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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:
772 The additional section <em>debian-installer</em>
773 contains special packages used by the installer and is not used
774 for normal Debian packages.
778 For more information about the sections and their definitions,
779 see the <url id="http://packages.debian.org/unstable/"
780 name="list of sections in unstable">.
784 <sect id="priorities">
785 <heading>Priorities</heading>
788 Each package should have a <em>priority</em> value, which is
789 included in the package's <em>control record</em>
790 (see <ref id="f-Priority">).
791 This information is used by the Debian package management tools to
792 separate high-priority packages from less-important packages.
796 The following <em>priority levels</em> are recognized by the
797 Debian package management tools.
799 <tag><tt>required</tt></tag>
801 Packages which are necessary for the proper
802 functioning of the system (usually, this means that
803 dpkg functionality depends on these packages).
804 Removing a <tt>required</tt> package may cause your
805 system to become totally broken and you may not even
806 be able to use <prgn>dpkg</prgn> to put things back,
807 so only do so if you know what you are doing. Systems
808 with only the <tt>required</tt> packages are probably
809 unusable, but they do have enough functionality to
810 allow the sysadmin to boot and install more software.
812 <tag><tt>important</tt></tag>
814 Important programs, including those which one would
815 expect to find on any Unix-like system. If the
816 expectation is that an experienced Unix person who
817 found it missing would say "What on earth is going on,
818 where is <prgn>foo</prgn>?", it must be an
819 <tt>important</tt> package.<footnote>
820 This is an important criterion because we are
821 trying to produce, amongst other things, a free
824 Other packages without which the system will not run
825 well or be usable must also have priority
826 <tt>important</tt>. This does
827 <em>not</em> include Emacs, the X Window System, TeX
828 or any other large applications. The
829 <tt>important</tt> packages are just a bare minimum of
830 commonly-expected and necessary tools.
832 <tag><tt>standard</tt></tag>
834 These packages provide a reasonably small but not too
835 limited character-mode system. This is what will be
836 installed by default if the user doesn't select anything
837 else. It doesn't include many large applications.
839 <tag><tt>optional</tt></tag>
841 (In a sense everything that isn't required is
842 optional, but that's not what is meant here.) This is
843 all the software that you might reasonably want to
844 install if you didn't know what it was and don't have
845 specialized requirements. This is a much larger system
846 and includes the X Window System, a full TeX
847 distribution, and many applications. Note that
848 optional packages should not conflict with each other.
850 <tag><tt>extra</tt></tag>
852 This contains all packages that conflict with others
853 with required, important, standard or optional
854 priorities, or are only likely to be useful if you
855 already know what they are or have specialized
856 requirements (such as packages containing only detached
863 Packages must not depend on packages with lower priority
864 values (excluding build-time dependencies). In order to
865 ensure this, the priorities of one or more packages may need
874 <heading>Binary packages</heading>
877 The Debian distribution is based on the Debian
878 package management system, called <prgn>dpkg</prgn>. Thus,
879 all packages in the Debian distribution must be provided
880 in the <tt>.deb</tt> file format.
884 A <tt>.deb</tt> package contains two sets of files: a set of files
885 to install on the system when the package is installed, and a set
886 of files that provide additional metadata about the package or
887 which are executed when the package is installed or removed. This
888 second set of files is called <em>control information files</em>.
889 Among those files are the package maintainer scripts
890 and <file>control</file>, the <qref id="binarycontrolfiles">binary
891 package control file</qref> that contains the control fields for
892 the package. Other control information files
893 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
894 file</qref> used to store shared library dependency information
895 and the <file>conffiles</file> file that lists the package's
896 configuration files (described in <ref id="config-files">).
900 There is unfortunately a collision of terminology here between
901 control information files and files in the Debian control file
902 format. Throughout this document, a <em>control file</em> refers
903 to a file in the Debian control file format. These files are
904 documented in <ref id="controlfields">. Only files referred to
905 specifically as <em>control information files</em> are the files
906 included in the control information file member of
907 the <file>.deb</file> file format used by binary packages. Most
908 control information files are not in the Debian control file
913 <heading>The package name</heading>
916 Every package must have a name that's unique within the Debian
921 The package name is included in the control field
922 <tt>Package</tt>, the format of which is described
923 in <ref id="f-Package">.
924 The package name is also included as a part of the file name
925 of the <tt>.deb</tt> file.
930 <heading>The version of a package</heading>
933 Every package has a version number recorded in its
934 <tt>Version</tt> control file field, described in
935 <ref id="f-Version">.
939 The package management system imposes an ordering on version
940 numbers, so that it can tell whether packages are being up- or
941 downgraded and so that package system front end applications
942 can tell whether a package it finds available is newer than
943 the one installed on the system. The version number format
944 has the most significant parts (as far as comparison is
945 concerned) at the beginning.
949 If an upstream package has problematic version numbers they
950 should be converted to a sane form for use in the
951 <tt>Version</tt> field.
955 <heading>Version numbers based on dates</heading>
958 In general, Debian packages should use the same version
959 numbers as the upstream sources. However, upstream version
960 numbers based on some date formats (sometimes used for
961 development or "snapshot" releases) will not be ordered
962 correctly by the package management software. For
963 example, <prgn>dpkg</prgn> will consider "96May01" to be
964 greater than "96Dec24".
968 To prevent having to use epochs for every new upstream
969 version, the date-based portion of any upstream version number
970 should be given in a way that sorts correctly: four-digit year
971 first, followed by a two-digit numeric month, followed by a
972 two-digit numeric date, possibly with punctuation between the
977 Native Debian packages (i.e., packages which have been written
978 especially for Debian) whose version numbers include dates
979 should also follow these rules. If punctuation is desired
980 between the date components, remember that hyphen (<tt>-</tt>)
981 cannot be used in native package versions. Period
982 (<tt>.</tt>) is normally a good choice.
988 <sect id="maintainer">
989 <heading>The maintainer of a package</heading>
992 Every package must have a maintainer, except for orphaned
993 packages as described below. The maintainer may be one person
994 or a group of people reachable from a common email address, such
995 as a mailing list. The maintainer is responsible for
996 maintaining the Debian packaging files, evaluating and
997 responding appropriately to reported bugs, uploading new
998 versions of the package (either directly or through a sponsor),
999 ensuring that the package is placed in the appropriate archive
1000 area and included in Debian releases as appropriate for the
1001 stability and utility of the package, and requesting removal of
1002 the package from the Debian distribution if it is no longer
1003 useful or maintainable.
1007 The maintainer must be specified in the <tt>Maintainer</tt>
1008 control field with their correct name and a working email
1009 address. The email address given in the <tt>Maintainer</tt>
1010 control field must accept mail from those role accounts in
1011 Debian used to send automated mails regarding the package. This
1012 includes non-spam mail from the bug-tracking system, all mail
1013 from the Debian archive maintenance software, and other role
1014 accounts or automated processes that are commonly agreed on by
1015 the project.<footnote>
1016 A sample implementation of such a whitelist written for the
1017 Mailman mailing list management software is used for mailing
1018 lists hosted by alioth.debian.org.
1020 If one person or team maintains several packages, they should
1021 use the same form of their name and email address in
1022 the <tt>Maintainer</tt> fields of those packages.
1026 The format of the <tt>Maintainer</tt> control field is
1027 described in <ref id="f-Maintainer">.
1031 If the maintainer of the package is a team of people with a
1032 shared email address, the <tt>Uploaders</tt> control field must
1033 be present and must contain at least one human with their
1034 personal email address. See <ref id="f-Uploaders"> for the
1035 syntax of that field.
1039 An orphaned package is one with no current maintainer. Orphaned
1040 packages should have their <tt>Maintainer</tt> control field set
1041 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1042 These packages are considered maintained by the Debian project
1043 as a whole until someone else volunteers to take over
1044 maintenance.<footnote>
1045 The detailed procedure for gracefully orphaning a package can
1046 be found in the Debian Developer's Reference
1047 (see <ref id="related">).
1052 <sect id="descriptions">
1053 <heading>The description of a package</heading>
1056 Every Debian package must have a <tt>Description</tt> control
1057 field which contains a synopsis and extended description of the
1058 package. Technical information about the format of the
1059 <tt>Description</tt> field is in <ref id="f-Description">.
1063 The description should describe the package (the program) to a
1064 user (system administrator) who has never met it before so that
1065 they have enough information to decide whether they want to
1066 install it. This description should not just be copied verbatim
1067 from the program's documentation.
1071 Put important information first, both in the synopsis and
1072 extended description. Sometimes only the first part of the
1073 synopsis or of the description will be displayed. You can
1074 assume that there will usually be a way to see the whole
1075 extended description.
1079 The description should also give information about the
1080 significant dependencies and conflicts between this package
1081 and others, so that the user knows why these dependencies and
1082 conflicts have been declared.
1086 Instructions for configuring or using the package should
1087 not be included (that is what installation scripts,
1088 manual pages, info files, etc., are for). Copyright
1089 statements and other administrivia should not be included
1090 either (that is what the copyright file is for).
1093 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1096 The single line synopsis should be kept brief - certainly
1097 under 80 characters.
1101 Do not include the package name in the synopsis line. The
1102 display software knows how to display this already, and you
1103 do not need to state it. Remember that in many situations
1104 the user may only see the synopsis line - make it as
1105 informative as you can.
1110 <sect1 id="extendeddesc"><heading>The extended description</heading>
1113 Do not try to continue the single line synopsis into the
1114 extended description. This will not work correctly when
1115 the full description is displayed, and makes no sense
1116 where only the summary (the single line synopsis) is
1121 The extended description should describe what the package
1122 does and how it relates to the rest of the system (in terms
1123 of, for example, which subsystem it is which part of).
1127 The description field needs to make sense to anyone, even
1128 people who have no idea about any of the things the
1129 package deals with.<footnote>
1130 The blurb that comes with a program in its
1131 announcements and/or <prgn>README</prgn> files is
1132 rarely suitable for use in a description. It is
1133 usually aimed at people who are already in the
1134 community where the package is used.
1142 <sect id="dependencies">
1143 <heading>Dependencies</heading>
1146 Every package must specify the dependency information
1147 about other packages that are required for the first to
1152 For example, a dependency entry must be provided for any
1153 shared libraries required by a dynamically-linked executable
1154 binary in a package.
1158 Packages are not required to declare any dependencies they
1159 have on other packages which are marked <tt>Essential</tt>
1160 (see below), and should not do so unless they depend on a
1161 particular version of that package.<footnote>
1163 Essential is needed in part to avoid unresolvable dependency
1164 loops on upgrade. If packages add unnecessary dependencies
1165 on packages in this set, the chances that there
1166 <strong>will</strong> be an unresolvable dependency loop
1167 caused by forcing these Essential packages to be configured
1168 first before they need to be is greatly increased. It also
1169 increases the chances that frontends will be unable to
1170 <strong>calculate</strong> an upgrade path, even if one
1174 Also, functionality is rarely ever removed from the
1175 Essential set, but <em>packages</em> have been removed from
1176 the Essential set when the functionality moved to a
1177 different package. So depending on these packages <em>just
1178 in case</em> they stop being essential does way more harm
1185 Sometimes, unpacking one package requires that another package
1186 be first unpacked <em>and</em> configured. In this case, the
1187 depending package must specify this dependency in
1188 the <tt>Pre-Depends</tt> control field.
1192 You should not specify a <tt>Pre-Depends</tt> entry for a
1193 package before this has been discussed on the
1194 <tt>debian-devel</tt> mailing list and a consensus about
1195 doing that has been reached.
1199 The format of the package interrelationship control fields is
1200 described in <ref id="relationships">.
1204 <sect id="virtual_pkg">
1205 <heading>Virtual packages</heading>
1208 Sometimes, there are several packages which offer
1209 more-or-less the same functionality. In this case, it's
1210 useful to define a <em>virtual package</em> whose name
1211 describes that common functionality. (The virtual
1212 packages only exist logically, not physically; that's why
1213 they are called <em>virtual</em>.) The packages with this
1214 particular function will then <em>provide</em> the virtual
1215 package. Thus, any other package requiring that function
1216 can simply depend on the virtual package without having to
1217 specify all possible packages individually.
1221 All packages should use virtual package names where
1222 appropriate, and arrange to create new ones if necessary.
1223 They should not use virtual package names (except privately,
1224 amongst a cooperating group of packages) unless they have
1225 been agreed upon and appear in the list of virtual package
1226 names. (See also <ref id="virtual">)
1230 The latest version of the authoritative list of virtual
1231 package names can be found in the <tt>debian-policy</tt> package.
1232 It is also available from the Debian web mirrors at
1233 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1234 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1238 The procedure for updating the list is described in the preface
1245 <heading>Base system</heading>
1248 The <tt>base system</tt> is a minimum subset of the Debian
1249 system that is installed before everything else
1250 on a new system. Only very few packages are allowed to form
1251 part of the base system, in order to keep the required disk
1256 The base system consists of all those packages with priority
1257 <tt>required</tt> or <tt>important</tt>. Many of them will
1258 be tagged <tt>essential</tt> (see below).
1263 <heading>Essential packages</heading>
1266 Essential is defined as the minimal set of functionality that
1267 must be available and usable on the system at all times, even
1268 when packages are in an unconfigured (but unpacked) state.
1269 Packages are tagged <tt>essential</tt> for a system using the
1270 <tt>Essential</tt> control field. The format of the
1271 <tt>Essential</tt> control field is described in <ref
1276 Since these packages cannot be easily removed (one has to
1277 specify an extra <em>force option</em> to
1278 <prgn>dpkg</prgn> to do so), this flag must not be used
1279 unless absolutely necessary. A shared library package
1280 must not be tagged <tt>essential</tt>; dependencies will
1281 prevent its premature removal, and we need to be able to
1282 remove it when it has been superseded.
1286 Since dpkg will not prevent upgrading of other packages
1287 while an <tt>essential</tt> package is in an unconfigured
1288 state, all <tt>essential</tt> packages must supply all of
1289 their core functionality even when unconfigured. If the
1290 package cannot satisfy this requirement it must not be
1291 tagged as essential, and any packages depending on this
1292 package must instead have explicit dependency fields as
1297 Maintainers should take great care in adding any programs,
1298 interfaces, or functionality to <tt>essential</tt> packages.
1299 Packages may assume that functionality provided by
1300 <tt>essential</tt> packages is always available without
1301 declaring explicit dependencies, which means that removing
1302 functionality from the Essential set is very difficult and is
1303 almost never done. Any capability added to an
1304 <tt>essential</tt> package therefore creates an obligation to
1305 support that capability as part of the Essential set in
1310 You must not tag any packages <tt>essential</tt> before
1311 this has been discussed on the <tt>debian-devel</tt>
1312 mailing list and a consensus about doing that has been
1317 <sect id="maintscripts">
1318 <heading>Maintainer Scripts</heading>
1321 The package installation scripts should avoid producing
1322 output which is unnecessary for the user to see and
1323 should rely on <prgn>dpkg</prgn> to stave off boredom on
1324 the part of a user installing many packages. This means,
1325 amongst other things, using the <tt>--quiet</tt> option on
1326 <prgn>install-info</prgn>.
1330 Errors which occur during the execution of an installation
1331 script must be checked and the installation must not
1332 continue after an error.
1336 Note that in general <ref id="scripts"> applies to package
1337 maintainer scripts, too.
1341 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1342 to another package without consulting the maintainer of that
1343 package first. When adding or removing diversions, package
1344 maintainer scripts must provide the <tt>--package</tt> flag
1345 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1349 All packages which supply an instance of a common command
1350 name (or, in general, filename) should generally use
1351 <prgn>update-alternatives</prgn>, so that they may be
1352 installed together. If <prgn>update-alternatives</prgn>
1353 is not used, then each package must use
1354 <tt>Conflicts</tt> to ensure that other packages are
1355 de-installed. (In this case, it may be appropriate to
1356 specify a conflict against earlier versions of something
1357 that previously did not use
1358 <prgn>update-alternatives</prgn>; this is an exception to
1359 the usual rule that versioned conflicts should be
1363 <sect1 id="maintscriptprompt">
1364 <heading>Prompting in maintainer scripts</heading>
1366 Package maintainer scripts may prompt the user if
1367 necessary. Prompting must be done by communicating
1368 through a program, such as <prgn>debconf</prgn>, which
1369 conforms to the Debian Configuration Management
1370 Specification, version 2 or higher.
1374 Packages which are essential, or which are dependencies of
1375 essential packages, may fall back on another prompting method
1376 if no such interface is available when they are executed.
1380 The Debian Configuration Management Specification is included
1381 in the <file>debconf_specification</file> files in the
1382 <package>debian-policy</package> package.
1383 It is also available from the Debian web mirrors at
1384 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1385 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1389 Packages which use the Debian Configuration Management
1390 Specification may contain the additional control information
1391 files <file>config</file>
1392 and <file>templates</file>. <file>config</file> is an
1393 additional maintainer script used for package configuration,
1394 and <file>templates</file> contains templates used for user
1395 prompting. The <prgn>config</prgn> script might be run before
1396 the <prgn>preinst</prgn> script and before the package is
1397 unpacked or any of its dependencies or pre-dependencies are
1398 satisfied. Therefore it must work using only the tools
1399 present in <em>essential</em> packages.<footnote>
1400 <package>Debconf</package> or another tool that
1401 implements the Debian Configuration Management
1402 Specification will also be installed, and any
1403 versioned dependencies on it will be satisfied
1404 before preconfiguration begins.
1409 Packages which use the Debian Configuration Management
1410 Specification must allow for translation of their user-visible
1411 messages by using a gettext-based system such as the one
1412 provided by the <package>po-debconf</package> package.
1416 Packages should try to minimize the amount of prompting
1417 they need to do, and they should ensure that the user
1418 will only ever be asked each question once. This means
1419 that packages should try to use appropriate shared
1420 configuration files (such as <file>/etc/papersize</file> and
1421 <file>/etc/news/server</file>), and shared
1422 <package>debconf</package> variables rather than each
1423 prompting for their own list of required pieces of
1428 It also means that an upgrade should not ask the same
1429 questions again, unless the user has used
1430 <tt>dpkg --purge</tt> to remove the package's configuration.
1431 The answers to configuration questions should be stored in an
1432 appropriate place in <file>/etc</file> so that the user can
1433 modify them, and how this has been done should be
1438 If a package has a vitally important piece of
1439 information to pass to the user (such as "don't run me
1440 as I am, you must edit the following configuration files
1441 first or you risk your system emitting badly-formatted
1442 messages"), it should display this in the
1443 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1444 prompt the user to hit return to acknowledge the
1445 message. Copyright messages do not count as vitally
1446 important (they belong in
1447 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1448 neither do instructions on how to use a program (these
1449 should be in on-line documentation, where all the users
1454 Any necessary prompting should almost always be confined
1455 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1456 script. If it is done in the <prgn>postinst</prgn>, it
1457 should be protected with a conditional so that
1458 unnecessary prompting doesn't happen if a package's
1459 installation fails and the <prgn>postinst</prgn> is
1460 called with <tt>abort-upgrade</tt>,
1461 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1471 <heading>Source packages</heading>
1473 <sect id="standardsversion">
1474 <heading>Standards conformance</heading>
1477 Source packages should specify the most recent version number
1478 of this policy document with which your package complied
1479 when it was last updated.
1483 This information may be used to file bug reports
1484 automatically if your package becomes too much out of date.
1488 The version is specified in the <tt>Standards-Version</tt>
1490 The format of the <tt>Standards-Version</tt> field is
1491 described in <ref id="f-Standards-Version">.
1495 You should regularly, and especially if your package has
1496 become out of date, check for the newest Policy Manual
1497 available and update your package, if necessary. When your
1498 package complies with the new standards you should update the
1499 <tt>Standards-Version</tt> source package field and
1500 release it.<footnote>
1501 See the file <file>upgrading-checklist</file> for
1502 information about policy which has changed between
1503 different versions of this document.
1509 <sect id="pkg-relations">
1510 <heading>Package relationships</heading>
1513 Source packages should specify which binary packages they
1514 require to be installed or not to be installed in order to
1515 build correctly. For example, if building a package
1516 requires a certain compiler, then the compiler should be
1517 specified as a build-time dependency.
1521 It is not necessary to explicitly specify build-time
1522 relationships on a minimal set of packages that are always
1523 needed to compile, link and put in a Debian package a
1524 standard "Hello World!" program written in C or C++. The
1525 required packages are called <em>build-essential</em>, and
1526 an informational list can be found in
1527 <file>/usr/share/doc/build-essential/list</file> (which is
1528 contained in the <tt>build-essential</tt>
1531 <list compact="compact">
1533 This allows maintaining the list separately
1534 from the policy documents (the list does not
1535 need the kind of control that the policy
1539 Having a separate package allows one to install
1540 the build-essential packages on a machine, as
1541 well as allowing other packages such as tasks to
1542 require installation of the build-essential
1543 packages using the depends relation.
1546 The separate package allows bug reports against
1547 the list to be categorized separately from
1548 the policy management process in the BTS.
1555 When specifying the set of build-time dependencies, one
1556 should list only those packages explicitly required by the
1557 build. It is not necessary to list packages which are
1558 required merely because some other package in the list of
1559 build-time dependencies depends on them.<footnote>
1560 The reason for this is that dependencies change, and
1561 you should list all those packages, and <em>only</em>
1562 those packages that <em>you</em> need directly. What
1563 others need is their business. For example, if you
1564 only link against <file>libimlib</file>, you will need to
1565 build-depend on <package>libimlib2-dev</package> but
1566 not against any <tt>libjpeg*</tt> packages, even
1567 though <tt>libimlib2-dev</tt> currently depends on
1568 them: installation of <package>libimlib2-dev</package>
1569 will automatically ensure that all of its run-time
1570 dependencies are satisfied.
1575 If build-time dependencies are specified, it must be
1576 possible to build the package and produce working binaries
1577 on a system with only essential and build-essential
1578 packages installed and also those required to satisfy the
1579 build-time relationships (including any implied
1580 relationships). In particular, this means that version
1581 clauses should be used rigorously in build-time
1582 relationships so that one cannot produce bad or
1583 inconsistently configured packages when the relationships
1584 are properly satisfied.
1588 <ref id="relationships"> explains the technical details.
1593 <heading>Changes to the upstream sources</heading>
1596 If changes to the source code are made that are not
1597 specific to the needs of the Debian system, they should be
1598 sent to the upstream authors in whatever form they prefer
1599 so as to be included in the upstream version of the
1604 If you need to configure the package differently for
1605 Debian or for Linux, and the upstream source doesn't
1606 provide a way to do so, you should add such configuration
1607 facilities (for example, a new <prgn>autoconf</prgn> test
1608 or <tt>#define</tt>) and send the patch to the upstream
1609 authors, with the default set to the way they originally
1610 had it. You can then easily override the default in your
1611 <file>debian/rules</file> or wherever is appropriate.
1615 You should make sure that the <prgn>configure</prgn> utility
1616 detects the correct architecture specification string
1617 (refer to <ref id="arch-spec"> for details).
1621 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1622 <prgn>configure</prgn> scripts are used, you should edit the
1623 <file>.in</file> files rather than editing the
1624 <prgn>Makefile</prgn> directly. This allows the user to
1625 reconfigure the package if necessary. You should
1626 <em>not</em> configure the package and edit the generated
1627 <prgn>Makefile</prgn>! This makes it impossible for someone
1628 else to later reconfigure the package without losing the
1634 <sect id="dpkgchangelog">
1635 <heading>Debian changelog: <file>debian/changelog</file></heading>
1638 Changes in the Debian version of the package should be
1639 briefly explained in the Debian changelog file
1640 <file>debian/changelog</file>.<footnote>
1642 Mistakes in changelogs are usually best rectified by
1643 making a new changelog entry rather than "rewriting
1644 history" by editing old changelog entries.
1647 This includes modifications
1648 made in the Debian package compared to the upstream one
1649 as well as other changes and updates to the package.
1651 Although there is nothing stopping an author who is also
1652 the Debian maintainer from using this changelog for all
1653 their changes, it will have to be renamed if the Debian
1654 and upstream maintainers become different people. In such
1655 a case, however, it might be better to maintain the package
1656 as a non-native package.
1661 The format of the <file>debian/changelog</file> allows the
1662 package building tools to discover which version of the package
1663 is being built and find out other release-specific information.
1667 That format is a series of entries like this:
1669 <example compact="compact">
1670 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1672 [optional blank line(s), stripped]
1674 * <var>change details</var>
1675 <var>more change details</var>
1677 [blank line(s), included in output of dpkg-parsechangelog]
1679 * <var>even more change details</var>
1681 [optional blank line(s), stripped]
1683 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1688 <var>package</var> and <var>version</var> are the source
1689 package name and version number.
1693 <var>distribution(s)</var> lists the distributions where
1694 this version should be installed when it is uploaded - it
1695 is copied to the <tt>Distribution</tt> field in the
1696 <file>.changes</file> file. See <ref id="f-Distribution">.
1700 <var>urgency</var> is the value for the <tt>Urgency</tt>
1701 field in the <file>.changes</file> file for the upload
1702 (see <ref id="f-Urgency">). It is not possible to specify
1703 an urgency containing commas; commas are used to separate
1704 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1705 <prgn>dpkg</prgn> changelog format (though there is
1706 currently only one useful <var>keyword</var>,
1711 The change details may in fact be any series of lines
1712 starting with at least two spaces, but conventionally each
1713 change starts with an asterisk and a separating space and
1714 continuation lines are indented so as to bring them in
1715 line with the start of the text above. Blank lines may be
1716 used here to separate groups of changes, if desired.
1720 If this upload resolves bugs recorded in the Bug Tracking
1721 System (BTS), they may be automatically closed on the
1722 inclusion of this package into the Debian archive by
1723 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1724 in the change details.<footnote>
1725 To be precise, the string should match the following
1726 Perl regular expression:
1728 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1730 Then all of the bug numbers listed will be closed by the
1731 archive maintenance script (<prgn>katie</prgn>) using the
1732 <var>version</var> of the changelog entry.
1734 This information is conveyed via the <tt>Closes</tt> field
1735 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1739 The maintainer name and email address used in the changelog
1740 should be the details of the person uploading <em>this</em>
1741 version. They are <em>not</em> necessarily those of the
1742 usual package maintainer.<footnote>
1743 If the developer uploading the package is not one of the usual
1744 maintainers of the package (as listed in
1745 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1746 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1747 fields of the package), the first line of the changelog is
1748 conventionally used to explain why a non-maintainer is
1749 uploading the package. The Debian Developer's Reference
1750 (see <ref id="related">) documents the conventions
1752 The information here will be copied to the <tt>Changed-By</tt>
1753 field in the <tt>.changes</tt> file
1754 (see <ref id="f-Changed-By">), and then later used to send an
1755 acknowledgement when the upload has been installed.
1759 The <var>date</var> has the following format<footnote>
1760 This is the same as the format generated by <tt>date
1762 </footnote> (compatible and with the same semantics of
1763 RFC 2822 and RFC 5322):
1764 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1766 <list compact="compact">
1768 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1771 dd is a one- or two-digit day of the month (01-31)
1774 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1777 <item>yyyy is the four-digit year (e.g. 2010)</item>
1778 <item>hh is the two-digit hour (00-23)</item>
1779 <item>mm is the two-digit minutes (00-59)</item>
1780 <item>ss is the two-digit seconds (00-60)</item>
1782 +zzzz or -zzzz is the the time zone offset from Coordinated
1783 Universal Time (UTC). "+" indicates that the time is ahead
1784 of (i.e., east of) UTC and "-" indicates that the time is
1785 behind (i.e., west of) UTC. The first two digits indicate
1786 the hour difference from UTC and the last two digits
1787 indicate the number of additional minutes difference from
1788 UTC. The last two digits must be in the range 00-59.
1794 The first "title" line with the package name must start
1795 at the left hand margin. The "trailer" line with the
1796 maintainer and date details must be preceded by exactly
1797 one space. The maintainer details and the date must be
1798 separated by exactly two spaces.
1802 The entire changelog must be encoded in UTF-8.
1806 For more information on placement of the changelog files
1807 within binary packages, please see <ref id="changelogs">.
1811 <sect id="dpkgcopyright">
1812 <heading>Copyright: <file>debian/copyright</file></heading>
1814 Every package must be accompanied by a verbatim copy of its
1815 copyright information and distribution license in the file
1816 <file>/usr/share/doc/<var>package</var>/copyright</file>
1817 (see <ref id="copyrightfile"> for further details). Also see
1818 <ref id="pkgcopyright"> for further considerations related
1819 to copyrights for packages.
1823 <heading>Error trapping in makefiles</heading>
1826 When <prgn>make</prgn> invokes a command in a makefile
1827 (including your package's upstream makefiles and
1828 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1829 means that <prgn>sh</prgn>'s usual bad error handling
1830 properties apply: if you include a miniature script as one
1831 of the commands in your makefile you'll find that if you
1832 don't do anything about it then errors are not detected
1833 and <prgn>make</prgn> will blithely continue after
1838 Every time you put more than one shell command (this
1839 includes using a loop) in a makefile command you
1840 must make sure that errors are trapped. For
1841 simple compound commands, such as changing directory and
1842 then running a program, using <tt>&&</tt> rather
1843 than semicolon as a command separator is sufficient. For
1844 more complex commands including most loops and
1845 conditionals you should include a separate <tt>set -e</tt>
1846 command at the start of every makefile command that's
1847 actually one of these miniature shell scripts.
1851 <sect id="timestamps">
1852 <heading>Time Stamps</heading>
1854 Maintainers should preserve the modification times of the
1855 upstream source files in a package, as far as is reasonably
1857 The rationale is that there is some information conveyed
1858 by knowing the age of the file, for example, you could
1859 recognize that some documentation is very old by looking
1860 at the modification time, so it would be nice if the
1861 modification time of the upstream source would be
1867 <sect id="restrictions">
1868 <heading>Restrictions on objects in source packages</heading>
1871 The source package may not contain any hard links<footnote>
1873 This is not currently detected when building source
1874 packages, but only when extracting
1878 Hard links may be permitted at some point in the
1879 future, but would require a fair amount of
1882 </footnote>, device special files, sockets or setuid or
1883 setgid files.<footnote>
1884 Setgid directories are allowed.
1889 <sect id="debianrules">
1890 <heading>Main building script: <file>debian/rules</file></heading>
1893 This file must be an executable makefile, and contains the
1894 package-specific recipes for compiling the package and
1895 building binary package(s) from the source.
1899 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1900 so that it can be invoked by saying its name rather than
1901 invoking <prgn>make</prgn> explicitly. That is, invoking
1902 either of <tt>make -f debian/rules <em>args...</em></tt>
1903 or <tt>./debian/rules <em>args...</em></tt> must result in
1908 The following targets are required and must be implemented
1909 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1910 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1911 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1915 Since an interactive <file>debian/rules</file> script makes it
1916 impossible to auto-compile that package and also makes it hard
1917 for other people to reproduce the same binary package, all
1918 required targets must be non-interactive. It also follows that
1919 any target that these targets depend on must also be
1924 The targets are as follows:
1926 <tag><tt>build</tt> (required)</tag>
1929 The <tt>build</tt> target should perform all the
1930 configuration and compilation of the package.
1931 If a package has an interactive pre-build
1932 configuration routine, the Debian source package
1933 must either be built after this has taken place (so
1934 that the binary package can be built without rerunning
1935 the configuration) or the configuration routine
1936 modified to become non-interactive. (The latter is
1937 preferable if there are architecture-specific features
1938 detected by the configuration routine.)
1942 For some packages, notably ones where the same
1943 source tree is compiled in different ways to produce
1944 two binary packages, the <tt>build</tt> target
1945 does not make much sense. For these packages it is
1946 good enough to provide two (or more) targets
1947 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1948 for each of the ways of building the package, and a
1949 <tt>build</tt> target that does nothing. The
1950 <tt>binary</tt> target will have to build the
1951 package in each of the possible ways and make the
1952 binary package out of each.
1956 The <tt>build</tt> target must not do anything
1957 that might require root privilege.
1961 The <tt>build</tt> target may need to run the
1962 <tt>clean</tt> target first - see below.
1966 When a package has a configuration and build routine
1967 which takes a long time, or when the makefiles are
1968 poorly designed, or when <tt>build</tt> needs to
1969 run <tt>clean</tt> first, it is a good idea to
1970 <tt>touch build</tt> when the build process is
1971 complete. This will ensure that if <tt>debian/rules
1972 build</tt> is run again it will not rebuild the whole
1974 Another common way to do this is for <tt>build</tt>
1975 to depend on <prgn>build-stamp</prgn> and to do
1976 nothing else, and for the <prgn>build-stamp</prgn>
1977 target to do the building and to <tt>touch
1978 build-stamp</tt> on completion. This is
1979 especially useful if the build routine creates a
1980 file or directory called <tt>build</tt>; in such a
1981 case, <tt>build</tt> will need to be listed as
1982 a phony target (i.e., as a dependency of the
1983 <tt>.PHONY</tt> target). See the documentation of
1984 <prgn>make</prgn> for more information on phony
1990 <tag><tt>build-arch</tt> (optional),
1991 <tt>build-indep</tt> (optional)
1995 A package may also provide one or both of the targets
1996 <tt>build-arch</tt> and <tt>build-indep</tt>.
1997 The <tt>build-arch</tt> target, if provided, should
1998 perform all the configuration and compilation required for
1999 producing all architecture-dependant binary packages
2000 (those packages for which the body of the
2001 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2002 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2003 target, if provided, should perform all the configuration
2004 and compilation required for producing all
2005 architecture-independent binary packages (those packages
2006 for which the body of the <tt>Architecture</tt> field
2007 in <tt>debian/control</tt> is <tt>all</tt>).
2011 If <tt>build-arch</tt> or <tt>build-indep</tt> targets are
2012 provided in the rules file, the <tt>build</tt> target
2013 should either depend on those targets or take the same
2014 actions as invoking those targets would perform.<footnote>
2015 The intent of this split is so that binary-only builds
2016 need not install the dependencies required for
2017 the <tt>build-indep</tt> target. However, this is not
2018 yet used in practice since <tt>dpkg-buildpackage
2019 -B</tt>, and therefore the autobuilders,
2020 invoke <tt>build</tt> rather than <tt>build-arch</tt>
2021 due to the difficulties in determining whether the
2022 optional <tt>build-arch</tt> target exists.
2027 If one or both of the targets <tt>build-arch</tt> and
2028 <tt>build-indep</tt> are not provided, then invoking
2029 <file>debian/rules</file> with one of the not-provided
2030 targets as arguments should produce a exit status code
2031 of 2. Usually this is provided automatically by make
2032 if the target is missing.
2036 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2037 must not do anything that might require root privilege.
2041 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2042 (required), <tt>binary-indep</tt> (required)
2046 The <tt>binary</tt> target must be all that is
2047 necessary for the user to build the binary package(s)
2048 produced from this source package. It is
2049 split into two parts: <prgn>binary-arch</prgn> builds
2050 the binary packages which are specific to a particular
2051 architecture, and <tt>binary-indep</tt> builds
2052 those which are not.
2055 <tt>binary</tt> may be (and commonly is) a target with
2056 no commands which simply depends on
2057 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2060 Both <tt>binary-*</tt> targets should depend on the
2061 <tt>build</tt> target, or on the appropriate
2062 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2063 provided, so that the package is built if it has not
2064 been already. It should then create the relevant
2065 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2066 make their control files and <prgn>dpkg-deb</prgn> to
2067 build them and place them in the parent of the top
2072 Both the <tt>binary-arch</tt> and
2073 <tt>binary-indep</tt> targets <em>must</em> exist.
2074 If one of them has nothing to do (which will always be
2075 the case if the source generates only a single binary
2076 package, whether architecture-dependent or not), it
2077 must still exist and must always succeed.
2081 The <tt>binary</tt> targets must be invoked as
2083 The <prgn>fakeroot</prgn> package often allows one
2084 to build a package correctly even without being
2090 <tag><tt>clean</tt> (required)</tag>
2093 This must undo any effects that the <tt>build</tt>
2094 and <tt>binary</tt> targets may have had, except
2095 that it should leave alone any output files created in
2096 the parent directory by a run of a <tt>binary</tt>
2101 If a <tt>build</tt> file is touched at the end of
2102 the <tt>build</tt> target, as suggested above, it
2103 should be removed as the first action that
2104 <tt>clean</tt> performs, so that running
2105 <tt>build</tt> again after an interrupted
2106 <tt>clean</tt> doesn't think that everything is
2111 The <tt>clean</tt> target may need to be
2112 invoked as root if <tt>binary</tt> has been
2113 invoked since the last <tt>clean</tt>, or if
2114 <tt>build</tt> has been invoked as root (since
2115 <tt>build</tt> may create directories, for
2120 <tag><tt>get-orig-source</tt> (optional)</tag>
2123 This target fetches the most recent version of the
2124 original source package from a canonical archive site
2125 (via FTP or WWW, for example), does any necessary
2126 rearrangement to turn it into the original source
2127 tar file format described below, and leaves it in the
2132 This target may be invoked in any directory, and
2133 should take care to clean up any temporary files it
2138 This target is optional, but providing it if
2139 possible is a good idea.
2143 <tag><tt>patch</tt> (optional)</tag>
2146 This target performs whatever additional actions are
2147 required to make the source ready for editing (unpacking
2148 additional upstream archives, applying patches, etc.).
2149 It is recommended to be implemented for any package where
2150 <tt>dpkg-source -x</tt> does not result in source ready
2151 for additional modification. See
2152 <ref id="readmesource">.
2158 The <tt>build</tt>, <tt>binary</tt> and
2159 <tt>clean</tt> targets must be invoked with the current
2160 directory being the package's top-level directory.
2165 Additional targets may exist in <file>debian/rules</file>,
2166 either as published or undocumented interfaces or for the
2167 package's internal use.
2171 The architectures we build on and build for are determined
2172 by <prgn>make</prgn> variables using the
2173 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2174 You can determine the Debian architecture and the GNU style
2175 architecture specification string for the build architecture as
2176 well as for the host architecture. The build architecture is
2177 the architecture on which <file>debian/rules</file> is run and
2178 the package build is performed. The host architecture is the
2179 architecture on which the resulting package will be installed
2180 and run. These are normally the same, but may be different in
2181 the case of cross-compilation (building packages for one
2182 architecture on machines of a different architecture).
2186 Here is a list of supported <prgn>make</prgn> variables:
2187 <list compact="compact">
2189 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2192 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2195 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2198 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2199 specification string)
2202 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2203 <tt>DEB_*_GNU_TYPE</tt>)
2206 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2207 <tt>DEB_*_GNU_TYPE</tt>)
2209 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2210 the build architecture or <tt>HOST</tt> for specification of the
2215 Backward compatibility can be provided in the rules file
2216 by setting the needed variables to suitable default
2217 values; please refer to the documentation of
2218 <prgn>dpkg-architecture</prgn> for details.
2222 It is important to understand that the <tt>DEB_*_ARCH</tt>
2223 string only determines which Debian architecture we are
2224 building on or for. It should not be used to get the CPU
2225 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2226 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2227 GNU style variables should generally only be used with upstream
2231 <sect1 id="debianrules-options">
2232 <heading><file>debian/rules</file> and
2233 <tt>DEB_BUILD_OPTIONS</tt></heading>
2236 Supporting the standardized environment variable
2237 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2238 contain several flags to change how a package is compiled and
2239 built. Each flag must be in the form <var>flag</var> or
2240 <var>flag</var>=<var>options</var>. If multiple flags are
2241 given, they must be separated by whitespace.<footnote>
2242 Some packages support any delimiter, but whitespace is the
2243 easiest to parse inside a makefile and avoids ambiguity with
2244 flag values that contain commas.
2246 <var>flag</var> must start with a lowercase letter
2247 (<tt>a-z</tt>) and consist only of lowercase letters,
2248 numbers (<tt>0-9</tt>), and the characters
2249 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2250 <var>options</var> must not contain whitespace. The same
2251 tag should not be given multiple times with conflicting
2252 values. Package maintainers may assume that
2253 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2257 The meaning of the following tags has been standardized:
2261 This tag says to not run any build-time test suite
2262 provided by the package.
2266 The presence of this tag means that the package should
2267 be compiled with a minimum of optimization. For C
2268 programs, it is best to add <tt>-O0</tt> to
2269 <tt>CFLAGS</tt> (although this is usually the default).
2270 Some programs might fail to build or run at this level
2271 of optimization; it may be necessary to use
2272 <tt>-O1</tt>, for example.
2276 This tag means that the debugging symbols should not be
2277 stripped from the binary during installation, so that
2278 debugging information may be included in the package.
2280 <tag>parallel=n</tag>
2282 This tag means that the package should be built using up
2283 to <tt>n</tt> parallel processes if the package build
2284 system supports this.<footnote>
2285 Packages built with <tt>make</tt> can often implement
2286 this by passing the <tt>-j</tt><var>n</var> option to
2289 If the package build system does not support parallel
2290 builds, this string must be ignored. If the package
2291 build system only supports a lower level of concurrency
2292 than <var>n</var>, the package should be built using as
2293 many parallel processes as the package build system
2294 supports. It is up to the package maintainer to decide
2295 whether the package build times are long enough and the
2296 package build system is robust enough to make supporting
2297 parallel builds worthwhile.
2303 Unknown flags must be ignored by <file>debian/rules</file>.
2307 The following makefile snippet is an example of how one may
2308 implement the build options; you will probably have to
2309 massage this example in order to make it work for your
2311 <example compact="compact">
2314 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2315 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2316 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2317 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2319 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2324 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2325 INSTALL_PROGRAM += -s
2327 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2328 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2329 MAKEFLAGS += -j$(NUMJOBS)
2334 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2335 # Code to run the package test suite.
2342 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2343 <sect id="substvars">
2344 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2347 When <prgn>dpkg-gencontrol</prgn>
2348 generates <qref id="binarycontrolfiles">binary package control
2349 files</qref> (<file>DEBIAN/control</file>), it performs variable
2350 substitutions on its output just before writing it. Variable
2351 substitutions have the form <tt>${<var>variable</var>}</tt>.
2352 The optional file <file>debian/substvars</file> contains
2353 variable substitutions to be used; variables can also be set
2354 directly from <file>debian/rules</file> using the <tt>-V</tt>
2355 option to the source packaging commands, and certain predefined
2356 variables are also available.
2360 The <file>debian/substvars</file> file is usually generated and
2361 modified dynamically by <file>debian/rules</file> targets, in
2362 which case it must be removed by the <tt>clean</tt> target.
2366 See <manref name="deb-substvars" section="5"> for full
2367 details about source variable substitutions, including the
2368 format of <file>debian/substvars</file>.</p>
2371 <sect id="debianwatch">
2372 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2375 This is an optional, recommended configuration file for the
2376 <tt>uscan</tt> utility which defines how to automatically scan
2377 ftp or http sites for newly available updates of the
2378 package. This is used
2379 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2380 tools to help with quality control and maintenance of the
2381 distribution as a whole.
2386 <sect id="debianfiles">
2387 <heading>Generated files list: <file>debian/files</file></heading>
2390 This file is not a permanent part of the source tree; it
2391 is used while building packages to record which files are
2392 being generated. <prgn>dpkg-genchanges</prgn> uses it
2393 when it generates a <file>.changes</file> file.
2397 It should not exist in a shipped source package, and so it
2398 (and any backup files or temporary files such as
2399 <file>files.new</file><footnote>
2400 <file>files.new</file> is used as a temporary file by
2401 <prgn>dpkg-gencontrol</prgn> and
2402 <prgn>dpkg-distaddfile</prgn> - they write a new
2403 version of <tt>files</tt> here before renaming it,
2404 to avoid leaving a corrupted copy if an error
2406 </footnote>) should be removed by the
2407 <tt>clean</tt> target. It may also be wise to
2408 ensure a fresh start by emptying or removing it at the
2409 start of the <tt>binary</tt> target.
2413 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2414 package, it adds an entry to <file>debian/files</file> for the
2415 <file>.deb</file> file that will be created when <tt>dpkg-deb
2416 --build</tt> is run for that binary package. So for most
2417 packages all that needs to be done with this file is to
2418 delete it in the <tt>clean</tt> target.
2422 If a package upload includes files besides the source
2423 package and any binary packages whose control files were
2424 made with <prgn>dpkg-gencontrol</prgn> then they should be
2425 placed in the parent of the package's top-level directory
2426 and <prgn>dpkg-distaddfile</prgn> should be called to add
2427 the file to the list in <file>debian/files</file>.</p>
2430 <sect id="embeddedfiles">
2431 <heading>Convenience copies of code</heading>
2434 Some software packages include in their distribution convenience
2435 copies of code from other software packages, generally so that
2436 users compiling from source don't have to download multiple
2437 packages. Debian packages should not make use of these
2438 convenience copies unless the included package is explicitly
2439 intended to be used in this way.<footnote>
2440 For example, parts of the GNU build system work like this.
2442 If the included code is already in the Debian archive in the
2443 form of a library, the Debian packaging should ensure that
2444 binary packages reference the libraries already in Debian and
2445 the convenience copy is not used. If the included code is not
2446 already in Debian, it should be packaged separately as a
2447 prerequisite if possible.
2449 Having multiple copies of the same code in Debian is
2450 inefficient, often creates either static linking or shared
2451 library conflicts, and, most importantly, increases the
2452 difficulty of handling security vulnerabilities in the
2458 <sect id="readmesource">
2459 <heading>Source package handling:
2460 <file>debian/README.source</file></heading>
2463 If running <prgn>dpkg-source -x</prgn> on a source package
2464 doesn't produce the source of the package, ready for editing,
2465 and allow one to make changes and run
2466 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2467 without taking any additional steps, creating a
2468 <file>debian/README.source</file> documentation file is
2469 recommended. This file should explain how to do all of the
2472 <item>Generate the fully patched source, in a form ready for
2473 editing, that would be built to create Debian
2474 packages. Doing this with a <tt>patch</tt> target in
2475 <file>debian/rules</file> is recommended; see
2476 <ref id="debianrules">.</item>
2477 <item>Modify the source and save those modifications so that
2478 they will be applied when building the package.</item>
2479 <item>Remove source modifications that are currently being
2480 applied when building the package.</item>
2481 <item>Optionally, document what steps are necessary to
2482 upgrade the Debian source package to a new upstream version,
2483 if applicable.</item>
2485 This explanation should include specific commands and mention
2486 any additional required Debian packages. It should not assume
2487 familiarity with any specific Debian packaging system or patch
2492 This explanation may refer to a documentation file installed by
2493 one of the package's build dependencies provided that the
2494 referenced documentation clearly explains these tasks and is not
2495 a general reference manual.
2499 <file>debian/README.source</file> may also include any other
2500 information that would be helpful to someone modifying the
2501 source package. Even if the package doesn't fit the above
2502 description, maintainers are encouraged to document in a
2503 <file>debian/README.source</file> file any source package with a
2504 particularly complex or unintuitive source layout or build
2505 system (for example, a package that builds the same source
2506 multiple times to generate different binary packages).
2512 <chapt id="controlfields">
2513 <heading>Control files and their fields</heading>
2516 The package management system manipulates data represented in
2517 a common format, known as <em>control data</em>, stored in
2518 <em>control files</em>.
2519 Control files are used for source packages, binary packages and
2520 the <file>.changes</file> files which control the installation
2521 of uploaded files<footnote>
2522 <prgn>dpkg</prgn>'s internal databases are in a similar
2527 <sect id="controlsyntax">
2528 <heading>Syntax of control files</heading>
2531 A control file consists of one or more paragraphs of
2533 The paragraphs are also sometimes referred to as stanzas.
2535 The paragraphs are separated by empty lines. Parsers may accept
2536 lines consisting solely of spaces and tabs as paragraph
2537 separators, but control files should use empty lines. Some control
2538 files allow only one paragraph; others allow several, in
2539 which case each paragraph usually refers to a different
2540 package. (For example, in source packages, the first
2541 paragraph refers to the source package, and later paragraphs
2542 refer to binary packages generated from the source.) The
2543 ordering of the paragraphs in control files is significant.
2547 Each paragraph consists of a series of data fields. Each field
2548 consists of the field name followed by a colon and then the
2549 data/value associated with that field. The field name is
2550 composed of US-ASCII characters excluding control characters,
2551 space, and colon (i.e., characters in the ranges 33-57 and
2552 59-126, inclusive). Field names must not begin with the comment
2553 character, <tt>#</tt>.
2557 The field ends at the end of the line or at the end of the last
2558 continuation line (see below). Horizontal whitespace (spaces
2559 and tabs) may occur immediately before or after the value and is
2560 ignored there; it is conventional to put a single space after
2561 the colon. For example, a field might be:
2562 <example compact="compact">
2565 the field name is <tt>Package</tt> and the field value
2570 A paragraph must not contain more than one instance of a
2571 particular field name.
2575 There are three types of fields:
2579 The field, including its value, must be a single line. Folding
2580 of the field is not permitted. This is the default field type
2581 if the definition of the field does not specify a different
2586 The value of a folded field is a logical line that may span
2587 several lines. The lines after the first are called
2588 continuation lines and must start with a space or a tab.
2589 Whitespace, including any newlines, is not significant in the
2590 field values of folded fields.<footnote>
2591 This folding method is similar to RFC 5322, allowing control
2592 files that contain only one paragraph and no multiline fields
2593 to be read by parsers written for RFC 5322.
2596 <tag>multiline</tag>
2598 The value of a multiline field may comprise multiple continuation
2599 lines. The first line of the value, the part on the same line as
2600 the field name, often has special significance or may have to be
2601 empty. Other lines are added following the same syntax as the
2602 continuation lines of the folded fields. Whitespace, including newlines,
2603 is significant in the values of multiline fields.
2609 Whitespace must not appear
2610 inside names (of packages, architectures, files or anything
2611 else) or version numbers, or between the characters of
2612 multi-character version relationships.
2616 The presence and purpose of a field, and the syntax of its
2617 value may differ between types of control files.
2621 Field names are not case-sensitive, but it is usual to
2622 capitalize the field names using mixed case as shown below.
2623 Field values are case-sensitive unless the description of the
2624 field says otherwise.
2628 Paragraph separators (empty lines) and lines consisting only of
2629 spaces and tabs are not allowed within field values or between
2630 fields. Empty lines in field values are usually escaped by
2631 representing them by a space followed by a dot.
2635 Lines starting with # without any preceding whitespace are comments
2636 lines that are only permitted in source package control files
2637 (<file>debian/control</file>). These comment lines are ignored, even
2638 between two continuation lines. They do not end logical lines.
2642 All control files must be encoded in UTF-8.
2646 <sect id="sourcecontrolfiles">
2647 <heading>Source package control files -- <file>debian/control</file></heading>
2650 The <file>debian/control</file> file contains the most vital
2651 (and version-independent) information about the source package
2652 and about the binary packages it creates.
2656 The first paragraph of the control file contains information about
2657 the source package in general. The subsequent sets each describe a
2658 binary package that the source tree builds.
2662 The fields in the general paragraph (the first one, for the source
2665 <list compact="compact">
2666 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2667 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2668 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2669 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2670 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2671 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2672 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2673 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2674 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2675 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2680 The fields in the binary package paragraphs are:
2682 <list compact="compact">
2683 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2684 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2685 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2686 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2687 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2688 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2689 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2691 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2696 The syntax and semantics of the fields are described below.
2700 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2701 generate control files for binary packages (see below), by
2702 <prgn>dpkg-genchanges</prgn> to generate the
2703 <file>.changes</file> file to accompany the upload, and by
2704 <prgn>dpkg-source</prgn> when it creates the
2705 <file>.dsc</file> source control file as part of a source
2706 archive. Some fields are folded in <file>debian/control</file>,
2707 but not in any other control
2708 file. These tools are responsible for removing the line
2709 breaks from such fields when using fields from
2710 <file>debian/control</file> to generate other control files.
2714 The fields here may contain variable references - their
2715 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2716 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2717 when they generate output control files.
2718 See <ref id="substvars"> for details.
2722 <sect id="binarycontrolfiles">
2723 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2726 The <file>DEBIAN/control</file> file contains the most vital
2727 (and version-dependent) information about a binary package. It
2728 consists of a single paragraph.
2732 The fields in this file are:
2734 <list compact="compact">
2735 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2736 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2737 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2738 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2739 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2740 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2741 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2742 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2743 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2744 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2745 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2746 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2747 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2752 <sect id="debiansourcecontrolfiles">
2753 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2756 This file consists of a single paragraph, possibly surrounded by
2757 a PGP signature. The fields of that paragraph are listed below.
2758 Their syntax is described above, in <ref id="controlsyntax">.
2760 <list compact="compact">
2761 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2762 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2763 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2764 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2765 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2766 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2768 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2769 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2770 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2771 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2772 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2773 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2774 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2775 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2780 The Debian source control file is generated by
2781 <prgn>dpkg-source</prgn> when it builds the source
2782 archive, from other files in the source package,
2783 described above. When unpacking, it is checked against
2784 the files and directories in the other parts of the
2790 <sect id="debianchangesfiles">
2791 <heading>Debian changes files -- <file>.changes</file></heading>
2794 The <file>.changes</file> files are used by the Debian archive
2795 maintenance software to process updates to packages. They
2796 consist of a single paragraph, possibly surrounded by a PGP
2797 signature. That paragraph contains information from the
2798 <file>debian/control</file> file and other data about the
2799 source package gathered via <file>debian/changelog</file>
2800 and <file>debian/rules</file>.
2804 <file>.changes</file> files have a format version that is
2805 incremented whenever the documented fields or their meaning
2806 change. This document describes format &changesversion;.
2810 The fields in this file are:
2812 <list compact="compact">
2813 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2814 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2818 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2820 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2821 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2822 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2823 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2824 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2825 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2826 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2827 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2828 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2833 <sect id="controlfieldslist">
2834 <heading>List of fields</heading>
2836 <sect1 id="f-Source">
2837 <heading><tt>Source</tt></heading>
2840 This field identifies the source package name.
2844 In <file>debian/control</file> or a <file>.dsc</file> file,
2845 this field must contain only the name of the source package.
2849 In a binary package control file or a <file>.changes</file>
2850 file, the source package name may be followed by a version
2851 number in parentheses<footnote>
2852 It is customary to leave a space after the package name
2853 if a version number is specified.
2855 This version number may be omitted (and is, by
2856 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2857 the <tt>Version</tt> field of the binary package in
2858 question. The field itself may be omitted from a binary
2859 package control file when the source package has the same
2860 name and version as the binary package.
2864 Package names (both source and binary,
2865 see <ref id="f-Package">) must consist only of lower case
2866 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2867 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2868 (<tt>.</tt>). They must be at least two characters long and
2869 must start with an alphanumeric character.
2873 <sect1 id="f-Maintainer">
2874 <heading><tt>Maintainer</tt></heading>
2877 The package maintainer's name and email address. The name
2878 must come first, then the email address inside angle
2879 brackets <tt><></tt> (in RFC822 format).
2883 If the maintainer's name contains a full stop then the
2884 whole field will not work directly as an email address due
2885 to a misfeature in the syntax specified in RFC822; a
2886 program using this field as an address must check for this
2887 and correct the problem if necessary (for example by
2888 putting the name in round brackets and moving it to the
2889 end, and bringing the email address forward).
2893 See <ref id="maintainer"> for additional requirements and
2894 information about package maintainers.
2898 <sect1 id="f-Uploaders">
2899 <heading><tt>Uploaders</tt></heading>
2902 List of the names and email addresses of co-maintainers of the
2903 package, if any. If the package has other maintainers besides
2904 the one named in the <qref id="f-Maintainer">Maintainer
2905 field</qref>, their names and email addresses should be listed
2906 here. The format of each entry is the same as that of the
2907 Maintainer field, and multiple entries must be comma
2912 This is normally an optional field, but if
2913 the <tt>Maintainer</tt> control field names a group of people
2914 and a shared email address, the <tt>Uploaders</tt> field must
2915 be present and must contain at least one human with their
2916 personal email address.
2920 The Uploaders field in <file>debian/control</file> can be folded.
2924 <sect1 id="f-Changed-By">
2925 <heading><tt>Changed-By</tt></heading>
2928 The name and email address of the person who prepared this
2929 version of the package, usually a maintainer. The syntax is
2930 the same as for the <qref id="f-Maintainer">Maintainer
2935 <sect1 id="f-Section">
2936 <heading><tt>Section</tt></heading>
2939 This field specifies an application area into which the package
2940 has been classified. See <ref id="subsections">.
2944 When it appears in the <file>debian/control</file> file,
2945 it gives the value for the subfield of the same name in
2946 the <tt>Files</tt> field of the <file>.changes</file> file.
2947 It also gives the default for the same field in the binary
2952 <sect1 id="f-Priority">
2953 <heading><tt>Priority</tt></heading>
2956 This field represents how important it is that the user
2957 have the package installed. See <ref id="priorities">.
2961 When it appears in the <file>debian/control</file> file,
2962 it gives the value for the subfield of the same name in
2963 the <tt>Files</tt> field of the <file>.changes</file> file.
2964 It also gives the default for the same field in the binary
2969 <sect1 id="f-Package">
2970 <heading><tt>Package</tt></heading>
2973 The name of the binary package.
2977 Binary package names must follow the same syntax and
2978 restrictions as source package names. See <ref id="f-Source">
2983 <sect1 id="f-Architecture">
2984 <heading><tt>Architecture</tt></heading>
2987 Depending on context and the control file used, the
2988 <tt>Architecture</tt> field can include the following sets of
2992 A unique single word identifying a Debian machine
2993 architecture as described in <ref id="arch-spec">.
2996 An architecture wildcard identifying a set of Debian
2997 machine architectures, see <ref id="arch-wildcard-spec">.
2998 <tt>any</tt> matches all Debian machine architectures
2999 and is the most frequently used.
3002 <tt>all</tt>, which indicates an
3003 architecture-independent package.
3006 <tt>source</tt>, which indicates a source package.
3012 In the main <file>debian/control</file> file in the source
3013 package, this field may contain the special
3014 value <tt>all</tt>, the special architecture
3015 wildcard <tt>any</tt>, or a list of specific and wildcard
3016 architectures separated by spaces. If <tt>all</tt>
3017 or <tt>any</tt> appears, that value must be the entire
3018 contents of the field. Most packages will use
3019 either <tt>all</tt> or <tt>any</tt>.
3023 Specifying a specific list of architectures indicates that the
3024 source will build an architecture-dependent package only on
3025 architectures included in the list. Specifying a list of
3026 architecture wildcards indicates that the source will build an
3027 architecture-dependent package on only those architectures
3028 that match any of the specified architecture wildcards.
3029 Specifying a list of architectures or architecture wildcards
3030 other than <tt>any</tt> is for the minority of cases where a
3031 program is not portable or is not useful on some
3032 architectures. Where possible, the program should be made
3037 In the Debian source control file <file>.dsc</file>, this
3038 field contains a list of architectures and architecture
3039 wildcards separated by spaces. When the list contains the
3040 architecture wildcard <tt>any</tt>, the only other value
3041 allowed in the list is <tt>all</tt>.
3045 The list may include (or consist solely of) the special
3046 value <tt>all</tt>. In other words, in <file>.dsc</file>
3047 files unlike the <file>debian/control</file>, <tt>all</tt> may
3048 occur in combination with specific architectures.
3049 The <tt>Architecture</tt> field in the Debian source control
3050 file <file>.dsc</file> is generally constructed from
3051 the <tt>Architecture</tt> fields in
3052 the <file>debian/control</file> in the source package.
3056 Specifying only <tt>any</tt> indicates that the source package
3057 isn't dependent on any particular architecture and should
3058 compile fine on any one. The produced binary package(s)
3059 will be specific to whatever the current build architecture is.
3063 Specifying only <tt>all</tt> indicates that the source package
3064 will only build architecture-independent packages.
3068 Specifying <tt>any all</tt> indicates that the source package
3069 isn't dependent on any particular architecture. The set of
3070 produced binary packages will include at least one
3071 architecture-dependant package and one architecture-independent
3076 Specifying a list of architectures or architecture wildcards
3077 indicates that the source will build an architecture-dependent
3078 package, and will only work correctly on the listed or
3079 matching architectures. If the source package also builds at
3080 least one architecture-independent package, <tt>all</tt> will
3081 also be included in the list.
3085 In a <file>.changes</file> file, the <tt>Architecture</tt>
3086 field lists the architecture(s) of the package(s) currently
3087 being uploaded. This will be a list; if the source for the
3088 package is also being uploaded, the special
3089 entry <tt>source</tt> is also present. <tt>all</tt> will be
3090 present if any architecture-independent packages are being
3091 uploaded. Architecture wildcards such as <tt>any</tt> must
3092 never occur in the <tt>Architecture</tt> field in
3093 the <file>.changes</file> file.
3097 See <ref id="debianrules"> for information on how to get
3098 the architecture for the build process.
3102 <sect1 id="f-Essential">
3103 <heading><tt>Essential</tt></heading>
3106 This is a boolean field which may occur only in the
3107 control file of a binary package or in a per-package fields
3108 paragraph of a source package control file.
3112 If set to <tt>yes</tt> then the package management system
3113 will refuse to remove the package (upgrading and replacing
3114 it is still possible). The other possible value is <tt>no</tt>,
3115 which is the same as not having the field at all.
3120 <heading>Package interrelationship fields:
3121 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3122 <tt>Recommends</tt>, <tt>Suggests</tt>,
3123 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3124 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3128 These fields describe the package's relationships with
3129 other packages. Their syntax and semantics are described
3130 in <ref id="relationships">.</p>
3133 <sect1 id="f-Standards-Version">
3134 <heading><tt>Standards-Version</tt></heading>
3137 The most recent version of the standards (the policy
3138 manual and associated texts) with which the package
3143 The version number has four components: major and minor
3144 version number and major and minor patch level. When the
3145 standards change in a way that requires every package to
3146 change the major number will be changed. Significant
3147 changes that will require work in many packages will be
3148 signaled by a change to the minor number. The major patch
3149 level will be changed for any change to the meaning of the
3150 standards, however small; the minor patch level will be
3151 changed when only cosmetic, typographical or other edits
3152 are made which neither change the meaning of the document
3153 nor affect the contents of packages.
3157 Thus only the first three components of the policy version
3158 are significant in the <em>Standards-Version</em> control
3159 field, and so either these three components or all four
3160 components may be specified.<footnote>
3161 In the past, people specified the full version number
3162 in the Standards-Version field, for example "2.3.0.0".
3163 Since minor patch-level changes don't introduce new
3164 policy, it was thought it would be better to relax
3165 policy and only require the first 3 components to be
3166 specified, in this example "2.3.0". All four
3167 components may still be used if someone wishes to do so.
3173 <sect1 id="f-Version">
3174 <heading><tt>Version</tt></heading>
3177 The version number of a package. The format is:
3178 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3182 The three components here are:
3184 <tag><var>epoch</var></tag>
3187 This is a single (generally small) unsigned integer. It
3188 may be omitted, in which case zero is assumed. If it is
3189 omitted then the <var>upstream_version</var> may not
3194 It is provided to allow mistakes in the version numbers
3195 of older versions of a package, and also a package's
3196 previous version numbering schemes, to be left behind.
3200 <tag><var>upstream_version</var></tag>
3203 This is the main part of the version number. It is
3204 usually the version number of the original ("upstream")
3205 package from which the <file>.deb</file> file has been made,
3206 if this is applicable. Usually this will be in the same
3207 format as that specified by the upstream author(s);
3208 however, it may need to be reformatted to fit into the
3209 package management system's format and comparison
3214 The comparison behavior of the package management system
3215 with respect to the <var>upstream_version</var> is
3216 described below. The <var>upstream_version</var>
3217 portion of the version number is mandatory.
3221 The <var>upstream_version</var> may contain only
3222 alphanumerics<footnote>
3223 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3225 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3226 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3227 tilde) and should start with a digit. If there is no
3228 <var>debian_revision</var> then hyphens are not allowed;
3229 if there is no <var>epoch</var> then colons are not
3234 <tag><var>debian_revision</var></tag>
3237 This part of the version number specifies the version of
3238 the Debian package based on the upstream version. It
3239 may contain only alphanumerics and the characters
3240 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3241 tilde) and is compared in the same way as the
3242 <var>upstream_version</var> is.
3246 It is optional; if it isn't present then the
3247 <var>upstream_version</var> may not contain a hyphen.
3248 This format represents the case where a piece of
3249 software was written specifically to be a Debian
3250 package, where the Debian package source must always
3251 be identical to the pristine source and therefore no
3252 revision indication is required.
3256 It is conventional to restart the
3257 <var>debian_revision</var> at <tt>1</tt> each time the
3258 <var>upstream_version</var> is increased.
3262 The package management system will break the version
3263 number apart at the last hyphen in the string (if there
3264 is one) to determine the <var>upstream_version</var> and
3265 <var>debian_revision</var>. The absence of a
3266 <var>debian_revision</var> is equivalent to a
3267 <var>debian_revision</var> of <tt>0</tt>.
3274 When comparing two version numbers, first the <var>epoch</var>
3275 of each are compared, then the <var>upstream_version</var> if
3276 <var>epoch</var> is equal, and then <var>debian_revision</var>
3277 if <var>upstream_version</var> is also equal.
3278 <var>epoch</var> is compared numerically. The
3279 <var>upstream_version</var> and <var>debian_revision</var>
3280 parts are compared by the package management system using the
3281 following algorithm:
3285 The strings are compared from left to right.
3289 First the initial part of each string consisting entirely of
3290 non-digit characters is determined. These two parts (one of
3291 which may be empty) are compared lexically. If a difference
3292 is found it is returned. The lexical comparison is a
3293 comparison of ASCII values modified so that all the letters
3294 sort earlier than all the non-letters and so that a tilde
3295 sorts before anything, even the end of a part. For example,
3296 the following parts are in sorted order from earliest to
3297 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3298 <tt>a</tt>.<footnote>
3299 One common use of <tt>~</tt> is for upstream pre-releases.
3300 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3301 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3306 Then the initial part of the remainder of each string which
3307 consists entirely of digit characters is determined. The
3308 numerical values of these two parts are compared, and any
3309 difference found is returned as the result of the comparison.
3310 For these purposes an empty string (which can only occur at
3311 the end of one or both version strings being compared) counts
3316 These two steps (comparing and removing initial non-digit
3317 strings and initial digit strings) are repeated until a
3318 difference is found or both strings are exhausted.
3322 Note that the purpose of epochs is to allow us to leave behind
3323 mistakes in version numbering, and to cope with situations
3324 where the version numbering scheme changes. It is
3325 <em>not</em> intended to cope with version numbers containing
3326 strings of letters which the package management system cannot
3327 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3328 silly orderings.<footnote>
3329 The author of this manual has heard of a package whose
3330 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3331 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3337 <sect1 id="f-Description">
3338 <heading><tt>Description</tt></heading>
3341 In a source or binary control file, the <tt>Description</tt>
3342 field contains a description of the binary package, consisting
3343 of two parts, the synopsis or the short description, and the
3344 long description. It is a multiline field with the following
3350 Description: <single line synopsis>
3351 <extended description over several lines>
3356 The lines in the extended description can have these formats:
3362 Those starting with a single space are part of a paragraph.
3363 Successive lines of this form will be word-wrapped when
3364 displayed. The leading space will usually be stripped off.
3365 The line must contain at least one non-whitespace character.
3369 Those starting with two or more spaces. These will be
3370 displayed verbatim. If the display cannot be panned
3371 horizontally, the displaying program will line wrap them "hard"
3372 (i.e., without taking account of word breaks). If it can they
3373 will be allowed to trail off to the right. None, one or two
3374 initial spaces may be deleted, but the number of spaces
3375 deleted from each line will be the same (so that you can have
3376 indenting work correctly, for example). The line must
3377 contain at least one non-whitespace character.
3381 Those containing a single space followed by a single full stop
3382 character. These are rendered as blank lines. This is the
3383 <em>only</em> way to get a blank line<footnote>
3384 Completely empty lines will not be rendered as blank lines.
3385 Instead, they will cause the parser to think you're starting
3386 a whole new record in the control file, and will therefore
3387 likely abort with an error.
3392 Those containing a space, a full stop and some more characters.
3393 These are for future expansion. Do not use them.
3399 Do not use tab characters. Their effect is not predictable.
3403 See <ref id="descriptions"> for further information on this.
3407 In a <file>.changes</file> file, the <tt>Description</tt>
3408 field contains a summary of the descriptions for the packages
3409 being uploaded. For this case, the first line of the field
3410 value (the part on the same line as <tt>Description:</tt>) is
3411 always empty. It is a multiline field, with one
3412 line per package. Each line is
3413 indented by one space and contains the name of a binary
3414 package, a space, a hyphen (<tt>-</tt>), a space, and the
3415 short description line from that package.
3419 <sect1 id="f-Distribution">
3420 <heading><tt>Distribution</tt></heading>
3423 In a <file>.changes</file> file or parsed changelog output
3424 this contains the (space-separated) name(s) of the
3425 distribution(s) where this version of the package should
3426 be installed. Valid distributions are determined by the
3427 archive maintainers.<footnote>
3428 Example distribution names in the Debian archive used in
3429 <file>.changes</file> files are:
3430 <taglist compact="compact">
3431 <tag><em>unstable</em></tag>
3433 This distribution value refers to the
3434 <em>developmental</em> part of the Debian distribution
3435 tree. Most new packages, new upstream versions of
3436 packages and bug fixes go into the <em>unstable</em>
3440 <tag><em>experimental</em></tag>
3442 The packages with this distribution value are deemed
3443 by their maintainers to be high risk. Oftentimes they
3444 represent early beta or developmental packages from
3445 various sources that the maintainers want people to
3446 try, but are not ready to be a part of the other parts
3447 of the Debian distribution tree.
3452 Others are used for updating stable releases or for
3453 security uploads. More information is available in the
3454 Debian Developer's Reference, section "The Debian
3458 The Debian archive software only supports listing a single
3459 distribution. Migration of packages to other distributions is
3460 handled outside of the upload process.
3465 <heading><tt>Date</tt></heading>
3468 This field includes the date the package was built or last
3469 edited. It must be in the same format as the <var>date</var>
3470 in a <file>debian/changelog</file> entry.
3474 The value of this field is usually extracted from the
3475 <file>debian/changelog</file> file - see
3476 <ref id="dpkgchangelog">).
3480 <sect1 id="f-Format">
3481 <heading><tt>Format</tt></heading>
3484 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3485 files, this field declares the format version of that file.
3486 The syntax of the field value is the same as that of
3487 a <qref id="f-Version">package version number</qref> except
3488 that no epoch or Debian revision is allowed. The format
3489 described in this document is <tt>&changesversion;</tt>.
3493 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3494 Debian source control</qref> files, this field declares the
3495 format of the source package. The field value is used by
3496 programs acting on a source package to interpret the list of
3497 files in the source package and determine how to unpack it.
3498 The syntax of the field value is a numeric major revision, a
3499 period, a numeric minor revision, and then an optional subtype
3500 after whitespace, which if specified is an alphanumeric word
3501 in parentheses. The subtype is optional in the syntax but may
3502 be mandatory for particular source format revisions.
3504 The source formats currently supported by the Debian archive
3505 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3506 and <tt>3.0 (quilt)</tt>.
3511 <sect1 id="f-Urgency">
3512 <heading><tt>Urgency</tt></heading>
3515 This is a description of how important it is to upgrade to
3516 this version from previous ones. It consists of a single
3517 keyword taking one of the values <tt>low</tt>,
3518 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3519 <tt>critical</tt><footnote>
3520 Other urgency values are supported with configuration
3521 changes in the archive software but are not used in Debian.
3522 The urgency affects how quickly a package will be considered
3523 for inclusion into the <tt>testing</tt> distribution and
3524 gives an indication of the importance of any fixes included
3525 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3526 treated as synonymous.
3527 </footnote> (not case-sensitive) followed by an optional
3528 commentary (separated by a space) which is usually in
3529 parentheses. For example:
3532 Urgency: low (HIGH for users of diversions)
3538 The value of this field is usually extracted from the
3539 <file>debian/changelog</file> file - see
3540 <ref id="dpkgchangelog">.
3544 <sect1 id="f-Changes">
3545 <heading><tt>Changes</tt></heading>
3548 This multiline field contains the human-readable changes data, describing
3549 the differences between the last version and the current one.
3553 The first line of the field value (the part on the same line
3554 as <tt>Changes:</tt>) is always empty. The content of the
3555 field is expressed as continuation lines, with each line
3556 indented by at least one space. Blank lines must be
3557 represented by a line consisting only of a space and a full
3562 The value of this field is usually extracted from the
3563 <file>debian/changelog</file> file - see
3564 <ref id="dpkgchangelog">).
3568 Each version's change information should be preceded by a
3569 "title" line giving at least the version, distribution(s)
3570 and urgency, in a human-readable way.
3574 If data from several versions is being returned the entry
3575 for the most recent version should be returned first, and
3576 entries should be separated by the representation of a
3577 blank line (the "title" line may also be followed by the
3578 representation of a blank line).
3582 <sect1 id="f-Binary">
3583 <heading><tt>Binary</tt></heading>
3586 This folded field is a list of binary packages. Its syntax and
3587 meaning varies depending on the control file in which it
3592 When it appears in the <file>.dsc</file> file, it lists binary
3593 packages which a source package can produce, separated by
3595 A space after each comma is conventional.
3596 </footnote>. The source package
3597 does not necessarily produce all of these binary packages for
3598 every architecture. The source control file doesn't contain
3599 details of which architectures are appropriate for which of
3600 the binary packages.
3604 When it appears in a <file>.changes</file> file, it lists the
3605 names of the binary packages being uploaded, separated by
3606 whitespace (not commas).
3610 <sect1 id="f-Installed-Size">
3611 <heading><tt>Installed-Size</tt></heading>
3614 This field appears in the control files of binary packages,
3615 and in the <file>Packages</file> files. It gives an estimate
3616 of the total amount of disk space required to install the
3617 named package. Actual installed size may vary based on block
3618 size, file system properties, or actions taken by package
3623 The disk space is given as the integer value of the estimated
3624 installed size in bytes, divided by 1024 and rounded up.
3628 <sect1 id="f-Files">
3629 <heading><tt>Files</tt></heading>
3632 This field contains a list of files with information about
3633 each one. The exact information and syntax varies with
3638 In all cases, Files is a multiline field. The first line of
3639 the field value (the part on the same line as <tt>Files:</tt>)
3640 is always empty. The content of the field is expressed as
3641 continuation lines, one line per file. Each line must be
3642 indented by one space and contain a number of sub-fields,
3643 separated by spaces, as described below.
3647 In the <file>.dsc</file> file, each line contains the MD5
3648 checksum, size and filename of the tar file and (if
3649 applicable) diff file which make up the remainder of the
3650 source package<footnote>
3651 That is, the parts which are not the <tt>.dsc</tt>.
3652 </footnote>. For example:
3655 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3656 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3658 The exact forms of the filenames are described
3659 in <ref id="pkg-sourcearchives">.
3663 In the <file>.changes</file> file this contains one line per
3664 file being uploaded. Each line contains the MD5 checksum,
3665 size, section and priority and the filename. For example:
3668 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3669 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3670 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3671 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3673 The <qref id="f-Section">section</qref>
3674 and <qref id="f-Priority">priority</qref> are the values of
3675 the corresponding fields in the main source control file. If
3676 no section or priority is specified then <tt>-</tt> should be
3677 used, though section and priority values must be specified for
3678 new packages to be installed properly.
3682 The special value <tt>byhand</tt> for the section in a
3683 <tt>.changes</tt> file indicates that the file in question
3684 is not an ordinary package file and must by installed by
3685 hand by the distribution maintainers. If the section is
3686 <tt>byhand</tt> the priority should be <tt>-</tt>.
3690 If a new Debian revision of a package is being shipped and
3691 no new original source archive is being distributed the
3692 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3693 entry for the original source archive
3694 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3695 but the <file>.changes</file> file should leave it out. In
3696 this case the original source archive on the distribution
3697 site must match exactly, byte-for-byte, the original
3698 source archive which was used to generate the
3699 <file>.dsc</file> file and diff which are being uploaded.</p>
3702 <sect1 id="f-Closes">
3703 <heading><tt>Closes</tt></heading>
3706 A space-separated list of bug report numbers that the upload
3707 governed by the .changes file closes.
3711 <sect1 id="f-Homepage">
3712 <heading><tt>Homepage</tt></heading>
3715 The URL of the web site for this package, preferably (when
3716 applicable) the site from which the original source can be
3717 obtained and any additional upstream documentation or
3718 information may be found. The content of this field is a
3719 simple URL without any surrounding characters such as
3724 <sect1 id="f-Checksums">
3725 <heading><tt>Checksums-Sha1</tt>
3726 and <tt>Checksums-Sha256</tt></heading>
3729 These multiline fields contain a list of files with a checksum and size
3730 for each one. Both <tt>Checksums-Sha1</tt>
3731 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3732 only in the checksum algorithm used: SHA-1
3733 for <tt>Checksums-Sha1</tt> and SHA-256
3734 for <tt>Checksums-Sha256</tt>.
3738 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3739 multiline fields. The first line of the field value (the part
3740 on the same line as <tt>Checksums-Sha1:</tt>
3741 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3742 of the field is expressed as continuation lines, one line per
3743 file. Each line consists of the checksum, a space, the file
3744 size, a space, and the file name. For example (from
3745 a <file>.changes</file> file):
3748 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3749 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3750 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3751 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3753 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3754 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3755 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3756 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3761 In the <file>.dsc</file> file, these fields should list all
3762 files that make up the source package. In
3763 the <file>.changes</file> file, these fields should list all
3764 files being uploaded. The list of files in these fields
3765 must match the list of files in the <tt>Files</tt> field.
3769 <sect1 id="f-DM-Upload-Allowed">
3770 <heading><tt>DM-Upload-Allowed</tt></heading>
3773 Indicates that Debian Maintainers may upload this package to
3774 the Debian archive. The only valid value is <tt>yes</tt>. If
3775 the field <tt>DM-Upload-Allowed: yes</tt> is present in the
3776 source section of the source control file of the most recent
3777 version of a package in unstable or experimental, the Debian
3778 archive will accept uploads of this package signed with a key
3779 in the Debian Maintainer keyring. See the General
3780 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3781 name="Endorse the concept of Debian Maintainers"> for more
3786 <sect1 id="f-VCS-fields">
3787 <heading>Version Control System (VCS) fields</heading>
3790 Debian source packages are increasingly developed using VCSs. The
3791 purpose of the following fields is to indicate a publicly accessible
3792 repository where the Debian source package is developed.
3795 <tag><tt>Vcs-Browser</tt></tag>
3798 URL of a web interface for browsing the repository.
3803 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3804 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3805 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3810 The field name identifies the VCS. The field's value uses the
3811 version control system's conventional syntax for describing
3812 repository locations and should be sufficient to locate the
3813 repository used for packaging. Ideally, it also locates the
3814 branch used for development of new versions of the Debian
3818 In the case of Git, the value consists of a URL, optionally
3819 followed by the word <tt>-b</tt> and the name of a branch in
3820 the indicated repository, following the syntax of the
3821 <tt>git clone</tt> command. If no branch is specified, the
3822 packaging should be on the default branch.
3825 More than one different VCS may be specified for the same
3835 <heading>User-defined fields</heading>
3838 Additional user-defined fields may be added to the
3839 source package control file. Such fields will be
3840 ignored, and not copied to (for example) binary or
3841 Debian source control files or upload control files.
3845 If you wish to add additional unsupported fields to
3846 these output files you should use the mechanism
3851 Fields in the main source control information file with
3852 names starting <tt>X</tt>, followed by one or more of
3853 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3854 be copied to the output files. Only the part of the
3855 field name after the hyphen will be used in the output
3856 file. Where the letter <tt>B</tt> is used the field
3857 will appear in binary package control files, where the
3858 letter <tt>S</tt> is used in Debian source control
3859 files and where <tt>C</tt> is used in upload control
3860 (<tt>.changes</tt>) files.
3864 For example, if the main source information control file
3867 XBS-Comment: I stand between the candle and the star.
3869 then the binary and Debian source control files will contain the
3872 Comment: I stand between the candle and the star.
3881 <chapt id="maintainerscripts">
3882 <heading>Package maintainer scripts and installation procedure</heading>
3885 <heading>Introduction to package maintainer scripts</heading>
3888 It is possible to supply scripts as part of a package which
3889 the package management system will run for you when your
3890 package is installed, upgraded or removed.
3894 These scripts are the control information
3895 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3896 and <prgn>postrm</prgn>. They must be proper executable files;
3897 if they are scripts (which is recommended), they must start with
3898 the usual <tt>#!</tt> convention. They should be readable and
3899 executable by anyone, and must not be world-writable.
3903 The package management system looks at the exit status from
3904 these scripts. It is important that they exit with a
3905 non-zero status if there is an error, so that the package
3906 management system can stop its processing. For shell
3907 scripts this means that you <em>almost always</em> need to
3908 use <tt>set -e</tt> (this is usually true when writing shell
3909 scripts, in fact). It is also important, of course, that
3910 they exit with a zero status if everything went well.
3914 Additionally, packages interacting with users
3915 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3916 should install a <prgn>config</prgn> script as a control
3917 information file. See <ref id="maintscriptprompt"> for details.
3921 When a package is upgraded a combination of the scripts from
3922 the old and new packages is called during the upgrade
3923 procedure. If your scripts are going to be at all
3924 complicated you need to be aware of this, and may need to
3925 check the arguments to your scripts.
3929 Broadly speaking the <prgn>preinst</prgn> is called before
3930 (a particular version of) a package is unpacked, and the
3931 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3932 before (a version of) a package is removed and the
3933 <prgn>postrm</prgn> afterwards.
3937 Programs called from maintainer scripts should not normally
3938 have a path prepended to them. Before installation is
3939 started, the package management system checks to see if the
3940 programs <prgn>ldconfig</prgn>,
3941 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3942 and <prgn>update-rc.d</prgn> can be found via the
3943 <tt>PATH</tt> environment variable. Those programs, and any
3944 other program that one would expect to be in the
3945 <tt>PATH</tt>, should thus be invoked without an absolute
3946 pathname. Maintainer scripts should also not reset the
3947 <tt>PATH</tt>, though they might choose to modify it by
3948 prepending or appending package-specific directories. These
3949 considerations really apply to all shell scripts.</p>
3952 <sect id="idempotency">
3953 <heading>Maintainer scripts idempotency</heading>
3956 It is necessary for the error recovery procedures that the
3957 scripts be idempotent. This means that if it is run
3958 successfully, and then it is called again, it doesn't bomb
3959 out or cause any harm, but just ensures that everything is
3960 the way it ought to be. If the first call failed, or
3961 aborted half way through for some reason, the second call
3962 should merely do the things that were left undone the first
3963 time, if any, and exit with a success status if everything
3965 This is so that if an error occurs, the user interrupts
3966 <prgn>dpkg</prgn> or some other unforeseen circumstance
3967 happens you don't leave the user with a badly-broken
3968 package when <prgn>dpkg</prgn> attempts to repeat the
3974 <sect id="controllingterminal">
3975 <heading>Controlling terminal for maintainer scripts</heading>
3978 Maintainer scripts are not guaranteed to run with a controlling
3979 terminal and may not be able to interact with the user. They
3980 must be able to fall back to noninteractive behavior if no
3981 controlling terminal is available. Maintainer scripts that
3982 prompt via a program conforming to the Debian Configuration
3983 Management Specification (see <ref id="maintscriptprompt">) may
3984 assume that program will handle falling back to noninteractive
3989 For high-priority prompts without a reasonable default answer,
3990 maintainer scripts may abort if there is no controlling
3991 terminal. However, this situation should be avoided if at all
3992 possible, since it prevents automated or unattended installs.
3993 In most cases, users will consider this to be a bug in the
3998 <sect id="exitstatus">
3999 <heading>Exit status</heading>
4002 Each script must return a zero exit status for
4003 success, or a nonzero one for failure, since the package
4004 management system looks for the exit status of these scripts
4005 and determines what action to take next based on that datum.
4009 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4014 What follows is a summary of all the ways in which maintainer
4015 scripts may be called along with what facilities those scripts
4016 may rely on being available at that time. Script names preceded
4017 by <var>new-</var> are the scripts from the new version of a
4018 package being installed, upgraded to, or downgraded to. Script
4019 names preceded by <var>old-</var> are the scripts from the old
4020 version of a package that is being upgraded from or downgraded
4025 The <prgn>preinst</prgn> script may be called in the following
4028 <tag><var>new-preinst</var> <tt>install</tt></tag>
4029 <tag><var>new-preinst</var> <tt>install</tt>
4030 <var>old-version</var></tag>
4031 <tag><var>new-preinst</var> <tt>upgrade</tt>
4032 <var>old-version</var></tag>
4034 The package will not yet be unpacked, so
4035 the <prgn>preinst</prgn> script cannot rely on any files
4036 included in its package. Only essential packages and
4037 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4038 available. Pre-dependencies will have been configured at
4039 least once, but at the time the <prgn>preinst</prgn> is
4040 called they may only be in an unpacked or "Half-Configured"
4041 state if a previous version of the pre-dependency was
4042 completely configured and has not been removed since then.
4045 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4046 <var>new-version</var></tag>
4048 Called during error handling of an upgrade that failed after
4049 unpacking the new package because the <tt>postrm
4050 upgrade</tt> action failed. The unpacked files may be
4051 partly from the new version or partly missing, so the script
4052 cannot rely on files included in the package. Package
4053 dependencies may not be available. Pre-dependencies will be
4054 at least unpacked following the same rules as above, except
4055 they may be only "Half-Installed" if an upgrade of the
4056 pre-dependency failed.<footnote>
4057 This can happen if the new version of the package no
4058 longer pre-depends on a package that had been partially
4066 The <prgn>postinst</prgn> script may be called in the following
4069 <tag><var>postinst</var> <tt>configure</tt>
4070 <var>most-recently-configured-version</var></tag>
4072 The files contained in the package will be unpacked. All
4073 package dependencies will at least be unpacked. If there
4074 are no circular dependencies involved, all package
4075 dependencies will be configured. For behavior in the case
4076 of circular dependencies, see the discussion
4077 in <ref id="binarydeps">.
4080 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4081 <var>new-version</var></tag>
4082 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4083 <tt>in-favour</tt> <var>package</var>
4084 <var>new-version</var></tag>
4085 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4086 <tag><var>deconfigured's-postinst</var>
4087 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4088 <var>failed-install-package</var> <var>version</var>
4089 [<tt>removing</tt> <var>conflicting-package</var>
4090 <var>version</var>]</tag>
4092 The files contained in the package will be unpacked. All
4093 package dependencies will at least be "Half-Installed" and
4094 will have previously been configured and not removed.
4095 However, dependencies may not be configured or even fully
4096 unpacked in some error situations.<footnote>
4097 For example, suppose packages foo and bar are installed
4098 with foo depending on bar. If an upgrade of bar were
4099 started and then aborted, and then an attempt to remove
4100 foo failed because its <prgn>prerm</prgn> script failed,
4101 foo's <tt>postinst abort-remove</tt> would be called with
4102 bar only "Half-Installed".
4104 The <prgn>postinst</prgn> should still attempt any actions
4105 for which its dependencies are required, since they will
4106 normally be available, but consider the correct error
4107 handling approach if those actions fail. Aborting
4108 the <prgn>postinst</prgn> action if commands or facilities
4109 from the package dependencies are not available is often the
4116 The <prgn>prerm</prgn> script may be called in the following
4119 <tag><var>prerm</var> <tt>remove</tt></tag>
4120 <tag><var>old-prerm</var>
4121 <tt>upgrade</tt><var>new-version</var></tag>
4122 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4123 <tt>in-favour</tt> <var>package</var>
4124 <var>new-version</var></tag>
4125 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4126 <tt>in-favour</tt> <var>package-being-installed</var>
4127 <var>version</var> [<tt>removing</tt>
4128 <var>conflicting-package</var> <var>version</var>]</tag>
4130 The package whose <prgn>prerm</prgn> is being called will be
4131 at least "Half-Installed". All package dependencies will at
4132 least be "Half-Installed" and will have previously been
4133 configured and not removed. If there was no error, all
4134 dependencies will at least be unpacked, but these actions
4135 may be called in various error states where dependencies are
4136 only "Half-Installed" due to a partial upgrade.
4139 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4140 <var>old-version</var></tag>
4142 Called during error handling when <tt>prerm upgrade</tt>
4143 fails. The new package will not yet be unpacked, and all
4144 the same constraints as for <tt>preinst upgrade</tt> apply.
4150 The <prgn>postrm</prgn> script may be called in the following
4153 <tag><var>postrm</var> <tt>remove</tt></tag>
4154 <tag><var>postrm</var> <tt>purge</tt></tag>
4155 <tag><var>old-postrm</var> <tt>upgrade</tt>
4156 <var>new-version</var></tag>
4157 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4158 <var>overwriter</var> <var>overwriter-version</var></tag>
4160 The <prgn>postrm</prgn> script is called after the package's
4161 files have been removed or replaced. The package
4162 whose <prgn>postrm</prgn> is being called may have
4163 previously been deconfigured and only be unpacked, at which
4164 point subsequent package changes do not consider its
4165 dependencies. Therefore, all <prgn>postrm</prgn> actions
4166 may only rely on essential packages and must gracefully skip
4167 any actions that require the package's dependencies if those
4168 dependencies are unavailable.<footnote>
4169 This is often done by checking whether the command or
4170 facility the <prgn>postrm</prgn> intends to call is
4171 available before calling it. For example:
4173 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4174 . /usr/share/debconf/confmodule
4178 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4179 configuration for the package
4180 if <package>debconf</package> is installed.
4184 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4185 <var>old-version</var></tag>
4187 Called when the old <tt>postrm upgrade</tt> action fails.
4188 The new package will be unpacked, but only essential
4189 packages and pre-dependencies can be relied on.
4190 Pre-dependencies will either be configured or will be
4191 "Unpacked" or "Half-Configured" but previously had been
4192 configured and was never removed.
4195 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4196 <tag><var>new-postrm</var> <tt>abort-install</tt>
4197 <var>old-version</var></tag>
4198 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4199 <var>old-version</var></tag>
4201 Called before unpacking the new package as part of the
4202 error handling of <prgn>preinst</prgn> failures. May assume
4203 the same state as <prgn>preinst</prgn> can assume.
4209 <sect id="unpackphase">
4210 <heading>Details of unpack phase of installation or upgrade</heading>
4213 The procedure on installation/upgrade/overwrite/disappear
4214 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4215 stage of <tt>dpkg --install</tt>) is as follows. In each
4216 case, if a major error occurs (unless listed below) the
4217 actions are, in general, run backwards - this means that the
4218 maintainer scripts are run with different arguments in
4219 reverse order. These are the "error unwind" calls listed
4226 If a version of the package is already installed, call
4227 <example compact="compact">
4228 <var>old-prerm</var> upgrade <var>new-version</var>
4232 If the script runs but exits with a non-zero
4233 exit status, <prgn>dpkg</prgn> will attempt:
4234 <example compact="compact">
4235 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4237 If this works, the upgrade continues. If this
4238 does not work, the error unwind:
4239 <example compact="compact">
4240 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4242 If this works, then the old-version is
4243 "Installed", if not, the old version is in a
4244 "Half-Configured" state.
4250 If a "conflicting" package is being removed at the same time,
4251 or if any package will be broken (due to <tt>Breaks</tt>):
4254 If <tt>--auto-deconfigure</tt> is
4255 specified, call, for each package to be deconfigured
4256 due to <tt>Breaks</tt>:
4257 <example compact="compact">
4258 <var>deconfigured's-prerm</var> deconfigure \
4259 in-favour <var>package-being-installed</var> <var>version</var>
4262 <example compact="compact">
4263 <var>deconfigured's-postinst</var> abort-deconfigure \
4264 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4266 The deconfigured packages are marked as
4267 requiring configuration, so that if
4268 <tt>--install</tt> is used they will be
4269 configured again if possible.
4272 If any packages depended on a conflicting
4273 package being removed and <tt>--auto-deconfigure</tt> is
4274 specified, call, for each such package:
4275 <example compact="compact">
4276 <var>deconfigured's-prerm</var> deconfigure \
4277 in-favour <var>package-being-installed</var> <var>version</var> \
4278 removing <var>conflicting-package</var> <var>version</var>
4281 <example compact="compact">
4282 <var>deconfigured's-postinst</var> abort-deconfigure \
4283 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4284 removing <var>conflicting-package</var> <var>version</var>
4286 The deconfigured packages are marked as
4287 requiring configuration, so that if
4288 <tt>--install</tt> is used they will be
4289 configured again if possible.
4292 To prepare for removal of each conflicting package, call:
4293 <example compact="compact">
4294 <var>conflictor's-prerm</var> remove \
4295 in-favour <var>package</var> <var>new-version</var>
4298 <example compact="compact">
4299 <var>conflictor's-postinst</var> abort-remove \
4300 in-favour <var>package</var> <var>new-version</var>
4309 If the package is being upgraded, call:
4310 <example compact="compact">
4311 <var>new-preinst</var> upgrade <var>old-version</var>
4313 If this fails, we call:
4315 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4322 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4324 is called. If this works, then the old version
4325 is in an "Installed" state, or else it is left
4326 in an "Unpacked" state.
4331 If it fails, then the old version is left
4332 in an "Half-Installed" state.
4339 Otherwise, if the package had some configuration
4340 files from a previous version installed (i.e., it
4341 is in the "configuration files only" state):
4342 <example compact="compact">
4343 <var>new-preinst</var> install <var>old-version</var>
4347 <var>new-postrm</var> abort-install <var>old-version</var>
4349 If this fails, the package is left in a
4350 "Half-Installed" state, which requires a
4351 reinstall. If it works, the packages is left in
4352 a "Config-Files" state.
4355 Otherwise (i.e., the package was completely purged):
4356 <example compact="compact">
4357 <var>new-preinst</var> install
4360 <example compact="compact">
4361 <var>new-postrm</var> abort-install
4363 If the error-unwind fails, the package is in a
4364 "Half-Installed" phase, and requires a
4365 reinstall. If the error unwind works, the
4366 package is in a not installed state.
4373 The new package's files are unpacked, overwriting any
4374 that may be on the system already, for example any
4375 from the old version of the same package or from
4376 another package. Backups of the old files are kept
4377 temporarily, and if anything goes wrong the package
4378 management system will attempt to put them back as
4379 part of the error unwind.
4383 It is an error for a package to contain files which
4384 are on the system in another package, unless
4385 <tt>Replaces</tt> is used (see <ref id="replaces">).
4387 The following paragraph is not currently the case:
4388 Currently the <tt>- - force-overwrite</tt> flag is
4389 enabled, downgrading it to a warning, but this may not
4395 It is a more serious error for a package to contain a
4396 plain file or other kind of non-directory where another
4397 package has a directory (again, unless
4398 <tt>Replaces</tt> is used). This error can be
4399 overridden if desired using
4400 <tt>--force-overwrite-dir</tt>, but this is not
4405 Packages which overwrite each other's files produce
4406 behavior which, though deterministic, is hard for the
4407 system administrator to understand. It can easily
4408 lead to "missing" programs if, for example, a package
4409 is unpacked which overwrites a file from another
4410 package, and is then removed again.<footnote>
4411 Part of the problem is due to what is arguably a
4412 bug in <prgn>dpkg</prgn>.
4417 A directory will never be replaced by a symbolic link
4418 to a directory or vice versa; instead, the existing
4419 state (symlink or not) will be left alone and
4420 <prgn>dpkg</prgn> will follow the symlink if there is
4429 If the package is being upgraded, call
4430 <example compact="compact">
4431 <var>old-postrm</var> upgrade <var>new-version</var>
4435 If this fails, <prgn>dpkg</prgn> will attempt:
4436 <example compact="compact">
4437 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4439 If this works, installation continues. If not,
4441 <example compact="compact">
4442 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4444 If this fails, the old version is left in a
4445 "Half-Installed" state. If it works, dpkg now
4447 <example compact="compact">
4448 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4450 If this fails, the old version is left in a
4451 "Half-Installed" state. If it works, dpkg now
4453 <example compact="compact">
4454 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4456 If this fails, the old version is in an
4463 This is the point of no return - if
4464 <prgn>dpkg</prgn> gets this far, it won't back off
4465 past this point if an error occurs. This will
4466 leave the package in a fairly bad state, which
4467 will require a successful re-installation to clear
4468 up, but it's when <prgn>dpkg</prgn> starts doing
4469 things that are irreversible.
4474 Any files which were in the old version of the package
4475 but not in the new are removed.
4479 The new file list replaces the old.
4483 The new maintainer scripts replace the old.
4487 Any packages all of whose files have been overwritten
4488 during the installation, and which aren't required for
4489 dependencies, are considered to have been removed.
4490 For each such package
4493 <prgn>dpkg</prgn> calls:
4494 <example compact="compact">
4495 <var>disappearer's-postrm</var> disappear \
4496 <var>overwriter</var> <var>overwriter-version</var>
4500 The package's maintainer scripts are removed.
4503 It is noted in the status database as being in a
4504 sane state, namely not installed (any conffiles
4505 it may have are ignored, rather than being
4506 removed by <prgn>dpkg</prgn>). Note that
4507 disappearing packages do not have their prerm
4508 called, because <prgn>dpkg</prgn> doesn't know
4509 in advance that the package is going to
4516 Any files in the package we're unpacking that are also
4517 listed in the file lists of other packages are removed
4518 from those lists. (This will lobotomize the file list
4519 of the "conflicting" package if there is one.)
4523 The backup files made during installation, above, are
4529 The new package's status is now sane, and recorded as
4534 Here is another point of no return - if the
4535 conflicting package's removal fails we do not unwind
4536 the rest of the installation; the conflicting package
4537 is left in a half-removed limbo.
4542 If there was a conflicting package we go and do the
4543 removal actions (described below), starting with the
4544 removal of the conflicting package's files (any that
4545 are also in the package being unpacked have already
4546 been removed from the conflicting package's file list,
4547 and so do not get removed now).
4553 <sect id="configdetails"><heading>Details of configuration</heading>
4556 When we configure a package (this happens with <tt>dpkg
4557 --install</tt> and <tt>dpkg --configure</tt>), we first
4558 update any <tt>conffile</tt>s and then call:
4559 <example compact="compact">
4560 <var>postinst</var> configure <var>most-recently-configured-version</var>
4565 No attempt is made to unwind after errors during
4566 configuration. If the configuration fails, the package is in
4567 a "Failed Config" state, and an error message is generated.
4571 If there is no most recently configured version
4572 <prgn>dpkg</prgn> will pass a null argument.
4575 Historical note: Truly ancient (pre-1997) versions of
4576 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4577 (including the angle brackets) in this case. Even older
4578 ones did not pass a second argument at all, under any
4579 circumstance. Note that upgrades using such an old dpkg
4580 version are unlikely to work for other reasons, even if
4581 this old argument behavior is handled by your postinst script.
4587 <sect id="removedetails"><heading>Details of removal and/or
4588 configuration purging</heading>
4594 <example compact="compact">
4595 <var>prerm</var> remove
4599 If prerm fails during replacement due to conflict
4601 <var>conflictor's-postinst</var> abort-remove \
4602 in-favour <var>package</var> <var>new-version</var>
4606 <var>postinst</var> abort-remove
4610 If this fails, the package is in a "Half-Configured"
4611 state, or else it remains "Installed".
4615 The package's files are removed (except <tt>conffile</tt>s).
4618 <example compact="compact">
4619 <var>postrm</var> remove
4623 If it fails, there's no error unwind, and the package is in
4624 an "Half-Installed" state.
4629 All the maintainer scripts except the <prgn>postrm</prgn>
4634 If we aren't purging the package we stop here. Note
4635 that packages which have no <prgn>postrm</prgn> and no
4636 <tt>conffile</tt>s are automatically purged when
4637 removed, as there is no difference except for the
4638 <prgn>dpkg</prgn> status.
4642 The <tt>conffile</tt>s and any backup files
4643 (<tt>~</tt>-files, <tt>#*#</tt> files,
4644 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4649 <example compact="compact">
4650 <var>postrm</var> purge
4654 If this fails, the package remains in a "Config-Files"
4659 The package's file list is removed.
4668 <chapt id="relationships">
4669 <heading>Declaring relationships between packages</heading>
4671 <sect id="depsyntax">
4672 <heading>Syntax of relationship fields</heading>
4675 These fields all have a uniform syntax. They are a list of
4676 package names separated by commas.
4680 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4681 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4682 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4683 control fields of the package, which declare
4684 dependencies on other packages, the package names listed may
4685 also include lists of alternative package names, separated
4686 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4687 if any one of the alternative packages is installed, that
4688 part of the dependency is considered to be satisfied.
4692 All of the fields except for <tt>Provides</tt> may restrict
4693 their applicability to particular versions of each named
4694 package. This is done in parentheses after each individual
4695 package name; the parentheses should contain a relation from
4696 the list below followed by a version number, in the format
4697 described in <ref id="f-Version">.
4701 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4702 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4703 earlier, earlier or equal, exactly equal, later or equal and
4704 strictly later, respectively. The deprecated
4705 forms <tt><</tt> and <tt>></tt> were confusingly used to
4706 mean earlier/later or equal, rather than strictly earlier/later,
4707 and must not appear in new packages (though <prgn>dpkg</prgn>
4708 still supports them with a warning).
4712 Whitespace may appear at any point in the version
4713 specification subject to the rules in <ref
4714 id="controlsyntax">, and must appear where it's necessary to
4715 disambiguate; it is not otherwise significant. All of the
4716 relationship fields can only be folded in source package control files. For
4717 consistency and in case of future changes to
4718 <prgn>dpkg</prgn> it is recommended that a single space be
4719 used after a version relationship and before a version
4720 number; it is also conventional to put a single space after
4721 each comma, on either side of each vertical bar, and before
4722 each open parenthesis. When opening a continuation line in a relationship field, it
4723 is conventional to do so after a comma and before the space
4724 following that comma.
4728 For example, a list of dependencies might appear as:
4729 <example compact="compact">
4732 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4737 Relationships may be restricted to a certain set of
4738 architectures. This is indicated in brackets after each
4739 individual package name and the optional version specification.
4740 The brackets enclose a non-empty list of Debian architecture names
4741 in the format described in <ref id="arch-spec">,
4742 separated by whitespace. Exclamation marks may be prepended to
4743 each of the names. (It is not permitted for some names to be
4744 prepended with exclamation marks while others aren't.)
4748 For build relationship fields
4749 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4750 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4751 the current Debian host architecture is not in this list and
4752 there are no exclamation marks in the list, or it is in the list
4753 with a prepended exclamation mark, the package name and the
4754 associated version specification are ignored completely for the
4755 purposes of defining the relationships.
4760 <example compact="compact">
4762 Build-Depends-Indep: texinfo
4763 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4764 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4766 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4767 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4768 <tt>gnumach-dev</tt> only on hurd-i386.
4772 For binary relationship fields and the <tt>Built-Using</tt>
4773 field, the architecture restriction
4774 syntax is only supported in the source package control
4775 file <file>debian/control</file>. When the corresponding binary
4776 package control file is generated, the relationship will either
4777 be omitted or included without the architecture restriction
4778 based on the architecture of the binary package. This means
4779 that architecture restrictions must not be used in binary
4780 relationship fields for architecture-independent packages
4781 (<tt>Architecture: all</tt>).
4786 <example compact="compact">
4787 Depends: foo [i386], bar [amd64]
4789 becomes <tt>Depends: foo</tt> when the package is built on
4790 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4791 package is built on the <tt>amd64</tt> architecture, and omitted
4792 entirely in binary packages built on all other architectures.
4796 If the architecture-restricted dependency is part of a set of
4797 alternatives using <tt>|</tt>, that alternative is ignored
4798 completely on architectures that do not match the restriction.
4800 <example compact="compact">
4801 Build-Depends: foo [!i386] | bar [!amd64]
4803 is equivalent to <tt>bar</tt> on the i386 architecture, to
4804 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4805 bar</tt> on all other architectures.
4809 Relationships may also be restricted to a certain set of
4810 architectures using architecture wildcards in the format
4811 described in <ref id="arch-wildcard-spec">. The syntax for
4812 declaring such restrictions is the same as declaring
4813 restrictions using a certain set of architectures without
4814 architecture wildcards. For example:
4815 <example compact="compact">
4816 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4818 is equivalent to <tt>foo</tt> on architectures using the Linux
4819 kernel and any cpu, <tt>bar</tt> on architectures using any
4820 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4821 using a kernel other than Linux.
4825 Note that the binary package relationship fields such as
4826 <tt>Depends</tt> appear in one of the binary package
4827 sections of the control file, whereas the build-time
4828 relationships such as <tt>Build-Depends</tt> appear in the
4829 source package section of the control file (which is the
4834 <sect id="binarydeps">
4835 <heading>Binary Dependencies - <tt>Depends</tt>,
4836 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4837 <tt>Pre-Depends</tt>
4841 Packages can declare in their control file that they have
4842 certain relationships to other packages - for example, that
4843 they may not be installed at the same time as certain other
4844 packages, and/or that they depend on the presence of others.
4848 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4849 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4850 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4851 <tt>Breaks</tt> is described in <ref id="breaks">, and
4852 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4853 rest are described below.
4857 These seven fields are used to declare a dependency
4858 relationship by one package on another. Except for
4859 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4860 depending (binary) package's control file.
4861 (<tt>Enhances</tt> appears in the recommending package's
4862 control file, and <tt>Breaks</tt> appears in the version of
4863 depended-on package which causes the named package to
4868 A <tt>Depends</tt> field takes effect <em>only</em> when a
4869 package is to be configured. It does not prevent a package
4870 being on the system in an unconfigured state while its
4871 dependencies are unsatisfied, and it is possible to replace
4872 a package whose dependencies are satisfied and which is
4873 properly installed with a different version whose
4874 dependencies are not and cannot be satisfied; when this is
4875 done the depending package will be left unconfigured (since
4876 attempts to configure it will give errors) and will not
4877 function properly. If it is necessary, a
4878 <tt>Pre-Depends</tt> field can be used, which has a partial
4879 effect even when a package is being unpacked, as explained
4880 in detail below. (The other three dependency fields,
4881 <tt>Recommends</tt>, <tt>Suggests</tt> and
4882 <tt>Enhances</tt>, are only used by the various front-ends
4883 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4884 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4888 Since <tt>Depends</tt> only places requirements on the order in
4889 which packages are configured, packages in an installation run
4890 are usually all unpacked first and all configured later.
4892 This approach makes dependency resolution easier. If two
4893 packages A and B are being upgraded, the installed package A
4894 depends on exactly the installed package B, and the new
4895 package A depends on exactly the new package B (a common
4896 situation when upgrading shared libraries and their
4897 corresponding development packages), satisfying the
4898 dependencies at every stage of the upgrade would be
4899 impossible. This relaxed restriction means that both new
4900 packages can be unpacked together and then configured in their
4906 If there is a circular dependency among packages being installed
4907 or removed, installation or removal order honoring the
4908 dependency order is impossible, requiring the dependency loop be
4909 broken at some point and the dependency requirements violated
4910 for at least one package. Packages involved in circular
4911 dependencies may not be able to rely on their dependencies being
4912 configured before they themselves are configured, depending on
4913 which side of the break of the circular dependency loop they
4914 happen to be on. If one of the packages in the loop has
4915 no <prgn>postinst</prgn> script, then the cycle will be broken
4916 at that package; this ensures that all <prgn>postinst</prgn>
4917 scripts are run with their dependencies properly configured if
4918 this is possible. Otherwise the breaking point is arbitrary.
4919 Packages should therefore avoid circular dependencies where
4920 possible, particularly if they have <prgn>postinst</prgn>
4925 The meaning of the five dependency fields is as follows:
4927 <tag><tt>Depends</tt></tag>
4930 This declares an absolute dependency. A package will
4931 not be configured unless all of the packages listed in
4932 its <tt>Depends</tt> field have been correctly
4933 configured (unless there is a circular dependency as
4938 The <tt>Depends</tt> field should be used if the
4939 depended-on package is required for the depending
4940 package to provide a significant amount of
4945 The <tt>Depends</tt> field should also be used if the
4946 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4947 require the depended-on package to be unpacked or
4948 configured in order to run. In the case of <tt>postinst
4949 configure</tt>, the depended-on packages will be unpacked
4950 and configured first. (If both packages are involved in a
4951 dependency loop, this might not work as expected; see the
4952 explanation a few paragraphs back.) In the case
4953 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4954 actions, the package dependencies will normally be at
4955 least unpacked, but they may be only "Half-Installed" if a
4956 previous upgrade of the dependency failed.
4960 Finally, the <tt>Depends</tt> field should be used if the
4961 depended-on package is needed by the <prgn>postrm</prgn>
4962 script to fully clean up after the package removal. There
4963 is no guarantee that package dependencies will be
4964 available when <prgn>postrm</prgn> is run, but the
4965 depended-on package is more likely to be available if the
4966 package declares a dependency (particularly in the case
4967 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4968 script must gracefully skip actions that require a
4969 dependency if that dependency isn't available.
4973 <tag><tt>Recommends</tt></tag>
4976 This declares a strong, but not absolute, dependency.
4980 The <tt>Recommends</tt> field should list packages
4981 that would be found together with this one in all but
4982 unusual installations.
4986 <tag><tt>Suggests</tt></tag>
4988 This is used to declare that one package may be more
4989 useful with one or more others. Using this field
4990 tells the packaging system and the user that the
4991 listed packages are related to this one and can
4992 perhaps enhance its usefulness, but that installing
4993 this one without them is perfectly reasonable.
4996 <tag><tt>Enhances</tt></tag>
4998 This field is similar to Suggests but works in the
4999 opposite direction. It is used to declare that a
5000 package can enhance the functionality of another
5004 <tag><tt>Pre-Depends</tt></tag>
5007 This field is like <tt>Depends</tt>, except that it
5008 also forces <prgn>dpkg</prgn> to complete installation
5009 of the packages named before even starting the
5010 installation of the package which declares the
5011 pre-dependency, as follows:
5015 When a package declaring a pre-dependency is about to
5016 be <em>unpacked</em> the pre-dependency can be
5017 satisfied if the depended-on package is either fully
5018 configured, <em>or even if</em> the depended-on
5019 package(s) are only unpacked or in the "Half-Configured"
5020 state, provided that they have been configured
5021 correctly at some point in the past (and not removed
5022 or partially removed since). In this case, both the
5023 previously-configured and currently unpacked or
5024 "Half-Configured" versions must satisfy any version
5025 clause in the <tt>Pre-Depends</tt> field.
5029 When the package declaring a pre-dependency is about to
5030 be <em>configured</em>, the pre-dependency will be treated
5031 as a normal <tt>Depends</tt>. It will be considered
5032 satisfied only if the depended-on package has been
5033 correctly configured. However, unlike
5034 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5035 permit circular dependencies to be broken. If a circular
5036 dependency is encountered while attempting to honor
5037 <tt>Pre-Depends</tt>, the installation will be aborted.
5041 <tt>Pre-Depends</tt> are also required if the
5042 <prgn>preinst</prgn> script depends on the named package.
5043 It is best to avoid this situation if possible.
5047 <tt>Pre-Depends</tt> should be used sparingly,
5048 preferably only by packages whose premature upgrade or
5049 installation would hamper the ability of the system to
5050 continue with any upgrade that might be in progress.
5054 You should not specify a <tt>Pre-Depends</tt> entry for a
5055 package before this has been discussed on the
5056 <tt>debian-devel</tt> mailing list and a consensus about
5057 doing that has been reached. See <ref id="dependencies">.
5064 When selecting which level of dependency to use you should
5065 consider how important the depended-on package is to the
5066 functionality of the one declaring the dependency. Some
5067 packages are composed of components of varying degrees of
5068 importance. Such a package should list using
5069 <tt>Depends</tt> the package(s) which are required by the
5070 more important components. The other components'
5071 requirements may be mentioned as Suggestions or
5072 Recommendations, as appropriate to the components' relative
5078 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5081 When one binary package declares that it breaks another,
5082 <prgn>dpkg</prgn> will refuse to allow the package which
5083 declares <tt>Breaks</tt> to be unpacked unless the broken
5084 package is deconfigured first, and it will refuse to
5085 allow the broken package to be reconfigured.
5089 A package will not be regarded as causing breakage merely
5090 because its configuration files are still installed; it must
5091 be at least "Half-Installed".
5095 A special exception is made for packages which declare that
5096 they break their own package name or a virtual package which
5097 they provide (see below): this does not count as a real
5102 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5103 version clause; such a <tt>Breaks</tt> is introduced in the
5104 version of an (implicit or explicit) dependency which violates
5105 an assumption or reveals a bug in earlier versions of the broken
5106 package, or which takes over a file from earlier versions of the
5107 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5108 will inform higher-level package management tools that the
5109 broken package must be upgraded before the new one.
5113 If the breaking package also overwrites some files from the
5114 older package, it should use <tt>Replaces</tt> to ensure this
5115 goes smoothly. See <ref id="replaces"> for a full discussion
5116 of taking over files from other packages, including how to
5117 use <tt>Breaks</tt> in those cases.
5121 Many of the cases where <tt>Breaks</tt> should be used were
5122 previously handled with <tt>Conflicts</tt>
5123 because <tt>Breaks</tt> did not yet exist.
5124 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5125 See <ref id="conflicts"> for more information about the
5130 <sect id="conflicts">
5131 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5134 When one binary package declares a conflict with another using
5135 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5136 allow them to be unpacked on the system at the same time. This
5137 is a stronger restriction than <tt>Breaks</tt>, which prevents
5138 the broken package from being configured while the breaking
5139 package is in the "Unpacked" state but allows both packages to
5140 be unpacked at the same time.
5144 If one package is to be unpacked, the other must be removed
5145 first. If the package being unpacked is marked as replacing
5146 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5147 normally be used in this case) the one on the system, or the one
5148 on the system is marked as deselected, or both packages are
5149 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5150 automatically remove the package which is causing the conflict.
5151 Otherwise, it will halt the installation of the new package with
5152 an error. This mechanism is specifically designed to produce an
5153 error when the installed package is <tt>Essential</tt>, but the
5158 A package will not cause a conflict merely because its
5159 configuration files are still installed; it must be at least
5164 A special exception is made for packages which declare a
5165 conflict with their own package name, or with a virtual
5166 package which they provide (see below): this does not
5167 prevent their installation, and allows a package to conflict
5168 with others providing a replacement for it. You use this
5169 feature when you want the package in question to be the only
5170 package providing some feature.
5174 Normally, <tt>Breaks</tt> should be used instead
5175 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5176 stronger restriction on the ordering of package installation or
5177 upgrade and can make it more difficult for the package manager
5178 to find a correct solution to an upgrade or installation
5179 problem. <tt>Breaks</tt> should be used
5181 <item>when moving a file from one package to another (see
5182 <ref id="replaces">),</item>
5183 <item>when splitting a package (a special case of the previous
5185 <item>when the breaking package exposes a bug in or interacts
5186 badly with particular versions of the broken
5189 <tt>Conflicts</tt> should be used
5191 <item>when two packages provide the same file and will
5192 continue to do so,</item>
5193 <item>in conjunction with <tt>Provides</tt> when only one
5194 package providing a given virtual facility may be unpacked
5195 at a time (see <ref id="virtual">),</item>
5196 <item>in other cases where one must prevent simultaneous
5197 installation of two packages for reasons that are ongoing
5198 (not fixed in a later version of one of the packages) or
5199 that must prevent both packages from being unpacked at the
5200 same time, not just configured.</item>
5202 Be aware that adding <tt>Conflicts</tt> is normally not the best
5203 solution when two packages provide the same files. Depending on
5204 the reason for that conflict, using alternatives or renaming the
5205 files is often a better approach. See, for
5206 example, <ref id="binaries">.
5210 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5211 unless two packages cannot be installed at the same time or
5212 installing them both causes one of them to be broken or
5213 unusable. Having similar functionality or performing the same
5214 tasks as another package is not sufficient reason to
5215 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5219 A <tt>Conflicts</tt> entry may have an "earlier than" version
5220 clause if the reason for the conflict is corrected in a later
5221 version of one of the packages. However, normally the presence
5222 of an "earlier than" version clause is a sign
5223 that <tt>Breaks</tt> should have been used instead. An "earlier
5224 than" version clause in <tt>Conflicts</tt>
5225 prevents <prgn>dpkg</prgn> from upgrading or installing the
5226 package which declares such a conflict until the upgrade or
5227 removal of the conflicted-with package has been completed, which
5228 is a strong restriction.
5232 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5236 As well as the names of actual ("concrete") packages, the
5237 package relationship fields <tt>Depends</tt>,
5238 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5239 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5240 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5241 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5242 may mention "virtual packages".
5246 A <em>virtual package</em> is one which appears in the
5247 <tt>Provides</tt> control field of another package. The effect
5248 is as if the package(s) which provide a particular virtual
5249 package name had been listed by name everywhere the virtual
5250 package name appears. (See also <ref id="virtual_pkg">)
5254 If there are both concrete and virtual packages of the same
5255 name, then the dependency may be satisfied (or the conflict
5256 caused) by either the concrete package with the name in
5257 question or any other concrete package which provides the
5258 virtual package with the name in question. This is so that,
5259 for example, supposing we have
5260 <example compact="compact">
5263 </example> and someone else releases an enhanced version of
5264 the <tt>bar</tt> package they can say:
5265 <example compact="compact">
5269 and the <tt>bar-plus</tt> package will now also satisfy the
5270 dependency for the <tt>foo</tt> package.
5274 If a relationship field has a version number attached, only real
5275 packages will be considered to see whether the relationship is
5276 satisfied (or the prohibition violated, for a conflict or
5277 breakage). In other words, if a version number is specified,
5278 this is a request to ignore all <tt>Provides</tt> for that
5279 package name and consider only real packages. The package
5280 manager will assume that a package providing that virtual
5281 package is not of the "right" version. A <tt>Provides</tt>
5282 field may not contain version numbers, and the version number of
5283 the concrete package which provides a particular virtual package
5284 will not be considered when considering a dependency on or
5285 conflict with the virtual package name.<footnote>
5286 It is possible that a future release of <prgn>dpkg</prgn> may
5287 add the ability to specify a version number for each virtual
5288 package it provides. This feature is not yet present,
5289 however, and is expected to be used only infrequently.
5294 To specify which of a set of real packages should be the default
5295 to satisfy a particular dependency on a virtual package, list
5296 the real package as an alternative before the virtual one.
5300 If the virtual package represents a facility that can only be
5301 provided by one real package at a time, such as
5302 the <package>mail-transport-agent</package> virtual package that
5303 requires installation of a binary that would conflict with all
5304 other providers of that virtual package (see
5305 <ref id="mail-transport-agents">), all packages providing that
5306 virtual package should also declare a conflict with it
5307 using <tt>Conflicts</tt>. This will ensure that at most one
5308 provider of that virtual package is unpacked or installed at a
5313 <sect id="replaces"><heading>Overwriting files and replacing
5314 packages - <tt>Replaces</tt></heading>
5317 Packages can declare in their control file that they should
5318 overwrite files in certain other packages, or completely replace
5319 other packages. The <tt>Replaces</tt> control field has these
5320 two distinct purposes.
5323 <sect1><heading>Overwriting files in other packages</heading>
5326 It is usually an error for a package to contain files which
5327 are on the system in another package. However, if the
5328 overwriting package declares that it <tt>Replaces</tt> the one
5329 containing the file being overwritten, then <prgn>dpkg</prgn>
5330 will replace the file from the old package with that from the
5331 new. The file will no longer be listed as "owned" by the old
5332 package and will be taken over by the new package.
5333 Normally, <tt>Breaks</tt> should be used in conjunction
5334 with <tt>Replaces</tt>.<footnote>
5335 To see why <tt>Breaks</tt> is normally needed in addition
5336 to <tt>Replaces</tt>, consider the case of a file in the
5337 package <package>foo</package> being taken over by the
5338 package <package>foo-data</package>.
5339 <tt>Replaces</tt> will allow <package>foo-data</package> to
5340 be installed and take over that file. However,
5341 without <tt>Breaks</tt>, nothing
5342 requires <package>foo</package> to be upgraded to a newer
5343 version that knows it does not include that file and instead
5344 depends on <package>foo-data</package>. Nothing would
5345 prevent the new <package>foo-data</package> package from
5346 being installed and then removed, removing the file that it
5347 took over from <package>foo</package>. After that
5348 operation, the package manager would think the system was in
5349 a consistent state, but the <package>foo</package> package
5350 would be missing one of its files.
5355 For example, if a package <package>foo</package> is split
5356 into <package>foo</package> and <package>foo-data</package>
5357 starting at version 1.2-3, <package>foo-data</package> would
5359 <example compact="compact">
5360 Replaces: foo (<< 1.2-3)
5361 Breaks: foo (<< 1.2-3)
5363 in its control file. The new version of the
5364 package <package>foo</package> would normally have the field
5365 <example compact="compact">
5366 Depends: foo-data (>= 1.2-3)
5368 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5369 the files moved into <package>foo-data</package> are not
5370 required for normal operation).
5374 If a package is completely replaced in this way, so that
5375 <prgn>dpkg</prgn> does not know of any files it still
5376 contains, it is considered to have "disappeared". It will
5377 be marked as not wanted on the system (selected for
5378 removal) and not installed. Any <tt>conffile</tt>s
5379 details noted for the package will be ignored, as they
5380 will have been taken over by the overwriting package. The
5381 package's <prgn>postrm</prgn> script will be run with a
5382 special argument to allow the package to do any final
5383 cleanup required. See <ref id="mscriptsinstact">.
5385 Replaces is a one way relationship. You have to install
5386 the replacing package after the replaced package.
5391 For this usage of <tt>Replaces</tt>, virtual packages (see
5392 <ref id="virtual">) are not considered when looking at a
5393 <tt>Replaces</tt> field. The packages declared as being
5394 replaced must be mentioned by their real names.
5398 This usage of <tt>Replaces</tt> only takes effect when both
5399 packages are at least partially on the system at once. It is
5400 not relevant if the packages conflict unless the conflict has
5405 <sect1><heading>Replacing whole packages, forcing their
5409 Second, <tt>Replaces</tt> allows the packaging system to
5410 resolve which package should be removed when there is a
5411 conflict (see <ref id="conflicts">). This usage only takes
5412 effect when the two packages <em>do</em> conflict, so that the
5413 two usages of this field do not interfere with each other.
5417 In this situation, the package declared as being replaced
5418 can be a virtual package, so for example, all mail
5419 transport agents (MTAs) would have the following fields in
5420 their control files:
5421 <example compact="compact">
5422 Provides: mail-transport-agent
5423 Conflicts: mail-transport-agent
5424 Replaces: mail-transport-agent
5426 ensuring that only one MTA can be unpacked at any one
5427 time. See <ref id="virtual"> for more information about this
5432 <sect id="sourcebinarydeps">
5433 <heading>Relationships between source and binary packages -
5434 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5435 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5439 Source packages that require certain binary packages to be
5440 installed or absent at the time of building the package
5441 can declare relationships to those binary packages.
5445 This is done using the <tt>Build-Depends</tt>,
5446 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5447 <tt>Build-Conflicts-Indep</tt> control fields.
5451 Build-dependencies on "build-essential" binary packages can be
5452 omitted. Please see <ref id="pkg-relations"> for more information.
5456 The dependencies and conflicts they define must be satisfied
5457 (as defined earlier for binary packages) in order to invoke
5458 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5460 There is no Build-Depends-Arch; this role is essentially
5461 met with Build-Depends. Anyone building the
5462 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5463 assumed to be building the whole package, and therefore
5464 installation of all build dependencies is required.
5467 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5468 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5469 not yet know how to check for its existence, and
5470 <tt>binary-arch</tt>. The purpose of the original split
5471 between <tt>Build-Depends</tt> and
5472 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5473 wouldn't need to install extra packages needed only for the
5474 binary-indep targets. But without a build-arch/build-indep
5475 split, this didn't work, since most of the work is done in
5476 the build target, not in the binary target.
5480 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5481 <tt>binary-arch</tt></tag>
5483 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5484 fields must be satisfied when these targets are invoked.
5486 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5487 and <tt>binary-indep</tt></tag>
5489 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5490 <tt>Build-Depends-Indep</tt>, and
5491 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5492 these targets are invoked.
5498 <sect id="built-using">
5499 <heading>Additional source packages used to build the binary
5500 - <tt>Built-Using</tt>
5504 Some binary packages incorporate parts of other packages when built
5505 but do not have to depend on those packages. Examples include
5506 linking with static libraries or incorporating source code from
5507 another package during the build. In this case, the source packages
5508 of those other packages are a required part of the complete source
5509 (the binary package is not reproducible without them).
5513 A <tt>Built-Using</tt> field must list the corresponding source
5514 package for any such binary package incorporated during the build
5516 <tt>Build-Depends</tt> in the source package is not adequate since
5517 it (rightfully) does not document the exact version used in the
5520 including an "exactly equal" ("=") version relation on the version
5521 that was used to build that binary package<footnote>
5522 The archive software might reject packages that refer to
5523 non-existent sources.
5528 A package using the source code from the gcc-4.6-source
5529 binary package built from the gcc-4.6 source package would
5530 have this field in its control file:
5531 <example compact="compact">
5532 Built-Using: gcc-4.6 (= 4.6.0-11)
5537 A package including binaries from grub2 and loadlin would
5538 have this field in its control file:
5539 <example compact="compact">
5540 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5547 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5550 Packages containing shared libraries must be constructed with
5551 a little care to make sure that the shared library is always
5552 available. This is especially important for packages whose
5553 shared libraries are vitally important, such as the C library
5554 (currently <tt>libc6</tt>).
5558 This section deals only with public shared libraries: shared
5559 libraries that are placed in directories searched by the dynamic
5560 linker by default or which are intended to be linked against
5561 normally and possibly used by other, independent packages. Shared
5562 libraries that are internal to a particular package or that are
5563 only loaded as dynamic modules are not covered by this section and
5564 are not subject to its requirements.
5568 A shared library is identified by the <tt>SONAME</tt> attribute
5569 stored in its dynamic section. When a binary is linked against a
5570 shared library, the <tt>SONAME</tt> of the shared library is
5571 recorded in the binary's <tt>NEEDED</tt> section so that the
5572 dynamic linker knows that library must be loaded at runtime. The
5573 shared library file's full name (which usually contains additional
5574 version information not needed in the <tt>SONAME</tt>) is
5575 therefore normally not referenced directly. Instead, the shared
5576 library is loaded by its <tt>SONAME</tt>, which exists on the file
5577 system as a symlink pointing to the full name of the shared
5578 library. This symlink must be provided by the
5579 package. <ref id="sharedlibs-runtime"> describes how to do this.
5581 This is a convention of shared library versioning, but not a
5582 requirement. Some libraries use the <tt>SONAME</tt> as the full
5583 library file name instead and therefore do not need a symlink.
5584 Most, however, encode additional information about
5585 backwards-compatible revisions as a minor version number in the
5586 file name. The <tt>SONAME</tt> itself only changes when
5587 binaries linked with the earlier version of the shared library
5588 may no longer work, but the filename may change with each
5589 release of the library. See <ref id="sharedlibs-runtime"> for
5595 When linking a binary or another shared library against a shared
5596 library, the <tt>SONAME</tt> for that shared library is not yet
5597 known. Instead, the shared library is found by looking for a file
5598 matching the library name with <tt>.so</tt> appended. This file
5599 exists on the file system as a symlink pointing to the shared
5604 Shared libraries are normally split into several binary packages.
5605 The <tt>SONAME</tt> symlink is installed by the runtime shared
5606 library package, and the bare <tt>.so</tt> symlink is installed in
5607 the development package since it's only used when linking binaries
5608 or shared libraries. However, there are some exceptions for
5609 unusual shared libraries or for shared libraries that are also
5610 loaded as dynamic modules by other programs.
5614 This section is primarily concerned with how the separation of
5615 shared libraries into multiple packages should be done and how
5616 dependencies on and between shared library binary packages are
5617 managed in Debian. <ref id="libraries"> should be read in
5618 conjunction with this section and contains additional rules for
5619 the files contained in the shared library packages.
5622 <sect id="sharedlibs-runtime">
5623 <heading>Run-time shared libraries</heading>
5626 The run-time shared library must be placed in a package
5627 whose name changes whenever the <tt>SONAME</tt> of the shared
5628 library changes. This allows several versions of the shared
5629 library to be installed at the same time, allowing installation
5630 of the new version of the shared library without immediately
5631 breaking binaries that depend on the old version. Normally, the
5632 run-time shared library and its <tt>SONAME</tt> symlink should
5633 be placed in a package named
5634 <package><var>libraryname</var><var>soversion</var></package>,
5635 where <var>soversion</var> is the version number in
5636 the <tt>SONAME</tt> of the shared library.
5637 See <ref id="shlibs"> for detailed information on how to
5638 determine this version. Alternatively, if it would be confusing
5639 to directly append <var>soversion</var>
5640 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5641 itself ends in a number), you should use
5642 <package><var>libraryname</var>-<var>soversion</var></package>
5647 If you have several shared libraries built from the same source
5648 tree, you may lump them all together into a single shared
5649 library package provided that all of their <tt>SONAME</tt>s will
5650 always change together. Be aware that this is not normally the
5651 case, and if the <tt>SONAME</tt>s do not change together,
5652 upgrading such a merged shared library package will be
5653 unnecessarily difficult because of file conflicts with the old
5654 version of the package. When in doubt, always split shared
5655 library packages so that each binary package installs a single
5660 Every time the shared library ABI changes in a way that may
5661 break binaries linked against older versions of the shared
5662 library, the <tt>SONAME</tt> of the library and the
5663 corresponding name for the binary package containing the runtime
5664 shared library should change. Normally, this means
5665 the <tt>SONAME</tt> should change any time an interface is
5666 removed from the shared library or the signature of an interface
5667 (the number of parameters or the types of parameters that it
5668 takes, for example) is changed. This practice is vital to
5669 allowing clean upgrades from older versions of the package and
5670 clean transitions between the old ABI and new ABI without having
5671 to upgrade every affected package simultaneously.
5675 The <tt>SONAME</tt> and binary package name need not, and indeed
5676 normally should not, change if new interfaces are added but none
5677 are removed or changed, since this will not break binaries
5678 linked against the old shared library. Correct versioning of
5679 dependencies on the newer shared library by binaries that use
5680 the new interfaces is handled via
5681 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5682 system</qref> or via symbols files (see
5683 <manref name="deb-symbols" section="5">).
5687 The package should install the shared libraries under
5688 their normal names. For example, the <package>libgdbm3</package>
5689 package should install <file>libgdbm.so.3.0.0</file> as
5690 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5691 renamed or re-linked by any <prgn>prerm</prgn> or
5692 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5693 of renaming things safely without affecting running programs,
5694 and attempts to interfere with this are likely to lead to
5699 Shared libraries should not be installed executable, since
5700 the dynamic linker does not require this and trying to
5701 execute a shared library usually results in a core dump.
5705 The run-time library package should include the symbolic link for
5706 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5707 the shared libraries. For example,
5708 the <package>libgdbm3</package> package should include a symbolic
5709 link from <file>/usr/lib/libgdbm.so.3</file> to
5710 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5711 linker (for example <prgn>ld.so</prgn> or
5712 <prgn>ld-linux.so.*</prgn>) can find the library between the
5713 time that <prgn>dpkg</prgn> installs it and the time that
5714 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5716 The package management system requires the library to be
5717 placed before the symbolic link pointing to it in the
5718 <file>.deb</file> file. This is so that when
5719 <prgn>dpkg</prgn> comes to install the symlink
5720 (overwriting the previous symlink pointing at an older
5721 version of the library), the new shared library is already
5722 in place. In the past, this was achieved by creating the
5723 library in the temporary packaging directory before
5724 creating the symlink. Unfortunately, this was not always
5725 effective, since the building of the tar file in the
5726 <file>.deb</file> depended on the behavior of the underlying
5727 file system. Some file systems (such as reiserfs) reorder
5728 the files so that the order of creation is forgotten.
5729 Since version 1.7.0, <prgn>dpkg</prgn>
5730 reorders the files itself as necessary when building a
5731 package. Thus it is no longer important to concern
5732 oneself with the order of file creation.
5736 <sect1 id="ldconfig">
5737 <heading><tt>ldconfig</tt></heading>
5740 Any package installing shared libraries in one of the default
5741 library directories of the dynamic linker (which are currently
5742 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5743 listed in <file>/etc/ld.so.conf</file><footnote>
5744 These are currently <file>/usr/local/lib</file> plus
5745 directories under <file>/lib</file> and <file>/usr/lib</file>
5746 matching the multiarch triplet for the system architecture.
5748 must use <prgn>ldconfig</prgn> to update the shared library
5753 The package maintainer scripts must only call
5754 <prgn>ldconfig</prgn> under these circumstances:
5755 <list compact="compact">
5756 <item>When the <prgn>postinst</prgn> script is run with a
5757 first argument of <tt>configure</tt>, the script must call
5758 <prgn>ldconfig</prgn>, and may optionally invoke
5759 <prgn>ldconfig</prgn> at other times.
5761 <item>When the <prgn>postrm</prgn> script is run with a
5762 first argument of <tt>remove</tt>, the script should call
5763 <prgn>ldconfig</prgn>.
5768 During install or upgrade, the preinst is called before
5769 the new files are unpacked, so calling "ldconfig" is
5770 pointless. The preinst of an existing package can also be
5771 called if an upgrade fails. However, this happens during
5772 the critical time when a shared libs may exist on-disk
5773 under a temporary name. Thus, it is dangerous and
5774 forbidden by current policy to call "ldconfig" at this
5779 When a package is installed or upgraded, "postinst
5780 configure" runs after the new files are safely on-disk.
5781 Since it is perfectly safe to invoke ldconfig
5782 unconditionally in a postinst, it is OK for a package to
5783 simply put ldconfig in its postinst without checking the
5784 argument. The postinst can also be called to recover from
5785 a failed upgrade. This happens before any new files are
5786 unpacked, so there is no reason to call "ldconfig" at this
5791 For a package that is being removed, prerm is
5792 called with all the files intact, so calling ldconfig is
5793 useless. The other calls to "prerm" happen in the case of
5794 upgrade at a time when all the files of the old package
5795 are on-disk, so again calling "ldconfig" is pointless.
5799 postrm, on the other hand, is called with the "remove"
5800 argument just after the files are removed, so this is
5801 the proper time to call "ldconfig" to notify the system
5802 of the fact that the shared libraries from the package
5803 are removed. The postrm can be called at several other
5804 times. At the time of "postrm purge", "postrm
5805 abort-install", or "postrm abort-upgrade", calling
5806 "ldconfig" is useless because the shared lib files are
5807 not on-disk. However, when "postrm" is invoked with
5808 arguments "upgrade", "failed-upgrade", or "disappear", a
5809 shared lib may exist on-disk under a temporary filename.
5817 <sect id="sharedlibs-support-files">
5818 <heading>Shared library support files</heading>
5821 If your package contains files whose names do not change with
5822 each change in the library shared object version, you must not
5823 put them in the shared library package. Otherwise, several
5824 versions of the shared library cannot be installed at the same
5825 time without filename clashes, making upgrades and transitions
5826 unnecessarily difficult.
5830 It is recommended that supporting files and run-time support
5831 programs that do not need to be invoked manually by users, but
5832 are nevertheless required for the package to function, be placed
5833 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5834 preferably under <file>/usr/lib/</file><var>package-name</var>.
5835 If the program or file is architecture independent, the
5836 recommendation is for it to be placed in a subdirectory of
5837 <file>/usr/share</file> instead, preferably under
5838 <file>/usr/share/</file><var>package-name</var>. Following the
5839 <var>package-name</var> naming convention ensures that the file
5840 names change when the shared object version changes.
5844 Run-time support programs that use the shared library but are
5845 not required for the library to function or files used by the
5846 shared library that can be used by any version of the shared
5847 library package should instead be put in a separate package.
5848 This package might typically be named
5849 <package><var>libraryname</var>-tools</package>; note the
5850 absence of the <var>soversion</var> in the package name.
5854 Files and support programs only useful when compiling software
5855 against the library should be included in the development
5856 package for the library.<footnote>
5857 For example, a <file><var>package-name</var>-config</file>
5858 script or <package>pkg-config</package> configuration files.
5863 <sect id="sharedlibs-static">
5864 <heading>Static libraries</heading>
5867 The static library (<file><var>libraryname.a</var></file>)
5868 is usually provided in addition to the shared version.
5869 It is placed into the development package (see below).
5873 In some cases, it is acceptable for a library to be
5874 available in static form only; these cases include:
5876 <item>libraries for languages whose shared library support
5877 is immature or unstable</item>
5878 <item>libraries whose interfaces are in flux or under
5879 development (commonly the case when the library's
5880 major version number is zero, or where the ABI breaks
5881 across patchlevels)</item>
5882 <item>libraries which are explicitly intended to be
5883 available only in static form by their upstream
5888 <sect id="sharedlibs-dev">
5889 <heading>Development files</heading>
5892 If there are development files associated with a shared library,
5893 the source package needs to generate a binary development package
5894 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5895 or if you prefer only to support one development version at a
5896 time, <package><var>libraryname</var>-dev</package>. Installing
5897 the development package must result in installation of all the
5898 development files necessary for compiling programs against that
5899 shared library.<footnote>
5900 This wording allows the development files to be split into
5901 several packages, such as a separate architecture-independent
5902 <package><var>libraryname</var>-headers</package>, provided that
5903 the development package depends on all the required additional
5909 In case several development versions of a library exist, you may
5910 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5911 <ref id="conflicts">) to ensure that the user only installs one
5912 development version at a time (as different development versions are
5913 likely to have the same header files in them, which would cause a
5914 filename clash if both were unpacked).
5918 The development package should contain a symlink for the associated
5919 shared library without a version number. For example, the
5920 <package>libgdbm-dev</package> package should include a symlink
5921 from <file>/usr/lib/libgdbm.so</file> to
5922 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5923 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5924 <file>libgdbm.so</file> when compiling dynamically.
5928 If the package provides Ada Library Information
5929 (<file>*.ali</file>) files for use with GNAT, these files must be
5930 installed read-only (mode 0444) so that GNAT will not attempt to
5931 recompile them. This overrides the normal file mode requirements
5932 given in <ref id="permissions-owners">.
5936 <sect id="sharedlibs-intradeps">
5937 <heading>Dependencies between the packages of the same library</heading>
5940 Typically the development version should have an exact
5941 version dependency on the runtime library, to make sure that
5942 compilation and linking happens correctly. The
5943 <tt>${binary:Version}</tt> substitution variable can be
5944 useful for this purpose.
5946 Previously, <tt>${Source-Version}</tt> was used, but its name
5947 was confusing and it has been deprecated since dpkg 1.13.19.
5952 <sect id="sharedlibs-shlibdeps">
5953 <heading>Dependencies between the library and other packages -
5954 the <tt>shlibs</tt> system</heading>
5957 If a package contains a binary or library which links to a
5958 shared library, we must ensure that when the package is
5959 installed on the system, all of the libraries needed are
5960 also installed. This requirement led to the creation of the
5961 <tt>shlibs</tt> system, which is very simple in its design:
5962 any package which <em>provides</em> a shared library also
5963 provides information on the package dependencies required to
5964 ensure the presence of this library, and any package which
5965 <em>uses</em> a shared library uses this information to
5966 determine the dependencies it requires. The files which
5967 contain the mapping from shared libraries to the necessary
5968 dependency information are called <file>shlibs</file> files.
5972 When a package is built which contains any shared libraries, it
5973 must provide a <file>shlibs</file> file for other packages to
5974 use. When a package is built which contains any shared
5975 libraries or compiled binaries, it must run
5976 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5977 on these to determine the libraries used and hence the
5978 dependencies needed by this package.<footnote>
5980 <prgn>dpkg-shlibdeps</prgn> will use a program
5981 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5982 the libraries directly needed by the binaries or shared
5983 libraries in the package.
5987 We say that a binary <tt>foo</tt> <em>directly</em> uses
5988 a library <tt>libbar</tt> if it is explicitly linked
5989 with that library (that is, the library is listed in the ELF
5990 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5991 to the link line when the binary is created). Other
5992 libraries that are needed by <tt>libbar</tt> are linked
5993 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5994 linker will load them automatically when it loads
5995 <tt>libbar</tt>. A package should depend on the libraries
5996 it directly uses, but not the libraries it indirectly uses.
5997 The dependencies for those libraries will automatically pull
5998 in the other libraries.
6002 A good example of where this helps is the following. We
6003 could update <tt>libimlib</tt> with a new version that
6004 supports a new graphics format called dgf (but retaining the
6005 same major version number) and depends on <tt>libdgf</tt>.
6006 If we used <prgn>ldd</prgn> to add dependencies for every
6007 library directly or indirectly linked with a binary, every
6008 package that uses <tt>libimlib</tt> would need to be
6009 recompiled so it would also depend on <tt>libdgf</tt> or it
6010 wouldn't run due to missing symbols. Since dependencies are
6011 only added based on ELF <tt>NEEDED</tt> attribute, packages
6012 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6013 having the dependency on <tt>libdgf</tt> and so they would
6014 not need rebuilding.
6020 In the following sections, we will first describe where the
6021 various <tt>shlibs</tt> files are to be found, then how to
6022 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
6023 file format and how to create them if your package contains a
6028 <heading>The <tt>shlibs</tt> files present on the system</heading>
6031 There are several places where <tt>shlibs</tt> files are
6032 found. The following list gives them in the order in which
6034 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
6035 (The first one which gives the required information is used.)
6041 <p><file>debian/shlibs.local</file></p>
6044 This lists overrides for this package. This file should
6045 normally not be used, but may be needed temporarily in
6046 unusual situations to work around bugs in other packages,
6047 or in unusual cases where the normally declared dependency
6048 information in the installed <file>shlibs</file> file for
6049 a library cannot be used. This file overrides information
6050 obtained from any other source.
6055 <p><file>/etc/dpkg/shlibs.override</file></p>
6058 This lists global overrides. This list is normally
6059 empty. It is maintained by the local system
6065 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
6068 When packages are being built,
6069 any <file>debian/shlibs</file> files are copied into the
6070 control information file area of the temporary build
6071 directory and given the name <file>shlibs</file>. These
6072 files give details of any shared libraries included in the
6073 same package.<footnote>
6074 An example may help here. Let us say that the source
6075 package <tt>foo</tt> generates two binary
6076 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6077 When building the binary packages, the two packages are
6078 created in the directories <file>debian/libfoo2</file>
6079 and <file>debian/foo-runtime</file> respectively.
6080 (<file>debian/tmp</file> could be used instead of one of
6081 these.) Since <tt>libfoo2</tt> provides the
6082 <tt>libfoo</tt> shared library, it will require a
6083 <tt>shlibs</tt> file, which will be installed in
6084 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
6085 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
6086 When <prgn>dpkg-shlibdeps</prgn> is run on the
6087 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6089 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
6090 determine whether <tt>foo-prog</tt>'s library
6091 dependencies are satisfied by any of the libraries
6092 provided by <tt>libfoo2</tt>. For this reason,
6093 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
6094 the individual binary packages' <tt>shlibs</tt> files
6095 have been installed into the build directory.
6101 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
6104 These are the <file>shlibs</file> files corresponding to
6105 all of the packages installed on the system, and are
6106 maintained by the relevant package maintainers.
6111 <p><file>/etc/dpkg/shlibs.default</file></p>
6114 This file lists any shared libraries whose packages
6115 have failed to provide correct <file>shlibs</file> files.
6116 It was used when the <file>shlibs</file> setup was first
6117 introduced, but it is now normally empty. It is
6118 maintained by the <tt>dpkg</tt> maintainer.
6126 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
6127 <file>shlibs</file> files</heading>
6131 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
6132 into your <file>debian/rules</file> file. If your package
6133 contains only compiled binaries and libraries (but no scripts),
6134 you can use a command such as:
6135 <example compact="compact">
6136 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
6137 debian/tmp/usr/lib/*
6139 Otherwise, you will need to explicitly list the compiled
6140 binaries and libraries.<footnote>
6141 If you are using <tt>debhelper</tt>, the
6142 <prgn>dh_shlibdeps</prgn> program will do this work for you.
6143 It will also correctly handle multi-binary packages.
6148 This command puts the dependency information into the
6149 <file>debian/substvars</file> file, which is then used by
6150 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6151 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6152 field in the control file for this to work.
6156 If you have multiple binary packages, you will need to call
6157 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6158 compiled libraries or binaries. In such a case, you will
6159 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6160 utilities to specify a different <file>substvars</file> file.
6164 If you are creating a udeb for use in the Debian Installer,
6165 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6166 should use the dependency line of type <tt>udeb</tt> by
6167 adding the <tt>-tudeb</tt> option<footnote>
6168 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6169 will automatically add this option if it knows it is
6171 </footnote>. If there is no dependency line of
6172 type <tt>udeb</tt> in the <file>shlibs</file>
6173 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6178 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6179 <ref id="pkg-dpkg-shlibdeps"> and
6180 <manref name="dpkg-shlibdeps" section="1">.
6185 <heading>The <file>shlibs</file> File Format</heading>
6188 Each <file>shlibs</file> file has the same format. Lines
6189 beginning with <tt>#</tt> are considered to be comments and
6190 are ignored. Each line is of the form:
6191 <example compact="compact">
6192 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6197 We will explain this by reference to the example of the
6198 <tt>zlib1g</tt> package, which (at the time of writing)
6199 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6203 <var>type</var> is an optional element that indicates the type
6204 of package for which the line is valid. The only type currently
6205 in use is <tt>udeb</tt>. The colon and space after the type are
6210 <var>library-name</var> is the name of the shared library,
6211 in this case <tt>libz</tt>. (This must match the name part
6212 of the soname, see below.)
6216 <var>soname-version</var> is the version part of the soname of
6217 the library. The soname is the thing that must exactly match
6218 for the library to be recognized by the dynamic linker, and is
6220 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6221 example, <tt>libz.so.1</tt>.<footnote>
6222 This can be determined using the command
6223 <example compact="compact">
6224 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6227 The version part is the part which comes after
6228 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6229 instead be of the form
6230 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6231 as <tt>libdb-4.8.so</tt>, in which case the name would
6232 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6236 <var>dependencies</var> has the same syntax as a dependency
6237 field in a binary package control file. It should give
6238 details of which packages are required to satisfy a binary
6239 built against the version of the library contained in the
6240 package. See <ref id="depsyntax"> for details.
6244 In our example, if the first version of the <tt>zlib1g</tt>
6245 package which contained a minor number of at least
6246 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6247 <tt>shlibs</tt> entry for this library could say:
6248 <example compact="compact">
6249 libz 1 zlib1g (>= 1:1.1.3)
6251 The version-specific dependency is to avoid warnings from
6252 the dynamic linker about using older shared libraries with
6257 As zlib1g also provides a udeb containing the shared library,
6258 there would also be a second line:
6259 <example compact="compact">
6260 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6266 <heading>Providing a <file>shlibs</file> file</heading>
6269 If your package provides a shared library, you need to create
6270 a <file>shlibs</file> file following the format described above.
6271 It is usual to call this file <file>debian/shlibs</file> (but if
6272 you have multiple binary packages, you might want to call it
6273 <file>debian/shlibs.<var>package</var></file> instead). Then
6274 let <file>debian/rules</file> install it in the control
6275 information file area:
6276 <example compact="compact">
6277 install -m644 debian/shlibs debian/tmp/DEBIAN
6279 or, in the case of a multi-binary package:
6280 <example compact="compact">
6281 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6283 An alternative way of doing this is to create the
6284 <file>shlibs</file> file in the control information file area
6285 directly from <file>debian/rules</file> without using
6286 a <file>debian/shlibs</file> file at all,<footnote>
6287 This is what <prgn>dh_makeshlibs</prgn> in
6288 the <package>debhelper</package> suite does. If your package
6289 also has a udeb that provides a shared
6290 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6291 the <tt>udeb:</tt> lines if you specify the name of the udeb
6292 with the <tt>--add-udeb</tt> option.
6294 since the <file>debian/shlibs</file> file itself is ignored by
6295 <prgn>dpkg-shlibdeps</prgn>.
6299 As <prgn>dpkg-shlibdeps</prgn> reads the
6300 <file>DEBIAN/shlibs</file> files in all of the binary packages
6301 being built from this source package, all of the
6302 <file>DEBIAN/shlibs</file> files should be installed before
6303 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6311 <chapt id="opersys"><heading>The Operating System</heading>
6314 <heading>File system hierarchy</heading>
6318 <heading>File System Structure</heading>
6321 The location of all files and directories must comply with the
6322 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6323 exceptions noted below, and except where doing so would
6324 violate other terms of Debian Policy. The following
6325 exceptions to the FHS apply:
6330 The optional rules related to user specific
6331 configuration files for applications are stored in
6332 the user's home directory are relaxed. It is
6333 recommended that such files start with the
6334 '<tt>.</tt>' character (a "dot file"), and if an
6335 application needs to create more than one dot file
6336 then the preferred placement is in a subdirectory
6337 with a name starting with a '.' character, (a "dot
6338 directory"). In this case it is recommended the
6339 configuration files not start with the '.'
6345 The requirement for amd64 to use <file>/lib64</file>
6346 for 64 bit binaries is removed.
6351 The requirement for object files, internal binaries, and
6352 libraries, including <file>libc.so.*</file>, to be located
6353 directly under <file>/lib{,32}</file> and
6354 <file>/usr/lib{,32}</file> is amended, permitting files
6355 to instead be installed to
6356 <file>/lib/<var>triplet</var></file> and
6357 <file>/usr/lib/<var>triplet</var></file>, where
6358 <tt><var>triplet</var></tt> is the value returned by
6359 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6360 architecture of the package. Packages may <em>not</em>
6361 install files to any <var>triplet</var> path other
6362 than the one matching the architecture of that package;
6363 for instance, an <tt>Architecture: amd64</tt> package
6364 containing 32-bit x86 libraries may not install these
6365 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6367 This is necessary in order to reserve the directories for
6368 use in cross-installation of library packages from other
6369 architectures, as part of the planned deployment of
6374 Applications may also use a single subdirectory under
6375 <file>/usr/lib/<var>triplet</var></file>.
6378 The execution time linker/loader, ld*, must still be made
6379 available in the existing location under /lib or /lib64
6380 since this is part of the ELF ABI for the architecture.
6385 The requirement that
6386 <file>/usr/local/share/man</file> be "synonymous"
6387 with <file>/usr/local/man</file> is relaxed to a
6392 The requirement that windowmanagers with a single
6393 configuration file call it <file>system.*wmrc</file>
6394 is removed, as is the restriction that the window
6395 manager subdirectory be named identically to the
6396 window manager name itself.
6401 The requirement that boot manager configuration
6402 files live in <file>/etc</file>, or at least are
6403 symlinked there, is relaxed to a recommendation.
6408 The additional directory <file>/run</file> in the root
6409 file system is allowed. <file>/run</file>
6410 replaces <file>/var/run</file>, and the
6411 subdirectory <file>/run/lock</file>
6412 replaces <file>/var/lock</file>, with
6413 the <file>/var</file> directories replaced by symlinks
6414 for backwards compatibility. <file>/run</file>
6415 and <file>/run/lock</file> must follow all of the
6416 requirements in the FHS for <file>/var/run</file>
6417 and <file>/var/lock</file>, respectively, such as file
6418 naming conventions, file format requirements, or the
6419 requirement that files be cleared during the boot
6420 process. Files and directories residing
6421 in <file>/run</file> should be stored on a temporary
6427 The following directories in the root filesystem are
6428 additionally allowed: <file>/sys</file> and
6429 <file>/selinux</file>. <footnote>These directories
6430 are used as mount points to mount virtual filesystems
6431 to get access to kernel information.</footnote>
6436 On GNU/Hurd systems, the following additional
6437 directories are allowed in the root
6438 filesystem: <file>/hurd</file>
6439 and <file>/servers</file>.<footnote>
6440 These directories are used to store translators and as
6441 a set of standard names for mount points,
6450 The version of this document referred here can be
6451 found in the <tt>debian-policy</tt> package or on <url
6452 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6453 name="FHS (Debian copy)"> alongside this manual (or, if
6454 you have the <package>debian-policy</package> installed,
6456 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6457 (local copy)">). The
6458 latest version, which may be a more recent version, may
6460 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6461 Specific questions about following the standard may be
6462 asked on the <tt>debian-devel</tt> mailing list, or
6463 referred to the FHS mailing list (see the
6464 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6470 <heading>Site-specific programs</heading>
6473 As mandated by the FHS, packages must not place any
6474 files in <file>/usr/local</file>, either by putting them in
6475 the file system archive to be unpacked by <prgn>dpkg</prgn>
6476 or by manipulating them in their maintainer scripts.
6480 However, the package may create empty directories below
6481 <file>/usr/local</file> so that the system administrator knows
6482 where to place site-specific files. These are not
6483 directories <em>in</em> <file>/usr/local</file>, but are
6484 children of directories in <file>/usr/local</file>. These
6485 directories (<file>/usr/local/*/dir/</file>)
6486 should be removed on package removal if they are
6491 Note that this applies only to
6492 directories <em>below</em> <file>/usr/local</file>,
6493 not <em>in</em> <file>/usr/local</file>. Packages must
6494 not create sub-directories in the
6495 directory <file>/usr/local</file> itself, except those
6496 listed in FHS, section 4.5. However, you may create
6497 directories below them as you wish. You must not remove
6498 any of the directories listed in 4.5, even if you created
6503 Since <file>/usr/local</file> can be mounted read-only from a
6504 remote server, these directories must be created and
6505 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6506 maintainer scripts and not be included in the
6507 <file>.deb</file> archive. These scripts must not fail if
6508 either of these operations fail.
6512 For example, the <tt>emacsen-common</tt> package could
6513 contain something like
6514 <example compact="compact">
6515 if [ ! -e /usr/local/share/emacs ]; then
6516 if mkdir /usr/local/share/emacs 2>/dev/null; then
6517 if chown root:staff /usr/local/share/emacs; then
6518 chmod 2775 /usr/local/share/emacs || true
6523 in its <prgn>postinst</prgn> script, and
6524 <example compact="compact">
6525 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6526 rmdir /usr/local/share/emacs 2>/dev/null || true
6528 in the <prgn>prerm</prgn> script. (Note that this form is
6529 used to ensure that if the script is interrupted, the
6530 directory <file>/usr/local/share/emacs</file> will still be
6535 If you do create a directory in <file>/usr/local</file> for
6536 local additions to a package, you should ensure that
6537 settings in <file>/usr/local</file> take precedence over the
6538 equivalents in <file>/usr</file>.
6542 However, because <file>/usr/local</file> and its contents are
6543 for exclusive use of the local administrator, a package
6544 must not rely on the presence or absence of files or
6545 directories in <file>/usr/local</file> for normal operation.
6549 The <file>/usr/local</file> directory itself and all the
6550 subdirectories created by the package should (by default) have
6551 permissions 2775 (group-writable and set-group-id) and be
6552 owned by <tt>root:staff</tt>.
6557 <heading>The system-wide mail directory</heading>
6559 The system-wide mail directory
6560 is <file>/var/mail</file>. This directory is part of the
6561 base system and should not be owned by any particular mail
6562 agents. The use of the old
6563 location <file>/var/spool/mail</file> is deprecated, even
6564 though the spool may still be physically located there.
6568 <sect1 id="fhs-run">
6569 <heading><file>/run</file> and <file>/run/lock</file></heading>
6572 The directory <file>/run</file> is cleared at boot, normally
6573 by being a mount point for a temporary file system. Packages
6574 therefore must not assume that any files or directories
6575 under <file>/run</file> other than <file>/run/lock</file>
6576 exist unless the package has arranged to create those files or
6577 directories since the last reboot. Normally, this is done by
6578 the package via an init script. See <ref id="writing-init">
6579 for more information.
6583 Packages must not include files or directories
6584 under <file>/run</file>, or under the
6585 older <file>/var/run</file> and <file>/var/lock</file> paths.
6586 The latter paths will normally be symlinks or other
6587 redirections to <file>/run</file> for backwards compatibility.
6593 <heading>Users and groups</heading>
6596 <heading>Introduction</heading>
6598 The Debian system can be configured to use either plain or
6603 Some user ids (UIDs) and group ids (GIDs) are reserved
6604 globally for use by certain packages. Because some
6605 packages need to include files which are owned by these
6606 users or groups, or need the ids compiled into binaries,
6607 these ids must be used on any Debian system only for the
6608 purpose for which they are allocated. This is a serious
6609 restriction, and we should avoid getting in the way of
6610 local administration policies. In particular, many sites
6611 allocate users and/or local system groups starting at 100.
6615 Apart from this we should have dynamically allocated ids,
6616 which should by default be arranged in some sensible
6617 order, but the behavior should be configurable.
6621 Packages other than <tt>base-passwd</tt> must not modify
6622 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6623 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6628 <heading>UID and GID classes</heading>
6630 The UID and GID numbers are divided into classes as
6636 Globally allocated by the Debian project, the same
6637 on every Debian system. These ids will appear in
6638 the <file>passwd</file> and <file>group</file> files of all
6639 Debian systems, new ids in this range being added
6640 automatically as the <tt>base-passwd</tt> package is
6645 Packages which need a single statically allocated
6646 uid or gid should use one of these; their
6647 maintainers should ask the <tt>base-passwd</tt>
6655 Dynamically allocated system users and groups.
6656 Packages which need a user or group, but can have
6657 this user or group allocated dynamically and
6658 differently on each system, should use <tt>adduser
6659 --system</tt> to create the group and/or user.
6660 <prgn>adduser</prgn> will check for the existence of
6661 the user or group, and if necessary choose an unused
6662 id based on the ranges specified in
6663 <file>adduser.conf</file>.
6667 <tag>1000-59999:</tag>
6670 Dynamically allocated user accounts. By default
6671 <prgn>adduser</prgn> will choose UIDs and GIDs for
6672 user accounts in this range, though
6673 <file>adduser.conf</file> may be used to modify this
6678 <tag>60000-64999:</tag>
6681 Globally allocated by the Debian project, but only
6682 created on demand. The ids are allocated centrally
6683 and statically, but the actual accounts are only
6684 created on users' systems on demand.
6688 These ids are for packages which are obscure or
6689 which require many statically-allocated ids. These
6690 packages should check for and create the accounts in
6691 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6692 <prgn>adduser</prgn> if it has this facility) if
6693 necessary. Packages which are likely to require
6694 further allocations should have a "hole" left after
6695 them in the allocation, to give them room to
6700 <tag>65000-65533:</tag>
6708 User <tt>nobody</tt>. The corresponding gid refers
6709 to the group <tt>nogroup</tt>.
6716 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6717 not</em> be used, because it is the error return
6726 <sect id="sysvinit">
6727 <heading>System run levels and <file>init.d</file> scripts</heading>
6729 <sect1 id="/etc/init.d">
6730 <heading>Introduction</heading>
6733 The <file>/etc/init.d</file> directory contains the scripts
6734 executed by <prgn>init</prgn> at boot time and when the
6735 init state (or "runlevel") is changed (see <manref
6736 name="init" section="8">).
6740 There are at least two different, yet functionally
6741 equivalent, ways of handling these scripts. For the sake
6742 of simplicity, this document describes only the symbolic
6743 link method. However, it must not be assumed by maintainer
6744 scripts that this method is being used, and any automated
6745 manipulation of the various runlevel behaviors by
6746 maintainer scripts must be performed using
6747 <prgn>update-rc.d</prgn> as described below and not by
6748 manually installing or removing symlinks. For information
6749 on the implementation details of the other method,
6750 implemented in the <tt>file-rc</tt> package, please refer
6751 to the documentation of that package.
6755 These scripts are referenced by symbolic links in the
6756 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6757 runlevels, <prgn>init</prgn> looks in the directory
6758 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6759 execute, where <tt><var>n</var></tt> is the runlevel that
6760 is being changed to, or <tt>S</tt> for the boot-up
6765 The names of the links all have the form
6766 <file>S<var>mm</var><var>script</var></file> or
6767 <file>K<var>mm</var><var>script</var></file> where
6768 <var>mm</var> is a two-digit number and <var>script</var>
6769 is the name of the script (this should be the same as the
6770 name of the actual script in <file>/etc/init.d</file>).
6774 When <prgn>init</prgn> changes runlevel first the targets
6775 of the links whose names start with a <tt>K</tt> are
6776 executed, each with the single argument <tt>stop</tt>,
6777 followed by the scripts prefixed with an <tt>S</tt>, each
6778 with the single argument <tt>start</tt>. (The links are
6779 those in the <file>/etc/rc<var>n</var>.d</file> directory
6780 corresponding to the new runlevel.) The <tt>K</tt> links
6781 are responsible for killing services and the <tt>S</tt>
6782 link for starting services upon entering the runlevel.
6786 For example, if we are changing from runlevel 2 to
6787 runlevel 3, init will first execute all of the <tt>K</tt>
6788 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6789 all of the <tt>S</tt> prefixed scripts in that directory.
6790 The links starting with <tt>K</tt> will cause the
6791 referred-to file to be executed with an argument of
6792 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6797 The two-digit number <var>mm</var> is used to determine
6798 the order in which to run the scripts: low-numbered links
6799 have their scripts run first. For example, the
6800 <tt>K20</tt> scripts will be executed before the
6801 <tt>K30</tt> scripts. This is used when a certain service
6802 must be started before another. For example, the name
6803 server <prgn>bind</prgn> might need to be started before
6804 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6805 can set up its access lists. In this case, the script
6806 that starts <prgn>bind</prgn> would have a lower number
6807 than the script that starts <prgn>inn</prgn> so that it
6809 <example compact="compact">
6816 The two runlevels 0 (halt) and 6 (reboot) are slightly
6817 different. In these runlevels, the links with an
6818 <tt>S</tt> prefix are still called after those with a
6819 <tt>K</tt> prefix, but they too are called with the single
6820 argument <tt>stop</tt>.
6824 <sect1 id="writing-init">
6825 <heading>Writing the scripts</heading>
6828 Packages that include daemons for system services should
6829 place scripts in <file>/etc/init.d</file> to start or stop
6830 services at boot time or during a change of runlevel.
6831 These scripts should be named
6832 <file>/etc/init.d/<var>package</var></file>, and they should
6833 accept one argument, saying what to do:
6836 <tag><tt>start</tt></tag>
6837 <item>start the service,</item>
6839 <tag><tt>stop</tt></tag>
6840 <item>stop the service,</item>
6842 <tag><tt>restart</tt></tag>
6843 <item>stop and restart the service if it's already running,
6844 otherwise start the service</item>
6846 <tag><tt>reload</tt></tag>
6847 <item><p>cause the configuration of the service to be
6848 reloaded without actually stopping and restarting
6851 <tag><tt>force-reload</tt></tag>
6852 <item>cause the configuration to be reloaded if the
6853 service supports this, otherwise restart the
6857 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6858 <tt>force-reload</tt> options should be supported by all
6859 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6864 The <file>init.d</file> scripts must ensure that they will
6865 behave sensibly (i.e., returning success and not starting
6866 multiple copies of a service) if invoked with <tt>start</tt>
6867 when the service is already running, or with <tt>stop</tt>
6868 when it isn't, and that they don't kill unfortunately-named
6869 user processes. The best way to achieve this is usually to
6870 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6875 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6876 scripts. Writing correct <file>init.d</file> scripts requires
6877 accepting various error exit statuses when daemons are already
6878 running or already stopped without aborting
6879 the <file>init.d</file> script, and common <file>init.d</file>
6880 function libraries are not safe to call with <tt>set -e</tt>
6882 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6883 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6884 in effect and echoing status messages to the console fails,
6886 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6887 to not use <tt>set -e</tt> and instead check the result of
6888 each command separately.
6892 If a service reloads its configuration automatically (as
6893 in the case of <prgn>cron</prgn>, for example), the
6894 <tt>reload</tt> option of the <file>init.d</file> script
6895 should behave as if the configuration has been reloaded
6900 The <file>/etc/init.d</file> scripts must be treated as
6901 configuration files, either (if they are present in the
6902 package, that is, in the .deb file) by marking them as
6903 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6904 by managing them correctly in the maintainer scripts (see
6905 <ref id="config-files">). This is important since we want
6906 to give the local system administrator the chance to adapt
6907 the scripts to the local system, e.g., to disable a
6908 service without de-installing the package, or to specify
6909 some special command line options when starting a service,
6910 while making sure their changes aren't lost during the next
6915 These scripts should not fail obscurely when the
6916 configuration files remain but the package has been
6917 removed, as configuration files remain on the system after
6918 the package has been removed. Only when <prgn>dpkg</prgn>
6919 is executed with the <tt>--purge</tt> option will
6920 configuration files be removed. In particular, as the
6921 <file>/etc/init.d/<var>package</var></file> script itself is
6922 usually a <tt>conffile</tt>, it will remain on the system
6923 if the package is removed but not purged. Therefore, you
6924 should include a <tt>test</tt> statement at the top of the
6926 <example compact="compact">
6927 test -f <var>program-executed-later-in-script</var> || exit 0
6932 Often there are some variables in the <file>init.d</file>
6933 scripts whose values control the behavior of the scripts,
6934 and which a system administrator is likely to want to
6935 change. As the scripts themselves are frequently
6936 <tt>conffile</tt>s, modifying them requires that the
6937 administrator merge in their changes each time the package
6938 is upgraded and the <tt>conffile</tt> changes. To ease
6939 the burden on the system administrator, such configurable
6940 values should not be placed directly in the script.
6941 Instead, they should be placed in a file in
6942 <file>/etc/default</file>, which typically will have the same
6943 base name as the <file>init.d</file> script. This extra file
6944 should be sourced by the script when the script runs. It
6945 must contain only variable settings and comments in SUSv3
6946 <prgn>sh</prgn> format. It may either be a
6947 <tt>conffile</tt> or a configuration file maintained by
6948 the package maintainer scripts. See <ref id="config-files">
6953 To ensure that vital configurable values are always
6954 available, the <file>init.d</file> script should set default
6955 values for each of the shell variables it uses, either
6956 before sourcing the <file>/etc/default/</file> file or
6957 afterwards using something like the <tt>:
6958 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6959 script must behave sensibly and not fail if the
6960 <file>/etc/default</file> file is deleted.
6964 Files and directories under <file>/run</file>, including ones
6965 referred to via the compatibility paths <file>/var/run</file>
6966 and <file>/var/lock</file>, are normally stored on a temporary
6967 filesystem and are normally not persistent across a reboot.
6968 The <file>init.d</file> scripts must handle this correctly.
6969 This will typically mean creating any required subdirectories
6970 dynamically when the <file>init.d</file> script is run.
6971 See <ref id="fhs-run"> for more information.
6976 <heading>Interfacing with the initscript system</heading>
6979 Maintainers should use the abstraction layer provided by
6980 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6981 programs to deal with initscripts in their packages'
6982 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6983 and <prgn>postrm</prgn>.
6987 Directly managing the /etc/rc?.d links and directly
6988 invoking the <file>/etc/init.d/</file> initscripts should
6989 be done only by packages providing the initscript
6990 subsystem (such as <prgn>sysv-rc</prgn> and
6991 <prgn>file-rc</prgn>).
6995 <heading>Managing the links</heading>
6998 The program <prgn>update-rc.d</prgn> is provided for
6999 package maintainers to arrange for the proper creation and
7000 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7001 or their functional equivalent if another method is being
7002 used. This may be used by maintainers in their packages'
7003 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7007 You must not include any <file>/etc/rc<var>n</var>.d</file>
7008 symbolic links in the actual archive or manually create or
7009 remove the symbolic links in maintainer scripts; you must
7010 use the <prgn>update-rc.d</prgn> program instead. (The
7011 former will fail if an alternative method of maintaining
7012 runlevel information is being used.) You must not include
7013 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7014 in the archive either. (Only the <tt>sysvinit</tt>
7019 By default <prgn>update-rc.d</prgn> will start services in
7020 each of the multi-user state runlevels (2, 3, 4, and 5)
7021 and stop them in the halt runlevel (0), the single-user
7022 runlevel (1) and the reboot runlevel (6). The system
7023 administrator will have the opportunity to customize
7024 runlevels by simply adding, moving, or removing the
7025 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7026 symbolic links are being used, or by modifying
7027 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7032 To get the default behavior for your package, put in your
7033 <prgn>postinst</prgn> script
7034 <example compact="compact">
7035 update-rc.d <var>package</var> defaults
7037 and in your <prgn>postrm</prgn>
7038 <example compact="compact">
7039 if [ "$1" = purge ]; then
7040 update-rc.d <var>package</var> remove
7042 </example>. Note that if your package changes runlevels
7043 or priority, you may have to remove and recreate the links,
7044 since otherwise the old links may persist. Refer to the
7045 documentation of <prgn>update-rc.d</prgn>.
7049 This will use a default sequence number of 20. If it does
7050 not matter when or in which order the <file>init.d</file>
7051 script is run, use this default. If it does, then you
7052 should talk to the maintainer of the <prgn>sysvinit</prgn>
7053 package or post to <tt>debian-devel</tt>, and they will
7054 help you choose a number.
7058 For more information about using <tt>update-rc.d</tt>,
7059 please consult its man page <manref name="update-rc.d"
7065 <heading>Running initscripts</heading>
7067 The program <prgn>invoke-rc.d</prgn> is provided to make
7068 it easier for package maintainers to properly invoke an
7069 initscript, obeying runlevel and other locally-defined
7070 constraints that might limit a package's right to start,
7071 stop and otherwise manage services. This program may be
7072 used by maintainers in their packages' scripts.
7076 The package maintainer scripts must use
7077 <prgn>invoke-rc.d</prgn> to invoke the
7078 <file>/etc/init.d/*</file> initscripts, instead of
7079 calling them directly.
7083 By default, <prgn>invoke-rc.d</prgn> will pass any
7084 action requests (start, stop, reload, restart...) to the
7085 <file>/etc/init.d</file> script, filtering out requests
7086 to start or restart a service out of its intended
7091 Most packages will simply need to change:
7092 <example compact="compact">/etc/init.d/<package>
7093 <action></example> in their <prgn>postinst</prgn>
7094 and <prgn>prerm</prgn> scripts to:
7095 <example compact="compact">
7096 if which invoke-rc.d >/dev/null 2>&1; then
7097 invoke-rc.d <var>package</var> <action>
7099 /etc/init.d/<var>package</var> <action>
7105 A package should register its initscript services using
7106 <prgn>update-rc.d</prgn> before it tries to invoke them
7107 using <prgn>invoke-rc.d</prgn>. Invocation of
7108 unregistered services may fail.
7112 For more information about using
7113 <prgn>invoke-rc.d</prgn>, please consult its man page
7114 <manref name="invoke-rc.d" section="8">.
7120 <heading>Boot-time initialization</heading>
7123 There used to be another directory, <file>/etc/rc.boot</file>,
7124 which contained scripts which were run once per machine
7125 boot. This has been deprecated in favour of links from
7126 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7127 described in <ref id="/etc/init.d">. Packages must not
7128 place files in <file>/etc/rc.boot</file>.
7133 <heading>Example</heading>
7136 An example on which you can base your
7137 <file>/etc/init.d</file> scripts is found in
7138 <file>/etc/init.d/skeleton</file>.
7145 <heading>Console messages from <file>init.d</file> scripts</heading>
7148 This section describes the formats to be used for messages
7149 written to standard output by the <file>/etc/init.d</file>
7150 scripts. The intent is to improve the consistency of
7151 Debian's startup and shutdown look and feel. For this
7152 reason, please look very carefully at the details. We want
7153 the messages to have the same format in terms of wording,
7154 spaces, punctuation and case of letters.
7158 Here is a list of overall rules that should be used for
7159 messages generated by <file>/etc/init.d</file> scripts.
7165 The message should fit in one line (fewer than 80
7166 characters), start with a capital letter and end with
7167 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7171 If the script is performing some time consuming task in
7172 the background (not merely starting or stopping a
7173 program, for instance), an ellipsis (three dots:
7174 <tt>...</tt>) should be output to the screen, with no
7175 leading or tailing whitespace or line feeds.
7179 The messages should appear as if the computer is telling
7180 the user what it is doing (politely :-), but should not
7181 mention "it" directly. For example, instead of:
7182 <example compact="compact">
7183 I'm starting network daemons: nfsd mountd.
7185 the message should say
7186 <example compact="compact">
7187 Starting network daemons: nfsd mountd.
7194 <tt>init.d</tt> script should use the following standard
7195 message formats for the situations enumerated below.
7201 <p>When daemons are started</p>
7204 If the script starts one or more daemons, the output
7205 should look like this (a single line, no leading
7207 <example compact="compact">
7208 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7210 The <var>description</var> should describe the
7211 subsystem the daemon or set of daemons are part of,
7212 while <var>daemon-1</var> up to <var>daemon-n</var>
7213 denote each daemon's name (typically the file name of
7218 For example, the output of <file>/etc/init.d/lpd</file>
7220 <example compact="compact">
7221 Starting printer spooler: lpd.
7226 This can be achieved by saying
7227 <example compact="compact">
7228 echo -n "Starting printer spooler: lpd"
7229 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7232 in the script. If there are more than one daemon to
7233 start, the output should look like this:
7234 <example compact="compact">
7235 echo -n "Starting remote file system services:"
7236 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7237 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7238 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7241 This makes it possible for the user to see what is
7242 happening and when the final daemon has been started.
7243 Care should be taken in the placement of white spaces:
7244 in the example above the system administrators can
7245 easily comment out a line if they don't want to start
7246 a specific daemon, while the displayed message still
7252 <p>When a system parameter is being set</p>
7255 If you have to set up different system parameters
7256 during the system boot, you should use this format:
7257 <example compact="compact">
7258 Setting <var>parameter</var> to "<var>value</var>".
7263 You can use a statement such as the following to get
7265 <example compact="compact">
7266 echo "Setting DNS domainname to \"$domainname\"."
7271 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7272 for the left and right quotation marks. A grave accent
7273 (<tt>`</tt>) is not a quote character; neither is an
7274 apostrophe (<tt>'</tt>).
7279 <p>When a daemon is stopped or restarted</p>
7282 When you stop or restart a daemon, you should issue a
7283 message identical to the startup message, except that
7284 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7285 or <tt>Restarting</tt> respectively.
7289 For example, stopping the printer daemon will look like
7291 <example compact="compact">
7292 Stopping printer spooler: lpd.
7298 <p>When something is executed</p>
7301 There are several examples where you have to run a
7302 program at system startup or shutdown to perform a
7303 specific task, for example, setting the system's clock
7304 using <prgn>netdate</prgn> or killing all processes
7305 when the system shuts down. Your message should look
7307 <example compact="compact">
7308 Doing something very useful...done.
7310 You should print the <tt>done.</tt> immediately after
7311 the job has been completed, so that the user is
7312 informed why they have to wait. You can get this
7314 <example compact="compact">
7315 echo -n "Doing something very useful..."
7324 <p>When the configuration is reloaded</p>
7327 When a daemon is forced to reload its configuration
7328 files you should use the following format:
7329 <example compact="compact">
7330 Reloading <var>description</var> configuration...done.
7332 where <var>description</var> is the same as in the
7333 daemon starting message.
7340 <sect id="cron-jobs">
7341 <heading>Cron jobs</heading>
7344 Packages must not modify the configuration file
7345 <file>/etc/crontab</file>, and they must not modify the files in
7346 <file>/var/spool/cron/crontabs</file>.
7350 If a package wants to install a job that has to be executed via
7351 cron, it should place a file named as specified
7352 in <ref id="cron-files"> into one or more of the following
7354 <example compact="compact">
7360 As these directory names imply, the files within them are
7361 executed on an hourly, daily, weekly, or monthly basis,
7362 respectively. The exact times are listed in
7363 <file>/etc/crontab</file>.
7367 All files installed in any of these directories must be
7368 scripts (e.g., shell scripts or Perl scripts) so that they
7369 can easily be modified by the local system administrator.
7370 In addition, they must be treated as configuration files.
7374 If a certain job has to be executed at some other frequency or
7375 at a specific time, the package should install a file in
7376 <file>/etc/cron.d</file> with a name as specified
7377 in <ref id="cron-files">. This file uses the same syntax
7378 as <file>/etc/crontab</file> and is processed
7379 by <prgn>cron</prgn> automatically. The file must also be
7380 treated as a configuration file. (Note that entries in the
7381 <file>/etc/cron.d</file> directory are not handled by
7382 <prgn>anacron</prgn>. Thus, you should only use this
7383 directory for jobs which may be skipped if the system is not
7388 Unlike <file>crontab</file> files described in the IEEE Std
7389 1003.1-2008 (POSIX.1) available from
7390 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7391 name="The Open Group">, the files in
7392 <file>/etc/cron.d</file> and the file
7393 <file>/etc/crontab</file> have seven fields; namely:
7395 <item>Minute [0,59]</item>
7396 <item>Hour [0,23]</item>
7397 <item>Day of the month [1,31]</item>
7398 <item>Month of the year [1,12]</item>
7399 <item>Day of the week ([0,6] with 0=Sunday)</item>
7400 <item>Username</item>
7401 <item>Command to be run</item>
7403 Ranges of numbers are allowed. Ranges are two numbers
7404 separated with a hyphen. The specified range is inclusive.
7405 Lists are allowed. A list is a set of numbers (or ranges)
7406 separated by commas. Step values can be used in conjunction
7411 The scripts or <tt>crontab</tt> entries in these directories should
7412 check if all necessary programs are installed before they
7413 try to execute them. Otherwise, problems will arise when a
7414 package was removed but not purged since configuration files
7415 are kept on the system in this situation.
7419 Any <tt>cron</tt> daemon must provide
7420 <file>/usr/bin/crontab</file> and support normal
7421 <tt>crontab</tt> entries as specified in POSIX. The daemon
7422 must also support names for days and months, ranges, and
7423 step values. It has to support <file>/etc/crontab</file>,
7424 and correctly execute the scripts in
7425 <file>/etc/cron.d</file>. The daemon must also correctly
7427 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7430 <sect1 id="cron-files">
7431 <heading>Cron job file names</heading>
7434 The file name of a cron job file should normally match the
7435 name of the package from which it comes.
7439 If a package supplies multiple cron job files files in the
7440 same directory, the file names should all start with the name
7441 of the package (possibly modified as described below) followed
7442 by a hyphen (<tt>-</tt>) and a suitable suffix.
7446 A cron job file name must not include any period or plus
7447 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7448 cause cron to ignore the file. Underscores (<tt>_</tt>)
7449 should be used instead of <tt>.</tt> and <tt>+</tt>
7456 <heading>Menus</heading>
7459 The Debian <tt>menu</tt> package provides a standard
7460 interface between packages providing applications and
7461 <em>menu programs</em> (either X window managers or
7462 text-based menu programs such as <prgn>pdmenu</prgn>).
7466 All packages that provide applications that need not be
7467 passed any special command line arguments for normal
7468 operation should register a menu entry for those
7469 applications, so that users of the <tt>menu</tt> package
7470 will automatically get menu entries in their window
7471 managers, as well in shells like <tt>pdmenu</tt>.
7475 Menu entries should follow the current menu policy.
7479 The menu policy can be found in the <tt>menu-policy</tt>
7480 files in the <tt>debian-policy</tt> package.
7481 It is also available from the Debian web mirrors at
7482 <tt><url name="/doc/packaging-manuals/menu-policy/"
7483 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7487 Please also refer to the <em>Debian Menu System</em>
7488 documentation that comes with the <package>menu</package>
7489 package for information about how to register your
7495 <heading>Multimedia handlers</heading>
7498 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7499 is a mechanism for encoding files and data streams and
7500 providing meta-information about them, in particular their
7501 type (e.g. audio or video) and format (e.g. PNG, HTML,
7506 Registration of MIME type handlers allows programs like mail
7507 user agents and web browsers to invoke these handlers to
7508 view, edit or display MIME types they don't support directly.
7512 Packages which provide the ability to view/show/play,
7513 compose, edit or print MIME types should register themselves
7514 as such following the current MIME support policy.
7518 The <package>mime-support</package> package provides the
7519 <prgn>update-mime</prgn> program which allows packages to
7520 register programs that can show, compose, edit or print
7525 Packages containing such programs must register them
7526 with <prgn>update-mime</prgn> as documented in <manref
7527 name="update-mime" section="8">. They should <em>not</em> depend
7528 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7529 they should just put something like the following in the
7530 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7533 if [ -x /usr/sbin/update-mime ]; then
7542 <heading>Keyboard configuration</heading>
7545 To achieve a consistent keyboard configuration so that all
7546 applications interpret a keyboard event the same way, all
7547 programs in the Debian distribution must be configured to
7548 comply with the following guidelines.
7552 The following keys must have the specified interpretations:
7555 <tag><tt><--</tt></tag>
7556 <item>delete the character to the left of the cursor</item>
7558 <tag><tt>Delete</tt></tag>
7559 <item>delete the character to the right of the cursor</item>
7561 <tag><tt>Control+H</tt></tag>
7562 <item>emacs: the help prefix</item>
7565 The interpretation of any keyboard events should be
7566 independent of the terminal that is used, be it a virtual
7567 console, an X terminal emulator, an rlogin/telnet session,
7572 The following list explains how the different programs
7573 should be set up to achieve this:
7579 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7583 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7587 X translations are set up to make
7588 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7589 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7590 is the vt220 escape code for the "delete character"
7591 key). This must be done by loading the X resources
7592 using <prgn>xrdb</prgn> on all local X displays, not
7593 using the application defaults, so that the
7594 translation resources used correspond to the
7595 <prgn>xmodmap</prgn> settings.
7599 The Linux console is configured to make
7600 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7601 generate <tt>ESC [ 3 ~</tt>.
7605 X applications are configured so that <tt><</tt>
7606 deletes left, and <tt>Delete</tt> deletes right. Motif
7607 applications already work like this.
7611 Terminals should have <tt>stty erase ^?</tt> .
7615 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7616 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7617 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7621 Emacs is programmed to map <tt>KB_Backspace</tt> or
7622 the <tt>stty erase</tt> character to
7623 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7624 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7625 <tt>^H</tt> to <tt>help</tt> as always.
7629 Other applications use the <tt>stty erase</tt>
7630 character and <tt>kdch1</tt> for the two delete keys,
7631 with ASCII DEL being "delete previous character" and
7632 <tt>kdch1</tt> being "delete character under
7640 This will solve the problem except for the following
7647 Some terminals have a <tt><--</tt> key that cannot
7648 be made to produce anything except <tt>^H</tt>. On
7649 these terminals Emacs help will be unavailable on
7650 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7651 character takes precedence in Emacs, and has been set
7652 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7653 available) can be used instead.
7657 Some operating systems use <tt>^H</tt> for <tt>stty
7658 erase</tt>. However, modern telnet versions and all
7659 rlogin versions propagate <tt>stty</tt> settings, and
7660 almost all UNIX versions honour <tt>stty erase</tt>.
7661 Where the <tt>stty</tt> settings are not propagated
7662 correctly, things can be made to work by using
7663 <tt>stty</tt> manually.
7667 Some systems (including previous Debian versions) use
7668 <prgn>xmodmap</prgn> to arrange for both
7669 <tt><--</tt> and <tt>Delete</tt> to generate
7670 <tt>KB_Delete</tt>. We can change the behavior of
7671 their X clients using the same X resources that we use
7672 to do it for our own clients, or configure our clients
7673 using their resources when things are the other way
7674 around. On displays configured like this
7675 <tt>Delete</tt> will not work, but <tt><--</tt>
7680 Some operating systems have different <tt>kdch1</tt>
7681 settings in their <tt>terminfo</tt> database for
7682 <tt>xterm</tt> and others. On these systems the
7683 <tt>Delete</tt> key will not work correctly when you
7684 log in from a system conforming to our policy, but
7685 <tt><--</tt> will.
7692 <heading>Environment variables</heading>
7695 A program must not depend on environment variables to get
7696 reasonable defaults. (That's because these environment
7697 variables would have to be set in a system-wide
7698 configuration file like <file>/etc/profile</file>, which is not
7699 supported by all shells.)
7703 If a program usually depends on environment variables for its
7704 configuration, the program should be changed to fall back to
7705 a reasonable default configuration if these environment
7706 variables are not present. If this cannot be done easily
7707 (e.g., if the source code of a non-free program is not
7708 available), the program must be replaced by a small
7709 "wrapper" shell script which sets the environment variables
7710 if they are not already defined, and calls the original program.
7714 Here is an example of a wrapper script for this purpose:
7716 <example compact="compact">
7718 BAR=${BAR:-/var/lib/fubar}
7720 exec /usr/lib/foo/foo "$@"
7725 Furthermore, as <file>/etc/profile</file> is a configuration
7726 file of the <prgn>base-files</prgn> package, other packages must
7727 not put any environment variables or other commands into that
7732 <sect id="doc-base">
7733 <heading>Registering Documents using doc-base</heading>
7736 The <package>doc-base</package> package implements a
7737 flexible mechanism for handling and presenting
7738 documentation. The recommended practice is for every Debian
7739 package that provides online documentation (other than just
7740 manual pages) to register these documents with
7741 <package>doc-base</package> by installing a
7742 <package>doc-base</package> control file in
7743 <file>/usr/share/doc-base/</file>.
7746 Please refer to the documentation that comes with the
7747 <package>doc-base</package> package for information and
7756 <heading>Files</heading>
7758 <sect id="binaries">
7759 <heading>Binaries</heading>
7762 Two different packages must not install programs with
7763 different functionality but with the same filenames. (The
7764 case of two programs having the same functionality but
7765 different implementations is handled via "alternatives" or
7766 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7767 <ref id="conflicts"> respectively.) If this case happens,
7768 one of the programs must be renamed. The maintainers should
7769 report this to the <tt>debian-devel</tt> mailing list and
7770 try to find a consensus about which program will have to be
7771 renamed. If a consensus cannot be reached, <em>both</em>
7772 programs must be renamed.
7776 By default, when a package is being built, any binaries
7777 created should include debugging information, as well as
7778 being compiled with optimization. You should also turn on
7779 as many reasonable compilation warnings as possible; this
7780 makes life easier for porters, who can then look at build
7781 logs for possible problems. For the C programming language,
7782 this means the following compilation parameters should be
7784 <example compact="compact">
7786 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7788 INSTALL = install -s # (or use strip on the files in debian/tmp)
7793 Note that by default all installed binaries should be stripped,
7794 either by using the <tt>-s</tt> flag to
7795 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7796 the binaries after they have been copied into
7797 <file>debian/tmp</file> but before the tree is made into a
7802 Although binaries in the build tree should be compiled with
7803 debugging information by default, it can often be difficult to
7804 debug programs if they are also subjected to compiler
7805 optimization. For this reason, it is recommended to support the
7806 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7807 (see <ref id="debianrules-options">). This variable can contain
7808 several flags to change how a package is compiled and built.
7812 It is up to the package maintainer to decide what
7813 compilation options are best for the package. Certain
7814 binaries (such as computationally-intensive programs) will
7815 function better with certain flags (<tt>-O3</tt>, for
7816 example); feel free to use them. Please use good judgment
7817 here. Don't use flags for the sake of it; only use them
7818 if there is good reason to do so. Feel free to override
7819 the upstream author's ideas about which compilation
7820 options are best: they are often inappropriate for our
7826 <sect id="libraries">
7827 <heading>Libraries</heading>
7830 If the package is <strong>architecture: any</strong>, then
7831 the shared library compilation and linking flags must have
7832 <tt>-fPIC</tt>, or the package shall not build on some of
7833 the supported architectures<footnote>
7835 If you are using GCC, <tt>-fPIC</tt> produces code with
7836 relocatable position independent code, which is required for
7837 most architectures to create a shared library, with i386 and
7838 perhaps some others where non position independent code is
7839 permitted in a shared library.
7842 Position independent code may have a performance penalty,
7843 especially on <tt>i386</tt>. However, in most cases the
7844 speed penalty must be measured against the memory wasted on
7845 the few architectures where non position independent code is
7848 </footnote>. Any exception to this rule must be discussed on
7849 the mailing list <em>debian-devel@lists.debian.org</em>, and
7850 a rough consensus obtained. The reasons for not compiling
7851 with <tt>-fPIC</tt> flag must be recorded in the file
7852 <tt>README.Debian</tt>, and care must be taken to either
7853 restrict the architecture or arrange for <tt>-fPIC</tt> to
7854 be used on architectures where it is required.<footnote>
7856 Some of the reasons why this might be required is if the
7857 library contains hand crafted assembly code that is not
7858 relocatable, the speed penalty is excessive for compute
7859 intensive libs, and similar reasons.
7864 As to the static libraries, the common case is not to have
7865 relocatable code, since there is no benefit, unless in specific
7866 cases; therefore the static version must not be compiled
7867 with the <tt>-fPIC</tt> flag. Any exception to this rule
7868 should be discussed on the mailing list
7869 <em>debian-devel@lists.debian.org</em>, and the reasons for
7870 compiling with the <tt>-fPIC</tt> flag must be recorded in
7871 the file <tt>README.Debian</tt>. <footnote>
7873 Some of the reasons for linking static libraries with
7874 the <tt>-fPIC</tt> flag are if, for example, one needs a
7875 Perl API for a library that is under rapid development,
7876 and has an unstable API, so shared libraries are
7877 pointless at this phase of the library's development. In
7878 that case, since Perl needs a library with relocatable
7879 code, it may make sense to create a static library with
7880 relocatable code. Another reason cited is if you are
7881 distilling various libraries into a common shared
7882 library, like <tt>mklibs</tt> does in the Debian
7888 In other words, if both a shared and a static library is
7889 being built, each source unit (<tt>*.c</tt>, for example,
7890 for C files) will need to be compiled twice, for the normal
7895 Libraries should be built with threading support and to be
7896 thread-safe if the library supports this.
7900 Although not enforced by the build tools, shared libraries
7901 must be linked against all libraries that they use symbols from
7902 in the same way that binaries are. This ensures the correct
7903 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7904 system and guarantees that all libraries can be safely opened
7905 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7906 option <tt>-Wl,-z,defs</tt> when building a shared library.
7907 Since this option enforces symbol resolution at build time,
7908 a missing library reference will be caught early as a fatal
7913 All installed shared libraries should be stripped with
7914 <example compact="compact">
7915 strip --strip-unneeded <var>your-lib</var>
7917 (The option <tt>--strip-unneeded</tt> makes
7918 <prgn>strip</prgn> remove only the symbols which aren't
7919 needed for relocation processing.) Shared libraries can
7920 function perfectly well when stripped, since the symbols for
7921 dynamic linking are in a separate part of the ELF object
7923 You might also want to use the options
7924 <tt>--remove-section=.comment</tt> and
7925 <tt>--remove-section=.note</tt> on both shared libraries
7926 and executables, and <tt>--strip-debug</tt> on static
7932 Note that under some circumstances it may be useful to
7933 install a shared library unstripped, for example when
7934 building a separate package to support debugging.
7938 Shared object files (often <file>.so</file> files) that are not
7939 public libraries, that is, they are not meant to be linked
7940 to by third party executables (binaries of other packages),
7941 should be installed in subdirectories of the
7942 <file>/usr/lib</file> directory. Such files are exempt from the
7943 rules that govern ordinary shared libraries, except that
7944 they must not be installed executable and should be
7946 A common example are the so-called "plug-ins",
7947 internal shared objects that are dynamically loaded by
7948 programs using <manref name="dlopen" section="3">.
7953 Packages that use <prgn>libtool</prgn> to create and install
7954 their shared libraries install a file containing additional
7955 metadata (ending in <file>.la</file>) alongside the library.
7956 For public libraries intended for use by other packages, these
7957 files normally should not be included in the Debian package,
7958 since the information they include is not necessary to link with
7959 the shared library on Debian and can add unnecessary additional
7960 dependencies to other programs or libraries.<footnote>
7961 These files store, among other things, all libraries on which
7962 that shared library depends. Unfortunately, if
7963 the <file>.la</file> file is present and contains that
7964 dependency information, using <prgn>libtool</prgn> when
7965 linking against that library will cause the resulting program
7966 or library to be linked against those dependencies as well,
7967 even if this is unnecessary. This can create unneeded
7968 dependencies on shared library packages that would otherwise
7969 be hidden behind the library ABI, and can make library
7970 transitions to new SONAMEs unnecessarily complicated and
7971 difficult to manage.
7973 If the <file>.la</file> file is required for that library (if,
7974 for instance, it's loaded via <tt>libltdl</tt> in a way that
7975 requires that meta-information), the <tt>dependency_libs</tt>
7976 setting in the <file>.la</file> file should normally be set to
7977 the empty string. If the shared library development package has
7978 historically included the <file>.la</file>, it must be retained
7979 in the development package (with <tt>dependency_libs</tt>
7980 emptied) until all libraries that depend on it have removed or
7981 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7982 files to prevent linking with those other libraries
7983 using <prgn>libtool</prgn> from failing.
7987 If the <file>.la</file> must be included, it should be included
7988 in the development (<tt>-dev</tt>) package, unless the library
7989 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7990 library. If it is intended for use with <tt>libltdl</tt>,
7991 the <file>.la</file> files must go in the run-time library
7996 These requirements for handling of <file>.la</file> files do not
7997 apply to loadable modules or libraries not installed in
7998 directories searched by default by the dynamic linker. Packages
7999 installing loadable modules will frequently need to install
8000 the <file>.la</file> files alongside the modules so that they
8001 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8002 does not need to be modified for libraries or modules that are
8003 not installed in directories searched by the dynamic linker by
8004 default and not intended for use by other packages.
8008 You must make sure that you use only released versions of
8009 shared libraries to build your packages; otherwise other
8010 users will not be able to run your binaries
8011 properly. Producing source packages that depend on
8012 unreleased compilers is also usually a bad
8019 <heading>Shared libraries</heading>
8021 This section has moved to <ref id="sharedlibs">.
8027 <heading>Scripts</heading>
8030 All command scripts, including the package maintainer
8031 scripts inside the package and used by <prgn>dpkg</prgn>,
8032 should have a <tt>#!</tt> line naming the shell to be used
8037 In the case of Perl scripts this should be
8038 <tt>#!/usr/bin/perl</tt>.
8042 When scripts are installed into a directory in the system
8043 PATH, the script name should not include an extension such
8044 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8045 language currently used to implement it.
8048 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8049 <file>init.d</file> scripts should almost certainly start
8050 with <tt>set -e</tt> so that errors are detected.
8051 <file>init.d</file> scripts are something of a special case, due
8052 to how frequently they need to call commands that are allowed to
8053 fail, and it may instead be easier to check the exit status of
8054 commands directly. See <ref id="writing-init"> for more
8055 information about writing <file>init.d</file> scripts.
8058 Every script should use <tt>set -e</tt> or check the exit status
8059 of <em>every</em> command.
8062 Scripts may assume that <file>/bin/sh</file> implements the
8063 SUSv3 Shell Command Language<footnote>
8064 Single UNIX Specification, version 3, which is also IEEE
8065 1003.1-2004 (POSIX), and is available on the World Wide Web
8066 from <url id="http://www.unix.org/version3/online.html"
8067 name="The Open Group"> after free
8068 registration.</footnote>
8069 plus the following additional features not mandated by
8071 These features are in widespread use in the Linux community
8072 and are implemented in all of bash, dash, and ksh, the most
8073 common shells users may wish to use as <file>/bin/sh</file>.
8076 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8077 must not generate a newline.</item>
8078 <item><tt>test</tt>, if implemented as a shell built-in, must
8079 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8081 <item><tt>local</tt> to create a scoped variable must be
8082 supported, including listing multiple variables in a single
8083 local command and assigning a value to a variable at the
8084 same time as localizing it. <tt>local</tt> may or
8085 may not preserve the variable value from an outer scope if
8086 no assignment is present. Uses such as:
8090 # ... use a, b, c, d ...
8093 must be supported and must set the value of <tt>c</tt> to
8096 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8097 -<var>signal</var></tt>, where <var>signal</var> is either
8098 the name of a signal or one of the numeric signals listed in
8099 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8100 supported if <prgn>kill</prgn> is implemented as a shell
8103 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8104 signals must be supported. In addition to the signal
8105 numbers listed in the extension, which are the same as for
8106 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8109 If a shell script requires non-SUSv3 features from the shell
8110 interpreter other than those listed above, the appropriate shell
8111 must be specified in the first line of the script (e.g.,
8112 <tt>#!/bin/bash</tt>) and the package must depend on the package
8113 providing the shell (unless the shell package is marked
8114 "Essential", as in the case of <prgn>bash</prgn>).
8118 You may wish to restrict your script to SUSv3 features plus the
8119 above set when possible so that it may use <file>/bin/sh</file>
8120 as its interpreter. Checking your script
8121 with <prgn>checkbashisms</prgn> from
8122 the <package>devscripts</package> package or running your script
8123 with an alternate shell such as <prgn>posh</prgn> may help
8124 uncover violations of the above requirements. If in doubt
8125 whether a script complies with these requirements,
8126 use <file>/bin/bash</file>.
8130 Perl scripts should check for errors when making any
8131 system calls, including <tt>open</tt>, <tt>print</tt>,
8132 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8136 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8137 scripting languages. See <em>Csh Programming Considered
8138 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8139 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8140 If an upstream package comes with <prgn>csh</prgn> scripts
8141 then you must make sure that they start with
8142 <tt>#!/bin/csh</tt> and make your package depend on the
8143 <prgn>c-shell</prgn> virtual package.
8147 Any scripts which create files in world-writeable
8148 directories (e.g., in <file>/tmp</file>) must use a
8149 mechanism which will fail atomically if a file with the same
8150 name already exists.
8154 The Debian base system provides the <prgn>tempfile</prgn>
8155 and <prgn>mktemp</prgn> utilities for use by scripts for
8162 <heading>Symbolic links</heading>
8165 In general, symbolic links within a top-level directory should
8166 be relative, and symbolic links pointing from one top-level
8167 directory to or into another should be absolute. (A top-level
8168 directory is a sub-directory of the root
8169 directory <file>/</file>.) For example, a symbolic link
8170 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8171 should be relative (<file>../share/bar</file>), but a symbolic
8172 link from <file>/var/run</file> to <file>/run</file> should be
8174 This is necessary to allow top-level directories to be
8175 symlinks. If linking <file>/var/run</file>
8176 to <file>/run</file> were done with the relative symbolic
8177 link <file>../run</file>, but <file>/var</file> were a
8178 symbolic link to <file>/srv/disk1</file>, the symbolic link
8179 would point to <file>/srv/run</file> rather than the intended
8185 In addition, symbolic links should be specified as short as
8186 possible, i.e., link targets like <file>foo/../bar</file> are
8191 Note that when creating a relative link using
8192 <prgn>ln</prgn> it is not necessary for the target of the
8193 link to exist relative to the working directory you're
8194 running <prgn>ln</prgn> from, nor is it necessary to change
8195 directory to the directory where the link is to be made.
8196 Simply include the string that should appear as the target
8197 of the link (this will be a pathname relative to the
8198 directory in which the link resides) as the first argument
8203 For example, in your <prgn>Makefile</prgn> or
8204 <file>debian/rules</file>, you can do things like:
8205 <example compact="compact">
8206 ln -fs gcc $(prefix)/bin/cc
8207 ln -fs gcc debian/tmp/usr/bin/cc
8208 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8209 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8214 A symbolic link pointing to a compressed file should always
8215 have the same file extension as the referenced file. (For
8216 example, if a file <file>foo.gz</file> is referenced by a
8217 symbolic link, the filename of the link has to end with
8218 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8223 <heading>Device files</heading>
8226 Packages must not include device files or named pipes in the
8231 If a package needs any special device files that are not
8232 included in the base system, it must call
8233 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8234 after notifying the user<footnote>
8235 This notification could be done via a (low-priority)
8236 debconf message, or an echo (printf) statement.
8241 Packages must not remove any device files in the
8242 <prgn>postrm</prgn> or any other script. This is left to the
8243 system administrator.
8247 Debian uses the serial devices
8248 <file>/dev/ttyS*</file>. Programs using the old
8249 <file>/dev/cu*</file> devices should be changed to use
8250 <file>/dev/ttyS*</file>.
8254 Named pipes needed by the package must be created in
8255 the <prgn>postinst</prgn> script<footnote>
8256 It's better to use <prgn>mkfifo</prgn> rather
8257 than <prgn>mknod</prgn> to create named pipes so that
8258 automated checks for packages incorrectly creating device
8259 files with <prgn>mknod</prgn> won't have false positives.
8260 </footnote> and removed in
8261 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8266 <sect id="config-files">
8267 <heading>Configuration files</heading>
8270 <heading>Definitions</heading>
8274 <tag>configuration file</tag>
8276 A file that affects the operation of a program, or
8277 provides site- or host-specific information, or
8278 otherwise customizes the behavior of a program.
8279 Typically, configuration files are intended to be
8280 modified by the system administrator (if needed or
8281 desired) to conform to local policy or to provide
8282 more useful site-specific behavior.
8285 <tag><tt>conffile</tt></tag>
8287 A file listed in a package's <tt>conffiles</tt>
8288 file, and is treated specially by <prgn>dpkg</prgn>
8289 (see <ref id="configdetails">).
8295 The distinction between these two is important; they are
8296 not interchangeable concepts. Almost all
8297 <tt>conffile</tt>s are configuration files, but many
8298 configuration files are not <tt>conffiles</tt>.
8302 As noted elsewhere, <file>/etc/init.d</file> scripts,
8303 <file>/etc/default</file> files, scripts installed in
8304 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8305 configuration installed in <file>/etc/cron.d</file> must be
8306 treated as configuration files. In general, any script that
8307 embeds configuration information is de-facto a configuration
8308 file and should be treated as such.
8313 <heading>Location</heading>
8316 Any configuration files created or used by your package
8317 must reside in <file>/etc</file>. If there are several,
8318 consider creating a subdirectory of <file>/etc</file>
8319 named after your package.
8323 If your package creates or uses configuration files
8324 outside of <file>/etc</file>, and it is not feasible to modify
8325 the package to use <file>/etc</file> directly, put the files
8326 in <file>/etc</file> and create symbolic links to those files
8327 from the location that the package requires.
8332 <heading>Behavior</heading>
8335 Configuration file handling must conform to the following
8337 <list compact="compact">
8339 local changes must be preserved during a package
8343 configuration files must be preserved when the
8344 package is removed, and only deleted when the
8348 Obsolete configuration files without local changes may be
8349 removed by the package during upgrade.
8353 The easy way to achieve this behavior is to make the
8354 configuration file a <tt>conffile</tt>. This is
8355 appropriate only if it is possible to distribute a default
8356 version that will work for most installations, although
8357 some system administrators may choose to modify it. This
8358 implies that the default version will be part of the
8359 package distribution, and must not be modified by the
8360 maintainer scripts during installation (or at any other
8365 In order to ensure that local changes are preserved
8366 correctly, no package may contain or make hard links to
8367 conffiles.<footnote>
8368 Rationale: There are two problems with hard links.
8369 The first is that some editors break the link while
8370 editing one of the files, so that the two files may
8371 unwittingly become unlinked and different. The second
8372 is that <prgn>dpkg</prgn> might break the hard link
8373 while upgrading <tt>conffile</tt>s.
8378 The other way to do it is via the maintainer scripts. In
8379 this case, the configuration file must not be listed as a
8380 <tt>conffile</tt> and must not be part of the package
8381 distribution. If the existence of a file is required for
8382 the package to be sensibly configured it is the
8383 responsibility of the package maintainer to provide
8384 maintainer scripts which correctly create, update and
8385 maintain the file and remove it on purge. (See <ref
8386 id="maintainerscripts"> for more information.) These
8387 scripts must be idempotent (i.e., must work correctly if
8388 <prgn>dpkg</prgn> needs to re-run them due to errors
8389 during installation or removal), must cope with all the
8390 variety of ways <prgn>dpkg</prgn> can call maintainer
8391 scripts, must not overwrite or otherwise mangle the user's
8392 configuration without asking, must not ask unnecessary
8393 questions (particularly during upgrades), and must
8394 otherwise be good citizens.
8398 The scripts are not required to configure every possible
8399 option for the package, but only those necessary to get
8400 the package running on a given system. Ideally the
8401 sysadmin should not have to do any configuration other
8402 than that done (semi-)automatically by the
8403 <prgn>postinst</prgn> script.
8407 A common practice is to create a script called
8408 <file><var>package</var>-configure</file> and have the
8409 package's <prgn>postinst</prgn> call it if and only if the
8410 configuration file does not already exist. In certain
8411 cases it is useful for there to be an example or template
8412 file which the maintainer scripts use. Such files should
8413 be in <file>/usr/share/<var>package</var></file> or
8414 <file>/usr/lib/<var>package</var></file> (depending on whether
8415 they are architecture-independent or not). There should
8416 be symbolic links to them from
8417 <file>/usr/share/doc/<var>package</var>/examples</file> if
8418 they are examples, and should be perfectly ordinary
8419 <prgn>dpkg</prgn>-handled files (<em>not</em>
8420 configuration files).
8424 These two styles of configuration file handling must
8425 not be mixed, for that way lies madness:
8426 <prgn>dpkg</prgn> will ask about overwriting the file
8427 every time the package is upgraded.
8432 <heading>Sharing configuration files</heading>
8435 If two or more packages use the same configuration file
8436 and it is reasonable for both to be installed at the same
8437 time, one of these packages must be defined as
8438 <em>owner</em> of the configuration file, i.e., it will be
8439 the package which handles that file as a configuration
8440 file. Other packages that use the configuration file must
8441 depend on the owning package if they require the
8442 configuration file to operate. If the other package will
8443 use the configuration file if present, but is capable of
8444 operating without it, no dependency need be declared.
8448 If it is desirable for two or more related packages to
8449 share a configuration file <em>and</em> for all of the
8450 related packages to be able to modify that configuration
8451 file, then the following should be done:
8452 <enumlist compact="compact">
8454 One of the related packages (the "owning" package)
8455 will manage the configuration file with maintainer
8456 scripts as described in the previous section.
8459 The owning package should also provide a program
8460 that the other packages may use to modify the
8464 The related packages must use the provided program
8465 to make any desired modifications to the
8466 configuration file. They should either depend on
8467 the core package to guarantee that the configuration
8468 modifier program is available or accept gracefully
8469 that they cannot modify the configuration file if it
8470 is not. (This is in addition to the fact that the
8471 configuration file may not even be present in the
8478 Sometimes it's appropriate to create a new package which
8479 provides the basic infrastructure for the other packages
8480 and which manages the shared configuration files. (The
8481 <tt>sgml-base</tt> package is a good example.)
8485 If the configuration file cannot be shared as described above,
8486 the packages must be marked as conflicting with each other.
8487 Two packages that specify the same file as
8488 a <tt>conffile</tt> must conflict. This is an instance of the
8489 general rule about not sharing files. Neither alternatives
8490 nor diversions are likely to be appropriate in this case; in
8491 particular, <prgn>dpkg</prgn> does not handle diverted
8492 <tt>conffile</tt>s well.
8496 When two packages both declare the same <tt>conffile</tt>, they
8497 may see left-over configuration files from each other even
8498 though they conflict with each other. If a user removes
8499 (without purging) one of the packages and installs the other,
8500 the new package will take over the <tt>conffile</tt> from the
8501 old package. If the file was modified by the user, it will be
8502 treated the same as any other locally
8503 modified <tt>conffile</tt> during an upgrade.
8507 The maintainer scripts must not alter a <tt>conffile</tt>
8508 of <em>any</em> package, including the one the scripts
8514 <heading>User configuration files ("dotfiles")</heading>
8517 The files in <file>/etc/skel</file> will automatically be
8518 copied into new user accounts by <prgn>adduser</prgn>.
8519 No other program should reference the files in
8520 <file>/etc/skel</file>.
8524 Therefore, if a program needs a dotfile to exist in
8525 advance in <file>$HOME</file> to work sensibly, that dotfile
8526 should be installed in <file>/etc/skel</file> and treated as a
8531 However, programs that require dotfiles in order to
8532 operate sensibly are a bad thing, unless they do create
8533 the dotfiles themselves automatically.
8537 Furthermore, programs should be configured by the Debian
8538 default installation to behave as closely to the upstream
8539 default behavior as possible.
8543 Therefore, if a program in a Debian package needs to be
8544 configured in some way in order to operate sensibly, that
8545 should be done using a site-wide configuration file placed
8546 in <file>/etc</file>. Only if the program doesn't support a
8547 site-wide default configuration and the package maintainer
8548 doesn't have time to add it may a default per-user file be
8549 placed in <file>/etc/skel</file>.
8553 <file>/etc/skel</file> should be as empty as we can make it.
8554 This is particularly true because there is no easy (or
8555 necessarily desirable) mechanism for ensuring that the
8556 appropriate dotfiles are copied into the accounts of
8557 existing users when a package is installed.
8563 <heading>Log files</heading>
8565 Log files should usually be named
8566 <file>/var/log/<var>package</var>.log</file>. If you have many
8567 log files, or need a separate directory for permission
8568 reasons (<file>/var/log</file> is writable only by
8569 <file>root</file>), you should usually create a directory named
8570 <file>/var/log/<var>package</var></file> and place your log
8575 Log files must be rotated occasionally so that they don't grow
8576 indefinitely. The best way to do this is to install a log
8577 rotation configuration file in the
8578 directory <file>/etc/logrotate.d</file>, normally
8579 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8580 the facilities provided by <prgn>logrotate</prgn>.
8583 The traditional approach to log files has been to set up
8584 <em>ad hoc</em> log rotation schemes using simple shell
8585 scripts and cron. While this approach is highly
8586 customizable, it requires quite a lot of sysadmin work.
8587 Even though the original Debian system helped a little
8588 by automatically installing a system which can be used
8589 as a template, this was deemed not enough.
8593 The use of <prgn>logrotate</prgn>, a program developed
8594 by Red Hat, is better, as it centralizes log management.
8595 It has both a configuration file
8596 (<file>/etc/logrotate.conf</file>) and a directory where
8597 packages can drop their individual log rotation
8598 configurations (<file>/etc/logrotate.d</file>).
8601 Here is a good example for a logrotate config
8602 file (for more information see <manref name="logrotate"
8604 <example compact="compact">
8605 /var/log/foo/*.log {
8611 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8615 This rotates all files under <file>/var/log/foo</file>, saves 12
8616 compressed generations, and tells the daemon to reopen its log
8617 files after the log rotation. It skips this log rotation
8618 (via <tt>missingok</tt>) if no such log file is present, which
8619 avoids errors if the package is removed but not purged.
8623 Log files should be removed when the package is
8624 purged (but not when it is only removed). This should be
8625 done by the <prgn>postrm</prgn> script when it is called
8626 with the argument <tt>purge</tt> (see <ref
8627 id="removedetails">).
8631 <sect id="permissions-owners">
8632 <heading>Permissions and owners</heading>
8635 The rules in this section are guidelines for general use.
8636 If necessary you may deviate from the details below.
8637 However, if you do so you must make sure that what is done
8638 is secure and you should try to be as consistent as possible
8639 with the rest of the system. You should probably also
8640 discuss it on <prgn>debian-devel</prgn> first.
8644 Files should be owned by <tt>root:root</tt>, and made
8645 writable only by the owner and universally readable (and
8646 executable, if appropriate), that is mode 644 or 755.
8650 Directories should be mode 755 or (for group-writability)
8651 mode 2775. The ownership of the directory should be
8652 consistent with its mode: if a directory is mode 2775, it
8653 should be owned by the group that needs write access to
8656 When a package is upgraded, and the owner or permissions
8657 of a file included in the package has changed, dpkg
8658 arranges for the ownership and permissions to be
8659 correctly set upon installation. However, this does not
8660 extend to directories; the permissions and ownership of
8661 directories already on the system does not change on
8662 install or upgrade of packages. This makes sense, since
8663 otherwise common directories like <tt>/usr</tt> would
8664 always be in flux. To correctly change permissions of a
8665 directory the package owns, explicit action is required,
8666 usually in the <tt>postinst</tt> script. Care must be
8667 taken to handle downgrades as well, in that case.
8673 Control information files should be owned by <tt>root:root</tt>
8674 and either mode 644 (for most files) or mode 755 (for
8675 executables such as <qref id="maintscripts">maintainer
8680 Setuid and setgid executables should be mode 4755 or 2755
8681 respectively, and owned by the appropriate user or group.
8682 They should not be made unreadable (modes like 4711 or
8683 2711 or even 4111); doing so achieves no extra security,
8684 because anyone can find the binary in the freely available
8685 Debian package; it is merely inconvenient. For the same
8686 reason you should not restrict read or execute permissions
8687 on non-set-id executables.
8691 Some setuid programs need to be restricted to particular
8692 sets of users, using file permissions. In this case they
8693 should be owned by the uid to which they are set-id, and by
8694 the group which should be allowed to execute them. They
8695 should have mode 4754; again there is no point in making
8696 them unreadable to those users who must not be allowed to
8701 It is possible to arrange that the system administrator can
8702 reconfigure the package to correspond to their local
8703 security policy by changing the permissions on a binary:
8704 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8705 described below.<footnote>
8706 Ordinary files installed by <prgn>dpkg</prgn> (as
8707 opposed to <tt>conffile</tt>s and other similar objects)
8708 normally have their permissions reset to the distributed
8709 permissions when the package is reinstalled. However,
8710 the use of <prgn>dpkg-statoverride</prgn> overrides this
8713 Another method you should consider is to create a group for
8714 people allowed to use the program(s) and make any setuid
8715 executables executable only by that group.
8719 If you need to create a new user or group for your package
8720 there are two possibilities. Firstly, you may need to
8721 make some files in the binary package be owned by this
8722 user or group, or you may need to compile the user or
8723 group id (rather than just the name) into the binary
8724 (though this latter should be avoided if possible, as in
8725 this case you need a statically allocated id).</p>
8728 If you need a statically allocated id, you must ask for a
8729 user or group id from the <tt>base-passwd</tt> maintainer,
8730 and must not release the package until you have been
8731 allocated one. Once you have been allocated one you must
8732 either make the package depend on a version of the
8733 <tt>base-passwd</tt> package with the id present in
8734 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8735 your package to create the user or group itself with the
8736 correct id (using <tt>adduser</tt>) in its
8737 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8738 the <prgn>postinst</prgn> is to be preferred if it is
8739 possible, otherwise a pre-dependency will be needed on the
8740 <tt>adduser</tt> package.)
8744 On the other hand, the program might be able to determine
8745 the uid or gid from the user or group name at runtime, so
8746 that a dynamically allocated id can be used. In this case
8747 you should choose an appropriate user or group name,
8748 discussing this on <prgn>debian-devel</prgn> and checking
8749 with the <package/base-passwd/ maintainer that it is unique and that
8750 they do not wish you to use a statically allocated id
8751 instead. When this has been checked you must arrange for
8752 your package to create the user or group if necessary using
8753 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8754 <prgn>postinst</prgn> script (again, the latter is to be
8755 preferred if it is possible).
8759 Note that changing the numeric value of an id associated
8760 with a name is very difficult, and involves searching the
8761 file system for all appropriate files. You need to think
8762 carefully whether a static or dynamic id is required, since
8763 changing your mind later will cause problems.
8766 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8768 This section is not intended as policy, but as a
8769 description of the use of <prgn>dpkg-statoverride</prgn>.
8773 If a system administrator wishes to have a file (or
8774 directory or other such thing) installed with owner and
8775 permissions different from those in the distributed Debian
8776 package, they can use the <prgn>dpkg-statoverride</prgn>
8777 program to instruct <prgn>dpkg</prgn> to use the different
8778 settings every time the file is installed. Thus the
8779 package maintainer should distribute the files with their
8780 normal permissions, and leave it for the system
8781 administrator to make any desired changes. For example, a
8782 daemon which is normally required to be setuid root, but
8783 in certain situations could be used without being setuid,
8784 should be installed setuid in the <tt>.deb</tt>. Then the
8785 local system administrator can change this if they wish.
8786 If there are two standard ways of doing it, the package
8787 maintainer can use <tt>debconf</tt> to find out the
8788 preference, and call <prgn>dpkg-statoverride</prgn> in the
8789 maintainer script if necessary to accommodate the system
8790 administrator's choice. Care must be taken during
8791 upgrades to not override an existing setting.
8795 Given the above, <prgn>dpkg-statoverride</prgn> is
8796 essentially a tool for system administrators and would not
8797 normally be needed in the maintainer scripts. There is
8798 one type of situation, though, where calls to
8799 <prgn>dpkg-statoverride</prgn> would be needed in the
8800 maintainer scripts, and that involves packages which use
8801 dynamically allocated user or group ids. In such a
8802 situation, something like the following idiom can be very
8803 helpful in the package's <prgn>postinst</prgn>, where
8804 <tt>sysuser</tt> is a dynamically allocated id:
8806 for i in /usr/bin/foo /usr/sbin/bar
8808 # only do something when no setting exists
8809 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8811 #include: debconf processing, question about foo and bar
8812 if [ "$RET" = "true" ] ; then
8813 dpkg-statoverride --update --add sysuser root 4755 $i
8818 The corresponding code to remove the override when the package
8821 for i in /usr/bin/foo /usr/sbin/bar
8823 if dpkg-statoverride --list $i >/dev/null 2>&1
8825 dpkg-statoverride --remove $i
8835 <chapt id="customized-programs">
8836 <heading>Customized programs</heading>
8838 <sect id="arch-spec">
8839 <heading>Architecture specification strings</heading>
8842 If a program needs to specify an <em>architecture specification
8843 string</em> in some place, it should select one of the strings
8844 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8845 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8846 part is sometimes elided, as when the OS is Linux.
8850 Note that we don't want to use
8851 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8852 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8853 since this would make our programs incompatible with other
8854 Linux distributions. We also don't use something like
8855 <tt><var>arch</var>-unknown-linux</tt>, since the
8856 <tt>unknown</tt> does not look very good.
8859 <sect1 id="arch-wildcard-spec">
8860 <heading>Architecture wildcards</heading>
8863 A package may specify an architecture wildcard. Architecture
8864 wildcards are in the format <tt>any</tt> (which matches every
8865 architecture), <tt><var>os</var></tt>-any, or
8866 any-<tt><var>cpu</var></tt>. <footnote>
8867 Internally, the package system normalizes the GNU triplets
8868 and the Debian arches into Debian arch triplets (which are
8869 kind of inverted GNU triplets), with the first component of
8870 the triplet representing the libc and ABI in use, and then
8871 does matching against those triplets. However, such
8872 triplets are an internal implementation detail that should
8873 not be used by packages directly. The libc and ABI portion
8874 is handled internally by the package system based on
8875 the <var>os</var> and <var>cpu</var>.
8882 <heading>Daemons</heading>
8885 The configuration files <file>/etc/services</file>,
8886 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8887 by the <prgn>netbase</prgn> package and must not be modified
8892 If a package requires a new entry in one of these files, the
8893 maintainer should get in contact with the
8894 <prgn>netbase</prgn> maintainer, who will add the entries
8895 and release a new version of the <prgn>netbase</prgn>
8900 The configuration file <file>/etc/inetd.conf</file> must not be
8901 modified by the package's scripts except via the
8902 <prgn>update-inetd</prgn> script or the
8903 <file>DebianNet.pm</file> Perl module. See their documentation
8904 for details on how to add entries.
8908 If a package wants to install an example entry into
8909 <file>/etc/inetd.conf</file>, the entry must be preceded with
8910 exactly one hash character (<tt>#</tt>). Such lines are
8911 treated as "commented out by user" by the
8912 <prgn>update-inetd</prgn> script and are not changed or
8913 activated during package updates.
8918 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8922 Some programs need to create pseudo-ttys. This should be done
8923 using Unix98 ptys if the C library supports it. The resulting
8924 program must not be installed setuid root, unless that
8925 is required for other functionality.
8929 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8930 <file>/var/log/lastlog</file> must be installed writable by
8931 group <tt>utmp</tt>. Programs which need to modify those
8932 files must be installed setgid <tt>utmp</tt>.
8937 <heading>Editors and pagers</heading>
8940 Some programs have the ability to launch an editor or pager
8941 program to edit or display a text document. Since there are
8942 lots of different editors and pagers available in the Debian
8943 distribution, the system administrator and each user should
8944 have the possibility to choose their preferred editor and
8949 In addition, every program should choose a good default
8950 editor/pager if none is selected by the user or system
8955 Thus, every program that launches an editor or pager must
8956 use the EDITOR or PAGER environment variable to determine
8957 the editor or pager the user wishes to use. If these
8958 variables are not set, the programs <file>/usr/bin/editor</file>
8959 and <file>/usr/bin/pager</file> should be used, respectively.
8963 These two files are managed through the <prgn>dpkg</prgn>
8964 "alternatives" mechanism. Every package providing an editor or
8965 pager must call the <prgn>update-alternatives</prgn> script to
8966 register as an alternative for <file>/usr/bin/editor</file>
8967 or <file>/usr/bin/pager</file> as appropriate. The alternative
8968 should have a slave alternative
8969 for <file>/usr/share/man/man1/editor.1.gz</file>
8970 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8971 corresponding manual page.
8975 If it is very hard to adapt a program to make use of the
8976 EDITOR or PAGER variables, that program may be configured to
8977 use <file>/usr/bin/sensible-editor</file> and
8978 <file>/usr/bin/sensible-pager</file> as the editor or pager
8979 program respectively. These are two scripts provided in the
8980 <package>sensible-utils</package> package that check the EDITOR
8981 and PAGER variables and launch the appropriate program, and fall
8982 back to <file>/usr/bin/editor</file>
8983 and <file>/usr/bin/pager</file> if the variable is not set.
8987 A program may also use the VISUAL environment variable to
8988 determine the user's choice of editor. If it exists, it
8989 should take precedence over EDITOR. This is in fact what
8990 <file>/usr/bin/sensible-editor</file> does.
8994 It is not required for a package to depend on
8995 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8996 package to provide such virtual packages.<footnote>
8997 The Debian base system already provides an editor and a
9003 <sect id="web-appl">
9004 <heading>Web servers and applications</heading>
9007 This section describes the locations and URLs that should
9008 be used by all web servers and web applications in the
9015 Cgi-bin executable files are installed in the
9017 <example compact="compact">
9018 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9020 or a subdirectory of that directory, and should be
9022 <example compact="compact">
9023 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9025 (possibly with a subdirectory name
9026 before <var>cgi-bin-name</var>).
9030 <p>Access to HTML documents</p>
9033 HTML documents for a package are stored in
9034 <file>/usr/share/doc/<var>package</var></file>
9035 and can be referred to as
9036 <example compact="compact">
9037 http://localhost/doc/<var>package</var>/<var>filename</var>
9042 The web server should restrict access to the document
9043 tree so that only clients on the same host can read
9044 the documents. If the web server does not support such
9045 access controls, then it should not provide access at
9046 all, or ask about providing access during installation.
9051 <p>Access to images</p>
9053 It is recommended that images for a package be stored
9054 in <tt>/usr/share/images/<var>package</var></tt> and
9055 may be referred to through an alias <tt>/images/</tt>
9058 http://localhost/images/<package>/<filename>
9065 <p>Web Document Root</p>
9068 Web Applications should try to avoid storing files in
9069 the Web Document Root. Instead they should use the
9070 /usr/share/doc/<var>package</var> directory for
9071 documents and register the Web Application via the
9072 <package>doc-base</package> package. If access to the
9073 web document root is unavoidable then use
9074 <example compact="compact">
9077 as the Document Root. This might be just a symbolic
9078 link to the location where the system administrator
9079 has put the real document root.
9082 <item><p>Providing httpd and/or httpd-cgi</p>
9084 All web servers should provide the virtual package
9085 <tt>httpd</tt>. If a web server has CGI support it should
9086 provide <tt>httpd-cgi</tt> additionally.
9089 All web applications which do not contain CGI scripts should
9090 depend on <tt>httpd</tt>, all those web applications which
9091 <tt>do</tt> contain CGI scripts, should depend on
9099 <sect id="mail-transport-agents">
9100 <heading>Mail transport, delivery and user agents</heading>
9103 Debian packages which process electronic mail, whether mail
9104 user agents (MUAs) or mail transport agents (MTAs), must
9105 ensure that they are compatible with the configuration
9106 decisions below. Failure to do this may result in lost
9107 mail, broken <tt>From:</tt> lines, and other serious brain
9112 The mail spool is <file>/var/mail</file> and the interface to
9113 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9114 the FHS). On older systems, the mail spool may be
9115 physically located in <file>/var/spool/mail</file>, but all
9116 access to the mail spool should be via the
9117 <file>/var/mail</file> symlink. The mail spool is part of the
9118 base system and not part of the MTA package.
9122 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9123 programs (such as IMAP daemons) must lock the mailbox in an
9124 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9125 be combined with dot locking. To avoid deadlocks, a program
9126 should use <tt>fcntl()</tt> first and dot locking after
9127 this, or alternatively implement the two locking methods in
9128 a non blocking way<footnote>
9129 If it is not possible to establish both locks, the
9130 system shouldn't wait for the second lock to be
9131 established, but remove the first lock, wait a (random)
9132 time, and start over locking again.
9133 </footnote>. Using the functions <tt>maillock</tt> and
9134 <tt>mailunlock</tt> provided by the
9135 <tt>liblockfile*</tt><footnote>
9136 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9137 to use these functions.
9138 </footnote> packages is the recommended way to realize this.
9142 Mailboxes are generally either mode 600 and owned by
9143 <var>user</var> or mode 660 and owned by
9144 <tt><var>user</var>:mail</tt><footnote>
9145 There are two traditional permission schemes for mail spools:
9146 mode 600 with all mail delivery done by processes running as
9147 the destination user, or mode 660 and owned by group mail with
9148 mail delivery done by a process running as a system user in
9149 group mail. Historically, Debian required mode 660 mail
9150 spools to enable the latter model, but that model has become
9151 increasingly uncommon and the principle of least privilege
9152 indicates that mail systems that use the first model should
9153 use permissions of 600. If delivery to programs is permitted,
9154 it's easier to keep the mail system secure if the delivery
9155 agent runs as the destination user. Debian Policy therefore
9156 permits either scheme.
9157 </footnote>. The local system administrator may choose a
9158 different permission scheme; packages should not make
9159 assumptions about the permission and ownership of mailboxes
9160 unless required (such as when creating a new mailbox). A MUA
9161 may remove a mailbox (unless it has nonstandard permissions) in
9162 which case the MTA or another MUA must recreate it if needed.
9166 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9167 be setgid mail to do the locking mentioned above (and
9168 must obviously avoid accessing other users' mailboxes
9169 using this privilege).</p>
9172 <file>/etc/aliases</file> is the source file for the system mail
9173 aliases (e.g., postmaster, usenet, etc.), it is the one
9174 which the sysadmin and <prgn>postinst</prgn> scripts may
9175 edit. After <file>/etc/aliases</file> is edited the program or
9176 human editing it must call <prgn>newaliases</prgn>. All MTA
9177 packages must come with a <prgn>newaliases</prgn> program,
9178 even if it does nothing, but older MTA packages did not do
9179 this so programs should not fail if <prgn>newaliases</prgn>
9180 cannot be found. Note that because of this, all MTA
9181 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9182 <tt>Replaces: mail-transport-agent</tt> control fields.
9186 The convention of writing <tt>forward to
9187 <var>address</var></tt> in the mailbox itself is not
9188 supported. Use a <tt>.forward</tt> file instead.</p>
9191 The <prgn>rmail</prgn> program used by UUCP
9192 for incoming mail should be <file>/usr/sbin/rmail</file>.
9193 Likewise, <prgn>rsmtp</prgn>, for receiving
9194 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9198 If your package needs to know what hostname to use on (for
9199 example) outgoing news and mail messages which are generated
9200 locally, you should use the file <file>/etc/mailname</file>. It
9201 will contain the portion after the username and <tt>@</tt>
9202 (at) sign for email addresses of users on the machine
9203 (followed by a newline).
9207 Such a package should check for the existence of this file
9208 when it is being configured. If it exists, it should be
9209 used without comment, although an MTA's configuration script
9210 may wish to prompt the user even if it finds that this file
9211 exists. If the file does not exist, the package should
9212 prompt the user for the value (preferably using
9213 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9214 as well as using it in the package's configuration. The
9215 prompt should make it clear that the name will not just be
9216 used by that package. For example, in this situation the
9217 <tt>inn</tt> package could say something like:
9218 <example compact="compact">
9219 Please enter the "mail name" of your system. This is the
9220 hostname portion of the address to be shown on outgoing
9221 news and mail messages. The default is
9222 <var>syshostname</var>, your system's host name. Mail
9223 name ["<var>syshostname</var>"]:
9225 where <var>syshostname</var> is the output of <tt>hostname
9231 <heading>News system configuration</heading>
9234 All the configuration files related to the NNTP (news)
9235 servers and clients should be located under
9236 <file>/etc/news</file>.</p>
9239 There are some configuration issues that apply to a number
9240 of news clients and server packages on the machine. These
9244 <tag><file>/etc/news/organization</file></tag>
9246 A string which should appear as the
9247 organization header for all messages posted
9248 by NNTP clients on the machine
9251 <tag><file>/etc/news/server</file></tag>
9253 Contains the FQDN of the upstream NNTP
9254 server, or localhost if the local machine is
9259 Other global files may be added as required for cross-package news
9266 <heading>Programs for the X Window System</heading>
9269 <heading>Providing X support and package priorities</heading>
9272 Programs that can be configured with support for the X
9273 Window System must be configured to do so and must declare
9274 any package dependencies necessary to satisfy their
9275 runtime requirements when using the X Window System. If
9276 such a package is of higher priority than the X packages
9277 on which it depends, it is required that either the
9278 X-specific components be split into a separate package, or
9279 that an alternative version of the package, which includes
9280 X support, be provided, or that the package's priority be
9286 <heading>Packages providing an X server</heading>
9289 Packages that provide an X server that, directly or
9290 indirectly, communicates with real input and display
9291 hardware should declare in their <tt>Provides</tt> control
9292 field that they provide the virtual
9293 package <tt>xserver</tt>.<footnote>
9294 This implements current practice, and provides an
9295 actual policy for usage of the <tt>xserver</tt>
9296 virtual package which appears in the virtual packages
9297 list. In a nutshell, X servers that interface
9298 directly with the display and input hardware or via
9299 another subsystem (e.g., GGI) should provide
9300 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9301 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9307 <heading>Packages providing a terminal emulator</heading>
9310 Packages that provide a terminal emulator for the X Window
9311 System which meet the criteria listed below should declare in
9312 their <tt>Provides</tt> control field that they provide the
9313 virtual package <tt>x-terminal-emulator</tt>. They should
9314 also register themselves as an alternative for
9315 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9316 20. That alternative should have a slave alternative
9317 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9318 pointing to the corresponding manual page.
9322 To be an <tt>x-terminal-emulator</tt>, a program must:
9323 <list compact="compact">
9325 Be able to emulate a DEC VT100 terminal, or a
9326 compatible terminal.
9330 Support the command-line option <tt>-e
9331 <var>command</var></tt>, which creates a new
9332 terminal window<footnote>
9333 "New terminal window" does not necessarily mean
9334 a new top-level X window directly parented by
9335 the window manager; it could, if the terminal
9336 emulator application were so coded, be a new
9337 "view" in a multiple-document interface (MDI).
9339 and runs the specified <var>command</var>,
9340 interpreting the entirety of the rest of the command
9341 line as a command to pass straight to exec, in the
9342 manner that <tt>xterm</tt> does.
9346 Support the command-line option <tt>-T
9347 <var>title</var></tt>, which creates a new terminal
9348 window with the window title <var>title</var>.
9355 <heading>Packages providing a window manager</heading>
9358 Packages that provide a window manager should declare in
9359 their <tt>Provides</tt> control field that they provide the
9360 virtual package <tt>x-window-manager</tt>. They should also
9361 register themselves as an alternative for
9362 <file>/usr/bin/x-window-manager</file>, with a priority
9363 calculated as follows:
9364 <list compact="compact">
9366 Start with a priority of 20.
9370 If the window manager supports the Debian menu
9371 system, add 20 points if this support is available
9372 in the package's default configuration (i.e., no
9373 configuration files belonging to the system or user
9374 have to be edited to activate the feature); if
9375 configuration files must be modified, add only 10
9381 If the window manager complies with <url
9382 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9383 name="The Window Manager Specification Project">,
9384 written by the <url id="http://www.freedesktop.org/wiki/"
9385 name="Free Desktop Group">, add 40 points.
9389 If the window manager permits the X session to be
9390 restarted using a <em>different</em> window manager
9391 (without killing the X server) in its default
9392 configuration, add 10 points; otherwise add none.
9395 That alternative should have a slave alternative
9396 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9397 pointing to the corresponding manual page.
9402 <heading>Packages providing fonts</heading>
9405 Packages that provide fonts for the X Window
9407 For the purposes of Debian Policy, a "font for the X
9408 Window System" is one which is accessed via X protocol
9409 requests. Fonts for the Linux console, for PostScript
9410 renderer, or any other purpose, do not fit this
9411 definition. Any tool which makes such fonts available
9412 to the X Window System, however, must abide by this
9415 must do a number of things to ensure that they are both
9416 available without modification of the X or font server
9417 configuration, and that they do not corrupt files used by
9418 other font packages to register information about
9422 Fonts of any type supported by the X Window System
9423 must be in a separate binary package from any
9424 executables, libraries, or documentation (except
9425 that specific to the fonts shipped, such as their
9426 license information). If one or more of the fonts
9427 so packaged are necessary for proper operation of
9428 the package with which they are associated the font
9429 package may be Recommended; if the fonts merely
9430 provide an enhancement, a Suggests relationship may
9431 be used. Packages must not Depend on font
9433 This is because the X server may retrieve fonts
9434 from the local file system or over the network
9435 from an X font server; the Debian package system
9436 is empowered to deal only with the local
9442 BDF fonts must be converted to PCF fonts with the
9443 <prgn>bdftopcf</prgn> utility (available in the
9444 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9445 placed in a directory that corresponds to their
9447 <list compact="compact">
9449 100 dpi fonts must be placed in
9450 <file>/usr/share/fonts/X11/100dpi/</file>.
9454 75 dpi fonts must be placed in
9455 <file>/usr/share/fonts/X11/75dpi/</file>.
9459 Character-cell fonts, cursor fonts, and other
9460 low-resolution fonts must be placed in
9461 <file>/usr/share/fonts/X11/misc/</file>.
9467 Type 1 fonts must be placed in
9468 <file>/usr/share/fonts/X11/Type1/</file>. If font
9469 metric files are available, they must be placed here
9474 Subdirectories of <file>/usr/share/fonts/X11/</file>
9475 other than those listed above must be neither
9476 created nor used. (The <file>PEX</file>, <file>CID</file>,
9477 <file>Speedo</file>, and <file>cyrillic</file> directories
9478 are excepted for historical reasons, but installation of
9479 files into these directories remains discouraged.)
9483 Font packages may, instead of placing files directly
9484 in the X font directories listed above, provide
9485 symbolic links in that font directory pointing to
9486 the files' actual location in the filesystem. Such
9487 a location must comply with the FHS.
9491 Font packages should not contain both 75dpi and
9492 100dpi versions of a font. If both are available,
9493 they should be provided in separate binary packages
9494 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9495 the names of the packages containing the
9496 corresponding fonts.
9500 Fonts destined for the <file>misc</file> subdirectory
9501 should not be included in the same package as 75dpi
9502 or 100dpi fonts; instead, they should be provided in
9503 a separate package with <tt>-misc</tt> appended to
9508 Font packages must not provide the files
9509 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9510 <file>fonts.scale</file> in a font directory:
9513 <file>fonts.dir</file> files must not be provided at all.
9517 <file>fonts.alias</file> and <file>fonts.scale</file>
9518 files, if needed, should be provided in the
9520 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9521 where <var>fontdir</var> is the name of the
9523 <file>/usr/share/fonts/X11/</file> where the
9524 package's corresponding fonts are stored
9525 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9526 <var>package</var> is the name of the package
9527 that provides these fonts, and
9528 <var>extension</var> is either <tt>scale</tt>
9529 or <tt>alias</tt>, whichever corresponds to
9536 Font packages must declare a dependency on
9537 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9538 or <tt>Pre-Depends</tt> control field.
9542 Font packages that provide one or more
9543 <file>fonts.scale</file> files as described above must
9544 invoke <prgn>update-fonts-scale</prgn> on each
9545 directory into which they installed fonts
9546 <em>before</em> invoking
9547 <prgn>update-fonts-dir</prgn> on that directory.
9548 This invocation must occur in both the
9549 <prgn>postinst</prgn> (for all arguments) and
9550 <prgn>postrm</prgn> (for all arguments except
9551 <tt>upgrade</tt>) scripts.
9555 Font packages that provide one or more
9556 <file>fonts.alias</file> files as described above must
9557 invoke <prgn>update-fonts-alias</prgn> on each
9558 directory into which they installed fonts. This
9559 invocation must occur in both the
9560 <prgn>postinst</prgn> (for all arguments) and
9561 <prgn>postrm</prgn> (for all arguments except
9562 <tt>upgrade</tt>) scripts.
9566 Font packages must invoke
9567 <prgn>update-fonts-dir</prgn> on each directory into
9568 which they installed fonts. This invocation must
9569 occur in both the <prgn>postinst</prgn> (for all
9570 arguments) and <prgn>postrm</prgn> (for all
9571 arguments except <tt>upgrade</tt>) scripts.
9575 Font packages must not provide alias names for the
9576 fonts they include which collide with alias names
9577 already in use by fonts already packaged.
9581 Font packages must not provide fonts with the same
9582 XLFD registry name as another font already packaged.
9588 <sect1 id="appdefaults">
9589 <heading>Application defaults files</heading>
9592 Application defaults files must be installed in the
9593 directory <file>/etc/X11/app-defaults/</file> (use of a
9594 localized subdirectory of <file>/etc/X11/</file> as described
9595 in the <em>X Toolkit Intrinsics - C Language
9596 Interface</em> manual is also permitted). They must be
9597 registered as <tt>conffile</tt>s or handled as
9598 configuration files.
9602 Customization of programs' X resources may also be
9603 supported with the provision of a file with the same name
9604 as that of the package placed in
9605 the <file>/etc/X11/Xresources/</file> directory, which
9606 must be registered as a <tt>conffile</tt> or handled as a
9607 configuration file.<footnote>
9608 Note that this mechanism is not the same as using
9609 app-defaults; app-defaults are tied to the client
9610 binary on the local file system, whereas X resources
9611 are stored in the X server and affect all connecting
9618 <heading>Installation directory issues</heading>
9621 Historically, packages using the X Window System used a
9622 separate set of installation directories from other packages.
9623 This practice has been discontinued and packages using the X
9624 Window System should now generally be installed in the same
9625 directories as any other package. Specifically, packages must
9626 not install files under the <file>/usr/X11R6/</file> directory
9627 and the <file>/usr/X11R6/</file> directory hierarchy should be
9628 regarded as obsolete.
9632 Include files previously installed under
9633 <file>/usr/X11R6/include/X11/</file> should be installed into
9634 <file>/usr/include/X11/</file>. For files previously
9635 installed into subdirectories of
9636 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9637 determine if subdirectories of <file>/usr/lib/</file> and
9638 <file>/usr/share/</file> can be used. If not, a subdirectory
9639 of <file>/usr/lib/X11/</file> should be used.
9643 Configuration files for window, display, or session managers
9644 or other applications that are tightly integrated with the X
9645 Window System may be placed in a subdirectory
9646 of <file>/etc/X11/</file> corresponding to the package name.
9647 Other X Window System applications should use
9648 the <file>/etc/</file> directory unless otherwise mandated by
9649 policy (such as for <ref id="appdefaults">).
9655 <heading>Perl programs and modules</heading>
9658 Perl programs and modules should follow the current Perl policy.
9662 The Perl policy can be found in the <tt>perl-policy</tt>
9663 files in the <tt>debian-policy</tt> package.
9664 It is also available from the Debian web mirrors at
9665 <tt><url name="/doc/packaging-manuals/perl-policy/"
9666 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9671 <heading>Emacs lisp programs</heading>
9674 Please refer to the "Debian Emacs Policy" for details of how to
9675 package emacs lisp programs.
9679 The Emacs policy is available in
9680 <file>debian-emacs-policy.gz</file> of the
9681 <package>emacsen-common</package> package.
9682 It is also available from the Debian web mirrors at
9683 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9684 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9689 <heading>Games</heading>
9692 The permissions on <file>/var/games</file> are mode 755, owner
9693 <tt>root</tt> and group <tt>root</tt>.
9697 Each game decides on its own security policy.</p>
9700 Games which require protected, privileged access to
9701 high-score files, saved games, etc., may be made
9702 set-<em>group</em>-id (mode 2755) and owned by
9703 <tt>root:games</tt>, and use files and directories with
9704 appropriate permissions (770 <tt>root:games</tt>, for
9705 example). They must not be made
9706 set-<em>user</em>-id, as this causes security problems. (If
9707 an attacker can subvert any set-user-id game they can
9708 overwrite the executable of any other, causing other players
9709 of these games to run a Trojan horse program. With a
9710 set-group-id game the attacker only gets access to less
9711 important game data, and if they can get at the other
9712 players' accounts at all it will take considerably more
9716 Some packages, for example some fortune cookie programs, are
9717 configured by the upstream authors to install with their
9718 data files or other static information made unreadable so
9719 that they can only be accessed through set-id programs
9720 provided. You should not do this in a Debian package: anyone can
9721 download the <file>.deb</file> file and read the data from it,
9722 so there is no point making the files unreadable. Not
9723 making the files unreadable also means that you don't have
9724 to make so many programs set-id, which reduces the risk of a
9728 As described in the FHS, binaries of games should be
9729 installed in the directory <file>/usr/games</file>. This also
9730 applies to games that use the X Window System. Manual pages
9731 for games (X and non-X games) should be installed in
9732 <file>/usr/share/man/man6</file>.</p>
9738 <heading>Documentation</heading>
9741 <heading>Manual pages</heading>
9744 You should install manual pages in <prgn>nroff</prgn> source
9745 form, in appropriate places under <file>/usr/share/man</file>.
9746 You should only use sections 1 to 9 (see the FHS for more
9747 details). You must not install a pre-formatted "cat page".
9751 Each program, utility, and function should have an
9752 associated manual page included in the same package. It is
9753 suggested that all configuration files also have a manual
9754 page included as well. Manual pages for protocols and other
9755 auxiliary things are optional.
9759 If no manual page is available, this is considered as a bug
9760 and should be reported to the Debian Bug Tracking System (the
9761 maintainer of the package is allowed to write this bug report
9762 themselves, if they so desire). Do not close the bug report
9763 until a proper man page is available.<footnote>
9764 It is not very hard to write a man page. See the
9765 <url id="http://www.schweikhardt.net/man_page_howto.html"
9766 name="Man-Page-HOWTO">,
9767 <manref name="man" section="7">, the examples created
9768 by <prgn>dh_make</prgn>, the helper
9769 program <prgn>help2man</prgn>, or the
9770 directory <file>/usr/share/doc/man-db/examples</file>.
9775 You may forward a complaint about a missing man page to the
9776 upstream authors, and mark the bug as forwarded in the
9777 Debian bug tracking system. Even though the GNU Project do
9778 not in general consider the lack of a man page to be a bug,
9779 we do; if they tell you that they don't consider it a bug
9780 you should leave the bug in our bug tracking system open
9785 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9789 If one man page needs to be accessible via several names it
9790 is better to use a symbolic link than the <file>.so</file>
9791 feature, but there is no need to fiddle with the relevant
9792 parts of the upstream source to change from <file>.so</file> to
9793 symlinks: don't do it unless it's easy. You should not
9794 create hard links in the manual page directories, nor put
9795 absolute filenames in <file>.so</file> directives. The filename
9796 in a <file>.so</file> in a man page should be relative to the
9797 base of the man page tree (usually
9798 <file>/usr/share/man</file>). If you do not create any links
9799 (whether symlinks, hard links, or <tt>.so</tt> directives)
9800 in the file system to the alternate names of the man page,
9801 then you should not rely on <prgn>man</prgn> finding your
9802 man page under those names based solely on the information in
9803 the man page's header.<footnote>
9804 Supporting this in <prgn>man</prgn> often requires
9805 unreasonable processing time to find a manual page or to
9806 report that none exists, and moves knowledge into man's
9807 database that would be better left in the file system.
9808 This support is therefore deprecated and will cease to
9809 be present in the future.
9814 Manual pages in locale-specific subdirectories of
9815 <file>/usr/share/man</file> should use either UTF-8 or the usual
9816 legacy encoding for that language (normally the one corresponding
9817 to the shortest relevant locale name in
9818 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9819 <file>/usr/share/man/fr</file> should use either UTF-8 or
9820 ISO-8859-1.<footnote>
9821 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9822 use. In future, all manual pages will be required to use
9828 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9829 included in the subdirectory name unless it indicates a
9830 significant difference in the language, as this excludes
9831 speakers of the language in other countries.<footnote>
9832 At the time of writing, Chinese and Portuguese are the main
9833 languages with such differences, so <file>pt_BR</file>,
9834 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9839 If a localized version of a manual page is provided, it should
9840 either be up-to-date or it should be obvious to the reader that
9841 it is outdated and the original manual page should be used
9842 instead. This can be done either by a note at the beginning of
9843 the manual page or by showing the missing or changed portions in
9844 the original language instead of the target language.
9849 <heading>Info documents</heading>
9852 Info documents should be installed in <file>/usr/share/info</file>.
9853 They should be compressed with <tt>gzip -9</tt>.
9857 The <prgn>install-info</prgn> program maintains a directory of
9858 installed info documents in <file>/usr/share/info/dir</file> for
9859 the use of info readers.<footnote>
9860 It was previously necessary for packages installing info
9861 documents to run <prgn>install-info</prgn> from maintainer
9862 scripts. This is no longer necessary. The installation
9863 system now uses dpkg triggers.
9865 This file must not be included in packages. Packages containing
9866 info documents should depend on <tt>dpkg (>= 1.15.4) |
9867 install-info</tt> to ensure that the directory file is properly
9868 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9873 Info documents should contain section and directory entry
9874 information in the document for the use
9875 of <prgn>install-info</prgn>. The section should be specified
9876 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9877 space and the section of this info page. The directory entry or
9878 entries should be included between
9879 a <tt>START-INFO-DIR-ENTRY</tt> line and
9880 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9882 INFO-DIR-SECTION Individual utilities
9883 START-INFO-DIR-ENTRY
9884 * example: (example). An example info directory entry.
9887 To determine which section to use, you should look
9888 at <file>/usr/share/info/dir</file> on your system and choose
9889 the most relevant (or create a new section if none of the
9890 current sections are relevant).<footnote>
9891 Normally, info documents are generated from Texinfo source.
9892 To include this information in the generated info document, if
9893 it is absent, add commands like:
9895 @dircategory Individual utilities
9897 * example: (example). An example info directory entry.
9900 to the Texinfo source of the document and ensure that the info
9901 documents are rebuilt from source during the package build.
9907 <heading>Additional documentation</heading>
9910 Any additional documentation that comes with the package may
9911 be installed at the discretion of the package maintainer.
9912 Plain text documentation should be installed in the directory
9913 <file>/usr/share/doc/<var>package</var></file>, where
9914 <var>package</var> is the name of the package, and
9915 compressed with <tt>gzip -9</tt> unless it is small.
9919 If a package comes with large amounts of documentation which
9920 many users of the package will not require you should create
9921 a separate binary package to contain it, so that it does not
9922 take up disk space on the machines of users who do not need
9923 or want it installed.</p>
9926 It is often a good idea to put text information files
9927 (<file>README</file>s, changelogs, and so forth) that come with
9928 the source package in <file>/usr/share/doc/<var>package</var></file>
9929 in the binary package. However, you don't need to install
9930 the instructions for building and installing the package, of
9934 Packages must not require the existence of any files in
9935 <file>/usr/share/doc/</file> in order to function
9937 The system administrator should be able to
9938 delete files in <file>/usr/share/doc/</file> without causing
9939 any programs to break.
9941 Any files that are referenced by programs but are also
9942 useful as stand alone documentation should be installed under
9943 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9944 <file>/usr/share/doc/<var>package</var></file>.
9948 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9949 link to another directory in <file>/usr/share/doc</file> only if
9950 the two packages both come from the same source and the
9951 first package Depends on the second.<footnote>
9953 Please note that this does not override the section on
9954 changelog files below, so the file
9955 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9956 must refer to the changelog for the current version of
9957 <var>package</var> in question. In practice, this means
9958 that the sources of the target and the destination of the
9959 symlink must be the same (same source package and
9966 Former Debian releases placed all additional documentation
9967 in <file>/usr/doc/<var>package</var></file>. This has been
9968 changed to <file>/usr/share/doc/<var>package</var></file>,
9969 and packages must not put documentation in the directory
9970 <file>/usr/doc/<var>package</var></file>. <footnote>
9971 At this phase of the transition, we no longer require a
9972 symbolic link in <file>/usr/doc/</file>. At a later point,
9973 policy shall change to make the symbolic links a bug.
9979 <heading>Preferred documentation formats</heading>
9982 The unification of Debian documentation is being carried out
9986 If your package comes with extensive documentation in a
9987 markup format that can be converted to various other formats
9988 you should if possible ship HTML versions in a binary
9989 package, in the directory
9990 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9991 its subdirectories.<footnote>
9992 The rationale: The important thing here is that HTML
9993 docs should be available in <em>some</em> package, not
9994 necessarily in the main binary package.
9999 Other formats such as PostScript may be provided at the
10000 package maintainer's discretion.
10004 <sect id="copyrightfile">
10005 <heading>Copyright information</heading>
10008 Every package must be accompanied by a verbatim copy of its
10009 copyright information and distribution license in the file
10010 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10011 file must neither be compressed nor be a symbolic link.
10015 In addition, the copyright file must say where the upstream
10016 sources (if any) were obtained, and should name the original
10021 Packages in the <em>contrib</em> or <em>non-free</em> archive
10022 areas should state in the copyright file that the package is not
10023 part of the Debian distribution and briefly explain why.
10027 A copy of the file which will be installed in
10028 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10029 be in <file>debian/copyright</file> in the source package.
10033 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10034 link to another directory in <file>/usr/share/doc</file> only if
10035 the two packages both come from the same source and the
10036 first package Depends on the second. These rules are important
10037 because <file>copyright</file> files must be extractable by
10042 Packages distributed under the Apache license (version 2.0), the
10043 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10044 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10045 1.3) should refer to the corresponding files
10046 under <file>/usr/share/common-licenses</file>,<footnote>
10049 <file>/usr/share/common-licenses/Apache-2.0</file>,
10050 <file>/usr/share/common-licenses/Artistic</file>,
10051 <file>/usr/share/common-licenses/GPL-1</file>,
10052 <file>/usr/share/common-licenses/GPL-2</file>,
10053 <file>/usr/share/common-licenses/GPL-3</file>,
10054 <file>/usr/share/common-licenses/LGPL-2</file>,
10055 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10056 <file>/usr/share/common-licenses/LGPL-3</file>,
10057 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10058 <file>/usr/share/common-licenses/GFDL-1.3</file>
10059 respectively. The University of California BSD license is
10060 also included in <package>base-files</package> as
10061 <file>/usr/share/common-licenses/BSD</file>, but given the
10062 brevity of this license, its specificity to code whose
10063 copyright is held by the Regents of the University of
10064 California, and the frequency of minor wording changes, its
10065 text should be included in the copyright file rather than
10066 referencing this file.
10068 </footnote> rather than quoting them in the copyright
10073 You should not use the copyright file as a general <file>README</file>
10074 file. If your package has such a file it should be
10075 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10076 <file>README.Debian</file> or some other appropriate place.
10080 All copyright files must be encoded in UTF-8.
10083 <sect1 id="copyrightformat">
10084 <heading>Machine-readable copyright information</heading>
10087 A specification for a standard, machine-readable format
10088 for <file>debian/copyright</file> files is maintained as part
10089 of the <package>debian-policy</package> package. This
10090 document may be found in the <file>copyright-format</file>
10091 files in the <package>debian-policy</package> package. It is
10092 also available from the Debian web mirrors at
10093 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10094 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10098 Use of this format is optional.
10104 <heading>Examples</heading>
10107 Any examples (configurations, source files, whatever),
10108 should be installed in a directory
10109 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10110 files should not be referenced by any program: they're there
10111 for the benefit of the system administrator and users as
10112 documentation only. Architecture-specific example files
10113 should be installed in a directory
10114 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10116 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10117 latter directory itself may be a symbolic link to the
10122 If the purpose of a package is to provide examples, then the
10123 example files may be installed into
10124 <file>/usr/share/doc/<var>package</var></file>.
10128 <sect id="changelogs">
10129 <heading>Changelog files</heading>
10132 Packages that are not Debian-native must contain a
10133 compressed copy of the <file>debian/changelog</file> file from
10134 the Debian source tree in
10135 <file>/usr/share/doc/<var>package</var></file> with the name
10136 <file>changelog.Debian.gz</file>.
10140 If an upstream changelog is available, it should be accessible as
10141 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10142 plain text. If the upstream changelog is distributed in
10143 HTML, it should be made available in that form as
10144 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10145 and a plain text <file>changelog.gz</file> should be generated
10146 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10147 the upstream changelog files do not already conform to this
10148 naming convention, then this may be achieved either by
10149 renaming the files, or by adding a symbolic link, at the
10150 maintainer's discretion.<footnote>
10151 Rationale: People should not have to look in places for
10152 upstream changelogs merely because they are given
10153 different names or are distributed in HTML format.
10158 All of these files should be installed compressed using
10159 <tt>gzip -9</tt>, as they will become large with time even
10160 if they start out small.
10164 If the package has only one changelog which is used both as
10165 the Debian changelog and the upstream one because there is
10166 no separate upstream maintainer then that changelog should
10167 usually be installed as
10168 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10169 there is a separate upstream maintainer, but no upstream
10170 changelog, then the Debian changelog should still be called
10171 <file>changelog.Debian.gz</file>.
10175 For details about the format and contents of the Debian
10176 changelog file, please see <ref id="dpkgchangelog">.
10181 <appendix id="pkg-scope">
10182 <heading>Introduction and scope of these appendices</heading>
10185 These appendices are taken essentially verbatim from the
10186 now-deprecated Packaging Manual, version 3.2.1.0. They are
10187 the chapters which are likely to be of use to package
10188 maintainers and which have not already been included in the
10189 policy document itself. Most of these sections are very likely
10190 not relevant to policy; they should be treated as
10191 documentation for the packaging system. Please note that these
10192 appendices are included for convenience, and for historical
10193 reasons: they used to be part of policy package, and they have
10194 not yet been incorporated into dpkg documentation. However,
10195 they still have value, and hence they are presented here.
10199 They have not yet been checked to ensure that they are
10200 compatible with the contents of policy, and if there are any
10201 contradictions, the version in the main policy document takes
10202 precedence. The remaining chapters of the old Packaging
10203 Manual have also not been read in detail to ensure that there
10204 are not parts which have been left out. Both of these will be
10205 done in due course.
10209 Certain parts of the Packaging manual were integrated into the
10210 Policy Manual proper, and removed from the appendices. Links
10211 have been placed from the old locations to the new ones.
10215 <prgn>dpkg</prgn> is a suite of programs for creating binary
10216 package files and installing and removing them on Unix
10218 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10219 work on or be ported to other systems.
10224 The binary packages are designed for the management of
10225 installed executable programs (usually compiled binaries) and
10226 their associated data, though source code examples and
10227 documentation are provided as part of some packages.</p>
10230 This manual describes the technical aspects of creating Debian
10231 binary packages (<file>.deb</file> files). It documents the
10232 behavior of the package management programs
10233 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10234 they interact with packages.</p>
10237 It also documents the interaction between
10238 <prgn>dselect</prgn>'s core and the access method scripts it
10239 uses to actually install the selected packages, and describes
10240 how to create a new access method.</p>
10243 This manual does not go into detail about the options and
10244 usage of the package building and installation tools. It
10245 should therefore be read in conjunction with those programs'
10250 The utility programs which are provided with <prgn>dpkg</prgn>
10251 for managing various system configuration and similar issues,
10252 such as <prgn>update-rc.d</prgn> and
10253 <prgn>install-info</prgn>, are not described in detail here -
10254 please see their man pages.
10258 It is assumed that the reader is reasonably familiar with the
10259 <prgn>dpkg</prgn> System Administrators' manual.
10260 Unfortunately this manual does not yet exist.
10264 The Debian version of the FSF's GNU hello program is provided as
10265 an example for people wishing to create Debian packages. However,
10266 while the examples are helpful, they do not replace the need to
10267 read and follow the Policy and Programmer's Manual.</p>
10270 <appendix id="pkg-binarypkg">
10271 <heading>Binary packages (from old Packaging Manual)</heading>
10274 The binary package has two main sections. The first part
10275 consists of various control information files and scripts used
10276 by <prgn>dpkg</prgn> when installing and removing. See <ref
10277 id="pkg-controlarea">.
10281 The second part is an archive containing the files and
10282 directories to be installed.
10286 In the future binary packages may also contain other
10287 components, such as checksums and digital signatures. The
10288 format for the archive is described in full in the
10289 <file>deb(5)</file> man page.
10293 <sect id="pkg-bincreating"><heading>Creating package files -
10294 <prgn>dpkg-deb</prgn>
10298 All manipulation of binary package files is done by
10299 <prgn>dpkg-deb</prgn>; it's the only program that has
10300 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10301 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10302 will spot that the options requested are appropriate to
10303 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10308 In order to create a binary package you must make a
10309 directory tree which contains all the files and directories
10310 you want to have in the file system data part of the package.
10311 In Debian-format source packages this directory is usually
10312 <file>debian/tmp</file>, relative to the top of the package's
10317 They should have the locations (relative to the root of the
10318 directory tree you're constructing) ownerships and
10319 permissions which you want them to have on the system when
10320 they are installed.
10324 With current versions of <prgn>dpkg</prgn> the uid/username
10325 and gid/groupname mappings for the users and groups being
10326 used should be the same on the system where the package is
10327 built and the one where it is installed.
10331 You need to add one special directory to the root of the
10332 miniature file system tree you're creating:
10333 <prgn>DEBIAN</prgn>. It should contain the control
10334 information files, notably the binary package control file
10335 (see <ref id="pkg-controlfile">).
10339 The <prgn>DEBIAN</prgn> directory will not appear in the
10340 file system archive of the package, and so won't be installed
10341 by <prgn>dpkg</prgn> when the package is unpacked.
10345 When you've prepared the package, you should invoke:
10347 dpkg --build <var>directory</var>
10352 This will build the package in
10353 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10354 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10355 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10356 build the package.)
10360 See the man page <manref name="dpkg-deb" section="8"> for details of how
10361 to examine the contents of this newly-created file. You may find the
10362 output of following commands enlightening:
10364 dpkg-deb --info <var>filename</var>.deb
10365 dpkg-deb --contents <var>filename</var>.deb
10366 dpkg --contents <var>filename</var>.deb
10368 To view the copyright file for a package you could use this command:
10370 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10375 <sect id="pkg-controlarea">
10376 <heading>Package control information files</heading>
10379 The control information portion of a binary package is a
10380 collection of files with names known to <prgn>dpkg</prgn>.
10381 It will treat the contents of these files specially - some
10382 of them contain information used by <prgn>dpkg</prgn> when
10383 installing or removing the package; others are scripts which
10384 the package maintainer wants <prgn>dpkg</prgn> to run.
10388 It is possible to put other files in the package control
10389 information file area, but this is not generally a good idea
10390 (though they will largely be ignored).
10394 Here is a brief list of the control information files supported
10395 by <prgn>dpkg</prgn> and a summary of what they're used for.
10400 <tag><tt>control</tt>
10403 This is the key description file used by
10404 <prgn>dpkg</prgn>. It specifies the package's name
10405 and version, gives its description for the user,
10406 states its relationships with other packages, and so
10407 forth. See <ref id="sourcecontrolfiles"> and
10408 <ref id="binarycontrolfiles">.
10412 It is usually generated automatically from information
10413 in the source package by the
10414 <prgn>dpkg-gencontrol</prgn> program, and with
10415 assistance from <prgn>dpkg-shlibdeps</prgn>.
10416 See <ref id="pkg-sourcetools">.
10420 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10425 These are executable files (usually scripts) which
10426 <prgn>dpkg</prgn> runs during installation, upgrade
10427 and removal of packages. They allow the package to
10428 deal with matters which are particular to that package
10429 or require more complicated processing than that
10430 provided by <prgn>dpkg</prgn>. Details of when and
10431 how they are called are in <ref id="maintainerscripts">.
10435 It is very important to make these scripts idempotent.
10436 See <ref id="idempotency">.
10440 The maintainer scripts are not guaranteed to run with a
10441 controlling terminal and may not be able to interact with
10442 the user. See <ref id="controllingterminal">.
10446 <tag><tt>conffiles</tt>
10449 This file contains a list of configuration files which
10450 are to be handled automatically by <prgn>dpkg</prgn>
10451 (see <ref id="pkg-conffiles">). Note that not necessarily
10452 every configuration file should be listed here.
10455 <tag><tt>shlibs</tt>
10458 This file contains a list of the shared libraries
10459 supplied by the package, with dependency details for
10460 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10461 when it determines what dependencies are required in a
10462 package control file. The <tt>shlibs</tt> file format
10463 is described on <ref id="shlibs">.
10468 <sect id="pkg-controlfile">
10469 <heading>The main control information file: <tt>control</tt></heading>
10472 The most important control information file used by
10473 <prgn>dpkg</prgn> when it installs a package is
10474 <tt>control</tt>. It contains all the package's "vital
10479 The binary package control files of packages built from
10480 Debian sources are made by a special tool,
10481 <prgn>dpkg-gencontrol</prgn>, which reads
10482 <file>debian/control</file> and <file>debian/changelog</file> to
10483 find the information it needs. See <ref id="pkg-sourcepkg"> for
10488 The fields in binary package control files are listed in
10489 <ref id="binarycontrolfiles">.
10493 A description of the syntax of control files and the purpose
10494 of the fields is available in <ref id="controlfields">.
10499 <heading>Time Stamps</heading>
10502 See <ref id="timestamps">.
10507 <appendix id="pkg-sourcepkg">
10508 <heading>Source packages (from old Packaging Manual) </heading>
10511 The Debian binary packages in the distribution are generated
10512 from Debian sources, which are in a special format to assist
10513 the easy and automatic building of binaries.
10516 <sect id="pkg-sourcetools">
10517 <heading>Tools for processing source packages</heading>
10520 Various tools are provided for manipulating source packages;
10521 they pack and unpack sources and help build of binary
10522 packages and help manage the distribution of new versions.
10526 They are introduced and typical uses described here; see
10527 <manref name="dpkg-source" section="1"> for full
10528 documentation about their arguments and operation.
10532 For examples of how to construct a Debian source package,
10533 and how to use those utilities that are used by Debian
10534 source packages, please see the <prgn>hello</prgn> example
10538 <sect1 id="pkg-dpkg-source">
10540 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10545 This program is frequently used by hand, and is also
10546 called from package-independent automated building scripts
10547 such as <prgn>dpkg-buildpackage</prgn>.
10551 To unpack a package it is typically invoked with
10553 dpkg-source -x <var>.../path/to/filename</var>.dsc
10558 with the <file><var>filename</var>.tar.gz</file> and
10559 <file><var>filename</var>.diff.gz</file> (if applicable) in
10560 the same directory. It unpacks into
10561 <file><var>package</var>-<var>version</var></file>, and if
10563 <file><var>package</var>-<var>version</var>.orig</file>, in
10564 the current directory.
10568 To create a packed source archive it is typically invoked:
10570 dpkg-source -b <var>package</var>-<var>version</var>
10575 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10576 <file>.diff.gz</file> (if appropriate) in the current
10577 directory. <prgn>dpkg-source</prgn> does not clean the
10578 source tree first - this must be done separately if it is
10583 See also <ref id="pkg-sourcearchives">.</p>
10587 <sect1 id="pkg-dpkg-buildpackage">
10589 <prgn>dpkg-buildpackage</prgn> - overall package-building
10594 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10595 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10596 targets <tt>clean</tt>, <tt>build</tt> and
10597 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10598 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10599 source and binary package upload.
10603 It is usually invoked by hand from the top level of the
10604 built or unbuilt source directory. It may be invoked with
10605 no arguments; useful arguments include:
10606 <taglist compact="compact">
10607 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10610 Do not sign the <tt>.changes</tt> file or the
10611 source package <tt>.dsc</tt> file, respectively.</p>
10613 <tag><tt>-p<var>sign-command</var></tt></tag>
10616 Invoke <var>sign-command</var> instead of finding
10617 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10618 <var>sign-command</var> must behave just like
10619 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10621 <tag><tt>-r<var>root-command</var></tt></tag>
10624 When root privilege is required, invoke the command
10625 <var>root-command</var>. <var>root-command</var>
10626 should invoke its first argument as a command, from
10627 the <prgn>PATH</prgn> if necessary, and pass its
10628 second and subsequent arguments to the command it
10629 calls. If no <var>root-command</var> is supplied
10630 then <var>dpkg-buildpackage</var> will use
10631 the <prgn>fakeroot</prgn> command, which is sufficient
10632 to build most packages without actually requiring root
10635 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10638 Two types of binary-only build and upload - see
10639 <manref name="dpkg-source" section="1">.
10646 <sect1 id="pkg-dpkg-gencontrol">
10648 <prgn>dpkg-gencontrol</prgn> - generates binary package
10653 This program is usually called from <file>debian/rules</file>
10654 (see <ref id="pkg-sourcetree">) in the top level of the source
10659 This is usually done just before the files and directories in the
10660 temporary directory tree where the package is being built have their
10661 permissions and ownerships set and the package is constructed using
10662 <prgn>dpkg-deb/</prgn>
10664 This is so that the control file which is produced has
10665 the right permissions
10670 <prgn>dpkg-gencontrol</prgn> must be called after all the
10671 files which are to go into the package have been placed in
10672 the temporary build directory, so that its calculation of
10673 the installed size of a package is correct.
10677 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10678 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10679 variable substitutions created by
10680 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10685 For a package which generates only one binary package, and
10686 which builds it in <file>debian/tmp</file> relative to the top
10687 of the source package, it is usually sufficient to call
10688 <prgn>dpkg-gencontrol</prgn>.
10692 Sources which build several binaries will typically need
10695 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10696 </example> The <tt>-P</tt> tells
10697 <prgn>dpkg-gencontrol</prgn> that the package is being
10698 built in a non-default directory, and the <tt>-p</tt>
10699 tells it which package's control file should be generated.
10703 <prgn>dpkg-gencontrol</prgn> also adds information to the
10704 list of files in <file>debian/files</file>, for the benefit of
10705 (for example) a future invocation of
10706 <prgn>dpkg-genchanges</prgn>.</p>
10709 <sect1 id="pkg-dpkg-shlibdeps">
10711 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10716 This program is usually called from <file>debian/rules</file>
10717 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10718 id="pkg-sourcetree">), in the top level of the source tree.
10722 Its arguments are executables and shared libraries
10725 They may be specified either in the locations in the
10726 source tree where they are created or in the locations
10727 in the temporary build tree where they are installed
10728 prior to binary package creation.
10730 </footnote> for which shared library dependencies should
10731 be included in the binary package's control file.
10735 If some of the found shared libraries should only
10736 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10737 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10738 by using the <tt>-d<var>dependency-field</var></tt> option
10739 before those executable(s). (Each <tt>-d</tt> option
10740 takes effect until the next <tt>-d</tt>.)
10744 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10745 output control file to be modified. Instead by default it
10746 adds to the <file>debian/substvars</file> file variable
10747 settings like <tt>shlibs:Depends</tt>. These variable
10748 settings must be referenced in dependency fields in the
10749 appropriate per-binary-package sections of the source
10754 For example, a package that generates an essential part
10755 which requires dependencies, and optional parts that
10756 which only require a recommendation, would separate those
10757 two sets of dependencies into two different fields.<footnote>
10758 At the time of writing, an example for this was the
10759 <package/xmms/ package, with Depends used for the xmms
10760 executable, Recommends for the plug-ins and Suggests for
10761 even more optional features provided by unzip.
10763 It can say in its <file>debian/rules</file>:
10765 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10766 -dRecommends <var>optionalpart anotheroptionalpart</var>
10768 and then in its main control file <file>debian/control</file>:
10771 Depends: ${shlibs:Depends}
10772 Recommends: ${shlibs:Recommends}
10778 Sources which produce several binary packages with
10779 different shared library dependency requirements can use
10780 the <tt>-p<var>varnameprefix</var></tt> option to override
10781 the default <tt>shlibs:</tt> prefix (one invocation of
10782 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10783 They can thus produce several sets of dependency
10784 variables, each of the form
10785 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10786 which can be referred to in the appropriate parts of the
10787 binary package control files.
10792 <sect1 id="pkg-dpkg-distaddfile">
10794 <prgn>dpkg-distaddfile</prgn> - adds a file to
10795 <file>debian/files</file>
10799 Some packages' uploads need to include files other than
10800 the source and binary package files.
10804 <prgn>dpkg-distaddfile</prgn> adds a file to the
10805 <file>debian/files</file> file so that it will be included in
10806 the <file>.changes</file> file when
10807 <prgn>dpkg-genchanges</prgn> is run.
10811 It is usually invoked from the <tt>binary</tt> target of
10812 <file>debian/rules</file>:
10814 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10816 The <var>filename</var> is relative to the directory where
10817 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10818 is usually the directory above the top level of the source
10819 tree. The <file>debian/rules</file> target should put the
10820 file there just before or just after calling
10821 <prgn>dpkg-distaddfile</prgn>.
10825 The <var>section</var> and <var>priority</var> are passed
10826 unchanged into the resulting <file>.changes</file> file.
10831 <sect1 id="pkg-dpkg-genchanges">
10833 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10834 upload control file
10838 This program is usually called by package-independent
10839 automatic building scripts such as
10840 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10845 It is usually called in the top level of a built source
10846 tree, and when invoked with no arguments will print out a
10847 straightforward <file>.changes</file> file based on the
10848 information in the source package's changelog and control
10849 file and the binary and source packages which should have
10855 <sect1 id="pkg-dpkg-parsechangelog">
10857 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10858 representation of a changelog
10862 This program is used internally by
10863 <prgn>dpkg-source</prgn> et al. It may also occasionally
10864 be useful in <file>debian/rules</file> and elsewhere. It
10865 parses a changelog, <file>debian/changelog</file> by default,
10866 and prints a control-file format representation of the
10867 information in it to standard output.
10871 <sect1 id="pkg-dpkg-architecture">
10873 <prgn>dpkg-architecture</prgn> - information about the build and
10878 This program can be used manually, but is also invoked by
10879 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10880 environment or make variables which specify the build and host
10881 architecture for the package building process.
10886 <sect id="pkg-sourcetree">
10887 <heading>The Debian package source tree</heading>
10890 The source archive scheme described later is intended to
10891 allow a Debian package source tree with some associated
10892 control information to be reproduced and transported easily.
10893 The Debian package source tree is a version of the original
10894 program with certain files added for the benefit of the
10895 packaging process, and with any other changes required
10896 made to the rest of the source code and installation
10901 The extra files created for Debian are in the subdirectory
10902 <file>debian</file> of the top level of the Debian package
10903 source tree. They are described below.
10906 <sect1 id="pkg-debianrules">
10907 <heading><file>debian/rules</file> - the main building script</heading>
10910 See <ref id="debianrules">.
10914 <sect1 id="pkg-srcsubstvars">
10915 <heading><file>debian/substvars</file> and variable substitutions</heading>
10918 See <ref id="substvars">.
10924 <heading><file>debian/files</file></heading>
10927 See <ref id="debianfiles">.
10931 <sect1><heading><file>debian/tmp</file>
10935 This is the canonical temporary location for the
10936 construction of binary packages by the <tt>binary</tt>
10937 target. The directory <file>tmp</file> serves as the root of
10938 the file system tree as it is being constructed (for
10939 example, by using the package's upstream makefiles install
10940 targets and redirecting the output there), and it also
10941 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10942 id="pkg-bincreating">.
10946 If several binary packages are generated from the same
10947 source tree it is usual to use several
10948 <file>debian/tmp<var>something</var></file> directories, for
10949 example <file>tmp-a</file> or <file>tmp-doc</file>.
10953 Whatever <file>tmp</file> directories are created and used by
10954 <tt>binary</tt> must of course be removed by the
10955 <tt>clean</tt> target.</p></sect1>
10959 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10963 As it exists on the FTP site, a Debian source package
10964 consists of three related files. You must have the right
10965 versions of all three to be able to use them.
10970 <tag>Debian source control file - <tt>.dsc</tt></tag>
10972 This file is a control file used by <prgn>dpkg-source</prgn>
10973 to extract a source package.
10974 See <ref id="debiansourcecontrolfiles">.
10978 Original source archive -
10980 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10986 This is a compressed (with <tt>gzip -9</tt>)
10987 <prgn>tar</prgn> file containing the source code from
10988 the upstream authors of the program.
10993 Debian package diff -
10995 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11001 This is a unified context diff (<tt>diff -u</tt>)
11002 giving the changes which are required to turn the
11003 original source into the Debian source. These changes
11004 may only include editing and creating plain files.
11005 The permissions of files, the targets of symbolic
11006 links and the characteristics of special files or
11007 pipes may not be changed and no files may be removed
11012 All the directories in the diff must exist, except the
11013 <file>debian</file> subdirectory of the top of the source
11014 tree, which will be created by
11015 <prgn>dpkg-source</prgn> if necessary when unpacking.
11019 The <prgn>dpkg-source</prgn> program will
11020 automatically make the <file>debian/rules</file> file
11021 executable (see below).</p></item>
11026 If there is no original source code - for example, if the
11027 package is specially prepared for Debian or the Debian
11028 maintainer is the same as the upstream maintainer - the
11029 format is slightly different: then there is no diff, and the
11031 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11032 and preferably contains a directory named
11033 <file><var>package</var>-<var>version</var></file>.
11038 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11041 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11042 Debian source package. However, if it is not available it
11043 is possible to unpack a Debian source archive as follows:
11044 <enumlist compact="compact">
11047 Untar the tarfile, which will create a <file>.orig</file>
11051 <p>Rename the <file>.orig</file> directory to
11052 <file><var>package</var>-<var>version</var></file>.</p>
11056 Create the subdirectory <file>debian</file> at the top of
11057 the source tree.</p>
11059 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11061 <item><p>Untar the tarfile again if you want a copy of the original
11062 source code alongside the Debian version.</p>
11067 It is not possible to generate a valid Debian source archive
11068 without using <prgn>dpkg-source</prgn>. In particular,
11069 attempting to use <prgn>diff</prgn> directly to generate the
11070 <file>.diff.gz</file> file will not work.
11074 <heading>Restrictions on objects in source packages</heading>
11077 The source package may not contain any hard links
11079 This is not currently detected when building source
11080 packages, but only when extracting
11084 Hard links may be permitted at some point in the
11085 future, but would require a fair amount of
11087 </footnote>, device special files, sockets or setuid or
11090 Setgid directories are allowed.
11095 The source packaging tools manage the changes between the
11096 original and Debian source using <prgn>diff</prgn> and
11097 <prgn>patch</prgn>. Turning the original source tree as
11098 included in the <file>.orig.tar.gz</file> into the Debian
11099 package source must not involve any changes which cannot be
11100 handled by these tools. Problematic changes which cause
11101 <prgn>dpkg-source</prgn> to halt with an error when
11102 building the source package are:
11103 <list compact="compact">
11104 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11106 <item><p>Changing the targets of symbolic links.</p>
11108 <item><p>Creating directories, other than <file>debian</file>.</p>
11110 <item><p>Changes to the contents of binary files.</p></item>
11111 </list> Changes which cause <prgn>dpkg-source</prgn> to
11112 print a warning but continue anyway are:
11113 <list compact="compact">
11116 Removing files, directories or symlinks.
11118 Renaming a file is not treated specially - it is
11119 seen as the removal of the old file (which
11120 generates a warning, but is otherwise ignored),
11121 and the creation of the new one.
11127 Changed text files which are missing the usual final
11128 newline (either in the original or the modified
11133 Changes which are not represented, but which are not detected by
11134 <prgn>dpkg-source</prgn>, are:
11135 <list compact="compact">
11136 <item><p>Changing the permissions of files (other than
11137 <file>debian/rules</file>) and directories.</p></item>
11142 The <file>debian</file> directory and <file>debian/rules</file>
11143 are handled specially by <prgn>dpkg-source</prgn> - before
11144 applying the changes it will create the <file>debian</file>
11145 directory, and afterwards it will make
11146 <file>debian/rules</file> world-executable.
11152 <appendix id="pkg-controlfields">
11153 <heading>Control files and their fields (from old Packaging Manual)</heading>
11156 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11157 data in a common format, known as control files. Binary and
11158 source packages have control data as do the <file>.changes</file>
11159 files which control the installation of uploaded files, and
11160 <prgn>dpkg</prgn>'s internal databases are in a similar
11165 <heading>Syntax of control files</heading>
11168 See <ref id="controlsyntax">.
11172 It is important to note that there are several fields which
11173 are optional as far as <prgn>dpkg</prgn> and the related
11174 tools are concerned, but which must appear in every Debian
11175 package, or whose omission may cause problems.
11180 <heading>List of fields</heading>
11183 See <ref id="controlfieldslist">.
11187 This section now contains only the fields that didn't belong
11188 to the Policy manual.
11191 <sect1 id="pkg-f-Filename">
11192 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11195 These fields in <tt>Packages</tt> files give the
11196 filename(s) of (the parts of) a package in the
11197 distribution directories, relative to the root of the
11198 Debian hierarchy. If the package has been split into
11199 several parts the parts are all listed in order, separated
11204 <sect1 id="pkg-f-Size">
11205 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11208 These fields in <file>Packages</file> files give the size (in
11209 bytes, expressed in decimal) and MD5 checksum of the
11210 file(s) which make(s) up a binary package in the
11211 distribution. If the package is split into several parts
11212 the values for the parts are listed in order, separated by
11217 <sect1 id="pkg-f-Status">
11218 <heading><tt>Status</tt></heading>
11221 This field in <prgn>dpkg</prgn>'s status file records
11222 whether the user wants a package installed, removed or
11223 left alone, whether it is broken (requiring
11224 re-installation) or not and what its current state on the
11225 system is. Each of these pieces of information is a
11230 <sect1 id="pkg-f-Config-Version">
11231 <heading><tt>Config-Version</tt></heading>
11234 If a package is not installed or not configured, this
11235 field in <prgn>dpkg</prgn>'s status file records the last
11236 version of the package which was successfully
11241 <sect1 id="pkg-f-Conffiles">
11242 <heading><tt>Conffiles</tt></heading>
11245 This field in <prgn>dpkg</prgn>'s status file contains
11246 information about the automatically-managed configuration
11247 files held by a package. This field should <em>not</em>
11248 appear anywhere in a package!
11253 <heading>Obsolete fields</heading>
11256 These are still recognized by <prgn>dpkg</prgn> but should
11257 not appear anywhere any more.
11259 <taglist compact="compact">
11261 <tag><tt>Revision</tt></tag>
11262 <tag><tt>Package-Revision</tt></tag>
11263 <tag><tt>Package_Revision</tt></tag>
11265 The Debian revision part of the package version was
11266 at one point in a separate control field. This
11267 field went through several names.
11270 <tag><tt>Recommended</tt></tag>
11271 <item>Old name for <tt>Recommends</tt>.</item>
11273 <tag><tt>Optional</tt></tag>
11274 <item>Old name for <tt>Suggests</tt>.</item>
11276 <tag><tt>Class</tt></tag>
11277 <item>Old name for <tt>Priority</tt>.</item>
11286 <appendix id="pkg-conffiles">
11287 <heading>Configuration file handling (from old Packaging Manual)</heading>
11290 <prgn>dpkg</prgn> can do a certain amount of automatic
11291 handling of package configuration files.
11295 Whether this mechanism is appropriate depends on a number of
11296 factors, but basically there are two approaches to any
11297 particular configuration file.
11301 The easy method is to ship a best-effort configuration in the
11302 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11303 handle updates. If the user is unlikely to want to edit the
11304 file, but you need them to be able to without losing their
11305 changes, and a new package with a changed version of the file
11306 is only released infrequently, this is a good approach.
11310 The hard method is to build the configuration file from
11311 scratch in the <prgn>postinst</prgn> script, and to take the
11312 responsibility for fixing any mistakes made in earlier
11313 versions of the package automatically. This will be
11314 appropriate if the file is likely to need to be different on
11318 <sect><heading>Automatic handling of configuration files by
11323 A package may contain a control information file called
11324 <tt>conffiles</tt>. This file should be a list of filenames
11325 of configuration files needing automatic handling, separated
11326 by newlines. The filenames should be absolute pathnames,
11327 and the files referred to should actually exist in the
11332 When a package is upgraded <prgn>dpkg</prgn> will process
11333 the configuration files during the configuration stage,
11334 shortly before it runs the package's <prgn>postinst</prgn>
11339 For each file it checks to see whether the version of the
11340 file included in the package is the same as the one that was
11341 included in the last version of the package (the one that is
11342 being upgraded from); it also compares the version currently
11343 installed on the system with the one shipped with the last
11348 If neither the user nor the package maintainer has changed
11349 the file, it is left alone. If one or the other has changed
11350 their version, then the changed version is preferred - i.e.,
11351 if the user edits their file, but the package maintainer
11352 doesn't ship a different version, the user's changes will
11353 stay, silently, but if the maintainer ships a new version
11354 and the user hasn't edited it the new version will be
11355 installed (with an informative message). If both have
11356 changed their version the user is prompted about the problem
11357 and must resolve the differences themselves.
11361 The comparisons are done by calculating the MD5 message
11362 digests of the files, and storing the MD5 of the file as it
11363 was included in the most recent version of the package.
11367 When a package is installed for the first time
11368 <prgn>dpkg</prgn> will install the file that comes with it,
11369 unless that would mean overwriting a file already on the
11374 However, note that <prgn>dpkg</prgn> will <em>not</em>
11375 replace a conffile that was removed by the user (or by a
11376 script). This is necessary because with some programs a
11377 missing file produces an effect hard or impossible to
11378 achieve in another way, so that a missing file needs to be
11379 kept that way if the user did it.
11383 Note that a package should <em>not</em> modify a
11384 <prgn>dpkg</prgn>-handled conffile in its maintainer
11385 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11386 the user confusing and possibly dangerous options for
11387 conffile update when the package is upgraded.</p>
11390 <sect><heading>Fully-featured maintainer script configuration
11395 For files which contain site-specific information such as
11396 the hostname and networking details and so forth, it is
11397 better to create the file in the package's
11398 <prgn>postinst</prgn> script.
11402 This will typically involve examining the state of the rest
11403 of the system to determine values and other information, and
11404 may involve prompting the user for some information which
11405 can't be obtained some other way.
11409 When using this method there are a couple of important
11410 issues which should be considered:
11414 If you discover a bug in the program which generates the
11415 configuration file, or if the format of the file changes
11416 from one version to the next, you will have to arrange for
11417 the postinst script to do something sensible - usually this
11418 will mean editing the installed configuration file to remove
11419 the problem or change the syntax. You will have to do this
11420 very carefully, since the user may have changed the file,
11421 perhaps to fix the very problem that your script is trying
11422 to deal with - you will have to detect these situations and
11423 deal with them correctly.
11427 If you do go down this route it's probably a good idea to
11428 make the program that generates the configuration file(s) a
11429 separate program in <file>/usr/sbin</file>, by convention called
11430 <file><var>package</var>config</file> and then run that if
11431 appropriate from the post-installation script. The
11432 <tt><var>package</var>config</tt> program should not
11433 unquestioningly overwrite an existing configuration - if its
11434 mode of operation is geared towards setting up a package for
11435 the first time (rather than any arbitrary reconfiguration
11436 later) you should have it check whether the configuration
11437 already exists, and require a <tt>--force</tt> flag to
11438 overwrite it.</p></sect>
11441 <appendix id="pkg-alternatives"><heading>Alternative versions of
11442 an interface - <prgn>update-alternatives</prgn> (from old
11447 When several packages all provide different versions of the
11448 same program or file it is useful to have the system select a
11449 default, but to allow the system administrator to change it
11450 and have their decisions respected.
11454 For example, there are several versions of the <prgn>vi</prgn>
11455 editor, and there is no reason to prevent all of them from
11456 being installed at once, each under their own name
11457 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11458 Nevertheless it is desirable to have the name <tt>vi</tt>
11459 refer to something, at least by default.
11463 If all the packages involved cooperate, this can be done with
11464 <prgn>update-alternatives</prgn>.
11468 Each package provides its own version under its own name, and
11469 calls <prgn>update-alternatives</prgn> in its postinst to
11470 register its version (and again in its prerm to deregister
11475 See the man page <manref name="update-alternatives"
11476 section="8"> for details.
11480 If <prgn>update-alternatives</prgn> does not seem appropriate
11481 you may wish to consider using diversions instead.</p>
11484 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11485 package's version of a file (from old Packaging Manual)
11489 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11490 when it reinstalls the package it belongs to, and to have it
11491 put the file from the package somewhere else instead.
11495 This can be used locally to override a package's version of a
11496 file, or by one package to override another's version (or
11497 provide a wrapper for it).
11501 Before deciding to use a diversion, read <ref
11502 id="pkg-alternatives"> to see if you really want a diversion
11503 rather than several alternative versions of a program.
11507 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11508 and updated by a special program <prgn>dpkg-divert</prgn>.
11509 Please see <manref name="dpkg-divert" section="8"> for full
11510 details of its operation.
11514 When a package wishes to divert a file from another, it should
11515 call <prgn>dpkg-divert</prgn> in its preinst to add the
11516 diversion and rename the existing file. For example,
11517 supposing that a <prgn>smailwrapper</prgn> package wishes to
11518 install a wrapper around <file>/usr/sbin/smail</file>:
11520 dpkg-divert --package smailwrapper --add --rename \
11521 --divert /usr/sbin/smail.real /usr/sbin/smail
11522 </example> The <tt>--package smailwrapper</tt> ensures that
11523 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11524 can bypass the diversion and get installed as the true version.
11525 It's safe to add the diversion unconditionally on upgrades since
11526 it will be left unchanged if it already exists, but
11527 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11528 message, make the command conditional on the version from which
11529 the package is being upgraded:
11531 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11532 dpkg-divert --package smailwrapper --add --rename \
11533 --divert /usr/sbin/smail.real /usr/sbin/smail
11535 </example> where <tt>1.0-2</tt> is the version at which the
11536 diversion was first added to the package. Running the command
11537 during abort-upgrade is pointless but harmless.
11541 The postrm has to do the reverse:
11543 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11544 dpkg-divert --package smailwrapper --remove --rename \
11545 --divert /usr/sbin/smail.real /usr/sbin/smail
11547 </example> If the diversion was added at a particular version, the
11548 postrm should also handle the failure case of upgrading from an
11549 older version (unless the older version is so old that direct
11550 upgrades are no longer supported):
11552 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11553 dpkg-divert --package smailwrapper --remove --rename \
11554 --divert /usr/sbin/smail.real /usr/sbin/smail
11556 </example> where <tt>1.0-2</tt> is the version at which the
11557 diversion was first added to the package. The postrm should not
11558 remove the diversion on upgrades both because there's no reason to
11559 remove the diversion only to immediately re-add it and since the
11560 postrm of the old package is run after unpacking so the removal of
11561 the diversion will fail.
11565 Do not attempt to divert a file which is vitally important for
11566 the system's operation - when using <prgn>dpkg-divert</prgn>
11567 there is a time, after it has been diverted but before
11568 <prgn>dpkg</prgn> has installed the new version, when the file
11569 does not exist.</p>
11574 <!-- Local variables: -->
11575 <!-- indent-tabs-mode: t -->
11577 <!-- vim:set ai sts=2 sw=2 tw=76: -->