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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources.
885 However, in some cases where the upstream version number is
886 based on a date (e.g., a development "snapshot" release) the
887 package management system cannot handle these version
888 numbers without epochs. For example, dpkg will consider
889 "96May01" to be greater than "96Dec24".
893 To prevent having to use epochs for every new upstream
894 version, the date based portion of the version number
895 should be changed to the following format in such cases:
896 "19960501", "19961224". It is up to the maintainer whether
897 they want to bother the upstream maintainer to change
898 the version numbers upstream, too.
902 Note that other version formats based on dates which are
903 parsed correctly by the package management system should
904 <em>not</em> be changed.
908 Native Debian packages (i.e., packages which have been
909 written especially for Debian) whose version numbers include
910 dates should always use the "YYYYMMDD" format.
917 <heading>The maintainer of a package</heading>
920 Every package must have a Debian maintainer (the
921 maintainer may be one person or a group of people
922 reachable from a common email address, such as a mailing
923 list). The maintainer is responsible for ensuring that
924 the package is placed in the appropriate distributions.
928 The maintainer must be specified in the
929 <tt>Maintainer</tt> control field with their correct name
930 and a working email address. If one person maintains
931 several packages, they should try to avoid having
932 different forms of their name and email address in
933 the <tt>Maintainer</tt> fields of those packages.
937 The format of the <tt>Maintainer</tt> control field is
938 described in <ref id="f-Maintainer">.
942 If the maintainer of a package quits from the Debian
943 project, "Debian QA Group"
944 <email>packages@qa.debian.org</email> takes over the
945 maintainer-ship of the package until someone else
946 volunteers for that task. These packages are called
947 <em>orphaned packages</em>.<footnote>
948 The detailed procedure for doing this gracefully can
949 be found in the Debian Developer's Reference,
950 see <ref id="related">.
955 <sect id="descriptions">
956 <heading>The description of a package</heading>
959 Every Debian package must have a <tt>Description</tt> control
960 field which contains a synopsis and extended description of the
961 package. Technical information about the format of the
962 <tt>Description</tt> field is in <ref id="f-Description">.
966 The description should describe the package (the program) to a
967 user (system administrator) who has never met it before so that
968 they have enough information to decide whether they want to
969 install it. This description should not just be copied verbatim
970 from the program's documentation.
974 Put important information first, both in the synopsis and
975 extended description. Sometimes only the first part of the
976 synopsis or of the description will be displayed. You can
977 assume that there will usually be a way to see the whole
978 extended description.
982 The description should also give information about the
983 significant dependencies and conflicts between this package
984 and others, so that the user knows why these dependencies and
985 conflicts have been declared.
989 Instructions for configuring or using the package should
990 not be included (that is what installation scripts,
991 manual pages, info files, etc., are for). Copyright
992 statements and other administrivia should not be included
993 either (that is what the copyright file is for).
996 <sect1 id="synopsis"><heading>The single line synopsis</heading>
999 The single line synopsis should be kept brief - certainly
1000 under 80 characters.
1004 Do not include the package name in the synopsis line. The
1005 display software knows how to display this already, and you
1006 do not need to state it. Remember that in many situations
1007 the user may only see the synopsis line - make it as
1008 informative as you can.
1013 <sect1 id="extendeddesc"><heading>The extended description</heading>
1016 Do not try to continue the single line synopsis into the
1017 extended description. This will not work correctly when
1018 the full description is displayed, and makes no sense
1019 where only the summary (the single line synopsis) is
1024 The extended description should describe what the package
1025 does and how it relates to the rest of the system (in terms
1026 of, for example, which subsystem it is which part of).
1030 The description field needs to make sense to anyone, even
1031 people who have no idea about any of the things the
1032 package deals with.<footnote>
1033 The blurb that comes with a program in its
1034 announcements and/or <prgn>README</prgn> files is
1035 rarely suitable for use in a description. It is
1036 usually aimed at people who are already in the
1037 community where the package is used.
1046 <heading>Dependencies</heading>
1049 Every package must specify the dependency information
1050 about other packages that are required for the first to
1055 For example, a dependency entry must be provided for any
1056 shared libraries required by a dynamically-linked executable
1057 binary in a package.
1061 Packages are not required to declare any dependencies they
1062 have on other packages which are marked <tt>Essential</tt>
1063 (see below), and should not do so unless they depend on a
1064 particular version of that package.<footnote>
1066 Essential is needed in part to avoid unresolvable dependency
1067 loops on upgrade. If packages add unnecessary dependencies
1068 on packages in this set, the chances that there
1069 <strong>will</strong> be an unresolvable dependency loop
1070 caused by forcing these Essential packages to be configured
1071 first before they need to be is greatly increased. It also
1072 increases the chances that frontends will be unable to
1073 <strong>calculate</strong> an upgrade path, even if one
1077 Also, functionality is rarely ever removed from the
1078 Essential set, but <em>packages</em> have been removed from
1079 the Essential set when the functionality moved to a
1080 different package. So depending on these packages <em>just
1081 in case</em> they stop being essential does way more harm
1088 Sometimes, a package requires another package to be installed
1089 <em>and</em> configured before it can be installed. In this
1090 case, you must specify a <tt>Pre-Depends</tt> entry for
1095 You should not specify a <tt>Pre-Depends</tt> entry for a
1096 package before this has been discussed on the
1097 <tt>debian-devel</tt> mailing list and a consensus about
1098 doing that has been reached.
1102 The format of the package interrelationship control fields is
1103 described in <ref id="relationships">.
1107 <sect id="virtual_pkg">
1108 <heading>Virtual packages</heading>
1111 Sometimes, there are several packages which offer
1112 more-or-less the same functionality. In this case, it's
1113 useful to define a <em>virtual package</em> whose name
1114 describes that common functionality. (The virtual
1115 packages only exist logically, not physically; that's why
1116 they are called <em>virtual</em>.) The packages with this
1117 particular function will then <em>provide</em> the virtual
1118 package. Thus, any other package requiring that function
1119 can simply depend on the virtual package without having to
1120 specify all possible packages individually.
1124 All packages should use virtual package names where
1125 appropriate, and arrange to create new ones if necessary.
1126 They should not use virtual package names (except privately,
1127 amongst a cooperating group of packages) unless they have
1128 been agreed upon and appear in the list of virtual package
1129 names. (See also <ref id="virtual">)
1133 The latest version of the authoritative list of virtual
1134 package names can be found in the <tt>debian-policy</tt> package.
1135 It is also available from the Debian web mirrors at
1136 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1137 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1141 The procedure for updating the list is described in the preface
1148 <heading>Base system</heading>
1151 The <tt>base system</tt> is a minimum subset of the Debian
1152 GNU/Linux system that is installed before everything else
1153 on a new system. Only very few packages are allowed to form
1154 part of the base system, in order to keep the required disk
1159 The base system consists of all those packages with priority
1160 <tt>required</tt> or <tt>important</tt>. Many of them will
1161 be tagged <tt>essential</tt> (see below).
1166 <heading>Essential packages</heading>
1169 Essential is defined as the minimal set of functionality that
1170 must be available and usable on the system at all times, even
1171 when packages are in an unconfigured (but unpacked) state.
1172 Packages are tagged <tt>essential</tt> for a system using the
1173 <tt>Essential</tt> control field. The format of the
1174 <tt>Essential</tt> control field is described in <ref
1179 Since these packages cannot be easily removed (one has to
1180 specify an extra <em>force option</em> to
1181 <prgn>dpkg</prgn> to do so), this flag must not be used
1182 unless absolutely necessary. A shared library package
1183 must not be tagged <tt>essential</tt>; dependencies will
1184 prevent its premature removal, and we need to be able to
1185 remove it when it has been superseded.
1189 Since dpkg will not prevent upgrading of other packages
1190 while an <tt>essential</tt> package is in an unconfigured
1191 state, all <tt>essential</tt> packages must supply all of
1192 their core functionality even when unconfigured. If the
1193 package cannot satisfy this requirement it must not be
1194 tagged as essential, and any packages depending on this
1195 package must instead have explicit dependency fields as
1200 Maintainers should take great care in adding any programs,
1201 interfaces, or functionality to <tt>essential</tt> packages.
1202 Packages may assume that functionality provided by
1203 <tt>essential</tt> packages is always available without
1204 declaring explicit dependencies, which means that removing
1205 functionality from the Essential set is very difficult and is
1206 almost never done. Any capability added to an
1207 <tt>essential</tt> package therefore creates an obligation to
1208 support that capability as part of the Essential set in
1213 You must not tag any packages <tt>essential</tt> before
1214 this has been discussed on the <tt>debian-devel</tt>
1215 mailing list and a consensus about doing that has been
1220 <sect id="maintscripts">
1221 <heading>Maintainer Scripts</heading>
1224 The package installation scripts should avoid producing
1225 output which is unnecessary for the user to see and
1226 should rely on <prgn>dpkg</prgn> to stave off boredom on
1227 the part of a user installing many packages. This means,
1228 amongst other things, using the <tt>--quiet</tt> option on
1229 <prgn>install-info</prgn>.
1233 Errors which occur during the execution of an installation
1234 script must be checked and the installation must not
1235 continue after an error.
1239 Note that in general <ref id="scripts"> applies to package
1240 maintainer scripts, too.
1244 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1245 to another package without consulting the maintainer of that
1246 package first. When adding or removing diversions, package
1247 maintainer scripts must provide the <tt>--package</tt> flag
1248 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1252 All packages which supply an instance of a common command
1253 name (or, in general, filename) should generally use
1254 <prgn>update-alternatives</prgn>, so that they may be
1255 installed together. If <prgn>update-alternatives</prgn>
1256 is not used, then each package must use
1257 <tt>Conflicts</tt> to ensure that other packages are
1258 de-installed. (In this case, it may be appropriate to
1259 specify a conflict against earlier versions of something
1260 that previously did not use
1261 <prgn>update-alternatives</prgn>; this is an exception to
1262 the usual rule that versioned conflicts should be
1266 <sect1 id="maintscriptprompt">
1267 <heading>Prompting in maintainer scripts</heading>
1269 Package maintainer scripts may prompt the user if
1270 necessary. Prompting must be done by communicating
1271 through a program, such as <prgn>debconf</prgn>, which
1272 conforms to the Debian Configuration Management
1273 Specification, version 2 or higher.
1277 Packages which are essential, or which are dependencies of
1278 essential packages, may fall back on another prompting method
1279 if no such interface is available when they are executed.
1283 The Debian Configuration Management Specification is included
1284 in the <file>debconf_specification</file> files in the
1285 <package>debian-policy</package> package.
1286 It is also available from the Debian web mirrors at
1287 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1288 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1292 Packages which use the Debian Configuration Management
1293 Specification may contain the additional control information
1294 files <file>config</file>
1295 and <file>templates</file>. <file>config</file> is an
1296 additional maintainer script used for package configuration,
1297 and <file>templates</file> contains templates used for user
1298 prompting. The <prgn>config</prgn> script might be run before
1299 the <prgn>preinst</prgn> script and before the package is
1300 unpacked or any of its dependencies or pre-dependencies are
1301 satisfied. Therefore it must work using only the tools
1302 present in <em>essential</em> packages.<footnote>
1303 <package>Debconf</package> or another tool that
1304 implements the Debian Configuration Management
1305 Specification will also be installed, and any
1306 versioned dependencies on it will be satisfied
1307 before preconfiguration begins.
1312 Packages which use the Debian Configuration Management
1313 Specification must allow for translation of their user-visible
1314 messages by using a gettext-based system such as the one
1315 provided by the <package>po-debconf</package> package.
1319 Packages should try to minimize the amount of prompting
1320 they need to do, and they should ensure that the user
1321 will only ever be asked each question once. This means
1322 that packages should try to use appropriate shared
1323 configuration files (such as <file>/etc/papersize</file> and
1324 <file>/etc/news/server</file>), and shared
1325 <package>debconf</package> variables rather than each
1326 prompting for their own list of required pieces of
1331 It also means that an upgrade should not ask the same
1332 questions again, unless the user has used
1333 <tt>dpkg --purge</tt> to remove the package's configuration.
1334 The answers to configuration questions should be stored in an
1335 appropriate place in <file>/etc</file> so that the user can
1336 modify them, and how this has been done should be
1341 If a package has a vitally important piece of
1342 information to pass to the user (such as "don't run me
1343 as I am, you must edit the following configuration files
1344 first or you risk your system emitting badly-formatted
1345 messages"), it should display this in the
1346 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1347 prompt the user to hit return to acknowledge the
1348 message. Copyright messages do not count as vitally
1349 important (they belong in
1350 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1351 neither do instructions on how to use a program (these
1352 should be in on-line documentation, where all the users
1357 Any necessary prompting should almost always be confined
1358 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1359 script. If it is done in the <prgn>postinst</prgn>, it
1360 should be protected with a conditional so that
1361 unnecessary prompting doesn't happen if a package's
1362 installation fails and the <prgn>postinst</prgn> is
1363 called with <tt>abort-upgrade</tt>,
1364 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1374 <heading>Source packages</heading>
1376 <sect id="standardsversion">
1377 <heading>Standards conformance</heading>
1380 Source packages should specify the most recent version number
1381 of this policy document with which your package complied
1382 when it was last updated.
1386 This information may be used to file bug reports
1387 automatically if your package becomes too much out of date.
1391 The version is specified in the <tt>Standards-Version</tt>
1393 The format of the <tt>Standards-Version</tt> field is
1394 described in <ref id="f-Standards-Version">.
1398 You should regularly, and especially if your package has
1399 become out of date, check for the newest Policy Manual
1400 available and update your package, if necessary. When your
1401 package complies with the new standards you should update the
1402 <tt>Standards-Version</tt> source package field and
1403 release it.<footnote>
1404 See the file <file>upgrading-checklist</file> for
1405 information about policy which has changed between
1406 different versions of this document.
1412 <sect id="pkg-relations">
1413 <heading>Package relationships</heading>
1416 Source packages should specify which binary packages they
1417 require to be installed or not to be installed in order to
1418 build correctly. For example, if building a package
1419 requires a certain compiler, then the compiler should be
1420 specified as a build-time dependency.
1424 It is not necessary to explicitly specify build-time
1425 relationships on a minimal set of packages that are always
1426 needed to compile, link and put in a Debian package a
1427 standard "Hello World!" program written in C or C++. The
1428 required packages are called <em>build-essential</em>, and
1429 an informational list can be found in
1430 <file>/usr/share/doc/build-essential/list</file> (which is
1431 contained in the <tt>build-essential</tt>
1434 <list compact="compact">
1436 This allows maintaining the list separately
1437 from the policy documents (the list does not
1438 need the kind of control that the policy
1442 Having a separate package allows one to install
1443 the build-essential packages on a machine, as
1444 well as allowing other packages such as tasks to
1445 require installation of the build-essential
1446 packages using the depends relation.
1449 The separate package allows bug reports against
1450 the list to be categorized separately from
1451 the policy management process in the BTS.
1458 When specifying the set of build-time dependencies, one
1459 should list only those packages explicitly required by the
1460 build. It is not necessary to list packages which are
1461 required merely because some other package in the list of
1462 build-time dependencies depends on them.<footnote>
1463 The reason for this is that dependencies change, and
1464 you should list all those packages, and <em>only</em>
1465 those packages that <em>you</em> need directly. What
1466 others need is their business. For example, if you
1467 only link against <file>libimlib</file>, you will need to
1468 build-depend on <package>libimlib2-dev</package> but
1469 not against any <tt>libjpeg*</tt> packages, even
1470 though <tt>libimlib2-dev</tt> currently depends on
1471 them: installation of <package>libimlib2-dev</package>
1472 will automatically ensure that all of its run-time
1473 dependencies are satisfied.
1478 If build-time dependencies are specified, it must be
1479 possible to build the package and produce working binaries
1480 on a system with only essential and build-essential
1481 packages installed and also those required to satisfy the
1482 build-time relationships (including any implied
1483 relationships). In particular, this means that version
1484 clauses should be used rigorously in build-time
1485 relationships so that one cannot produce bad or
1486 inconsistently configured packages when the relationships
1487 are properly satisfied.
1491 <ref id="relationships"> explains the technical details.
1496 <heading>Changes to the upstream sources</heading>
1499 If changes to the source code are made that are not
1500 specific to the needs of the Debian system, they should be
1501 sent to the upstream authors in whatever form they prefer
1502 so as to be included in the upstream version of the
1507 If you need to configure the package differently for
1508 Debian or for Linux, and the upstream source doesn't
1509 provide a way to do so, you should add such configuration
1510 facilities (for example, a new <prgn>autoconf</prgn> test
1511 or <tt>#define</tt>) and send the patch to the upstream
1512 authors, with the default set to the way they originally
1513 had it. You can then easily override the default in your
1514 <file>debian/rules</file> or wherever is appropriate.
1518 You should make sure that the <prgn>configure</prgn> utility
1519 detects the correct architecture specification string
1520 (refer to <ref id="arch-spec"> for details).
1524 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1525 <prgn>configure</prgn> scripts are used, you should edit the
1526 <file>.in</file> files rather than editing the
1527 <prgn>Makefile</prgn> directly. This allows the user to
1528 reconfigure the package if necessary. You should
1529 <em>not</em> configure the package and edit the generated
1530 <prgn>Makefile</prgn>! This makes it impossible for someone
1531 else to later reconfigure the package without losing the
1537 <sect id="dpkgchangelog">
1538 <heading>Debian changelog: <file>debian/changelog</file></heading>
1541 Changes in the Debian version of the package should be
1542 briefly explained in the Debian changelog file
1543 <file>debian/changelog</file>.<footnote>
1545 Mistakes in changelogs are usually best rectified by
1546 making a new changelog entry rather than "rewriting
1547 history" by editing old changelog entries.
1550 This includes modifications
1551 made in the Debian package compared to the upstream one
1552 as well as other changes and updates to the package.
1554 Although there is nothing stopping an author who is also
1555 the Debian maintainer from using this changelog for all
1556 their changes, it will have to be renamed if the Debian
1557 and upstream maintainers become different people. In such
1558 a case, however, it might be better to maintain the package
1559 as a non-native package.
1564 The format of the <file>debian/changelog</file> allows the
1565 package building tools to discover which version of the package
1566 is being built and find out other release-specific information.
1570 That format is a series of entries like this:
1572 <example compact="compact">
1573 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1575 [optional blank line(s), stripped]
1577 * <var>change details</var>
1578 <var>more change details</var>
1580 [blank line(s), included in output of dpkg-parsechangelog]
1582 * <var>even more change details</var>
1584 [optional blank line(s), stripped]
1586 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1591 <var>package</var> and <var>version</var> are the source
1592 package name and version number.
1596 <var>distribution(s)</var> lists the distributions where
1597 this version should be installed when it is uploaded - it
1598 is copied to the <tt>Distribution</tt> field in the
1599 <file>.changes</file> file. See <ref id="f-Distribution">.
1603 <var>urgency</var> is the value for the <tt>Urgency</tt>
1604 field in the <file>.changes</file> file for the upload
1605 (see <ref id="f-Urgency">). It is not possible to specify
1606 an urgency containing commas; commas are used to separate
1607 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1608 <prgn>dpkg</prgn> changelog format (though there is
1609 currently only one useful <var>keyword</var>,
1614 The change details may in fact be any series of lines
1615 starting with at least two spaces, but conventionally each
1616 change starts with an asterisk and a separating space and
1617 continuation lines are indented so as to bring them in
1618 line with the start of the text above. Blank lines may be
1619 used here to separate groups of changes, if desired.
1623 If this upload resolves bugs recorded in the Bug Tracking
1624 System (BTS), they may be automatically closed on the
1625 inclusion of this package into the Debian archive by
1626 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1627 in the change details.<footnote>
1628 To be precise, the string should match the following
1629 Perl regular expression:
1631 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1633 Then all of the bug numbers listed will be closed by the
1634 archive maintenance script (<prgn>katie</prgn>) using the
1635 <var>version</var> of the changelog entry.
1637 This information is conveyed via the <tt>Closes</tt> field
1638 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1642 The maintainer name and email address used in the changelog
1643 should be the details of the person uploading <em>this</em>
1644 version. They are <em>not</em> necessarily those of the
1645 usual package maintainer. The information here will be
1646 copied to the <tt>Changed-By</tt> field in the
1647 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1648 and then later used to send an acknowledgement when the
1649 upload has been installed.
1653 The <var>date</var> has the following format<footnote>
1654 This is the same as the format generated by <tt>date
1656 </footnote> (compatible and with the same semantics of
1657 RFC 2822 and RFC 5322):
1658 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1660 <list compact="compact">
1662 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1665 dd is a one- or two-digit day of the month (01-31)
1668 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1671 <item>yyyy is the four-digit year (e.g. 2010)</item>
1672 <item>hh is the two-digit hour (00-23)</item>
1673 <item>mm is the two-digit minutes (00-59)</item>
1674 <item>ss is the two-digit seconds (00-60)</item>
1676 +zzzz or -zzzz is the the time zone offset from Coordinated
1677 Universal Time (UTC). "+" indicates that the time is ahead
1678 of (i.e., east of) UTC and "-" indicates that the time is
1679 behind (i.e., west of) UTC. The first two digits indicate
1680 the hour difference from UTC and the last two digits
1681 indicate the number of additional minutes difference from
1682 UTC. The last two digits must be in the range 00-59.
1688 The first "title" line with the package name must start
1689 at the left hand margin. The "trailer" line with the
1690 maintainer and date details must be preceded by exactly
1691 one space. The maintainer details and the date must be
1692 separated by exactly two spaces.
1696 The entire changelog must be encoded in UTF-8.
1700 For more information on placement of the changelog files
1701 within binary packages, please see <ref id="changelogs">.
1705 <sect id="dpkgcopyright">
1706 <heading>Copyright: <file>debian/copyright</file></heading>
1708 Every package must be accompanied by a verbatim copy of its
1709 copyright information and distribution license in the file
1710 <file>/usr/share/doc/<var>package</var>/copyright</file>
1711 (see <ref id="copyrightfile"> for further details). Also see
1712 <ref id="pkgcopyright"> for further considerations related
1713 to copyrights for packages.
1717 <heading>Error trapping in makefiles</heading>
1720 When <prgn>make</prgn> invokes a command in a makefile
1721 (including your package's upstream makefiles and
1722 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1723 means that <prgn>sh</prgn>'s usual bad error handling
1724 properties apply: if you include a miniature script as one
1725 of the commands in your makefile you'll find that if you
1726 don't do anything about it then errors are not detected
1727 and <prgn>make</prgn> will blithely continue after
1732 Every time you put more than one shell command (this
1733 includes using a loop) in a makefile command you
1734 must make sure that errors are trapped. For
1735 simple compound commands, such as changing directory and
1736 then running a program, using <tt>&&</tt> rather
1737 than semicolon as a command separator is sufficient. For
1738 more complex commands including most loops and
1739 conditionals you should include a separate <tt>set -e</tt>
1740 command at the start of every makefile command that's
1741 actually one of these miniature shell scripts.
1745 <sect id="timestamps">
1746 <heading>Time Stamps</heading>
1748 Maintainers should preserve the modification times of the
1749 upstream source files in a package, as far as is reasonably
1751 The rationale is that there is some information conveyed
1752 by knowing the age of the file, for example, you could
1753 recognize that some documentation is very old by looking
1754 at the modification time, so it would be nice if the
1755 modification time of the upstream source would be
1761 <sect id="restrictions">
1762 <heading>Restrictions on objects in source packages</heading>
1765 The source package may not contain any hard links<footnote>
1767 This is not currently detected when building source
1768 packages, but only when extracting
1772 Hard links may be permitted at some point in the
1773 future, but would require a fair amount of
1776 </footnote>, device special files, sockets or setuid or
1777 setgid files.<footnote>
1778 Setgid directories are allowed.
1783 <sect id="debianrules">
1784 <heading>Main building script: <file>debian/rules</file></heading>
1787 This file must be an executable makefile, and contains the
1788 package-specific recipes for compiling the package and
1789 building binary package(s) from the source.
1793 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1794 so that it can be invoked by saying its name rather than
1795 invoking <prgn>make</prgn> explicitly. That is, invoking
1796 either of <tt>make -f debian/rules <em>args...</em></tt>
1797 or <tt>./debian/rules <em>args...</em></tt> must result in
1802 Since an interactive <file>debian/rules</file> script makes it
1803 impossible to auto-compile that package and also makes it
1804 hard for other people to reproduce the same binary
1805 package, all <em>required targets</em> must be
1806 non-interactive. At a minimum, required targets are the
1807 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1808 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1809 <em>binary-indep</em>, and <em>build</em>. It also follows
1810 that any target that these targets depend on must also be
1815 The targets are as follows (required unless stated otherwise):
1817 <tag><tt>build</tt></tag>
1820 The <tt>build</tt> target should perform all the
1821 configuration and compilation of the package.
1822 If a package has an interactive pre-build
1823 configuration routine, the Debian source package
1824 must either be built after this has taken place (so
1825 that the binary package can be built without rerunning
1826 the configuration) or the configuration routine
1827 modified to become non-interactive. (The latter is
1828 preferable if there are architecture-specific features
1829 detected by the configuration routine.)
1833 For some packages, notably ones where the same
1834 source tree is compiled in different ways to produce
1835 two binary packages, the <tt>build</tt> target
1836 does not make much sense. For these packages it is
1837 good enough to provide two (or more) targets
1838 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1839 for each of the ways of building the package, and a
1840 <tt>build</tt> target that does nothing. The
1841 <tt>binary</tt> target will have to build the
1842 package in each of the possible ways and make the
1843 binary package out of each.
1847 The <tt>build</tt> target must not do anything
1848 that might require root privilege.
1852 The <tt>build</tt> target may need to run the
1853 <tt>clean</tt> target first - see below.
1857 When a package has a configuration and build routine
1858 which takes a long time, or when the makefiles are
1859 poorly designed, or when <tt>build</tt> needs to
1860 run <tt>clean</tt> first, it is a good idea to
1861 <tt>touch build</tt> when the build process is
1862 complete. This will ensure that if <tt>debian/rules
1863 build</tt> is run again it will not rebuild the whole
1865 Another common way to do this is for <tt>build</tt>
1866 to depend on <prgn>build-stamp</prgn> and to do
1867 nothing else, and for the <prgn>build-stamp</prgn>
1868 target to do the building and to <tt>touch
1869 build-stamp</tt> on completion. This is
1870 especially useful if the build routine creates a
1871 file or directory called <tt>build</tt>; in such a
1872 case, <tt>build</tt> will need to be listed as
1873 a phony target (i.e., as a dependency of the
1874 <tt>.PHONY</tt> target). See the documentation of
1875 <prgn>make</prgn> for more information on phony
1881 <tag><tt>build-arch</tt> (optional),
1882 <tt>build-indep</tt> (optional)
1886 A package may also provide both of the targets
1887 <tt>build-arch</tt> and <tt>build-indep</tt>.
1888 The <tt>build-arch</tt> target, if provided, should
1889 perform all the configuration and compilation required for
1890 producing all architecture-dependant binary packages
1891 (those packages for which the body of the
1892 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1893 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1894 target, if provided, should perform all the configuration
1895 and compilation required for producing all
1896 architecture-independent binary packages (those packages
1897 for which the body of the <tt>Architecture</tt> field
1898 in <tt>debian/control</tt> is <tt>all</tt>).
1899 The <tt>build</tt> target should depend on those of the
1900 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1901 are provided in the rules file.<footnote>
1902 The intent of this split is so that binary-only builds
1903 need not install the dependencies required for
1904 the <tt>build-indep</tt> target. However, this is not
1905 yet used in practice since <tt>dpkg-buildpackage
1906 -B</tt>, and therefore the autobuilders,
1907 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1908 due to the difficulties in determining whether the
1909 optional <tt>build-arch</tt> target exists.
1914 If one or both of the targets <tt>build-arch</tt> and
1915 <tt>build-indep</tt> are not provided, then invoking
1916 <file>debian/rules</file> with one of the not-provided
1917 targets as arguments should produce a exit status code
1918 of 2. Usually this is provided automatically by make
1919 if the target is missing.
1923 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1924 must not do anything that might require root privilege.
1928 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1929 <tt>binary-indep</tt>
1933 The <tt>binary</tt> target must be all that is
1934 necessary for the user to build the binary package(s)
1935 produced from this source package. It is
1936 split into two parts: <prgn>binary-arch</prgn> builds
1937 the binary packages which are specific to a particular
1938 architecture, and <tt>binary-indep</tt> builds
1939 those which are not.
1942 <tt>binary</tt> may be (and commonly is) a target with
1943 no commands which simply depends on
1944 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1947 Both <tt>binary-*</tt> targets should depend on the
1948 <tt>build</tt> target, or on the appropriate
1949 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1950 provided, so that the package is built if it has not
1951 been already. It should then create the relevant
1952 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1953 make their control files and <prgn>dpkg-deb</prgn> to
1954 build them and place them in the parent of the top
1959 Both the <tt>binary-arch</tt> and
1960 <tt>binary-indep</tt> targets <em>must</em> exist.
1961 If one of them has nothing to do (which will always be
1962 the case if the source generates only a single binary
1963 package, whether architecture-dependent or not), it
1964 must still exist and must always succeed.
1968 The <tt>binary</tt> targets must be invoked as
1970 The <prgn>fakeroot</prgn> package often allows one
1971 to build a package correctly even without being
1977 <tag><tt>clean</tt></tag>
1980 This must undo any effects that the <tt>build</tt>
1981 and <tt>binary</tt> targets may have had, except
1982 that it should leave alone any output files created in
1983 the parent directory by a run of a <tt>binary</tt>
1988 If a <tt>build</tt> file is touched at the end of
1989 the <tt>build</tt> target, as suggested above, it
1990 should be removed as the first action that
1991 <tt>clean</tt> performs, so that running
1992 <tt>build</tt> again after an interrupted
1993 <tt>clean</tt> doesn't think that everything is
1998 The <tt>clean</tt> target may need to be
1999 invoked as root if <tt>binary</tt> has been
2000 invoked since the last <tt>clean</tt>, or if
2001 <tt>build</tt> has been invoked as root (since
2002 <tt>build</tt> may create directories, for
2007 <tag><tt>get-orig-source</tt> (optional)</tag>
2010 This target fetches the most recent version of the
2011 original source package from a canonical archive site
2012 (via FTP or WWW, for example), does any necessary
2013 rearrangement to turn it into the original source
2014 tar file format described below, and leaves it in the
2019 This target may be invoked in any directory, and
2020 should take care to clean up any temporary files it
2025 This target is optional, but providing it if
2026 possible is a good idea.
2030 <tag><tt>patch</tt> (optional)</tag>
2033 This target performs whatever additional actions are
2034 required to make the source ready for editing (unpacking
2035 additional upstream archives, applying patches, etc.).
2036 It is recommended to be implemented for any package where
2037 <tt>dpkg-source -x</tt> does not result in source ready
2038 for additional modification. See
2039 <ref id="readmesource">.
2045 The <tt>build</tt>, <tt>binary</tt> and
2046 <tt>clean</tt> targets must be invoked with the current
2047 directory being the package's top-level directory.
2052 Additional targets may exist in <file>debian/rules</file>,
2053 either as published or undocumented interfaces or for the
2054 package's internal use.
2058 The architectures we build on and build for are determined
2059 by <prgn>make</prgn> variables using the utility
2060 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2061 You can determine the
2062 Debian architecture and the GNU style architecture
2063 specification string for the build machine (the machine type
2064 we are building on) as well as for the host machine (the
2065 machine type we are building for). Here is a list of
2066 supported <prgn>make</prgn> variables:
2067 <list compact="compact">
2069 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2072 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2075 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2078 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2079 specification string)
2082 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2083 <tt>DEB_*_GNU_TYPE</tt>)
2086 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2087 <tt>DEB_*_GNU_TYPE</tt>)
2089 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2090 the build machine or <tt>HOST</tt> for specification of the
2095 Backward compatibility can be provided in the rules file
2096 by setting the needed variables to suitable default
2097 values; please refer to the documentation of
2098 <prgn>dpkg-architecture</prgn> for details.
2102 It is important to understand that the <tt>DEB_*_ARCH</tt>
2103 string only determines which Debian architecture we are
2104 building on or for. It should not be used to get the CPU
2105 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2106 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2107 GNU style variables should generally only be used with upstream
2111 <sect1 id="debianrules-options">
2112 <heading><file>debian/rules</file> and
2113 <tt>DEB_BUILD_OPTIONS</tt></heading>
2116 Supporting the standardized environment variable
2117 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2118 contain several flags to change how a package is compiled and
2119 built. Each flag must be in the form <var>flag</var> or
2120 <var>flag</var>=<var>options</var>. If multiple flags are
2121 given, they must be separated by whitespace.<footnote>
2122 Some packages support any delimiter, but whitespace is the
2123 easiest to parse inside a makefile and avoids ambiguity with
2124 flag values that contain commas.
2126 <var>flag</var> must start with a lowercase letter
2127 (<tt>a-z</tt>) and consist only of lowercase letters,
2128 numbers (<tt>0-9</tt>), and the characters
2129 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2130 <var>options</var> must not contain whitespace. The same
2131 tag should not be given multiple times with conflicting
2132 values. Package maintainers may assume that
2133 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2137 The meaning of the following tags has been standardized:
2141 This tag says to not run any build-time test suite
2142 provided by the package.
2146 The presence of this tag means that the package should
2147 be compiled with a minimum of optimization. For C
2148 programs, it is best to add <tt>-O0</tt> to
2149 <tt>CFLAGS</tt> (although this is usually the default).
2150 Some programs might fail to build or run at this level
2151 of optimization; it may be necessary to use
2152 <tt>-O1</tt>, for example.
2156 This tag means that the debugging symbols should not be
2157 stripped from the binary during installation, so that
2158 debugging information may be included in the package.
2160 <tag>parallel=n</tag>
2162 This tag means that the package should be built using up
2163 to <tt>n</tt> parallel processes if the package build
2164 system supports this.<footnote>
2165 Packages built with <tt>make</tt> can often implement
2166 this by passing the <tt>-j</tt><var>n</var> option to
2169 If the package build system does not support parallel
2170 builds, this string must be ignored. If the package
2171 build system only supports a lower level of concurrency
2172 than <var>n</var>, the package should be built using as
2173 many parallel processes as the package build system
2174 supports. It is up to the package maintainer to decide
2175 whether the package build times are long enough and the
2176 package build system is robust enough to make supporting
2177 parallel builds worthwhile.
2183 Unknown flags must be ignored by <file>debian/rules</file>.
2187 The following makefile snippet is an example of how one may
2188 implement the build options; you will probably have to
2189 massage this example in order to make it work for your
2191 <example compact="compact">
2194 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2195 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2196 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2197 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2199 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2204 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2205 INSTALL_PROGRAM += -s
2207 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2208 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2209 MAKEFLAGS += -j$(NUMJOBS)
2214 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2215 # Code to run the package test suite.
2222 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2223 <sect id="substvars">
2224 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2227 When <prgn>dpkg-gencontrol</prgn>,
2228 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2229 generate control files, they perform variable substitutions
2230 on their output just before writing it. Variable
2231 substitutions have the form <tt>${<var>variable</var>}</tt>.
2232 The optional file <file>debian/substvars</file> contains
2233 variable substitutions to be used; variables can also be set
2234 directly from <file>debian/rules</file> using the <tt>-V</tt>
2235 option to the source packaging commands, and certain
2236 predefined variables are also available.
2240 The <file>debian/substvars</file> file is usually generated and
2241 modified dynamically by <file>debian/rules</file> targets, in
2242 which case it must be removed by the <tt>clean</tt> target.
2246 See <manref name="deb-substvars" section="5"> for full
2247 details about source variable substitutions, including the
2248 format of <file>debian/substvars</file>.</p>
2251 <sect id="debianwatch">
2252 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2255 This is an optional, recommended configuration file for the
2256 <tt>uscan</tt> utility which defines how to automatically scan
2257 ftp or http sites for newly available updates of the
2258 package. This is used
2259 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2260 tools to help with quality control and maintenance of the
2261 distribution as a whole.
2266 <sect id="debianfiles">
2267 <heading>Generated files list: <file>debian/files</file></heading>
2270 This file is not a permanent part of the source tree; it
2271 is used while building packages to record which files are
2272 being generated. <prgn>dpkg-genchanges</prgn> uses it
2273 when it generates a <file>.changes</file> file.
2277 It should not exist in a shipped source package, and so it
2278 (and any backup files or temporary files such as
2279 <file>files.new</file><footnote>
2280 <file>files.new</file> is used as a temporary file by
2281 <prgn>dpkg-gencontrol</prgn> and
2282 <prgn>dpkg-distaddfile</prgn> - they write a new
2283 version of <tt>files</tt> here before renaming it,
2284 to avoid leaving a corrupted copy if an error
2286 </footnote>) should be removed by the
2287 <tt>clean</tt> target. It may also be wise to
2288 ensure a fresh start by emptying or removing it at the
2289 start of the <tt>binary</tt> target.
2293 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2294 package, it adds an entry to <file>debian/files</file> for the
2295 <file>.deb</file> file that will be created when <tt>dpkg-deb
2296 --build</tt> is run for that binary package. So for most
2297 packages all that needs to be done with this file is to
2298 delete it in the <tt>clean</tt> target.
2302 If a package upload includes files besides the source
2303 package and any binary packages whose control files were
2304 made with <prgn>dpkg-gencontrol</prgn> then they should be
2305 placed in the parent of the package's top-level directory
2306 and <prgn>dpkg-distaddfile</prgn> should be called to add
2307 the file to the list in <file>debian/files</file>.</p>
2310 <sect id="embeddedfiles">
2311 <heading>Convenience copies of code</heading>
2314 Some software packages include in their distribution convenience
2315 copies of code from other software packages, generally so that
2316 users compiling from source don't have to download multiple
2317 packages. Debian packages should not make use of these
2318 convenience copies unless the included package is explicitly
2319 intended to be used in this way.<footnote>
2320 For example, parts of the GNU build system work like this.
2322 If the included code is already in the Debian archive in the
2323 form of a library, the Debian packaging should ensure that
2324 binary packages reference the libraries already in Debian and
2325 the convenience copy is not used. If the included code is not
2326 already in Debian, it should be packaged separately as a
2327 prerequisite if possible.
2329 Having multiple copies of the same code in Debian is
2330 inefficient, often creates either static linking or shared
2331 library conflicts, and, most importantly, increases the
2332 difficulty of handling security vulnerabilities in the
2338 <sect id="readmesource">
2339 <heading>Source package handling:
2340 <file>debian/README.source</file></heading>
2343 If running <prgn>dpkg-source -x</prgn> on a source package
2344 doesn't produce the source of the package, ready for editing,
2345 and allow one to make changes and run
2346 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2347 without taking any additional steps, creating a
2348 <file>debian/README.source</file> documentation file is
2349 recommended. This file should explain how to do all of the
2352 <item>Generate the fully patched source, in a form ready for
2353 editing, that would be built to create Debian
2354 packages. Doing this with a <tt>patch</tt> target in
2355 <file>debian/rules</file> is recommended; see
2356 <ref id="debianrules">.</item>
2357 <item>Modify the source and save those modifications so that
2358 they will be applied when building the package.</item>
2359 <item>Remove source modifications that are currently being
2360 applied when building the package.</item>
2361 <item>Optionally, document what steps are necessary to
2362 upgrade the Debian source package to a new upstream version,
2363 if applicable.</item>
2365 This explanation should include specific commands and mention
2366 any additional required Debian packages. It should not assume
2367 familiarity with any specific Debian packaging system or patch
2372 This explanation may refer to a documentation file installed by
2373 one of the package's build dependencies provided that the
2374 referenced documentation clearly explains these tasks and is not
2375 a general reference manual.
2379 <file>debian/README.source</file> may also include any other
2380 information that would be helpful to someone modifying the
2381 source package. Even if the package doesn't fit the above
2382 description, maintainers are encouraged to document in a
2383 <file>debian/README.source</file> file any source package with a
2384 particularly complex or unintuitive source layout or build
2385 system (for example, a package that builds the same source
2386 multiple times to generate different binary packages).
2392 <chapt id="controlfields">
2393 <heading>Control files and their fields</heading>
2396 The package management system manipulates data represented in
2397 a common format, known as <em>control data</em>, stored in
2398 <em>control files</em>.
2399 Control files are used for source packages, binary packages and
2400 the <file>.changes</file> files which control the installation
2401 of uploaded files<footnote>
2402 <prgn>dpkg</prgn>'s internal databases are in a similar
2407 <sect id="controlsyntax">
2408 <heading>Syntax of control files</heading>
2411 A control file consists of one or more paragraphs of
2413 The paragraphs are also sometimes referred to as stanzas.
2415 The paragraphs are separated by blank lines. Some control
2416 files allow only one paragraph; others allow several, in
2417 which case each paragraph usually refers to a different
2418 package. (For example, in source packages, the first
2419 paragraph refers to the source package, and later paragraphs
2420 refer to binary packages generated from the source.)
2424 Each paragraph consists of a series of data fields; each
2425 field consists of the field name, followed by a colon and
2426 then the data/value associated with that field. It ends at
2427 the end of the (logical) line. Horizontal whitespace
2428 (spaces and tabs) may occur immediately before or after the
2429 value and is ignored there; it is conventional to put a
2430 single space after the colon. For example, a field might
2432 <example compact="compact">
2435 the field name is <tt>Package</tt> and the field value
2440 A paragraph must not contain more than one instance of a
2441 particular field name.
2445 Many fields' values may span several lines; in this case
2446 each continuation line must start with a space or a tab.
2447 Any trailing spaces or tabs at the end of individual
2448 lines of a field value are ignored.
2452 In fields where it is specified that lines may not wrap,
2453 only a single line of data is allowed and whitespace is not
2454 significant in a field body. Whitespace must not appear
2455 inside names (of packages, architectures, files or anything
2456 else) or version numbers, or between the characters of
2457 multi-character version relationships.
2461 Field names are not case-sensitive, but it is usual to
2462 capitalize the field names using mixed case as shown below.
2463 Field values are case-sensitive unless the description of the
2464 field says otherwise.
2468 Blank lines, or lines consisting only of spaces and tabs,
2469 are not allowed within field values or between fields - that
2470 would mean a new paragraph.
2474 All control files must be encoded in UTF-8.
2478 <sect id="sourcecontrolfiles">
2479 <heading>Source package control files -- <file>debian/control</file></heading>
2482 The <file>debian/control</file> file contains the most vital
2483 (and version-independent) information about the source package
2484 and about the binary packages it creates.
2488 The first paragraph of the control file contains information about
2489 the source package in general. The subsequent sets each describe a
2490 binary package that the source tree builds.
2494 The fields in the general paragraph (the first one, for the source
2497 <list compact="compact">
2498 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2499 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2500 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2501 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2502 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2503 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2504 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2505 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2510 The fields in the binary package paragraphs are:
2512 <list compact="compact">
2513 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2516 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2517 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2518 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2519 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2520 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2525 The syntax and semantics of the fields are described below.
2529 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2530 generate control files for binary packages (see below), by
2531 <prgn>dpkg-genchanges</prgn> to generate the
2532 <file>.changes</file> file to accompany the upload, and by
2533 <prgn>dpkg-source</prgn> when it creates the
2534 <file>.dsc</file> source control file as part of a source
2535 archive. Many fields are permitted to span multiple lines in
2536 <file>debian/control</file> but not in any other control
2537 file. These tools are responsible for removing the line
2538 breaks from such fields when using fields from
2539 <file>debian/control</file> to generate other control files.
2543 The fields here may contain variable references - their
2544 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2545 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2546 when they generate output control files.
2547 See <ref id="substvars"> for details.
2551 In addition to the control file syntax described <qref
2552 id="controlsyntax">above</qref>, this file may also contain
2553 comment lines starting with <tt>#</tt> without any preceding
2554 whitespace. All such lines are ignored, even in the middle of
2555 continuation lines for a multiline field, and do not end a
2561 <sect id="binarycontrolfiles">
2562 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2565 The <file>DEBIAN/control</file> file contains the most vital
2566 (and version-dependent) information about a binary package. It
2567 consists of a single paragraph.
2571 The fields in this file are:
2573 <list compact="compact">
2574 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2575 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2576 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2578 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2579 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2580 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2581 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2582 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2583 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2584 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2585 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2590 <sect id="debiansourcecontrolfiles">
2591 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2594 This file consists of a single paragraph, possibly surrounded by
2595 a PGP signature. The fields of that paragraph are listed below.
2596 Their syntax is described above, in <ref id="pkg-controlfields">.
2598 <list compact="compact">
2599 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2600 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2601 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2602 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2603 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2604 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2605 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2606 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2607 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2608 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2609 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2610 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2611 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2616 The source package control file is generated by
2617 <prgn>dpkg-source</prgn> when it builds the source
2618 archive, from other files in the source package,
2619 described above. When unpacking, it is checked against
2620 the files and directories in the other parts of the
2626 <sect id="debianchangesfiles">
2627 <heading>Debian changes files -- <file>.changes</file></heading>
2630 The <file>.changes</file> files are used by the Debian archive
2631 maintenance software to process updates to packages. They
2632 consist of a single paragraph, possibly surrounded by a PGP
2633 signature. That paragraph contains information from the
2634 <file>debian/control</file> file and other data about the
2635 source package gathered via <file>debian/changelog</file>
2636 and <file>debian/rules</file>.
2640 <file>.changes</file> files have a format version that is
2641 incremented whenever the documented fields or their meaning
2642 change. This document describes format &changesversion;.
2646 The fields in this file are:
2648 <list compact="compact">
2649 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2651 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2655 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2657 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2659 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2660 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2661 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2662 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2663 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2664 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2669 <sect id="controlfieldslist">
2670 <heading>List of fields</heading>
2672 <sect1 id="f-Source">
2673 <heading><tt>Source</tt></heading>
2676 This field identifies the source package name.
2680 In <file>debian/control</file> or a <file>.dsc</file> file,
2681 this field must contain only the name of the source package.
2685 In a binary package control file or a <file>.changes</file>
2686 file, the source package name may be followed by a version
2687 number in parentheses<footnote>
2688 It is customary to leave a space after the package name
2689 if a version number is specified.
2691 This version number may be omitted (and is, by
2692 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2693 the <tt>Version</tt> field of the binary package in
2694 question. The field itself may be omitted from a binary
2695 package control file when the source package has the same
2696 name and version as the binary package.
2700 Package names (both source and binary,
2701 see <ref id="f-Package">) must consist only of lower case
2702 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2703 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2704 (<tt>.</tt>). They must be at least two characters long and
2705 must start with an alphanumeric character.
2709 <sect1 id="f-Maintainer">
2710 <heading><tt>Maintainer</tt></heading>
2713 The package maintainer's name and email address. The name
2714 must come first, then the email address inside angle
2715 brackets <tt><></tt> (in RFC822 format).
2719 If the maintainer's name contains a full stop then the
2720 whole field will not work directly as an email address due
2721 to a misfeature in the syntax specified in RFC822; a
2722 program using this field as an address must check for this
2723 and correct the problem if necessary (for example by
2724 putting the name in round brackets and moving it to the
2725 end, and bringing the email address forward).
2729 <sect1 id="f-Uploaders">
2730 <heading><tt>Uploaders</tt></heading>
2733 List of the names and email addresses of co-maintainers of
2734 the package, if any. If the package has other maintainers
2735 beside the one named in the
2736 <qref id="f-Maintainer">Maintainer field</qref>, their names
2737 and email addresses should be listed here. The format of each
2738 entry is the same as that of the Maintainer field, and
2739 multiple entries must be comma separated. This is an optional
2744 Any parser that interprets the Uploaders field in
2745 <file>debian/control</file> must permit it to span multiple
2746 lines. Line breaks in an Uploaders field that spans multiple
2747 lines are not significant and the semantics of the field are
2748 the same as if the line breaks had not been present.
2752 <sect1 id="f-Changed-By">
2753 <heading><tt>Changed-By</tt></heading>
2756 The name and email address of the person who prepared this
2757 version of the package, usually a maintainer. The syntax is
2758 the same as for the <qref id="f-Maintainer">Maintainer
2763 <sect1 id="f-Section">
2764 <heading><tt>Section</tt></heading>
2767 This field specifies an application area into which the package
2768 has been classified. See <ref id="subsections">.
2772 When it appears in the <file>debian/control</file> file,
2773 it gives the value for the subfield of the same name in
2774 the <tt>Files</tt> field of the <file>.changes</file> file.
2775 It also gives the default for the same field in the binary
2780 <sect1 id="f-Priority">
2781 <heading><tt>Priority</tt></heading>
2784 This field represents how important it is that the user
2785 have the package installed. See <ref id="priorities">.
2789 When it appears in the <file>debian/control</file> file,
2790 it gives the value for the subfield of the same name in
2791 the <tt>Files</tt> field of the <file>.changes</file> file.
2792 It also gives the default for the same field in the binary
2797 <sect1 id="f-Package">
2798 <heading><tt>Package</tt></heading>
2801 The name of the binary package.
2805 Binary package names must follow the same syntax and
2806 restrictions as source package names. See <ref id="f-Source">
2811 <sect1 id="f-Architecture">
2812 <heading><tt>Architecture</tt></heading>
2815 Depending on context and the control file used, the
2816 <tt>Architecture</tt> field can include the following sets of
2820 A unique single word identifying a Debian machine
2821 architecture as described in <ref id="arch-spec">.
2824 An architecture wildcard identifying a set of Debian
2825 machine architectures, see <ref id="arch-wildcard-spec">.
2826 <tt>any</tt> matches all Debian machine architectures
2827 and is the most frequently used.
2830 <tt>all</tt>, which indicates an
2831 architecture-independent package.
2834 <tt>source</tt>, which indicates a source package.
2840 In the main <file>debian/control</file> file in the source
2841 package, this field may contain the special
2842 value <tt>all</tt>, the special architecture
2843 wildcard <tt>any</tt>, or a list of specific and wildcard
2844 architectures separated by spaces. If <tt>all</tt>
2845 or <tt>any</tt> appears, that value must be the entire
2846 contents of the field. Most packages will use
2847 either <tt>all</tt> or <tt>any</tt>.
2851 Specifying a specific list of architectures indicates that the
2852 source will build an architecture-dependent package only on
2853 architectures included in the list. Specifying a list of
2854 architecture wildcards indicates that the source will build an
2855 architecture-dependent package on only those architectures
2856 that match any of the specified architecture wildcards.
2857 Specifying a list of architectures or architecture wildcards
2858 other than <tt>any</tt> is for the minority of cases where a
2859 program is not portable or is not useful on some
2860 architectures. Where possible, the program should be made
2865 In the source package control file <file>.dsc</file>, this
2866 field may contain either the architecture
2867 wildcard <tt>any</tt> or a list of architectures and
2868 architecture wildcards separated by spaces. If a list is
2869 given, it may include (or consist solely of) the special
2870 value <tt>all</tt>. In other words, in <file>.dsc</file>
2871 files unlike the <file>debian/control</file>, <tt>all</tt> may
2872 occur in combination with specific architectures.
2873 The <tt>Architecture</tt> field in the source package control
2874 file <file>.dsc</file> is generally constructed from
2875 the <tt>Architecture</tt> fields in
2876 the <file>debian/control</file> in the source package.
2880 Specifying <tt>any</tt> indicates that the source package
2881 isn't dependent on any particular architecture and should
2882 compile fine on any one. The produced binary package(s)
2883 will either be specific to whatever the current build
2884 architecture is or will be architecture-independent.
2888 Specifying only <tt>all</tt> indicates that the source package
2889 will only build architecture-independent packages. If this is
2890 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2891 <tt>any</tt> implies that the source package will build at
2892 least one architecture-dependent package.
2896 Specifying a list of architectures or architecture wildcards
2897 indicates that the source will build an architecture-dependent
2898 package, and will only work correctly on the listed or
2899 matching architectures. If the source package also builds at
2900 least one architecture-independent package, <tt>all</tt> will
2901 also be included in the list.
2905 In a <file>.changes</file> file, the <tt>Architecture</tt>
2906 field lists the architecture(s) of the package(s) currently
2907 being uploaded. This will be a list; if the source for the
2908 package is also being uploaded, the special
2909 entry <tt>source</tt> is also present. <tt>all</tt> will be
2910 present if any architecture-independent packages are being
2911 uploaded. Architecture wildcards such as <tt>any</tt> must
2912 never occur in the <tt>Architecture</tt> field in
2913 the <file>.changes</file> file.
2917 See <ref id="debianrules"> for information on how to get
2918 the architecture for the build process.
2922 <sect1 id="f-Essential">
2923 <heading><tt>Essential</tt></heading>
2926 This is a boolean field which may occur only in the
2927 control file of a binary package or in a per-package fields
2928 paragraph of a main source control data file.
2932 If set to <tt>yes</tt> then the package management system
2933 will refuse to remove the package (upgrading and replacing
2934 it is still possible). The other possible value is <tt>no</tt>,
2935 which is the same as not having the field at all.
2940 <heading>Package interrelationship fields:
2941 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2942 <tt>Recommends</tt>, <tt>Suggests</tt>,
2943 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2944 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2948 These fields describe the package's relationships with
2949 other packages. Their syntax and semantics are described
2950 in <ref id="relationships">.</p>
2953 <sect1 id="f-Standards-Version">
2954 <heading><tt>Standards-Version</tt></heading>
2957 The most recent version of the standards (the policy
2958 manual and associated texts) with which the package
2963 The version number has four components: major and minor
2964 version number and major and minor patch level. When the
2965 standards change in a way that requires every package to
2966 change the major number will be changed. Significant
2967 changes that will require work in many packages will be
2968 signaled by a change to the minor number. The major patch
2969 level will be changed for any change to the meaning of the
2970 standards, however small; the minor patch level will be
2971 changed when only cosmetic, typographical or other edits
2972 are made which neither change the meaning of the document
2973 nor affect the contents of packages.
2977 Thus only the first three components of the policy version
2978 are significant in the <em>Standards-Version</em> control
2979 field, and so either these three components or all four
2980 components may be specified.<footnote>
2981 In the past, people specified the full version number
2982 in the Standards-Version field, for example "2.3.0.0".
2983 Since minor patch-level changes don't introduce new
2984 policy, it was thought it would be better to relax
2985 policy and only require the first 3 components to be
2986 specified, in this example "2.3.0". All four
2987 components may still be used if someone wishes to do so.
2993 <sect1 id="f-Version">
2994 <heading><tt>Version</tt></heading>
2997 The version number of a package. The format is:
2998 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3002 The three components here are:
3004 <tag><var>epoch</var></tag>
3007 This is a single (generally small) unsigned integer. It
3008 may be omitted, in which case zero is assumed. If it is
3009 omitted then the <var>upstream_version</var> may not
3014 It is provided to allow mistakes in the version numbers
3015 of older versions of a package, and also a package's
3016 previous version numbering schemes, to be left behind.
3020 <tag><var>upstream_version</var></tag>
3023 This is the main part of the version number. It is
3024 usually the version number of the original ("upstream")
3025 package from which the <file>.deb</file> file has been made,
3026 if this is applicable. Usually this will be in the same
3027 format as that specified by the upstream author(s);
3028 however, it may need to be reformatted to fit into the
3029 package management system's format and comparison
3034 The comparison behavior of the package management system
3035 with respect to the <var>upstream_version</var> is
3036 described below. The <var>upstream_version</var>
3037 portion of the version number is mandatory.
3041 The <var>upstream_version</var> may contain only
3042 alphanumerics<footnote>
3043 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3045 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3046 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3047 tilde) and should start with a digit. If there is no
3048 <var>debian_revision</var> then hyphens are not allowed;
3049 if there is no <var>epoch</var> then colons are not
3054 <tag><var>debian_revision</var></tag>
3057 This part of the version number specifies the version of
3058 the Debian package based on the upstream version. It
3059 may contain only alphanumerics and the characters
3060 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3061 tilde) and is compared in the same way as the
3062 <var>upstream_version</var> is.
3066 It is optional; if it isn't present then the
3067 <var>upstream_version</var> may not contain a hyphen.
3068 This format represents the case where a piece of
3069 software was written specifically to be a Debian
3070 package, where the Debian package source must always
3071 be identical to the pristine source and therefore no
3072 revision indication is required.
3076 It is conventional to restart the
3077 <var>debian_revision</var> at <tt>1</tt> each time the
3078 <var>upstream_version</var> is increased.
3082 The package management system will break the version
3083 number apart at the last hyphen in the string (if there
3084 is one) to determine the <var>upstream_version</var> and
3085 <var>debian_revision</var>. The absence of a
3086 <var>debian_revision</var> is equivalent to a
3087 <var>debian_revision</var> of <tt>0</tt>.
3094 When comparing two version numbers, first the <var>epoch</var>
3095 of each are compared, then the <var>upstream_version</var> if
3096 <var>epoch</var> is equal, and then <var>debian_revision</var>
3097 if <var>upstream_version</var> is also equal.
3098 <var>epoch</var> is compared numerically. The
3099 <var>upstream_version</var> and <var>debian_revision</var>
3100 parts are compared by the package management system using the
3101 following algorithm:
3105 The strings are compared from left to right.
3109 First the initial part of each string consisting entirely of
3110 non-digit characters is determined. These two parts (one of
3111 which may be empty) are compared lexically. If a difference
3112 is found it is returned. The lexical comparison is a
3113 comparison of ASCII values modified so that all the letters
3114 sort earlier than all the non-letters and so that a tilde
3115 sorts before anything, even the end of a part. For example,
3116 the following parts are in sorted order from earliest to
3117 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3118 <tt>a</tt>.<footnote>
3119 One common use of <tt>~</tt> is for upstream pre-releases.
3120 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3121 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3126 Then the initial part of the remainder of each string which
3127 consists entirely of digit characters is determined. The
3128 numerical values of these two parts are compared, and any
3129 difference found is returned as the result of the comparison.
3130 For these purposes an empty string (which can only occur at
3131 the end of one or both version strings being compared) counts
3136 These two steps (comparing and removing initial non-digit
3137 strings and initial digit strings) are repeated until a
3138 difference is found or both strings are exhausted.
3142 Note that the purpose of epochs is to allow us to leave behind
3143 mistakes in version numbering, and to cope with situations
3144 where the version numbering scheme changes. It is
3145 <em>not</em> intended to cope with version numbers containing
3146 strings of letters which the package management system cannot
3147 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3148 silly orderings.<footnote>
3149 The author of this manual has heard of a package whose
3150 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3151 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3157 <sect1 id="f-Description">
3158 <heading><tt>Description</tt></heading>
3161 In a source or binary control file, the <tt>Description</tt>
3162 field contains a description of the binary package, consisting
3163 of two parts, the synopsis or the short description, and the
3164 long description. The field's format is as follows:
3169 Description: <single line synopsis>
3170 <extended description over several lines>
3175 The lines in the extended description can have these formats:
3181 Those starting with a single space are part of a paragraph.
3182 Successive lines of this form will be word-wrapped when
3183 displayed. The leading space will usually be stripped off.
3187 Those starting with two or more spaces. These will be
3188 displayed verbatim. If the display cannot be panned
3189 horizontally, the displaying program will line wrap them "hard"
3190 (i.e., without taking account of word breaks). If it can they
3191 will be allowed to trail off to the right. None, one or two
3192 initial spaces may be deleted, but the number of spaces
3193 deleted from each line will be the same (so that you can have
3194 indenting work correctly, for example).
3198 Those containing a single space followed by a single full stop
3199 character. These are rendered as blank lines. This is the
3200 <em>only</em> way to get a blank line<footnote>
3201 Completely empty lines will not be rendered as blank lines.
3202 Instead, they will cause the parser to think you're starting
3203 a whole new record in the control file, and will therefore
3204 likely abort with an error.
3209 Those containing a space, a full stop and some more characters.
3210 These are for future expansion. Do not use them.
3216 Do not use tab characters. Their effect is not predictable.
3220 See <ref id="descriptions"> for further information on this.
3224 In a <file>.changes</file> file, the <tt>Description</tt>
3225 field contains a summary of the descriptions for the packages
3226 being uploaded. For this case, the first line of the field
3227 value (the part on the same line as <tt>Description:</tt>) is
3228 always empty. The content of the field is expressed as
3229 continuation lines, one line per package. Each line is
3230 indented by one space and contains the name of a binary
3231 package, a space, a hyphen (<tt>-</tt>), a space, and the
3232 short description line from that package.
3236 <sect1 id="f-Distribution">
3237 <heading><tt>Distribution</tt></heading>
3240 In a <file>.changes</file> file or parsed changelog output
3241 this contains the (space-separated) name(s) of the
3242 distribution(s) where this version of the package should
3243 be installed. Valid distributions are determined by the
3244 archive maintainers.<footnote>
3245 Example distribution names in the Debian archive used in
3246 <file>.changes</file> files are:
3247 <taglist compact="compact">
3248 <tag><em>unstable</em></tag>
3250 This distribution value refers to the
3251 <em>developmental</em> part of the Debian distribution
3252 tree. Most new packages, new upstream versions of
3253 packages and bug fixes go into the <em>unstable</em>
3257 <tag><em>experimental</em></tag>
3259 The packages with this distribution value are deemed
3260 by their maintainers to be high risk. Oftentimes they
3261 represent early beta or developmental packages from
3262 various sources that the maintainers want people to
3263 try, but are not ready to be a part of the other parts
3264 of the Debian distribution tree.
3269 Others are used for updating stable releases or for
3270 security uploads. More information is available in the
3271 Debian Developer's Reference, section "The Debian
3275 The Debian archive software only supports listing a single
3276 distribution. Migration of packages to other distributions is
3277 handled outside of the upload process.
3282 <heading><tt>Date</tt></heading>
3285 This field includes the date the package was built or last
3286 edited. It must be in the same format as the <var>date</var>
3287 in a <file>debian/changelog</file> entry.
3291 The value of this field is usually extracted from the
3292 <file>debian/changelog</file> file - see
3293 <ref id="dpkgchangelog">).
3297 <sect1 id="f-Format">
3298 <heading><tt>Format</tt></heading>
3301 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3302 files, this field declares the format version of that file.
3303 The syntax of the field value is the same as that of
3304 a <qref id="f-Version">package version number</qref> except
3305 that no epoch or Debian revision is allowed. The format
3306 described in this document is <tt>&changesversion;</tt>.
3310 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3311 Debian source control</qref> files, this field declares the
3312 format of the source package. The field value is used by
3313 programs acting on a source package to interpret the list of
3314 files in the source package and determine how to unpack it.
3315 The syntax of the field value is a numeric major revision, a
3316 period, a numeric minor revision, and then an optional subtype
3317 after whitespace, which if specified is an alphanumeric word
3318 in parentheses. The subtype is optional in the syntax but may
3319 be mandatory for particular source format revisions.
3321 The source formats currently supported by the Debian archive
3322 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3323 and <tt>3.0 (quilt)</tt>.
3328 <sect1 id="f-Urgency">
3329 <heading><tt>Urgency</tt></heading>
3332 This is a description of how important it is to upgrade to
3333 this version from previous ones. It consists of a single
3334 keyword taking one of the values <tt>low</tt>,
3335 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3336 <tt>critical</tt><footnote>
3337 Other urgency values are supported with configuration
3338 changes in the archive software but are not used in Debian.
3339 The urgency affects how quickly a package will be considered
3340 for inclusion into the <tt>testing</tt> distribution and
3341 gives an indication of the importance of any fixes included
3342 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3343 treated as synonymous.
3344 </footnote> (not case-sensitive) followed by an optional
3345 commentary (separated by a space) which is usually in
3346 parentheses. For example:
3349 Urgency: low (HIGH for users of diversions)
3355 The value of this field is usually extracted from the
3356 <file>debian/changelog</file> file - see
3357 <ref id="dpkgchangelog">.
3361 <sect1 id="f-Changes">
3362 <heading><tt>Changes</tt></heading>
3365 This field contains the human-readable changes data, describing
3366 the differences between the last version and the current one.
3370 The first line of the field value (the part on the same line
3371 as <tt>Changes:</tt>) is always empty. The content of the
3372 field is expressed as continuation lines, with each line
3373 indented by at least one space. Blank lines must be
3374 represented by a line consisting only of a space and a full
3379 The value of this field is usually extracted from the
3380 <file>debian/changelog</file> file - see
3381 <ref id="dpkgchangelog">).
3385 Each version's change information should be preceded by a
3386 "title" line giving at least the version, distribution(s)
3387 and urgency, in a human-readable way.
3391 If data from several versions is being returned the entry
3392 for the most recent version should be returned first, and
3393 entries should be separated by the representation of a
3394 blank line (the "title" line may also be followed by the
3395 representation of a blank line).
3399 <sect1 id="f-Binary">
3400 <heading><tt>Binary</tt></heading>
3403 This field is a list of binary packages. Its syntax and
3404 meaning varies depending on the control file in which it
3409 When it appears in the <file>.dsc</file> file, it lists binary
3410 packages which a source package can produce, separated by
3412 A space after each comma is conventional.
3413 </footnote>. It may span multiple lines. The source package
3414 does not necessarily produce all of these binary packages for
3415 every architecture. The source control file doesn't contain
3416 details of which architectures are appropriate for which of
3417 the binary packages.
3421 When it appears in a <file>.changes</file> file, it lists the
3422 names of the binary packages being uploaded, separated by
3423 whitespace (not commas). It may span multiple lines.
3427 <sect1 id="f-Installed-Size">
3428 <heading><tt>Installed-Size</tt></heading>
3431 This field appears in the control files of binary packages,
3432 and in the <file>Packages</file> files. It gives an estimate
3433 of the total amount of disk space required to install the
3434 named package. Actual installed size may vary based on block
3435 size, file system properties, or actions taken by package
3440 The disk space is given as the integer value of the estimated
3441 installed size in bytes, divided by 1024 and rounded up.
3445 <sect1 id="f-Files">
3446 <heading><tt>Files</tt></heading>
3449 This field contains a list of files with information about
3450 each one. The exact information and syntax varies with
3455 In all cases, Files is a multiline field. The first line of
3456 the field value (the part on the same line as <tt>Files:</tt>)
3457 is always empty. The content of the field is expressed as
3458 continuation lines, one line per file. Each line must be
3459 indented by one space and contain a number of sub-fields,
3460 separated by spaces, as described below.
3464 In the <file>.dsc</file> file, each line contains the MD5
3465 checksum, size and filename of the tar file and (if
3466 applicable) diff file which make up the remainder of the
3467 source package<footnote>
3468 That is, the parts which are not the <tt>.dsc</tt>.
3469 </footnote>. For example:
3472 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3473 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3475 The exact forms of the filenames are described
3476 in <ref id="pkg-sourcearchives">.
3480 In the <file>.changes</file> file this contains one line per
3481 file being uploaded. Each line contains the MD5 checksum,
3482 size, section and priority and the filename. For example:
3485 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3486 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3487 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3488 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3490 The <qref id="f-Section">section</qref>
3491 and <qref id="f-Priority">priority</qref> are the values of
3492 the corresponding fields in the main source control file. If
3493 no section or priority is specified then <tt>-</tt> should be
3494 used, though section and priority values must be specified for
3495 new packages to be installed properly.
3499 The special value <tt>byhand</tt> for the section in a
3500 <tt>.changes</tt> file indicates that the file in question
3501 is not an ordinary package file and must by installed by
3502 hand by the distribution maintainers. If the section is
3503 <tt>byhand</tt> the priority should be <tt>-</tt>.
3507 If a new Debian revision of a package is being shipped and
3508 no new original source archive is being distributed the
3509 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3510 entry for the original source archive
3511 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3512 but the <file>.changes</file> file should leave it out. In
3513 this case the original source archive on the distribution
3514 site must match exactly, byte-for-byte, the original
3515 source archive which was used to generate the
3516 <file>.dsc</file> file and diff which are being uploaded.</p>
3519 <sect1 id="f-Closes">
3520 <heading><tt>Closes</tt></heading>
3523 A space-separated list of bug report numbers that the upload
3524 governed by the .changes file closes.
3528 <sect1 id="f-Homepage">
3529 <heading><tt>Homepage</tt></heading>
3532 The URL of the web site for this package, preferably (when
3533 applicable) the site from which the original source can be
3534 obtained and any additional upstream documentation or
3535 information may be found. The content of this field is a
3536 simple URL without any surrounding characters such as
3541 <sect1 id="f-Checksums">
3542 <heading><tt>Checksums-Sha1</tt>
3543 and <tt>Checksums-Sha256</tt></heading>
3546 These fields contain a list of files with a checksum and size
3547 for each one. Both <tt>Checksums-Sha1</tt>
3548 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3549 only in the checksum algorithm used: SHA-1
3550 for <tt>Checksums-Sha1</tt> and SHA-256
3551 for <tt>Checksums-Sha256</tt>.
3555 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3556 multiline fields. The first line of the field value (the part
3557 on the same line as <tt>Checksums-Sha1:</tt>
3558 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3559 of the field is expressed as continuation lines, one line per
3560 file. Each line consists of the checksum, a space, the file
3561 size, a space, and the file name. For example (from
3562 a <file>.changes</file> file):
3565 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3566 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3567 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3568 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3570 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3571 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3572 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3573 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3578 In the <file>.dsc</file> file, these fields should list all
3579 files that make up the source package. In
3580 the <file>.changes</file> file, these fields should list all
3581 files being uploaded. The list of files in these fields
3582 must match the list of files in the <tt>Files</tt> field.
3588 <heading>User-defined fields</heading>
3591 Additional user-defined fields may be added to the
3592 source package control file. Such fields will be
3593 ignored, and not copied to (for example) binary or
3594 source package control files or upload control files.
3598 If you wish to add additional unsupported fields to
3599 these output files you should use the mechanism
3604 Fields in the main source control information file with
3605 names starting <tt>X</tt>, followed by one or more of
3606 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3607 be copied to the output files. Only the part of the
3608 field name after the hyphen will be used in the output
3609 file. Where the letter <tt>B</tt> is used the field
3610 will appear in binary package control files, where the
3611 letter <tt>S</tt> is used in source package control
3612 files and where <tt>C</tt> is used in upload control
3613 (<tt>.changes</tt>) files.
3617 For example, if the main source information control file
3620 XBS-Comment: I stand between the candle and the star.
3622 then the binary and source package control files will contain the
3625 Comment: I stand between the candle and the star.
3634 <chapt id="maintainerscripts">
3635 <heading>Package maintainer scripts and installation procedure</heading>
3638 <heading>Introduction to package maintainer scripts</heading>
3641 It is possible to supply scripts as part of a package which
3642 the package management system will run for you when your
3643 package is installed, upgraded or removed.
3647 These scripts are the control information
3648 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3649 and <prgn>postrm</prgn>. They must be proper executable files;
3650 if they are scripts (which is recommended), they must start with
3651 the usual <tt>#!</tt> convention. They should be readable and
3652 executable by anyone, and must not be world-writable.
3656 The package management system looks at the exit status from
3657 these scripts. It is important that they exit with a
3658 non-zero status if there is an error, so that the package
3659 management system can stop its processing. For shell
3660 scripts this means that you <em>almost always</em> need to
3661 use <tt>set -e</tt> (this is usually true when writing shell
3662 scripts, in fact). It is also important, of course, that
3663 they exit with a zero status if everything went well.
3667 Additionally, packages interacting with users
3668 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3669 should install a <prgn>config</prgn> script as a control
3670 information file. See <ref id="maintscriptprompt"> for details.
3674 When a package is upgraded a combination of the scripts from
3675 the old and new packages is called during the upgrade
3676 procedure. If your scripts are going to be at all
3677 complicated you need to be aware of this, and may need to
3678 check the arguments to your scripts.
3682 Broadly speaking the <prgn>preinst</prgn> is called before
3683 (a particular version of) a package is installed, and the
3684 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3685 before (a version of) a package is removed and the
3686 <prgn>postrm</prgn> afterwards.
3690 Programs called from maintainer scripts should not normally
3691 have a path prepended to them. Before installation is
3692 started, the package management system checks to see if the
3693 programs <prgn>ldconfig</prgn>,
3694 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3695 and <prgn>update-rc.d</prgn> can be found via the
3696 <tt>PATH</tt> environment variable. Those programs, and any
3697 other program that one would expect to be in the
3698 <tt>PATH</tt>, should thus be invoked without an absolute
3699 pathname. Maintainer scripts should also not reset the
3700 <tt>PATH</tt>, though they might choose to modify it by
3701 prepending or appending package-specific directories. These
3702 considerations really apply to all shell scripts.</p>
3705 <sect id="idempotency">
3706 <heading>Maintainer scripts idempotency</heading>
3709 It is necessary for the error recovery procedures that the
3710 scripts be idempotent. This means that if it is run
3711 successfully, and then it is called again, it doesn't bomb
3712 out or cause any harm, but just ensures that everything is
3713 the way it ought to be. If the first call failed, or
3714 aborted half way through for some reason, the second call
3715 should merely do the things that were left undone the first
3716 time, if any, and exit with a success status if everything
3718 This is so that if an error occurs, the user interrupts
3719 <prgn>dpkg</prgn> or some other unforeseen circumstance
3720 happens you don't leave the user with a badly-broken
3721 package when <prgn>dpkg</prgn> attempts to repeat the
3727 <sect id="controllingterminal">
3728 <heading>Controlling terminal for maintainer scripts</heading>
3731 Maintainer scripts are not guaranteed to run with a controlling
3732 terminal and may not be able to interact with the user. They
3733 must be able to fall back to noninteractive behavior if no
3734 controlling terminal is available. Maintainer scripts that
3735 prompt via a program conforming to the Debian Configuration
3736 Management Specification (see <ref id="maintscriptprompt">) may
3737 assume that program will handle falling back to noninteractive
3742 For high-priority prompts without a reasonable default answer,
3743 maintainer scripts may abort if there is no controlling
3744 terminal. However, this situation should be avoided if at all
3745 possible, since it prevents automated or unattended installs.
3746 In most cases, users will consider this to be a bug in the
3751 <sect id="exitstatus">
3752 <heading>Exit status</heading>
3755 Each script must return a zero exit status for
3756 success, or a nonzero one for failure, since the package
3757 management system looks for the exit status of these scripts
3758 and determines what action to take next based on that datum.
3762 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3767 <list compact="compact">
3769 <var>new-preinst</var> <tt>install</tt>
3772 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3775 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3778 <var>old-preinst</var> <tt>abort-upgrade</tt>
3779 <var>new-version</var>
3784 <list compact="compact">
3786 <var>postinst</var> <tt>configure</tt>
3787 <var>most-recently-configured-version</var>
3790 <var>old-postinst</var> <tt>abort-upgrade</tt>
3791 <var>new-version</var>
3794 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3795 <tt>in-favour</tt> <var>package</var>
3796 <var>new-version</var>
3799 <var>postinst</var> <tt>abort-remove</tt>
3802 <var>deconfigured's-postinst</var>
3803 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3804 <var>failed-install-package</var> <var>version</var>
3805 [<tt>removing</tt> <var>conflicting-package</var>
3811 <list compact="compact">
3813 <var>prerm</var> <tt>remove</tt>
3816 <var>old-prerm</var> <tt>upgrade</tt>
3817 <var>new-version</var>
3820 <var>new-prerm</var> <tt>failed-upgrade</tt>
3821 <var>old-version</var>
3824 <var>conflictor's-prerm</var> <tt>remove</tt>
3825 <tt>in-favour</tt> <var>package</var>
3826 <var>new-version</var>
3829 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3830 <tt>in-favour</tt> <var>package-being-installed</var>
3831 <var>version</var> [<tt>removing</tt>
3832 <var>conflicting-package</var>
3838 <list compact="compact">
3840 <var>postrm</var> <tt>remove</tt>
3843 <var>postrm</var> <tt>purge</tt>
3846 <var>old-postrm</var> <tt>upgrade</tt>
3847 <var>new-version</var>
3850 <var>new-postrm</var> <tt>failed-upgrade</tt>
3851 <var>old-version</var>
3854 <var>new-postrm</var> <tt>abort-install</tt>
3857 <var>new-postrm</var> <tt>abort-install</tt>
3858 <var>old-version</var>
3861 <var>new-postrm</var> <tt>abort-upgrade</tt>
3862 <var>old-version</var>
3865 <var>disappearer's-postrm</var> <tt>disappear</tt>
3866 <var>overwriter</var>
3867 <var>overwriter-version</var>
3873 <sect id="unpackphase">
3874 <heading>Details of unpack phase of installation or upgrade</heading>
3877 The procedure on installation/upgrade/overwrite/disappear
3878 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3879 stage of <tt>dpkg --install</tt>) is as follows. In each
3880 case, if a major error occurs (unless listed below) the
3881 actions are, in general, run backwards - this means that the
3882 maintainer scripts are run with different arguments in
3883 reverse order. These are the "error unwind" calls listed
3890 If a version of the package is already installed, call
3891 <example compact="compact">
3892 <var>old-prerm</var> upgrade <var>new-version</var>
3896 If the script runs but exits with a non-zero
3897 exit status, <prgn>dpkg</prgn> will attempt:
3898 <example compact="compact">
3899 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3901 If this works, the upgrade continues. If this
3902 does not work, the error unwind:
3903 <example compact="compact">
3904 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3906 If this works, then the old-version is
3907 "Installed", if not, the old version is in a
3908 "Half-Configured" state.
3914 If a "conflicting" package is being removed at the same time,
3915 or if any package will be broken (due to <tt>Breaks</tt>):
3918 If <tt>--auto-deconfigure</tt> is
3919 specified, call, for each package to be deconfigured
3920 due to <tt>Breaks</tt>:
3921 <example compact="compact">
3922 <var>deconfigured's-prerm</var> deconfigure \
3923 in-favour <var>package-being-installed</var> <var>version</var>
3926 <example compact="compact">
3927 <var>deconfigured's-postinst</var> abort-deconfigure \
3928 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3930 The deconfigured packages are marked as
3931 requiring configuration, so that if
3932 <tt>--install</tt> is used they will be
3933 configured again if possible.
3936 If any packages depended on a conflicting
3937 package being removed and <tt>--auto-deconfigure</tt> is
3938 specified, call, for each such package:
3939 <example compact="compact">
3940 <var>deconfigured's-prerm</var> deconfigure \
3941 in-favour <var>package-being-installed</var> <var>version</var> \
3942 removing <var>conflicting-package</var> <var>version</var>
3945 <example compact="compact">
3946 <var>deconfigured's-postinst</var> abort-deconfigure \
3947 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3948 removing <var>conflicting-package</var> <var>version</var>
3950 The deconfigured packages are marked as
3951 requiring configuration, so that if
3952 <tt>--install</tt> is used they will be
3953 configured again if possible.
3956 To prepare for removal of each conflicting package, call:
3957 <example compact="compact">
3958 <var>conflictor's-prerm</var> remove \
3959 in-favour <var>package</var> <var>new-version</var>
3962 <example compact="compact">
3963 <var>conflictor's-postinst</var> abort-remove \
3964 in-favour <var>package</var> <var>new-version</var>
3973 If the package is being upgraded, call:
3974 <example compact="compact">
3975 <var>new-preinst</var> upgrade <var>old-version</var>
3977 If this fails, we call:
3979 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3986 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3988 is called. If this works, then the old version
3989 is in an "Installed" state, or else it is left
3990 in an "Unpacked" state.
3995 If it fails, then the old version is left
3996 in an "Half-Installed" state.
4003 Otherwise, if the package had some configuration
4004 files from a previous version installed (i.e., it
4005 is in the "configuration files only" state):
4006 <example compact="compact">
4007 <var>new-preinst</var> install <var>old-version</var>
4011 <var>new-postrm</var> abort-install <var>old-version</var>
4013 If this fails, the package is left in a
4014 "Half-Installed" state, which requires a
4015 reinstall. If it works, the packages is left in
4016 a "Config-Files" state.
4019 Otherwise (i.e., the package was completely purged):
4020 <example compact="compact">
4021 <var>new-preinst</var> install
4024 <example compact="compact">
4025 <var>new-postrm</var> abort-install
4027 If the error-unwind fails, the package is in a
4028 "Half-Installed" phase, and requires a
4029 reinstall. If the error unwind works, the
4030 package is in a not installed state.
4037 The new package's files are unpacked, overwriting any
4038 that may be on the system already, for example any
4039 from the old version of the same package or from
4040 another package. Backups of the old files are kept
4041 temporarily, and if anything goes wrong the package
4042 management system will attempt to put them back as
4043 part of the error unwind.
4047 It is an error for a package to contain files which
4048 are on the system in another package, unless
4049 <tt>Replaces</tt> is used (see <ref id="replaces">).
4051 The following paragraph is not currently the case:
4052 Currently the <tt>- - force-overwrite</tt> flag is
4053 enabled, downgrading it to a warning, but this may not
4059 It is a more serious error for a package to contain a
4060 plain file or other kind of non-directory where another
4061 package has a directory (again, unless
4062 <tt>Replaces</tt> is used). This error can be
4063 overridden if desired using
4064 <tt>--force-overwrite-dir</tt>, but this is not
4069 Packages which overwrite each other's files produce
4070 behavior which, though deterministic, is hard for the
4071 system administrator to understand. It can easily
4072 lead to "missing" programs if, for example, a package
4073 is installed which overwrites a file from another
4074 package, and is then removed again.<footnote>
4075 Part of the problem is due to what is arguably a
4076 bug in <prgn>dpkg</prgn>.
4081 A directory will never be replaced by a symbolic link
4082 to a directory or vice versa; instead, the existing
4083 state (symlink or not) will be left alone and
4084 <prgn>dpkg</prgn> will follow the symlink if there is
4093 If the package is being upgraded, call
4094 <example compact="compact">
4095 <var>old-postrm</var> upgrade <var>new-version</var>
4099 If this fails, <prgn>dpkg</prgn> will attempt:
4100 <example compact="compact">
4101 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4103 If this works, installation continues. If not,
4105 <example compact="compact">
4106 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4108 If this fails, the old version is left in a
4109 "Half-Installed" state. If it works, dpkg now
4111 <example compact="compact">
4112 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4114 If this fails, the old version is left in a
4115 "Half-Installed" state. If it works, dpkg now
4117 <example compact="compact">
4118 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4120 If this fails, the old version is in an
4127 This is the point of no return - if
4128 <prgn>dpkg</prgn> gets this far, it won't back off
4129 past this point if an error occurs. This will
4130 leave the package in a fairly bad state, which
4131 will require a successful re-installation to clear
4132 up, but it's when <prgn>dpkg</prgn> starts doing
4133 things that are irreversible.
4138 Any files which were in the old version of the package
4139 but not in the new are removed.
4143 The new file list replaces the old.
4147 The new maintainer scripts replace the old.
4151 Any packages all of whose files have been overwritten
4152 during the installation, and which aren't required for
4153 dependencies, are considered to have been removed.
4154 For each such package
4157 <prgn>dpkg</prgn> calls:
4158 <example compact="compact">
4159 <var>disappearer's-postrm</var> disappear \
4160 <var>overwriter</var> <var>overwriter-version</var>
4164 The package's maintainer scripts are removed.
4167 It is noted in the status database as being in a
4168 sane state, namely not installed (any conffiles
4169 it may have are ignored, rather than being
4170 removed by <prgn>dpkg</prgn>). Note that
4171 disappearing packages do not have their prerm
4172 called, because <prgn>dpkg</prgn> doesn't know
4173 in advance that the package is going to
4180 Any files in the package we're unpacking that are also
4181 listed in the file lists of other packages are removed
4182 from those lists. (This will lobotomize the file list
4183 of the "conflicting" package if there is one.)
4187 The backup files made during installation, above, are
4193 The new package's status is now sane, and recorded as
4198 Here is another point of no return - if the
4199 conflicting package's removal fails we do not unwind
4200 the rest of the installation; the conflicting package
4201 is left in a half-removed limbo.
4206 If there was a conflicting package we go and do the
4207 removal actions (described below), starting with the
4208 removal of the conflicting package's files (any that
4209 are also in the package being installed have already
4210 been removed from the conflicting package's file list,
4211 and so do not get removed now).
4217 <sect id="configdetails"><heading>Details of configuration</heading>
4220 When we configure a package (this happens with <tt>dpkg
4221 --install</tt> and <tt>dpkg --configure</tt>), we first
4222 update any <tt>conffile</tt>s and then call:
4223 <example compact="compact">
4224 <var>postinst</var> configure <var>most-recently-configured-version</var>
4229 No attempt is made to unwind after errors during
4230 configuration. If the configuration fails, the package is in
4231 a "Failed Config" state, and an error message is generated.
4235 If there is no most recently configured version
4236 <prgn>dpkg</prgn> will pass a null argument.
4239 Historical note: Truly ancient (pre-1997) versions of
4240 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4241 (including the angle brackets) in this case. Even older
4242 ones did not pass a second argument at all, under any
4243 circumstance. Note that upgrades using such an old dpkg
4244 version are unlikely to work for other reasons, even if
4245 this old argument behavior is handled by your postinst script.
4251 <sect id="removedetails"><heading>Details of removal and/or
4252 configuration purging</heading>
4258 <example compact="compact">
4259 <var>prerm</var> remove
4263 If prerm fails during replacement due to conflict
4265 <var>conflictor's-postinst</var> abort-remove \
4266 in-favour <var>package</var> <var>new-version</var>
4270 <var>postinst</var> abort-remove
4274 If this fails, the package is in a "Half-Configured"
4275 state, or else it remains "Installed".
4279 The package's files are removed (except <tt>conffile</tt>s).
4282 <example compact="compact">
4283 <var>postrm</var> remove
4287 If it fails, there's no error unwind, and the package is in
4288 an "Half-Installed" state.
4293 All the maintainer scripts except the <prgn>postrm</prgn>
4298 If we aren't purging the package we stop here. Note
4299 that packages which have no <prgn>postrm</prgn> and no
4300 <tt>conffile</tt>s are automatically purged when
4301 removed, as there is no difference except for the
4302 <prgn>dpkg</prgn> status.
4306 The <tt>conffile</tt>s and any backup files
4307 (<tt>~</tt>-files, <tt>#*#</tt> files,
4308 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4313 <example compact="compact">
4314 <var>postrm</var> purge
4318 If this fails, the package remains in a "Config-Files"
4323 The package's file list is removed.
4332 <chapt id="relationships">
4333 <heading>Declaring relationships between packages</heading>
4335 <sect id="depsyntax">
4336 <heading>Syntax of relationship fields</heading>
4339 These fields all have a uniform syntax. They are a list of
4340 package names separated by commas.
4344 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4345 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4346 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4347 control fields of the package, which declare
4348 dependencies on other packages, the package names listed may
4349 also include lists of alternative package names, separated
4350 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4351 if any one of the alternative packages is installed, that
4352 part of the dependency is considered to be satisfied.
4356 All of the fields except for <tt>Provides</tt> may restrict
4357 their applicability to particular versions of each named
4358 package. This is done in parentheses after each individual
4359 package name; the parentheses should contain a relation from
4360 the list below followed by a version number, in the format
4361 described in <ref id="f-Version">.
4365 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4366 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4367 strictly earlier, earlier or equal, exactly equal, later or
4368 equal and strictly later, respectively. The deprecated
4369 forms <tt><</tt> and <tt>></tt> were used to mean
4370 earlier/later or equal, rather than strictly earlier/later,
4371 so they should not appear in new packages (though
4372 <prgn>dpkg</prgn> still supports them).
4376 Whitespace may appear at any point in the version
4377 specification subject to the rules in <ref
4378 id="controlsyntax">, and must appear where it's necessary to
4379 disambiguate; it is not otherwise significant. All of the
4380 relationship fields may span multiple lines. For
4381 consistency and in case of future changes to
4382 <prgn>dpkg</prgn> it is recommended that a single space be
4383 used after a version relationship and before a version
4384 number; it is also conventional to put a single space after
4385 each comma, on either side of each vertical bar, and before
4386 each open parenthesis. When wrapping a relationship field, it
4387 is conventional to do so after a comma and before the space
4388 following that comma.
4392 For example, a list of dependencies might appear as:
4393 <example compact="compact">
4396 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4401 Relationships may be restricted to a certain set of
4402 architectures. This is indicated in brackets after each
4403 individual package name and the optional version specification.
4404 The brackets enclose a list of Debian architecture names
4405 separated by whitespace. Exclamation marks may be prepended to
4406 each of the names. (It is not permitted for some names to be
4407 prepended with exclamation marks while others aren't.)
4411 For build relationship fields
4412 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4413 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4414 the current Debian host architecture is not in this list and
4415 there are no exclamation marks in the list, or it is in the list
4416 with a prepended exclamation mark, the package name and the
4417 associated version specification are ignored completely for the
4418 purposes of defining the relationships.
4423 <example compact="compact">
4425 Build-Depends-Indep: texinfo
4426 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4427 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4429 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4430 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4431 <tt>gnumach-dev</tt> only on hurd-i386.
4435 For binary relationship fields, the architecture restriction
4436 syntax is only supported in the source package control
4437 file <file>debian/control</file>. When the corresponding binary
4438 package control file is generated, the relationship will either
4439 be omitted or included without the architecture restriction
4440 based on the architecture of the binary package. This means
4441 that architecture restrictions must not be used in binary
4442 relationship fields for architecture-independent packages
4443 (<tt>Architecture: all</tt>).
4448 <example compact="compact">
4449 Depends: foo [i386], bar [amd64]
4451 becomes <tt>Depends: foo</tt> when the package is built on
4452 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4453 package is built on the <tt>amd64</tt> architecture, and omitted
4454 entirely in binary packages built on all other architectures.
4458 If the architecture-restricted dependency is part of a set of
4459 alternatives using <tt>|</tt>, that alternative is ignored
4460 completely on architectures that do not match the restriction.
4462 <example compact="compact">
4463 Build-Depends: foo [!i386] | bar [!amd64]
4465 is equivalent to <tt>bar</tt> on the i386 architecture, to
4466 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4467 bar</tt> on all other architectures.
4471 Relationships may also be restricted to a certain set of
4472 architectures using architecture wildcards. The syntax for
4473 declaring such restrictions is the same as declaring
4474 restrictions using a certain set of architectures without
4475 architecture wildcards. For example:
4476 <example compact="compact">
4477 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4479 is equivalent to <tt>foo</tt> on architectures using the Linux
4480 kernel and any cpu, <tt>bar</tt> on architectures using any
4481 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4482 using a kernel other than Linux.
4486 Note that the binary package relationship fields such as
4487 <tt>Depends</tt> appear in one of the binary package
4488 sections of the control file, whereas the build-time
4489 relationships such as <tt>Build-Depends</tt> appear in the
4490 source package section of the control file (which is the
4495 <sect id="binarydeps">
4496 <heading>Binary Dependencies - <tt>Depends</tt>,
4497 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4498 <tt>Pre-Depends</tt>
4502 Packages can declare in their control file that they have
4503 certain relationships to other packages - for example, that
4504 they may not be installed at the same time as certain other
4505 packages, and/or that they depend on the presence of others.
4509 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4510 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4511 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4512 <tt>Breaks</tt> is described in <ref id="breaks">, and
4513 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4514 rest are described below.
4518 These seven fields are used to declare a dependency
4519 relationship by one package on another. Except for
4520 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4521 depending (binary) package's control file.
4522 (<tt>Enhances</tt> appears in the recommending package's
4523 control file, and <tt>Breaks</tt> appears in the version of
4524 depended-on package which causes the named package to
4529 A <tt>Depends</tt> field takes effect <em>only</em> when a
4530 package is to be configured. It does not prevent a package
4531 being on the system in an unconfigured state while its
4532 dependencies are unsatisfied, and it is possible to replace
4533 a package whose dependencies are satisfied and which is
4534 properly installed with a different version whose
4535 dependencies are not and cannot be satisfied; when this is
4536 done the depending package will be left unconfigured (since
4537 attempts to configure it will give errors) and will not
4538 function properly. If it is necessary, a
4539 <tt>Pre-Depends</tt> field can be used, which has a partial
4540 effect even when a package is being unpacked, as explained
4541 in detail below. (The other three dependency fields,
4542 <tt>Recommends</tt>, <tt>Suggests</tt> and
4543 <tt>Enhances</tt>, are only used by the various front-ends
4544 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4545 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4549 For this reason packages in an installation run are usually
4550 all unpacked first and all configured later; this gives
4551 later versions of packages with dependencies on later
4552 versions of other packages the opportunity to have their
4553 dependencies satisfied.
4557 In case of circular dependencies, since installation or
4558 removal order honoring the dependency order can't be
4559 established, dependency loops are broken at some point
4560 (based on rules below), and some packages may not be able to
4561 rely on their dependencies being present when being
4562 installed or removed, depending on which side of the break
4563 of the circular dependency loop they happen to be on. If one
4564 of the packages in the loop has no postinst script, then the
4565 cycle will be broken at that package, so as to ensure that
4566 all postinst scripts run with the dependencies properly
4567 configured if this is possible. Otherwise the breaking point
4572 The <tt>Depends</tt> field thus allows package maintainers
4573 to impose an order in which packages should be configured.
4577 The meaning of the five dependency fields is as follows:
4579 <tag><tt>Depends</tt></tag>
4582 This declares an absolute dependency. A package will
4583 not be configured unless all of the packages listed in
4584 its <tt>Depends</tt> field have been correctly
4589 The <tt>Depends</tt> field should be used if the
4590 depended-on package is required for the depending
4591 package to provide a significant amount of
4596 The <tt>Depends</tt> field should also be used if the
4597 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4598 <prgn>postrm</prgn> scripts require the package to be
4599 present in order to run. Note, however, that the
4600 <prgn>postrm</prgn> cannot rely on any non-essential
4601 packages to be present during the <tt>purge</tt>
4605 <tag><tt>Recommends</tt></tag>
4608 This declares a strong, but not absolute, dependency.
4612 The <tt>Recommends</tt> field should list packages
4613 that would be found together with this one in all but
4614 unusual installations.
4618 <tag><tt>Suggests</tt></tag>
4620 This is used to declare that one package may be more
4621 useful with one or more others. Using this field
4622 tells the packaging system and the user that the
4623 listed packages are related to this one and can
4624 perhaps enhance its usefulness, but that installing
4625 this one without them is perfectly reasonable.
4628 <tag><tt>Enhances</tt></tag>
4630 This field is similar to Suggests but works in the
4631 opposite direction. It is used to declare that a
4632 package can enhance the functionality of another
4636 <tag><tt>Pre-Depends</tt></tag>
4639 This field is like <tt>Depends</tt>, except that it
4640 also forces <prgn>dpkg</prgn> to complete installation
4641 of the packages named before even starting the
4642 installation of the package which declares the
4643 pre-dependency, as follows:
4647 When a package declaring a pre-dependency is about to
4648 be <em>unpacked</em> the pre-dependency can be
4649 satisfied if the depended-on package is either fully
4650 configured, <em>or even if</em> the depended-on
4651 package(s) are only unpacked or in the "Half-Configured"
4652 state, provided that they have been configured
4653 correctly at some point in the past (and not removed
4654 or partially removed since). In this case, both the
4655 previously-configured and currently unpacked or
4656 "Half-Configured" versions must satisfy any version
4657 clause in the <tt>Pre-Depends</tt> field.
4661 When the package declaring a pre-dependency is about
4662 to be <em>configured</em>, the pre-dependency will be
4663 treated as a normal <tt>Depends</tt>, that is, it will
4664 be considered satisfied only if the depended-on
4665 package has been correctly configured.
4669 <tt>Pre-Depends</tt> should be used sparingly,
4670 preferably only by packages whose premature upgrade or
4671 installation would hamper the ability of the system to
4672 continue with any upgrade that might be in progress.
4676 <tt>Pre-Depends</tt> are also required if the
4677 <prgn>preinst</prgn> script depends on the named
4678 package. It is best to avoid this situation if
4686 When selecting which level of dependency to use you should
4687 consider how important the depended-on package is to the
4688 functionality of the one declaring the dependency. Some
4689 packages are composed of components of varying degrees of
4690 importance. Such a package should list using
4691 <tt>Depends</tt> the package(s) which are required by the
4692 more important components. The other components'
4693 requirements may be mentioned as Suggestions or
4694 Recommendations, as appropriate to the components' relative
4700 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4703 When one binary package declares that it breaks another,
4704 <prgn>dpkg</prgn> will refuse to allow the package which
4705 declares <tt>Breaks</tt> be installed unless the broken
4706 package is deconfigured first, and it will refuse to
4707 allow the broken package to be reconfigured.
4711 A package will not be regarded as causing breakage merely
4712 because its configuration files are still installed; it must
4713 be at least "Half-Installed".
4717 A special exception is made for packages which declare that
4718 they break their own package name or a virtual package which
4719 they provide (see below): this does not count as a real
4724 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4725 version clause; such a <tt>Breaks</tt> is introduced in the
4726 version of an (implicit or explicit) dependency which violates
4727 an assumption or reveals a bug in earlier versions of the broken
4728 package, or which takes over a file from earlier versions of the
4729 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4730 will inform higher-level package management tools that the
4731 broken package must be upgraded before the new one.
4735 If the breaking package also overwrites some files from the
4736 older package, it should use <tt>Replaces</tt> to ensure this
4737 goes smoothly. See <ref id="replaces"> for a full discussion
4738 of taking over files from other packages, including how to
4739 use <tt>Breaks</tt> in those cases.
4743 Many of the cases where <tt>Breaks</tt> should be used were
4744 previously handled with <tt>Conflicts</tt>
4745 because <tt>Breaks</tt> did not yet exist.
4746 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4747 See <ref id="conflicts"> for more information about the
4752 <sect id="conflicts">
4753 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4756 When one binary package declares a conflict with another
4757 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4758 refuse to allow them to be installed on the system at the
4759 same time. This is a stronger restriction than <tt>Breaks</tt>,
4760 which just prevents both packages from being configured at the
4761 same time. Conflicting packages cannot be unpacked on the
4762 system at the same time.
4766 If one package is to be installed, the other must be removed
4767 first. If the package being installed is marked as replacing
4768 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4769 normally be used in this case) the one on the system, or the one
4770 on the system is marked as deselected, or both packages are
4771 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4772 automatically remove the package which is causing the conflict.
4773 Otherwise, it will halt the installation of the new package with
4774 an error. This mechanism is specifically designed to produce an
4775 error when the installed package is <tt>Essential</tt>, but the
4780 A package will not cause a conflict merely because its
4781 configuration files are still installed; it must be at least
4786 A special exception is made for packages which declare a
4787 conflict with their own package name, or with a virtual
4788 package which they provide (see below): this does not
4789 prevent their installation, and allows a package to conflict
4790 with others providing a replacement for it. You use this
4791 feature when you want the package in question to be the only
4792 package providing some feature.
4796 Normally, <tt>Breaks</tt> should be used instead
4797 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4798 stronger restriction on the ordering of package installation or
4799 upgrade and can make it more difficult for the package manager
4800 to find a correct solution to an upgrade or installation
4801 problem. <tt>Breaks</tt> should be used
4803 <item>when moving a file from one package to another (see
4804 <ref id="replaces">),</item>
4805 <item>when splitting a package (a special case of the previous
4807 <item>when the breaking package exposes a bug in or interacts
4808 badly with particular versions of the broken
4811 <tt>Conflicts</tt> should be used
4813 <item>when two packages provide the same file and will
4814 continue to do so,</item>
4815 <item>in conjunction with <tt>Provides</tt> when only one
4816 package providing a given virtual facility may be installed
4817 at a time (see <ref id="virtual">),</item>
4818 <item>in other cases where one must prevent simultaneous
4819 installation of two packages for reasons that are ongoing
4820 (not fixed in a later version of one of the packages) or
4821 that must prevent both packages from being unpacked at the
4822 same time, not just configured.</item>
4824 Be aware that adding <tt>Conflicts</tt> is normally not the best
4825 solution when two packages provide the same files. Depending on
4826 the reason for that conflict, using alternatives or renaming the
4827 files is often a better approach. See, for
4828 example, <ref id="binaries">.
4832 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4833 unless two packages cannot be installed at the same time or
4834 installing them both causes one of them to be broken or
4835 unusable. Having similar functionality or performing the same
4836 tasks as another package is not sufficient reason to
4837 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4841 A <tt>Conflicts</tt> entry may have an "earlier than" version
4842 clause if the reason for the conflict is corrected in a later
4843 version of one of the packages. However, normally the presence
4844 of an "earlier than" version clause is a sign
4845 that <tt>Breaks</tt> should have been used instead. An "earlier
4846 than" version clause in <tt>Conflicts</tt>
4847 prevents <prgn>dpkg</prgn> from upgrading or installing the
4848 package which declares such a conflict until the upgrade or
4849 removal of the conflicted-with package has been completed, which
4850 is a strong restriction.
4854 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4858 As well as the names of actual ("concrete") packages, the
4859 package relationship fields <tt>Depends</tt>,
4860 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4861 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4862 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4863 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4864 may mention "virtual packages".
4868 A <em>virtual package</em> is one which appears in the
4869 <tt>Provides</tt> control field of another package. The effect
4870 is as if the package(s) which provide a particular virtual
4871 package name had been listed by name everywhere the virtual
4872 package name appears. (See also <ref id="virtual_pkg">)
4876 If there are both concrete and virtual packages of the same
4877 name, then the dependency may be satisfied (or the conflict
4878 caused) by either the concrete package with the name in
4879 question or any other concrete package which provides the
4880 virtual package with the name in question. This is so that,
4881 for example, supposing we have
4882 <example compact="compact">
4885 </example> and someone else releases an enhanced version of
4886 the <tt>bar</tt> package they can say:
4887 <example compact="compact">
4891 and the <tt>bar-plus</tt> package will now also satisfy the
4892 dependency for the <tt>foo</tt> package.
4896 If a relationship field has a version number attached, only real
4897 packages will be considered to see whether the relationship is
4898 satisfied (or the prohibition violated, for a conflict or
4899 breakage). In other words, if a version number is specified,
4900 this is a request to ignore all <tt>Provides</tt> for that
4901 package name and consider only real packages. The package
4902 manager will assume that a package providing that virtual
4903 package is not of the "right" version. A <tt>Provides</tt>
4904 field may not contain version numbers, and the version number of
4905 the concrete package which provides a particular virtual package
4906 will not be considered when considering a dependency on or
4907 conflict with the virtual package name.<footnote>
4908 It is possible that a future release of <prgn>dpkg</prgn> may
4909 add the ability to specify a version number for each virtual
4910 package it provides. This feature is not yet present,
4911 however, and is expected to be used only infrequently.
4916 To specify which of a set of real packages should be the default
4917 to satisfy a particular dependency on a virtual package, list
4918 the real package as an alternative before the virtual one.
4922 If the virtual package represents a facility that can only be
4923 provided by one real package at a time, such as
4924 the <package>mail-transport-agent</package> virtual package that
4925 requires installation of a binary that would conflict with all
4926 other providers of that virtual package (see
4927 <ref id="mail-transport-agents">), all packages providing that
4928 virtual package should also declare a conflict with it
4929 using <tt>Conflicts</tt>. This will ensure that at most one
4930 provider of that virtual package is unpacked or installed at a
4935 <sect id="replaces"><heading>Overwriting files and replacing
4936 packages - <tt>Replaces</tt></heading>
4939 Packages can declare in their control file that they should
4940 overwrite files in certain other packages, or completely replace
4941 other packages. The <tt>Replaces</tt> control field has these
4942 two distinct purposes.
4945 <sect1><heading>Overwriting files in other packages</heading>
4948 It is usually an error for a package to contain files which
4949 are on the system in another package. However, if the
4950 overwriting package declares that it <tt>Replaces</tt> the one
4951 containing the file being overwritten, then <prgn>dpkg</prgn>
4952 will replace the file from the old package with that from the
4953 new. The file will no longer be listed as "owned" by the old
4954 package and will be taken over by the new package.
4955 Normally, <tt>Breaks</tt> should be used in conjunction
4956 with <tt>Replaces</tt>.<footnote>
4957 To see why <tt>Breaks</tt> is normally needed in addition
4958 to <tt>Replaces</tt>, consider the case of a file in the
4959 package <package>foo</package> being taken over by the
4960 package <package>foo-data</package>.
4961 <tt>Replaces</tt> will allow <package>foo-data</package> to
4962 be installed and take over that file. However,
4963 without <tt>Breaks</tt>, nothing
4964 requires <package>foo</package> to be upgraded to a newer
4965 version that knows it does not include that file and instead
4966 depends on <package>foo-data</package>. Nothing would
4967 prevent the new <package>foo-data</package> package from
4968 being installed and then removed, removing the file that it
4969 took over from <package>foo</package>. After that
4970 operation, the package manager would think the system was in
4971 a consistent state, but the <package>foo</package> package
4972 would be missing one of its files.
4977 For example, if a package <package>foo</package> is split
4978 into <package>foo</package> and <package>foo-data</package>
4979 starting at version 1.2-3, <package>foo-data</package> would
4981 <example compact="compact">
4982 Replaces: foo (<< 1.2-3)
4983 Breaks: foo (<< 1.2-3)
4985 in its control file. The new version of the
4986 package <package>foo</package> would normally have the field
4987 <example compact="compact">
4988 Depends: foo-data (>= 1.2-3)
4990 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4991 the files moved into <package>foo-data</package> are not
4992 required for normal operation).
4996 If a package is completely replaced in this way, so that
4997 <prgn>dpkg</prgn> does not know of any files it still
4998 contains, it is considered to have "disappeared". It will
4999 be marked as not wanted on the system (selected for
5000 removal) and not installed. Any <tt>conffile</tt>s
5001 details noted for the package will be ignored, as they
5002 will have been taken over by the overwriting package. The
5003 package's <prgn>postrm</prgn> script will be run with a
5004 special argument to allow the package to do any final
5005 cleanup required. See <ref id="mscriptsinstact">.
5007 Replaces is a one way relationship. You have to install
5008 the replacing package after the replaced package.
5013 For this usage of <tt>Replaces</tt>, virtual packages (see
5014 <ref id="virtual">) are not considered when looking at a
5015 <tt>Replaces</tt> field. The packages declared as being
5016 replaced must be mentioned by their real names.
5020 This usage of <tt>Replaces</tt> only takes effect when both
5021 packages are at least partially on the system at once. It is
5022 not relevant if the packages conflict unless the conflict has
5027 <sect1><heading>Replacing whole packages, forcing their
5031 Second, <tt>Replaces</tt> allows the packaging system to
5032 resolve which package should be removed when there is a
5033 conflict (see <ref id="conflicts">). This usage only takes
5034 effect when the two packages <em>do</em> conflict, so that the
5035 two usages of this field do not interfere with each other.
5039 In this situation, the package declared as being replaced
5040 can be a virtual package, so for example, all mail
5041 transport agents (MTAs) would have the following fields in
5042 their control files:
5043 <example compact="compact">
5044 Provides: mail-transport-agent
5045 Conflicts: mail-transport-agent
5046 Replaces: mail-transport-agent
5048 ensuring that only one MTA can be installed at any one
5049 time. See <ref id="virtual"> for more information about this
5054 <sect id="sourcebinarydeps">
5055 <heading>Relationships between source and binary packages -
5056 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5057 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5061 Source packages that require certain binary packages to be
5062 installed or absent at the time of building the package
5063 can declare relationships to those binary packages.
5067 This is done using the <tt>Build-Depends</tt>,
5068 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5069 <tt>Build-Conflicts-Indep</tt> control fields.
5073 Build-dependencies on "build-essential" binary packages can be
5074 omitted. Please see <ref id="pkg-relations"> for more information.
5078 The dependencies and conflicts they define must be satisfied
5079 (as defined earlier for binary packages) in order to invoke
5080 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5082 There is no Build-Depends-Arch; this role is essentially
5083 met with Build-Depends. Anyone building the
5084 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5085 assumed to be building the whole package, and therefore
5086 installation of all build dependencies is required.
5089 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5090 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5091 not yet know how to check for its existence, and
5092 <tt>binary-arch</tt>. The purpose of the original split
5093 between <tt>Build-Depends</tt> and
5094 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5095 wouldn't need to install extra packages needed only for the
5096 binary-indep targets. But without a build-arch/build-indep
5097 split, this didn't work, since most of the work is done in
5098 the build target, not in the binary target.
5102 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5103 <tt>binary-arch</tt></tag>
5105 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5106 fields must be satisfied when these targets are invoked.
5108 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5109 and <tt>binary-indep</tt></tag>
5111 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5112 <tt>Build-Depends-Indep</tt>, and
5113 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5114 these targets are invoked.
5122 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5125 Packages containing shared libraries must be constructed with
5126 a little care to make sure that the shared library is always
5127 available. This is especially important for packages whose
5128 shared libraries are vitally important, such as the C library
5129 (currently <tt>libc6</tt>).
5133 Packages involving shared libraries should be split up into
5134 several binary packages. This section mostly deals with how
5135 this separation is to be accomplished; rules for files within
5136 the shared library packages are in <ref id="libraries"> instead.
5139 <sect id="sharedlibs-runtime">
5140 <heading>Run-time shared libraries</heading>
5143 The run-time shared library needs to be placed in a package
5144 whose name changes whenever the shared object version
5147 Since it is common place to install several versions of a
5148 package that just provides shared libraries, it is a
5149 good idea that the library package should not
5150 contain any extraneous non-versioned files, unless they
5151 happen to be in versioned directories.</p>
5153 The most common mechanism is to place it in a package
5155 <package><var>libraryname</var><var>soversion</var></package>,
5156 where <file><var>soversion</var></file> is the version number
5157 in the soname of the shared library<footnote>
5158 The soname is the shared object name: it's the thing
5159 that has to match exactly between building an executable
5160 and running it for the dynamic linker to be able run the
5161 program. For example, if the soname of the library is
5162 <file>libfoo.so.6</file>, the library package would be
5163 called <file>libfoo6</file>.
5165 Alternatively, if it would be confusing to directly append
5166 <var>soversion</var> to <var>libraryname</var> (e.g. because
5167 <var>libraryname</var> itself ends in a number), you may use
5168 <package><var>libraryname</var>-<var>soversion</var></package> and
5169 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5174 If you have several shared libraries built from the same
5175 source tree you may lump them all together into a single
5176 shared library package, provided that you change all of
5177 their sonames at once (so that you don't get filename
5178 clashes if you try to install different versions of the
5179 combined shared libraries package).
5183 The package should install the shared libraries under
5184 their normal names. For example, the <package>libgdbm3</package>
5185 package should install <file>libgdbm.so.3.0.0</file> as
5186 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5187 renamed or re-linked by any <prgn>prerm</prgn> or
5188 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5189 of renaming things safely without affecting running programs,
5190 and attempts to interfere with this are likely to lead to
5195 Shared libraries should not be installed executable, since
5196 the dynamic linker does not require this and trying to
5197 execute a shared library usually results in a core dump.
5201 The run-time library package should include the symbolic link that
5202 <prgn>ldconfig</prgn> would create for the shared libraries.
5203 For example, the <package>libgdbm3</package> package should include
5204 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5205 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5206 linker (for example <prgn>ld.so</prgn> or
5207 <prgn>ld-linux.so.*</prgn>) can find the library between the
5208 time that <prgn>dpkg</prgn> installs it and the time that
5209 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5211 The package management system requires the library to be
5212 placed before the symbolic link pointing to it in the
5213 <file>.deb</file> file. This is so that when
5214 <prgn>dpkg</prgn> comes to install the symlink
5215 (overwriting the previous symlink pointing at an older
5216 version of the library), the new shared library is already
5217 in place. In the past, this was achieved by creating the
5218 library in the temporary packaging directory before
5219 creating the symlink. Unfortunately, this was not always
5220 effective, since the building of the tar file in the
5221 <file>.deb</file> depended on the behavior of the underlying
5222 file system. Some file systems (such as reiserfs) reorder
5223 the files so that the order of creation is forgotten.
5224 Since version 1.7.0, <prgn>dpkg</prgn>
5225 reorders the files itself as necessary when building a
5226 package. Thus it is no longer important to concern
5227 oneself with the order of file creation.
5231 <sect1 id="ldconfig">
5232 <heading><tt>ldconfig</tt></heading>
5235 Any package installing shared libraries in one of the default
5236 library directories of the dynamic linker (which are currently
5237 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5238 listed in <file>/etc/ld.so.conf</file><footnote>
5240 <list compact="compact">
5241 <item>/usr/local/lib</item>
5242 <item>/usr/lib/libc5-compat</item>
5243 <item>/lib/libc5-compat</item>
5246 must use <prgn>ldconfig</prgn> to update the shared library
5251 The package maintainer scripts must only call
5252 <prgn>ldconfig</prgn> under these circumstances:
5253 <list compact="compact">
5254 <item>When the <prgn>postinst</prgn> script is run with a
5255 first argument of <tt>configure</tt>, the script must call
5256 <prgn>ldconfig</prgn>, and may optionally invoke
5257 <prgn>ldconfig</prgn> at other times.
5259 <item>When the <prgn>postrm</prgn> script is run with a
5260 first argument of <tt>remove</tt>, the script should call
5261 <prgn>ldconfig</prgn>.
5266 During install or upgrade, the preinst is called before
5267 the new files are installed, so calling "ldconfig" is
5268 pointless. The preinst of an existing package can also be
5269 called if an upgrade fails. However, this happens during
5270 the critical time when a shared libs may exist on-disk
5271 under a temporary name. Thus, it is dangerous and
5272 forbidden by current policy to call "ldconfig" at this
5277 When a package is installed or upgraded, "postinst
5278 configure" runs after the new files are safely on-disk.
5279 Since it is perfectly safe to invoke ldconfig
5280 unconditionally in a postinst, it is OK for a package to
5281 simply put ldconfig in its postinst without checking the
5282 argument. The postinst can also be called to recover from
5283 a failed upgrade. This happens before any new files are
5284 unpacked, so there is no reason to call "ldconfig" at this
5289 For a package that is being removed, prerm is
5290 called with all the files intact, so calling ldconfig is
5291 useless. The other calls to "prerm" happen in the case of
5292 upgrade at a time when all the files of the old package
5293 are on-disk, so again calling "ldconfig" is pointless.
5297 postrm, on the other hand, is called with the "remove"
5298 argument just after the files are removed, so this is
5299 the proper time to call "ldconfig" to notify the system
5300 of the fact that the shared libraries from the package
5301 are removed. The postrm can be called at several other
5302 times. At the time of "postrm purge", "postrm
5303 abort-install", or "postrm abort-upgrade", calling
5304 "ldconfig" is useless because the shared lib files are
5305 not on-disk. However, when "postrm" is invoked with
5306 arguments "upgrade", "failed-upgrade", or "disappear", a
5307 shared lib may exist on-disk under a temporary filename.
5315 <sect id="sharedlibs-support-files">
5316 <heading>Shared library support files</heading>
5319 If your package contains files whose names do not change with
5320 each change in the library shared object version, you must not
5321 put them in the shared library package. Otherwise, several
5322 versions of the shared library cannot be installed at the same
5323 time without filename clashes, making upgrades and transitions
5324 unnecessarily difficult.
5328 It is recommended that supporting files and run-time support
5329 programs that do not need to be invoked manually by users, but
5330 are nevertheless required for the package to function, be placed
5331 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5332 preferably under <file>/usr/lib/</file><var>package-name</var>.
5333 If the program or file is architecture independent, the
5334 recommendation is for it to be placed in a subdirectory of
5335 <file>/usr/share</file> instead, preferably under
5336 <file>/usr/share/</file><var>package-name</var>. Following the
5337 <var>package-name</var> naming convention ensures that the file
5338 names change when the shared object version changes.
5342 Run-time support programs that use the shared library but are
5343 not required for the library to function or files used by the
5344 shared library that can be used by any version of the shared
5345 library package should instead be put in a separate package.
5346 This package might typically be named
5347 <package><var>libraryname</var>-tools</package>; note the
5348 absence of the <var>soversion</var> in the package name.
5352 Files and support programs only useful when compiling software
5353 against the library should be included in the development
5354 package for the library.<footnote>
5355 For example, a <file><var>package-name</var>-config</file>
5356 script or <package>pkg-config</package> configuration files.
5361 <sect id="sharedlibs-static">
5362 <heading>Static libraries</heading>
5365 The static library (<file><var>libraryname.a</var></file>)
5366 is usually provided in addition to the shared version.
5367 It is placed into the development package (see below).
5371 In some cases, it is acceptable for a library to be
5372 available in static form only; these cases include:
5374 <item>libraries for languages whose shared library support
5375 is immature or unstable</item>
5376 <item>libraries whose interfaces are in flux or under
5377 development (commonly the case when the library's
5378 major version number is zero, or where the ABI breaks
5379 across patchlevels)</item>
5380 <item>libraries which are explicitly intended to be
5381 available only in static form by their upstream
5386 <sect id="sharedlibs-dev">
5387 <heading>Development files</heading>
5390 If there are development files associated with a shared library,
5391 the source package needs to generate a binary development package
5392 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5393 or if you prefer only to support one development version at a
5394 time, <package><var>libraryname</var>-dev</package>. Installing
5395 the development package must result in installation of all the
5396 development files necessary for compiling programs against that
5397 shared library.<footnote>
5398 This wording allows the development files to be split into
5399 several packages, such as a separate architecture-independent
5400 <package><var>libraryname</var>-headers</package>, provided that
5401 the development package depends on all the required additional
5407 In case several development versions of a library exist, you may
5408 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5409 <ref id="conflicts">) to ensure that the user only installs one
5410 development version at a time (as different development versions are
5411 likely to have the same header files in them, which would cause a
5412 filename clash if both were installed).
5416 The development package should contain a symlink for the associated
5417 shared library without a version number. For example, the
5418 <package>libgdbm-dev</package> package should include a symlink
5419 from <file>/usr/lib/libgdbm.so</file> to
5420 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5421 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5422 <file>libgdbm.so</file> when compiling dynamically.
5426 <sect id="sharedlibs-intradeps">
5427 <heading>Dependencies between the packages of the same library</heading>
5430 Typically the development version should have an exact
5431 version dependency on the runtime library, to make sure that
5432 compilation and linking happens correctly. The
5433 <tt>${binary:Version}</tt> substitution variable can be
5434 useful for this purpose.
5436 Previously, <tt>${Source-Version}</tt> was used, but its name
5437 was confusing and it has been deprecated since dpkg 1.13.19.
5442 <sect id="sharedlibs-shlibdeps">
5443 <heading>Dependencies between the library and other packages -
5444 the <tt>shlibs</tt> system</heading>
5447 If a package contains a binary or library which links to a
5448 shared library, we must ensure that when the package is
5449 installed on the system, all of the libraries needed are
5450 also installed. This requirement led to the creation of the
5451 <tt>shlibs</tt> system, which is very simple in its design:
5452 any package which <em>provides</em> a shared library also
5453 provides information on the package dependencies required to
5454 ensure the presence of this library, and any package which
5455 <em>uses</em> a shared library uses this information to
5456 determine the dependencies it requires. The files which
5457 contain the mapping from shared libraries to the necessary
5458 dependency information are called <file>shlibs</file> files.
5462 When a package is built which contains any shared libraries, it
5463 must provide a <file>shlibs</file> file for other packages to
5464 use. When a package is built which contains any shared
5465 libraries or compiled binaries, it must run
5466 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5467 on these to determine the libraries used and hence the
5468 dependencies needed by this package.<footnote>
5470 <prgn>dpkg-shlibdeps</prgn> will use a program
5471 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5472 the libraries directly needed by the binaries or shared
5473 libraries in the package.
5477 We say that a binary <tt>foo</tt> <em>directly</em> uses
5478 a library <tt>libbar</tt> if it is explicitly linked
5479 with that library (that is, the library is listed in the ELF
5480 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5481 to the link line when the binary is created). Other
5482 libraries that are needed by <tt>libbar</tt> are linked
5483 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5484 linker will load them automatically when it loads
5485 <tt>libbar</tt>. A package should depend on the libraries
5486 it directly uses, but not the libraries it indirectly uses.
5487 The dependencies for those libraries will automatically pull
5488 in the other libraries.
5492 A good example of where this helps is the following. We
5493 could update <tt>libimlib</tt> with a new version that
5494 supports a new graphics format called dgf (but retaining the
5495 same major version number) and depends on <tt>libdgf</tt>.
5496 If we used <prgn>ldd</prgn> to add dependencies for every
5497 library directly or indirectly linked with a binary, every
5498 package that uses <tt>libimlib</tt> would need to be
5499 recompiled so it would also depend on <tt>libdgf</tt> or it
5500 wouldn't run due to missing symbols. Since dependencies are
5501 only added based on ELF <tt>NEEDED</tt> attribute, packages
5502 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5503 having the dependency on <tt>libdgf</tt> and so they would
5504 not need rebuilding.
5510 In the following sections, we will first describe where the
5511 various <tt>shlibs</tt> files are to be found, then how to
5512 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5513 file format and how to create them if your package contains a
5518 <heading>The <tt>shlibs</tt> files present on the system</heading>
5521 There are several places where <tt>shlibs</tt> files are
5522 found. The following list gives them in the order in which
5524 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5525 (The first one which gives the required information is used.)
5531 <p><file>debian/shlibs.local</file></p>
5534 This lists overrides for this package. This file should
5535 normally not be used, but may be needed temporarily in
5536 unusual situations to work around bugs in other packages,
5537 or in unusual cases where the normally declared dependency
5538 information in the installed <file>shlibs</file> file for
5539 a library cannot be used. This file overrides information
5540 obtained from any other source.
5545 <p><file>/etc/dpkg/shlibs.override</file></p>
5548 This lists global overrides. This list is normally
5549 empty. It is maintained by the local system
5555 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5558 When packages are being built,
5559 any <file>debian/shlibs</file> files are copied into the
5560 control information file area of the temporary build
5561 directory and given the name <file>shlibs</file>. These
5562 files give details of any shared libraries included in the
5563 same package.<footnote>
5564 An example may help here. Let us say that the source
5565 package <tt>foo</tt> generates two binary
5566 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5567 When building the binary packages, the two packages are
5568 created in the directories <file>debian/libfoo2</file>
5569 and <file>debian/foo-runtime</file> respectively.
5570 (<file>debian/tmp</file> could be used instead of one of
5571 these.) Since <tt>libfoo2</tt> provides the
5572 <tt>libfoo</tt> shared library, it will require a
5573 <tt>shlibs</tt> file, which will be installed in
5574 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5575 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5576 When <prgn>dpkg-shlibdeps</prgn> is run on the
5577 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5579 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5580 determine whether <tt>foo-prog</tt>'s library
5581 dependencies are satisfied by any of the libraries
5582 provided by <tt>libfoo2</tt>. For this reason,
5583 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5584 the individual binary packages' <tt>shlibs</tt> files
5585 have been installed into the build directory.
5591 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5594 These are the <file>shlibs</file> files corresponding to
5595 all of the packages installed on the system, and are
5596 maintained by the relevant package maintainers.
5601 <p><file>/etc/dpkg/shlibs.default</file></p>
5604 This file lists any shared libraries whose packages
5605 have failed to provide correct <file>shlibs</file> files.
5606 It was used when the <file>shlibs</file> setup was first
5607 introduced, but it is now normally empty. It is
5608 maintained by the <tt>dpkg</tt> maintainer.
5616 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5617 <file>shlibs</file> files</heading>
5621 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5622 into your <file>debian/rules</file> file. If your package
5623 contains only compiled binaries and libraries (but no scripts),
5624 you can use a command such as:
5625 <example compact="compact">
5626 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5627 debian/tmp/usr/lib/*
5629 Otherwise, you will need to explicitly list the compiled
5630 binaries and libraries.<footnote>
5631 If you are using <tt>debhelper</tt>, the
5632 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5633 It will also correctly handle multi-binary packages.
5638 This command puts the dependency information into the
5639 <file>debian/substvars</file> file, which is then used by
5640 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5641 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5642 field in the control file for this to work.
5646 If you have multiple binary packages, you will need to call
5647 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5648 compiled libraries or binaries. In such a case, you will
5649 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5650 utilities to specify a different <file>substvars</file> file.
5654 If you are creating a udeb for use in the Debian Installer,
5655 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5656 should use the dependency line of type <tt>udeb</tt> by
5657 adding the <tt>-tudeb</tt> option<footnote>
5658 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5659 will automatically add this option if it knows it is
5661 </footnote>. If there is no dependency line of
5662 type <tt>udeb</tt> in the <file>shlibs</file>
5663 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5668 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5669 <ref id="pkg-dpkg-shlibdeps"> and
5670 <manref name="dpkg-shlibdeps" section="1">.
5675 <heading>The <file>shlibs</file> File Format</heading>
5678 Each <file>shlibs</file> file has the same format. Lines
5679 beginning with <tt>#</tt> are considered to be comments and
5680 are ignored. Each line is of the form:
5681 <example compact="compact">
5682 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5687 We will explain this by reference to the example of the
5688 <tt>zlib1g</tt> package, which (at the time of writing)
5689 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5693 <var>type</var> is an optional element that indicates the type
5694 of package for which the line is valid. The only type currently
5695 in use is <tt>udeb</tt>. The colon and space after the type are
5700 <var>library-name</var> is the name of the shared library,
5701 in this case <tt>libz</tt>. (This must match the name part
5702 of the soname, see below.)
5706 <var>soname-version</var> is the version part of the soname of
5707 the library. The soname is the thing that must exactly match
5708 for the library to be recognized by the dynamic linker, and is
5710 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5711 example, <tt>libz.so.1</tt>.<footnote>
5712 This can be determined using the command
5713 <example compact="compact">
5714 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5717 The version part is the part which comes after
5718 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5719 instead be of the form
5720 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5721 as <tt>libdb-4.8.so</tt>, in which case the name would
5722 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5726 <var>dependencies</var> has the same syntax as a dependency
5727 field in a binary package control file. It should give
5728 details of which packages are required to satisfy a binary
5729 built against the version of the library contained in the
5730 package. See <ref id="depsyntax"> for details.
5734 In our example, if the first version of the <tt>zlib1g</tt>
5735 package which contained a minor number of at least
5736 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5737 <tt>shlibs</tt> entry for this library could say:
5738 <example compact="compact">
5739 libz 1 zlib1g (>= 1:1.1.3)
5741 The version-specific dependency is to avoid warnings from
5742 the dynamic linker about using older shared libraries with
5747 As zlib1g also provides a udeb containing the shared library,
5748 there would also be a second line:
5749 <example compact="compact">
5750 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5756 <heading>Providing a <file>shlibs</file> file</heading>
5759 If your package provides a shared library, you need to create
5760 a <file>shlibs</file> file following the format described above.
5761 It is usual to call this file <file>debian/shlibs</file> (but if
5762 you have multiple binary packages, you might want to call it
5763 <file>debian/shlibs.<var>package</var></file> instead). Then
5764 let <file>debian/rules</file> install it in the control
5765 information file area:
5766 <example compact="compact">
5767 install -m644 debian/shlibs debian/tmp/DEBIAN
5769 or, in the case of a multi-binary package:
5770 <example compact="compact">
5771 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5773 An alternative way of doing this is to create the
5774 <file>shlibs</file> file in the control information file area
5775 directly from <file>debian/rules</file> without using
5776 a <file>debian/shlibs</file> file at all,<footnote>
5777 This is what <prgn>dh_makeshlibs</prgn> in
5778 the <package>debhelper</package> suite does. If your package
5779 also has a udeb that provides a shared
5780 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5781 the <tt>udeb:</tt> lines if you specify the name of the udeb
5782 with the <tt>--add-udeb</tt> option.
5784 since the <file>debian/shlibs</file> file itself is ignored by
5785 <prgn>dpkg-shlibdeps</prgn>.
5789 As <prgn>dpkg-shlibdeps</prgn> reads the
5790 <file>DEBIAN/shlibs</file> files in all of the binary packages
5791 being built from this source package, all of the
5792 <file>DEBIAN/shlibs</file> files should be installed before
5793 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5801 <chapt id="opersys"><heading>The Operating System</heading>
5804 <heading>File system hierarchy</heading>
5808 <heading>File System Structure</heading>
5811 The location of all installed files and directories must
5812 comply with the Filesystem Hierarchy Standard (FHS),
5813 version 2.3, with the exceptions noted below, and except
5814 where doing so would violate other terms of Debian
5815 Policy. The following exceptions to the FHS apply:
5820 The optional rules related to user specific
5821 configuration files for applications are stored in
5822 the user's home directory are relaxed. It is
5823 recommended that such files start with the
5824 '<tt>.</tt>' character (a "dot file"), and if an
5825 application needs to create more than one dot file
5826 then the preferred placement is in a subdirectory
5827 with a name starting with a '.' character, (a "dot
5828 directory"). In this case it is recommended the
5829 configuration files not start with the '.'
5835 The requirement for amd64 to use <file>/lib64</file>
5836 for 64 bit binaries is removed.
5841 The requirement for object files, internal binaries, and
5842 libraries, including <file>libc.so.*</file>, to be located
5843 directly under <file>/lib{,32}</file> and
5844 <file>/usr/lib{,32}</file> is amended, permitting files
5845 to instead be installed to
5846 <file>/lib/<var>triplet</var></file> and
5847 <file>/usr/lib/<var>triplet</var></file>, where
5848 <tt><var>triplet</var></tt> is the value returned by
5849 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5850 architecture of the package. Packages may <em>not</em>
5851 install files to any <var>triplet</var> path other
5852 than the one matching the architecture of that package;
5853 for instance, an <tt>Architecture: amd64</tt> package
5854 containing 32-bit x86 libraries may not install these
5855 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5857 This is necessary in order to reserve the directories for
5858 use in cross-installation of library packages from other
5859 architectures, as part of the planned deployment of
5864 Applications may also use a single subdirectory under
5865 <file>/usr/lib/<var>triplet</var></file>.
5868 The execution time linker/loader, ld*, must still be made
5869 available in the existing location under /lib or /lib64
5870 since this is part of the ELF ABI for the architecture.
5875 The requirement that
5876 <file>/usr/local/share/man</file> be "synonymous"
5877 with <file>/usr/local/man</file> is relaxed to a
5882 The requirement that windowmanagers with a single
5883 configuration file call it <file>system.*wmrc</file>
5884 is removed, as is the restriction that the window
5885 manager subdirectory be named identically to the
5886 window manager name itself.
5891 The requirement that boot manager configuration
5892 files live in <file>/etc</file>, or at least are
5893 symlinked there, is relaxed to a recommendation.
5898 The following directories in the root filesystem are
5899 additionally allowed: <file>/sys</file> and
5900 <file>/selinux</file>. <footnote>These directories
5901 are used as mount points to mount virtual filesystems
5902 to get access to kernel information.</footnote>
5909 The version of this document referred here can be
5910 found in the <tt>debian-policy</tt> package or on <url
5911 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5912 name="FHS (Debian copy)"> alongside this manual (or, if
5913 you have the <package>debian-policy</package> installed,
5915 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5916 (local copy)">). The
5917 latest version, which may be a more recent version, may
5919 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5920 Specific questions about following the standard may be
5921 asked on the <tt>debian-devel</tt> mailing list, or
5922 referred to the FHS mailing list (see the
5923 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5929 <heading>Site-specific programs</heading>
5932 As mandated by the FHS, packages must not place any
5933 files in <file>/usr/local</file>, either by putting them in
5934 the file system archive to be unpacked by <prgn>dpkg</prgn>
5935 or by manipulating them in their maintainer scripts.
5939 However, the package may create empty directories below
5940 <file>/usr/local</file> so that the system administrator knows
5941 where to place site-specific files. These are not
5942 directories <em>in</em> <file>/usr/local</file>, but are
5943 children of directories in <file>/usr/local</file>. These
5944 directories (<file>/usr/local/*/dir/</file>)
5945 should be removed on package removal if they are
5950 Note that this applies only to
5951 directories <em>below</em> <file>/usr/local</file>,
5952 not <em>in</em> <file>/usr/local</file>. Packages must
5953 not create sub-directories in the
5954 directory <file>/usr/local</file> itself, except those
5955 listed in FHS, section 4.5. However, you may create
5956 directories below them as you wish. You must not remove
5957 any of the directories listed in 4.5, even if you created
5962 Since <file>/usr/local</file> can be mounted read-only from a
5963 remote server, these directories must be created and
5964 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5965 maintainer scripts and not be included in the
5966 <file>.deb</file> archive. These scripts must not fail if
5967 either of these operations fail.
5971 For example, the <tt>emacsen-common</tt> package could
5972 contain something like
5973 <example compact="compact">
5974 if [ ! -e /usr/local/share/emacs ]
5976 if mkdir /usr/local/share/emacs 2>/dev/null
5978 chown root:staff /usr/local/share/emacs
5979 chmod 2775 /usr/local/share/emacs
5983 in its <prgn>postinst</prgn> script, and
5984 <example compact="compact">
5985 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5986 rmdir /usr/local/share/emacs 2>/dev/null || true
5988 in the <prgn>prerm</prgn> script. (Note that this form is
5989 used to ensure that if the script is interrupted, the
5990 directory <file>/usr/local/share/emacs</file> will still be
5995 If you do create a directory in <file>/usr/local</file> for
5996 local additions to a package, you should ensure that
5997 settings in <file>/usr/local</file> take precedence over the
5998 equivalents in <file>/usr</file>.
6002 However, because <file>/usr/local</file> and its contents are
6003 for exclusive use of the local administrator, a package
6004 must not rely on the presence or absence of files or
6005 directories in <file>/usr/local</file> for normal operation.
6009 The <file>/usr/local</file> directory itself and all the
6010 subdirectories created by the package should (by default) have
6011 permissions 2775 (group-writable and set-group-id) and be
6012 owned by <tt>root:staff</tt>.
6017 <heading>The system-wide mail directory</heading>
6019 The system-wide mail directory
6020 is <file>/var/mail</file>. This directory is part of the
6021 base system and should not be owned by any particular mail
6022 agents. The use of the old
6023 location <file>/var/spool/mail</file> is deprecated, even
6024 though the spool may still be physically located there.
6030 <heading>Users and groups</heading>
6033 <heading>Introduction</heading>
6035 The Debian system can be configured to use either plain or
6040 Some user ids (UIDs) and group ids (GIDs) are reserved
6041 globally for use by certain packages. Because some
6042 packages need to include files which are owned by these
6043 users or groups, or need the ids compiled into binaries,
6044 these ids must be used on any Debian system only for the
6045 purpose for which they are allocated. This is a serious
6046 restriction, and we should avoid getting in the way of
6047 local administration policies. In particular, many sites
6048 allocate users and/or local system groups starting at 100.
6052 Apart from this we should have dynamically allocated ids,
6053 which should by default be arranged in some sensible
6054 order, but the behavior should be configurable.
6058 Packages other than <tt>base-passwd</tt> must not modify
6059 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6060 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6065 <heading>UID and GID classes</heading>
6067 The UID and GID numbers are divided into classes as
6073 Globally allocated by the Debian project, the same
6074 on every Debian system. These ids will appear in
6075 the <file>passwd</file> and <file>group</file> files of all
6076 Debian systems, new ids in this range being added
6077 automatically as the <tt>base-passwd</tt> package is
6082 Packages which need a single statically allocated
6083 uid or gid should use one of these; their
6084 maintainers should ask the <tt>base-passwd</tt>
6092 Dynamically allocated system users and groups.
6093 Packages which need a user or group, but can have
6094 this user or group allocated dynamically and
6095 differently on each system, should use <tt>adduser
6096 --system</tt> to create the group and/or user.
6097 <prgn>adduser</prgn> will check for the existence of
6098 the user or group, and if necessary choose an unused
6099 id based on the ranges specified in
6100 <file>adduser.conf</file>.
6104 <tag>1000-59999:</tag>
6107 Dynamically allocated user accounts. By default
6108 <prgn>adduser</prgn> will choose UIDs and GIDs for
6109 user accounts in this range, though
6110 <file>adduser.conf</file> may be used to modify this
6115 <tag>60000-64999:</tag>
6118 Globally allocated by the Debian project, but only
6119 created on demand. The ids are allocated centrally
6120 and statically, but the actual accounts are only
6121 created on users' systems on demand.
6125 These ids are for packages which are obscure or
6126 which require many statically-allocated ids. These
6127 packages should check for and create the accounts in
6128 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6129 <prgn>adduser</prgn> if it has this facility) if
6130 necessary. Packages which are likely to require
6131 further allocations should have a "hole" left after
6132 them in the allocation, to give them room to
6137 <tag>65000-65533:</tag>
6145 User <tt>nobody</tt>. The corresponding gid refers
6146 to the group <tt>nogroup</tt>.
6153 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6154 not</em> be used, because it is the error return
6163 <sect id="sysvinit">
6164 <heading>System run levels and <file>init.d</file> scripts</heading>
6166 <sect1 id="/etc/init.d">
6167 <heading>Introduction</heading>
6170 The <file>/etc/init.d</file> directory contains the scripts
6171 executed by <prgn>init</prgn> at boot time and when the
6172 init state (or "runlevel") is changed (see <manref
6173 name="init" section="8">).
6177 There are at least two different, yet functionally
6178 equivalent, ways of handling these scripts. For the sake
6179 of simplicity, this document describes only the symbolic
6180 link method. However, it must not be assumed by maintainer
6181 scripts that this method is being used, and any automated
6182 manipulation of the various runlevel behaviors by
6183 maintainer scripts must be performed using
6184 <prgn>update-rc.d</prgn> as described below and not by
6185 manually installing or removing symlinks. For information
6186 on the implementation details of the other method,
6187 implemented in the <tt>file-rc</tt> package, please refer
6188 to the documentation of that package.
6192 These scripts are referenced by symbolic links in the
6193 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6194 runlevels, <prgn>init</prgn> looks in the directory
6195 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6196 execute, where <tt><var>n</var></tt> is the runlevel that
6197 is being changed to, or <tt>S</tt> for the boot-up
6202 The names of the links all have the form
6203 <file>S<var>mm</var><var>script</var></file> or
6204 <file>K<var>mm</var><var>script</var></file> where
6205 <var>mm</var> is a two-digit number and <var>script</var>
6206 is the name of the script (this should be the same as the
6207 name of the actual script in <file>/etc/init.d</file>).
6211 When <prgn>init</prgn> changes runlevel first the targets
6212 of the links whose names start with a <tt>K</tt> are
6213 executed, each with the single argument <tt>stop</tt>,
6214 followed by the scripts prefixed with an <tt>S</tt>, each
6215 with the single argument <tt>start</tt>. (The links are
6216 those in the <file>/etc/rc<var>n</var>.d</file> directory
6217 corresponding to the new runlevel.) The <tt>K</tt> links
6218 are responsible for killing services and the <tt>S</tt>
6219 link for starting services upon entering the runlevel.
6223 For example, if we are changing from runlevel 2 to
6224 runlevel 3, init will first execute all of the <tt>K</tt>
6225 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6226 all of the <tt>S</tt> prefixed scripts in that directory.
6227 The links starting with <tt>K</tt> will cause the
6228 referred-to file to be executed with an argument of
6229 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6234 The two-digit number <var>mm</var> is used to determine
6235 the order in which to run the scripts: low-numbered links
6236 have their scripts run first. For example, the
6237 <tt>K20</tt> scripts will be executed before the
6238 <tt>K30</tt> scripts. This is used when a certain service
6239 must be started before another. For example, the name
6240 server <prgn>bind</prgn> might need to be started before
6241 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6242 can set up its access lists. In this case, the script
6243 that starts <prgn>bind</prgn> would have a lower number
6244 than the script that starts <prgn>inn</prgn> so that it
6246 <example compact="compact">
6253 The two runlevels 0 (halt) and 6 (reboot) are slightly
6254 different. In these runlevels, the links with an
6255 <tt>S</tt> prefix are still called after those with a
6256 <tt>K</tt> prefix, but they too are called with the single
6257 argument <tt>stop</tt>.
6261 <sect1 id="writing-init">
6262 <heading>Writing the scripts</heading>
6265 Packages that include daemons for system services should
6266 place scripts in <file>/etc/init.d</file> to start or stop
6267 services at boot time or during a change of runlevel.
6268 These scripts should be named
6269 <file>/etc/init.d/<var>package</var></file>, and they should
6270 accept one argument, saying what to do:
6273 <tag><tt>start</tt></tag>
6274 <item>start the service,</item>
6276 <tag><tt>stop</tt></tag>
6277 <item>stop the service,</item>
6279 <tag><tt>restart</tt></tag>
6280 <item>stop and restart the service if it's already running,
6281 otherwise start the service</item>
6283 <tag><tt>reload</tt></tag>
6284 <item><p>cause the configuration of the service to be
6285 reloaded without actually stopping and restarting
6288 <tag><tt>force-reload</tt></tag>
6289 <item>cause the configuration to be reloaded if the
6290 service supports this, otherwise restart the
6294 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6295 <tt>force-reload</tt> options should be supported by all
6296 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6301 The <file>init.d</file> scripts must ensure that they will
6302 behave sensibly (i.e., returning success and not starting
6303 multiple copies of a service) if invoked with <tt>start</tt>
6304 when the service is already running, or with <tt>stop</tt>
6305 when it isn't, and that they don't kill unfortunately-named
6306 user processes. The best way to achieve this is usually to
6307 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6312 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6313 scripts. Writing correct <file>init.d</file> scripts requires
6314 accepting various error exit statuses when daemons are already
6315 running or already stopped without aborting
6316 the <file>init.d</file> script, and common <file>init.d</file>
6317 function libraries are not safe to call with <tt>set -e</tt>
6319 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6320 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6321 in effect and echoing status messages to the console fails,
6323 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6324 to not use <tt>set -e</tt> and instead check the result of
6325 each command separately.
6329 If a service reloads its configuration automatically (as
6330 in the case of <prgn>cron</prgn>, for example), the
6331 <tt>reload</tt> option of the <file>init.d</file> script
6332 should behave as if the configuration has been reloaded
6337 The <file>/etc/init.d</file> scripts must be treated as
6338 configuration files, either (if they are present in the
6339 package, that is, in the .deb file) by marking them as
6340 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6341 by managing them correctly in the maintainer scripts (see
6342 <ref id="config-files">). This is important since we want
6343 to give the local system administrator the chance to adapt
6344 the scripts to the local system, e.g., to disable a
6345 service without de-installing the package, or to specify
6346 some special command line options when starting a service,
6347 while making sure their changes aren't lost during the next
6352 These scripts should not fail obscurely when the
6353 configuration files remain but the package has been
6354 removed, as configuration files remain on the system after
6355 the package has been removed. Only when <prgn>dpkg</prgn>
6356 is executed with the <tt>--purge</tt> option will
6357 configuration files be removed. In particular, as the
6358 <file>/etc/init.d/<var>package</var></file> script itself is
6359 usually a <tt>conffile</tt>, it will remain on the system
6360 if the package is removed but not purged. Therefore, you
6361 should include a <tt>test</tt> statement at the top of the
6363 <example compact="compact">
6364 test -f <var>program-executed-later-in-script</var> || exit 0
6369 Often there are some variables in the <file>init.d</file>
6370 scripts whose values control the behavior of the scripts,
6371 and which a system administrator is likely to want to
6372 change. As the scripts themselves are frequently
6373 <tt>conffile</tt>s, modifying them requires that the
6374 administrator merge in their changes each time the package
6375 is upgraded and the <tt>conffile</tt> changes. To ease
6376 the burden on the system administrator, such configurable
6377 values should not be placed directly in the script.
6378 Instead, they should be placed in a file in
6379 <file>/etc/default</file>, which typically will have the same
6380 base name as the <file>init.d</file> script. This extra file
6381 should be sourced by the script when the script runs. It
6382 must contain only variable settings and comments in SUSv3
6383 <prgn>sh</prgn> format. It may either be a
6384 <tt>conffile</tt> or a configuration file maintained by
6385 the package maintainer scripts. See <ref id="config-files">
6390 To ensure that vital configurable values are always
6391 available, the <file>init.d</file> script should set default
6392 values for each of the shell variables it uses, either
6393 before sourcing the <file>/etc/default/</file> file or
6394 afterwards using something like the <tt>:
6395 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6396 script must behave sensibly and not fail if the
6397 <file>/etc/default</file> file is deleted.
6401 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6402 as temporary filesystems<footnote>
6403 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6404 options in <file>/etc/default/rcS</file>.
6405 </footnote>, so the <file>init.d</file> scripts must handle this
6406 correctly. This will typically amount to creating any required
6407 subdirectories dynamically when the <file>init.d</file> script
6408 is run, rather than including them in the package and relying on
6409 <prgn>dpkg</prgn> to create them.
6414 <heading>Interfacing with the initscript system</heading>
6417 Maintainers should use the abstraction layer provided by
6418 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6419 programs to deal with initscripts in their packages'
6420 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6421 and <prgn>postrm</prgn>.
6425 Directly managing the /etc/rc?.d links and directly
6426 invoking the <file>/etc/init.d/</file> initscripts should
6427 be done only by packages providing the initscript
6428 subsystem (such as <prgn>sysv-rc</prgn> and
6429 <prgn>file-rc</prgn>).
6433 <heading>Managing the links</heading>
6436 The program <prgn>update-rc.d</prgn> is provided for
6437 package maintainers to arrange for the proper creation and
6438 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6439 or their functional equivalent if another method is being
6440 used. This may be used by maintainers in their packages'
6441 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6445 You must not include any <file>/etc/rc<var>n</var>.d</file>
6446 symbolic links in the actual archive or manually create or
6447 remove the symbolic links in maintainer scripts; you must
6448 use the <prgn>update-rc.d</prgn> program instead. (The
6449 former will fail if an alternative method of maintaining
6450 runlevel information is being used.) You must not include
6451 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6452 in the archive either. (Only the <tt>sysvinit</tt>
6457 By default <prgn>update-rc.d</prgn> will start services in
6458 each of the multi-user state runlevels (2, 3, 4, and 5)
6459 and stop them in the halt runlevel (0), the single-user
6460 runlevel (1) and the reboot runlevel (6). The system
6461 administrator will have the opportunity to customize
6462 runlevels by simply adding, moving, or removing the
6463 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6464 symbolic links are being used, or by modifying
6465 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6470 To get the default behavior for your package, put in your
6471 <prgn>postinst</prgn> script
6472 <example compact="compact">
6473 update-rc.d <var>package</var> defaults
6475 and in your <prgn>postrm</prgn>
6476 <example compact="compact">
6477 if [ "$1" = purge ]; then
6478 update-rc.d <var>package</var> remove
6480 </example>. Note that if your package changes runlevels
6481 or priority, you may have to remove and recreate the links,
6482 since otherwise the old links may persist. Refer to the
6483 documentation of <prgn>update-rc.d</prgn>.
6487 This will use a default sequence number of 20. If it does
6488 not matter when or in which order the <file>init.d</file>
6489 script is run, use this default. If it does, then you
6490 should talk to the maintainer of the <prgn>sysvinit</prgn>
6491 package or post to <tt>debian-devel</tt>, and they will
6492 help you choose a number.
6496 For more information about using <tt>update-rc.d</tt>,
6497 please consult its man page <manref name="update-rc.d"
6503 <heading>Running initscripts</heading>
6505 The program <prgn>invoke-rc.d</prgn> is provided to make
6506 it easier for package maintainers to properly invoke an
6507 initscript, obeying runlevel and other locally-defined
6508 constraints that might limit a package's right to start,
6509 stop and otherwise manage services. This program may be
6510 used by maintainers in their packages' scripts.
6514 The package maintainer scripts must use
6515 <prgn>invoke-rc.d</prgn> to invoke the
6516 <file>/etc/init.d/*</file> initscripts, instead of
6517 calling them directly.
6521 By default, <prgn>invoke-rc.d</prgn> will pass any
6522 action requests (start, stop, reload, restart...) to the
6523 <file>/etc/init.d</file> script, filtering out requests
6524 to start or restart a service out of its intended
6529 Most packages will simply need to change:
6530 <example compact="compact">/etc/init.d/<package>
6531 <action></example> in their <prgn>postinst</prgn>
6532 and <prgn>prerm</prgn> scripts to:
6533 <example compact="compact">
6534 if which invoke-rc.d >/dev/null 2>&1; then
6535 invoke-rc.d <var>package</var> <action>
6537 /etc/init.d/<var>package</var> <action>
6543 A package should register its initscript services using
6544 <prgn>update-rc.d</prgn> before it tries to invoke them
6545 using <prgn>invoke-rc.d</prgn>. Invocation of
6546 unregistered services may fail.
6550 For more information about using
6551 <prgn>invoke-rc.d</prgn>, please consult its man page
6552 <manref name="invoke-rc.d" section="8">.
6558 <heading>Boot-time initialization</heading>
6561 There used to be another directory, <file>/etc/rc.boot</file>,
6562 which contained scripts which were run once per machine
6563 boot. This has been deprecated in favour of links from
6564 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6565 described in <ref id="/etc/init.d">. Packages must not
6566 place files in <file>/etc/rc.boot</file>.
6571 <heading>Example</heading>
6574 An example on which you can base your
6575 <file>/etc/init.d</file> scripts is found in
6576 <file>/etc/init.d/skeleton</file>.
6583 <heading>Console messages from <file>init.d</file> scripts</heading>
6586 This section describes the formats to be used for messages
6587 written to standard output by the <file>/etc/init.d</file>
6588 scripts. The intent is to improve the consistency of
6589 Debian's startup and shutdown look and feel. For this
6590 reason, please look very carefully at the details. We want
6591 the messages to have the same format in terms of wording,
6592 spaces, punctuation and case of letters.
6596 Here is a list of overall rules that should be used for
6597 messages generated by <file>/etc/init.d</file> scripts.
6603 The message should fit in one line (fewer than 80
6604 characters), start with a capital letter and end with
6605 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6609 If the script is performing some time consuming task in
6610 the background (not merely starting or stopping a
6611 program, for instance), an ellipsis (three dots:
6612 <tt>...</tt>) should be output to the screen, with no
6613 leading or tailing whitespace or line feeds.
6617 The messages should appear as if the computer is telling
6618 the user what it is doing (politely :-), but should not
6619 mention "it" directly. For example, instead of:
6620 <example compact="compact">
6621 I'm starting network daemons: nfsd mountd.
6623 the message should say
6624 <example compact="compact">
6625 Starting network daemons: nfsd mountd.
6632 <tt>init.d</tt> script should use the following standard
6633 message formats for the situations enumerated below.
6639 <p>When daemons are started</p>
6642 If the script starts one or more daemons, the output
6643 should look like this (a single line, no leading
6645 <example compact="compact">
6646 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6648 The <var>description</var> should describe the
6649 subsystem the daemon or set of daemons are part of,
6650 while <var>daemon-1</var> up to <var>daemon-n</var>
6651 denote each daemon's name (typically the file name of
6656 For example, the output of <file>/etc/init.d/lpd</file>
6658 <example compact="compact">
6659 Starting printer spooler: lpd.
6664 This can be achieved by saying
6665 <example compact="compact">
6666 echo -n "Starting printer spooler: lpd"
6667 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6670 in the script. If there are more than one daemon to
6671 start, the output should look like this:
6672 <example compact="compact">
6673 echo -n "Starting remote file system services:"
6674 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6675 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6676 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6679 This makes it possible for the user to see what is
6680 happening and when the final daemon has been started.
6681 Care should be taken in the placement of white spaces:
6682 in the example above the system administrators can
6683 easily comment out a line if they don't want to start
6684 a specific daemon, while the displayed message still
6690 <p>When a system parameter is being set</p>
6693 If you have to set up different system parameters
6694 during the system boot, you should use this format:
6695 <example compact="compact">
6696 Setting <var>parameter</var> to "<var>value</var>".
6701 You can use a statement such as the following to get
6703 <example compact="compact">
6704 echo "Setting DNS domainname to \"$domainname\"."
6709 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6710 for the left and right quotation marks. A grave accent
6711 (<tt>`</tt>) is not a quote character; neither is an
6712 apostrophe (<tt>'</tt>).
6717 <p>When a daemon is stopped or restarted</p>
6720 When you stop or restart a daemon, you should issue a
6721 message identical to the startup message, except that
6722 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6723 or <tt>Restarting</tt> respectively.
6727 For example, stopping the printer daemon will look like
6729 <example compact="compact">
6730 Stopping printer spooler: lpd.
6736 <p>When something is executed</p>
6739 There are several examples where you have to run a
6740 program at system startup or shutdown to perform a
6741 specific task, for example, setting the system's clock
6742 using <prgn>netdate</prgn> or killing all processes
6743 when the system shuts down. Your message should look
6745 <example compact="compact">
6746 Doing something very useful...done.
6748 You should print the <tt>done.</tt> immediately after
6749 the job has been completed, so that the user is
6750 informed why they have to wait. You can get this
6752 <example compact="compact">
6753 echo -n "Doing something very useful..."
6762 <p>When the configuration is reloaded</p>
6765 When a daemon is forced to reload its configuration
6766 files you should use the following format:
6767 <example compact="compact">
6768 Reloading <var>description</var> configuration...done.
6770 where <var>description</var> is the same as in the
6771 daemon starting message.
6779 <heading>Cron jobs</heading>
6782 Packages must not modify the configuration file
6783 <file>/etc/crontab</file>, and they must not modify the files in
6784 <file>/var/spool/cron/crontabs</file>.</p>
6787 If a package wants to install a job that has to be executed
6788 via cron, it should place a file with the name of the
6789 package in one or more of the following directories:
6790 <example compact="compact">
6796 As these directory names imply, the files within them are
6797 executed on an hourly, daily, weekly, or monthly basis,
6798 respectively. The exact times are listed in
6799 <file>/etc/crontab</file>.</p>
6802 All files installed in any of these directories must be
6803 scripts (e.g., shell scripts or Perl scripts) so that they
6804 can easily be modified by the local system administrator.
6805 In addition, they must be treated as configuration files.
6809 If a certain job has to be executed at some other frequency or
6810 at a specific time, the package should install a file
6811 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6812 same syntax as <file>/etc/crontab</file> and is processed by
6813 <prgn>cron</prgn> automatically. The file must also be
6814 treated as a configuration file. (Note that entries in the
6815 <file>/etc/cron.d</file> directory are not handled by
6816 <prgn>anacron</prgn>. Thus, you should only use this
6817 directory for jobs which may be skipped if the system is not
6820 Unlike <file>crontab</file> files described in the IEEE Std
6821 1003.1-2008 (POSIX.1) available from
6822 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6823 name="The Open Group">, the files in
6824 <file>/etc/cron.d</file> and the file
6825 <file>/etc/crontab</file> have seven fields; namely:
6827 <item>Minute [0,59]</item>
6828 <item>Hour [0,23]</item>
6829 <item>Day of the month [1,31]</item>
6830 <item>Month of the year [1,12]</item>
6831 <item>Day of the week ([0,6] with 0=Sunday)</item>
6832 <item>Username</item>
6833 <item>Command to be run</item>
6835 Ranges of numbers are allowed. Ranges are two numbers
6836 separated with a hyphen. The specified range is inclusive.
6837 Lists are allowed. A list is a set of numbers (or ranges)
6838 separated by commas. Step values can be used in conjunction
6843 The scripts or <tt>crontab</tt> entries in these directories should
6844 check if all necessary programs are installed before they
6845 try to execute them. Otherwise, problems will arise when a
6846 package was removed but not purged since configuration files
6847 are kept on the system in this situation.
6851 Any <tt>cron</tt> daemon must provide
6852 <file>/usr/bin/crontab</file> and support normal
6853 <tt>crontab</tt> entries as specified in POSIX. The daemon
6854 must also support names for days and months, ranges, and
6855 step values. It has to support <file>/etc/crontab</file>,
6856 and correctly execute the scripts in
6857 <file>/etc/cron.d</file>. The daemon must also correctly
6859 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6864 <heading>Menus</heading>
6867 The Debian <tt>menu</tt> package provides a standard
6868 interface between packages providing applications and
6869 <em>menu programs</em> (either X window managers or
6870 text-based menu programs such as <prgn>pdmenu</prgn>).
6874 All packages that provide applications that need not be
6875 passed any special command line arguments for normal
6876 operation should register a menu entry for those
6877 applications, so that users of the <tt>menu</tt> package
6878 will automatically get menu entries in their window
6879 managers, as well in shells like <tt>pdmenu</tt>.
6883 Menu entries should follow the current menu policy.
6887 The menu policy can be found in the <tt>menu-policy</tt>
6888 files in the <tt>debian-policy</tt> package.
6889 It is also available from the Debian web mirrors at
6890 <tt><url name="/doc/packaging-manuals/menu-policy/"
6891 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6895 Please also refer to the <em>Debian Menu System</em>
6896 documentation that comes with the <package>menu</package>
6897 package for information about how to register your
6903 <heading>Multimedia handlers</heading>
6906 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6907 is a mechanism for encoding files and data streams and
6908 providing meta-information about them, in particular their
6909 type (e.g. audio or video) and format (e.g. PNG, HTML,
6914 Registration of MIME type handlers allows programs like mail
6915 user agents and web browsers to invoke these handlers to
6916 view, edit or display MIME types they don't support directly.
6920 Packages which provide the ability to view/show/play,
6921 compose, edit or print MIME types should register themselves
6922 as such following the current MIME support policy.
6926 The MIME support policy can be found in the <tt>mime-policy</tt>
6927 files in the <tt>debian-policy</tt> package.
6928 It is also available from the Debian web mirrors at
6929 <tt><url name="/doc/packaging-manuals/mime-policy/"
6930 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6936 <heading>Keyboard configuration</heading>
6939 To achieve a consistent keyboard configuration so that all
6940 applications interpret a keyboard event the same way, all
6941 programs in the Debian distribution must be configured to
6942 comply with the following guidelines.
6946 The following keys must have the specified interpretations:
6949 <tag><tt><--</tt></tag>
6950 <item>delete the character to the left of the cursor</item>
6952 <tag><tt>Delete</tt></tag>
6953 <item>delete the character to the right of the cursor</item>
6955 <tag><tt>Control+H</tt></tag>
6956 <item>emacs: the help prefix</item>
6959 The interpretation of any keyboard events should be
6960 independent of the terminal that is used, be it a virtual
6961 console, an X terminal emulator, an rlogin/telnet session,
6966 The following list explains how the different programs
6967 should be set up to achieve this:
6973 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6977 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6981 X translations are set up to make
6982 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6983 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6984 is the vt220 escape code for the "delete character"
6985 key). This must be done by loading the X resources
6986 using <prgn>xrdb</prgn> on all local X displays, not
6987 using the application defaults, so that the
6988 translation resources used correspond to the
6989 <prgn>xmodmap</prgn> settings.
6993 The Linux console is configured to make
6994 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6995 generate <tt>ESC [ 3 ~</tt>.
6999 X applications are configured so that <tt><</tt>
7000 deletes left, and <tt>Delete</tt> deletes right. Motif
7001 applications already work like this.
7005 Terminals should have <tt>stty erase ^?</tt> .
7009 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7010 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7011 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7015 Emacs is programmed to map <tt>KB_Backspace</tt> or
7016 the <tt>stty erase</tt> character to
7017 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7018 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7019 <tt>^H</tt> to <tt>help</tt> as always.
7023 Other applications use the <tt>stty erase</tt>
7024 character and <tt>kdch1</tt> for the two delete keys,
7025 with ASCII DEL being "delete previous character" and
7026 <tt>kdch1</tt> being "delete character under
7034 This will solve the problem except for the following
7041 Some terminals have a <tt><--</tt> key that cannot
7042 be made to produce anything except <tt>^H</tt>. On
7043 these terminals Emacs help will be unavailable on
7044 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7045 character takes precedence in Emacs, and has been set
7046 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7047 available) can be used instead.
7051 Some operating systems use <tt>^H</tt> for <tt>stty
7052 erase</tt>. However, modern telnet versions and all
7053 rlogin versions propagate <tt>stty</tt> settings, and
7054 almost all UNIX versions honour <tt>stty erase</tt>.
7055 Where the <tt>stty</tt> settings are not propagated
7056 correctly, things can be made to work by using
7057 <tt>stty</tt> manually.
7061 Some systems (including previous Debian versions) use
7062 <prgn>xmodmap</prgn> to arrange for both
7063 <tt><--</tt> and <tt>Delete</tt> to generate
7064 <tt>KB_Delete</tt>. We can change the behavior of
7065 their X clients using the same X resources that we use
7066 to do it for our own clients, or configure our clients
7067 using their resources when things are the other way
7068 around. On displays configured like this
7069 <tt>Delete</tt> will not work, but <tt><--</tt>
7074 Some operating systems have different <tt>kdch1</tt>
7075 settings in their <tt>terminfo</tt> database for
7076 <tt>xterm</tt> and others. On these systems the
7077 <tt>Delete</tt> key will not work correctly when you
7078 log in from a system conforming to our policy, but
7079 <tt><--</tt> will.
7086 <heading>Environment variables</heading>
7089 A program must not depend on environment variables to get
7090 reasonable defaults. (That's because these environment
7091 variables would have to be set in a system-wide
7092 configuration file like <file>/etc/profile</file>, which is not
7093 supported by all shells.)
7097 If a program usually depends on environment variables for its
7098 configuration, the program should be changed to fall back to
7099 a reasonable default configuration if these environment
7100 variables are not present. If this cannot be done easily
7101 (e.g., if the source code of a non-free program is not
7102 available), the program must be replaced by a small
7103 "wrapper" shell script which sets the environment variables
7104 if they are not already defined, and calls the original program.
7108 Here is an example of a wrapper script for this purpose:
7110 <example compact="compact">
7112 BAR=${BAR:-/var/lib/fubar}
7114 exec /usr/lib/foo/foo "$@"
7119 Furthermore, as <file>/etc/profile</file> is a configuration
7120 file of the <prgn>base-files</prgn> package, other packages must
7121 not put any environment variables or other commands into that
7126 <sect id="doc-base">
7127 <heading>Registering Documents using doc-base</heading>
7130 The <package>doc-base</package> package implements a
7131 flexible mechanism for handling and presenting
7132 documentation. The recommended practice is for every Debian
7133 package that provides online documentation (other than just
7134 manual pages) to register these documents with
7135 <package>doc-base</package> by installing a
7136 <package>doc-base</package> control file via the
7137 <prgn/install-docs/ script at installation time and
7138 de-register the manuals again when the package is removed.
7141 Please refer to the documentation that comes with the
7142 <package>doc-base</package> package for information and
7151 <heading>Files</heading>
7153 <sect id="binaries">
7154 <heading>Binaries</heading>
7157 Two different packages must not install programs with
7158 different functionality but with the same filenames. (The
7159 case of two programs having the same functionality but
7160 different implementations is handled via "alternatives" or
7161 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7162 <ref id="conflicts"> respectively.) If this case happens,
7163 one of the programs must be renamed. The maintainers should
7164 report this to the <tt>debian-devel</tt> mailing list and
7165 try to find a consensus about which program will have to be
7166 renamed. If a consensus cannot be reached, <em>both</em>
7167 programs must be renamed.
7171 By default, when a package is being built, any binaries
7172 created should include debugging information, as well as
7173 being compiled with optimization. You should also turn on
7174 as many reasonable compilation warnings as possible; this
7175 makes life easier for porters, who can then look at build
7176 logs for possible problems. For the C programming language,
7177 this means the following compilation parameters should be
7179 <example compact="compact">
7181 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7183 INSTALL = install -s # (or use strip on the files in debian/tmp)
7188 Note that by default all installed binaries should be stripped,
7189 either by using the <tt>-s</tt> flag to
7190 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7191 the binaries after they have been copied into
7192 <file>debian/tmp</file> but before the tree is made into a
7197 Although binaries in the build tree should be compiled with
7198 debugging information by default, it can often be difficult to
7199 debug programs if they are also subjected to compiler
7200 optimization. For this reason, it is recommended to support the
7201 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7202 (see <ref id="debianrules-options">). This variable can contain
7203 several flags to change how a package is compiled and built.
7207 It is up to the package maintainer to decide what
7208 compilation options are best for the package. Certain
7209 binaries (such as computationally-intensive programs) will
7210 function better with certain flags (<tt>-O3</tt>, for
7211 example); feel free to use them. Please use good judgment
7212 here. Don't use flags for the sake of it; only use them
7213 if there is good reason to do so. Feel free to override
7214 the upstream author's ideas about which compilation
7215 options are best: they are often inappropriate for our
7221 <sect id="libraries">
7222 <heading>Libraries</heading>
7225 If the package is <strong>architecture: any</strong>, then
7226 the shared library compilation and linking flags must have
7227 <tt>-fPIC</tt>, or the package shall not build on some of
7228 the supported architectures<footnote>
7230 If you are using GCC, <tt>-fPIC</tt> produces code with
7231 relocatable position independent code, which is required for
7232 most architectures to create a shared library, with i386 and
7233 perhaps some others where non position independent code is
7234 permitted in a shared library.
7237 Position independent code may have a performance penalty,
7238 especially on <tt>i386</tt>. However, in most cases the
7239 speed penalty must be measured against the memory wasted on
7240 the few architectures where non position independent code is
7243 </footnote>. Any exception to this rule must be discussed on
7244 the mailing list <em>debian-devel@lists.debian.org</em>, and
7245 a rough consensus obtained. The reasons for not compiling
7246 with <tt>-fPIC</tt> flag must be recorded in the file
7247 <tt>README.Debian</tt>, and care must be taken to either
7248 restrict the architecture or arrange for <tt>-fPIC</tt> to
7249 be used on architectures where it is required.<footnote>
7251 Some of the reasons why this might be required is if the
7252 library contains hand crafted assembly code that is not
7253 relocatable, the speed penalty is excessive for compute
7254 intensive libs, and similar reasons.
7259 As to the static libraries, the common case is not to have
7260 relocatable code, since there is no benefit, unless in specific
7261 cases; therefore the static version must not be compiled
7262 with the <tt>-fPIC</tt> flag. Any exception to this rule
7263 should be discussed on the mailing list
7264 <em>debian-devel@lists.debian.org</em>, and the reasons for
7265 compiling with the <tt>-fPIC</tt> flag must be recorded in
7266 the file <tt>README.Debian</tt>. <footnote>
7268 Some of the reasons for linking static libraries with
7269 the <tt>-fPIC</tt> flag are if, for example, one needs a
7270 Perl API for a library that is under rapid development,
7271 and has an unstable API, so shared libraries are
7272 pointless at this phase of the library's development. In
7273 that case, since Perl needs a library with relocatable
7274 code, it may make sense to create a static library with
7275 relocatable code. Another reason cited is if you are
7276 distilling various libraries into a common shared
7277 library, like <tt>mklibs</tt> does in the Debian
7283 In other words, if both a shared and a static library is
7284 being built, each source unit (<tt>*.c</tt>, for example,
7285 for C files) will need to be compiled twice, for the normal
7290 Libraries should be built with threading support and to be
7291 thread-safe if the library supports this.
7295 Although not enforced by the build tools, shared libraries
7296 must be linked against all libraries that they use symbols from
7297 in the same way that binaries are. This ensures the correct
7298 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7299 system and guarantees that all libraries can be safely opened
7300 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7301 option <tt>-Wl,-z,defs</tt> when building a shared library.
7302 Since this option enforces symbol resolution at build time,
7303 a missing library reference will be caught early as a fatal
7308 All installed shared libraries should be stripped with
7309 <example compact="compact">
7310 strip --strip-unneeded <var>your-lib</var>
7312 (The option <tt>--strip-unneeded</tt> makes
7313 <prgn>strip</prgn> remove only the symbols which aren't
7314 needed for relocation processing.) Shared libraries can
7315 function perfectly well when stripped, since the symbols for
7316 dynamic linking are in a separate part of the ELF object
7318 You might also want to use the options
7319 <tt>--remove-section=.comment</tt> and
7320 <tt>--remove-section=.note</tt> on both shared libraries
7321 and executables, and <tt>--strip-debug</tt> on static
7327 Note that under some circumstances it may be useful to
7328 install a shared library unstripped, for example when
7329 building a separate package to support debugging.
7333 Shared object files (often <file>.so</file> files) that are not
7334 public libraries, that is, they are not meant to be linked
7335 to by third party executables (binaries of other packages),
7336 should be installed in subdirectories of the
7337 <file>/usr/lib</file> directory. Such files are exempt from the
7338 rules that govern ordinary shared libraries, except that
7339 they must not be installed executable and should be
7341 A common example are the so-called "plug-ins",
7342 internal shared objects that are dynamically loaded by
7343 programs using <manref name="dlopen" section="3">.
7348 Packages that use <prgn>libtool</prgn> to create and install
7349 their shared libraries install a file containing additional
7350 metadata (ending in <file>.la</file>) alongside the library.
7351 For public libraries intended for use by other packages, these
7352 files normally should not be included in the Debian package,
7353 since the information they include is not necessary to link with
7354 the shared library on Debian and can add unnecessary additional
7355 dependencies to other programs or libraries.<footnote>
7356 These files store, among other things, all libraries on which
7357 that shared library depends. Unfortunately, if
7358 the <file>.la</file> file is present and contains that
7359 dependency information, using <prgn>libtool</prgn> when
7360 linking against that library will cause the resulting program
7361 or library to be linked against those dependencies as well,
7362 even if this is unnecessary. This can create unneeded
7363 dependencies on shared library packages that would otherwise
7364 be hidden behind the library ABI, and can make library
7365 transitions to new SONAMEs unnecessarily complicated and
7366 difficult to manage.
7368 If the <file>.la</file> file is required for that library (if,
7369 for instance, it's loaded via <tt>libltdl</tt> in a way that
7370 requires that meta-information), the <tt>dependency_libs</tt>
7371 setting in the <file>.la</file> file should normally be set to
7372 the empty string. If the shared library development package has
7373 historically included the <file>.la</file>, it must be retained
7374 in the development package (with <tt>dependency_libs</tt>
7375 emptied) until all libraries that depend on it have removed or
7376 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7377 files to prevent linking with those other libraries
7378 using <prgn>libtool</prgn> from failing.
7382 If the <file>.la</file> must be included, it should be included
7383 in the development (<tt>-dev</tt>) package, unless the library
7384 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7385 library. If it is intended for use with <tt>libltdl</tt>,
7386 the <file>.la</file> files must go in the run-time library
7391 These requirements for handling of <file>.la</file> files do not
7392 apply to loadable modules or libraries not installed in
7393 directories searched by default by the dynamic linker. Packages
7394 installing loadable modules will frequently need to install
7395 the <file>.la</file> files alongside the modules so that they
7396 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7397 does not need to be modified for libraries or modules that are
7398 not installed in directories searched by the dynamic linker by
7399 default and not intended for use by other packages.
7403 You must make sure that you use only released versions of
7404 shared libraries to build your packages; otherwise other
7405 users will not be able to run your binaries
7406 properly. Producing source packages that depend on
7407 unreleased compilers is also usually a bad
7414 <heading>Shared libraries</heading>
7416 This section has moved to <ref id="sharedlibs">.
7422 <heading>Scripts</heading>
7425 All command scripts, including the package maintainer
7426 scripts inside the package and used by <prgn>dpkg</prgn>,
7427 should have a <tt>#!</tt> line naming the shell to be used
7432 In the case of Perl scripts this should be
7433 <tt>#!/usr/bin/perl</tt>.
7437 When scripts are installed into a directory in the system
7438 PATH, the script name should not include an extension such
7439 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7440 language currently used to implement it.
7443 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7444 <file>init.d</file> scripts should almost certainly start
7445 with <tt>set -e</tt> so that errors are detected.
7446 <file>init.d</file> scripts are something of a special case, due
7447 to how frequently they need to call commands that are allowed to
7448 fail, and it may instead be easier to check the exit status of
7449 commands directly. See <ref id="writing-init"> for more
7450 information about writing <file>init.d</file> scripts.
7453 Every script should use <tt>set -e</tt> or check the exit status
7454 of <em>every</em> command.
7457 Scripts may assume that <file>/bin/sh</file> implements the
7458 SUSv3 Shell Command Language<footnote>
7459 Single UNIX Specification, version 3, which is also IEEE
7460 1003.1-2004 (POSIX), and is available on the World Wide Web
7461 from <url id="http://www.unix.org/version3/online.html"
7462 name="The Open Group"> after free
7463 registration.</footnote>
7464 plus the following additional features not mandated by
7466 These features are in widespread use in the Linux community
7467 and are implemented in all of bash, dash, and ksh, the most
7468 common shells users may wish to use as <file>/bin/sh</file>.
7471 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7472 must not generate a newline.</item>
7473 <item><tt>test</tt>, if implemented as a shell built-in, must
7474 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7476 <item><tt>local</tt> to create a scoped variable must be
7477 supported, including listing multiple variables in a single
7478 local command and assigning a value to a variable at the
7479 same time as localizing it. <tt>local</tt> may or
7480 may not preserve the variable value from an outer scope if
7481 no assignment is present. Uses such as:
7485 # ... use a, b, c, d ...
7488 must be supported and must set the value of <tt>c</tt> to
7492 If a shell script requires non-SUSv3 features from the shell
7493 interpreter other than those listed above, the appropriate shell
7494 must be specified in the first line of the script (e.g.,
7495 <tt>#!/bin/bash</tt>) and the package must depend on the package
7496 providing the shell (unless the shell package is marked
7497 "Essential", as in the case of <prgn>bash</prgn>).
7501 You may wish to restrict your script to SUSv3 features plus the
7502 above set when possible so that it may use <file>/bin/sh</file>
7503 as its interpreter. If your script works with <prgn>dash</prgn>
7504 (originally called <prgn>ash</prgn>), it probably complies with
7505 the above requirements, but if you are in doubt, use
7506 <file>/bin/bash</file>.
7510 Perl scripts should check for errors when making any
7511 system calls, including <tt>open</tt>, <tt>print</tt>,
7512 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7516 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7517 scripting languages. See <em>Csh Programming Considered
7518 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7519 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7520 If an upstream package comes with <prgn>csh</prgn> scripts
7521 then you must make sure that they start with
7522 <tt>#!/bin/csh</tt> and make your package depend on the
7523 <prgn>c-shell</prgn> virtual package.
7527 Any scripts which create files in world-writeable
7528 directories (e.g., in <file>/tmp</file>) must use a
7529 mechanism which will fail atomically if a file with the same
7530 name already exists.
7534 The Debian base system provides the <prgn>tempfile</prgn>
7535 and <prgn>mktemp</prgn> utilities for use by scripts for
7542 <heading>Symbolic links</heading>
7545 In general, symbolic links within a top-level directory
7546 should be relative, and symbolic links pointing from one
7547 top-level directory into another should be absolute. (A
7548 top-level directory is a sub-directory of the root
7549 directory <file>/</file>.)
7553 In addition, symbolic links should be specified as short as
7554 possible, i.e., link targets like <file>foo/../bar</file> are
7559 Note that when creating a relative link using
7560 <prgn>ln</prgn> it is not necessary for the target of the
7561 link to exist relative to the working directory you're
7562 running <prgn>ln</prgn> from, nor is it necessary to change
7563 directory to the directory where the link is to be made.
7564 Simply include the string that should appear as the target
7565 of the link (this will be a pathname relative to the
7566 directory in which the link resides) as the first argument
7571 For example, in your <prgn>Makefile</prgn> or
7572 <file>debian/rules</file>, you can do things like:
7573 <example compact="compact">
7574 ln -fs gcc $(prefix)/bin/cc
7575 ln -fs gcc debian/tmp/usr/bin/cc
7576 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7577 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7582 A symbolic link pointing to a compressed file should always
7583 have the same file extension as the referenced file. (For
7584 example, if a file <file>foo.gz</file> is referenced by a
7585 symbolic link, the filename of the link has to end with
7586 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7591 <heading>Device files</heading>
7594 Packages must not include device files or named pipes in the
7599 If a package needs any special device files that are not
7600 included in the base system, it must call
7601 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7602 after notifying the user<footnote>
7603 This notification could be done via a (low-priority)
7604 debconf message, or an echo (printf) statement.
7609 Packages must not remove any device files in the
7610 <prgn>postrm</prgn> or any other script. This is left to the
7611 system administrator.
7615 Debian uses the serial devices
7616 <file>/dev/ttyS*</file>. Programs using the old
7617 <file>/dev/cu*</file> devices should be changed to use
7618 <file>/dev/ttyS*</file>.
7622 Named pipes needed by the package must be created in
7623 the <prgn>postinst</prgn> script<footnote>
7624 It's better to use <prgn>mkfifo</prgn> rather
7625 than <prgn>mknod</prgn> to create named pipes so that
7626 automated checks for packages incorrectly creating device
7627 files with <prgn>mknod</prgn> won't have false positives.
7628 </footnote> and removed in
7629 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7634 <sect id="config-files">
7635 <heading>Configuration files</heading>
7638 <heading>Definitions</heading>
7642 <tag>configuration file</tag>
7644 A file that affects the operation of a program, or
7645 provides site- or host-specific information, or
7646 otherwise customizes the behavior of a program.
7647 Typically, configuration files are intended to be
7648 modified by the system administrator (if needed or
7649 desired) to conform to local policy or to provide
7650 more useful site-specific behavior.
7653 <tag><tt>conffile</tt></tag>
7655 A file listed in a package's <tt>conffiles</tt>
7656 file, and is treated specially by <prgn>dpkg</prgn>
7657 (see <ref id="configdetails">).
7663 The distinction between these two is important; they are
7664 not interchangeable concepts. Almost all
7665 <tt>conffile</tt>s are configuration files, but many
7666 configuration files are not <tt>conffiles</tt>.
7670 As noted elsewhere, <file>/etc/init.d</file> scripts,
7671 <file>/etc/default</file> files, scripts installed in
7672 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7673 configuration installed in <file>/etc/cron.d</file> must be
7674 treated as configuration files. In general, any script that
7675 embeds configuration information is de-facto a configuration
7676 file and should be treated as such.
7681 <heading>Location</heading>
7684 Any configuration files created or used by your package
7685 must reside in <file>/etc</file>. If there are several,
7686 consider creating a subdirectory of <file>/etc</file>
7687 named after your package.
7691 If your package creates or uses configuration files
7692 outside of <file>/etc</file>, and it is not feasible to modify
7693 the package to use <file>/etc</file> directly, put the files
7694 in <file>/etc</file> and create symbolic links to those files
7695 from the location that the package requires.
7700 <heading>Behavior</heading>
7703 Configuration file handling must conform to the following
7705 <list compact="compact">
7707 local changes must be preserved during a package
7711 configuration files must be preserved when the
7712 package is removed, and only deleted when the
7716 Obsolete configuration files without local changes may be
7717 removed by the package during upgrade.
7721 The easy way to achieve this behavior is to make the
7722 configuration file a <tt>conffile</tt>. This is
7723 appropriate only if it is possible to distribute a default
7724 version that will work for most installations, although
7725 some system administrators may choose to modify it. This
7726 implies that the default version will be part of the
7727 package distribution, and must not be modified by the
7728 maintainer scripts during installation (or at any other
7733 In order to ensure that local changes are preserved
7734 correctly, no package may contain or make hard links to
7735 conffiles.<footnote>
7736 Rationale: There are two problems with hard links.
7737 The first is that some editors break the link while
7738 editing one of the files, so that the two files may
7739 unwittingly become unlinked and different. The second
7740 is that <prgn>dpkg</prgn> might break the hard link
7741 while upgrading <tt>conffile</tt>s.
7746 The other way to do it is via the maintainer scripts. In
7747 this case, the configuration file must not be listed as a
7748 <tt>conffile</tt> and must not be part of the package
7749 distribution. If the existence of a file is required for
7750 the package to be sensibly configured it is the
7751 responsibility of the package maintainer to provide
7752 maintainer scripts which correctly create, update and
7753 maintain the file and remove it on purge. (See <ref
7754 id="maintainerscripts"> for more information.) These
7755 scripts must be idempotent (i.e., must work correctly if
7756 <prgn>dpkg</prgn> needs to re-run them due to errors
7757 during installation or removal), must cope with all the
7758 variety of ways <prgn>dpkg</prgn> can call maintainer
7759 scripts, must not overwrite or otherwise mangle the user's
7760 configuration without asking, must not ask unnecessary
7761 questions (particularly during upgrades), and must
7762 otherwise be good citizens.
7766 The scripts are not required to configure every possible
7767 option for the package, but only those necessary to get
7768 the package running on a given system. Ideally the
7769 sysadmin should not have to do any configuration other
7770 than that done (semi-)automatically by the
7771 <prgn>postinst</prgn> script.
7775 A common practice is to create a script called
7776 <file><var>package</var>-configure</file> and have the
7777 package's <prgn>postinst</prgn> call it if and only if the
7778 configuration file does not already exist. In certain
7779 cases it is useful for there to be an example or template
7780 file which the maintainer scripts use. Such files should
7781 be in <file>/usr/share/<var>package</var></file> or
7782 <file>/usr/lib/<var>package</var></file> (depending on whether
7783 they are architecture-independent or not). There should
7784 be symbolic links to them from
7785 <file>/usr/share/doc/<var>package</var>/examples</file> if
7786 they are examples, and should be perfectly ordinary
7787 <prgn>dpkg</prgn>-handled files (<em>not</em>
7788 configuration files).
7792 These two styles of configuration file handling must
7793 not be mixed, for that way lies madness:
7794 <prgn>dpkg</prgn> will ask about overwriting the file
7795 every time the package is upgraded.
7800 <heading>Sharing configuration files</heading>
7803 Packages which specify the same file as a
7804 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7805 with each other. (This is an instance of the general rule
7806 about not sharing files. Note that neither alternatives
7807 nor diversions are likely to be appropriate in this case;
7808 in particular, <prgn>dpkg</prgn> does not handle diverted
7809 <tt>conffile</tt>s well.)
7813 The maintainer scripts must not alter a <tt>conffile</tt>
7814 of <em>any</em> package, including the one the scripts
7819 If two or more packages use the same configuration file
7820 and it is reasonable for both to be installed at the same
7821 time, one of these packages must be defined as
7822 <em>owner</em> of the configuration file, i.e., it will be
7823 the package which handles that file as a configuration
7824 file. Other packages that use the configuration file must
7825 depend on the owning package if they require the
7826 configuration file to operate. If the other package will
7827 use the configuration file if present, but is capable of
7828 operating without it, no dependency need be declared.
7832 If it is desirable for two or more related packages to
7833 share a configuration file <em>and</em> for all of the
7834 related packages to be able to modify that configuration
7835 file, then the following should be done:
7836 <enumlist compact="compact">
7838 One of the related packages (the "owning" package)
7839 will manage the configuration file with maintainer
7840 scripts as described in the previous section.
7843 The owning package should also provide a program
7844 that the other packages may use to modify the
7848 The related packages must use the provided program
7849 to make any desired modifications to the
7850 configuration file. They should either depend on
7851 the core package to guarantee that the configuration
7852 modifier program is available or accept gracefully
7853 that they cannot modify the configuration file if it
7854 is not. (This is in addition to the fact that the
7855 configuration file may not even be present in the
7862 Sometimes it's appropriate to create a new package which
7863 provides the basic infrastructure for the other packages
7864 and which manages the shared configuration files. (The
7865 <tt>sgml-base</tt> package is a good example.)
7870 <heading>User configuration files ("dotfiles")</heading>
7873 The files in <file>/etc/skel</file> will automatically be
7874 copied into new user accounts by <prgn>adduser</prgn>.
7875 No other program should reference the files in
7876 <file>/etc/skel</file>.
7880 Therefore, if a program needs a dotfile to exist in
7881 advance in <file>$HOME</file> to work sensibly, that dotfile
7882 should be installed in <file>/etc/skel</file> and treated as a
7887 However, programs that require dotfiles in order to
7888 operate sensibly are a bad thing, unless they do create
7889 the dotfiles themselves automatically.
7893 Furthermore, programs should be configured by the Debian
7894 default installation to behave as closely to the upstream
7895 default behavior as possible.
7899 Therefore, if a program in a Debian package needs to be
7900 configured in some way in order to operate sensibly, that
7901 should be done using a site-wide configuration file placed
7902 in <file>/etc</file>. Only if the program doesn't support a
7903 site-wide default configuration and the package maintainer
7904 doesn't have time to add it may a default per-user file be
7905 placed in <file>/etc/skel</file>.
7909 <file>/etc/skel</file> should be as empty as we can make it.
7910 This is particularly true because there is no easy (or
7911 necessarily desirable) mechanism for ensuring that the
7912 appropriate dotfiles are copied into the accounts of
7913 existing users when a package is installed.
7919 <heading>Log files</heading>
7921 Log files should usually be named
7922 <file>/var/log/<var>package</var>.log</file>. If you have many
7923 log files, or need a separate directory for permission
7924 reasons (<file>/var/log</file> is writable only by
7925 <file>root</file>), you should usually create a directory named
7926 <file>/var/log/<var>package</var></file> and place your log
7931 Log files must be rotated occasionally so that they don't
7932 grow indefinitely; the best way to do this is to drop a log
7933 rotation configuration file into the directory
7934 <file>/etc/logrotate.d</file> and use the facilities provided by
7935 logrotate.<footnote>
7937 The traditional approach to log files has been to set up
7938 <em>ad hoc</em> log rotation schemes using simple shell
7939 scripts and cron. While this approach is highly
7940 customizable, it requires quite a lot of sysadmin work.
7941 Even though the original Debian system helped a little
7942 by automatically installing a system which can be used
7943 as a template, this was deemed not enough.
7947 The use of <prgn>logrotate</prgn>, a program developed
7948 by Red Hat, is better, as it centralizes log management.
7949 It has both a configuration file
7950 (<file>/etc/logrotate.conf</file>) and a directory where
7951 packages can drop their individual log rotation
7952 configurations (<file>/etc/logrotate.d</file>).
7955 Here is a good example for a logrotate config
7956 file (for more information see <manref name="logrotate"
7958 <example compact="compact">
7959 /var/log/foo/*.log {
7964 /etc/init.d/foo force-reload
7968 This rotates all files under <file>/var/log/foo</file>, saves 12
7969 compressed generations, and forces the daemon to reload its
7970 configuration information after the log rotation.
7974 Log files should be removed when the package is
7975 purged (but not when it is only removed). This should be
7976 done by the <prgn>postrm</prgn> script when it is called
7977 with the argument <tt>purge</tt> (see <ref
7978 id="removedetails">).
7983 <heading>Permissions and owners</heading>
7986 The rules in this section are guidelines for general use.
7987 If necessary you may deviate from the details below.
7988 However, if you do so you must make sure that what is done
7989 is secure and you should try to be as consistent as possible
7990 with the rest of the system. You should probably also
7991 discuss it on <prgn>debian-devel</prgn> first.
7995 Files should be owned by <tt>root:root</tt>, and made
7996 writable only by the owner and universally readable (and
7997 executable, if appropriate), that is mode 644 or 755.
8001 Directories should be mode 755 or (for group-writability)
8002 mode 2775. The ownership of the directory should be
8003 consistent with its mode: if a directory is mode 2775, it
8004 should be owned by the group that needs write access to
8007 When a package is upgraded, and the owner or permissions
8008 of a file included in the package has changed, dpkg
8009 arranges for the ownership and permissions to be
8010 correctly set upon installation. However, this does not
8011 extend to directories; the permissions and ownership of
8012 directories already on the system does not change on
8013 install or upgrade of packages. This makes sense, since
8014 otherwise common directories like <tt>/usr</tt> would
8015 always be in flux. To correctly change permissions of a
8016 directory the package owns, explicit action is required,
8017 usually in the <tt>postinst</tt> script. Care must be
8018 taken to handle downgrades as well, in that case.
8025 Setuid and setgid executables should be mode 4755 or 2755
8026 respectively, and owned by the appropriate user or group.
8027 They should not be made unreadable (modes like 4711 or
8028 2711 or even 4111); doing so achieves no extra security,
8029 because anyone can find the binary in the freely available
8030 Debian package; it is merely inconvenient. For the same
8031 reason you should not restrict read or execute permissions
8032 on non-set-id executables.
8036 Some setuid programs need to be restricted to particular
8037 sets of users, using file permissions. In this case they
8038 should be owned by the uid to which they are set-id, and by
8039 the group which should be allowed to execute them. They
8040 should have mode 4754; again there is no point in making
8041 them unreadable to those users who must not be allowed to
8046 It is possible to arrange that the system administrator can
8047 reconfigure the package to correspond to their local
8048 security policy by changing the permissions on a binary:
8049 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8050 described below.<footnote>
8051 Ordinary files installed by <prgn>dpkg</prgn> (as
8052 opposed to <tt>conffile</tt>s and other similar objects)
8053 normally have their permissions reset to the distributed
8054 permissions when the package is reinstalled. However,
8055 the use of <prgn>dpkg-statoverride</prgn> overrides this
8058 Another method you should consider is to create a group for
8059 people allowed to use the program(s) and make any setuid
8060 executables executable only by that group.
8064 If you need to create a new user or group for your package
8065 there are two possibilities. Firstly, you may need to
8066 make some files in the binary package be owned by this
8067 user or group, or you may need to compile the user or
8068 group id (rather than just the name) into the binary
8069 (though this latter should be avoided if possible, as in
8070 this case you need a statically allocated id).</p>
8073 If you need a statically allocated id, you must ask for a
8074 user or group id from the <tt>base-passwd</tt> maintainer,
8075 and must not release the package until you have been
8076 allocated one. Once you have been allocated one you must
8077 either make the package depend on a version of the
8078 <tt>base-passwd</tt> package with the id present in
8079 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8080 your package to create the user or group itself with the
8081 correct id (using <tt>adduser</tt>) in its
8082 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8083 the <prgn>postinst</prgn> is to be preferred if it is
8084 possible, otherwise a pre-dependency will be needed on the
8085 <tt>adduser</tt> package.)
8089 On the other hand, the program might be able to determine
8090 the uid or gid from the user or group name at runtime, so
8091 that a dynamically allocated id can be used. In this case
8092 you should choose an appropriate user or group name,
8093 discussing this on <prgn>debian-devel</prgn> and checking
8094 with the <package/base-passwd/ maintainer that it is unique and that
8095 they do not wish you to use a statically allocated id
8096 instead. When this has been checked you must arrange for
8097 your package to create the user or group if necessary using
8098 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8099 <prgn>postinst</prgn> script (again, the latter is to be
8100 preferred if it is possible).
8104 Note that changing the numeric value of an id associated
8105 with a name is very difficult, and involves searching the
8106 file system for all appropriate files. You need to think
8107 carefully whether a static or dynamic id is required, since
8108 changing your mind later will cause problems.
8111 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8113 This section is not intended as policy, but as a
8114 description of the use of <prgn>dpkg-statoverride</prgn>.
8118 If a system administrator wishes to have a file (or
8119 directory or other such thing) installed with owner and
8120 permissions different from those in the distributed Debian
8121 package, they can use the <prgn>dpkg-statoverride</prgn>
8122 program to instruct <prgn>dpkg</prgn> to use the different
8123 settings every time the file is installed. Thus the
8124 package maintainer should distribute the files with their
8125 normal permissions, and leave it for the system
8126 administrator to make any desired changes. For example, a
8127 daemon which is normally required to be setuid root, but
8128 in certain situations could be used without being setuid,
8129 should be installed setuid in the <tt>.deb</tt>. Then the
8130 local system administrator can change this if they wish.
8131 If there are two standard ways of doing it, the package
8132 maintainer can use <tt>debconf</tt> to find out the
8133 preference, and call <prgn>dpkg-statoverride</prgn> in the
8134 maintainer script if necessary to accommodate the system
8135 administrator's choice. Care must be taken during
8136 upgrades to not override an existing setting.
8140 Given the above, <prgn>dpkg-statoverride</prgn> is
8141 essentially a tool for system administrators and would not
8142 normally be needed in the maintainer scripts. There is
8143 one type of situation, though, where calls to
8144 <prgn>dpkg-statoverride</prgn> would be needed in the
8145 maintainer scripts, and that involves packages which use
8146 dynamically allocated user or group ids. In such a
8147 situation, something like the following idiom can be very
8148 helpful in the package's <prgn>postinst</prgn>, where
8149 <tt>sysuser</tt> is a dynamically allocated id:
8151 for i in /usr/bin/foo /usr/sbin/bar
8153 # only do something when no setting exists
8154 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8156 #include: debconf processing, question about foo and bar
8157 if [ "$RET" = "true" ] ; then
8158 dpkg-statoverride --update --add sysuser root 4755 $i
8163 The corresponding code to remove the override when the package
8166 for i in /usr/bin/foo /usr/sbin/bar
8168 if dpkg-statoverride --list $i >/dev/null 2>&1
8170 dpkg-statoverride --remove $i
8180 <chapt id="customized-programs">
8181 <heading>Customized programs</heading>
8183 <sect id="arch-spec">
8184 <heading>Architecture specification strings</heading>
8187 If a program needs to specify an <em>architecture specification
8188 string</em> in some place, it should select one of the strings
8189 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8190 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8191 part is sometimes elided, as when the OS is Linux.
8195 Note that we don't want to use
8196 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8197 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8198 since this would make our programs incompatible with other
8199 Linux distributions. We also don't use something like
8200 <tt><var>arch</var>-unknown-linux</tt>, since the
8201 <tt>unknown</tt> does not look very good.
8204 <sect1 id="arch-wildcard-spec">
8205 <heading>Architecture wildcards</heading>
8208 A package may specify an architecture wildcard. Architecture
8209 wildcards are in the format <tt>any</tt> (which matches every
8210 architecture), <tt><var>os</var></tt>-any, or
8211 any-<tt><var>cpu</var></tt>. <footnote>
8212 Internally, the package system normalizes the GNU triplets
8213 and the Debian arches into Debian arch triplets (which are
8214 kind of inverted GNU triplets), with the first component of
8215 the triplet representing the libc and ABI in use, and then
8216 does matching against those triplets. However, such
8217 triplets are an internal implementation detail that should
8218 not be used by packages directly. The libc and ABI portion
8219 is handled internally by the package system based on
8220 the <var>os</var> and <var>cpu</var>.
8227 <heading>Daemons</heading>
8230 The configuration files <file>/etc/services</file>,
8231 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8232 by the <prgn>netbase</prgn> package and must not be modified
8237 If a package requires a new entry in one of these files, the
8238 maintainer should get in contact with the
8239 <prgn>netbase</prgn> maintainer, who will add the entries
8240 and release a new version of the <prgn>netbase</prgn>
8245 The configuration file <file>/etc/inetd.conf</file> must not be
8246 modified by the package's scripts except via the
8247 <prgn>update-inetd</prgn> script or the
8248 <file>DebianNet.pm</file> Perl module. See their documentation
8249 for details on how to add entries.
8253 If a package wants to install an example entry into
8254 <file>/etc/inetd.conf</file>, the entry must be preceded with
8255 exactly one hash character (<tt>#</tt>). Such lines are
8256 treated as "commented out by user" by the
8257 <prgn>update-inetd</prgn> script and are not changed or
8258 activated during package updates.
8263 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8267 Some programs need to create pseudo-ttys. This should be done
8268 using Unix98 ptys if the C library supports it. The resulting
8269 program must not be installed setuid root, unless that
8270 is required for other functionality.
8274 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8275 <file>/var/log/lastlog</file> must be installed writable by
8276 group <tt>utmp</tt>. Programs which need to modify those
8277 files must be installed setgid <tt>utmp</tt>.
8282 <heading>Editors and pagers</heading>
8285 Some programs have the ability to launch an editor or pager
8286 program to edit or display a text document. Since there are
8287 lots of different editors and pagers available in the Debian
8288 distribution, the system administrator and each user should
8289 have the possibility to choose their preferred editor and
8294 In addition, every program should choose a good default
8295 editor/pager if none is selected by the user or system
8300 Thus, every program that launches an editor or pager must
8301 use the EDITOR or PAGER environment variable to determine
8302 the editor or pager the user wishes to use. If these
8303 variables are not set, the programs <file>/usr/bin/editor</file>
8304 and <file>/usr/bin/pager</file> should be used, respectively.
8308 These two files are managed through the <prgn>dpkg</prgn>
8309 "alternatives" mechanism. Thus every package providing an
8310 editor or pager must call the
8311 <prgn>update-alternatives</prgn> script to register these
8316 If it is very hard to adapt a program to make use of the
8317 EDITOR or PAGER variables, that program may be configured to
8318 use <file>/usr/bin/sensible-editor</file> and
8319 <file>/usr/bin/sensible-pager</file> as the editor or pager
8320 program respectively. These are two scripts provided in the
8321 <package>sensible-utils</package> package that check the EDITOR
8322 and PAGER variables and launch the appropriate program, and fall
8323 back to <file>/usr/bin/editor</file>
8324 and <file>/usr/bin/pager</file> if the variable is not set.
8328 A program may also use the VISUAL environment variable to
8329 determine the user's choice of editor. If it exists, it
8330 should take precedence over EDITOR. This is in fact what
8331 <file>/usr/bin/sensible-editor</file> does.
8335 It is not required for a package to depend on
8336 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8337 package to provide such virtual packages.<footnote>
8338 The Debian base system already provides an editor and a
8344 <sect id="web-appl">
8345 <heading>Web servers and applications</heading>
8348 This section describes the locations and URLs that should
8349 be used by all web servers and web applications in the
8356 Cgi-bin executable files are installed in the
8358 <example compact="compact">
8359 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8361 or a subdirectory of that directory, and should be
8363 <example compact="compact">
8364 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8366 (possibly with a subdirectory name
8367 before <var>cgi-bin-name</var>).
8371 <p>Access to HTML documents</p>
8374 HTML documents for a package are stored in
8375 <file>/usr/share/doc/<var>package</var></file>
8376 and can be referred to as
8377 <example compact="compact">
8378 http://localhost/doc/<var>package</var>/<var>filename</var>
8383 The web server should restrict access to the document
8384 tree so that only clients on the same host can read
8385 the documents. If the web server does not support such
8386 access controls, then it should not provide access at
8387 all, or ask about providing access during installation.
8392 <p>Access to images</p>
8394 It is recommended that images for a package be stored
8395 in <tt>/usr/share/images/<var>package</var></tt> and
8396 may be referred to through an alias <tt>/images/</tt>
8399 http://localhost/images/<package>/<filename>
8406 <p>Web Document Root</p>
8409 Web Applications should try to avoid storing files in
8410 the Web Document Root. Instead they should use the
8411 /usr/share/doc/<var>package</var> directory for
8412 documents and register the Web Application via the
8413 <package>doc-base</package> package. If access to the
8414 web document root is unavoidable then use
8415 <example compact="compact">
8418 as the Document Root. This might be just a symbolic
8419 link to the location where the system administrator
8420 has put the real document root.
8423 <item><p>Providing httpd and/or httpd-cgi</p>
8425 All web servers should provide the virtual package
8426 <tt>httpd</tt>. If a web server has CGI support it should
8427 provide <tt>httpd-cgi</tt> additionally.
8430 All web applications which do not contain CGI scripts should
8431 depend on <tt>httpd</tt>, all those web applications which
8432 <tt>do</tt> contain CGI scripts, should depend on
8440 <sect id="mail-transport-agents">
8441 <heading>Mail transport, delivery and user agents</heading>
8444 Debian packages which process electronic mail, whether mail
8445 user agents (MUAs) or mail transport agents (MTAs), must
8446 ensure that they are compatible with the configuration
8447 decisions below. Failure to do this may result in lost
8448 mail, broken <tt>From:</tt> lines, and other serious brain
8453 The mail spool is <file>/var/mail</file> and the interface to
8454 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8455 the FHS). On older systems, the mail spool may be
8456 physically located in <file>/var/spool/mail</file>, but all
8457 access to the mail spool should be via the
8458 <file>/var/mail</file> symlink. The mail spool is part of the
8459 base system and not part of the MTA package.
8463 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8464 programs (such as IMAP daemons) must lock the mailbox in an
8465 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8466 be combined with dot locking. To avoid deadlocks, a program
8467 should use <tt>fcntl()</tt> first and dot locking after
8468 this, or alternatively implement the two locking methods in
8469 a non blocking way<footnote>
8470 If it is not possible to establish both locks, the
8471 system shouldn't wait for the second lock to be
8472 established, but remove the first lock, wait a (random)
8473 time, and start over locking again.
8474 </footnote>. Using the functions <tt>maillock</tt> and
8475 <tt>mailunlock</tt> provided by the
8476 <tt>liblockfile*</tt><footnote>
8477 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8478 to use these functions.
8479 </footnote> packages is the recommended way to realize this.
8483 Mailboxes are generally either mode 600 and owned by
8484 <var>user</var> or mode 660 and owned by
8485 <tt><var>user</var>:mail</tt><footnote>
8486 There are two traditional permission schemes for mail spools:
8487 mode 600 with all mail delivery done by processes running as
8488 the destination user, or mode 660 and owned by group mail with
8489 mail delivery done by a process running as a system user in
8490 group mail. Historically, Debian required mode 660 mail
8491 spools to enable the latter model, but that model has become
8492 increasingly uncommon and the principle of least privilege
8493 indicates that mail systems that use the first model should
8494 use permissions of 600. If delivery to programs is permitted,
8495 it's easier to keep the mail system secure if the delivery
8496 agent runs as the destination user. Debian Policy therefore
8497 permits either scheme.
8498 </footnote>. The local system administrator may choose a
8499 different permission scheme; packages should not make
8500 assumptions about the permission and ownership of mailboxes
8501 unless required (such as when creating a new mailbox). A MUA
8502 may remove a mailbox (unless it has nonstandard permissions) in
8503 which case the MTA or another MUA must recreate it if needed.
8507 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8508 be setgid mail to do the locking mentioned above (and
8509 must obviously avoid accessing other users' mailboxes
8510 using this privilege).</p>
8513 <file>/etc/aliases</file> is the source file for the system mail
8514 aliases (e.g., postmaster, usenet, etc.), it is the one
8515 which the sysadmin and <prgn>postinst</prgn> scripts may
8516 edit. After <file>/etc/aliases</file> is edited the program or
8517 human editing it must call <prgn>newaliases</prgn>. All MTA
8518 packages must come with a <prgn>newaliases</prgn> program,
8519 even if it does nothing, but older MTA packages did not do
8520 this so programs should not fail if <prgn>newaliases</prgn>
8521 cannot be found. Note that because of this, all MTA
8522 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8523 <tt>Replaces: mail-transport-agent</tt> control fields.
8527 The convention of writing <tt>forward to
8528 <var>address</var></tt> in the mailbox itself is not
8529 supported. Use a <tt>.forward</tt> file instead.</p>
8532 The <prgn>rmail</prgn> program used by UUCP
8533 for incoming mail should be <file>/usr/sbin/rmail</file>.
8534 Likewise, <prgn>rsmtp</prgn>, for receiving
8535 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8539 If your package needs to know what hostname to use on (for
8540 example) outgoing news and mail messages which are generated
8541 locally, you should use the file <file>/etc/mailname</file>. It
8542 will contain the portion after the username and <tt>@</tt>
8543 (at) sign for email addresses of users on the machine
8544 (followed by a newline).
8548 Such a package should check for the existence of this file
8549 when it is being configured. If it exists, it should be
8550 used without comment, although an MTA's configuration script
8551 may wish to prompt the user even if it finds that this file
8552 exists. If the file does not exist, the package should
8553 prompt the user for the value (preferably using
8554 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8555 as well as using it in the package's configuration. The
8556 prompt should make it clear that the name will not just be
8557 used by that package. For example, in this situation the
8558 <tt>inn</tt> package could say something like:
8559 <example compact="compact">
8560 Please enter the "mail name" of your system. This is the
8561 hostname portion of the address to be shown on outgoing
8562 news and mail messages. The default is
8563 <var>syshostname</var>, your system's host name. Mail
8564 name ["<var>syshostname</var>"]:
8566 where <var>syshostname</var> is the output of <tt>hostname
8572 <heading>News system configuration</heading>
8575 All the configuration files related to the NNTP (news)
8576 servers and clients should be located under
8577 <file>/etc/news</file>.</p>
8580 There are some configuration issues that apply to a number
8581 of news clients and server packages on the machine. These
8585 <tag><file>/etc/news/organization</file></tag>
8587 A string which should appear as the
8588 organization header for all messages posted
8589 by NNTP clients on the machine
8592 <tag><file>/etc/news/server</file></tag>
8594 Contains the FQDN of the upstream NNTP
8595 server, or localhost if the local machine is
8600 Other global files may be added as required for cross-package news
8607 <heading>Programs for the X Window System</heading>
8610 <heading>Providing X support and package priorities</heading>
8613 Programs that can be configured with support for the X
8614 Window System must be configured to do so and must declare
8615 any package dependencies necessary to satisfy their
8616 runtime requirements when using the X Window System. If
8617 such a package is of higher priority than the X packages
8618 on which it depends, it is required that either the
8619 X-specific components be split into a separate package, or
8620 that an alternative version of the package, which includes
8621 X support, be provided, or that the package's priority be
8627 <heading>Packages providing an X server</heading>
8630 Packages that provide an X server that, directly or
8631 indirectly, communicates with real input and display
8632 hardware should declare in their <tt>Provides</tt> control
8633 field that they provide the virtual
8634 package <tt>xserver</tt>.<footnote>
8635 This implements current practice, and provides an
8636 actual policy for usage of the <tt>xserver</tt>
8637 virtual package which appears in the virtual packages
8638 list. In a nutshell, X servers that interface
8639 directly with the display and input hardware or via
8640 another subsystem (e.g., GGI) should provide
8641 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8642 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8648 <heading>Packages providing a terminal emulator</heading>
8651 Packages that provide a terminal emulator for the X Window
8652 System which meet the criteria listed below should declare in
8653 their <tt>Provides</tt> control field that they provide the
8654 virtual package <tt>x-terminal-emulator</tt>. They should
8655 also register themselves as an alternative for
8656 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8661 To be an <tt>x-terminal-emulator</tt>, a program must:
8662 <list compact="compact">
8664 Be able to emulate a DEC VT100 terminal, or a
8665 compatible terminal.
8669 Support the command-line option <tt>-e
8670 <var>command</var></tt>, which creates a new
8671 terminal window<footnote>
8672 "New terminal window" does not necessarily mean
8673 a new top-level X window directly parented by
8674 the window manager; it could, if the terminal
8675 emulator application were so coded, be a new
8676 "view" in a multiple-document interface (MDI).
8678 and runs the specified <var>command</var>,
8679 interpreting the entirety of the rest of the command
8680 line as a command to pass straight to exec, in the
8681 manner that <tt>xterm</tt> does.
8685 Support the command-line option <tt>-T
8686 <var>title</var></tt>, which creates a new terminal
8687 window with the window title <var>title</var>.
8694 <heading>Packages providing a window manager</heading>
8697 Packages that provide a window manager should declare in
8698 their <tt>Provides</tt> control field that they provide the
8699 virtual package <tt>x-window-manager</tt>. They should also
8700 register themselves as an alternative for
8701 <file>/usr/bin/x-window-manager</file>, with a priority
8702 calculated as follows:
8703 <list compact="compact">
8705 Start with a priority of 20.
8709 If the window manager supports the Debian menu
8710 system, add 20 points if this support is available
8711 in the package's default configuration (i.e., no
8712 configuration files belonging to the system or user
8713 have to be edited to activate the feature); if
8714 configuration files must be modified, add only 10
8720 If the window manager complies with <url
8721 id="http://www.freedesktop.org/Standards/wm-spec"
8722 name="The Window Manager Specification Project">,
8723 written by the <url id="http://www.freedesktop.org/"
8724 name="Free Desktop Group">, add 40 points.
8728 If the window manager permits the X session to be
8729 restarted using a <em>different</em> window manager
8730 (without killing the X server) in its default
8731 configuration, add 10 points; otherwise add none.
8738 <heading>Packages providing fonts</heading>
8741 Packages that provide fonts for the X Window
8743 For the purposes of Debian Policy, a "font for the X
8744 Window System" is one which is accessed via X protocol
8745 requests. Fonts for the Linux console, for PostScript
8746 renderer, or any other purpose, do not fit this
8747 definition. Any tool which makes such fonts available
8748 to the X Window System, however, must abide by this
8751 must do a number of things to ensure that they are both
8752 available without modification of the X or font server
8753 configuration, and that they do not corrupt files used by
8754 other font packages to register information about
8758 Fonts of any type supported by the X Window System
8759 must be in a separate binary package from any
8760 executables, libraries, or documentation (except
8761 that specific to the fonts shipped, such as their
8762 license information). If one or more of the fonts
8763 so packaged are necessary for proper operation of
8764 the package with which they are associated the font
8765 package may be Recommended; if the fonts merely
8766 provide an enhancement, a Suggests relationship may
8767 be used. Packages must not Depend on font
8769 This is because the X server may retrieve fonts
8770 from the local file system or over the network
8771 from an X font server; the Debian package system
8772 is empowered to deal only with the local
8778 BDF fonts must be converted to PCF fonts with the
8779 <prgn>bdftopcf</prgn> utility (available in the
8780 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8781 placed in a directory that corresponds to their
8783 <list compact="compact">
8785 100 dpi fonts must be placed in
8786 <file>/usr/share/fonts/X11/100dpi/</file>.
8790 75 dpi fonts must be placed in
8791 <file>/usr/share/fonts/X11/75dpi/</file>.
8795 Character-cell fonts, cursor fonts, and other
8796 low-resolution fonts must be placed in
8797 <file>/usr/share/fonts/X11/misc/</file>.
8803 Type 1 fonts must be placed in
8804 <file>/usr/share/fonts/X11/Type1/</file>. If font
8805 metric files are available, they must be placed here
8810 Subdirectories of <file>/usr/share/fonts/X11/</file>
8811 other than those listed above must be neither
8812 created nor used. (The <file>PEX</file>, <file>CID</file>,
8813 <file>Speedo</file>, and <file>cyrillic</file> directories
8814 are excepted for historical reasons, but installation of
8815 files into these directories remains discouraged.)
8819 Font packages may, instead of placing files directly
8820 in the X font directories listed above, provide
8821 symbolic links in that font directory pointing to
8822 the files' actual location in the filesystem. Such
8823 a location must comply with the FHS.
8827 Font packages should not contain both 75dpi and
8828 100dpi versions of a font. If both are available,
8829 they should be provided in separate binary packages
8830 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8831 the names of the packages containing the
8832 corresponding fonts.
8836 Fonts destined for the <file>misc</file> subdirectory
8837 should not be included in the same package as 75dpi
8838 or 100dpi fonts; instead, they should be provided in
8839 a separate package with <tt>-misc</tt> appended to
8844 Font packages must not provide the files
8845 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8846 <file>fonts.scale</file> in a font directory:
8849 <file>fonts.dir</file> files must not be provided at all.
8853 <file>fonts.alias</file> and <file>fonts.scale</file>
8854 files, if needed, should be provided in the
8856 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8857 where <var>fontdir</var> is the name of the
8859 <file>/usr/share/fonts/X11/</file> where the
8860 package's corresponding fonts are stored
8861 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8862 <var>package</var> is the name of the package
8863 that provides these fonts, and
8864 <var>extension</var> is either <tt>scale</tt>
8865 or <tt>alias</tt>, whichever corresponds to
8872 Font packages must declare a dependency on
8873 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8874 or <tt>Pre-Depends</tt> control field.
8878 Font packages that provide one or more
8879 <file>fonts.scale</file> files as described above must
8880 invoke <prgn>update-fonts-scale</prgn> on each
8881 directory into which they installed fonts
8882 <em>before</em> invoking
8883 <prgn>update-fonts-dir</prgn> on that directory.
8884 This invocation must occur in both the
8885 <prgn>postinst</prgn> (for all arguments) and
8886 <prgn>postrm</prgn> (for all arguments except
8887 <tt>upgrade</tt>) scripts.
8891 Font packages that provide one or more
8892 <file>fonts.alias</file> files as described above must
8893 invoke <prgn>update-fonts-alias</prgn> on each
8894 directory into which they installed fonts. This
8895 invocation must occur in both the
8896 <prgn>postinst</prgn> (for all arguments) and
8897 <prgn>postrm</prgn> (for all arguments except
8898 <tt>upgrade</tt>) scripts.
8902 Font packages must invoke
8903 <prgn>update-fonts-dir</prgn> on each directory into
8904 which they installed fonts. This invocation must
8905 occur in both the <prgn>postinst</prgn> (for all
8906 arguments) and <prgn>postrm</prgn> (for all
8907 arguments except <tt>upgrade</tt>) scripts.
8911 Font packages must not provide alias names for the
8912 fonts they include which collide with alias names
8913 already in use by fonts already packaged.
8917 Font packages must not provide fonts with the same
8918 XLFD registry name as another font already packaged.
8924 <sect1 id="appdefaults">
8925 <heading>Application defaults files</heading>
8928 Application defaults files must be installed in the
8929 directory <file>/etc/X11/app-defaults/</file> (use of a
8930 localized subdirectory of <file>/etc/X11/</file> as described
8931 in the <em>X Toolkit Intrinsics - C Language
8932 Interface</em> manual is also permitted). They must be
8933 registered as <tt>conffile</tt>s or handled as
8934 configuration files.
8938 Customization of programs' X resources may also be
8939 supported with the provision of a file with the same name
8940 as that of the package placed in
8941 the <file>/etc/X11/Xresources/</file> directory, which
8942 must be registered as a <tt>conffile</tt> or handled as a
8943 configuration file.<footnote>
8944 Note that this mechanism is not the same as using
8945 app-defaults; app-defaults are tied to the client
8946 binary on the local file system, whereas X resources
8947 are stored in the X server and affect all connecting
8954 <heading>Installation directory issues</heading>
8957 Historically, packages using the X Window System used a
8958 separate set of installation directories from other packages.
8959 This practice has been discontinued and packages using the X
8960 Window System should now generally be installed in the same
8961 directories as any other package. Specifically, packages must
8962 not install files under the <file>/usr/X11R6/</file> directory
8963 and the <file>/usr/X11R6/</file> directory hierarchy should be
8964 regarded as obsolete.
8968 Include files previously installed under
8969 <file>/usr/X11R6/include/X11/</file> should be installed into
8970 <file>/usr/include/X11/</file>. For files previously
8971 installed into subdirectories of
8972 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8973 determine if subdirectories of <file>/usr/lib/</file> and
8974 <file>/usr/share/</file> can be used. If not, a subdirectory
8975 of <file>/usr/lib/X11/</file> should be used.
8979 Configuration files for window, display, or session managers
8980 or other applications that are tightly integrated with the X
8981 Window System may be placed in a subdirectory
8982 of <file>/etc/X11/</file> corresponding to the package name.
8983 Other X Window System applications should use
8984 the <file>/etc/</file> directory unless otherwise mandated by
8985 policy (such as for <ref id="appdefaults">).
8990 <heading>The OSF/Motif and OpenMotif libraries</heading>
8993 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8994 OpenMotif libraries</em><footnote>
8995 OSF/Motif and OpenMotif are collectively referred to as
8996 "Motif" in this policy document.
8998 should be compiled against and tested with LessTif (a free
8999 re-implementation of Motif) instead. If the maintainer
9000 judges that the program or programs do not work
9001 sufficiently well with LessTif to be distributed and
9002 supported, but do so when compiled against Motif, then two
9003 versions of the package should be created; one linked
9004 statically against Motif and with <tt>-smotif</tt>
9005 appended to the package name, and one linked dynamically
9006 against Motif and with <tt>-dmotif</tt> appended to the
9011 Both Motif-linked versions are dependent
9012 upon non-DFSG-compliant software and thus cannot be
9013 uploaded to the <em>main</em> distribution; if the
9014 software is itself DFSG-compliant it may be uploaded to
9015 the <em>contrib</em> distribution. While known existing
9016 versions of Motif permit unlimited redistribution of
9017 binaries linked against the library (whether statically or
9018 dynamically), it is the package maintainer's
9019 responsibility to determine whether this is permitted by
9020 the license of the copy of Motif in their possession.
9026 <heading>Perl programs and modules</heading>
9029 Perl programs and modules should follow the current Perl policy.
9033 The Perl policy can be found in the <tt>perl-policy</tt>
9034 files in the <tt>debian-policy</tt> package.
9035 It is also available from the Debian web mirrors at
9036 <tt><url name="/doc/packaging-manuals/perl-policy/"
9037 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9042 <heading>Emacs lisp programs</heading>
9045 Please refer to the "Debian Emacs Policy" for details of how to
9046 package emacs lisp programs.
9050 The Emacs policy is available in
9051 <file>debian-emacs-policy.gz</file> of the
9052 <package>emacsen-common</package> package.
9053 It is also available from the Debian web mirrors at
9054 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9055 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9060 <heading>Games</heading>
9063 The permissions on <file>/var/games</file> are mode 755, owner
9064 <tt>root</tt> and group <tt>root</tt>.
9068 Each game decides on its own security policy.</p>
9071 Games which require protected, privileged access to
9072 high-score files, saved games, etc., may be made
9073 set-<em>group</em>-id (mode 2755) and owned by
9074 <tt>root:games</tt>, and use files and directories with
9075 appropriate permissions (770 <tt>root:games</tt>, for
9076 example). They must not be made
9077 set-<em>user</em>-id, as this causes security problems. (If
9078 an attacker can subvert any set-user-id game they can
9079 overwrite the executable of any other, causing other players
9080 of these games to run a Trojan horse program. With a
9081 set-group-id game the attacker only gets access to less
9082 important game data, and if they can get at the other
9083 players' accounts at all it will take considerably more
9087 Some packages, for example some fortune cookie programs, are
9088 configured by the upstream authors to install with their
9089 data files or other static information made unreadable so
9090 that they can only be accessed through set-id programs
9091 provided. You should not do this in a Debian package: anyone can
9092 download the <file>.deb</file> file and read the data from it,
9093 so there is no point making the files unreadable. Not
9094 making the files unreadable also means that you don't have
9095 to make so many programs set-id, which reduces the risk of a
9099 As described in the FHS, binaries of games should be
9100 installed in the directory <file>/usr/games</file>. This also
9101 applies to games that use the X Window System. Manual pages
9102 for games (X and non-X games) should be installed in
9103 <file>/usr/share/man/man6</file>.</p>
9109 <heading>Documentation</heading>
9112 <heading>Manual pages</heading>
9115 You should install manual pages in <prgn>nroff</prgn> source
9116 form, in appropriate places under <file>/usr/share/man</file>.
9117 You should only use sections 1 to 9 (see the FHS for more
9118 details). You must not install a pre-formatted "cat page".
9122 Each program, utility, and function should have an
9123 associated manual page included in the same package. It is
9124 suggested that all configuration files also have a manual
9125 page included as well. Manual pages for protocols and other
9126 auxiliary things are optional.
9130 If no manual page is available, this is considered as a bug
9131 and should be reported to the Debian Bug Tracking System (the
9132 maintainer of the package is allowed to write this bug report
9133 themselves, if they so desire). Do not close the bug report
9134 until a proper man page is available.<footnote>
9135 It is not very hard to write a man page. See the
9136 <url id="http://www.schweikhardt.net/man_page_howto.html"
9137 name="Man-Page-HOWTO">,
9138 <manref name="man" section="7">, the examples
9139 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9140 the helper program <prgn>help2man</prgn>, or the
9141 directory <file>/usr/share/doc/man-db/examples</file>.
9146 You may forward a complaint about a missing man page to the
9147 upstream authors, and mark the bug as forwarded in the
9148 Debian bug tracking system. Even though the GNU Project do
9149 not in general consider the lack of a man page to be a bug,
9150 we do; if they tell you that they don't consider it a bug
9151 you should leave the bug in our bug tracking system open
9156 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9160 If one man page needs to be accessible via several names it
9161 is better to use a symbolic link than the <file>.so</file>
9162 feature, but there is no need to fiddle with the relevant
9163 parts of the upstream source to change from <file>.so</file> to
9164 symlinks: don't do it unless it's easy. You should not
9165 create hard links in the manual page directories, nor put
9166 absolute filenames in <file>.so</file> directives. The filename
9167 in a <file>.so</file> in a man page should be relative to the
9168 base of the man page tree (usually
9169 <file>/usr/share/man</file>). If you do not create any links
9170 (whether symlinks, hard links, or <tt>.so</tt> directives)
9171 in the file system to the alternate names of the man page,
9172 then you should not rely on <prgn>man</prgn> finding your
9173 man page under those names based solely on the information in
9174 the man page's header.<footnote>
9175 Supporting this in <prgn>man</prgn> often requires
9176 unreasonable processing time to find a manual page or to
9177 report that none exists, and moves knowledge into man's
9178 database that would be better left in the file system.
9179 This support is therefore deprecated and will cease to
9180 be present in the future.
9185 Manual pages in locale-specific subdirectories of
9186 <file>/usr/share/man</file> should use either UTF-8 or the usual
9187 legacy encoding for that language (normally the one corresponding
9188 to the shortest relevant locale name in
9189 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9190 <file>/usr/share/man/fr</file> should use either UTF-8 or
9191 ISO-8859-1.<footnote>
9192 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9193 use. In future, all manual pages will be required to use
9199 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9200 included in the subdirectory name unless it indicates a
9201 significant difference in the language, as this excludes
9202 speakers of the language in other countries.<footnote>
9203 At the time of writing, Chinese and Portuguese are the main
9204 languages with such differences, so <file>pt_BR</file>,
9205 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9210 If a localized version of a manual page is provided, it should
9211 either be up-to-date or it should be obvious to the reader that
9212 it is outdated and the original manual page should be used
9213 instead. This can be done either by a note at the beginning of
9214 the manual page or by showing the missing or changed portions in
9215 the original language instead of the target language.
9220 <heading>Info documents</heading>
9223 Info documents should be installed in <file>/usr/share/info</file>.
9224 They should be compressed with <tt>gzip -9</tt>.
9228 The <prgn>install-info</prgn> program maintains a directory of
9229 installed info documents in <file>/usr/share/info/dir</file> for
9230 the use of info readers.<footnote>
9231 It was previously necessary for packages installing info
9232 documents to run <prgn>install-info</prgn> from maintainer
9233 scripts. This is no longer necessary. The installation
9234 system now uses dpkg triggers.
9236 This file must not be included in packages. Packages containing
9237 info documents should depend on <tt>dpkg (>= 1.15.4) |
9238 install-info</tt> to ensure that the directory file is properly
9239 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9244 Info documents should contain section and directory entry
9245 information in the document for the use
9246 of <prgn>install-info</prgn>. The section should be specified
9247 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9248 space and the section of this info page. The directory entry or
9249 entries should be included between
9250 a <tt>START-INFO-DIR-ENTRY</tt> line and
9251 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9253 INFO-DIR-SECTION Individual utilities
9254 START-INFO-DIR-ENTRY
9255 * example: (example). An example info directory entry.
9258 To determine which section to use, you should look
9259 at <file>/usr/share/info/dir</file> on your system and choose
9260 the most relevant (or create a new section if none of the
9261 current sections are relevant).<footnote>
9262 Normally, info documents are generated from Texinfo source.
9263 To include this information in the generated info document, if
9264 it is absent, add commands like:
9266 @dircategory Individual utilities
9268 * example: (example). An example info directory entry.
9271 to the Texinfo source of the document and ensure that the info
9272 documents are rebuilt from source during the package build.
9278 <heading>Additional documentation</heading>
9281 Any additional documentation that comes with the package may
9282 be installed at the discretion of the package maintainer.
9283 Plain text documentation should be installed in the directory
9284 <file>/usr/share/doc/<var>package</var></file>, where
9285 <var>package</var> is the name of the package, and
9286 compressed with <tt>gzip -9</tt> unless it is small.
9290 If a package comes with large amounts of documentation which
9291 many users of the package will not require you should create
9292 a separate binary package to contain it, so that it does not
9293 take up disk space on the machines of users who do not need
9294 or want it installed.</p>
9297 It is often a good idea to put text information files
9298 (<file>README</file>s, changelogs, and so forth) that come with
9299 the source package in <file>/usr/share/doc/<var>package</var></file>
9300 in the binary package. However, you don't need to install
9301 the instructions for building and installing the package, of
9305 Packages must not require the existence of any files in
9306 <file>/usr/share/doc/</file> in order to function
9308 The system administrator should be able to
9309 delete files in <file>/usr/share/doc/</file> without causing
9310 any programs to break.
9312 Any files that are referenced by programs but are also
9313 useful as stand alone documentation should be installed under
9314 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9315 <file>/usr/share/doc/<var>package</var></file>.
9319 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9320 link to another directory in <file>/usr/share/doc</file> only if
9321 the two packages both come from the same source and the
9322 first package Depends on the second.<footnote>
9324 Please note that this does not override the section on
9325 changelog files below, so the file
9326 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9327 must refer to the changelog for the current version of
9328 <var>package</var> in question. In practice, this means
9329 that the sources of the target and the destination of the
9330 symlink must be the same (same source package and
9337 Former Debian releases placed all additional documentation
9338 in <file>/usr/doc/<var>package</var></file>. This has been
9339 changed to <file>/usr/share/doc/<var>package</var></file>,
9340 and packages must not put documentation in the directory
9341 <file>/usr/doc/<var>package</var></file>. <footnote>
9342 At this phase of the transition, we no longer require a
9343 symbolic link in <file>/usr/doc/</file>. At a later point,
9344 policy shall change to make the symbolic links a bug.
9350 <heading>Preferred documentation formats</heading>
9353 The unification of Debian documentation is being carried out
9357 If your package comes with extensive documentation in a
9358 markup format that can be converted to various other formats
9359 you should if possible ship HTML versions in a binary
9360 package, in the directory
9361 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9362 its subdirectories.<footnote>
9363 The rationale: The important thing here is that HTML
9364 docs should be available in <em>some</em> package, not
9365 necessarily in the main binary package.
9370 Other formats such as PostScript may be provided at the
9371 package maintainer's discretion.
9375 <sect id="copyrightfile">
9376 <heading>Copyright information</heading>
9379 Every package must be accompanied by a verbatim copy of its
9380 copyright information and distribution license in the file
9381 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9382 file must neither be compressed nor be a symbolic link.
9386 In addition, the copyright file must say where the upstream
9387 sources (if any) were obtained. It should name the original
9388 authors of the package and the Debian maintainer(s) who were
9389 involved with its creation.
9393 Packages in the <em>contrib</em> or <em>non-free</em> archive
9394 areas should state in the copyright file that the package is not
9395 part of the Debian GNU/Linux distribution and briefly explain
9400 A copy of the file which will be installed in
9401 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9402 be in <file>debian/copyright</file> in the source package.
9406 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9407 link to another directory in <file>/usr/share/doc</file> only if
9408 the two packages both come from the same source and the
9409 first package Depends on the second. These rules are
9410 important because copyrights must be extractable by
9415 Packages distributed under the Apache license (version 2.0), the
9416 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9417 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9418 1.3) should refer to the corresponding files
9419 under <file>/usr/share/common-licenses</file>,<footnote>
9422 <file>/usr/share/common-licenses/Apache-2.0</file>,
9423 <file>/usr/share/common-licenses/Artistic</file>,
9424 <file>/usr/share/common-licenses/GPL-1</file>,
9425 <file>/usr/share/common-licenses/GPL-2</file>,
9426 <file>/usr/share/common-licenses/GPL-3</file>,
9427 <file>/usr/share/common-licenses/LGPL-2</file>,
9428 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9429 <file>/usr/share/common-licenses/LGPL-3</file>,
9430 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9431 <file>/usr/share/common-licenses/GFDL-1.3</file>
9432 respectively. The University of California BSD license is
9433 also included in <package>base-files</package> as
9434 <file>/usr/share/common-licenses/BSD</file>, but given the
9435 brevity of this license, its specificity to code whose
9436 copyright is held by the Regents of the University of
9437 California, and the frequency of minor wording changes, its
9438 text should be included in the copyright file rather than
9439 referencing this file.
9441 </footnote> rather than quoting them in the copyright
9446 You should not use the copyright file as a general <file>README</file>
9447 file. If your package has such a file it should be
9448 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9449 <file>README.Debian</file> or some other appropriate place.</p>
9453 <heading>Examples</heading>
9456 Any examples (configurations, source files, whatever),
9457 should be installed in a directory
9458 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9459 files should not be referenced by any program: they're there
9460 for the benefit of the system administrator and users as
9461 documentation only. Architecture-specific example files
9462 should be installed in a directory
9463 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9465 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9466 latter directory itself may be a symbolic link to the
9471 If the purpose of a package is to provide examples, then the
9472 example files may be installed into
9473 <file>/usr/share/doc/<var>package</var></file>.
9477 <sect id="changelogs">
9478 <heading>Changelog files</heading>
9481 Packages that are not Debian-native must contain a
9482 compressed copy of the <file>debian/changelog</file> file from
9483 the Debian source tree in
9484 <file>/usr/share/doc/<var>package</var></file> with the name
9485 <file>changelog.Debian.gz</file>.
9489 If an upstream changelog is available, it should be accessible as
9490 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9491 plain text. If the upstream changelog is distributed in
9492 HTML, it should be made available in that form as
9493 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9494 and a plain text <file>changelog.gz</file> should be generated
9495 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9496 the upstream changelog files do not already conform to this
9497 naming convention, then this may be achieved either by
9498 renaming the files, or by adding a symbolic link, at the
9499 maintainer's discretion.<footnote>
9500 Rationale: People should not have to look in places for
9501 upstream changelogs merely because they are given
9502 different names or are distributed in HTML format.
9507 All of these files should be installed compressed using
9508 <tt>gzip -9</tt>, as they will become large with time even
9509 if they start out small.
9513 If the package has only one changelog which is used both as
9514 the Debian changelog and the upstream one because there is
9515 no separate upstream maintainer then that changelog should
9516 usually be installed as
9517 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9518 there is a separate upstream maintainer, but no upstream
9519 changelog, then the Debian changelog should still be called
9520 <file>changelog.Debian.gz</file>.
9524 For details about the format and contents of the Debian
9525 changelog file, please see <ref id="dpkgchangelog">.
9530 <appendix id="pkg-scope">
9531 <heading>Introduction and scope of these appendices</heading>
9534 These appendices are taken essentially verbatim from the
9535 now-deprecated Packaging Manual, version 3.2.1.0. They are
9536 the chapters which are likely to be of use to package
9537 maintainers and which have not already been included in the
9538 policy document itself. Most of these sections are very likely
9539 not relevant to policy; they should be treated as
9540 documentation for the packaging system. Please note that these
9541 appendices are included for convenience, and for historical
9542 reasons: they used to be part of policy package, and they have
9543 not yet been incorporated into dpkg documentation. However,
9544 they still have value, and hence they are presented here.
9548 They have not yet been checked to ensure that they are
9549 compatible with the contents of policy, and if there are any
9550 contradictions, the version in the main policy document takes
9551 precedence. The remaining chapters of the old Packaging
9552 Manual have also not been read in detail to ensure that there
9553 are not parts which have been left out. Both of these will be
9558 Certain parts of the Packaging manual were integrated into the
9559 Policy Manual proper, and removed from the appendices. Links
9560 have been placed from the old locations to the new ones.
9564 <prgn>dpkg</prgn> is a suite of programs for creating binary
9565 package files and installing and removing them on Unix
9567 <prgn>dpkg</prgn> is targeted primarily at Debian
9568 GNU/Linux, but may work on or be ported to other
9574 The binary packages are designed for the management of
9575 installed executable programs (usually compiled binaries) and
9576 their associated data, though source code examples and
9577 documentation are provided as part of some packages.</p>
9580 This manual describes the technical aspects of creating Debian
9581 binary packages (<file>.deb</file> files). It documents the
9582 behavior of the package management programs
9583 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9584 they interact with packages.</p>
9587 It also documents the interaction between
9588 <prgn>dselect</prgn>'s core and the access method scripts it
9589 uses to actually install the selected packages, and describes
9590 how to create a new access method.</p>
9593 This manual does not go into detail about the options and
9594 usage of the package building and installation tools. It
9595 should therefore be read in conjunction with those programs'
9600 The utility programs which are provided with <prgn>dpkg</prgn>
9601 for managing various system configuration and similar issues,
9602 such as <prgn>update-rc.d</prgn> and
9603 <prgn>install-info</prgn>, are not described in detail here -
9604 please see their man pages.
9608 It is assumed that the reader is reasonably familiar with the
9609 <prgn>dpkg</prgn> System Administrators' manual.
9610 Unfortunately this manual does not yet exist.
9614 The Debian version of the FSF's GNU hello program is provided
9615 as an example for people wishing to create Debian
9616 packages. The Debian <prgn>debmake</prgn> package is
9617 recommended as a very helpful tool in creating and maintaining
9618 Debian packages. However, while the tools and examples are
9619 helpful, they do not replace the need to read and follow the
9620 Policy and Programmer's Manual.</p>
9623 <appendix id="pkg-binarypkg">
9624 <heading>Binary packages (from old Packaging Manual)</heading>
9627 The binary package has two main sections. The first part
9628 consists of various control information files and scripts used
9629 by <prgn>dpkg</prgn> when installing and removing. See <ref
9630 id="pkg-controlarea">.
9634 The second part is an archive containing the files and
9635 directories to be installed.
9639 In the future binary packages may also contain other
9640 components, such as checksums and digital signatures. The
9641 format for the archive is described in full in the
9642 <file>deb(5)</file> man page.
9646 <sect id="pkg-bincreating"><heading>Creating package files -
9647 <prgn>dpkg-deb</prgn>
9651 All manipulation of binary package files is done by
9652 <prgn>dpkg-deb</prgn>; it's the only program that has
9653 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9654 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9655 will spot that the options requested are appropriate to
9656 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9661 In order to create a binary package you must make a
9662 directory tree which contains all the files and directories
9663 you want to have in the file system data part of the package.
9664 In Debian-format source packages this directory is usually
9665 <file>debian/tmp</file>, relative to the top of the package's
9670 They should have the locations (relative to the root of the
9671 directory tree you're constructing) ownerships and
9672 permissions which you want them to have on the system when
9677 With current versions of <prgn>dpkg</prgn> the uid/username
9678 and gid/groupname mappings for the users and groups being
9679 used should be the same on the system where the package is
9680 built and the one where it is installed.
9684 You need to add one special directory to the root of the
9685 miniature file system tree you're creating:
9686 <prgn>DEBIAN</prgn>. It should contain the control
9687 information files, notably the binary package control file
9688 (see <ref id="pkg-controlfile">).
9692 The <prgn>DEBIAN</prgn> directory will not appear in the
9693 file system archive of the package, and so won't be installed
9694 by <prgn>dpkg</prgn> when the package is installed.
9698 When you've prepared the package, you should invoke:
9700 dpkg --build <var>directory</var>
9705 This will build the package in
9706 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9707 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9708 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9713 See the man page <manref name="dpkg-deb" section="8"> for details of how
9714 to examine the contents of this newly-created file. You may find the
9715 output of following commands enlightening:
9717 dpkg-deb --info <var>filename</var>.deb
9718 dpkg-deb --contents <var>filename</var>.deb
9719 dpkg --contents <var>filename</var>.deb
9721 To view the copyright file for a package you could use this command:
9723 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9728 <sect id="pkg-controlarea">
9729 <heading>Package control information files</heading>
9732 The control information portion of a binary package is a
9733 collection of files with names known to <prgn>dpkg</prgn>.
9734 It will treat the contents of these files specially - some
9735 of them contain information used by <prgn>dpkg</prgn> when
9736 installing or removing the package; others are scripts which
9737 the package maintainer wants <prgn>dpkg</prgn> to run.
9741 It is possible to put other files in the package control
9742 information file area, but this is not generally a good idea
9743 (though they will largely be ignored).
9747 Here is a brief list of the control information files supported
9748 by <prgn>dpkg</prgn> and a summary of what they're used for.
9753 <tag><tt>control</tt>
9756 This is the key description file used by
9757 <prgn>dpkg</prgn>. It specifies the package's name
9758 and version, gives its description for the user,
9759 states its relationships with other packages, and so
9760 forth. See <ref id="sourcecontrolfiles"> and
9761 <ref id="binarycontrolfiles">.
9765 It is usually generated automatically from information
9766 in the source package by the
9767 <prgn>dpkg-gencontrol</prgn> program, and with
9768 assistance from <prgn>dpkg-shlibdeps</prgn>.
9769 See <ref id="pkg-sourcetools">.
9773 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9778 These are executable files (usually scripts) which
9779 <prgn>dpkg</prgn> runs during installation, upgrade
9780 and removal of packages. They allow the package to
9781 deal with matters which are particular to that package
9782 or require more complicated processing than that
9783 provided by <prgn>dpkg</prgn>. Details of when and
9784 how they are called are in <ref id="maintainerscripts">.
9788 It is very important to make these scripts idempotent.
9789 See <ref id="idempotency">.
9793 The maintainer scripts are not guaranteed to run with a
9794 controlling terminal and may not be able to interact with
9795 the user. See <ref id="controllingterminal">.
9799 <tag><tt>conffiles</tt>
9802 This file contains a list of configuration files which
9803 are to be handled automatically by <prgn>dpkg</prgn>
9804 (see <ref id="pkg-conffiles">). Note that not necessarily
9805 every configuration file should be listed here.
9808 <tag><tt>shlibs</tt>
9811 This file contains a list of the shared libraries
9812 supplied by the package, with dependency details for
9813 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9814 when it determines what dependencies are required in a
9815 package control file. The <tt>shlibs</tt> file format
9816 is described on <ref id="shlibs">.
9821 <sect id="pkg-controlfile">
9822 <heading>The main control information file: <tt>control</tt></heading>
9825 The most important control information file used by
9826 <prgn>dpkg</prgn> when it installs a package is
9827 <tt>control</tt>. It contains all the package's "vital
9832 The binary package control files of packages built from
9833 Debian sources are made by a special tool,
9834 <prgn>dpkg-gencontrol</prgn>, which reads
9835 <file>debian/control</file> and <file>debian/changelog</file> to
9836 find the information it needs. See <ref id="pkg-sourcepkg"> for
9841 The fields in binary package control files are listed in
9842 <ref id="binarycontrolfiles">.
9846 A description of the syntax of control files and the purpose
9847 of the fields is available in <ref id="controlfields">.
9852 <heading>Time Stamps</heading>
9855 See <ref id="timestamps">.
9860 <appendix id="pkg-sourcepkg">
9861 <heading>Source packages (from old Packaging Manual) </heading>
9864 The Debian binary packages in the distribution are generated
9865 from Debian sources, which are in a special format to assist
9866 the easy and automatic building of binaries.
9869 <sect id="pkg-sourcetools">
9870 <heading>Tools for processing source packages</heading>
9873 Various tools are provided for manipulating source packages;
9874 they pack and unpack sources and help build of binary
9875 packages and help manage the distribution of new versions.
9879 They are introduced and typical uses described here; see
9880 <manref name="dpkg-source" section="1"> for full
9881 documentation about their arguments and operation.
9885 For examples of how to construct a Debian source package,
9886 and how to use those utilities that are used by Debian
9887 source packages, please see the <prgn>hello</prgn> example
9891 <sect1 id="pkg-dpkg-source">
9893 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9898 This program is frequently used by hand, and is also
9899 called from package-independent automated building scripts
9900 such as <prgn>dpkg-buildpackage</prgn>.
9904 To unpack a package it is typically invoked with
9906 dpkg-source -x <var>.../path/to/filename</var>.dsc
9911 with the <file><var>filename</var>.tar.gz</file> and
9912 <file><var>filename</var>.diff.gz</file> (if applicable) in
9913 the same directory. It unpacks into
9914 <file><var>package</var>-<var>version</var></file>, and if
9916 <file><var>package</var>-<var>version</var>.orig</file>, in
9917 the current directory.
9921 To create a packed source archive it is typically invoked:
9923 dpkg-source -b <var>package</var>-<var>version</var>
9928 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9929 <file>.diff.gz</file> (if appropriate) in the current
9930 directory. <prgn>dpkg-source</prgn> does not clean the
9931 source tree first - this must be done separately if it is
9936 See also <ref id="pkg-sourcearchives">.</p>
9940 <sect1 id="pkg-dpkg-buildpackage">
9942 <prgn>dpkg-buildpackage</prgn> - overall package-building
9947 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9948 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9949 targets <tt>clean</tt>, <tt>build</tt> and
9950 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9951 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9952 source and binary package upload.
9956 It is usually invoked by hand from the top level of the
9957 built or unbuilt source directory. It may be invoked with
9958 no arguments; useful arguments include:
9959 <taglist compact="compact">
9960 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9963 Do not sign the <tt>.changes</tt> file or the
9964 source package <tt>.dsc</tt> file, respectively.</p>
9966 <tag><tt>-p<var>sign-command</var></tt></tag>
9969 Invoke <var>sign-command</var> instead of finding
9970 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9971 <var>sign-command</var> must behave just like
9972 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9974 <tag><tt>-r<var>root-command</var></tt></tag>
9977 When root privilege is required, invoke the command
9978 <var>root-command</var>. <var>root-command</var>
9979 should invoke its first argument as a command, from
9980 the <prgn>PATH</prgn> if necessary, and pass its
9981 second and subsequent arguments to the command it
9982 calls. If no <var>root-command</var> is supplied
9983 then <var>dpkg-buildpackage</var> will take no
9984 special action to gain root privilege, so that for
9985 most packages it will have to be invoked as root to
9988 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9991 Two types of binary-only build and upload - see
9992 <manref name="dpkg-source" section="1">.
9999 <sect1 id="pkg-dpkg-gencontrol">
10001 <prgn>dpkg-gencontrol</prgn> - generates binary package
10006 This program is usually called from <file>debian/rules</file>
10007 (see <ref id="pkg-sourcetree">) in the top level of the source
10012 This is usually done just before the files and directories in the
10013 temporary directory tree where the package is being built have their
10014 permissions and ownerships set and the package is constructed using
10015 <prgn>dpkg-deb/</prgn>
10017 This is so that the control file which is produced has
10018 the right permissions
10023 <prgn>dpkg-gencontrol</prgn> must be called after all the
10024 files which are to go into the package have been placed in
10025 the temporary build directory, so that its calculation of
10026 the installed size of a package is correct.
10030 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10031 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10032 variable substitutions created by
10033 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10038 For a package which generates only one binary package, and
10039 which builds it in <file>debian/tmp</file> relative to the top
10040 of the source package, it is usually sufficient to call
10041 <prgn>dpkg-gencontrol</prgn>.
10045 Sources which build several binaries will typically need
10048 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10049 </example> The <tt>-P</tt> tells
10050 <prgn>dpkg-gencontrol</prgn> that the package is being
10051 built in a non-default directory, and the <tt>-p</tt>
10052 tells it which package's control file should be generated.
10056 <prgn>dpkg-gencontrol</prgn> also adds information to the
10057 list of files in <file>debian/files</file>, for the benefit of
10058 (for example) a future invocation of
10059 <prgn>dpkg-genchanges</prgn>.</p>
10062 <sect1 id="pkg-dpkg-shlibdeps">
10064 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10069 This program is usually called from <file>debian/rules</file>
10070 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10071 id="pkg-sourcetree">), in the top level of the source tree.
10075 Its arguments are executables and shared libraries
10078 They may be specified either in the locations in the
10079 source tree where they are created or in the locations
10080 in the temporary build tree where they are installed
10081 prior to binary package creation.
10083 </footnote> for which shared library dependencies should
10084 be included in the binary package's control file.
10088 If some of the found shared libraries should only
10089 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10090 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10091 by using the <tt>-d<var>dependency-field</var></tt> option
10092 before those executable(s). (Each <tt>-d</tt> option
10093 takes effect until the next <tt>-d</tt>.)
10097 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10098 output control file to be modified. Instead by default it
10099 adds to the <file>debian/substvars</file> file variable
10100 settings like <tt>shlibs:Depends</tt>. These variable
10101 settings must be referenced in dependency fields in the
10102 appropriate per-binary-package sections of the source
10107 For example, a package that generates an essential part
10108 which requires dependencies, and optional parts that
10109 which only require a recommendation, would separate those
10110 two sets of dependencies into two different fields.<footnote>
10111 At the time of writing, an example for this was the
10112 <package/xmms/ package, with Depends used for the xmms
10113 executable, Recommends for the plug-ins and Suggests for
10114 even more optional features provided by unzip.
10116 It can say in its <file>debian/rules</file>:
10118 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10119 -dRecommends <var>optionalpart anotheroptionalpart</var>
10121 and then in its main control file <file>debian/control</file>:
10124 Depends: ${shlibs:Depends}
10125 Recommends: ${shlibs:Recommends}
10131 Sources which produce several binary packages with
10132 different shared library dependency requirements can use
10133 the <tt>-p<var>varnameprefix</var></tt> option to override
10134 the default <tt>shlibs:</tt> prefix (one invocation of
10135 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10136 They can thus produce several sets of dependency
10137 variables, each of the form
10138 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10139 which can be referred to in the appropriate parts of the
10140 binary package control files.
10145 <sect1 id="pkg-dpkg-distaddfile">
10147 <prgn>dpkg-distaddfile</prgn> - adds a file to
10148 <file>debian/files</file>
10152 Some packages' uploads need to include files other than
10153 the source and binary package files.
10157 <prgn>dpkg-distaddfile</prgn> adds a file to the
10158 <file>debian/files</file> file so that it will be included in
10159 the <file>.changes</file> file when
10160 <prgn>dpkg-genchanges</prgn> is run.
10164 It is usually invoked from the <tt>binary</tt> target of
10165 <file>debian/rules</file>:
10167 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10169 The <var>filename</var> is relative to the directory where
10170 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10171 is usually the directory above the top level of the source
10172 tree. The <file>debian/rules</file> target should put the
10173 file there just before or just after calling
10174 <prgn>dpkg-distaddfile</prgn>.
10178 The <var>section</var> and <var>priority</var> are passed
10179 unchanged into the resulting <file>.changes</file> file.
10184 <sect1 id="pkg-dpkg-genchanges">
10186 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10187 upload control file
10191 This program is usually called by package-independent
10192 automatic building scripts such as
10193 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10198 It is usually called in the top level of a built source
10199 tree, and when invoked with no arguments will print out a
10200 straightforward <file>.changes</file> file based on the
10201 information in the source package's changelog and control
10202 file and the binary and source packages which should have
10208 <sect1 id="pkg-dpkg-parsechangelog">
10210 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10211 representation of a changelog
10215 This program is used internally by
10216 <prgn>dpkg-source</prgn> et al. It may also occasionally
10217 be useful in <file>debian/rules</file> and elsewhere. It
10218 parses a changelog, <file>debian/changelog</file> by default,
10219 and prints a control-file format representation of the
10220 information in it to standard output.
10224 <sect1 id="pkg-dpkg-architecture">
10226 <prgn>dpkg-architecture</prgn> - information about the build and
10231 This program can be used manually, but is also invoked by
10232 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10233 environment or make variables which specify the build and host
10234 architecture for the package building process.
10239 <sect id="pkg-sourcetree">
10240 <heading>The Debian package source tree</heading>
10243 The source archive scheme described later is intended to
10244 allow a Debian package source tree with some associated
10245 control information to be reproduced and transported easily.
10246 The Debian package source tree is a version of the original
10247 program with certain files added for the benefit of the
10248 packaging process, and with any other changes required
10249 made to the rest of the source code and installation
10254 The extra files created for Debian are in the subdirectory
10255 <file>debian</file> of the top level of the Debian package
10256 source tree. They are described below.
10259 <sect1 id="pkg-debianrules">
10260 <heading><file>debian/rules</file> - the main building script</heading>
10263 See <ref id="debianrules">.
10267 <sect1 id="pkg-srcsubstvars">
10268 <heading><file>debian/substvars</file> and variable substitutions</heading>
10271 See <ref id="substvars">.
10277 <heading><file>debian/files</file></heading>
10280 See <ref id="debianfiles">.
10284 <sect1><heading><file>debian/tmp</file>
10288 This is the canonical temporary location for the
10289 construction of binary packages by the <tt>binary</tt>
10290 target. The directory <file>tmp</file> serves as the root of
10291 the file system tree as it is being constructed (for
10292 example, by using the package's upstream makefiles install
10293 targets and redirecting the output there), and it also
10294 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10295 id="pkg-bincreating">.
10299 If several binary packages are generated from the same
10300 source tree it is usual to use several
10301 <file>debian/tmp<var>something</var></file> directories, for
10302 example <file>tmp-a</file> or <file>tmp-doc</file>.
10306 Whatever <file>tmp</file> directories are created and used by
10307 <tt>binary</tt> must of course be removed by the
10308 <tt>clean</tt> target.</p></sect1>
10312 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10316 As it exists on the FTP site, a Debian source package
10317 consists of three related files. You must have the right
10318 versions of all three to be able to use them.
10323 <tag>Debian source control file - <tt>.dsc</tt></tag>
10325 This file is a control file used by <prgn>dpkg-source</prgn>
10326 to extract a source package.
10327 See <ref id="debiansourcecontrolfiles">.
10331 Original source archive -
10333 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10339 This is a compressed (with <tt>gzip -9</tt>)
10340 <prgn>tar</prgn> file containing the source code from
10341 the upstream authors of the program.
10346 Debian package diff -
10348 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10354 This is a unified context diff (<tt>diff -u</tt>)
10355 giving the changes which are required to turn the
10356 original source into the Debian source. These changes
10357 may only include editing and creating plain files.
10358 The permissions of files, the targets of symbolic
10359 links and the characteristics of special files or
10360 pipes may not be changed and no files may be removed
10365 All the directories in the diff must exist, except the
10366 <file>debian</file> subdirectory of the top of the source
10367 tree, which will be created by
10368 <prgn>dpkg-source</prgn> if necessary when unpacking.
10372 The <prgn>dpkg-source</prgn> program will
10373 automatically make the <file>debian/rules</file> file
10374 executable (see below).</p></item>
10379 If there is no original source code - for example, if the
10380 package is specially prepared for Debian or the Debian
10381 maintainer is the same as the upstream maintainer - the
10382 format is slightly different: then there is no diff, and the
10384 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10385 and preferably contains a directory named
10386 <file><var>package</var>-<var>version</var></file>.
10391 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10394 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10395 Debian source package. However, if it is not available it
10396 is possible to unpack a Debian source archive as follows:
10397 <enumlist compact="compact">
10400 Untar the tarfile, which will create a <file>.orig</file>
10404 <p>Rename the <file>.orig</file> directory to
10405 <file><var>package</var>-<var>version</var></file>.</p>
10409 Create the subdirectory <file>debian</file> at the top of
10410 the source tree.</p>
10412 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10414 <item><p>Untar the tarfile again if you want a copy of the original
10415 source code alongside the Debian version.</p>
10420 It is not possible to generate a valid Debian source archive
10421 without using <prgn>dpkg-source</prgn>. In particular,
10422 attempting to use <prgn>diff</prgn> directly to generate the
10423 <file>.diff.gz</file> file will not work.
10427 <heading>Restrictions on objects in source packages</heading>
10430 The source package may not contain any hard links
10432 This is not currently detected when building source
10433 packages, but only when extracting
10437 Hard links may be permitted at some point in the
10438 future, but would require a fair amount of
10440 </footnote>, device special files, sockets or setuid or
10443 Setgid directories are allowed.
10448 The source packaging tools manage the changes between the
10449 original and Debian source using <prgn>diff</prgn> and
10450 <prgn>patch</prgn>. Turning the original source tree as
10451 included in the <file>.orig.tar.gz</file> into the Debian
10452 package source must not involve any changes which cannot be
10453 handled by these tools. Problematic changes which cause
10454 <prgn>dpkg-source</prgn> to halt with an error when
10455 building the source package are:
10456 <list compact="compact">
10457 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10459 <item><p>Changing the targets of symbolic links.</p>
10461 <item><p>Creating directories, other than <file>debian</file>.</p>
10463 <item><p>Changes to the contents of binary files.</p></item>
10464 </list> Changes which cause <prgn>dpkg-source</prgn> to
10465 print a warning but continue anyway are:
10466 <list compact="compact">
10469 Removing files, directories or symlinks.
10471 Renaming a file is not treated specially - it is
10472 seen as the removal of the old file (which
10473 generates a warning, but is otherwise ignored),
10474 and the creation of the new one.
10480 Changed text files which are missing the usual final
10481 newline (either in the original or the modified
10486 Changes which are not represented, but which are not detected by
10487 <prgn>dpkg-source</prgn>, are:
10488 <list compact="compact">
10489 <item><p>Changing the permissions of files (other than
10490 <file>debian/rules</file>) and directories.</p></item>
10495 The <file>debian</file> directory and <file>debian/rules</file>
10496 are handled specially by <prgn>dpkg-source</prgn> - before
10497 applying the changes it will create the <file>debian</file>
10498 directory, and afterwards it will make
10499 <file>debian/rules</file> world-executable.
10505 <appendix id="pkg-controlfields">
10506 <heading>Control files and their fields (from old Packaging Manual)</heading>
10509 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10510 data in a common format, known as control files. Binary and
10511 source packages have control data as do the <file>.changes</file>
10512 files which control the installation of uploaded files, and
10513 <prgn>dpkg</prgn>'s internal databases are in a similar
10518 <heading>Syntax of control files</heading>
10521 See <ref id="controlsyntax">.
10525 It is important to note that there are several fields which
10526 are optional as far as <prgn>dpkg</prgn> and the related
10527 tools are concerned, but which must appear in every Debian
10528 package, or whose omission may cause problems.
10533 <heading>List of fields</heading>
10536 See <ref id="controlfieldslist">.
10540 This section now contains only the fields that didn't belong
10541 to the Policy manual.
10544 <sect1 id="pkg-f-Filename">
10545 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10548 These fields in <tt>Packages</tt> files give the
10549 filename(s) of (the parts of) a package in the
10550 distribution directories, relative to the root of the
10551 Debian hierarchy. If the package has been split into
10552 several parts the parts are all listed in order, separated
10557 <sect1 id="pkg-f-Size">
10558 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10561 These fields in <file>Packages</file> files give the size (in
10562 bytes, expressed in decimal) and MD5 checksum of the
10563 file(s) which make(s) up a binary package in the
10564 distribution. If the package is split into several parts
10565 the values for the parts are listed in order, separated by
10570 <sect1 id="pkg-f-Status">
10571 <heading><tt>Status</tt></heading>
10574 This field in <prgn>dpkg</prgn>'s status file records
10575 whether the user wants a package installed, removed or
10576 left alone, whether it is broken (requiring
10577 re-installation) or not and what its current state on the
10578 system is. Each of these pieces of information is a
10583 <sect1 id="pkg-f-Config-Version">
10584 <heading><tt>Config-Version</tt></heading>
10587 If a package is not installed or not configured, this
10588 field in <prgn>dpkg</prgn>'s status file records the last
10589 version of the package which was successfully
10594 <sect1 id="pkg-f-Conffiles">
10595 <heading><tt>Conffiles</tt></heading>
10598 This field in <prgn>dpkg</prgn>'s status file contains
10599 information about the automatically-managed configuration
10600 files held by a package. This field should <em>not</em>
10601 appear anywhere in a package!
10606 <heading>Obsolete fields</heading>
10609 These are still recognized by <prgn>dpkg</prgn> but should
10610 not appear anywhere any more.
10612 <taglist compact="compact">
10614 <tag><tt>Revision</tt></tag>
10615 <tag><tt>Package-Revision</tt></tag>
10616 <tag><tt>Package_Revision</tt></tag>
10618 The Debian revision part of the package version was
10619 at one point in a separate control field. This
10620 field went through several names.
10623 <tag><tt>Recommended</tt></tag>
10624 <item>Old name for <tt>Recommends</tt>.</item>
10626 <tag><tt>Optional</tt></tag>
10627 <item>Old name for <tt>Suggests</tt>.</item>
10629 <tag><tt>Class</tt></tag>
10630 <item>Old name for <tt>Priority</tt>.</item>
10639 <appendix id="pkg-conffiles">
10640 <heading>Configuration file handling (from old Packaging Manual)</heading>
10643 <prgn>dpkg</prgn> can do a certain amount of automatic
10644 handling of package configuration files.
10648 Whether this mechanism is appropriate depends on a number of
10649 factors, but basically there are two approaches to any
10650 particular configuration file.
10654 The easy method is to ship a best-effort configuration in the
10655 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10656 handle updates. If the user is unlikely to want to edit the
10657 file, but you need them to be able to without losing their
10658 changes, and a new package with a changed version of the file
10659 is only released infrequently, this is a good approach.
10663 The hard method is to build the configuration file from
10664 scratch in the <prgn>postinst</prgn> script, and to take the
10665 responsibility for fixing any mistakes made in earlier
10666 versions of the package automatically. This will be
10667 appropriate if the file is likely to need to be different on
10671 <sect><heading>Automatic handling of configuration files by
10676 A package may contain a control information file called
10677 <tt>conffiles</tt>. This file should be a list of filenames
10678 of configuration files needing automatic handling, separated
10679 by newlines. The filenames should be absolute pathnames,
10680 and the files referred to should actually exist in the
10685 When a package is upgraded <prgn>dpkg</prgn> will process
10686 the configuration files during the configuration stage,
10687 shortly before it runs the package's <prgn>postinst</prgn>
10692 For each file it checks to see whether the version of the
10693 file included in the package is the same as the one that was
10694 included in the last version of the package (the one that is
10695 being upgraded from); it also compares the version currently
10696 installed on the system with the one shipped with the last
10701 If neither the user nor the package maintainer has changed
10702 the file, it is left alone. If one or the other has changed
10703 their version, then the changed version is preferred - i.e.,
10704 if the user edits their file, but the package maintainer
10705 doesn't ship a different version, the user's changes will
10706 stay, silently, but if the maintainer ships a new version
10707 and the user hasn't edited it the new version will be
10708 installed (with an informative message). If both have
10709 changed their version the user is prompted about the problem
10710 and must resolve the differences themselves.
10714 The comparisons are done by calculating the MD5 message
10715 digests of the files, and storing the MD5 of the file as it
10716 was included in the most recent version of the package.
10720 When a package is installed for the first time
10721 <prgn>dpkg</prgn> will install the file that comes with it,
10722 unless that would mean overwriting a file already on the
10727 However, note that <prgn>dpkg</prgn> will <em>not</em>
10728 replace a conffile that was removed by the user (or by a
10729 script). This is necessary because with some programs a
10730 missing file produces an effect hard or impossible to
10731 achieve in another way, so that a missing file needs to be
10732 kept that way if the user did it.
10736 Note that a package should <em>not</em> modify a
10737 <prgn>dpkg</prgn>-handled conffile in its maintainer
10738 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10739 the user confusing and possibly dangerous options for
10740 conffile update when the package is upgraded.</p>
10743 <sect><heading>Fully-featured maintainer script configuration
10748 For files which contain site-specific information such as
10749 the hostname and networking details and so forth, it is
10750 better to create the file in the package's
10751 <prgn>postinst</prgn> script.
10755 This will typically involve examining the state of the rest
10756 of the system to determine values and other information, and
10757 may involve prompting the user for some information which
10758 can't be obtained some other way.
10762 When using this method there are a couple of important
10763 issues which should be considered:
10767 If you discover a bug in the program which generates the
10768 configuration file, or if the format of the file changes
10769 from one version to the next, you will have to arrange for
10770 the postinst script to do something sensible - usually this
10771 will mean editing the installed configuration file to remove
10772 the problem or change the syntax. You will have to do this
10773 very carefully, since the user may have changed the file,
10774 perhaps to fix the very problem that your script is trying
10775 to deal with - you will have to detect these situations and
10776 deal with them correctly.
10780 If you do go down this route it's probably a good idea to
10781 make the program that generates the configuration file(s) a
10782 separate program in <file>/usr/sbin</file>, by convention called
10783 <file><var>package</var>config</file> and then run that if
10784 appropriate from the post-installation script. The
10785 <tt><var>package</var>config</tt> program should not
10786 unquestioningly overwrite an existing configuration - if its
10787 mode of operation is geared towards setting up a package for
10788 the first time (rather than any arbitrary reconfiguration
10789 later) you should have it check whether the configuration
10790 already exists, and require a <tt>--force</tt> flag to
10791 overwrite it.</p></sect>
10794 <appendix id="pkg-alternatives"><heading>Alternative versions of
10795 an interface - <prgn>update-alternatives</prgn> (from old
10800 When several packages all provide different versions of the
10801 same program or file it is useful to have the system select a
10802 default, but to allow the system administrator to change it
10803 and have their decisions respected.
10807 For example, there are several versions of the <prgn>vi</prgn>
10808 editor, and there is no reason to prevent all of them from
10809 being installed at once, each under their own name
10810 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10811 Nevertheless it is desirable to have the name <tt>vi</tt>
10812 refer to something, at least by default.
10816 If all the packages involved cooperate, this can be done with
10817 <prgn>update-alternatives</prgn>.
10821 Each package provides its own version under its own name, and
10822 calls <prgn>update-alternatives</prgn> in its postinst to
10823 register its version (and again in its prerm to deregister
10828 See the man page <manref name="update-alternatives"
10829 section="8"> for details.
10833 If <prgn>update-alternatives</prgn> does not seem appropriate
10834 you may wish to consider using diversions instead.</p>
10837 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10838 package's version of a file (from old Packaging Manual)
10842 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10843 when it reinstalls the package it belongs to, and to have it
10844 put the file from the package somewhere else instead.
10848 This can be used locally to override a package's version of a
10849 file, or by one package to override another's version (or
10850 provide a wrapper for it).
10854 Before deciding to use a diversion, read <ref
10855 id="pkg-alternatives"> to see if you really want a diversion
10856 rather than several alternative versions of a program.
10860 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10861 and updated by a special program <prgn>dpkg-divert</prgn>.
10862 Please see <manref name="dpkg-divert" section="8"> for full
10863 details of its operation.
10867 When a package wishes to divert a file from another, it should
10868 call <prgn>dpkg-divert</prgn> in its preinst to add the
10869 diversion and rename the existing file. For example,
10870 supposing that a <prgn>smailwrapper</prgn> package wishes to
10871 install a wrapper around <file>/usr/sbin/smail</file>:
10873 dpkg-divert --package smailwrapper --add --rename \
10874 --divert /usr/sbin/smail.real /usr/sbin/smail
10875 </example> The <tt>--package smailwrapper</tt> ensures that
10876 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10877 can bypass the diversion and get installed as the true version.
10878 It's safe to add the diversion unconditionally on upgrades since
10879 it will be left unchanged if it already exists, but
10880 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10881 message, make the command conditional on the version from which
10882 the package is being upgraded:
10884 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10885 dpkg-divert --package smailwrapper --add --rename \
10886 --divert /usr/sbin/smail.real /usr/sbin/smail
10888 </example> where <tt>1.0-2</tt> is the version at which the
10889 diversion was first added to the package. Running the command
10890 during abort-upgrade is pointless but harmless.
10894 The postrm has to do the reverse:
10896 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10897 dpkg-divert --package smailwrapper --remove --rename \
10898 --divert /usr/sbin/smail.real /usr/sbin/smail
10900 </example> If the diversion was added at a particular version, the
10901 postrm should also handle the failure case of upgrading from an
10902 older version (unless the older version is so old that direct
10903 upgrades are no longer supported):
10905 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10906 dpkg-divert --package smailwrapper --remove --rename \
10907 --divert /usr/sbin/smail.real /usr/sbin/smail
10909 </example> where <tt>1.02-2</tt> is the version at which the
10910 diversion was first added to the package. The postrm should not
10911 remove the diversion on upgrades both because there's no reason to
10912 remove the diversion only to immediately re-add it and since the
10913 postrm of the old package is run after unpacking so the removal of
10914 the diversion will fail.
10918 Do not attempt to divert a file which is vitally important for
10919 the system's operation - when using <prgn>dpkg-divert</prgn>
10920 there is a time, after it has been diverted but before
10921 <prgn>dpkg</prgn> has installed the new version, when the file
10922 does not exist.</p>
10927 <!-- Local variables: -->
10928 <!-- indent-tabs-mode: t -->
10930 <!-- vim:set ai et sts=2 sw=2 tw=76: -->