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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).
884 <heading>Dependencies</heading>
887 Every package must specify the dependency information
888 about other packages that are required for the first to
892 For example, a dependency entry must be provided for any
893 shared libraries required by a dynamically-linked executable
894 binary in a package.</p>
897 Packages are not required to declare any dependencies they
898 have on other packages which are marked <tt>Essential</tt>
899 (see below), and should not do so unless they depend on a
900 particular version of that package.</p>
903 Sometimes, a package requires another package to be installed
904 <em>and</em> configured before it can be installed. In this
905 case, you must specify a <tt>Pre-Depends</tt> entry for
909 You should not specify a <tt>Pre-Depends</tt> entry for a
910 package before this has been discussed on the
911 <tt>debian-devel</tt> mailing list and a consensus about
912 doing that has been reached.</p></sect1>
915 <sect1 id="virtual_pkg_sect">
916 <heading>Virtual packages</heading>
919 Sometimes, there are several packages which offer
920 more-or-less the same functionality. In this case, it's
921 useful to define a <em>virtual package</em> whose name
922 describes that common functionality. (The virtual
923 packages only exist logically, not physically; that's why
924 they are called <em>virtual</em>.) The packages with this
925 particular function will then <em>provide</em> the virtual
926 package. Thus, any other package requiring that function
927 can simply depend on the virtual package without having to
928 specify all possible packages individually.</p>
931 All packages should use virtual package names where
932 appropriate, and arrange to create new ones if necessary.
933 They should not use virtual package names (except privately,
934 amongst a cooperating group of packages) unless they have
935 been agreed upon and appear in the list of virtual package
936 names. (See also <ref id="virtual">)</p>
939 The latest version of the authoritative list of virtual
940 package names can be found on
941 <ftpsite>ftp.debian.org</ftpsite> in
942 <ftppath>/debian/doc/package-developer/virtual-package-names-list.txt</ftppath>
943 or your local mirror. In addition, it is included in the
944 <tt>debian-policy</tt> package. The procedure for updating
945 the list is described at the top of the file.</p></sect1>
949 <heading>Base system</heading>
952 The <tt>base system</tt> is a minimum subset of the Debian
953 GNU/Linux system that is installed before everything else
954 on a new system. Thus, only very few packages are allowed
955 to go into the <tt>base</tt> section to keep the required
956 disk usage very small.</p>
959 Most of these packages will have the priority value
960 <tt>required</tt> or at least <tt>important</tt>, and many
961 of them will be tagged <tt>essential</tt> (see below).</p>
968 <heading>Essential packages</heading>
971 Some packages are tagged <tt>essential</tt>. (They have
972 <tt>Essential: yes</tt> in their package control record.)
973 This flag is used for packages that are <em>essential</em>
977 Since these packages cannot be easily removed (one has to
978 specify an extra <em>force option</em> to
979 <prgn>dpkg</prgn> to do so), this flag must not be used
980 unless absolutely necessary. A shared library package
981 must not be tagged <tt>essential</tt>; dependencies will
982 prevent its premature removal, and we need to be able to
983 remove it when it has been superseded.
987 Since dpkg will not prevent upgrading of other packages
988 while an <tt>essential</tt> package is in an unconfigured
989 state, all <tt>essential</tt> packages must supply all of
990 their core functionality even when unconfigured. If the
991 package cannot satisfy this requirement it must not be
992 tagged as essential, and any packages depending on this
993 package must instead have explicit dependency fields as
998 You must not tag any packages <tt>essential</tt> before
999 this has been discussed on the <tt>debian-devel</tt>
1000 mailing list and a consensus about doing that has been
1005 <heading>Tasks</heading>
1008 The Debian install process allows the user to choose from
1009 a number of common tasks which a Debian system can be used to
1010 perform. Selecting a task with <prgn>tasksel</prgn> causes
1011 a set of packages that are useful in performing that task to be
1016 This set of packages is all available packages which have the
1017 name of the selected task in the <tt>Task</tt> field of their
1018 control file. The format of this field is a list of tasks,
1019 separated by commas.
1023 You should not tag any packages as belonging to a task
1024 before this has been discussed on the
1025 <em>debian-devel</em> mailing list and a consensus about
1026 doing that has been reached.
1030 For third parties (and historical reasons), tasksel also
1031 supports constructing tasks based on <em>task
1032 packages</em>. These are packages whose names begin with
1033 <em>task-</em>. Task packages should not be included in the
1038 <sect1 id="maintscripts">
1039 <heading>Maintainer Scripts</heading>
1042 The package installation scripts should avoid producing
1043 output which it is unnecessary for the user to see and
1044 should rely on <prgn>dpkg</prgn> to stave off boredom on
1045 the part of a user installing many packages. This means,
1046 amongst other things, using the <tt>--quiet</tt> option on
1047 <prgn>install-info</prgn>.</p>
1050 Errors which occur during the execution of an installation
1051 script must be checked and the installation must not
1052 continue after an error.
1056 Note that in general <ref id="scripts"> applies to package
1057 maintainer scripts, too.
1061 You should not use <prgn>dpkg-divert</prgn> on a file
1062 belonging to another package without consulting the
1063 maintainer of that package first.
1067 All packages which supply an instance of a common command
1068 name (or, in general, filename) should generally use
1069 <prgn>update-alternatives</prgn>, so that they may be
1070 installed together. If <prgn>update-alternatives</prgn>
1071 is not used, then each package must use
1072 <tt>Conflicts</tt> to ensure that other packages are
1073 de-installed. (In this case, it may be appropriate to
1074 specify a conflict against earlier versions of something
1075 that previously did not use
1076 <prgn>update-alternatives</prgn>; this is an exception to
1077 the usual rule that versioned conflicts should be
1083 <heading>Prompting in maintainer scripts</heading>
1085 Package maintainer scripts may prompt the user if
1086 necessary. Prompting may be accomplished by hand, or by
1087 communicating with a program, such as
1088 <prgn>debconf</prgn>, which conforms to the Debian
1089 Configuration management specification, version 2 or
1090 higher. These are included in the
1091 <file>debconf_specification</file> files in the
1092 <package>debian-policy</package> package.
1093 You may also find this file on the FTP site
1094 <ftpsite>ftp.debian.org</ftpsite> in
1095 <ftppath>/debian/doc/package-developer/debconf_specification.txt.gz</ftppath>
1096 or on your local mirror.<footnote>
1098 4% of Debian packages [see <url
1099 id="http://kitenet.net/programs/debconf/stats/"
1100 name="Debconf stats">] currently use
1101 <package>debconf</package> to prompt the user at
1102 install time, and this number is growing daily. The
1103 benefits of using debconf are briefly explained at
1105 id="http://kitenet.net/doc/debconf-doc/introduction.html"
1106 name="Debconf introduction">; they include
1107 preconfiguration, (mostly) noninteractive
1108 installation, elimination of redundant prompting,
1109 consistency of user interface, etc.
1112 With this increasing number of packages using
1113 <package>debconf</package>, plus the existance of a
1114 nascent second implementation of the Debian
1115 configuration management system
1116 (<package>cdebconf</package>), and the stabilization
1117 of the protocol these things use, the time has
1118 finally come to reflect the use of these things in
1125 Packages which use the Debian Configuration management
1126 specification may contain an additional
1127 <prgn>config</prgn> script and a <tt>templates</tt>
1128 file in their control archive. The <prgn>config</prgn>
1129 script might be run before the <prgn>preinst</prgn>
1130 script, and before the package is unpacked or any of its
1131 dependencies or pre-dependancies are satisfied.
1132 Therefore it must work using only the tools present in
1133 <em>essential</em> packages.<footnote>
1135 <package>Debconf</package> or another tool that
1136 implements the Debian Configuration management
1137 specification will also be installed, and any
1138 versioned dependencies on it will be satisfied
1139 before preconfiguration begins.
1145 Packages should try to minimize the amount of prompting
1146 they need to do, and they should ensure that the user
1147 will only ever be asked each question once. This means
1148 that packages should try to use appropriate shared
1149 configuration files (such as <file>/etc/papersize</file> and
1150 <file>/etc/news/server</file>), and shared
1151 <package>debconf</package> variables rather than each
1152 prompting for their own list of required pieces of
1157 It also means that an upgrade should not ask the same
1158 questions again, unless the user has used <tt>dpkg
1159 --purge</tt> to remove the package's configuration. The
1160 answers to configuration questions should be stored in an
1161 appropriate place in <file>/etc</file> so that the user can
1162 modify them, and how this has been done should be
1166 If a package has a vitally important piece of
1167 information to pass to the user (such as "don't run me
1168 as I am, you must edit the following configuration files
1169 first or you risk your system emitting badly-formatted
1170 messages"), it should display this in the
1171 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1172 prompt the user to hit return to acknowledge the
1173 message. Copyright messages do not count as vitally
1174 important (they belong in
1175 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1176 neither do instructions on how to use a program (these
1177 should be in on-line documentation, where all the users
1181 Any necessary prompting should almost always be confined
1182 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1183 script. If it is done in the <prgn>postinst</prgn>, it
1184 should be protected with a conditional so that
1185 unnecessary prompting doesn't happen if a package's
1186 installation fails and the <prgn>postinst</prgn> is
1187 called with <tt>abort-upgrade</tt>,
1188 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.</p>
1193 <heading>Source packages</heading>
1195 <sect1 id="standardsversion">
1196 <heading>Standards conformance</heading>
1199 In the source package's <tt>Standards-Version</tt> control
1200 field, you should specify the most recent version number
1201 of this policy document with which your package complied
1202 when it was last updated. The current version number is
1207 This information may be used to file bug reports
1208 automatically if your package becomes too much out of
1213 The version number has four components: major and minor
1214 version number and major and minor patch level. When the
1215 standards change in a way that requires every package to
1216 change the major number will be changed. Significant
1217 changes that will require work in many packages will be
1218 signaled by a change to the minor number. The major patch
1219 level will be changed for any change to the meaning of the
1220 standards, however small; the minor patch level will be
1221 changed when only cosmetic, typographical or other edits
1222 are made which neither change the meaning of the document
1223 nor affect the contents of packages.</p>
1226 Thus only the first three components of the policy version
1227 are significant in the <em>Standards-Version</em> control
1228 field, and so either these three components or the all
1229 four components may be specified.<footnote>
1231 In the past, people specified the full version number
1232 in the Standards-Version field, for example "2.3.0.0".
1233 Since minor patch-level changes don"t introduce new
1234 policy, it was thought it would be better to relax
1235 policy and only require the first 3 components to be
1236 specified, in this example "2.3.0". All four
1237 components may still be used if someone wishes to do
1244 You should regularly, and especially if your package has
1245 become out of date, check for the newest Policy Manual
1246 available and update your package, if necessary. When your
1247 package complies with the new standards you should update the
1248 <tt>Standards-Version</tt> source package field and
1249 release it.<footnote>
1251 See the file <file>upgrading-checklist</file> for
1252 information about policy which has changed between
1253 different versions of this document.
1261 <heading>Package relationships</heading>
1264 Source packages should specify which binary packages they
1265 require to be installed or not to be installed in order to
1266 build correctly. For example, if building a package
1267 requires a certain compiler, then the compiler should be
1268 specified as a build-time dependency.
1272 It is not necessary to explicitly specify build-time
1273 relationships on a minimal set of packages that are always
1274 needed to compile, link and put in a Debian package a
1275 standard "Hello World!" program written in C or C++. The
1276 required packages are called <em>build-essential</em>, and
1277 an informational list can be found in
1278 <file>/usr/share/doc/build-essential/list</file> (which is
1279 contained in the <tt>build-essential</tt>
1282 <list compact="compact">
1284 <p>This allows maintaining the list separately
1285 from the policy documents (the list does not
1286 need the kind of control that the policy
1292 Having a separate package allows one to install
1293 the build-essential packages on a machine, as
1294 well as allowing other packages such as tasks to
1295 require installation of the build-essential
1296 packages using the depends relation.
1301 The separate package allows bug reports against
1302 the list to be categorized separately from
1303 the policy management process in the BTS.
1313 When specifying the set of build-time dependencies, one
1314 should list only those packages explicitly required by the
1315 build. It is not necessary to list packages which are
1316 required merely because some other package in the list of
1317 build-time dependencies depends on them.<footnote>
1319 The reason for this is that dependencies change, and
1320 you should list all those packages, and <em>only</em>
1321 those packages that <em>you</em> need directly. What
1322 others need is their business. For example, if you
1323 only link against <file>libimlib</file>, you will need to
1324 build-depend on <package>libimlib2-dev</package> but
1325 not against any <tt>libjpeg*</tt> packages, even
1326 though <tt>libimlib2-dev</tt> currently depends on
1327 them: installation of <package>libimlib2-dev</package>
1328 will automatically ensure that all of its run-time
1329 dependencies are satisfied.
1335 If build-time dependencies are specified, it must be
1336 possible to build the package and produce working binaries
1337 on a system with only essential and build-essential
1338 packages installed and also those required to satisfy the
1339 build-time relationships (including any implied
1340 relationships). In particular, this means that version
1341 clauses should be used rigorously in build-time
1342 relationships so that one cannot produce bad or
1343 inconsistently configured packages when the relationships
1344 are properly satisfied.
1348 <heading>Changes to the upstream sources</heading>
1351 If changes to the source code are made that are not
1352 specific to the needs of the Debian system, they should be
1353 sent to the upstream authors in whatever form they prefer
1354 so as to be included in the upstream version of the
1358 If you need to configure the package differently for
1359 Debian or for Linux, and the upstream source doesn't
1360 provide a way to do so, you should add such configuration
1361 facilities (for example, a new <prgn>autoconf</prgn> test
1362 or <tt>#define</tt>) and send the patch to the upstream
1363 authors, with the default set to the way they originally
1364 had it. You can then easily override the default in your
1365 <file>debian/rules</file> or wherever is appropriate.</p>
1368 You should make sure that the <prgn>configure</prgn> utility
1369 detects the correct architecture specification string
1370 (refer to <ref id="arch-spec"> for details).</p>
1373 If you need to edit a <prgn>Makefile</prgn> where
1374 GNU-style <prgn>configure</prgn> scripts are used, you
1375 should edit the <file>.in</file> files rather than editing the
1376 <prgn>Makefile</prgn> directly. This allows the user to
1377 reconfigure the package if necessary. You should
1378 <em>not</em> configure the package and edit the generated
1379 <prgn>Makefile</prgn>! This makes it impossible for
1380 someone else to later reconfigure the package.</p>
1383 You should document your changes and updates to the source
1384 package properly in the <file>debian/changelog</file> file.
1385 For more information, please see <ref id="changelogs">.
1391 <heading>Error trapping in makefiles</heading>
1394 When <prgn>make</prgn> invokes a command in a makefile
1395 (including your package's upstream makefiles and
1396 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1397 means that <prgn>sh</prgn>'s usual bad error handling
1398 properties apply: if you include a miniature script as one
1399 of the commands in your makefile you'll find that if you
1400 don't do anything about it then errors are not detected
1401 and <prgn>make</prgn> will blithely continue after
1405 Every time you put more than one shell command (this
1406 includes using a loop) in a makefile command you
1407 must make sure that errors are trapped. For
1408 simple compound commands, such as changing directory and
1409 then running a program, using <tt>&&</tt> rather
1410 than semicolon as a command separator is sufficient. For
1411 more complex commands including most loops and
1412 conditionals you should include a separate <tt>set -e</tt>
1413 command at the start of every makefile command that's
1414 actually one of these miniature shell scripts.</p></sect1>
1418 <heading>Obsolete constructs and libraries</heading>
1421 The include file <tt><varargs.h></tt> is
1422 provided to support end-users compiling very old software;
1423 the library <tt>libtermcap</tt> is provided to support the
1424 execution of software which has been linked against it
1425 (either old programs or those such as Netscape which are
1426 only available in binary form).</p>
1429 Debian packages should be patched to use
1430 <tt><stdarg.h></tt> and <tt>ncurses</tt>
1437 <chapt id="controlfields"><heading>Control files and their fields</heading>
1440 Many of the tools in the package management suite manipulate
1441 data represented in a common format, known as <em>control
1442 data</em>. The data is often stored in <em>control
1443 files</em>. Binary and source packages have control files,
1444 and the <file>.changes</file> files which control the installation
1445 of uploaded files are also in control file format.
1446 <prgn>dpkg</prgn>'s internal databases are in a similar
1450 <sect id="controlsyntax"><heading>Syntax of control files</heading>
1453 A control file consists of one or more paragraphs of fields.
1454 The paragraphs are separated by blank lines. Some control
1455 files allow only one paragraph; others allow several, in
1456 which case each paragraph usually refers to a different
1457 package. (For example, in source packages, the first
1458 paragraph refers to the source package, and later paragraphs
1459 refer to binary packages generated from the source.)
1463 Each paragraph consists of a series of data fields; each
1464 field consists of the field name, followed by a colon and
1465 then the data/value associated with that field. It ends at
1466 the end of the line. Horizontal whitespace (spaces and
1467 tabs) may occur immediately before or after the value and is
1468 ignored there; it is conventional to put a single space
1469 after the colon. For example, a field might be:
1470 <example compact="compact">
1473 the field name is <tt>Package</tt> and the field value
1478 Some fields' values may span several lines; in this case
1479 each continuation line <em>must</em> start with a space or
1480 tab. Any trailing spaces or tabs at the end of individual
1481 lines of a field value are ignored.
1485 Except where otherwise stated only a single line of data is
1486 allowed and whitespace is not significant in a field body.
1487 Whitespace must not appear inside names (of packages,
1488 architectures, files or anything else) or version numbers,
1489 or between the characters of multi-character version
1494 Field names are not case-sensitive, but it is usual to
1495 capitalize the field names using mixed case as shown below.
1499 Blank lines, or lines consisting only of spaces and tabs,
1500 are not allowed within field values or between fields - that
1501 would mean a new paragraph.
1506 <sect><heading>List of fields</heading>
1508 This list here is not supposed to be exhaustive. Most fields
1509 are dealt with elsewhere in this document.
1511 <sect1 id="f-Package"><heading><tt>Package</tt>
1515 The name of the binary package. Package names consist of
1516 lower case letters (<tt>a-z</tt>), digits (<tt>0-9</tt>),
1517 plus (<tt>+</tt>) and minus (<tt>-</tt>) signs, and
1518 periods (<tt>.</tt>).
1522 They must be at least two characters long and must start
1523 with an alphanumeric character. The use of lowercase
1524 package names is required unless the package you're
1525 building (or referring to, in other fields) is already
1526 using uppercase characters.</p>
1529 <sect1 id="f-Version"><heading><tt>Version</tt>
1533 This lists the source or binary package's version number -
1534 see <ref id="versions">.
1540 id="f-Standards-Version"><heading><tt>Standards-Version</tt>
1544 The most recent version of the standards (the policy
1545 manual and associated texts) with which the package
1546 complies. This is updated manually when editing the
1547 source package to conform to newer standards; it can
1548 sometimes be used to tell when a package needs attention.
1549 Its format is described above; see
1550 <ref id="standardsversion">.
1555 <sect1 id="f-Distribution"><heading><tt>Distribution</tt>
1559 In a <file>.changes</file> file or parsed changelog output
1560 this contains the (space-separated) name(s) of the
1561 distribution(s) where this version of the package should
1562 be installed. Valid distributions are determined by the
1563 archive maintainers.<footnote>
1564 Current distribution names are:
1565 <taglist compact="compact">
1566 <tag><em>stable</em></tag>
1569 This is the current "released" version of Debian
1570 GNU/Linux. Once the distribution is
1571 <em>stable</em> only security fixes and other
1572 major bug fixes are allowed. When changes are
1573 made to this distribution, the release number is
1574 increased (for example: 2.2r1 becomes 2.2r2 then
1579 <tag><em>unstable</em></tag>
1582 This distribution value refers to the
1583 <em>developmental</em> part of the Debian
1584 distribution tree. New packages, new upstream
1585 versions of packages and bug fixes go into the
1586 <em>unstable</em> directory tree. Download from
1587 this distribution at your own risk.
1591 <tag><em>testing</em></tag>
1594 This distribution value refers to the
1595 <em>testing</em> part of the Debian distribution
1596 tree. It receives its packages from the
1597 unstable distribution after a short time lag to
1598 ensure that there are no major issues with the
1599 unstable packages. It is less prone to breakage
1600 than unstable, but still risky. It is not
1601 possible to upload packages directly to
1606 <tag><em>frozen</em></tag>
1609 From time to time, the <em>testing</em>
1610 distribution enters a state of "code-freeze" in
1611 anticipation of release as a <em>stable</em>
1612 version. During this period of testing only
1613 fixes for existing or newly-discovered bugs will
1614 be allowed. The exact details of this stage are
1615 determined by the Release Manager.
1619 <tag><em>experimental</em></tag>
1622 The packages with this distribution value are
1623 deemed by their maintainers to be high
1624 risk. Oftentimes they represent early beta or
1625 developmental packages from various sources that
1626 the maintainers want people to try, but are not
1627 ready to be a part of the other parts of the
1628 Debian distribution tree. Download at your own
1634 You should list <em>all</em> distributions that the
1635 package should be installed into.
1644 <chapt id="versions"><heading>Version numbering</heading>
1647 Every package has a version number recorded in its
1648 <tt>Version</tt> control file field.
1652 The package management system imposes an ordering on version
1653 numbers, so that it can tell whether packages are being up- or
1654 downgraded and so that package system front end applications
1655 can tell whether a package it finds available is newer than
1656 the one installed on the system. The version number format
1657 has the most significant parts (as far as comparison is
1658 concerned) at the beginning.
1662 The version number format is:
1663 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
1667 The three components here are:
1669 <tag><var>epoch</var></tag>
1672 This is a single (generally small) unsigned integer. It
1673 may be omitted, in which case zero is assumed. If it is
1674 omitted then the <var>upstream_version</var> may not
1679 It is provided to allow mistakes in the version numbers
1680 of older versions of a package, and also a package's
1681 previous version numbering schemes, to be left behind.
1685 <tag><var>upstream_version</var></tag>
1688 This is the main part of the version number. It is
1689 usually the version number of the original ("upstream")
1690 package from which the <file>.deb</file> file has been made,
1691 if this is applicable. Usually this will be in the same
1692 format as that specified by the upstream author(s);
1693 however, it may need to be reformatted to fit into the
1694 package management system's format and comparison
1699 The comparison behavior of the package management system
1700 with respect to the <var>upstream_version</var> is
1701 described below. The <var>upstream_version</var>
1702 portion of the version number is mandatory.
1706 The <var>upstream_version</var> may contain only
1707 alphanumerics<footnote>
1708 <p>Alphanumerics are <tt>A-Za-z0-9</tt> only.</p>
1710 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
1711 <tt>:</tt> (full stop, plus, hyphen, colon) and should
1712 start with a digit. If there is no
1713 <var>debian_revision</var> then hyphens are not allowed;
1714 if there is no <var>epoch</var> then colons are not
1718 <tag><var>debian_revision</var></tag>
1721 This part of the version number specifies the version of
1722 the Debian package based on the upstream version. It
1723 may contain only alphanumerics and the characters
1724 <tt>+</tt> and <tt>.</tt> (plus and full stop) and is
1725 compared in the same way as the
1726 <var>upstream_version</var> is.
1730 It is optional; if it isn't present then the
1731 <var>upstream_version</var> may not contain a hyphen.
1732 This format represents the case where a piece of
1733 software was written specifically to be turned into a
1734 Debian package, and so there is only one "debianization"
1735 of it and therefore no revision indication is required.
1739 It is conventional to restart the
1740 <var>debian_revision</var> at <tt>1</tt> each time the
1741 <var>upstream_version</var> is increased.
1745 The package management system will break the version
1746 number apart at the last hyphen in the string (if there
1747 is one) to determine the <var>upstream_version</var> and
1748 <var>debian_revision</var>. The absence of a
1749 <var>debian_revision</var> compares earlier than the
1750 presence of one (but note that the
1751 <var>debian_revision</var> is the least significant part
1752 of the version number).
1759 The <var>upstream_version</var> and <var>debian_revision</var>
1760 parts are compared by the package management system using the
1765 The strings are compared from left to right.
1769 First the initial part of each string consisting entirely of
1770 non-digit characters is determined. These two parts (one of
1771 which may be empty) are compared lexically. If a difference
1772 is found it is returned. The lexical comparison is a
1773 comparison of ASCII values modified so that all the letters
1774 sort earlier than all the non-letters.
1778 Then the initial part of the remainder of each string which
1779 consists entirely of digit characters is determined. The
1780 numerical values of these two parts are compared, and any
1781 difference found is returned as the result of the comparison.
1782 For these purposes an empty string (which can only occur at
1783 the end of one or both version strings being compared) counts
1788 These two steps (comparing and removing initial non-digit
1789 strings and initial digit strings) are repeated until a
1790 difference is found or both strings are exhausted.
1794 Note that the purpose of epochs is to allow us to leave behind
1795 mistakes in version numbering, and to cope with situations
1796 where the version numbering scheme changes. It is
1797 <em>not</em> intended to cope with version numbers containing
1798 strings of letters which the package management system cannot
1799 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
1800 silly orderings (the author of this manual has heard of a
1801 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
1802 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
1803 <tt>2</tt> and so forth).
1807 If an upstream package has problematic version numbers they
1808 should be converted to a sane form for use in the
1809 <tt>Version</tt> field.
1813 <heading>Version numbers based on dates</heading>
1815 In general, Debian packages should use the same version
1816 numbers as the upstream sources.</p>
1819 However, in some cases where the upstream version number is
1820 based on a date (e.g., a development "snapshot" release) the
1821 package management system cannot handle these version
1822 numbers without epochs. For example, dpkg will consider
1823 "96May01" to be greater than "96Dec24".</p>
1826 To prevent having to use epochs for every new upstream
1827 version, the version number should be changed to the
1828 following format in such cases: "19960501", "19961224". It
1829 is up to the maintainer whether he/she wants to bother the
1830 upstream maintainer to change the version numbers upstream,
1834 Note that other version formats based on dates which are
1835 parsed correctly by the package management system should
1836 <em>not</em> be changed.</p>
1839 Native Debian packages (i.e., packages which have been
1840 written especially for Debian) whose version numbers include
1841 dates should always use the "YYYYMMDD" format.</p>
1845 <chapt id="miscellaneous"><heading>Packaging Considerations</heading>
1847 <sect id="timestamps"><heading>Time Stamps</heading>
1849 Maintainers should preserve the modification times of the
1850 upstream source files in a package, as far as is reasonably
1853 The rationale is that there is some information conveyed
1854 by knowing the age of the file, for example, you could
1855 recognize that some documentation is very old by looking
1856 at the modification time, so it would be nice if the
1857 modification time of the upstream source would be
1864 <sect id="debianrules"><heading><file>debian/rules</file> - the
1865 main building script</heading>
1868 This file must be an executable makefile, and contains the
1869 package-specific recipes for compiling the package and
1870 building binary package(s) from the source.
1874 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1875 so that it can be invoked by saying its name rather than
1876 invoking <prgn>make</prgn> explicitly.
1880 Since an interactive <file>debian/rules</file> script makes it
1881 impossible to auto-compile that package and also makes it
1882 hard for other people to reproduce the same binary
1883 package, all <em>required targets</em> MUST be
1884 non-interactive. At a minimum, required targets are the
1885 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1886 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1887 <em>binary-indep</em>, and <em>build</em>. It also follows
1888 that any target that these targets depend on must also be
1893 The required and optional targets are as follows:
1895 <tag><tt>build</tt>, <tt>build-arch</tt> (optional),
1896 <tt>build-indep</tt> (optional)</tag>
1899 The <tt>build</tt> target should perform all
1900 non-interactive configuration and compilation of the
1901 package. If a package has an interactive pre-build
1902 configuration routine, the Debianized source package
1903 must either be built after this has taken place (so
1904 that the binary package can be built without rerunning
1905 the configuration) or the configuration routine
1906 modified to become non-interactive. (The latter is
1907 preferable if there are architecture-specific features
1908 detected by the configuration routine.)
1912 For some packages, notably ones where the same
1913 source tree is compiled in different ways to produce
1914 two binary packages, the <tt>build</tt> target
1915 does not make much sense. For these packages it is
1916 good enough to provide two (or more) targets
1917 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1918 for each of the ways of building the package, and a
1919 <tt>build</tt> target that does nothing. The
1920 <tt>binary</tt> target will have to build the
1921 package in each of the possible ways and make the
1922 binary package out of each.
1926 The <tt>build</tt> target must not do anything
1927 that might require root privilege.
1931 The <tt>build</tt> target may need to run the
1932 <tt>clean</tt> target first - see below.
1936 When a package has a configuration and build routine
1937 which takes a long time, or when the makefiles are
1938 poorly designed, or when <tt>build</tt> needs to
1939 run <tt>clean</tt> first, it is a good idea to
1940 <tt>touch build</tt> when the build process is
1941 complete. This will ensure that if <tt>debian/rules
1942 build</tt> is run again it will not rebuild the whole
1945 Another common way to do this is for <tt>build</tt>
1946 to depend on <prgn>build-stamp</prgn> and to do
1947 nothing else, and for the <prgn>build-stamp</prgn>
1948 target to do the building and to <tt>touch
1949 build-stamp</tt> on completion. This is
1950 especially useful if the build routine creates a
1951 file or directory called <tt>build</tt>; in such a
1952 case, <tt>build</tt> will need to be listed as
1953 a phony target (i.e., as a dependency of the
1954 <tt>.PHONY</tt> target). See the documentation of
1955 <prgn>make</prgn> for more information on phony
1962 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1963 <tt>binary-indep</tt>
1967 The <tt>binary</tt> target must be all that is
1968 necessary for the user to build the binary package(s)
1969 produced from this source package. All of these
1970 targets are required to be non-interactive. It is
1971 split into two parts: <prgn>binary-arch</prgn> builds
1972 the binary packages which are specific to a particular
1973 architecture, and <tt>binary-indep</tt> builds
1974 those which are not.
1977 <tt>binary</tt> may be (and commonly is) a target with
1978 no commands which simply depends on
1979 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1982 Both <tt>binary-*</tt> targets should depend on the
1983 <tt>build</tt> target, or on the appropriate
1984 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1985 provided, so that the package is built if it has not
1986 been already. It should then create the relevant
1987 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1988 make their control files and <prgn>dpkg-deb</prgn> to
1989 build them and place them in the parent of the top
1994 Both the <tt>binary-arch</tt> and
1995 <tt>binary-indep</tt> targets <em>must</em> exist.
1996 If one of them has nothing to do (which will always be
1997 the case if the source generates only a single binary
1998 package, whether architecture-dependent or not), it
1999 must still exist and must always succeed.
2003 The <tt>binary</tt> targets must be invoked as
2006 The <prgn>fakeroot</prgn> package often allows one
2007 to build a package correctly even without being
2014 <tag><tt>clean</tt></tag>
2017 This must undo any effects that the <tt>build</tt>
2018 and <tt>binary</tt> targets may have had, except
2019 that it should leave alone any output files created in
2020 the parent directory by a run of a <tt>binary</tt>
2021 target. This target must be non-interactive.
2025 If a <tt>build</tt> file is touched at the end of
2026 the <tt>build</tt> target, as suggested above, it
2027 should be removed as the first action that
2028 <tt>clean</tt> performs, so that running
2029 <tt>build</tt> again after an interrupted
2030 <tt>clean</tt> doesn't think that everything is
2035 The <tt>clean</tt> target may need to be
2036 invoked as root if <tt>binary</tt> has been
2037 invoked since the last <tt>clean</tt>, or if
2038 <tt>build</tt> has been invoked as root (since
2039 <tt>build</tt> may create directories, for
2044 <tag><tt>get-orig-source</tt> (optional)</tag>
2047 This target fetches the most recent version of the
2048 original source package from a canonical archive site
2049 (via FTP or WWW, for example), does any necessary
2050 rearrangement to turn it into the original source
2051 tar file format described below, and leaves it in the
2056 This target may be invoked in any directory, and
2057 should take care to clean up any temporary files it
2062 This target is optional, but providing it if
2063 possible is a good idea.
2069 The <tt>build</tt>, <tt>binary</tt> and
2070 <tt>clean</tt> targets must be invoked with the current
2071 directory being the package's top-level directory.
2076 Additional targets may exist in <file>debian/rules</file>,
2077 either as published or undocumented interfaces or for the
2078 package's internal use.
2082 The architectures we build on and build for are determined
2083 by <prgn>make</prgn> variables using the utility
2084 <prgn>dpkg-architecture</prgn>. You can determine the
2085 Debian architecture and the GNU style architecture
2086 specification string for the build machine (the machine type
2087 we are building on) as well as for the host machine (the
2088 machine type we are building for). Here is a list of
2089 supported <prgn>make</prgn> variables:
2090 <list compact="compact">
2092 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
2095 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2096 specification string)</p>
2099 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of
2100 <tt>DEB_*_GNU_TYPE</tt>)</p>
2103 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2104 <tt>DEB_*_GNU_TYPE</tt>)</p>
2106 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2107 the build machine or <tt>HOST</tt> for specification of the
2112 Backward compatibility can be provided in the rules file
2113 by setting the needed variables to suitable default
2114 values; please refer to the documentation of
2115 <prgn>dpkg-architecture</prgn> for details.
2119 It is important to understand that the <tt>DEB_*_ARCH</tt>
2120 string only determines which Debian architecture we are
2121 building on or for. It should not be used to get the CPU
2122 or system information; the GNU style variables should be
2127 <sect id="dpkgchangelog"><heading><file>debian/changelog</file>
2131 This file records the changes to the Debian-specific parts of the
2134 Though there is nothing stopping an author who is also
2135 the Debian maintainer from using it for all their
2136 changes, it will have to be renamed if the Debian and
2137 upstream maintainers become different people. In such a
2138 case, however, it might be better to maintain the
2139 package as a non-native package.
2145 It has a special format which allows the package building
2146 tools to discover which version of the package is being
2147 built and find out other release-specific information.
2151 That format is a series of entries like this:
2152 <example compact="compact">
2153 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
2155 <p>[optional blank line(s), stripped]</p>
2157 * <var>change details</var>
2158 <var>more change details</var>
2160 <p>[blank line(s), included in output of dpkg-parsechangelog]</p>
2162 * <var>even more change details</var>
2164 <p>[optional blank line(s), stripped]</p>
2166 -- <var>maintainer name</var> <<var>email
2167 address</var>><var>[two spaces]</var> <var>date</var>
2172 <var>package</var> and <var>version</var> are the source
2173 package name and version number.
2177 <var>distribution(s)</var> lists the distributions where
2178 this version should be installed when it is uploaded - it
2179 is copied to the <tt>Distribution</tt> field in the
2180 <file>.changes</file> file. See <ref id="f-Distribution">.
2184 <var>urgency</var> is the value for the <tt>Urgency</tt>
2185 field in the <file>.changes</file> file for the upload. It is
2186 not possible to specify an urgency containing commas; commas
2187 are used to separate
2188 <tt><var>keyword</var>=<var>value</var></tt> settings in the
2189 <prgn>dpkg</prgn> changelog format (though there is
2190 currently only one useful <var>keyword</var>,
2191 <tt>urgency</tt>).<footnote>
2193 Recognised urgency values are <tt>low</tt>,
2194 <tt>medium</tt>, <tt>high</tt> and <tt>emergency</tt>.
2195 They have an effect on how quickly a package will be
2196 considered for inclusion into the <tt>testing</tt>
2197 distribution, and give an indication of the importance
2198 of any fixes included in this upload.
2204 The change details may in fact be any series of lines
2205 starting with at least two spaces, but conventionally each
2206 change starts with an asterisk and a separating space and
2207 continuation lines are indented so as to bring them in
2208 line with the start of the text above. Blank lines may be
2209 used here to separate groups of changes, if desired.
2213 If this upload resolves bugs recorded in the Bug Tracking
2214 System (BTS), they may be automatically closed on the
2215 inclusion of this package into the Debian archive by
2216 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
2217 in the change details.<footnote>
2219 To be precise, the string should match the following
2220 Perl regular expression:
2222 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
2224 Then all of the bug numbers listed will be closed by the
2225 archive maintenance script (<prgn>katie</prgn>), or in
2226 the case of an NMU, marked as fixed.
2232 The maintainer name and email address used in the changelog
2233 should be the details of the person uploading <em>this</em>
2234 version. They are <em>not</em> necessarily those of the
2235 usual package maintainer. The information here will be
2236 copied to the <tt>Changed-By</tt> field in the
2237 <tt>.changes</tt> file, and then later used to send an
2238 acknowledgement when the upload has been installed.
2242 The <var>date</var> should be in RFC822 format<footnote>
2244 This is generated by the <prgn>822-date</prgn>
2247 </footnote>; it should include the time zone specified
2248 numerically, with the time zone name or abbreviation
2249 optionally present as a comment in parentheses.
2253 The first "title" line with the package name should start
2254 at the left hand margin; the "trailer" line with the
2255 maintainer and date details should be preceded by exactly
2256 one space. The maintainer details and the date must be
2257 separated by exactly two spaces.
2260 <sect1><heading>Defining alternative changelog formats</heading>
2263 It is possible to use a different format to the standard
2264 one, by providing a parser for the format you wish to
2268 A changelog parser must not interact with the user at
2274 <sect id="srcsubstvars"><heading><file>debian/substvars</file>
2275 and variable substitutions </heading>
2278 When <prgn>dpkg-gencontrol</prgn>,
2279 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2280 generate control files they perform variable substitutions
2281 on their output just before writing it. Variable
2282 substitutions have the form <tt>${<var>variable</var>}</tt>.
2283 The optional file <file>debian/substvars</file> contains
2284 variable substitutions to be used; variables can also be set
2285 directly from <file>debian/rules</file> using the <tt>-V</tt>
2286 option to the source packaging commands, and certain
2287 predefined variables are also available.
2291 The <file>debian/substvars</file> file is usually generated and
2292 modified dynamically by <file>debian/rules</file> targets; in
2293 this case it must be removed by the <tt>clean</tt>
2298 See <manref name="dpkg-source" section="1"> for full
2299 details about source variable substitutions, including the
2300 format of <file>debian/substvars</file>.</p>
2303 <sect id="debianfiles"><heading><file>debian/files</file>
2307 This file is not a permanent part of the source tree; it
2308 is used while building packages to record which files are
2309 being generated. <prgn>dpkg-genchanges</prgn> uses it
2310 when it generates a <file>.changes</file> file.
2314 It should not exist in a shipped source package, and so it
2315 (and any backup files or temporary files such as
2316 <file>files.new</file><footnote>
2318 <file>files.new</file> is used as a temporary file by
2319 <prgn>dpkg-gencontrol</prgn> and
2320 <prgn>dpkg-distaddfile</prgn> - they write a new
2321 version of <tt>files</tt> here before renaming it,
2322 to avoid leaving a corrupted copy if an error
2325 </footnote>) should be removed by the
2326 <tt>clean</tt> target. It may also be wise to
2327 ensure a fresh start by emptying or removing it at the
2328 start of the <tt>binary</tt> target.
2332 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2333 package, it adds an entry to <file>debian/files</file> for the
2334 <file>.deb</file> file that will be created when <tt>dpkg-deb
2335 --build</tt> is run for that binary package. So for most
2336 packages all that needs to be done with this file is to
2337 delete it in the <tt>clean</tt> target.
2341 If a package upload includes files besides the source
2342 package and any binary packages whose control files were
2343 made with <prgn>dpkg-gencontrol</prgn> then they should be
2344 placed in the parent of the package's top-level directory
2345 and <prgn>dpkg-distaddfile</prgn> should be called to add
2346 the file to the list in <file>debian/files</file>.</p>
2349 <sect id="restrictions"><heading>Restrictions on objects in source packages
2353 The source package may not contain any hard links<footnote>
2355 This is not currently detected when building source
2356 packages, but only when extracting
2360 Hard links may be permitted at some point in the
2361 future, but would require a fair amount of
2364 </footnote>, device special files, sockets or setuid or
2365 setgid files.<footnote>
2367 Setgid directories are allowed.
2372 <sect id="descriptions"><heading>Descriptions of packages - the
2373 <tt>Description</tt> field </heading>
2376 The description is intended to describe the program to a user
2377 who has never met it before so that they know whether they
2378 want to install it. It should also give information about the
2379 significant dependencies and conflicts between this package
2380 and others, so that the user knows why these dependencies and
2381 conflicts have been declared.
2384 <sect1><heading>Notes about writing descriptions
2388 The single line synopsis should be kept brief - certainly
2389 under 80 characters.
2393 Do not include the package name in the synopsis line. The
2394 display software knows how to display this already, and you
2395 do not need to state it. Remember that in many situations
2396 the user may only see the synopsis line - make it as
2397 informative as you can.
2401 Do not try to continue the single line synopsis into the
2402 extended description. This will not work correctly when
2403 the full description is displayed, and makes no sense
2404 where only the summary (the single line synopsis) is
2409 The extended description should describe what the package
2410 does and how it relates to the rest of the system (in terms
2411 of, for example, which subsystem it is which part of).
2415 The description field needs to make sense to anyone, even
2416 people who have no idea about any of the things the
2417 package deals with.<footnote>
2419 The blurb that comes with a program in its
2420 announcements and/or <prgn>README</prgn> files is
2421 rarely suitable for use in a description. It is
2422 usually aimed at people who are already in the
2423 community where the package is used.
2429 Put important information first, both in the synopsis and
2430 extended description. Sometimes only the first part of the
2431 synopsis or of the description will be displayed. You can
2432 assume that there will usually be a way to see the whole
2433 extended description.
2437 You may include information about dependencies and so forth
2438 in the extended description, if you wish.
2442 Do not use tab characters. Their effect is not predictable.
2450 <chapt id="maintainerscripts"><heading>Package maintainer scripts
2451 and installation procedure
2454 <sect><heading>Introduction to package maintainer scripts
2458 It is possible to supply scripts as part of a package which
2459 the package management system will run for you when your
2460 package is installed, upgraded or removed.
2464 These scripts are the files <prgn>preinst</prgn>,
2465 <prgn>postinst</prgn>, <prgn>prerm</prgn> and <prgn>postrm</prgn> in the
2466 control area of the package. They must be proper executable
2467 files; if they are scripts (which is recommended), they must
2468 start with the usual <tt>#!</tt> convention. They should be
2469 readable and executable by anyone, and not world-writable.
2473 The package management system looks at the exit status from
2474 these scripts. It is important that they exit with a
2475 non-zero status if there is an error, so that the package
2476 management system can stop its processing. For shell
2477 scripts this means that you <em>almost always</em> need to
2478 use <tt>set -e</tt> (this is usually true when writing shell
2479 scripts, in fact). It is also important, of course, that
2480 they don't exit with a non-zero status if everything went
2485 When a package is upgraded a combination of the scripts from
2486 the old and new packages is called during the upgrade
2487 procedure. If your scripts are going to be at all
2488 complicated you need to be aware of this, and may need to
2489 check the arguments to your scripts.
2493 Broadly speaking the <prgn>preinst</prgn> is called before
2494 (a particular version of) a package is installed, and the
2495 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
2496 before (a version of) a package is removed and the
2497 <prgn>postrm</prgn> afterwards.
2501 Programs called from maintainer scripts should not normally
2502 have a path prepended to them. Before installation is
2503 started, the package management system checks to see if the
2504 programs <prgn>ldconfig</prgn>,
2505 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
2506 and <prgn>update-rc.d</prgn> can be found via the
2507 <tt>PATH</tt> environment variable. Those programs, and any
2508 other program that one would expect to be on the
2509 <tt>PATH</tt>, should thus be invoked without an absolute
2510 pathname. Maintainer scripts should also not reset the
2511 <tt>PATH</tt>, though they might choose to modify it by
2512 prepending or appending package-specific directories. These
2513 considerations really apply to all shell scripts.</p>
2517 <heading>Maintainer scripts Idempotency</heading>
2520 It is necessary for the error recovery procedures that the
2521 scripts be idempotent. This means that if it is run
2522 successfully, and then it is called again, it doesn't bomb
2523 out or cause any harm, but just ensures that everything is
2524 the way it ought to be. If the first call failed, or
2525 aborted half way through for some reason, the second call
2526 should merely do the things that were left undone the first
2527 time, if any, and exit with a success status if everything
2530 This is so that if an error occurs, the user interrupts
2531 <prgn>dpkg</prgn> or some other unforeseen circumstance
2532 happens you don't leave the user with a badly-broken
2533 package when <prgn>dpkg</prgn> attempts to repeat the
2541 <heading>Controlling terminal for maintainer scripts</heading>
2544 The maintainer scripts are guaranteed to run with a
2545 controlling terminal and can interact with the user.
2546 If they need to prompt for passwords, do full-screen
2547 interaction or something similar you should do these
2548 things to and from <file>/dev/tty</file>, since
2549 <prgn>dpkg</prgn> will at some point redirect scripts'
2550 standard input and output so that it can log the
2551 installation process. Likewise, because these scripts
2552 may be executed with standard output redirected into a
2553 pipe for logging purposes, Perl scripts should set
2554 unbuffered output by setting <tt>$|=1</tt> so that the
2555 output is printed immediately rather than being
2560 Each script should return a zero exit status for
2561 success, or a nonzero one for failure.
2565 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
2570 <list compact="compact">
2572 <p><var>new-preinst</var> <tt>install</tt></p>
2575 <p><var>new-preinst</var> <tt>install</tt>
2576 <var>old-version</var></p>
2579 <p><var>new-preinst</var> <tt>upgrade</tt>
2580 <var>old-version</var></p>
2583 <p><var>old-preinst</var> <tt>abort-upgrade</tt>
2584 <var>new-version</var>
2590 <list compact="compact">
2592 <p><var>postinst</var> <tt>configure</tt>
2593 <var>most-recently-configured-version</var></p>
2596 <p><var>old-postinst</var> <tt>abort-upgrade</tt>
2597 <var>new-version</var></p>
2600 <p><var>conflictor's-postinst</var> <tt>abort-remove</tt>
2601 <tt>in-favour</tt> <var>package</var>
2602 <var>new-version</var></p>
2606 <var>deconfigured's-postinst</var>
2607 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
2608 <var>failed-install-package</var> <var>version</var>
2609 <tt>removing</tt> <var>conflicting-package</var>
2616 <list compact="compact">
2618 <p><var>prerm</var> <tt>remove</tt></p>
2621 <p><var>old-prerm</var> <tt>upgrade</tt>
2622 <var>new-version</var></p>
2625 <p><var>new-prerm</var> <tt>failed-upgrade</tt>
2626 <var>old-version</var></p>
2629 <p><var>conflictor's-prerm</var> <tt>remove</tt>
2630 <tt>in-favour</tt> <var>package</var>
2631 <var>new-version</var></p>
2635 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
2636 <tt>in-favour</tt> <var>package-being-installed</var>
2637 <var>version</var> <tt>removing</tt>
2638 <var>conflicting-package</var>
2645 <list compact="compact">
2647 <p><var>postrm</var> <tt>remove</tt></p>
2650 <p><var>postrm</var> <tt>purge</tt></p>
2654 <var>old-postrm</var> <tt>upgrade</tt>
2655 <var>new-version</var></p>
2658 <p><var>new-postrm</var> <tt>failed-upgrade</tt>
2659 <var>old-version</var></p>
2662 <p><var>new-postrm</var> <tt>abort-install</tt></p>
2665 <p><var>new-postrm</var> <tt>abort-install</tt>
2666 <var>old-version</var></p>
2669 <p><var>new-postrm</var> <tt>abort-upgrade</tt>
2670 <var>old-version</var></p>
2674 <var>disappearer's-postrm</var> <tt>disappear</tt>
2675 <var>overwriter</var>
2676 <var>overwriter-version</var></p></item>
2681 <sect id="unpackphase"><heading>Details of unpack phase of
2682 installation or upgrade
2686 The procedure on installation/upgrade/overwrite/disappear
2687 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
2688 stage of <tt>dpkg --install</tt>) is as follows. In each
2689 case, if a major error occurs (unless listed below) the
2690 actions are, in general, run backwards - this means that the
2691 maintainer scripts are run with different arguments in
2692 reverse order. These are the "error unwind" calls listed
2700 <p>If a version of the package is already
2702 <example compact="compact">
2703 <var>old-prerm</var> upgrade <var>new-version</var>
2708 If the script runs but exits with a non-zero
2709 exit status, <prgn>dpkg</prgn> will attempt:
2710 <example compact="compact">
2711 <var>new-prerm</var> failed-upgrade <var>old-version</var>
2713 Error unwind, for both the above cases:
2714 <example compact="compact">
2715 <var>old-postinst</var> abort-upgrade <var>new-version</var>
2723 <p>If a "conflicting" package is being removed at the same time:
2727 If any packages depended on that conflicting
2728 package and <tt>--auto-deconfigure</tt> is
2729 specified, call, for each such package:
2730 <example compact="compact">
2731 <var>deconfigured's-prerm</var> deconfigure \
2732 in-favour <var>package-being-installed</var> <var>version</var> \
2733 removing <var>conflicting-package</var> <var>version</var>
2736 <example compact="compact">
2737 <var>deconfigured's-postinst</var> abort-deconfigure \
2738 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
2739 removing <var>conflicting-package</var> <var>version</var>
2741 The deconfigured packages are marked as
2742 requiring configuration, so that if
2743 <tt>--install</tt> is used they will be
2744 configured again if possible.</p>
2747 <p>To prepare for removal of the conflicting package, call:
2748 <example compact="compact">
2749 <var>conflictor's-prerm</var> remove \
2750 in-favour <var>package</var> <var>new-version</var>
2753 <example compact="compact">
2754 <var>conflictor's-postinst</var> abort-remove \
2755 in-favour <var>package</var> <var>new-version</var>
2766 <p>If the package is being upgraded, call:
2767 <example compact="compact">
2768 <var>new-preinst</var> upgrade <var>old-version</var>
2773 Otherwise, if the package had some configuration
2774 files from a previous version installed (i.e., it
2775 is in the "configuration files only" state):
2776 <example compact="compact">
2777 <var>new-preinst</var> install <var>old-version</var>
2781 <p>Otherwise (i.e., the package was completely purged):
2782 <example compact="compact">
2783 <var>new-preinst</var> install
2785 Error unwind actions, respectively:
2786 <example compact="compact">
2787 <var>new-postrm</var> abort-upgrade <var>old-version</var>
2788 <var>new-postrm</var> abort-install <var>old-version</var>
2789 <var>new-postrm</var> abort-install
2798 The new package's files are unpacked, overwriting any
2799 that may be on the system already, for example any
2800 from the old version of the same package or from
2801 another package. Backups of the old files are kept
2802 temporarily, and if anything goes wrong the package
2803 management system will attempt to put them back as
2804 part of the error unwind.
2808 It is an error for a package to contains files which
2809 are on the system in another package, unless
2810 <tt>Replaces</tt> is used (see <ref id="replaces">).
2812 The following paragraph is not currently the case:
2813 Currently the <tt>- - force-overwrite</tt> flag is
2814 enabled, downgrading it to a warning, but this may not
2820 It is a more serious error for a package to contain a
2821 plain file or other kind of non-directory where another
2822 package has a directory (again, unless
2823 <tt>Replaces</tt> is used). This error can be
2824 overridden if desired using
2825 <tt>--force-overwrite-dir</tt>, but this is not
2830 Packages which overwrite each other's files produce
2831 behavior which, though deterministic, is hard for the
2832 system administrator to understand. It can easily
2833 lead to "missing" programs if, for example, a package
2834 is installed which overwrites a file from another
2835 package, and is then removed again.<footnote>
2837 Part of the problem is due to what is arguably a
2838 bug in <prgn>dpkg</prgn>.
2844 A directory will never be replaced by a symbolic link
2845 to a directory or vice versa; instead, the existing
2846 state (symlink or not) will be left alone and
2847 <prgn>dpkg</prgn> will follow the symlink if there is
2855 <p>If the package is being upgraded, call
2856 <example compact="compact">
2857 <var>old-postrm</var> upgrade <var>new-version</var>
2862 <p>If this fails, <prgn>dpkg</prgn> will attempt:
2863 <example compact="compact">
2864 <var>new-postrm</var> failed-upgrade <var>old-version</var>
2866 Error unwind, for both cases:
2867 <example compact="compact">
2868 <var>old-preinst</var> abort-upgrade <var>new-version</var>
2875 This is the point of no return - if
2876 <prgn>dpkg</prgn> gets this far, it won't back off
2877 past this point if an error occurs. This will
2878 leave the package in a fairly bad state, which
2879 will require a successful re-installation to clear
2880 up, but it's when <prgn>dpkg</prgn> starts doing
2881 things that are irreversible.
2886 Any files which were in the old version of the package
2887 but not in the new are removed.</p>
2890 <p>The new file list replaces the old.</p>
2893 <p>The new maintainer scripts replace the old.</p>
2897 <p>Any packages all of whose files have been overwritten during the
2898 installation, and which aren't required for
2899 dependencies, are considered to have been removed.
2900 For each such package
2903 <p><prgn>dpkg</prgn> calls:
2904 <example compact="compact">
2905 <var>disappearer's-postrm</var> disappear \
2906 <var>overwriter</var> <var>overwriter-version</var>
2911 <p>The package's maintainer scripts are removed.
2916 It is noted in the status database as being in a
2917 sane state, namely not installed (any conffiles
2918 it may have are ignored, rather than being
2919 removed by <prgn>dpkg</prgn>). Note that
2920 disappearing packages do not have their prerm
2921 called, because <prgn>dpkg</prgn> doesn't know
2922 in advance that the package is going to
2931 Any files in the package we're unpacking that are also
2932 listed in the file lists of other packages are removed
2933 from those lists. (This will lobotomize the file list
2934 of the "conflicting" package if there is one.)
2939 The backup files made during installation, above, are
2946 The new package's status is now sane, and recorded as
2951 Here is another point of no return - if the
2952 conflicting package's removal fails we do not unwind
2953 the rest of the installation; the conflicting package
2954 is left in a half-removed limbo.
2960 If there was a conflicting package we go and do the
2961 removal actions (described below), starting with the
2962 removal of the conflicting package's files (any that
2963 are also in the package being installed have already
2964 been removed from the conflicting package's file list,
2965 and so do not get removed now).
2972 <sect id="configdetails"><heading>Details of configuration</heading>
2975 When we configure a package (this happens with <tt>dpkg
2976 --install</tt> and <tt>dpkg --configure</tt>), we first
2977 update any <tt>conffile</tt>s and then call:
2978 <example compact="compact">
2979 <var>postinst</var> configure <var>most-recently-configured-version</var>
2984 No attempt is made to unwind after errors during
2989 If there is no most recently configured version
2990 <prgn>dpkg</prgn> will pass a null argument; older versions
2991 of dpkg may pass <tt><unknown></tt> (including the
2992 angle brackets) in this case. Even older ones do not pass a
2993 second argument at all, under any circumstances.
2997 <sect id="removedetails"><heading>Details of removal and/or
2998 configuration purging</heading>
3004 <example compact="compact">
3005 <var>prerm</var> remove
3011 The package's files are removed (except <tt>conffile</tt>s).
3016 <example compact="compact">
3017 <var>postrm</var> remove
3023 All the maintainer scripts except the <prgn>postrm</prgn>
3028 If we aren't purging the package we stop here. Note
3029 that packages which have no <prgn>postrm</prgn> and no
3030 <tt>conffile</tt>s are automatically purged when
3031 removed, as there is no difference except for the
3032 <prgn>dpkg</prgn> status.</p>
3036 The <tt>conffile</tt>s and any backup files
3037 (<tt>~</tt>-files, <tt>#*#</tt> files,
3038 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3043 <example compact="compact">
3044 <var>postrm</var> purge
3049 <p>The package's file list is removed.</p>
3052 No attempt is made to unwind after errors during
3059 <chapt id="relationships"><heading>Declaring relationships between
3063 Packages can declare in their control file that they have
3064 certain relationships to other packages - for example, that
3065 they may not be installed at the same time as certain other
3066 packages, and/or that they depend on the presence of others,
3067 or that they should overwrite files in certain other packages
3072 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3073 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3074 <tt>Conflicts</tt>, <tt>Provides</tt> and <tt>Replaces</tt>
3075 control file fields.
3079 Source packages may declare relationships to binary packages,
3080 saying that they require certain binary packages to be
3081 installed or absent at the time of building the package.
3085 This is done using the <tt>Build-Depends</tt>,
3086 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
3087 <tt>Build-Conflicts-Indep</tt> control file fields.
3090 <sect id="depsyntax"><heading>Syntax of relationship fields
3094 These fields all have a uniform syntax. They are a list of
3095 package names separated by commas.
3099 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3100 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3101 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3102 control file fields of the package, which declare
3103 dependencies on other packages, the package names listed may
3104 also include lists of alternative package names, separated
3105 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3106 if any one of the alternative packages is installed, that
3107 part of the dependency is considered to be satisfied.
3111 All of the fields except for <tt>Provides</tt> may restrict
3112 their applicability to particular versions of each named
3113 package. This is done in parentheses after each individual
3114 package name; the parentheses should contain a relation from
3115 the list below followed by a version number, in the format
3116 described in <ref id="versions">.
3120 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3121 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3122 strictly earlier, earlier or equal, exactly equal, later or
3123 equal and strictly later, respectively. The deprecated
3124 forms <tt><</tt> and <tt>></tt> were used to mean
3125 earlier/later or equal, rather than strictly earlier/later,
3126 so they should not appear in new packages (though
3127 <prgn>dpkg</prgn> still supports them).
3131 Whitespace may appear at any point in the version
3132 specification subject to the rules in <ref
3133 id="controlsyntax">, and must appear where it's necessary to
3134 disambiguate; it is not otherwise significant. For
3135 consistency and in case of future changes to
3136 <prgn>dpkg</prgn> it is recommended that a single space be
3137 used after a version relationship and before a version
3138 number; it is also conventional to put a single space after
3139 each comma, on either side of each vertical bar, and before
3140 each open parenthesis.
3144 For example, a list of dependencies might appear as:
3145 <example compact="compact">
3148 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3153 All fields that specify build-time relationships
3154 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3155 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3156 may be restricted to a certain set of architectures. This
3157 is indicated in brackets after each individual package name and
3158 the optional version specification. The brackets enclose a
3159 list of Debian architecture names separated by whitespace.
3160 Exclamation marks may be prepended to each of the names.
3161 (It is not permitted for some names to be prepended with
3162 exclamation marks and others not.) If the current Debian
3163 host architecture is not in this list and there are no
3164 exclamation marks in the list, or it is in the list with a
3165 prepended exclamation mark, the package name and the
3166 associated version specification are ignored completely for
3167 the purposes of defining the relationships.
3172 <example compact="compact">
3174 Build-Depends-Indep: texinfo
3175 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3176 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3181 Note that the binary package relationship fields such as
3182 <tt>Depends</tt> appear in one of the binary package
3183 sections of the control file, whereas the build-time
3184 relationships such as <tt>Build-Depends</tt> appear in the
3185 source package section of the control file (which is the
3191 <heading>Binary Dependencies - <tt>Depends</tt>,
3192 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3193 <tt>Pre-Depends</tt>
3197 These five fields are used to declare a dependency
3198 relationship by one package on another. Except for
3199 <tt>Enhances</tt>, they appear in the depending (binary)
3200 package's control file. (<tt>Enhances</tt> appears in the
3201 recommending package's control file.)
3205 A <tt>Depends</tt> field takes effect <em>only</em> when a
3206 package is to be configured. It does not prevent a package
3207 being on the system in an unconfigured state while its
3208 dependencies are unsatisfied, and it is possible to replace
3209 a package whose dependencies are satisfied and which is
3210 properly installed with a different version whose
3211 dependencies are not and cannot be satisfied; when this is
3212 done the depending package will be left unconfigured (since
3213 attempts to configure it will give errors) and will not
3214 function properly. If it is necessary, a
3215 <tt>Pre-Depends</tt> field can be used, which has a partial
3216 effect even when a package is being unpacked, as explained
3217 in detail below. (The other three dependency fields,
3218 <tt>Recommends</tt>, <tt>Suggests</tt> and
3219 <tt>Enhances</tt>, are only used by the various front-ends
3220 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3224 For this reason packages in an installation run are usually
3225 all unpacked first and all configured later; this gives
3226 later versions of packages with dependencies on later
3227 versions of other packages the opportunity to have their
3228 dependencies satisfied.
3232 The <tt>Depends</tt> field thus allows package maintainers
3233 to impose an order in which packages should be configured.
3237 The meaning of the five dependency fields is as follows:
3239 <tag><tt>Depends</tt></tag>
3242 This declares an absolute dependency. A package will
3243 not be configured unless all of the packages listed in
3244 its <tt>Depends</tt> field have been correctly
3249 The <tt>Depends</tt> field should be used if the
3250 depended-on package is required for the depending
3251 package to provide a significant amount of
3255 The <tt>Depends</tt> field should also be used if the
3256 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
3257 <prgn>postrm</prgn> scripts require the package to be
3258 present in order to run. Note, however, that the
3259 <prgn>postrm</prgn> cannot rely on any non-essential
3260 packages to be present during the <tt>purge</tt>
3264 <tag><tt>Recommends</tt></tag>
3266 <p>This declares a strong, but not absolute, dependency.
3270 The <tt>Recommends</tt> field should list packages
3271 that would be found together with this one in all but
3272 unusual installations.</p>
3275 <tag><tt>Suggests</tt></tag>
3278 This is used to declare that one package may be more
3279 useful with one or more others. Using this field
3280 tells the packaging system and the user that the
3281 listed packages are related to this one and can
3282 perhaps enhance its usefulness, but that installing
3283 this one without them is perfectly reasonable.
3287 <tag><tt>Enhances</tt></tag>
3290 This field is similar to Suggests but works in the
3291 opposite direction. It is used to declare that a
3292 package can enhance the functionality of another
3297 <tag><tt>Pre-Depends</tt></tag>
3300 This field is like <tt>Depends</tt>, except that it
3301 also forces <prgn>dpkg</prgn> to complete installation
3302 of the packages named before even starting the
3303 installation of the package which declares the
3304 pre-dependency, as follows:
3308 When a package declaring a pre-dependency is about to
3309 be <em>unpacked</em> the pre-dependency can be
3310 satisfied if the depended-on package is either fully
3311 configured, <em>or even if</em> the depended-on
3312 package(s) are only unpacked or half-configured,
3313 provided that they have been configured correctly at
3314 some point in the past (and not removed or partially
3315 removed since). In this case, both the
3316 previously-configured and currently unpacked or
3317 half-configured versions must satisfy any version
3318 clause in the <tt>Pre-Depends</tt> field.
3322 When the package declaring a pre-dependency is about
3323 to be <em>configured</em>, the pre-dependency will be
3324 treated as a normal <tt>Depends</tt>, that is, it will
3325 be considered satisfied only if the depended-on
3326 package has been correctly configured.
3330 <tt>Pre-Depends</tt> should be used sparingly,
3331 preferably only by packages whose premature upgrade or
3332 installation would hamper the ability of the system to
3333 continue with any upgrade that might be in progress.
3337 <tt>Pre-Depends</tt> are also required if the
3338 <prgn>preinst</prgn> script depends on the named
3339 package. It is best to avoid this situation if
3345 When selecting which level of dependency to use you should
3346 consider how important the depended-on package is to the
3347 functionality of the one declaring the dependency. Some
3348 packages are composed of components of varying degrees of
3349 importance. Such a package should list using
3350 <tt>Depends</tt> the package(s) which are required by the
3351 more important components. The other components'
3352 requirements may be mentioned as Suggestions or
3353 Recommendations, as appropriate to the components' relative
3358 <sect id="conflicts"><heading>Conflicting binary packages -
3359 <tt>Conflicts</tt></heading>
3362 When one binary package declares a conflict with another
3363 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
3364 refuse to allow them to be installed on the system at the
3369 If one package is to be installed, the other must be removed
3370 first - if the package being installed is marked as
3371 replacing (see <ref id="replaces">) the one on the system,
3372 or the one on the system is marked as deselected, or both
3373 packages are marked <tt>Essential</tt>, then
3374 <prgn>dpkg</prgn> will automatically remove the package
3375 which is causing the conflict, otherwise it will halt the
3376 installation of the new package with an error. This
3377 mechanism is specifically designed to produce an error when
3378 the installed package is <tt>Essential</tt>, but the new
3383 A package will not cause a conflict merely because its
3384 configuration files are still installed; it must be at least
3389 A special exception is made for packages which declare a
3390 conflict with their own package name, or with a virtual
3391 package which they provide (see below): this does not
3392 prevent their installation, and allows a package to conflict
3393 with others providing a replacement for it. You use this
3394 feature when you want the package in question to be the only
3395 package providing some feature.
3399 A <tt>Conflicts</tt> entry should almost never have an
3400 "earlier than" version clause. This would prevent
3401 <prgn>dpkg</prgn> from upgrading or installing the package
3402 which declared such a conflict until the upgrade or removal
3403 of the conflicted-with package had been completed.
3407 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
3411 As well as the names of actual ("concrete") packages, the
3412 package relationship fields <tt>Depends</tt>,
3413 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3414 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
3415 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3416 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
3417 may mention "virtual packages".
3421 A <em>virtual package</em> is one which appears in the
3422 <tt>Provides</tt> control file field of another package.
3423 The effect is as if the package(s) which provide a
3424 particular virtual package name had been listed by name
3425 everywhere the virtual package name appears. (See also <ref
3426 id="virtual_pkg_sect">)
3430 If there are both concrete and virtual packages of the same
3431 name, then the dependency may be satisfied (or the conflict
3432 caused) by either the concrete package with the name in
3433 question or any other concrete package which provides the
3434 virtual package with the name in question. This is so that,
3435 for example, supposing we have
3436 <example compact="compact">
3440 and someone else releases an enhanced version of the
3441 <tt>bar</tt> package (for example, a non-US variant), they
3443 <example compact="compact">
3447 and the <tt>bar-plus</tt> package will now also satisfy the
3448 dependency for the <tt>foo</tt> package.
3452 If a dependency or a conflict has a version number attached
3453 then only real packages will be considered to see whether
3454 the relationship is satisfied (or the prohibition violated,
3455 for a conflict) - it is assumed that a real package which
3456 provides the virtual package is not of the "right" version.
3457 So, a <tt>Provides</tt> field may not contain version
3458 numbers, and the version number of the concrete package
3459 which provides a particular virtual package will not be
3460 looked at when considering a dependency on or conflict with
3461 the virtual package name.
3465 It is likely that the ability will be added in a future
3466 release of <prgn>dpkg</prgn> to specify a version number for
3467 each virtual package it provides. This feature is not yet
3468 present, however, and is expected to be used only
3473 If you want to specify which of a set of real packages
3474 should be the default to satisfy a particular dependency on
3475 a virtual package, you should list the real package as an
3476 alternative before the virtual one.
3481 <sect id="replaces"><heading>Overwriting files and replacing
3482 packages - <tt>Replaces</tt></heading>
3485 The <tt>Replaces</tt> control file field has two distinct
3486 purposes, which come into play in different situations.
3489 <sect1><heading>Overwriting files in other packages</heading>
3492 Firstly, as mentioned before, it is usually an error for a
3493 package to contain files which are on the system in
3498 However, if the overwriting package declares that it
3499 <tt>Replaces</tt> the one containing the file being
3500 overwritten, then <prgn>dpkg</prgn> will replace the file
3501 from the old package with that from the new. The file
3502 will no longer be listed as "owned" by the old package.
3506 If a package is completely replaced in this way, so that
3507 <prgn>dpkg</prgn> does not know of any files it still
3508 contains, it is considered to have "disappeared". It will
3509 be marked as not wanted on the system (selected for
3510 removal) and not installed. Any <tt>conffile</tt>s
3511 details noted for the package will be ignored, as they
3512 will have been taken over by the overwriting package. The
3513 package's <prgn>postrm</prgn> script will be run with a
3514 special argument to allow the package to do any final
3515 cleanup required. See <ref id="mscriptsinstact">.
3519 If an installed package, <tt>foo</tt> say, declares that
3520 it replaces another, <tt>bar</tt>, and an attempt is made
3521 to install <tt>bar</tt>, <prgn>dpkg</prgn> will discard
3522 files in the <tt>bar</tt> package which would overwrite
3523 those already present in <tt>foo</tt>. This is so that
3524 you can install an older version of a package without
3529 For this usage of <tt>Replaces</tt>, virtual packages (see
3530 <ref id="virtual">) are not considered when looking at a
3531 <tt>Replaces</tt> field - the packages declared as being
3532 replaced must be mentioned by their real names.
3536 Furthermore, this usage of <tt>Replaces</tt> only takes
3537 effect when both packages are at least partially on the
3538 system at once, so that it can only happen if they do not
3539 conflict or if the conflict has been overridden.
3544 <sect1><heading>Replacing whole packages, forcing their
3548 Secondly, <tt>Replaces</tt> allows the packaging system to
3549 resolve which package should be removed when there is a
3550 conflict - see <ref id="conflicts">. This usage only
3551 takes effect when the two packages <em>do</em> conflict,
3552 so that the two usages of this field do not interfere with
3557 In this situation, the package declared as being replaced
3558 can be a virtual package, so for example, all mail
3559 transport agents (MTAs) would have the following fields in
3560 their control files:
3561 <example compact="compact">
3562 Provides: mail-transport-agent
3563 Conflicts: mail-transport-agent
3564 Replaces: mail-transport-agent
3566 ensuring that only one MTA can be installed at any one
3571 <sect><heading>Relationships between source and binary packages -
3572 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3573 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
3577 A source package may declare a dependency or a conflict on a
3578 binary package, indicating which packages are required to be
3579 present on the system in order to build the binary packages
3580 from the source package. This is done with the control file
3581 fields <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3582 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>.
3583 The dependencies and conflicts they define must be satisfied
3584 (as defined earlier for binary packages) in order to invoke
3585 the targets in <tt>debian/rules</tt>, as follows:<footnote>
3587 If you make "build-arch" or "binary-arch", you need
3588 Build-Depends. If you make "build-indep" or
3589 "binary-indep", you need Build-Depends and
3590 Build-Depends-Indep. If you make "build" or "binary",
3594 There is no Build-Depends-Arch; the autobuilders will
3595 only need the Build-Depends if they know how to build
3596 only build-arch and binary-arch. Anyone building the
3597 build-indep/binary-indep targets is basically assumed to
3598 be building the whole package and so installs all build
3602 The purpose of the original split, I recall, was so that
3603 the autobuilders wouldn't need to install extra packages
3604 needed only for the binary-indep targets. But without a
3605 build-arch/build-indep split, this didn't work, since
3606 most of the work is done in the build target, not in the
3612 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
3615 The <tt>Build-Depends</tt> and
3616 <tt>Build-Conflicts</tt> fields must be satisfied when
3617 any of the following targets is invoked:
3618 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
3619 <tt>binary-arch</tt>, <tt>build-arch</tt>,
3620 <tt>build-indep</tt> and <tt>binary-indep</tt>.
3623 <tag><tt>Build-Depends-Indep</tt>,
3624 <tt>Build-Conflicts-Indep</tt></tag>
3627 The <tt>Build-Depends-Indep</tt> and
3628 <tt>Build-Conflicts-Indep</tt> fields must be
3629 satisfied when any of the following targets is
3630 invoked: <tt>build</tt>, <tt>clean</tt>,
3631 <tt>build-indep</tt>, <tt>binary</tt> and
3632 <tt>binary-indep</tt>.
3643 <chapt id="conffiles"><heading>Configuration file handling
3647 This chapter has been superseded by <ref id="config-files">.
3651 <chapt id="sharedlibs"><heading>Shared libraries</heading>
3654 Packages containing shared libraries must be constructed with
3655 a little care to make sure that the shared library is always
3656 available. This is especially important for packages whose
3657 shared libraries are vitally important, such as the C library
3658 (currently <tt>libc6</tt>).
3662 Firstly, the package should install the shared libraries under
3663 their normal names. For example, the <tt>libgdbmg1</tt>
3664 package should install <tt>libgdbm.so.1.7.3</tt> as
3665 <file>/usr/lib/libgdbm.so.1.7.3</file>. The files should not be
3666 renamed or re-linked by any <prgn>prerm</prgn> or
3667 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
3668 of renaming things safely without affecting running programs,
3669 and attempts to interfere with this are likely to lead to
3674 Secondly, the package should include the symbolic link that
3675 <prgn>ldconfig</prgn> would create for the shared libraries.
3676 For example, the <prgn>libgdbmg1</prgn> package should include
3677 a symbolic link from <file>/usr/lib/libgdbm.so.1</file> to
3678 <file>libgdbm.so.1.7.3</file>. This is needed so that the dynamic
3679 linker (for example <prgn>ld.so</prgn> or
3680 <prgn>ld-linux.so.*</prgn>) can find the library between the
3681 time that <prgn>dpkg</prgn> installs it and the time that
3682 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
3685 The package management system requires the library to be
3686 placed before the symbolic link pointing to it in the
3687 <file>.deb</file> file. This is so that when
3688 <prgn>dpkg</prgn> comes to install the symlink
3689 (overwriting the previous symlink pointing at an older
3690 version of the library), the new shared library is already
3691 in place. In the past, this was achieved by creating the
3692 library in the temporary packaging directory before
3693 creating the symlink. Unfortunately, this was not always
3694 effective, since the building of the tar file in the
3695 <file>.deb</file> depended on the behavior of the underlying
3696 file system. Some file systems (such as reiserfs) reorder
3697 the files so that the order of creation is forgotten.
3698 Starting with release <tt>1.7.0</tt>, <prgn>dpkg</prgn>
3699 will reorder the files itself as necessary when building a
3700 package. Thus it is no longer important to concern
3701 oneself with the order of file creation.
3707 Thirdly, the associated development package should contain a
3708 symlink for the shared library without a version number. For
3709 example, the <tt>libgdbmg1-dev</tt> package should include a
3710 symlink from <tt>/usr/lib/libgdbm.so</tt> to
3711 <file>libgdbm.so.1.7.3</file>. This symlink is needed by the
3712 linker (<prgn>ld</prgn>) when compiling packages, as it will
3713 only look for <file>libgdbm.so</file> when compiling dynamically.
3717 Any package installing shared libraries in one of the default
3718 library directories of the dynamic linker (which are currently
3719 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
3720 listed in <file>/etc/ld.so.conf</file><footnote>
3723 <list compact="compact">
3724 <item><p>/usr/X11R6/lib/Xaw3d</p></item>
3725 <item><p>/usr/local/lib</p></item>
3726 <item><p>/usr/lib/libc5-compat</p></item>
3727 <item><p>/lib/libc5-compat</p></item>
3728 <item><p>/usr/X11R6/lib</p></item>
3732 must use <prgn>ldconfig</prgn> to update the shared library
3733 system. The package must call <prgn>ldconfig</prgn> in the
3734 <prgn>postinst</prgn> script if the first argument is
3735 <tt>configure</tt>; the <prgn>postinst</prgn> script may
3736 optionally invoke <prgn>ldconfig</prgn> at other times. The
3737 package should call <prgn>ldconfig</prgn> in the
3738 <prgn>postrm</prgn> script if the first argument is
3739 <tt>remove</tt>. The maintainer scripts must not invoke
3740 <prgn>ldconfig</prgn> under any circumstances other than those
3741 described in this paragraph.<footnote>
3742 <p>During install or upgrade, the preinst is called before
3743 the new files are installed, so calling "ldconfig" is
3744 pointless. The preinst of an existing package can also be
3745 called if an upgrade fails. However, this happens during
3746 the critical time when a shared libs may exist on-disk
3747 under a temporary name. Thus, it is dangerous and
3748 forbidden by current policy to call "ldconfig" at this
3751 <p>When a package is installed or upgraded, "postinst
3752 configure" runs after the new files are safely on-disk.
3753 Since it is perfectly safe to invoke ldconfig
3754 unconditionally in a postinst, it is OK for a package to
3755 simply put ldconfig in its postinst without checking the
3756 argument. The postinst can also be called to recover from
3757 a failed upgrade. This happens before any new files are
3758 unpacked, so there is no reason to call "ldconfig" at this
3761 <p>For a package that is being removed, prerm is
3762 called with all the files intact, so calling ldconfig is
3763 useless. The other calls to "prerm" happen in the case of
3764 upgrade at a time when all the files of the old package
3765 are on-disk, so again calling "ldconfig" is pointless.
3767 <p>postrm, on the other hand, is called with the "remove"
3768 argument just after the files are removed, so this is the
3769 proper time to call "ldconfig" to notify the system of the
3770 fact shared libraries from the package are removed.
3771 The postrm can be called at several other times. At the
3772 time of "postrm purge", "postrm abort-install", or "postrm
3773 abort-upgrade", calling "ldconfig" is useless because the
3774 shared lib files are not on-disk. However, when "postrm"
3775 is invoked with arguments "upgrade", "failed-upgrade", or
3776 "disappear", a shared lib may exist on-disk under a
3783 <heading>Handling shared library dependencies - the
3784 <tt>shlibs</tt> system</heading>
3787 If a package contains a binary or library which links to a
3788 shared library, we must ensure that when the package is
3789 installed on the system, all of the libraries needed are
3790 also installed. This requirement led to the creation of the
3791 <tt>shlibs</tt> system, which is very simple in its design:
3792 any package which <em>provides</em> a shared library also
3793 provides information on the package dependencies required to
3794 ensure the presence of this library, and any package which
3795 <em>uses</em> a shared library uses this information to
3796 determine the dependencies it requires. The files which
3797 contain the mapping from shared libraries to the necessary
3798 dependency information are called <file>shlibs</file> files.
3802 Thus, when a package is built which contains any shared
3803 libraries, it must provide a <file>shlibs</file> file for other
3804 packages to use, and when a package is built which contains
3805 any shared libraries or compiled binaries, it must run
3806 <prgn>dpkg-shlibdeps</prgn> on these to determine the
3807 libraries used and hence the dependencies needed by this
3810 In the past, the shared libraries linked to were
3811 determined by calling <prgn>ldd</prgn>, but now
3812 <prgn>objdump</prgn> is used to do this. The only
3813 change this makes to package building is that
3814 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
3815 libraries, whereas in the past this was unnecessary.
3816 The rest of this footnote explains the advantage that
3821 We say that a binary <tt>foo</tt> <em>directly</em> uses
3822 a library <tt>libbar</tt> if it is explicitly linked
3823 with that library (that is, it uses the flag
3824 <tt>-lbar</tt> during the linking stage). Other
3825 libraries that are needed by <tt>libbar</tt> are linked
3826 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
3827 linker will load them automatically when it loads
3828 <tt>libbar</tt>. A package should depend on
3829 the libraries it directly uses, and the dependencies for
3830 those libraries should automatically pull in the other
3835 Unfortunately, the <prgn>ldd</prgn> program shows both
3836 the directly and indirectly used libraries, meaning that
3837 the dependencies determined included both direct and
3838 indirect dependencies. The use of <prgn>objdump</prgn>
3839 avoids this problem by determining only the directly
3844 A good example of where this helps is the following. We
3845 could update <tt>libimlib</tt> with a new version that
3846 supports a new graphics format called dgf (but retaining
3847 the same major version number). If we used the old
3848 <prgn>ldd</prgn> method, every package that uses
3849 <tt>libimlib</tt> would need to be recompiled so it
3850 would also depend on <tt>libdgf</tt> or it wouldn't run
3851 due to missing symbols. However with the new system,
3852 packages using <tt>libimlib</tt> can rely on
3853 <tt>libimlib</tt> itself having the dependency on
3854 <tt>libdgf</tt> and so they would not need rebuilding.
3860 In the following sections, we will first describe where the
3861 various <tt>shlibs</tt> files are to be found, then how to
3862 use <prgn>dpkg-shlibdeps</prgn>, and finally the
3863 <tt>shlibs</tt> file format and how to create them if your
3864 package contains a shared library.
3868 <sect><heading>The <tt>shlibs</tt> files present on the system
3872 There are several places where <tt>shlibs</tt> files are
3873 found. The following list gives them in the order in which
3874 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
3875 one which gives the required information is used.)
3881 <p><file>debian/shlibs.local</file></p>
3883 This lists overrides for this package. Its use is
3884 described below (see <ref id="shlibslocal">).
3889 <p><file>/etc/dpkg/shlibs.override</file></p>
3891 This lists global overrides. This list is normally
3892 empty. It is maintained by the local system
3898 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
3900 When packages are being built, any
3901 <file>debian/shlibs</file> files are copied into the
3902 control file area of the temporary build directory and
3903 given the name <file>shlibs</file>. These files give
3904 details of any shared libraries included in the
3907 An example may help here. Let us say that the
3908 source package <tt>foo</tt> generates two binary
3909 packages, <tt>libfoo2</tt> and
3910 <tt>foo-runtime</tt>. When building the binary
3911 packages, the two packages are created in the
3912 directories <file>debian/libfoo2</file> and
3913 <file>debian/foo-runtime</file> respectively.
3914 (<file>debian/tmp</file> could be used instead of one
3915 of these.) Since <tt>libfoo2</tt> provides the
3916 <tt>libfoo</tt> shared library, it will require a
3917 <tt>shlibs</tt> file, which will be installed in
3918 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
3920 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
3921 when <prgn>dpkg-shlibdeps</prgn> is run on the
3923 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
3925 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
3926 determine whether <tt>foo-prog</tt>'s library
3927 dependencies are satisfied by any of the libraries
3928 provided by <tt>libfoo2</tt>. For this reason,
3929 <prgn>dpkg-shlibdeps</prgn> must only be run once
3930 all of the individual binary packages'
3931 <tt>shlibs</tt> files have been installed into the
3939 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
3941 These are the <file>shlibs</file> files corresponding to
3942 all of the packages installed on the system, and are
3943 maintained by the relevant package maintainers.
3948 <p><file>/etc/dpkg/shlibs.default</file></p>
3950 This file lists any shared libraries whose packages
3951 have failed to provide correct <file>shlibs</file> files.
3952 It was used when the <file>shlibs</file> setup was first
3953 introduced, but it is now normally empty. It is
3954 maintained by the <tt>dpkg</tt> maintainer.
3962 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
3963 <file>shlibs</file> files</heading>
3966 Put a call to <prgn>dpkg-shlibdeps</prgn> into your
3967 <file>debian/rules</file> file. If your package contains only
3968 compiled binaries and libraries (but no scripts), you can
3969 use a command such as:
3970 <example compact="compact">
3971 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
3972 debian/tmp/usr/lib/*
3974 Otherwise, you will need to explicitly list the compiled
3975 binaries and libraries.<footnote>
3977 If you are using <tt>debhelper</tt>, the
3978 <prgn>dh_shlibdeps</prgn> program will do this work for
3979 you. It will also correctly handle multi-binary
3986 This command puts the dependency information into the
3987 <file>debian/substvars</file> file, which is then used by
3988 <prgn>dpkg-gencontrol</prgn>. You will need to place a
3989 <tt>${shlib:Depends}</tt> variable in the <tt>Depends</tt>
3990 field in the control file for this to work.
3994 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
3995 done. If it does complain you might need to create your own
3996 <file>debian/shlibs.local</file> file, as explained below (see
3997 <ref id="shlibslocal">).
4001 If you have multiple binary packages, you will need to call
4002 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4003 compiled libraries or binaries. In such a case, you will
4004 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4005 utilities to specify a different <file>substvars</file> file.
4006 For more details on this and other options, see <manref
4007 name="dpkg-shlibdeps" section="1">.
4011 <sect id="shlibs"><heading>The <file>shlibs</file> File Format
4015 Each <file>shlibs</file> file has the same format. Lines
4016 beginning with <tt>#</tt> are considered to be comments and
4017 are ignored. Each line is of the form:
4018 <example compact="compact">
4019 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4024 We will explain this by reference to the example of the
4025 <tt>zlib1g</tt> package, which (at the time of writing)
4026 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4030 <var>library-name</var> is the name of the shared library,
4031 in this case <tt>libz</tt>. (This must match the name part
4032 of the soname, see below.)
4036 <var>soname-version-number</var> is the version part of the
4037 soname of the library. The soname is the thing that must
4038 exactly match for the library to be recognized by the
4039 dynamic linker, and is usually of the form
4040 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4041 example, <tt>libz.so.1</tt>.<footnote>
4043 This can be determined using the command
4044 <example compact="compact">
4045 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
4049 The version part is the part which comes after
4050 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
4054 <var>dependencies</var> has the same syntax as a dependency
4055 field in a binary package control file. It should give
4056 details of which packages are required to satisfy a binary
4057 built against the version of the library contained in the
4058 package. See <ref id="depsyntax"> for details.
4062 In our example, if the first version of the <tt>zlib1g</tt>
4063 package which contained a minor number of at least
4064 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
4065 <tt>shlibs</tt> entry for this library could say:
4066 <example compact="compact">
4067 libz 1 zlib1g (>= 1:1.1.3)
4069 The version-specific dependency is to avoid warnings from
4070 the dynamic linker about using older shared libraries with
4076 <heading>Providing a <file>shlibs</file> file</heading>
4079 If your package provides a shared library, you should create
4080 a <file>shlibs</file> file following the format described above.
4081 It is usual to call this file <file>debian/shlibs</file> (but if
4082 you have multiple binary packages, you might want to call it
4083 <file>debian/shlibs.<var>package</var></file> instead). Then
4084 let <file>debian/rules</file> install it in the control area:
4085 <example compact="compact">
4086 install -m644 debian/shlibs debian/tmp/DEBIAN
4088 or, in the case of a multi-binary package:
4089 <example compact="compact">
4090 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
4092 An alternative way of doing this is to create the
4093 <file>shlibs</file> file in the control area directly from
4094 <file>debian/rules</file> without using a <file>debian/shlibs</file>
4095 file at all,<footnote>
4097 This is what <prgn>dh_makeshlibs</prgn> in the
4098 <tt>debhelper</tt> suite does.
4101 since the <file>debian/shlibs</file> file itself is ignored by
4102 <prgn>dpkg-shlibdeps</prgn>.
4106 As <prgn>dpkg-shlibdeps</prgn> reads the
4107 <file>DEBIAN/shlibs</file> files in all of the binary packages
4108 being built from this source package, all of the
4109 <file>DEBIAN/shlibs</file> files should be installed before
4110 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
4115 <sect id="shlibslocal">
4116 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
4119 This file is intended only as a <em>temporary</em> fix if
4120 your binaries or libraries depend on a library whose package
4121 does not yet provide a correct <file>shlibs</file> file.
4125 We will assume that you are trying to package a binary
4126 <tt>foo</tt>. When you try running
4127 <prgn>dpkg-shlibdeps</prgn> you get the following error
4128 message (<tt>-O</tt> displays the dependency information on
4129 <tt>stdout</tt> instead of writing it to
4130 <tt>debian/substvars</tt>, and the lines have been wrapped
4131 for ease of reading):
4132 <example compact="compact">
4133 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
4134 dpkg-shlibdeps: warning: unable to find dependency
4135 information for shared library libbar (soname 1,
4136 path /usr/lib/libbar.so.1, dependency field Depends)
4137 shlibs:Depends=libc6 (>= 2.2.2-2)
4139 You can then run <prgn>ldd</prgn> on the binary to find the
4140 full location of the library concerned:
4141 <example compact="compact">
4143 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
4144 libc.so.6 => /lib/libc.so.6 (0x40032000)
4145 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
4147 So the <prgn>foo</prgn> binary depends on the
4148 <prgn>libbar</prgn> shared library, but no package seems to
4149 provide a <file>*.shlibs</file> file handling
4150 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
4151 determine the package responsible:
4152 <example compact="compact">
4153 $ dpkg -S /usr/lib/libbar.so.1
4154 bar1: /usr/lib/libbar.so.1
4155 $ dpkg -s bar1 | grep Version
4158 This tells us that the <tt>bar1</tt> package, version 1.0-1,
4159 is the one we are using. Now we can file a bug against the
4160 <tt>bar1</tt> package and create our own
4161 <file>debian/shlibs.local</file> to locally fix the problem.
4162 Including the following line into your
4163 <file>debian/shlibs.local</file> file:
4164 <example compact="compact">
4165 libbar 1 bar1 (>= 1.0-1)
4167 should allow the package build to work.
4171 As soon as the maintainer of <tt>bar1</tt> provides a
4172 correct <file>shlibs</file> file, you should remove this line
4173 from your <file>debian/shlibs.local</file> file. (You should
4174 probably also then have a versioned <tt>Build-Depends</tt>
4175 on <tt>bar1</tt> to help ensure that others do not have the
4176 same problem building your package.)
4181 <chapt id="opersys"><heading>The Operating System</heading>
4184 <heading>Filesystem hierarchy</heading>
4188 <heading>Filesystem Structure</heading>
4191 The location of all installed files and directories must
4192 comply with the Filesystem Hierarchy Standard (FHS),
4193 version 2.1, except where doing so would violate other
4194 terms of Debian Policy. The version of this document
4195 referred here can be found in the <tt>debian-policy</tt>
4197 <url id="http://www.debian.org/doc/packaging-manuals/fhs/"
4198 name="FHS (Debian copy)"> alongside this manual (or, if
4199 you have the <package>debian-policy</package> installed,
4201 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
4202 (local copy)">). The
4203 latest version, which may be a more recent version, may
4205 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
4206 Specific questions about following the standard may be
4207 asked on the <tt>debian-devel</tt> mailing list, or
4208 referred to the FHS mailing list (see the
4209 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
4215 <heading>Site-specific programs</heading>
4218 As mandated by the FHS, packages must not place any
4219 files in <file>/usr/local</file>, either by putting them in
4220 the file system archive to be unpacked by <prgn>dpkg</prgn>
4221 or by manipulating them in their maintainer scripts.
4225 However, the package may create empty directories below
4226 <file>/usr/local</file> so that the system administrator knows
4227 where to place site-specific files. These directories
4228 should be removed on package removal if they are
4233 Note, that this applies only to directories <em>below</em>
4234 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
4235 Packages must not create sub-directories in the directory
4236 <file>/usr/local</file> itself, except those listed in FHS,
4237 section 4.5. However, you may create directories below
4238 them as you wish. You must not remove any of the
4239 directories listed in 4.5, even if you created them.
4243 Since <file>/usr/local</file> can be mounted read-only from a
4244 remote server, these directories must be created and
4245 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
4246 maintainer scripts and not be included in the
4247 <file>.deb</file> archive. These scripts must not fail if
4248 either of these operations fail.
4252 For example, the <tt>emacsen-common</tt> package could
4253 contain something like
4254 <example compact="compact">
4255 if [ ! -e /usr/local/share/emacs ]
4257 if mkdir /usr/local/share/emacs 2>/dev/null
4259 chown root:staff /usr/local/share/emacs
4260 chmod 2775 /usr/local/share/emacs
4264 in its <prgn>postinst</prgn> script, and
4265 <example compact="compact">
4266 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
4267 rmdir /usr/local/share/emacs 2>/dev/null || true
4269 in the <prgn>prerm</prgn> script. (Note that this form is
4270 used to ensure that if the script is interrupted, the
4271 directory <file>/usr/local/share/emacs</file> will still be
4276 If you do create a directory in <file>/usr/local</file> for
4277 local additions to a package, you should ensure that
4278 settings in <file>/usr/local</file> take precedence over the
4279 equivalents in <file>/usr</file>.
4283 However, because <file>/usr/local</file> and its contents are
4284 for exclusive use of the local administrator, a package
4285 must not rely on the presence or absence of files or
4286 directories in <file>/usr/local</file> for normal operation.
4290 The <file>/usr/local</file> directory itself and all the
4291 subdirectories created by the package should (by default) have
4292 permissions 2775 (group-writable and set-group-id) and be
4293 owned by <tt>root.staff</tt>.
4298 <heading>The system-wide mail directory</heading>
4300 The system-wide mail directory is <file>/var/mail</file>. This
4301 directory is part of the base system and should not owned
4302 by any particular mail agents. The use of the old
4303 location <file>/var/spool/mail</file> is deprecated, even
4304 though the spool may still be physically located there.
4305 To maintain partial upgrade compatibility for systems
4306 which have <file>/var/spool/mail</file> as their physical mail
4307 spool, packages using <file>/var/mail</file> must depend on
4308 either <package>libc6</package> (>= 2.1.3-13), or on
4309 <package>base-files</package> (>= 2.2.0), or on later
4310 versions of either one of these packages.
4316 <heading>Users and groups</heading>
4319 <heading>Introduction</heading>
4321 The Debian system can be configured to use either plain or
4326 Some user ids (UIDs) and group ids (GIDs) are reserved
4327 globally for use by certain packages. Because some
4328 packages need to include files which are owned by these
4329 users or groups, or need the ids compiled into binaries,
4330 these ids must be used on any Debian system only for the
4331 purpose for which they are allocated. This is a serious
4332 restriction, and we should avoid getting in the way of
4333 local administration policies. In particular, many sites
4334 allocate users and/or local system groups starting at 100.
4338 Apart from this we should have dynamically allocated ids,
4339 which should by default be arranged in some sensible
4340 order, but the behavior should be configurable.
4344 Packages other than <tt>base-passwd</tt> must not modify
4345 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
4346 <file>/etc/group</file> or <file>/etc/gshadow</file>.
4351 <heading>UID and GID classes</heading>
4353 The UID and GID numbers are divided into classes as
4359 Globally allocated by the Debian project, the same
4360 on every Debian system. These ids will appear in
4361 the <file>passwd</file> and <file>group</file> files of all
4362 Debian systems, new ids in this range being added
4363 automatically as the <tt>base-passwd</tt> package is
4368 Packages which need a single statically allocated
4369 uid or gid should use one of these; their
4370 maintainers should ask the <tt>base-passwd</tt>
4378 Dynamically allocated system users and groups.
4379 Packages which need a user or group, but can have
4380 this user or group allocated dynamically and
4381 differently on each system, should use <tt>adduser
4382 --system</tt> to create the group and/or user.
4383 <prgn>adduser</prgn> will check for the existence of
4384 the user or group, and if necessary choose an unused
4385 id based on the ranges specified in
4386 <file>adduser.conf</file>.
4390 <tag>1000-29999:</tag>
4393 Dynamically allocated user accounts. By default
4394 <prgn>adduser</prgn> will choose UIDs and GIDs for
4395 user accounts in this range, though
4396 <file>adduser.conf</file> may be used to modify this
4401 <tag>30000-59999:</tag>
4406 <tag>60000-64999:</tag>
4409 Globally allocated by the Debian project, but only
4410 created on demand. The ids are allocated centrally
4411 and statically, but the actual accounts are only
4412 created on users' systems on demand.
4416 These ids are for packages which are obscure or
4417 which require many statically-allocated ids. These
4418 packages should check for and create the accounts in
4419 <file>/etc/passwd</file> or <file>/etc/group</file> (using
4420 <prgn>adduser</prgn> if it has this facility) if
4421 necessary. Packages which are likely to require
4422 further allocations should have a "hole" left after
4423 them in the allocation, to give them room to
4428 <tag>65000-65533:</tag>
4436 User <tt>nobody</tt>. The corresponding gid refers
4437 to the group <tt>nogroup</tt>.
4444 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
4445 not</em> be used, because it is the error return
4454 <sect id="sysvinit">
4455 <heading>System run levels and <file>init.d</file> scripts</heading>
4457 <sect1 id="/etc/init.d">
4458 <heading>Introduction</heading>
4461 The <file>/etc/init.d</file> directory contains the scripts
4462 executed by <prgn>init</prgn> at boot time and when the
4463 init state (or "runlevel") is changed (see <manref
4464 name="init" section="8">).
4468 There are at least two different, yet functionally
4469 equivalent, ways of handling these scripts. For the sake
4470 of simplicity, this document describes only the symbolic
4471 link method. However, it must not be assumed by maintainer
4472 scripts that this method is being used, and any automated
4473 manipulation of the various runlevel behaviours by
4474 maintainer scripts must be performed using
4475 <prgn>update-rc.d</prgn> as described below and not by
4476 manually installing or removing symlinks. For information
4477 on the implementation details of the other method,
4478 implemented in the <tt>file-rc</tt> package, please refer
4479 to the documentation of that package.
4483 These scripts are referenced by symbolic links in the
4484 <file>/etc/rc<var>n</var>.d</file> directories. When changing
4485 runlevels, <prgn>init</prgn> looks in the directory
4486 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
4487 execute, where <tt><var>n</var></tt> is the runlevel that
4488 is being changed to, or <tt>S</tt> for the boot-up
4493 The names of the links all have the form
4494 <file>S<var>mm</var><var>script</var></file> or
4495 <file>K<var>mm</var><var>script</var></file> where
4496 <var>mm</var> is a two-digit number and <var>script</var>
4497 is the name of the script (this should be the same as the
4498 name of the actual script in <file>/etc/init.d</file>).
4502 When <prgn>init</prgn> changes runlevel first the targets
4503 of the links whose names start with a <tt>K</tt> are
4504 executed, each with the single argument <tt>stop</tt>,
4505 followed by the scripts prefixed with an <tt>S</tt>, each
4506 with the single argument <tt>start</tt>. (The links are
4507 those in the <file>/etc/rc<var>n</var>.d</file> directory
4508 corresponding to the new runlevel.) The <tt>K</tt> links
4509 are responsible for killing services and the <tt>S</tt>
4510 link for starting services upon entering the runlevel.
4514 For example, if we are changing from runlevel 2 to
4515 runlevel 3, init will first execute all of the <tt>K</tt>
4516 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
4517 all of the <tt>S</tt> prefixed scripts in that directory.
4518 The links starting with <tt>K</tt> will cause the
4519 referred-to file to be executed with an argument of
4520 <tt>stop</tt>, and the <tt>S</tt> links with an argument
4525 The two-digit number <var>mm</var> is used to determine
4526 the order in which to run the scripts: low-numbered links
4527 have their scripts run first. For example, the
4528 <tt>K20</tt> scripts will be executed before the
4529 <tt>K30</tt> scripts. This is used when a certain service
4530 must be started before another. For example, the name
4531 server <prgn>bind</prgn> might need to be started before
4532 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
4533 can set up its access lists. In this case, the script
4534 that starts <prgn>bind</prgn> would have a lower number
4535 than the script that starts <prgn>inn</prgn> so that it
4537 <example compact="compact">
4544 The two runlevels 0 (halt) and 6 (reboot) are slightly
4545 different. In these runlevels, the links with an
4546 <tt>S</tt> prefix are still called after those with a
4547 <tt>K</tt> prefix, but they too are called with the single
4548 argument <tt>stop</tt>.
4552 Also, if the script name ends <tt>.sh</tt>, the script
4553 will be sourced in runlevel <tt>S</tt> rather that being
4554 run in a forked subprocess, but will be explicitly run by
4555 <prgn>sh</prgn> in all other runlevels.
4560 <heading>Writing the scripts</heading>
4563 Packages that include daemons for system services should
4564 place scripts in <file>/etc/init.d</file> to start or stop
4565 services at boot time or during a change of runlevel.
4566 These scripts should be named
4567 <file>/etc/init.d/<var>package</var></file>, and they should
4568 accept one argument, saying what to do:
4571 <tag><tt>start</tt></tag>
4572 <item><p>start the service,</p></item>
4574 <tag><tt>stop</tt></tag>
4575 <item><p>stop the service,</p></item>
4577 <tag><tt>restart</tt></tag>
4578 <item><p>stop and restart the service,</p></item>
4580 <tag><tt>reload</tt></tag>
4581 <item><p>cause the configuration of the service to be
4582 reloaded without actually stopping and restarting
4583 the service,</p></item>
4585 <tag><tt>force-reload</tt></tag>
4586 <item><p>cause the configuration to be reloaded if the
4587 service supports this, otherwise restart the
4591 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
4592 <tt>force-reload</tt> options should be supported by all
4593 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
4594 option is optional.</p>
4597 The <file>init.d</file> scripts should ensure that they will
4598 behave sensibly if invoked with <tt>start</tt> when the
4599 service is already running, or with <tt>stop</tt> when it
4600 isn't, and that they don't kill unfortunately-named user
4601 processes. The best way to achieve this is usually to use
4602 <prgn>start-stop-daemon</prgn>.</p>
4605 If a service reloads its configuration automatically (as
4606 in the case of <prgn>cron</prgn>, for example), the
4607 <tt>reload</tt> option of the <file>init.d</file> script
4608 should behave as if the configuration has been reloaded
4612 The <file>/etc/init.d</file> scripts must be treated as
4613 configuration files, either (if they are present in the
4614 package, that is, in the .deb file) by marking them as
4615 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
4616 by managing them correctly in the maintainer scripts (see
4617 <ref id="config-files">). This is important since we want
4618 to give the local system administrator the chance to adapt
4619 the scripts to the local system, e.g., to disable a
4620 service without de-installing the package, or to specify
4621 some special command line options when starting a service,
4622 while making sure her changes aren't lost during the next
4627 These scripts should not fail obscurely when the
4628 configuration files remain but the package has been
4629 removed, as configuration files remain on the system after
4630 the package has been removed. Only when <prgn>dpkg</prgn>
4631 is executed with the <tt>--purge</tt> option will
4632 configuration files be removed. In particular, as the
4633 <file>/etc/init.d/<var>package</var></file> script itself is
4634 usually a <tt>conffile</tt>, it will remain on the system
4635 if the package is removed but not purged. Therefore, you
4636 should include a <tt>test</tt> statement at the top of the
4638 <example compact="compact">
4639 test -f <var>program-executed-later-in-script</var> || exit 0
4644 Often there are some variables in the <file>init.d</file>
4645 scripts whose values control the behaviour of the scripts,
4646 and which a system administrator is likely to want to
4647 change. As the scripts themselves are frequently
4648 <tt>conffile</tt>s, modifying them requires that the
4649 administrator merge in their changes each time the package
4650 is upgraded and the <tt>conffile</tt> changes. To ease
4651 the burden on the system administrator, such configurable
4652 values should not be placed directly in the script.
4653 Instead, they should be placed in a file in
4654 <file>/etc/default</file>, which typically will have the same
4655 base name as the <file>init.d</file> script. This extra file
4656 should be sourced by the script when the script runs. It
4657 must contain only variable settings and comments in POSIX
4658 <prgn>sh</prgn> format. It may either be a
4659 <tt>conffile</tt> or a configuration file maintained by
4660 the package maintainer scripts. See <ref id="config-files">
4665 To ensure that vital configurable values are always
4666 available, the <file>init.d</file> script should set default
4667 values for each of the shell variables it uses, either
4668 before sourcing the <file>/etc/default/</file> file or
4669 afterwards using something like the <tt>:
4670 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
4671 script must behave sensibly and not fail if the
4672 <file>/etc/default</file> file is deleted.
4677 <heading>Interfacing with the initscript system</heading>
4680 Maintainers should use the abstraction layer provided by
4681 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
4682 programs to deal with initscripts in their packages'
4683 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
4684 and <prgn>postrm</prgn>.
4687 Directly managing the /etc/rc?.d links and directly
4688 invoking the <file>/etc/init.d/</file> initscripts should
4689 be done only by packages providing the initscript
4690 subsystem (such as <prgn>sysvinit</prgn> and
4691 <prgn>file-rc</prgn>).
4696 <heading>Managing the links</heading>
4699 The program <prgn>update-rc.d</prgn> is provided for
4700 package maintainers to arrange for the proper creation and
4701 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
4702 or their functional equivalent if another method is being
4703 used. This may be used by maintainers in their packages'
4704 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.</p>
4707 You must not include any <file>/etc/rc<var>n</var>.d</file>
4708 symbolic links in the actual archive or manually create or
4709 remove the symbolic links in maintainer scripts; you must
4710 use the <prgn>update-rc.d</prgn> program instead. (The
4711 former will fail if an alternative method of maintaining
4712 runlevel information is being used.) You must not include
4713 the <file>/etc/rc<var>n</var>.d</file> directories themselves
4714 in the archive either. (Only the <tt>sysvinit</tt>
4719 By default <prgn>update-rc.d</prgn> will start services in
4720 each of the multi-user state runlevels (2, 3, 4, and 5)
4721 and stop them in the halt runlevel (0), the single-user
4722 runlevel (1) and the reboot runlevel (6). The system
4723 administrator will have the opportunity to customize
4724 runlevels by simply adding, moving, or removing the
4725 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
4726 symbolic links are being used, or by modifying
4727 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
4732 To get the default behavior for your package, put in your
4733 <prgn>postinst</prgn> script
4734 <example compact="compact">
4735 update-rc.d <var>package</var> defaults
4737 and in your <prgn>postrm</prgn>
4738 <example compact="compact">
4739 if [ "$1" = purge ]; then
4740 update-rc.d <var>package</var> remove
4742 </example>. Note that if your package changes runlevels
4743 or priority, you may have to remove and recreate the links,
4744 since otherwise the old links may persist. Refer to the
4745 documentation of <prgn>update-rc.d</prgn></p>
4748 This will use a default sequence number of 20. If it does
4749 not matter when or in which order the <file>init.d</file>
4750 script is run, use this default. If it does, then you
4751 should talk to the maintainer of the <prgn>sysvinit</prgn>
4752 package or post to <tt>debian-devel</tt>, and they will
4753 help you choose a number.
4757 For more information about using <tt>update-rc.d</tt>,
4758 please consult its manpage <manref name="update-rc.d"
4764 <heading>Running initscripts</heading>
4766 The program <prgn>invoke-rc.d</prgn> is provided to make
4767 it easier for package maintainers to properly invoke an
4768 initscript, obeying runlevel and other locally-defined
4769 constraints that might limit a package's right to start,
4770 stop and otherwise manage services. This program may be
4771 used by maintainers in their packages' scripts.
4774 The use of <prgn>invoke-rc.d</prgn> to invoke the
4775 <file>/etc/init.d/*</file> initscripts is strongly
4776 recommended<footnote>
4778 In the future, the use of invoke-rc.d to invoke
4779 initscripts shall be made mandatory. Maintainers are
4780 advised to switch to invoke-rc.d as soon as
4782 </footnote>, instead of calling them directly.
4786 By default, <prgn>invoke-rc.d</prgn> will pass any
4787 action requests (start, stop, reload, restart...) to the
4788 <file>/etc/init.d</file> script, filtering out requests
4789 to start or restart a service out of its intended
4793 Most packages will simply need to change:
4794 <example compact="compact">/etc/init.d/<package>
4795 <action></example> in their <prgn>postinst</prgn>
4796 and <prgn>prerm</prgn> scripts to:
4797 <example compact="compact">
4798 if [ -x /usr/sbin/invoke-rc.d ] ; then
4799 invoke-rc.d <var>package</var> <action>
4801 /etc/init.d/<var>package</var> <action>
4805 A package should register its initscript services using
4806 <prgn>update-rc.d</prgn> before it tries to invoke them
4807 using <prgn>invoke-rc.d</prgn>. Invocation of
4808 unregistered services may fail.
4811 For more information about using
4812 <prgn>invoke-rc.d</prgn>, please consult its manpage
4813 <manref name="invoke-rc.d" section="8">.
4820 <heading>Boot-time initialization</heading>
4823 There used to be another directory, <file>/etc/rc.boot</file>,
4824 which contained scripts which were run once per machine
4825 boot. This has been deprecated in favour of links from
4826 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
4827 described in <ref id="/etc/init.d">. Packages must not
4828 place files in <file>/etc/rc.boot</file>.</p>
4831 <heading>Example</heading>
4834 The <prgn>bind</prgn> DNS (nameserver) package wants to
4835 make sure that the nameserver is running in multiuser
4836 runlevels, and is properly shut down with the system. It
4837 puts a script in <file>/etc/init.d</file>, naming the script
4838 appropriately <tt>bind</tt>. As you can see, the script
4839 interprets the argument <tt>reload</tt> to send the
4840 nameserver a <tt>HUP</tt> signal (causing it to reload its
4841 configuration); this way the system administrator can say
4842 <file>/etc/init.d/bind reload</file> to reload the name
4843 server. The script has one configurable value, which can
4844 be used to pass parameters to the named program at
4845 startup; this value is read from
4846 <file>/etc/default/bind</file> (see below).
4850 <example compact="compact">
4853 # Original version by Robert Leslie
4854 # <rob@mars.org>, edited by iwj and cs
4856 test -x /usr/sbin/named || exit 0
4858 # Source defaults file.
4860 if [ -f /etc/default/bind ]; then
4867 echo -n "Starting domain name service: named"
4868 start-stop-daemon --start --quiet --exec /usr/sbin/named \
4873 echo -n "Stopping domain name service: named"
4874 start-stop-daemon --stop --quiet \
4875 --pidfile /var/run/named.pid --exec /usr/sbin/named
4879 echo -n "Restarting domain name service: named"
4880 start-stop-daemon --stop --quiet \
4881 --pidfile /var/run/named.pid --exec /usr/sbin/named
4882 start-stop-daemon --start --verbose --exec /usr/sbin/named \
4886 force-reload|reload)
4887 echo -n "Reloading configuration of domain name service: named"
4888 start-stop-daemon --stop --signal 1 --quiet \
4889 --pidfile /var/run/named.pid --exec /usr/sbin/named
4893 echo "Usage: /etc/init.d/bind " \
4894 " {start|stop|restart|reload|force-reload}" >&2
4904 Complementing the above init script is a configuration
4905 file <file>/etc/default/bind</file>, which contains
4906 configurable parameters used by the script. This would be
4907 created by the <prgn>postinst</prgn> script if it was not
4908 already present, and removed on purge by the
4909 <prgn>postrm</prgn> script.
4910 <example compact="compact">
4911 # Specified parameters to pass to named. See named(8).
4912 # You may uncomment the following line, and edit to taste.
4918 Another example on which you can base your
4919 <file>/etc/init.d</file> scripts is found in
4920 <file>/etc/init.d/skeleton</file>.
4924 If this package is happy with the default setup from
4925 <prgn>update-rc.d</prgn>, namely an ordering number of 20
4926 and having named running in all runlevels, it can say in
4927 its <prgn>postinst</prgn>:
4928 <example compact="compact">
4929 update-rc.d bind defaults >/dev/null
4931 And in its <prgn>postrm</prgn>, to remove the links when the
4933 <example compact="compact">
4934 if [ "$1" = purge ]; then
4935 update-rc.d bind remove >/dev/null
4943 <heading>Console messages from <file>init.d</file> scripts</heading>
4946 This section describes the formats to be used for messages
4947 written to standard output by the <file>/etc/init.d</file>
4948 scripts. The intent is to improve the consistency of
4949 Debian's startup and shutdown look and feel. For this
4950 reason, please look very carefully at the details. We want
4951 the messages to have the same format in terms of wording,
4952 spaces, punctuation and case of letters.
4956 Here is a list of overall rules that you should use when you
4957 create output messages. They can be useful if you have a
4958 non-standard message that is not covered specifically in the
4966 Every message should fit in one line (fewer than 80
4967 characters), start with a capital letter and end with
4968 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
4974 If you want to express that the computer is working on
4975 something (that is, performing a specific task, not
4976 starting or stopping a program), we use an "ellipsis"
4977 (three dots: <tt>...</tt>). Note that we don't insert
4978 spaces before or after the dots. If the task has been
4979 completed we write <tt>done.</tt> and a line feed.
4985 Design your messages as if the computer is telling you
4986 what he is doing (let him be polite :-), but don't
4987 mention "him" directly. For example, if you think of
4989 <example compact="compact">
4990 I'm starting network daemons: nfsd mountd.
4993 <example compact="compact">
4994 Starting network daemons: nfsd mountd.
5002 There are standard message formats for the following
5003 situations. They should be used by the <tt>init.d</tt>
5010 <p>When daemons are started</p>
5013 If your script starts one or more daemons, the output
5014 should look like this (a single line, no leading
5016 <example compact="compact">
5017 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5019 The <var>description</var> should describe the
5020 subsystem the daemon or set of daemons are part of,
5021 while <var>daemon-1</var> up to <var>daemon-n</var>
5022 denote each daemon's name (typically the file name of
5027 For example, the output of <file>/etc/init.d/lpd</file>
5029 <example compact="compact">
5030 Starting printer spooler: lpd.
5035 This can be achieved by saying
5036 <example compact="compact">
5037 echo -n "Starting printer spooler: lpd"
5038 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5041 in the script. If you have more than one daemon to
5042 start, you should do the following:
5043 <example compact="compact">
5044 echo -n "Starting remote file system services:"
5045 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5046 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5047 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5050 This makes it possible for the user to see what takes
5051 so long and when the final daemon has been started.
5052 You should be careful where to put spaces: in the
5053 example above the system administrator can easily
5054 comment out a line if he don't wants to start a
5055 specific daemon, while the displayed message still
5061 <p>When a system parameter is being set</p>
5064 If you have to set up different system parameters
5065 during the system boot, you should use this format:
5066 <example compact="compact">
5067 Setting <var>parameter</var> to "<var>value</var>".
5072 You can use a statement such as the following to get
5074 <example compact="compact">
5075 echo "Setting DNS domainname to \"$domainname\"."
5080 Note that the same symbol (<tt>"</tt>) is used for the left
5081 and right quotation marks. A grave accent (<tt>`</tt>) is
5082 not a quote character; neither is an apostrophe
5088 <p>When a daemon is stopped or restarted</p>
5091 When you stop or restart a daemon, you should issue a
5092 message identical to the startup message, except that
5093 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5094 or <tt>Restarting</tt> respectively.
5098 For example, stopping the printer daemon will like
5100 <example compact="compact">
5101 Stopping printer spooler: lpd.
5107 <p>When something is executed</p>
5110 There are several examples where you have to run a
5111 program at system startup or shutdown to perform a
5112 specific task, for example, setting the system's clock
5113 using <prgn>netdate</prgn> or killing all processes
5114 when the system shuts down. Your message should look
5116 <example compact="compact">
5117 Doing something very useful...done.
5119 You should print the <tt>done.</tt> immediately after
5120 the job has been completed, so that the user is
5121 informed why she has to wait. You can get this
5123 <example compact="compact">
5124 echo -n "Doing something very useful..."
5133 <p>When the configuration is reloaded</p>
5136 When a daemon is forced to reload its configuration
5137 files you should use the following format:
5138 <example compact="compact">
5139 Reloading <var>description</var> configuration...done.
5141 where <var>description</var> is the same as in the
5142 daemon starting message.
5150 <heading>Cron jobs</heading>
5153 Packages must not modify the configuration file
5154 <file>/etc/crontab</file>, and they must not modify the files in
5155 <file>/var/spool/cron/crontabs</file>.</p>
5158 If a package wants to install a job that has to be executed
5159 via cron, it should place a file with the name of the
5160 package in one or more of the following directories:
5161 <example compact="compact">
5166 As these directory names imply, the files within them are
5167 executed on a daily, weekly, or monthly basis,
5168 respectively. The exact times are listed in
5169 <file>/etc/crontab</file>.</p>
5172 All files installed in any of these directories must be
5173 scripts (e.g., shell scripts or Perl scripts) so that they
5174 can easily be modified by the local system administrator.
5175 In addition, they should be treated as configuration
5180 If a certain job has to be executed more frequently than
5181 daily, the package should install a file
5182 <file>/etc/cron.d/<var>package</var></file>. This file uses the
5183 same syntax as <file>/etc/crontab</file> and is processed by
5184 <prgn>cron</prgn> automatically. The file must also be
5185 treated as a configuration file. (Note that entries in the
5186 <file>/etc/cron.d</file> directory are not handled by
5187 <prgn>anacron</prgn>. Thus, you should only use this
5188 directory for jobs which may be skipped if the system is not
5192 The scripts or crontab entries in these directories should
5193 check if all necessary programs are installed before they
5194 try to execute them. Otherwise, problems will arise when a
5195 package was removed but not purged since configuration files
5196 are kept on the system in this situation.</p>
5200 <heading>Menus</heading>
5203 Menu entries should follow the current menu policy found in
5204 the <tt>menu-policy</tt> files in the <tt>debian-policy</tt>
5205 package. It may also be found on the Debian FTP site
5206 <ftpsite>ftp.debian.org</ftpsite> as the file
5207 <ftppath>/debian/doc/package-developer/menu-policy.txt.gz</ftppath>,
5208 or in the equivalent location on your local mirror.
5212 The Debian <tt>menu</tt> package provides a standard
5213 interface between packages providing applications and
5214 documents, and <em>menu programs</em> (either X window
5215 managers or text-based menu programs such as
5216 <prgn>pdmenu</prgn>).
5220 All packages that provide applications that need not be
5221 passed any special command line arguments for normal
5222 operation should register a menu entry for those
5223 applications, so that users of the <tt>menu</tt> package
5224 will automatically get menu entries in their window
5225 managers, as well in shells like <tt>pdmenu</tt>.</p>
5228 Please also refer to the <em>Debian Menu System</em>
5229 documentation that comes with the <tt>menu</tt> package for
5230 information about how to register your applications and web
5236 <heading>Multimedia handlers</heading>
5239 Packages which provide the ability to view/show/play,
5240 compose, edit or print MIME types should register themselves
5241 as such following the current MIME support policy found in
5242 the <tt>mime-policy</tt> files in the <tt>debian-policy</tt>
5243 package. It may also be found on the Debian FTP site
5244 <ftpsite>ftp.debian.org</ftpsite> as the file
5245 <ftppath>/debian/doc/package-developer/mime-policy.txt.gz</ftppath>,
5246 or in the equivalent location on your local mirror.
5250 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
5251 is a mechanism for encoding files and data streams and
5252 providing meta-information about them, in particular their
5253 type (e.g. audio or video) and format (e.g. PNG, HTML,
5258 Registration of MIME type handlers allows programs like mail
5259 user agents and web browsers to to invoke these handlers to
5260 view, edit or display MIME types they don't support
5266 <heading>Keyboard configuration</heading>
5269 To achieve a consistent keyboard configuration so that all
5270 applications interpret a keyboard event the same way, all
5271 programs in the Debian distribution must be configured to
5272 comply with the following guidelines.
5276 The following keys must have the specified interpretations:
5279 <tag><tt><--</tt></tag>
5280 <item><p>delete the character to the left of the cursor</p></item>
5282 <tag><tt>Delete</tt></tag>
5283 <item><p>delete the character to the right of the cursor</p></item>
5285 <tag><tt>Control+H</tt></tag>
5286 <item><p>emacs: the help prefix</p></item>
5289 The interpretation of any keyboard events should be
5290 independent of the terminal that is used, be it a virtual
5291 console, an X terminal emulator, an rlogin/telnet session,
5296 The following list explains how the different programs
5297 should be set up to achieve this:
5302 <item><p><tt><--</tt> generates <tt>KB_BackSpace</tt>
5305 <item><p><tt>Delete</tt> generates <tt>KB_Delete</tt> in
5310 X translations are set up to make
5311 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
5312 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
5313 is the vt220 escape code for the "delete character"
5314 key). This must be done by loading the X resources
5315 using <prgn>xrdb</prgn> on all local X displays, not
5316 using the application defaults, so that the
5317 translation resources used correspond to the
5318 <prgn>xmodmap</prgn> settings.</p></item>
5322 The Linux console is configured to make
5323 <tt><--</tt> generate DEL, and <tt>Delete</tt>
5324 generate <tt>ESC [ 3 ~</tt>.</p></item>
5328 X applications are configured so that <tt><</tt>
5329 deletes left, and <tt>Delete</tt> deletes right. Motif
5330 applications already work like this.</p></item>
5332 <item><p>Terminals should have <tt>stty erase ^?</tt> .</p></item>
5336 The <tt>xterm</tt> terminfo entry should have <tt>ESC
5337 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
5338 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.</p></item>
5342 Emacs is programmed to map <tt>KB_Backspace</tt> or
5343 the <tt>stty erase</tt> character to
5344 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
5345 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
5346 <tt>^H</tt> to <tt>help</tt> as always.</p></item>
5350 Other applications use the <tt>stty erase</tt>
5351 character and <tt>kdch1</tt> for the two delete keys,
5352 with ASCII DEL being "delete previous character" and
5353 <tt>kdch1</tt> being "delete character under
5360 This will solve the problem except for the following
5368 Some terminals have a <tt><--</tt> key that cannot
5369 be made to produce anything except <tt>^H</tt>. On
5370 these terminals Emacs help will be unavailable on
5371 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
5372 character takes precedence in Emacs, and has been set
5373 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
5374 available) can be used instead.</p></item>
5378 Some operating systems use <tt>^H</tt> for <tt>stty
5379 erase</tt>. However, modern telnet versions and all
5380 rlogin versions propagate <tt>stty</tt> settings, and
5381 almost all UNIX versions honour <tt>stty erase</tt>.
5382 Where the <tt>stty</tt> settings are not propagated
5383 correctly, things can be made to work by using
5384 <tt>stty</tt> manually.</p></item>
5388 Some systems (including previous Debian versions) use
5389 <prgn>xmodmap</prgn> to arrange for both
5390 <tt><--</tt> and <tt>Delete</tt> to generate
5391 <tt>KB_Delete</tt>. We can change the behavior of
5392 their X clients using the same X resources that we use
5393 to do it for our own clients, or configure our clients
5394 using their resources when things are the other way
5395 around. On displays configured like this
5396 <tt>Delete</tt> will not work, but <tt><--</tt>
5401 Some operating systems have different <tt>kdch1</tt>
5402 settings in their <tt>terminfo</tt> database for
5403 <tt>xterm</tt> and others. On these systems the
5404 <tt>Delete</tt> key will not work correctly when you
5405 log in from a system conforming to our policy, but
5406 <tt><--</tt> will.</p></item>
5412 <heading>Environment variables</heading>
5415 A program must not depend on environment variables to get
5416 reasonable defaults. (That's because these environment
5417 variables would have to be set in a system-wide
5418 configuration file like <file>/etc/profile</file>, which is not
5419 supported by all shells.)</p>
5422 If a program usually depends on environment variables for its
5423 configuration, the program should be changed to fall back to
5424 a reasonable default configuration if these environment
5425 variables are not present. If this cannot be done easily
5426 (e.g., if the source code of a non-free program is not
5427 available), the program must be replaced by a small
5428 "wrapper" shell script which sets the environment variables
5429 if they are not already defined, and calls the original program.</p>
5432 Here is an example of a wrapper script for this purpose:
5434 <example compact="compact">
5436 BAR=${BAR:-/var/lib/fubar}
5438 exec /usr/lib/foo/foo "$@"
5443 Furthermore, as <file>/etc/profile</file> is a configuration
5444 file of the <prgn>base-files</prgn> package, other packages must not
5445 put any environment variables or other commands into that
5451 <heading>Files</heading>
5454 <heading>Binaries</heading>
5457 Two different packages must not install programs with
5458 different functionality but with the same filenames. (The
5459 case of two programs having the same functionality but
5460 different implementations is handled via "alternatives" or
5461 the "Conflicts" mechanism. See <ref id="maintscripts"> and
5462 <ref id="conflicts"> respectively.) If this case happens,
5463 one of the programs must be renamed. The maintainers should
5464 report this to the <tt>debian-devel</tt> mailing list and
5465 try to find a consensus about which program will have to be
5466 renamed. If a consensus cannot be reached, <em>both</em>
5467 programs must be renamed.
5471 By default, when a package is being built, any binaries
5472 created should include debugging information, as well as
5473 being compiled with optimization. You should also turn on
5474 as many reasonable compilation warnings as possible; this
5475 makes life easier for porters, who can then look at build
5476 logs for possible problems. For the C programming language,
5477 this means the following compilation parameters should be
5479 <example compact="compact">
5481 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
5483 install -s # (or use strip on the files in debian/tmp)
5488 Note that by default all installed binaries should be stripped,
5489 either by using the <tt>-s</tt> flag to
5490 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
5491 the binaries after they have been copied into
5492 <file>debian/tmp</file> but before the tree is made into a
5496 Although binaries in the build tree should be compiled with
5497 debugging information by default, it can often be difficult
5498 to debug programs if they are also subjected to compiler
5499 optimization. For this reason, it is recommended to support
5500 the standardized environment
5501 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
5502 contain several flags to change how a package is compiled
5510 The presence of this string means that the package
5511 should be complied with a minimum of optimization.
5512 For C programs, it is best to add <tt>-O0</tt>
5513 to <tt>CFLAGS</tt> (although this is usually the
5514 default). Some programs might fail to build or run at
5515 this level of optimization; it may be necessary to
5516 use <tt>-O1</tt>, for example.
5522 This string means that the debugging symbols should
5523 not be stripped from the binary during installation,
5524 so that debugging information may be included in the package.
5530 The following makefile snippet is an example of how one may
5531 implement the build options; you will probably have to
5532 massage this example in order to make it work for your
5534 <example compact="compact">
5537 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
5538 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
5539 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
5540 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
5542 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
5547 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
5548 INSTALL_PROGRAM += -s
5554 It is up to the package maintainer to decide what
5555 compilation options are best for the package. Certain
5556 binaries (such as computationally-intensive programs) will
5557 function better with certain flags (<tt>-O3</tt>, for
5558 example); feel free to use them. Please use good judgment
5559 here. Don't use flags for the sake of it; only use them
5560 if there is good reason to do so. Feel free to override
5561 the upstream author's ideas about which compilation
5562 options are best: they are often inappropriate for our
5569 <heading>Libraries</heading>
5571 In general, libraries must have a shared version in the
5572 library package and a static version in the development
5573 package. The shared version must be compiled with
5574 <tt>-fPIC</tt>, and the static version must not be. In
5575 other words, each source unit ( <tt>*.c</tt>, for example,
5576 for C files) will need to be compiled twice.
5579 In some cases, it is acceptable for a library to be
5580 available in static form only; these cases include:
5583 <p>libraries for languages whose shared library support
5584 is immature or unstable</p>
5588 libraries whose interfaces are in flux or under
5589 development (commonly the case when the library's
5590 major version number is zero, or where the ABI breaks
5596 libraries which are explicitly intended to be
5597 available only in static form by their upstream
5601 If a library is available only in static form, then it must follow
5602 the conventions for a development package.
5605 All libraries must have a shared version in the
5606 <tt>lib*</tt> package and a static version in the
5607 <tt>lib*-dev</tt> package. The shared version must be
5608 compiled with <tt>-fPIC</tt>, and the static version must
5609 not be. In other words, each <tt>*.c</tt> file will need to
5610 be compiled twice.</p>
5613 You must specify the gcc option <tt>-D_REENTRANT</tt>
5614 when building a library (either static or shared) to make
5615 the library compatible with LinuxThreads.</p>
5618 Note that all installed shared libraries should be
5620 <example compact="compact">
5621 strip --strip-unneeded <var>your-lib</var>
5623 (The option <tt>--strip-unneeded</tt> makes
5624 <prgn>strip</prgn> remove only the symbols which aren't
5625 needed for relocation processing.) Shared libraries can
5626 function perfectly well when stripped, since the symbols for
5627 dynamic linking are in a separate part of the ELF object
5630 You might also want to use the options
5631 <tt>--remove-section=.comment</tt> and
5632 <tt>--remove-section=.note</tt> on both shared libraries
5633 and executables, and <tt>--strip-debug</tt> on static
5640 Note that under some circumstances it may be useful to
5641 install a shared library unstripped, for example when
5642 building a separate package to support debugging.
5646 Shared object files (often <file>.so</file> files) that are not
5647 public libraries, that is, they are not meant to be linked
5648 to by third party executables (binaries of other packages),
5649 should be installed in subdirectories of the
5650 <file>/usr/lib</file> directory. Such files are exempt from the
5651 rules that govern ordinary shared libraries, except that
5652 they must not be installed executable and should be
5655 A common example are the so-called "plug-ins",
5656 internal shared objects that are dynamically loaded by
5657 programs using <manref name="dlopen" section="3">.
5663 Packages containing shared libraries that may be linked to
5664 by other packages' binaries, but which for some
5665 <em>compelling</em> reason can not be installed in
5666 <file>/usr/lib</file> directory, may install the shared library
5667 files in subdirectories of the <file>/usr/lib</file> directory,
5668 in which case they should arrange to add that directory in
5669 <file>/etc/ld.so.conf</file> in the package's post-installation
5670 script, and remove it in the package's post-removal script.
5674 An ever increasing number of packages are using
5675 <prgn>libtool</prgn> to do their linking. The latest GNU
5676 libtools (>= 1.3a) can take advantage of the metadata in the
5677 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
5678 files). The main advantage of <prgn>libtool</prgn>'s
5679 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
5680 store and subsequently access metadata with respect to the
5681 libraries it builds. <prgn>libtool</prgn> will search for
5682 those files, which contain a lot of useful information about
5683 a library (such as library dependency information for static
5684 linking). Also, they're <em>essential</em> for programs
5685 using <tt>libltdl</tt>.<footnote>
5687 Although <prgn>libtool</prgn> is fully capable of
5688 linking against shared libraries which don't have
5689 <tt>.la</tt> files, as it is a mere shell script it can
5690 add considerably to the build time of a
5691 <prgn>libtool</prgn>-using package if that shell script
5692 has to derive all this information from first principles
5693 for each library every time it is linked. With the
5694 advent of <prgn>libtool</prgn> version 1.4 (and to a
5695 lesser extent <prgn>libtool</prgn> version 1.3), the
5696 <file>.la</file> files also store information about
5697 inter-library dependencies which cannot necessarily be
5698 derived after the <file>.la</file> file is deleted.
5704 Packages that use <prgn>libtool</prgn> to create shared
5705 libraries should include the <file>.la</file> files in the
5706 <tt>-dev</tt> package, unless the package relies on
5707 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
5708 the <tt>.la</tt> files must go in the run-time library
5713 You must make sure that you use only released versions of
5714 shared libraries to build your packages; otherwise other
5715 users will not be able to run your binaries
5716 properly. Producing source packages that depend on
5717 unreleased compilers is also usually a bad
5723 <heading>Shared libraries</heading>
5726 Packages involving shared libraries should be split up
5727 into several binary packages.</p>
5730 For a straightforward library which has a development
5731 environment and a runtime kit including just shared
5732 libraries you need to create two packages:
5733 <file><var>libraryname</var><var>soversion</var></file>, where
5734 <file><var>soversion</var></file> is the version number in the
5735 soname of the shared library<footnote>
5737 The soname is the shared object name: it's the thing
5738 that has to match exactly between building an executable
5739 and running it for the dynamic linker to be able run the
5740 program. For example, if the soname of the library is
5741 <file>libfoo.so.6</file>, the library package would be
5742 called <file>libfoo6</file>.
5745 and <tt><var>libraryname</var><var>soversion</var>-dev</tt>.
5746 Alternatively, if it would be confusing to directly append
5747 <var>soversion</var> to <var>libraryname</var> (e.g. because
5748 <var>libraryname</var> itself ends in a number), you may use
5749 <tt><var>libraryname</var>-<var>soversion</var></tt> and
5750 <tt><var>libraryname</var>-<var>soversion</var>-dev</tt>
5755 If you prefer only to support one development version at a
5756 time you may name the development package
5757 <file><var>libraryname</var>-dev</file>; otherwise you may need
5758 to use <prgn>dpkg</prgn>'s Conflicts mechanism (see <ref
5759 id="conflicts">) to ensure that the user only installs one
5760 development version at a time (as different development
5761 versions are likely to have the same header files in them,
5762 which would cause a filename clash if both were installed).
5763 Typically the development version should also have an exact
5764 version dependency on the runtime library, to make sure that
5765 compilation and linking happens correctly. The
5766 <tt>${Source-Version}</tt> substitution variable can be
5767 useful for this purpose.
5771 Packages which use the shared library should have a
5772 dependency on the name of the shared library package,
5773 <file><var>libraryname</var><var>soversion</var></file>. When
5774 the soname changes you can have both versions of the library
5775 installed while migrating from the old library to the new.
5779 If your package has some run-time support programs which use
5780 the shared library you must not put them in the shared
5781 library package. If you do that then you won't be able to
5782 install several versions of the shared library without
5783 getting filename clashes. Instead, either create a third
5784 package for the runtime binaries (this package might
5785 typically be named <tt><var>libraryname</var>-runtime</tt>;
5786 note the absence of the <var>soversion</var> in the package
5787 name), or if the development package is small you may
5788 include them in there.
5792 If you have several shared libraries built from the same
5793 source tree you may lump them all together into a single
5794 shared library package, provided that you change all of
5795 their sonames at once (so that you don't get filename
5796 clashes if you try to install different versions of the
5797 combined shared libraries package).
5801 Shared libraries should not be installed executable, since
5802 the dynamic linker does not require this and trying to
5803 execute a shared library usually results in a core dump.
5808 <heading>Scripts</heading>
5811 All command scripts, including the package maintainer
5812 scripts inside the package and used by <prgn>dpkg</prgn>,
5813 should have a <tt>#!</tt> line naming the shell to be used
5814 to interpret them.</p>
5817 In the case of Perl scripts this should be
5818 <tt>#!/usr/bin/perl</tt>.</p>
5821 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
5822 should almost certainly start with <tt>set -e</tt> so that
5823 errors are detected. Every script should use
5824 <tt>set -e</tt> or check the exit status of <em>every</em>
5828 The standard shell interpreter <file>/bin/sh</file> can be a
5829 symbolic link to any POSIX compatible shell, if <tt>echo
5830 -n</tt> does not generate a newline.<footnote>
5832 Debian policy specifies POSIX behavior for
5833 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
5834 use in the Linux community (in particular including this
5835 policy, the Linux kernel source, many Debian scripts,
5836 etc.). This <tt>echo -n</tt> mechanism is valid but not
5837 required under POSIX, hence this explicit addition.
5838 Also, rumour has it that this shall be mandated under
5842 Thus, shell scripts specifying <file>/bin/sh</file> as
5843 interpreter should only use POSIX features. If a script
5844 requires non-POSIX features from the shell interpreter, the
5845 appropriate shell must be specified in the first line of the
5846 script (e.g., <tt>#!/bin/bash</tt>) and the package must
5847 depend on the package providing the shell (unless the shell
5848 package is marked "Essential", as in the case of
5853 You may wish to restrict your script to POSIX features when
5854 possible so that it may use <file>/bin/sh</file> as its
5855 interpreter. If your script works with <prgn>dash</prgn>
5856 (originally called <prgn>ash</prgn>), it's probably POSIX
5857 compliant, but if you are in doubt, use
5858 <file>/bin/bash</file>.
5862 Perl scripts should check for errors when making any
5863 system calls, including <tt>open</tt>, <tt>print</tt>,
5864 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
5868 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
5869 scripting languages. See <em>Csh Programming Considered
5870 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
5871 can be found at <url
5872 id="http://language.perl.com/versus/csh.whynot">.<footnote>
5874 It can also be found on
5875 <url id="http://www.cpan.org/doc/FMTEYEWTK/versus/csh.whynot">
5876 or on the ftp site <ftpsite>ftp.cpan.org</ftpsite> as
5877 <ftppath>/pub/perl/CPAN/doc/FMTEYEWTK/versus/csh.whynot</ftppath>.
5880 If an upstream package comes with <prgn>csh</prgn> scripts
5881 then you must make sure that they start with
5882 <tt>#!/bin/csh</tt> and make your package depend on the
5883 <prgn>c-shell</prgn> virtual package.
5887 Any scripts which create files in world-writeable
5888 directories (e.g., in <file>/tmp</file>) must use a
5889 mechanism which will fail if a file with the same name
5893 The Debian base system provides the <prgn>tempfile</prgn>
5894 and <prgn>mktemp</prgn> utilities for use by scripts for
5895 this purpose.</p></sect>
5899 <heading>Symbolic links</heading>
5902 In general, symbolic links within a top-level directory
5903 should be relative, and symbolic links pointing from one
5904 top-level directory into another should be absolute. (A
5905 top-level directory is a sub-directory of the root
5906 directory <file>/</file>.)</p>
5909 In addition, symbolic links should be specified as short as
5910 possible, i.e., link targets like <file>foo/../bar</file> are
5914 Note that when creating a relative link using
5915 <prgn>ln</prgn> it is not necessary for the target of the
5916 link to exist relative to the working directory you're
5917 running <prgn>ln</prgn> from, nor is it necessary to change
5918 directory to the directory where the link is to be made.
5919 Simply include the string that should appear as the target
5920 of the link (this will be a pathname relative to the
5921 directory in which the link resides) as the first argument
5922 to <prgn>ln</prgn>.</p>
5925 For example, in your <prgn>Makefile</prgn> or
5926 <file>debian/rules</file>, you can do things like:
5927 <example compact="compact">
5928 ln -fs gcc $(prefix)/bin/cc
5929 ln -fs gcc debian/tmp/usr/bin/cc
5930 ln -fs ../sbin/sendmail $(prefix)/bin/runq
5931 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
5935 A symbolic link pointing to a compressed file should always
5936 have the same file extension as the referenced file. (For
5937 example, if a file <file>foo.gz</file> is referenced by a
5938 symbolic link, the filename of the link has to end with
5939 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
5944 <heading>Device files</heading>
5947 Packages must not include device files in the package file
5951 If a package needs any special device files that are not
5952 included in the base system, it must call
5953 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
5954 after notifying the user<footnote>
5956 This notification could be done via a (low-priority)
5957 debconf message, or an echo (printf) statement.
5963 Packages must not remove any device files in the
5964 <prgn>postrm</prgn> or any other script. This is left to the
5965 system administrator.</p>
5968 Debian uses the serial devices
5969 <file>/dev/ttyS*</file>. Programs using the old
5970 <file>/dev/cu*</file> devices should be changed to use
5971 <file>/dev/ttyS*</file>.</p>
5974 <sect id="config-files">
5975 <heading>Configuration files</heading>
5977 <heading>Definitions</heading>
5980 <tag>configuration file</tag>
5983 A file that affects the operation of a program, or
5984 provides site- or host-specific information, or
5985 otherwise customizes the behavior of a program.
5986 Typically, configuration files are intended to be
5987 modified by the system administrator (if needed or
5988 desired) to conform to local policy or to provide
5989 more useful site-specific behavior.
5993 <tag><tt>conffile</tt></tag>
5996 A file listed in a package's <tt>conffiles</tt>
5997 file, and is treated specially by <prgn>dpkg</prgn>
5998 (see <ref id="configdetails">).
6005 The distinction between these two is important; they are
6006 not interchangeable concepts. Almost all
6007 <tt>conffile</tt>s are configuration files, but many
6008 configuration files are not <tt>conffiles</tt>.
6012 Note that a script that embeds configuration information
6013 (such as most of the files in <file>/etc/default</file> and
6014 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6015 configuration file and should be treated as such.
6020 <heading>Location</heading>
6022 Any configuration files created or used by your package
6023 must reside in <file>/etc</file>. If there are several you
6024 should consider creating a subdirectory of <file>/etc</file>
6025 named after your package.</p>
6028 If your package creates or uses configuration files
6029 outside of <file>/etc</file>, and it is not feasible to modify
6030 the package to use the <file>/etc</file>, you should still put
6031 the files in <file>/etc</file> and create symbolic links to
6032 those files from the location that the package
6037 <heading>Behavior</heading>
6039 Configuration file handling must conform to the following
6041 <list compact="compact">
6044 local changes must be preserved during a package
6050 configuration files must be preserved when the
6051 package is removed, and only deleted when the
6059 The easy way to achieve this behavior is to make the
6060 configuration file a <tt>conffile</tt>. This is
6061 appropriate only if it is possible to distribute a default
6062 version that will work for most installations, although
6063 some system administrators may choose to modify it. This
6064 implies that the default version will be part of the
6065 package distribution, and must not be modified by the
6066 maintainer scripts during installation (or at any other
6071 In order to ensure that local changes are preserved
6072 correctly, no package may contain or make hard links to
6073 conffiles.<footnote>
6075 Rationale: There are two problems with hard links.
6076 The first is that some editors break the link while
6077 editing one of the files, so that the two files may
6078 unwittingly become unlinked and different. The second
6079 is that <prgn>dpkg</prgn> might break the hard link
6080 while upgrading <tt>conffile</tt>s.
6086 The other way to do it is via the maintainer scripts. In
6087 this case, the configuration file must not be listed as a
6088 <tt>conffile</tt> and must not be part of the package
6089 distribution. If the existence of a file is required for
6090 the package to be sensibly configured it is the
6091 responsibility of the package maintainer to provide
6092 maintainer scripts which correctly create, update and
6093 maintain the file and remove it on purge. (See <ref
6094 id="maintainerscripts"> for more information.) These
6095 scripts must be idempotent (i.e., must work correctly if
6096 <prgn>dpkg</prgn> needs to re-run them due to errors
6097 during installation or removal), must cope with all the
6098 variety of ways <prgn>dpkg</prgn> can call maintainer
6099 scripts, must not overwrite or otherwise mangle the user's
6100 configuration without asking, must not ask unnecessary
6101 questions (particularly during upgrades), and otherwise be
6106 The scripts are not required to configure every possible
6107 option for the package, but only those necessary to get
6108 the package running on a given system. Ideally the
6109 sysadmin should not have to do any configuration other
6110 than that done (semi-)automatically by the
6111 <prgn>postinst</prgn> script.
6115 A common practice is to create a script called
6116 <file><var>package</var>-configure</file> and have the
6117 package's <prgn>postinst</prgn> call it if and only if the
6118 configuration file does not already exist. In certain
6119 cases it is useful for there to be an example or template
6120 file which the maintainer scripts use. Such files should
6121 be in <file>/usr/share/<var>package</var></file> or
6122 <file>/usr/lib/<var>package</var></file> (depending on whether
6123 they are architecture-independent or not). There should
6124 be symbolic links to them from
6125 <file>/usr/share/doc/<var>package</var>/examples</file> if
6126 they are examples, and should be perfectly ordinary
6127 <prgn>dpkg</prgn>-handled files (<em>not</em>
6128 configuration files).
6132 These two styles of configuration file handling must
6133 not be mixed, for that way lies madness:
6134 <prgn>dpkg</prgn> will ask about overwriting the file
6135 every time the package is upgraded.
6140 <heading>Sharing configuration files</heading>
6142 Packages which specify the same file as a
6143 <tt>conffile</tt> must be tagged as <em>conflicting</em>
6144 with each other. (This is an instance of the general rule
6145 about not sharing files. Note that neither alternatives
6146 nor diversions are likely to be appropriate in this case;
6147 in particular, <prgn>dpkg</prgn> does not handle diverted
6148 <tt>conffile</tt>s well.)
6152 The maintainer scripts must not alter a <tt>conffile</tt>
6153 of <em>any</em> package, including the one the scripts
6158 If two or more packages use the same configuration file
6159 and it is reasonable for both to be installed at the same
6160 time, one of these packages must be defined as
6161 <em>owner</em> of the configuration file, i.e., it will be
6162 the package which handles that file as a configuration
6163 file. Other packages that use the configuration file must
6164 depend on the owning package if they require the
6165 configuration file to operate. If the other package will
6166 use the configuration file if present, but is capable of
6167 operating without it, no dependency need be declared.</p>
6170 If it is desirable for two or more related packages to
6171 share a configuration file <em>and</em> for all of the
6172 related packages to be able to modify that configuration
6173 file, then the following should be done:
6174 <enumlist compact="compact">
6177 One of the related packages (the "owning" package)
6178 will manage the configuration file with maintainer
6179 scripts as described in the previous section.
6184 The owning package should also provide a program
6185 that the other packages may use to modify the
6191 The related packages must use the provided program
6192 to make any desired modifications to the
6193 configuration file. They should either depend on
6194 the core package to guarantee that the configuration
6195 modifier program is available or accept gracefully
6196 that they cannot modify the configuration file if it
6197 is not. (This is in addition to the fact that the
6198 configuration file may not even be present in the
6206 Sometimes it's appropriate to create a new package which
6207 provides the basic infrastructure for the other packages
6208 and which manages the shared configuration files. (The
6209 <tt>sgml-base</tt> package is a good example.)
6214 <heading>User configuration files ("dotfiles")</heading>
6217 The files in <file>/etc/skel</file> will automatically be
6218 copied into new user accounts by <prgn>adduser</prgn>.
6219 No other program should reference the files in
6220 <file>/etc/skel</file>.
6224 Therefore, if a program needs a dotfile to exist in
6225 advance in <file>$HOME</file> to work sensibly, that dotfile
6226 should be installed in <file>/etc/skel</file> and treated as a
6231 However, programs that require dotfiles in order to
6232 operate sensibly (dotfiles that they do not create
6233 themselves automatically, that is) are a bad thing.
6234 Furthermore, programs should be configured by the Debian
6235 default installation to behave as closely to the upstream
6236 default behaviour as possible.
6240 Therefore, if a program in a Debian package needs to be
6241 configured in some way in order to operate sensibly, that
6242 should be done using a site-wide configuration file placed
6243 in <file>/etc</file>. Only if the program doesn't support a
6244 site-wide default configuration and the package maintainer
6245 doesn't have time to add it may a default per-user file be
6246 placed in <file>/etc/skel</file>.
6250 <file>/etc/skel</file> should be as empty as we can make it.
6251 This is particularly true because there is no easy (or
6252 necessarily desirable) mechanism for ensuring that the
6253 appropriate dotfiles are copied into the accounts of
6254 existing users when a package is installed.
6260 <heading>Log files</heading>
6262 Log files should usually be named
6263 <file>/var/log/<var>package</var>.log</file>. If you have many
6264 log files, or need a separate directory for permission
6265 reasons (<file>/var/log</file> is writable only by
6266 <file>root</file>), you should usually create a directory named
6267 <file>/var/log/<var>package</var></file> and place your log
6272 Log files must be rotated occasionally so that they don't
6273 grow indefinitely; the best way to do this is to drop a log
6274 rotation configuration file into the directory
6275 <file>/etc/logrotate.d</file> and use the facilities provided by
6276 logrotate.<footnote>
6278 The traditional approach to log files has been to set up
6279 <em>ad hoc</em> log rotation schemes using simple shell
6280 scripts and cron. While this approach is highly
6281 customizable, it requires quite a lot of sysadmin work.
6282 Even though the original Debian system helped a little
6283 by automatically installing a system which can be used
6284 as a template, this was deemed not enough.
6288 The use of <prgn>logrotate</prgn>, a program developed
6289 by Red Hat, is better, as it centralizes log management.
6290 It has both a configuration file
6291 (<file>/etc/logrotate.conf</file>) and a directory where
6292 packages can drop their individual log rotation
6293 configurations (<file>/etc/logrotate.d</file>).
6296 Here is a good example for a logrotate config
6297 file (for more information see <manref name="logrotate"
6299 <example compact="compact">
6305 /etc/init.d/foo force-reload
6309 This rotates all files under <file>/var/log/foo</file>, saves 12
6310 compressed generations, and forces the daemon to reload its
6311 configuration information after the log rotation.
6315 Log files should be removed when the package is
6316 purged (but not when it is only removed). This should be
6317 done by the <prgn>postrm</prgn> script when it is called
6318 with the argument <tt>purge</tt> (see <ref
6319 id="removedetails">).
6324 <heading>Permissions and owners</heading>
6327 The rules in this section are guidelines for general use.
6328 If necessary you may deviate from the details below.
6329 However, if you do so you must make sure that what is done
6330 is secure and you should try to be as consistent as possible
6331 with the rest of the system. You should probably also
6332 discuss it on <prgn>debian-devel</prgn> first.
6336 Files should be owned by <tt>root.root</tt>, and made
6337 writable only by the owner and universally readable (and
6338 executable, if appropriate), that is mode 644 or 755.
6342 Directories should be mode 755 or (for group-writability)
6343 mode 2775. The ownership of the directory should be
6344 consistent with its mode: if a directory is mode 2775, it
6345 should be owned by the group that needs write access to
6350 Setuid and setgid executables should be mode 4755 or 2755
6351 respectively, and owned by the appropriate user or group.
6352 They should not be made unreadable (modes like 4711 or
6353 2711 or even 4111); doing so achieves no extra security,
6354 because anyone can find the binary in the freely available
6355 Debian package; it is merely inconvenient. For the same
6356 reason you should not restrict read or execute permissions
6357 on non-set-id executables.
6361 Some setuid programs need to be restricted to particular
6362 sets of users, using file permissions. In this case they
6363 should be owned by the uid to which they are set-id, and by
6364 the group which should be allowed to execute them. They
6365 should have mode 4754; again there is no point in making
6366 them unreadable to those users who must not be allowed to
6371 It is possible to arrange that the system administrator can
6372 reconfigure the package to correspond to their local
6373 security policy by changing the permissions on a binary:
6374 they can do this by using <prgn>dpkg-statoverride</prgn>, as
6375 described below.<footnote>
6377 Ordinary files installed by <prgn>dpkg</prgn> (as
6378 opposed to <tt>conffile</tt>s and other similar objects)
6379 normally have their permissions reset to the distributed
6380 permissions when the package is reinstalled. However,
6381 the use of <prgn>dpkg-statoverride</prgn> overrides this
6382 default behaviour. If you use this method, you should
6383 remember to describe <prgn>dpkg-statoverride</prgn> in
6384 the package documentation; being a relatively new
6385 addition to Debian, it is probably not yet well-known.
6388 Another method you should consider is to create a group for
6389 people allowed to use the program(s) and make any setuid
6390 executables executable only by that group.
6394 If you need to create a new user or group for your package
6395 there are two possibilities. Firstly, you may need to
6396 make some files in the binary package be owned by this
6397 user or group, or you may need to compile the user or
6398 group id (rather than just the name) into the binary
6399 (though this latter should be avoided if possible, as in
6400 this case you need a statically allocated id).</p>
6403 If you need a statically allocated id, you must ask for a
6404 user or group id from the <tt>base-passwd</tt> maintainer,
6405 and must not release the package until you have been
6406 allocated one. Once you have been allocated one you must
6407 either make the package depend on a version of the
6408 <tt>base-passwd</tt> package with the id present in
6409 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
6410 your package to create the user or group itself with the
6411 correct id (using <tt>adduser</tt>) in its
6412 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
6413 the <prgn>postinst</prgn> is to be preferred if it is
6414 possible, otherwise a pre-dependency will be needed on the
6415 <tt>adduser</tt> package.)
6419 On the other hand, the program might be able to determine
6420 the uid or gid from the user or group name at runtime, so
6421 that a dynamically allocated id can be used. In this case
6422 you should choose an appropriate user or group name,
6423 discussing this on <prgn>debian-devel</prgn> and checking
6424 with the base system maintainer that it is unique and that
6425 they do not wish you to use a statically allocated id
6426 instead. When this has been checked you must arrange for
6427 your package to create the user or group if necessary using
6428 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
6429 <prgn>postinst</prgn> script (again, the latter is to be
6430 preferred if it is possible).
6434 Note that changing the numeric value of an id associated
6435 with a name is very difficult, and involves searching the
6436 file system for all appropriate files. You need to think
6437 carefully whether a static or dynamic id is required, since
6438 changing your mind later will cause problems.
6441 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
6443 This section is not intended as policy, but as a
6444 description of the use of <prgn>dpkg-statoverride</prgn>.
6448 <prgn>dpkg-statoverride</prgn> is a replacement for the
6449 deprecated <tt>suidmanager</tt> package. Packages which
6450 previously used <tt>suidmanager</tt> should have a
6451 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
6452 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
6453 and <tt>suidunregister</tt> should now be simply removed
6454 from the maintainer scripts.
6458 If a system administrator wishes to have a file (or
6459 directory or other such thing) installed with owner and
6460 permissions different from those in the distributed Debian
6461 package, he can use the <prgn>dpkg-statoverride</prgn>
6462 program to instruct <prgn>dpkg</prgn> to use the different
6463 settings every time the file is installed. Thus the
6464 package maintainer should distribute the files with their
6465 normal permissions, and leave it for the system
6466 administrator to make any desired changes. For example, a
6467 daemon which is normally required to be setuid root, but
6468 in certain situations could be used without being setuid,
6469 should be installed setuid in the <tt>.deb</tt>. Then the
6470 local system administrator can change this if they wish.
6471 If there are two standard ways of doing it, the package
6472 maintainer can use <tt>debconf</tt> to find out the
6473 preference, and call <prgn>dpkg-statoverride</prgn> in the
6474 maintainer script if necessary to accommodate the system
6475 administrator's choice.
6479 Given the above, <prgn>dpkg-statoverride</prgn> is
6480 essentially a tool for system administrators and would not
6481 normally be needed in the maintainer scripts. There is
6482 one type of situation, though, where calls to
6483 <prgn>dpkg-statoverride</prgn> would be needed in the
6484 maintainer scripts, and that involves packages which use
6485 dynamically allocated user or group ids. In such a
6486 situation, something like the following idiom can be very
6487 helpful in the package's <prgn>postinst</prgn>, where
6488 <tt>sysuser</tt> is a dynamically allocated id:
6490 for i in /usr/bin/foo /usr/sbin/bar
6492 if ! dpkg-statoverride --list $i >/dev/null
6494 dpkg-statoverride --update --add sysuser root 4755 $i
6498 The corresponding <tt>dpkg-statoverride --remove</tt>
6499 calls can then be made unconditionally when the package is
6506 <chapt id="customized-programs">
6507 <heading>Customized programs</heading>
6509 <sect id="arch-spec">
6510 <heading>Architecture specification strings</heading>
6513 If a program needs to specify an <em>architecture specification
6514 string</em> in some place, the following format should be
6515 used: <var>arch</var>-<var>os</var><footnote>
6517 The following architectures and operating systems are
6518 currently recognised by <prgn>dpkg-archictecture</prgn>.
6519 The architecture, <tt><var>arch</var></tt>, is one of
6520 the following: <tt>alpha</tt>, <tt>arm</tt>,
6521 <tt>hppa</tt>, <tt>i386</tt>, <tt>ia64</tt>,
6522 <tt>m68k</tt>, <tt>mips</tt>, <tt>mipsel</tt>,
6523 <tt>powerpc</tt>, <tt>s390</tt>, <tt>sh</tt>,
6524 <tt>sheb</tt>, <tt>sparc</tt> and <tt>sparc64</tt>. The
6525 operating system, <tt><var>os</var></tt>, is one of:
6526 <tt>linux</tt>, <tt>gnu</tt>, <tt>freebsd</tt> and
6527 <tt>openbsd</tt>. Use of <tt>gnu</tt> in this string is
6528 reserved for the GNU/Hurd operating system.
6534 Note that we don't want to use
6535 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
6536 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
6537 since this would make our programs incompatible with other
6538 Linux distributions. We also don't use something like
6539 <tt><var>arch</var>-unknown-linux</tt>, since the
6540 <tt>unknown</tt> does not look very good.
6545 <heading>Daemons</heading>
6548 The configuration files <file>/etc/services</file>,
6549 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
6550 by the <prgn>netbase</prgn> package and must not be modified
6555 If a package requires a new entry in one of these files, the
6556 maintainer should get in contact with the
6557 <prgn>netbase</prgn> maintainer, who will add the entries
6558 and release a new version of the <prgn>netbase</prgn>
6563 The configuration file <file>/etc/inetd.conf</file> must not be
6564 modified by the package's scripts except via the
6565 <prgn>update-inetd</prgn> script or the
6566 <file>DebianNet.pm</file> Perl module. See their documentation
6567 for details on how to add entries.
6571 If a package wants to install an example entry into
6572 <file>/etc/inetd.conf</file>, the entry must be preceded with
6573 exactly one hash character (<tt>#</tt>). Such lines are
6574 treated as "commented out by user" by the
6575 <prgn>update-inetd</prgn> script and are not changed or
6576 activated during package updates.
6581 <heading>Using pseudo-ttys and modifying wtmp, utmp and
6585 Some programs need to create pseudo-ttys. This should be done
6586 using Unix98 ptys if the C library supports it. The resulting
6587 program must not be installed setuid root, unless that
6588 is required for other functionality.
6592 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
6593 <file>/var/log/lastlog</file> must be installed writeable by
6594 group <tt>utmp</tt>. Programs which need to modify those
6595 files must be installed setgid <tt>utmp</tt>.
6600 <heading>Editors and pagers</heading>
6603 Some programs have the ability to launch an editor or pager
6604 program to edit or display a text document. Since there are
6605 lots of different editors and pagers available in the Debian
6606 distribution, the system administrator and each user should
6607 have the possibility to choose his/her preferred editor and
6612 In addition, every program should choose a good default
6613 editor/pager if none is selected by the user or system
6618 Thus, every program that launches an editor or pager must
6619 use the EDITOR or PAGER environment variable to determine
6620 the editor or pager the user wishes to use. If these
6621 variables are not set, the programs <file>/usr/bin/editor</file>
6622 and <file>/usr/bin/pager</file> should be used, respectively.
6626 These two files are managed through the <prgn>dpkg</prgn>
6627 "alternatives" mechanism. Thus every package providing an
6628 editor or pager must call the
6629 <prgn>update-alternatives</prgn> script to register these
6634 If it is very hard to adapt a program to make use of the
6635 EDITOR or PAGER variables, that program may be configured to
6636 use <file>/usr/bin/sensible-editor</file> and
6637 <file>/usr/bin/sensible-pager</file> as the editor or pager
6638 program respectively. These are two scripts provided in the
6639 Debian base system that check the EDITOR and PAGER variables
6640 and launch the appropriate program, and fall back to
6641 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
6642 variable is not set.
6646 A program may also use the VISUAL environment variable to
6647 determine the user's choice of editor. If it exists, it
6648 should take precedence over EDITOR. This is in fact what
6649 <file>/usr/bin/sensible-editor</file> does.
6653 It is not required for a package to depend on
6654 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
6655 package to provide such virtual packages.<footnote>
6657 The Debian base system already provides an editor and a
6664 <sect id="web-appl">
6665 <heading>Web servers and applications</heading>
6668 This section describes the locations and URLs that should
6669 be used by all web servers and web applications in the
6677 Cgi-bin executable files are installed in the
6679 <example compact="compact">
6680 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
6682 and should be referred to as
6683 <example compact="compact">
6684 http://localhost/cgi-bin/<var>cgi-bin-name</var>
6689 <item><p>Access to HTML documents</p>
6692 HTML documents for a package are stored in
6693 <file>/usr/share/doc/<var>package</var></file>
6694 and can be referred to as
6695 <example compact="compact">
6696 http://localhost/doc/<var>package</var>/<var>filename</var>
6700 The web server should restrict access to the document
6701 tree so that only clients on the same host can read
6702 the documents. If the web server does not support such
6703 access controls, then it should not provide access at
6704 all, or ask about providing access during installation.
6708 <item><p>Web Document Root</p>
6711 Web Applications should try to avoid storing files in
6712 the Web Document Root. Instead they should use the
6713 /usr/share/doc/<var>package</var> directory for
6714 documents and register the Web Application via the
6715 menu package. If access to the web document root is
6716 unavoidable then use
6717 <example compact="compact">
6720 as the Document Root. This might be just a symbolic
6721 link to the location where the system administrator
6722 has put the real document root.
6726 </enumlist></p></sect>
6729 <sect id="mail-transport-agents">
6730 <heading>Mail transport, delivery and user agents</heading>
6733 Debian packages which process electronic mail, whether mail
6734 user agents (MUAs) or mail transport agents (MTAs), must
6735 ensure that they are compatible with the configuration
6736 decisions below. Failure to do this may result in lost
6737 mail, broken <tt>From:</tt> lines, and other serious brain
6742 The mail spool is <file>/var/mail</file> and the interface to
6743 send a mail message is <file>/usr/sbin/sendmail</file> (as per
6744 the FHS). On older systems, the mail spool may be
6745 physically located in <file>/var/spool/mail</file>, but all
6746 access to the mail spool should be via the
6747 <file>/var/mail</file> symlink. The mail spool is part of the
6748 base system and not part of the MTA package.
6752 All Debian MUAs, MTAs, MDAs and other mailbox accessing
6753 programs (such as IMAP daemons) must lock the mailbox in an
6754 NFS-safe way. This means that <tt>fcntl()</tt> locking must
6755 be combined with dot locking. To avoid deadlocks, a program
6756 should use <tt>fcntl()</tt> first and dot locking after
6757 this, or alternatively implement the two locking methods in
6758 a non blocking way<footnote>
6760 If it is not possible to establish both locks, the
6761 system shouldn't wait for the second lock to be
6762 established, but remove the first lock, wait a (random)
6763 time, and start over locking again.
6765 </footnote>. Using the functions <tt>maillock</tt> and
6766 <tt>mailunlock</tt> provided by the
6767 <tt>liblockfile*</tt><footnote>
6769 You will need to depend on <tt>liblockfile1
6770 (>>1.01)</tt> to use these functions.
6772 </footnote> packages is the recommended way to realize this.
6776 Mailboxes are generally mode 660
6777 <tt><var>user</var>.mail</tt> unless the system
6778 administrator has chosen otherwise. A MUA may remove a
6779 mailbox (unless it has nonstandard permissions) in which
6780 case the MTA or another MUA must recreate it if needed.
6781 Mailboxes must be writable by group mail.
6785 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
6786 be setgid mail to do the locking mentioned above (and
6787 must obviously avoid accessing other users' mailboxes
6788 using this privilege).</p>
6791 <file>/etc/aliases</file> is the source file for the system mail
6792 aliases (e.g., postmaster, usenet, etc.), it is the one
6793 which the sysadmin and <prgn>postinst</prgn> scripts may
6794 edit. After <file>/etc/aliases</file> is edited the program or
6795 human editing it must call <prgn>newaliases</prgn>. All MTA
6796 packages must come with a <prgn>newaliases</prgn> program,
6797 even if it does nothing, but older MTA packages did not do
6798 this so programs should not fail if <prgn>newaliases</prgn>
6799 cannot be found. Note that because of this, all MTA
6800 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
6801 <tt>Replaces: mail-transport-agent</tt> control file
6806 The convention of writing <tt>forward to
6807 <var>address</var></tt> in the mailbox itself is not
6808 supported. Use a <tt>.forward</tt> file instead.</p>
6811 The <prgn>rmail</prgn> program used by UUCP
6812 for incoming mail should be <file>/usr/sbin/rmail</file>.
6813 Likewise, <prgn>rsmtp</prgn>, for receiving
6814 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
6818 If your package needs to know what hostname to use on (for
6819 example) outgoing news and mail messages which are generated
6820 locally, you should use the file <file>/etc/mailname</file>. It
6821 will contain the portion after the username and <tt>@</tt>
6822 (at) sign for email addresses of users on the machine
6823 (followed by a newline).
6827 Such package should check for the existence of this file
6828 when it is being configured. If it exists, it should be
6829 used without comment, although an MTA's configuration script
6830 may wish to prompt the user even if it finds that this file
6831 exists. If the file does not exist, the package should
6832 prompt the user for the value (preferably using
6833 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
6834 as well as using it in the package's configuration. The
6835 prompt should make it clear that the name will not just be
6836 used by that package. For example, in this situation the
6837 <tt>inn</tt> package could say something like:
6838 <example compact="compact">
6839 Please enter the "mail name" of your system. This is the
6840 hostname portion of the address to be shown on outgoing
6841 news and mail messages. The default is
6842 <var>syshostname</var>, your system's host name. Mail
6843 name ["<var>syshostname</var>"]:
6845 where <var>syshostname</var> is the output of <tt>hostname
6851 <heading>News system configuration</heading>
6854 All the configuration files related to the NNTP (news)
6855 servers and clients should be located under
6856 <file>/etc/news</file>.</p>
6859 There are some configuration issues that apply to a number
6860 of news clients and server packages on the machine. These
6864 <tag><file>/etc/news/organization</file></tag>
6865 <item><p>A string which should appear as the
6866 organization header for all messages posted
6867 by NNTP clients on the machine</p></item>
6869 <tag><file>/etc/news/server</file></tag>
6870 <item><p>Contains the FQDN of the upstream NNTP
6871 server, or localhost if the local machine is
6872 an NNTP server.</p></item>
6875 Other global files may be added as required for cross-package news
6876 configuration.</p></sect>
6880 <heading>Programs for the X Window System</heading>
6883 <heading>Providing X support and package priorities</heading>
6886 Programs that can be configured with support for the X
6887 Window System must be configured to do so and must declare
6888 any package dependencies necessary to satisfy their
6889 runtime requirements when using the X Window System. If
6890 such a package is of higher priority than the X packages
6891 on which it depends, it is required that either the
6892 X-specific components be split into a separate package, or
6893 that an alternative version of the package, which includes
6894 X support, be provided, or that the package's priority be
6900 <heading>Packages providing an X server</heading>
6903 Packages that provide an X server that, directly or
6904 indirectly, communicates with real input and display
6905 hardware should declare in their control data that they
6906 provide the virtual package <tt>xserver</tt>.<footnote>
6908 This implements current practice, and provides an
6909 actual policy for usage of the <tt>xserver</tt>
6910 virtual package which appears in the virtual packages
6911 list. In a nutshell, X servers that interface
6912 directly with the display and input hardware or via
6913 another subsystem (e.g., GGI) should provide
6914 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
6915 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
6922 <heading>Packages providing a terminal emulator</heading>
6925 Packages that provide a terminal emulator for the X Window
6926 System which meet the criteria listed below should declare
6927 in their control data that they provide the virtual
6928 package <tt>x-terminal-emulator</tt>. They should also
6929 register themselves as an alternative for
6930 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
6935 To be an <tt>x-terminal-emulator</tt>, a program must:
6936 <list compact="compact">
6938 Be able to emulate a DEC VT100 terminal, or a
6939 compatible terminal.
6943 Support the command-line option <tt>-e
6944 <var>command</var></tt>, which creates a new
6945 terminal window<footnote>
6947 "New terminal window" does not necessarily mean
6948 a new top-level X window directly parented by
6949 the window manager; it could, if the terminal
6950 emulator application were so coded, be a new
6951 "view" in a multiple-document interface (MDI).
6954 and runs the specified <var>command</var>.
6958 Support the command-line option <tt>-T
6959 <var>title</var></tt>, which creates a new terminal
6960 window with the window title <var>title</var>.
6967 <heading>Packages providing a window manager</heading>
6970 Packages that provide a window manager should declare in
6971 their control data that they provide the virtual package
6972 <tt>x-window-manager</tt>. They should also register
6973 themselves as an alternative for
6974 <file>/usr/bin/x-window-manager</file>, with a priority
6975 calculated as follows:
6976 <list compact="compact">
6977 <item><p>Start with a priority of 20.</p></item>
6981 If the window manager supports the Debian menu
6982 system, add 20 points if this support is available
6983 in the package's default configuration (i.e., no
6984 configuration files belonging to the system or user
6985 have to be edited to activate the feature); if
6986 configuration files must be modified, add only 10
6992 If the window manager complies with <url
6993 id="http://www.freedesktop.org/standards/wm-spec.html"
6994 name="The Window Manager Specification Project">,
6995 written by the <url id="http://www.freedesktop.org"
6996 name="Free Desktop Group">, add 20 points.
7002 If the window manager permits the X session to be
7003 restarted using a <em>different</em> window manager
7004 (without killing the X server) in its default
7005 configuration, add 10 points; otherwise add none.
7013 <heading>Packages providing fonts</heading>
7016 Packages that provide fonts for the X Window
7019 For the purposes of Debian Policy, a "font for the X
7020 Window System" is one which is accessed via X protocol
7021 requests. Fonts for the Linux console, for PostScript
7022 renderers, or any other purpose, do not fit this
7023 definition. Any tool which makes such fonts available
7024 to the X Window System, however, must abide by this
7028 must do a number of things to ensure that they are both
7029 available without modification of the X or font server
7030 configuration, and that they do not corrupt files used by
7031 other font packages to register information about
7036 Fonts of any type supported by the X Window System
7037 must be in a separate binary package from any
7038 executables, libraries, or documentation (except
7039 that specific to the fonts shipped, such as their
7040 license information). If one or more of the fonts
7041 so packaged are necessary for proper operation of
7042 the package with which they are associated the font
7043 package may be Recommended; if the fonts merely
7044 provide an enhancement, a Suggests relationship may
7045 be used. Packages must not Depend on font
7048 This is because the X server may retrieve fonts
7049 from the local filesystem or over the network
7050 from an X font server; the Debian package system
7051 is empowered to deal only with the local
7060 BDF fonts must be converted to PCF fonts with the
7061 <prgn>bdftopcf</prgn> utility (available in the
7062 <tt>xutils</tt> package, <prgn>gzip</prgn>ped, and
7063 placed in a directory that corresponds to their
7065 <list compact="compact">
7067 100 dpi fonts must be placed in
7068 <file>/usr/X11R6/lib/X11/fonts/100dpi/</file>.
7072 75 dpi fonts must be placed in
7073 <file>/usr/X11R6/lib/X11/fonts/75dpi/</file>.
7077 Character-cell fonts, cursor fonts, and other
7078 low-resolution fonts must be placed in
7079 <file>/usr/X11R6/lib/X11/fonts/misc/</file>.
7086 Speedo fonts must be placed in
7087 <file>/usr/X11R6/lib/X11/fonts/Speedo/</file>.
7091 Type 1 fonts must be placed in
7092 <file>/usr/X11R6/lib/X11/fonts/Type1/</file>. If font
7093 metric files are available, they must be placed here
7099 Subdirectories of <file>/usr/X11R6/lib/X11/fonts/</file>
7100 other than those listed above must be neither
7101 created nor used. (The <file>PEX</file>, <file>CID</file>,
7102 and <file>cyrillic</file> directories are excepted for
7103 historical reasons, but installation of files into
7104 these directories remains discouraged.)
7110 Font packages may, instead of placing files directly
7111 in the X font directories listed above, provide
7112 symbolic links in that font directory pointing to
7113 the files' actual location in the filesystem. Such
7114 a location must comply with the FHS.
7120 Font packages should not contain both 75dpi and
7121 100dpi versions of a font. If both are available,
7122 they should be provided in separate binary packages
7123 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
7124 the names of the packages containing the
7125 corresponding fonts.
7131 Fonts destined for the <file>misc</file> subdirectory
7132 should not be included in the same package as 75dpi
7133 or 100dpi fonts; instead, they should be provided in
7134 a separate package with <tt>-misc</tt> appended to
7141 Font packages must not provide the files
7142 <file>fonts.dir</file>, <file>fonts.alias</file>, or
7143 <file>fonts.scale</file> in a font directory:
7146 <file>fonts.dir</file> files must not be provided at all.
7151 <file>fonts.alias</file> and <file>fonts.scale</file>
7152 files, if needed, should be provided in the
7154 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
7155 where <var>fontdir</var> is the name of the
7157 <file>/usr/X11R6/lib/X11/fonts/</file> where the
7158 package's corresponding fonts are stored
7159 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
7160 <var>package</var> is the name of the package
7161 that provides these fonts, and
7162 <var>extension</var> is either <tt>scale</tt>
7163 or <tt>alias</tt>, whichever corresponds to
7173 Font packages must declare a dependency on
7174 <tt>xutils (>> 4.0.3)</tt> in their control
7181 Font packages that provide one or more
7182 <file>fonts.scale</file> files as described above must
7183 invoke <prgn>update-fonts-scale</prgn> on each
7184 directory into which they installed fonts
7185 <em>before</em> invoking
7186 <prgn>update-fonts-dir</prgn> on that directory.
7187 This invocation must occur in both the
7188 <prgn>postinst</prgn> (for all arguments) and
7189 <prgn>postrm</prgn> (for all arguments except
7190 <tt>upgrade</tt>) scripts.
7196 Font packages that provide one or more
7197 <file>fonts.alias</file> files as described above must
7198 invoke <prgn>update-fonts-alias</prgn> on each
7199 directory into which they installed fonts. This
7200 invocation must occur in both the
7201 <prgn>postinst</prgn> (for all arguments) and
7202 <prgn>postrm</prgn> (for all arguments except
7203 <tt>upgrade</tt>) scripts.
7209 Font packages must invoke
7210 <prgn>update-fonts-dir</prgn> on each directory into
7211 which they installed fonts. This invocation must
7212 occur in both the <prgn>postinst</prgn> (for all
7213 arguments) and <prgn>postrm</prgn> (for all
7214 arguments except <tt>upgrade</tt>) scripts.
7220 Font packages must not provide alias names for the
7221 fonts they include which collide with alias names
7222 already in use by fonts already packaged.
7228 Font packages must not provide fonts with the same
7229 XLFD registry name as another font already packaged.
7237 <heading>Application defaults files</heading>
7240 Application defaults files must be installed in the
7241 directory <file>/etc/X11/app-defaults/</file> (use of a
7242 localized subdirectory of <file>/etc/X11/</file> as described
7243 in the <em>X Toolkit Intrinsics - C Language
7244 Interface</em> manual is also permitted). They must be
7245 registered as <tt>conffile</tt>s or handled as
7246 configuration files. Packages must not provide the
7247 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
7251 Customization of programs' X resources may also be
7252 supported with the provision of a file with the same name
7253 as that of the package placed in the
7254 <file>/etc/X11/Xresources/</file> directory, which must
7255 registered as a <tt>conffile</tt> or handled as a
7256 configuration file.<footnote>
7258 Note that this mechanism is not the same as using
7259 app-defaults; app-defaults are tied to the client
7260 binary on the local filesystem, whereas X resources
7261 are stored in the X server and affect all connecting
7265 <em>Important:</em> packages that install files into the
7266 <file>/etc/X11/Xresources/</file> directory must conflict with
7267 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
7268 it is possible for the installing package to destroy a
7269 previously-existing <file>/etc/X11/Xresources</file> file
7270 which had been customized by the system administrator.
7275 <heading>Installation directory issues</heading>
7278 Packages using the X Window System should not be
7279 configured to install files under the <file>/usr/X11R6/</file>
7280 directory unless they use <prgn>imake</prgn>. The
7281 <file>/usr/X11R6/</file> directory hierarchy should be
7282 regarded as deprecated for all packages except the X
7283 Window System itself, and those which use the
7284 <prgn>imake</prgn> program it provides, in which case the
7285 packages may transition out of the <file>/usr/X11R6/</file>
7286 directory at the maintainer's discretion.<footnote>
7288 <prgn>Imake</prgn>-using programs are exempt because,
7289 as long as they are written correctly, the pathnames
7290 they use to locate resources and install themselves
7291 are derived wholly from the X Window System
7292 configuration. Thus, in the event that the X Window
7293 System moves to <file>/usr/X11R7/</file>,
7294 <file>/usr/X12/</file>, or just plain <file>/usr/</file>, all
7295 that is required for these programs is a recompile
7296 against the corresponding X Window System library
7297 development packages.
7300 Programs that use GNU <prgn>autoconf</prgn> and
7301 <prgn>automake</prgn> are usually easily configured at
7302 compile time to use <file>/usr/</file> instead of
7303 <file>/usr/X11R6/</file>, and this should be done whenever
7304 possible. Configuration files for window managers and
7305 display managers should be placed in a subdirectory of
7306 <file>/etc/X11/</file> corresponding to the package name due
7307 to these programs' tight integration with the mechanisms
7308 of the X Window System. Application-level programs should
7309 use the <file>/etc/</file> directory unless otherwise mandated
7310 by policy. The installation of files into subdirectories
7311 of <file>/usr/X11R6/include/X11/</file> and
7312 <file>/usr/X11R6/lib/X11/</file> is permitted but discouraged;
7313 package maintainers should determine if subdirectories of
7314 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
7315 instead. (The use of symbolic links from the
7316 <file>X11R6</file> directories to other FHS-compliant
7317 locations is encouraged if the program is not easily
7318 configured to look elsewhere for its files.) Packages
7319 must not provide or install files into the directories
7320 <file>/usr/bin/X11/</file>, <file>/usr/include/X11/</file> or
7321 <file>/usr/lib/X11/</file>. Files within a package should,
7322 however, make reference to these directories, rather than
7323 their <tt>X11R6</tt>-named counterparts
7324 <file>/usr/X11R6/bin/</file>, <file>/usr/X11R6/include/X11/</file>
7325 and <file>/usr/X11R6/lib/X11/</file>, if the resources being
7326 referred to have not been moved to other FHS-compliant
7332 <heading>The OSF/Motif and OpenMotif libraries</heading>
7335 <em>Programs that require the non-DFSG-compliant OSF/Motif or
7336 OpenMotif libraries</em><footnote>
7338 OSF/Motif and OpenMotif are collectively referred to as
7339 "Motif" in this policy document.
7342 should be compiled against and tested with LessTif (a free
7343 re-implementation of Motif) instead. If the maintainer
7344 judges that the program or programs do not work
7345 sufficiently well with LessTif to be distributed and
7346 supported, but do so when compiled against Motif, then two
7347 versions of the package should be created; one linked
7348 statically against Motif and with <tt>-smotif</tt>
7349 appended to the package name, and one linked dynamically
7350 against Motif and with <tt>-dmotif</tt> appended to the
7351 package name. Both Motif-linked versions are dependent
7352 upon non-DFSG-compliant software and thus cannot be
7353 uploaded to the <em>main</em> distribution; if the
7354 software is itself DFSG-compliant it may be uploaded to
7355 the <em>contrib</em> distribution. While known existing
7356 versions of Motif permit unlimited redistribution of
7357 binaries linked against the library (whether statically or
7358 dynamically), it is the package maintainer's
7359 responsibility to determine whether this is permitted by
7360 the license of the copy of Motif in his or her possession.
7366 <heading>Perl programs and modules</heading>
7368 Perl programs and modules should follow the current Perl
7369 policy as defined in the file found on
7370 <ftpsite>ftp.debian.org</ftpsite> in
7371 <ftppath>/debian/doc/package-developer/perl-policy.txt.gz</ftppath>
7372 or your local mirror. In addition, it is included in the
7373 <tt>debian-policy</tt> package.
7378 <heading>Emacs lisp programs</heading>
7381 Please refer to the "Debian Emacs Policy" (documented in
7382 <file>debian-emacs-policy.gz</file> of the
7383 <prgn>emacsen-common</prgn> package) for details of how to
7384 package emacs lisp programs.
7389 <heading>Games</heading>
7392 The permissions on <file>/var/games</file> are mode 755, owner
7393 <tt>root</tt> and group <tt>root</tt>.
7397 Each game decides on its own security policy.</p>
7400 Games which require protected, privileged access to
7401 high-score files, savegames, etc., may be made
7402 set-<em>group</em>-id (mode 2755) and owned by
7403 <tt>root.games</tt>, and use files and directories with
7404 appropriate permissions (770 <tt>root.games</tt>, for
7405 example). They must not be made
7406 set-<em>user</em>-id, as this causes security problems. (If
7407 an attacker can subvert any set-user-id game they can
7408 overwrite the executable of any other, causing other players
7409 of these games to run a Trojan horse program. With a
7410 set-group-id game the attacker only gets access to less
7411 important game data, and if they can get at the other
7412 players' accounts at all it will take considerably more
7416 Some packages, for example some fortune cookie programs, are
7417 configured by the upstream authors to install with their
7418 data files or other static information made unreadable so
7419 that they can only be accessed through set-id programs
7420 provided. You should not do this in a Debian package: anyone can
7421 download the <file>.deb</file> file and read the data from it,
7422 so there is no point making the files unreadable. Not
7423 making the files unreadable also means that you don't have
7424 to make so many programs set-id, which reduces the risk of a
7428 As described in the FHS, binaries of games should be
7429 installed in the directory <file>/usr/games</file>. This also
7430 applies to games that use the X Window System. Manual pages
7431 for games (X and non-X games) should be installed in
7432 <file>/usr/share/man/man6</file>.</p>
7436 <chapt id="docs"><heading>Documentation</heading>
7440 <heading>Manual pages</heading>
7443 You should install manual pages in <prgn>nroff</prgn> source
7444 form, in appropriate places under <file>/usr/share/man</file>. You
7445 should only use sections 1 to 9 (see the FHS for more
7446 details). You must not install a preformatted "cat
7450 Each program, utility, and function should have an
7451 associated manpage included in the same package. It is
7452 suggested that all configuration files also have a manual
7453 page included as well.
7457 There should be a manual page at for every program at the
7458 very least, and possibly one for every configuration file,
7459 protocol, utility, and function. If no manual page is
7460 available, this is considered as a bug and should be
7461 reported to the Debian Bug Tracking System (the maintainer
7462 of the package is allowed to write this bug report
7463 themselves, if they so desire). Do not close the bug report
7464 until a proper manpage is available.<footnote>
7466 It is not very hard to write a man page. See the
7467 <url id="http://www.schweikhardt.net/man_page_howto.html"
7468 name="Man-Page-HOWTO">,
7469 <manref name="man" section="7">, the examples
7470 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
7471 the helper programs <prgn>help2man</prgn>, or the
7472 directory <file>/usr/share/doc/man-db/examples</file>.
7478 You may forward a complaint about a missing manpage to the
7479 upstream authors, and mark the bug as forwarded in the
7480 Debian bug tracking system. Even though the GNU Project do
7481 not in general consider the lack of a manpage to be a bug,
7482 we do; if they tell you that they don't consider it a bug
7483 you should leave the bug in our bug tracking system open
7488 Manual pages should be installed compressed using <tt>gzip -9</tt>.
7492 If one manpage needs to be accessible via several names it
7493 is better to use a symbolic link than the <file>.so</file>
7494 feature, but there is no need to fiddle with the relevant
7495 parts of the upstream source to change from <file>.so</file> to
7496 symlinks: don't do it unless it's easy. You should not
7497 create hard links in the manual page directories, nor put
7498 absolute filenames in <file>.so</file> directives. The filename
7499 in a <file>.so</file> in a manpage should be relative to the
7500 base of the manpage tree (usually
7501 <file>/usr/share/man</file>). If you do not create any links
7502 (whether symlinks, hard links, or <tt>.so</tt> directives)
7503 in the filesystem to the alternate names of the manpage,
7504 then you should not rely on <prgn>man</prgn> finding your
7505 manpage under those names based solely on the information in
7506 the manpage's header.<footnote>
7508 Supporting this in <prgn>man</prgn> often requires
7509 unreasonable processing time to find a manual page or to
7510 report that none exists, and moves knowledge into man's
7511 database that would be better left in the filesystem.
7512 This support is therefore deprecated and will cease to
7513 be present in the future.
7520 <heading>Info documents</heading>
7523 Info documents should be installed in <file>/usr/share/info</file>.
7524 They should be compressed with <tt>gzip -9</tt>.
7528 Your package should call <prgn>install-info</prgn> to update
7529 the Info <file>dir</file> file in its <prgn>postinst</prgn>
7530 script when called with a <tt>configure</tt> argument, for
7532 <example compact="compact">
7533 install-info --quiet --section Development Development \
7534 /usr/share/info/foobar.info
7538 It is a good idea to specify a section for the location of
7539 your program; this is done with the <tt>--section</tt>
7540 switch. To determine which section to use, you should look
7541 at <file>/usr/share/info/dir</file> on your system and choose the most
7542 relevant (or create a new section if none of the current
7543 sections are relevant). Note that the <tt>--section</tt>
7544 flag takes two arguments; the first is a regular expression
7545 to match (case-insensitively) against an existing section,
7546 the second is used when creating a new one.</p>
7549 You should remove the entries in the <prgn>prerm</prgn>
7550 script when called with a <tt>remove</tt> argument:
7551 <example compact="compact">
7552 install-info --quiet --remove /usr/share/info/foobar.info
7556 If <prgn>install-info</prgn> cannot find a description entry
7557 in the Info file you must supply one. See <manref
7558 name="install-info" section="8"> for details.</p>
7562 <heading>Additional documentation</heading>
7565 Any additional documentation that comes with the package may
7566 be installed at the discretion of the package maintainer.
7567 Text documentation should be installed in the directory
7568 <file>/usr/share/doc/<var>package</var></file>, where
7569 <var>package</var> is the name of the package, and
7570 compressed with <tt>gzip -9</tt> unless it is small.
7574 If a package comes with large amounts of documentation which
7575 many users of the package will not require you should create
7576 a separate binary package to contain it, so that it does not
7577 take up disk space on the machines of users who do not need
7578 or want it installed.</p>
7581 It is often a good idea to put text information files
7582 (<file>README</file>s, changelogs, and so forth) that come with
7583 the source package in <file>/usr/share/doc/<var>package</var></file>
7584 in the binary package. However, you don't need to install
7585 the instructions for building and installing the package, of
7589 Packages must not require the existance of any files in
7590 <file>/usr/share/doc/</file> in order to function
7593 The system administrator should be able to
7594 delete files in <file>/usr/share/doc/</file> without causing
7595 any programs to break.
7598 Any files that are referenced by programs but are also
7599 useful as standalone documentation should be installed under
7600 <file>/usr/share/doc/</file> with symbolic links from
7601 <file>/usr/share/doc/<var>package</var></file>.
7605 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7606 link to another directory in <file>/usr/share/doc</file> only if
7607 the two packages both come from the same source and the
7608 first package Depends on the second.
7612 Former Debian releases placed all additional documentation
7613 in <file>/usr/doc/<var>package</var></file>. This has been
7614 changed to <file>/usr/share/doc/<var>package</var></file>,
7615 and packages must not put documentation in the directory
7616 <file>/usr/doc/<var>package</var></file>. <footnote>
7617 <p>At this phase of the transition, we no longer require a
7618 symbolic link in <file>/usr/doc/</file>. At a later point,
7619 policy shall change to make the symbolic links a bug.</p>
7625 <heading>Preferred documentation formats</heading>
7628 The unification of Debian documentation is being carried out
7632 If your package comes with extensive documentation in a
7633 markup format that can be converted to various other formats
7634 you should if possible ship HTML versions in a binary
7635 package, in the directory
7636 <file>/usr/share/doc/<var>appropriate-package</var></file> or
7637 its subdirectories.<footnote>
7639 The rationale: The important thing here is that HTML
7640 docs should be available in <em>some</em> package, not
7641 necessarily in the main binary package.
7647 Other formats such as PostScript may be provided at the
7648 package maintainer's discretion.
7652 <sect id="copyrightfile">
7653 <heading>Copyright information</heading>
7656 Every package must be accompanied by a verbatim copy of its
7657 copyright and distribution license in the file
7658 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
7659 file must neither be compressed nor be a symbolic link.
7663 In addition, the copyright file must say where the upstream
7664 sources (if any) were obtained. It should name the original
7665 authors of the package and the Debian maintainer(s) who were
7666 involved with its creation.</p>
7669 A copy of the file which will be installed in
7670 <file>/usr/share/doc/<var>package</var>/copyright</file> should
7671 be in <file>debian/copyright</file> in the source package.
7675 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
7676 link to another directory in <file>/usr/share/doc</file> only if
7677 the two packages both come from the same source and the
7678 first package Depends on the second. These rules are
7679 important because copyrights must be extractable by
7684 Packages distributed under the UCB BSD license, the Artistic
7685 license, the GNU GPL, and the GNU LGPL should refer to the
7686 files <file>/usr/share/common-licenses/BSD</file>,
7687 <file>/usr/share/common-licenses/Artistic</file>,
7688 <file>/usr/share/common-licenses/GPL</file>, and
7689 <file>/usr/share/common-licenses/LGPL</file> respectively,
7690 rather than quoting them in the copyright file.
7694 You should not use the copyright file as a general <file>README</file>
7695 file. If your package has such a file it should be
7696 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
7697 <file>README.Debian</file> or some other appropriate place.</p>
7701 <heading>Examples</heading>
7704 Any examples (configurations, source files, whatever),
7705 should be installed in a directory
7706 <file>/usr/share/doc/<var>package</var>/examples</file>. These
7707 files should not be referenced by any program: they're there
7708 for the benefit of the system administrator and users as
7709 documentation only. Architecture-specific example files
7710 should be installed in a directory
7711 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
7713 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
7714 latter directory itself may be a symbolic link to the
7719 <sect id="changelogs">
7720 <heading>Changelog files</heading>
7723 The Debian changelog file (<file>debian/changelog</file>) should
7724 explain briefly what modifications were made in the Debian version
7725 of the package compared to the upstream one. Other changes and
7726 updates to the package should also be documented in this file.
7730 Mistakes in changelogs are usually best rectified by
7731 making a new changelog entry rather than "rewriting history"
7732 by editing old changelog entries.
7736 The format of the <file>debian/changelog</file> file is described
7737 in <ref id="dpkgchangelog">. In non-experimental packages you must
7738 use a format for <file>debian/changelog</file> which is supported
7739 by the most recent released version of <prgn>dpkg</prgn>.<footnote>
7741 If you wish to use an alternative format, you may do so as
7742 long as you include a parser for it in your source package.
7743 The parser must have an API compatible with that expected by
7744 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-gencontrol</prgn>.
7745 If there is general interest in the new format, you should
7746 contact the <package>dpkg</package> maintainer to have the
7747 parser script for it included in the <prgn>dpkg</prgn>
7748 package. (You will need to agree that the parser and its
7749 manpage may be distributed under the GNU GPL, just as the rest
7750 of <prgn>dpkg</prgn> is.)
7756 Packages that are not Debian-native must contain a
7757 compressed copy of the <file>debian/changelog</file> file from
7758 the Debian source tree in
7759 <file>/usr/share/doc/<var>package</var></file> with the name
7760 <file>changelog.Debian.gz</file>.
7764 If an upstream changelog is available, it should be accessible as
7765 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
7766 plain text. If the upstream changelog is distributed in
7767 HTML, it should be made available in that form as
7768 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
7769 and a plain text <file>changelog.gz</file> should be generated
7770 from it using, for example, <tt>lynx -dump -nolist</tt>. If
7771 the upstream changelog files do not already conform to this
7772 naming convention, then this may be achieved either by
7773 renaming the files, or by adding a symbolic link, at the
7774 maintainer's discretion.<footnote>
7776 Rationale: People should not have to look in places for
7777 upstream changelogs merely because they are given
7778 different names or are distributed in HTML format.
7784 All of these files should be installed compressed using
7785 <tt>gzip -9</tt>, as they will become large with time even
7786 if they start out small.
7790 If the package has only one changelog which is used both as
7791 the Debian changelog and the upstream one because there is
7792 no separate upstream maintainer then that changelog should
7793 usually be installed as
7794 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
7795 there is a separate upstream maintainer, but no upstream
7796 changelog, then the Debian changelog should still be called
7797 <file>changelog.Debian.gz</file>.</p>
7802 <appendix id="pkg-scope">
7803 <heading>Introduction and scope of these appendices</heading>
7806 These appendices are taken essentially verbatim from the
7807 now-deprecated Packaging Manual, version 3.2.1.0. They are
7808 the chapters which are likely to be of use to package
7809 maintainers and which have not already been included in the
7810 policy document itself. Most of these sections are very likely
7811 not relevant to policy; they should be treated as
7812 documentation for the packaging system. Please note that these
7813 appendices are included for convenience, and for historical
7814 reasons: they used to be part of policy package, and they have
7815 not yet been incorporated into dpkg documentation. However,
7816 they still have value, and hence they are presented here.
7819 They have not yet been checked to ensure that they are
7820 compatible with the contents of policy, and if there are any
7821 contradictions, the version in the main policy document takes
7822 precedence. The remaining chapters of the old Packaging
7823 Manual have also not been read in detail to ensure that there
7824 are not parts which have been left out. Both of these will be
7829 <prgn>dpkg</prgn> is a suite of programs for creating binary
7830 package files and installing and removing them on Unix
7833 <prgn>dpkg</prgn> is targetted primarily at Debian
7834 GNU/Linux, but may work on or be ported to other
7841 The binary packages are designed for the management of
7842 installed executable programs (usually compiled binaries) and
7843 their associated data, though source code examples and
7844 documentation are provided as part of some packages.</p>
7847 This manual describes the technical aspects of creating Debian
7848 binary packages (<file>.deb</file> files). It documents the
7849 behaviour of the package management programs
7850 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
7851 they interact with packages.</p>
7854 It also documents the interaction between
7855 <prgn>dselect</prgn>'s core and the access method scripts it
7856 uses to actually install the selected packages, and describes
7857 how to create a new access method.</p>
7860 This manual does not go into detail about the options and
7861 usage of the package building and installation tools. It
7862 should therefore be read in conjuction with those programs'
7867 The utility programs which are provided with <prgn>dpkg</prgn>
7868 for managing various system configuration and similar issues,
7869 such as <prgn>update-rc.d</prgn> and
7870 <prgn>install-info</prgn>, are not described in detail here -
7871 please see their manpages.
7875 It does <em>not</em> describe the policy requirements imposed
7876 on Debian packages, such as the permissions on files and
7877 directories, documentation requirements, upload procedure, and
7878 so on. You should see the Debian packaging policy manual for
7879 these details. (Many of them will probably turn out to be
7880 helpful even if you don't plan to upload your package and make
7881 it available as part of the distribution.)
7885 It is assumed that the reader is reasonably familiar with the
7886 <prgn>dpkg</prgn> System Administrators' manual.
7887 Unfortunately this manual does not yet exist.
7891 The Debian version of the FSF's GNU hello program is provided
7892 as an example for people wishing to create Debian
7893 packages. The Debian <prgn>debmake</prgn> package is
7894 recommended as a very helpful tool in creating and maintaining
7895 Debian packages. However, while the tools and examples are
7896 helpful, they do not replace the need to read and follow the
7897 Policy and Programmer's Manual.</p>
7900 <appendix id="pkg-binarypkg"><heading>Binary packages (from old
7905 The binary package has two main sections. The first part
7906 consists of various control information files and scripts used
7907 by <prgn>dpkg</prgn> when installing and removing. See <ref
7908 id="pkg-controlarea">.
7912 The second part is an archive containing the files and
7913 directories to be installed.
7917 In the future binary packages may also contain other
7918 components, such as checksums and digital signatures. The
7919 format for the archive is described in full in the
7920 <file>deb(5)</file> manpage.
7924 <sect id="pkg-bincreating"><heading>Creating package files -
7925 <prgn>dpkg-deb</prgn>
7929 All manipulation of binary package files is done by
7930 <prgn>dpkg-deb</prgn>; it's the only program that has
7931 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
7932 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
7933 will spot that the options requested are appropriate to
7934 <prgn>dpkg-deb</prgn> and invoke that instead with the same
7939 In order to create a binary package you must make a
7940 directory tree which contains all the files and directories
7941 you want to have in the filesystem data part of the package.
7942 In Debian-format source packages this directory is usually
7943 <file>debian/tmp</file>, relative to the top of the package's
7948 They should have the locations (relative to the root of the
7949 directory tree you're constructing) ownerships and
7950 permissions which you want them to have on the system when
7955 With current versions of <prgn>dpkg</prgn> the uid/username
7956 and gid/groupname mappings for the users and groups being
7957 used should be the same on the system where the package is
7958 built and the one where it is installed.
7962 You need to add one special directory to the root of the
7963 miniature filesystem tree you're creating:
7964 <prgn>DEBIAN</prgn>. It should contain the control
7965 information files, notably the binary package control file
7966 (see <ref id="pkg-controlfile">).
7970 The <prgn>DEBIAN</prgn> directory will not appear in the
7971 filesystem archive of the package, and so won't be installed
7972 by <prgn>dpkg</prgn> when the package is installed.
7976 When you've prepared the package, you should invoke:
7978 dpkg --build <var>directory</var>
7983 This will build the package in
7984 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
7985 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
7986 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
7991 See the manpage <manref name="dpkg-deb" section="8"> for details of how
7992 to examine the contents of this newly-created file. You may find the
7993 output of following commands enlightening:
7995 dpkg-deb --info <var>filename</var>.deb
7996 dpkg-deb --contents <var>filename</var>.deb
7997 dpkg --contents <var>filename</var>.deb
7999 To view the copyright file for a package you could use this command:
8001 dpkg --fsys-tarfile <var>filename</var>.deb | tar xof usr/share/doc/<var>\*</var>copyright | less
8006 <sect id="pkg-controlarea">
8008 Package control information files
8012 The control information portion of a binary package is a
8013 collection of files with names known to <prgn>dpkg</prgn>.
8014 It will treat the contents of these files specially - some
8015 of them contain information used by <prgn>dpkg</prgn> when
8016 installing or removing the package; others are scripts which
8017 the package maintainer wants <prgn>dpkg</prgn> to run.
8021 It is possible to put other files in the package control
8022 area, but this is not generally a good idea (though they
8023 will largely be ignored).
8027 Here is a brief list of the control info files supported by
8028 <prgn>dpkg</prgn> and a summary of what they're used for.
8033 <tag><tt>control</tt>
8037 This is the key description file used by
8038 <prgn>dpkg</prgn>. It specifies the package's name
8039 and version, gives its description for the user,
8040 states its relationships with other packages, and so
8041 forth. See <ref id="pkg-controlfile">.
8045 It is usually generated automatically from information
8046 in the source package by the
8047 <prgn>dpkg-gencontrol</prgn> program, and with
8048 assistance from <prgn>dpkg-shlibdeps</prgn>. See <ref
8049 id="pkg-sourcetools">.</p>
8052 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8058 These are exectuable files (usually scripts) which
8059 <prgn>dpkg</prgn> runs during installation, upgrade
8060 and removal of packages. They allow the package to
8061 deal with matters which are particular to that package
8062 or require more complicated processing than that
8063 provided by <prgn>dpkg</prgn>. Details of when and
8064 how they are called are in <ref
8065 id="maintainerscripts">.
8069 It is very important to make these scripts
8073 That means that if it runs successfully or fails
8074 and then you call it again it doesn't bomb out,
8075 but just ensures that everything is the way it
8078 </footnote> This is so that if an error occurs, the
8079 user interrupts <prgn>dpkg</prgn> or some other
8080 unforeseen circumstance happens you don't leave the
8081 user with a badly-broken package.
8085 The maintainer scripts are guaranteed to run with a
8086 controlling terminal and can interact with the user.
8087 If they need to prompt for passwords, do full-screen
8088 interaction or something similar you should do these
8089 things to and from <file>/dev/tty</file>, since
8090 <prgn>dpkg</prgn> will at some point redirect scripts'
8091 standard input and output so that it can log the
8092 installation process. Likewise, because these scripts
8093 may be executed with standard output redirected into a
8094 pipe for logging purposes, Perl scripts should set
8095 unbuffered output by setting <tt>$|=1</tt> so that the
8096 output is printed immediately rather than being
8101 Each script should return a zero exit status for
8102 success, or a nonzero one for failure.</p>
8105 <tag><tt>conffiles</tt>
8110 This file contains a list of configuration files which
8111 are to be handled automatically by <prgn>dpkg</prgn>
8112 (see <ref id="pkg-conffiles">). Note that not necessarily
8113 every configuration file should be listed here.</p>
8116 <tag><tt>shlibs</tt>
8121 This file contains a list of the shared libraries
8122 supplied by the package, with dependency details for
8123 each. This is used by <prgn>dpkg-shlibdeps</prgn>
8124 when it determines what dependencies are required in a
8125 package control file. The <tt>shlibs</tt> file format
8126 is described on <ref id="shlibs">.
8132 <sect id="pkg-controlfile">
8134 The main control information file: <tt>control</tt>
8137 The most important control information file used by
8138 <prgn>dpkg</prgn> when it installs a package is
8139 <tt>control</tt>. It contains all the package"s "vital
8144 The binary package control files of packages built from
8145 Debian sources are made by a special tool,
8146 <prgn>dpkg-gencontrol</prgn>, which reads
8147 <file>debian/control</file> and <file>debian/changelog</file> to
8148 find the information it needs. See <ref id="pkg-sourcepkg"> for
8153 The fields in binary package control files are:
8154 <list compact="compact">
8156 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8159 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
8161 <item><p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8165 This field should appear in all packages, though
8166 <prgn>dpkg</prgn> doesn't require it yet so that
8167 old packages can still be installed.
8173 <p><qref id="relationships"><tt>Depends</tt>,
8174 <tt>Provides</tt> et al.</qref></p>
8177 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8180 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8183 <p><qref id="pkg-f-classification"><tt>Section</tt>,
8184 <tt>Priority</tt></qref></p>
8187 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
8190 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8194 <qref id="pkg-f-Installed-Size"><tt>Installed-Size</tt></qref>
8200 A description of the syntax of control files and the purpose
8201 of these fields is available in <ref id="pkg-controlfields">.
8206 <heading>Time Stamps</heading>
8208 Maintainers are encouraged to preserve the modification
8209 times of the upstream source files in a package, as far as
8210 is reasonably possible.
8213 The rationale is that there is some information conveyed
8214 by knowing the age of the file, for example, you could
8215 recognize that some documentation is very old by looking
8216 at the modification time, so it would be nice if the
8217 modification time of the upstream source would be
8225 <appendix id="pkg-sourcepkg">
8226 <heading>Source packages (from old Packaging Manual) </heading>
8229 The Debian binary packages in the distribution are generated
8230 from Debian sources, which are in a special format to assist
8231 the easy and automatic building of binaries.
8235 There was a previous version of the Debian source format,
8236 which is now being phased out. Instructions for converting an
8237 old-style package are given in the Debian policy manual.
8240 <sect id="pkg-sourcetools">
8241 <heading>Tools for processing source packages</heading>
8244 Various tools are provided for manipulating source packages;
8245 they pack and unpack sources and help build of binary
8246 packages and help manage the distribution of new versions.
8250 They are introduced and typical uses described here; see
8251 <manref name="dpkg-source" section="1"> for full
8252 documentation about their arguments and operation.
8256 For examples of how to construct a Debian source package,
8257 and how to use those utilities that are used by Debian
8258 source packages, please see the <prgn>hello</prgn> example
8264 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
8269 This program is frequently used by hand, and is also
8270 called from package-independent automated building scripts
8271 such as <prgn>dpkg-buildpackage</prgn>.
8275 To unpack a package it is typically invoked with
8277 dpkg-source -x <var>.../path/to/filename</var>.dsc
8282 with the <file><var>filename</var>.tar.gz</file> and
8283 <file><var>filename</var>.diff.gz</file> (if applicable) in
8284 the same directory. It unpacks into
8285 <file><var>package</var>-<var>version</var></file>, and if
8287 <file><var>package</var>-<var>version</var>.orig</file>, in
8288 the current directory.
8292 To create a packed source archive it is typically invoked:
8294 dpkg-source -b <var>package</var>-<var>version</var>
8299 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
8300 <file>.diff.gz</file> (if appropriate) in the current
8301 directory. <prgn>dpkg-source</prgn> does not clean the
8302 source tree first - this must be done separately if it is
8307 See also <ref id="pkg-sourcearchives">.</p>
8313 <prgn>dpkg-buildpackage</prgn> - overall package-building
8318 <prgn>dpkg-buildpackage</prgn> is a script which invokes
8319 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
8320 targets <tt>clean</tt>, <tt>build</tt> and
8321 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
8322 <prgn>pgp</prgn> to build a signed source and binary
8327 It is usually invoked by hand from the top level of the
8328 built or unbuilt source directory. It may be invoked with
8329 no arguments; useful arguments include:
8330 <taglist compact="compact">
8331 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
8334 Do not PGP-sign the <tt>.changes</tt> file or the
8335 source package <tt>.dsc</tt> file, respectively.</p>
8337 <tag><tt>-p<var>pgp-command</var></tt></tag>
8340 Invoke <var>pgp-command</var> instead of finding
8341 <tt>pgp</tt> on the <prgn>PATH</prgn>.
8342 <var>pgp-command</var> must behave just like
8343 <prgn>pgp</prgn>.</p>
8345 <tag><tt>-r<var>root-command</var></tt></tag>
8348 When root privilege is required, invoke the command
8349 <var>root-command</var>. <var>root-command</var>
8350 should invoke its first argument as a command, from
8351 the <prgn>PATH</prgn> if necessary, and pass its
8352 second and subsequent arguments to the command it
8353 calls. If no <var>root-command</var> is supplied
8354 then <var>dpkg-buildpackage</var> will take no
8355 special action to gain root privilege, so that for
8356 most packages it will have to be invoked as root to
8359 <tag><tt>-b</tt>, <tt>-B</tt></tag>
8362 Two types of binary-only build and upload - see
8363 <manref name="dpkg-source" section="1">.
8372 <prgn>dpkg-gencontrol</prgn> - generates binary package
8377 This program is usually called from <file>debian/rules</file>
8378 (see <ref id="pkg-sourcetree">) in the top level of the source
8383 This is usually done just before the files and directories in the
8384 temporary directory tree where the package is being built have their
8385 permissions and ownerships set and the package is constructed using
8386 <prgn>dpkg-deb/</prgn>
8389 This is so that the control file which is produced has
8390 the right permissions
8396 <prgn>dpkg-gencontrol</prgn> must be called after all the
8397 files which are to go into the package have been placed in
8398 the temporary build directory, so that its calculation of
8399 the installed size of a package is correct.
8403 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
8404 be run after <prgn>dpkg-shlibdeps</prgn> so that the
8405 variable substitutions created by
8406 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
8411 For a package which generates only one binary package, and
8412 which builds it in <file>debian/tmp</file> relative to the top
8413 of the source package, it is usually sufficient to call
8414 <prgn>dpkg-gencontrol</prgn>.
8418 Sources which build several binaries will typically need
8421 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
8422 </example> The <tt>-P</tt> tells
8423 <prgn>dpkg-gencontrol</prgn> that the package is being
8424 built in a non-default directory, and the <tt>-p</tt>
8425 tells it which package's control file should be generated.
8429 <prgn>dpkg-gencontrol</prgn> also adds information to the
8430 list of files in <file>debian/files</file>, for the benefit of
8431 (for example) a future invocation of
8432 <prgn>dpkg-genchanges</prgn>.</p>
8437 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
8442 This program is usually called from <file>debian/rules</file>
8443 just before <prgn>dpkg-gencontrol</prgn> (see <ref
8444 id="pkg-sourcetree">), in the top level of the source tree.
8448 Its arguments are executables.
8451 In a forthcoming dpkg version,
8452 <prgn>dpkg-shlibdeps</prgn> would be required to be
8453 called on shared libraries as well.
8456 They may be specified either in the locations in the
8457 source tree where they are created or in the locations
8458 in the temporary build tree where they are installed
8459 prior to binary package creation.
8461 </footnote> for which shared library dependencies should
8462 be included in the binary package's control file.
8466 If some of the found shared libraries should only
8467 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
8468 some warrant a <tt>Pre-Depends</tt>, this can be achieved
8469 by using the <tt>-d<var>dependency-field</var></tt> option
8470 before those executable(s). (Each <tt>-d</tt> option
8471 takes effect until the next <tt>-d</tt>.)
8475 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
8476 output control file to be modified. Instead by default it
8477 adds to the <file>debian/substvars</file> file variable
8478 settings like <tt>shlibs:Depends</tt>. These variable
8479 settings must be referenced in dependency fields in the
8480 appropriate per-binary-package sections of the source
8485 For example, the <prgn>procps</prgn> package generates two
8486 kinds of binaries, simple C binaries like <prgn>ps</prgn>
8487 which require a predependency and full-screen ncurses
8488 binaries like <prgn>top</prgn> which require only a
8489 recommendation. It can say in its <file>debian/rules</file>:
8491 dpkg-shlibdeps -dPre-Depends ps -dRecommends top
8493 and then in its main control file <file>debian/control</file>:
8497 Pre-Depends: ${shlibs:Pre-Depends}
8498 Recommends: ${shlibs:Recommends}
8504 Sources which produce several binary packages with
8505 different shared library dependency requirements can use
8506 the <tt>-p<var>varnameprefix</var></tt> option to override
8507 the default <tt>shlibs:</tt> prefix (one invocation of
8508 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
8509 They can thus produce several sets of dependency
8510 variables, each of the form
8511 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
8512 which can be referred to in the appropriate parts of the
8513 binary package control files.
8520 <prgn>dpkg-distaddfile</prgn> - adds a file to
8521 <file>debian/files</file>
8525 Some packages' uploads need to include files other than
8526 the source and binary package files.
8530 <prgn>dpkg-distaddfile</prgn> adds a file to the
8531 <file>debian/files</file> file so that it will be included in
8532 the <file>.changes</file> file when
8533 <prgn>dpkg-genchanges</prgn> is run.
8537 It is usually invoked from the <tt>binary</tt> target of
8538 <file>debian/rules</file>:
8540 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
8542 The <var>filename</var> is relative to the directory where
8543 <prgn>dpkg-genchanges</prgn> will expect to find it - this
8544 is usually the directory above the top level of the source
8545 tree. The <file>debian/rules</file> target should put the
8546 file there just before or just after calling
8547 <prgn>dpkg-distaddfile</prgn>.
8551 The <var>section</var> and <var>priority</var> are passed
8552 unchanged into the resulting <file>.changes</file> file. See
8553 <ref id="pkg-f-classification">.
8558 <sect1><heading><prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file> upload
8563 This program is usually called by package-independent
8564 automatic building scripts such as
8565 <prgn>dpkg-buildpackage</prgn>, but it may also be called
8570 It is usually called in the top level of a built source
8571 tree, and when invoked with no arguments will print out a
8572 straightforward <file>.changes</file> file based on the
8573 information in the source package's changelog and control
8574 file and the binary and source packages which should have
8580 <sect1><heading><prgn>dpkg-parsechangelog</prgn> - produces parsed representation of
8585 This program is used internally by
8586 <prgn>dpkg-source</prgn> et al. It may also occasionally
8587 be useful in <file>debian/rules</file> and elsewhere. It
8588 parses a changelog, <file>debian/changelog</file> by default,
8589 and prints a control-file format representation of the
8590 information in it to standard output.
8594 <sect1 id="pkg-dpkgarch"><heading><prgn>dpkg-architecture</prgn> -
8595 information about the build and host system
8599 This program can be used manually, but is also invoked by
8600 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
8601 to set environment or make variables which specify the build and
8602 host architecture for the package building process.
8607 <sect id="pkg-sourcetree"><heading>The Debianised source tree
8611 The source archive scheme described later is intended to
8612 allow a Debianised source tree with some associated control
8613 information to be reproduced and transported easily. The
8614 Debianised source tree is a version of the original program
8615 with certain files added for the benefit of the
8616 Debianisation process, and with any other changes required
8617 made to the rest of the source code and installation
8622 The extra files created for Debian are in the subdirectory
8623 <file>debian</file> of the top level of the Debianised source
8624 tree. They are described below.
8627 <sect1 id="pkg-debianrules"><heading><file>debian/rules</file> - the main building
8632 This file is an executable makefile, and contains the
8633 package-specific recipies for compiling the package and
8634 building binary package(s) out of the source.
8638 It must start with the line <tt>#!/usr/bin/make -f</tt>,
8639 so that it can be invoked by saying its name rather than
8640 invoking <prgn>make</prgn> explicitly.
8644 Since an interactive <file>debian/rules</file> script makes it
8645 impossible to autocompile that package and also makes it
8646 hard for other people to reproduce the same binary
8647 package, all <strong>required targets</strong> have to be
8648 non-interactive. At a minimul, required targets are the
8649 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
8650 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>, and
8651 <em>build</em>. It also follows that any target that these
8652 targets depend on must also be non-interactive.
8656 The targets which are required to be present are:
8658 <tag><tt>build</tt></tag>
8661 This should perform all non-interactive
8662 configuration and compilation of the package. If a
8663 package has an interactive pre-build configuration
8664 routine, the Debianised source package should be
8665 built after this has taken place, so that it can be
8666 built without rerunning the configuration.
8670 A package may also provide both of the targets
8671 <tt>build-arch</tt> and <tt>build-indep</tt>. The
8672 <tt>build-arch</tt> target, if provided, should
8673 perform all non-interactive configuration and
8674 compilation required for producing all
8675 architecture-dependant binary packages (those packages
8676 for which the body of the <tt>Architecture</tt> field
8677 in <tt>debian/control</tt> is not <tt>all</tt>).
8678 Similarly, the <tt>build-indep</tt> target, if
8679 provided, should perform all non-interactive
8680 configuration and compilation required for producing
8681 all architecture-independent binary packages (those
8682 packages for which the body of the
8683 <tt>Architecture</tt> field in <tt>debian/control</tt>
8684 is <tt>all</tt>). The <tt>build</tt> target should
8685 depend on those of the targets <tt>build-arch</tt> and
8686 <tt>build-indep</tt> that are provided in the rules
8691 If one or both of the targets <tt>build-arch</tt> and
8692 <tt>build-indep</tt> are not provided, then invoking
8693 <file>debian/rules</file> with one of the not-provided
8694 targets as arguments should produce a exit status code
8695 of 2. Usually this is provided automatically by make
8696 if the target is missing.
8700 For some packages, notably ones where the same
8701 source tree is compiled in different ways to produce
8702 two binary packages, the <tt>build</tt> target does
8703 not make much sense. For these packages it is good
8704 enough to provide two (or more) targets
8705 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
8706 for each of the ways of building the package, and a
8707 <tt>build</tt> target that does nothing. The
8708 <tt>binary</tt> target will have to build the
8709 package in each of the possible ways and make the
8710 binary package out of each.
8714 The targets <tt>build</tt>, <tt>build-arch</tt>
8715 and <tt>build-indep</tt> target must not do
8716 anything that might require root privilege.
8720 The <tt>build</tt> target may need to run
8721 <tt>clean</tt> first - see below.
8725 When a package has a configuration routine that takes
8726 a long time, or when the makefiles are poorly
8727 designed, or when <tt>build</tt> needs to run
8728 <tt>clean</tt> first, it is a good idea to <tt>touch
8729 build</tt> when the build process is complete. This
8730 will ensure that if <tt>debian/rules build</tt> is run
8731 again it will not rebuild the whole program.
8735 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
8736 <tt>binary-indep</tt>
8740 The <tt>binary</tt> target should be all that is
8741 necessary for the user to build the binary
8742 package. All these targets are required to be
8743 non-interactive. It is split into two parts:
8744 <tt>binary-arch</tt> builds the packages' output
8745 files which are specific to a particular
8746 architecture, and <tt>binary-indep</tt> builds
8747 those which are not.
8751 <tt>binary</tt> should usually be a target with
8752 no commands which simply depends on
8753 <prgn>binary-arch</prgn> and
8754 <prgn>binary-indep</prgn>.
8758 Both <prgn>binary-*</prgn> targets should depend on
8759 the <tt>build</tt> target, above, so that the
8760 package is built if it has not been already. It
8761 should then create the relevant binary package(s),
8762 using <prgn>dpkg-gencontrol</prgn> to make their
8763 control files and <prgn>dpkg-deb</prgn> to build
8764 them and place them in the parent of the top level
8769 If one of the <prgn>binary-*</prgn> targets has
8770 nothing to do (this will be always be the case if
8771 the source generates only a single binary package,
8772 whether architecture-dependent or not) it
8773 <em>must</em> still exist, but should always
8778 <ref id="pkg-binarypkg"> describes how to construct
8783 The <tt>binary</tt> targets must be invoked as
8788 <tag><tt>clean</tt></tag>
8792 This should undo any effects that the
8793 <tt>build</tt> and <tt>binary</tt> targets
8794 may have had, except that it should leave alone any
8795 output files created in the parent directory by a
8796 run of <tt>binary</tt>. This target is required
8797 to be non-interactive.
8801 If a <tt>build</tt> file is touched at the end
8802 of the <tt>build</tt> target, as suggested
8803 above, it must be removed as the first thing that
8804 <tt>clean</tt> does, so that running
8805 <tt>build</tt> again after an interrupted
8806 <tt>clean</tt> doesn't think that everything is
8811 The <tt>clean</tt> target must be invoked as
8812 root if <tt>binary</tt> has been invoked since
8813 the last <tt>clean</tt>, or if
8814 <tt>build</tt> has been invoked as root (since
8815 <tt>build</tt> may create directories, for
8820 <tag><tt>get-orig-source</tt> (optional)</tag>
8824 This target fetches the most recent version of the
8825 original source package from a canonical archive
8826 site (via FTP or WWW, for example), does any
8827 necessary rearrangement to turn it into the original
8828 source tarfile format described below, and leaves it
8829 in the current directory.
8833 This target may be invoked in any directory, and
8834 should take care to clean up any temporary files it
8839 This target is optional, but providing it if
8840 possible is a good idea.
8846 The <tt>build</tt>, <tt>binary</tt> and
8847 <tt>clean</tt> targets must be invoked with a current
8848 directory of the package's top-level directory.
8853 Additional targets may exist in <file>debian/rules</file>,
8854 either as published or undocumented interfaces or for the
8855 package's internal use.
8859 The architecture we build on and build for is determined by make
8860 variables via dpkg-architecture (see <ref id="pkg-dpkgarch">). You can
8861 get the Debian architecture and the GNU style architecture
8862 specification string for the build machine as well as the host
8863 machine. Here is a list of supported make variables:
8864 <list compact="compact">
8866 <p><tt>DEB_*_ARCH</tt> (the Debian architecture)</p>
8869 <p><tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
8870 specification string)</p>
8873 <p><tt>DEB_*_GNU_CPU</tt> (the CPU part of DEB_*_GNU_TYPE)</p>
8876 <p><tt>DEB_*_GNU_SYSTEM</tt> (the System part of
8882 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
8883 the build machine or <tt>HOST</tt> for specification of the machine
8888 Backward compatibility can be provided in the rules file
8889 by setting the needed variables to suitable default
8890 values, please refer to the documentation of
8891 dpkg-architecture for details.
8895 It is important to understand that the <tt>DEB_*_ARCH</tt>
8896 string does only determine which Debian architecture we
8897 build on resp. for. It should not be used to get the CPU
8898 or System information, the GNU style variables should be
8904 <sect1><heading><file>debian/control</file>
8908 This file contains version-independent details about the
8909 source package and about the binary packages it creates.
8913 It is a series of sets of control fields, each
8914 syntactically similar to a binary package control file.
8915 The sets are separated by one or more blank lines. The
8916 first set is information about the source package in
8917 general; each subsequent set describes one binary package
8918 that the source tree builds.
8922 The syntax and semantics of the fields are described below
8923 in <ref id="pkg-controlfields">.
8927 The general (binary-package-independent) fields are:
8928 <list compact="compact">
8930 <p><qref id="pkg-f-Source"><tt>Source</tt></qref> (mandatory)</p>
8933 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
8937 <qref id="pkg-f-classification"><tt>Section</tt> and
8938 <tt>Priority</tt></qref>
8939 (classification, mandatory)
8944 <qref id="relationships"><tt>Build-Depends</tt> et
8945 al.</qref> (source package interrelationships)
8950 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref>
8956 The per-binary-package fields are:
8957 <list compact="compact">
8959 <p><qref id="pkg-f-Package"><tt>Package</tt></qref> (mandatory)</p>
8963 <qref id="pkg-f-Architecture"><tt>Architecture</tt></qref>
8967 <p><qref id="descriptions"><tt>Description</tt></qref></p>
8971 <qref id="pkg-f-classification"><tt>Section</tt> and
8972 <tt>Priority</tt></qref> (classification)</p>
8975 <p><qref id="pkg-f-Essential"><tt>Essential</tt></qref></p>
8979 <qref id="relationships"><tt>Depends</tt> et
8980 al.</qref> (binary package interrelationships)
8986 These fields are used by <prgn>dpkg-gencontrol</prgn> to
8987 generate control files for binary packages (see below), by
8988 <prgn>dpkg-genchanges</prgn> to generate the
8989 <tt>.changes</tt> file to accompany the upload, and by
8990 <prgn>dpkg-source</prgn> when it creates the <file>.dsc</file>
8991 source control file as part of a source archive.
8995 The fields here may contain variable references - their
8996 values will be substituted by
8997 <prgn>dpkg-gencontrol</prgn>, <prgn>dpkg-genchanges</prgn>
8998 or <prgn>dpkg-source</prgn> when they generate output
8999 control files. See <ref id="pkg-srcsubstvars"> for details.
9002 <p> <sect2><heading>User-defined fields
9006 Additional user-defined fields may be added to the
9007 source package control file. Such fields will be
9008 ignored, and not copied to (for example) binary or
9009 source package control files or upload control files.
9013 If you wish to add additional unsupported fields to
9014 these output files you should use the mechanism
9019 Fields in the main source control information file with
9020 names starting <tt>X</tt>, followed by one or more of
9021 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
9022 be copied to the output files. Only the part of the
9023 field name after the hyphen will be used in the output
9024 file. Where the letter <tt>B</tt> is used the field
9025 will appear in binary package control files, where the
9026 letter <tt>S</tt> is used in source package control
9027 files and where <tt>C</tt> is used in upload control
9028 (<tt>.changes</tt>) files.
9032 For example, if the main source information control file
9035 XBS-Comment: I stand between the candle and the star.
9037 then the binary and source package control files will contain the
9040 Comment: I stand between the candle and the star.
9047 <sect1 id="pkg-dpkgchangelog"><heading><file>debian/changelog</file>
9051 This file records the changes to the Debian-specific parts of the
9055 Though there is nothing stopping an author who is also
9056 the Debian maintainer from using it for all their
9057 changes, it will have to be renamed if the Debian and
9058 upstream maintainers become different
9065 It has a special format which allows the package building
9066 tools to discover which version of the package is being
9067 built and find out other release-specific information.
9071 That format is a series of entries like this:
9073 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
9075 * <var>change details</var>
9076 <var>more change details</var>
9077 * <var>even more change details</var>
9079 -- <var>maintainer name and email address</var> <var>date</var>
9084 <var>package</var> and <var>version</var> are the source
9085 package name and version number.
9089 <var>distribution(s)</var> lists the distributions where
9090 this version should be installed when it is uploaded - it
9091 is copied to the <tt>Distribution</tt> field in the
9092 <tt>.changes</tt> file. See <ref id="pkg-f-Distribution">.
9096 <var>urgency</var> is the value for the <tt>Urgency</tt>
9097 field in the <file>.changes</file> file for the upload. See
9098 <ref id="pkg-f-Urgency">. It is not possible to specify an
9099 urgency containing commas; commas are used to separate
9100 <tt><var>keyword</var>=<var>value</var></tt> settings in
9101 the <prgn>dpkg</prgn> changelog format (though there is
9102 currently only one useful <var>keyword</var>,
9107 The change details may in fact be any series of lines
9108 starting with at least two spaces, but conventionally each
9109 change starts with an asterisk and a separating space and
9110 continuation lines are indented so as to bring them in
9111 line with the start of the text above. Blank lines may be
9112 used here to separate groups of changes, if desired.
9116 The maintainer name and email address should <em>not</em>
9117 necessarily be those of the usual package maintainer.
9118 They should be the details of the person doing
9119 <em>this</em> version. The information here will be
9120 copied to the <file>.changes</file> file, and then later used
9121 to send an acknowledgement when the upload has been
9126 The <var>date</var> should be in RFC822 format
9129 This is generated by the <prgn>822-date</prgn>
9132 </footnote>; it should include the timezone specified
9133 numerically, with the timezone name or abbreviation
9134 optionally present as a comment.
9138 The first "title" line with the package name should start
9139 at the left hand margin; the "trailer" line with the
9140 maintainer and date details should be preceded by exactly
9141 one space. The maintainer details and the date must be
9142 separated by exactly two spaces.
9146 An Emacs mode for editing this format is available: it is
9147 called <tt>debian-changelog-mode</tt>. You can have this
9148 mode selected automatically when you edit a Debian
9149 changelog by adding a local variables clause to the end of
9153 <sect2><heading>Defining alternative changelog formats
9157 It is possible to use a different format to the standard
9158 one, by providing a parser for the format you wish to
9163 In order to have <tt>dpkg-parsechangelog</tt> run your
9164 parser, you must include a line within the last 40 lines
9165 of your file matching the Perl regular expression:
9166 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9167 parentheses should be the name of the format. For
9168 example, you might say:
9170 @@@ changelog-format: joebloggs @@@
9172 Changelog format names are non-empty strings of alphanumerics.
9176 If such a line exists then <tt>dpkg-parsechangelog</tt>
9177 will look for the parser as
9178 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9180 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9181 it is an error for it not to find it, or for it not to
9182 be an executable program. The default changelog format
9183 is <tt>dpkg</tt>, and a parser for it is provided with
9184 the <tt>dpkg</tt> package.
9188 The parser will be invoked with the changelog open on
9189 standard input at the start of the file. It should read
9190 the file (it may seek if it wishes) to determine the
9191 information required and return the parsed information
9192 to standard output in the form of a series of control
9193 fields in the standard format. By default it should
9194 return information about only the most recent version in
9195 the changelog; it should accept a
9196 <tt>-v<var>version</var></tt> option to return changes
9197 information from all versions present <em>strictly
9198 after</em> <var>version</var>, and it should then be an
9199 error for <var>version</var> not to be present in the
9205 <list compact="compact">
9207 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9210 <p><qref id="versions"><tt>Version</tt></qref> (mandatory)</p>
9214 <qref id="pkg-f-Distribution"><tt>Distribution</tt></qref>
9219 <p><qref id="pkg-f-Urgency"><tt>Urgency</tt></qref> (mandatory)</p>
9223 <qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref>
9228 <p><qref id="pkg-f-Date"><tt>Date</tt></qref></p>
9232 <qref id="pkg-f-Changes"><tt>Changes</tt></qref>
9239 If several versions are being returned (due to the use
9240 of <tt>-v</tt>), the urgency value should be of the
9241 highest urgency code listed at the start of any of the
9242 versions requested followed by the concatenated
9243 (space-separated) comments from all the versions
9244 requested; the maintainer, version, distribution and
9245 date should always be from the most recent version.
9249 For the format of the <tt>Changes</tt> field see <ref
9250 id="pkg-f-Changes">.
9254 If the changelog format which is being parsed always or
9255 almost always leaves a blank line between individual
9256 change notes these blank lines should be stripped out,
9257 so as to make the resulting output compact.
9261 If the changelog format does not contain date or package
9262 name information this information should be omitted from
9263 the output. The parser should not attempt to synthesise
9264 it or find it from other sources.
9268 If the changelog does not have the expected format the
9269 parser should exit with a nonzero exit status, rather
9270 than trying to muddle through and possibly generating
9275 A changelog parser may not interact with the user at
9279 <sect1 id="pkg-srcsubstvars"><heading><file>debian/substvars</file>
9280 and variable substitutions
9284 When <prgn>dpkg-gencontrol</prgn>,
9285 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
9286 generate control files they do variable substitutions on
9287 their output just before writing it. Variable
9288 substitutions have the form
9289 <tt>${<var>variable-name</var>}</tt>. The optional file
9290 <file>debian/substvars</file> contains variable substitutions
9291 to be used; variables can also be set directly from
9292 <file>debian/rules</file> using the <tt>-V</tt> option to the
9293 source packaging commands, and certain predefined
9294 variables are available.
9298 The is usually generated and modified dynamically by
9299 <file>debian/rules</file> targets; in this case it must be
9300 removed by the <tt>clean</tt> target.
9304 See <manref name="dpkg-source" section="1"> for full
9305 details about source variable substitutions, including the
9306 format of <file>debian/substvars</file>.</p>
9309 <sect1><heading><file>debian/files</file>
9313 This file is not a permanent part of the source tree; it
9314 is used while building packages to record which files are
9315 being generated. <prgn>dpkg-genchanges</prgn> uses it
9316 when it generates a <file>.changes</file> file.
9320 It should not exist in a shipped source package, and so it
9321 (and any backup files or temporary files such as
9322 <file>files.new</file>
9325 <file>files.new</file> is used as a temporary file by
9326 <prgn>dpkg-gencontrol</prgn> and
9327 <prgn>dpkg-distaddfile</prgn> - they write a new
9328 version of <file>files</file> here before renaming it,
9329 to avoid leaving a corrupted copy if an error
9332 </footnote>) should be removed by the
9333 <tt>clean</tt> target. It may also be wise to
9334 ensure a fresh start by emptying or removing it at the
9335 start of the <tt>binary</tt> target.
9339 <prgn>dpkg-gencontrol</prgn> adds an entry to this file
9340 for the <file>.deb</file> file that will be created by
9341 <prgn>dpkg-deb</prgn> from the control file that it
9342 generates, so for most packages all that needs to be done
9343 with this file is to delete it in <tt>clean</tt>.
9347 If a package upload includes files besides the source
9348 package and any binary packages whose control files were
9349 made with <prgn>dpkg-gencontrol</prgn> then they should be
9350 placed in the parent of the package's top-level directory
9351 and <prgn>dpkg-distaddfile</prgn> should be called to add
9352 the file to the list in <file>debian/files</file>.</p>
9355 <sect1><heading><file>debian/tmp</file>
9359 This is the canonical temporary location for the
9360 construction of binary packages by the <tt>binary</tt>
9361 target. The directory <file>tmp</file> serves as the root of
9362 the filesystem tree as it is being constructed (for
9363 example, by using the package's upstream makefiles install
9364 targets and redirecting the output there), and it also
9365 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9366 id="pkg-bincreating">.
9370 If several binary packages are generated from the same
9371 source tree it is usual to use several
9372 <file>debian/tmp<var>something</var></file> directories, for
9373 example <file>tmp-a</file> or <file>tmp-doc</file>.
9377 Whatever <file>tmp</file> directories are created and used by
9378 <tt>binary</tt> must of course be removed by the
9379 <tt>clean</tt> target.</p></sect1>
9383 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9387 As it exists on the FTP site, a Debian source package
9388 consists of three related files. You must have the right
9389 versions of all three to be able to use them.
9394 <tag>Debian source control file - <tt>.dsc</tt></tag>
9398 This file contains a series of fields, identified and
9399 separated just like the fields in the control file of
9400 a binary package. The fields are listed below; their
9401 syntax is described above, in <ref id="pkg-controlfields">.
9402 <list compact="compact">
9404 <p><qref id="pkg-f-Source"><tt>Source</tt></qref></p>
9407 <p><qref id="versions"><tt>Version</tt></qref></p>
9410 <p><qref id="pkg-f-Maintainer"><tt>Maintainer</tt></qref></p>
9413 <p><qref id="pkg-f-Binary"><tt>Binary</tt></qref></p>
9416 <p><qref id="pkg-f-Architecture"><tt>Architecture</tt></qref></p>
9420 <qref id="relationships"><tt>Build-Depends</tt> et
9421 al.</qref> (source package interrelationships)
9426 <qref id="pkg-f-Standards-Version"><tt>Standards-Version</tt></qref></p>
9429 <p><qref id="pkg-f-Files"><tt>Files</tt></qref></p>
9434 The source package control file is generated by
9435 <prgn>dpkg-source</prgn> when it builds the source
9436 archive, from other files in the source package,
9437 described above. When unpacking it is checked against
9438 the files and directories in the other parts of the
9439 source package, as described below.</p>
9443 Original source archive -
9445 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9452 This is a compressed (with <tt>gzip -9</tt>)
9453 <prgn>tar</prgn> file containing the source code from
9454 the upstream authors of the program. The tarfile
9455 unpacks into a directory
9456 <file><var>package</var>-<var>upstream-version</var>.orig</file>,
9457 and does not contain files anywhere other than in
9458 there or in its subdirectories.</p>
9462 Debianisation diff -
9464 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9470 This is a unified context diff (<tt>diff -u</tt>)
9471 giving the changes which are required to turn the
9472 original source into the Debian source. These changes
9473 may only include editing and creating plain files.
9474 The permissions of files, the targets of symbolic
9475 links and the characteristics of special files or
9476 pipes may not be changed and no files may be removed
9481 All the directories in the diff must exist, except the
9482 <file>debian</file> subdirectory of the top of the source
9483 tree, which will be created by
9484 <prgn>dpkg-source</prgn> if necessary when unpacking.
9488 The <prgn>dpkg-source</prgn> program will
9489 automatically make the <file>debian/rules</file> file
9490 executable (see below).</p></item>
9495 If there is no original source code - for example, if the
9496 package is specially prepared for Debian or the Debian
9497 maintainer is the same as the upstream maintainer - the
9498 format is slightly different: then there is no diff, and the
9500 <file><var>package</var>_<var>version</var>.tar.gz</file> and
9501 contains a directory
9502 <file><var>package</var>-<var>version</var></file>.
9506 <sect><heading>Unpacking a Debian source package without
9507 <prgn>dpkg-source</prgn>
9511 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9512 Debian source package. However, if it is not available it
9513 is possible to unpack a Debian source archive as follows:
9514 <enumlist compact="compact">
9517 Untar the tarfile, which will create a <file>.orig</file>
9521 <p>Rename the <file>.orig</file> directory to
9522 <file><var>package</var>-<var>version</var></file>.</p>
9526 Create the subdirectory <file>debian</file> at the top of
9527 the source tree.</p>
9529 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9531 <item><p>Untar the tarfile again if you want a copy of the original
9532 source code alongside the Debianised version.</p>
9537 It is not possible to generate a valid Debian source archive
9538 without using <prgn>dpkg-source</prgn>. In particular,
9539 attempting to use <prgn>diff</prgn> directly to generate the
9540 <file>.diff.gz</file> file will not work.
9543 <sect1><heading>Restrictions on objects in source packages
9547 The source package may not contain any hard links
9550 This is not currently detected when building source
9551 packages, but only when extracting
9557 Hard links may be permitted at some point in the
9558 future, but would require a fair amount of
9561 </footnote>, device special files, sockets or setuid or
9565 Setgid directories are allowed.
9571 The source packaging tools manage the changes between the
9572 original and Debianised source using <prgn>diff</prgn> and
9573 <prgn>patch</prgn>. Turning the original source tree as
9574 included in the <file>.orig.tar.gz</file> into the debianised
9575 source must not involve any changes which cannot be
9576 handled by these tools. Problematic changes which cause
9577 <prgn>dpkg-source</prgn> to halt with an error when
9578 building the source package are:
9579 <list compact="compact">
9580 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9582 <item><p>Changing the targets of symbolic links.</p>
9584 <item><p>Creating directories, other than <file>debian</file>.</p>
9586 <item><p>Changes to the contents of binary files.</p></item>
9587 </list> Changes which cause <prgn>dpkg-source</prgn> to
9588 print a warning but continue anyway are:
9589 <list compact="compact">
9592 Removing files, directories or symlinks.
9595 Renaming a file is not treated specially - it is
9596 seen as the removal of the old file (which
9597 generates a warning, but is otherwise ignored),
9598 and the creation of the new
9605 Changed text files which are missing the usual final
9606 newline (either in the original or the modified
9611 Changes which are not represented, but which are not detected by
9612 <prgn>dpkg-source</prgn>, are:
9613 <list compact="compact">
9614 <item><p>Changing the permissions of files (other than
9615 <file>debian/rules</file>) and directories.</p></item>
9620 The <file>debian</file> directory and <file>debian/rules</file>
9621 are handled specially by <prgn>dpkg-source</prgn> - before
9622 applying the changes it will create the <file>debian</file>
9623 directory, and afterwards it will make
9624 <file>debian/rules</file> world-exectuable.
9630 <appendix id="pkg-controlfields"><heading>Control files and their
9631 fields (from old Packaging Manual)
9635 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9636 data in a common format, known as control files. Binary and
9637 source packages have control data as do the <file>.changes</file>
9638 files which control the installation of uploaded files, and
9639 <prgn>dpkg</prgn>'s internal databases are in a similar
9643 <sect><heading>Syntax of control files
9647 A file consists of one or more paragraphs of fields. The
9648 paragraphs are separated by blank lines. Some control files
9649 only allow one paragraph; others allow several, in which
9650 case each paragraph often refers to a different package.
9654 Each paragraph is a series of fields and values; each field
9655 consists of a name, followed by a colon and the value. It
9656 ends at the end of the line. Horizontal whitespace (spaces
9657 and tabs) may occur before or after the value and is ignored
9658 there; it is conventional to put a single space after the
9663 Some fields' values may span several lines; in this case
9664 each continuation line <em>must</em> start with a space or
9665 tab. Any trailing spaces or tabs at the end of individual
9666 lines of a field value are ignored.
9670 Except where otherwise stated only a single line of data is
9671 allowed and whitespace is not significant in a field body.
9672 Whitespace may never appear inside names (of packages,
9673 architectures, files or anything else), version numbers or
9674 in between the characters of multi-character version
9679 Field names are not case-sensitive, but it is usual to
9680 capitalise the field names using mixed case as shown below.
9684 Blank lines, or lines consisting only of spaces and tabs,
9685 are not allowed within field values or between fields - that
9686 would mean a new paragraph.
9690 It is important to note that there are several fields which
9691 are optional as far as <prgn>dpkg</prgn> and the related
9692 tools are concerned, but which must appear in every Debian
9693 package, or whose omission may cause problems. When writing
9694 the control files for Debian packages you <em>must</em> read
9695 the Debian policy manual in conjuction with the details
9696 below and the list of fields for the particular file.</p>
9699 <sect><heading>List of fields
9702 <sect1 id="pkg-f-Package"><heading><tt>Package</tt>
9706 The name of the binary package. Package names consist of
9707 the alphanumerics and <tt>+</tt> <tt>-</tt> <tt>.</tt>
9708 (plus, minus and full stop).
9711 The characters <tt>@</tt> <tt>:</tt> <tt>=</tt>
9712 <tt>%</tt> <tt>_</tt> (at, colon, equals, percent
9713 and underscore) used to be legal and are still
9714 accepted when found in a package file, but may not be
9715 used in new packages
9721 They must be at least two characters and must start with
9722 an alphanumeric. In current versions of dpkg they are
9723 sort of case-sensitive<footnote><p>This is a
9724 bug.</p></footnote>; use lowercase package names unless
9725 the package you're building (or referring to, in other
9726 fields) is already using uppercase.</p>
9729 <sect1 id="pkg-f-Version"><heading><tt>Version</tt>
9733 This lists the source or binary package's version number -
9734 see <ref id="versions">.
9739 <sect1 id="pkg-f-Architecture"><heading><tt>Architecture</tt>
9743 This is the architecture string; it is a single word for
9744 the Debian architecture.
9748 <prgn>dpkg</prgn> will check the declared architecture of
9749 a binary package against its own compiled-in value before
9754 The special value <tt>all</tt> indicates that the package
9755 is architecture-independent.
9759 In the main <file>debian/control</file> file in the source
9760 package, or in the source package control file
9761 <file>.dsc</file>, a list of architectures (separated by
9762 spaces) is also allowed, as is the special value
9763 <tt>any</tt>. A list indicates that the source will build
9764 an architecture-dependent package, and will only work
9765 correctly on the listed architectures. <tt>any</tt>
9766 indicates that though the source package isn't dependent
9767 on any particular architecture and should compile fine on
9768 any one, the binary package(s) produced are not
9769 architecture-independent but will instead be specific to
9770 whatever the current build architecture is.
9774 In a <file>.changes</file> file the <tt>Architecture</tt>
9775 field lists the architecture(s) of the package(s)
9776 currently being uploaded. This will be a list; if the
9777 source for the package is being uploaded too the special
9778 entry <tt>source</tt> is also present.
9782 See <ref id="pkg-debianrules"> for information how to get the
9783 architecture for the build process.
9787 <sect1 id="pkg-f-Maintainer"><heading><tt>Maintainer</tt>
9791 The package maintainer's name and email address. The name
9792 should come first, then the email address inside angle
9793 brackets <tt><></tt> (in RFC822 format).
9797 If the maintainer's name contains a full stop then the
9798 whole field will not work directly as an email address due
9799 to a misfeature in the syntax specified in RFC822; a
9800 program using this field as an address must check for this
9801 and correct the problem if necessary (for example by
9802 putting the name in round brackets and moving it to the
9803 end, and bringing the email address forward).
9807 In a <file>.changes</file> file or parsed changelog data this
9808 contains the name and email address of the person
9809 responsible for the particular version in question - this
9810 may not be the package's usual maintainer.
9814 This field is usually optional in as far as the
9815 <prgn>dpkg</prgn> are concerned, but its absence when
9816 building packages usually generates a warning.</p>
9819 <sect1 id="pkg-f-Source"><heading><tt>Source</tt>
9823 This field identifies the source package name.
9827 In a main source control information or a
9828 <file>.changes</file> or <file>.dsc</file> file or parsed
9829 changelog data this may contain only the name of the
9834 In the control file of a binary package (or in a
9835 <file>Packages</file> file) it may be followed by a version
9836 number in parentheses.
9839 It is usual to leave a space after the package name if
9840 a version number is specified.
9842 </footnote> This version number may be omitted (and is, by
9843 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
9844 the <tt>Version</tt> field of the binary package in
9845 question. The field itself may be omitted from a binary
9846 package control file when the source package has the same
9847 name and version as the binary package.
9851 <sect1><heading>Package interrelationship fields:
9852 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
9853 <tt>Recommends</tt> <tt>Suggests</tt>, <tt>Conflicts</tt>,
9854 <tt>Provides</tt>, <tt>Replaces</tt>
9858 These fields describe the package's relationships with
9859 other packages. Their syntax and semantics are described
9860 in <ref id="relationships">.</p>
9863 <sect1 id="pkg-f-Description"><heading><tt>Description</tt>
9867 In a binary package <tt>Packages</tt> file or main source
9868 control file this field contains a description of the
9869 binary package, in a special format. See <ref
9870 id="descriptions"> for details.
9874 In a <file>.changes</file> file it contains a summary of the
9875 descriptions for the packages being uploaded. The part of
9876 the field before the first newline is empty; thereafter
9877 each line has the name of a binary package and the summary
9878 description line from that binary package. Each line is
9879 indented by one space.</p>
9882 <sect1 id="pkg-f-Essential"><heading><tt>Essential</tt>
9886 This is a boolean field which may occur only in the
9887 control file of a binary package (or in the
9888 <file>Packages</file> file) or in a per-package fields
9889 paragraph of a main source control data file.
9893 If set to <tt>yes</tt> then <prgn>dpkg</prgn> and
9894 <prgn>dselect</prgn> will refuse to remove the package
9895 (though it can be upgraded and/or replaced). The other
9896 possible value is <tt>no</tt>, which is the same as not
9897 having the field at all.</p>
9900 <sect1 id="pkg-f-classification"><heading><tt>Section</tt> and
9905 These two fields classify the package. The
9906 <tt>Priority</tt> represents how important that it is that
9907 the user have it installed; the <tt>Section</tt>
9908 represents an application area into which the package has
9913 When they appear in the <file>debian/control</file> file these
9914 fields give values for the section and priority subfields
9915 of the <tt>Files</tt> field of the <file>.changes</file> file,
9916 and give defaults for the section and priority of the
9921 The section and priority are represented, though not as
9922 separate fields, in the information for each file in the
9923 <qref id="pkg-f-Files"><tt>-File</tt></qref>field of a
9924 <file>.changes</file> file. The section value in a
9925 <file>.changes</file> file is used to decide where to install
9926 a package in the FTP archive.
9930 These fields are not used by by <prgn>dpkg</prgn> proper,
9931 but by <prgn>dselect</prgn> when it sorts packages and
9932 selects defaults. See the Debian policy manual for the
9933 priorities in use and the criteria for selecting the
9934 priority for a Debian package, and look at the Debian FTP
9935 archive for a list of currently in-use priorities.
9939 These fields may appear in binary package control files,
9940 in which case they provide a default value in case the
9941 <file>Packages</file> files are missing the information.
9942 <prgn>dpkg</prgn> and <prgn>dselect</prgn> will only use
9943 the value from a <file>.deb</file> file if they have no other
9944 information; a value listed in a <file>Packages</file> file
9945 will always take precedence. By default
9946 <prgn>dpkg-gencontrol</prgn> does not include the section
9947 and priority in the control file of a binary package - use
9948 the <tt>-isp</tt>, <tt>-is</tt> or <tt>-ip</tt> options to
9949 achieve this effect.</p>
9952 <sect1 id="pkg-f-Binary"><heading><tt>Binary</tt>
9956 This field is a list of binary packages.
9960 When it appears in the <file>.dsc</file> file it is the list
9961 of binary packages which a source package can produce. It
9962 does not necessarily produce all of these binary packages
9963 for every architecture. The source control file doesn't
9964 contain details of which architectures are appropriate for
9965 which of the binary packages.
9969 When it appears in a <file>.changes</file> file it lists the
9970 names of the binary packages actually being uploaded.
9974 The syntax is a list of binary packages separated by
9978 A space after each comma is conventional.
9980 </footnote> Currently the packages must be separated using
9981 only spaces in the <file>.changes</file> file.</p>
9984 <sect1 id="pkg-f-Installed-Size"><heading><tt>Installed-Size</tt>
9988 This field appears in the control files of binary
9989 packages, and in the <file>Packages</file> files. It gives
9990 the total amount of disk space required to install the
9995 The disk space is represented in kilobytes as a simple
9999 <sect1 id="pkg-f-Files"><heading><tt>Files</tt>
10003 This field contains a list of files with information about
10004 each one. The exact information and syntax varies with
10005 the context. In all cases the the part of the field
10006 contents on the same line as the field name is empty. The
10007 remainder of the field is one line per file, each line
10008 being indented by one space and containing a number of
10009 sub-fields separated by spaces.
10013 In the <file>.dsc</file> (Debian source control) file each
10014 line contains the MD5 checksum, size and filename of the
10015 tarfile and (if applicable) diff file which make up the
10016 remainder of the source package.
10019 That is, the parts which are not the
10022 </footnote> The exact forms of the filenames are described
10023 in <ref id="pkg-sourcearchives">.
10027 In the <file>.changes</file> file this contains one line per
10028 file being uploaded. Each line contains the MD5 checksum,
10029 size, section and priority and the filename. The section
10030 and priority are the values of the corresponding fields in
10031 the main source control file - see <ref
10032 id="pkg-f-classification">. If no section or priority is
10033 specified then <tt>-</tt> should be used, though section
10034 and priority values must be specified for new packages to
10035 be installed properly.
10039 The special value <tt>byhand</tt> for the section in a
10040 <tt>.changes</tt> file indicates that the file in question
10041 is not an ordinary package file and must by installed by
10042 hand by the distribution maintainers. If the section is
10043 <tt>byhand</tt> the priority should be <tt>-</tt>.
10047 If a new Debian revision of a package is being shipped and
10048 no new original source archive is being distributed the
10049 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
10050 entry for the original source archive
10051 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
10052 but the <file>.changes</file> file should leave it out. In
10053 this case the original source archive on the distribution
10054 site must match exactly, byte-for-byte, the original
10055 source archive which was used to generate the
10056 <file>.dsc</file> file and diff which are being uploaded.</p>
10061 id="pkg-f-Standards-Version"><heading><tt>Standards-Version</tt>
10065 The most recent version of the standards (the
10066 <prgn>dpkg</prgn> programmers' and policy manuals and
10067 associated texts) with which the package complies. This
10068 is updated manually when editing the source package to
10069 conform to newer standards; it can sometimes be used to
10070 tell when a package needs attention.
10074 Its format is the same as that of a version number except
10075 that no epoch or Debian revision is allowed - see <ref
10076 id="versions">.</p>
10080 <sect1 id="pkg-f-Distribution"><heading><tt>Distribution</tt>
10084 In a <file>.changes</file> file or parsed changelog output
10085 this contains the (space-separated) name(s) of the
10086 distribution(s) where this version of the package should
10087 be or was installed. Distribution names follow the rules
10088 for package names. (See <ref id="pkg-f-Package">).
10092 Current distribution values are:
10094 <tag><em>stable</em></tag>
10097 This is the current "released" version of Debian
10098 GNU/Linux. A new version is released approximately
10099 every 3 months after the <em>development</em> code has
10100 been <em>frozen</em> for a month of testing. Once the
10101 distribution is <em>stable</em> only major bug fixes
10102 are allowed. When changes are made to this
10103 distribution, the release number is increased
10104 (for example: 1.2r1 becomes 1.2r2 then 1.2r3, etc).
10108 <tag><em>unstable</em></tag>
10111 This distribution value refers to the
10112 <em>developmental</em> part of the Debian distribution
10113 tree. New packages, new upstream versions of packages
10114 and bug fixes go into the <em>unstable</em> directory
10115 tree. Download from this distribution at your own
10119 <tag><em>contrib</em></tag>
10122 The packages with this distribution value do not meet
10123 the criteria for inclusion in the main Debian
10124 distribution as defined by the Policy Manual, but meet
10125 the criteria for the <em>contrib</em>
10126 Distribution. There is currently no distinction
10127 between stable and unstable packages in the
10128 <em>contrib</em> or <em>non-free</em>
10129 distributions. Use your best judgement in downloading
10130 from this Distribution.</p>
10133 <tag><em>non-free</em></tag>
10136 Like the packages in the <em>contrib</em> seciton,
10137 the packages in <em>non-free</em> do not meet the
10138 criteria for inclusion in the main Debian distribution
10139 as defined by the Policy Manual. Again, use your best
10140 judgement in downloading from this Distribution.</p>
10142 <tag><em>experimental</em></tag>
10145 The packages with this distribution value are deemed
10146 by their maintainers to be high risk. Oftentimes they
10147 represent early beta or developmental packages from
10148 various sources that the maintainers want people to
10149 try, but are not ready to be a part of the other parts
10150 of the Debian distribution tree. Download at your own
10154 <tag><em>frozen</em></tag>
10157 From time to time, (currently, every 3 months) the
10158 <em>unstable</em> distribution enters a state of
10159 "code-freeze" in anticipation of release as a
10160 <em>stable</em> version. During this period of testing
10161 (usually 4 weeks) only fixes for existing or
10162 newly-discovered bugs will be allowed.
10165 </taglist> You should list <em>all</em> distributions that
10166 the package should be installed into. Except in unusual
10167 circumstances, installations to <em>stable</em> should also
10168 go into <em>frozen</em> (if it exists) and
10169 <em>unstable</em>. Likewise, installations into
10170 <em>frozen</em> should also go into <em>unstable</em>.</p>
10173 <sect1 id="pkg-f-Urgency"><heading><tt>Urgency</tt>
10177 This is a description of how important it is to upgrade to
10178 this version from previous ones. It consists of a single
10179 keyword usually taking one of the values <tt>LOW</tt>,
10180 <tt>MEDIUM</tt> or <tt>HIGH</tt>) followed by an optional
10181 commentary (separated by a space) which is usually in
10182 parentheses. For example:
10184 Urgency: LOW (HIGH for diversions users)
10189 This field appears in the <file>.changes</file> file and in
10190 parsed changelogs; its value appears as the value of the
10191 <tt>urgency</tt> attribute in a <prgn>dpkg</prgn>-style
10192 changelog (see <ref id="pkg-dpkgchangelog">).
10196 Urgency keywords are not case-sensitive.</p>
10199 <sect1 id="pkg-f-Date"><heading><tt>Date</tt>
10203 In <tt>.changes</tt> files and parsed changelogs, this
10204 gives the date the package was built or last edited.</p>
10207 <sect1 id="pkg-f-Format"><heading><tt>Format</tt>
10211 This field occurs in <file>.changes</file> files, and
10212 specifies a format revision for the file. The format
10213 described here is version <tt>1.5</tt>. The syntax of the
10214 format value is the same as that of a package version
10215 number except that no epoch or Debian revision is allowed
10216 - see <ref id="versions">.</p>
10219 <sect1 id="pkg-f-Changes"><heading><tt>Changes</tt>
10223 In a <file>.changes</file> file or parsed changelog this field
10224 contains the human-readable changes data, describing the
10225 differences between the last version and the current one.
10229 There should be nothing in this field before the first
10230 newline; all the subsequent lines must be indented by at
10231 least one space; blank lines must be represented by a line
10232 consiting only of a space and a full stop.
10236 Each version's change information should be preceded by a
10237 "title" line giving at least the version, distribution(s)
10238 and urgency, in a human-readable way.
10242 If data from several versions is being returned the entry
10243 for the most recent version should be returned first, and
10244 entries should be separated by the representation of a
10245 blank line (the "title" line may also be followed by the
10246 representation of blank line).</p>
10249 <sect1 id="pkg-f-Filename"><heading><tt>Filename</tt> and
10250 <tt>MSDOS-Filename</tt>
10254 These fields in <tt>Packages</tt> files give the
10255 filename(s) of (the parts of) a package in the
10256 distribution directories, relative to the root of the
10257 Debian hierarchy. If the package has been split into
10258 several parts the parts are all listed in order, separated
10262 <sect1 id="pkg-f-Size"><heading><tt>Size</tt> and <tt>MD5sum</tt>
10266 These fields in <file>Packages</file> files give the size (in
10267 bytes, expressed in decimal) and MD5 checksum of the
10268 file(s) which make(s) up a binary package in the
10269 distribution. If the package is split into several parts
10270 the values for the parts are listed in order, separated by
10274 <sect1 id="pkg-f-Status"><heading><tt>Status</tt>
10278 This field in <prgn>dpkg</prgn>'s status file records
10279 whether the user wants a package installed, removed or
10280 left alone, whether it is broken (requiring
10281 reinstallation) or not and what its current state on the
10282 system is. Each of these pieces of information is a
10286 <sect1 id="pkg-f-Config-Version"><heading><tt>Config-Version</tt>
10290 If a package is not installed or not configured, this
10291 field in <prgn>dpkg</prgn>'s status file records the last
10292 version of the package which was successfully
10296 <sect1 id="pkg-f-Conffiles"><heading><tt>Conffiles</tt>
10300 This field in <prgn>dpkg</prgn>'s status file contains
10301 information about the automatically-managed configuration
10302 files held by a package. This field should <em>not</em>
10303 appear anywhere in a package!</p>
10306 <sect1><heading>Obsolete fields
10310 These are still recognised by <prgn>dpkg</prgn> but should
10311 not appear anywhere any more.
10312 <taglist compact="compact">
10314 <tag><tt>Revision</tt></tag>
10315 <tag><tt>Package-Revision</tt></tag>
10316 <tag><tt>Package_Revision</tt></tag>
10319 The Debian revision part of the package version was
10320 at one point in a separate control file field. This
10321 field went through several names.</p>
10324 <tag><tt>Recommended</tt></tag>
10325 <item><p>Old name for <tt>Recommends</tt></p>
10328 <tag><tt>Optional</tt></tag>
10329 <item><p>Old name for <tt>Suggests</tt>.</p>
10331 <tag><tt>Class</tt></tag>
10332 <item><p>Old name for <tt>Priority</tt>.</p>
10340 <appendix id="pkg-conffiles"><heading>Configuration file handling
10341 (from old Packaging Manual)
10345 <prgn>dpkg</prgn> can do a certain amount of automatic
10346 handling of package configuration files.
10350 Whether this mechanism is appropriate depends on a number of
10351 factors, but basically there are two approaches to any
10352 particular configuration file.
10356 The easy method is to ship a best-effort configuration in the
10357 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10358 handle updates. If the user is unlikely to want to edit the
10359 file, but you need them to be able to without losing their
10360 changes, and a new package with a changed version of the file
10361 is only released infrequently, this is a good approach.
10365 The hard method is to build the configuration file from
10366 scratch in the <prgn>postinst</prgn> script, and to take the
10367 responsibility for fixing any mistakes made in earlier
10368 versions of the package automatically. This will be
10369 appropriate if the file is likely to need to be different on
10373 <sect><heading>Automatic handling of configuration files by
10378 A package may contain a control area file called
10379 <tt>conffiles</tt>. This file should be a list of filenames
10380 of configuration files needing automatic handling, separated
10381 by newlines. The filenames should be absolute pathnames,
10382 and the files referred to should actually exist in the
10387 When a package is upgraded <prgn>dpkg</prgn> will process
10388 the configuration files during the configuration stage,
10389 shortly before it runs the package's <prgn>postinst</prgn>
10394 For each file it checks to see whether the version of the
10395 file included in the package is the same as the one that was
10396 included in the last version of the package (the one that is
10397 being upgraded from); it also compares the version currently
10398 installed on the system with the one shipped with the last
10403 If neither the user nor the package maintainer has changed
10404 the file, it is left alone. If one or the other has changed
10405 their version, then the changed version is preferred - i.e.,
10406 if the user edits their file, but the package maintainer
10407 doesn't ship a different version, the user's changes will
10408 stay, silently, but if the maintainer ships a new version
10409 and the user hasn't edited it the new version will be
10410 installed (with an informative message). If both have
10411 changed their version the user is prompted about the problem
10412 and must resolve the differences themselves.
10416 The comparisons are done by calculating the MD5 message
10417 digests of the files, and storing the MD5 of the file as it
10418 was included in the most recent version of the package.
10422 When a package is installed for the first time
10423 <prgn>dpkg</prgn> will install the file that comes with it,
10424 unless that would mean overwriting a file already on the
10429 However, note that <prgn>dpkg</prgn> will <em>not</em>
10430 replace a conffile that was removed by the user (or by a
10431 script). This is necessary because with some programs a
10432 missing file produces an effect hard or impossible to
10433 achieve in another way, so that a missing file needs to be
10434 kept that way if the user did it.
10438 Note that a package should <em>not</em> modify a
10439 <prgn>dpkg</prgn>-handled conffile in its maintainer
10440 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10441 the user confusing and possibly dangerous options for
10442 conffile update when the package is upgraded.</p>
10445 <sect><heading>Fully-featured maintainer script configuration
10450 For files which contain site-specific information such as
10451 the hostname and networking details and so forth, it is
10452 better to create the file in the package's
10453 <prgn>postinst</prgn> script.
10457 This will typically involve examining the state of the rest
10458 of the system to determine values and other information, and
10459 may involve prompting the user for some information which
10460 can't be obtained some other way.
10464 When using this method there are a couple of important
10465 issues which should be considered:
10469 If you discover a bug in the program which generates the
10470 configuration file, or if the format of the file changes
10471 from one version to the next, you will have to arrange for
10472 the postinst script to do something sensible - usually this
10473 will mean editing the installed configuration file to remove
10474 the problem or change the syntax. You will have to do this
10475 very carefully, since the user may have changed the file,
10476 perhaps to fix the very problem that your script is trying
10477 to deal with - you will have to detect these situations and
10478 deal with them correctly.
10482 If you do go down this route it's probably a good idea to
10483 make the program that generates the configuration file(s) a
10484 separate program in <file>/usr/sbin</file>, by convention called
10485 <file><var>package</var>config</file> and then run that if
10486 appropriate from the post-installation script. The
10487 <tt><var>package</var>config</tt> program should not
10488 unquestioningly overwrite an existing configuration - if its
10489 mode of operation is geared towards setting up a package for
10490 the first time (rather than any arbitrary reconfiguration
10491 later) you should have it check whether the configuration
10492 already exists, and require a <tt>--force</tt> flag to
10493 overwrite it.</p></sect>
10496 <appendix id="pkg-alternatives"><heading>Alternative versions of
10497 an interface - <prgn>update-alternatives</prgn> (from old
10502 When several packages all provide different versions of the
10503 same program or file it is useful to have the system select a
10504 default, but to allow the system administrator to change it
10505 and have their decisions respected.
10509 For example, there are several versions of the <prgn>vi</prgn>
10510 editor, and there is no reason to prevent all of them from
10511 being installed at once, each under their own name
10512 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10513 Nevertheless it is desirable to have the name <tt>vi</tt>
10514 refer to something, at least by default.
10518 If all the packages involved cooperate, this can be done with
10519 <prgn>update-alternatives</prgn>.
10523 Each package provides its own version under its own name, and
10524 calls <prgn>update-alternatives</prgn> in its postinst to
10525 register its version (and again in its prerm to deregister
10530 See the manpage <manref name="update-alternatives"
10531 section="8"> for details.
10535 If <prgn>update-alternatives</prgn> does not seem appropriate
10536 you may wish to consider using diversions instead.</p>
10539 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10540 package's version of a file (from old Packaging Manual)
10544 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10545 when it reinstalls the package it belongs to, and to have it
10546 put the file from the package somewhere else instead.
10550 This can be used locally to override a package's version of a
10551 file, or by one package to override another's version (or
10552 provide a wrapper for it).
10556 Before deciding to use a diversion, read <ref
10557 id="pkg-alternatives"> to see if you really want a diversion
10558 rather than several alternative versions of a program.
10562 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10563 and updated by a special program <prgn>dpkg-divert</prgn>.
10564 Please see <manref name="dpkg-divert" section="8"> for full
10565 details of its operation.
10569 When a package wishes to divert a file from another, it should
10570 call <prgn>dpkg-divert</prgn> in its preinst to add the
10571 diversion and rename the existing file. For example,
10572 supposing that a <prgn>smailwrapper</prgn> package wishes to
10573 install a wrapper around <file>/usr/sbin/smail</file>:
10575 if [ install = "$1" ]; then
10576 dpkg-divert --package smailwrapper --add --rename \
10577 --divert /usr/sbin/smail.real /usr/sbin/smail
10579 </example> Testing <tt>$1</tt> is necessary so that the script
10580 doesn't try to add the diversion again when
10581 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10582 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10583 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10584 get installed as the true version.
10588 The postrm has to do the reverse:
10590 if [ remove = "$1" ]; then
10591 dpkg-divert --package smailwrapper --remove --rename \
10592 --divert /usr/sbin/smail.real /usr/sbin/smail
10598 Do not attempt to divert a file which is vitally important for
10599 the system's operation - when using <prgn>dpkg-divert</prgn>
10600 there is a time, after it has been diverted but before
10601 <prgn>dpkg</prgn> has installed the new version, when the file
10602 does not exist.</p>
10607 <!-- vim:set ai et sts=2 sw=2 tw=76: -->