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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 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
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 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>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></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 Finally, a <qref id="copyrightformat">specification for
285 machine-readable copyright files</qref> is maintained as part of
286 the <package>debian-policy</package> package using the same
287 procedure as the other policy documents. Use of this format is
292 <sect id="definitions">
293 <heading>Definitions</heading>
296 The following terms are used in this Policy Manual:
300 The character encoding specified by ANSI X3.4-1986 and its
301 predecessor standards, referred to in MIME as US-ASCII, and
302 corresponding to an encoding in eight bits per character of
303 the first 128 <url id="http://www.unicode.org/"
304 name="Unicode"> characters, with the eighth bit always zero.
308 The transformation format (sometimes called encoding) of
309 <url id="http://www.unicode.org/" name="Unicode"> defined by
310 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
311 name="RFC 3629">. UTF-8 has the useful property of having
312 ASCII as a subset, so any text encoded in ASCII is trivially
322 <heading>The Debian Archive</heading>
325 The Debian system is maintained and distributed as a
326 collection of <em>packages</em>. Since there are so many of
327 them (currently well over 15000), they are split into
328 <em>sections</em> and given <em>priorities</em> to simplify
329 the handling of them.
333 The effort of the Debian project is to build a free operating
334 system, but not every package we want to make accessible is
335 <em>free</em> in our sense (see the Debian Free Software
336 Guidelines, below), or may be imported/exported without
337 restrictions. Thus, the archive is split into areas<footnote>
338 The Debian archive software uses the term "component" internally
339 and in the Release file format to refer to the division of an
340 archive. The Debian Social Contract simply refers to "areas."
341 This document uses terminology similar to the Social Contract.
342 </footnote> based on their licenses and other restrictions.
346 The aims of this are:
348 <list compact="compact">
349 <item>to allow us to make as much software available as we can</item>
350 <item>to allow us to encourage everyone to write free software,
352 <item>to allow us to make it easy for people to produce
353 CD-ROMs of our system without violating any licenses,
354 import/export restrictions, or any other laws.</item>
359 The <em>main</em> archive area forms the <em>Debian distribution</em>.
363 Packages in the other archive areas (<tt>contrib</tt>,
364 <tt>non-free</tt>) are not considered to be part of the Debian
365 distribution, although we support their use and provide
366 infrastructure for them (such as our bug-tracking system and
367 mailing lists). This Debian Policy Manual applies to these
372 <heading>The Debian Free Software Guidelines</heading>
374 The Debian Free Software Guidelines (DFSG) form our
375 definition of "free software". These are:
377 <tag>1. Free Redistribution
380 The license of a Debian component may not restrict any
381 party from selling or giving away the software as a
382 component of an aggregate software distribution
383 containing programs from several different
384 sources. The license may not require a royalty or
385 other fee for such sale.
390 The program must include source code, and must allow
391 distribution in source code as well as compiled form.
393 <tag>3. Derived Works
396 The license must allow modifications and derived
397 works, and must allow them to be distributed under the
398 same terms as the license of the original software.
400 <tag>4. Integrity of The Author's Source Code
403 The license may restrict source-code from being
404 distributed in modified form <em>only</em> if the
405 license allows the distribution of "patch files"
406 with the source code for the purpose of modifying the
407 program at build time. The license must explicitly
408 permit distribution of software built from modified
409 source code. The license may require derived works to
410 carry a different name or version number from the
411 original software. (This is a compromise. The Debian
412 Project encourages all authors to not restrict any
413 files, source or binary, from being modified.)
415 <tag>5. No Discrimination Against Persons or Groups
418 The license must not discriminate against any person
421 <tag>6. No Discrimination Against Fields of Endeavor
424 The license must not restrict anyone from making use
425 of the program in a specific field of endeavor. For
426 example, it may not restrict the program from being
427 used in a business, or from being used for genetic
430 <tag>7. Distribution of License
433 The rights attached to the program must apply to all
434 to whom the program is redistributed without the need
435 for execution of an additional license by those
438 <tag>8. License Must Not Be Specific to Debian
441 The rights attached to the program must not depend on
442 the program's being part of a Debian system. If the
443 program is extracted from Debian and used or
444 distributed without Debian but otherwise within the
445 terms of the program's license, all parties to whom
446 the program is redistributed must have the same
447 rights as those that are granted in conjunction with
450 <tag>9. License Must Not Contaminate Other Software
453 The license must not place restrictions on other
454 software that is distributed along with the licensed
455 software. For example, the license must not insist
456 that all other programs distributed on the same medium
457 must be free software.
459 <tag>10. Example Licenses
462 The "GPL," "BSD," and "Artistic" licenses are examples of
463 licenses that we consider <em>free</em>.
470 <heading>Archive areas</heading>
473 <heading>The main archive area</heading>
476 The <em>main</em> archive area comprises the Debian
477 distribution. Only the packages in this area are considered
478 part of the distribution. None of the packages in
479 the <em>main</em> archive area require software outside of
480 that area to function. Anyone may use, share, modify and
481 redistribute the packages in this archive area
483 See <url id="http://www.debian.org/intro/free"
484 name="What Does Free Mean?"> for
485 more about what we mean by free software.
490 Every package in <em>main</em> must comply with the DFSG
491 (Debian Free Software Guidelines).
495 In addition, the packages in <em>main</em>
496 <list compact="compact">
498 must not require or recommend a package outside
499 of <em>main</em> for compilation or execution (thus, the
500 package must not declare a "Pre-Depends", "Depends",
501 "Recommends", "Build-Depends", or "Build-Depends-Indep"
502 relationship on a non-<em>main</em> package),
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
518 <heading>The contrib archive area</heading>
521 The <em>contrib</em> archive area contains supplemental
522 packages intended to work with the Debian distribution, but
523 which require software outside of the distribution to either
528 Every package in <em>contrib</em> must comply with the DFSG.
532 In addition, the packages in <em>contrib</em>
533 <list compact="compact">
535 must not be so buggy that we refuse to support them,
539 must meet all policy requirements presented in this
546 Examples of packages which would be included in
547 <em>contrib</em> are:
548 <list compact="compact">
550 free packages which require <em>contrib</em>,
551 <em>non-free</em> packages or packages which are not
552 in our archive at all for compilation or execution,
556 wrapper packages or other sorts of free accessories for
563 <sect1 id="non-free">
564 <heading>The non-free archive area</heading>
567 The <em>non-free</em> archive area contains supplemental
568 packages intended to work with the Debian distribution that do
569 not comply with the DFSG or have other problems that make
570 their distribution problematic. They may not comply with all
571 of the policy requirements in this manual due to restrictions
572 on modifications or other limitations.
576 Packages must be placed in <em>non-free</em> if they are
577 not compliant with the DFSG or are encumbered by patents
578 or other legal issues that make their distribution
583 In addition, the packages in <em>non-free</em>
584 <list compact="compact">
586 must not be so buggy that we refuse to support them,
590 must meet all policy requirements presented in this
591 manual that it is possible for them to meet.
593 It is possible that there are policy
594 requirements which the package is unable to
595 meet, for example, if the source is
596 unavailable. These situations will need to be
597 handled on a case-by-case basis.
606 <sect id="pkgcopyright">
607 <heading>Copyright considerations</heading>
610 Every package must be accompanied by a verbatim copy of its
611 copyright information and distribution license in the file
612 <file>/usr/share/doc/<var>package</var>/copyright</file>
613 (see <ref id="copyrightfile"> for further details).
617 We reserve the right to restrict files from being included
618 anywhere in our archives if
619 <list compact="compact">
621 their use or distribution would break a law,
624 there is an ethical conflict in their distribution or
628 we would have to sign a license for them, or
631 their distribution would conflict with other project
638 Programs whose authors encourage the user to make
639 donations are fine for the main distribution, provided
640 that the authors do not claim that not donating is
641 immoral, unethical, illegal or something similar; in such
642 a case they must go in <em>non-free</em>.
646 Packages whose copyright permission notices (or patent
647 problems) do not even allow redistribution of binaries
648 only, and where no special permission has been obtained,
649 must not be placed on the Debian FTP site and its mirrors
654 Note that under international copyright law (this applies
655 in the United States, too), <em>no</em> distribution or
656 modification of a work is allowed without an explicit
657 notice saying so. Therefore a program without a copyright
658 notice <em>is</em> copyrighted and you may not do anything
659 to it without risking being sued! Likewise if a program
660 has a copyright notice but no statement saying what is
661 permitted then nothing is permitted.
665 Many authors are unaware of the problems that restrictive
666 copyrights (or lack of copyright notices) can cause for
667 the users of their supposedly-free software. It is often
668 worthwhile contacting such authors diplomatically to ask
669 them to modify their license terms. However, this can be a
670 politically difficult thing to do and you should ask for
671 advice on the <tt>debian-legal</tt> mailing list first, as
676 When in doubt about a copyright, send mail to
677 <email>debian-legal@lists.debian.org</email>. Be prepared
678 to provide us with the copyright statement. Software
679 covered by the GPL, public domain software and BSD-like
680 copyrights are safe; be wary of the phrases "commercial
681 use prohibited" and "distribution restricted".
685 <sect id="subsections">
686 <heading>Sections</heading>
689 The packages in the archive areas <em>main</em>,
690 <em>contrib</em> and <em>non-free</em> are grouped further into
691 <em>sections</em> to simplify handling.
695 The archive area and section for each package should be
696 specified in the package's <tt>Section</tt> control record (see
697 <ref id="f-Section">). However, the maintainer of the Debian
698 archive may override this selection to ensure the consistency of
699 the Debian distribution. The <tt>Section</tt> field should be
701 <list compact="compact">
703 <em>section</em> if the package is in the
704 <em>main</em> archive area,
707 <em>area/section</em> if the package is in
708 the <em>contrib</em> or <em>non-free</em>
715 The Debian archive maintainers provide the authoritative
716 list of sections. At present, they are:
717 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
718 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
719 <em>education</em>, <em>electronics</em>, <em>embedded</em>,
720 <em>fonts</em>, <em>games</em>, <em>gnome</em>, <em>graphics</em>,
721 <em>gnu-r</em>, <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
722 <em>httpd</em>, <em>interpreters</em>, <em>introspection</em>,
723 <em>java</em>, <em>kde</em>, <em>kernel</em>, <em>libs</em>,
724 <em>libdevel</em>, <em>lisp</em>, <em>localization</em>,
725 <em>mail</em>, <em>math</em>, <em>metapackages</em>, <em>misc</em>,
726 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
727 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
728 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
729 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
730 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
731 <em>zope</em>. The additional section <em>debian-installer</em>
732 contains special packages used by the installer and is not used
733 for normal Debian packages.
737 For more information about the sections and their definitions,
738 see the <url id="http://packages.debian.org/unstable/"
739 name="list of sections in unstable">.
743 <sect id="priorities">
744 <heading>Priorities</heading>
747 Each package should have a <em>priority</em> value, which is
748 included in the package's <em>control record</em>
749 (see <ref id="f-Priority">).
750 This information is used by the Debian package management tools to
751 separate high-priority packages from less-important packages.
755 The following <em>priority levels</em> are recognized by the
756 Debian package management tools.
758 <tag><tt>required</tt></tag>
760 Packages which are necessary for the proper
761 functioning of the system (usually, this means that
762 dpkg functionality depends on these packages).
763 Removing a <tt>required</tt> package may cause your
764 system to become totally broken and you may not even
765 be able to use <prgn>dpkg</prgn> to put things back,
766 so only do so if you know what you are doing. Systems
767 with only the <tt>required</tt> packages are probably
768 unusable, but they do have enough functionality to
769 allow the sysadmin to boot and install more software.
771 <tag><tt>important</tt></tag>
773 Important programs, including those which one would
774 expect to find on any Unix-like system. If the
775 expectation is that an experienced Unix person who
776 found it missing would say "What on earth is going on,
777 where is <prgn>foo</prgn>?", it must be an
778 <tt>important</tt> package.<footnote>
779 This is an important criterion because we are
780 trying to produce, amongst other things, a free
783 Other packages without which the system will not run
784 well or be usable must also have priority
785 <tt>important</tt>. This does
786 <em>not</em> include Emacs, the X Window System, TeX
787 or any other large applications. The
788 <tt>important</tt> packages are just a bare minimum of
789 commonly-expected and necessary tools.
791 <tag><tt>standard</tt></tag>
793 These packages provide a reasonably small but not too
794 limited character-mode system. This is what will be
795 installed by default if the user doesn't select anything
796 else. It doesn't include many large applications.
798 <tag><tt>optional</tt></tag>
800 (In a sense everything that isn't required is
801 optional, but that's not what is meant here.) This is
802 all the software that you might reasonably want to
803 install if you didn't know what it was and don't have
804 specialized requirements. This is a much larger system
805 and includes the X Window System, a full TeX
806 distribution, and many applications. Note that
807 optional packages should not conflict with each other.
809 <tag><tt>extra</tt></tag>
811 This contains all packages that conflict with others
812 with required, important, standard or optional
813 priorities, or are only likely to be useful if you
814 already know what they are or have specialized
815 requirements (such as packages containing only detached
822 Packages must not depend on packages with lower priority
823 values (excluding build-time dependencies). In order to
824 ensure this, the priorities of one or more packages may need
833 <heading>Binary packages</heading>
836 The Debian distribution is based on the Debian
837 package management system, called <prgn>dpkg</prgn>. Thus,
838 all packages in the Debian distribution must be provided
839 in the <tt>.deb</tt> file format.
843 A <tt>.deb</tt> package contains two sets of files: a set of files
844 to install on the system when the package is installed, and a set
845 of files that provide additional metadata about the package or
846 which are executed when the package is installed or removed. This
847 second set of files is called <em>control information files</em>.
848 Among those files are the package maintainer scripts
849 and <file>control</file>, the <qref id="binarycontrolfiles">binary
850 package control file</qref> that contains the control fields for
851 the package. Other control information files include
852 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
853 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
854 used to store shared library dependency information and
855 the <file>conffiles</file> file that lists the package's
856 configuration files (described in <ref id="config-files">).
860 There is unfortunately a collision of terminology here between
861 control information files and files in the Debian control file
862 format. Throughout this document, a <em>control file</em> refers
863 to a file in the Debian control file format. These files are
864 documented in <ref id="controlfields">. Only files referred to
865 specifically as <em>control information files</em> are the files
866 included in the control information file member of
867 the <file>.deb</file> file format used by binary packages. Most
868 control information files are not in the Debian control file
873 <heading>The package name</heading>
876 Every package must have a name that's unique within the Debian
881 The package name is included in the control field
882 <tt>Package</tt>, the format of which is described
883 in <ref id="f-Package">.
884 The package name is also included as a part of the file name
885 of the <tt>.deb</tt> file.
890 <heading>The version of a package</heading>
893 Every package has a version number recorded in its
894 <tt>Version</tt> control file field, described in
895 <ref id="f-Version">.
899 The package management system imposes an ordering on version
900 numbers, so that it can tell whether packages are being up- or
901 downgraded and so that package system front end applications
902 can tell whether a package it finds available is newer than
903 the one installed on the system. The version number format
904 has the most significant parts (as far as comparison is
905 concerned) at the beginning.
909 If an upstream package has problematic version numbers they
910 should be converted to a sane form for use in the
911 <tt>Version</tt> field.
915 <heading>Version numbers based on dates</heading>
918 In general, Debian packages should use the same version
919 numbers as the upstream sources. However, upstream version
920 numbers based on some date formats (sometimes used for
921 development or "snapshot" releases) will not be ordered
922 correctly by the package management software. For
923 example, <prgn>dpkg</prgn> will consider "96May01" to be
924 greater than "96Dec24".
928 To prevent having to use epochs for every new upstream
929 version, the date-based portion of any upstream version number
930 should be given in a way that sorts correctly: four-digit year
931 first, followed by a two-digit numeric month, followed by a
932 two-digit numeric date, possibly with punctuation between the
937 Native Debian packages (i.e., packages which have been written
938 especially for Debian) whose version numbers include dates
939 should also follow these rules. If punctuation is desired
940 between the date components, remember that hyphen (<tt>-</tt>)
941 cannot be used in native package versions. Period
942 (<tt>.</tt>) is normally a good choice.
948 <sect id="maintainer">
949 <heading>The maintainer of a package</heading>
952 Every package must have a maintainer, except for orphaned
953 packages as described below. The maintainer may be one person
954 or a group of people reachable from a common email address, such
955 as a mailing list. The maintainer is responsible for
956 maintaining the Debian packaging files, evaluating and
957 responding appropriately to reported bugs, uploading new
958 versions of the package (either directly or through a sponsor),
959 ensuring that the package is placed in the appropriate archive
960 area and included in Debian releases as appropriate for the
961 stability and utility of the package, and requesting removal of
962 the package from the Debian distribution if it is no longer
963 useful or maintainable.
967 The maintainer must be specified in the <tt>Maintainer</tt>
968 control field with their correct name and a working email
969 address. The email address given in the <tt>Maintainer</tt>
970 control field must accept mail from those role accounts in
971 Debian used to send automated mails regarding the package. This
972 includes non-spam mail from the bug-tracking system, all mail
973 from the Debian archive maintenance software, and other role
974 accounts or automated processes that are commonly agreed on by
975 the project.<footnote>
976 A sample implementation of such a whitelist written for the
977 Mailman mailing list management software is used for mailing
978 lists hosted by alioth.debian.org.
980 If one person or team maintains several packages, they should
981 use the same form of their name and email address in
982 the <tt>Maintainer</tt> fields of those packages.
986 The format of the <tt>Maintainer</tt> control field is
987 described in <ref id="f-Maintainer">.
991 If the maintainer of the package is a team of people with a
992 shared email address, the <tt>Uploaders</tt> control field must
993 be present and must contain at least one human with their
994 personal email address. See <ref id="f-Uploaders"> for the
995 syntax of that field.
999 An orphaned package is one with no current maintainer. Orphaned
1000 packages should have their <tt>Maintainer</tt> control field set
1001 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1002 These packages are considered maintained by the Debian project
1003 as a whole until someone else volunteers to take over
1004 maintenance.<footnote>
1005 The detailed procedure for gracefully orphaning a package can
1006 be found in the Debian Developer's Reference
1007 (see <ref id="related">).
1012 <sect id="descriptions">
1013 <heading>The description of a package</heading>
1016 Every Debian package must have a <tt>Description</tt> control
1017 field which contains a synopsis and extended description of the
1018 package. Technical information about the format of the
1019 <tt>Description</tt> field is in <ref id="f-Description">.
1023 The description should describe the package (the program) to a
1024 user (system administrator) who has never met it before so that
1025 they have enough information to decide whether they want to
1026 install it. This description should not just be copied verbatim
1027 from the program's documentation.
1031 Put important information first, both in the synopsis and
1032 extended description. Sometimes only the first part of the
1033 synopsis or of the description will be displayed. You can
1034 assume that there will usually be a way to see the whole
1035 extended description.
1039 The description should also give information about the
1040 significant dependencies and conflicts between this package
1041 and others, so that the user knows why these dependencies and
1042 conflicts have been declared.
1046 Instructions for configuring or using the package should
1047 not be included (that is what installation scripts,
1048 manual pages, info files, etc., are for). Copyright
1049 statements and other administrivia should not be included
1050 either (that is what the copyright file is for).
1053 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1056 The single line synopsis should be kept brief - certainly
1057 under 80 characters.
1061 Do not include the package name in the synopsis line. The
1062 display software knows how to display this already, and you
1063 do not need to state it. Remember that in many situations
1064 the user may only see the synopsis line - make it as
1065 informative as you can.
1070 <sect1 id="extendeddesc"><heading>The extended description</heading>
1073 Do not try to continue the single line synopsis into the
1074 extended description. This will not work correctly when
1075 the full description is displayed, and makes no sense
1076 where only the summary (the single line synopsis) is
1081 The extended description should describe what the package
1082 does and how it relates to the rest of the system (in terms
1083 of, for example, which subsystem it is which part of).
1087 The description field needs to make sense to anyone, even
1088 people who have no idea about any of the things the
1089 package deals with.<footnote>
1090 The blurb that comes with a program in its
1091 announcements and/or <prgn>README</prgn> files is
1092 rarely suitable for use in a description. It is
1093 usually aimed at people who are already in the
1094 community where the package is used.
1102 <sect id="dependencies">
1103 <heading>Dependencies</heading>
1106 Every package must specify the dependency information
1107 about other packages that are required for the first to
1112 For example, a dependency entry must be provided for any
1113 shared libraries required by a dynamically-linked executable
1114 binary in a package.
1118 Packages are not required to declare any dependencies they
1119 have on other packages which are marked <tt>Essential</tt>
1120 (see below), and should not do so unless they depend on a
1121 particular version of that package.<footnote>
1123 Essential is needed in part to avoid unresolvable dependency
1124 loops on upgrade. If packages add unnecessary dependencies
1125 on packages in this set, the chances that there
1126 <strong>will</strong> be an unresolvable dependency loop
1127 caused by forcing these Essential packages to be configured
1128 first before they need to be is greatly increased. It also
1129 increases the chances that frontends will be unable to
1130 <strong>calculate</strong> an upgrade path, even if one
1134 Also, functionality is rarely ever removed from the
1135 Essential set, but <em>packages</em> have been removed from
1136 the Essential set when the functionality moved to a
1137 different package. So depending on these packages <em>just
1138 in case</em> they stop being essential does way more harm
1145 Sometimes, unpacking one package requires that another package
1146 be first unpacked <em>and</em> configured. In this case, the
1147 depending package must specify this dependency in
1148 the <tt>Pre-Depends</tt> control field.
1152 You should not specify a <tt>Pre-Depends</tt> entry for a
1153 package before this has been discussed on the
1154 <tt>debian-devel</tt> mailing list and a consensus about
1155 doing that has been reached.
1159 The format of the package interrelationship control fields is
1160 described in <ref id="relationships">.
1164 <sect id="virtual_pkg">
1165 <heading>Virtual packages</heading>
1168 Sometimes, there are several packages which offer
1169 more-or-less the same functionality. In this case, it's
1170 useful to define a <em>virtual package</em> whose name
1171 describes that common functionality. (The virtual
1172 packages only exist logically, not physically; that's why
1173 they are called <em>virtual</em>.) The packages with this
1174 particular function will then <em>provide</em> the virtual
1175 package. Thus, any other package requiring that function
1176 can simply depend on the virtual package without having to
1177 specify all possible packages individually.
1181 All packages should use virtual package names where
1182 appropriate, and arrange to create new ones if necessary.
1183 They should not use virtual package names (except privately,
1184 amongst a cooperating group of packages) unless they have
1185 been agreed upon and appear in the list of virtual package
1186 names. (See also <ref id="virtual">)
1190 The latest version of the authoritative list of virtual
1191 package names can be found in the <tt>debian-policy</tt> package.
1192 It is also available from the Debian web mirrors at
1193 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1194 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1198 The procedure for updating the list is described in the preface
1205 <heading>Base system</heading>
1208 The <tt>base system</tt> is a minimum subset of the Debian
1209 system that is installed before everything else
1210 on a new system. Only very few packages are allowed to form
1211 part of the base system, in order to keep the required disk
1216 The base system consists of all those packages with priority
1217 <tt>required</tt> or <tt>important</tt>. Many of them will
1218 be tagged <tt>essential</tt> (see below).
1223 <heading>Essential packages</heading>
1226 Essential is defined as the minimal set of functionality that
1227 must be available and usable on the system at all times, even
1228 when packages are in an unconfigured (but unpacked) state.
1229 Packages are tagged <tt>essential</tt> for a system using the
1230 <tt>Essential</tt> control field. The format of the
1231 <tt>Essential</tt> control field is described in <ref
1236 Since these packages cannot be easily removed (one has to
1237 specify an extra <em>force option</em> to
1238 <prgn>dpkg</prgn> to do so), this flag must not be used
1239 unless absolutely necessary. A shared library package
1240 must not be tagged <tt>essential</tt>; dependencies will
1241 prevent its premature removal, and we need to be able to
1242 remove it when it has been superseded.
1246 Since dpkg will not prevent upgrading of other packages
1247 while an <tt>essential</tt> package is in an unconfigured
1248 state, all <tt>essential</tt> packages must supply all of
1249 their core functionality even when unconfigured. If the
1250 package cannot satisfy this requirement it must not be
1251 tagged as essential, and any packages depending on this
1252 package must instead have explicit dependency fields as
1257 Maintainers should take great care in adding any programs,
1258 interfaces, or functionality to <tt>essential</tt> packages.
1259 Packages may assume that functionality provided by
1260 <tt>essential</tt> packages is always available without
1261 declaring explicit dependencies, which means that removing
1262 functionality from the Essential set is very difficult and is
1263 almost never done. Any capability added to an
1264 <tt>essential</tt> package therefore creates an obligation to
1265 support that capability as part of the Essential set in
1270 You must not tag any packages <tt>essential</tt> before
1271 this has been discussed on the <tt>debian-devel</tt>
1272 mailing list and a consensus about doing that has been
1277 <sect id="maintscripts">
1278 <heading>Maintainer Scripts</heading>
1281 The package installation scripts should avoid producing
1282 output which is unnecessary for the user to see and
1283 should rely on <prgn>dpkg</prgn> to stave off boredom on
1284 the part of a user installing many packages. This means,
1285 amongst other things, using the <tt>--quiet</tt> option on
1286 <prgn>install-info</prgn>.
1290 Errors which occur during the execution of an installation
1291 script must be checked and the installation must not
1292 continue after an error.
1296 Note that in general <ref id="scripts"> applies to package
1297 maintainer scripts, too.
1301 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1302 to another package without consulting the maintainer of that
1303 package first. When adding or removing diversions, package
1304 maintainer scripts must provide the <tt>--package</tt> flag
1305 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1309 All packages which supply an instance of a common command
1310 name (or, in general, filename) should generally use
1311 <prgn>update-alternatives</prgn>, so that they may be
1312 installed together. If <prgn>update-alternatives</prgn>
1313 is not used, then each package must use
1314 <tt>Conflicts</tt> to ensure that other packages are
1315 de-installed. (In this case, it may be appropriate to
1316 specify a conflict against earlier versions of something
1317 that previously did not use
1318 <prgn>update-alternatives</prgn>; this is an exception to
1319 the usual rule that versioned conflicts should be
1323 <sect1 id="maintscriptprompt">
1324 <heading>Prompting in maintainer scripts</heading>
1326 Package maintainer scripts may prompt the user if
1327 necessary. Prompting must be done by communicating
1328 through a program, such as <prgn>debconf</prgn>, which
1329 conforms to the Debian Configuration Management
1330 Specification, version 2 or higher.
1334 Packages which are essential, or which are dependencies of
1335 essential packages, may fall back on another prompting method
1336 if no such interface is available when they are executed.
1340 The Debian Configuration Management Specification is included
1341 in the <file>debconf_specification</file> files in the
1342 <package>debian-policy</package> package.
1343 It is also available from the Debian web mirrors at
1344 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1345 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1349 Packages which use the Debian Configuration Management
1350 Specification may contain the additional control information
1351 files <file>config</file>
1352 and <file>templates</file>. <file>config</file> is an
1353 additional maintainer script used for package configuration,
1354 and <file>templates</file> contains templates used for user
1355 prompting. The <prgn>config</prgn> script might be run before
1356 the <prgn>preinst</prgn> script and before the package is
1357 unpacked or any of its dependencies or pre-dependencies are
1358 satisfied. Therefore it must work using only the tools
1359 present in <em>essential</em> packages.<footnote>
1360 <package>Debconf</package> or another tool that
1361 implements the Debian Configuration Management
1362 Specification will also be installed, and any
1363 versioned dependencies on it will be satisfied
1364 before preconfiguration begins.
1369 Packages which use the Debian Configuration Management
1370 Specification must allow for translation of their user-visible
1371 messages by using a gettext-based system such as the one
1372 provided by the <package>po-debconf</package> package.
1376 Packages should try to minimize the amount of prompting
1377 they need to do, and they should ensure that the user
1378 will only ever be asked each question once. This means
1379 that packages should try to use appropriate shared
1380 configuration files (such as <file>/etc/papersize</file> and
1381 <file>/etc/news/server</file>), and shared
1382 <package>debconf</package> variables rather than each
1383 prompting for their own list of required pieces of
1388 It also means that an upgrade should not ask the same
1389 questions again, unless the user has used
1390 <tt>dpkg --purge</tt> to remove the package's configuration.
1391 The answers to configuration questions should be stored in an
1392 appropriate place in <file>/etc</file> so that the user can
1393 modify them, and how this has been done should be
1398 If a package has a vitally important piece of
1399 information to pass to the user (such as "don't run me
1400 as I am, you must edit the following configuration files
1401 first or you risk your system emitting badly-formatted
1402 messages"), it should display this in the
1403 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1404 prompt the user to hit return to acknowledge the
1405 message. Copyright messages do not count as vitally
1406 important (they belong in
1407 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1408 neither do instructions on how to use a program (these
1409 should be in on-line documentation, where all the users
1414 Any necessary prompting should almost always be confined
1415 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1416 script. If it is done in the <prgn>postinst</prgn>, it
1417 should be protected with a conditional so that
1418 unnecessary prompting doesn't happen if a package's
1419 installation fails and the <prgn>postinst</prgn> is
1420 called with <tt>abort-upgrade</tt>,
1421 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1431 <heading>Source packages</heading>
1433 <sect id="standardsversion">
1434 <heading>Standards conformance</heading>
1437 Source packages should specify the most recent version number
1438 of this policy document with which your package complied
1439 when it was last updated.
1443 This information may be used to file bug reports
1444 automatically if your package becomes too much out of date.
1448 The version is specified in the <tt>Standards-Version</tt>
1450 The format of the <tt>Standards-Version</tt> field is
1451 described in <ref id="f-Standards-Version">.
1455 You should regularly, and especially if your package has
1456 become out of date, check for the newest Policy Manual
1457 available and update your package, if necessary. When your
1458 package complies with the new standards you should update the
1459 <tt>Standards-Version</tt> source package field and
1460 release it.<footnote>
1461 See the file <file>upgrading-checklist</file> for
1462 information about policy which has changed between
1463 different versions of this document.
1469 <sect id="pkg-relations">
1470 <heading>Package relationships</heading>
1473 Source packages should specify which binary packages they
1474 require to be installed or not to be installed in order to
1475 build correctly. For example, if building a package
1476 requires a certain compiler, then the compiler should be
1477 specified as a build-time dependency.
1481 It is not necessary to explicitly specify build-time
1482 relationships on a minimal set of packages that are always
1483 needed to compile, link and put in a Debian package a
1484 standard "Hello World!" program written in C or C++. The
1485 required packages are called <em>build-essential</em>, and
1486 an informational list can be found in
1487 <file>/usr/share/doc/build-essential/list</file> (which is
1488 contained in the <tt>build-essential</tt>
1491 <list compact="compact">
1493 This allows maintaining the list separately
1494 from the policy documents (the list does not
1495 need the kind of control that the policy
1499 Having a separate package allows one to install
1500 the build-essential packages on a machine, as
1501 well as allowing other packages such as tasks to
1502 require installation of the build-essential
1503 packages using the depends relation.
1506 The separate package allows bug reports against
1507 the list to be categorized separately from
1508 the policy management process in the BTS.
1515 When specifying the set of build-time dependencies, one
1516 should list only those packages explicitly required by the
1517 build. It is not necessary to list packages which are
1518 required merely because some other package in the list of
1519 build-time dependencies depends on them.<footnote>
1520 The reason for this is that dependencies change, and
1521 you should list all those packages, and <em>only</em>
1522 those packages that <em>you</em> need directly. What
1523 others need is their business. For example, if you
1524 only link against <file>libimlib</file>, you will need to
1525 build-depend on <package>libimlib2-dev</package> but
1526 not against any <tt>libjpeg*</tt> packages, even
1527 though <tt>libimlib2-dev</tt> currently depends on
1528 them: installation of <package>libimlib2-dev</package>
1529 will automatically ensure that all of its run-time
1530 dependencies are satisfied.
1535 If build-time dependencies are specified, it must be
1536 possible to build the package and produce working binaries
1537 on a system with only essential and build-essential
1538 packages installed and also those required to satisfy the
1539 build-time relationships (including any implied
1540 relationships). In particular, this means that version
1541 clauses should be used rigorously in build-time
1542 relationships so that one cannot produce bad or
1543 inconsistently configured packages when the relationships
1544 are properly satisfied.
1548 <ref id="relationships"> explains the technical details.
1553 <heading>Changes to the upstream sources</heading>
1556 If changes to the source code are made that are not
1557 specific to the needs of the Debian system, they should be
1558 sent to the upstream authors in whatever form they prefer
1559 so as to be included in the upstream version of the
1564 If you need to configure the package differently for
1565 Debian or for Linux, and the upstream source doesn't
1566 provide a way to do so, you should add such configuration
1567 facilities (for example, a new <prgn>autoconf</prgn> test
1568 or <tt>#define</tt>) and send the patch to the upstream
1569 authors, with the default set to the way they originally
1570 had it. You can then easily override the default in your
1571 <file>debian/rules</file> or wherever is appropriate.
1575 You should make sure that the <prgn>configure</prgn> utility
1576 detects the correct architecture specification string
1577 (refer to <ref id="arch-spec"> for details).
1581 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1582 <prgn>configure</prgn> scripts are used, you should edit the
1583 <file>.in</file> files rather than editing the
1584 <prgn>Makefile</prgn> directly. This allows the user to
1585 reconfigure the package if necessary. You should
1586 <em>not</em> configure the package and edit the generated
1587 <prgn>Makefile</prgn>! This makes it impossible for someone
1588 else to later reconfigure the package without losing the
1594 <sect id="dpkgchangelog">
1595 <heading>Debian changelog: <file>debian/changelog</file></heading>
1598 Changes in the Debian version of the package should be
1599 briefly explained in the Debian changelog file
1600 <file>debian/changelog</file>.<footnote>
1602 Mistakes in changelogs are usually best rectified by
1603 making a new changelog entry rather than "rewriting
1604 history" by editing old changelog entries.
1607 This includes modifications
1608 made in the Debian package compared to the upstream one
1609 as well as other changes and updates to the package.
1611 Although there is nothing stopping an author who is also
1612 the Debian maintainer from using this changelog for all
1613 their changes, it will have to be renamed if the Debian
1614 and upstream maintainers become different people. In such
1615 a case, however, it might be better to maintain the package
1616 as a non-native package.
1621 The format of the <file>debian/changelog</file> allows the
1622 package building tools to discover which version of the package
1623 is being built and find out other release-specific information.
1627 That format is a series of entries like this:
1629 <example compact="compact">
1630 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1632 [optional blank line(s), stripped]
1634 * <var>change details</var>
1635 <var>more change details</var>
1637 [blank line(s), included in output of dpkg-parsechangelog]
1639 * <var>even more change details</var>
1641 [optional blank line(s), stripped]
1643 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1648 <var>package</var> and <var>version</var> are the source
1649 package name and version number.
1653 <var>distribution(s)</var> lists the distributions where
1654 this version should be installed when it is uploaded - it
1655 is copied to the <tt>Distribution</tt> field in the
1656 <file>.changes</file> file. See <ref id="f-Distribution">.
1660 <var>urgency</var> is the value for the <tt>Urgency</tt>
1661 field in the <file>.changes</file> file for the upload
1662 (see <ref id="f-Urgency">). It is not possible to specify
1663 an urgency containing commas; commas are used to separate
1664 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1665 <prgn>dpkg</prgn> changelog format (though there is
1666 currently only one useful <var>keyword</var>,
1671 The change details may in fact be any series of lines
1672 starting with at least two spaces, but conventionally each
1673 change starts with an asterisk and a separating space and
1674 continuation lines are indented so as to bring them in
1675 line with the start of the text above. Blank lines may be
1676 used here to separate groups of changes, if desired.
1680 If this upload resolves bugs recorded in the Bug Tracking
1681 System (BTS), they may be automatically closed on the
1682 inclusion of this package into the Debian archive by
1683 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1684 in the change details.<footnote>
1685 To be precise, the string should match the following
1686 Perl regular expression:
1688 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1690 Then all of the bug numbers listed will be closed by the
1691 archive maintenance script (<prgn>katie</prgn>) using the
1692 <var>version</var> of the changelog entry.
1694 This information is conveyed via the <tt>Closes</tt> field
1695 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1699 The maintainer name and email address used in the changelog
1700 should be the details of the person uploading <em>this</em>
1701 version. They are <em>not</em> necessarily those of the
1702 usual package maintainer.<footnote>
1703 If the developer uploading the package is not one of the usual
1704 maintainers of the package (as listed in
1705 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1706 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1707 fields of the package), the first line of the changelog is
1708 conventionally used to explain why a non-maintainer is
1709 uploading the package. The Debian Developer's Reference
1710 (see <ref id="related">) documents the conventions
1712 The information here will be copied to the <tt>Changed-By</tt>
1713 field in the <tt>.changes</tt> file
1714 (see <ref id="f-Changed-By">), and then later used to send an
1715 acknowledgement when the upload has been installed.
1719 The <var>date</var> has the following format<footnote>
1720 This is the same as the format generated by <tt>date
1722 </footnote> (compatible and with the same semantics of
1723 RFC 2822 and RFC 5322):
1724 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1726 <list compact="compact">
1728 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1731 dd is a one- or two-digit day of the month (01-31)
1734 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1737 <item>yyyy is the four-digit year (e.g. 2010)</item>
1738 <item>hh is the two-digit hour (00-23)</item>
1739 <item>mm is the two-digit minutes (00-59)</item>
1740 <item>ss is the two-digit seconds (00-60)</item>
1742 +zzzz or -zzzz is the the time zone offset from Coordinated
1743 Universal Time (UTC). "+" indicates that the time is ahead
1744 of (i.e., east of) UTC and "-" indicates that the time is
1745 behind (i.e., west of) UTC. The first two digits indicate
1746 the hour difference from UTC and the last two digits
1747 indicate the number of additional minutes difference from
1748 UTC. The last two digits must be in the range 00-59.
1754 The first "title" line with the package name must start
1755 at the left hand margin. The "trailer" line with the
1756 maintainer and date details must be preceded by exactly
1757 one space. The maintainer details and the date must be
1758 separated by exactly two spaces.
1762 The entire changelog must be encoded in UTF-8.
1766 For more information on placement of the changelog files
1767 within binary packages, please see <ref id="changelogs">.
1771 <sect id="dpkgcopyright">
1772 <heading>Copyright: <file>debian/copyright</file></heading>
1774 Every package must be accompanied by a verbatim copy of its
1775 copyright information and distribution license in the file
1776 <file>/usr/share/doc/<var>package</var>/copyright</file>
1777 (see <ref id="copyrightfile"> for further details). Also see
1778 <ref id="pkgcopyright"> for further considerations related
1779 to copyrights for packages.
1783 <heading>Error trapping in makefiles</heading>
1786 When <prgn>make</prgn> invokes a command in a makefile
1787 (including your package's upstream makefiles and
1788 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1789 means that <prgn>sh</prgn>'s usual bad error handling
1790 properties apply: if you include a miniature script as one
1791 of the commands in your makefile you'll find that if you
1792 don't do anything about it then errors are not detected
1793 and <prgn>make</prgn> will blithely continue after
1798 Every time you put more than one shell command (this
1799 includes using a loop) in a makefile command you
1800 must make sure that errors are trapped. For
1801 simple compound commands, such as changing directory and
1802 then running a program, using <tt>&&</tt> rather
1803 than semicolon as a command separator is sufficient. For
1804 more complex commands including most loops and
1805 conditionals you should include a separate <tt>set -e</tt>
1806 command at the start of every makefile command that's
1807 actually one of these miniature shell scripts.
1811 <sect id="timestamps">
1812 <heading>Time Stamps</heading>
1814 Maintainers should preserve the modification times of the
1815 upstream source files in a package, as far as is reasonably
1817 The rationale is that there is some information conveyed
1818 by knowing the age of the file, for example, you could
1819 recognize that some documentation is very old by looking
1820 at the modification time, so it would be nice if the
1821 modification time of the upstream source would be
1827 <sect id="restrictions">
1828 <heading>Restrictions on objects in source packages</heading>
1831 The source package may not contain any hard links<footnote>
1833 This is not currently detected when building source
1834 packages, but only when extracting
1838 Hard links may be permitted at some point in the
1839 future, but would require a fair amount of
1842 </footnote>, device special files, sockets or setuid or
1843 setgid files.<footnote>
1844 Setgid directories are allowed.
1849 <sect id="debianrules">
1850 <heading>Main building script: <file>debian/rules</file></heading>
1853 This file must be an executable makefile, and contains the
1854 package-specific recipes for compiling the package and
1855 building binary package(s) from the source.
1859 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1860 so that it can be invoked by saying its name rather than
1861 invoking <prgn>make</prgn> explicitly. That is, invoking
1862 either of <tt>make -f debian/rules <em>args...</em></tt>
1863 or <tt>./debian/rules <em>args...</em></tt> must result in
1868 The following targets are required and must be implemented
1869 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1870 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1871 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1875 Since an interactive <file>debian/rules</file> script makes it
1876 impossible to auto-compile that package and also makes it hard
1877 for other people to reproduce the same binary package, all
1878 required targets must be non-interactive. It also follows that
1879 any target that these targets depend on must also be
1884 The targets are as follows:
1886 <tag><tt>build</tt> (required)</tag>
1889 The <tt>build</tt> target should perform all the
1890 configuration and compilation of the package.
1891 If a package has an interactive pre-build
1892 configuration routine, the Debian source package
1893 must either be built after this has taken place (so
1894 that the binary package can be built without rerunning
1895 the configuration) or the configuration routine
1896 modified to become non-interactive. (The latter is
1897 preferable if there are architecture-specific features
1898 detected by the configuration routine.)
1902 For some packages, notably ones where the same
1903 source tree is compiled in different ways to produce
1904 two binary packages, the <tt>build</tt> target
1905 does not make much sense. For these packages it is
1906 good enough to provide two (or more) targets
1907 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1908 for each of the ways of building the package, and a
1909 <tt>build</tt> target that does nothing. The
1910 <tt>binary</tt> target will have to build the
1911 package in each of the possible ways and make the
1912 binary package out of each.
1916 The <tt>build</tt> target must not do anything
1917 that might require root privilege.
1921 The <tt>build</tt> target may need to run the
1922 <tt>clean</tt> target first - see below.
1926 When a package has a configuration and build routine
1927 which takes a long time, or when the makefiles are
1928 poorly designed, or when <tt>build</tt> needs to
1929 run <tt>clean</tt> first, it is a good idea to
1930 <tt>touch build</tt> when the build process is
1931 complete. This will ensure that if <tt>debian/rules
1932 build</tt> is run again it will not rebuild the whole
1934 Another common way to do this is for <tt>build</tt>
1935 to depend on <prgn>build-stamp</prgn> and to do
1936 nothing else, and for the <prgn>build-stamp</prgn>
1937 target to do the building and to <tt>touch
1938 build-stamp</tt> on completion. This is
1939 especially useful if the build routine creates a
1940 file or directory called <tt>build</tt>; in such a
1941 case, <tt>build</tt> will need to be listed as
1942 a phony target (i.e., as a dependency of the
1943 <tt>.PHONY</tt> target). See the documentation of
1944 <prgn>make</prgn> for more information on phony
1950 <tag><tt>build-arch</tt> (optional),
1951 <tt>build-indep</tt> (optional)
1955 A package may also provide one or both of the targets
1956 <tt>build-arch</tt> and <tt>build-indep</tt>.
1957 The <tt>build-arch</tt> target, if provided, should
1958 perform all the configuration and compilation required for
1959 producing all architecture-dependant binary packages
1960 (those packages for which the body of the
1961 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1962 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1963 target, if provided, should perform all the configuration
1964 and compilation required for producing all
1965 architecture-independent binary packages (those packages
1966 for which the body of the <tt>Architecture</tt> field
1967 in <tt>debian/control</tt> is <tt>all</tt>).
1971 If <tt>build-arch</tt> or <tt>build-indep</tt> targets are
1972 provided in the rules file, the <tt>build</tt> target
1973 should either depend on those targets or take the same
1974 actions as invoking those targets would perform.<footnote>
1975 The intent of this split is so that binary-only builds
1976 need not install the dependencies required for
1977 the <tt>build-indep</tt> target. However, this is not
1978 yet used in practice since <tt>dpkg-buildpackage
1979 -B</tt>, and therefore the autobuilders,
1980 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1981 due to the difficulties in determining whether the
1982 optional <tt>build-arch</tt> target exists.
1987 If one or both of the targets <tt>build-arch</tt> and
1988 <tt>build-indep</tt> are not provided, then invoking
1989 <file>debian/rules</file> with one of the not-provided
1990 targets as arguments should produce a exit status code
1991 of 2. Usually this is provided automatically by make
1992 if the target is missing.
1996 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1997 must not do anything that might require root privilege.
2001 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2002 (required), <tt>binary-indep</tt> (required)
2006 The <tt>binary</tt> target must be all that is
2007 necessary for the user to build the binary package(s)
2008 produced from this source package. It is
2009 split into two parts: <prgn>binary-arch</prgn> builds
2010 the binary packages which are specific to a particular
2011 architecture, and <tt>binary-indep</tt> builds
2012 those which are not.
2015 <tt>binary</tt> may be (and commonly is) a target with
2016 no commands which simply depends on
2017 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2020 Both <tt>binary-*</tt> targets should depend on the
2021 <tt>build</tt> target, or on the appropriate
2022 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2023 provided, so that the package is built if it has not
2024 been already. It should then create the relevant
2025 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2026 make their control files and <prgn>dpkg-deb</prgn> to
2027 build them and place them in the parent of the top
2032 Both the <tt>binary-arch</tt> and
2033 <tt>binary-indep</tt> targets <em>must</em> exist.
2034 If one of them has nothing to do (which will always be
2035 the case if the source generates only a single binary
2036 package, whether architecture-dependent or not), it
2037 must still exist and must always succeed.
2041 The <tt>binary</tt> targets must be invoked as
2043 The <prgn>fakeroot</prgn> package often allows one
2044 to build a package correctly even without being
2050 <tag><tt>clean</tt> (required)</tag>
2053 This must undo any effects that the <tt>build</tt>
2054 and <tt>binary</tt> targets may have had, except
2055 that it should leave alone any output files created in
2056 the parent directory by a run of a <tt>binary</tt>
2061 If a <tt>build</tt> file is touched at the end of
2062 the <tt>build</tt> target, as suggested above, it
2063 should be removed as the first action that
2064 <tt>clean</tt> performs, so that running
2065 <tt>build</tt> again after an interrupted
2066 <tt>clean</tt> doesn't think that everything is
2071 The <tt>clean</tt> target may need to be
2072 invoked as root if <tt>binary</tt> has been
2073 invoked since the last <tt>clean</tt>, or if
2074 <tt>build</tt> has been invoked as root (since
2075 <tt>build</tt> may create directories, for
2080 <tag><tt>get-orig-source</tt> (optional)</tag>
2083 This target fetches the most recent version of the
2084 original source package from a canonical archive site
2085 (via FTP or WWW, for example), does any necessary
2086 rearrangement to turn it into the original source
2087 tar file format described below, and leaves it in the
2092 This target may be invoked in any directory, and
2093 should take care to clean up any temporary files it
2098 This target is optional, but providing it if
2099 possible is a good idea.
2103 <tag><tt>patch</tt> (optional)</tag>
2106 This target performs whatever additional actions are
2107 required to make the source ready for editing (unpacking
2108 additional upstream archives, applying patches, etc.).
2109 It is recommended to be implemented for any package where
2110 <tt>dpkg-source -x</tt> does not result in source ready
2111 for additional modification. See
2112 <ref id="readmesource">.
2118 The <tt>build</tt>, <tt>binary</tt> and
2119 <tt>clean</tt> targets must be invoked with the current
2120 directory being the package's top-level directory.
2125 Additional targets may exist in <file>debian/rules</file>,
2126 either as published or undocumented interfaces or for the
2127 package's internal use.
2131 The architectures we build on and build for are determined
2132 by <prgn>make</prgn> variables using the
2133 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2134 You can determine the Debian architecture and the GNU style
2135 architecture specification string for the build architecture as
2136 well as for the host architecture. The build architecture is
2137 the architecture on which <file>debian/rules</file> is run and
2138 the package build is performed. The host architecture is the
2139 architecture on which the resulting package will be installed
2140 and run. These are normally the same, but may be different in
2141 the case of cross-compilation (building packages for one
2142 architecture on machines of a different architecture).
2146 Here is a list of supported <prgn>make</prgn> variables:
2147 <list compact="compact">
2149 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2152 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2155 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2158 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2159 specification string)
2162 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2163 <tt>DEB_*_GNU_TYPE</tt>)
2166 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2167 <tt>DEB_*_GNU_TYPE</tt>)
2169 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2170 the build architecture or <tt>HOST</tt> for specification of the
2175 Backward compatibility can be provided in the rules file
2176 by setting the needed variables to suitable default
2177 values; please refer to the documentation of
2178 <prgn>dpkg-architecture</prgn> for details.
2182 It is important to understand that the <tt>DEB_*_ARCH</tt>
2183 string only determines which Debian architecture we are
2184 building on or for. It should not be used to get the CPU
2185 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2186 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2187 GNU style variables should generally only be used with upstream
2191 <sect1 id="debianrules-options">
2192 <heading><file>debian/rules</file> and
2193 <tt>DEB_BUILD_OPTIONS</tt></heading>
2196 Supporting the standardized environment variable
2197 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2198 contain several flags to change how a package is compiled and
2199 built. Each flag must be in the form <var>flag</var> or
2200 <var>flag</var>=<var>options</var>. If multiple flags are
2201 given, they must be separated by whitespace.<footnote>
2202 Some packages support any delimiter, but whitespace is the
2203 easiest to parse inside a makefile and avoids ambiguity with
2204 flag values that contain commas.
2206 <var>flag</var> must start with a lowercase letter
2207 (<tt>a-z</tt>) and consist only of lowercase letters,
2208 numbers (<tt>0-9</tt>), and the characters
2209 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2210 <var>options</var> must not contain whitespace. The same
2211 tag should not be given multiple times with conflicting
2212 values. Package maintainers may assume that
2213 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2217 The meaning of the following tags has been standardized:
2221 This tag says to not run any build-time test suite
2222 provided by the package.
2226 The presence of this tag means that the package should
2227 be compiled with a minimum of optimization. For C
2228 programs, it is best to add <tt>-O0</tt> to
2229 <tt>CFLAGS</tt> (although this is usually the default).
2230 Some programs might fail to build or run at this level
2231 of optimization; it may be necessary to use
2232 <tt>-O1</tt>, for example.
2236 This tag means that the debugging symbols should not be
2237 stripped from the binary during installation, so that
2238 debugging information may be included in the package.
2240 <tag>parallel=n</tag>
2242 This tag means that the package should be built using up
2243 to <tt>n</tt> parallel processes if the package build
2244 system supports this.<footnote>
2245 Packages built with <tt>make</tt> can often implement
2246 this by passing the <tt>-j</tt><var>n</var> option to
2249 If the package build system does not support parallel
2250 builds, this string must be ignored. If the package
2251 build system only supports a lower level of concurrency
2252 than <var>n</var>, the package should be built using as
2253 many parallel processes as the package build system
2254 supports. It is up to the package maintainer to decide
2255 whether the package build times are long enough and the
2256 package build system is robust enough to make supporting
2257 parallel builds worthwhile.
2263 Unknown flags must be ignored by <file>debian/rules</file>.
2267 The following makefile snippet is an example of how one may
2268 implement the build options; you will probably have to
2269 massage this example in order to make it work for your
2271 <example compact="compact">
2274 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2275 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2276 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2277 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2279 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2284 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2285 INSTALL_PROGRAM += -s
2287 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2288 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2289 MAKEFLAGS += -j$(NUMJOBS)
2294 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2295 # Code to run the package test suite.
2302 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2303 <sect id="substvars">
2304 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2307 When <prgn>dpkg-gencontrol</prgn>
2308 generates <qref id="binarycontrolfiles">binary package control
2309 files</qref> (<file>DEBIAN/control</file>), it performs variable
2310 substitutions on its output just before writing it. Variable
2311 substitutions have the form <tt>${<var>variable</var>}</tt>.
2312 The optional file <file>debian/substvars</file> contains
2313 variable substitutions to be used; variables can also be set
2314 directly from <file>debian/rules</file> using the <tt>-V</tt>
2315 option to the source packaging commands, and certain predefined
2316 variables are also available.
2320 The <file>debian/substvars</file> file is usually generated and
2321 modified dynamically by <file>debian/rules</file> targets, in
2322 which case it must be removed by the <tt>clean</tt> target.
2326 See <manref name="deb-substvars" section="5"> for full
2327 details about source variable substitutions, including the
2328 format of <file>debian/substvars</file>.</p>
2331 <sect id="debianwatch">
2332 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2335 This is an optional, recommended configuration file for the
2336 <tt>uscan</tt> utility which defines how to automatically scan
2337 ftp or http sites for newly available updates of the
2338 package. This is used
2339 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2340 tools to help with quality control and maintenance of the
2341 distribution as a whole.
2346 <sect id="debianfiles">
2347 <heading>Generated files list: <file>debian/files</file></heading>
2350 This file is not a permanent part of the source tree; it
2351 is used while building packages to record which files are
2352 being generated. <prgn>dpkg-genchanges</prgn> uses it
2353 when it generates a <file>.changes</file> file.
2357 It should not exist in a shipped source package, and so it
2358 (and any backup files or temporary files such as
2359 <file>files.new</file><footnote>
2360 <file>files.new</file> is used as a temporary file by
2361 <prgn>dpkg-gencontrol</prgn> and
2362 <prgn>dpkg-distaddfile</prgn> - they write a new
2363 version of <tt>files</tt> here before renaming it,
2364 to avoid leaving a corrupted copy if an error
2366 </footnote>) should be removed by the
2367 <tt>clean</tt> target. It may also be wise to
2368 ensure a fresh start by emptying or removing it at the
2369 start of the <tt>binary</tt> target.
2373 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2374 package, it adds an entry to <file>debian/files</file> for the
2375 <file>.deb</file> file that will be created when <tt>dpkg-deb
2376 --build</tt> is run for that binary package. So for most
2377 packages all that needs to be done with this file is to
2378 delete it in the <tt>clean</tt> target.
2382 If a package upload includes files besides the source
2383 package and any binary packages whose control files were
2384 made with <prgn>dpkg-gencontrol</prgn> then they should be
2385 placed in the parent of the package's top-level directory
2386 and <prgn>dpkg-distaddfile</prgn> should be called to add
2387 the file to the list in <file>debian/files</file>.</p>
2390 <sect id="embeddedfiles">
2391 <heading>Convenience copies of code</heading>
2394 Some software packages include in their distribution convenience
2395 copies of code from other software packages, generally so that
2396 users compiling from source don't have to download multiple
2397 packages. Debian packages should not make use of these
2398 convenience copies unless the included package is explicitly
2399 intended to be used in this way.<footnote>
2400 For example, parts of the GNU build system work like this.
2402 If the included code is already in the Debian archive in the
2403 form of a library, the Debian packaging should ensure that
2404 binary packages reference the libraries already in Debian and
2405 the convenience copy is not used. If the included code is not
2406 already in Debian, it should be packaged separately as a
2407 prerequisite if possible.
2409 Having multiple copies of the same code in Debian is
2410 inefficient, often creates either static linking or shared
2411 library conflicts, and, most importantly, increases the
2412 difficulty of handling security vulnerabilities in the
2418 <sect id="readmesource">
2419 <heading>Source package handling:
2420 <file>debian/README.source</file></heading>
2423 If running <prgn>dpkg-source -x</prgn> on a source package
2424 doesn't produce the source of the package, ready for editing,
2425 and allow one to make changes and run
2426 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2427 without taking any additional steps, creating a
2428 <file>debian/README.source</file> documentation file is
2429 recommended. This file should explain how to do all of the
2432 <item>Generate the fully patched source, in a form ready for
2433 editing, that would be built to create Debian
2434 packages. Doing this with a <tt>patch</tt> target in
2435 <file>debian/rules</file> is recommended; see
2436 <ref id="debianrules">.</item>
2437 <item>Modify the source and save those modifications so that
2438 they will be applied when building the package.</item>
2439 <item>Remove source modifications that are currently being
2440 applied when building the package.</item>
2441 <item>Optionally, document what steps are necessary to
2442 upgrade the Debian source package to a new upstream version,
2443 if applicable.</item>
2445 This explanation should include specific commands and mention
2446 any additional required Debian packages. It should not assume
2447 familiarity with any specific Debian packaging system or patch
2452 This explanation may refer to a documentation file installed by
2453 one of the package's build dependencies provided that the
2454 referenced documentation clearly explains these tasks and is not
2455 a general reference manual.
2459 <file>debian/README.source</file> may also include any other
2460 information that would be helpful to someone modifying the
2461 source package. Even if the package doesn't fit the above
2462 description, maintainers are encouraged to document in a
2463 <file>debian/README.source</file> file any source package with a
2464 particularly complex or unintuitive source layout or build
2465 system (for example, a package that builds the same source
2466 multiple times to generate different binary packages).
2472 <chapt id="controlfields">
2473 <heading>Control files and their fields</heading>
2476 The package management system manipulates data represented in
2477 a common format, known as <em>control data</em>, stored in
2478 <em>control files</em>.
2479 Control files are used for source packages, binary packages and
2480 the <file>.changes</file> files which control the installation
2481 of uploaded files<footnote>
2482 <prgn>dpkg</prgn>'s internal databases are in a similar
2487 <sect id="controlsyntax">
2488 <heading>Syntax of control files</heading>
2491 A control file consists of one or more paragraphs of
2493 The paragraphs are also sometimes referred to as stanzas.
2495 The paragraphs are separated by empty lines. Parsers may accept
2496 lines consisting solely of spaces and tabs as paragraph
2497 separators, but control files should use empty lines. Some control
2498 files allow only one paragraph; others allow several, in
2499 which case each paragraph usually refers to a different
2500 package. (For example, in source packages, the first
2501 paragraph refers to the source package, and later paragraphs
2502 refer to binary packages generated from the source.) The
2503 ordering of the paragraphs in control files is significant.
2507 Each paragraph consists of a series of data fields. Each field
2508 consists of the field name followed by a colon and then the
2509 data/value associated with that field. The field name is
2510 composed of US-ASCII characters excluding control characters,
2511 space, and colon (i.e., characters in the ranges 33-57 and
2512 59-126, inclusive). Field names must not begin with the comment
2513 character, <tt>#</tt>.
2517 The field ends at the end of the line or at the end of the last
2518 continuation line (see below). Horizontal whitespace (spaces
2519 and tabs) may occur immediately before or after the value and is
2520 ignored there; it is conventional to put a single space after
2521 the colon. For example, a field might be:
2522 <example compact="compact">
2525 the field name is <tt>Package</tt> and the field value
2530 A paragraph must not contain more than one instance of a
2531 particular field name.
2535 There are three types of fields:
2539 The field, including its value, must be a single line. Folding
2540 of the field is not permitted. This is the default field type
2541 if the definition of the field does not specify a different
2546 The value of a folded field is a logical line that may span
2547 several lines. The lines after the first are called
2548 continuation lines and must start with a space or a tab.
2549 Whitespace, including any newlines, is not significant in the
2550 field values of folded fields.<footnote>
2551 This folding method is similar to RFC 5322, allowing control
2552 files that contain only one paragraph and no multiline fields
2553 to be read by parsers written for RFC 5322.
2556 <tag>multiline</tag>
2558 The value of a multiline field may comprise multiple continuation
2559 lines. The first line of the value, the part on the same line as
2560 the field name, often has special significance or may have to be
2561 empty. Other lines are added following the same syntax as the
2562 continuation lines of the folded fields. Whitespace, including newlines,
2563 is significant in the values of multiline fields.
2569 Whitespace must not appear
2570 inside names (of packages, architectures, files or anything
2571 else) or version numbers, or between the characters of
2572 multi-character version relationships.
2576 The presence and purpose of a field, and the syntax of its
2577 value may differ between types of control files.
2581 Field names are not case-sensitive, but it is usual to
2582 capitalize the field names using mixed case as shown below.
2583 Field values are case-sensitive unless the description of the
2584 field says otherwise.
2588 Paragraph separators (empty lines) and lines consisting only of
2589 spaces and tabs are not allowed within field values or between
2590 fields. Empty lines in field values are usually escaped by
2591 representing them by a space followed by a dot.
2595 Lines starting with # without any preceding whitespace are comments
2596 lines that are only permitted in source package control files
2597 (<file>debian/control</file>). These comment lines are ignored, even
2598 between two continuation lines. They do not end logical lines.
2602 All control files must be encoded in UTF-8.
2606 <sect id="sourcecontrolfiles">
2607 <heading>Source package control files -- <file>debian/control</file></heading>
2610 The <file>debian/control</file> file contains the most vital
2611 (and version-independent) information about the source package
2612 and about the binary packages it creates.
2616 The first paragraph of the control file contains information about
2617 the source package in general. The subsequent sets each describe a
2618 binary package that the source tree builds.
2622 The fields in the general paragraph (the first one, for the source
2625 <list compact="compact">
2626 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2629 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2630 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2631 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2632 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2633 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2634 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2639 The fields in the binary package paragraphs are:
2641 <list compact="compact">
2642 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2645 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2646 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2647 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2648 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2654 The syntax and semantics of the fields are described below.
2658 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2659 generate control files for binary packages (see below), by
2660 <prgn>dpkg-genchanges</prgn> to generate the
2661 <file>.changes</file> file to accompany the upload, and by
2662 <prgn>dpkg-source</prgn> when it creates the
2663 <file>.dsc</file> source control file as part of a source
2664 archive. Some fields are folded in <file>debian/control</file>,
2665 but not in any other control
2666 file. These tools are responsible for removing the line
2667 breaks from such fields when using fields from
2668 <file>debian/control</file> to generate other control files.
2672 The fields here may contain variable references - their
2673 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2674 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2675 when they generate output control files.
2676 See <ref id="substvars"> for details.
2680 <sect id="binarycontrolfiles">
2681 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2684 The <file>DEBIAN/control</file> file contains the most vital
2685 (and version-dependent) information about a binary package. It
2686 consists of a single paragraph.
2690 The fields in this file are:
2692 <list compact="compact">
2693 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2694 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2695 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2696 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2697 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2698 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2699 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2700 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2701 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2702 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2703 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2704 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2709 <sect id="debiansourcecontrolfiles">
2710 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2713 This file consists of a single paragraph, possibly surrounded by
2714 a PGP signature. The fields of that paragraph are listed below.
2715 Their syntax is described above, in <ref id="controlsyntax">.
2717 <list compact="compact">
2718 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2719 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2720 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2721 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2722 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2723 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2724 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2725 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2726 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2727 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2728 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2729 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2730 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2731 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2736 The Debian source control file is generated by
2737 <prgn>dpkg-source</prgn> when it builds the source
2738 archive, from other files in the source package,
2739 described above. When unpacking, it is checked against
2740 the files and directories in the other parts of the
2746 <sect id="debianchangesfiles">
2747 <heading>Debian changes files -- <file>.changes</file></heading>
2750 The <file>.changes</file> files are used by the Debian archive
2751 maintenance software to process updates to packages. They
2752 consist of a single paragraph, possibly surrounded by a PGP
2753 signature. That paragraph contains information from the
2754 <file>debian/control</file> file and other data about the
2755 source package gathered via <file>debian/changelog</file>
2756 and <file>debian/rules</file>.
2760 <file>.changes</file> files have a format version that is
2761 incremented whenever the documented fields or their meaning
2762 change. This document describes format &changesversion;.
2766 The fields in this file are:
2768 <list compact="compact">
2769 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2770 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2771 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2772 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2773 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2774 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2775 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2776 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2777 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2778 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2779 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2780 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2781 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2782 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2783 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2784 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2789 <sect id="controlfieldslist">
2790 <heading>List of fields</heading>
2792 <sect1 id="f-Source">
2793 <heading><tt>Source</tt></heading>
2796 This field identifies the source package name.
2800 In <file>debian/control</file> or a <file>.dsc</file> file,
2801 this field must contain only the name of the source package.
2805 In a binary package control file or a <file>.changes</file>
2806 file, the source package name may be followed by a version
2807 number in parentheses<footnote>
2808 It is customary to leave a space after the package name
2809 if a version number is specified.
2811 This version number may be omitted (and is, by
2812 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2813 the <tt>Version</tt> field of the binary package in
2814 question. The field itself may be omitted from a binary
2815 package control file when the source package has the same
2816 name and version as the binary package.
2820 Package names (both source and binary,
2821 see <ref id="f-Package">) must consist only of lower case
2822 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2823 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2824 (<tt>.</tt>). They must be at least two characters long and
2825 must start with an alphanumeric character.
2829 <sect1 id="f-Maintainer">
2830 <heading><tt>Maintainer</tt></heading>
2833 The package maintainer's name and email address. The name
2834 must come first, then the email address inside angle
2835 brackets <tt><></tt> (in RFC822 format).
2839 If the maintainer's name contains a full stop then the
2840 whole field will not work directly as an email address due
2841 to a misfeature in the syntax specified in RFC822; a
2842 program using this field as an address must check for this
2843 and correct the problem if necessary (for example by
2844 putting the name in round brackets and moving it to the
2845 end, and bringing the email address forward).
2849 See <ref id="maintainer"> for additional requirements and
2850 information about package maintainers.
2854 <sect1 id="f-Uploaders">
2855 <heading><tt>Uploaders</tt></heading>
2858 List of the names and email addresses of co-maintainers of the
2859 package, if any. If the package has other maintainers besides
2860 the one named in the <qref id="f-Maintainer">Maintainer
2861 field</qref>, their names and email addresses should be listed
2862 here. The format of each entry is the same as that of the
2863 Maintainer field, and multiple entries must be comma
2868 This is normally an optional field, but if
2869 the <tt>Maintainer</tt> control field names a group of people
2870 and a shared email address, the <tt>Uploaders</tt> field must
2871 be present and must contain at least one human with their
2872 personal email address.
2876 The Uploaders field in <file>debian/control</file> can be folded.
2880 <sect1 id="f-Changed-By">
2881 <heading><tt>Changed-By</tt></heading>
2884 The name and email address of the person who prepared this
2885 version of the package, usually a maintainer. The syntax is
2886 the same as for the <qref id="f-Maintainer">Maintainer
2891 <sect1 id="f-Section">
2892 <heading><tt>Section</tt></heading>
2895 This field specifies an application area into which the package
2896 has been classified. See <ref id="subsections">.
2900 When it appears in the <file>debian/control</file> file,
2901 it gives the value for the subfield of the same name in
2902 the <tt>Files</tt> field of the <file>.changes</file> file.
2903 It also gives the default for the same field in the binary
2908 <sect1 id="f-Priority">
2909 <heading><tt>Priority</tt></heading>
2912 This field represents how important it is that the user
2913 have the package installed. See <ref id="priorities">.
2917 When it appears in the <file>debian/control</file> file,
2918 it gives the value for the subfield of the same name in
2919 the <tt>Files</tt> field of the <file>.changes</file> file.
2920 It also gives the default for the same field in the binary
2925 <sect1 id="f-Package">
2926 <heading><tt>Package</tt></heading>
2929 The name of the binary package.
2933 Binary package names must follow the same syntax and
2934 restrictions as source package names. See <ref id="f-Source">
2939 <sect1 id="f-Architecture">
2940 <heading><tt>Architecture</tt></heading>
2943 Depending on context and the control file used, the
2944 <tt>Architecture</tt> field can include the following sets of
2948 A unique single word identifying a Debian machine
2949 architecture as described in <ref id="arch-spec">.
2952 An architecture wildcard identifying a set of Debian
2953 machine architectures, see <ref id="arch-wildcard-spec">.
2954 <tt>any</tt> matches all Debian machine architectures
2955 and is the most frequently used.
2958 <tt>all</tt>, which indicates an
2959 architecture-independent package.
2962 <tt>source</tt>, which indicates a source package.
2968 In the main <file>debian/control</file> file in the source
2969 package, this field may contain the special
2970 value <tt>all</tt>, the special architecture
2971 wildcard <tt>any</tt>, or a list of specific and wildcard
2972 architectures separated by spaces. If <tt>all</tt>
2973 or <tt>any</tt> appears, that value must be the entire
2974 contents of the field. Most packages will use
2975 either <tt>all</tt> or <tt>any</tt>.
2979 Specifying a specific list of architectures indicates that the
2980 source will build an architecture-dependent package only on
2981 architectures included in the list. Specifying a list of
2982 architecture wildcards indicates that the source will build an
2983 architecture-dependent package on only those architectures
2984 that match any of the specified architecture wildcards.
2985 Specifying a list of architectures or architecture wildcards
2986 other than <tt>any</tt> is for the minority of cases where a
2987 program is not portable or is not useful on some
2988 architectures. Where possible, the program should be made
2993 In the Debian source control file <file>.dsc</file>, this
2994 field contains a list of architectures and architecture
2995 wildcards separated by spaces. When the list contains the
2996 architecture wildcard <tt>any</tt>, the only other value
2997 allowed in the list is <tt>all</tt>.
3001 The list may include (or consist solely of) the special
3002 value <tt>all</tt>. In other words, in <file>.dsc</file>
3003 files unlike the <file>debian/control</file>, <tt>all</tt> may
3004 occur in combination with specific architectures.
3005 The <tt>Architecture</tt> field in the Debian source control
3006 file <file>.dsc</file> is generally constructed from
3007 the <tt>Architecture</tt> fields in
3008 the <file>debian/control</file> in the source package.
3012 Specifying only <tt>any</tt> indicates that the source package
3013 isn't dependent on any particular architecture and should
3014 compile fine on any one. The produced binary package(s)
3015 will be specific to whatever the current build architecture is.
3019 Specifying only <tt>all</tt> indicates that the source package
3020 will only build architecture-independent packages.
3024 Specifying <tt>any all</tt> indicates that the source package
3025 isn't dependent on any particular architecture. The set of
3026 produced binary packages will include at least one
3027 architecture-dependant package and one architecture-independent
3032 Specifying a list of architectures or architecture wildcards
3033 indicates that the source will build an architecture-dependent
3034 package, and will only work correctly on the listed or
3035 matching architectures. If the source package also builds at
3036 least one architecture-independent package, <tt>all</tt> will
3037 also be included in the list.
3041 In a <file>.changes</file> file, the <tt>Architecture</tt>
3042 field lists the architecture(s) of the package(s) currently
3043 being uploaded. This will be a list; if the source for the
3044 package is also being uploaded, the special
3045 entry <tt>source</tt> is also present. <tt>all</tt> will be
3046 present if any architecture-independent packages are being
3047 uploaded. Architecture wildcards such as <tt>any</tt> must
3048 never occur in the <tt>Architecture</tt> field in
3049 the <file>.changes</file> file.
3053 See <ref id="debianrules"> for information on how to get
3054 the architecture for the build process.
3058 <sect1 id="f-Essential">
3059 <heading><tt>Essential</tt></heading>
3062 This is a boolean field which may occur only in the
3063 control file of a binary package or in a per-package fields
3064 paragraph of a source package control file.
3068 If set to <tt>yes</tt> then the package management system
3069 will refuse to remove the package (upgrading and replacing
3070 it is still possible). The other possible value is <tt>no</tt>,
3071 which is the same as not having the field at all.
3076 <heading>Package interrelationship fields:
3077 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3078 <tt>Recommends</tt>, <tt>Suggests</tt>,
3079 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3080 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3084 These fields describe the package's relationships with
3085 other packages. Their syntax and semantics are described
3086 in <ref id="relationships">.</p>
3089 <sect1 id="f-Standards-Version">
3090 <heading><tt>Standards-Version</tt></heading>
3093 The most recent version of the standards (the policy
3094 manual and associated texts) with which the package
3099 The version number has four components: major and minor
3100 version number and major and minor patch level. When the
3101 standards change in a way that requires every package to
3102 change the major number will be changed. Significant
3103 changes that will require work in many packages will be
3104 signaled by a change to the minor number. The major patch
3105 level will be changed for any change to the meaning of the
3106 standards, however small; the minor patch level will be
3107 changed when only cosmetic, typographical or other edits
3108 are made which neither change the meaning of the document
3109 nor affect the contents of packages.
3113 Thus only the first three components of the policy version
3114 are significant in the <em>Standards-Version</em> control
3115 field, and so either these three components or all four
3116 components may be specified.<footnote>
3117 In the past, people specified the full version number
3118 in the Standards-Version field, for example "2.3.0.0".
3119 Since minor patch-level changes don't introduce new
3120 policy, it was thought it would be better to relax
3121 policy and only require the first 3 components to be
3122 specified, in this example "2.3.0". All four
3123 components may still be used if someone wishes to do so.
3129 <sect1 id="f-Version">
3130 <heading><tt>Version</tt></heading>
3133 The version number of a package. The format is:
3134 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3138 The three components here are:
3140 <tag><var>epoch</var></tag>
3143 This is a single (generally small) unsigned integer. It
3144 may be omitted, in which case zero is assumed. If it is
3145 omitted then the <var>upstream_version</var> may not
3150 It is provided to allow mistakes in the version numbers
3151 of older versions of a package, and also a package's
3152 previous version numbering schemes, to be left behind.
3156 <tag><var>upstream_version</var></tag>
3159 This is the main part of the version number. It is
3160 usually the version number of the original ("upstream")
3161 package from which the <file>.deb</file> file has been made,
3162 if this is applicable. Usually this will be in the same
3163 format as that specified by the upstream author(s);
3164 however, it may need to be reformatted to fit into the
3165 package management system's format and comparison
3170 The comparison behavior of the package management system
3171 with respect to the <var>upstream_version</var> is
3172 described below. The <var>upstream_version</var>
3173 portion of the version number is mandatory.
3177 The <var>upstream_version</var> may contain only
3178 alphanumerics<footnote>
3179 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3181 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3182 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3183 tilde) and should start with a digit. If there is no
3184 <var>debian_revision</var> then hyphens are not allowed;
3185 if there is no <var>epoch</var> then colons are not
3190 <tag><var>debian_revision</var></tag>
3193 This part of the version number specifies the version of
3194 the Debian package based on the upstream version. It
3195 may contain only alphanumerics and the characters
3196 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3197 tilde) and is compared in the same way as the
3198 <var>upstream_version</var> is.
3202 It is optional; if it isn't present then the
3203 <var>upstream_version</var> may not contain a hyphen.
3204 This format represents the case where a piece of
3205 software was written specifically to be a Debian
3206 package, where the Debian package source must always
3207 be identical to the pristine source and therefore no
3208 revision indication is required.
3212 It is conventional to restart the
3213 <var>debian_revision</var> at <tt>1</tt> each time the
3214 <var>upstream_version</var> is increased.
3218 The package management system will break the version
3219 number apart at the last hyphen in the string (if there
3220 is one) to determine the <var>upstream_version</var> and
3221 <var>debian_revision</var>. The absence of a
3222 <var>debian_revision</var> is equivalent to a
3223 <var>debian_revision</var> of <tt>0</tt>.
3230 When comparing two version numbers, first the <var>epoch</var>
3231 of each are compared, then the <var>upstream_version</var> if
3232 <var>epoch</var> is equal, and then <var>debian_revision</var>
3233 if <var>upstream_version</var> is also equal.
3234 <var>epoch</var> is compared numerically. The
3235 <var>upstream_version</var> and <var>debian_revision</var>
3236 parts are compared by the package management system using the
3237 following algorithm:
3241 The strings are compared from left to right.
3245 First the initial part of each string consisting entirely of
3246 non-digit characters is determined. These two parts (one of
3247 which may be empty) are compared lexically. If a difference
3248 is found it is returned. The lexical comparison is a
3249 comparison of ASCII values modified so that all the letters
3250 sort earlier than all the non-letters and so that a tilde
3251 sorts before anything, even the end of a part. For example,
3252 the following parts are in sorted order from earliest to
3253 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3254 <tt>a</tt>.<footnote>
3255 One common use of <tt>~</tt> is for upstream pre-releases.
3256 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3257 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3262 Then the initial part of the remainder of each string which
3263 consists entirely of digit characters is determined. The
3264 numerical values of these two parts are compared, and any
3265 difference found is returned as the result of the comparison.
3266 For these purposes an empty string (which can only occur at
3267 the end of one or both version strings being compared) counts
3272 These two steps (comparing and removing initial non-digit
3273 strings and initial digit strings) are repeated until a
3274 difference is found or both strings are exhausted.
3278 Note that the purpose of epochs is to allow us to leave behind
3279 mistakes in version numbering, and to cope with situations
3280 where the version numbering scheme changes. It is
3281 <em>not</em> intended to cope with version numbers containing
3282 strings of letters which the package management system cannot
3283 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3284 silly orderings.<footnote>
3285 The author of this manual has heard of a package whose
3286 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3287 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3293 <sect1 id="f-Description">
3294 <heading><tt>Description</tt></heading>
3297 In a source or binary control file, the <tt>Description</tt>
3298 field contains a description of the binary package, consisting
3299 of two parts, the synopsis or the short description, and the
3300 long description. It is a multiline field with the following
3306 Description: <single line synopsis>
3307 <extended description over several lines>
3312 The lines in the extended description can have these formats:
3318 Those starting with a single space are part of a paragraph.
3319 Successive lines of this form will be word-wrapped when
3320 displayed. The leading space will usually be stripped off.
3321 The line must contain at least one non-whitespace character.
3325 Those starting with two or more spaces. These will be
3326 displayed verbatim. If the display cannot be panned
3327 horizontally, the displaying program will line wrap them "hard"
3328 (i.e., without taking account of word breaks). If it can they
3329 will be allowed to trail off to the right. None, one or two
3330 initial spaces may be deleted, but the number of spaces
3331 deleted from each line will be the same (so that you can have
3332 indenting work correctly, for example). The line must
3333 contain at least one non-whitespace character.
3337 Those containing a single space followed by a single full stop
3338 character. These are rendered as blank lines. This is the
3339 <em>only</em> way to get a blank line<footnote>
3340 Completely empty lines will not be rendered as blank lines.
3341 Instead, they will cause the parser to think you're starting
3342 a whole new record in the control file, and will therefore
3343 likely abort with an error.
3348 Those containing a space, a full stop and some more characters.
3349 These are for future expansion. Do not use them.
3355 Do not use tab characters. Their effect is not predictable.
3359 See <ref id="descriptions"> for further information on this.
3363 In a <file>.changes</file> file, the <tt>Description</tt>
3364 field contains a summary of the descriptions for the packages
3365 being uploaded. For this case, the first line of the field
3366 value (the part on the same line as <tt>Description:</tt>) is
3367 always empty. It is a multiline field, with one
3368 line per package. Each line is
3369 indented by one space and contains the name of a binary
3370 package, a space, a hyphen (<tt>-</tt>), a space, and the
3371 short description line from that package.
3375 <sect1 id="f-Distribution">
3376 <heading><tt>Distribution</tt></heading>
3379 In a <file>.changes</file> file or parsed changelog output
3380 this contains the (space-separated) name(s) of the
3381 distribution(s) where this version of the package should
3382 be installed. Valid distributions are determined by the
3383 archive maintainers.<footnote>
3384 Example distribution names in the Debian archive used in
3385 <file>.changes</file> files are:
3386 <taglist compact="compact">
3387 <tag><em>unstable</em></tag>
3389 This distribution value refers to the
3390 <em>developmental</em> part of the Debian distribution
3391 tree. Most new packages, new upstream versions of
3392 packages and bug fixes go into the <em>unstable</em>
3396 <tag><em>experimental</em></tag>
3398 The packages with this distribution value are deemed
3399 by their maintainers to be high risk. Oftentimes they
3400 represent early beta or developmental packages from
3401 various sources that the maintainers want people to
3402 try, but are not ready to be a part of the other parts
3403 of the Debian distribution tree.
3408 Others are used for updating stable releases or for
3409 security uploads. More information is available in the
3410 Debian Developer's Reference, section "The Debian
3414 The Debian archive software only supports listing a single
3415 distribution. Migration of packages to other distributions is
3416 handled outside of the upload process.
3421 <heading><tt>Date</tt></heading>
3424 This field includes the date the package was built or last
3425 edited. It must be in the same format as the <var>date</var>
3426 in a <file>debian/changelog</file> entry.
3430 The value of this field is usually extracted from the
3431 <file>debian/changelog</file> file - see
3432 <ref id="dpkgchangelog">).
3436 <sect1 id="f-Format">
3437 <heading><tt>Format</tt></heading>
3440 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3441 files, this field declares the format version of that file.
3442 The syntax of the field value is the same as that of
3443 a <qref id="f-Version">package version number</qref> except
3444 that no epoch or Debian revision is allowed. The format
3445 described in this document is <tt>&changesversion;</tt>.
3449 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3450 Debian source control</qref> files, this field declares the
3451 format of the source package. The field value is used by
3452 programs acting on a source package to interpret the list of
3453 files in the source package and determine how to unpack it.
3454 The syntax of the field value is a numeric major revision, a
3455 period, a numeric minor revision, and then an optional subtype
3456 after whitespace, which if specified is an alphanumeric word
3457 in parentheses. The subtype is optional in the syntax but may
3458 be mandatory for particular source format revisions.
3460 The source formats currently supported by the Debian archive
3461 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3462 and <tt>3.0 (quilt)</tt>.
3467 <sect1 id="f-Urgency">
3468 <heading><tt>Urgency</tt></heading>
3471 This is a description of how important it is to upgrade to
3472 this version from previous ones. It consists of a single
3473 keyword taking one of the values <tt>low</tt>,
3474 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3475 <tt>critical</tt><footnote>
3476 Other urgency values are supported with configuration
3477 changes in the archive software but are not used in Debian.
3478 The urgency affects how quickly a package will be considered
3479 for inclusion into the <tt>testing</tt> distribution and
3480 gives an indication of the importance of any fixes included
3481 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3482 treated as synonymous.
3483 </footnote> (not case-sensitive) followed by an optional
3484 commentary (separated by a space) which is usually in
3485 parentheses. For example:
3488 Urgency: low (HIGH for users of diversions)
3494 The value of this field is usually extracted from the
3495 <file>debian/changelog</file> file - see
3496 <ref id="dpkgchangelog">.
3500 <sect1 id="f-Changes">
3501 <heading><tt>Changes</tt></heading>
3504 This multiline field contains the human-readable changes data, describing
3505 the differences between the last version and the current one.
3509 The first line of the field value (the part on the same line
3510 as <tt>Changes:</tt>) is always empty. The content of the
3511 field is expressed as continuation lines, with each line
3512 indented by at least one space. Blank lines must be
3513 represented by a line consisting only of a space and a full
3518 The value of this field is usually extracted from the
3519 <file>debian/changelog</file> file - see
3520 <ref id="dpkgchangelog">).
3524 Each version's change information should be preceded by a
3525 "title" line giving at least the version, distribution(s)
3526 and urgency, in a human-readable way.
3530 If data from several versions is being returned the entry
3531 for the most recent version should be returned first, and
3532 entries should be separated by the representation of a
3533 blank line (the "title" line may also be followed by the
3534 representation of a blank line).
3538 <sect1 id="f-Binary">
3539 <heading><tt>Binary</tt></heading>
3542 This folded field is a list of binary packages. Its syntax and
3543 meaning varies depending on the control file in which it
3548 When it appears in the <file>.dsc</file> file, it lists binary
3549 packages which a source package can produce, separated by
3551 A space after each comma is conventional.
3552 </footnote>. The source package
3553 does not necessarily produce all of these binary packages for
3554 every architecture. The source control file doesn't contain
3555 details of which architectures are appropriate for which of
3556 the binary packages.
3560 When it appears in a <file>.changes</file> file, it lists the
3561 names of the binary packages being uploaded, separated by
3562 whitespace (not commas).
3566 <sect1 id="f-Installed-Size">
3567 <heading><tt>Installed-Size</tt></heading>
3570 This field appears in the control files of binary packages,
3571 and in the <file>Packages</file> files. It gives an estimate
3572 of the total amount of disk space required to install the
3573 named package. Actual installed size may vary based on block
3574 size, file system properties, or actions taken by package
3579 The disk space is given as the integer value of the estimated
3580 installed size in bytes, divided by 1024 and rounded up.
3584 <sect1 id="f-Files">
3585 <heading><tt>Files</tt></heading>
3588 This field contains a list of files with information about
3589 each one. The exact information and syntax varies with
3594 In all cases, Files is a multiline field. The first line of
3595 the field value (the part on the same line as <tt>Files:</tt>)
3596 is always empty. The content of the field is expressed as
3597 continuation lines, one line per file. Each line must be
3598 indented by one space and contain a number of sub-fields,
3599 separated by spaces, as described below.
3603 In the <file>.dsc</file> file, each line contains the MD5
3604 checksum, size and filename of the tar file and (if
3605 applicable) diff file which make up the remainder of the
3606 source package<footnote>
3607 That is, the parts which are not the <tt>.dsc</tt>.
3608 </footnote>. For example:
3611 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3612 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3614 The exact forms of the filenames are described
3615 in <ref id="pkg-sourcearchives">.
3619 In the <file>.changes</file> file this contains one line per
3620 file being uploaded. Each line contains the MD5 checksum,
3621 size, section and priority and the filename. For example:
3624 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3625 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3626 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3627 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3629 The <qref id="f-Section">section</qref>
3630 and <qref id="f-Priority">priority</qref> are the values of
3631 the corresponding fields in the main source control file. If
3632 no section or priority is specified then <tt>-</tt> should be
3633 used, though section and priority values must be specified for
3634 new packages to be installed properly.
3638 The special value <tt>byhand</tt> for the section in a
3639 <tt>.changes</tt> file indicates that the file in question
3640 is not an ordinary package file and must by installed by
3641 hand by the distribution maintainers. If the section is
3642 <tt>byhand</tt> the priority should be <tt>-</tt>.
3646 If a new Debian revision of a package is being shipped and
3647 no new original source archive is being distributed the
3648 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3649 entry for the original source archive
3650 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3651 but the <file>.changes</file> file should leave it out. In
3652 this case the original source archive on the distribution
3653 site must match exactly, byte-for-byte, the original
3654 source archive which was used to generate the
3655 <file>.dsc</file> file and diff which are being uploaded.</p>
3658 <sect1 id="f-Closes">
3659 <heading><tt>Closes</tt></heading>
3662 A space-separated list of bug report numbers that the upload
3663 governed by the .changes file closes.
3667 <sect1 id="f-Homepage">
3668 <heading><tt>Homepage</tt></heading>
3671 The URL of the web site for this package, preferably (when
3672 applicable) the site from which the original source can be
3673 obtained and any additional upstream documentation or
3674 information may be found. The content of this field is a
3675 simple URL without any surrounding characters such as
3680 <sect1 id="f-Checksums">
3681 <heading><tt>Checksums-Sha1</tt>
3682 and <tt>Checksums-Sha256</tt></heading>
3685 These multiline fields contain a list of files with a checksum and size
3686 for each one. Both <tt>Checksums-Sha1</tt>
3687 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3688 only in the checksum algorithm used: SHA-1
3689 for <tt>Checksums-Sha1</tt> and SHA-256
3690 for <tt>Checksums-Sha256</tt>.
3694 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3695 multiline fields. The first line of the field value (the part
3696 on the same line as <tt>Checksums-Sha1:</tt>
3697 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3698 of the field is expressed as continuation lines, one line per
3699 file. Each line consists of the checksum, a space, the file
3700 size, a space, and the file name. For example (from
3701 a <file>.changes</file> file):
3704 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3705 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3706 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3707 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3709 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3710 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3711 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3712 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3717 In the <file>.dsc</file> file, these fields should list all
3718 files that make up the source package. In
3719 the <file>.changes</file> file, these fields should list all
3720 files being uploaded. The list of files in these fields
3721 must match the list of files in the <tt>Files</tt> field.
3725 <sect1 id="f-DM-Upload-Allowed">
3726 <heading><tt>DM-Upload-Allowed</tt></heading>
3729 Indicates that Debian Maintainers may upload this package to
3730 the Debian archive. The only valid value is <tt>yes</tt>. If
3731 the field <tt>DM-Upload-Allowed: yes</tt> is present in the
3732 source section of the source control file of the most recent
3733 version of a package in unstable or experimental, the Debian
3734 archive will accept uploads of this package signed with a key
3735 in the Debian Maintainer keyring. See the General
3736 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3737 name="Endorse the concept of Debian Maintainers"> for more
3744 <heading>User-defined fields</heading>
3747 Additional user-defined fields may be added to the
3748 source package control file. Such fields will be
3749 ignored, and not copied to (for example) binary or
3750 Debian source control files or upload control files.
3754 If you wish to add additional unsupported fields to
3755 these output files you should use the mechanism
3760 Fields in the main source control information file with
3761 names starting <tt>X</tt>, followed by one or more of
3762 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3763 be copied to the output files. Only the part of the
3764 field name after the hyphen will be used in the output
3765 file. Where the letter <tt>B</tt> is used the field
3766 will appear in binary package control files, where the
3767 letter <tt>S</tt> is used in Debian source control
3768 files and where <tt>C</tt> is used in upload control
3769 (<tt>.changes</tt>) files.
3773 For example, if the main source information control file
3776 XBS-Comment: I stand between the candle and the star.
3778 then the binary and Debian source control files will contain the
3781 Comment: I stand between the candle and the star.
3790 <chapt id="maintainerscripts">
3791 <heading>Package maintainer scripts and installation procedure</heading>
3794 <heading>Introduction to package maintainer scripts</heading>
3797 It is possible to supply scripts as part of a package which
3798 the package management system will run for you when your
3799 package is installed, upgraded or removed.
3803 These scripts are the control information
3804 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3805 and <prgn>postrm</prgn>. They must be proper executable files;
3806 if they are scripts (which is recommended), they must start with
3807 the usual <tt>#!</tt> convention. They should be readable and
3808 executable by anyone, and must not be world-writable.
3812 The package management system looks at the exit status from
3813 these scripts. It is important that they exit with a
3814 non-zero status if there is an error, so that the package
3815 management system can stop its processing. For shell
3816 scripts this means that you <em>almost always</em> need to
3817 use <tt>set -e</tt> (this is usually true when writing shell
3818 scripts, in fact). It is also important, of course, that
3819 they exit with a zero status if everything went well.
3823 Additionally, packages interacting with users
3824 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3825 should install a <prgn>config</prgn> script as a control
3826 information file. See <ref id="maintscriptprompt"> for details.
3830 When a package is upgraded a combination of the scripts from
3831 the old and new packages is called during the upgrade
3832 procedure. If your scripts are going to be at all
3833 complicated you need to be aware of this, and may need to
3834 check the arguments to your scripts.
3838 Broadly speaking the <prgn>preinst</prgn> is called before
3839 (a particular version of) a package is unpacked, and the
3840 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3841 before (a version of) a package is removed and the
3842 <prgn>postrm</prgn> afterwards.
3846 Programs called from maintainer scripts should not normally
3847 have a path prepended to them. Before installation is
3848 started, the package management system checks to see if the
3849 programs <prgn>ldconfig</prgn>,
3850 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3851 and <prgn>update-rc.d</prgn> can be found via the
3852 <tt>PATH</tt> environment variable. Those programs, and any
3853 other program that one would expect to be in the
3854 <tt>PATH</tt>, should thus be invoked without an absolute
3855 pathname. Maintainer scripts should also not reset the
3856 <tt>PATH</tt>, though they might choose to modify it by
3857 prepending or appending package-specific directories. These
3858 considerations really apply to all shell scripts.</p>
3861 <sect id="idempotency">
3862 <heading>Maintainer scripts idempotency</heading>
3865 It is necessary for the error recovery procedures that the
3866 scripts be idempotent. This means that if it is run
3867 successfully, and then it is called again, it doesn't bomb
3868 out or cause any harm, but just ensures that everything is
3869 the way it ought to be. If the first call failed, or
3870 aborted half way through for some reason, the second call
3871 should merely do the things that were left undone the first
3872 time, if any, and exit with a success status if everything
3874 This is so that if an error occurs, the user interrupts
3875 <prgn>dpkg</prgn> or some other unforeseen circumstance
3876 happens you don't leave the user with a badly-broken
3877 package when <prgn>dpkg</prgn> attempts to repeat the
3883 <sect id="controllingterminal">
3884 <heading>Controlling terminal for maintainer scripts</heading>
3887 Maintainer scripts are not guaranteed to run with a controlling
3888 terminal and may not be able to interact with the user. They
3889 must be able to fall back to noninteractive behavior if no
3890 controlling terminal is available. Maintainer scripts that
3891 prompt via a program conforming to the Debian Configuration
3892 Management Specification (see <ref id="maintscriptprompt">) may
3893 assume that program will handle falling back to noninteractive
3898 For high-priority prompts without a reasonable default answer,
3899 maintainer scripts may abort if there is no controlling
3900 terminal. However, this situation should be avoided if at all
3901 possible, since it prevents automated or unattended installs.
3902 In most cases, users will consider this to be a bug in the
3907 <sect id="exitstatus">
3908 <heading>Exit status</heading>
3911 Each script must return a zero exit status for
3912 success, or a nonzero one for failure, since the package
3913 management system looks for the exit status of these scripts
3914 and determines what action to take next based on that datum.
3918 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3923 What follows is a summary of all the ways in which maintainer
3924 scripts may be called along with what facilities those scripts
3925 may rely on being available at that time. Script names preceded
3926 by <var>new-</var> are the scripts from the new version of a
3927 package being installed, upgraded to, or downgraded to. Script
3928 names preceded by <var>old-</var> are the scripts from the old
3929 version of a package that is being upgraded from or downgraded
3934 The <prgn>preinst</prgn> script may be called in the following
3937 <tag><var>new-preinst</var> <tt>install</tt></tag>
3938 <tag><var>new-preinst</var> <tt>install</tt>
3939 <var>old-version</var></tag>
3940 <tag><var>new-preinst</var> <tt>upgrade</tt>
3941 <var>old-version</var></tag>
3943 The package will not yet be unpacked, so
3944 the <prgn>preinst</prgn> script cannot rely on any files
3945 included in its package. Only essential packages and
3946 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3947 available. Pre-dependencies will have been configured at
3948 least once, but at the time the <prgn>preinst</prgn> is
3949 called they may only be in an unpacked or "Half-Configured"
3950 state if a previous version of the pre-dependency was
3951 completely configured and has not been removed since then.
3954 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3955 <var>new-version</var></tag>
3957 Called during error handling of an upgrade that failed after
3958 unpacking the new package because the <tt>postrm
3959 upgrade</tt> action failed. The unpacked files may be
3960 partly from the new version or partly missing, so the script
3961 cannot rely on files included in the package. Package
3962 dependencies may not be available. Pre-dependencies will be
3963 at least unpacked following the same rules as above, except
3964 they may be only "Half-Installed" if an upgrade of the
3965 pre-dependency failed.<footnote>
3966 This can happen if the new version of the package no
3967 longer pre-depends on a package that had been partially
3975 The <prgn>postinst</prgn> script may be called in the following
3978 <tag><var>postinst</var> <tt>configure</tt>
3979 <var>most-recently-configured-version</var></tag>
3981 The files contained in the package will be unpacked. All
3982 package dependencies will at least be unpacked. If there
3983 are no circular dependencies involved, all package
3984 dependencies will be configured. For behavior in the case
3985 of circular dependencies, see the discussion
3986 in <ref id="binarydeps">.
3989 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3990 <var>new-version</var></tag>
3991 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3992 <tt>in-favour</tt> <var>package</var>
3993 <var>new-version</var></tag>
3994 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3995 <tag><var>deconfigured's-postinst</var>
3996 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3997 <var>failed-install-package</var> <var>version</var>
3998 [<tt>removing</tt> <var>conflicting-package</var>
3999 <var>version</var>]</tag>
4001 The files contained in the package will be unpacked. All
4002 package dependencies will at least be "Half-Installed" and
4003 will have previously been configured and not removed.
4004 However, dependencies may not be configured or even fully
4005 unpacked in some error situations.<footnote>
4006 For example, suppose packages foo and bar are installed
4007 with foo depending on bar. If an upgrade of bar were
4008 started and then aborted, and then an attempt to remove
4009 foo failed because its <prgn>prerm</prgn> script failed,
4010 foo's <tt>postinst abort-remove</tt> would be called with
4011 bar only "Half-Installed".
4013 The <prgn>postinst</prgn> should still attempt any actions
4014 for which its dependencies are required, since they will
4015 normally be available, but consider the correct error
4016 handling approach if those actions fail. Aborting
4017 the <prgn>postinst</prgn> action if commands or facilities
4018 from the package dependencies are not available is often the
4025 The <prgn>prerm</prgn> script may be called in the following
4028 <tag><var>prerm</var> <tt>remove</tt></tag>
4029 <tag><var>old-prerm</var>
4030 <tt>upgrade</tt><var>new-version</var></tag>
4031 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4032 <tt>in-favour</tt> <var>package</var>
4033 <var>new-version</var></tag>
4034 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4035 <tt>in-favour</tt> <var>package-being-installed</var>
4036 <var>version</var> [<tt>removing</tt>
4037 <var>conflicting-package</var> <var>version</var>]</tag>
4039 The package whose <prgn>prerm</prgn> is being called will be
4040 at least "Half-Installed". All package dependencies will at
4041 least be "Half-Installed" and will have previously been
4042 configured and not removed. If there was no error, all
4043 dependencies will at least be unpacked, but these actions
4044 may be called in various error states where dependencies are
4045 only "Half-Installed" due to a partial upgrade.
4048 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4049 <var>old-version</var></tag>
4051 Called during error handling when <tt>prerm upgrade</tt>
4052 fails. The new package will not yet be unpacked, and all
4053 the same constraints as for <tt>preinst upgrade</tt> apply.
4059 The <prgn>postrm</prgn> script may be called in the following
4062 <tag><var>postrm</var> <tt>remove</tt></tag>
4063 <tag><var>postrm</var> <tt>purge</tt></tag>
4064 <tag><var>old-postrm</var> <tt>upgrade</tt>
4065 <var>new-version</var></tag>
4066 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4067 <var>overwriter</var> <var>overwriter-version</var></tag>
4069 The <prgn>postrm</prgn> script is called after the package's
4070 files have been removed or replaced. The package
4071 whose <prgn>postrm</prgn> is being called may have
4072 previously been deconfigured and only be unpacked, at which
4073 point subsequent package changes do not consider its
4074 dependencies. Therefore, all <prgn>postrm</prgn> actions
4075 may only rely on essential packages and must gracefully skip
4076 any actions that require the package's dependencies if those
4077 dependencies are unavailable.<footnote>
4078 This is often done by checking whether the command or
4079 facility the <prgn>postrm</prgn> intends to call is
4080 available before calling it. For example:
4082 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4083 . /usr/share/debconf/confmodule
4087 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4088 configuration for the package
4089 if <package>debconf</package> is installed.
4093 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4094 <var>old-version</var></tag>
4096 Called when the old <tt>postrm upgrade</tt> action fails.
4097 The new package will be unpacked, but only essential
4098 packages and pre-dependencies can be relied on.
4099 Pre-dependencies will either be configured or will be
4100 "Unpacked" or "Half-Configured" but previously had been
4101 configured and was never removed.
4104 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4105 <tag><var>new-postrm</var> <tt>abort-install</tt>
4106 <var>old-version</var></tag>
4107 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4108 <var>old-version</var></tag>
4110 Called before unpacking the new package as part of the
4111 error handling of <prgn>preinst</prgn> failures. May assume
4112 the same state as <prgn>preinst</prgn> can assume.
4118 <sect id="unpackphase">
4119 <heading>Details of unpack phase of installation or upgrade</heading>
4122 The procedure on installation/upgrade/overwrite/disappear
4123 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4124 stage of <tt>dpkg --install</tt>) is as follows. In each
4125 case, if a major error occurs (unless listed below) the
4126 actions are, in general, run backwards - this means that the
4127 maintainer scripts are run with different arguments in
4128 reverse order. These are the "error unwind" calls listed
4135 If a version of the package is already installed, call
4136 <example compact="compact">
4137 <var>old-prerm</var> upgrade <var>new-version</var>
4141 If the script runs but exits with a non-zero
4142 exit status, <prgn>dpkg</prgn> will attempt:
4143 <example compact="compact">
4144 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4146 If this works, the upgrade continues. If this
4147 does not work, the error unwind:
4148 <example compact="compact">
4149 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4151 If this works, then the old-version is
4152 "Installed", if not, the old version is in a
4153 "Half-Configured" state.
4159 If a "conflicting" package is being removed at the same time,
4160 or if any package will be broken (due to <tt>Breaks</tt>):
4163 If <tt>--auto-deconfigure</tt> is
4164 specified, call, for each package to be deconfigured
4165 due to <tt>Breaks</tt>:
4166 <example compact="compact">
4167 <var>deconfigured's-prerm</var> deconfigure \
4168 in-favour <var>package-being-installed</var> <var>version</var>
4171 <example compact="compact">
4172 <var>deconfigured's-postinst</var> abort-deconfigure \
4173 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4175 The deconfigured packages are marked as
4176 requiring configuration, so that if
4177 <tt>--install</tt> is used they will be
4178 configured again if possible.
4181 If any packages depended on a conflicting
4182 package being removed and <tt>--auto-deconfigure</tt> is
4183 specified, call, for each such package:
4184 <example compact="compact">
4185 <var>deconfigured's-prerm</var> deconfigure \
4186 in-favour <var>package-being-installed</var> <var>version</var> \
4187 removing <var>conflicting-package</var> <var>version</var>
4190 <example compact="compact">
4191 <var>deconfigured's-postinst</var> abort-deconfigure \
4192 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4193 removing <var>conflicting-package</var> <var>version</var>
4195 The deconfigured packages are marked as
4196 requiring configuration, so that if
4197 <tt>--install</tt> is used they will be
4198 configured again if possible.
4201 To prepare for removal of each conflicting package, call:
4202 <example compact="compact">
4203 <var>conflictor's-prerm</var> remove \
4204 in-favour <var>package</var> <var>new-version</var>
4207 <example compact="compact">
4208 <var>conflictor's-postinst</var> abort-remove \
4209 in-favour <var>package</var> <var>new-version</var>
4218 If the package is being upgraded, call:
4219 <example compact="compact">
4220 <var>new-preinst</var> upgrade <var>old-version</var>
4222 If this fails, we call:
4224 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4231 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4233 is called. If this works, then the old version
4234 is in an "Installed" state, or else it is left
4235 in an "Unpacked" state.
4240 If it fails, then the old version is left
4241 in an "Half-Installed" state.
4248 Otherwise, if the package had some configuration
4249 files from a previous version installed (i.e., it
4250 is in the "configuration files only" state):
4251 <example compact="compact">
4252 <var>new-preinst</var> install <var>old-version</var>
4256 <var>new-postrm</var> abort-install <var>old-version</var>
4258 If this fails, the package is left in a
4259 "Half-Installed" state, which requires a
4260 reinstall. If it works, the packages is left in
4261 a "Config-Files" state.
4264 Otherwise (i.e., the package was completely purged):
4265 <example compact="compact">
4266 <var>new-preinst</var> install
4269 <example compact="compact">
4270 <var>new-postrm</var> abort-install
4272 If the error-unwind fails, the package is in a
4273 "Half-Installed" phase, and requires a
4274 reinstall. If the error unwind works, the
4275 package is in a not installed state.
4282 The new package's files are unpacked, overwriting any
4283 that may be on the system already, for example any
4284 from the old version of the same package or from
4285 another package. Backups of the old files are kept
4286 temporarily, and if anything goes wrong the package
4287 management system will attempt to put them back as
4288 part of the error unwind.
4292 It is an error for a package to contain files which
4293 are on the system in another package, unless
4294 <tt>Replaces</tt> is used (see <ref id="replaces">).
4296 The following paragraph is not currently the case:
4297 Currently the <tt>- - force-overwrite</tt> flag is
4298 enabled, downgrading it to a warning, but this may not
4304 It is a more serious error for a package to contain a
4305 plain file or other kind of non-directory where another
4306 package has a directory (again, unless
4307 <tt>Replaces</tt> is used). This error can be
4308 overridden if desired using
4309 <tt>--force-overwrite-dir</tt>, but this is not
4314 Packages which overwrite each other's files produce
4315 behavior which, though deterministic, is hard for the
4316 system administrator to understand. It can easily
4317 lead to "missing" programs if, for example, a package
4318 is unpacked which overwrites a file from another
4319 package, and is then removed again.<footnote>
4320 Part of the problem is due to what is arguably a
4321 bug in <prgn>dpkg</prgn>.
4326 A directory will never be replaced by a symbolic link
4327 to a directory or vice versa; instead, the existing
4328 state (symlink or not) will be left alone and
4329 <prgn>dpkg</prgn> will follow the symlink if there is
4338 If the package is being upgraded, call
4339 <example compact="compact">
4340 <var>old-postrm</var> upgrade <var>new-version</var>
4344 If this fails, <prgn>dpkg</prgn> will attempt:
4345 <example compact="compact">
4346 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4348 If this works, installation continues. If not,
4350 <example compact="compact">
4351 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4353 If this fails, the old version is left in a
4354 "Half-Installed" state. If it works, dpkg now
4356 <example compact="compact">
4357 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4359 If this fails, the old version is left in a
4360 "Half-Installed" state. If it works, dpkg now
4362 <example compact="compact">
4363 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4365 If this fails, the old version is in an
4372 This is the point of no return - if
4373 <prgn>dpkg</prgn> gets this far, it won't back off
4374 past this point if an error occurs. This will
4375 leave the package in a fairly bad state, which
4376 will require a successful re-installation to clear
4377 up, but it's when <prgn>dpkg</prgn> starts doing
4378 things that are irreversible.
4383 Any files which were in the old version of the package
4384 but not in the new are removed.
4388 The new file list replaces the old.
4392 The new maintainer scripts replace the old.
4396 Any packages all of whose files have been overwritten
4397 during the installation, and which aren't required for
4398 dependencies, are considered to have been removed.
4399 For each such package
4402 <prgn>dpkg</prgn> calls:
4403 <example compact="compact">
4404 <var>disappearer's-postrm</var> disappear \
4405 <var>overwriter</var> <var>overwriter-version</var>
4409 The package's maintainer scripts are removed.
4412 It is noted in the status database as being in a
4413 sane state, namely not installed (any conffiles
4414 it may have are ignored, rather than being
4415 removed by <prgn>dpkg</prgn>). Note that
4416 disappearing packages do not have their prerm
4417 called, because <prgn>dpkg</prgn> doesn't know
4418 in advance that the package is going to
4425 Any files in the package we're unpacking that are also
4426 listed in the file lists of other packages are removed
4427 from those lists. (This will lobotomize the file list
4428 of the "conflicting" package if there is one.)
4432 The backup files made during installation, above, are
4438 The new package's status is now sane, and recorded as
4443 Here is another point of no return - if the
4444 conflicting package's removal fails we do not unwind
4445 the rest of the installation; the conflicting package
4446 is left in a half-removed limbo.
4451 If there was a conflicting package we go and do the
4452 removal actions (described below), starting with the
4453 removal of the conflicting package's files (any that
4454 are also in the package being unpacked have already
4455 been removed from the conflicting package's file list,
4456 and so do not get removed now).
4462 <sect id="configdetails"><heading>Details of configuration</heading>
4465 When we configure a package (this happens with <tt>dpkg
4466 --install</tt> and <tt>dpkg --configure</tt>), we first
4467 update any <tt>conffile</tt>s and then call:
4468 <example compact="compact">
4469 <var>postinst</var> configure <var>most-recently-configured-version</var>
4474 No attempt is made to unwind after errors during
4475 configuration. If the configuration fails, the package is in
4476 a "Failed Config" state, and an error message is generated.
4480 If there is no most recently configured version
4481 <prgn>dpkg</prgn> will pass a null argument.
4484 Historical note: Truly ancient (pre-1997) versions of
4485 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4486 (including the angle brackets) in this case. Even older
4487 ones did not pass a second argument at all, under any
4488 circumstance. Note that upgrades using such an old dpkg
4489 version are unlikely to work for other reasons, even if
4490 this old argument behavior is handled by your postinst script.
4496 <sect id="removedetails"><heading>Details of removal and/or
4497 configuration purging</heading>
4503 <example compact="compact">
4504 <var>prerm</var> remove
4508 If prerm fails during replacement due to conflict
4510 <var>conflictor's-postinst</var> abort-remove \
4511 in-favour <var>package</var> <var>new-version</var>
4515 <var>postinst</var> abort-remove
4519 If this fails, the package is in a "Half-Configured"
4520 state, or else it remains "Installed".
4524 The package's files are removed (except <tt>conffile</tt>s).
4527 <example compact="compact">
4528 <var>postrm</var> remove
4532 If it fails, there's no error unwind, and the package is in
4533 an "Half-Installed" state.
4538 All the maintainer scripts except the <prgn>postrm</prgn>
4543 If we aren't purging the package we stop here. Note
4544 that packages which have no <prgn>postrm</prgn> and no
4545 <tt>conffile</tt>s are automatically purged when
4546 removed, as there is no difference except for the
4547 <prgn>dpkg</prgn> status.
4551 The <tt>conffile</tt>s and any backup files
4552 (<tt>~</tt>-files, <tt>#*#</tt> files,
4553 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4558 <example compact="compact">
4559 <var>postrm</var> purge
4563 If this fails, the package remains in a "Config-Files"
4568 The package's file list is removed.
4577 <chapt id="relationships">
4578 <heading>Declaring relationships between packages</heading>
4580 <sect id="depsyntax">
4581 <heading>Syntax of relationship fields</heading>
4584 These fields all have a uniform syntax. They are a list of
4585 package names separated by commas.
4589 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4590 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4591 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4592 control fields of the package, which declare
4593 dependencies on other packages, the package names listed may
4594 also include lists of alternative package names, separated
4595 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4596 if any one of the alternative packages is installed, that
4597 part of the dependency is considered to be satisfied.
4601 All of the fields except for <tt>Provides</tt> may restrict
4602 their applicability to particular versions of each named
4603 package. This is done in parentheses after each individual
4604 package name; the parentheses should contain a relation from
4605 the list below followed by a version number, in the format
4606 described in <ref id="f-Version">.
4610 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4611 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4612 strictly earlier, earlier or equal, exactly equal, later or
4613 equal and strictly later, respectively. The deprecated
4614 forms <tt><</tt> and <tt>></tt> were used to mean
4615 earlier/later or equal, rather than strictly earlier/later,
4616 so they should not appear in new packages (though
4617 <prgn>dpkg</prgn> still supports them).
4621 Whitespace may appear at any point in the version
4622 specification subject to the rules in <ref
4623 id="controlsyntax">, and must appear where it's necessary to
4624 disambiguate; it is not otherwise significant. All of the
4625 relationship fields can only be folded in source package control files. For
4626 consistency and in case of future changes to
4627 <prgn>dpkg</prgn> it is recommended that a single space be
4628 used after a version relationship and before a version
4629 number; it is also conventional to put a single space after
4630 each comma, on either side of each vertical bar, and before
4631 each open parenthesis. When opening a continuation line in a relationship field, it
4632 is conventional to do so after a comma and before the space
4633 following that comma.
4637 For example, a list of dependencies might appear as:
4638 <example compact="compact">
4641 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4646 Relationships may be restricted to a certain set of
4647 architectures. This is indicated in brackets after each
4648 individual package name and the optional version specification.
4649 The brackets enclose a non-empty list of Debian architecture names
4650 in the format described in <ref id="arch-spec">,
4651 separated by whitespace. Exclamation marks may be prepended to
4652 each of the names. (It is not permitted for some names to be
4653 prepended with exclamation marks while others aren't.)
4657 For build relationship fields
4658 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4659 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4660 the current Debian host architecture is not in this list and
4661 there are no exclamation marks in the list, or it is in the list
4662 with a prepended exclamation mark, the package name and the
4663 associated version specification are ignored completely for the
4664 purposes of defining the relationships.
4669 <example compact="compact">
4671 Build-Depends-Indep: texinfo
4672 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4673 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4675 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4676 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4677 <tt>gnumach-dev</tt> only on hurd-i386.
4681 For binary relationship fields, the architecture restriction
4682 syntax is only supported in the source package control
4683 file <file>debian/control</file>. When the corresponding binary
4684 package control file is generated, the relationship will either
4685 be omitted or included without the architecture restriction
4686 based on the architecture of the binary package. This means
4687 that architecture restrictions must not be used in binary
4688 relationship fields for architecture-independent packages
4689 (<tt>Architecture: all</tt>).
4694 <example compact="compact">
4695 Depends: foo [i386], bar [amd64]
4697 becomes <tt>Depends: foo</tt> when the package is built on
4698 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4699 package is built on the <tt>amd64</tt> architecture, and omitted
4700 entirely in binary packages built on all other architectures.
4704 If the architecture-restricted dependency is part of a set of
4705 alternatives using <tt>|</tt>, that alternative is ignored
4706 completely on architectures that do not match the restriction.
4708 <example compact="compact">
4709 Build-Depends: foo [!i386] | bar [!amd64]
4711 is equivalent to <tt>bar</tt> on the i386 architecture, to
4712 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4713 bar</tt> on all other architectures.
4717 Relationships may also be restricted to a certain set of
4718 architectures using architecture wildcards in the format
4719 described in <ref id="arch-wildcard-spec">. The syntax for
4720 declaring such restrictions is the same as declaring
4721 restrictions using a certain set of architectures without
4722 architecture wildcards. For example:
4723 <example compact="compact">
4724 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4726 is equivalent to <tt>foo</tt> on architectures using the Linux
4727 kernel and any cpu, <tt>bar</tt> on architectures using any
4728 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4729 using a kernel other than Linux.
4733 Note that the binary package relationship fields such as
4734 <tt>Depends</tt> appear in one of the binary package
4735 sections of the control file, whereas the build-time
4736 relationships such as <tt>Build-Depends</tt> appear in the
4737 source package section of the control file (which is the
4742 <sect id="binarydeps">
4743 <heading>Binary Dependencies - <tt>Depends</tt>,
4744 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4745 <tt>Pre-Depends</tt>
4749 Packages can declare in their control file that they have
4750 certain relationships to other packages - for example, that
4751 they may not be installed at the same time as certain other
4752 packages, and/or that they depend on the presence of others.
4756 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4757 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4758 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4759 <tt>Breaks</tt> is described in <ref id="breaks">, and
4760 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4761 rest are described below.
4765 These seven fields are used to declare a dependency
4766 relationship by one package on another. Except for
4767 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4768 depending (binary) package's control file.
4769 (<tt>Enhances</tt> appears in the recommending package's
4770 control file, and <tt>Breaks</tt> appears in the version of
4771 depended-on package which causes the named package to
4776 A <tt>Depends</tt> field takes effect <em>only</em> when a
4777 package is to be configured. It does not prevent a package
4778 being on the system in an unconfigured state while its
4779 dependencies are unsatisfied, and it is possible to replace
4780 a package whose dependencies are satisfied and which is
4781 properly installed with a different version whose
4782 dependencies are not and cannot be satisfied; when this is
4783 done the depending package will be left unconfigured (since
4784 attempts to configure it will give errors) and will not
4785 function properly. If it is necessary, a
4786 <tt>Pre-Depends</tt> field can be used, which has a partial
4787 effect even when a package is being unpacked, as explained
4788 in detail below. (The other three dependency fields,
4789 <tt>Recommends</tt>, <tt>Suggests</tt> and
4790 <tt>Enhances</tt>, are only used by the various front-ends
4791 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4792 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4796 Since <tt>Depends</tt> only places requirements on the order in
4797 which packages are configured, packages in an installation run
4798 are usually all unpacked first and all configured later.
4800 This approach makes dependency resolution easier. If two
4801 packages A and B are being upgraded, the installed package A
4802 depends on exactly the installed package B, and the new
4803 package A depends on exactly the new package B (a common
4804 situation when upgrading shared libraries and their
4805 corresponding development packages), satisfying the
4806 dependencies at every stage of the upgrade would be
4807 impossible. This relaxed restriction means that both new
4808 packages can be unpacked together and then configured in their
4814 If there is a circular dependency among packages being installed
4815 or removed, installation or removal order honoring the
4816 dependency order is impossible, requiring the dependency loop be
4817 broken at some point and the dependency requirements violated
4818 for at least one package. Packages involved in circular
4819 dependencies may not be able to rely on their dependencies being
4820 configured before they themselves are configured, depending on
4821 which side of the break of the circular dependency loop they
4822 happen to be on. If one of the packages in the loop has
4823 no <prgn>postinst</prgn> script, then the cycle will be broken
4824 at that package; this ensures that all <prgn>postinst</prgn>
4825 scripts are run with their dependencies properly configured if
4826 this is possible. Otherwise the breaking point is arbitrary.
4827 Packages should therefore avoid circular dependencies where
4828 possible, particularly if they have <prgn>postinst</prgn>
4833 The meaning of the five dependency fields is as follows:
4835 <tag><tt>Depends</tt></tag>
4838 This declares an absolute dependency. A package will
4839 not be configured unless all of the packages listed in
4840 its <tt>Depends</tt> field have been correctly
4841 configured (unless there is a circular dependency as
4846 The <tt>Depends</tt> field should be used if the
4847 depended-on package is required for the depending
4848 package to provide a significant amount of
4853 The <tt>Depends</tt> field should also be used if the
4854 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4855 require the depended-on package to be unpacked or
4856 configured in order to run. In the case of <tt>postinst
4857 configure</tt>, the depended-on packages will be unpacked
4858 and configured first. (If both packages are involved in a
4859 dependency loop, this might not work as expected; see the
4860 explanation a few paragraphs back.) In the case
4861 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4862 actions, the package dependencies will normally be at
4863 least unpacked, but they may be only "Half-Installed" if a
4864 previous upgrade of the dependency failed.
4868 Finally, the <tt>Depends</tt> field should be used if the
4869 depended-on package is needed by the <prgn>postrm</prgn>
4870 script to fully clean up after the package removal. There
4871 is no guarantee that package dependencies will be
4872 available when <prgn>postrm</prgn> is run, but the
4873 depended-on package is more likely to be available if the
4874 package declares a dependency (particularly in the case
4875 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4876 script must gracefully skip actions that require a
4877 dependency if that dependency isn't available.
4881 <tag><tt>Recommends</tt></tag>
4884 This declares a strong, but not absolute, dependency.
4888 The <tt>Recommends</tt> field should list packages
4889 that would be found together with this one in all but
4890 unusual installations.
4894 <tag><tt>Suggests</tt></tag>
4896 This is used to declare that one package may be more
4897 useful with one or more others. Using this field
4898 tells the packaging system and the user that the
4899 listed packages are related to this one and can
4900 perhaps enhance its usefulness, but that installing
4901 this one without them is perfectly reasonable.
4904 <tag><tt>Enhances</tt></tag>
4906 This field is similar to Suggests but works in the
4907 opposite direction. It is used to declare that a
4908 package can enhance the functionality of another
4912 <tag><tt>Pre-Depends</tt></tag>
4915 This field is like <tt>Depends</tt>, except that it
4916 also forces <prgn>dpkg</prgn> to complete installation
4917 of the packages named before even starting the
4918 installation of the package which declares the
4919 pre-dependency, as follows:
4923 When a package declaring a pre-dependency is about to
4924 be <em>unpacked</em> the pre-dependency can be
4925 satisfied if the depended-on package is either fully
4926 configured, <em>or even if</em> the depended-on
4927 package(s) are only unpacked or in the "Half-Configured"
4928 state, provided that they have been configured
4929 correctly at some point in the past (and not removed
4930 or partially removed since). In this case, both the
4931 previously-configured and currently unpacked or
4932 "Half-Configured" versions must satisfy any version
4933 clause in the <tt>Pre-Depends</tt> field.
4937 When the package declaring a pre-dependency is about to
4938 be <em>configured</em>, the pre-dependency will be treated
4939 as a normal <tt>Depends</tt>. It will be considered
4940 satisfied only if the depended-on package has been
4941 correctly configured. However, unlike
4942 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4943 permit circular dependencies to be broken. If a circular
4944 dependency is encountered while attempting to honor
4945 <tt>Pre-Depends</tt>, the installation will be aborted.
4949 <tt>Pre-Depends</tt> are also required if the
4950 <prgn>preinst</prgn> script depends on the named package.
4951 It is best to avoid this situation if possible.
4955 <tt>Pre-Depends</tt> should be used sparingly,
4956 preferably only by packages whose premature upgrade or
4957 installation would hamper the ability of the system to
4958 continue with any upgrade that might be in progress.
4962 You should not specify a <tt>Pre-Depends</tt> entry for a
4963 package before this has been discussed on the
4964 <tt>debian-devel</tt> mailing list and a consensus about
4965 doing that has been reached. See <ref id="dependencies">.
4972 When selecting which level of dependency to use you should
4973 consider how important the depended-on package is to the
4974 functionality of the one declaring the dependency. Some
4975 packages are composed of components of varying degrees of
4976 importance. Such a package should list using
4977 <tt>Depends</tt> the package(s) which are required by the
4978 more important components. The other components'
4979 requirements may be mentioned as Suggestions or
4980 Recommendations, as appropriate to the components' relative
4986 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4989 When one binary package declares that it breaks another,
4990 <prgn>dpkg</prgn> will refuse to allow the package which
4991 declares <tt>Breaks</tt> to be unpacked unless the broken
4992 package is deconfigured first, and it will refuse to
4993 allow the broken package to be reconfigured.
4997 A package will not be regarded as causing breakage merely
4998 because its configuration files are still installed; it must
4999 be at least "Half-Installed".
5003 A special exception is made for packages which declare that
5004 they break their own package name or a virtual package which
5005 they provide (see below): this does not count as a real
5010 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5011 version clause; such a <tt>Breaks</tt> is introduced in the
5012 version of an (implicit or explicit) dependency which violates
5013 an assumption or reveals a bug in earlier versions of the broken
5014 package, or which takes over a file from earlier versions of the
5015 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5016 will inform higher-level package management tools that the
5017 broken package must be upgraded before the new one.
5021 If the breaking package also overwrites some files from the
5022 older package, it should use <tt>Replaces</tt> to ensure this
5023 goes smoothly. See <ref id="replaces"> for a full discussion
5024 of taking over files from other packages, including how to
5025 use <tt>Breaks</tt> in those cases.
5029 Many of the cases where <tt>Breaks</tt> should be used were
5030 previously handled with <tt>Conflicts</tt>
5031 because <tt>Breaks</tt> did not yet exist.
5032 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5033 See <ref id="conflicts"> for more information about the
5038 <sect id="conflicts">
5039 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5042 When one binary package declares a conflict with another using
5043 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5044 allow them to be unpacked on the system at the same time. This
5045 is a stronger restriction than <tt>Breaks</tt>, which prevents
5046 the broken package from being configured while the breaking
5047 package is in the "Unpacked" state but allows both packages to
5048 be unpacked at the same time.
5052 If one package is to be unpacked, the other must be removed
5053 first. If the package being unpacked is marked as replacing
5054 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5055 normally be used in this case) the one on the system, or the one
5056 on the system is marked as deselected, or both packages are
5057 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5058 automatically remove the package which is causing the conflict.
5059 Otherwise, it will halt the installation of the new package with
5060 an error. This mechanism is specifically designed to produce an
5061 error when the installed package is <tt>Essential</tt>, but the
5066 A package will not cause a conflict merely because its
5067 configuration files are still installed; it must be at least
5072 A special exception is made for packages which declare a
5073 conflict with their own package name, or with a virtual
5074 package which they provide (see below): this does not
5075 prevent their installation, and allows a package to conflict
5076 with others providing a replacement for it. You use this
5077 feature when you want the package in question to be the only
5078 package providing some feature.
5082 Normally, <tt>Breaks</tt> should be used instead
5083 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5084 stronger restriction on the ordering of package installation or
5085 upgrade and can make it more difficult for the package manager
5086 to find a correct solution to an upgrade or installation
5087 problem. <tt>Breaks</tt> should be used
5089 <item>when moving a file from one package to another (see
5090 <ref id="replaces">),</item>
5091 <item>when splitting a package (a special case of the previous
5093 <item>when the breaking package exposes a bug in or interacts
5094 badly with particular versions of the broken
5097 <tt>Conflicts</tt> should be used
5099 <item>when two packages provide the same file and will
5100 continue to do so,</item>
5101 <item>in conjunction with <tt>Provides</tt> when only one
5102 package providing a given virtual facility may be unpacked
5103 at a time (see <ref id="virtual">),</item>
5104 <item>in other cases where one must prevent simultaneous
5105 installation of two packages for reasons that are ongoing
5106 (not fixed in a later version of one of the packages) or
5107 that must prevent both packages from being unpacked at the
5108 same time, not just configured.</item>
5110 Be aware that adding <tt>Conflicts</tt> is normally not the best
5111 solution when two packages provide the same files. Depending on
5112 the reason for that conflict, using alternatives or renaming the
5113 files is often a better approach. See, for
5114 example, <ref id="binaries">.
5118 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5119 unless two packages cannot be installed at the same time or
5120 installing them both causes one of them to be broken or
5121 unusable. Having similar functionality or performing the same
5122 tasks as another package is not sufficient reason to
5123 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5127 A <tt>Conflicts</tt> entry may have an "earlier than" version
5128 clause if the reason for the conflict is corrected in a later
5129 version of one of the packages. However, normally the presence
5130 of an "earlier than" version clause is a sign
5131 that <tt>Breaks</tt> should have been used instead. An "earlier
5132 than" version clause in <tt>Conflicts</tt>
5133 prevents <prgn>dpkg</prgn> from upgrading or installing the
5134 package which declares such a conflict until the upgrade or
5135 removal of the conflicted-with package has been completed, which
5136 is a strong restriction.
5140 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5144 As well as the names of actual ("concrete") packages, the
5145 package relationship fields <tt>Depends</tt>,
5146 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5147 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5148 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5149 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5150 may mention "virtual packages".
5154 A <em>virtual package</em> is one which appears in the
5155 <tt>Provides</tt> control field of another package. The effect
5156 is as if the package(s) which provide a particular virtual
5157 package name had been listed by name everywhere the virtual
5158 package name appears. (See also <ref id="virtual_pkg">)
5162 If there are both concrete and virtual packages of the same
5163 name, then the dependency may be satisfied (or the conflict
5164 caused) by either the concrete package with the name in
5165 question or any other concrete package which provides the
5166 virtual package with the name in question. This is so that,
5167 for example, supposing we have
5168 <example compact="compact">
5171 </example> and someone else releases an enhanced version of
5172 the <tt>bar</tt> package they can say:
5173 <example compact="compact">
5177 and the <tt>bar-plus</tt> package will now also satisfy the
5178 dependency for the <tt>foo</tt> package.
5182 If a relationship field has a version number attached, only real
5183 packages will be considered to see whether the relationship is
5184 satisfied (or the prohibition violated, for a conflict or
5185 breakage). In other words, if a version number is specified,
5186 this is a request to ignore all <tt>Provides</tt> for that
5187 package name and consider only real packages. The package
5188 manager will assume that a package providing that virtual
5189 package is not of the "right" version. A <tt>Provides</tt>
5190 field may not contain version numbers, and the version number of
5191 the concrete package which provides a particular virtual package
5192 will not be considered when considering a dependency on or
5193 conflict with the virtual package name.<footnote>
5194 It is possible that a future release of <prgn>dpkg</prgn> may
5195 add the ability to specify a version number for each virtual
5196 package it provides. This feature is not yet present,
5197 however, and is expected to be used only infrequently.
5202 To specify which of a set of real packages should be the default
5203 to satisfy a particular dependency on a virtual package, list
5204 the real package as an alternative before the virtual one.
5208 If the virtual package represents a facility that can only be
5209 provided by one real package at a time, such as
5210 the <package>mail-transport-agent</package> virtual package that
5211 requires installation of a binary that would conflict with all
5212 other providers of that virtual package (see
5213 <ref id="mail-transport-agents">), all packages providing that
5214 virtual package should also declare a conflict with it
5215 using <tt>Conflicts</tt>. This will ensure that at most one
5216 provider of that virtual package is unpacked or installed at a
5221 <sect id="replaces"><heading>Overwriting files and replacing
5222 packages - <tt>Replaces</tt></heading>
5225 Packages can declare in their control file that they should
5226 overwrite files in certain other packages, or completely replace
5227 other packages. The <tt>Replaces</tt> control field has these
5228 two distinct purposes.
5231 <sect1><heading>Overwriting files in other packages</heading>
5234 It is usually an error for a package to contain files which
5235 are on the system in another package. However, if the
5236 overwriting package declares that it <tt>Replaces</tt> the one
5237 containing the file being overwritten, then <prgn>dpkg</prgn>
5238 will replace the file from the old package with that from the
5239 new. The file will no longer be listed as "owned" by the old
5240 package and will be taken over by the new package.
5241 Normally, <tt>Breaks</tt> should be used in conjunction
5242 with <tt>Replaces</tt>.<footnote>
5243 To see why <tt>Breaks</tt> is normally needed in addition
5244 to <tt>Replaces</tt>, consider the case of a file in the
5245 package <package>foo</package> being taken over by the
5246 package <package>foo-data</package>.
5247 <tt>Replaces</tt> will allow <package>foo-data</package> to
5248 be installed and take over that file. However,
5249 without <tt>Breaks</tt>, nothing
5250 requires <package>foo</package> to be upgraded to a newer
5251 version that knows it does not include that file and instead
5252 depends on <package>foo-data</package>. Nothing would
5253 prevent the new <package>foo-data</package> package from
5254 being installed and then removed, removing the file that it
5255 took over from <package>foo</package>. After that
5256 operation, the package manager would think the system was in
5257 a consistent state, but the <package>foo</package> package
5258 would be missing one of its files.
5263 For example, if a package <package>foo</package> is split
5264 into <package>foo</package> and <package>foo-data</package>
5265 starting at version 1.2-3, <package>foo-data</package> would
5267 <example compact="compact">
5268 Replaces: foo (<< 1.2-3)
5269 Breaks: foo (<< 1.2-3)
5271 in its control file. The new version of the
5272 package <package>foo</package> would normally have the field
5273 <example compact="compact">
5274 Depends: foo-data (>= 1.2-3)
5276 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5277 the files moved into <package>foo-data</package> are not
5278 required for normal operation).
5282 If a package is completely replaced in this way, so that
5283 <prgn>dpkg</prgn> does not know of any files it still
5284 contains, it is considered to have "disappeared". It will
5285 be marked as not wanted on the system (selected for
5286 removal) and not installed. Any <tt>conffile</tt>s
5287 details noted for the package will be ignored, as they
5288 will have been taken over by the overwriting package. The
5289 package's <prgn>postrm</prgn> script will be run with a
5290 special argument to allow the package to do any final
5291 cleanup required. See <ref id="mscriptsinstact">.
5293 Replaces is a one way relationship. You have to install
5294 the replacing package after the replaced package.
5299 For this usage of <tt>Replaces</tt>, virtual packages (see
5300 <ref id="virtual">) are not considered when looking at a
5301 <tt>Replaces</tt> field. The packages declared as being
5302 replaced must be mentioned by their real names.
5306 This usage of <tt>Replaces</tt> only takes effect when both
5307 packages are at least partially on the system at once. It is
5308 not relevant if the packages conflict unless the conflict has
5313 <sect1><heading>Replacing whole packages, forcing their
5317 Second, <tt>Replaces</tt> allows the packaging system to
5318 resolve which package should be removed when there is a
5319 conflict (see <ref id="conflicts">). This usage only takes
5320 effect when the two packages <em>do</em> conflict, so that the
5321 two usages of this field do not interfere with each other.
5325 In this situation, the package declared as being replaced
5326 can be a virtual package, so for example, all mail
5327 transport agents (MTAs) would have the following fields in
5328 their control files:
5329 <example compact="compact">
5330 Provides: mail-transport-agent
5331 Conflicts: mail-transport-agent
5332 Replaces: mail-transport-agent
5334 ensuring that only one MTA can be unpacked at any one
5335 time. See <ref id="virtual"> for more information about this
5340 <sect id="sourcebinarydeps">
5341 <heading>Relationships between source and binary packages -
5342 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5343 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5347 Source packages that require certain binary packages to be
5348 installed or absent at the time of building the package
5349 can declare relationships to those binary packages.
5353 This is done using the <tt>Build-Depends</tt>,
5354 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5355 <tt>Build-Conflicts-Indep</tt> control fields.
5359 Build-dependencies on "build-essential" binary packages can be
5360 omitted. Please see <ref id="pkg-relations"> for more information.
5364 The dependencies and conflicts they define must be satisfied
5365 (as defined earlier for binary packages) in order to invoke
5366 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5368 There is no Build-Depends-Arch; this role is essentially
5369 met with Build-Depends. Anyone building the
5370 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5371 assumed to be building the whole package, and therefore
5372 installation of all build dependencies is required.
5375 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5376 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5377 not yet know how to check for its existence, and
5378 <tt>binary-arch</tt>. The purpose of the original split
5379 between <tt>Build-Depends</tt> and
5380 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5381 wouldn't need to install extra packages needed only for the
5382 binary-indep targets. But without a build-arch/build-indep
5383 split, this didn't work, since most of the work is done in
5384 the build target, not in the binary target.
5388 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5389 <tt>binary-arch</tt></tag>
5391 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5392 fields must be satisfied when these targets are invoked.
5394 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5395 and <tt>binary-indep</tt></tag>
5397 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5398 <tt>Build-Depends-Indep</tt>, and
5399 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5400 these targets are invoked.
5408 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5411 Packages containing shared libraries must be constructed with
5412 a little care to make sure that the shared library is always
5413 available. This is especially important for packages whose
5414 shared libraries are vitally important, such as the C library
5415 (currently <tt>libc6</tt>).
5419 This section deals only with public shared libraries: shared
5420 libraries that are placed in directories searched by the dynamic
5421 linker by default or which are intended to be linked against
5422 normally and possibly used by other, independent packages. Shared
5423 libraries that are internal to a particular package or that are
5424 only loaded as dynamic modules are not covered by this section and
5425 are not subject to its requirements.
5429 A shared library is identified by the <tt>SONAME</tt> attribute
5430 stored in its dynamic section. When a binary is linked against a
5431 shared library, the <tt>SONAME</tt> of the shared library is
5432 recorded in the binary's <tt>NEEDED</tt> section so that the
5433 dynamic linker knows that library must be loaded at runtime. The
5434 shared library file's full name (which usually contains additional
5435 version information not needed in the <tt>SONAME</tt>) is
5436 therefore normally not referenced directly. Instead, the shared
5437 library is loaded by its <tt>SONAME</tt>, which exists on the file
5438 system as a symlink pointing to the full name of the shared
5439 library. This symlink must be provided by the
5440 package. <ref id="sharedlibs-runtime"> describes how to do this.
5442 This is a convention of shared library versioning, but not a
5443 requirement. Some libraries use the <tt>SONAME</tt> as the full
5444 library file name instead and therefore do not need a symlink.
5445 Most, however, encode additional information about
5446 backwards-compatible revisions as a minor version number in the
5447 file name. The <tt>SONAME</tt> itself only changes when
5448 binaries linked with the earlier version of the shared library
5449 may no longer work, but the filename may change with each
5450 release of the library. See <ref id="sharedlibs-runtime"> for
5456 When linking a binary or another shared library against a shared
5457 library, the <tt>SONAME</tt> for that shared library is not yet
5458 known. Instead, the shared library is found by looking for a file
5459 matching the library name with <tt>.so</tt> appended. This file
5460 exists on the file system as a symlink pointing to the shared
5465 Shared libraries are normally split into several binary packages.
5466 The <tt>SONAME</tt> symlink is installed by the runtime shared
5467 library package, and the bare <tt>.so</tt> symlink is installed in
5468 the development package since it's only used when linking binaries
5469 or shared libraries. However, there are some exceptions for
5470 unusual shared libraries or for shared libraries that are also
5471 loaded as dynamic modules by other programs.
5475 This section is primarily concerned with how the separation of
5476 shared libraries into multiple packages should be done and how
5477 dependencies on and between shared library binary packages are
5478 managed in Debian. <ref id="libraries"> should be read in
5479 conjunction with this section and contains additional rules for
5480 the files contained in the shared library packages.
5483 <sect id="sharedlibs-runtime">
5484 <heading>Run-time shared libraries</heading>
5487 The run-time shared library must be placed in a package
5488 whose name changes whenever the <tt>SONAME</tt> of the shared
5489 library changes. This allows several versions of the shared
5490 library to be installed at the same time, allowing installation
5491 of the new version of the shared library without immediately
5492 breaking binaries that depend on the old version. Normally, the
5493 run-time shared library and its <tt>SONAME</tt> symlink should
5494 be placed in a package named
5495 <package><var>libraryname</var><var>soversion</var></package>,
5496 where <var>soversion</var> is the version number in
5497 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5498 would be confusing to directly append <var>soversion</var>
5499 to <var>libraryname</var> (if, for
5500 example, <var>libraryname</var> itself ends in a number), you
5502 <package><var>libraryname</var>-<var>soversion</var></package>
5507 To determine the <var>soversion</var>, look at
5508 the <tt>SONAME</tt> of the library, stored in the
5509 ELF <tt>SONAME</tt> attribute. it is usually of the
5510 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5511 example, <tt>libz.so.1</tt>). The version part is the part
5512 which comes after <tt>.so.</tt>, so in that example it
5513 is <tt>1</tt>. The soname may instead be of the
5514 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5515 as <tt>libdb-5.1.so</tt>, in which case the name would
5516 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5520 If you have several shared libraries built from the same source
5521 tree, you may lump them all together into a single shared
5522 library package provided that all of their <tt>SONAME</tt>s will
5523 always change together. Be aware that this is not normally the
5524 case, and if the <tt>SONAME</tt>s do not change together,
5525 upgrading such a merged shared library package will be
5526 unnecessarily difficult because of file conflicts with the old
5527 version of the package. When in doubt, always split shared
5528 library packages so that each binary package installs a single
5533 Every time the shared library ABI changes in a way that may
5534 break binaries linked against older versions of the shared
5535 library, the <tt>SONAME</tt> of the library and the
5536 corresponding name for the binary package containing the runtime
5537 shared library should change. Normally, this means
5538 the <tt>SONAME</tt> should change any time an interface is
5539 removed from the shared library or the signature of an interface
5540 (the number of parameters or the types of parameters that it
5541 takes, for example) is changed. This practice is vital to
5542 allowing clean upgrades from older versions of the package and
5543 clean transitions between the old ABI and new ABI without having
5544 to upgrade every affected package simultaneously.
5548 The <tt>SONAME</tt> and binary package name need not, and indeed
5549 normally should not, change if new interfaces are added but none
5550 are removed or changed, since this will not break binaries
5551 linked against the old shared library. Correct versioning of
5552 dependencies on the newer shared library by binaries that use
5553 the new interfaces is handled via
5554 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5555 or <tt>shlibs</tt> system</qref>.
5559 The package should install the shared libraries under
5560 their normal names. For example, the <package>libgdbm3</package>
5561 package should install <file>libgdbm.so.3.0.0</file> as
5562 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5563 renamed or re-linked by any <prgn>prerm</prgn> or
5564 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5565 of renaming things safely without affecting running programs,
5566 and attempts to interfere with this are likely to lead to
5571 Shared libraries should not be installed executable, since
5572 the dynamic linker does not require this and trying to
5573 execute a shared library usually results in a core dump.
5577 The run-time library package should include the symbolic link for
5578 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5579 the shared libraries. For example,
5580 the <package>libgdbm3</package> package should include a symbolic
5581 link from <file>/usr/lib/libgdbm.so.3</file> to
5582 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5583 linker (for example <prgn>ld.so</prgn> or
5584 <prgn>ld-linux.so.*</prgn>) can find the library between the
5585 time that <prgn>dpkg</prgn> installs it and the time that
5586 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5588 The package management system requires the library to be
5589 placed before the symbolic link pointing to it in the
5590 <file>.deb</file> file. This is so that when
5591 <prgn>dpkg</prgn> comes to install the symlink
5592 (overwriting the previous symlink pointing at an older
5593 version of the library), the new shared library is already
5594 in place. In the past, this was achieved by creating the
5595 library in the temporary packaging directory before
5596 creating the symlink. Unfortunately, this was not always
5597 effective, since the building of the tar file in the
5598 <file>.deb</file> depended on the behavior of the underlying
5599 file system. Some file systems (such as reiserfs) reorder
5600 the files so that the order of creation is forgotten.
5601 Since version 1.7.0, <prgn>dpkg</prgn>
5602 reorders the files itself as necessary when building a
5603 package. Thus it is no longer important to concern
5604 oneself with the order of file creation.
5608 <sect1 id="ldconfig">
5609 <heading><tt>ldconfig</tt></heading>
5612 Any package installing shared libraries in one of the default
5613 library directories of the dynamic linker (which are currently
5614 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5615 listed in <file>/etc/ld.so.conf</file><footnote>
5616 These are currently <file>/usr/local/lib</file> plus
5617 directories under <file>/lib</file> and <file>/usr/lib</file>
5618 matching the multiarch triplet for the system architecture.
5620 must use <prgn>ldconfig</prgn> to update the shared library
5625 The package maintainer scripts must only call
5626 <prgn>ldconfig</prgn> under these circumstances:
5627 <list compact="compact">
5628 <item>When the <prgn>postinst</prgn> script is run with a
5629 first argument of <tt>configure</tt>, the script must call
5630 <prgn>ldconfig</prgn>, and may optionally invoke
5631 <prgn>ldconfig</prgn> at other times.
5633 <item>When the <prgn>postrm</prgn> script is run with a
5634 first argument of <tt>remove</tt>, the script should call
5635 <prgn>ldconfig</prgn>.
5640 During install or upgrade, the preinst is called before
5641 the new files are unpacked, so calling "ldconfig" is
5642 pointless. The preinst of an existing package can also be
5643 called if an upgrade fails. However, this happens during
5644 the critical time when a shared libs may exist on-disk
5645 under a temporary name. Thus, it is dangerous and
5646 forbidden by current policy to call "ldconfig" at this
5651 When a package is installed or upgraded, "postinst
5652 configure" runs after the new files are safely on-disk.
5653 Since it is perfectly safe to invoke ldconfig
5654 unconditionally in a postinst, it is OK for a package to
5655 simply put ldconfig in its postinst without checking the
5656 argument. The postinst can also be called to recover from
5657 a failed upgrade. This happens before any new files are
5658 unpacked, so there is no reason to call "ldconfig" at this
5663 For a package that is being removed, prerm is
5664 called with all the files intact, so calling ldconfig is
5665 useless. The other calls to "prerm" happen in the case of
5666 upgrade at a time when all the files of the old package
5667 are on-disk, so again calling "ldconfig" is pointless.
5671 postrm, on the other hand, is called with the "remove"
5672 argument just after the files are removed, so this is
5673 the proper time to call "ldconfig" to notify the system
5674 of the fact that the shared libraries from the package
5675 are removed. The postrm can be called at several other
5676 times. At the time of "postrm purge", "postrm
5677 abort-install", or "postrm abort-upgrade", calling
5678 "ldconfig" is useless because the shared lib files are
5679 not on-disk. However, when "postrm" is invoked with
5680 arguments "upgrade", "failed-upgrade", or "disappear", a
5681 shared lib may exist on-disk under a temporary filename.
5689 <sect id="sharedlibs-support-files">
5690 <heading>Shared library support files</heading>
5693 If your package contains files whose names do not change with
5694 each change in the library shared object version, you must not
5695 put them in the shared library package. Otherwise, several
5696 versions of the shared library cannot be installed at the same
5697 time without filename clashes, making upgrades and transitions
5698 unnecessarily difficult.
5702 It is recommended that supporting files and run-time support
5703 programs that do not need to be invoked manually by users, but
5704 are nevertheless required for the package to function, be placed
5705 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5706 preferably under <file>/usr/lib/</file><var>package-name</var>.
5707 If the program or file is architecture independent, the
5708 recommendation is for it to be placed in a subdirectory of
5709 <file>/usr/share</file> instead, preferably under
5710 <file>/usr/share/</file><var>package-name</var>. Following the
5711 <var>package-name</var> naming convention ensures that the file
5712 names change when the shared object version changes.
5716 Run-time support programs that use the shared library but are
5717 not required for the library to function or files used by the
5718 shared library that can be used by any version of the shared
5719 library package should instead be put in a separate package.
5720 This package might typically be named
5721 <package><var>libraryname</var>-tools</package>; note the
5722 absence of the <var>soversion</var> in the package name.
5726 Files and support programs only useful when compiling software
5727 against the library should be included in the development
5728 package for the library.<footnote>
5729 For example, a <file><var>package-name</var>-config</file>
5730 script or <package>pkg-config</package> configuration files.
5735 <sect id="sharedlibs-static">
5736 <heading>Static libraries</heading>
5739 The static library (<file><var>libraryname.a</var></file>)
5740 is usually provided in addition to the shared version.
5741 It is placed into the development package (see below).
5745 In some cases, it is acceptable for a library to be
5746 available in static form only; these cases include:
5748 <item>libraries for languages whose shared library support
5749 is immature or unstable</item>
5750 <item>libraries whose interfaces are in flux or under
5751 development (commonly the case when the library's
5752 major version number is zero, or where the ABI breaks
5753 across patchlevels)</item>
5754 <item>libraries which are explicitly intended to be
5755 available only in static form by their upstream
5760 <sect id="sharedlibs-dev">
5761 <heading>Development files</heading>
5764 If there are development files associated with a shared library,
5765 the source package needs to generate a binary development package
5766 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5767 or if you prefer only to support one development version at a
5768 time, <package><var>libraryname</var>-dev</package>. Installing
5769 the development package must result in installation of all the
5770 development files necessary for compiling programs against that
5771 shared library.<footnote>
5772 This wording allows the development files to be split into
5773 several packages, such as a separate architecture-independent
5774 <package><var>libraryname</var>-headers</package>, provided that
5775 the development package depends on all the required additional
5781 In case several development versions of a library exist, you may
5782 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5783 <ref id="conflicts">) to ensure that the user only installs one
5784 development version at a time (as different development versions are
5785 likely to have the same header files in them, which would cause a
5786 filename clash if both were unpacked).
5790 The development package should contain a symlink for the associated
5791 shared library without a version number. For example, the
5792 <package>libgdbm-dev</package> package should include a symlink
5793 from <file>/usr/lib/libgdbm.so</file> to
5794 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5795 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5796 <file>libgdbm.so</file> when compiling dynamically.
5800 If the package provides Ada Library Information
5801 (<file>*.ali</file>) files for use with GNAT, these files must be
5802 installed read-only (mode 0444) so that GNAT will not attempt to
5803 recompile them. This overrides the normal file mode requirements
5804 given in <ref id="permissions-owners">.
5808 <sect id="sharedlibs-intradeps">
5809 <heading>Dependencies between the packages of the same library</heading>
5812 Typically the development version should have an exact
5813 version dependency on the runtime library, to make sure that
5814 compilation and linking happens correctly. The
5815 <tt>${binary:Version}</tt> substitution variable can be
5816 useful for this purpose.
5818 Previously, <tt>${Source-Version}</tt> was used, but its name
5819 was confusing and it has been deprecated since dpkg 1.13.19.
5824 <sect id="sharedlibs-depends">
5825 <heading>Dependencies between the library and other
5829 If a package contains a binary or library which links to a
5830 shared library, we must ensure that, when the package is
5831 installed on the system, all of the libraries needed are also
5832 installed. These dependencies must be added to the binary
5833 package when it is built, since they may change based on which
5834 version of a shared library the binary or library was linked
5835 with even if there are no changes to the source of the binary
5836 (for example, symbol versions change, macros become functions or
5837 vice versa, or the binary package may determine at compile-time
5838 whether new library interfaces are available and can be called).
5839 To allow these dependencies to be constructed, shared libraries
5840 must provide either a <file>symbols</file> file or
5841 a <file>shlibs</file> file, which provide information on the
5842 package dependencies required to ensure the presence of this
5843 library. Any package which uses a shared library must use these
5844 files to determine the required dependencies when it is built.
5848 These two mechanisms differ in the degree of detail that they
5849 provide. A <file>symbols</file> file documents every symbol
5850 that is part of the library ABI and, for each, the version of
5851 the package in which it was introduced. This permits detailed
5852 analysis of the symbols used by a particular package and
5853 construction of an accurate dependency, but it requires the
5854 package maintainer to track more information about the shared
5855 library. A <file>shlibs</file> file, in contrast, only
5856 documents the last time the library ABI changed in any way. It
5857 only provides information about the library as a whole, not
5858 individual symbols. When a package is built using a shared
5859 library with only a <file>shlibs</file> file, the generated
5860 dependency will require a version of the shared library equal to
5861 or newer than the version of the last ABI change. This
5862 generates unnecessarily restrictive dependencies compared
5863 to <file>symbols</file> files if none of the symbols used by the
5864 package have changed. This, in turn, may make upgrades
5865 needlessly complex and unnecessarily restrict use of the package
5866 on systems with older versions of the shared libraries.
5870 <file>shlibs<file> files also have a flawed representation of
5871 library SONAMEs, making it difficult to use <file>shlibs</file>
5872 files in some unusual corner cases.
5876 <file>symbols</file> files are therefore recommended for most
5877 shared library packages since they provide more accurate
5878 dependencies. For most C libraries, the additional detail
5879 required by <file>symbols</file> files is not too difficult to
5880 maintain. However, maintaining exhaustive symbols information
5881 for a C++ library can be quite onerous, so <file>shlibs</file>
5882 files may be more appropriate for most C++ libraries. udebs
5883 must also use <file>shlibs</file>, since the udeb infrastructure
5884 does not use <file>symbols</file>.
5887 <sect1 id="dpkg-shlibdeps">
5888 <heading>Generating dependencies on shared libraries</heading>
5891 When a package that contains any shared libraries or compiled
5892 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
5893 each shared library and compiled binary to determine the
5894 libraries used and hence the dependencies needed by the
5896 <prgn>dpkg-shlibdeps</prgn> will use a program
5897 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5898 the libraries and the symbols in those libraries directly
5899 needed by the binaries or shared libraries in the package.
5901 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
5902 your <file>debian/rules</file> file in the source package.
5903 List all of the compiled binaries, libraries, or loadable
5904 modules in your package.<footnote>
5905 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
5906 correctly is to use a package helper framework such
5907 as <package>debhelper</package>. If you are
5908 using <package>debhelper</package>,
5909 the <prgn>dh_shlibdeps</prgn> program will do this work for
5910 you. It will also correctly handle multi-binary packages.
5912 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
5913 or <file>shlibs</file> files installed by the shared libraries
5914 to generate dependency information. The package must then
5915 provide a substitution variable into which the discovered
5916 dependency information can be placed.
5920 If you are creating a udeb for use in the Debian Installer,
5921 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5922 should use the dependency line of type <tt>udeb</tt> by adding
5923 the <tt>-tudeb</tt> option<footnote>
5924 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5925 will automatically add this option if it knows it is
5927 </footnote>. If there is no dependency line of
5928 type <tt>udeb</tt> in the <file>shlibs</file>
5929 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
5930 regular dependency line.
5934 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
5935 into the <file>debian/substvars</file> file by default, which
5936 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
5937 to place a <tt>${shlibs:Depends}</tt> variable in
5938 the <tt>Depends</tt> field in the control file of every binary
5939 package built by this source package that contains compiled
5940 binaries, libraries, or loadable modules. If you have
5941 multiple binary packages, you will need to
5942 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
5943 compiled libraries or binaries, using the <tt>-T</tt> option
5944 to the <tt>dpkg</tt> utilities to specify a
5945 different <file>substvars</file> file for each binary
5947 Again, <prgn>dh_shlibdeps</prgn>
5948 and <prgn>dh_gencontrol</prgn> will handle everything except
5949 the addition of the variable to the control file for you if
5950 you're using <package>debhelper</package>, including
5951 generating separate <file>substvars</file> files for each
5952 binary package and calling <prgn>dpkg-gencontrol</prgn> with
5953 the appropriate flags.
5958 For more details on <prgn>dpkg-shlibdeps</prgn>,
5959 see <manref name="dpkg-shlibdeps" section="1">.
5963 We say that a binary <tt>foo</tt> <em>directly</em> uses a
5964 library <tt>libbar</tt> if it is explicitly linked with that
5965 library (that is, the library is listed in the
5966 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5967 to the link line when the binary is created). Other libraries
5968 that are needed by <tt>libbar</tt> are
5969 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5970 linker will load them automatically when it
5971 loads <tt>libbar</tt>. A package should depend on the
5972 libraries it directly uses, but not the libraries it
5973 indirectly uses. The dependencies for the libraries used
5974 directly will automatically pull in the indirectly-used
5975 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
5976 automatically, but package maintainers need to be aware of
5977 this distinction between directly and indirectly using a
5978 library if they have to override its results for some reason.
5980 A good example of where this helps is the following. We
5981 could update <tt>libimlib</tt> with a new version that
5982 supports a new revision of a graphics format called dgf (but
5983 retaining the same major version number) and depends on a
5984 new library package <package>libdgf4</package> instead of
5985 the older <package>libdgf3</package>. If we
5986 used <prgn>ldd</prgn> to add dependencies for every library
5987 directly or indirectly linked with a binary, every package
5988 that uses <tt>libimlib</tt> would need to be recompiled so
5989 it would also depend on <package>libdgf4</package> in order
5990 to retire the older <package>libdgf3</package> package.
5991 Since dependencies are only added based on
5992 ELF <tt>NEEDED</tt> attribute, packages
5993 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5994 having the dependency on an appropriate version
5995 of <tt>libdgf</tt> and do not need rebuilding.
6000 <sect1 id="sharedlibs-updates">
6001 <heading>Shared library ABI changes</heading>
6004 Maintaining a shared library package using
6005 either <file>symbols</file> or <file>shlibs</file> files
6006 requires being aware of the exposed ABI of the shared library
6007 and any changes to it. Both <file>symbols</file>
6008 and <file>shlibs</file> files record every change to the ABI
6009 of the shared library; <file>symbols</file> files do so per
6010 public symbol, whereas <file>shlibs</file> files record only
6011 the last change for the entire library.
6015 There are two types of ABI changes: ones that are
6016 backward-compatible and ones that are not. An ABI change is
6017 backward-compatible if any binary was linked with the previous
6018 version of the shared library will still work correctly with
6019 the new version of the shared library. Adding new symbols to
6020 the shared library is a backward-compatible change. Removing
6021 symbols from the shared library is not. Changing the behavior
6022 of a symbol may or may not be backward-compatible depending on
6023 the change; for example, changing a function to accept a new
6024 enum constant not previously used by the library is generally
6025 backward-compatible, but changing the members of a struct that
6026 is passed into library functions is generally not unless the
6027 library takes special precautions to accept old versions of
6032 ABI changes that are not backward-compatible normally require
6033 changing the <tt>SONAME</tt> of the library and therefore the
6034 shared library package name, which forces rebuilding all
6035 packages using that shared library to update their
6036 dependencies and allow them to use the new version of the
6037 shared library. For more information,
6038 see <ref id="sharedlibs-runtime">. The remainder of this
6039 section will deal with backward-compatible changes.
6043 Backward-compatible changes require either updating or
6044 recording the <var>minimal-version</var> for that symbol
6045 in <file>symbols</file> files or updating the version in
6046 the <var>dependencies</var> in <file>shlibs</file> files. For
6047 more information on how to do this in the two formats, see
6048 <ref id="symbols"> and <ref id="shlibs">. Below are general
6049 rules that apply to both files.
6053 The easy case is when a public symbol is added. Simply add
6054 the version at which the symbol was introduced
6055 (for <file>symbols</file> files) or update the dependency
6056 version (for <file>shlibs</file>) files. But special care
6057 should be taken to update dependency versions when the
6058 behavior of a public symbol changes. This is easy to neglect,
6059 since there is no automated method of determining such
6060 changes, but failing to update versions in this case may
6061 result in binary packages with too-weak dependencies that will
6062 fail at runtime, possibly in ways that can cause security
6063 vulnerabilities. If the package maintainer believes that a
6064 symbol behavior change may have occurred but isn't sure, it's
6065 safer to update the version rather than leave it unmodified.
6066 This may result in unnecessarily strict dependencies, but it
6067 ensures that packages whose dependencies are satisfied will
6072 A common example of when a change to the is required is a
6073 function that takes an enum or struct argument that controls
6074 what the function does. For example:
6076 enum library_op { OP_FOO, OP_BAR };
6077 int library_do_operation(enum library_op);
6079 If a new operation, <tt>OP_BAZ</tt>, is added,
6080 the <var>minimal-version</var>
6081 of <tt>library_do_operation</tt> (for <file>symbols</file>
6082 files) or the version in the dependency for the shared library
6083 (for <file>shlibs</file> files) must be increased to the
6084 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6085 binary built against the new version of the library (having
6086 detected at compile-time that the library
6087 supports <tt>OP_BAZ</tt>) may be installed with a shared
6088 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6089 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6094 Dependency versions in either <file>symbols</file>
6095 or <file>shlibs</file> files normally should not contain the
6096 Debian revision of the package, since the library behavior is
6097 normally fixed for a particular upstream version and any
6098 Debian packaging of that upstream version will have the same
6099 behavior. In the rare case that the library behavior was
6100 changed in a particular Debian revision, appending <tt>~</tt>
6101 to the end of the version that includes the Debian revision is
6102 recommended, since this allows backports of the shared library
6103 package using the normal backport versioning convention to
6104 satisfy the dependency.
6108 <sect1 id="sharedlibs-symbols">
6109 <heading>The <tt>symbols</tt> system</heading>
6112 In the following sections, we will first describe where the
6113 various <file>symbols</file> files are to be found, then
6114 the <file>symbols</file> file format, and finally how to
6115 create <file>symbols</file> files if your package contains a
6119 <sect2 id="symbols-paths">
6120 <heading>The <file>symbols</file> files present on the
6124 <file>symbols</file> files for a shared library are normally
6125 provided by the shared library package, but there are
6126 several override paths that are checked first in case that
6127 information is wrong or missing. The following list gives
6128 them in the order in which they are read
6129 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6130 the required information is used.
6133 <p><file>debian/*/DEBIAN/symbols</file></p>
6136 During the package build, if the package itself
6137 contains shared libraries with <file>symbols</file>
6138 files, they will be generated in these staging
6139 directories by <prgn>dpkg-gensymbols</prgn>
6140 (see <ref id="providing-symbols">). <file>symbols</file>
6141 files found in the build tree take precedence
6142 over <file>symbols</file> files from other binary
6147 These files must exist
6148 before <prgn>dpkg-shlibdeps</prgn> is run or the
6149 dependencies of binaries and libraries from a source
6150 package on other libraries from that same source
6151 package will not be correct. In practice, this means
6152 that <prgn>dpkg-gensymbols</prgn> must be run
6153 before <prgn>dpkg-shlibdeps</prgn> during the package
6155 An example may clarify. Suppose the source
6156 package <tt>foo</tt> generates two binary
6157 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6158 When building the binary packages, the contents of
6159 the packages are staged in the
6160 directories <file>debian/libfoo2</file>
6161 and <file>debian/foo-runtime</file> respectively.
6162 (<file>debian/tmp</file> could be used instead of
6163 one of these.) Since <tt>libfoo2</tt> provides
6164 the <tt>libfoo</tt> shared library, it will contain
6165 a <tt>symbols</tt> file, which will be installed
6166 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6167 eventually to be included as a control file in that
6168 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6170 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6172 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6173 to determine whether <tt>foo-prog</tt>'s library
6174 dependencies are satisfied by any of the libraries
6175 provided by <tt>libfoo2</tt>. Since those binaries
6176 were linked against the just-built shared library as
6177 part of the build process, the <file>symbols</file>
6178 file for the newly-built <tt>libfoo2</tt> must take
6179 precedence over a <file>symbols</file> file for any
6180 other <tt>libfoo2</tt> package already installed on
6188 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6189 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6193 Per-system overrides of shared library dependencies.
6194 These files normally do not exist. They are
6195 maintained by the local system administrator and must
6196 not be created by any Debian package.
6201 <p><file>symbols</file> control files for packages
6202 installed on the system</p>
6205 The <file>symbols</file> control files for all the
6206 packages currently installed on the system are
6207 searched last. This will be the most common source of
6208 shared library dependency information. These are
6210 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6211 packages should not rely on this and instead should
6212 use <tt>dpkg-query --control-path <var>package</var>
6213 symbols</tt> if for some reason these files need to be
6221 Be aware that if a <file>debian/shlibs.local</file> exists
6222 in the source package, it will override
6223 any <file>symbols</file> files. This is the only case where
6224 a <file>shlibs</file> is used despite <file>symbols</file>
6225 files being present. See <ref id="shlibs-paths">
6226 and <ref id="sharedlibs-shlibdeps"> for more information.
6230 <sect2 id="symbols">
6231 <heading>The <file>symbols</file> File Format</heading>
6234 The following documents the format of
6235 the <file>symbols</file> control file as included in binary
6236 packages. These files are built from
6237 template <file>symbols</file> files in the source package
6238 by <prgn>dpkg-gensymbols</prgn>. The template files support
6239 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6240 do some of the tedious work involved in
6241 maintaining <file>symbols</file> files, such as handling C++
6242 symbols or optional symbols that may not exist on particular
6243 architectures. When writing <file>symbols</file> files for
6244 a shared library package, refer
6245 to <manref name="dpkg-gensymbols" section="1"> for the
6250 A <file>symbols</file> may contain one or more entries, one
6251 for each shared library contained in the package
6252 corresponding to that <file>symbols</file>. Each entry has
6253 the following format:
6258 <var>library-soname</var> <var>main-dependency-template</var>
6259 [| <var>alternative-dependency-template</var>]
6261 [* <var>field-name</var>: <var>field-value</var>]
6263 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6268 To explain this format, we'll use the the <tt>zlib1g</tt>
6269 package as an example, which (at the time of writing)
6271 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6272 lines will be described first, followed by optional lines.
6276 <var>library-soname</var> must contain exactly the value of
6277 the ELF <tt>SONAME</tt> attribute of the shared library. In
6278 our example, this is <tt>libz.so.1</tt>.<footnote>
6279 This can be determined by using the command
6280 <example compact="compact">
6281 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6287 <var>main-dependency-template</var> has the same syntax as a
6288 dependency field in a binary package control file, except
6289 that the string <tt>#MINVER#</tt> is replaced by a version
6290 restriction like <tt>(>= <var>version</var>)</tt> or by
6291 nothing if an unversioned dependency is deemed sufficient.
6292 The version restriction will be based on which symbols from
6293 the shared library are referenced and the version at which
6294 they were introduced (see below). In nearly all
6295 cases, <var>main-dependency-template</var> will
6296 be <tt><var>package</var> #MINVER#</tt>,
6297 where <var>package</var> is the name of the binary package
6298 containing the shared library. This adds a simple,
6299 possibly-versioned dependency on the shared library package.
6300 In some rare cases, such as when multiple packages provide
6301 the same shared library ABI, the dependency template may
6302 need to be more complex.
6306 In our example, the first line of
6307 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6308 <example compact="compact">
6309 libz.so.1 zlib1g #MINVER#
6314 Each public symbol exported by the shared library must have
6315 a corresponding symbol line, indented by one
6316 space. <var>symbol</var> is the exported symbol (which, for
6317 C++, means the mangled symbol) followed by <tt>@</tt> and
6318 the symbol version, or the string <tt>Base</tt> if there is
6319 no symbol version. <var>minimal-version</var> is the most
6320 recent version of the shared library that changed the
6321 behavior of that symbol, whether by adding it, changing its
6322 function signature (the parameters, their types, or the
6323 return type), or its behavior in a way that is visible to a
6324 caller. <var>id-of-dependency-template</var> is an optional
6325 field that references
6326 an <var>alternative-dependency-template</var>; see below for
6331 For example, <tt>libz.so.1</tt> contains the
6332 symbols <tt>compress</tt>
6333 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6334 version and last changed its behavior in upstream
6335 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6336 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6337 upstream version <tt>1:1.2.0</tt>, and has not changed its
6338 behavior. Its <file>symbols</file> file therefore contains
6340 <example compact="compact">
6341 compress@Base 1:1.1.4
6342 compressBound@ZLIB_1.2.0 1:1.2.0
6344 Packages using only <tt>compress</tt> would then get a
6345 dependency of <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6346 using <tt>compressBound</tt> would get a dependency
6347 of <tt>zlib1g (>= 1:1.2.0)</tt>.
6351 One or more <var>alternative-dependency-template</var> lines
6352 may be provided. These are used in cases where some symbols
6353 in the shared library should use one dependency template
6354 while others should use a different template. The
6355 alternative dependency templates are used only if a symbol
6356 line contains the <var>id-of-dependency-template</var>
6357 field. The first alternative dependency template is
6358 numbered 1, the second 2, and so forth.<footnote>
6359 An example of where this may be needed is with a library
6360 that implements the libGL interface. All GL
6361 implementations provide the same set of base interfaces,
6362 and then may provide some additional interfaces only used
6363 by programs that require that specific GL implementation.
6364 So, for example, libgl1-mesa-glx may use the
6365 following <file>symbols</file> file:
6368 | libgl1-mesa-glx #MINVER#
6369 publicGlSymbol@Base 6.3-1
6371 implementationSpecificSymbol@Base 6.5.2-7 1
6374 Binaries or shared libraries using
6375 only <tt>publicGlSymbol</tt> would depend only
6376 on <tt>libgl1</tt> (which may be provided by multiple
6378 using <tt>implementationSpecificSymbol</tt> would get a
6379 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6384 Finally, the entry for the library may contain one or more
6385 metadata fields. Currently, the only
6386 supported <var>field-name</var>
6387 is <tt>Build-Depends-Package</tt>, whose value lists
6388 the <qref id="sharedlibs-dev">library development
6389 package</qref> on which packages using this shared library
6390 declare a build dependency. If this field is
6391 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6392 the resulting binary package dependency on the shared
6393 library is at least as strict as the source package
6394 dependency on the shared library development
6396 This field should normally not be necessary, since if the
6397 behavior of any symbol has changed, the corresponding
6398 symbol <var>minimal-version</var> should have been
6399 increased. But including it makes the <tt>symbols</tt>
6400 system more robust by tightening the dependency in cases
6401 where the package using the shared library specifically
6402 requires at least a particular version of the shared
6403 library development package for some reason.
6405 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6407 <example compact="compact">
6408 * Build-Depends-Package: zlib1g-dev
6413 Also see <manref name="deb-symbols" section="5">.
6417 <sect2 id="providing-symbols">
6418 <heading>Providing a <file>symbols</file> file</heading>
6421 If your package provides a shared library, you should
6422 arrange to include a <file>symbols</file> control file
6423 following the format described above in that package. You
6424 must include either a <file>symbols</file> control file or
6425 a <file>shlibs</file> control file.
6429 Normally, this is done by creating a <file>symbols</file> in
6431 named <file>debian/<var>package</var>.symbols</file>
6432 or <file>debian/symbols</file>, possibly
6433 with <file>.<var>arch</var></file> appended if the symbols
6434 information varies by architecture. This file may use the
6435 extended syntax documented in <manref name="dpkg-gensymbols"
6436 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6437 part of the package build process. It will
6438 create <file>symbols</file> files in the package staging
6439 area based on the binaries and libraries in the package
6440 staging area and the <file>symbols</file> files in the
6441 source package.<footnote>
6443 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6444 take care of calling either <prgn>dpkg-gensymbols</prgn>
6445 or generating a <file>shlibs</file> file as appropriate.
6450 Packages that provide <file>symbols</file> files must keep
6451 them up-to-date to ensure correct dependencies in packages
6452 that use the shared libraries. This means updating
6453 the <file>symbols</file> file whenever a new public symbol
6454 is added, changing the <var>minimal-version</var> field
6455 whenever a symbol changes behavior or signature in a
6456 backward-compatible way (see <ref id="sharedlibs-updates">),
6457 and changing the <var>library-soname</var>
6458 and <var>main-dependency-template</var>, and probably all of
6459 the <var>minimal-version</var> fields, when the library
6460 changes <tt>SONAME</tt>. Removing a public symbol from
6461 the <file>symbols</file> file because it's no longer
6462 provided by the library normally requires changing
6463 the <tt>SONAME</tt> of the library.
6464 See <ref id="sharedlibs-runtime"> for more information
6465 on <tt>SONAME</tt>s.
6470 <sect1 id="sharedlibs-shlibdeps">
6471 <heading>The <tt>shlibs</tt> system</heading>
6474 The <tt>shlibs</tt> system is an simpler alternative to
6475 the <tt>symbols</tt> system for declaring dependencies for
6476 shared libraries. It may be more appropriate for C++
6477 libraries and other cases where tracking individual symbols is
6478 too difficult. It predated the <tt>symbols</tt> system and is
6479 therefore frequently seen in older packages. It is also
6480 required for udebs, which do not support <tt>symbols</tt>.
6484 In the following sections, we will first describe where the
6485 various <file>shlibs</file> files are to be found, then how to
6486 use <prgn>dpkg-shlibdeps</prgn>, and finally
6487 the <file>shlibs</file> file format and how to create them.
6490 <sect2 id="shlibs-paths">
6491 <heading>The <file>shlibs</file> files present on the
6495 There are several places where <tt>shlibs</tt> files are
6496 found. The following list gives them in the order in which
6497 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6498 one which gives the required information is used.)
6501 <p><file>debian/shlibs.local</file></p>
6504 This lists overrides for this package. This file
6505 should normally not be used, but may be needed
6506 temporarily in unusual situations to work around bugs
6507 in other packages, or in unusual cases where the
6508 normally declared dependency information in the
6509 installed <file>shlibs</file> file for a library
6510 cannot be used. This file overrides information
6511 obtained from any other source.
6516 <p><file>/etc/dpkg/shlibs.override</file></p>
6519 This lists global overrides. This list is normally
6520 empty. It is maintained by the local system
6526 <p><file>DEBIAN/shlibs</file> files in the "build
6530 These files are generated as part of the package build
6531 process and staged for inclusion as control files in
6532 the binary packages being built. They provide details
6533 of any shared libraries included in the same package.
6538 <p><file>shlibs</file> control files for packages
6539 installed on the system</p>
6542 The <file>shlibs</file> control files for all the
6543 packages currently installed on the system. These are
6545 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6546 packages should not rely on this and instead should
6547 use <tt>dpkg-query --control-path <var>package</var>
6548 shlibs</tt> if for some reason these files need to be
6554 <p><file>/etc/dpkg/shlibs.default</file></p>
6557 This file lists any shared libraries whose packages
6558 have failed to provide correct <file>shlibs</file>
6559 files. It was used when the <file>shlibs</file> setup
6560 was first introduced, but it is now normally empty.
6561 It is maintained by the <tt>dpkg</tt> maintainer.
6568 If a <file>symbols</file> file for a shared library package
6569 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6570 in preference to a <file>shlibs</file>, with the exception
6571 of <file>debian/shlibs.local</file>. The latter overrides
6572 any other <file>shlibs</file> or <file>symbols</file> files.
6577 <heading>The <file>shlibs</file> File Format</heading>
6580 Each <file>shlibs</file> file has the same format. Lines
6581 beginning with <tt>#</tt> are considered to be comments and
6582 are ignored. Each line is of the form:
6583 <example compact="compact">
6584 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6589 We will explain this by reference to the example of the
6590 <tt>zlib1g</tt> package, which (at the time of writing)
6592 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6596 <var>type</var> is an optional element that indicates the
6597 type of package for which the line is valid. The only type
6598 currently in use is <tt>udeb</tt>. The colon and space
6599 after the type are required.
6603 <var>library-name</var> is the name of the shared library,
6604 in this case <tt>libz</tt>. (This must match the name part
6605 of the soname, see below.)
6609 <var>soname-version</var> is the version part of the
6610 ELF <tt>SONAME</tt> attribute of the library, determined the
6611 same way that the <var>soversion</var> component of the
6612 recommended shared library package name is determined.
6613 See <ref id="sharedlibs-runtime"> for the details.
6617 <var>dependencies</var> has the same syntax as a dependency
6618 field in a binary package control file. It should give
6619 details of which packages are required to satisfy a binary
6620 built against the version of the library contained in the
6621 package. See <ref id="depsyntax"> for details on the
6622 syntax, and <ref id="sharedlibs-updates"> for details on how
6623 to maintain the dependency version constraint.
6627 In our example, if the last change to the <tt>zlib1g</tt>
6628 package that could change behavior for a client of that
6629 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6630 the <tt>shlibs</tt> entry for this library could say:
6631 <example compact="compact">
6632 libz 1 zlib1g (>= 1:1.2.3.3.dfsg-1)
6634 This version restriction must be new enough that any binary
6635 built against the current version of the library will work
6636 with any version of the shared library that satisfies that
6641 As zlib1g also provides a udeb containing the shared
6642 library, there would also be a second line:
6643 <example compact="compact">
6644 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg-1)
6650 <heading>Providing a <file>shlibs</file> file</heading>
6653 To provide a <file>shlibs</file> file for a shared library
6654 binary package, create a <file>shlibs</file> file following
6655 the format described above and place it in
6656 the <file>DEBIAN</file> directory for that package during
6657 the build. It will then be included as a control file for
6658 that package<footnote>
6659 This is what <prgn>dh_makeshlibs</prgn> in
6660 the <package>debhelper</package> suite does. If your
6661 package also has a udeb that provides a shared
6662 library, <prgn>dh_makeshlibs</prgn> can automatically
6663 generate the <tt>udeb:</tt> lines if you specify the name
6664 of the udeb with the <tt>--add-udeb</tt> option.
6669 Since <prgn>dpkg-shlibdeps</prgn> reads
6670 the <file>DEBIAN/shlibs</file> files in all of the binary
6671 packages being built from this source package, all of
6672 the <file>DEBIAN/shlibs</file> files should be installed
6673 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6682 <chapt id="opersys"><heading>The Operating System</heading>
6685 <heading>File system hierarchy</heading>
6689 <heading>File System Structure</heading>
6692 The location of all files and directories must comply with the
6693 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6694 exceptions noted below, and except where doing so would
6695 violate other terms of Debian Policy. The following
6696 exceptions to the FHS apply:
6701 The optional rules related to user specific
6702 configuration files for applications are stored in
6703 the user's home directory are relaxed. It is
6704 recommended that such files start with the
6705 '<tt>.</tt>' character (a "dot file"), and if an
6706 application needs to create more than one dot file
6707 then the preferred placement is in a subdirectory
6708 with a name starting with a '.' character, (a "dot
6709 directory"). In this case it is recommended the
6710 configuration files not start with the '.'
6716 The requirement for amd64 to use <file>/lib64</file>
6717 for 64 bit binaries is removed.
6722 The requirement for object files, internal binaries, and
6723 libraries, including <file>libc.so.*</file>, to be located
6724 directly under <file>/lib{,32}</file> and
6725 <file>/usr/lib{,32}</file> is amended, permitting files
6726 to instead be installed to
6727 <file>/lib/<var>triplet</var></file> and
6728 <file>/usr/lib/<var>triplet</var></file>, where
6729 <tt><var>triplet</var></tt> is the value returned by
6730 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6731 architecture of the package. Packages may <em>not</em>
6732 install files to any <var>triplet</var> path other
6733 than the one matching the architecture of that package;
6734 for instance, an <tt>Architecture: amd64</tt> package
6735 containing 32-bit x86 libraries may not install these
6736 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6738 This is necessary in order to reserve the directories for
6739 use in cross-installation of library packages from other
6740 architectures, as part of the planned deployment of
6745 Applications may also use a single subdirectory under
6746 <file>/usr/lib/<var>triplet</var></file>.
6749 The execution time linker/loader, ld*, must still be made
6750 available in the existing location under /lib or /lib64
6751 since this is part of the ELF ABI for the architecture.
6756 The requirement that
6757 <file>/usr/local/share/man</file> be "synonymous"
6758 with <file>/usr/local/man</file> is relaxed to a
6763 The requirement that windowmanagers with a single
6764 configuration file call it <file>system.*wmrc</file>
6765 is removed, as is the restriction that the window
6766 manager subdirectory be named identically to the
6767 window manager name itself.
6772 The requirement that boot manager configuration
6773 files live in <file>/etc</file>, or at least are
6774 symlinked there, is relaxed to a recommendation.
6779 The additional directory <file>/run</file> in the root
6780 file system is allowed. <file>/run</file>
6781 replaces <file>/var/run</file>, and the
6782 subdirectory <file>/run/lock</file>
6783 replaces <file>/var/lock</file>, with
6784 the <file>/var</file> directories replaced by symlinks
6785 for backwards compatibility. <file>/run</file>
6786 and <file>/run/lock</file> must follow all of the
6787 requirements in the FHS for <file>/var/run</file>
6788 and <file>/var/lock</file>, respectively, such as file
6789 naming conventions, file format requirements, or the
6790 requirement that files be cleared during the boot
6791 process. Files and directories residing
6792 in <file>/run</file> should be stored on a temporary
6798 The following directories in the root filesystem are
6799 additionally allowed: <file>/sys</file> and
6800 <file>/selinux</file>. <footnote>These directories
6801 are used as mount points to mount virtual filesystems
6802 to get access to kernel information.</footnote>
6807 On GNU/Hurd systems, the following additional
6808 directories are allowed in the root
6809 filesystem: <file>/hurd</file>
6810 and <file>/servers</file>.<footnote>
6811 These directories are used to store translators and as
6812 a set of standard names for mount points,
6821 The version of this document referred here can be
6822 found in the <tt>debian-policy</tt> package or on <url
6823 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6824 name="FHS (Debian copy)"> alongside this manual (or, if
6825 you have the <package>debian-policy</package> installed,
6827 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6828 (local copy)">). The
6829 latest version, which may be a more recent version, may
6831 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6832 Specific questions about following the standard may be
6833 asked on the <tt>debian-devel</tt> mailing list, or
6834 referred to the FHS mailing list (see the
6835 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6841 <heading>Site-specific programs</heading>
6844 As mandated by the FHS, packages must not place any
6845 files in <file>/usr/local</file>, either by putting them in
6846 the file system archive to be unpacked by <prgn>dpkg</prgn>
6847 or by manipulating them in their maintainer scripts.
6851 However, the package may create empty directories below
6852 <file>/usr/local</file> so that the system administrator knows
6853 where to place site-specific files. These are not
6854 directories <em>in</em> <file>/usr/local</file>, but are
6855 children of directories in <file>/usr/local</file>. These
6856 directories (<file>/usr/local/*/dir/</file>)
6857 should be removed on package removal if they are
6862 Note that this applies only to
6863 directories <em>below</em> <file>/usr/local</file>,
6864 not <em>in</em> <file>/usr/local</file>. Packages must
6865 not create sub-directories in the
6866 directory <file>/usr/local</file> itself, except those
6867 listed in FHS, section 4.5. However, you may create
6868 directories below them as you wish. You must not remove
6869 any of the directories listed in 4.5, even if you created
6874 Since <file>/usr/local</file> can be mounted read-only from a
6875 remote server, these directories must be created and
6876 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6877 maintainer scripts and not be included in the
6878 <file>.deb</file> archive. These scripts must not fail if
6879 either of these operations fail.
6883 For example, the <tt>emacsen-common</tt> package could
6884 contain something like
6885 <example compact="compact">
6886 if [ ! -e /usr/local/share/emacs ]; then
6887 if mkdir /usr/local/share/emacs 2>/dev/null; then
6888 if chown root:staff /usr/local/share/emacs; then
6889 chmod 2775 /usr/local/share/emacs || true
6894 in its <prgn>postinst</prgn> script, and
6895 <example compact="compact">
6896 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6897 rmdir /usr/local/share/emacs 2>/dev/null || true
6899 in the <prgn>prerm</prgn> script. (Note that this form is
6900 used to ensure that if the script is interrupted, the
6901 directory <file>/usr/local/share/emacs</file> will still be
6906 If you do create a directory in <file>/usr/local</file> for
6907 local additions to a package, you should ensure that
6908 settings in <file>/usr/local</file> take precedence over the
6909 equivalents in <file>/usr</file>.
6913 However, because <file>/usr/local</file> and its contents are
6914 for exclusive use of the local administrator, a package
6915 must not rely on the presence or absence of files or
6916 directories in <file>/usr/local</file> for normal operation.
6920 The <file>/usr/local</file> directory itself and all the
6921 subdirectories created by the package should (by default) have
6922 permissions 2775 (group-writable and set-group-id) and be
6923 owned by <tt>root:staff</tt>.
6928 <heading>The system-wide mail directory</heading>
6930 The system-wide mail directory
6931 is <file>/var/mail</file>. This directory is part of the
6932 base system and should not be owned by any particular mail
6933 agents. The use of the old
6934 location <file>/var/spool/mail</file> is deprecated, even
6935 though the spool may still be physically located there.
6939 <sect1 id="fhs-run">
6940 <heading><file>/run</file> and <file>/run/lock</file></heading>
6943 The directory <file>/run</file> is cleared at boot, normally
6944 by being a mount point for a temporary file system. Packages
6945 therefore must not assume that any files or directories
6946 under <file>/run</file> other than <file>/run/lock</file>
6947 exist unless the package has arranged to create those files or
6948 directories since the last reboot. Normally, this is done by
6949 the package via an init script. See <ref id="writing-init">
6950 for more information.
6954 Packages must not include files or directories
6955 under <file>/run</file>, or under the
6956 older <file>/var/run</file> and <file>/var/lock</file> paths.
6957 The latter paths will normally be symlinks or other
6958 redirections to <file>/run</file> for backwards compatibility.
6964 <heading>Users and groups</heading>
6967 <heading>Introduction</heading>
6969 The Debian system can be configured to use either plain or
6974 Some user ids (UIDs) and group ids (GIDs) are reserved
6975 globally for use by certain packages. Because some
6976 packages need to include files which are owned by these
6977 users or groups, or need the ids compiled into binaries,
6978 these ids must be used on any Debian system only for the
6979 purpose for which they are allocated. This is a serious
6980 restriction, and we should avoid getting in the way of
6981 local administration policies. In particular, many sites
6982 allocate users and/or local system groups starting at 100.
6986 Apart from this we should have dynamically allocated ids,
6987 which should by default be arranged in some sensible
6988 order, but the behavior should be configurable.
6992 Packages other than <tt>base-passwd</tt> must not modify
6993 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6994 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6999 <heading>UID and GID classes</heading>
7001 The UID and GID numbers are divided into classes as
7007 Globally allocated by the Debian project, the same
7008 on every Debian system. These ids will appear in
7009 the <file>passwd</file> and <file>group</file> files of all
7010 Debian systems, new ids in this range being added
7011 automatically as the <tt>base-passwd</tt> package is
7016 Packages which need a single statically allocated
7017 uid or gid should use one of these; their
7018 maintainers should ask the <tt>base-passwd</tt>
7026 Dynamically allocated system users and groups.
7027 Packages which need a user or group, but can have
7028 this user or group allocated dynamically and
7029 differently on each system, should use <tt>adduser
7030 --system</tt> to create the group and/or user.
7031 <prgn>adduser</prgn> will check for the existence of
7032 the user or group, and if necessary choose an unused
7033 id based on the ranges specified in
7034 <file>adduser.conf</file>.
7038 <tag>1000-59999:</tag>
7041 Dynamically allocated user accounts. By default
7042 <prgn>adduser</prgn> will choose UIDs and GIDs for
7043 user accounts in this range, though
7044 <file>adduser.conf</file> may be used to modify this
7049 <tag>60000-64999:</tag>
7052 Globally allocated by the Debian project, but only
7053 created on demand. The ids are allocated centrally
7054 and statically, but the actual accounts are only
7055 created on users' systems on demand.
7059 These ids are for packages which are obscure or
7060 which require many statically-allocated ids. These
7061 packages should check for and create the accounts in
7062 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7063 <prgn>adduser</prgn> if it has this facility) if
7064 necessary. Packages which are likely to require
7065 further allocations should have a "hole" left after
7066 them in the allocation, to give them room to
7071 <tag>65000-65533:</tag>
7079 User <tt>nobody</tt>. The corresponding gid refers
7080 to the group <tt>nogroup</tt>.
7087 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7088 not</em> be used, because it is the error return
7097 <sect id="sysvinit">
7098 <heading>System run levels and <file>init.d</file> scripts</heading>
7100 <sect1 id="/etc/init.d">
7101 <heading>Introduction</heading>
7104 The <file>/etc/init.d</file> directory contains the scripts
7105 executed by <prgn>init</prgn> at boot time and when the
7106 init state (or "runlevel") is changed (see <manref
7107 name="init" section="8">).
7111 There are at least two different, yet functionally
7112 equivalent, ways of handling these scripts. For the sake
7113 of simplicity, this document describes only the symbolic
7114 link method. However, it must not be assumed by maintainer
7115 scripts that this method is being used, and any automated
7116 manipulation of the various runlevel behaviors by
7117 maintainer scripts must be performed using
7118 <prgn>update-rc.d</prgn> as described below and not by
7119 manually installing or removing symlinks. For information
7120 on the implementation details of the other method,
7121 implemented in the <tt>file-rc</tt> package, please refer
7122 to the documentation of that package.
7126 These scripts are referenced by symbolic links in the
7127 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7128 runlevels, <prgn>init</prgn> looks in the directory
7129 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7130 execute, where <tt><var>n</var></tt> is the runlevel that
7131 is being changed to, or <tt>S</tt> for the boot-up
7136 The names of the links all have the form
7137 <file>S<var>mm</var><var>script</var></file> or
7138 <file>K<var>mm</var><var>script</var></file> where
7139 <var>mm</var> is a two-digit number and <var>script</var>
7140 is the name of the script (this should be the same as the
7141 name of the actual script in <file>/etc/init.d</file>).
7145 When <prgn>init</prgn> changes runlevel first the targets
7146 of the links whose names start with a <tt>K</tt> are
7147 executed, each with the single argument <tt>stop</tt>,
7148 followed by the scripts prefixed with an <tt>S</tt>, each
7149 with the single argument <tt>start</tt>. (The links are
7150 those in the <file>/etc/rc<var>n</var>.d</file> directory
7151 corresponding to the new runlevel.) The <tt>K</tt> links
7152 are responsible for killing services and the <tt>S</tt>
7153 link for starting services upon entering the runlevel.
7157 For example, if we are changing from runlevel 2 to
7158 runlevel 3, init will first execute all of the <tt>K</tt>
7159 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7160 all of the <tt>S</tt> prefixed scripts in that directory.
7161 The links starting with <tt>K</tt> will cause the
7162 referred-to file to be executed with an argument of
7163 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7168 The two-digit number <var>mm</var> is used to determine
7169 the order in which to run the scripts: low-numbered links
7170 have their scripts run first. For example, the
7171 <tt>K20</tt> scripts will be executed before the
7172 <tt>K30</tt> scripts. This is used when a certain service
7173 must be started before another. For example, the name
7174 server <prgn>bind</prgn> might need to be started before
7175 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7176 can set up its access lists. In this case, the script
7177 that starts <prgn>bind</prgn> would have a lower number
7178 than the script that starts <prgn>inn</prgn> so that it
7180 <example compact="compact">
7187 The two runlevels 0 (halt) and 6 (reboot) are slightly
7188 different. In these runlevels, the links with an
7189 <tt>S</tt> prefix are still called after those with a
7190 <tt>K</tt> prefix, but they too are called with the single
7191 argument <tt>stop</tt>.
7195 <sect1 id="writing-init">
7196 <heading>Writing the scripts</heading>
7199 Packages that include daemons for system services should
7200 place scripts in <file>/etc/init.d</file> to start or stop
7201 services at boot time or during a change of runlevel.
7202 These scripts should be named
7203 <file>/etc/init.d/<var>package</var></file>, and they should
7204 accept one argument, saying what to do:
7207 <tag><tt>start</tt></tag>
7208 <item>start the service,</item>
7210 <tag><tt>stop</tt></tag>
7211 <item>stop the service,</item>
7213 <tag><tt>restart</tt></tag>
7214 <item>stop and restart the service if it's already running,
7215 otherwise start the service</item>
7217 <tag><tt>reload</tt></tag>
7218 <item><p>cause the configuration of the service to be
7219 reloaded without actually stopping and restarting
7222 <tag><tt>force-reload</tt></tag>
7223 <item>cause the configuration to be reloaded if the
7224 service supports this, otherwise restart the
7228 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7229 <tt>force-reload</tt> options should be supported by all
7230 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7235 The <file>init.d</file> scripts must ensure that they will
7236 behave sensibly (i.e., returning success and not starting
7237 multiple copies of a service) if invoked with <tt>start</tt>
7238 when the service is already running, or with <tt>stop</tt>
7239 when it isn't, and that they don't kill unfortunately-named
7240 user processes. The best way to achieve this is usually to
7241 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7246 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7247 scripts. Writing correct <file>init.d</file> scripts requires
7248 accepting various error exit statuses when daemons are already
7249 running or already stopped without aborting
7250 the <file>init.d</file> script, and common <file>init.d</file>
7251 function libraries are not safe to call with <tt>set -e</tt>
7253 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7254 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7255 in effect and echoing status messages to the console fails,
7257 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7258 to not use <tt>set -e</tt> and instead check the result of
7259 each command separately.
7263 If a service reloads its configuration automatically (as
7264 in the case of <prgn>cron</prgn>, for example), the
7265 <tt>reload</tt> option of the <file>init.d</file> script
7266 should behave as if the configuration has been reloaded
7271 The <file>/etc/init.d</file> scripts must be treated as
7272 configuration files, either (if they are present in the
7273 package, that is, in the .deb file) by marking them as
7274 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7275 by managing them correctly in the maintainer scripts (see
7276 <ref id="config-files">). This is important since we want
7277 to give the local system administrator the chance to adapt
7278 the scripts to the local system, e.g., to disable a
7279 service without de-installing the package, or to specify
7280 some special command line options when starting a service,
7281 while making sure their changes aren't lost during the next
7286 These scripts should not fail obscurely when the
7287 configuration files remain but the package has been
7288 removed, as configuration files remain on the system after
7289 the package has been removed. Only when <prgn>dpkg</prgn>
7290 is executed with the <tt>--purge</tt> option will
7291 configuration files be removed. In particular, as the
7292 <file>/etc/init.d/<var>package</var></file> script itself is
7293 usually a <tt>conffile</tt>, it will remain on the system
7294 if the package is removed but not purged. Therefore, you
7295 should include a <tt>test</tt> statement at the top of the
7297 <example compact="compact">
7298 test -f <var>program-executed-later-in-script</var> || exit 0
7303 Often there are some variables in the <file>init.d</file>
7304 scripts whose values control the behavior of the scripts,
7305 and which a system administrator is likely to want to
7306 change. As the scripts themselves are frequently
7307 <tt>conffile</tt>s, modifying them requires that the
7308 administrator merge in their changes each time the package
7309 is upgraded and the <tt>conffile</tt> changes. To ease
7310 the burden on the system administrator, such configurable
7311 values should not be placed directly in the script.
7312 Instead, they should be placed in a file in
7313 <file>/etc/default</file>, which typically will have the same
7314 base name as the <file>init.d</file> script. This extra file
7315 should be sourced by the script when the script runs. It
7316 must contain only variable settings and comments in SUSv3
7317 <prgn>sh</prgn> format. It may either be a
7318 <tt>conffile</tt> or a configuration file maintained by
7319 the package maintainer scripts. See <ref id="config-files">
7324 To ensure that vital configurable values are always
7325 available, the <file>init.d</file> script should set default
7326 values for each of the shell variables it uses, either
7327 before sourcing the <file>/etc/default/</file> file or
7328 afterwards using something like the <tt>:
7329 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7330 script must behave sensibly and not fail if the
7331 <file>/etc/default</file> file is deleted.
7335 Files and directories under <file>/run</file>, including ones
7336 referred to via the compatibility paths <file>/var/run</file>
7337 and <file>/var/lock</file>, are normally stored on a temporary
7338 filesystem and are normally not persistent across a reboot.
7339 The <file>init.d</file> scripts must handle this correctly.
7340 This will typically mean creating any required subdirectories
7341 dynamically when the <file>init.d</file> script is run.
7342 See <ref id="fhs-run"> for more information.
7347 <heading>Interfacing with the initscript system</heading>
7350 Maintainers should use the abstraction layer provided by
7351 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7352 programs to deal with initscripts in their packages'
7353 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7354 and <prgn>postrm</prgn>.
7358 Directly managing the /etc/rc?.d links and directly
7359 invoking the <file>/etc/init.d/</file> initscripts should
7360 be done only by packages providing the initscript
7361 subsystem (such as <prgn>sysv-rc</prgn> and
7362 <prgn>file-rc</prgn>).
7366 <heading>Managing the links</heading>
7369 The program <prgn>update-rc.d</prgn> is provided for
7370 package maintainers to arrange for the proper creation and
7371 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7372 or their functional equivalent if another method is being
7373 used. This may be used by maintainers in their packages'
7374 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7378 You must not include any <file>/etc/rc<var>n</var>.d</file>
7379 symbolic links in the actual archive or manually create or
7380 remove the symbolic links in maintainer scripts; you must
7381 use the <prgn>update-rc.d</prgn> program instead. (The
7382 former will fail if an alternative method of maintaining
7383 runlevel information is being used.) You must not include
7384 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7385 in the archive either. (Only the <tt>sysvinit</tt>
7390 By default <prgn>update-rc.d</prgn> will start services in
7391 each of the multi-user state runlevels (2, 3, 4, and 5)
7392 and stop them in the halt runlevel (0), the single-user
7393 runlevel (1) and the reboot runlevel (6). The system
7394 administrator will have the opportunity to customize
7395 runlevels by simply adding, moving, or removing the
7396 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7397 symbolic links are being used, or by modifying
7398 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7403 To get the default behavior for your package, put in your
7404 <prgn>postinst</prgn> script
7405 <example compact="compact">
7406 update-rc.d <var>package</var> defaults
7408 and in your <prgn>postrm</prgn>
7409 <example compact="compact">
7410 if [ "$1" = purge ]; then
7411 update-rc.d <var>package</var> remove
7413 </example>. Note that if your package changes runlevels
7414 or priority, you may have to remove and recreate the links,
7415 since otherwise the old links may persist. Refer to the
7416 documentation of <prgn>update-rc.d</prgn>.
7420 This will use a default sequence number of 20. If it does
7421 not matter when or in which order the <file>init.d</file>
7422 script is run, use this default. If it does, then you
7423 should talk to the maintainer of the <prgn>sysvinit</prgn>
7424 package or post to <tt>debian-devel</tt>, and they will
7425 help you choose a number.
7429 For more information about using <tt>update-rc.d</tt>,
7430 please consult its man page <manref name="update-rc.d"
7436 <heading>Running initscripts</heading>
7438 The program <prgn>invoke-rc.d</prgn> is provided to make
7439 it easier for package maintainers to properly invoke an
7440 initscript, obeying runlevel and other locally-defined
7441 constraints that might limit a package's right to start,
7442 stop and otherwise manage services. This program may be
7443 used by maintainers in their packages' scripts.
7447 The package maintainer scripts must use
7448 <prgn>invoke-rc.d</prgn> to invoke the
7449 <file>/etc/init.d/*</file> initscripts, instead of
7450 calling them directly.
7454 By default, <prgn>invoke-rc.d</prgn> will pass any
7455 action requests (start, stop, reload, restart...) to the
7456 <file>/etc/init.d</file> script, filtering out requests
7457 to start or restart a service out of its intended
7462 Most packages will simply need to change:
7463 <example compact="compact">/etc/init.d/<package>
7464 <action></example> in their <prgn>postinst</prgn>
7465 and <prgn>prerm</prgn> scripts to:
7466 <example compact="compact">
7467 if which invoke-rc.d >/dev/null 2>&1; then
7468 invoke-rc.d <var>package</var> <action>
7470 /etc/init.d/<var>package</var> <action>
7476 A package should register its initscript services using
7477 <prgn>update-rc.d</prgn> before it tries to invoke them
7478 using <prgn>invoke-rc.d</prgn>. Invocation of
7479 unregistered services may fail.
7483 For more information about using
7484 <prgn>invoke-rc.d</prgn>, please consult its man page
7485 <manref name="invoke-rc.d" section="8">.
7491 <heading>Boot-time initialization</heading>
7494 There used to be another directory, <file>/etc/rc.boot</file>,
7495 which contained scripts which were run once per machine
7496 boot. This has been deprecated in favour of links from
7497 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7498 described in <ref id="/etc/init.d">. Packages must not
7499 place files in <file>/etc/rc.boot</file>.
7504 <heading>Example</heading>
7507 An example on which you can base your
7508 <file>/etc/init.d</file> scripts is found in
7509 <file>/etc/init.d/skeleton</file>.
7516 <heading>Console messages from <file>init.d</file> scripts</heading>
7519 This section describes the formats to be used for messages
7520 written to standard output by the <file>/etc/init.d</file>
7521 scripts. The intent is to improve the consistency of
7522 Debian's startup and shutdown look and feel. For this
7523 reason, please look very carefully at the details. We want
7524 the messages to have the same format in terms of wording,
7525 spaces, punctuation and case of letters.
7529 Here is a list of overall rules that should be used for
7530 messages generated by <file>/etc/init.d</file> scripts.
7536 The message should fit in one line (fewer than 80
7537 characters), start with a capital letter and end with
7538 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7542 If the script is performing some time consuming task in
7543 the background (not merely starting or stopping a
7544 program, for instance), an ellipsis (three dots:
7545 <tt>...</tt>) should be output to the screen, with no
7546 leading or tailing whitespace or line feeds.
7550 The messages should appear as if the computer is telling
7551 the user what it is doing (politely :-), but should not
7552 mention "it" directly. For example, instead of:
7553 <example compact="compact">
7554 I'm starting network daemons: nfsd mountd.
7556 the message should say
7557 <example compact="compact">
7558 Starting network daemons: nfsd mountd.
7565 <tt>init.d</tt> script should use the following standard
7566 message formats for the situations enumerated below.
7572 <p>When daemons are started</p>
7575 If the script starts one or more daemons, the output
7576 should look like this (a single line, no leading
7578 <example compact="compact">
7579 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7581 The <var>description</var> should describe the
7582 subsystem the daemon or set of daemons are part of,
7583 while <var>daemon-1</var> up to <var>daemon-n</var>
7584 denote each daemon's name (typically the file name of
7589 For example, the output of <file>/etc/init.d/lpd</file>
7591 <example compact="compact">
7592 Starting printer spooler: lpd.
7597 This can be achieved by saying
7598 <example compact="compact">
7599 echo -n "Starting printer spooler: lpd"
7600 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7603 in the script. If there are more than one daemon to
7604 start, the output should look like this:
7605 <example compact="compact">
7606 echo -n "Starting remote file system services:"
7607 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7608 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7609 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7612 This makes it possible for the user to see what is
7613 happening and when the final daemon has been started.
7614 Care should be taken in the placement of white spaces:
7615 in the example above the system administrators can
7616 easily comment out a line if they don't want to start
7617 a specific daemon, while the displayed message still
7623 <p>When a system parameter is being set</p>
7626 If you have to set up different system parameters
7627 during the system boot, you should use this format:
7628 <example compact="compact">
7629 Setting <var>parameter</var> to "<var>value</var>".
7634 You can use a statement such as the following to get
7636 <example compact="compact">
7637 echo "Setting DNS domainname to \"$domainname\"."
7642 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7643 for the left and right quotation marks. A grave accent
7644 (<tt>`</tt>) is not a quote character; neither is an
7645 apostrophe (<tt>'</tt>).
7650 <p>When a daemon is stopped or restarted</p>
7653 When you stop or restart a daemon, you should issue a
7654 message identical to the startup message, except that
7655 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7656 or <tt>Restarting</tt> respectively.
7660 For example, stopping the printer daemon will look like
7662 <example compact="compact">
7663 Stopping printer spooler: lpd.
7669 <p>When something is executed</p>
7672 There are several examples where you have to run a
7673 program at system startup or shutdown to perform a
7674 specific task, for example, setting the system's clock
7675 using <prgn>netdate</prgn> or killing all processes
7676 when the system shuts down. Your message should look
7678 <example compact="compact">
7679 Doing something very useful...done.
7681 You should print the <tt>done.</tt> immediately after
7682 the job has been completed, so that the user is
7683 informed why they have to wait. You can get this
7685 <example compact="compact">
7686 echo -n "Doing something very useful..."
7695 <p>When the configuration is reloaded</p>
7698 When a daemon is forced to reload its configuration
7699 files you should use the following format:
7700 <example compact="compact">
7701 Reloading <var>description</var> configuration...done.
7703 where <var>description</var> is the same as in the
7704 daemon starting message.
7711 <sect id="cron-jobs">
7712 <heading>Cron jobs</heading>
7715 Packages must not modify the configuration file
7716 <file>/etc/crontab</file>, and they must not modify the files in
7717 <file>/var/spool/cron/crontabs</file>.
7721 If a package wants to install a job that has to be executed via
7722 cron, it should place a file named as specified
7723 in <ref id="cron-files"> into one or more of the following
7725 <example compact="compact">
7731 As these directory names imply, the files within them are
7732 executed on an hourly, daily, weekly, or monthly basis,
7733 respectively. The exact times are listed in
7734 <file>/etc/crontab</file>.
7738 All files installed in any of these directories must be
7739 scripts (e.g., shell scripts or Perl scripts) so that they
7740 can easily be modified by the local system administrator.
7741 In addition, they must be treated as configuration files.
7745 If a certain job has to be executed at some other frequency or
7746 at a specific time, the package should install a file in
7747 <file>/etc/cron.d</file> with a name as specified
7748 in <ref id="cron-files">. This file uses the same syntax
7749 as <file>/etc/crontab</file> and is processed
7750 by <prgn>cron</prgn> automatically. The file must also be
7751 treated as a configuration file. (Note that entries in the
7752 <file>/etc/cron.d</file> directory are not handled by
7753 <prgn>anacron</prgn>. Thus, you should only use this
7754 directory for jobs which may be skipped if the system is not
7759 Unlike <file>crontab</file> files described in the IEEE Std
7760 1003.1-2008 (POSIX.1) available from
7761 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7762 name="The Open Group">, the files in
7763 <file>/etc/cron.d</file> and the file
7764 <file>/etc/crontab</file> have seven fields; namely:
7766 <item>Minute [0,59]</item>
7767 <item>Hour [0,23]</item>
7768 <item>Day of the month [1,31]</item>
7769 <item>Month of the year [1,12]</item>
7770 <item>Day of the week ([0,6] with 0=Sunday)</item>
7771 <item>Username</item>
7772 <item>Command to be run</item>
7774 Ranges of numbers are allowed. Ranges are two numbers
7775 separated with a hyphen. The specified range is inclusive.
7776 Lists are allowed. A list is a set of numbers (or ranges)
7777 separated by commas. Step values can be used in conjunction
7782 The scripts or <tt>crontab</tt> entries in these directories should
7783 check if all necessary programs are installed before they
7784 try to execute them. Otherwise, problems will arise when a
7785 package was removed but not purged since configuration files
7786 are kept on the system in this situation.
7790 Any <tt>cron</tt> daemon must provide
7791 <file>/usr/bin/crontab</file> and support normal
7792 <tt>crontab</tt> entries as specified in POSIX. The daemon
7793 must also support names for days and months, ranges, and
7794 step values. It has to support <file>/etc/crontab</file>,
7795 and correctly execute the scripts in
7796 <file>/etc/cron.d</file>. The daemon must also correctly
7798 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7801 <sect1 id="cron-files">
7802 <heading>Cron job file names</heading>
7805 The file name of a cron job file should normally match the
7806 name of the package from which it comes.
7810 If a package supplies multiple cron job files files in the
7811 same directory, the file names should all start with the name
7812 of the package (possibly modified as described below) followed
7813 by a hyphen (<tt>-</tt>) and a suitable suffix.
7817 A cron job file name must not include any period or plus
7818 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7819 cause cron to ignore the file. Underscores (<tt>_</tt>)
7820 should be used instead of <tt>.</tt> and <tt>+</tt>
7827 <heading>Menus</heading>
7830 The Debian <tt>menu</tt> package provides a standard
7831 interface between packages providing applications and
7832 <em>menu programs</em> (either X window managers or
7833 text-based menu programs such as <prgn>pdmenu</prgn>).
7837 All packages that provide applications that need not be
7838 passed any special command line arguments for normal
7839 operation should register a menu entry for those
7840 applications, so that users of the <tt>menu</tt> package
7841 will automatically get menu entries in their window
7842 managers, as well in shells like <tt>pdmenu</tt>.
7846 Menu entries should follow the current menu policy.
7850 The menu policy can be found in the <tt>menu-policy</tt>
7851 files in the <tt>debian-policy</tt> package.
7852 It is also available from the Debian web mirrors at
7853 <tt><url name="/doc/packaging-manuals/menu-policy/"
7854 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7858 Please also refer to the <em>Debian Menu System</em>
7859 documentation that comes with the <package>menu</package>
7860 package for information about how to register your
7866 <heading>Multimedia handlers</heading>
7869 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7870 is a mechanism for encoding files and data streams and
7871 providing meta-information about them, in particular their
7872 type (e.g. audio or video) and format (e.g. PNG, HTML,
7877 Registration of MIME type handlers allows programs like mail
7878 user agents and web browsers to invoke these handlers to
7879 view, edit or display MIME types they don't support directly.
7883 Packages which provide the ability to view/show/play,
7884 compose, edit or print MIME types should register themselves
7885 as such following the current MIME support policy.
7889 The <package>mime-support</package> package provides the
7890 <prgn>update-mime</prgn> program which allows packages to
7891 register programs that can show, compose, edit or print
7896 Packages containing such programs must register them
7897 with <prgn>update-mime</prgn> as documented in <manref
7898 name="update-mime" section="8">. They should <em>not</em> depend
7899 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7900 they should just put something like the following in the
7901 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7904 if [ -x /usr/sbin/update-mime ]; then
7913 <heading>Keyboard configuration</heading>
7916 To achieve a consistent keyboard configuration so that all
7917 applications interpret a keyboard event the same way, all
7918 programs in the Debian distribution must be configured to
7919 comply with the following guidelines.
7923 The following keys must have the specified interpretations:
7926 <tag><tt><--</tt></tag>
7927 <item>delete the character to the left of the cursor</item>
7929 <tag><tt>Delete</tt></tag>
7930 <item>delete the character to the right of the cursor</item>
7932 <tag><tt>Control+H</tt></tag>
7933 <item>emacs: the help prefix</item>
7936 The interpretation of any keyboard events should be
7937 independent of the terminal that is used, be it a virtual
7938 console, an X terminal emulator, an rlogin/telnet session,
7943 The following list explains how the different programs
7944 should be set up to achieve this:
7950 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7954 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7958 X translations are set up to make
7959 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7960 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7961 is the vt220 escape code for the "delete character"
7962 key). This must be done by loading the X resources
7963 using <prgn>xrdb</prgn> on all local X displays, not
7964 using the application defaults, so that the
7965 translation resources used correspond to the
7966 <prgn>xmodmap</prgn> settings.
7970 The Linux console is configured to make
7971 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7972 generate <tt>ESC [ 3 ~</tt>.
7976 X applications are configured so that <tt><</tt>
7977 deletes left, and <tt>Delete</tt> deletes right. Motif
7978 applications already work like this.
7982 Terminals should have <tt>stty erase ^?</tt> .
7986 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7987 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7988 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7992 Emacs is programmed to map <tt>KB_Backspace</tt> or
7993 the <tt>stty erase</tt> character to
7994 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7995 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7996 <tt>^H</tt> to <tt>help</tt> as always.
8000 Other applications use the <tt>stty erase</tt>
8001 character and <tt>kdch1</tt> for the two delete keys,
8002 with ASCII DEL being "delete previous character" and
8003 <tt>kdch1</tt> being "delete character under
8011 This will solve the problem except for the following
8018 Some terminals have a <tt><--</tt> key that cannot
8019 be made to produce anything except <tt>^H</tt>. On
8020 these terminals Emacs help will be unavailable on
8021 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8022 character takes precedence in Emacs, and has been set
8023 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8024 available) can be used instead.
8028 Some operating systems use <tt>^H</tt> for <tt>stty
8029 erase</tt>. However, modern telnet versions and all
8030 rlogin versions propagate <tt>stty</tt> settings, and
8031 almost all UNIX versions honour <tt>stty erase</tt>.
8032 Where the <tt>stty</tt> settings are not propagated
8033 correctly, things can be made to work by using
8034 <tt>stty</tt> manually.
8038 Some systems (including previous Debian versions) use
8039 <prgn>xmodmap</prgn> to arrange for both
8040 <tt><--</tt> and <tt>Delete</tt> to generate
8041 <tt>KB_Delete</tt>. We can change the behavior of
8042 their X clients using the same X resources that we use
8043 to do it for our own clients, or configure our clients
8044 using their resources when things are the other way
8045 around. On displays configured like this
8046 <tt>Delete</tt> will not work, but <tt><--</tt>
8051 Some operating systems have different <tt>kdch1</tt>
8052 settings in their <tt>terminfo</tt> database for
8053 <tt>xterm</tt> and others. On these systems the
8054 <tt>Delete</tt> key will not work correctly when you
8055 log in from a system conforming to our policy, but
8056 <tt><--</tt> will.
8063 <heading>Environment variables</heading>
8066 A program must not depend on environment variables to get
8067 reasonable defaults. (That's because these environment
8068 variables would have to be set in a system-wide
8069 configuration file like <file>/etc/profile</file>, which is not
8070 supported by all shells.)
8074 If a program usually depends on environment variables for its
8075 configuration, the program should be changed to fall back to
8076 a reasonable default configuration if these environment
8077 variables are not present. If this cannot be done easily
8078 (e.g., if the source code of a non-free program is not
8079 available), the program must be replaced by a small
8080 "wrapper" shell script which sets the environment variables
8081 if they are not already defined, and calls the original program.
8085 Here is an example of a wrapper script for this purpose:
8087 <example compact="compact">
8089 BAR=${BAR:-/var/lib/fubar}
8091 exec /usr/lib/foo/foo "$@"
8096 Furthermore, as <file>/etc/profile</file> is a configuration
8097 file of the <prgn>base-files</prgn> package, other packages must
8098 not put any environment variables or other commands into that
8103 <sect id="doc-base">
8104 <heading>Registering Documents using doc-base</heading>
8107 The <package>doc-base</package> package implements a
8108 flexible mechanism for handling and presenting
8109 documentation. The recommended practice is for every Debian
8110 package that provides online documentation (other than just
8111 manual pages) to register these documents with
8112 <package>doc-base</package> by installing a
8113 <package>doc-base</package> control file in
8114 <file>/usr/share/doc-base/</file>.
8117 Please refer to the documentation that comes with the
8118 <package>doc-base</package> package for information and
8127 <heading>Files</heading>
8129 <sect id="binaries">
8130 <heading>Binaries</heading>
8133 Two different packages must not install programs with
8134 different functionality but with the same filenames. (The
8135 case of two programs having the same functionality but
8136 different implementations is handled via "alternatives" or
8137 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8138 <ref id="conflicts"> respectively.) If this case happens,
8139 one of the programs must be renamed. The maintainers should
8140 report this to the <tt>debian-devel</tt> mailing list and
8141 try to find a consensus about which program will have to be
8142 renamed. If a consensus cannot be reached, <em>both</em>
8143 programs must be renamed.
8147 By default, when a package is being built, any binaries
8148 created should include debugging information, as well as
8149 being compiled with optimization. You should also turn on
8150 as many reasonable compilation warnings as possible; this
8151 makes life easier for porters, who can then look at build
8152 logs for possible problems. For the C programming language,
8153 this means the following compilation parameters should be
8155 <example compact="compact">
8157 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8159 INSTALL = install -s # (or use strip on the files in debian/tmp)
8164 Note that by default all installed binaries should be stripped,
8165 either by using the <tt>-s</tt> flag to
8166 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8167 the binaries after they have been copied into
8168 <file>debian/tmp</file> but before the tree is made into a
8173 Although binaries in the build tree should be compiled with
8174 debugging information by default, it can often be difficult to
8175 debug programs if they are also subjected to compiler
8176 optimization. For this reason, it is recommended to support the
8177 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8178 (see <ref id="debianrules-options">). This variable can contain
8179 several flags to change how a package is compiled and built.
8183 It is up to the package maintainer to decide what
8184 compilation options are best for the package. Certain
8185 binaries (such as computationally-intensive programs) will
8186 function better with certain flags (<tt>-O3</tt>, for
8187 example); feel free to use them. Please use good judgment
8188 here. Don't use flags for the sake of it; only use them
8189 if there is good reason to do so. Feel free to override
8190 the upstream author's ideas about which compilation
8191 options are best: they are often inappropriate for our
8197 <sect id="libraries">
8198 <heading>Libraries</heading>
8201 If the package is <strong>architecture: any</strong>, then
8202 the shared library compilation and linking flags must have
8203 <tt>-fPIC</tt>, or the package shall not build on some of
8204 the supported architectures<footnote>
8206 If you are using GCC, <tt>-fPIC</tt> produces code with
8207 relocatable position independent code, which is required for
8208 most architectures to create a shared library, with i386 and
8209 perhaps some others where non position independent code is
8210 permitted in a shared library.
8213 Position independent code may have a performance penalty,
8214 especially on <tt>i386</tt>. However, in most cases the
8215 speed penalty must be measured against the memory wasted on
8216 the few architectures where non position independent code is
8219 </footnote>. Any exception to this rule must be discussed on
8220 the mailing list <em>debian-devel@lists.debian.org</em>, and
8221 a rough consensus obtained. The reasons for not compiling
8222 with <tt>-fPIC</tt> flag must be recorded in the file
8223 <tt>README.Debian</tt>, and care must be taken to either
8224 restrict the architecture or arrange for <tt>-fPIC</tt> to
8225 be used on architectures where it is required.<footnote>
8227 Some of the reasons why this might be required is if the
8228 library contains hand crafted assembly code that is not
8229 relocatable, the speed penalty is excessive for compute
8230 intensive libs, and similar reasons.
8235 As to the static libraries, the common case is not to have
8236 relocatable code, since there is no benefit, unless in specific
8237 cases; therefore the static version must not be compiled
8238 with the <tt>-fPIC</tt> flag. Any exception to this rule
8239 should be discussed on the mailing list
8240 <em>debian-devel@lists.debian.org</em>, and the reasons for
8241 compiling with the <tt>-fPIC</tt> flag must be recorded in
8242 the file <tt>README.Debian</tt>. <footnote>
8244 Some of the reasons for linking static libraries with
8245 the <tt>-fPIC</tt> flag are if, for example, one needs a
8246 Perl API for a library that is under rapid development,
8247 and has an unstable API, so shared libraries are
8248 pointless at this phase of the library's development. In
8249 that case, since Perl needs a library with relocatable
8250 code, it may make sense to create a static library with
8251 relocatable code. Another reason cited is if you are
8252 distilling various libraries into a common shared
8253 library, like <tt>mklibs</tt> does in the Debian
8259 In other words, if both a shared and a static library is
8260 being built, each source unit (<tt>*.c</tt>, for example,
8261 for C files) will need to be compiled twice, for the normal
8266 Libraries should be built with threading support and to be
8267 thread-safe if the library supports this.
8271 Although not enforced by the build tools, shared libraries
8272 must be linked against all libraries that they use symbols from
8273 in the same way that binaries are. This ensures the correct
8274 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8275 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8276 systems and guarantees that all libraries can be safely opened
8277 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8278 option <tt>-Wl,-z,defs</tt> when building a shared library.
8279 Since this option enforces symbol resolution at build time,
8280 a missing library reference will be caught early as a fatal
8285 All installed shared libraries should be stripped with
8286 <example compact="compact">
8287 strip --strip-unneeded <var>your-lib</var>
8289 (The option <tt>--strip-unneeded</tt> makes
8290 <prgn>strip</prgn> remove only the symbols which aren't
8291 needed for relocation processing.) Shared libraries can
8292 function perfectly well when stripped, since the symbols for
8293 dynamic linking are in a separate part of the ELF object
8295 You might also want to use the options
8296 <tt>--remove-section=.comment</tt> and
8297 <tt>--remove-section=.note</tt> on both shared libraries
8298 and executables, and <tt>--strip-debug</tt> on static
8304 Note that under some circumstances it may be useful to
8305 install a shared library unstripped, for example when
8306 building a separate package to support debugging.
8310 Shared object files (often <file>.so</file> files) that are not
8311 public libraries, that is, they are not meant to be linked
8312 to by third party executables (binaries of other packages),
8313 should be installed in subdirectories of the
8314 <file>/usr/lib</file> directory. Such files are exempt from the
8315 rules that govern ordinary shared libraries, except that
8316 they must not be installed executable and should be
8318 A common example are the so-called "plug-ins",
8319 internal shared objects that are dynamically loaded by
8320 programs using <manref name="dlopen" section="3">.
8325 Packages that use <prgn>libtool</prgn> to create and install
8326 their shared libraries install a file containing additional
8327 metadata (ending in <file>.la</file>) alongside the library.
8328 For public libraries intended for use by other packages, these
8329 files normally should not be included in the Debian package,
8330 since the information they include is not necessary to link with
8331 the shared library on Debian and can add unnecessary additional
8332 dependencies to other programs or libraries.<footnote>
8333 These files store, among other things, all libraries on which
8334 that shared library depends. Unfortunately, if
8335 the <file>.la</file> file is present and contains that
8336 dependency information, using <prgn>libtool</prgn> when
8337 linking against that library will cause the resulting program
8338 or library to be linked against those dependencies as well,
8339 even if this is unnecessary. This can create unneeded
8340 dependencies on shared library packages that would otherwise
8341 be hidden behind the library ABI, and can make library
8342 transitions to new SONAMEs unnecessarily complicated and
8343 difficult to manage.
8345 If the <file>.la</file> file is required for that library (if,
8346 for instance, it's loaded via <tt>libltdl</tt> in a way that
8347 requires that meta-information), the <tt>dependency_libs</tt>
8348 setting in the <file>.la</file> file should normally be set to
8349 the empty string. If the shared library development package has
8350 historically included the <file>.la</file>, it must be retained
8351 in the development package (with <tt>dependency_libs</tt>
8352 emptied) until all libraries that depend on it have removed or
8353 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8354 files to prevent linking with those other libraries
8355 using <prgn>libtool</prgn> from failing.
8359 If the <file>.la</file> must be included, it should be included
8360 in the development (<tt>-dev</tt>) package, unless the library
8361 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8362 library. If it is intended for use with <tt>libltdl</tt>,
8363 the <file>.la</file> files must go in the run-time library
8368 These requirements for handling of <file>.la</file> files do not
8369 apply to loadable modules or libraries not installed in
8370 directories searched by default by the dynamic linker. Packages
8371 installing loadable modules will frequently need to install
8372 the <file>.la</file> files alongside the modules so that they
8373 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8374 does not need to be modified for libraries or modules that are
8375 not installed in directories searched by the dynamic linker by
8376 default and not intended for use by other packages.
8380 You must make sure that you use only released versions of
8381 shared libraries to build your packages; otherwise other
8382 users will not be able to run your binaries
8383 properly. Producing source packages that depend on
8384 unreleased compilers is also usually a bad
8391 <heading>Shared libraries</heading>
8393 This section has moved to <ref id="sharedlibs">.
8399 <heading>Scripts</heading>
8402 All command scripts, including the package maintainer
8403 scripts inside the package and used by <prgn>dpkg</prgn>,
8404 should have a <tt>#!</tt> line naming the shell to be used
8409 In the case of Perl scripts this should be
8410 <tt>#!/usr/bin/perl</tt>.
8414 When scripts are installed into a directory in the system
8415 PATH, the script name should not include an extension such
8416 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8417 language currently used to implement it.
8420 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8421 <file>init.d</file> scripts should almost certainly start
8422 with <tt>set -e</tt> so that errors are detected.
8423 <file>init.d</file> scripts are something of a special case, due
8424 to how frequently they need to call commands that are allowed to
8425 fail, and it may instead be easier to check the exit status of
8426 commands directly. See <ref id="writing-init"> for more
8427 information about writing <file>init.d</file> scripts.
8430 Every script should use <tt>set -e</tt> or check the exit status
8431 of <em>every</em> command.
8434 Scripts may assume that <file>/bin/sh</file> implements the
8435 SUSv3 Shell Command Language<footnote>
8436 Single UNIX Specification, version 3, which is also IEEE
8437 1003.1-2004 (POSIX), and is available on the World Wide Web
8438 from <url id="http://www.unix.org/version3/online.html"
8439 name="The Open Group"> after free
8440 registration.</footnote>
8441 plus the following additional features not mandated by
8443 These features are in widespread use in the Linux community
8444 and are implemented in all of bash, dash, and ksh, the most
8445 common shells users may wish to use as <file>/bin/sh</file>.
8448 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8449 must not generate a newline.</item>
8450 <item><tt>test</tt>, if implemented as a shell built-in, must
8451 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8453 <item><tt>local</tt> to create a scoped variable must be
8454 supported, including listing multiple variables in a single
8455 local command and assigning a value to a variable at the
8456 same time as localizing it. <tt>local</tt> may or
8457 may not preserve the variable value from an outer scope if
8458 no assignment is present. Uses such as:
8462 # ... use a, b, c, d ...
8465 must be supported and must set the value of <tt>c</tt> to
8468 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8469 -<var>signal</var></tt>, where <var>signal</var> is either
8470 the name of a signal or one of the numeric signals listed in
8471 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8472 supported if <prgn>kill</prgn> is implemented as a shell
8475 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8476 signals must be supported. In addition to the signal
8477 numbers listed in the extension, which are the same as for
8478 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8481 If a shell script requires non-SUSv3 features from the shell
8482 interpreter other than those listed above, the appropriate shell
8483 must be specified in the first line of the script (e.g.,
8484 <tt>#!/bin/bash</tt>) and the package must depend on the package
8485 providing the shell (unless the shell package is marked
8486 "Essential", as in the case of <prgn>bash</prgn>).
8490 You may wish to restrict your script to SUSv3 features plus the
8491 above set when possible so that it may use <file>/bin/sh</file>
8492 as its interpreter. Checking your script
8493 with <prgn>checkbashisms</prgn> from
8494 the <package>devscripts</package> package or running your script
8495 with an alternate shell such as <prgn>posh</prgn> may help
8496 uncover violations of the above requirements. If in doubt
8497 whether a script complies with these requirements,
8498 use <file>/bin/bash</file>.
8502 Perl scripts should check for errors when making any
8503 system calls, including <tt>open</tt>, <tt>print</tt>,
8504 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8508 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8509 scripting languages. See <em>Csh Programming Considered
8510 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8511 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8512 If an upstream package comes with <prgn>csh</prgn> scripts
8513 then you must make sure that they start with
8514 <tt>#!/bin/csh</tt> and make your package depend on the
8515 <prgn>c-shell</prgn> virtual package.
8519 Any scripts which create files in world-writeable
8520 directories (e.g., in <file>/tmp</file>) must use a
8521 mechanism which will fail atomically if a file with the same
8522 name already exists.
8526 The Debian base system provides the <prgn>tempfile</prgn>
8527 and <prgn>mktemp</prgn> utilities for use by scripts for
8534 <heading>Symbolic links</heading>
8537 In general, symbolic links within a top-level directory should
8538 be relative, and symbolic links pointing from one top-level
8539 directory to or into another should be absolute. (A top-level
8540 directory is a sub-directory of the root
8541 directory <file>/</file>.) For example, a symbolic link
8542 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8543 should be relative (<file>../share/bar</file>), but a symbolic
8544 link from <file>/var/run</file> to <file>/run</file> should be
8546 This is necessary to allow top-level directories to be
8547 symlinks. If linking <file>/var/run</file>
8548 to <file>/run</file> were done with the relative symbolic
8549 link <file>../run</file>, but <file>/var</file> were a
8550 symbolic link to <file>/srv/disk1</file>, the symbolic link
8551 would point to <file>/srv/run</file> rather than the intended
8557 In addition, symbolic links should be specified as short as
8558 possible, i.e., link targets like <file>foo/../bar</file> are
8563 Note that when creating a relative link using
8564 <prgn>ln</prgn> it is not necessary for the target of the
8565 link to exist relative to the working directory you're
8566 running <prgn>ln</prgn> from, nor is it necessary to change
8567 directory to the directory where the link is to be made.
8568 Simply include the string that should appear as the target
8569 of the link (this will be a pathname relative to the
8570 directory in which the link resides) as the first argument
8575 For example, in your <prgn>Makefile</prgn> or
8576 <file>debian/rules</file>, you can do things like:
8577 <example compact="compact">
8578 ln -fs gcc $(prefix)/bin/cc
8579 ln -fs gcc debian/tmp/usr/bin/cc
8580 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8581 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8586 A symbolic link pointing to a compressed file should always
8587 have the same file extension as the referenced file. (For
8588 example, if a file <file>foo.gz</file> is referenced by a
8589 symbolic link, the filename of the link has to end with
8590 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8595 <heading>Device files</heading>
8598 Packages must not include device files or named pipes in the
8603 If a package needs any special device files that are not
8604 included in the base system, it must call
8605 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8606 after notifying the user<footnote>
8607 This notification could be done via a (low-priority)
8608 debconf message, or an echo (printf) statement.
8613 Packages must not remove any device files in the
8614 <prgn>postrm</prgn> or any other script. This is left to the
8615 system administrator.
8619 Debian uses the serial devices
8620 <file>/dev/ttyS*</file>. Programs using the old
8621 <file>/dev/cu*</file> devices should be changed to use
8622 <file>/dev/ttyS*</file>.
8626 Named pipes needed by the package must be created in
8627 the <prgn>postinst</prgn> script<footnote>
8628 It's better to use <prgn>mkfifo</prgn> rather
8629 than <prgn>mknod</prgn> to create named pipes so that
8630 automated checks for packages incorrectly creating device
8631 files with <prgn>mknod</prgn> won't have false positives.
8632 </footnote> and removed in
8633 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8638 <sect id="config-files">
8639 <heading>Configuration files</heading>
8642 <heading>Definitions</heading>
8646 <tag>configuration file</tag>
8648 A file that affects the operation of a program, or
8649 provides site- or host-specific information, or
8650 otherwise customizes the behavior of a program.
8651 Typically, configuration files are intended to be
8652 modified by the system administrator (if needed or
8653 desired) to conform to local policy or to provide
8654 more useful site-specific behavior.
8657 <tag><tt>conffile</tt></tag>
8659 A file listed in a package's <tt>conffiles</tt>
8660 file, and is treated specially by <prgn>dpkg</prgn>
8661 (see <ref id="configdetails">).
8667 The distinction between these two is important; they are
8668 not interchangeable concepts. Almost all
8669 <tt>conffile</tt>s are configuration files, but many
8670 configuration files are not <tt>conffiles</tt>.
8674 As noted elsewhere, <file>/etc/init.d</file> scripts,
8675 <file>/etc/default</file> files, scripts installed in
8676 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8677 configuration installed in <file>/etc/cron.d</file> must be
8678 treated as configuration files. In general, any script that
8679 embeds configuration information is de-facto a configuration
8680 file and should be treated as such.
8685 <heading>Location</heading>
8688 Any configuration files created or used by your package
8689 must reside in <file>/etc</file>. If there are several,
8690 consider creating a subdirectory of <file>/etc</file>
8691 named after your package.
8695 If your package creates or uses configuration files
8696 outside of <file>/etc</file>, and it is not feasible to modify
8697 the package to use <file>/etc</file> directly, put the files
8698 in <file>/etc</file> and create symbolic links to those files
8699 from the location that the package requires.
8704 <heading>Behavior</heading>
8707 Configuration file handling must conform to the following
8709 <list compact="compact">
8711 local changes must be preserved during a package
8715 configuration files must be preserved when the
8716 package is removed, and only deleted when the
8720 Obsolete configuration files without local changes may be
8721 removed by the package during upgrade.
8725 The easy way to achieve this behavior is to make the
8726 configuration file a <tt>conffile</tt>. This is
8727 appropriate only if it is possible to distribute a default
8728 version that will work for most installations, although
8729 some system administrators may choose to modify it. This
8730 implies that the default version will be part of the
8731 package distribution, and must not be modified by the
8732 maintainer scripts during installation (or at any other
8737 In order to ensure that local changes are preserved
8738 correctly, no package may contain or make hard links to
8739 conffiles.<footnote>
8740 Rationale: There are two problems with hard links.
8741 The first is that some editors break the link while
8742 editing one of the files, so that the two files may
8743 unwittingly become unlinked and different. The second
8744 is that <prgn>dpkg</prgn> might break the hard link
8745 while upgrading <tt>conffile</tt>s.
8750 The other way to do it is via the maintainer scripts. In
8751 this case, the configuration file must not be listed as a
8752 <tt>conffile</tt> and must not be part of the package
8753 distribution. If the existence of a file is required for
8754 the package to be sensibly configured it is the
8755 responsibility of the package maintainer to provide
8756 maintainer scripts which correctly create, update and
8757 maintain the file and remove it on purge. (See <ref
8758 id="maintainerscripts"> for more information.) These
8759 scripts must be idempotent (i.e., must work correctly if
8760 <prgn>dpkg</prgn> needs to re-run them due to errors
8761 during installation or removal), must cope with all the
8762 variety of ways <prgn>dpkg</prgn> can call maintainer
8763 scripts, must not overwrite or otherwise mangle the user's
8764 configuration without asking, must not ask unnecessary
8765 questions (particularly during upgrades), and must
8766 otherwise be good citizens.
8770 The scripts are not required to configure every possible
8771 option for the package, but only those necessary to get
8772 the package running on a given system. Ideally the
8773 sysadmin should not have to do any configuration other
8774 than that done (semi-)automatically by the
8775 <prgn>postinst</prgn> script.
8779 A common practice is to create a script called
8780 <file><var>package</var>-configure</file> and have the
8781 package's <prgn>postinst</prgn> call it if and only if the
8782 configuration file does not already exist. In certain
8783 cases it is useful for there to be an example or template
8784 file which the maintainer scripts use. Such files should
8785 be in <file>/usr/share/<var>package</var></file> or
8786 <file>/usr/lib/<var>package</var></file> (depending on whether
8787 they are architecture-independent or not). There should
8788 be symbolic links to them from
8789 <file>/usr/share/doc/<var>package</var>/examples</file> if
8790 they are examples, and should be perfectly ordinary
8791 <prgn>dpkg</prgn>-handled files (<em>not</em>
8792 configuration files).
8796 These two styles of configuration file handling must
8797 not be mixed, for that way lies madness:
8798 <prgn>dpkg</prgn> will ask about overwriting the file
8799 every time the package is upgraded.
8804 <heading>Sharing configuration files</heading>
8807 If two or more packages use the same configuration file
8808 and it is reasonable for both to be installed at the same
8809 time, one of these packages must be defined as
8810 <em>owner</em> of the configuration file, i.e., it will be
8811 the package which handles that file as a configuration
8812 file. Other packages that use the configuration file must
8813 depend on the owning package if they require the
8814 configuration file to operate. If the other package will
8815 use the configuration file if present, but is capable of
8816 operating without it, no dependency need be declared.
8820 If it is desirable for two or more related packages to
8821 share a configuration file <em>and</em> for all of the
8822 related packages to be able to modify that configuration
8823 file, then the following should be done:
8824 <enumlist compact="compact">
8826 One of the related packages (the "owning" package)
8827 will manage the configuration file with maintainer
8828 scripts as described in the previous section.
8831 The owning package should also provide a program
8832 that the other packages may use to modify the
8836 The related packages must use the provided program
8837 to make any desired modifications to the
8838 configuration file. They should either depend on
8839 the core package to guarantee that the configuration
8840 modifier program is available or accept gracefully
8841 that they cannot modify the configuration file if it
8842 is not. (This is in addition to the fact that the
8843 configuration file may not even be present in the
8850 Sometimes it's appropriate to create a new package which
8851 provides the basic infrastructure for the other packages
8852 and which manages the shared configuration files. (The
8853 <tt>sgml-base</tt> package is a good example.)
8857 If the configuration file cannot be shared as described above,
8858 the packages must be marked as conflicting with each other.
8859 Two packages that specify the same file as
8860 a <tt>conffile</tt> must conflict. This is an instance of the
8861 general rule about not sharing files. Neither alternatives
8862 nor diversions are likely to be appropriate in this case; in
8863 particular, <prgn>dpkg</prgn> does not handle diverted
8864 <tt>conffile</tt>s well.
8868 When two packages both declare the same <tt>conffile</tt>, they
8869 may see left-over configuration files from each other even
8870 though they conflict with each other. If a user removes
8871 (without purging) one of the packages and installs the other,
8872 the new package will take over the <tt>conffile</tt> from the
8873 old package. If the file was modified by the user, it will be
8874 treated the same as any other locally
8875 modified <tt>conffile</tt> during an upgrade.
8879 The maintainer scripts must not alter a <tt>conffile</tt>
8880 of <em>any</em> package, including the one the scripts
8886 <heading>User configuration files ("dotfiles")</heading>
8889 The files in <file>/etc/skel</file> will automatically be
8890 copied into new user accounts by <prgn>adduser</prgn>.
8891 No other program should reference the files in
8892 <file>/etc/skel</file>.
8896 Therefore, if a program needs a dotfile to exist in
8897 advance in <file>$HOME</file> to work sensibly, that dotfile
8898 should be installed in <file>/etc/skel</file> and treated as a
8903 However, programs that require dotfiles in order to
8904 operate sensibly are a bad thing, unless they do create
8905 the dotfiles themselves automatically.
8909 Furthermore, programs should be configured by the Debian
8910 default installation to behave as closely to the upstream
8911 default behavior as possible.
8915 Therefore, if a program in a Debian package needs to be
8916 configured in some way in order to operate sensibly, that
8917 should be done using a site-wide configuration file placed
8918 in <file>/etc</file>. Only if the program doesn't support a
8919 site-wide default configuration and the package maintainer
8920 doesn't have time to add it may a default per-user file be
8921 placed in <file>/etc/skel</file>.
8925 <file>/etc/skel</file> should be as empty as we can make it.
8926 This is particularly true because there is no easy (or
8927 necessarily desirable) mechanism for ensuring that the
8928 appropriate dotfiles are copied into the accounts of
8929 existing users when a package is installed.
8935 <heading>Log files</heading>
8937 Log files should usually be named
8938 <file>/var/log/<var>package</var>.log</file>. If you have many
8939 log files, or need a separate directory for permission
8940 reasons (<file>/var/log</file> is writable only by
8941 <file>root</file>), you should usually create a directory named
8942 <file>/var/log/<var>package</var></file> and place your log
8947 Log files must be rotated occasionally so that they don't grow
8948 indefinitely. The best way to do this is to install a log
8949 rotation configuration file in the
8950 directory <file>/etc/logrotate.d</file>, normally
8951 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8952 the facilities provided by <prgn>logrotate</prgn>.
8955 The traditional approach to log files has been to set up
8956 <em>ad hoc</em> log rotation schemes using simple shell
8957 scripts and cron. While this approach is highly
8958 customizable, it requires quite a lot of sysadmin work.
8959 Even though the original Debian system helped a little
8960 by automatically installing a system which can be used
8961 as a template, this was deemed not enough.
8965 The use of <prgn>logrotate</prgn>, a program developed
8966 by Red Hat, is better, as it centralizes log management.
8967 It has both a configuration file
8968 (<file>/etc/logrotate.conf</file>) and a directory where
8969 packages can drop their individual log rotation
8970 configurations (<file>/etc/logrotate.d</file>).
8973 Here is a good example for a logrotate config
8974 file (for more information see <manref name="logrotate"
8976 <example compact="compact">
8977 /var/log/foo/*.log {
8983 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8987 This rotates all files under <file>/var/log/foo</file>, saves 12
8988 compressed generations, and tells the daemon to reopen its log
8989 files after the log rotation. It skips this log rotation
8990 (via <tt>missingok</tt>) if no such log file is present, which
8991 avoids errors if the package is removed but not purged.
8995 Log files should be removed when the package is
8996 purged (but not when it is only removed). This should be
8997 done by the <prgn>postrm</prgn> script when it is called
8998 with the argument <tt>purge</tt> (see <ref
8999 id="removedetails">).
9003 <sect id="permissions-owners">
9004 <heading>Permissions and owners</heading>
9007 The rules in this section are guidelines for general use.
9008 If necessary you may deviate from the details below.
9009 However, if you do so you must make sure that what is done
9010 is secure and you should try to be as consistent as possible
9011 with the rest of the system. You should probably also
9012 discuss it on <prgn>debian-devel</prgn> first.
9016 Files should be owned by <tt>root:root</tt>, and made
9017 writable only by the owner and universally readable (and
9018 executable, if appropriate), that is mode 644 or 755.
9022 Directories should be mode 755 or (for group-writability)
9023 mode 2775. The ownership of the directory should be
9024 consistent with its mode: if a directory is mode 2775, it
9025 should be owned by the group that needs write access to
9028 When a package is upgraded, and the owner or permissions
9029 of a file included in the package has changed, dpkg
9030 arranges for the ownership and permissions to be
9031 correctly set upon installation. However, this does not
9032 extend to directories; the permissions and ownership of
9033 directories already on the system does not change on
9034 install or upgrade of packages. This makes sense, since
9035 otherwise common directories like <tt>/usr</tt> would
9036 always be in flux. To correctly change permissions of a
9037 directory the package owns, explicit action is required,
9038 usually in the <tt>postinst</tt> script. Care must be
9039 taken to handle downgrades as well, in that case.
9045 Control information files should be owned by <tt>root:root</tt>
9046 and either mode 644 (for most files) or mode 755 (for
9047 executables such as <qref id="maintscripts">maintainer
9052 Setuid and setgid executables should be mode 4755 or 2755
9053 respectively, and owned by the appropriate user or group.
9054 They should not be made unreadable (modes like 4711 or
9055 2711 or even 4111); doing so achieves no extra security,
9056 because anyone can find the binary in the freely available
9057 Debian package; it is merely inconvenient. For the same
9058 reason you should not restrict read or execute permissions
9059 on non-set-id executables.
9063 Some setuid programs need to be restricted to particular
9064 sets of users, using file permissions. In this case they
9065 should be owned by the uid to which they are set-id, and by
9066 the group which should be allowed to execute them. They
9067 should have mode 4754; again there is no point in making
9068 them unreadable to those users who must not be allowed to
9073 It is possible to arrange that the system administrator can
9074 reconfigure the package to correspond to their local
9075 security policy by changing the permissions on a binary:
9076 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9077 described below.<footnote>
9078 Ordinary files installed by <prgn>dpkg</prgn> (as
9079 opposed to <tt>conffile</tt>s and other similar objects)
9080 normally have their permissions reset to the distributed
9081 permissions when the package is reinstalled. However,
9082 the use of <prgn>dpkg-statoverride</prgn> overrides this
9085 Another method you should consider is to create a group for
9086 people allowed to use the program(s) and make any setuid
9087 executables executable only by that group.
9091 If you need to create a new user or group for your package
9092 there are two possibilities. Firstly, you may need to
9093 make some files in the binary package be owned by this
9094 user or group, or you may need to compile the user or
9095 group id (rather than just the name) into the binary
9096 (though this latter should be avoided if possible, as in
9097 this case you need a statically allocated id).</p>
9100 If you need a statically allocated id, you must ask for a
9101 user or group id from the <tt>base-passwd</tt> maintainer,
9102 and must not release the package until you have been
9103 allocated one. Once you have been allocated one you must
9104 either make the package depend on a version of the
9105 <tt>base-passwd</tt> package with the id present in
9106 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9107 your package to create the user or group itself with the
9108 correct id (using <tt>adduser</tt>) in its
9109 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9110 the <prgn>postinst</prgn> is to be preferred if it is
9111 possible, otherwise a pre-dependency will be needed on the
9112 <tt>adduser</tt> package.)
9116 On the other hand, the program might be able to determine
9117 the uid or gid from the user or group name at runtime, so
9118 that a dynamically allocated id can be used. In this case
9119 you should choose an appropriate user or group name,
9120 discussing this on <prgn>debian-devel</prgn> and checking
9121 with the <package/base-passwd/ maintainer that it is unique and that
9122 they do not wish you to use a statically allocated id
9123 instead. When this has been checked you must arrange for
9124 your package to create the user or group if necessary using
9125 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9126 <prgn>postinst</prgn> script (again, the latter is to be
9127 preferred if it is possible).
9131 Note that changing the numeric value of an id associated
9132 with a name is very difficult, and involves searching the
9133 file system for all appropriate files. You need to think
9134 carefully whether a static or dynamic id is required, since
9135 changing your mind later will cause problems.
9138 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9140 This section is not intended as policy, but as a
9141 description of the use of <prgn>dpkg-statoverride</prgn>.
9145 If a system administrator wishes to have a file (or
9146 directory or other such thing) installed with owner and
9147 permissions different from those in the distributed Debian
9148 package, they can use the <prgn>dpkg-statoverride</prgn>
9149 program to instruct <prgn>dpkg</prgn> to use the different
9150 settings every time the file is installed. Thus the
9151 package maintainer should distribute the files with their
9152 normal permissions, and leave it for the system
9153 administrator to make any desired changes. For example, a
9154 daemon which is normally required to be setuid root, but
9155 in certain situations could be used without being setuid,
9156 should be installed setuid in the <tt>.deb</tt>. Then the
9157 local system administrator can change this if they wish.
9158 If there are two standard ways of doing it, the package
9159 maintainer can use <tt>debconf</tt> to find out the
9160 preference, and call <prgn>dpkg-statoverride</prgn> in the
9161 maintainer script if necessary to accommodate the system
9162 administrator's choice. Care must be taken during
9163 upgrades to not override an existing setting.
9167 Given the above, <prgn>dpkg-statoverride</prgn> is
9168 essentially a tool for system administrators and would not
9169 normally be needed in the maintainer scripts. There is
9170 one type of situation, though, where calls to
9171 <prgn>dpkg-statoverride</prgn> would be needed in the
9172 maintainer scripts, and that involves packages which use
9173 dynamically allocated user or group ids. In such a
9174 situation, something like the following idiom can be very
9175 helpful in the package's <prgn>postinst</prgn>, where
9176 <tt>sysuser</tt> is a dynamically allocated id:
9178 for i in /usr/bin/foo /usr/sbin/bar
9180 # only do something when no setting exists
9181 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9183 #include: debconf processing, question about foo and bar
9184 if [ "$RET" = "true" ] ; then
9185 dpkg-statoverride --update --add sysuser root 4755 $i
9190 The corresponding code to remove the override when the package
9193 for i in /usr/bin/foo /usr/sbin/bar
9195 if dpkg-statoverride --list $i >/dev/null 2>&1
9197 dpkg-statoverride --remove $i
9207 <chapt id="customized-programs">
9208 <heading>Customized programs</heading>
9210 <sect id="arch-spec">
9211 <heading>Architecture specification strings</heading>
9214 If a program needs to specify an <em>architecture specification
9215 string</em> in some place, it should select one of the strings
9216 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9217 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9218 part is sometimes elided, as when the OS is Linux.
9222 Note that we don't want to use
9223 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9224 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9225 since this would make our programs incompatible with other
9226 Linux distributions. We also don't use something like
9227 <tt><var>arch</var>-unknown-linux</tt>, since the
9228 <tt>unknown</tt> does not look very good.
9231 <sect1 id="arch-wildcard-spec">
9232 <heading>Architecture wildcards</heading>
9235 A package may specify an architecture wildcard. Architecture
9236 wildcards are in the format <tt>any</tt> (which matches every
9237 architecture), <tt><var>os</var></tt>-any, or
9238 any-<tt><var>cpu</var></tt>. <footnote>
9239 Internally, the package system normalizes the GNU triplets
9240 and the Debian arches into Debian arch triplets (which are
9241 kind of inverted GNU triplets), with the first component of
9242 the triplet representing the libc and ABI in use, and then
9243 does matching against those triplets. However, such
9244 triplets are an internal implementation detail that should
9245 not be used by packages directly. The libc and ABI portion
9246 is handled internally by the package system based on
9247 the <var>os</var> and <var>cpu</var>.
9254 <heading>Daemons</heading>
9257 The configuration files <file>/etc/services</file>,
9258 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9259 by the <prgn>netbase</prgn> package and must not be modified
9264 If a package requires a new entry in one of these files, the
9265 maintainer should get in contact with the
9266 <prgn>netbase</prgn> maintainer, who will add the entries
9267 and release a new version of the <prgn>netbase</prgn>
9272 The configuration file <file>/etc/inetd.conf</file> must not be
9273 modified by the package's scripts except via the
9274 <prgn>update-inetd</prgn> script or the
9275 <file>DebianNet.pm</file> Perl module. See their documentation
9276 for details on how to add entries.
9280 If a package wants to install an example entry into
9281 <file>/etc/inetd.conf</file>, the entry must be preceded with
9282 exactly one hash character (<tt>#</tt>). Such lines are
9283 treated as "commented out by user" by the
9284 <prgn>update-inetd</prgn> script and are not changed or
9285 activated during package updates.
9290 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9294 Some programs need to create pseudo-ttys. This should be done
9295 using Unix98 ptys if the C library supports it. The resulting
9296 program must not be installed setuid root, unless that
9297 is required for other functionality.
9301 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9302 <file>/var/log/lastlog</file> must be installed writable by
9303 group <tt>utmp</tt>. Programs which need to modify those
9304 files must be installed setgid <tt>utmp</tt>.
9309 <heading>Editors and pagers</heading>
9312 Some programs have the ability to launch an editor or pager
9313 program to edit or display a text document. Since there are
9314 lots of different editors and pagers available in the Debian
9315 distribution, the system administrator and each user should
9316 have the possibility to choose their preferred editor and
9321 In addition, every program should choose a good default
9322 editor/pager if none is selected by the user or system
9327 Thus, every program that launches an editor or pager must
9328 use the EDITOR or PAGER environment variable to determine
9329 the editor or pager the user wishes to use. If these
9330 variables are not set, the programs <file>/usr/bin/editor</file>
9331 and <file>/usr/bin/pager</file> should be used, respectively.
9335 These two files are managed through the <prgn>dpkg</prgn>
9336 "alternatives" mechanism. Every package providing an editor or
9337 pager must call the <prgn>update-alternatives</prgn> script to
9338 register as an alternative for <file>/usr/bin/editor</file>
9339 or <file>/usr/bin/pager</file> as appropriate. The alternative
9340 should have a slave alternative
9341 for <file>/usr/share/man/man1/editor.1.gz</file>
9342 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9343 corresponding manual page.
9347 If it is very hard to adapt a program to make use of the
9348 EDITOR or PAGER variables, that program may be configured to
9349 use <file>/usr/bin/sensible-editor</file> and
9350 <file>/usr/bin/sensible-pager</file> as the editor or pager
9351 program respectively. These are two scripts provided in the
9352 <package>sensible-utils</package> package that check the EDITOR
9353 and PAGER variables and launch the appropriate program, and fall
9354 back to <file>/usr/bin/editor</file>
9355 and <file>/usr/bin/pager</file> if the variable is not set.
9359 A program may also use the VISUAL environment variable to
9360 determine the user's choice of editor. If it exists, it
9361 should take precedence over EDITOR. This is in fact what
9362 <file>/usr/bin/sensible-editor</file> does.
9366 It is not required for a package to depend on
9367 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9368 package to provide such virtual packages.<footnote>
9369 The Debian base system already provides an editor and a
9375 <sect id="web-appl">
9376 <heading>Web servers and applications</heading>
9379 This section describes the locations and URLs that should
9380 be used by all web servers and web applications in the
9387 Cgi-bin executable files are installed in the
9389 <example compact="compact">
9390 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9392 or a subdirectory of that directory, and should be
9394 <example compact="compact">
9395 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9397 (possibly with a subdirectory name
9398 before <var>cgi-bin-name</var>).
9402 <p>Access to HTML documents</p>
9405 HTML documents for a package are stored in
9406 <file>/usr/share/doc/<var>package</var></file>
9407 and can be referred to as
9408 <example compact="compact">
9409 http://localhost/doc/<var>package</var>/<var>filename</var>
9414 The web server should restrict access to the document
9415 tree so that only clients on the same host can read
9416 the documents. If the web server does not support such
9417 access controls, then it should not provide access at
9418 all, or ask about providing access during installation.
9423 <p>Access to images</p>
9425 It is recommended that images for a package be stored
9426 in <tt>/usr/share/images/<var>package</var></tt> and
9427 may be referred to through an alias <tt>/images/</tt>
9430 http://localhost/images/<package>/<filename>
9437 <p>Web Document Root</p>
9440 Web Applications should try to avoid storing files in
9441 the Web Document Root. Instead they should use the
9442 /usr/share/doc/<var>package</var> directory for
9443 documents and register the Web Application via the
9444 <package>doc-base</package> package. If access to the
9445 web document root is unavoidable then use
9446 <example compact="compact">
9449 as the Document Root. This might be just a symbolic
9450 link to the location where the system administrator
9451 has put the real document root.
9454 <item><p>Providing httpd and/or httpd-cgi</p>
9456 All web servers should provide the virtual package
9457 <tt>httpd</tt>. If a web server has CGI support it should
9458 provide <tt>httpd-cgi</tt> additionally.
9461 All web applications which do not contain CGI scripts should
9462 depend on <tt>httpd</tt>, all those web applications which
9463 <tt>do</tt> contain CGI scripts, should depend on
9471 <sect id="mail-transport-agents">
9472 <heading>Mail transport, delivery and user agents</heading>
9475 Debian packages which process electronic mail, whether mail
9476 user agents (MUAs) or mail transport agents (MTAs), must
9477 ensure that they are compatible with the configuration
9478 decisions below. Failure to do this may result in lost
9479 mail, broken <tt>From:</tt> lines, and other serious brain
9484 The mail spool is <file>/var/mail</file> and the interface to
9485 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9486 the FHS). On older systems, the mail spool may be
9487 physically located in <file>/var/spool/mail</file>, but all
9488 access to the mail spool should be via the
9489 <file>/var/mail</file> symlink. The mail spool is part of the
9490 base system and not part of the MTA package.
9494 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9495 programs (such as IMAP daemons) must lock the mailbox in an
9496 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9497 be combined with dot locking. To avoid deadlocks, a program
9498 should use <tt>fcntl()</tt> first and dot locking after
9499 this, or alternatively implement the two locking methods in
9500 a non blocking way<footnote>
9501 If it is not possible to establish both locks, the
9502 system shouldn't wait for the second lock to be
9503 established, but remove the first lock, wait a (random)
9504 time, and start over locking again.
9505 </footnote>. Using the functions <tt>maillock</tt> and
9506 <tt>mailunlock</tt> provided by the
9507 <tt>liblockfile*</tt><footnote>
9508 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9509 to use these functions.
9510 </footnote> packages is the recommended way to realize this.
9514 Mailboxes are generally either mode 600 and owned by
9515 <var>user</var> or mode 660 and owned by
9516 <tt><var>user</var>:mail</tt><footnote>
9517 There are two traditional permission schemes for mail spools:
9518 mode 600 with all mail delivery done by processes running as
9519 the destination user, or mode 660 and owned by group mail with
9520 mail delivery done by a process running as a system user in
9521 group mail. Historically, Debian required mode 660 mail
9522 spools to enable the latter model, but that model has become
9523 increasingly uncommon and the principle of least privilege
9524 indicates that mail systems that use the first model should
9525 use permissions of 600. If delivery to programs is permitted,
9526 it's easier to keep the mail system secure if the delivery
9527 agent runs as the destination user. Debian Policy therefore
9528 permits either scheme.
9529 </footnote>. The local system administrator may choose a
9530 different permission scheme; packages should not make
9531 assumptions about the permission and ownership of mailboxes
9532 unless required (such as when creating a new mailbox). A MUA
9533 may remove a mailbox (unless it has nonstandard permissions) in
9534 which case the MTA or another MUA must recreate it if needed.
9538 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9539 be setgid mail to do the locking mentioned above (and
9540 must obviously avoid accessing other users' mailboxes
9541 using this privilege).</p>
9544 <file>/etc/aliases</file> is the source file for the system mail
9545 aliases (e.g., postmaster, usenet, etc.), it is the one
9546 which the sysadmin and <prgn>postinst</prgn> scripts may
9547 edit. After <file>/etc/aliases</file> is edited the program or
9548 human editing it must call <prgn>newaliases</prgn>. All MTA
9549 packages must come with a <prgn>newaliases</prgn> program,
9550 even if it does nothing, but older MTA packages did not do
9551 this so programs should not fail if <prgn>newaliases</prgn>
9552 cannot be found. Note that because of this, all MTA
9553 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9554 <tt>Replaces: mail-transport-agent</tt> control fields.
9558 The convention of writing <tt>forward to
9559 <var>address</var></tt> in the mailbox itself is not
9560 supported. Use a <tt>.forward</tt> file instead.</p>
9563 The <prgn>rmail</prgn> program used by UUCP
9564 for incoming mail should be <file>/usr/sbin/rmail</file>.
9565 Likewise, <prgn>rsmtp</prgn>, for receiving
9566 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9570 If your package needs to know what hostname to use on (for
9571 example) outgoing news and mail messages which are generated
9572 locally, you should use the file <file>/etc/mailname</file>. It
9573 will contain the portion after the username and <tt>@</tt>
9574 (at) sign for email addresses of users on the machine
9575 (followed by a newline).
9579 Such a package should check for the existence of this file
9580 when it is being configured. If it exists, it should be
9581 used without comment, although an MTA's configuration script
9582 may wish to prompt the user even if it finds that this file
9583 exists. If the file does not exist, the package should
9584 prompt the user for the value (preferably using
9585 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9586 as well as using it in the package's configuration. The
9587 prompt should make it clear that the name will not just be
9588 used by that package. For example, in this situation the
9589 <tt>inn</tt> package could say something like:
9590 <example compact="compact">
9591 Please enter the "mail name" of your system. This is the
9592 hostname portion of the address to be shown on outgoing
9593 news and mail messages. The default is
9594 <var>syshostname</var>, your system's host name. Mail
9595 name ["<var>syshostname</var>"]:
9597 where <var>syshostname</var> is the output of <tt>hostname
9603 <heading>News system configuration</heading>
9606 All the configuration files related to the NNTP (news)
9607 servers and clients should be located under
9608 <file>/etc/news</file>.</p>
9611 There are some configuration issues that apply to a number
9612 of news clients and server packages on the machine. These
9616 <tag><file>/etc/news/organization</file></tag>
9618 A string which should appear as the
9619 organization header for all messages posted
9620 by NNTP clients on the machine
9623 <tag><file>/etc/news/server</file></tag>
9625 Contains the FQDN of the upstream NNTP
9626 server, or localhost if the local machine is
9631 Other global files may be added as required for cross-package news
9638 <heading>Programs for the X Window System</heading>
9641 <heading>Providing X support and package priorities</heading>
9644 Programs that can be configured with support for the X
9645 Window System must be configured to do so and must declare
9646 any package dependencies necessary to satisfy their
9647 runtime requirements when using the X Window System. If
9648 such a package is of higher priority than the X packages
9649 on which it depends, it is required that either the
9650 X-specific components be split into a separate package, or
9651 that an alternative version of the package, which includes
9652 X support, be provided, or that the package's priority be
9658 <heading>Packages providing an X server</heading>
9661 Packages that provide an X server that, directly or
9662 indirectly, communicates with real input and display
9663 hardware should declare in their <tt>Provides</tt> control
9664 field that they provide the virtual
9665 package <tt>xserver</tt>.<footnote>
9666 This implements current practice, and provides an
9667 actual policy for usage of the <tt>xserver</tt>
9668 virtual package which appears in the virtual packages
9669 list. In a nutshell, X servers that interface
9670 directly with the display and input hardware or via
9671 another subsystem (e.g., GGI) should provide
9672 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9673 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9679 <heading>Packages providing a terminal emulator</heading>
9682 Packages that provide a terminal emulator for the X Window
9683 System which meet the criteria listed below should declare in
9684 their <tt>Provides</tt> control field that they provide the
9685 virtual package <tt>x-terminal-emulator</tt>. They should
9686 also register themselves as an alternative for
9687 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9688 20. That alternative should have a slave alternative
9689 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9690 pointing to the corresponding manual page.
9694 To be an <tt>x-terminal-emulator</tt>, a program must:
9695 <list compact="compact">
9697 Be able to emulate a DEC VT100 terminal, or a
9698 compatible terminal.
9702 Support the command-line option <tt>-e
9703 <var>command</var></tt>, which creates a new
9704 terminal window<footnote>
9705 "New terminal window" does not necessarily mean
9706 a new top-level X window directly parented by
9707 the window manager; it could, if the terminal
9708 emulator application were so coded, be a new
9709 "view" in a multiple-document interface (MDI).
9711 and runs the specified <var>command</var>,
9712 interpreting the entirety of the rest of the command
9713 line as a command to pass straight to exec, in the
9714 manner that <tt>xterm</tt> does.
9718 Support the command-line option <tt>-T
9719 <var>title</var></tt>, which creates a new terminal
9720 window with the window title <var>title</var>.
9727 <heading>Packages providing a window manager</heading>
9730 Packages that provide a window manager should declare in
9731 their <tt>Provides</tt> control field that they provide the
9732 virtual package <tt>x-window-manager</tt>. They should also
9733 register themselves as an alternative for
9734 <file>/usr/bin/x-window-manager</file>, with a priority
9735 calculated as follows:
9736 <list compact="compact">
9738 Start with a priority of 20.
9742 If the window manager supports the Debian menu
9743 system, add 20 points if this support is available
9744 in the package's default configuration (i.e., no
9745 configuration files belonging to the system or user
9746 have to be edited to activate the feature); if
9747 configuration files must be modified, add only 10
9753 If the window manager complies with <url
9754 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9755 name="The Window Manager Specification Project">,
9756 written by the <url id="http://www.freedesktop.org/wiki/"
9757 name="Free Desktop Group">, add 40 points.
9761 If the window manager permits the X session to be
9762 restarted using a <em>different</em> window manager
9763 (without killing the X server) in its default
9764 configuration, add 10 points; otherwise add none.
9767 That alternative should have a slave alternative
9768 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9769 pointing to the corresponding manual page.
9774 <heading>Packages providing fonts</heading>
9777 Packages that provide fonts for the X Window
9779 For the purposes of Debian Policy, a "font for the X
9780 Window System" is one which is accessed via X protocol
9781 requests. Fonts for the Linux console, for PostScript
9782 renderer, or any other purpose, do not fit this
9783 definition. Any tool which makes such fonts available
9784 to the X Window System, however, must abide by this
9787 must do a number of things to ensure that they are both
9788 available without modification of the X or font server
9789 configuration, and that they do not corrupt files used by
9790 other font packages to register information about
9794 Fonts of any type supported by the X Window System
9795 must be in a separate binary package from any
9796 executables, libraries, or documentation (except
9797 that specific to the fonts shipped, such as their
9798 license information). If one or more of the fonts
9799 so packaged are necessary for proper operation of
9800 the package with which they are associated the font
9801 package may be Recommended; if the fonts merely
9802 provide an enhancement, a Suggests relationship may
9803 be used. Packages must not Depend on font
9805 This is because the X server may retrieve fonts
9806 from the local file system or over the network
9807 from an X font server; the Debian package system
9808 is empowered to deal only with the local
9814 BDF fonts must be converted to PCF fonts with the
9815 <prgn>bdftopcf</prgn> utility (available in the
9816 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9817 placed in a directory that corresponds to their
9819 <list compact="compact">
9821 100 dpi fonts must be placed in
9822 <file>/usr/share/fonts/X11/100dpi/</file>.
9826 75 dpi fonts must be placed in
9827 <file>/usr/share/fonts/X11/75dpi/</file>.
9831 Character-cell fonts, cursor fonts, and other
9832 low-resolution fonts must be placed in
9833 <file>/usr/share/fonts/X11/misc/</file>.
9839 Type 1 fonts must be placed in
9840 <file>/usr/share/fonts/X11/Type1/</file>. If font
9841 metric files are available, they must be placed here
9846 Subdirectories of <file>/usr/share/fonts/X11/</file>
9847 other than those listed above must be neither
9848 created nor used. (The <file>PEX</file>, <file>CID</file>,
9849 <file>Speedo</file>, and <file>cyrillic</file> directories
9850 are excepted for historical reasons, but installation of
9851 files into these directories remains discouraged.)
9855 Font packages may, instead of placing files directly
9856 in the X font directories listed above, provide
9857 symbolic links in that font directory pointing to
9858 the files' actual location in the filesystem. Such
9859 a location must comply with the FHS.
9863 Font packages should not contain both 75dpi and
9864 100dpi versions of a font. If both are available,
9865 they should be provided in separate binary packages
9866 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9867 the names of the packages containing the
9868 corresponding fonts.
9872 Fonts destined for the <file>misc</file> subdirectory
9873 should not be included in the same package as 75dpi
9874 or 100dpi fonts; instead, they should be provided in
9875 a separate package with <tt>-misc</tt> appended to
9880 Font packages must not provide the files
9881 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9882 <file>fonts.scale</file> in a font directory:
9885 <file>fonts.dir</file> files must not be provided at all.
9889 <file>fonts.alias</file> and <file>fonts.scale</file>
9890 files, if needed, should be provided in the
9892 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9893 where <var>fontdir</var> is the name of the
9895 <file>/usr/share/fonts/X11/</file> where the
9896 package's corresponding fonts are stored
9897 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9898 <var>package</var> is the name of the package
9899 that provides these fonts, and
9900 <var>extension</var> is either <tt>scale</tt>
9901 or <tt>alias</tt>, whichever corresponds to
9908 Font packages must declare a dependency on
9909 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9910 or <tt>Pre-Depends</tt> control field.
9914 Font packages that provide one or more
9915 <file>fonts.scale</file> files as described above must
9916 invoke <prgn>update-fonts-scale</prgn> on each
9917 directory into which they installed fonts
9918 <em>before</em> invoking
9919 <prgn>update-fonts-dir</prgn> on that directory.
9920 This invocation must occur in both the
9921 <prgn>postinst</prgn> (for all arguments) and
9922 <prgn>postrm</prgn> (for all arguments except
9923 <tt>upgrade</tt>) scripts.
9927 Font packages that provide one or more
9928 <file>fonts.alias</file> files as described above must
9929 invoke <prgn>update-fonts-alias</prgn> on each
9930 directory into which they installed fonts. This
9931 invocation must occur in both the
9932 <prgn>postinst</prgn> (for all arguments) and
9933 <prgn>postrm</prgn> (for all arguments except
9934 <tt>upgrade</tt>) scripts.
9938 Font packages must invoke
9939 <prgn>update-fonts-dir</prgn> on each directory into
9940 which they installed fonts. This invocation must
9941 occur in both the <prgn>postinst</prgn> (for all
9942 arguments) and <prgn>postrm</prgn> (for all
9943 arguments except <tt>upgrade</tt>) scripts.
9947 Font packages must not provide alias names for the
9948 fonts they include which collide with alias names
9949 already in use by fonts already packaged.
9953 Font packages must not provide fonts with the same
9954 XLFD registry name as another font already packaged.
9960 <sect1 id="appdefaults">
9961 <heading>Application defaults files</heading>
9964 Application defaults files must be installed in the
9965 directory <file>/etc/X11/app-defaults/</file> (use of a
9966 localized subdirectory of <file>/etc/X11/</file> as described
9967 in the <em>X Toolkit Intrinsics - C Language
9968 Interface</em> manual is also permitted). They must be
9969 registered as <tt>conffile</tt>s or handled as
9970 configuration files.
9974 Customization of programs' X resources may also be
9975 supported with the provision of a file with the same name
9976 as that of the package placed in
9977 the <file>/etc/X11/Xresources/</file> directory, which
9978 must be registered as a <tt>conffile</tt> or handled as a
9979 configuration file.<footnote>
9980 Note that this mechanism is not the same as using
9981 app-defaults; app-defaults are tied to the client
9982 binary on the local file system, whereas X resources
9983 are stored in the X server and affect all connecting
9990 <heading>Installation directory issues</heading>
9993 Historically, packages using the X Window System used a
9994 separate set of installation directories from other packages.
9995 This practice has been discontinued and packages using the X
9996 Window System should now generally be installed in the same
9997 directories as any other package. Specifically, packages must
9998 not install files under the <file>/usr/X11R6/</file> directory
9999 and the <file>/usr/X11R6/</file> directory hierarchy should be
10000 regarded as obsolete.
10004 Include files previously installed under
10005 <file>/usr/X11R6/include/X11/</file> should be installed into
10006 <file>/usr/include/X11/</file>. For files previously
10007 installed into subdirectories of
10008 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10009 determine if subdirectories of <file>/usr/lib/</file> and
10010 <file>/usr/share/</file> can be used. If not, a subdirectory
10011 of <file>/usr/lib/X11/</file> should be used.
10015 Configuration files for window, display, or session managers
10016 or other applications that are tightly integrated with the X
10017 Window System may be placed in a subdirectory
10018 of <file>/etc/X11/</file> corresponding to the package name.
10019 Other X Window System applications should use
10020 the <file>/etc/</file> directory unless otherwise mandated by
10021 policy (such as for <ref id="appdefaults">).
10027 <heading>Perl programs and modules</heading>
10030 Perl programs and modules should follow the current Perl policy.
10034 The Perl policy can be found in the <tt>perl-policy</tt>
10035 files in the <tt>debian-policy</tt> package.
10036 It is also available from the Debian web mirrors at
10037 <tt><url name="/doc/packaging-manuals/perl-policy/"
10038 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10043 <heading>Emacs lisp programs</heading>
10046 Please refer to the "Debian Emacs Policy" for details of how to
10047 package emacs lisp programs.
10051 The Emacs policy is available in
10052 <file>debian-emacs-policy.gz</file> of the
10053 <package>emacsen-common</package> package.
10054 It is also available from the Debian web mirrors at
10055 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10056 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10061 <heading>Games</heading>
10064 The permissions on <file>/var/games</file> are mode 755, owner
10065 <tt>root</tt> and group <tt>root</tt>.
10069 Each game decides on its own security policy.</p>
10072 Games which require protected, privileged access to
10073 high-score files, saved games, etc., may be made
10074 set-<em>group</em>-id (mode 2755) and owned by
10075 <tt>root:games</tt>, and use files and directories with
10076 appropriate permissions (770 <tt>root:games</tt>, for
10077 example). They must not be made
10078 set-<em>user</em>-id, as this causes security problems. (If
10079 an attacker can subvert any set-user-id game they can
10080 overwrite the executable of any other, causing other players
10081 of these games to run a Trojan horse program. With a
10082 set-group-id game the attacker only gets access to less
10083 important game data, and if they can get at the other
10084 players' accounts at all it will take considerably more
10088 Some packages, for example some fortune cookie programs, are
10089 configured by the upstream authors to install with their
10090 data files or other static information made unreadable so
10091 that they can only be accessed through set-id programs
10092 provided. You should not do this in a Debian package: anyone can
10093 download the <file>.deb</file> file and read the data from it,
10094 so there is no point making the files unreadable. Not
10095 making the files unreadable also means that you don't have
10096 to make so many programs set-id, which reduces the risk of a
10100 As described in the FHS, binaries of games should be
10101 installed in the directory <file>/usr/games</file>. This also
10102 applies to games that use the X Window System. Manual pages
10103 for games (X and non-X games) should be installed in
10104 <file>/usr/share/man/man6</file>.</p>
10110 <heading>Documentation</heading>
10113 <heading>Manual pages</heading>
10116 You should install manual pages in <prgn>nroff</prgn> source
10117 form, in appropriate places under <file>/usr/share/man</file>.
10118 You should only use sections 1 to 9 (see the FHS for more
10119 details). You must not install a pre-formatted "cat page".
10123 Each program, utility, and function should have an
10124 associated manual page included in the same package. It is
10125 suggested that all configuration files also have a manual
10126 page included as well. Manual pages for protocols and other
10127 auxiliary things are optional.
10131 If no manual page is available, this is considered as a bug
10132 and should be reported to the Debian Bug Tracking System (the
10133 maintainer of the package is allowed to write this bug report
10134 themselves, if they so desire). Do not close the bug report
10135 until a proper man page is available.<footnote>
10136 It is not very hard to write a man page. See the
10137 <url id="http://www.schweikhardt.net/man_page_howto.html"
10138 name="Man-Page-HOWTO">,
10139 <manref name="man" section="7">, the examples created
10140 by <prgn>dh_make</prgn>, the helper
10141 program <prgn>help2man</prgn>, or the
10142 directory <file>/usr/share/doc/man-db/examples</file>.
10147 You may forward a complaint about a missing man page to the
10148 upstream authors, and mark the bug as forwarded in the
10149 Debian bug tracking system. Even though the GNU Project do
10150 not in general consider the lack of a man page to be a bug,
10151 we do; if they tell you that they don't consider it a bug
10152 you should leave the bug in our bug tracking system open
10157 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10161 If one man page needs to be accessible via several names it
10162 is better to use a symbolic link than the <file>.so</file>
10163 feature, but there is no need to fiddle with the relevant
10164 parts of the upstream source to change from <file>.so</file> to
10165 symlinks: don't do it unless it's easy. You should not
10166 create hard links in the manual page directories, nor put
10167 absolute filenames in <file>.so</file> directives. The filename
10168 in a <file>.so</file> in a man page should be relative to the
10169 base of the man page tree (usually
10170 <file>/usr/share/man</file>). If you do not create any links
10171 (whether symlinks, hard links, or <tt>.so</tt> directives)
10172 in the file system to the alternate names of the man page,
10173 then you should not rely on <prgn>man</prgn> finding your
10174 man page under those names based solely on the information in
10175 the man page's header.<footnote>
10176 Supporting this in <prgn>man</prgn> often requires
10177 unreasonable processing time to find a manual page or to
10178 report that none exists, and moves knowledge into man's
10179 database that would be better left in the file system.
10180 This support is therefore deprecated and will cease to
10181 be present in the future.
10186 Manual pages in locale-specific subdirectories of
10187 <file>/usr/share/man</file> should use either UTF-8 or the usual
10188 legacy encoding for that language (normally the one corresponding
10189 to the shortest relevant locale name in
10190 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10191 <file>/usr/share/man/fr</file> should use either UTF-8 or
10192 ISO-8859-1.<footnote>
10193 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10194 use. In future, all manual pages will be required to use
10200 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10201 included in the subdirectory name unless it indicates a
10202 significant difference in the language, as this excludes
10203 speakers of the language in other countries.<footnote>
10204 At the time of writing, Chinese and Portuguese are the main
10205 languages with such differences, so <file>pt_BR</file>,
10206 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10211 If a localized version of a manual page is provided, it should
10212 either be up-to-date or it should be obvious to the reader that
10213 it is outdated and the original manual page should be used
10214 instead. This can be done either by a note at the beginning of
10215 the manual page or by showing the missing or changed portions in
10216 the original language instead of the target language.
10221 <heading>Info documents</heading>
10224 Info documents should be installed in <file>/usr/share/info</file>.
10225 They should be compressed with <tt>gzip -9</tt>.
10229 The <prgn>install-info</prgn> program maintains a directory of
10230 installed info documents in <file>/usr/share/info/dir</file> for
10231 the use of info readers.<footnote>
10232 It was previously necessary for packages installing info
10233 documents to run <prgn>install-info</prgn> from maintainer
10234 scripts. This is no longer necessary. The installation
10235 system now uses dpkg triggers.
10237 This file must not be included in packages. Packages containing
10238 info documents should depend on <tt>dpkg (>= 1.15.4) |
10239 install-info</tt> to ensure that the directory file is properly
10240 rebuilt during partial upgrades from Debian 5.0 (lenny) and
10245 Info documents should contain section and directory entry
10246 information in the document for the use
10247 of <prgn>install-info</prgn>. The section should be specified
10248 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10249 space and the section of this info page. The directory entry or
10250 entries should be included between
10251 a <tt>START-INFO-DIR-ENTRY</tt> line and
10252 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10254 INFO-DIR-SECTION Individual utilities
10255 START-INFO-DIR-ENTRY
10256 * example: (example). An example info directory entry.
10259 To determine which section to use, you should look
10260 at <file>/usr/share/info/dir</file> on your system and choose
10261 the most relevant (or create a new section if none of the
10262 current sections are relevant).<footnote>
10263 Normally, info documents are generated from Texinfo source.
10264 To include this information in the generated info document, if
10265 it is absent, add commands like:
10267 @dircategory Individual utilities
10269 * example: (example). An example info directory entry.
10272 to the Texinfo source of the document and ensure that the info
10273 documents are rebuilt from source during the package build.
10279 <heading>Additional documentation</heading>
10282 Any additional documentation that comes with the package may
10283 be installed at the discretion of the package maintainer.
10284 Plain text documentation should be installed in the directory
10285 <file>/usr/share/doc/<var>package</var></file>, where
10286 <var>package</var> is the name of the package, and
10287 compressed with <tt>gzip -9</tt> unless it is small.
10291 If a package comes with large amounts of documentation which
10292 many users of the package will not require you should create
10293 a separate binary package to contain it, so that it does not
10294 take up disk space on the machines of users who do not need
10295 or want it installed.</p>
10298 It is often a good idea to put text information files
10299 (<file>README</file>s, changelogs, and so forth) that come with
10300 the source package in <file>/usr/share/doc/<var>package</var></file>
10301 in the binary package. However, you don't need to install
10302 the instructions for building and installing the package, of
10306 Packages must not require the existence of any files in
10307 <file>/usr/share/doc/</file> in order to function
10309 The system administrator should be able to
10310 delete files in <file>/usr/share/doc/</file> without causing
10311 any programs to break.
10313 Any files that are referenced by programs but are also
10314 useful as stand alone documentation should be installed under
10315 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10316 <file>/usr/share/doc/<var>package</var></file>.
10320 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10321 link to another directory in <file>/usr/share/doc</file> only if
10322 the two packages both come from the same source and the
10323 first package Depends on the second.<footnote>
10325 Please note that this does not override the section on
10326 changelog files below, so the file
10327 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10328 must refer to the changelog for the current version of
10329 <var>package</var> in question. In practice, this means
10330 that the sources of the target and the destination of the
10331 symlink must be the same (same source package and
10338 Former Debian releases placed all additional documentation
10339 in <file>/usr/doc/<var>package</var></file>. This has been
10340 changed to <file>/usr/share/doc/<var>package</var></file>,
10341 and packages must not put documentation in the directory
10342 <file>/usr/doc/<var>package</var></file>. <footnote>
10343 At this phase of the transition, we no longer require a
10344 symbolic link in <file>/usr/doc/</file>. At a later point,
10345 policy shall change to make the symbolic links a bug.
10351 <heading>Preferred documentation formats</heading>
10354 The unification of Debian documentation is being carried out
10358 If your package comes with extensive documentation in a
10359 markup format that can be converted to various other formats
10360 you should if possible ship HTML versions in a binary
10361 package, in the directory
10362 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10363 its subdirectories.<footnote>
10364 The rationale: The important thing here is that HTML
10365 docs should be available in <em>some</em> package, not
10366 necessarily in the main binary package.
10371 Other formats such as PostScript may be provided at the
10372 package maintainer's discretion.
10376 <sect id="copyrightfile">
10377 <heading>Copyright information</heading>
10380 Every package must be accompanied by a verbatim copy of its
10381 copyright information and distribution license in the file
10382 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10383 file must neither be compressed nor be a symbolic link.
10387 In addition, the copyright file must say where the upstream
10388 sources (if any) were obtained, and should name the original
10393 Packages in the <em>contrib</em> or <em>non-free</em> archive
10394 areas should state in the copyright file that the package is not
10395 part of the Debian distribution and briefly explain why.
10399 A copy of the file which will be installed in
10400 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10401 be in <file>debian/copyright</file> in the source package.
10405 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10406 link to another directory in <file>/usr/share/doc</file> only if
10407 the two packages both come from the same source and the
10408 first package Depends on the second. These rules are important
10409 because <file>copyright</file> files must be extractable by
10414 Packages distributed under the Apache license (version 2.0), the
10415 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10416 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10417 1.3) should refer to the corresponding files
10418 under <file>/usr/share/common-licenses</file>,<footnote>
10421 <file>/usr/share/common-licenses/Apache-2.0</file>,
10422 <file>/usr/share/common-licenses/Artistic</file>,
10423 <file>/usr/share/common-licenses/GPL-1</file>,
10424 <file>/usr/share/common-licenses/GPL-2</file>,
10425 <file>/usr/share/common-licenses/GPL-3</file>,
10426 <file>/usr/share/common-licenses/LGPL-2</file>,
10427 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10428 <file>/usr/share/common-licenses/LGPL-3</file>,
10429 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10430 <file>/usr/share/common-licenses/GFDL-1.3</file>
10431 respectively. The University of California BSD license is
10432 also included in <package>base-files</package> as
10433 <file>/usr/share/common-licenses/BSD</file>, but given the
10434 brevity of this license, its specificity to code whose
10435 copyright is held by the Regents of the University of
10436 California, and the frequency of minor wording changes, its
10437 text should be included in the copyright file rather than
10438 referencing this file.
10440 </footnote> rather than quoting them in the copyright
10445 You should not use the copyright file as a general <file>README</file>
10446 file. If your package has such a file it should be
10447 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10448 <file>README.Debian</file> or some other appropriate place.
10451 <sect1 id="copyrightformat">
10452 <heading>Machine-readable copyright information</heading>
10455 A specification for a standard, machine-readable format
10456 for <file>debian/copyright</file> files is maintained as part
10457 of the <package>debian-policy</package> package. This
10458 document may be found in the <file>copyright-format</file>
10459 files in the <package>debian-policy</package> package. It is
10460 also available from the Debian web mirrors at
10461 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10462 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10466 Use of this format is optional.
10472 <heading>Examples</heading>
10475 Any examples (configurations, source files, whatever),
10476 should be installed in a directory
10477 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10478 files should not be referenced by any program: they're there
10479 for the benefit of the system administrator and users as
10480 documentation only. Architecture-specific example files
10481 should be installed in a directory
10482 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10484 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10485 latter directory itself may be a symbolic link to the
10490 If the purpose of a package is to provide examples, then the
10491 example files may be installed into
10492 <file>/usr/share/doc/<var>package</var></file>.
10496 <sect id="changelogs">
10497 <heading>Changelog files</heading>
10500 Packages that are not Debian-native must contain a
10501 compressed copy of the <file>debian/changelog</file> file from
10502 the Debian source tree in
10503 <file>/usr/share/doc/<var>package</var></file> with the name
10504 <file>changelog.Debian.gz</file>.
10508 If an upstream changelog is available, it should be accessible as
10509 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10510 plain text. If the upstream changelog is distributed in
10511 HTML, it should be made available in that form as
10512 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10513 and a plain text <file>changelog.gz</file> should be generated
10514 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10515 the upstream changelog files do not already conform to this
10516 naming convention, then this may be achieved either by
10517 renaming the files, or by adding a symbolic link, at the
10518 maintainer's discretion.<footnote>
10519 Rationale: People should not have to look in places for
10520 upstream changelogs merely because they are given
10521 different names or are distributed in HTML format.
10526 All of these files should be installed compressed using
10527 <tt>gzip -9</tt>, as they will become large with time even
10528 if they start out small.
10532 If the package has only one changelog which is used both as
10533 the Debian changelog and the upstream one because there is
10534 no separate upstream maintainer then that changelog should
10535 usually be installed as
10536 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10537 there is a separate upstream maintainer, but no upstream
10538 changelog, then the Debian changelog should still be called
10539 <file>changelog.Debian.gz</file>.
10543 For details about the format and contents of the Debian
10544 changelog file, please see <ref id="dpkgchangelog">.
10549 <appendix id="pkg-scope">
10550 <heading>Introduction and scope of these appendices</heading>
10553 These appendices are taken essentially verbatim from the
10554 now-deprecated Packaging Manual, version 3.2.1.0. They are
10555 the chapters which are likely to be of use to package
10556 maintainers and which have not already been included in the
10557 policy document itself. Most of these sections are very likely
10558 not relevant to policy; they should be treated as
10559 documentation for the packaging system. Please note that these
10560 appendices are included for convenience, and for historical
10561 reasons: they used to be part of policy package, and they have
10562 not yet been incorporated into dpkg documentation. However,
10563 they still have value, and hence they are presented here.
10567 They have not yet been checked to ensure that they are
10568 compatible with the contents of policy, and if there are any
10569 contradictions, the version in the main policy document takes
10570 precedence. The remaining chapters of the old Packaging
10571 Manual have also not been read in detail to ensure that there
10572 are not parts which have been left out. Both of these will be
10573 done in due course.
10577 Certain parts of the Packaging manual were integrated into the
10578 Policy Manual proper, and removed from the appendices. Links
10579 have been placed from the old locations to the new ones.
10583 <prgn>dpkg</prgn> is a suite of programs for creating binary
10584 package files and installing and removing them on Unix
10586 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10587 work on or be ported to other systems.
10592 The binary packages are designed for the management of
10593 installed executable programs (usually compiled binaries) and
10594 their associated data, though source code examples and
10595 documentation are provided as part of some packages.</p>
10598 This manual describes the technical aspects of creating Debian
10599 binary packages (<file>.deb</file> files). It documents the
10600 behavior of the package management programs
10601 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10602 they interact with packages.</p>
10605 It also documents the interaction between
10606 <prgn>dselect</prgn>'s core and the access method scripts it
10607 uses to actually install the selected packages, and describes
10608 how to create a new access method.</p>
10611 This manual does not go into detail about the options and
10612 usage of the package building and installation tools. It
10613 should therefore be read in conjunction with those programs'
10618 The utility programs which are provided with <prgn>dpkg</prgn>
10619 for managing various system configuration and similar issues,
10620 such as <prgn>update-rc.d</prgn> and
10621 <prgn>install-info</prgn>, are not described in detail here -
10622 please see their man pages.
10626 It is assumed that the reader is reasonably familiar with the
10627 <prgn>dpkg</prgn> System Administrators' manual.
10628 Unfortunately this manual does not yet exist.
10632 The Debian version of the FSF's GNU hello program is provided as
10633 an example for people wishing to create Debian packages. However,
10634 while the examples are helpful, they do not replace the need to
10635 read and follow the Policy and Programmer's Manual.</p>
10638 <appendix id="pkg-binarypkg">
10639 <heading>Binary packages (from old Packaging Manual)</heading>
10642 The binary package has two main sections. The first part
10643 consists of various control information files and scripts used
10644 by <prgn>dpkg</prgn> when installing and removing. See <ref
10645 id="pkg-controlarea">.
10649 The second part is an archive containing the files and
10650 directories to be installed.
10654 In the future binary packages may also contain other
10655 components, such as checksums and digital signatures. The
10656 format for the archive is described in full in the
10657 <file>deb(5)</file> man page.
10661 <sect id="pkg-bincreating"><heading>Creating package files -
10662 <prgn>dpkg-deb</prgn>
10666 All manipulation of binary package files is done by
10667 <prgn>dpkg-deb</prgn>; it's the only program that has
10668 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10669 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10670 will spot that the options requested are appropriate to
10671 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10676 In order to create a binary package you must make a
10677 directory tree which contains all the files and directories
10678 you want to have in the file system data part of the package.
10679 In Debian-format source packages this directory is usually
10680 <file>debian/tmp</file>, relative to the top of the package's
10685 They should have the locations (relative to the root of the
10686 directory tree you're constructing) ownerships and
10687 permissions which you want them to have on the system when
10688 they are installed.
10692 With current versions of <prgn>dpkg</prgn> the uid/username
10693 and gid/groupname mappings for the users and groups being
10694 used should be the same on the system where the package is
10695 built and the one where it is installed.
10699 You need to add one special directory to the root of the
10700 miniature file system tree you're creating:
10701 <prgn>DEBIAN</prgn>. It should contain the control
10702 information files, notably the binary package control file
10703 (see <ref id="pkg-controlfile">).
10707 The <prgn>DEBIAN</prgn> directory will not appear in the
10708 file system archive of the package, and so won't be installed
10709 by <prgn>dpkg</prgn> when the package is unpacked.
10713 When you've prepared the package, you should invoke:
10715 dpkg --build <var>directory</var>
10720 This will build the package in
10721 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10722 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10723 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10724 build the package.)
10728 See the man page <manref name="dpkg-deb" section="8"> for details of how
10729 to examine the contents of this newly-created file. You may find the
10730 output of following commands enlightening:
10732 dpkg-deb --info <var>filename</var>.deb
10733 dpkg-deb --contents <var>filename</var>.deb
10734 dpkg --contents <var>filename</var>.deb
10736 To view the copyright file for a package you could use this command:
10738 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10743 <sect id="pkg-controlarea">
10744 <heading>Package control information files</heading>
10747 The control information portion of a binary package is a
10748 collection of files with names known to <prgn>dpkg</prgn>.
10749 It will treat the contents of these files specially - some
10750 of them contain information used by <prgn>dpkg</prgn> when
10751 installing or removing the package; others are scripts which
10752 the package maintainer wants <prgn>dpkg</prgn> to run.
10756 It is possible to put other files in the package control
10757 information file area, but this is not generally a good idea
10758 (though they will largely be ignored).
10762 Here is a brief list of the control information files supported
10763 by <prgn>dpkg</prgn> and a summary of what they're used for.
10768 <tag><tt>control</tt>
10771 This is the key description file used by
10772 <prgn>dpkg</prgn>. It specifies the package's name
10773 and version, gives its description for the user,
10774 states its relationships with other packages, and so
10775 forth. See <ref id="sourcecontrolfiles"> and
10776 <ref id="binarycontrolfiles">.
10780 It is usually generated automatically from information
10781 in the source package by the
10782 <prgn>dpkg-gencontrol</prgn> program, and with
10783 assistance from <prgn>dpkg-shlibdeps</prgn>.
10784 See <ref id="pkg-sourcetools">.
10788 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10793 These are executable files (usually scripts) which
10794 <prgn>dpkg</prgn> runs during installation, upgrade
10795 and removal of packages. They allow the package to
10796 deal with matters which are particular to that package
10797 or require more complicated processing than that
10798 provided by <prgn>dpkg</prgn>. Details of when and
10799 how they are called are in <ref id="maintainerscripts">.
10803 It is very important to make these scripts idempotent.
10804 See <ref id="idempotency">.
10808 The maintainer scripts are not guaranteed to run with a
10809 controlling terminal and may not be able to interact with
10810 the user. See <ref id="controllingterminal">.
10814 <tag><tt>conffiles</tt>
10817 This file contains a list of configuration files which
10818 are to be handled automatically by <prgn>dpkg</prgn>
10819 (see <ref id="pkg-conffiles">). Note that not necessarily
10820 every configuration file should be listed here.
10823 <tag><tt>shlibs</tt>
10826 This file contains a list of the shared libraries
10827 supplied by the package, with dependency details for
10828 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10829 when it determines what dependencies are required in a
10830 package control file. The <tt>shlibs</tt> file format
10831 is described on <ref id="shlibs">.
10836 <sect id="pkg-controlfile">
10837 <heading>The main control information file: <tt>control</tt></heading>
10840 The most important control information file used by
10841 <prgn>dpkg</prgn> when it installs a package is
10842 <tt>control</tt>. It contains all the package's "vital
10847 The binary package control files of packages built from
10848 Debian sources are made by a special tool,
10849 <prgn>dpkg-gencontrol</prgn>, which reads
10850 <file>debian/control</file> and <file>debian/changelog</file> to
10851 find the information it needs. See <ref id="pkg-sourcepkg"> for
10856 The fields in binary package control files are listed in
10857 <ref id="binarycontrolfiles">.
10861 A description of the syntax of control files and the purpose
10862 of the fields is available in <ref id="controlfields">.
10867 <heading>Time Stamps</heading>
10870 See <ref id="timestamps">.
10875 <appendix id="pkg-sourcepkg">
10876 <heading>Source packages (from old Packaging Manual) </heading>
10879 The Debian binary packages in the distribution are generated
10880 from Debian sources, which are in a special format to assist
10881 the easy and automatic building of binaries.
10884 <sect id="pkg-sourcetools">
10885 <heading>Tools for processing source packages</heading>
10888 Various tools are provided for manipulating source packages;
10889 they pack and unpack sources and help build of binary
10890 packages and help manage the distribution of new versions.
10894 They are introduced and typical uses described here; see
10895 <manref name="dpkg-source" section="1"> for full
10896 documentation about their arguments and operation.
10900 For examples of how to construct a Debian source package,
10901 and how to use those utilities that are used by Debian
10902 source packages, please see the <prgn>hello</prgn> example
10906 <sect1 id="pkg-dpkg-source">
10908 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10913 This program is frequently used by hand, and is also
10914 called from package-independent automated building scripts
10915 such as <prgn>dpkg-buildpackage</prgn>.
10919 To unpack a package it is typically invoked with
10921 dpkg-source -x <var>.../path/to/filename</var>.dsc
10926 with the <file><var>filename</var>.tar.gz</file> and
10927 <file><var>filename</var>.diff.gz</file> (if applicable) in
10928 the same directory. It unpacks into
10929 <file><var>package</var>-<var>version</var></file>, and if
10931 <file><var>package</var>-<var>version</var>.orig</file>, in
10932 the current directory.
10936 To create a packed source archive it is typically invoked:
10938 dpkg-source -b <var>package</var>-<var>version</var>
10943 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10944 <file>.diff.gz</file> (if appropriate) in the current
10945 directory. <prgn>dpkg-source</prgn> does not clean the
10946 source tree first - this must be done separately if it is
10951 See also <ref id="pkg-sourcearchives">.</p>
10955 <sect1 id="pkg-dpkg-buildpackage">
10957 <prgn>dpkg-buildpackage</prgn> - overall package-building
10962 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10963 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10964 targets <tt>clean</tt>, <tt>build</tt> and
10965 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10966 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10967 source and binary package upload.
10971 It is usually invoked by hand from the top level of the
10972 built or unbuilt source directory. It may be invoked with
10973 no arguments; useful arguments include:
10974 <taglist compact="compact">
10975 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10978 Do not sign the <tt>.changes</tt> file or the
10979 source package <tt>.dsc</tt> file, respectively.</p>
10981 <tag><tt>-p<var>sign-command</var></tt></tag>
10984 Invoke <var>sign-command</var> instead of finding
10985 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10986 <var>sign-command</var> must behave just like
10987 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10989 <tag><tt>-r<var>root-command</var></tt></tag>
10992 When root privilege is required, invoke the command
10993 <var>root-command</var>. <var>root-command</var>
10994 should invoke its first argument as a command, from
10995 the <prgn>PATH</prgn> if necessary, and pass its
10996 second and subsequent arguments to the command it
10997 calls. If no <var>root-command</var> is supplied
10998 then <var>dpkg-buildpackage</var> will use
10999 the <prgn>fakeroot</prgn> command, which is sufficient
11000 to build most packages without actually requiring root
11003 <tag><tt>-b</tt>, <tt>-B</tt></tag>
11006 Two types of binary-only build and upload - see
11007 <manref name="dpkg-source" section="1">.
11014 <sect1 id="pkg-dpkg-gencontrol">
11016 <prgn>dpkg-gencontrol</prgn> - generates binary package
11021 This program is usually called from <file>debian/rules</file>
11022 (see <ref id="pkg-sourcetree">) in the top level of the source
11027 This is usually done just before the files and directories in the
11028 temporary directory tree where the package is being built have their
11029 permissions and ownerships set and the package is constructed using
11030 <prgn>dpkg-deb/</prgn>
11032 This is so that the control file which is produced has
11033 the right permissions
11038 <prgn>dpkg-gencontrol</prgn> must be called after all the
11039 files which are to go into the package have been placed in
11040 the temporary build directory, so that its calculation of
11041 the installed size of a package is correct.
11045 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11046 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11047 variable substitutions created by
11048 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11053 For a package which generates only one binary package, and
11054 which builds it in <file>debian/tmp</file> relative to the top
11055 of the source package, it is usually sufficient to call
11056 <prgn>dpkg-gencontrol</prgn>.
11060 Sources which build several binaries will typically need
11063 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11064 </example> The <tt>-P</tt> tells
11065 <prgn>dpkg-gencontrol</prgn> that the package is being
11066 built in a non-default directory, and the <tt>-p</tt>
11067 tells it which package's control file should be generated.
11071 <prgn>dpkg-gencontrol</prgn> also adds information to the
11072 list of files in <file>debian/files</file>, for the benefit of
11073 (for example) a future invocation of
11074 <prgn>dpkg-genchanges</prgn>.</p>
11077 <sect1 id="pkg-dpkg-shlibdeps">
11079 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11084 See <manref name="dpkg-shlibdeps" section="1">.
11088 <sect1 id="pkg-dpkg-distaddfile">
11090 <prgn>dpkg-distaddfile</prgn> - adds a file to
11091 <file>debian/files</file>
11095 Some packages' uploads need to include files other than
11096 the source and binary package files.
11100 <prgn>dpkg-distaddfile</prgn> adds a file to the
11101 <file>debian/files</file> file so that it will be included in
11102 the <file>.changes</file> file when
11103 <prgn>dpkg-genchanges</prgn> is run.
11107 It is usually invoked from the <tt>binary</tt> target of
11108 <file>debian/rules</file>:
11110 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11112 The <var>filename</var> is relative to the directory where
11113 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11114 is usually the directory above the top level of the source
11115 tree. The <file>debian/rules</file> target should put the
11116 file there just before or just after calling
11117 <prgn>dpkg-distaddfile</prgn>.
11121 The <var>section</var> and <var>priority</var> are passed
11122 unchanged into the resulting <file>.changes</file> file.
11127 <sect1 id="pkg-dpkg-genchanges">
11129 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11130 upload control file
11134 This program is usually called by package-independent
11135 automatic building scripts such as
11136 <prgn>dpkg-buildpackage</prgn>, but it may also be called
11141 It is usually called in the top level of a built source
11142 tree, and when invoked with no arguments will print out a
11143 straightforward <file>.changes</file> file based on the
11144 information in the source package's changelog and control
11145 file and the binary and source packages which should have
11151 <sect1 id="pkg-dpkg-parsechangelog">
11153 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11154 representation of a changelog
11158 This program is used internally by
11159 <prgn>dpkg-source</prgn> et al. It may also occasionally
11160 be useful in <file>debian/rules</file> and elsewhere. It
11161 parses a changelog, <file>debian/changelog</file> by default,
11162 and prints a control-file format representation of the
11163 information in it to standard output.
11167 <sect1 id="pkg-dpkg-architecture">
11169 <prgn>dpkg-architecture</prgn> - information about the build and
11174 This program can be used manually, but is also invoked by
11175 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
11176 environment or make variables which specify the build and host
11177 architecture for the package building process.
11182 <sect id="pkg-sourcetree">
11183 <heading>The Debian package source tree</heading>
11186 The source archive scheme described later is intended to
11187 allow a Debian package source tree with some associated
11188 control information to be reproduced and transported easily.
11189 The Debian package source tree is a version of the original
11190 program with certain files added for the benefit of the
11191 packaging process, and with any other changes required
11192 made to the rest of the source code and installation
11197 The extra files created for Debian are in the subdirectory
11198 <file>debian</file> of the top level of the Debian package
11199 source tree. They are described below.
11202 <sect1 id="pkg-debianrules">
11203 <heading><file>debian/rules</file> - the main building script</heading>
11206 See <ref id="debianrules">.
11210 <sect1 id="pkg-srcsubstvars">
11211 <heading><file>debian/substvars</file> and variable substitutions</heading>
11214 See <ref id="substvars">.
11220 <heading><file>debian/files</file></heading>
11223 See <ref id="debianfiles">.
11227 <sect1><heading><file>debian/tmp</file>
11231 This is the canonical temporary location for the
11232 construction of binary packages by the <tt>binary</tt>
11233 target. The directory <file>tmp</file> serves as the root of
11234 the file system tree as it is being constructed (for
11235 example, by using the package's upstream makefiles install
11236 targets and redirecting the output there), and it also
11237 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11238 id="pkg-bincreating">.
11242 If several binary packages are generated from the same
11243 source tree it is usual to use several
11244 <file>debian/tmp<var>something</var></file> directories, for
11245 example <file>tmp-a</file> or <file>tmp-doc</file>.
11249 Whatever <file>tmp</file> directories are created and used by
11250 <tt>binary</tt> must of course be removed by the
11251 <tt>clean</tt> target.</p></sect1>
11255 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11259 As it exists on the FTP site, a Debian source package
11260 consists of three related files. You must have the right
11261 versions of all three to be able to use them.
11266 <tag>Debian source control file - <tt>.dsc</tt></tag>
11268 This file is a control file used by <prgn>dpkg-source</prgn>
11269 to extract a source package.
11270 See <ref id="debiansourcecontrolfiles">.
11274 Original source archive -
11276 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11282 This is a compressed (with <tt>gzip -9</tt>)
11283 <prgn>tar</prgn> file containing the source code from
11284 the upstream authors of the program.
11289 Debian package diff -
11291 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11297 This is a unified context diff (<tt>diff -u</tt>)
11298 giving the changes which are required to turn the
11299 original source into the Debian source. These changes
11300 may only include editing and creating plain files.
11301 The permissions of files, the targets of symbolic
11302 links and the characteristics of special files or
11303 pipes may not be changed and no files may be removed
11308 All the directories in the diff must exist, except the
11309 <file>debian</file> subdirectory of the top of the source
11310 tree, which will be created by
11311 <prgn>dpkg-source</prgn> if necessary when unpacking.
11315 The <prgn>dpkg-source</prgn> program will
11316 automatically make the <file>debian/rules</file> file
11317 executable (see below).</p></item>
11322 If there is no original source code - for example, if the
11323 package is specially prepared for Debian or the Debian
11324 maintainer is the same as the upstream maintainer - the
11325 format is slightly different: then there is no diff, and the
11327 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11328 and preferably contains a directory named
11329 <file><var>package</var>-<var>version</var></file>.
11334 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11337 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11338 Debian source package. However, if it is not available it
11339 is possible to unpack a Debian source archive as follows:
11340 <enumlist compact="compact">
11343 Untar the tarfile, which will create a <file>.orig</file>
11347 <p>Rename the <file>.orig</file> directory to
11348 <file><var>package</var>-<var>version</var></file>.</p>
11352 Create the subdirectory <file>debian</file> at the top of
11353 the source tree.</p>
11355 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11357 <item><p>Untar the tarfile again if you want a copy of the original
11358 source code alongside the Debian version.</p>
11363 It is not possible to generate a valid Debian source archive
11364 without using <prgn>dpkg-source</prgn>. In particular,
11365 attempting to use <prgn>diff</prgn> directly to generate the
11366 <file>.diff.gz</file> file will not work.
11370 <heading>Restrictions on objects in source packages</heading>
11373 The source package may not contain any hard links
11375 This is not currently detected when building source
11376 packages, but only when extracting
11380 Hard links may be permitted at some point in the
11381 future, but would require a fair amount of
11383 </footnote>, device special files, sockets or setuid or
11386 Setgid directories are allowed.
11391 The source packaging tools manage the changes between the
11392 original and Debian source using <prgn>diff</prgn> and
11393 <prgn>patch</prgn>. Turning the original source tree as
11394 included in the <file>.orig.tar.gz</file> into the Debian
11395 package source must not involve any changes which cannot be
11396 handled by these tools. Problematic changes which cause
11397 <prgn>dpkg-source</prgn> to halt with an error when
11398 building the source package are:
11399 <list compact="compact">
11400 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11402 <item><p>Changing the targets of symbolic links.</p>
11404 <item><p>Creating directories, other than <file>debian</file>.</p>
11406 <item><p>Changes to the contents of binary files.</p></item>
11407 </list> Changes which cause <prgn>dpkg-source</prgn> to
11408 print a warning but continue anyway are:
11409 <list compact="compact">
11412 Removing files, directories or symlinks.
11414 Renaming a file is not treated specially - it is
11415 seen as the removal of the old file (which
11416 generates a warning, but is otherwise ignored),
11417 and the creation of the new one.
11423 Changed text files which are missing the usual final
11424 newline (either in the original or the modified
11429 Changes which are not represented, but which are not detected by
11430 <prgn>dpkg-source</prgn>, are:
11431 <list compact="compact">
11432 <item><p>Changing the permissions of files (other than
11433 <file>debian/rules</file>) and directories.</p></item>
11438 The <file>debian</file> directory and <file>debian/rules</file>
11439 are handled specially by <prgn>dpkg-source</prgn> - before
11440 applying the changes it will create the <file>debian</file>
11441 directory, and afterwards it will make
11442 <file>debian/rules</file> world-executable.
11448 <appendix id="pkg-controlfields">
11449 <heading>Control files and their fields (from old Packaging Manual)</heading>
11452 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11453 data in a common format, known as control files. Binary and
11454 source packages have control data as do the <file>.changes</file>
11455 files which control the installation of uploaded files, and
11456 <prgn>dpkg</prgn>'s internal databases are in a similar
11461 <heading>Syntax of control files</heading>
11464 See <ref id="controlsyntax">.
11468 It is important to note that there are several fields which
11469 are optional as far as <prgn>dpkg</prgn> and the related
11470 tools are concerned, but which must appear in every Debian
11471 package, or whose omission may cause problems.
11476 <heading>List of fields</heading>
11479 See <ref id="controlfieldslist">.
11483 This section now contains only the fields that didn't belong
11484 to the Policy manual.
11487 <sect1 id="pkg-f-Filename">
11488 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11491 These fields in <tt>Packages</tt> files give the
11492 filename(s) of (the parts of) a package in the
11493 distribution directories, relative to the root of the
11494 Debian hierarchy. If the package has been split into
11495 several parts the parts are all listed in order, separated
11500 <sect1 id="pkg-f-Size">
11501 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11504 These fields in <file>Packages</file> files give the size (in
11505 bytes, expressed in decimal) and MD5 checksum of the
11506 file(s) which make(s) up a binary package in the
11507 distribution. If the package is split into several parts
11508 the values for the parts are listed in order, separated by
11513 <sect1 id="pkg-f-Status">
11514 <heading><tt>Status</tt></heading>
11517 This field in <prgn>dpkg</prgn>'s status file records
11518 whether the user wants a package installed, removed or
11519 left alone, whether it is broken (requiring
11520 re-installation) or not and what its current state on the
11521 system is. Each of these pieces of information is a
11526 <sect1 id="pkg-f-Config-Version">
11527 <heading><tt>Config-Version</tt></heading>
11530 If a package is not installed or not configured, this
11531 field in <prgn>dpkg</prgn>'s status file records the last
11532 version of the package which was successfully
11537 <sect1 id="pkg-f-Conffiles">
11538 <heading><tt>Conffiles</tt></heading>
11541 This field in <prgn>dpkg</prgn>'s status file contains
11542 information about the automatically-managed configuration
11543 files held by a package. This field should <em>not</em>
11544 appear anywhere in a package!
11549 <heading>Obsolete fields</heading>
11552 These are still recognized by <prgn>dpkg</prgn> but should
11553 not appear anywhere any more.
11555 <taglist compact="compact">
11557 <tag><tt>Revision</tt></tag>
11558 <tag><tt>Package-Revision</tt></tag>
11559 <tag><tt>Package_Revision</tt></tag>
11561 The Debian revision part of the package version was
11562 at one point in a separate control field. This
11563 field went through several names.
11566 <tag><tt>Recommended</tt></tag>
11567 <item>Old name for <tt>Recommends</tt>.</item>
11569 <tag><tt>Optional</tt></tag>
11570 <item>Old name for <tt>Suggests</tt>.</item>
11572 <tag><tt>Class</tt></tag>
11573 <item>Old name for <tt>Priority</tt>.</item>
11582 <appendix id="pkg-conffiles">
11583 <heading>Configuration file handling (from old Packaging Manual)</heading>
11586 <prgn>dpkg</prgn> can do a certain amount of automatic
11587 handling of package configuration files.
11591 Whether this mechanism is appropriate depends on a number of
11592 factors, but basically there are two approaches to any
11593 particular configuration file.
11597 The easy method is to ship a best-effort configuration in the
11598 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11599 handle updates. If the user is unlikely to want to edit the
11600 file, but you need them to be able to without losing their
11601 changes, and a new package with a changed version of the file
11602 is only released infrequently, this is a good approach.
11606 The hard method is to build the configuration file from
11607 scratch in the <prgn>postinst</prgn> script, and to take the
11608 responsibility for fixing any mistakes made in earlier
11609 versions of the package automatically. This will be
11610 appropriate if the file is likely to need to be different on
11614 <sect><heading>Automatic handling of configuration files by
11619 A package may contain a control information file called
11620 <tt>conffiles</tt>. This file should be a list of filenames
11621 of configuration files needing automatic handling, separated
11622 by newlines. The filenames should be absolute pathnames,
11623 and the files referred to should actually exist in the
11628 When a package is upgraded <prgn>dpkg</prgn> will process
11629 the configuration files during the configuration stage,
11630 shortly before it runs the package's <prgn>postinst</prgn>
11635 For each file it checks to see whether the version of the
11636 file included in the package is the same as the one that was
11637 included in the last version of the package (the one that is
11638 being upgraded from); it also compares the version currently
11639 installed on the system with the one shipped with the last
11644 If neither the user nor the package maintainer has changed
11645 the file, it is left alone. If one or the other has changed
11646 their version, then the changed version is preferred - i.e.,
11647 if the user edits their file, but the package maintainer
11648 doesn't ship a different version, the user's changes will
11649 stay, silently, but if the maintainer ships a new version
11650 and the user hasn't edited it the new version will be
11651 installed (with an informative message). If both have
11652 changed their version the user is prompted about the problem
11653 and must resolve the differences themselves.
11657 The comparisons are done by calculating the MD5 message
11658 digests of the files, and storing the MD5 of the file as it
11659 was included in the most recent version of the package.
11663 When a package is installed for the first time
11664 <prgn>dpkg</prgn> will install the file that comes with it,
11665 unless that would mean overwriting a file already on the
11670 However, note that <prgn>dpkg</prgn> will <em>not</em>
11671 replace a conffile that was removed by the user (or by a
11672 script). This is necessary because with some programs a
11673 missing file produces an effect hard or impossible to
11674 achieve in another way, so that a missing file needs to be
11675 kept that way if the user did it.
11679 Note that a package should <em>not</em> modify a
11680 <prgn>dpkg</prgn>-handled conffile in its maintainer
11681 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11682 the user confusing and possibly dangerous options for
11683 conffile update when the package is upgraded.</p>
11686 <sect><heading>Fully-featured maintainer script configuration
11691 For files which contain site-specific information such as
11692 the hostname and networking details and so forth, it is
11693 better to create the file in the package's
11694 <prgn>postinst</prgn> script.
11698 This will typically involve examining the state of the rest
11699 of the system to determine values and other information, and
11700 may involve prompting the user for some information which
11701 can't be obtained some other way.
11705 When using this method there are a couple of important
11706 issues which should be considered:
11710 If you discover a bug in the program which generates the
11711 configuration file, or if the format of the file changes
11712 from one version to the next, you will have to arrange for
11713 the postinst script to do something sensible - usually this
11714 will mean editing the installed configuration file to remove
11715 the problem or change the syntax. You will have to do this
11716 very carefully, since the user may have changed the file,
11717 perhaps to fix the very problem that your script is trying
11718 to deal with - you will have to detect these situations and
11719 deal with them correctly.
11723 If you do go down this route it's probably a good idea to
11724 make the program that generates the configuration file(s) a
11725 separate program in <file>/usr/sbin</file>, by convention called
11726 <file><var>package</var>config</file> and then run that if
11727 appropriate from the post-installation script. The
11728 <tt><var>package</var>config</tt> program should not
11729 unquestioningly overwrite an existing configuration - if its
11730 mode of operation is geared towards setting up a package for
11731 the first time (rather than any arbitrary reconfiguration
11732 later) you should have it check whether the configuration
11733 already exists, and require a <tt>--force</tt> flag to
11734 overwrite it.</p></sect>
11737 <appendix id="pkg-alternatives"><heading>Alternative versions of
11738 an interface - <prgn>update-alternatives</prgn> (from old
11743 When several packages all provide different versions of the
11744 same program or file it is useful to have the system select a
11745 default, but to allow the system administrator to change it
11746 and have their decisions respected.
11750 For example, there are several versions of the <prgn>vi</prgn>
11751 editor, and there is no reason to prevent all of them from
11752 being installed at once, each under their own name
11753 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11754 Nevertheless it is desirable to have the name <tt>vi</tt>
11755 refer to something, at least by default.
11759 If all the packages involved cooperate, this can be done with
11760 <prgn>update-alternatives</prgn>.
11764 Each package provides its own version under its own name, and
11765 calls <prgn>update-alternatives</prgn> in its postinst to
11766 register its version (and again in its prerm to deregister
11771 See the man page <manref name="update-alternatives"
11772 section="8"> for details.
11776 If <prgn>update-alternatives</prgn> does not seem appropriate
11777 you may wish to consider using diversions instead.</p>
11780 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11781 package's version of a file (from old Packaging Manual)
11785 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11786 when it reinstalls the package it belongs to, and to have it
11787 put the file from the package somewhere else instead.
11791 This can be used locally to override a package's version of a
11792 file, or by one package to override another's version (or
11793 provide a wrapper for it).
11797 Before deciding to use a diversion, read <ref
11798 id="pkg-alternatives"> to see if you really want a diversion
11799 rather than several alternative versions of a program.
11803 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11804 and updated by a special program <prgn>dpkg-divert</prgn>.
11805 Please see <manref name="dpkg-divert" section="8"> for full
11806 details of its operation.
11810 When a package wishes to divert a file from another, it should
11811 call <prgn>dpkg-divert</prgn> in its preinst to add the
11812 diversion and rename the existing file. For example,
11813 supposing that a <prgn>smailwrapper</prgn> package wishes to
11814 install a wrapper around <file>/usr/sbin/smail</file>:
11816 dpkg-divert --package smailwrapper --add --rename \
11817 --divert /usr/sbin/smail.real /usr/sbin/smail
11818 </example> The <tt>--package smailwrapper</tt> ensures that
11819 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11820 can bypass the diversion and get installed as the true version.
11821 It's safe to add the diversion unconditionally on upgrades since
11822 it will be left unchanged if it already exists, but
11823 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11824 message, make the command conditional on the version from which
11825 the package is being upgraded:
11827 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11828 dpkg-divert --package smailwrapper --add --rename \
11829 --divert /usr/sbin/smail.real /usr/sbin/smail
11831 </example> where <tt>1.0-2</tt> is the version at which the
11832 diversion was first added to the package. Running the command
11833 during abort-upgrade is pointless but harmless.
11837 The postrm has to do the reverse:
11839 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11840 dpkg-divert --package smailwrapper --remove --rename \
11841 --divert /usr/sbin/smail.real /usr/sbin/smail
11843 </example> If the diversion was added at a particular version, the
11844 postrm should also handle the failure case of upgrading from an
11845 older version (unless the older version is so old that direct
11846 upgrades are no longer supported):
11848 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11849 dpkg-divert --package smailwrapper --remove --rename \
11850 --divert /usr/sbin/smail.real /usr/sbin/smail
11852 </example> where <tt>1.0-2</tt> is the version at which the
11853 diversion was first added to the package. The postrm should not
11854 remove the diversion on upgrades both because there's no reason to
11855 remove the diversion only to immediately re-add it and since the
11856 postrm of the old package is run after unpacking so the removal of
11857 the diversion will fail.
11861 Do not attempt to divert a file which is vitally important for
11862 the system's operation - when using <prgn>dpkg-divert</prgn>
11863 there is a time, after it has been diverted but before
11864 <prgn>dpkg</prgn> has installed the new version, when the file
11865 does not exist.</p>
11870 <!-- Local variables: -->
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