted for
7163 historical reasons, but installation of files into
7164 these directories remains discouraged.)
7170 Font packages may, instead of placing files directly
7171 in the X font directories listed above, provide
7172 symbolic links in that font directory pointing to
7173 the files' actual location in the filesystem. Such
7174 a location must comply with the FHS.
7180 Font packages should not contain both 75dpi and
7181 100dpi versions of a font. If both are available,
7182 they should be provided in separate binary packages
7183 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
7184 the names of the packages containing the
7185 corresponding fonts.
7191 Fonts destined for the <file>misc</file> subdirectory
7192 should not be included in the same package as 75dpi
7193 or 100dpi fonts; instead, they should be provided in
7194 a separate package with <tt>-misc</tt> appended to
7201 Font packages must not provide the files
7202 <file>fonts.dir</file>, <file>fonts.alias</file>, or
7203 <file>fonts.scale</file> in a font directory:
7206 <file>fonts.dir</file> files must not be provided at all.
7211 <file>fonts.alias</file> and <file>fonts.scale</file>
7212 files, if needed, should be provided in the
7214 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
7215 where <var>fontdir</var> is the name of the
7217 <file>/usr/X11R6/lib/X11/fonts/</file> where the
7218 package's corresponding fonts are stored
7219 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
7220 <var>package</var> is the name of the package
7221 that provides these fonts, and
7222 <var>extension</var> is either <tt>scale</tt>
7223 or <tt>alias</tt>, whichever corresponds to
7233 Font packages must declare a dependency on
7234 <tt>xutils (>> 4.0.3)</tt> in their control
7241 Font packages that provide one or more
7242 <file>fonts.scale</file> files as described above must
7243 invoke <prgn>update-fonts-scale</prgn> on each
7244 directory into which they installed fonts
7245 <em>before</em> invoking
7246 <prgn>update-fonts-dir</prgn> on that directory.
7247 This invocation must occur in both the
7248 <prgn>postinst</prgn> (for all arguments) and
7249 <prgn>postrm</prgn> (for all arguments except
7250 <tt>upgrade</tt>) scripts.
7256 Font packages that provide one or more
7257 <file>fonts.alias</file> files as described above must
7258 invoke <prgn>update-fonts-alias</prgn> on each
7259 directory into which they installed fonts. This
7260 invocation must occur in both the
7261 <prgn>postinst</prgn> (for all arguments) and
7262 <prgn>postrm</prgn> (for all arguments except
7263 <tt>upgrade</tt>) scripts.
7269 Font packages must invoke
7270 <prgn>update-fonts-dir</prgn> on each directory into
7271 which they installed fonts. This invocation must
7272 occur in both the <prgn>postinst</prgn> (for all
7273 arguments) and <prgn>postrm</prgn> (for all
7274 arguments except <tt>upgrade</tt>) scripts.
7280 Font packages must not provide alias names for the
7281 fonts they include which collide with alias names
7282 already in use by fonts already packaged.
7288 Font packages must not provide fonts with the same
7289 XLFD registry name as another font already packaged.
7297 <heading>Application defaults files</heading>
7300 Application defaults files must be installed in the
7301 directory <file>/etc/X11/app-defaults/</file> (use of a
7302 localized subdirectory of <file>/etc/X11/</file> as described
7303 in the <em>X Toolkit Intrinsics - C Language
7304 Interface</em> manual is also permitted). They must be
7305 registered as <tt>conffile</tt>s or handled as
7306 configuration files. Packages must not provide the
7307 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
7311 Customization of programs' X resources may also be
7312 supported with the provision of a file with the same name
7313 as that of the package placed in the
7314 <file>/etc/X11/Xresources/</file> directory, which must
7315 registered as a <tt>conffile</tt> or handled as a
7316 configuration file.<footnote>
7318 Note that this mechanism is not the same as using
7319 app-defaults; app-defaults are tied to the client
7320 binary on the local filesystem, whereas X resources
7321 are stored in the X server and affect all connecting
7325 <em>Important:</em> packages that install files into the
7326 <file>/etc/X11/Xresources/</file> directory must conflict with
7327 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
7328 it is possible for the installing package to destroy a
7329 previously-existing <file>/etc/X11/Xresources</file> file
7330 which had been customized by the system administrator.
7335 <heading>Installation directory issues</heading>
7338 Packages using the X Window System should not be
7339 configured to install files under the <file>/usr/X11R6/</file>
7340 directory unless they use <prgn>imake</prgn>. The
7341 <file>/usr/X11R6/</file> directory hierarchy should be
7342 regarded as deprecated for all packages except the X
7343 Window System itself, and those which use the
7344 <prgn>imake</prgn> program it provides, in which case the
7345 packages may transition out of the <file>/usr/X11R6/</file>
7346 directory at the maintainer's discretion.<footnote>
7348 <prgn>Imake</prgn>-using programs are exempt because,
7349 as long as they are written correctly, the pathnames
7350 they use to locate resources and install themselves
7351 are derived wholly from the X Window System
7352 configuration. Thus, in the event that the X Window
7353 System moves to <file>/usr/X11R7/</file>,
7354 <file>/usr/X12/</file>, or just plain <file>/usr/</file>, all
7355 that is required for these programs is a recompile
7356 against the corresponding X Window System library
7357 development packages.
7360 Programs that use GNU <prgn>autoconf</prgn> and
7361 <prgn>automake</prgn> are usually easily configured at
7362 compile time to use <file>/usr/</file> instead of
7363 <file>/usr/X11R6/</file>, and this should be done whenever
7364 possible. Configuration files for window managers and
7365 display managers should be placed in a subdirectory of
7366 <file>/etc/X11/</file> corresponding to the package name due
7367 to these programs' tight integration with the mechanisms
7368 of the X Window System. Application-level programs should
7369 use the <file>/etc/</file> directory unless otherwise mandated
7370 by policy. The installation of files into subdirectories
7371 of <file>/usr/X11R6/include/X11/</file> and
7372 <file>/usr/X11R6/lib/X11/</file> is permitted but discouraged;
7373 package maintainers should determine if subdirectories of
7374 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
7375 instead. (The use of symbolic links from the
7376 <file>X11R6</file> directories to other FHS-compliant
7377 locations is encouraged if the program is not easily
7378 configured to look elsewhere for its files.) Packages
7379 must not provide or install files into the directories
7380 <file>/usr/bin/X11/</file>, <file>/usr/include/X11/</file> or
7381 <file>/usr/lib/X11/</file>. Files within a package should,
7382 however, make reference to these directories, rather than
7383 their <tt>X11R6</tt>-named counterparts
7384 <file>/usr/X11R6/bin/</file>, <file>/usr/X11R6/include/X11/</file>
7385 and <file>/usr/X11R6/lib/X11/</file>, if the resources being
7386 referred to have not been moved to other FHS-compliant
7392 <heading>The OSF/Motif and OpenMotif libraries</heading>
7395 <em>Programs that require the non-DFSG-compliant OSF/Motif or
7396 OpenMotif libraries</em><footnote>
7398 OSF/Motif and OpenMotif are collectively referred to as
7399 "Motif" in this policy document.
7402 should be compiled against and tested with LessTif (a free
7403 re-implementation of Motif) instead. If the maintainer
7404 judges that the program or programs do not work
7405 sufficiently well with LessTif to be distributed and
7406 supported, but do so when compiled against Motif, then two
7407 versions of the package should be created; one linked
7408 statically against Motif and with <tt>-smotif</tt>
7409 appended to the package name, and one linked dynamically
7410 against Motif and with <tt>-dmotif</tt> appended to the
7411 package name. Both Motif-linked versions are dependent
7412 upon non-DFSG-compliant software and thus cannot be
7413 uploaded to the <em>main</em> distribution; if the
7414 software is itself DFSG-compliant it may be uploaded to
7415 the <em>contrib</em> distribution. While known existing
7416 versions of Motif permit unlimited redistribution of
7417 binaries linked against the library (whether statically or
7418 dynamically), it is the package maintainer's
7419 responsibility to determine whether this is permitted by
7420 the license of the copy of Motif in his or her possession.
7426 <heading>Perl programs and modules</heading>
7428 Perl programs and modules should follow the current Perl
7429 policy as defined in the file found on
7430 <ftpsite>ftp.debian.org</ftpsite> in
7431 <ftppath>/debian/doc/package-developer/perl-policy.txt.gz</ftppath>
7432 or your local mirror. In addition, it is included in the
7433 <tt>debian-policy</tt> package.
7438 <heading>Emacs lisp programs</heading>
7441 Please refer to the "Debian Emacs Policy" (documented in
7442 <file>debian-emacs-policy.gz</file> of the
7443 <prgn>emacsen-common</prgn> package) for details of how to
7444 package emacs lisp programs.
7449 <heading>Games</heading>
7452 The permissions on <file>/var/games</file> are mode 755, owner
7453 <tt>root</tt> and group <tt>root</tt>.
7457 Each game decides on its own security policy.</p>
7460 Games which require protected, privileged access to
7461 high-score files, savegames, etc., may be made
7462 set-<em>group</em>-id (mode 2755) and owned by
7463 <tt>root.games</tt>, and use files and directories with
7464 appropriate permissions (770 <tt>root.games</tt>, for
7465 example). They must not be made
7466 set-<em>user</em>-id, as this causes security problems. (If
7467 an attacker can subvert any set-user-id game they can
7468 overwrite the executable of any other, causing other players
7469 of these games to run a Trojan horse program. With a
7470 set-group-id game the attacker only gets access to less
7471 important game data, and if they can get at the other
7472 players' accounts at all it will take considerably more
7476 Some packages, for example some fortune cookie programs, are
7477 configured by the upstream authors to install with their
7478 data files or other static information made unreadable so
7479 that they can only be accessed through set-id programs
7480 provided. You should not do this in a Debian package: anyone can
7481 download the <file>.deb</file> file and read the data from it,
7482 so there is no point making the files unreadable. Not
7483 making the files unreadable also means that you don't have
7484 to make so many programs set-id, which reduces the risk of a
7488 As described in the FHS, binaries of games should be
7489 installed in the directory <file>/usr/games</file>. This also
7490 applies to games that use the X Window System. Manual pages
7491 for games (X and non-X games) should be installed in
7492 <file>/usr/share/man/man6</file>.</p>
7496 <chapt id="docs"><heading>Documentation</heading>
7500 <heading>Manual pages</heading>
7503 You should install manual pages in <prgn>nroff</prgn> source
7504 form, in appropriate places under <file>/usr/share/man</file>.
7505 You should only use sections 1 to 9 (see the FHS for more
7506 details). You must not install a preformatted "cat page".
7510 Each program, utility, and function should have an
7511 associated manual page included in the same package. It is
7512 suggested that all configuration files also have a manual
7513 page included as well. Manual pages for protocols and other
7514 auxiliary things are optional.
7518 If no manual page is available, this is considered as a bug
7519 and should be reported to the Debian Bug Tracking System (the
7520 maintainer of the package is allowed to write this bug report
7521 themselves, if they so desire). Do not close the bug report
7522 until a proper manpage is available.<footnote>
7524 It is not very hard to write a man page. See the
7525 <url id="http://www.schweikhardt.net/man_page_howto.html"
7526 name="Man-Page-HOWTO">,
7527 <manref name="man" section="7">, the examples
7528 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
7529 the helper programs <prgn>help2man</prgn>, or the
7530 directory <file>/usr/share/doc/man-db/examples</file>.
7536 You may forward a complaint about a missing manpage to the
7537 upstream authors, and mark the bug as forwarded in the
7538 Debian bug tracking system. Even though the GNU Project do
7539 not in general consider the lack of a manpage to be a bug,
7540 we do; if they tell you that they don't consider it a bug
7541 you should leave the bug in our bug tracking system open
7546 Manual pages should be installed compressed using <tt>gzip -9</tt>.
7550 If one manpage needs to be accessible via several names it
7551 is better to use a symbolic link than the <file>.so</file>
7552 feature, but there is no need to fiddle with the relevant
7553 parts of the upstream source to change from <file>.so</file> to
7554 symlinks: don't do it unless it's easy. You should not
7555 create hard links in the manual page directories, nor put
7556 absolute filenames in <file>.so</file> directives. The filename
7557 in a <file>.so</file> in a manpage should be relative to the
7558 base of the manpage tree (usually
7559 <file>/usr/share/man</file>). If you do not create any links
7560 (whether symlinks, hard links, or <tt>.so</tt> directives)
7561 in the filesystem to the alternate names of the manpage,
7562 then you should not rely on <prgn>man</prgn> finding your
7563 manpage under those names based solely on the information in
7564 the manpage's header.<footnote>
7566 Supporting this in <prgn>man</prgn> often requires
7567 unreasonable processing time to find a manual page or to
7568 report that none exists, and moves knowledge into man's
7569 database that would be better left in the filesystem.
7570 This support is therefore deprecated and will cease to
7571 be present in the future.
7578 <heading>Info documents</heading>
7581 Info documents should be installed in <file>/usr/share/info</file>.
7582 They should be compressed with <tt>gzip -9</tt>.
7586 Your package should call <prgn>install-info</prgn> to update
7587 the Info <file>dir</file> file in its <prgn>postinst</prgn>
7588 script when called with a <tt>configure</tt> argument, for
7590 <example compact="compact">
7591 install-info --quiet --section Development Development \
7592 /usr/share/info/foobar.info
7596 It is a good idea to specify a section for the location of
7597 your program; this is done with the <tt>--section</tt>
7598 switch. To determine which section to use, you should look
7599 at <file>/usr/share/info/dir</file> on your system and choose the most
7600 relevant (or create a new section if none of the current
7601 sections are relevant). Note that the <tt>--section</tt>
7602 flag takes two arguments; the first is a regular expression
7603 to match (case-insensitively) against an existing section,
7604 the second is used when creating a new one.</p>
7607 You should remove the entries in the <prgn>prerm</prgn>
7608 script when called with a <tt>remove</tt> argument:
7609 <example compact="compact">
7610 install-info --quiet --remove /usr/share/info/foobar.info
7614 If <prgn>install-info</prgn> cannot find a description entry
7615 in the Info file you must supply one. See <manref
7616 name="install-info" section="8"> for details.</p>
7620 <heading>Additional documentation</heading>
7623 Any additional documentation that comes with the package may
7624 be installed at the discretion of the package maintainer.
7625 Text documentation should be installed in the directory
7626 <file>/usr/share/doc/<var>package</var></file>, where
7627 <var>package</var> is the name of the package, and
7628 compressed with <tt>gzip -9</tt> unless it is small.
7632 If a package comes with large amounts of documentation which
7633 many users of the package will not require you should create
7634 a separate binary package to contain it, so that it does not
7635 take up disk space on the machines of users who do not need
7636 or want it installed.</p>
7639 It is often a good idea to put text information files
7640 (<file>README</file>s, changelogs, and so forth) that come with
7641 the source package in <file>/usr/share/doc/<var>package</var></file>
7642 in the binary package. However, you don't need to install
7643 the instructions for building and installing the package, of
7647 Packages must not require the existance of any files in
7648 <file>/usr/share/doc/</file> in order to function
7651 The system administrator should be able to
7652 delete files in <file>/usr/share/doc/</file> without causing
7653 any programs to break.
7656 Any files that are referenced by programs but are also
7657 useful as standalone documentation should be installed under
7658 <file>/usr/share/<var>package</var>/</file> with symbolic links from
7659 <file>/usr/share/doc/<var>package</var></file>.
7663 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7664 link to another directory in <file>/usr/share/doc</file> only if
7665 the two packages both come from the same source and the
7666 first package Depends on the second.
7670 Former Debian releases placed all additional documentation
7671 in <file>/usr/doc/<var>package</var></file>. This has been
7672 changed to <file>/usr/share/doc/<var>package</var></file>,
7673 and packages must not put documentation in the directory
7674 <file>/usr/doc/<var>package</var></file>. <footnote>
7675 <p>At this phase of the transition, we no longer require a
7676 symbolic link in <file>/usr/doc/</file>. At a later point,
7677 policy shall change to make the symbolic links a bug.</p>
7683 <heading>Preferred documentation formats</heading>
7686 The unification of Debian documentation is being carried out
7690 If your package comes with extensive documentation in a
7691 markup format that can be converted to various other formats
7692 you should if possible ship HTML versions in a binary
7693 package, in the directory
7694 <file>/usr/share/doc/<var>appropriate-package</var></file> or
7695 its subdirectories.<footnote>
7697 The rationale: The important thing here is that HTML
7698 docs should be available in <em>some</em> package, not
7699 necessarily in the main binary package.
7705 Other formats such as PostScript may be provided at the
7706 package maintainer's discretion.
7710 <sect id="copyrightfile">
7711 <heading>Copyright information</heading>
7714 Every package must be accompanied by a verbatim copy of its
7715 copyright and distribution license in the file
7716 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
7717 file must neither be compressed nor be a symbolic link.
7721 In addition, the copyright file must say where the upstream
7722 sources (if any) were obtained. It should name the original
7723 authors of the package and the Debian maintainer(s) who were
7724 involved with its creation.</p>
7727 A copy of the file which will be installed in
7728 <file>/usr/share/doc/<var>package</var>/copyright</file> should
7729 be in <file>debian/copyright</file> in the source package.
7733 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7734 link to another directory in <file>/usr/share/doc</file> only if
7735 the two packages both come from the same source and the
7736 first package Depends on the second. These rules are
7737 important because copyrights must be extractable by
7742 Packages distributed under the UCB BSD license, the Artistic
7743 license, the GNU GPL, and the GNU LGPL should refer to the
7744 files <file>/usr/share/common-licenses/BSD</file>,
7745 <file>/usr/share/common-licenses/Artistic</file>,
7746 <file>/usr/share/common-licenses/GPL</file>, and
7747 <file>/usr/share/common-licenses/LGPL</file> respectively,
7748 rather than quoting them in the copyright file.
7752 You should not use the copyright file as a general <file>README</file>
7753 file. If your package has such a file it should be
7754 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
7755 <file>README.Debian</file> or some other appropriate place.</p>
7759 <heading>Examples</heading>
7762 Any examples (configurations, source files, whatever),
7763 should be installed in a directory
7764 <file>/usr/share/doc/<var>package</var>/examples</file>. These
7765 files should not be referenced by any program: they're there
7766 for the benefit of the system administrator and users as
7767 documentation only. Architecture-specific example files
7768 should be installed in a directory
7769 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
7771 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
7772 latter directory itself may be a symbolic link to the
7777 <sect id="changelogs">
7778 <heading>Changelog files</heading>
7781 The Debian changelog file (<file>debian/changelog</file>) should
7782 explain briefly what modifications were made in the Debian version
7783 of the package compared to the upstream one. Other changes and
7784 updates to the package should also be documented in this file.
7788 Mistakes in changelogs are usually best rectified by
7789 making a new changelog entry rather than "rewriting history"
7790 by editing old changelog entries.
7794 The format of the <file>debian/changelog</file> file is described
7795 in <ref id="dpkgchangelog">. In non-experimental packages you must
7796 use a format for <file>debian/changelog</file> which is supported
7797 by the most recent released version of <prgn>dpkg</prgn>.<footnote>
7799 If you wish to use an alternative format, you may do so as
7800 long as you include a parser for it in your source package.
7801 The parser must have an API compatible with that expected by
7802 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-gencontrol</prgn>.
7803 If there is general interest in the new format, you should
7804 contact the <package>dpkg</package> maintainer to have the
7805 parser script for it included in the <prgn>dpkg</prgn>
7806 package. (You will need to agree that the parser and its
7807 manpage may be distributed under the GNU GPL, just as the rest
7808 of <prgn>dpkg</prgn> is.)
7814 Packages that are not Debian-native must contain a
7815 compressed copy of the <file>debian/changelog</file> file from
7816 the Debian source tree in
7817 <file>/usr/share/doc/<var>package</var></file> with the name
7818 <file>changelog.Debian.gz</file>.
7822 If an upstream changelog is available, it should be accessible as
7823 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
7824 plain text. If the upstream changelog is distributed in
7825 HTML, it should be made available in that form as
7826 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
7827 and a plain text <file>changelog.gz</file> should be generated
7828 from it using, for example, <tt>lynx -dump -nolist</tt>. If
7829 the upstream changelog files do not already conform to this
7830 naming convention, then this may be achieved either by
7831 renaming the files, or by adding a symbolic link, at the
7832 maintainer's discretion.<footnote>
7834 Rationale: People should not have to look in places for
7835 upstream changelogs merely because they are given
7836 different names or are distributed in HTML format.
7842 All of these files should be installed compressed using
7843 <tt>gzip -9</tt>, as they will become large with time even
7844 if they start out small.
7848 If the package has only one changelog which is used both as
7849 the Debian changelog and the upstream one because there is
7850 no separate upstream maintainer then that changelog should
7851 usually be installed as
7852 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
7853 there is a separate upstream maintainer, but no upstream
7854 changelog, then the Debian changelog should still be called
7855 <file>changelog.Debian.gz</file>.</p>
7860 <appendix id="pkg-scope">
7861 <heading>Introduction and scope of these appendices</heading>
7864 These appendices are taken essentially verbatim from the
7865 now-deprecated Packaging Manual, version 3.2.1.0. They are
7866 the chapters which are likely to be of use to package
7867 maintainers and which have not already been included in the
7868 policy document itself. Most of these sections are very likely
7869 not relevant to policy; they should be treated as
7870 documentation for the packaging system. Please note that these
7871 appendices are included for convenience, and for historical
7872 reasons: they used to be part of policy package, and they have
7873 not yet been incorporated into dpkg documentation. However,
7874 they still have value, and hence they are presented here.
7877 They have not yet been checked to ensure that they are
7878 compatible with the contents of policy, and if there are any
7879 contradictions, the version in the main policy document takes
7880 precedence. The remaining chapters of the old Packaging
7881 Manual have also not been read in detail to ensure that there
7882 are not parts which have been left out. Both of these will be
7887 <prgn>dpkg</prgn> is a suite of programs for creating binary
7888 package files and installing and removing them on Unix
7891 <prgn>dpkg</prgn> is targetted primarily at Debian
7892 GNU/Linux, but may work on or be ported to other
7899 The binary packages are designed for the management of
7900 installed executable programs (usually compiled binaries) and
7901 their associated data, though source code examples and
7902 documentation are provided as part of some packages.</p>
7905 This manual describes the technical aspects of creating Debian
7906 binary packages (<file>.deb</file> files). It documents the
7907 behaviour of the package management programs
7908 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
7909 they interact with packages.</p>
7912 It also documents the interaction between
7913 <prgn>dselect</prgn>'s core and the access method scripts it
7914 uses to actually install the selected packages, and describes
7915 how to create a new access method.</p>
7918 This manual does not go into detail about the options and
7919 usage of the package building and installation tools. It
7920 should therefore be read in conjuction with those programs'
7925 The utility programs which are provided with <prgn>dpkg</prgn>
7926 for managing various system configuration and similar issues,
7927 such as <prgn>update-rc.d</prgn> and
7928 <prgn>install-info</prgn>, are not described in detail here -
7929 please see their manpages.
7933 It does <em>not</em> describe the policy requirements imposed
7934 on Debian packages, such as the permissions on files and
7935 directories, documentation requirements, upload procedure, and
7936 so on. You should see the Debian packaging policy manual for
7937 these details. (Many of them will probably turn out to be
7938 helpful even if you don't plan to upload your package and make
7939 it available as part of the distribution.)
7943 It is assumed that the reader is reasonably familiar with the
7944 <prgn>dpkg</prgn> System Administrators' manual.
7945 Unfortunately this manual does not yet exist.
7949 The Debian version of the FSF's GNU hello program is provided
7950 as an example for people wishing to create Debian
7951 packages. The Debian <prgn>debmake</prgn> package is
7952 recommended as a very helpful tool in creating and maintaining
7953 Debian packages. However, while the tools and examples are
7954 helpful, they do not replace the need to read and follow the
7955 Policy and Programmer's Manual.</p>
7958 <appendix id="pkg-binarypkg"><heading>Binary packages (from old
7963 The binary package has two main sections. The first part
7964 consists of various control information files and scripts used
7965 by <prgn>dpkg</prgn> when installing and removing. See <ref
7966 id="pkg-controlarea">.
7970 The second part is an archive containing the files and
7971 directories to be installed.
7975 In the future binary packages may also contain other
7976 components, such as checksums and digital signatures. The
7977 format for the archive is described in full in the
7978 <file>deb(5)</file> manpage.
7982 <sect id="pkg-bincreating"><heading>Creating package files -
7983 <prgn>dpkg-deb</prgn>
7987 All manipulation of binary package files is done by
7988 <prgn>dpkg-deb</prgn>; it's the only program that has
7989 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
7990 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
7991 will spot that the options requested are appropriate to
7992 <prgn>dpkg-deb</prgn> and invoke that instead with the same
7997 In order to create a binary package you must make a
7998 directory tree which contains all the files and directories
7999 you want to have in the filesystem data part of the package.
8000 In Debian-format source packages this directory is usually
8001 <file>debian/tmp</file>, relative to the top of the package's
8006 They should have the locations (relative to the root of the
8007 directory tree you're constructing) ownerships and
8008 permissions which you want them to have on the system when
8013 With current versions of <prgn>dpkg</prgn> the uid/username
8014 and gid/groupname mappings for the users and groups being
8015 used should be the same on the system where the package is
8016 built and the one where it is installed.
8020 You need to add one special directory to the root of the
8021 miniature filesystem tree you're creating:
8022 <prgn>DEBIAN</prgn>. It should contain the control
8023 information files, notably the binary package control file
8024 (see <ref id="pkg-controlfile">).
8028 The <prgn>DEBIAN</prgn> directory will not appear in the
8029 filesystem archive of the package, and so won't be installed
8030 by <prgn>dpkg</prgn> when the package is installed.
8034 When you've prepared the package, you should invoke:
8036 dpkg --build <var>directory</var>
8041 This will build the package in
8042 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8043 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8044 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8049 See the manpage <manref name="dpkg-deb" section="8"> for details of how
8050 to examine the contents of this newly-created file. You may find the
8051 output of following commands enlightening:
8053 dpkg-deb --info <var>filename</var>.deb
8054 dpkg-deb --contents <var>filename</var>.deb
8055 dpkg --contents <var>filename</var>.deb
8057 To view the copyright file for a package you could use this command:
8059 dpkg --fsys-tarfile <var>filename</var>.deb | tar xof usr/share/doc/<var>\*</var>copyright | less
8064 <sect id="pkg-controlarea">
8066 Package control information files
8070 The control information portion of a binary package is a
8071 collection of files with names known to <prgn>dpkg</prgn>.
8072 It will treat the contents of these files specially - some
8073 of them contain information used by <prgn>dpkg</prgn> when
8074 installing or removing the package; others are scripts which
8075 the package maintainer wants <prgn>dpkg</prgn> to run.
8079 It is possible to put other files in the package control
8080 area, but this is not generally a good idea (though they
8081 will largely be ignored).
8085 Here is a brief list of the control info files supported by
8086 <prgn>dpkg</prgn> and a summary of what they're used for.
8091 <tag><tt>control</tt>
8095 This is the key description file used by
8096 <prgn>dpkg</prgn>. It specifies the package's name
8097 and version, gives its description for the user,
8098 states its relationships with other packages, and so
8099 forth. See <ref id="pkg-controlfile">.
8103 It is usually generated automatically from information
8104 in the source package by the
8105 <prgn>dpkg-gencontrol</prgn> program, and with
8106 assistance from <prgn>dpkg-shlibdeps</prgn>. See <ref
8107 id="pkg-sourcetools">.</p>
8110 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8116 These are exectuable files (usually scripts) which
8117 <prgn>dpkg</prgn> runs during installation, upgrade
8118 and removal of packages. They allow the package to
8119 deal with matters which are particular to that package
8120 or require more complicated processing than that
8121 provided by <prgn>dpkg</prgn>. Details of when and
8122 how they are called are in <ref
8123 id="maintainerscripts">.
8127 It is very important to make these scripts
8131 That means that if it runs successfully or fails
8132 and then you call it again it doesn't bomb out,
8133 but just ensures that everything is the way it
8136 </footnote> This is so that if an error occurs, the
8137 user interrupts <prgn>dpkg</prgn> or some other
8138 unforeseen circumstance happens you don't leave the
8139 user with a badly-broken package.
8143 The maintainer scripts are guaranteed to run with a
8144 controlling terminal and can interact with the user.
8145 If they need to prompt for passwords, do full-screen
8146 interaction or something similar you should do these
8147 things to and from <file>/dev/tty</file>, since
8148 <prgn>dpkg</prgn> will at some point redirect scripts'
8149 standard input and output so that it can log the
8150 installation process. Likewise, because these scripts
8151 may be executed with standard output redirected into a
8152 pipe for logging purposes, Perl scripts should set
8153 unbuffered output by setting <tt>$|=1</tt> so that the
8154 output is printed immediately rather than being
8159 Each script should return a zero exit status for
8160 success, or a nonzero one for failure.</p>
8163 <tag><tt>conffiles</tt>
8168 This file contains a list of configuration files which
8169 are to be handled automatically by <prgn>dpkg</prgn>
8170 (see <ref id="pkg-conffiles">). Note that not necessarily
8171 every configuration file should be listed here.</p>
8174 <tag><tt>shlibs</tt>
8179 This file contains a list of the shared libraries
8180 supplied by the package, with dependency details for
8181 each. This is used by <prgn>dpkg-shlibdeps</prgn>
8182 when it determines what dependencies are required in a
8183 package control file. The <tt>shlibs</tt> file format
8184 is described on <ref id="shlibs">.
8190 <sect id="pkg-controlfile">
8192 The main control information file: <tt>control</tt>
8195 The most important control information file used by
8196 <prgn>dpkg</prgn> when it installs a package is
8197 <tt>control</tt>. It contains all the package"s "vital
8202 The binary package control files of packages built from
8203 Debian sources are made by a special tool,
8204 <prgn>dpkg-gencontrol</prgn>, which reads
8205 <file>debian/control</file> and <file>debian/changelog</file> to
8206 find the information it needs. See <ref id="pkg-sourcepkg"> for
8211 The fields in binary package control files are:
8212 <list compact="compact">
8214 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8217 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
8219 <item><p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8223 This field should appear in all packages, though
8224 <prgn>dpkg</prgn> doesn't require it yet so that
8225 old packages can still be installed.
8231 <p><qref id="relationships"><tt>Depends</tt>,
8232 <tt>Provides</tt> et al.</qref></p>
8235 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8238 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8241 <p><qref id="pkg-f-classification"><tt>Section</tt>,
8242 <tt>Priority</tt></qref></p>
8245 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
8248 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8252 <qref id="pkg-f-Installed-Size"><tt>Installed-Size</tt></qref>
8258 A description of the syntax of control files and the purpose
8259 of these fields is available in <ref id="pkg-controlfields">.
8264 <heading>Time Stamps</heading>
8266 Maintainers are encouraged to preserve the modification
8267 times of the upstream source files in a package, as far as
8268 is reasonably possible.
8271 The rationale is that there is some information conveyed
8272 by knowing the age of the file, for example, you could
8273 recognize that some documentation is very old by looking
8274 at the modification time, so it would be nice if the
8275 modification time of the upstream source would be
8283 <appendix id="pkg-sourcepkg">
8284 <heading>Source packages (from old Packaging Manual) </heading>
8287 The Debian binary packages in the distribution are generated
8288 from Debian sources, which are in a special format to assist
8289 the easy and automatic building of binaries.
8293 There was a previous version of the Debian source format,
8294 which is now being phased out. Instructions for converting an
8295 old-style package are given in the Debian policy manual.
8298 <sect id="pkg-sourcetools">
8299 <heading>Tools for processing source packages</heading>
8302 Various tools are provided for manipulating source packages;
8303 they pack and unpack sources and help build of binary
8304 packages and help manage the distribution of new versions.
8308 They are introduced and typical uses described here; see
8309 <manref name="dpkg-source" section="1"> for full
8310 documentation about their arguments and operation.
8314 For examples of how to construct a Debian source package,
8315 and how to use those utilities that are used by Debian
8316 source packages, please see the <prgn>hello</prgn> example
8322 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
8327 This program is frequently used by hand, and is also
8328 called from package-independent automated building scripts
8329 such as <prgn>dpkg-buildpackage</prgn>.
8333 To unpack a package it is typically invoked with
8335 dpkg-source -x <var>.../path/to/filename</var>.dsc
8340 with the <file><var>filename</var>.tar.gz</file> and
8341 <file><var>filename</var>.diff.gz</file> (if applicable) in
8342 the same directory. It unpacks into
8343 <file><var>package</var>-<var>version</var></file>, and if
8345 <file><var>package</var>-<var>version</var>.orig</file>, in
8346 the current directory.
8350 To create a packed source archive it is typically invoked:
8352 dpkg-source -b <var>package</var>-<var>version</var>
8357 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
8358 <file>.diff.gz</file> (if appropriate) in the current
8359 directory. <prgn>dpkg-source</prgn> does not clean the
8360 source tree first - this must be done separately if it is
8365 See also <ref id="pkg-sourcearchives">.</p>
8371 <prgn>dpkg-buildpackage</prgn> - overall package-building
8376 <prgn>dpkg-buildpackage</prgn> is a script which invokes
8377 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
8378 targets <tt>clean</tt>, <tt>build</tt> and
8379 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
8380 <prgn>pgp</prgn> to build a signed source and binary
8385 It is usually invoked by hand from the top level of the
8386 built or unbuilt source directory. It may be invoked with
8387 no arguments; useful arguments include:
8388 <taglist compact="compact">
8389 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
8392 Do not PGP-sign the <tt>.changes</tt> file or the
8393 source package <tt>.dsc</tt> file, respectively.</p>
8395 <tag><tt>-p<var>pgp-command</var></tt></tag>
8398 Invoke <var>pgp-command</var> instead of finding
8399 <tt>pgp</tt> on the <prgn>PATH</prgn>.
8400 <var>pgp-command</var> must behave just like
8401 <prgn>pgp</prgn>.</p>
8403 <tag><tt>-r<var>root-command</var></tt></tag>
8406 When root privilege is required, invoke the command
8407 <var>root-command</var>. <var>root-command</var>
8408 should invoke its first argument as a command, from
8409 the <prgn>PATH</prgn> if necessary, and pass its
8410 second and subsequent arguments to the command it
8411 calls. If no <var>root-command</var> is supplied
8412 then <var>dpkg-buildpackage</var> will take no
8413 special action to gain root privilege, so that for
8414 most packages it will have to be invoked as root to
8417 <tag><tt>-b</tt>, <tt>-B</tt></tag>
8420 Two types of binary-only build and upload - see
8421 <manref name="dpkg-source" section="1">.
8430 <prgn>dpkg-gencontrol</prgn> - generates binary package
8435 This program is usually called from <file>debian/rules</file>
8436 (see <ref id="pkg-sourcetree">) in the top level of the source
8441 This is usually done just before the files and directories in the
8442 temporary directory tree where the package is being built have their
8443 permissions and ownerships set and the package is constructed using
8444 <prgn>dpkg-deb/</prgn>
8447 This is so that the control file which is produced has
8448 the right permissions
8454 <prgn>dpkg-gencontrol</prgn> must be called after all the
8455 files which are to go into the package have been placed in
8456 the temporary build directory, so that its calculation of
8457 the installed size of a package is correct.
8461 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
8462 be run after <prgn>dpkg-shlibdeps</prgn> so that the
8463 variable substitutions created by
8464 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
8469 For a package which generates only one binary package, and
8470 which builds it in <file>debian/tmp</file> relative to the top
8471 of the source package, it is usually sufficient to call
8472 <prgn>dpkg-gencontrol</prgn>.
8476 Sources which build several binaries will typically need
8479 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
8480 </example> The <tt>-P</tt> tells
8481 <prgn>dpkg-gencontrol</prgn> that the package is being
8482 built in a non-default directory, and the <tt>-p</tt>
8483 tells it which package's control file should be generated.
8487 <prgn>dpkg-gencontrol</prgn> also adds information to the
8488 list of files in <file>debian/files</file>, for the benefit of
8489 (for example) a future invocation of
8490 <prgn>dpkg-genchanges</prgn>.</p>
8495 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
8500 This program is usually called from <file>debian/rules</file>
8501 just before <prgn>dpkg-gencontrol</prgn> (see <ref
8502 id="pkg-sourcetree">), in the top level of the source tree.
8506 Its arguments are executables.
8509 In a forthcoming dpkg version,
8510 <prgn>dpkg-shlibdeps</prgn> would be required to be
8511 called on shared libraries as well.
8514 They may be specified either in the locations in the
8515 source tree where they are created or in the locations
8516 in the temporary build tree where they are installed
8517 prior to binary package creation.
8519 </footnote> for which shared library dependencies should
8520 be included in the binary package's control file.
8524 If some of the found shared libraries should only
8525 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
8526 some warrant a <tt>Pre-Depends</tt>, this can be achieved
8527 by using the <tt>-d<var>dependency-field</var></tt> option
8528 before those executable(s). (Each <tt>-d</tt> option
8529 takes effect until the next <tt>-d</tt>.)
8533 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
8534 output control file to be modified. Instead by default it
8535 adds to the <file>debian/substvars</file> file variable
8536 settings like <tt>shlibs:Depends</tt>. These variable
8537 settings must be referenced in dependency fields in the
8538 appropriate per-binary-package sections of the source
8543 For example, the <prgn>procps</prgn> package generates two
8544 kinds of binaries, simple C binaries like <prgn>ps</prgn>
8545 which require a predependency and full-screen ncurses
8546 binaries like <prgn>top</prgn> which require only a
8547 recommendation. It can say in its <file>debian/rules</file>:
8549 dpkg-shlibdeps -dPre-Depends ps -dRecommends top
8551 and then in its main control file <file>debian/control</file>:
8555 Pre-Depends: ${shlibs:Pre-Depends}
8556 Recommends: ${shlibs:Recommends}
8562 Sources which produce several binary packages with
8563 different shared library dependency requirements can use
8564 the <tt>-p<var>varnameprefix</var></tt> option to override
8565 the default <tt>shlibs:</tt> prefix (one invocation of
8566 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
8567 They can thus produce several sets of dependency
8568 variables, each of the form
8569 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
8570 which can be referred to in the appropriate parts of the
8571 binary package control files.
8578 <prgn>dpkg-distaddfile</prgn> - adds a file to
8579 <file>debian/files</file>
8583 Some packages' uploads need to include files other than
8584 the source and binary package files.
8588 <prgn>dpkg-distaddfile</prgn> adds a file to the
8589 <file>debian/files</file> file so that it will be included in
8590 the <file>.changes</file> file when
8591 <prgn>dpkg-genchanges</prgn> is run.
8595 It is usually invoked from the <tt>binary</tt> target of
8596 <file>debian/rules</file>:
8598 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
8600 The <var>filename</var> is relative to the directory where
8601 <prgn>dpkg-genchanges</prgn> will expect to find it - this
8602 is usually the directory above the top level of the source
8603 tree. The <file>debian/rules</file> target should put the
8604 file there just before or just after calling
8605 <prgn>dpkg-distaddfile</prgn>.
8609 The <var>section</var> and <var>priority</var> are passed
8610 unchanged into the resulting <file>.changes</file> file. See
8611 <ref id="pkg-f-classification">.
8616 <sect1><heading><prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file> upload
8621 This program is usually called by package-independent
8622 automatic building scripts such as
8623 <prgn>dpkg-buildpackage</prgn>, but it may also be called
8628 It is usually called in the top level of a built source
8629 tree, and when invoked with no arguments will print out a
8630 straightforward <file>.changes</file> file based on the
8631 information in the source package's changelog and control
8632 file and the binary and source packages which should have
8638 <sect1><heading><prgn>dpkg-parsechangelog</prgn> - produces parsed representation of
8643 This program is used internally by
8644 <prgn>dpkg-source</prgn> et al. It may also occasionally
8645 be useful in <file>debian/rules</file> and elsewhere. It
8646 parses a changelog, <file>debian/changelog</file> by default,
8647 and prints a control-file format representation of the
8648 information in it to standard output.
8652 <sect1 id="pkg-dpkgarch"><heading><prgn>dpkg-architecture</prgn> -
8653 information about the build and host system
8657 This program can be used manually, but is also invoked by
8658 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
8659 to set environment or make variables which specify the build and
8660 host architecture for the package building process.
8665 <sect id="pkg-sourcetree"><heading>The Debianised source tree
8669 The source archive scheme described later is intended to
8670 allow a Debianised source tree with some associated control
8671 information to be reproduced and transported easily. The
8672 Debianised source tree is a version of the original program
8673 with certain files added for the benefit of the
8674 Debianisation process, and with any other changes required
8675 made to the rest of the source code and installation
8680 The extra files created for Debian are in the subdirectory
8681 <file>debian</file> of the top level of the Debianised source
8682 tree. They are described below.
8685 <sect1 id="pkg-debianrules"><heading><file>debian/rules</file> - the main building
8690 This file is an executable makefile, and contains the
8691 package-specific recipies for compiling the package and
8692 building binary package(s) out of the source.
8696 It must start with the line <tt>#!/usr/bin/make -f</tt>,
8697 so that it can be invoked by saying its name rather than
8698 invoking <prgn>make</prgn> explicitly.
8702 Since an interactive <file>debian/rules</file> script makes it
8703 impossible to autocompile that package and also makes it
8704 hard for other people to reproduce the same binary
8705 package, all <strong>required targets</strong> have to be
8706 non-interactive. At a minimul, required targets are the
8707 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
8708 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>, and
8709 <em>build</em>. It also follows that any target that these
8710 targets depend on must also be non-interactive.
8714 The targets which are required to be present are:
8716 <tag><tt>build</tt></tag>
8719 This should perform all non-interactive
8720 configuration and compilation of the package. If a
8721 package has an interactive pre-build configuration
8722 routine, the Debianised source package should be
8723 built after this has taken place, so that it can be
8724 built without rerunning the configuration.
8728 A package may also provide both of the targets
8729 <tt>build-arch</tt> and <tt>build-indep</tt>. The
8730 <tt>build-arch</tt> target, if provided, should
8731 perform all non-interactive configuration and
8732 compilation required for producing all
8733 architecture-dependant binary packages (those packages
8734 for which the body of the <tt>Architecture</tt> field
8735 in <tt>debian/control</tt> is not <tt>all</tt>).
8736 Similarly, the <tt>build-indep</tt> target, if
8737 provided, should perform all non-interactive
8738 configuration and compilation required for producing
8739 all architecture-independent binary packages (those
8740 packages for which the body of the
8741 <tt>Architecture</tt> field in <tt>debian/control</tt>
8742 is <tt>all</tt>). The <tt>build</tt> target should
8743 depend on those of the targets <tt>build-arch</tt> and
8744 <tt>build-indep</tt> that are provided in the rules
8749 If one or both of the targets <tt>build-arch</tt> and
8750 <tt>build-indep</tt> are not provided, then invoking
8751 <file>debian/rules</file> with one of the not-provided
8752 targets as arguments should produce a exit status code
8753 of 2. Usually this is provided automatically by make
8754 if the target is missing.
8758 For some packages, notably ones where the same
8759 source tree is compiled in different ways to produce
8760 two binary packages, the <tt>build</tt> target does
8761 not make much sense. For these packages it is good
8762 enough to provide two (or more) targets
8763 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
8764 for each of the ways of building the package, and a
8765 <tt>build</tt> target that does nothing. The
8766 <tt>binary</tt> target will have to build the
8767 package in each of the possible ways and make the
8768 binary package out of each.
8772 The targets <tt>build</tt>, <tt>build-arch</tt>
8773 and <tt>build-indep</tt> target must not do
8774 anything that might require root privilege.
8778 The <tt>build</tt> target may need to run
8779 <tt>clean</tt> first - see below.
8783 When a package has a configuration routine that takes
8784 a long time, or when the makefiles are poorly
8785 designed, or when <tt>build</tt> needs to run
8786 <tt>clean</tt> first, it is a good idea to <tt>touch
8787 build</tt> when the build process is complete. This
8788 will ensure that if <tt>debian/rules build</tt> is run
8789 again it will not rebuild the whole program.
8793 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
8794 <tt>binary-indep</tt>
8798 The <tt>binary</tt> target should be all that is
8799 necessary for the user to build the binary
8800 package. All these targets are required to be
8801 non-interactive. It is split into two parts:
8802 <tt>binary-arch</tt> builds the packages' output
8803 files which are specific to a particular
8804 architecture, and <tt>binary-indep</tt> builds
8805 those which are not.
8809 <tt>binary</tt> should usually be a target with
8810 no commands which simply depends on
8811 <prgn>binary-arch</prgn> and
8812 <prgn>binary-indep</prgn>.
8816 Both <prgn>binary-*</prgn> targets should depend on
8817 the <tt>build</tt> target, above, so that the
8818 package is built if it has not been already. It
8819 should then create the relevant binary package(s),
8820 using <prgn>dpkg-gencontrol</prgn> to make their
8821 control files and <prgn>dpkg-deb</prgn> to build
8822 them and place them in the parent of the top level
8827 If one of the <prgn>binary-*</prgn> targets has
8828 nothing to do (this will be always be the case if
8829 the source generates only a single binary package,
8830 whether architecture-dependent or not) it
8831 <em>must</em> still exist, but should always
8836 <ref id="pkg-binarypkg"> describes how to construct
8841 The <tt>binary</tt> targets must be invoked as
8846 <tag><tt>clean</tt></tag>
8850 This should undo any effects that the
8851 <tt>build</tt> and <tt>binary</tt> targets
8852 may have had, except that it should leave alone any
8853 output files created in the parent directory by a
8854 run of <tt>binary</tt>. This target is required
8855 to be non-interactive.
8859 If a <tt>build</tt> file is touched at the end
8860 of the <tt>build</tt> target, as suggested
8861 above, it must be removed as the first thing that
8862 <tt>clean</tt> does, so that running
8863 <tt>build</tt> again after an interrupted
8864 <tt>clean</tt> doesn't think that everything is
8869 The <tt>clean</tt> target must be invoked as
8870 root if <tt>binary</tt> has been invoked since
8871 the last <tt>clean</tt>, or if
8872 <tt>build</tt> has been invoked as root (since
8873 <tt>build</tt> may create directories, for
8878 <tag><tt>get-orig-source</tt> (optional)</tag>
8882 This target fetches the most recent version of the
8883 original source package from a canonical archive
8884 site (via FTP or WWW, for example), does any
8885 necessary rearrangement to turn it into the original
8886 source tarfile format described below, and leaves it
8887 in the current directory.
8891 This target may be invoked in any directory, and
8892 should take care to clean up any temporary files it
8897 This target is optional, but providing it if
8898 possible is a good idea.
8904 The <tt>build</tt>, <tt>binary</tt> and
8905 <tt>clean</tt> targets must be invoked with a current
8906 directory of the package's top-level directory.
8911 Additional targets may exist in <file>debian/rules</file>,
8912 either as published or undocumented interfaces or for the
8913 package's internal use.
8917 The architecture we build on and build for is determined by make
8918 variables via dpkg-architecture (see <ref id="pkg-dpkgarch">). You can
8919 get the Debian architecture and the GNU style architecture
8920 specification string for the build machine as well as the host
8921 machine. Here is a list of supported make variables:
8922 <list compact="compact">
8924 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
8927 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
8928 specification string)</p>
8931 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of DEB_*_GNU_TYPE)</p>
8934 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
8940 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
8941 the build machine or <tt>HOST</tt> for specification of the machine
8946 Backward compatibility can be provided in the rules file
8947 by setting the needed variables to suitable default
8948 values, please refer to the documentation of
8949 dpkg-architecture for details.
8953 It is important to understand that the <tt>DEB_*_ARCH</tt>
8954 string does only determine which Debian architecture we
8955 build on resp. for. It should not be used to get the CPU
8956 or System information, the GNU style variables should be
8962 <sect1><heading><file>debian/control</file>
8966 This file contains version-independent details about the
8967 source package and about the binary packages it creates.
8971 It is a series of sets of control fields, each
8972 syntactically similar to a binary package control file.
8973 The sets are separated by one or more blank lines. The
8974 first set is information about the source package in
8975 general; each subsequent set describes one binary package
8976 that the source tree builds.
8980 The syntax and semantics of the fields are described below
8981 in <ref id="pkg-controlfields">.
8985 The general (binary-package-independent) fields are:
8986 <list compact="compact">
8988 <p><qref id="pkg-f-Source"><tt>Source</tt></qref> (mandatory)</p>
8991 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8995 <qref id="pkg-f-classification"><tt>Section</tt> and
8996 <tt>Priority</tt></qref>
8997 (classification, mandatory)
9002 <qref id="relationships"><tt>Build-Depends</tt> et
9003 al.</qref> (source package interrelationships)
9008 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref>
9014 The per-binary-package fields are:
9015 <list compact="compact">
9017 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
9021 <qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
9025 <p><qref id="descriptions"><tt>Description</tt></qref></p>
9029 <qref id="pkg-f-classification"><tt>Section</tt> and
9030 <tt>Priority</tt></qref> (classification)</p>
9033 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
9037 <qref id="relationships"><tt>Depends</tt> et
9038 al.</qref> (binary package interrelationships)
9044 These fields are used by <prgn>dpkg-gencontrol</prgn> to
9045 generate control files for binary packages (see below), by
9046 <prgn>dpkg-genchanges</prgn> to generate the
9047 <tt>.changes</tt> file to accompany the upload, and by
9048 <prgn>dpkg-source</prgn> when it creates the <file>.dsc</file>
9049 source control file as part of a source archive.
9053 The fields here may contain variable references - their
9054 values will be substituted by
9055 <prgn>dpkg-gencontrol</prgn>, <prgn>dpkg-genchanges</prgn>
9056 or <prgn>dpkg-source</prgn> when they generate output
9057 control files. See <ref id="pkg-srcsubstvars"> for details.
9060 <p> <sect2><heading>User-defined fields
9064 Additional user-defined fields may be added to the
9065 source package control file. Such fields will be
9066 ignored, and not copied to (for example) binary or
9067 source package control files or upload control files.
9071 If you wish to add additional unsupported fields to
9072 these output files you should use the mechanism
9077 Fields in the main source control information file with
9078 names starting <tt>X</tt>, followed by one or more of
9079 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
9080 be copied to the output files. Only the part of the
9081 field name after the hyphen will be used in the output
9082 file. Where the letter <tt>B</tt> is used the field
9083 will appear in binary package control files, where the
9084 letter <tt>S</tt> is used in source package control
9085 files and where <tt>C</tt> is used in upload control
9086 (<tt>.changes</tt>) files.
9090 For example, if the main source information control file
9093 XBS-Comment: I stand between the candle and the star.
9095 then the binary and source package control files will contain the
9098 Comment: I stand between the candle and the star.
9105 <sect1 id="pkg-dpkgchangelog"><heading><file>debian/changelog</file>
9109 This file records the changes to the Debian-specific parts of the
9113 Though there is nothing stopping an author who is also
9114 the Debian maintainer from using it for all their
9115 changes, it will have to be renamed if the Debian and
9116 upstream maintainers become different
9123 It has a special format which allows the package building
9124 tools to discover which version of the package is being
9125 built and find out other release-specific information.
9129 That format is a series of entries like this:
9131 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
9133 * <var>change details</var>
9134 <var>more change details</var>
9135 * <var>even more change details</var>
9137 -- <var>maintainer name and email address</var> <var>date</var>
9142 <var>package</var> and <var>version</var> are the source
9143 package name and version number.
9147 <var>distribution(s)</var> lists the distributions where
9148 this version should be installed when it is uploaded - it
9149 is copied to the <tt>Distribution</tt> field in the
9150 <tt>.changes</tt> file. See <ref id="pkg-f-Distribution">.
9154 <var>urgency</var> is the value for the <tt>Urgency</tt>
9155 field in the <file>.changes</file> file for the upload. See
9156 <ref id="pkg-f-Urgency">. It is not possible to specify an
9157 urgency containing commas; commas are used to separate
9158 <tt><var>keyword</var>=<var>value</var></tt> settings in
9159 the <prgn>dpkg</prgn> changelog format (though there is
9160 currently only one useful <var>keyword</var>,
9165 The change details may in fact be any series of lines
9166 starting with at least two spaces, but conventionally each
9167 change starts with an asterisk and a separating space and
9168 continuation lines are indented so as to bring them in
9169 line with the start of the text above. Blank lines may be
9170 used here to separate groups of changes, if desired.
9174 The maintainer name and email address should <em>not</em>
9175 necessarily be those of the usual package maintainer.
9176 They should be the details of the person doing
9177 <em>this</em> version. The information here will be
9178 copied to the <file>.changes</file> file, and then later used
9179 to send an acknowledgement when the upload has been
9184 The <var>date</var> should be in RFC822 format
9187 This is generated by the <prgn>822-date</prgn>
9190 </footnote>; it should include the timezone specified
9191 numerically, with the timezone name or abbreviation
9192 optionally present as a comment.
9196 The first "title" line with the package name should start
9197 at the left hand margin; the "trailer" line with the
9198 maintainer and date details should be preceded by exactly
9199 one space. The maintainer details and the date must be
9200 separated by exactly two spaces.
9204 An Emacs mode for editing this format is available: it is
9205 called <tt>debian-changelog-mode</tt>. You can have this
9206 mode selected automatically when you edit a Debian
9207 changelog by adding a local variables clause to the end of
9211 <sect2><heading>Defining alternative changelog formats
9215 It is possible to use a different format to the standard
9216 one, by providing a parser for the format you wish to
9221 In order to have <tt>dpkg-parsechangelog</tt> run your
9222 parser, you must include a line within the last 40 lines
9223 of your file matching the Perl regular expression:
9224 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9225 parentheses should be the name of the format. For
9226 example, you might say:
9228 @@@ changelog-format: joebloggs @@@
9230 Changelog format names are non-empty strings of alphanumerics.
9234 If such a line exists then <tt>dpkg-parsechangelog</tt>
9235 will look for the parser as
9236 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9238 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9239 it is an error for it not to find it, or for it not to
9240 be an executable program. The default changelog format
9241 is <tt>dpkg</tt>, and a parser for it is provided with
9242 the <tt>dpkg</tt> package.
9246 The parser will be invoked with the changelog open on
9247 standard input at the start of the file. It should read
9248 the file (it may seek if it wishes) to determine the
9249 information required and return the parsed information
9250 to standard output in the form of a series of control
9251 fields in the standard format. By default it should
9252 return information about only the most recent version in
9253 the changelog; it should accept a
9254 <tt>-v<var>version</var></tt> option to return changes
9255 information from all versions present <em>strictly
9256 after</em> <var>version</var>, and it should then be an
9257 error for <var>version</var> not to be present in the
9263 <list compact="compact">
9265 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9268 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
9272 <qref id="pkg-f-Distribution"><tt>Distribution</tt></qref>
9277 <p><qref id="pkg-f-Urgency"><tt>Urgency</tt></qref> (mandatory)</p>
9281 <qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref>
9286 <p><qref id="pkg-f-Date"><tt>Date</tt></qref></p>
9290 <qref id="pkg-f-Changes"><tt>Changes</tt></qref>
9297 If several versions are being returned (due to the use
9298 of <tt>-v</tt>), the urgency value should be of the
9299 highest urgency code listed at the start of any of the
9300 versions requested followed by the concatenated
9301 (space-separated) comments from all the versions
9302 requested; the maintainer, version, distribution and
9303 date should always be from the most recent version.
9307 For the format of the <tt>Changes</tt> field see <ref
9308 id="pkg-f-Changes">.
9312 If the changelog format which is being parsed always or
9313 almost always leaves a blank line between individual
9314 change notes these blank lines should be stripped out,
9315 so as to make the resulting output compact.
9319 If the changelog format does not contain date or package
9320 name information this information should be omitted from
9321 the output. The parser should not attempt to synthesise
9322 it or find it from other sources.
9326 If the changelog does not have the expected format the
9327 parser should exit with a nonzero exit status, rather
9328 than trying to muddle through and possibly generating
9333 A changelog parser may not interact with the user at
9337 <!-- FIXME: section pkg-srcsubstvars is the same as srcsubstvars -->
9339 <sect1 id="pkg-srcsubstvars"><heading><file>debian/substvars</file>
9340 and variable substitutions
9344 When <prgn>dpkg-gencontrol</prgn>,
9345 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
9346 generate control files they do variable substitutions on
9347 their output just before writing it. Variable
9348 substitutions have the form
9349 <tt>${<var>variable-name</var>}</tt>. The optional file
9350 <file>debian/substvars</file> contains variable substitutions
9351 to be used; variables can also be set directly from
9352 <file>debian/rules</file> using the <tt>-V</tt> option to the
9353 source packaging commands, and certain predefined
9354 variables are available.
9358 This file is usually generated and modified dynamically by
9359 <file>debian/rules</file> targets, in which case it must be
9360 removed by the <tt>clean</tt> target.
9364 See <manref name="dpkg-source" section="1"> for full
9365 details about source variable substitutions, including the
9366 format of <file>debian/substvars</file>.</p>
9369 <sect1><heading><file>debian/files</file>
9373 This file is not a permanent part of the source tree; it
9374 is used while building packages to record which files are
9375 being generated. <prgn>dpkg-genchanges</prgn> uses it
9376 when it generates a <file>.changes</file> file.
9380 It should not exist in a shipped source package, and so it
9381 (and any backup files or temporary files such as
9382 <file>files.new</file>
9385 <file>files.new</file> is used as a temporary file by
9386 <prgn>dpkg-gencontrol</prgn> and
9387 <prgn>dpkg-distaddfile</prgn> - they write a new
9388 version of <file>files</file> here before renaming it,
9389 to avoid leaving a corrupted copy if an error
9392 </footnote>) should be removed by the
9393 <tt>clean</tt> target. It may also be wise to
9394 ensure a fresh start by emptying or removing it at the
9395 start of the <tt>binary</tt> target.
9399 <prgn>dpkg-gencontrol</prgn> adds an entry to this file
9400 for the <file>.deb</file> file that will be created by
9401 <prgn>dpkg-deb</prgn> from the control file that it
9402 generates, so for most packages all that needs to be done
9403 with this file is to delete it in <tt>clean</tt>.
9407 If a package upload includes files besides the source
9408 package and any binary packages whose control files were
9409 made with <prgn>dpkg-gencontrol</prgn> then they should be
9410 placed in the parent of the package's top-level directory
9411 and <prgn>dpkg-distaddfile</prgn> should be called to add
9412 the file to the list in <file>debian/files</file>.</p>
9415 <sect1><heading><file>debian/tmp</file>
9419 This is the canonical temporary location for the
9420 construction of binary packages by the <tt>binary</tt>
9421 target. The directory <file>tmp</file> serves as the root of
9422 the filesystem tree as it is being constructed (for
9423 example, by using the package's upstream makefiles install
9424 targets and redirecting the output there), and it also
9425 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9426 id="pkg-bincreating">.
9430 If several binary packages are generated from the same
9431 source tree it is usual to use several
9432 <file>debian/tmp<var>something</var></file> directories, for
9433 example <file>tmp-a</file> or <file>tmp-doc</file>.
9437 Whatever <file>tmp</file> directories are created and used by
9438 <tt>binary</tt> must of course be removed by the
9439 <tt>clean</tt> target.</p></sect1>
9443 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9447 As it exists on the FTP site, a Debian source package
9448 consists of three related files. You must have the right
9449 versions of all three to be able to use them.
9454 <tag>Debian source control file - <tt>.dsc</tt></tag>
9458 This file contains a series of fields, identified and
9459 separated just like the fields in the control file of
9460 a binary package. The fields are listed below; their
9461 syntax is described above, in <ref id="pkg-controlfields">.
9462 <list compact="compact">
9464 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9467 <p><qref id="versions"><tt>Version</tt></qref></p>
9470 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
9473 <p><qref id="pkg-f-Binary"><tt>Binary</tt></qref></p>
9476 <p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref></p>
9480 <qref id="relationships"><tt>Build-Depends</tt> et
9481 al.</qref> (source package interrelationships)
9486 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref></p>
9489 <p><qref id="pkg-f-Files"><tt>Files</tt></qref></p>
9494 The source package control file is generated by
9495 <prgn>dpkg-source</prgn> when it builds the source
9496 archive, from other files in the source package,
9497 described above. When unpacking it is checked against
9498 the files and directories in the other parts of the
9499 source package, as described below.</p>
9503 Original source archive -
9505 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9512 This is a compressed (with <tt>gzip -9</tt>)
9513 <prgn>tar</prgn> file containing the source code from
9514 the upstream authors of the program. The tarfile
9515 unpacks into a directory
9516 <file><var>package</var>-<var>upstream-version</var>.orig</file>,
9517 and does not contain files anywhere other than in
9518 there or in its subdirectories.</p>
9522 Debianisation diff -
9524 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9530 This is a unified context diff (<tt>diff -u</tt>)
9531 giving the changes which are required to turn the
9532 original source into the Debian source. These changes
9533 may only include editing and creating plain files.
9534 The permissions of files, the targets of symbolic
9535 links and the characteristics of special files or
9536 pipes may not be changed and no files may be removed
9541 All the directories in the diff must exist, except the
9542 <file>debian</file> subdirectory of the top of the source
9543 tree, which will be created by
9544 <prgn>dpkg-source</prgn> if necessary when unpacking.
9548 The <prgn>dpkg-source</prgn> program will
9549 automatically make the <file>debian/rules</file> file
9550 executable (see below).</p></item>
9555 If there is no original source code - for example, if the
9556 package is specially prepared for Debian or the Debian
9557 maintainer is the same as the upstream maintainer - the
9558 format is slightly different: then there is no diff, and the
9560 <file><var>package</var>_<var>version</var>.tar.gz</file> and
9561 contains a directory
9562 <file><var>package</var>-<var>version</var></file>.
9566 <sect><heading>Unpacking a Debian source package without
9567 <prgn>dpkg-source</prgn>
9571 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9572 Debian source package. However, if it is not available it
9573 is possible to unpack a Debian source archive as follows:
9574 <enumlist compact="compact">
9577 Untar the tarfile, which will create a <file>.orig</file>
9581 <p>Rename the <file>.orig</file> directory to
9582 <file><var>package</var>-<var>version</var></file>.</p>
9586 Create the subdirectory <file>debian</file> at the top of
9587 the source tree.</p>
9589 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9591 <item><p>Untar the tarfile again if you want a copy of the original
9592 source code alongside the Debianised version.</p>
9597 It is not possible to generate a valid Debian source archive
9598 without using <prgn>dpkg-source</prgn>. In particular,
9599 attempting to use <prgn>diff</prgn> directly to generate the
9600 <file>.diff.gz</file> file will not work.
9603 <sect1><heading>Restrictions on objects in source packages
9607 The source package may not contain any hard links
9610 This is not currently detected when building source
9611 packages, but only when extracting
9617 Hard links may be permitted at some point in the
9618 future, but would require a fair amount of
9621 </footnote>, device special files, sockets or setuid or
9625 Setgid directories are allowed.
9631 The source packaging tools manage the changes between the
9632 original and Debianised source using <prgn>diff</prgn> and
9633 <prgn>patch</prgn>. Turning the original source tree as
9634 included in the <file>.orig.tar.gz</file> into the debianised
9635 source must not involve any changes which cannot be
9636 handled by these tools. Problematic changes which cause
9637 <prgn>dpkg-source</prgn> to halt with an error when
9638 building the source package are:
9639 <list compact="compact">
9640 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9642 <item><p>Changing the targets of symbolic links.</p>
9644 <item><p>Creating directories, other than <file>debian</file>.</p>
9646 <item><p>Changes to the contents of binary files.</p></item>
9647 </list> Changes which cause <prgn>dpkg-source</prgn> to
9648 print a warning but continue anyway are:
9649 <list compact="compact">
9652 Removing files, directories or symlinks.
9655 Renaming a file is not treated specially - it is
9656 seen as the removal of the old file (which
9657 generates a warning, but is otherwise ignored),
9658 and the creation of the new
9665 Changed text files which are missing the usual final
9666 newline (either in the original or the modified
9671 Changes which are not represented, but which are not detected by
9672 <prgn>dpkg-source</prgn>, are:
9673 <list compact="compact">
9674 <item><p>Changing the permissions of files (other than
9675 <file>debian/rules</file>) and directories.</p></item>
9680 The <file>debian</file> directory and <file>debian/rules</file>
9681 are handled specially by <prgn>dpkg-source</prgn> - before
9682 applying the changes it will create the <file>debian</file>
9683 directory, and afterwards it will make
9684 <file>debian/rules</file> world-exectuable.
9690 <appendix id="pkg-controlfields"><heading>Control files and their
9691 fields (from old Packaging Manual)
9695 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9696 data in a common format, known as control files. Binary and
9697 source packages have control data as do the <file>.changes</file>
9698 files which control the installation of uploaded files, and
9699 <prgn>dpkg</prgn>'s internal databases are in a similar
9703 <sect><heading>Syntax of control files
9707 A file consists of one or more paragraphs of fields. The
9708 paragraphs are separated by blank lines. Some control files
9709 only allow one paragraph; others allow several, in which
9710 case each paragraph often refers to a different package.
9714 Each paragraph is a series of fields and values; each field
9715 consists of a name, followed by a colon and the value. It
9716 ends at the end of the line. Horizontal whitespace (spaces
9717 and tabs) may occur before or after the value and is ignored
9718 there; it is conventional to put a single space after the
9723 Some fields' values may span several lines; in this case
9724 each continuation line <em>must</em> start with a space or
9725 tab. Any trailing spaces or tabs at the end of individual
9726 lines of a field value are ignored.
9730 Except where otherwise stated only a single line of data is
9731 allowed and whitespace is not significant in a field body.
9732 Whitespace may never appear inside names (of packages,
9733 architectures, files or anything else), version numbers or
9734 in between the characters of multi-character version
9739 Field names are not case-sensitive, but it is usual to
9740 capitalise the field names using mixed case as shown below.
9744 Blank lines, or lines consisting only of spaces and tabs,
9745 are not allowed within field values or between fields - that
9746 would mean a new paragraph.
9750 It is important to note that there are several fields which
9751 are optional as far as <prgn>dpkg</prgn> and the related
9752 tools are concerned, but which must appear in every Debian
9753 package, or whose omission may cause problems. When writing
9754 the control files for Debian packages you <em>must</em> read
9755 the Debian policy manual in conjuction with the details
9756 below and the list of fields for the particular file.</p>
9759 <sect><heading>List of fields
9762 <sect1 id="pkg-f-Package"><heading><tt>Package</tt>
9766 The name of the binary package. Package names consist of
9767 the alphanumerics and <tt>+</tt> <tt>-</tt> <tt>.</tt>
9768 (plus, minus and full stop).
9771 The characters <tt>@</tt> <tt>:</tt> <tt>=</tt>
9772 <tt>%</tt> <tt>_</tt> (at, colon, equals, percent
9773 and underscore) used to be legal and are still
9774 accepted when found in a package file, but may not be
9775 used in new packages
9781 They must be at least two characters and must start with
9782 an alphanumeric. In current versions of dpkg they are
9783 sort of case-sensitive<footnote><p>This is a
9784 bug.</p></footnote>; use lowercase package names unless
9785 the package you're building (or referring to, in other
9786 fields) is already using uppercase.</p>
9789 <sect1 id="pkg-f-Version"><heading><tt>Version</tt>
9793 This lists the source or binary package's version number -
9794 see <ref id="versions">.
9799 <sect1 id="pkg-f-Architecture"><heading><tt>Architecture</tt>
9803 This is the architecture string; it is a single word for
9804 the Debian architecture.
9808 <prgn>dpkg</prgn> will check the declared architecture of
9809 a binary package against its own compiled-in value before
9814 The special value <tt>all</tt> indicates that the package
9815 is architecture-independent.
9819 In the main <file>debian/control</file> file in the source
9820 package, or in the source package control file
9821 <file>.dsc</file>, a list of architectures (separated by
9822 spaces) is also allowed, as is the special value
9823 <tt>any</tt>. A list indicates that the source will build
9824 an architecture-dependent package, and will only work
9825 correctly on the listed architectures. <tt>any</tt>
9826 indicates that though the source package isn't dependent
9827 on any particular architecture and should compile fine on
9828 any one, the binary package(s) produced are not
9829 architecture-independent but will instead be specific to
9830 whatever the current build architecture is.
9834 In a <file>.changes</file> file the <tt>Architecture</tt>
9835 field lists the architecture(s) of the package(s)
9836 currently being uploaded. This will be a list; if the
9837 source for the package is being uploaded too the special
9838 entry <tt>source</tt> is also present.
9842 See <ref id="pkg-debianrules"> for information how to get the
9843 architecture for the build process.
9847 <sect1 id="pkg-f-Maintainer"><heading><tt>Maintainer</tt>
9851 The package maintainer's name and email address. The name
9852 should come first, then the email address inside angle
9853 brackets <tt><></tt> (in RFC822 format).
9857 If the maintainer's name contains a full stop then the
9858 whole field will not work directly as an email address due
9859 to a misfeature in the syntax specified in RFC822; a
9860 program using this field as an address must check for this
9861 and correct the problem if necessary (for example by
9862 putting the name in round brackets and moving it to the
9863 end, and bringing the email address forward).
9867 In a <file>.changes</file> file or parsed changelog data this
9868 contains the name and email address of the person
9869 responsible for the particular version in question - this
9870 may not be the package's usual maintainer.
9874 This field is usually optional in as far as the
9875 <prgn>dpkg</prgn> are concerned, but its absence when
9876 building packages usually generates a warning.</p>
9879 <sect1 id="pkg-f-Source"><heading><tt>Source</tt>
9883 This field identifies the source package name.
9887 In a main source control information or a
9888 <file>.changes</file> or <file>.dsc</file> file or parsed
9889 changelog data this may contain only the name of the
9894 In the control file of a binary package (or in a
9895 <file>Packages</file> file) it may be followed by a version
9896 number in parentheses.
9899 It is usual to leave a space after the package name if
9900 a version number is specified.
9902 </footnote> This version number may be omitted (and is, by
9903 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
9904 the <tt>Version</tt> field of the binary package in
9905 question. The field itself may be omitted from a binary
9906 package control file when the source package has the same
9907 name and version as the binary package.
9911 <sect1><heading>Package interrelationship fields:
9912 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
9913 <tt>Recommends</tt> <tt>Suggests</tt>, <tt>Conflicts</tt>,
9914 <tt>Provides</tt>, <tt>Replaces</tt>
9918 These fields describe the package's relationships with
9919 other packages. Their syntax and semantics are described
9920 in <ref id="relationships">.</p>
9923 <sect1 id="pkg-f-Description"><heading><tt>Description</tt>
9927 In a binary package <tt>Packages</tt> file or main source
9928 control file this field contains a description of the
9929 binary package, in a special format. See <ref
9930 id="descriptions"> for details.
9934 In a <file>.changes</file> file it contains a summary of the
9935 descriptions for the packages being uploaded. The part of
9936 the field before the first newline is empty; thereafter
9937 each line has the name of a binary package and the summary
9938 description line from that binary package. Each line is
9939 indented by one space.</p>
9942 <sect1 id="pkg-f-Essential"><heading><tt>Essential</tt>
9946 This is a boolean field which may occur only in the
9947 control file of a binary package (or in the
9948 <file>Packages</file> file) or in a per-package fields
9949 paragraph of a main source control data file.
9953 If set to <tt>yes</tt> then <prgn>dpkg</prgn> and
9954 <prgn>dselect</prgn> will refuse to remove the package
9955 (though it can be upgraded and/or replaced). The other
9956 possible value is <tt>no</tt>, which is the same as not
9957 having the field at all.</p>
9960 <sect1 id="pkg-f-classification"><heading><tt>Section</tt> and
9965 These two fields classify the package. The
9966 <tt>Priority</tt> represents how important that it is that
9967 the user have it installed; the <tt>Section</tt>
9968 represents an application area into which the package has
9973 When they appear in the <file>debian/control</file> file these
9974 fields give values for the section and priority subfields
9975 of the <tt>Files</tt> field of the <file>.changes</file> file,
9976 and give defaults for the section and priority of the
9981 The section and priority are represented, though not as
9982 separate fields, in the information for each file in the
9983 <qref id="pkg-f-Files"><tt>-File</tt></qref>field of a
9984 <file>.changes</file> file. The section value in a
9985 <file>.changes</file> file is used to decide where to install
9986 a package in the FTP archive.
9990 These fields are not used by by <prgn>dpkg</prgn> proper,
9991 but by <prgn>dselect</prgn> when it sorts packages and
9992 selects defaults. See the Debian policy manual for the
9993 priorities in use and the criteria for selecting the
9994 priority for a Debian package, and look at the Debian FTP
9995 archive for a list of currently in-use priorities.
9999 These fields may appear in binary package control files,
10000 in which case they provide a default value in case the
10001 <file>Packages</file> files are missing the information.
10002 <prgn>dpkg</prgn> and <prgn>dselect</prgn> will only use
10003 the value from a <file>.deb</file> file if they have no other
10004 information; a value listed in a <file>Packages</file> file
10005 will always take precedence. By default
10006 <prgn>dpkg-gencontrol</prgn> does not include the section
10007 and priority in the control file of a binary package - use
10008 the <tt>-isp</tt>, <tt>-is</tt> or <tt>-ip</tt> options to
10009 achieve this effect.</p>
10012 <sect1 id="pkg-f-Binary"><heading><tt>Binary</tt>
10016 This field is a list of binary packages.
10020 When it appears in the <file>.dsc</file> file it is the list
10021 of binary packages which a source package can produce. It
10022 does not necessarily produce all of these binary packages
10023 for every architecture. The source control file doesn't
10024 contain details of which architectures are appropriate for
10025 which of the binary packages.
10029 When it appears in a <file>.changes</file> file it lists the
10030 names of the binary packages actually being uploaded.
10034 The syntax is a list of binary packages separated by
10038 A space after each comma is conventional.
10040 </footnote> Currently the packages must be separated using
10041 only spaces in the <file>.changes</file> file.</p>
10044 <sect1 id="pkg-f-Installed-Size"><heading><tt>Installed-Size</tt>
10048 This field appears in the control files of binary
10049 packages, and in the <file>Packages</file> files. It gives
10050 the total amount of disk space required to install the
10055 The disk space is represented in kilobytes as a simple
10056 decimal number.</p>
10059 <sect1 id="pkg-f-Files"><heading><tt>Files</tt>
10063 This field contains a list of files with information about
10064 each one. The exact information and syntax varies with
10065 the context. In all cases the part of the field
10066 contents on the same line as the field name is empty. The
10067 remainder of the field is one line per file, each line
10068 being indented by one space and containing a number of
10069 sub-fields separated by spaces.
10073 In the <file>.dsc</file> (Debian source control) file each
10074 line contains the MD5 checksum, size and filename of the
10075 tarfile and (if applicable) diff file which make up the
10076 remainder of the source package.
10079 That is, the parts which are not the
10082 </footnote> The exact forms of the filenames are described
10083 in <ref id="pkg-sourcearchives">.
10087 In the <file>.changes</file> file this contains one line per
10088 file being uploaded. Each line contains the MD5 checksum,
10089 size, section and priority and the filename. The section
10090 and priority are the values of the corresponding fields in
10091 the main source control file - see <ref
10092 id="pkg-f-classification">. If no section or priority is
10093 specified then <tt>-</tt> should be used, though section
10094 and priority values must be specified for new packages to
10095 be installed properly.
10099 The special value <tt>byhand</tt> for the section in a
10100 <tt>.changes</tt> file indicates that the file in question
10101 is not an ordinary package file and must by installed by
10102 hand by the distribution maintainers. If the section is
10103 <tt>byhand</tt> the priority should be <tt>-</tt>.
10107 If a new Debian revision of a package is being shipped and
10108 no new original source archive is being distributed the
10109 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
10110 entry for the original source archive
10111 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
10112 but the <file>.changes</file> file should leave it out. In
10113 this case the original source archive on the distribution
10114 site must match exactly, byte-for-byte, the original
10115 source archive which was used to generate the
10116 <file>.dsc</file> file and diff which are being uploaded.</p>
10121 id="pkg-f-Standards-Version"><heading><tt>Standards-Version</tt>
10125 The most recent version of the standards (the
10126 <prgn>dpkg</prgn> programmers' and policy manuals and
10127 associated texts) with which the package complies. This
10128 is updated manually when editing the source package to
10129 conform to newer standards; it can sometimes be used to
10130 tell when a package needs attention.
10134 Its format is the same as that of a version number except
10135 that no epoch or Debian revision is allowed - see <ref
10136 id="versions">.</p>
10140 <sect1 id="pkg-f-Distribution"><heading><tt>Distribution</tt>
10144 In a <file>.changes</file> file or parsed changelog output
10145 this contains the (space-separated) name(s) of the
10146 distribution(s) where this version of the package should
10147 be or was installed. Distribution names follow the rules
10148 for package names. (See <ref id="pkg-f-Package">).
10152 Current distribution values are:
10154 <tag><em>stable</em></tag>
10157 This is the current "released" version of Debian
10158 GNU/Linux. A new version is released approximately
10159 every 3 months after the <em>development</em> code has
10160 been <em>frozen</em> for a month of testing. Once the
10161 distribution is <em>stable</em> only major bug fixes
10162 are allowed. When changes are made to this
10163 distribution, the release number is increased
10164 (for example: 1.2r1 becomes 1.2r2 then 1.2r3, etc).
10168 <tag><em>unstable</em></tag>
10171 This distribution value refers to the
10172 <em>developmental</em> part of the Debian distribution
10173 tree. New packages, new upstream versions of packages
10174 and bug fixes go into the <em>unstable</em> directory
10175 tree. Download from this distribution at your own
10179 <tag><em>contrib</em></tag>
10182 The packages with this distribution value do not meet
10183 the criteria for inclusion in the main Debian
10184 distribution as defined by the Policy Manual, but meet
10185 the criteria for the <em>contrib</em>
10186 Distribution. There is currently no distinction
10187 between stable and unstable packages in the
10188 <em>contrib</em> or <em>non-free</em>
10189 distributions. Use your best judgement in downloading
10190 from this Distribution.</p>
10193 <tag><em>non-free</em></tag>
10196 Like the packages in the <em>contrib</em> seciton,
10197 the packages in <em>non-free</em> do not meet the
10198 criteria for inclusion in the main Debian distribution
10199 as defined by the Policy Manual. Again, use your best
10200 judgement in downloading from this Distribution.</p>
10202 <tag><em>experimental</em></tag>
10205 The packages with this distribution value are deemed
10206 by their maintainers to be high risk. Oftentimes they
10207 represent early beta or developmental packages from
10208 various sources that the maintainers want people to
10209 try, but are not ready to be a part of the other parts
10210 of the Debian distribution tree. Download at your own
10214 <tag><em>frozen</em></tag>
10217 From time to time, (currently, every 3 months) the
10218 <em>unstable</em> distribution enters a state of
10219 "code-freeze" in anticipation of release as a
10220 <em>stable</em> version. During this period of testing
10221 (usually 4 weeks) only fixes for existing or
10222 newly-discovered bugs will be allowed.
10225 </taglist> You should list <em>all</em> distributions that
10226 the package should be installed into. Except in unusual
10227 circumstances, installations to <em>stable</em> should also
10228 go into <em>frozen</em> (if it exists) and
10229 <em>unstable</em>. Likewise, installations into
10230 <em>frozen</em> should also go into <em>unstable</em>.</p>
10233 <sect1 id="pkg-f-Urgency"><heading><tt>Urgency</tt>
10237 This is a description of how important it is to upgrade to
10238 this version from previous ones. It consists of a single
10239 keyword usually taking one of the values <tt>LOW</tt>,
10240 <tt>MEDIUM</tt> or <tt>HIGH</tt>) followed by an optional
10241 commentary (separated by a space) which is usually in
10242 parentheses. For example:
10244 Urgency: LOW (HIGH for diversions users)
10249 This field appears in the <file>.changes</file> file and in
10250 parsed changelogs; its value appears as the value of the
10251 <tt>urgency</tt> attribute in a <prgn>dpkg</prgn>-style
10252 changelog (see <ref id="pkg-dpkgchangelog">).
10256 Urgency keywords are not case-sensitive.</p>
10259 <sect1 id="pkg-f-Date"><heading><tt>Date</tt>
10263 In <tt>.changes</tt> files and parsed changelogs, this
10264 gives the date the package was built or last edited.</p>
10267 <sect1 id="pkg-f-Format"><heading><tt>Format</tt>
10271 This field occurs in <file>.changes</file> files, and
10272 specifies a format revision for the file. The format
10273 described here is version <tt>1.5</tt>. The syntax of the
10274 format value is the same as that of a package version
10275 number except that no epoch or Debian revision is allowed
10276 - see <ref id="versions">.</p>
10279 <sect1 id="pkg-f-Changes"><heading><tt>Changes</tt>
10283 In a <file>.changes</file> file or parsed changelog this field
10284 contains the human-readable changes data, describing the
10285 differences between the last version and the current one.
10289 There should be nothing in this field before the first
10290 newline; all the subsequent lines must be indented by at
10291 least one space; blank lines must be represented by a line
10292 consiting only of a space and a full stop.
10296 Each version's change information should be preceded by a
10297 "title" line giving at least the version, distribution(s)
10298 and urgency, in a human-readable way.
10302 If data from several versions is being returned the entry
10303 for the most recent version should be returned first, and
10304 entries should be separated by the representation of a
10305 blank line (the "title" line may also be followed by the
10306 representation of blank line).</p>
10309 <sect1 id="pkg-f-Filename"><heading><tt>Filename</tt> and
10310 <tt>MSDOS-Filename</tt>
10314 These fields in <tt>Packages</tt> files give the
10315 filename(s) of (the parts of) a package in the
10316 distribution directories, relative to the root of the
10317 Debian hierarchy. If the package has been split into
10318 several parts the parts are all listed in order, separated
10322 <sect1 id="pkg-f-Size"><heading><tt>Size</tt> and <tt>MD5sum</tt>
10326 These fields in <file>Packages</file> files give the size (in
10327 bytes, expressed in decimal) and MD5 checksum of the
10328 file(s) which make(s) up a binary package in the
10329 distribution. If the package is split into several parts
10330 the values for the parts are listed in order, separated by
10334 <sect1 id="pkg-f-Status"><heading><tt>Status</tt>
10338 This field in <prgn>dpkg</prgn>'s status file records
10339 whether the user wants a package installed, removed or
10340 left alone, whether it is broken (requiring
10341 reinstallation) or not and what its current state on the
10342 system is. Each of these pieces of information is a
10346 <sect1 id="pkg-f-Config-Version"><heading><tt>Config-Version</tt>
10350 If a package is not installed or not configured, this
10351 field in <prgn>dpkg</prgn>'s status file records the last
10352 version of the package which was successfully
10356 <sect1 id="pkg-f-Conffiles"><heading><tt>Conffiles</tt>
10360 This field in <prgn>dpkg</prgn>'s status file contains
10361 information about the automatically-managed configuration
10362 files held by a package. This field should <em>not</em>
10363 appear anywhere in a package!</p>
10366 <sect1><heading>Obsolete fields
10370 These are still recognised by <prgn>dpkg</prgn> but should
10371 not appear anywhere any more.
10372 <taglist compact="compact">
10374 <tag><tt>Revision</tt></tag>
10375 <tag><tt>Package-Revision</tt></tag>
10376 <tag><tt>Package_Revision</tt></tag>
10379 The Debian revision part of the package version was
10380 at one point in a separate control file field. This
10381 field went through several names.</p>
10384 <tag><tt>Recommended</tt></tag>
10385 <item><p>Old name for <tt>Recommends</tt></p>
10388 <tag><tt>Optional</tt></tag>
10389 <item><p>Old name for <tt>Suggests</tt>.</p>
10391 <tag><tt>Class</tt></tag>
10392 <item><p>Old name for <tt>Priority</tt>.</p>
10400 <appendix id="pkg-conffiles"><heading>Configuration file handling
10401 (from old Packaging Manual)
10405 <prgn>dpkg</prgn> can do a certain amount of automatic
10406 handling of package configuration files.
10410 Whether this mechanism is appropriate depends on a number of
10411 factors, but basically there are two approaches to any
10412 particular configuration file.
10416 The easy method is to ship a best-effort configuration in the
10417 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10418 handle updates. If the user is unlikely to want to edit the
10419 file, but you need them to be able to without losing their
10420 changes, and a new package with a changed version of the file
10421 is only released infrequently, this is a good approach.
10425 The hard method is to build the configuration file from
10426 scratch in the <prgn>postinst</prgn> script, and to take the
10427 responsibility for fixing any mistakes made in earlier
10428 versions of the package automatically. This will be
10429 appropriate if the file is likely to need to be different on
10433 <sect><heading>Automatic handling of configuration files by
10438 A package may contain a control area file called
10439 <tt>conffiles</tt>. This file should be a list of filenames
10440 of configuration files needing automatic handling, separated
10441 by newlines. The filenames should be absolute pathnames,
10442 and the files referred to should actually exist in the
10447 When a package is upgraded <prgn>dpkg</prgn> will process
10448 the configuration files during the configuration stage,
10449 shortly before it runs the package's <prgn>postinst</prgn>
10454 For each file it checks to see whether the version of the
10455 file included in the package is the same as the one that was
10456 included in the last version of the package (the one that is
10457 being upgraded from); it also compares the version currently
10458 installed on the system with the one shipped with the last
10463 If neither the user nor the package maintainer has changed
10464 the file, it is left alone. If one or the other has changed
10465 their version, then the changed version is preferred - i.e.,
10466 if the user edits their file, but the package maintainer
10467 doesn't ship a different version, the user's changes will
10468 stay, silently, but if the maintainer ships a new version
10469 and the user hasn't edited it the new version will be
10470 installed (with an informative message). If both have
10471 changed their version the user is prompted about the problem
10472 and must resolve the differences themselves.
10476 The comparisons are done by calculating the MD5 message
10477 digests of the files, and storing the MD5 of the file as it
10478 was included in the most recent version of the package.
10482 When a package is installed for the first time
10483 <prgn>dpkg</prgn> will install the file that comes with it,
10484 unless that would mean overwriting a file already on the
10489 However, note that <prgn>dpkg</prgn> will <em>not</em>
10490 replace a conffile that was removed by the user (or by a
10491 script). This is necessary because with some programs a
10492 missing file produces an effect hard or impossible to
10493 achieve in another way, so that a missing file needs to be
10494 kept that way if the user did it.
10498 Note that a package should <em>not</em> modify a
10499 <prgn>dpkg</prgn>-handled conffile in its maintainer
10500 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10501 the user confusing and possibly dangerous options for
10502 conffile update when the package is upgraded.</p>
10505 <sect><heading>Fully-featured maintainer script configuration
10510 For files which contain site-specific information such as
10511 the hostname and networking details and so forth, it is
10512 better to create the file in the package's
10513 <prgn>postinst</prgn> script.
10517 This will typically involve examining the state of the rest
10518 of the system to determine values and other information, and
10519 may involve prompting the user for some information which
10520 can't be obtained some other way.
10524 When using this method there are a couple of important
10525 issues which should be considered:
10529 If you discover a bug in the program which generates the
10530 configuration file, or if the format of the file changes
10531 from one version to the next, you will have to arrange for
10532 the postinst script to do something sensible - usually this
10533 will mean editing the installed configuration file to remove
10534 the problem or change the syntax. You will have to do this
10535 very carefully, since the user may have changed the file,
10536 perhaps to fix the very problem that your script is trying
10537 to deal with - you will have to detect these situations and
10538 deal with them correctly.
10542 If you do go down this route it's probably a good idea to
10543 make the program that generates the configuration file(s) a
10544 separate program in <file>/usr/sbin</file>, by convention called
10545 <file><var>package</var>config</file> and then run that if
10546 appropriate from the post-installation script. The
10547 <tt><var>package</var>config</tt> program should not
10548 unquestioningly overwrite an existing configuration - if its
10549 mode of operation is geared towards setting up a package for
10550 the first time (rather than any arbitrary reconfiguration
10551 later) you should have it check whether the configuration
10552 already exists, and require a <tt>--force</tt> flag to
10553 overwrite it.</p></sect>
10556 <appendix id="pkg-alternatives"><heading>Alternative versions of
10557 an interface - <prgn>update-alternatives</prgn> (from old
10562 When several packages all provide different versions of the
10563 same program or file it is useful to have the system select a
10564 default, but to allow the system administrator to change it
10565 and have their decisions respected.
10569 For example, there are several versions of the <prgn>vi</prgn>
10570 editor, and there is no reason to prevent all of them from
10571 being installed at once, each under their own name
10572 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10573 Nevertheless it is desirable to have the name <tt>vi</tt>
10574 refer to something, at least by default.
10578 If all the packages involved cooperate, this can be done with
10579 <prgn>update-alternatives</prgn>.
10583 Each package provides its own version under its own name, and
10584 calls <prgn>update-alternatives</prgn> in its postinst to
10585 register its version (and again in its prerm to deregister
10590 See the manpage <manref name="update-alternatives"
10591 section="8"> for details.
10595 If <prgn>update-alternatives</prgn> does not seem appropriate
10596 you may wish to consider using diversions instead.</p>
10599 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10600 package's version of a file (from old Packaging Manual)
10604 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10605 when it reinstalls the package it belongs to, and to have it
10606 put the file from the package somewhere else instead.
10610 This can be used locally to override a package's version of a
10611 file, or by one package to override another's version (or
10612 provide a wrapper for it).
10616 Before deciding to use a diversion, read <ref
10617 id="pkg-alternatives"> to see if you really want a diversion
10618 rather than several alternative versions of a program.
10622 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10623 and updated by a special program <prgn>dpkg-divert</prgn>.
10624 Please see <manref name="dpkg-divert" section="8"> for full
10625 details of its operation.
10629 When a package wishes to divert a file from another, it should
10630 call <prgn>dpkg-divert</prgn> in its preinst to add the
10631 diversion and rename the existing file. For example,
10632 supposing that a <prgn>smailwrapper</prgn> package wishes to
10633 install a wrapper around <file>/usr/sbin/smail</file>:
10635 if [ install = "$1" ]; then
10636 dpkg-divert --package smailwrapper --add --rename \
10637 --divert /usr/sbin/smail.real /usr/sbin/smail
10639 </example> Testing <tt>$1</tt> is necessary so that the script
10640 doesn't try to add the diversion again when
10641 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10642 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10643 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10644 get installed as the true version.
10648 The postrm has to do the reverse:
10650 if [ remove = "$1" ]; then
10651 dpkg-divert --package smailwrapper --remove --rename \
10652 --divert /usr/sbin/smail.real /usr/sbin/smail
10658 Do not attempt to divert a file which is vitally important for
10659 the system's operation - when using <prgn>dpkg-divert</prgn>
10660 there is a time, after it has been diverted but before
10661 <prgn>dpkg</prgn> has installed the new version, when the file
10662 does not exist.</p>
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