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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> (required),
1991 <tt>build-indep</tt> (required)
1995 The <tt>build-arch</tt> target must
1996 perform all the configuration and compilation required for
1997 producing all architecture-dependant binary packages
1998 (those packages for which the body of the
1999 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2000 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2001 target must perform all the configuration
2002 and compilation required for producing all
2003 architecture-independent binary packages (those packages
2004 for which the body of the <tt>Architecture</tt> field
2005 in <tt>debian/control</tt> is <tt>all</tt>).
2006 The <tt>build</tt> target
2007 should either depend on those targets or take the same
2008 actions as invoking those targets would perform.<footnote>
2009 This split allows binary-only builds to not install the
2010 dependencies required for the <tt>build-indep</tt>
2011 target and skip any resource-intensive build tasks that
2012 are only required when building architecture-independent
2018 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2019 must not do anything that might require root privilege.
2023 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2024 (required), <tt>binary-indep</tt> (required)
2028 The <tt>binary</tt> target must be all that is
2029 necessary for the user to build the binary package(s)
2030 produced from this source package. It is
2031 split into two parts: <prgn>binary-arch</prgn> builds
2032 the binary packages which are specific to a particular
2033 architecture, and <tt>binary-indep</tt> builds
2034 those which are not.
2037 <tt>binary</tt> may be (and commonly is) a target with
2038 no commands which simply depends on
2039 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2042 Both <tt>binary-*</tt> targets should depend on the
2043 <tt>build</tt> target, or on the appropriate
2044 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2045 provided, so that the package is built if it has not
2046 been already. It should then create the relevant
2047 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2048 make their control files and <prgn>dpkg-deb</prgn> to
2049 build them and place them in the parent of the top
2054 Both the <tt>binary-arch</tt> and
2055 <tt>binary-indep</tt> targets <em>must</em> exist.
2056 If one of them has nothing to do (which will always be
2057 the case if the source generates only a single binary
2058 package, whether architecture-dependent or not), it
2059 must still exist and must always succeed.
2063 The <tt>binary</tt> targets must be invoked as
2065 The <prgn>fakeroot</prgn> package often allows one
2066 to build a package correctly even without being
2072 <tag><tt>clean</tt> (required)</tag>
2075 This must undo any effects that the <tt>build</tt>
2076 and <tt>binary</tt> targets may have had, except
2077 that it should leave alone any output files created in
2078 the parent directory by a run of a <tt>binary</tt>
2083 If a <tt>build</tt> file is touched at the end of
2084 the <tt>build</tt> target, as suggested above, it
2085 should be removed as the first action that
2086 <tt>clean</tt> performs, so that running
2087 <tt>build</tt> again after an interrupted
2088 <tt>clean</tt> doesn't think that everything is
2093 The <tt>clean</tt> target may need to be
2094 invoked as root if <tt>binary</tt> has been
2095 invoked since the last <tt>clean</tt>, or if
2096 <tt>build</tt> has been invoked as root (since
2097 <tt>build</tt> may create directories, for
2102 <tag><tt>get-orig-source</tt> (optional)</tag>
2105 This target fetches the most recent version of the
2106 original source package from a canonical archive site
2107 (via FTP or WWW, for example), does any necessary
2108 rearrangement to turn it into the original source
2109 tar file format described below, and leaves it in the
2114 This target may be invoked in any directory, and
2115 should take care to clean up any temporary files it
2120 This target is optional, but providing it if
2121 possible is a good idea.
2125 <tag><tt>patch</tt> (optional)</tag>
2128 This target performs whatever additional actions are
2129 required to make the source ready for editing (unpacking
2130 additional upstream archives, applying patches, etc.).
2131 It is recommended to be implemented for any package where
2132 <tt>dpkg-source -x</tt> does not result in source ready
2133 for additional modification. See
2134 <ref id="readmesource">.
2140 The <tt>build</tt>, <tt>binary</tt> and
2141 <tt>clean</tt> targets must be invoked with the current
2142 directory being the package's top-level directory.
2147 Additional targets may exist in <file>debian/rules</file>,
2148 either as published or undocumented interfaces or for the
2149 package's internal use.
2153 The architectures we build on and build for are determined
2154 by <prgn>make</prgn> variables using the
2155 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2156 You can determine the Debian architecture and the GNU style
2157 architecture specification string for the build architecture as
2158 well as for the host architecture. The build architecture is
2159 the architecture on which <file>debian/rules</file> is run and
2160 the package build is performed. The host architecture is the
2161 architecture on which the resulting package will be installed
2162 and run. These are normally the same, but may be different in
2163 the case of cross-compilation (building packages for one
2164 architecture on machines of a different architecture).
2168 Here is a list of supported <prgn>make</prgn> variables:
2169 <list compact="compact">
2171 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2174 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2177 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2180 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2181 specification string)
2184 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2185 <tt>DEB_*_GNU_TYPE</tt>)
2188 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2189 <tt>DEB_*_GNU_TYPE</tt>)
2191 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2192 the build architecture or <tt>HOST</tt> for specification of the
2197 Backward compatibility can be provided in the rules file
2198 by setting the needed variables to suitable default
2199 values; please refer to the documentation of
2200 <prgn>dpkg-architecture</prgn> for details.
2204 It is important to understand that the <tt>DEB_*_ARCH</tt>
2205 string only determines which Debian architecture we are
2206 building on or for. It should not be used to get the CPU
2207 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2208 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2209 GNU style variables should generally only be used with upstream
2213 <sect1 id="debianrules-options">
2214 <heading><file>debian/rules</file> and
2215 <tt>DEB_BUILD_OPTIONS</tt></heading>
2218 Supporting the standardized environment variable
2219 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2220 contain several flags to change how a package is compiled and
2221 built. Each flag must be in the form <var>flag</var> or
2222 <var>flag</var>=<var>options</var>. If multiple flags are
2223 given, they must be separated by whitespace.<footnote>
2224 Some packages support any delimiter, but whitespace is the
2225 easiest to parse inside a makefile and avoids ambiguity with
2226 flag values that contain commas.
2228 <var>flag</var> must start with a lowercase letter
2229 (<tt>a-z</tt>) and consist only of lowercase letters,
2230 numbers (<tt>0-9</tt>), and the characters
2231 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2232 <var>options</var> must not contain whitespace. The same
2233 tag should not be given multiple times with conflicting
2234 values. Package maintainers may assume that
2235 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2239 The meaning of the following tags has been standardized:
2243 This tag says to not run any build-time test suite
2244 provided by the package.
2248 The presence of this tag means that the package should
2249 be compiled with a minimum of optimization. For C
2250 programs, it is best to add <tt>-O0</tt> to
2251 <tt>CFLAGS</tt> (although this is usually the default).
2252 Some programs might fail to build or run at this level
2253 of optimization; it may be necessary to use
2254 <tt>-O1</tt>, for example.
2258 This tag means that the debugging symbols should not be
2259 stripped from the binary during installation, so that
2260 debugging information may be included in the package.
2262 <tag>parallel=n</tag>
2264 This tag means that the package should be built using up
2265 to <tt>n</tt> parallel processes if the package build
2266 system supports this.<footnote>
2267 Packages built with <tt>make</tt> can often implement
2268 this by passing the <tt>-j</tt><var>n</var> option to
2271 If the package build system does not support parallel
2272 builds, this string must be ignored. If the package
2273 build system only supports a lower level of concurrency
2274 than <var>n</var>, the package should be built using as
2275 many parallel processes as the package build system
2276 supports. It is up to the package maintainer to decide
2277 whether the package build times are long enough and the
2278 package build system is robust enough to make supporting
2279 parallel builds worthwhile.
2285 Unknown flags must be ignored by <file>debian/rules</file>.
2289 The following makefile snippet is an example of how one may
2290 implement the build options; you will probably have to
2291 massage this example in order to make it work for your
2293 <example compact="compact">
2296 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2297 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2298 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2299 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2301 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2306 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2307 INSTALL_PROGRAM += -s
2309 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2310 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2311 MAKEFLAGS += -j$(NUMJOBS)
2316 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2317 # Code to run the package test suite.
2324 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2325 <sect id="substvars">
2326 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2329 When <prgn>dpkg-gencontrol</prgn>
2330 generates <qref id="binarycontrolfiles">binary package control
2331 files</qref> (<file>DEBIAN/control</file>), it performs variable
2332 substitutions on its output just before writing it. Variable
2333 substitutions have the form <tt>${<var>variable</var>}</tt>.
2334 The optional file <file>debian/substvars</file> contains
2335 variable substitutions to be used; variables can also be set
2336 directly from <file>debian/rules</file> using the <tt>-V</tt>
2337 option to the source packaging commands, and certain predefined
2338 variables are also available.
2342 The <file>debian/substvars</file> file is usually generated and
2343 modified dynamically by <file>debian/rules</file> targets, in
2344 which case it must be removed by the <tt>clean</tt> target.
2348 See <manref name="deb-substvars" section="5"> for full
2349 details about source variable substitutions, including the
2350 format of <file>debian/substvars</file>.</p>
2353 <sect id="debianwatch">
2354 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2357 This is an optional, recommended configuration file for the
2358 <tt>uscan</tt> utility which defines how to automatically scan
2359 ftp or http sites for newly available updates of the
2360 package. This is used
2361 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2362 tools to help with quality control and maintenance of the
2363 distribution as a whole.
2368 <sect id="debianfiles">
2369 <heading>Generated files list: <file>debian/files</file></heading>
2372 This file is not a permanent part of the source tree; it
2373 is used while building packages to record which files are
2374 being generated. <prgn>dpkg-genchanges</prgn> uses it
2375 when it generates a <file>.changes</file> file.
2379 It should not exist in a shipped source package, and so it
2380 (and any backup files or temporary files such as
2381 <file>files.new</file><footnote>
2382 <file>files.new</file> is used as a temporary file by
2383 <prgn>dpkg-gencontrol</prgn> and
2384 <prgn>dpkg-distaddfile</prgn> - they write a new
2385 version of <tt>files</tt> here before renaming it,
2386 to avoid leaving a corrupted copy if an error
2388 </footnote>) should be removed by the
2389 <tt>clean</tt> target. It may also be wise to
2390 ensure a fresh start by emptying or removing it at the
2391 start of the <tt>binary</tt> target.
2395 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2396 package, it adds an entry to <file>debian/files</file> for the
2397 <file>.deb</file> file that will be created when <tt>dpkg-deb
2398 --build</tt> is run for that binary package. So for most
2399 packages all that needs to be done with this file is to
2400 delete it in the <tt>clean</tt> target.
2404 If a package upload includes files besides the source
2405 package and any binary packages whose control files were
2406 made with <prgn>dpkg-gencontrol</prgn> then they should be
2407 placed in the parent of the package's top-level directory
2408 and <prgn>dpkg-distaddfile</prgn> should be called to add
2409 the file to the list in <file>debian/files</file>.</p>
2412 <sect id="embeddedfiles">
2413 <heading>Convenience copies of code</heading>
2416 Some software packages include in their distribution convenience
2417 copies of code from other software packages, generally so that
2418 users compiling from source don't have to download multiple
2419 packages. Debian packages should not make use of these
2420 convenience copies unless the included package is explicitly
2421 intended to be used in this way.<footnote>
2422 For example, parts of the GNU build system work like this.
2424 If the included code is already in the Debian archive in the
2425 form of a library, the Debian packaging should ensure that
2426 binary packages reference the libraries already in Debian and
2427 the convenience copy is not used. If the included code is not
2428 already in Debian, it should be packaged separately as a
2429 prerequisite if possible.
2431 Having multiple copies of the same code in Debian is
2432 inefficient, often creates either static linking or shared
2433 library conflicts, and, most importantly, increases the
2434 difficulty of handling security vulnerabilities in the
2440 <sect id="readmesource">
2441 <heading>Source package handling:
2442 <file>debian/README.source</file></heading>
2445 If running <prgn>dpkg-source -x</prgn> on a source package
2446 doesn't produce the source of the package, ready for editing,
2447 and allow one to make changes and run
2448 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2449 without taking any additional steps, creating a
2450 <file>debian/README.source</file> documentation file is
2451 recommended. This file should explain how to do all of the
2454 <item>Generate the fully patched source, in a form ready for
2455 editing, that would be built to create Debian
2456 packages. Doing this with a <tt>patch</tt> target in
2457 <file>debian/rules</file> is recommended; see
2458 <ref id="debianrules">.</item>
2459 <item>Modify the source and save those modifications so that
2460 they will be applied when building the package.</item>
2461 <item>Remove source modifications that are currently being
2462 applied when building the package.</item>
2463 <item>Optionally, document what steps are necessary to
2464 upgrade the Debian source package to a new upstream version,
2465 if applicable.</item>
2467 This explanation should include specific commands and mention
2468 any additional required Debian packages. It should not assume
2469 familiarity with any specific Debian packaging system or patch
2474 This explanation may refer to a documentation file installed by
2475 one of the package's build dependencies provided that the
2476 referenced documentation clearly explains these tasks and is not
2477 a general reference manual.
2481 <file>debian/README.source</file> may also include any other
2482 information that would be helpful to someone modifying the
2483 source package. Even if the package doesn't fit the above
2484 description, maintainers are encouraged to document in a
2485 <file>debian/README.source</file> file any source package with a
2486 particularly complex or unintuitive source layout or build
2487 system (for example, a package that builds the same source
2488 multiple times to generate different binary packages).
2494 <chapt id="controlfields">
2495 <heading>Control files and their fields</heading>
2498 The package management system manipulates data represented in
2499 a common format, known as <em>control data</em>, stored in
2500 <em>control files</em>.
2501 Control files are used for source packages, binary packages and
2502 the <file>.changes</file> files which control the installation
2503 of uploaded files<footnote>
2504 <prgn>dpkg</prgn>'s internal databases are in a similar
2509 <sect id="controlsyntax">
2510 <heading>Syntax of control files</heading>
2513 A control file consists of one or more paragraphs of
2515 The paragraphs are also sometimes referred to as stanzas.
2517 The paragraphs are separated by empty lines. Parsers may accept
2518 lines consisting solely of spaces and tabs as paragraph
2519 separators, but control files should use empty lines. Some control
2520 files allow only one paragraph; others allow several, in
2521 which case each paragraph usually refers to a different
2522 package. (For example, in source packages, the first
2523 paragraph refers to the source package, and later paragraphs
2524 refer to binary packages generated from the source.) The
2525 ordering of the paragraphs in control files is significant.
2529 Each paragraph consists of a series of data fields. Each field
2530 consists of the field name followed by a colon and then the
2531 data/value associated with that field. The field name is
2532 composed of US-ASCII characters excluding control characters,
2533 space, and colon (i.e., characters in the ranges 33-57 and
2534 59-126, inclusive). Field names must not begin with the comment
2535 character, <tt>#</tt>.
2539 The field ends at the end of the line or at the end of the last
2540 continuation line (see below). Horizontal whitespace (spaces
2541 and tabs) may occur immediately before or after the value and is
2542 ignored there; it is conventional to put a single space after
2543 the colon. For example, a field might be:
2544 <example compact="compact">
2547 the field name is <tt>Package</tt> and the field value
2552 A paragraph must not contain more than one instance of a
2553 particular field name.
2557 There are three types of fields:
2561 The field, including its value, must be a single line. Folding
2562 of the field is not permitted. This is the default field type
2563 if the definition of the field does not specify a different
2568 The value of a folded field is a logical line that may span
2569 several lines. The lines after the first are called
2570 continuation lines and must start with a space or a tab.
2571 Whitespace, including any newlines, is not significant in the
2572 field values of folded fields.<footnote>
2573 This folding method is similar to RFC 5322, allowing control
2574 files that contain only one paragraph and no multiline fields
2575 to be read by parsers written for RFC 5322.
2578 <tag>multiline</tag>
2580 The value of a multiline field may comprise multiple continuation
2581 lines. The first line of the value, the part on the same line as
2582 the field name, often has special significance or may have to be
2583 empty. Other lines are added following the same syntax as the
2584 continuation lines of the folded fields. Whitespace, including newlines,
2585 is significant in the values of multiline fields.
2591 Whitespace must not appear
2592 inside names (of packages, architectures, files or anything
2593 else) or version numbers, or between the characters of
2594 multi-character version relationships.
2598 The presence and purpose of a field, and the syntax of its
2599 value may differ between types of control files.
2603 Field names are not case-sensitive, but it is usual to
2604 capitalize the field names using mixed case as shown below.
2605 Field values are case-sensitive unless the description of the
2606 field says otherwise.
2610 Paragraph separators (empty lines) and lines consisting only of
2611 spaces and tabs are not allowed within field values or between
2612 fields. Empty lines in field values are usually escaped by
2613 representing them by a space followed by a dot.
2617 Lines starting with # without any preceding whitespace are comments
2618 lines that are only permitted in source package control files
2619 (<file>debian/control</file>). These comment lines are ignored, even
2620 between two continuation lines. They do not end logical lines.
2624 All control files must be encoded in UTF-8.
2628 <sect id="sourcecontrolfiles">
2629 <heading>Source package control files -- <file>debian/control</file></heading>
2632 The <file>debian/control</file> file contains the most vital
2633 (and version-independent) information about the source package
2634 and about the binary packages it creates.
2638 The first paragraph of the control file contains information about
2639 the source package in general. The subsequent sets each describe a
2640 binary package that the source tree builds.
2644 The fields in the general paragraph (the first one, for the source
2647 <list compact="compact">
2648 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2651 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2652 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2653 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2654 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2655 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2656 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2657 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2662 The fields in the binary package paragraphs are:
2664 <list compact="compact">
2665 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2666 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2667 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2668 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2669 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2670 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2671 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2672 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2673 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2678 The syntax and semantics of the fields are described below.
2682 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2683 generate control files for binary packages (see below), by
2684 <prgn>dpkg-genchanges</prgn> to generate the
2685 <file>.changes</file> file to accompany the upload, and by
2686 <prgn>dpkg-source</prgn> when it creates the
2687 <file>.dsc</file> source control file as part of a source
2688 archive. Some fields are folded in <file>debian/control</file>,
2689 but not in any other control
2690 file. These tools are responsible for removing the line
2691 breaks from such fields when using fields from
2692 <file>debian/control</file> to generate other control files.
2696 The fields here may contain variable references - their
2697 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2698 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2699 when they generate output control files.
2700 See <ref id="substvars"> for details.
2704 <sect id="binarycontrolfiles">
2705 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2708 The <file>DEBIAN/control</file> file contains the most vital
2709 (and version-dependent) information about a binary package. It
2710 consists of a single paragraph.
2714 The fields in this file are:
2716 <list compact="compact">
2717 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2718 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2719 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2720 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2721 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2722 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2723 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2724 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2725 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2726 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2727 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2728 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2729 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2734 <sect id="debiansourcecontrolfiles">
2735 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2738 This file consists of a single paragraph, possibly surrounded by
2739 a PGP signature. The fields of that paragraph are listed below.
2740 Their syntax is described above, in <ref id="controlsyntax">.
2742 <list compact="compact">
2743 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2744 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2745 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2746 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2747 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2748 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2749 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2750 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2751 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2752 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2753 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2754 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2755 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2756 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2757 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2762 The Debian source control file is generated by
2763 <prgn>dpkg-source</prgn> when it builds the source
2764 archive, from other files in the source package,
2765 described above. When unpacking, it is checked against
2766 the files and directories in the other parts of the
2772 <sect id="debianchangesfiles">
2773 <heading>Debian changes files -- <file>.changes</file></heading>
2776 The <file>.changes</file> files are used by the Debian archive
2777 maintenance software to process updates to packages. They
2778 consist of a single paragraph, possibly surrounded by a PGP
2779 signature. That paragraph contains information from the
2780 <file>debian/control</file> file and other data about the
2781 source package gathered via <file>debian/changelog</file>
2782 and <file>debian/rules</file>.
2786 <file>.changes</file> files have a format version that is
2787 incremented whenever the documented fields or their meaning
2788 change. This document describes format &changesversion;.
2792 The fields in this file are:
2794 <list compact="compact">
2795 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2796 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2797 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2798 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2799 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2800 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2801 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2802 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2803 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2804 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2805 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2806 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2807 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2808 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2809 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2810 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2815 <sect id="controlfieldslist">
2816 <heading>List of fields</heading>
2818 <sect1 id="f-Source">
2819 <heading><tt>Source</tt></heading>
2822 This field identifies the source package name.
2826 In <file>debian/control</file> or a <file>.dsc</file> file,
2827 this field must contain only the name of the source package.
2831 In a binary package control file or a <file>.changes</file>
2832 file, the source package name may be followed by a version
2833 number in parentheses<footnote>
2834 It is customary to leave a space after the package name
2835 if a version number is specified.
2837 This version number may be omitted (and is, by
2838 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2839 the <tt>Version</tt> field of the binary package in
2840 question. The field itself may be omitted from a binary
2841 package control file when the source package has the same
2842 name and version as the binary package.
2846 Package names (both source and binary,
2847 see <ref id="f-Package">) must consist only of lower case
2848 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2849 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2850 (<tt>.</tt>). They must be at least two characters long and
2851 must start with an alphanumeric character.
2855 <sect1 id="f-Maintainer">
2856 <heading><tt>Maintainer</tt></heading>
2859 The package maintainer's name and email address. The name
2860 must come first, then the email address inside angle
2861 brackets <tt><></tt> (in RFC822 format).
2865 If the maintainer's name contains a full stop then the
2866 whole field will not work directly as an email address due
2867 to a misfeature in the syntax specified in RFC822; a
2868 program using this field as an address must check for this
2869 and correct the problem if necessary (for example by
2870 putting the name in round brackets and moving it to the
2871 end, and bringing the email address forward).
2875 See <ref id="maintainer"> for additional requirements and
2876 information about package maintainers.
2880 <sect1 id="f-Uploaders">
2881 <heading><tt>Uploaders</tt></heading>
2884 List of the names and email addresses of co-maintainers of the
2885 package, if any. If the package has other maintainers besides
2886 the one named in the <qref id="f-Maintainer">Maintainer
2887 field</qref>, their names and email addresses should be listed
2888 here. The format of each entry is the same as that of the
2889 Maintainer field, and multiple entries must be comma
2894 This is normally an optional field, but if
2895 the <tt>Maintainer</tt> control field names a group of people
2896 and a shared email address, the <tt>Uploaders</tt> field must
2897 be present and must contain at least one human with their
2898 personal email address.
2902 The Uploaders field in <file>debian/control</file> can be folded.
2906 <sect1 id="f-Changed-By">
2907 <heading><tt>Changed-By</tt></heading>
2910 The name and email address of the person who prepared this
2911 version of the package, usually a maintainer. The syntax is
2912 the same as for the <qref id="f-Maintainer">Maintainer
2917 <sect1 id="f-Section">
2918 <heading><tt>Section</tt></heading>
2921 This field specifies an application area into which the package
2922 has been classified. See <ref id="subsections">.
2926 When it appears in the <file>debian/control</file> file,
2927 it gives the value for the subfield of the same name in
2928 the <tt>Files</tt> field of the <file>.changes</file> file.
2929 It also gives the default for the same field in the binary
2934 <sect1 id="f-Priority">
2935 <heading><tt>Priority</tt></heading>
2938 This field represents how important it is that the user
2939 have the package installed. See <ref id="priorities">.
2943 When it appears in the <file>debian/control</file> file,
2944 it gives the value for the subfield of the same name in
2945 the <tt>Files</tt> field of the <file>.changes</file> file.
2946 It also gives the default for the same field in the binary
2951 <sect1 id="f-Package">
2952 <heading><tt>Package</tt></heading>
2955 The name of the binary package.
2959 Binary package names must follow the same syntax and
2960 restrictions as source package names. See <ref id="f-Source">
2965 <sect1 id="f-Architecture">
2966 <heading><tt>Architecture</tt></heading>
2969 Depending on context and the control file used, the
2970 <tt>Architecture</tt> field can include the following sets of
2974 A unique single word identifying a Debian machine
2975 architecture as described in <ref id="arch-spec">.
2978 An architecture wildcard identifying a set of Debian
2979 machine architectures, see <ref id="arch-wildcard-spec">.
2980 <tt>any</tt> matches all Debian machine architectures
2981 and is the most frequently used.
2984 <tt>all</tt>, which indicates an
2985 architecture-independent package.
2988 <tt>source</tt>, which indicates a source package.
2994 In the main <file>debian/control</file> file in the source
2995 package, this field may contain the special
2996 value <tt>all</tt>, the special architecture
2997 wildcard <tt>any</tt>, or a list of specific and wildcard
2998 architectures separated by spaces. If <tt>all</tt>
2999 or <tt>any</tt> appears, that value must be the entire
3000 contents of the field. Most packages will use
3001 either <tt>all</tt> or <tt>any</tt>.
3005 Specifying a specific list of architectures indicates that the
3006 source will build an architecture-dependent package only on
3007 architectures included in the list. Specifying a list of
3008 architecture wildcards indicates that the source will build an
3009 architecture-dependent package on only those architectures
3010 that match any of the specified architecture wildcards.
3011 Specifying a list of architectures or architecture wildcards
3012 other than <tt>any</tt> is for the minority of cases where a
3013 program is not portable or is not useful on some
3014 architectures. Where possible, the program should be made
3019 In the Debian source control file <file>.dsc</file>, this
3020 field contains a list of architectures and architecture
3021 wildcards separated by spaces. When the list contains the
3022 architecture wildcard <tt>any</tt>, the only other value
3023 allowed in the list is <tt>all</tt>.
3027 The list may include (or consist solely of) the special
3028 value <tt>all</tt>. In other words, in <file>.dsc</file>
3029 files unlike the <file>debian/control</file>, <tt>all</tt> may
3030 occur in combination with specific architectures.
3031 The <tt>Architecture</tt> field in the Debian source control
3032 file <file>.dsc</file> is generally constructed from
3033 the <tt>Architecture</tt> fields in
3034 the <file>debian/control</file> in the source package.
3038 Specifying only <tt>any</tt> indicates that the source package
3039 isn't dependent on any particular architecture and should
3040 compile fine on any one. The produced binary package(s)
3041 will be specific to whatever the current build architecture is.
3045 Specifying only <tt>all</tt> indicates that the source package
3046 will only build architecture-independent packages.
3050 Specifying <tt>any all</tt> indicates that the source package
3051 isn't dependent on any particular architecture. The set of
3052 produced binary packages will include at least one
3053 architecture-dependant package and one architecture-independent
3058 Specifying a list of architectures or architecture wildcards
3059 indicates that the source will build an architecture-dependent
3060 package, and will only work correctly on the listed or
3061 matching architectures. If the source package also builds at
3062 least one architecture-independent package, <tt>all</tt> will
3063 also be included in the list.
3067 In a <file>.changes</file> file, the <tt>Architecture</tt>
3068 field lists the architecture(s) of the package(s) currently
3069 being uploaded. This will be a list; if the source for the
3070 package is also being uploaded, the special
3071 entry <tt>source</tt> is also present. <tt>all</tt> will be
3072 present if any architecture-independent packages are being
3073 uploaded. Architecture wildcards such as <tt>any</tt> must
3074 never occur in the <tt>Architecture</tt> field in
3075 the <file>.changes</file> file.
3079 See <ref id="debianrules"> for information on how to get
3080 the architecture for the build process.
3084 <sect1 id="f-Essential">
3085 <heading><tt>Essential</tt></heading>
3088 This is a boolean field which may occur only in the
3089 control file of a binary package or in a per-package fields
3090 paragraph of a source package control file.
3094 If set to <tt>yes</tt> then the package management system
3095 will refuse to remove the package (upgrading and replacing
3096 it is still possible). The other possible value is <tt>no</tt>,
3097 which is the same as not having the field at all.
3102 <heading>Package interrelationship fields:
3103 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3104 <tt>Recommends</tt>, <tt>Suggests</tt>,
3105 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3106 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3110 These fields describe the package's relationships with
3111 other packages. Their syntax and semantics are described
3112 in <ref id="relationships">.</p>
3115 <sect1 id="f-Standards-Version">
3116 <heading><tt>Standards-Version</tt></heading>
3119 The most recent version of the standards (the policy
3120 manual and associated texts) with which the package
3125 The version number has four components: major and minor
3126 version number and major and minor patch level. When the
3127 standards change in a way that requires every package to
3128 change the major number will be changed. Significant
3129 changes that will require work in many packages will be
3130 signaled by a change to the minor number. The major patch
3131 level will be changed for any change to the meaning of the
3132 standards, however small; the minor patch level will be
3133 changed when only cosmetic, typographical or other edits
3134 are made which neither change the meaning of the document
3135 nor affect the contents of packages.
3139 Thus only the first three components of the policy version
3140 are significant in the <em>Standards-Version</em> control
3141 field, and so either these three components or all four
3142 components may be specified.<footnote>
3143 In the past, people specified the full version number
3144 in the Standards-Version field, for example "2.3.0.0".
3145 Since minor patch-level changes don't introduce new
3146 policy, it was thought it would be better to relax
3147 policy and only require the first 3 components to be
3148 specified, in this example "2.3.0". All four
3149 components may still be used if someone wishes to do so.
3155 <sect1 id="f-Version">
3156 <heading><tt>Version</tt></heading>
3159 The version number of a package. The format is:
3160 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3164 The three components here are:
3166 <tag><var>epoch</var></tag>
3169 This is a single (generally small) unsigned integer. It
3170 may be omitted, in which case zero is assumed. If it is
3171 omitted then the <var>upstream_version</var> may not
3176 It is provided to allow mistakes in the version numbers
3177 of older versions of a package, and also a package's
3178 previous version numbering schemes, to be left behind.
3182 <tag><var>upstream_version</var></tag>
3185 This is the main part of the version number. It is
3186 usually the version number of the original ("upstream")
3187 package from which the <file>.deb</file> file has been made,
3188 if this is applicable. Usually this will be in the same
3189 format as that specified by the upstream author(s);
3190 however, it may need to be reformatted to fit into the
3191 package management system's format and comparison
3196 The comparison behavior of the package management system
3197 with respect to the <var>upstream_version</var> is
3198 described below. The <var>upstream_version</var>
3199 portion of the version number is mandatory.
3203 The <var>upstream_version</var> may contain only
3204 alphanumerics<footnote>
3205 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3207 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3208 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3209 tilde) and should start with a digit. If there is no
3210 <var>debian_revision</var> then hyphens are not allowed;
3211 if there is no <var>epoch</var> then colons are not
3216 <tag><var>debian_revision</var></tag>
3219 This part of the version number specifies the version of
3220 the Debian package based on the upstream version. It
3221 may contain only alphanumerics and the characters
3222 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3223 tilde) and is compared in the same way as the
3224 <var>upstream_version</var> is.
3228 It is optional; if it isn't present then the
3229 <var>upstream_version</var> may not contain a hyphen.
3230 This format represents the case where a piece of
3231 software was written specifically to be a Debian
3232 package, where the Debian package source must always
3233 be identical to the pristine source and therefore no
3234 revision indication is required.
3238 It is conventional to restart the
3239 <var>debian_revision</var> at <tt>1</tt> each time the
3240 <var>upstream_version</var> is increased.
3244 The package management system will break the version
3245 number apart at the last hyphen in the string (if there
3246 is one) to determine the <var>upstream_version</var> and
3247 <var>debian_revision</var>. The absence of a
3248 <var>debian_revision</var> is equivalent to a
3249 <var>debian_revision</var> of <tt>0</tt>.
3256 When comparing two version numbers, first the <var>epoch</var>
3257 of each are compared, then the <var>upstream_version</var> if
3258 <var>epoch</var> is equal, and then <var>debian_revision</var>
3259 if <var>upstream_version</var> is also equal.
3260 <var>epoch</var> is compared numerically. The
3261 <var>upstream_version</var> and <var>debian_revision</var>
3262 parts are compared by the package management system using the
3263 following algorithm:
3267 The strings are compared from left to right.
3271 First the initial part of each string consisting entirely of
3272 non-digit characters is determined. These two parts (one of
3273 which may be empty) are compared lexically. If a difference
3274 is found it is returned. The lexical comparison is a
3275 comparison of ASCII values modified so that all the letters
3276 sort earlier than all the non-letters and so that a tilde
3277 sorts before anything, even the end of a part. For example,
3278 the following parts are in sorted order from earliest to
3279 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3280 <tt>a</tt>.<footnote>
3281 One common use of <tt>~</tt> is for upstream pre-releases.
3282 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3283 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3288 Then the initial part of the remainder of each string which
3289 consists entirely of digit characters is determined. The
3290 numerical values of these two parts are compared, and any
3291 difference found is returned as the result of the comparison.
3292 For these purposes an empty string (which can only occur at
3293 the end of one or both version strings being compared) counts
3298 These two steps (comparing and removing initial non-digit
3299 strings and initial digit strings) are repeated until a
3300 difference is found or both strings are exhausted.
3304 Note that the purpose of epochs is to allow us to leave behind
3305 mistakes in version numbering, and to cope with situations
3306 where the version numbering scheme changes. It is
3307 <em>not</em> intended to cope with version numbers containing
3308 strings of letters which the package management system cannot
3309 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3310 silly orderings.<footnote>
3311 The author of this manual has heard of a package whose
3312 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3313 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3319 <sect1 id="f-Description">
3320 <heading><tt>Description</tt></heading>
3323 In a source or binary control file, the <tt>Description</tt>
3324 field contains a description of the binary package, consisting
3325 of two parts, the synopsis or the short description, and the
3326 long description. It is a multiline field with the following
3332 Description: <single line synopsis>
3333 <extended description over several lines>
3338 The lines in the extended description can have these formats:
3344 Those starting with a single space are part of a paragraph.
3345 Successive lines of this form will be word-wrapped when
3346 displayed. The leading space will usually be stripped off.
3347 The line must contain at least one non-whitespace character.
3351 Those starting with two or more spaces. These will be
3352 displayed verbatim. If the display cannot be panned
3353 horizontally, the displaying program will line wrap them "hard"
3354 (i.e., without taking account of word breaks). If it can they
3355 will be allowed to trail off to the right. None, one or two
3356 initial spaces may be deleted, but the number of spaces
3357 deleted from each line will be the same (so that you can have
3358 indenting work correctly, for example). The line must
3359 contain at least one non-whitespace character.
3363 Those containing a single space followed by a single full stop
3364 character. These are rendered as blank lines. This is the
3365 <em>only</em> way to get a blank line<footnote>
3366 Completely empty lines will not be rendered as blank lines.
3367 Instead, they will cause the parser to think you're starting
3368 a whole new record in the control file, and will therefore
3369 likely abort with an error.
3374 Those containing a space, a full stop and some more characters.
3375 These are for future expansion. Do not use them.
3381 Do not use tab characters. Their effect is not predictable.
3385 See <ref id="descriptions"> for further information on this.
3389 In a <file>.changes</file> file, the <tt>Description</tt>
3390 field contains a summary of the descriptions for the packages
3391 being uploaded. For this case, the first line of the field
3392 value (the part on the same line as <tt>Description:</tt>) is
3393 always empty. It is a multiline field, with one
3394 line per package. Each line is
3395 indented by one space and contains the name of a binary
3396 package, a space, a hyphen (<tt>-</tt>), a space, and the
3397 short description line from that package.
3401 <sect1 id="f-Distribution">
3402 <heading><tt>Distribution</tt></heading>
3405 In a <file>.changes</file> file or parsed changelog output
3406 this contains the (space-separated) name(s) of the
3407 distribution(s) where this version of the package should
3408 be installed. Valid distributions are determined by the
3409 archive maintainers.<footnote>
3410 Example distribution names in the Debian archive used in
3411 <file>.changes</file> files are:
3412 <taglist compact="compact">
3413 <tag><em>unstable</em></tag>
3415 This distribution value refers to the
3416 <em>developmental</em> part of the Debian distribution
3417 tree. Most new packages, new upstream versions of
3418 packages and bug fixes go into the <em>unstable</em>
3422 <tag><em>experimental</em></tag>
3424 The packages with this distribution value are deemed
3425 by their maintainers to be high risk. Oftentimes they
3426 represent early beta or developmental packages from
3427 various sources that the maintainers want people to
3428 try, but are not ready to be a part of the other parts
3429 of the Debian distribution tree.
3434 Others are used for updating stable releases or for
3435 security uploads. More information is available in the
3436 Debian Developer's Reference, section "The Debian
3440 The Debian archive software only supports listing a single
3441 distribution. Migration of packages to other distributions is
3442 handled outside of the upload process.
3447 <heading><tt>Date</tt></heading>
3450 This field includes the date the package was built or last
3451 edited. It must be in the same format as the <var>date</var>
3452 in a <file>debian/changelog</file> entry.
3456 The value of this field is usually extracted from the
3457 <file>debian/changelog</file> file - see
3458 <ref id="dpkgchangelog">).
3462 <sect1 id="f-Format">
3463 <heading><tt>Format</tt></heading>
3466 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3467 files, this field declares the format version of that file.
3468 The syntax of the field value is the same as that of
3469 a <qref id="f-Version">package version number</qref> except
3470 that no epoch or Debian revision is allowed. The format
3471 described in this document is <tt>&changesversion;</tt>.
3475 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3476 Debian source control</qref> files, this field declares the
3477 format of the source package. The field value is used by
3478 programs acting on a source package to interpret the list of
3479 files in the source package and determine how to unpack it.
3480 The syntax of the field value is a numeric major revision, a
3481 period, a numeric minor revision, and then an optional subtype
3482 after whitespace, which if specified is an alphanumeric word
3483 in parentheses. The subtype is optional in the syntax but may
3484 be mandatory for particular source format revisions.
3486 The source formats currently supported by the Debian archive
3487 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3488 and <tt>3.0 (quilt)</tt>.
3493 <sect1 id="f-Urgency">
3494 <heading><tt>Urgency</tt></heading>
3497 This is a description of how important it is to upgrade to
3498 this version from previous ones. It consists of a single
3499 keyword taking one of the values <tt>low</tt>,
3500 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3501 <tt>critical</tt><footnote>
3502 Other urgency values are supported with configuration
3503 changes in the archive software but are not used in Debian.
3504 The urgency affects how quickly a package will be considered
3505 for inclusion into the <tt>testing</tt> distribution and
3506 gives an indication of the importance of any fixes included
3507 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3508 treated as synonymous.
3509 </footnote> (not case-sensitive) followed by an optional
3510 commentary (separated by a space) which is usually in
3511 parentheses. For example:
3514 Urgency: low (HIGH for users of diversions)
3520 The value of this field is usually extracted from the
3521 <file>debian/changelog</file> file - see
3522 <ref id="dpkgchangelog">.
3526 <sect1 id="f-Changes">
3527 <heading><tt>Changes</tt></heading>
3530 This multiline field contains the human-readable changes data, describing
3531 the differences between the last version and the current one.
3535 The first line of the field value (the part on the same line
3536 as <tt>Changes:</tt>) is always empty. The content of the
3537 field is expressed as continuation lines, with each line
3538 indented by at least one space. Blank lines must be
3539 represented by a line consisting only of a space and a full
3544 The value of this field is usually extracted from the
3545 <file>debian/changelog</file> file - see
3546 <ref id="dpkgchangelog">).
3550 Each version's change information should be preceded by a
3551 "title" line giving at least the version, distribution(s)
3552 and urgency, in a human-readable way.
3556 If data from several versions is being returned the entry
3557 for the most recent version should be returned first, and
3558 entries should be separated by the representation of a
3559 blank line (the "title" line may also be followed by the
3560 representation of a blank line).
3564 <sect1 id="f-Binary">
3565 <heading><tt>Binary</tt></heading>
3568 This folded field is a list of binary packages. Its syntax and
3569 meaning varies depending on the control file in which it
3574 When it appears in the <file>.dsc</file> file, it lists binary
3575 packages which a source package can produce, separated by
3577 A space after each comma is conventional.
3578 </footnote>. The source package
3579 does not necessarily produce all of these binary packages for
3580 every architecture. The source control file doesn't contain
3581 details of which architectures are appropriate for which of
3582 the binary packages.
3586 When it appears in a <file>.changes</file> file, it lists the
3587 names of the binary packages being uploaded, separated by
3588 whitespace (not commas).
3592 <sect1 id="f-Installed-Size">
3593 <heading><tt>Installed-Size</tt></heading>
3596 This field appears in the control files of binary packages,
3597 and in the <file>Packages</file> files. It gives an estimate
3598 of the total amount of disk space required to install the
3599 named package. Actual installed size may vary based on block
3600 size, file system properties, or actions taken by package
3605 The disk space is given as the integer value of the estimated
3606 installed size in bytes, divided by 1024 and rounded up.
3610 <sect1 id="f-Files">
3611 <heading><tt>Files</tt></heading>
3614 This field contains a list of files with information about
3615 each one. The exact information and syntax varies with
3620 In all cases, Files is a multiline field. The first line of
3621 the field value (the part on the same line as <tt>Files:</tt>)
3622 is always empty. The content of the field is expressed as
3623 continuation lines, one line per file. Each line must be
3624 indented by one space and contain a number of sub-fields,
3625 separated by spaces, as described below.
3629 In the <file>.dsc</file> file, each line contains the MD5
3630 checksum, size and filename of the tar file and (if
3631 applicable) diff file which make up the remainder of the
3632 source package<footnote>
3633 That is, the parts which are not the <tt>.dsc</tt>.
3634 </footnote>. For example:
3637 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3638 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3640 The exact forms of the filenames are described
3641 in <ref id="pkg-sourcearchives">.
3645 In the <file>.changes</file> file this contains one line per
3646 file being uploaded. Each line contains the MD5 checksum,
3647 size, section and priority and the filename. For example:
3650 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3651 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3652 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3653 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3655 The <qref id="f-Section">section</qref>
3656 and <qref id="f-Priority">priority</qref> are the values of
3657 the corresponding fields in the main source control file. If
3658 no section or priority is specified then <tt>-</tt> should be
3659 used, though section and priority values must be specified for
3660 new packages to be installed properly.
3664 The special value <tt>byhand</tt> for the section in a
3665 <tt>.changes</tt> file indicates that the file in question
3666 is not an ordinary package file and must by installed by
3667 hand by the distribution maintainers. If the section is
3668 <tt>byhand</tt> the priority should be <tt>-</tt>.
3672 If a new Debian revision of a package is being shipped and
3673 no new original source archive is being distributed the
3674 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3675 entry for the original source archive
3676 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3677 but the <file>.changes</file> file should leave it out. In
3678 this case the original source archive on the distribution
3679 site must match exactly, byte-for-byte, the original
3680 source archive which was used to generate the
3681 <file>.dsc</file> file and diff which are being uploaded.</p>
3684 <sect1 id="f-Closes">
3685 <heading><tt>Closes</tt></heading>
3688 A space-separated list of bug report numbers that the upload
3689 governed by the .changes file closes.
3693 <sect1 id="f-Homepage">
3694 <heading><tt>Homepage</tt></heading>
3697 The URL of the web site for this package, preferably (when
3698 applicable) the site from which the original source can be
3699 obtained and any additional upstream documentation or
3700 information may be found. The content of this field is a
3701 simple URL without any surrounding characters such as
3706 <sect1 id="f-Checksums">
3707 <heading><tt>Checksums-Sha1</tt>
3708 and <tt>Checksums-Sha256</tt></heading>
3711 These multiline fields contain a list of files with a checksum and size
3712 for each one. Both <tt>Checksums-Sha1</tt>
3713 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3714 only in the checksum algorithm used: SHA-1
3715 for <tt>Checksums-Sha1</tt> and SHA-256
3716 for <tt>Checksums-Sha256</tt>.
3720 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3721 multiline fields. The first line of the field value (the part
3722 on the same line as <tt>Checksums-Sha1:</tt>
3723 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3724 of the field is expressed as continuation lines, one line per
3725 file. Each line consists of the checksum, a space, the file
3726 size, a space, and the file name. For example (from
3727 a <file>.changes</file> file):
3730 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3731 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3732 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3733 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3735 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3736 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3737 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3738 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3743 In the <file>.dsc</file> file, these fields should list all
3744 files that make up the source package. In
3745 the <file>.changes</file> file, these fields should list all
3746 files being uploaded. The list of files in these fields
3747 must match the list of files in the <tt>Files</tt> field.
3751 <sect1 id="f-DM-Upload-Allowed">
3752 <heading><tt>DM-Upload-Allowed</tt></heading>
3755 Indicates that Debian Maintainers may upload this package to
3756 the Debian archive. The only valid value is <tt>yes</tt>. If
3757 the field <tt>DM-Upload-Allowed: yes</tt> is present in the
3758 source section of the source control file of the most recent
3759 version of a package in unstable or experimental, the Debian
3760 archive will accept uploads of this package signed with a key
3761 in the Debian Maintainer keyring. See the General
3762 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3763 name="Endorse the concept of Debian Maintainers"> for more
3768 <sect1 id="f-VCS-fields">
3769 <heading>Version Control System (VCS) fields</heading>
3772 Debian source packages are increasingly developed using VCSs. The
3773 purpose of the following fields is to indicate a publicly accessible
3774 repository where the Debian source package is developed.
3777 <tag><tt>Vcs-Browser</tt></tag>
3780 URL of a web interface for browsing the repository.
3785 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3786 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3787 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3792 The field name identifies the VCS. The field's value uses the
3793 version control system's conventional syntax for describing
3794 repository locations and should be sufficient to locate the
3795 repository used for packaging. Ideally, it also locates the
3796 branch used for development of new versions of the Debian
3800 In the case of Git, the value consists of a URL, optionally
3801 followed by the word <tt>-b</tt> and the name of a branch in
3802 the indicated repository, following the syntax of the
3803 <tt>git clone</tt> command. If no branch is specified, the
3804 packaging should be on the default branch.
3807 More than one different VCS may be specified for the same
3817 <heading>User-defined fields</heading>
3820 Additional user-defined fields may be added to the
3821 source package control file. Such fields will be
3822 ignored, and not copied to (for example) binary or
3823 Debian source control files or upload control files.
3827 If you wish to add additional unsupported fields to
3828 these output files you should use the mechanism
3833 Fields in the main source control information file with
3834 names starting <tt>X</tt>, followed by one or more of
3835 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3836 be copied to the output files. Only the part of the
3837 field name after the hyphen will be used in the output
3838 file. Where the letter <tt>B</tt> is used the field
3839 will appear in binary package control files, where the
3840 letter <tt>S</tt> is used in Debian source control
3841 files and where <tt>C</tt> is used in upload control
3842 (<tt>.changes</tt>) files.
3846 For example, if the main source information control file
3849 XBS-Comment: I stand between the candle and the star.
3851 then the binary and Debian source control files will contain the
3854 Comment: I stand between the candle and the star.
3863 <chapt id="maintainerscripts">
3864 <heading>Package maintainer scripts and installation procedure</heading>
3867 <heading>Introduction to package maintainer scripts</heading>
3870 It is possible to supply scripts as part of a package which
3871 the package management system will run for you when your
3872 package is installed, upgraded or removed.
3876 These scripts are the control information
3877 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3878 and <prgn>postrm</prgn>. They must be proper executable files;
3879 if they are scripts (which is recommended), they must start with
3880 the usual <tt>#!</tt> convention. They should be readable and
3881 executable by anyone, and must not be world-writable.
3885 The package management system looks at the exit status from
3886 these scripts. It is important that they exit with a
3887 non-zero status if there is an error, so that the package
3888 management system can stop its processing. For shell
3889 scripts this means that you <em>almost always</em> need to
3890 use <tt>set -e</tt> (this is usually true when writing shell
3891 scripts, in fact). It is also important, of course, that
3892 they exit with a zero status if everything went well.
3896 Additionally, packages interacting with users
3897 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3898 should install a <prgn>config</prgn> script as a control
3899 information file. See <ref id="maintscriptprompt"> for details.
3903 When a package is upgraded a combination of the scripts from
3904 the old and new packages is called during the upgrade
3905 procedure. If your scripts are going to be at all
3906 complicated you need to be aware of this, and may need to
3907 check the arguments to your scripts.
3911 Broadly speaking the <prgn>preinst</prgn> is called before
3912 (a particular version of) a package is unpacked, and the
3913 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3914 before (a version of) a package is removed and the
3915 <prgn>postrm</prgn> afterwards.
3919 Programs called from maintainer scripts should not normally
3920 have a path prepended to them. Before installation is
3921 started, the package management system checks to see if the
3922 programs <prgn>ldconfig</prgn>,
3923 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3924 and <prgn>update-rc.d</prgn> can be found via the
3925 <tt>PATH</tt> environment variable. Those programs, and any
3926 other program that one would expect to be in the
3927 <tt>PATH</tt>, should thus be invoked without an absolute
3928 pathname. Maintainer scripts should also not reset the
3929 <tt>PATH</tt>, though they might choose to modify it by
3930 prepending or appending package-specific directories. These
3931 considerations really apply to all shell scripts.</p>
3934 <sect id="idempotency">
3935 <heading>Maintainer scripts idempotency</heading>
3938 It is necessary for the error recovery procedures that the
3939 scripts be idempotent. This means that if it is run
3940 successfully, and then it is called again, it doesn't bomb
3941 out or cause any harm, but just ensures that everything is
3942 the way it ought to be. If the first call failed, or
3943 aborted half way through for some reason, the second call
3944 should merely do the things that were left undone the first
3945 time, if any, and exit with a success status if everything
3947 This is so that if an error occurs, the user interrupts
3948 <prgn>dpkg</prgn> or some other unforeseen circumstance
3949 happens you don't leave the user with a badly-broken
3950 package when <prgn>dpkg</prgn> attempts to repeat the
3956 <sect id="controllingterminal">
3957 <heading>Controlling terminal for maintainer scripts</heading>
3960 Maintainer scripts are not guaranteed to run with a controlling
3961 terminal and may not be able to interact with the user. They
3962 must be able to fall back to noninteractive behavior if no
3963 controlling terminal is available. Maintainer scripts that
3964 prompt via a program conforming to the Debian Configuration
3965 Management Specification (see <ref id="maintscriptprompt">) may
3966 assume that program will handle falling back to noninteractive
3971 For high-priority prompts without a reasonable default answer,
3972 maintainer scripts may abort if there is no controlling
3973 terminal. However, this situation should be avoided if at all
3974 possible, since it prevents automated or unattended installs.
3975 In most cases, users will consider this to be a bug in the
3980 <sect id="exitstatus">
3981 <heading>Exit status</heading>
3984 Each script must return a zero exit status for
3985 success, or a nonzero one for failure, since the package
3986 management system looks for the exit status of these scripts
3987 and determines what action to take next based on that datum.
3991 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3996 What follows is a summary of all the ways in which maintainer
3997 scripts may be called along with what facilities those scripts
3998 may rely on being available at that time. Script names preceded
3999 by <var>new-</var> are the scripts from the new version of a
4000 package being installed, upgraded to, or downgraded to. Script
4001 names preceded by <var>old-</var> are the scripts from the old
4002 version of a package that is being upgraded from or downgraded
4007 The <prgn>preinst</prgn> script may be called in the following
4010 <tag><var>new-preinst</var> <tt>install</tt></tag>
4011 <tag><var>new-preinst</var> <tt>install</tt>
4012 <var>old-version</var></tag>
4013 <tag><var>new-preinst</var> <tt>upgrade</tt>
4014 <var>old-version</var></tag>
4016 The package will not yet be unpacked, so
4017 the <prgn>preinst</prgn> script cannot rely on any files
4018 included in its package. Only essential packages and
4019 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4020 available. Pre-dependencies will have been configured at
4021 least once, but at the time the <prgn>preinst</prgn> is
4022 called they may only be in an unpacked or "Half-Configured"
4023 state if a previous version of the pre-dependency was
4024 completely configured and has not been removed since then.
4027 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4028 <var>new-version</var></tag>
4030 Called during error handling of an upgrade that failed after
4031 unpacking the new package because the <tt>postrm
4032 upgrade</tt> action failed. The unpacked files may be
4033 partly from the new version or partly missing, so the script
4034 cannot rely on files included in the package. Package
4035 dependencies may not be available. Pre-dependencies will be
4036 at least unpacked following the same rules as above, except
4037 they may be only "Half-Installed" if an upgrade of the
4038 pre-dependency failed.<footnote>
4039 This can happen if the new version of the package no
4040 longer pre-depends on a package that had been partially
4048 The <prgn>postinst</prgn> script may be called in the following
4051 <tag><var>postinst</var> <tt>configure</tt>
4052 <var>most-recently-configured-version</var></tag>
4054 The files contained in the package will be unpacked. All
4055 package dependencies will at least be unpacked. If there
4056 are no circular dependencies involved, all package
4057 dependencies will be configured. For behavior in the case
4058 of circular dependencies, see the discussion
4059 in <ref id="binarydeps">.
4062 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4063 <var>new-version</var></tag>
4064 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4065 <tt>in-favour</tt> <var>package</var>
4066 <var>new-version</var></tag>
4067 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4068 <tag><var>deconfigured's-postinst</var>
4069 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4070 <var>failed-install-package</var> <var>version</var>
4071 [<tt>removing</tt> <var>conflicting-package</var>
4072 <var>version</var>]</tag>
4074 The files contained in the package will be unpacked. All
4075 package dependencies will at least be "Half-Installed" and
4076 will have previously been configured and not removed.
4077 However, dependencies may not be configured or even fully
4078 unpacked in some error situations.<footnote>
4079 For example, suppose packages foo and bar are installed
4080 with foo depending on bar. If an upgrade of bar were
4081 started and then aborted, and then an attempt to remove
4082 foo failed because its <prgn>prerm</prgn> script failed,
4083 foo's <tt>postinst abort-remove</tt> would be called with
4084 bar only "Half-Installed".
4086 The <prgn>postinst</prgn> should still attempt any actions
4087 for which its dependencies are required, since they will
4088 normally be available, but consider the correct error
4089 handling approach if those actions fail. Aborting
4090 the <prgn>postinst</prgn> action if commands or facilities
4091 from the package dependencies are not available is often the
4098 The <prgn>prerm</prgn> script may be called in the following
4101 <tag><var>prerm</var> <tt>remove</tt></tag>
4102 <tag><var>old-prerm</var>
4103 <tt>upgrade</tt><var>new-version</var></tag>
4104 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4105 <tt>in-favour</tt> <var>package</var>
4106 <var>new-version</var></tag>
4107 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4108 <tt>in-favour</tt> <var>package-being-installed</var>
4109 <var>version</var> [<tt>removing</tt>
4110 <var>conflicting-package</var> <var>version</var>]</tag>
4112 The package whose <prgn>prerm</prgn> is being called will be
4113 at least "Half-Installed". All package dependencies will at
4114 least be "Half-Installed" and will have previously been
4115 configured and not removed. If there was no error, all
4116 dependencies will at least be unpacked, but these actions
4117 may be called in various error states where dependencies are
4118 only "Half-Installed" due to a partial upgrade.
4121 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4122 <var>old-version</var></tag>
4124 Called during error handling when <tt>prerm upgrade</tt>
4125 fails. The new package will not yet be unpacked, and all
4126 the same constraints as for <tt>preinst upgrade</tt> apply.
4132 The <prgn>postrm</prgn> script may be called in the following
4135 <tag><var>postrm</var> <tt>remove</tt></tag>
4136 <tag><var>postrm</var> <tt>purge</tt></tag>
4137 <tag><var>old-postrm</var> <tt>upgrade</tt>
4138 <var>new-version</var></tag>
4139 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4140 <var>overwriter</var> <var>overwriter-version</var></tag>
4142 The <prgn>postrm</prgn> script is called after the package's
4143 files have been removed or replaced. The package
4144 whose <prgn>postrm</prgn> is being called may have
4145 previously been deconfigured and only be unpacked, at which
4146 point subsequent package changes do not consider its
4147 dependencies. Therefore, all <prgn>postrm</prgn> actions
4148 may only rely on essential packages and must gracefully skip
4149 any actions that require the package's dependencies if those
4150 dependencies are unavailable.<footnote>
4151 This is often done by checking whether the command or
4152 facility the <prgn>postrm</prgn> intends to call is
4153 available before calling it. For example:
4155 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4156 . /usr/share/debconf/confmodule
4160 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4161 configuration for the package
4162 if <package>debconf</package> is installed.
4166 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4167 <var>old-version</var></tag>
4169 Called when the old <tt>postrm upgrade</tt> action fails.
4170 The new package will be unpacked, but only essential
4171 packages and pre-dependencies can be relied on.
4172 Pre-dependencies will either be configured or will be
4173 "Unpacked" or "Half-Configured" but previously had been
4174 configured and was never removed.
4177 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4178 <tag><var>new-postrm</var> <tt>abort-install</tt>
4179 <var>old-version</var></tag>
4180 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4181 <var>old-version</var></tag>
4183 Called before unpacking the new package as part of the
4184 error handling of <prgn>preinst</prgn> failures. May assume
4185 the same state as <prgn>preinst</prgn> can assume.
4191 <sect id="unpackphase">
4192 <heading>Details of unpack phase of installation or upgrade</heading>
4195 The procedure on installation/upgrade/overwrite/disappear
4196 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4197 stage of <tt>dpkg --install</tt>) is as follows. In each
4198 case, if a major error occurs (unless listed below) the
4199 actions are, in general, run backwards - this means that the
4200 maintainer scripts are run with different arguments in
4201 reverse order. These are the "error unwind" calls listed
4208 If a version of the package is already installed, call
4209 <example compact="compact">
4210 <var>old-prerm</var> upgrade <var>new-version</var>
4214 If the script runs but exits with a non-zero
4215 exit status, <prgn>dpkg</prgn> will attempt:
4216 <example compact="compact">
4217 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4219 If this works, the upgrade continues. If this
4220 does not work, the error unwind:
4221 <example compact="compact">
4222 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4224 If this works, then the old-version is
4225 "Installed", if not, the old version is in a
4226 "Half-Configured" state.
4232 If a "conflicting" package is being removed at the same time,
4233 or if any package will be broken (due to <tt>Breaks</tt>):
4236 If <tt>--auto-deconfigure</tt> is
4237 specified, call, for each package to be deconfigured
4238 due to <tt>Breaks</tt>:
4239 <example compact="compact">
4240 <var>deconfigured's-prerm</var> deconfigure \
4241 in-favour <var>package-being-installed</var> <var>version</var>
4244 <example compact="compact">
4245 <var>deconfigured's-postinst</var> abort-deconfigure \
4246 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4248 The deconfigured packages are marked as
4249 requiring configuration, so that if
4250 <tt>--install</tt> is used they will be
4251 configured again if possible.
4254 If any packages depended on a conflicting
4255 package being removed and <tt>--auto-deconfigure</tt> is
4256 specified, call, for each such package:
4257 <example compact="compact">
4258 <var>deconfigured's-prerm</var> deconfigure \
4259 in-favour <var>package-being-installed</var> <var>version</var> \
4260 removing <var>conflicting-package</var> <var>version</var>
4263 <example compact="compact">
4264 <var>deconfigured's-postinst</var> abort-deconfigure \
4265 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4266 removing <var>conflicting-package</var> <var>version</var>
4268 The deconfigured packages are marked as
4269 requiring configuration, so that if
4270 <tt>--install</tt> is used they will be
4271 configured again if possible.
4274 To prepare for removal of each conflicting package, call:
4275 <example compact="compact">
4276 <var>conflictor's-prerm</var> remove \
4277 in-favour <var>package</var> <var>new-version</var>
4280 <example compact="compact">
4281 <var>conflictor's-postinst</var> abort-remove \
4282 in-favour <var>package</var> <var>new-version</var>
4291 If the package is being upgraded, call:
4292 <example compact="compact">
4293 <var>new-preinst</var> upgrade <var>old-version</var>
4295 If this fails, we call:
4297 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4304 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4306 is called. If this works, then the old version
4307 is in an "Installed" state, or else it is left
4308 in an "Unpacked" state.
4313 If it fails, then the old version is left
4314 in an "Half-Installed" state.
4321 Otherwise, if the package had some configuration
4322 files from a previous version installed (i.e., it
4323 is in the "configuration files only" state):
4324 <example compact="compact">
4325 <var>new-preinst</var> install <var>old-version</var>
4329 <var>new-postrm</var> abort-install <var>old-version</var>
4331 If this fails, the package is left in a
4332 "Half-Installed" state, which requires a
4333 reinstall. If it works, the packages is left in
4334 a "Config-Files" state.
4337 Otherwise (i.e., the package was completely purged):
4338 <example compact="compact">
4339 <var>new-preinst</var> install
4342 <example compact="compact">
4343 <var>new-postrm</var> abort-install
4345 If the error-unwind fails, the package is in a
4346 "Half-Installed" phase, and requires a
4347 reinstall. If the error unwind works, the
4348 package is in a not installed state.
4355 The new package's files are unpacked, overwriting any
4356 that may be on the system already, for example any
4357 from the old version of the same package or from
4358 another package. Backups of the old files are kept
4359 temporarily, and if anything goes wrong the package
4360 management system will attempt to put them back as
4361 part of the error unwind.
4365 It is an error for a package to contain files which
4366 are on the system in another package, unless
4367 <tt>Replaces</tt> is used (see <ref id="replaces">).
4369 The following paragraph is not currently the case:
4370 Currently the <tt>- - force-overwrite</tt> flag is
4371 enabled, downgrading it to a warning, but this may not
4377 It is a more serious error for a package to contain a
4378 plain file or other kind of non-directory where another
4379 package has a directory (again, unless
4380 <tt>Replaces</tt> is used). This error can be
4381 overridden if desired using
4382 <tt>--force-overwrite-dir</tt>, but this is not
4387 Packages which overwrite each other's files produce
4388 behavior which, though deterministic, is hard for the
4389 system administrator to understand. It can easily
4390 lead to "missing" programs if, for example, a package
4391 is unpacked which overwrites a file from another
4392 package, and is then removed again.<footnote>
4393 Part of the problem is due to what is arguably a
4394 bug in <prgn>dpkg</prgn>.
4399 A directory will never be replaced by a symbolic link
4400 to a directory or vice versa; instead, the existing
4401 state (symlink or not) will be left alone and
4402 <prgn>dpkg</prgn> will follow the symlink if there is
4411 If the package is being upgraded, call
4412 <example compact="compact">
4413 <var>old-postrm</var> upgrade <var>new-version</var>
4417 If this fails, <prgn>dpkg</prgn> will attempt:
4418 <example compact="compact">
4419 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4421 If this works, installation continues. If not,
4423 <example compact="compact">
4424 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4426 If this fails, the old version is left in a
4427 "Half-Installed" state. If it works, dpkg now
4429 <example compact="compact">
4430 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4432 If this fails, the old version is left in a
4433 "Half-Installed" state. If it works, dpkg now
4435 <example compact="compact">
4436 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4438 If this fails, the old version is in an
4445 This is the point of no return - if
4446 <prgn>dpkg</prgn> gets this far, it won't back off
4447 past this point if an error occurs. This will
4448 leave the package in a fairly bad state, which
4449 will require a successful re-installation to clear
4450 up, but it's when <prgn>dpkg</prgn> starts doing
4451 things that are irreversible.
4456 Any files which were in the old version of the package
4457 but not in the new are removed.
4461 The new file list replaces the old.
4465 The new maintainer scripts replace the old.
4469 Any packages all of whose files have been overwritten
4470 during the installation, and which aren't required for
4471 dependencies, are considered to have been removed.
4472 For each such package
4475 <prgn>dpkg</prgn> calls:
4476 <example compact="compact">
4477 <var>disappearer's-postrm</var> disappear \
4478 <var>overwriter</var> <var>overwriter-version</var>
4482 The package's maintainer scripts are removed.
4485 It is noted in the status database as being in a
4486 sane state, namely not installed (any conffiles
4487 it may have are ignored, rather than being
4488 removed by <prgn>dpkg</prgn>). Note that
4489 disappearing packages do not have their prerm
4490 called, because <prgn>dpkg</prgn> doesn't know
4491 in advance that the package is going to
4498 Any files in the package we're unpacking that are also
4499 listed in the file lists of other packages are removed
4500 from those lists. (This will lobotomize the file list
4501 of the "conflicting" package if there is one.)
4505 The backup files made during installation, above, are
4511 The new package's status is now sane, and recorded as
4516 Here is another point of no return - if the
4517 conflicting package's removal fails we do not unwind
4518 the rest of the installation; the conflicting package
4519 is left in a half-removed limbo.
4524 If there was a conflicting package we go and do the
4525 removal actions (described below), starting with the
4526 removal of the conflicting package's files (any that
4527 are also in the package being unpacked have already
4528 been removed from the conflicting package's file list,
4529 and so do not get removed now).
4535 <sect id="configdetails"><heading>Details of configuration</heading>
4538 When we configure a package (this happens with <tt>dpkg
4539 --install</tt> and <tt>dpkg --configure</tt>), we first
4540 update any <tt>conffile</tt>s and then call:
4541 <example compact="compact">
4542 <var>postinst</var> configure <var>most-recently-configured-version</var>
4547 No attempt is made to unwind after errors during
4548 configuration. If the configuration fails, the package is in
4549 a "Failed Config" state, and an error message is generated.
4553 If there is no most recently configured version
4554 <prgn>dpkg</prgn> will pass a null argument.
4557 Historical note: Truly ancient (pre-1997) versions of
4558 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4559 (including the angle brackets) in this case. Even older
4560 ones did not pass a second argument at all, under any
4561 circumstance. Note that upgrades using such an old dpkg
4562 version are unlikely to work for other reasons, even if
4563 this old argument behavior is handled by your postinst script.
4569 <sect id="removedetails"><heading>Details of removal and/or
4570 configuration purging</heading>
4576 <example compact="compact">
4577 <var>prerm</var> remove
4581 If prerm fails during replacement due to conflict
4583 <var>conflictor's-postinst</var> abort-remove \
4584 in-favour <var>package</var> <var>new-version</var>
4588 <var>postinst</var> abort-remove
4592 If this fails, the package is in a "Half-Configured"
4593 state, or else it remains "Installed".
4597 The package's files are removed (except <tt>conffile</tt>s).
4600 <example compact="compact">
4601 <var>postrm</var> remove
4605 If it fails, there's no error unwind, and the package is in
4606 an "Half-Installed" state.
4611 All the maintainer scripts except the <prgn>postrm</prgn>
4616 If we aren't purging the package we stop here. Note
4617 that packages which have no <prgn>postrm</prgn> and no
4618 <tt>conffile</tt>s are automatically purged when
4619 removed, as there is no difference except for the
4620 <prgn>dpkg</prgn> status.
4624 The <tt>conffile</tt>s and any backup files
4625 (<tt>~</tt>-files, <tt>#*#</tt> files,
4626 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4631 <example compact="compact">
4632 <var>postrm</var> purge
4636 If this fails, the package remains in a "Config-Files"
4641 The package's file list is removed.
4650 <chapt id="relationships">
4651 <heading>Declaring relationships between packages</heading>
4653 <sect id="depsyntax">
4654 <heading>Syntax of relationship fields</heading>
4657 These fields all have a uniform syntax. They are a list of
4658 package names separated by commas.
4662 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4663 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4664 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4665 control fields of the package, which declare
4666 dependencies on other packages, the package names listed may
4667 also include lists of alternative package names, separated
4668 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4669 if any one of the alternative packages is installed, that
4670 part of the dependency is considered to be satisfied.
4674 All of the fields except for <tt>Provides</tt> may restrict
4675 their applicability to particular versions of each named
4676 package. This is done in parentheses after each individual
4677 package name; the parentheses should contain a relation from
4678 the list below followed by a version number, in the format
4679 described in <ref id="f-Version">.
4683 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4684 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4685 earlier, earlier or equal, exactly equal, later or equal and
4686 strictly later, respectively. The deprecated
4687 forms <tt><</tt> and <tt>></tt> were confusingly used to
4688 mean earlier/later or equal, rather than strictly earlier/later,
4689 and must not appear in new packages (though <prgn>dpkg</prgn>
4690 still supports them with a warning).
4694 Whitespace may appear at any point in the version
4695 specification subject to the rules in <ref
4696 id="controlsyntax">, and must appear where it's necessary to
4697 disambiguate; it is not otherwise significant. All of the
4698 relationship fields can only be folded in source package control files. For
4699 consistency and in case of future changes to
4700 <prgn>dpkg</prgn> it is recommended that a single space be
4701 used after a version relationship and before a version
4702 number; it is also conventional to put a single space after
4703 each comma, on either side of each vertical bar, and before
4704 each open parenthesis. When opening a continuation line in a relationship field, it
4705 is conventional to do so after a comma and before the space
4706 following that comma.
4710 For example, a list of dependencies might appear as:
4711 <example compact="compact">
4714 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4719 Relationships may be restricted to a certain set of
4720 architectures. This is indicated in brackets after each
4721 individual package name and the optional version specification.
4722 The brackets enclose a non-empty list of Debian architecture names
4723 in the format described in <ref id="arch-spec">,
4724 separated by whitespace. Exclamation marks may be prepended to
4725 each of the names. (It is not permitted for some names to be
4726 prepended with exclamation marks while others aren't.)
4730 For build relationship fields
4731 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4732 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4733 the current Debian host architecture is not in this list and
4734 there are no exclamation marks in the list, or it is in the list
4735 with a prepended exclamation mark, the package name and the
4736 associated version specification are ignored completely for the
4737 purposes of defining the relationships.
4742 <example compact="compact">
4744 Build-Depends-Indep: texinfo
4745 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4746 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4748 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4749 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4750 <tt>gnumach-dev</tt> only on hurd-i386.
4754 For binary relationship fields and the <tt>Built-Using</tt>
4755 field, the architecture restriction
4756 syntax is only supported in the source package control
4757 file <file>debian/control</file>. When the corresponding binary
4758 package control file is generated, the relationship will either
4759 be omitted or included without the architecture restriction
4760 based on the architecture of the binary package. This means
4761 that architecture restrictions must not be used in binary
4762 relationship fields for architecture-independent packages
4763 (<tt>Architecture: all</tt>).
4768 <example compact="compact">
4769 Depends: foo [i386], bar [amd64]
4771 becomes <tt>Depends: foo</tt> when the package is built on
4772 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4773 package is built on the <tt>amd64</tt> architecture, and omitted
4774 entirely in binary packages built on all other architectures.
4778 If the architecture-restricted dependency is part of a set of
4779 alternatives using <tt>|</tt>, that alternative is ignored
4780 completely on architectures that do not match the restriction.
4782 <example compact="compact">
4783 Build-Depends: foo [!i386] | bar [!amd64]
4785 is equivalent to <tt>bar</tt> on the i386 architecture, to
4786 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4787 bar</tt> on all other architectures.
4791 Relationships may also be restricted to a certain set of
4792 architectures using architecture wildcards in the format
4793 described in <ref id="arch-wildcard-spec">. The syntax for
4794 declaring such restrictions is the same as declaring
4795 restrictions using a certain set of architectures without
4796 architecture wildcards. For example:
4797 <example compact="compact">
4798 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4800 is equivalent to <tt>foo</tt> on architectures using the Linux
4801 kernel and any cpu, <tt>bar</tt> on architectures using any
4802 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4803 using a kernel other than Linux.
4807 Note that the binary package relationship fields such as
4808 <tt>Depends</tt> appear in one of the binary package
4809 sections of the control file, whereas the build-time
4810 relationships such as <tt>Build-Depends</tt> appear in the
4811 source package section of the control file (which is the
4816 <sect id="binarydeps">
4817 <heading>Binary Dependencies - <tt>Depends</tt>,
4818 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4819 <tt>Pre-Depends</tt>
4823 Packages can declare in their control file that they have
4824 certain relationships to other packages - for example, that
4825 they may not be installed at the same time as certain other
4826 packages, and/or that they depend on the presence of others.
4830 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4831 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4832 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4833 <tt>Breaks</tt> is described in <ref id="breaks">, and
4834 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4835 rest are described below.
4839 These seven fields are used to declare a dependency
4840 relationship by one package on another. Except for
4841 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4842 depending (binary) package's control file.
4843 (<tt>Enhances</tt> appears in the recommending package's
4844 control file, and <tt>Breaks</tt> appears in the version of
4845 depended-on package which causes the named package to
4850 A <tt>Depends</tt> field takes effect <em>only</em> when a
4851 package is to be configured. It does not prevent a package
4852 being on the system in an unconfigured state while its
4853 dependencies are unsatisfied, and it is possible to replace
4854 a package whose dependencies are satisfied and which is
4855 properly installed with a different version whose
4856 dependencies are not and cannot be satisfied; when this is
4857 done the depending package will be left unconfigured (since
4858 attempts to configure it will give errors) and will not
4859 function properly. If it is necessary, a
4860 <tt>Pre-Depends</tt> field can be used, which has a partial
4861 effect even when a package is being unpacked, as explained
4862 in detail below. (The other three dependency fields,
4863 <tt>Recommends</tt>, <tt>Suggests</tt> and
4864 <tt>Enhances</tt>, are only used by the various front-ends
4865 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4866 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4870 Since <tt>Depends</tt> only places requirements on the order in
4871 which packages are configured, packages in an installation run
4872 are usually all unpacked first and all configured later.
4874 This approach makes dependency resolution easier. If two
4875 packages A and B are being upgraded, the installed package A
4876 depends on exactly the installed package B, and the new
4877 package A depends on exactly the new package B (a common
4878 situation when upgrading shared libraries and their
4879 corresponding development packages), satisfying the
4880 dependencies at every stage of the upgrade would be
4881 impossible. This relaxed restriction means that both new
4882 packages can be unpacked together and then configured in their
4888 If there is a circular dependency among packages being installed
4889 or removed, installation or removal order honoring the
4890 dependency order is impossible, requiring the dependency loop be
4891 broken at some point and the dependency requirements violated
4892 for at least one package. Packages involved in circular
4893 dependencies may not be able to rely on their dependencies being
4894 configured before they themselves are configured, depending on
4895 which side of the break of the circular dependency loop they
4896 happen to be on. If one of the packages in the loop has
4897 no <prgn>postinst</prgn> script, then the cycle will be broken
4898 at that package; this ensures that all <prgn>postinst</prgn>
4899 scripts are run with their dependencies properly configured if
4900 this is possible. Otherwise the breaking point is arbitrary.
4901 Packages should therefore avoid circular dependencies where
4902 possible, particularly if they have <prgn>postinst</prgn>
4907 The meaning of the five dependency fields is as follows:
4909 <tag><tt>Depends</tt></tag>
4912 This declares an absolute dependency. A package will
4913 not be configured unless all of the packages listed in
4914 its <tt>Depends</tt> field have been correctly
4915 configured (unless there is a circular dependency as
4920 The <tt>Depends</tt> field should be used if the
4921 depended-on package is required for the depending
4922 package to provide a significant amount of
4927 The <tt>Depends</tt> field should also be used if the
4928 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4929 require the depended-on package to be unpacked or
4930 configured in order to run. In the case of <tt>postinst
4931 configure</tt>, the depended-on packages will be unpacked
4932 and configured first. (If both packages are involved in a
4933 dependency loop, this might not work as expected; see the
4934 explanation a few paragraphs back.) In the case
4935 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4936 actions, the package dependencies will normally be at
4937 least unpacked, but they may be only "Half-Installed" if a
4938 previous upgrade of the dependency failed.
4942 Finally, the <tt>Depends</tt> field should be used if the
4943 depended-on package is needed by the <prgn>postrm</prgn>
4944 script to fully clean up after the package removal. There
4945 is no guarantee that package dependencies will be
4946 available when <prgn>postrm</prgn> is run, but the
4947 depended-on package is more likely to be available if the
4948 package declares a dependency (particularly in the case
4949 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4950 script must gracefully skip actions that require a
4951 dependency if that dependency isn't available.
4955 <tag><tt>Recommends</tt></tag>
4958 This declares a strong, but not absolute, dependency.
4962 The <tt>Recommends</tt> field should list packages
4963 that would be found together with this one in all but
4964 unusual installations.
4968 <tag><tt>Suggests</tt></tag>
4970 This is used to declare that one package may be more
4971 useful with one or more others. Using this field
4972 tells the packaging system and the user that the
4973 listed packages are related to this one and can
4974 perhaps enhance its usefulness, but that installing
4975 this one without them is perfectly reasonable.
4978 <tag><tt>Enhances</tt></tag>
4980 This field is similar to Suggests but works in the
4981 opposite direction. It is used to declare that a
4982 package can enhance the functionality of another
4986 <tag><tt>Pre-Depends</tt></tag>
4989 This field is like <tt>Depends</tt>, except that it
4990 also forces <prgn>dpkg</prgn> to complete installation
4991 of the packages named before even starting the
4992 installation of the package which declares the
4993 pre-dependency, as follows:
4997 When a package declaring a pre-dependency is about to
4998 be <em>unpacked</em> the pre-dependency can be
4999 satisfied if the depended-on package is either fully
5000 configured, <em>or even if</em> the depended-on
5001 package(s) are only unpacked or in the "Half-Configured"
5002 state, provided that they have been configured
5003 correctly at some point in the past (and not removed
5004 or partially removed since). In this case, both the
5005 previously-configured and currently unpacked or
5006 "Half-Configured" versions must satisfy any version
5007 clause in the <tt>Pre-Depends</tt> field.
5011 When the package declaring a pre-dependency is about to
5012 be <em>configured</em>, the pre-dependency will be treated
5013 as a normal <tt>Depends</tt>. It will be considered
5014 satisfied only if the depended-on package has been
5015 correctly configured. However, unlike
5016 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5017 permit circular dependencies to be broken. If a circular
5018 dependency is encountered while attempting to honor
5019 <tt>Pre-Depends</tt>, the installation will be aborted.
5023 <tt>Pre-Depends</tt> are also required if the
5024 <prgn>preinst</prgn> script depends on the named package.
5025 It is best to avoid this situation if possible.
5029 <tt>Pre-Depends</tt> should be used sparingly,
5030 preferably only by packages whose premature upgrade or
5031 installation would hamper the ability of the system to
5032 continue with any upgrade that might be in progress.
5036 You should not specify a <tt>Pre-Depends</tt> entry for a
5037 package before this has been discussed on the
5038 <tt>debian-devel</tt> mailing list and a consensus about
5039 doing that has been reached. See <ref id="dependencies">.
5046 When selecting which level of dependency to use you should
5047 consider how important the depended-on package is to the
5048 functionality of the one declaring the dependency. Some
5049 packages are composed of components of varying degrees of
5050 importance. Such a package should list using
5051 <tt>Depends</tt> the package(s) which are required by the
5052 more important components. The other components'
5053 requirements may be mentioned as Suggestions or
5054 Recommendations, as appropriate to the components' relative
5060 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5063 When one binary package declares that it breaks another,
5064 <prgn>dpkg</prgn> will refuse to allow the package which
5065 declares <tt>Breaks</tt> to be unpacked unless the broken
5066 package is deconfigured first, and it will refuse to
5067 allow the broken package to be reconfigured.
5071 A package will not be regarded as causing breakage merely
5072 because its configuration files are still installed; it must
5073 be at least "Half-Installed".
5077 A special exception is made for packages which declare that
5078 they break their own package name or a virtual package which
5079 they provide (see below): this does not count as a real
5084 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5085 version clause; such a <tt>Breaks</tt> is introduced in the
5086 version of an (implicit or explicit) dependency which violates
5087 an assumption or reveals a bug in earlier versions of the broken
5088 package, or which takes over a file from earlier versions of the
5089 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5090 will inform higher-level package management tools that the
5091 broken package must be upgraded before the new one.
5095 If the breaking package also overwrites some files from the
5096 older package, it should use <tt>Replaces</tt> to ensure this
5097 goes smoothly. See <ref id="replaces"> for a full discussion
5098 of taking over files from other packages, including how to
5099 use <tt>Breaks</tt> in those cases.
5103 Many of the cases where <tt>Breaks</tt> should be used were
5104 previously handled with <tt>Conflicts</tt>
5105 because <tt>Breaks</tt> did not yet exist.
5106 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5107 See <ref id="conflicts"> for more information about the
5112 <sect id="conflicts">
5113 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5116 When one binary package declares a conflict with another using
5117 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5118 allow them to be unpacked on the system at the same time. This
5119 is a stronger restriction than <tt>Breaks</tt>, which prevents
5120 the broken package from being configured while the breaking
5121 package is in the "Unpacked" state but allows both packages to
5122 be unpacked at the same time.
5126 If one package is to be unpacked, the other must be removed
5127 first. If the package being unpacked is marked as replacing
5128 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5129 normally be used in this case) the one on the system, or the one
5130 on the system is marked as deselected, or both packages are
5131 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5132 automatically remove the package which is causing the conflict.
5133 Otherwise, it will halt the installation of the new package with
5134 an error. This mechanism is specifically designed to produce an
5135 error when the installed package is <tt>Essential</tt>, but the
5140 A package will not cause a conflict merely because its
5141 configuration files are still installed; it must be at least
5146 A special exception is made for packages which declare a
5147 conflict with their own package name, or with a virtual
5148 package which they provide (see below): this does not
5149 prevent their installation, and allows a package to conflict
5150 with others providing a replacement for it. You use this
5151 feature when you want the package in question to be the only
5152 package providing some feature.
5156 Normally, <tt>Breaks</tt> should be used instead
5157 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5158 stronger restriction on the ordering of package installation or
5159 upgrade and can make it more difficult for the package manager
5160 to find a correct solution to an upgrade or installation
5161 problem. <tt>Breaks</tt> should be used
5163 <item>when moving a file from one package to another (see
5164 <ref id="replaces">),</item>
5165 <item>when splitting a package (a special case of the previous
5167 <item>when the breaking package exposes a bug in or interacts
5168 badly with particular versions of the broken
5171 <tt>Conflicts</tt> should be used
5173 <item>when two packages provide the same file and will
5174 continue to do so,</item>
5175 <item>in conjunction with <tt>Provides</tt> when only one
5176 package providing a given virtual facility may be unpacked
5177 at a time (see <ref id="virtual">),</item>
5178 <item>in other cases where one must prevent simultaneous
5179 installation of two packages for reasons that are ongoing
5180 (not fixed in a later version of one of the packages) or
5181 that must prevent both packages from being unpacked at the
5182 same time, not just configured.</item>
5184 Be aware that adding <tt>Conflicts</tt> is normally not the best
5185 solution when two packages provide the same files. Depending on
5186 the reason for that conflict, using alternatives or renaming the
5187 files is often a better approach. See, for
5188 example, <ref id="binaries">.
5192 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5193 unless two packages cannot be installed at the same time or
5194 installing them both causes one of them to be broken or
5195 unusable. Having similar functionality or performing the same
5196 tasks as another package is not sufficient reason to
5197 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5201 A <tt>Conflicts</tt> entry may have an "earlier than" version
5202 clause if the reason for the conflict is corrected in a later
5203 version of one of the packages. However, normally the presence
5204 of an "earlier than" version clause is a sign
5205 that <tt>Breaks</tt> should have been used instead. An "earlier
5206 than" version clause in <tt>Conflicts</tt>
5207 prevents <prgn>dpkg</prgn> from upgrading or installing the
5208 package which declares such a conflict until the upgrade or
5209 removal of the conflicted-with package has been completed, which
5210 is a strong restriction.
5214 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5218 As well as the names of actual ("concrete") packages, the
5219 package relationship fields <tt>Depends</tt>,
5220 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5221 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5222 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5223 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5224 may mention "virtual packages".
5228 A <em>virtual package</em> is one which appears in the
5229 <tt>Provides</tt> control field of another package. The effect
5230 is as if the package(s) which provide a particular virtual
5231 package name had been listed by name everywhere the virtual
5232 package name appears. (See also <ref id="virtual_pkg">)
5236 If there are both concrete and virtual packages of the same
5237 name, then the dependency may be satisfied (or the conflict
5238 caused) by either the concrete package with the name in
5239 question or any other concrete package which provides the
5240 virtual package with the name in question. This is so that,
5241 for example, supposing we have
5242 <example compact="compact">
5245 </example> and someone else releases an enhanced version of
5246 the <tt>bar</tt> package they can say:
5247 <example compact="compact">
5251 and the <tt>bar-plus</tt> package will now also satisfy the
5252 dependency for the <tt>foo</tt> package.
5256 If a relationship field has a version number attached, only real
5257 packages will be considered to see whether the relationship is
5258 satisfied (or the prohibition violated, for a conflict or
5259 breakage). In other words, if a version number is specified,
5260 this is a request to ignore all <tt>Provides</tt> for that
5261 package name and consider only real packages. The package
5262 manager will assume that a package providing that virtual
5263 package is not of the "right" version. A <tt>Provides</tt>
5264 field may not contain version numbers, and the version number of
5265 the concrete package which provides a particular virtual package
5266 will not be considered when considering a dependency on or
5267 conflict with the virtual package name.<footnote>
5268 It is possible that a future release of <prgn>dpkg</prgn> may
5269 add the ability to specify a version number for each virtual
5270 package it provides. This feature is not yet present,
5271 however, and is expected to be used only infrequently.
5276 To specify which of a set of real packages should be the default
5277 to satisfy a particular dependency on a virtual package, list
5278 the real package as an alternative before the virtual one.
5282 If the virtual package represents a facility that can only be
5283 provided by one real package at a time, such as
5284 the <package>mail-transport-agent</package> virtual package that
5285 requires installation of a binary that would conflict with all
5286 other providers of that virtual package (see
5287 <ref id="mail-transport-agents">), all packages providing that
5288 virtual package should also declare a conflict with it
5289 using <tt>Conflicts</tt>. This will ensure that at most one
5290 provider of that virtual package is unpacked or installed at a
5295 <sect id="replaces"><heading>Overwriting files and replacing
5296 packages - <tt>Replaces</tt></heading>
5299 Packages can declare in their control file that they should
5300 overwrite files in certain other packages, or completely replace
5301 other packages. The <tt>Replaces</tt> control field has these
5302 two distinct purposes.
5305 <sect1><heading>Overwriting files in other packages</heading>
5308 It is usually an error for a package to contain files which
5309 are on the system in another package. However, if the
5310 overwriting package declares that it <tt>Replaces</tt> the one
5311 containing the file being overwritten, then <prgn>dpkg</prgn>
5312 will replace the file from the old package with that from the
5313 new. The file will no longer be listed as "owned" by the old
5314 package and will be taken over by the new package.
5315 Normally, <tt>Breaks</tt> should be used in conjunction
5316 with <tt>Replaces</tt>.<footnote>
5317 To see why <tt>Breaks</tt> is normally needed in addition
5318 to <tt>Replaces</tt>, consider the case of a file in the
5319 package <package>foo</package> being taken over by the
5320 package <package>foo-data</package>.
5321 <tt>Replaces</tt> will allow <package>foo-data</package> to
5322 be installed and take over that file. However,
5323 without <tt>Breaks</tt>, nothing
5324 requires <package>foo</package> to be upgraded to a newer
5325 version that knows it does not include that file and instead
5326 depends on <package>foo-data</package>. Nothing would
5327 prevent the new <package>foo-data</package> package from
5328 being installed and then removed, removing the file that it
5329 took over from <package>foo</package>. After that
5330 operation, the package manager would think the system was in
5331 a consistent state, but the <package>foo</package> package
5332 would be missing one of its files.
5337 For example, if a package <package>foo</package> is split
5338 into <package>foo</package> and <package>foo-data</package>
5339 starting at version 1.2-3, <package>foo-data</package> would
5341 <example compact="compact">
5342 Replaces: foo (<< 1.2-3)
5343 Breaks: foo (<< 1.2-3)
5345 in its control file. The new version of the
5346 package <package>foo</package> would normally have the field
5347 <example compact="compact">
5348 Depends: foo-data (>= 1.2-3)
5350 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5351 the files moved into <package>foo-data</package> are not
5352 required for normal operation).
5356 If a package is completely replaced in this way, so that
5357 <prgn>dpkg</prgn> does not know of any files it still
5358 contains, it is considered to have "disappeared". It will
5359 be marked as not wanted on the system (selected for
5360 removal) and not installed. Any <tt>conffile</tt>s
5361 details noted for the package will be ignored, as they
5362 will have been taken over by the overwriting package. The
5363 package's <prgn>postrm</prgn> script will be run with a
5364 special argument to allow the package to do any final
5365 cleanup required. See <ref id="mscriptsinstact">.
5367 Replaces is a one way relationship. You have to install
5368 the replacing package after the replaced package.
5373 For this usage of <tt>Replaces</tt>, virtual packages (see
5374 <ref id="virtual">) are not considered when looking at a
5375 <tt>Replaces</tt> field. The packages declared as being
5376 replaced must be mentioned by their real names.
5380 This usage of <tt>Replaces</tt> only takes effect when both
5381 packages are at least partially on the system at once. It is
5382 not relevant if the packages conflict unless the conflict has
5387 <sect1><heading>Replacing whole packages, forcing their
5391 Second, <tt>Replaces</tt> allows the packaging system to
5392 resolve which package should be removed when there is a
5393 conflict (see <ref id="conflicts">). This usage only takes
5394 effect when the two packages <em>do</em> conflict, so that the
5395 two usages of this field do not interfere with each other.
5399 In this situation, the package declared as being replaced
5400 can be a virtual package, so for example, all mail
5401 transport agents (MTAs) would have the following fields in
5402 their control files:
5403 <example compact="compact">
5404 Provides: mail-transport-agent
5405 Conflicts: mail-transport-agent
5406 Replaces: mail-transport-agent
5408 ensuring that only one MTA can be unpacked at any one
5409 time. See <ref id="virtual"> for more information about this
5414 <sect id="sourcebinarydeps">
5415 <heading>Relationships between source and binary packages -
5416 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5417 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5421 Source packages that require certain binary packages to be
5422 installed or absent at the time of building the package
5423 can declare relationships to those binary packages.
5427 This is done using the <tt>Build-Depends</tt>,
5428 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5429 <tt>Build-Conflicts-Indep</tt> control fields.
5433 Build-dependencies on "build-essential" binary packages can be
5434 omitted. Please see <ref id="pkg-relations"> for more information.
5438 The dependencies and conflicts they define must be satisfied
5439 (as defined earlier for binary packages) in order to invoke
5440 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5442 There is no Build-Depends-Arch; this role is essentially
5443 met with Build-Depends. Anyone building the
5444 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5445 assumed to be building the whole package, and therefore
5446 installation of all build dependencies is required.
5449 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5450 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5451 not yet know how to check for its existence, and
5452 <tt>binary-arch</tt>. The purpose of the original split
5453 between <tt>Build-Depends</tt> and
5454 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5455 wouldn't need to install extra packages needed only for the
5456 binary-indep targets. But without a build-arch/build-indep
5457 split, this didn't work, since most of the work is done in
5458 the build target, not in the binary target.
5462 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5463 <tt>binary-arch</tt></tag>
5465 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5466 fields must be satisfied when these targets are invoked.
5468 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5469 and <tt>binary-indep</tt></tag>
5471 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5472 <tt>Build-Depends-Indep</tt>, and
5473 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5474 these targets are invoked.
5480 <sect id="built-using">
5481 <heading>Additional source packages used to build the binary
5482 - <tt>Built-Using</tt>
5486 Some binary packages incorporate parts of other packages when built
5487 but do not have to depend on those packages. Examples include
5488 linking with static libraries or incorporating source code from
5489 another package during the build. In this case, the source packages
5490 of those other packages are a required part of the complete source
5491 (the binary package is not reproducible without them).
5495 A <tt>Built-Using</tt> field must list the corresponding source
5496 package for any such binary package incorporated during the build
5498 <tt>Build-Depends</tt> in the source package is not adequate since
5499 it (rightfully) does not document the exact version used in the
5502 including an "exactly equal" ("=") version relation on the version
5503 that was used to build that binary package<footnote>
5504 The archive software might reject packages that refer to
5505 non-existent sources.
5510 A package using the source code from the gcc-4.6-source
5511 binary package built from the gcc-4.6 source package would
5512 have this field in its control file:
5513 <example compact="compact">
5514 Built-Using: gcc-4.6 (= 4.6.0-11)
5519 A package including binaries from grub2 and loadlin would
5520 have this field in its control file:
5521 <example compact="compact">
5522 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5529 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5532 Packages containing shared libraries must be constructed with
5533 a little care to make sure that the shared library is always
5534 available. This is especially important for packages whose
5535 shared libraries are vitally important, such as the C library
5536 (currently <tt>libc6</tt>).
5540 This section deals only with public shared libraries: shared
5541 libraries that are placed in directories searched by the dynamic
5542 linker by default or which are intended to be linked against
5543 normally and possibly used by other, independent packages. Shared
5544 libraries that are internal to a particular package or that are
5545 only loaded as dynamic modules are not covered by this section and
5546 are not subject to its requirements.
5550 A shared library is identified by the <tt>SONAME</tt> attribute
5551 stored in its dynamic section. When a binary is linked against a
5552 shared library, the <tt>SONAME</tt> of the shared library is
5553 recorded in the binary's <tt>NEEDED</tt> section so that the
5554 dynamic linker knows that library must be loaded at runtime. The
5555 shared library file's full name (which usually contains additional
5556 version information not needed in the <tt>SONAME</tt>) is
5557 therefore normally not referenced directly. Instead, the shared
5558 library is loaded by its <tt>SONAME</tt>, which exists on the file
5559 system as a symlink pointing to the full name of the shared
5560 library. This symlink must be provided by the
5561 package. <ref id="sharedlibs-runtime"> describes how to do this.
5563 This is a convention of shared library versioning, but not a
5564 requirement. Some libraries use the <tt>SONAME</tt> as the full
5565 library file name instead and therefore do not need a symlink.
5566 Most, however, encode additional information about
5567 backwards-compatible revisions as a minor version number in the
5568 file name. The <tt>SONAME</tt> itself only changes when
5569 binaries linked with the earlier version of the shared library
5570 may no longer work, but the filename may change with each
5571 release of the library. See <ref id="sharedlibs-runtime"> for
5577 When linking a binary or another shared library against a shared
5578 library, the <tt>SONAME</tt> for that shared library is not yet
5579 known. Instead, the shared library is found by looking for a file
5580 matching the library name with <tt>.so</tt> appended. This file
5581 exists on the file system as a symlink pointing to the shared
5586 Shared libraries are normally split into several binary packages.
5587 The <tt>SONAME</tt> symlink is installed by the runtime shared
5588 library package, and the bare <tt>.so</tt> symlink is installed in
5589 the development package since it's only used when linking binaries
5590 or shared libraries. However, there are some exceptions for
5591 unusual shared libraries or for shared libraries that are also
5592 loaded as dynamic modules by other programs.
5596 This section is primarily concerned with how the separation of
5597 shared libraries into multiple packages should be done and how
5598 dependencies on and between shared library binary packages are
5599 managed in Debian. <ref id="libraries"> should be read in
5600 conjunction with this section and contains additional rules for
5601 the files contained in the shared library packages.
5604 <sect id="sharedlibs-runtime">
5605 <heading>Run-time shared libraries</heading>
5608 The run-time shared library must be placed in a package
5609 whose name changes whenever the <tt>SONAME</tt> of the shared
5610 library changes. This allows several versions of the shared
5611 library to be installed at the same time, allowing installation
5612 of the new version of the shared library without immediately
5613 breaking binaries that depend on the old version. Normally, the
5614 run-time shared library and its <tt>SONAME</tt> symlink should
5615 be placed in a package named
5616 <package><var>libraryname</var><var>soversion</var></package>,
5617 where <var>soversion</var> is the version number in
5618 the <tt>SONAME</tt> of the shared library.
5619 See <ref id="shlibs"> for detailed information on how to
5620 determine this version. Alternatively, if it would be confusing
5621 to directly append <var>soversion</var>
5622 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5623 itself ends in a number), you should use
5624 <package><var>libraryname</var>-<var>soversion</var></package>
5629 If you have several shared libraries built from the same source
5630 tree, you may lump them all together into a single shared
5631 library package provided that all of their <tt>SONAME</tt>s will
5632 always change together. Be aware that this is not normally the
5633 case, and if the <tt>SONAME</tt>s do not change together,
5634 upgrading such a merged shared library package will be
5635 unnecessarily difficult because of file conflicts with the old
5636 version of the package. When in doubt, always split shared
5637 library packages so that each binary package installs a single
5642 Every time the shared library ABI changes in a way that may
5643 break binaries linked against older versions of the shared
5644 library, the <tt>SONAME</tt> of the library and the
5645 corresponding name for the binary package containing the runtime
5646 shared library should change. Normally, this means
5647 the <tt>SONAME</tt> should change any time an interface is
5648 removed from the shared library or the signature of an interface
5649 (the number of parameters or the types of parameters that it
5650 takes, for example) is changed. This practice is vital to
5651 allowing clean upgrades from older versions of the package and
5652 clean transitions between the old ABI and new ABI without having
5653 to upgrade every affected package simultaneously.
5657 The <tt>SONAME</tt> and binary package name need not, and indeed
5658 normally should not, change if new interfaces are added but none
5659 are removed or changed, since this will not break binaries
5660 linked against the old shared library. Correct versioning of
5661 dependencies on the newer shared library by binaries that use
5662 the new interfaces is handled via
5663 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5664 system</qref> or via symbols files (see
5665 <manref name="deb-symbols" section="5">).
5669 The package should install the shared libraries under
5670 their normal names. For example, the <package>libgdbm3</package>
5671 package should install <file>libgdbm.so.3.0.0</file> as
5672 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5673 renamed or re-linked by any <prgn>prerm</prgn> or
5674 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5675 of renaming things safely without affecting running programs,
5676 and attempts to interfere with this are likely to lead to
5681 Shared libraries should not be installed executable, since
5682 the dynamic linker does not require this and trying to
5683 execute a shared library usually results in a core dump.
5687 The run-time library package should include the symbolic link for
5688 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5689 the shared libraries. For example,
5690 the <package>libgdbm3</package> package should include a symbolic
5691 link from <file>/usr/lib/libgdbm.so.3</file> to
5692 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5693 linker (for example <prgn>ld.so</prgn> or
5694 <prgn>ld-linux.so.*</prgn>) can find the library between the
5695 time that <prgn>dpkg</prgn> installs it and the time that
5696 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5698 The package management system requires the library to be
5699 placed before the symbolic link pointing to it in the
5700 <file>.deb</file> file. This is so that when
5701 <prgn>dpkg</prgn> comes to install the symlink
5702 (overwriting the previous symlink pointing at an older
5703 version of the library), the new shared library is already
5704 in place. In the past, this was achieved by creating the
5705 library in the temporary packaging directory before
5706 creating the symlink. Unfortunately, this was not always
5707 effective, since the building of the tar file in the
5708 <file>.deb</file> depended on the behavior of the underlying
5709 file system. Some file systems (such as reiserfs) reorder
5710 the files so that the order of creation is forgotten.
5711 Since version 1.7.0, <prgn>dpkg</prgn>
5712 reorders the files itself as necessary when building a
5713 package. Thus it is no longer important to concern
5714 oneself with the order of file creation.
5718 <sect1 id="ldconfig">
5719 <heading><tt>ldconfig</tt></heading>
5722 Any package installing shared libraries in one of the default
5723 library directories of the dynamic linker (which are currently
5724 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5725 listed in <file>/etc/ld.so.conf</file><footnote>
5726 These are currently <file>/usr/local/lib</file> plus
5727 directories under <file>/lib</file> and <file>/usr/lib</file>
5728 matching the multiarch triplet for the system architecture.
5730 must use <prgn>ldconfig</prgn> to update the shared library
5735 The package maintainer scripts must only call
5736 <prgn>ldconfig</prgn> under these circumstances:
5737 <list compact="compact">
5738 <item>When the <prgn>postinst</prgn> script is run with a
5739 first argument of <tt>configure</tt>, the script must call
5740 <prgn>ldconfig</prgn>, and may optionally invoke
5741 <prgn>ldconfig</prgn> at other times.
5743 <item>When the <prgn>postrm</prgn> script is run with a
5744 first argument of <tt>remove</tt>, the script should call
5745 <prgn>ldconfig</prgn>.
5750 During install or upgrade, the preinst is called before
5751 the new files are unpacked, so calling "ldconfig" is
5752 pointless. The preinst of an existing package can also be
5753 called if an upgrade fails. However, this happens during
5754 the critical time when a shared libs may exist on-disk
5755 under a temporary name. Thus, it is dangerous and
5756 forbidden by current policy to call "ldconfig" at this
5761 When a package is installed or upgraded, "postinst
5762 configure" runs after the new files are safely on-disk.
5763 Since it is perfectly safe to invoke ldconfig
5764 unconditionally in a postinst, it is OK for a package to
5765 simply put ldconfig in its postinst without checking the
5766 argument. The postinst can also be called to recover from
5767 a failed upgrade. This happens before any new files are
5768 unpacked, so there is no reason to call "ldconfig" at this
5773 For a package that is being removed, prerm is
5774 called with all the files intact, so calling ldconfig is
5775 useless. The other calls to "prerm" happen in the case of
5776 upgrade at a time when all the files of the old package
5777 are on-disk, so again calling "ldconfig" is pointless.
5781 postrm, on the other hand, is called with the "remove"
5782 argument just after the files are removed, so this is
5783 the proper time to call "ldconfig" to notify the system
5784 of the fact that the shared libraries from the package
5785 are removed. The postrm can be called at several other
5786 times. At the time of "postrm purge", "postrm
5787 abort-install", or "postrm abort-upgrade", calling
5788 "ldconfig" is useless because the shared lib files are
5789 not on-disk. However, when "postrm" is invoked with
5790 arguments "upgrade", "failed-upgrade", or "disappear", a
5791 shared lib may exist on-disk under a temporary filename.
5799 <sect id="sharedlibs-support-files">
5800 <heading>Shared library support files</heading>
5803 If your package contains files whose names do not change with
5804 each change in the library shared object version, you must not
5805 put them in the shared library package. Otherwise, several
5806 versions of the shared library cannot be installed at the same
5807 time without filename clashes, making upgrades and transitions
5808 unnecessarily difficult.
5812 It is recommended that supporting files and run-time support
5813 programs that do not need to be invoked manually by users, but
5814 are nevertheless required for the package to function, be placed
5815 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5816 preferably under <file>/usr/lib/</file><var>package-name</var>.
5817 If the program or file is architecture independent, the
5818 recommendation is for it to be placed in a subdirectory of
5819 <file>/usr/share</file> instead, preferably under
5820 <file>/usr/share/</file><var>package-name</var>. Following the
5821 <var>package-name</var> naming convention ensures that the file
5822 names change when the shared object version changes.
5826 Run-time support programs that use the shared library but are
5827 not required for the library to function or files used by the
5828 shared library that can be used by any version of the shared
5829 library package should instead be put in a separate package.
5830 This package might typically be named
5831 <package><var>libraryname</var>-tools</package>; note the
5832 absence of the <var>soversion</var> in the package name.
5836 Files and support programs only useful when compiling software
5837 against the library should be included in the development
5838 package for the library.<footnote>
5839 For example, a <file><var>package-name</var>-config</file>
5840 script or <package>pkg-config</package> configuration files.
5845 <sect id="sharedlibs-static">
5846 <heading>Static libraries</heading>
5849 The static library (<file><var>libraryname.a</var></file>)
5850 is usually provided in addition to the shared version.
5851 It is placed into the development package (see below).
5855 In some cases, it is acceptable for a library to be
5856 available in static form only; these cases include:
5858 <item>libraries for languages whose shared library support
5859 is immature or unstable</item>
5860 <item>libraries whose interfaces are in flux or under
5861 development (commonly the case when the library's
5862 major version number is zero, or where the ABI breaks
5863 across patchlevels)</item>
5864 <item>libraries which are explicitly intended to be
5865 available only in static form by their upstream
5870 <sect id="sharedlibs-dev">
5871 <heading>Development files</heading>
5874 If there are development files associated with a shared library,
5875 the source package needs to generate a binary development package
5876 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5877 or if you prefer only to support one development version at a
5878 time, <package><var>libraryname</var>-dev</package>. Installing
5879 the development package must result in installation of all the
5880 development files necessary for compiling programs against that
5881 shared library.<footnote>
5882 This wording allows the development files to be split into
5883 several packages, such as a separate architecture-independent
5884 <package><var>libraryname</var>-headers</package>, provided that
5885 the development package depends on all the required additional
5891 In case several development versions of a library exist, you may
5892 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5893 <ref id="conflicts">) to ensure that the user only installs one
5894 development version at a time (as different development versions are
5895 likely to have the same header files in them, which would cause a
5896 filename clash if both were unpacked).
5900 The development package should contain a symlink for the associated
5901 shared library without a version number. For example, the
5902 <package>libgdbm-dev</package> package should include a symlink
5903 from <file>/usr/lib/libgdbm.so</file> to
5904 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5905 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5906 <file>libgdbm.so</file> when compiling dynamically.
5910 If the package provides Ada Library Information
5911 (<file>*.ali</file>) files for use with GNAT, these files must be
5912 installed read-only (mode 0444) so that GNAT will not attempt to
5913 recompile them. This overrides the normal file mode requirements
5914 given in <ref id="permissions-owners">.
5918 <sect id="sharedlibs-intradeps">
5919 <heading>Dependencies between the packages of the same library</heading>
5922 Typically the development version should have an exact
5923 version dependency on the runtime library, to make sure that
5924 compilation and linking happens correctly. The
5925 <tt>${binary:Version}</tt> substitution variable can be
5926 useful for this purpose.
5928 Previously, <tt>${Source-Version}</tt> was used, but its name
5929 was confusing and it has been deprecated since dpkg 1.13.19.
5934 <sect id="sharedlibs-shlibdeps">
5935 <heading>Dependencies between the library and other packages -
5936 the <tt>shlibs</tt> system</heading>
5939 If a package contains a binary or library which links to a
5940 shared library, we must ensure that when the package is
5941 installed on the system, all of the libraries needed are
5942 also installed. This requirement led to the creation of the
5943 <tt>shlibs</tt> system, which is very simple in its design:
5944 any package which <em>provides</em> a shared library also
5945 provides information on the package dependencies required to
5946 ensure the presence of this library, and any package which
5947 <em>uses</em> a shared library uses this information to
5948 determine the dependencies it requires. The files which
5949 contain the mapping from shared libraries to the necessary
5950 dependency information are called <file>shlibs</file> files.
5954 When a package is built which contains any shared libraries, it
5955 must provide a <file>shlibs</file> file for other packages to
5956 use. When a package is built which contains any shared
5957 libraries or compiled binaries, it must run
5958 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5959 on these to determine the libraries used and hence the
5960 dependencies needed by this package.<footnote>
5962 <prgn>dpkg-shlibdeps</prgn> will use a program
5963 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5964 the libraries directly needed by the binaries or shared
5965 libraries in the package.
5969 We say that a binary <tt>foo</tt> <em>directly</em> uses
5970 a library <tt>libbar</tt> if it is explicitly linked
5971 with that library (that is, the library is listed in the ELF
5972 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5973 to the link line when the binary is created). Other
5974 libraries that are needed by <tt>libbar</tt> are linked
5975 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5976 linker will load them automatically when it loads
5977 <tt>libbar</tt>. A package should depend on the libraries
5978 it directly uses, but not the libraries it indirectly uses.
5979 The dependencies for those libraries will automatically pull
5980 in the other libraries.
5984 A good example of where this helps is the following. We
5985 could update <tt>libimlib</tt> with a new version that
5986 supports a new graphics format called dgf (but retaining the
5987 same major version number) and depends on <tt>libdgf</tt>.
5988 If we used <prgn>ldd</prgn> to add dependencies for every
5989 library directly or indirectly linked with a binary, every
5990 package that uses <tt>libimlib</tt> would need to be
5991 recompiled so it would also depend on <tt>libdgf</tt> or it
5992 wouldn't run due to missing symbols. Since dependencies are
5993 only added based on ELF <tt>NEEDED</tt> attribute, packages
5994 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5995 having the dependency on <tt>libdgf</tt> and so they would
5996 not need rebuilding.
6002 In the following sections, we will first describe where the
6003 various <tt>shlibs</tt> files are to be found, then how to
6004 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
6005 file format and how to create them if your package contains a
6010 <heading>The <tt>shlibs</tt> files present on the system</heading>
6013 There are several places where <tt>shlibs</tt> files are
6014 found. The following list gives them in the order in which
6016 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
6017 (The first one which gives the required information is used.)
6023 <p><file>debian/shlibs.local</file></p>
6026 This lists overrides for this package. This file should
6027 normally not be used, but may be needed temporarily in
6028 unusual situations to work around bugs in other packages,
6029 or in unusual cases where the normally declared dependency
6030 information in the installed <file>shlibs</file> file for
6031 a library cannot be used. This file overrides information
6032 obtained from any other source.
6037 <p><file>/etc/dpkg/shlibs.override</file></p>
6040 This lists global overrides. This list is normally
6041 empty. It is maintained by the local system
6047 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
6050 When packages are being built,
6051 any <file>debian/shlibs</file> files are copied into the
6052 control information file area of the temporary build
6053 directory and given the name <file>shlibs</file>. These
6054 files give details of any shared libraries included in the
6055 same package.<footnote>
6056 An example may help here. Let us say that the source
6057 package <tt>foo</tt> generates two binary
6058 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6059 When building the binary packages, the two packages are
6060 created in the directories <file>debian/libfoo2</file>
6061 and <file>debian/foo-runtime</file> respectively.
6062 (<file>debian/tmp</file> could be used instead of one of
6063 these.) Since <tt>libfoo2</tt> provides the
6064 <tt>libfoo</tt> shared library, it will require a
6065 <tt>shlibs</tt> file, which will be installed in
6066 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
6067 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
6068 When <prgn>dpkg-shlibdeps</prgn> is run on the
6069 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6071 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
6072 determine whether <tt>foo-prog</tt>'s library
6073 dependencies are satisfied by any of the libraries
6074 provided by <tt>libfoo2</tt>. For this reason,
6075 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
6076 the individual binary packages' <tt>shlibs</tt> files
6077 have been installed into the build directory.
6083 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
6086 These are the <file>shlibs</file> files corresponding to
6087 all of the packages installed on the system, and are
6088 maintained by the relevant package maintainers.
6093 <p><file>/etc/dpkg/shlibs.default</file></p>
6096 This file lists any shared libraries whose packages
6097 have failed to provide correct <file>shlibs</file> files.
6098 It was used when the <file>shlibs</file> setup was first
6099 introduced, but it is now normally empty. It is
6100 maintained by the <tt>dpkg</tt> maintainer.
6108 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
6109 <file>shlibs</file> files</heading>
6113 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
6114 into your <file>debian/rules</file> file. If your package
6115 contains only compiled binaries and libraries (but no scripts),
6116 you can use a command such as:
6117 <example compact="compact">
6118 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
6119 debian/tmp/usr/lib/*
6121 Otherwise, you will need to explicitly list the compiled
6122 binaries and libraries.<footnote>
6123 If you are using <tt>debhelper</tt>, the
6124 <prgn>dh_shlibdeps</prgn> program will do this work for you.
6125 It will also correctly handle multi-binary packages.
6130 This command puts the dependency information into the
6131 <file>debian/substvars</file> file, which is then used by
6132 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6133 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6134 field in the control file for this to work.
6138 If you have multiple binary packages, you will need to call
6139 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6140 compiled libraries or binaries. In such a case, you will
6141 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6142 utilities to specify a different <file>substvars</file> file.
6146 If you are creating a udeb for use in the Debian Installer,
6147 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6148 should use the dependency line of type <tt>udeb</tt> by
6149 adding the <tt>-tudeb</tt> option<footnote>
6150 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6151 will automatically add this option if it knows it is
6153 </footnote>. If there is no dependency line of
6154 type <tt>udeb</tt> in the <file>shlibs</file>
6155 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6160 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6161 <ref id="pkg-dpkg-shlibdeps"> and
6162 <manref name="dpkg-shlibdeps" section="1">.
6167 <heading>The <file>shlibs</file> File Format</heading>
6170 Each <file>shlibs</file> file has the same format. Lines
6171 beginning with <tt>#</tt> are considered to be comments and
6172 are ignored. Each line is of the form:
6173 <example compact="compact">
6174 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6179 We will explain this by reference to the example of the
6180 <tt>zlib1g</tt> package, which (at the time of writing)
6181 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6185 <var>type</var> is an optional element that indicates the type
6186 of package for which the line is valid. The only type currently
6187 in use is <tt>udeb</tt>. The colon and space after the type are
6192 <var>library-name</var> is the name of the shared library,
6193 in this case <tt>libz</tt>. (This must match the name part
6194 of the soname, see below.)
6198 <var>soname-version</var> is the version part of the soname of
6199 the library. The soname is the thing that must exactly match
6200 for the library to be recognized by the dynamic linker, and is
6202 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6203 example, <tt>libz.so.1</tt>.<footnote>
6204 This can be determined using the command
6205 <example compact="compact">
6206 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6209 The version part is the part which comes after
6210 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6211 instead be of the form
6212 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6213 as <tt>libdb-4.8.so</tt>, in which case the name would
6214 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6218 <var>dependencies</var> has the same syntax as a dependency
6219 field in a binary package control file. It should give
6220 details of which packages are required to satisfy a binary
6221 built against the version of the library contained in the
6222 package. See <ref id="depsyntax"> for details.
6226 In our example, if the first version of the <tt>zlib1g</tt>
6227 package which contained a minor number of at least
6228 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6229 <tt>shlibs</tt> entry for this library could say:
6230 <example compact="compact">
6231 libz 1 zlib1g (>= 1:1.1.3)
6233 The version-specific dependency is to avoid warnings from
6234 the dynamic linker about using older shared libraries with
6239 As zlib1g also provides a udeb containing the shared library,
6240 there would also be a second line:
6241 <example compact="compact">
6242 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6248 <heading>Providing a <file>shlibs</file> file</heading>
6251 If your package provides a shared library, you need to create
6252 a <file>shlibs</file> file following the format described above.
6253 It is usual to call this file <file>debian/shlibs</file> (but if
6254 you have multiple binary packages, you might want to call it
6255 <file>debian/shlibs.<var>package</var></file> instead). Then
6256 let <file>debian/rules</file> install it in the control
6257 information file area:
6258 <example compact="compact">
6259 install -m644 debian/shlibs debian/tmp/DEBIAN
6261 or, in the case of a multi-binary package:
6262 <example compact="compact">
6263 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6265 An alternative way of doing this is to create the
6266 <file>shlibs</file> file in the control information file area
6267 directly from <file>debian/rules</file> without using
6268 a <file>debian/shlibs</file> file at all,<footnote>
6269 This is what <prgn>dh_makeshlibs</prgn> in
6270 the <package>debhelper</package> suite does. If your package
6271 also has a udeb that provides a shared
6272 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6273 the <tt>udeb:</tt> lines if you specify the name of the udeb
6274 with the <tt>--add-udeb</tt> option.
6276 since the <file>debian/shlibs</file> file itself is ignored by
6277 <prgn>dpkg-shlibdeps</prgn>.
6281 As <prgn>dpkg-shlibdeps</prgn> reads the
6282 <file>DEBIAN/shlibs</file> files in all of the binary packages
6283 being built from this source package, all of the
6284 <file>DEBIAN/shlibs</file> files should be installed before
6285 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6293 <chapt id="opersys"><heading>The Operating System</heading>
6296 <heading>File system hierarchy</heading>
6300 <heading>File System Structure</heading>
6303 The location of all files and directories must comply with the
6304 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6305 exceptions noted below, and except where doing so would
6306 violate other terms of Debian Policy. The following
6307 exceptions to the FHS apply:
6312 The optional rules related to user specific
6313 configuration files for applications are stored in
6314 the user's home directory are relaxed. It is
6315 recommended that such files start with the
6316 '<tt>.</tt>' character (a "dot file"), and if an
6317 application needs to create more than one dot file
6318 then the preferred placement is in a subdirectory
6319 with a name starting with a '.' character, (a "dot
6320 directory"). In this case it is recommended the
6321 configuration files not start with the '.'
6327 The requirement for amd64 to use <file>/lib64</file>
6328 for 64 bit binaries is removed.
6333 The requirement for object files, internal binaries, and
6334 libraries, including <file>libc.so.*</file>, to be located
6335 directly under <file>/lib{,32}</file> and
6336 <file>/usr/lib{,32}</file> is amended, permitting files
6337 to instead be installed to
6338 <file>/lib/<var>triplet</var></file> and
6339 <file>/usr/lib/<var>triplet</var></file>, where
6340 <tt><var>triplet</var></tt> is the value returned by
6341 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6342 architecture of the package. Packages may <em>not</em>
6343 install files to any <var>triplet</var> path other
6344 than the one matching the architecture of that package;
6345 for instance, an <tt>Architecture: amd64</tt> package
6346 containing 32-bit x86 libraries may not install these
6347 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6349 This is necessary in order to reserve the directories for
6350 use in cross-installation of library packages from other
6351 architectures, as part of the planned deployment of
6356 Applications may also use a single subdirectory under
6357 <file>/usr/lib/<var>triplet</var></file>.
6360 The execution time linker/loader, ld*, must still be made
6361 available in the existing location under /lib or /lib64
6362 since this is part of the ELF ABI for the architecture.
6367 The requirement that
6368 <file>/usr/local/share/man</file> be "synonymous"
6369 with <file>/usr/local/man</file> is relaxed to a
6374 The requirement that windowmanagers with a single
6375 configuration file call it <file>system.*wmrc</file>
6376 is removed, as is the restriction that the window
6377 manager subdirectory be named identically to the
6378 window manager name itself.
6383 The requirement that boot manager configuration
6384 files live in <file>/etc</file>, or at least are
6385 symlinked there, is relaxed to a recommendation.
6390 The additional directory <file>/run</file> in the root
6391 file system is allowed. <file>/run</file>
6392 replaces <file>/var/run</file>, and the
6393 subdirectory <file>/run/lock</file>
6394 replaces <file>/var/lock</file>, with
6395 the <file>/var</file> directories replaced by symlinks
6396 for backwards compatibility. <file>/run</file>
6397 and <file>/run/lock</file> must follow all of the
6398 requirements in the FHS for <file>/var/run</file>
6399 and <file>/var/lock</file>, respectively, such as file
6400 naming conventions, file format requirements, or the
6401 requirement that files be cleared during the boot
6402 process. Files and directories residing
6403 in <file>/run</file> should be stored on a temporary
6409 The following directories in the root filesystem are
6410 additionally allowed: <file>/sys</file> and
6411 <file>/selinux</file>. <footnote>These directories
6412 are used as mount points to mount virtual filesystems
6413 to get access to kernel information.</footnote>
6418 On GNU/Hurd systems, the following additional
6419 directories are allowed in the root
6420 filesystem: <file>/hurd</file>
6421 and <file>/servers</file>.<footnote>
6422 These directories are used to store translators and as
6423 a set of standard names for mount points,
6432 The version of this document referred here can be
6433 found in the <tt>debian-policy</tt> package or on <url
6434 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6435 name="FHS (Debian copy)"> alongside this manual (or, if
6436 you have the <package>debian-policy</package> installed,
6438 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6439 (local copy)">). The
6440 latest version, which may be a more recent version, may
6442 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6443 Specific questions about following the standard may be
6444 asked on the <tt>debian-devel</tt> mailing list, or
6445 referred to the FHS mailing list (see the
6446 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6452 <heading>Site-specific programs</heading>
6455 As mandated by the FHS, packages must not place any
6456 files in <file>/usr/local</file>, either by putting them in
6457 the file system archive to be unpacked by <prgn>dpkg</prgn>
6458 or by manipulating them in their maintainer scripts.
6462 However, the package may create empty directories below
6463 <file>/usr/local</file> so that the system administrator knows
6464 where to place site-specific files. These are not
6465 directories <em>in</em> <file>/usr/local</file>, but are
6466 children of directories in <file>/usr/local</file>. These
6467 directories (<file>/usr/local/*/dir/</file>)
6468 should be removed on package removal if they are
6473 Note that this applies only to
6474 directories <em>below</em> <file>/usr/local</file>,
6475 not <em>in</em> <file>/usr/local</file>. Packages must
6476 not create sub-directories in the
6477 directory <file>/usr/local</file> itself, except those
6478 listed in FHS, section 4.5. However, you may create
6479 directories below them as you wish. You must not remove
6480 any of the directories listed in 4.5, even if you created
6485 Since <file>/usr/local</file> can be mounted read-only from a
6486 remote server, these directories must be created and
6487 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6488 maintainer scripts and not be included in the
6489 <file>.deb</file> archive. These scripts must not fail if
6490 either of these operations fail.
6494 For example, the <tt>emacsen-common</tt> package could
6495 contain something like
6496 <example compact="compact">
6497 if [ ! -e /usr/local/share/emacs ]; then
6498 if mkdir /usr/local/share/emacs 2>/dev/null; then
6499 if chown root:staff /usr/local/share/emacs; then
6500 chmod 2775 /usr/local/share/emacs || true
6505 in its <prgn>postinst</prgn> script, and
6506 <example compact="compact">
6507 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6508 rmdir /usr/local/share/emacs 2>/dev/null || true
6510 in the <prgn>prerm</prgn> script. (Note that this form is
6511 used to ensure that if the script is interrupted, the
6512 directory <file>/usr/local/share/emacs</file> will still be
6517 If you do create a directory in <file>/usr/local</file> for
6518 local additions to a package, you should ensure that
6519 settings in <file>/usr/local</file> take precedence over the
6520 equivalents in <file>/usr</file>.
6524 However, because <file>/usr/local</file> and its contents are
6525 for exclusive use of the local administrator, a package
6526 must not rely on the presence or absence of files or
6527 directories in <file>/usr/local</file> for normal operation.
6531 The <file>/usr/local</file> directory itself and all the
6532 subdirectories created by the package should (by default) have
6533 permissions 2775 (group-writable and set-group-id) and be
6534 owned by <tt>root:staff</tt>.
6539 <heading>The system-wide mail directory</heading>
6541 The system-wide mail directory
6542 is <file>/var/mail</file>. This directory is part of the
6543 base system and should not be owned by any particular mail
6544 agents. The use of the old
6545 location <file>/var/spool/mail</file> is deprecated, even
6546 though the spool may still be physically located there.
6550 <sect1 id="fhs-run">
6551 <heading><file>/run</file> and <file>/run/lock</file></heading>
6554 The directory <file>/run</file> is cleared at boot, normally
6555 by being a mount point for a temporary file system. Packages
6556 therefore must not assume that any files or directories
6557 under <file>/run</file> other than <file>/run/lock</file>
6558 exist unless the package has arranged to create those files or
6559 directories since the last reboot. Normally, this is done by
6560 the package via an init script. See <ref id="writing-init">
6561 for more information.
6565 Packages must not include files or directories
6566 under <file>/run</file>, or under the
6567 older <file>/var/run</file> and <file>/var/lock</file> paths.
6568 The latter paths will normally be symlinks or other
6569 redirections to <file>/run</file> for backwards compatibility.
6575 <heading>Users and groups</heading>
6578 <heading>Introduction</heading>
6580 The Debian system can be configured to use either plain or
6585 Some user ids (UIDs) and group ids (GIDs) are reserved
6586 globally for use by certain packages. Because some
6587 packages need to include files which are owned by these
6588 users or groups, or need the ids compiled into binaries,
6589 these ids must be used on any Debian system only for the
6590 purpose for which they are allocated. This is a serious
6591 restriction, and we should avoid getting in the way of
6592 local administration policies. In particular, many sites
6593 allocate users and/or local system groups starting at 100.
6597 Apart from this we should have dynamically allocated ids,
6598 which should by default be arranged in some sensible
6599 order, but the behavior should be configurable.
6603 Packages other than <tt>base-passwd</tt> must not modify
6604 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6605 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6610 <heading>UID and GID classes</heading>
6612 The UID and GID numbers are divided into classes as
6618 Globally allocated by the Debian project, the same
6619 on every Debian system. These ids will appear in
6620 the <file>passwd</file> and <file>group</file> files of all
6621 Debian systems, new ids in this range being added
6622 automatically as the <tt>base-passwd</tt> package is
6627 Packages which need a single statically allocated
6628 uid or gid should use one of these; their
6629 maintainers should ask the <tt>base-passwd</tt>
6637 Dynamically allocated system users and groups.
6638 Packages which need a user or group, but can have
6639 this user or group allocated dynamically and
6640 differently on each system, should use <tt>adduser
6641 --system</tt> to create the group and/or user.
6642 <prgn>adduser</prgn> will check for the existence of
6643 the user or group, and if necessary choose an unused
6644 id based on the ranges specified in
6645 <file>adduser.conf</file>.
6649 <tag>1000-59999:</tag>
6652 Dynamically allocated user accounts. By default
6653 <prgn>adduser</prgn> will choose UIDs and GIDs for
6654 user accounts in this range, though
6655 <file>adduser.conf</file> may be used to modify this
6660 <tag>60000-64999:</tag>
6663 Globally allocated by the Debian project, but only
6664 created on demand. The ids are allocated centrally
6665 and statically, but the actual accounts are only
6666 created on users' systems on demand.
6670 These ids are for packages which are obscure or
6671 which require many statically-allocated ids. These
6672 packages should check for and create the accounts in
6673 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6674 <prgn>adduser</prgn> if it has this facility) if
6675 necessary. Packages which are likely to require
6676 further allocations should have a "hole" left after
6677 them in the allocation, to give them room to
6682 <tag>65000-65533:</tag>
6690 User <tt>nobody</tt>. The corresponding gid refers
6691 to the group <tt>nogroup</tt>.
6698 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6699 not</em> be used, because it is the error return
6708 <sect id="sysvinit">
6709 <heading>System run levels and <file>init.d</file> scripts</heading>
6711 <sect1 id="/etc/init.d">
6712 <heading>Introduction</heading>
6715 The <file>/etc/init.d</file> directory contains the scripts
6716 executed by <prgn>init</prgn> at boot time and when the
6717 init state (or "runlevel") is changed (see <manref
6718 name="init" section="8">).
6722 There are at least two different, yet functionally
6723 equivalent, ways of handling these scripts. For the sake
6724 of simplicity, this document describes only the symbolic
6725 link method. However, it must not be assumed by maintainer
6726 scripts that this method is being used, and any automated
6727 manipulation of the various runlevel behaviors by
6728 maintainer scripts must be performed using
6729 <prgn>update-rc.d</prgn> as described below and not by
6730 manually installing or removing symlinks. For information
6731 on the implementation details of the other method,
6732 implemented in the <tt>file-rc</tt> package, please refer
6733 to the documentation of that package.
6737 These scripts are referenced by symbolic links in the
6738 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6739 runlevels, <prgn>init</prgn> looks in the directory
6740 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6741 execute, where <tt><var>n</var></tt> is the runlevel that
6742 is being changed to, or <tt>S</tt> for the boot-up
6747 The names of the links all have the form
6748 <file>S<var>mm</var><var>script</var></file> or
6749 <file>K<var>mm</var><var>script</var></file> where
6750 <var>mm</var> is a two-digit number and <var>script</var>
6751 is the name of the script (this should be the same as the
6752 name of the actual script in <file>/etc/init.d</file>).
6756 When <prgn>init</prgn> changes runlevel first the targets
6757 of the links whose names start with a <tt>K</tt> are
6758 executed, each with the single argument <tt>stop</tt>,
6759 followed by the scripts prefixed with an <tt>S</tt>, each
6760 with the single argument <tt>start</tt>. (The links are
6761 those in the <file>/etc/rc<var>n</var>.d</file> directory
6762 corresponding to the new runlevel.) The <tt>K</tt> links
6763 are responsible for killing services and the <tt>S</tt>
6764 link for starting services upon entering the runlevel.
6768 For example, if we are changing from runlevel 2 to
6769 runlevel 3, init will first execute all of the <tt>K</tt>
6770 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6771 all of the <tt>S</tt> prefixed scripts in that directory.
6772 The links starting with <tt>K</tt> will cause the
6773 referred-to file to be executed with an argument of
6774 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6779 The two-digit number <var>mm</var> is used to determine
6780 the order in which to run the scripts: low-numbered links
6781 have their scripts run first. For example, the
6782 <tt>K20</tt> scripts will be executed before the
6783 <tt>K30</tt> scripts. This is used when a certain service
6784 must be started before another. For example, the name
6785 server <prgn>bind</prgn> might need to be started before
6786 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6787 can set up its access lists. In this case, the script
6788 that starts <prgn>bind</prgn> would have a lower number
6789 than the script that starts <prgn>inn</prgn> so that it
6791 <example compact="compact">
6798 The two runlevels 0 (halt) and 6 (reboot) are slightly
6799 different. In these runlevels, the links with an
6800 <tt>S</tt> prefix are still called after those with a
6801 <tt>K</tt> prefix, but they too are called with the single
6802 argument <tt>stop</tt>.
6806 <sect1 id="writing-init">
6807 <heading>Writing the scripts</heading>
6810 Packages that include daemons for system services should
6811 place scripts in <file>/etc/init.d</file> to start or stop
6812 services at boot time or during a change of runlevel.
6813 These scripts should be named
6814 <file>/etc/init.d/<var>package</var></file>, and they should
6815 accept one argument, saying what to do:
6818 <tag><tt>start</tt></tag>
6819 <item>start the service,</item>
6821 <tag><tt>stop</tt></tag>
6822 <item>stop the service,</item>
6824 <tag><tt>restart</tt></tag>
6825 <item>stop and restart the service if it's already running,
6826 otherwise start the service</item>
6828 <tag><tt>reload</tt></tag>
6829 <item><p>cause the configuration of the service to be
6830 reloaded without actually stopping and restarting
6833 <tag><tt>force-reload</tt></tag>
6834 <item>cause the configuration to be reloaded if the
6835 service supports this, otherwise restart the
6839 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6840 <tt>force-reload</tt> options should be supported by all
6841 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6846 The <file>init.d</file> scripts must ensure that they will
6847 behave sensibly (i.e., returning success and not starting
6848 multiple copies of a service) if invoked with <tt>start</tt>
6849 when the service is already running, or with <tt>stop</tt>
6850 when it isn't, and that they don't kill unfortunately-named
6851 user processes. The best way to achieve this is usually to
6852 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6857 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6858 scripts. Writing correct <file>init.d</file> scripts requires
6859 accepting various error exit statuses when daemons are already
6860 running or already stopped without aborting
6861 the <file>init.d</file> script, and common <file>init.d</file>
6862 function libraries are not safe to call with <tt>set -e</tt>
6864 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6865 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6866 in effect and echoing status messages to the console fails,
6868 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6869 to not use <tt>set -e</tt> and instead check the result of
6870 each command separately.
6874 If a service reloads its configuration automatically (as
6875 in the case of <prgn>cron</prgn>, for example), the
6876 <tt>reload</tt> option of the <file>init.d</file> script
6877 should behave as if the configuration has been reloaded
6882 The <file>/etc/init.d</file> scripts must be treated as
6883 configuration files, either (if they are present in the
6884 package, that is, in the .deb file) by marking them as
6885 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6886 by managing them correctly in the maintainer scripts (see
6887 <ref id="config-files">). This is important since we want
6888 to give the local system administrator the chance to adapt
6889 the scripts to the local system, e.g., to disable a
6890 service without de-installing the package, or to specify
6891 some special command line options when starting a service,
6892 while making sure their changes aren't lost during the next
6897 These scripts should not fail obscurely when the
6898 configuration files remain but the package has been
6899 removed, as configuration files remain on the system after
6900 the package has been removed. Only when <prgn>dpkg</prgn>
6901 is executed with the <tt>--purge</tt> option will
6902 configuration files be removed. In particular, as the
6903 <file>/etc/init.d/<var>package</var></file> script itself is
6904 usually a <tt>conffile</tt>, it will remain on the system
6905 if the package is removed but not purged. Therefore, you
6906 should include a <tt>test</tt> statement at the top of the
6908 <example compact="compact">
6909 test -f <var>program-executed-later-in-script</var> || exit 0
6914 Often there are some variables in the <file>init.d</file>
6915 scripts whose values control the behavior of the scripts,
6916 and which a system administrator is likely to want to
6917 change. As the scripts themselves are frequently
6918 <tt>conffile</tt>s, modifying them requires that the
6919 administrator merge in their changes each time the package
6920 is upgraded and the <tt>conffile</tt> changes. To ease
6921 the burden on the system administrator, such configurable
6922 values should not be placed directly in the script.
6923 Instead, they should be placed in a file in
6924 <file>/etc/default</file>, which typically will have the same
6925 base name as the <file>init.d</file> script. This extra file
6926 should be sourced by the script when the script runs. It
6927 must contain only variable settings and comments in SUSv3
6928 <prgn>sh</prgn> format. It may either be a
6929 <tt>conffile</tt> or a configuration file maintained by
6930 the package maintainer scripts. See <ref id="config-files">
6935 To ensure that vital configurable values are always
6936 available, the <file>init.d</file> script should set default
6937 values for each of the shell variables it uses, either
6938 before sourcing the <file>/etc/default/</file> file or
6939 afterwards using something like the <tt>:
6940 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6941 script must behave sensibly and not fail if the
6942 <file>/etc/default</file> file is deleted.
6946 Files and directories under <file>/run</file>, including ones
6947 referred to via the compatibility paths <file>/var/run</file>
6948 and <file>/var/lock</file>, are normally stored on a temporary
6949 filesystem and are normally not persistent across a reboot.
6950 The <file>init.d</file> scripts must handle this correctly.
6951 This will typically mean creating any required subdirectories
6952 dynamically when the <file>init.d</file> script is run.
6953 See <ref id="fhs-run"> for more information.
6958 <heading>Interfacing with the initscript system</heading>
6961 Maintainers should use the abstraction layer provided by
6962 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6963 programs to deal with initscripts in their packages'
6964 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6965 and <prgn>postrm</prgn>.
6969 Directly managing the /etc/rc?.d links and directly
6970 invoking the <file>/etc/init.d/</file> initscripts should
6971 be done only by packages providing the initscript
6972 subsystem (such as <prgn>sysv-rc</prgn> and
6973 <prgn>file-rc</prgn>).
6977 <heading>Managing the links</heading>
6980 The program <prgn>update-rc.d</prgn> is provided for
6981 package maintainers to arrange for the proper creation and
6982 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6983 or their functional equivalent if another method is being
6984 used. This may be used by maintainers in their packages'
6985 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6989 You must not include any <file>/etc/rc<var>n</var>.d</file>
6990 symbolic links in the actual archive or manually create or
6991 remove the symbolic links in maintainer scripts; you must
6992 use the <prgn>update-rc.d</prgn> program instead. (The
6993 former will fail if an alternative method of maintaining
6994 runlevel information is being used.) You must not include
6995 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6996 in the archive either. (Only the <tt>sysvinit</tt>
7001 By default <prgn>update-rc.d</prgn> will start services in
7002 each of the multi-user state runlevels (2, 3, 4, and 5)
7003 and stop them in the halt runlevel (0), the single-user
7004 runlevel (1) and the reboot runlevel (6). The system
7005 administrator will have the opportunity to customize
7006 runlevels by simply adding, moving, or removing the
7007 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7008 symbolic links are being used, or by modifying
7009 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7014 To get the default behavior for your package, put in your
7015 <prgn>postinst</prgn> script
7016 <example compact="compact">
7017 update-rc.d <var>package</var> defaults
7019 and in your <prgn>postrm</prgn>
7020 <example compact="compact">
7021 if [ "$1" = purge ]; then
7022 update-rc.d <var>package</var> remove
7024 </example>. Note that if your package changes runlevels
7025 or priority, you may have to remove and recreate the links,
7026 since otherwise the old links may persist. Refer to the
7027 documentation of <prgn>update-rc.d</prgn>.
7031 This will use a default sequence number of 20. If it does
7032 not matter when or in which order the <file>init.d</file>
7033 script is run, use this default. If it does, then you
7034 should talk to the maintainer of the <prgn>sysvinit</prgn>
7035 package or post to <tt>debian-devel</tt>, and they will
7036 help you choose a number.
7040 For more information about using <tt>update-rc.d</tt>,
7041 please consult its man page <manref name="update-rc.d"
7047 <heading>Running initscripts</heading>
7049 The program <prgn>invoke-rc.d</prgn> is provided to make
7050 it easier for package maintainers to properly invoke an
7051 initscript, obeying runlevel and other locally-defined
7052 constraints that might limit a package's right to start,
7053 stop and otherwise manage services. This program may be
7054 used by maintainers in their packages' scripts.
7058 The package maintainer scripts must use
7059 <prgn>invoke-rc.d</prgn> to invoke the
7060 <file>/etc/init.d/*</file> initscripts, instead of
7061 calling them directly.
7065 By default, <prgn>invoke-rc.d</prgn> will pass any
7066 action requests (start, stop, reload, restart...) to the
7067 <file>/etc/init.d</file> script, filtering out requests
7068 to start or restart a service out of its intended
7073 Most packages will simply need to change:
7074 <example compact="compact">/etc/init.d/<package>
7075 <action></example> in their <prgn>postinst</prgn>
7076 and <prgn>prerm</prgn> scripts to:
7077 <example compact="compact">
7078 if which invoke-rc.d >/dev/null 2>&1; then
7079 invoke-rc.d <var>package</var> <action>
7081 /etc/init.d/<var>package</var> <action>
7087 A package should register its initscript services using
7088 <prgn>update-rc.d</prgn> before it tries to invoke them
7089 using <prgn>invoke-rc.d</prgn>. Invocation of
7090 unregistered services may fail.
7094 For more information about using
7095 <prgn>invoke-rc.d</prgn>, please consult its man page
7096 <manref name="invoke-rc.d" section="8">.
7102 <heading>Boot-time initialization</heading>
7105 There used to be another directory, <file>/etc/rc.boot</file>,
7106 which contained scripts which were run once per machine
7107 boot. This has been deprecated in favour of links from
7108 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7109 described in <ref id="/etc/init.d">. Packages must not
7110 place files in <file>/etc/rc.boot</file>.
7115 <heading>Example</heading>
7118 An example on which you can base your
7119 <file>/etc/init.d</file> scripts is found in
7120 <file>/etc/init.d/skeleton</file>.
7127 <heading>Console messages from <file>init.d</file> scripts</heading>
7130 This section describes the formats to be used for messages
7131 written to standard output by the <file>/etc/init.d</file>
7132 scripts. The intent is to improve the consistency of
7133 Debian's startup and shutdown look and feel. For this
7134 reason, please look very carefully at the details. We want
7135 the messages to have the same format in terms of wording,
7136 spaces, punctuation and case of letters.
7140 Here is a list of overall rules that should be used for
7141 messages generated by <file>/etc/init.d</file> scripts.
7147 The message should fit in one line (fewer than 80
7148 characters), start with a capital letter and end with
7149 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7153 If the script is performing some time consuming task in
7154 the background (not merely starting or stopping a
7155 program, for instance), an ellipsis (three dots:
7156 <tt>...</tt>) should be output to the screen, with no
7157 leading or tailing whitespace or line feeds.
7161 The messages should appear as if the computer is telling
7162 the user what it is doing (politely :-), but should not
7163 mention "it" directly. For example, instead of:
7164 <example compact="compact">
7165 I'm starting network daemons: nfsd mountd.
7167 the message should say
7168 <example compact="compact">
7169 Starting network daemons: nfsd mountd.
7176 <tt>init.d</tt> script should use the following standard
7177 message formats for the situations enumerated below.
7183 <p>When daemons are started</p>
7186 If the script starts one or more daemons, the output
7187 should look like this (a single line, no leading
7189 <example compact="compact">
7190 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7192 The <var>description</var> should describe the
7193 subsystem the daemon or set of daemons are part of,
7194 while <var>daemon-1</var> up to <var>daemon-n</var>
7195 denote each daemon's name (typically the file name of
7200 For example, the output of <file>/etc/init.d/lpd</file>
7202 <example compact="compact">
7203 Starting printer spooler: lpd.
7208 This can be achieved by saying
7209 <example compact="compact">
7210 echo -n "Starting printer spooler: lpd"
7211 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7214 in the script. If there are more than one daemon to
7215 start, the output should look like this:
7216 <example compact="compact">
7217 echo -n "Starting remote file system services:"
7218 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7219 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7220 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7223 This makes it possible for the user to see what is
7224 happening and when the final daemon has been started.
7225 Care should be taken in the placement of white spaces:
7226 in the example above the system administrators can
7227 easily comment out a line if they don't want to start
7228 a specific daemon, while the displayed message still
7234 <p>When a system parameter is being set</p>
7237 If you have to set up different system parameters
7238 during the system boot, you should use this format:
7239 <example compact="compact">
7240 Setting <var>parameter</var> to "<var>value</var>".
7245 You can use a statement such as the following to get
7247 <example compact="compact">
7248 echo "Setting DNS domainname to \"$domainname\"."
7253 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7254 for the left and right quotation marks. A grave accent
7255 (<tt>`</tt>) is not a quote character; neither is an
7256 apostrophe (<tt>'</tt>).
7261 <p>When a daemon is stopped or restarted</p>
7264 When you stop or restart a daemon, you should issue a
7265 message identical to the startup message, except that
7266 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7267 or <tt>Restarting</tt> respectively.
7271 For example, stopping the printer daemon will look like
7273 <example compact="compact">
7274 Stopping printer spooler: lpd.
7280 <p>When something is executed</p>
7283 There are several examples where you have to run a
7284 program at system startup or shutdown to perform a
7285 specific task, for example, setting the system's clock
7286 using <prgn>netdate</prgn> or killing all processes
7287 when the system shuts down. Your message should look
7289 <example compact="compact">
7290 Doing something very useful...done.
7292 You should print the <tt>done.</tt> immediately after
7293 the job has been completed, so that the user is
7294 informed why they have to wait. You can get this
7296 <example compact="compact">
7297 echo -n "Doing something very useful..."
7306 <p>When the configuration is reloaded</p>
7309 When a daemon is forced to reload its configuration
7310 files you should use the following format:
7311 <example compact="compact">
7312 Reloading <var>description</var> configuration...done.
7314 where <var>description</var> is the same as in the
7315 daemon starting message.
7322 <sect id="cron-jobs">
7323 <heading>Cron jobs</heading>
7326 Packages must not modify the configuration file
7327 <file>/etc/crontab</file>, and they must not modify the files in
7328 <file>/var/spool/cron/crontabs</file>.
7332 If a package wants to install a job that has to be executed via
7333 cron, it should place a file named as specified
7334 in <ref id="cron-files"> into one or more of the following
7336 <example compact="compact">
7342 As these directory names imply, the files within them are
7343 executed on an hourly, daily, weekly, or monthly basis,
7344 respectively. The exact times are listed in
7345 <file>/etc/crontab</file>.
7349 All files installed in any of these directories must be
7350 scripts (e.g., shell scripts or Perl scripts) so that they
7351 can easily be modified by the local system administrator.
7352 In addition, they must be treated as configuration files.
7356 If a certain job has to be executed at some other frequency or
7357 at a specific time, the package should install a file in
7358 <file>/etc/cron.d</file> with a name as specified
7359 in <ref id="cron-files">. This file uses the same syntax
7360 as <file>/etc/crontab</file> and is processed
7361 by <prgn>cron</prgn> automatically. The file must also be
7362 treated as a configuration file. (Note that entries in the
7363 <file>/etc/cron.d</file> directory are not handled by
7364 <prgn>anacron</prgn>. Thus, you should only use this
7365 directory for jobs which may be skipped if the system is not
7370 Unlike <file>crontab</file> files described in the IEEE Std
7371 1003.1-2008 (POSIX.1) available from
7372 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7373 name="The Open Group">, the files in
7374 <file>/etc/cron.d</file> and the file
7375 <file>/etc/crontab</file> have seven fields; namely:
7377 <item>Minute [0,59]</item>
7378 <item>Hour [0,23]</item>
7379 <item>Day of the month [1,31]</item>
7380 <item>Month of the year [1,12]</item>
7381 <item>Day of the week ([0,6] with 0=Sunday)</item>
7382 <item>Username</item>
7383 <item>Command to be run</item>
7385 Ranges of numbers are allowed. Ranges are two numbers
7386 separated with a hyphen. The specified range is inclusive.
7387 Lists are allowed. A list is a set of numbers (or ranges)
7388 separated by commas. Step values can be used in conjunction
7393 The scripts or <tt>crontab</tt> entries in these directories should
7394 check if all necessary programs are installed before they
7395 try to execute them. Otherwise, problems will arise when a
7396 package was removed but not purged since configuration files
7397 are kept on the system in this situation.
7401 Any <tt>cron</tt> daemon must provide
7402 <file>/usr/bin/crontab</file> and support normal
7403 <tt>crontab</tt> entries as specified in POSIX. The daemon
7404 must also support names for days and months, ranges, and
7405 step values. It has to support <file>/etc/crontab</file>,
7406 and correctly execute the scripts in
7407 <file>/etc/cron.d</file>. The daemon must also correctly
7409 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7412 <sect1 id="cron-files">
7413 <heading>Cron job file names</heading>
7416 The file name of a cron job file should normally match the
7417 name of the package from which it comes.
7421 If a package supplies multiple cron job files files in the
7422 same directory, the file names should all start with the name
7423 of the package (possibly modified as described below) followed
7424 by a hyphen (<tt>-</tt>) and a suitable suffix.
7428 A cron job file name must not include any period or plus
7429 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7430 cause cron to ignore the file. Underscores (<tt>_</tt>)
7431 should be used instead of <tt>.</tt> and <tt>+</tt>
7438 <heading>Menus</heading>
7441 The Debian <tt>menu</tt> package provides a standard
7442 interface between packages providing applications and
7443 <em>menu programs</em> (either X window managers or
7444 text-based menu programs such as <prgn>pdmenu</prgn>).
7448 All packages that provide applications that need not be
7449 passed any special command line arguments for normal
7450 operation should register a menu entry for those
7451 applications, so that users of the <tt>menu</tt> package
7452 will automatically get menu entries in their window
7453 managers, as well in shells like <tt>pdmenu</tt>.
7457 Menu entries should follow the current menu policy.
7461 The menu policy can be found in the <tt>menu-policy</tt>
7462 files in the <tt>debian-policy</tt> package.
7463 It is also available from the Debian web mirrors at
7464 <tt><url name="/doc/packaging-manuals/menu-policy/"
7465 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7469 Please also refer to the <em>Debian Menu System</em>
7470 documentation that comes with the <package>menu</package>
7471 package for information about how to register your
7477 <heading>Multimedia handlers</heading>
7480 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7481 is a mechanism for encoding files and data streams and
7482 providing meta-information about them, in particular their
7483 type (e.g. audio or video) and format (e.g. PNG, HTML,
7488 Registration of MIME type handlers allows programs like mail
7489 user agents and web browsers to invoke these handlers to
7490 view, edit or display MIME types they don't support directly.
7494 Packages which provide the ability to view/show/play,
7495 compose, edit or print MIME types should register themselves
7496 as such following the current MIME support policy.
7500 The <package>mime-support</package> package provides the
7501 <prgn>update-mime</prgn> program which allows packages to
7502 register programs that can show, compose, edit or print
7507 Packages containing such programs must register them
7508 with <prgn>update-mime</prgn> as documented in <manref
7509 name="update-mime" section="8">. They should <em>not</em> depend
7510 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7511 they should just put something like the following in the
7512 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7515 if [ -x /usr/sbin/update-mime ]; then
7524 <heading>Keyboard configuration</heading>
7527 To achieve a consistent keyboard configuration so that all
7528 applications interpret a keyboard event the same way, all
7529 programs in the Debian distribution must be configured to
7530 comply with the following guidelines.
7534 The following keys must have the specified interpretations:
7537 <tag><tt><--</tt></tag>
7538 <item>delete the character to the left of the cursor</item>
7540 <tag><tt>Delete</tt></tag>
7541 <item>delete the character to the right of the cursor</item>
7543 <tag><tt>Control+H</tt></tag>
7544 <item>emacs: the help prefix</item>
7547 The interpretation of any keyboard events should be
7548 independent of the terminal that is used, be it a virtual
7549 console, an X terminal emulator, an rlogin/telnet session,
7554 The following list explains how the different programs
7555 should be set up to achieve this:
7561 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7565 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7569 X translations are set up to make
7570 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7571 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7572 is the vt220 escape code for the "delete character"
7573 key). This must be done by loading the X resources
7574 using <prgn>xrdb</prgn> on all local X displays, not
7575 using the application defaults, so that the
7576 translation resources used correspond to the
7577 <prgn>xmodmap</prgn> settings.
7581 The Linux console is configured to make
7582 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7583 generate <tt>ESC [ 3 ~</tt>.
7587 X applications are configured so that <tt><</tt>
7588 deletes left, and <tt>Delete</tt> deletes right. Motif
7589 applications already work like this.
7593 Terminals should have <tt>stty erase ^?</tt> .
7597 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7598 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7599 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7603 Emacs is programmed to map <tt>KB_Backspace</tt> or
7604 the <tt>stty erase</tt> character to
7605 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7606 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7607 <tt>^H</tt> to <tt>help</tt> as always.
7611 Other applications use the <tt>stty erase</tt>
7612 character and <tt>kdch1</tt> for the two delete keys,
7613 with ASCII DEL being "delete previous character" and
7614 <tt>kdch1</tt> being "delete character under
7622 This will solve the problem except for the following
7629 Some terminals have a <tt><--</tt> key that cannot
7630 be made to produce anything except <tt>^H</tt>. On
7631 these terminals Emacs help will be unavailable on
7632 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7633 character takes precedence in Emacs, and has been set
7634 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7635 available) can be used instead.
7639 Some operating systems use <tt>^H</tt> for <tt>stty
7640 erase</tt>. However, modern telnet versions and all
7641 rlogin versions propagate <tt>stty</tt> settings, and
7642 almost all UNIX versions honour <tt>stty erase</tt>.
7643 Where the <tt>stty</tt> settings are not propagated
7644 correctly, things can be made to work by using
7645 <tt>stty</tt> manually.
7649 Some systems (including previous Debian versions) use
7650 <prgn>xmodmap</prgn> to arrange for both
7651 <tt><--</tt> and <tt>Delete</tt> to generate
7652 <tt>KB_Delete</tt>. We can change the behavior of
7653 their X clients using the same X resources that we use
7654 to do it for our own clients, or configure our clients
7655 using their resources when things are the other way
7656 around. On displays configured like this
7657 <tt>Delete</tt> will not work, but <tt><--</tt>
7662 Some operating systems have different <tt>kdch1</tt>
7663 settings in their <tt>terminfo</tt> database for
7664 <tt>xterm</tt> and others. On these systems the
7665 <tt>Delete</tt> key will not work correctly when you
7666 log in from a system conforming to our policy, but
7667 <tt><--</tt> will.
7674 <heading>Environment variables</heading>
7677 A program must not depend on environment variables to get
7678 reasonable defaults. (That's because these environment
7679 variables would have to be set in a system-wide
7680 configuration file like <file>/etc/profile</file>, which is not
7681 supported by all shells.)
7685 If a program usually depends on environment variables for its
7686 configuration, the program should be changed to fall back to
7687 a reasonable default configuration if these environment
7688 variables are not present. If this cannot be done easily
7689 (e.g., if the source code of a non-free program is not
7690 available), the program must be replaced by a small
7691 "wrapper" shell script which sets the environment variables
7692 if they are not already defined, and calls the original program.
7696 Here is an example of a wrapper script for this purpose:
7698 <example compact="compact">
7700 BAR=${BAR:-/var/lib/fubar}
7702 exec /usr/lib/foo/foo "$@"
7707 Furthermore, as <file>/etc/profile</file> is a configuration
7708 file of the <prgn>base-files</prgn> package, other packages must
7709 not put any environment variables or other commands into that
7714 <sect id="doc-base">
7715 <heading>Registering Documents using doc-base</heading>
7718 The <package>doc-base</package> package implements a
7719 flexible mechanism for handling and presenting
7720 documentation. The recommended practice is for every Debian
7721 package that provides online documentation (other than just
7722 manual pages) to register these documents with
7723 <package>doc-base</package> by installing a
7724 <package>doc-base</package> control file in
7725 <file>/usr/share/doc-base/</file>.
7728 Please refer to the documentation that comes with the
7729 <package>doc-base</package> package for information and
7738 <heading>Files</heading>
7740 <sect id="binaries">
7741 <heading>Binaries</heading>
7744 Two different packages must not install programs with
7745 different functionality but with the same filenames. (The
7746 case of two programs having the same functionality but
7747 different implementations is handled via "alternatives" or
7748 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7749 <ref id="conflicts"> respectively.) If this case happens,
7750 one of the programs must be renamed. The maintainers should
7751 report this to the <tt>debian-devel</tt> mailing list and
7752 try to find a consensus about which program will have to be
7753 renamed. If a consensus cannot be reached, <em>both</em>
7754 programs must be renamed.
7758 By default, when a package is being built, any binaries
7759 created should include debugging information, as well as
7760 being compiled with optimization. You should also turn on
7761 as many reasonable compilation warnings as possible; this
7762 makes life easier for porters, who can then look at build
7763 logs for possible problems. For the C programming language,
7764 this means the following compilation parameters should be
7766 <example compact="compact">
7768 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7770 INSTALL = install -s # (or use strip on the files in debian/tmp)
7775 Note that by default all installed binaries should be stripped,
7776 either by using the <tt>-s</tt> flag to
7777 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7778 the binaries after they have been copied into
7779 <file>debian/tmp</file> but before the tree is made into a
7784 Although binaries in the build tree should be compiled with
7785 debugging information by default, it can often be difficult to
7786 debug programs if they are also subjected to compiler
7787 optimization. For this reason, it is recommended to support the
7788 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7789 (see <ref id="debianrules-options">). This variable can contain
7790 several flags to change how a package is compiled and built.
7794 It is up to the package maintainer to decide what
7795 compilation options are best for the package. Certain
7796 binaries (such as computationally-intensive programs) will
7797 function better with certain flags (<tt>-O3</tt>, for
7798 example); feel free to use them. Please use good judgment
7799 here. Don't use flags for the sake of it; only use them
7800 if there is good reason to do so. Feel free to override
7801 the upstream author's ideas about which compilation
7802 options are best: they are often inappropriate for our
7808 <sect id="libraries">
7809 <heading>Libraries</heading>
7812 If the package is <strong>architecture: any</strong>, then
7813 the shared library compilation and linking flags must have
7814 <tt>-fPIC</tt>, or the package shall not build on some of
7815 the supported architectures<footnote>
7817 If you are using GCC, <tt>-fPIC</tt> produces code with
7818 relocatable position independent code, which is required for
7819 most architectures to create a shared library, with i386 and
7820 perhaps some others where non position independent code is
7821 permitted in a shared library.
7824 Position independent code may have a performance penalty,
7825 especially on <tt>i386</tt>. However, in most cases the
7826 speed penalty must be measured against the memory wasted on
7827 the few architectures where non position independent code is
7830 </footnote>. Any exception to this rule must be discussed on
7831 the mailing list <em>debian-devel@lists.debian.org</em>, and
7832 a rough consensus obtained. The reasons for not compiling
7833 with <tt>-fPIC</tt> flag must be recorded in the file
7834 <tt>README.Debian</tt>, and care must be taken to either
7835 restrict the architecture or arrange for <tt>-fPIC</tt> to
7836 be used on architectures where it is required.<footnote>
7838 Some of the reasons why this might be required is if the
7839 library contains hand crafted assembly code that is not
7840 relocatable, the speed penalty is excessive for compute
7841 intensive libs, and similar reasons.
7846 As to the static libraries, the common case is not to have
7847 relocatable code, since there is no benefit, unless in specific
7848 cases; therefore the static version must not be compiled
7849 with the <tt>-fPIC</tt> flag. Any exception to this rule
7850 should be discussed on the mailing list
7851 <em>debian-devel@lists.debian.org</em>, and the reasons for
7852 compiling with the <tt>-fPIC</tt> flag must be recorded in
7853 the file <tt>README.Debian</tt>. <footnote>
7855 Some of the reasons for linking static libraries with
7856 the <tt>-fPIC</tt> flag are if, for example, one needs a
7857 Perl API for a library that is under rapid development,
7858 and has an unstable API, so shared libraries are
7859 pointless at this phase of the library's development. In
7860 that case, since Perl needs a library with relocatable
7861 code, it may make sense to create a static library with
7862 relocatable code. Another reason cited is if you are
7863 distilling various libraries into a common shared
7864 library, like <tt>mklibs</tt> does in the Debian
7870 In other words, if both a shared and a static library is
7871 being built, each source unit (<tt>*.c</tt>, for example,
7872 for C files) will need to be compiled twice, for the normal
7877 Libraries should be built with threading support and to be
7878 thread-safe if the library supports this.
7882 Although not enforced by the build tools, shared libraries
7883 must be linked against all libraries that they use symbols from
7884 in the same way that binaries are. This ensures the correct
7885 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7886 system and guarantees that all libraries can be safely opened
7887 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7888 option <tt>-Wl,-z,defs</tt> when building a shared library.
7889 Since this option enforces symbol resolution at build time,
7890 a missing library reference will be caught early as a fatal
7895 All installed shared libraries should be stripped with
7896 <example compact="compact">
7897 strip --strip-unneeded <var>your-lib</var>
7899 (The option <tt>--strip-unneeded</tt> makes
7900 <prgn>strip</prgn> remove only the symbols which aren't
7901 needed for relocation processing.) Shared libraries can
7902 function perfectly well when stripped, since the symbols for
7903 dynamic linking are in a separate part of the ELF object
7905 You might also want to use the options
7906 <tt>--remove-section=.comment</tt> and
7907 <tt>--remove-section=.note</tt> on both shared libraries
7908 and executables, and <tt>--strip-debug</tt> on static
7914 Note that under some circumstances it may be useful to
7915 install a shared library unstripped, for example when
7916 building a separate package to support debugging.
7920 Shared object files (often <file>.so</file> files) that are not
7921 public libraries, that is, they are not meant to be linked
7922 to by third party executables (binaries of other packages),
7923 should be installed in subdirectories of the
7924 <file>/usr/lib</file> directory. Such files are exempt from the
7925 rules that govern ordinary shared libraries, except that
7926 they must not be installed executable and should be
7928 A common example are the so-called "plug-ins",
7929 internal shared objects that are dynamically loaded by
7930 programs using <manref name="dlopen" section="3">.
7935 Packages that use <prgn>libtool</prgn> to create and install
7936 their shared libraries install a file containing additional
7937 metadata (ending in <file>.la</file>) alongside the library.
7938 For public libraries intended for use by other packages, these
7939 files normally should not be included in the Debian package,
7940 since the information they include is not necessary to link with
7941 the shared library on Debian and can add unnecessary additional
7942 dependencies to other programs or libraries.<footnote>
7943 These files store, among other things, all libraries on which
7944 that shared library depends. Unfortunately, if
7945 the <file>.la</file> file is present and contains that
7946 dependency information, using <prgn>libtool</prgn> when
7947 linking against that library will cause the resulting program
7948 or library to be linked against those dependencies as well,
7949 even if this is unnecessary. This can create unneeded
7950 dependencies on shared library packages that would otherwise
7951 be hidden behind the library ABI, and can make library
7952 transitions to new SONAMEs unnecessarily complicated and
7953 difficult to manage.
7955 If the <file>.la</file> file is required for that library (if,
7956 for instance, it's loaded via <tt>libltdl</tt> in a way that
7957 requires that meta-information), the <tt>dependency_libs</tt>
7958 setting in the <file>.la</file> file should normally be set to
7959 the empty string. If the shared library development package has
7960 historically included the <file>.la</file>, it must be retained
7961 in the development package (with <tt>dependency_libs</tt>
7962 emptied) until all libraries that depend on it have removed or
7963 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7964 files to prevent linking with those other libraries
7965 using <prgn>libtool</prgn> from failing.
7969 If the <file>.la</file> must be included, it should be included
7970 in the development (<tt>-dev</tt>) package, unless the library
7971 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7972 library. If it is intended for use with <tt>libltdl</tt>,
7973 the <file>.la</file> files must go in the run-time library
7978 These requirements for handling of <file>.la</file> files do not
7979 apply to loadable modules or libraries not installed in
7980 directories searched by default by the dynamic linker. Packages
7981 installing loadable modules will frequently need to install
7982 the <file>.la</file> files alongside the modules so that they
7983 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7984 does not need to be modified for libraries or modules that are
7985 not installed in directories searched by the dynamic linker by
7986 default and not intended for use by other packages.
7990 You must make sure that you use only released versions of
7991 shared libraries to build your packages; otherwise other
7992 users will not be able to run your binaries
7993 properly. Producing source packages that depend on
7994 unreleased compilers is also usually a bad
8001 <heading>Shared libraries</heading>
8003 This section has moved to <ref id="sharedlibs">.
8009 <heading>Scripts</heading>
8012 All command scripts, including the package maintainer
8013 scripts inside the package and used by <prgn>dpkg</prgn>,
8014 should have a <tt>#!</tt> line naming the shell to be used
8019 In the case of Perl scripts this should be
8020 <tt>#!/usr/bin/perl</tt>.
8024 When scripts are installed into a directory in the system
8025 PATH, the script name should not include an extension such
8026 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8027 language currently used to implement it.
8030 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8031 <file>init.d</file> scripts should almost certainly start
8032 with <tt>set -e</tt> so that errors are detected.
8033 <file>init.d</file> scripts are something of a special case, due
8034 to how frequently they need to call commands that are allowed to
8035 fail, and it may instead be easier to check the exit status of
8036 commands directly. See <ref id="writing-init"> for more
8037 information about writing <file>init.d</file> scripts.
8040 Every script should use <tt>set -e</tt> or check the exit status
8041 of <em>every</em> command.
8044 Scripts may assume that <file>/bin/sh</file> implements the
8045 SUSv3 Shell Command Language<footnote>
8046 Single UNIX Specification, version 3, which is also IEEE
8047 1003.1-2004 (POSIX), and is available on the World Wide Web
8048 from <url id="http://www.unix.org/version3/online.html"
8049 name="The Open Group"> after free
8050 registration.</footnote>
8051 plus the following additional features not mandated by
8053 These features are in widespread use in the Linux community
8054 and are implemented in all of bash, dash, and ksh, the most
8055 common shells users may wish to use as <file>/bin/sh</file>.
8058 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8059 must not generate a newline.</item>
8060 <item><tt>test</tt>, if implemented as a shell built-in, must
8061 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8063 <item><tt>local</tt> to create a scoped variable must be
8064 supported, including listing multiple variables in a single
8065 local command and assigning a value to a variable at the
8066 same time as localizing it. <tt>local</tt> may or
8067 may not preserve the variable value from an outer scope if
8068 no assignment is present. Uses such as:
8072 # ... use a, b, c, d ...
8075 must be supported and must set the value of <tt>c</tt> to
8078 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8079 -<var>signal</var></tt>, where <var>signal</var> is either
8080 the name of a signal or one of the numeric signals listed in
8081 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8082 supported if <prgn>kill</prgn> is implemented as a shell
8085 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8086 signals must be supported. In addition to the signal
8087 numbers listed in the extension, which are the same as for
8088 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8091 If a shell script requires non-SUSv3 features from the shell
8092 interpreter other than those listed above, the appropriate shell
8093 must be specified in the first line of the script (e.g.,
8094 <tt>#!/bin/bash</tt>) and the package must depend on the package
8095 providing the shell (unless the shell package is marked
8096 "Essential", as in the case of <prgn>bash</prgn>).
8100 You may wish to restrict your script to SUSv3 features plus the
8101 above set when possible so that it may use <file>/bin/sh</file>
8102 as its interpreter. Checking your script
8103 with <prgn>checkbashisms</prgn> from
8104 the <package>devscripts</package> package or running your script
8105 with an alternate shell such as <prgn>posh</prgn> may help
8106 uncover violations of the above requirements. If in doubt
8107 whether a script complies with these requirements,
8108 use <file>/bin/bash</file>.
8112 Perl scripts should check for errors when making any
8113 system calls, including <tt>open</tt>, <tt>print</tt>,
8114 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8118 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8119 scripting languages. See <em>Csh Programming Considered
8120 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8121 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8122 If an upstream package comes with <prgn>csh</prgn> scripts
8123 then you must make sure that they start with
8124 <tt>#!/bin/csh</tt> and make your package depend on the
8125 <prgn>c-shell</prgn> virtual package.
8129 Any scripts which create files in world-writeable
8130 directories (e.g., in <file>/tmp</file>) must use a
8131 mechanism which will fail atomically if a file with the same
8132 name already exists.
8136 The Debian base system provides the <prgn>tempfile</prgn>
8137 and <prgn>mktemp</prgn> utilities for use by scripts for
8144 <heading>Symbolic links</heading>
8147 In general, symbolic links within a top-level directory should
8148 be relative, and symbolic links pointing from one top-level
8149 directory to or into another should be absolute. (A top-level
8150 directory is a sub-directory of the root
8151 directory <file>/</file>.) For example, a symbolic link
8152 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8153 should be relative (<file>../share/bar</file>), but a symbolic
8154 link from <file>/var/run</file> to <file>/run</file> should be
8156 This is necessary to allow top-level directories to be
8157 symlinks. If linking <file>/var/run</file>
8158 to <file>/run</file> were done with the relative symbolic
8159 link <file>../run</file>, but <file>/var</file> were a
8160 symbolic link to <file>/srv/disk1</file>, the symbolic link
8161 would point to <file>/srv/run</file> rather than the intended
8167 In addition, symbolic links should be specified as short as
8168 possible, i.e., link targets like <file>foo/../bar</file> are
8173 Note that when creating a relative link using
8174 <prgn>ln</prgn> it is not necessary for the target of the
8175 link to exist relative to the working directory you're
8176 running <prgn>ln</prgn> from, nor is it necessary to change
8177 directory to the directory where the link is to be made.
8178 Simply include the string that should appear as the target
8179 of the link (this will be a pathname relative to the
8180 directory in which the link resides) as the first argument
8185 For example, in your <prgn>Makefile</prgn> or
8186 <file>debian/rules</file>, you can do things like:
8187 <example compact="compact">
8188 ln -fs gcc $(prefix)/bin/cc
8189 ln -fs gcc debian/tmp/usr/bin/cc
8190 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8191 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8196 A symbolic link pointing to a compressed file should always
8197 have the same file extension as the referenced file. (For
8198 example, if a file <file>foo.gz</file> is referenced by a
8199 symbolic link, the filename of the link has to end with
8200 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8205 <heading>Device files</heading>
8208 Packages must not include device files or named pipes in the
8213 If a package needs any special device files that are not
8214 included in the base system, it must call
8215 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8216 after notifying the user<footnote>
8217 This notification could be done via a (low-priority)
8218 debconf message, or an echo (printf) statement.
8223 Packages must not remove any device files in the
8224 <prgn>postrm</prgn> or any other script. This is left to the
8225 system administrator.
8229 Debian uses the serial devices
8230 <file>/dev/ttyS*</file>. Programs using the old
8231 <file>/dev/cu*</file> devices should be changed to use
8232 <file>/dev/ttyS*</file>.
8236 Named pipes needed by the package must be created in
8237 the <prgn>postinst</prgn> script<footnote>
8238 It's better to use <prgn>mkfifo</prgn> rather
8239 than <prgn>mknod</prgn> to create named pipes so that
8240 automated checks for packages incorrectly creating device
8241 files with <prgn>mknod</prgn> won't have false positives.
8242 </footnote> and removed in
8243 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8248 <sect id="config-files">
8249 <heading>Configuration files</heading>
8252 <heading>Definitions</heading>
8256 <tag>configuration file</tag>
8258 A file that affects the operation of a program, or
8259 provides site- or host-specific information, or
8260 otherwise customizes the behavior of a program.
8261 Typically, configuration files are intended to be
8262 modified by the system administrator (if needed or
8263 desired) to conform to local policy or to provide
8264 more useful site-specific behavior.
8267 <tag><tt>conffile</tt></tag>
8269 A file listed in a package's <tt>conffiles</tt>
8270 file, and is treated specially by <prgn>dpkg</prgn>
8271 (see <ref id="configdetails">).
8277 The distinction between these two is important; they are
8278 not interchangeable concepts. Almost all
8279 <tt>conffile</tt>s are configuration files, but many
8280 configuration files are not <tt>conffiles</tt>.
8284 As noted elsewhere, <file>/etc/init.d</file> scripts,
8285 <file>/etc/default</file> files, scripts installed in
8286 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8287 configuration installed in <file>/etc/cron.d</file> must be
8288 treated as configuration files. In general, any script that
8289 embeds configuration information is de-facto a configuration
8290 file and should be treated as such.
8295 <heading>Location</heading>
8298 Any configuration files created or used by your package
8299 must reside in <file>/etc</file>. If there are several,
8300 consider creating a subdirectory of <file>/etc</file>
8301 named after your package.
8305 If your package creates or uses configuration files
8306 outside of <file>/etc</file>, and it is not feasible to modify
8307 the package to use <file>/etc</file> directly, put the files
8308 in <file>/etc</file> and create symbolic links to those files
8309 from the location that the package requires.
8314 <heading>Behavior</heading>
8317 Configuration file handling must conform to the following
8319 <list compact="compact">
8321 local changes must be preserved during a package
8325 configuration files must be preserved when the
8326 package is removed, and only deleted when the
8330 Obsolete configuration files without local changes may be
8331 removed by the package during upgrade.
8335 The easy way to achieve this behavior is to make the
8336 configuration file a <tt>conffile</tt>. This is
8337 appropriate only if it is possible to distribute a default
8338 version that will work for most installations, although
8339 some system administrators may choose to modify it. This
8340 implies that the default version will be part of the
8341 package distribution, and must not be modified by the
8342 maintainer scripts during installation (or at any other
8347 In order to ensure that local changes are preserved
8348 correctly, no package may contain or make hard links to
8349 conffiles.<footnote>
8350 Rationale: There are two problems with hard links.
8351 The first is that some editors break the link while
8352 editing one of the files, so that the two files may
8353 unwittingly become unlinked and different. The second
8354 is that <prgn>dpkg</prgn> might break the hard link
8355 while upgrading <tt>conffile</tt>s.
8360 The other way to do it is via the maintainer scripts. In
8361 this case, the configuration file must not be listed as a
8362 <tt>conffile</tt> and must not be part of the package
8363 distribution. If the existence of a file is required for
8364 the package to be sensibly configured it is the
8365 responsibility of the package maintainer to provide
8366 maintainer scripts which correctly create, update and
8367 maintain the file and remove it on purge. (See <ref
8368 id="maintainerscripts"> for more information.) These
8369 scripts must be idempotent (i.e., must work correctly if
8370 <prgn>dpkg</prgn> needs to re-run them due to errors
8371 during installation or removal), must cope with all the
8372 variety of ways <prgn>dpkg</prgn> can call maintainer
8373 scripts, must not overwrite or otherwise mangle the user's
8374 configuration without asking, must not ask unnecessary
8375 questions (particularly during upgrades), and must
8376 otherwise be good citizens.
8380 The scripts are not required to configure every possible
8381 option for the package, but only those necessary to get
8382 the package running on a given system. Ideally the
8383 sysadmin should not have to do any configuration other
8384 than that done (semi-)automatically by the
8385 <prgn>postinst</prgn> script.
8389 A common practice is to create a script called
8390 <file><var>package</var>-configure</file> and have the
8391 package's <prgn>postinst</prgn> call it if and only if the
8392 configuration file does not already exist. In certain
8393 cases it is useful for there to be an example or template
8394 file which the maintainer scripts use. Such files should
8395 be in <file>/usr/share/<var>package</var></file> or
8396 <file>/usr/lib/<var>package</var></file> (depending on whether
8397 they are architecture-independent or not). There should
8398 be symbolic links to them from
8399 <file>/usr/share/doc/<var>package</var>/examples</file> if
8400 they are examples, and should be perfectly ordinary
8401 <prgn>dpkg</prgn>-handled files (<em>not</em>
8402 configuration files).
8406 These two styles of configuration file handling must
8407 not be mixed, for that way lies madness:
8408 <prgn>dpkg</prgn> will ask about overwriting the file
8409 every time the package is upgraded.
8414 <heading>Sharing configuration files</heading>
8417 If two or more packages use the same configuration file
8418 and it is reasonable for both to be installed at the same
8419 time, one of these packages must be defined as
8420 <em>owner</em> of the configuration file, i.e., it will be
8421 the package which handles that file as a configuration
8422 file. Other packages that use the configuration file must
8423 depend on the owning package if they require the
8424 configuration file to operate. If the other package will
8425 use the configuration file if present, but is capable of
8426 operating without it, no dependency need be declared.
8430 If it is desirable for two or more related packages to
8431 share a configuration file <em>and</em> for all of the
8432 related packages to be able to modify that configuration
8433 file, then the following should be done:
8434 <enumlist compact="compact">
8436 One of the related packages (the "owning" package)
8437 will manage the configuration file with maintainer
8438 scripts as described in the previous section.
8441 The owning package should also provide a program
8442 that the other packages may use to modify the
8446 The related packages must use the provided program
8447 to make any desired modifications to the
8448 configuration file. They should either depend on
8449 the core package to guarantee that the configuration
8450 modifier program is available or accept gracefully
8451 that they cannot modify the configuration file if it
8452 is not. (This is in addition to the fact that the
8453 configuration file may not even be present in the
8460 Sometimes it's appropriate to create a new package which
8461 provides the basic infrastructure for the other packages
8462 and which manages the shared configuration files. (The
8463 <tt>sgml-base</tt> package is a good example.)
8467 If the configuration file cannot be shared as described above,
8468 the packages must be marked as conflicting with each other.
8469 Two packages that specify the same file as
8470 a <tt>conffile</tt> must conflict. This is an instance of the
8471 general rule about not sharing files. Neither alternatives
8472 nor diversions are likely to be appropriate in this case; in
8473 particular, <prgn>dpkg</prgn> does not handle diverted
8474 <tt>conffile</tt>s well.
8478 When two packages both declare the same <tt>conffile</tt>, they
8479 may see left-over configuration files from each other even
8480 though they conflict with each other. If a user removes
8481 (without purging) one of the packages and installs the other,
8482 the new package will take over the <tt>conffile</tt> from the
8483 old package. If the file was modified by the user, it will be
8484 treated the same as any other locally
8485 modified <tt>conffile</tt> during an upgrade.
8489 The maintainer scripts must not alter a <tt>conffile</tt>
8490 of <em>any</em> package, including the one the scripts
8496 <heading>User configuration files ("dotfiles")</heading>
8499 The files in <file>/etc/skel</file> will automatically be
8500 copied into new user accounts by <prgn>adduser</prgn>.
8501 No other program should reference the files in
8502 <file>/etc/skel</file>.
8506 Therefore, if a program needs a dotfile to exist in
8507 advance in <file>$HOME</file> to work sensibly, that dotfile
8508 should be installed in <file>/etc/skel</file> and treated as a
8513 However, programs that require dotfiles in order to
8514 operate sensibly are a bad thing, unless they do create
8515 the dotfiles themselves automatically.
8519 Furthermore, programs should be configured by the Debian
8520 default installation to behave as closely to the upstream
8521 default behavior as possible.
8525 Therefore, if a program in a Debian package needs to be
8526 configured in some way in order to operate sensibly, that
8527 should be done using a site-wide configuration file placed
8528 in <file>/etc</file>. Only if the program doesn't support a
8529 site-wide default configuration and the package maintainer
8530 doesn't have time to add it may a default per-user file be
8531 placed in <file>/etc/skel</file>.
8535 <file>/etc/skel</file> should be as empty as we can make it.
8536 This is particularly true because there is no easy (or
8537 necessarily desirable) mechanism for ensuring that the
8538 appropriate dotfiles are copied into the accounts of
8539 existing users when a package is installed.
8545 <heading>Log files</heading>
8547 Log files should usually be named
8548 <file>/var/log/<var>package</var>.log</file>. If you have many
8549 log files, or need a separate directory for permission
8550 reasons (<file>/var/log</file> is writable only by
8551 <file>root</file>), you should usually create a directory named
8552 <file>/var/log/<var>package</var></file> and place your log
8557 Log files must be rotated occasionally so that they don't grow
8558 indefinitely. The best way to do this is to install a log
8559 rotation configuration file in the
8560 directory <file>/etc/logrotate.d</file>, normally
8561 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8562 the facilities provided by <prgn>logrotate</prgn>.
8565 The traditional approach to log files has been to set up
8566 <em>ad hoc</em> log rotation schemes using simple shell
8567 scripts and cron. While this approach is highly
8568 customizable, it requires quite a lot of sysadmin work.
8569 Even though the original Debian system helped a little
8570 by automatically installing a system which can be used
8571 as a template, this was deemed not enough.
8575 The use of <prgn>logrotate</prgn>, a program developed
8576 by Red Hat, is better, as it centralizes log management.
8577 It has both a configuration file
8578 (<file>/etc/logrotate.conf</file>) and a directory where
8579 packages can drop their individual log rotation
8580 configurations (<file>/etc/logrotate.d</file>).
8583 Here is a good example for a logrotate config
8584 file (for more information see <manref name="logrotate"
8586 <example compact="compact">
8587 /var/log/foo/*.log {
8593 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8597 This rotates all files under <file>/var/log/foo</file>, saves 12
8598 compressed generations, and tells the daemon to reopen its log
8599 files after the log rotation. It skips this log rotation
8600 (via <tt>missingok</tt>) if no such log file is present, which
8601 avoids errors if the package is removed but not purged.
8605 Log files should be removed when the package is
8606 purged (but not when it is only removed). This should be
8607 done by the <prgn>postrm</prgn> script when it is called
8608 with the argument <tt>purge</tt> (see <ref
8609 id="removedetails">).
8613 <sect id="permissions-owners">
8614 <heading>Permissions and owners</heading>
8617 The rules in this section are guidelines for general use.
8618 If necessary you may deviate from the details below.
8619 However, if you do so you must make sure that what is done
8620 is secure and you should try to be as consistent as possible
8621 with the rest of the system. You should probably also
8622 discuss it on <prgn>debian-devel</prgn> first.
8626 Files should be owned by <tt>root:root</tt>, and made
8627 writable only by the owner and universally readable (and
8628 executable, if appropriate), that is mode 644 or 755.
8632 Directories should be mode 755 or (for group-writability)
8633 mode 2775. The ownership of the directory should be
8634 consistent with its mode: if a directory is mode 2775, it
8635 should be owned by the group that needs write access to
8638 When a package is upgraded, and the owner or permissions
8639 of a file included in the package has changed, dpkg
8640 arranges for the ownership and permissions to be
8641 correctly set upon installation. However, this does not
8642 extend to directories; the permissions and ownership of
8643 directories already on the system does not change on
8644 install or upgrade of packages. This makes sense, since
8645 otherwise common directories like <tt>/usr</tt> would
8646 always be in flux. To correctly change permissions of a
8647 directory the package owns, explicit action is required,
8648 usually in the <tt>postinst</tt> script. Care must be
8649 taken to handle downgrades as well, in that case.
8655 Control information files should be owned by <tt>root:root</tt>
8656 and either mode 644 (for most files) or mode 755 (for
8657 executables such as <qref id="maintscripts">maintainer
8662 Setuid and setgid executables should be mode 4755 or 2755
8663 respectively, and owned by the appropriate user or group.
8664 They should not be made unreadable (modes like 4711 or
8665 2711 or even 4111); doing so achieves no extra security,
8666 because anyone can find the binary in the freely available
8667 Debian package; it is merely inconvenient. For the same
8668 reason you should not restrict read or execute permissions
8669 on non-set-id executables.
8673 Some setuid programs need to be restricted to particular
8674 sets of users, using file permissions. In this case they
8675 should be owned by the uid to which they are set-id, and by
8676 the group which should be allowed to execute them. They
8677 should have mode 4754; again there is no point in making
8678 them unreadable to those users who must not be allowed to
8683 It is possible to arrange that the system administrator can
8684 reconfigure the package to correspond to their local
8685 security policy by changing the permissions on a binary:
8686 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8687 described below.<footnote>
8688 Ordinary files installed by <prgn>dpkg</prgn> (as
8689 opposed to <tt>conffile</tt>s and other similar objects)
8690 normally have their permissions reset to the distributed
8691 permissions when the package is reinstalled. However,
8692 the use of <prgn>dpkg-statoverride</prgn> overrides this
8695 Another method you should consider is to create a group for
8696 people allowed to use the program(s) and make any setuid
8697 executables executable only by that group.
8701 If you need to create a new user or group for your package
8702 there are two possibilities. Firstly, you may need to
8703 make some files in the binary package be owned by this
8704 user or group, or you may need to compile the user or
8705 group id (rather than just the name) into the binary
8706 (though this latter should be avoided if possible, as in
8707 this case you need a statically allocated id).</p>
8710 If you need a statically allocated id, you must ask for a
8711 user or group id from the <tt>base-passwd</tt> maintainer,
8712 and must not release the package until you have been
8713 allocated one. Once you have been allocated one you must
8714 either make the package depend on a version of the
8715 <tt>base-passwd</tt> package with the id present in
8716 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8717 your package to create the user or group itself with the
8718 correct id (using <tt>adduser</tt>) in its
8719 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8720 the <prgn>postinst</prgn> is to be preferred if it is
8721 possible, otherwise a pre-dependency will be needed on the
8722 <tt>adduser</tt> package.)
8726 On the other hand, the program might be able to determine
8727 the uid or gid from the user or group name at runtime, so
8728 that a dynamically allocated id can be used. In this case
8729 you should choose an appropriate user or group name,
8730 discussing this on <prgn>debian-devel</prgn> and checking
8731 with the <package/base-passwd/ maintainer that it is unique and that
8732 they do not wish you to use a statically allocated id
8733 instead. When this has been checked you must arrange for
8734 your package to create the user or group if necessary using
8735 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8736 <prgn>postinst</prgn> script (again, the latter is to be
8737 preferred if it is possible).
8741 Note that changing the numeric value of an id associated
8742 with a name is very difficult, and involves searching the
8743 file system for all appropriate files. You need to think
8744 carefully whether a static or dynamic id is required, since
8745 changing your mind later will cause problems.
8748 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8750 This section is not intended as policy, but as a
8751 description of the use of <prgn>dpkg-statoverride</prgn>.
8755 If a system administrator wishes to have a file (or
8756 directory or other such thing) installed with owner and
8757 permissions different from those in the distributed Debian
8758 package, they can use the <prgn>dpkg-statoverride</prgn>
8759 program to instruct <prgn>dpkg</prgn> to use the different
8760 settings every time the file is installed. Thus the
8761 package maintainer should distribute the files with their
8762 normal permissions, and leave it for the system
8763 administrator to make any desired changes. For example, a
8764 daemon which is normally required to be setuid root, but
8765 in certain situations could be used without being setuid,
8766 should be installed setuid in the <tt>.deb</tt>. Then the
8767 local system administrator can change this if they wish.
8768 If there are two standard ways of doing it, the package
8769 maintainer can use <tt>debconf</tt> to find out the
8770 preference, and call <prgn>dpkg-statoverride</prgn> in the
8771 maintainer script if necessary to accommodate the system
8772 administrator's choice. Care must be taken during
8773 upgrades to not override an existing setting.
8777 Given the above, <prgn>dpkg-statoverride</prgn> is
8778 essentially a tool for system administrators and would not
8779 normally be needed in the maintainer scripts. There is
8780 one type of situation, though, where calls to
8781 <prgn>dpkg-statoverride</prgn> would be needed in the
8782 maintainer scripts, and that involves packages which use
8783 dynamically allocated user or group ids. In such a
8784 situation, something like the following idiom can be very
8785 helpful in the package's <prgn>postinst</prgn>, where
8786 <tt>sysuser</tt> is a dynamically allocated id:
8788 for i in /usr/bin/foo /usr/sbin/bar
8790 # only do something when no setting exists
8791 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8793 #include: debconf processing, question about foo and bar
8794 if [ "$RET" = "true" ] ; then
8795 dpkg-statoverride --update --add sysuser root 4755 $i
8800 The corresponding code to remove the override when the package
8803 for i in /usr/bin/foo /usr/sbin/bar
8805 if dpkg-statoverride --list $i >/dev/null 2>&1
8807 dpkg-statoverride --remove $i
8817 <chapt id="customized-programs">
8818 <heading>Customized programs</heading>
8820 <sect id="arch-spec">
8821 <heading>Architecture specification strings</heading>
8824 If a program needs to specify an <em>architecture specification
8825 string</em> in some place, it should select one of the strings
8826 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8827 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8828 part is sometimes elided, as when the OS is Linux.
8832 Note that we don't want to use
8833 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8834 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8835 since this would make our programs incompatible with other
8836 Linux distributions. We also don't use something like
8837 <tt><var>arch</var>-unknown-linux</tt>, since the
8838 <tt>unknown</tt> does not look very good.
8841 <sect1 id="arch-wildcard-spec">
8842 <heading>Architecture wildcards</heading>
8845 A package may specify an architecture wildcard. Architecture
8846 wildcards are in the format <tt>any</tt> (which matches every
8847 architecture), <tt><var>os</var></tt>-any, or
8848 any-<tt><var>cpu</var></tt>. <footnote>
8849 Internally, the package system normalizes the GNU triplets
8850 and the Debian arches into Debian arch triplets (which are
8851 kind of inverted GNU triplets), with the first component of
8852 the triplet representing the libc and ABI in use, and then
8853 does matching against those triplets. However, such
8854 triplets are an internal implementation detail that should
8855 not be used by packages directly. The libc and ABI portion
8856 is handled internally by the package system based on
8857 the <var>os</var> and <var>cpu</var>.
8864 <heading>Daemons</heading>
8867 The configuration files <file>/etc/services</file>,
8868 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8869 by the <prgn>netbase</prgn> package and must not be modified
8874 If a package requires a new entry in one of these files, the
8875 maintainer should get in contact with the
8876 <prgn>netbase</prgn> maintainer, who will add the entries
8877 and release a new version of the <prgn>netbase</prgn>
8882 The configuration file <file>/etc/inetd.conf</file> must not be
8883 modified by the package's scripts except via the
8884 <prgn>update-inetd</prgn> script or the
8885 <file>DebianNet.pm</file> Perl module. See their documentation
8886 for details on how to add entries.
8890 If a package wants to install an example entry into
8891 <file>/etc/inetd.conf</file>, the entry must be preceded with
8892 exactly one hash character (<tt>#</tt>). Such lines are
8893 treated as "commented out by user" by the
8894 <prgn>update-inetd</prgn> script and are not changed or
8895 activated during package updates.
8900 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8904 Some programs need to create pseudo-ttys. This should be done
8905 using Unix98 ptys if the C library supports it. The resulting
8906 program must not be installed setuid root, unless that
8907 is required for other functionality.
8911 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8912 <file>/var/log/lastlog</file> must be installed writable by
8913 group <tt>utmp</tt>. Programs which need to modify those
8914 files must be installed setgid <tt>utmp</tt>.
8919 <heading>Editors and pagers</heading>
8922 Some programs have the ability to launch an editor or pager
8923 program to edit or display a text document. Since there are
8924 lots of different editors and pagers available in the Debian
8925 distribution, the system administrator and each user should
8926 have the possibility to choose their preferred editor and
8931 In addition, every program should choose a good default
8932 editor/pager if none is selected by the user or system
8937 Thus, every program that launches an editor or pager must
8938 use the EDITOR or PAGER environment variable to determine
8939 the editor or pager the user wishes to use. If these
8940 variables are not set, the programs <file>/usr/bin/editor</file>
8941 and <file>/usr/bin/pager</file> should be used, respectively.
8945 These two files are managed through the <prgn>dpkg</prgn>
8946 "alternatives" mechanism. Every package providing an editor or
8947 pager must call the <prgn>update-alternatives</prgn> script to
8948 register as an alternative for <file>/usr/bin/editor</file>
8949 or <file>/usr/bin/pager</file> as appropriate. The alternative
8950 should have a slave alternative
8951 for <file>/usr/share/man/man1/editor.1.gz</file>
8952 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8953 corresponding manual page.
8957 If it is very hard to adapt a program to make use of the
8958 EDITOR or PAGER variables, that program may be configured to
8959 use <file>/usr/bin/sensible-editor</file> and
8960 <file>/usr/bin/sensible-pager</file> as the editor or pager
8961 program respectively. These are two scripts provided in the
8962 <package>sensible-utils</package> package that check the EDITOR
8963 and PAGER variables and launch the appropriate program, and fall
8964 back to <file>/usr/bin/editor</file>
8965 and <file>/usr/bin/pager</file> if the variable is not set.
8969 A program may also use the VISUAL environment variable to
8970 determine the user's choice of editor. If it exists, it
8971 should take precedence over EDITOR. This is in fact what
8972 <file>/usr/bin/sensible-editor</file> does.
8976 It is not required for a package to depend on
8977 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8978 package to provide such virtual packages.<footnote>
8979 The Debian base system already provides an editor and a
8985 <sect id="web-appl">
8986 <heading>Web servers and applications</heading>
8989 This section describes the locations and URLs that should
8990 be used by all web servers and web applications in the
8997 Cgi-bin executable files are installed in the
8999 <example compact="compact">
9000 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9002 or a subdirectory of that directory, and should be
9004 <example compact="compact">
9005 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9007 (possibly with a subdirectory name
9008 before <var>cgi-bin-name</var>).
9012 <p>Access to HTML documents</p>
9015 HTML documents for a package are stored in
9016 <file>/usr/share/doc/<var>package</var></file>
9017 and can be referred to as
9018 <example compact="compact">
9019 http://localhost/doc/<var>package</var>/<var>filename</var>
9024 The web server should restrict access to the document
9025 tree so that only clients on the same host can read
9026 the documents. If the web server does not support such
9027 access controls, then it should not provide access at
9028 all, or ask about providing access during installation.
9033 <p>Access to images</p>
9035 It is recommended that images for a package be stored
9036 in <tt>/usr/share/images/<var>package</var></tt> and
9037 may be referred to through an alias <tt>/images/</tt>
9040 http://localhost/images/<package>/<filename>
9047 <p>Web Document Root</p>
9050 Web Applications should try to avoid storing files in
9051 the Web Document Root. Instead they should use the
9052 /usr/share/doc/<var>package</var> directory for
9053 documents and register the Web Application via the
9054 <package>doc-base</package> package. If access to the
9055 web document root is unavoidable then use
9056 <example compact="compact">
9059 as the Document Root. This might be just a symbolic
9060 link to the location where the system administrator
9061 has put the real document root.
9064 <item><p>Providing httpd and/or httpd-cgi</p>
9066 All web servers should provide the virtual package
9067 <tt>httpd</tt>. If a web server has CGI support it should
9068 provide <tt>httpd-cgi</tt> additionally.
9071 All web applications which do not contain CGI scripts should
9072 depend on <tt>httpd</tt>, all those web applications which
9073 <tt>do</tt> contain CGI scripts, should depend on
9081 <sect id="mail-transport-agents">
9082 <heading>Mail transport, delivery and user agents</heading>
9085 Debian packages which process electronic mail, whether mail
9086 user agents (MUAs) or mail transport agents (MTAs), must
9087 ensure that they are compatible with the configuration
9088 decisions below. Failure to do this may result in lost
9089 mail, broken <tt>From:</tt> lines, and other serious brain
9094 The mail spool is <file>/var/mail</file> and the interface to
9095 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9096 the FHS). On older systems, the mail spool may be
9097 physically located in <file>/var/spool/mail</file>, but all
9098 access to the mail spool should be via the
9099 <file>/var/mail</file> symlink. The mail spool is part of the
9100 base system and not part of the MTA package.
9104 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9105 programs (such as IMAP daemons) must lock the mailbox in an
9106 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9107 be combined with dot locking. To avoid deadlocks, a program
9108 should use <tt>fcntl()</tt> first and dot locking after
9109 this, or alternatively implement the two locking methods in
9110 a non blocking way<footnote>
9111 If it is not possible to establish both locks, the
9112 system shouldn't wait for the second lock to be
9113 established, but remove the first lock, wait a (random)
9114 time, and start over locking again.
9115 </footnote>. Using the functions <tt>maillock</tt> and
9116 <tt>mailunlock</tt> provided by the
9117 <tt>liblockfile*</tt><footnote>
9118 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9119 to use these functions.
9120 </footnote> packages is the recommended way to realize this.
9124 Mailboxes are generally either mode 600 and owned by
9125 <var>user</var> or mode 660 and owned by
9126 <tt><var>user</var>:mail</tt><footnote>
9127 There are two traditional permission schemes for mail spools:
9128 mode 600 with all mail delivery done by processes running as
9129 the destination user, or mode 660 and owned by group mail with
9130 mail delivery done by a process running as a system user in
9131 group mail. Historically, Debian required mode 660 mail
9132 spools to enable the latter model, but that model has become
9133 increasingly uncommon and the principle of least privilege
9134 indicates that mail systems that use the first model should
9135 use permissions of 600. If delivery to programs is permitted,
9136 it's easier to keep the mail system secure if the delivery
9137 agent runs as the destination user. Debian Policy therefore
9138 permits either scheme.
9139 </footnote>. The local system administrator may choose a
9140 different permission scheme; packages should not make
9141 assumptions about the permission and ownership of mailboxes
9142 unless required (such as when creating a new mailbox). A MUA
9143 may remove a mailbox (unless it has nonstandard permissions) in
9144 which case the MTA or another MUA must recreate it if needed.
9148 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9149 be setgid mail to do the locking mentioned above (and
9150 must obviously avoid accessing other users' mailboxes
9151 using this privilege).</p>
9154 <file>/etc/aliases</file> is the source file for the system mail
9155 aliases (e.g., postmaster, usenet, etc.), it is the one
9156 which the sysadmin and <prgn>postinst</prgn> scripts may
9157 edit. After <file>/etc/aliases</file> is edited the program or
9158 human editing it must call <prgn>newaliases</prgn>. All MTA
9159 packages must come with a <prgn>newaliases</prgn> program,
9160 even if it does nothing, but older MTA packages did not do
9161 this so programs should not fail if <prgn>newaliases</prgn>
9162 cannot be found. Note that because of this, all MTA
9163 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9164 <tt>Replaces: mail-transport-agent</tt> control fields.
9168 The convention of writing <tt>forward to
9169 <var>address</var></tt> in the mailbox itself is not
9170 supported. Use a <tt>.forward</tt> file instead.</p>
9173 The <prgn>rmail</prgn> program used by UUCP
9174 for incoming mail should be <file>/usr/sbin/rmail</file>.
9175 Likewise, <prgn>rsmtp</prgn>, for receiving
9176 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9180 If your package needs to know what hostname to use on (for
9181 example) outgoing news and mail messages which are generated
9182 locally, you should use the file <file>/etc/mailname</file>. It
9183 will contain the portion after the username and <tt>@</tt>
9184 (at) sign for email addresses of users on the machine
9185 (followed by a newline).
9189 Such a package should check for the existence of this file
9190 when it is being configured. If it exists, it should be
9191 used without comment, although an MTA's configuration script
9192 may wish to prompt the user even if it finds that this file
9193 exists. If the file does not exist, the package should
9194 prompt the user for the value (preferably using
9195 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9196 as well as using it in the package's configuration. The
9197 prompt should make it clear that the name will not just be
9198 used by that package. For example, in this situation the
9199 <tt>inn</tt> package could say something like:
9200 <example compact="compact">
9201 Please enter the "mail name" of your system. This is the
9202 hostname portion of the address to be shown on outgoing
9203 news and mail messages. The default is
9204 <var>syshostname</var>, your system's host name. Mail
9205 name ["<var>syshostname</var>"]:
9207 where <var>syshostname</var> is the output of <tt>hostname
9213 <heading>News system configuration</heading>
9216 All the configuration files related to the NNTP (news)
9217 servers and clients should be located under
9218 <file>/etc/news</file>.</p>
9221 There are some configuration issues that apply to a number
9222 of news clients and server packages on the machine. These
9226 <tag><file>/etc/news/organization</file></tag>
9228 A string which should appear as the
9229 organization header for all messages posted
9230 by NNTP clients on the machine
9233 <tag><file>/etc/news/server</file></tag>
9235 Contains the FQDN of the upstream NNTP
9236 server, or localhost if the local machine is
9241 Other global files may be added as required for cross-package news
9248 <heading>Programs for the X Window System</heading>
9251 <heading>Providing X support and package priorities</heading>
9254 Programs that can be configured with support for the X
9255 Window System must be configured to do so and must declare
9256 any package dependencies necessary to satisfy their
9257 runtime requirements when using the X Window System. If
9258 such a package is of higher priority than the X packages
9259 on which it depends, it is required that either the
9260 X-specific components be split into a separate package, or
9261 that an alternative version of the package, which includes
9262 X support, be provided, or that the package's priority be
9268 <heading>Packages providing an X server</heading>
9271 Packages that provide an X server that, directly or
9272 indirectly, communicates with real input and display
9273 hardware should declare in their <tt>Provides</tt> control
9274 field that they provide the virtual
9275 package <tt>xserver</tt>.<footnote>
9276 This implements current practice, and provides an
9277 actual policy for usage of the <tt>xserver</tt>
9278 virtual package which appears in the virtual packages
9279 list. In a nutshell, X servers that interface
9280 directly with the display and input hardware or via
9281 another subsystem (e.g., GGI) should provide
9282 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9283 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9289 <heading>Packages providing a terminal emulator</heading>
9292 Packages that provide a terminal emulator for the X Window
9293 System which meet the criteria listed below should declare in
9294 their <tt>Provides</tt> control field that they provide the
9295 virtual package <tt>x-terminal-emulator</tt>. They should
9296 also register themselves as an alternative for
9297 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9298 20. That alternative should have a slave alternative
9299 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9300 pointing to the corresponding manual page.
9304 To be an <tt>x-terminal-emulator</tt>, a program must:
9305 <list compact="compact">
9307 Be able to emulate a DEC VT100 terminal, or a
9308 compatible terminal.
9312 Support the command-line option <tt>-e
9313 <var>command</var></tt>, which creates a new
9314 terminal window<footnote>
9315 "New terminal window" does not necessarily mean
9316 a new top-level X window directly parented by
9317 the window manager; it could, if the terminal
9318 emulator application were so coded, be a new
9319 "view" in a multiple-document interface (MDI).
9321 and runs the specified <var>command</var>,
9322 interpreting the entirety of the rest of the command
9323 line as a command to pass straight to exec, in the
9324 manner that <tt>xterm</tt> does.
9328 Support the command-line option <tt>-T
9329 <var>title</var></tt>, which creates a new terminal
9330 window with the window title <var>title</var>.
9337 <heading>Packages providing a window manager</heading>
9340 Packages that provide a window manager should declare in
9341 their <tt>Provides</tt> control field that they provide the
9342 virtual package <tt>x-window-manager</tt>. They should also
9343 register themselves as an alternative for
9344 <file>/usr/bin/x-window-manager</file>, with a priority
9345 calculated as follows:
9346 <list compact="compact">
9348 Start with a priority of 20.
9352 If the window manager supports the Debian menu
9353 system, add 20 points if this support is available
9354 in the package's default configuration (i.e., no
9355 configuration files belonging to the system or user
9356 have to be edited to activate the feature); if
9357 configuration files must be modified, add only 10
9363 If the window manager complies with <url
9364 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9365 name="The Window Manager Specification Project">,
9366 written by the <url id="http://www.freedesktop.org/wiki/"
9367 name="Free Desktop Group">, add 40 points.
9371 If the window manager permits the X session to be
9372 restarted using a <em>different</em> window manager
9373 (without killing the X server) in its default
9374 configuration, add 10 points; otherwise add none.
9377 That alternative should have a slave alternative
9378 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9379 pointing to the corresponding manual page.
9384 <heading>Packages providing fonts</heading>
9387 Packages that provide fonts for the X Window
9389 For the purposes of Debian Policy, a "font for the X
9390 Window System" is one which is accessed via X protocol
9391 requests. Fonts for the Linux console, for PostScript
9392 renderer, or any other purpose, do not fit this
9393 definition. Any tool which makes such fonts available
9394 to the X Window System, however, must abide by this
9397 must do a number of things to ensure that they are both
9398 available without modification of the X or font server
9399 configuration, and that they do not corrupt files used by
9400 other font packages to register information about
9404 Fonts of any type supported by the X Window System
9405 must be in a separate binary package from any
9406 executables, libraries, or documentation (except
9407 that specific to the fonts shipped, such as their
9408 license information). If one or more of the fonts
9409 so packaged are necessary for proper operation of
9410 the package with which they are associated the font
9411 package may be Recommended; if the fonts merely
9412 provide an enhancement, a Suggests relationship may
9413 be used. Packages must not Depend on font
9415 This is because the X server may retrieve fonts
9416 from the local file system or over the network
9417 from an X font server; the Debian package system
9418 is empowered to deal only with the local
9424 BDF fonts must be converted to PCF fonts with the
9425 <prgn>bdftopcf</prgn> utility (available in the
9426 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9427 placed in a directory that corresponds to their
9429 <list compact="compact">
9431 100 dpi fonts must be placed in
9432 <file>/usr/share/fonts/X11/100dpi/</file>.
9436 75 dpi fonts must be placed in
9437 <file>/usr/share/fonts/X11/75dpi/</file>.
9441 Character-cell fonts, cursor fonts, and other
9442 low-resolution fonts must be placed in
9443 <file>/usr/share/fonts/X11/misc/</file>.
9449 Type 1 fonts must be placed in
9450 <file>/usr/share/fonts/X11/Type1/</file>. If font
9451 metric files are available, they must be placed here
9456 Subdirectories of <file>/usr/share/fonts/X11/</file>
9457 other than those listed above must be neither
9458 created nor used. (The <file>PEX</file>, <file>CID</file>,
9459 <file>Speedo</file>, and <file>cyrillic</file> directories
9460 are excepted for historical reasons, but installation of
9461 files into these directories remains discouraged.)
9465 Font packages may, instead of placing files directly
9466 in the X font directories listed above, provide
9467 symbolic links in that font directory pointing to
9468 the files' actual location in the filesystem. Such
9469 a location must comply with the FHS.
9473 Font packages should not contain both 75dpi and
9474 100dpi versions of a font. If both are available,
9475 they should be provided in separate binary packages
9476 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9477 the names of the packages containing the
9478 corresponding fonts.
9482 Fonts destined for the <file>misc</file> subdirectory
9483 should not be included in the same package as 75dpi
9484 or 100dpi fonts; instead, they should be provided in
9485 a separate package with <tt>-misc</tt> appended to
9490 Font packages must not provide the files
9491 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9492 <file>fonts.scale</file> in a font directory:
9495 <file>fonts.dir</file> files must not be provided at all.
9499 <file>fonts.alias</file> and <file>fonts.scale</file>
9500 files, if needed, should be provided in the
9502 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9503 where <var>fontdir</var> is the name of the
9505 <file>/usr/share/fonts/X11/</file> where the
9506 package's corresponding fonts are stored
9507 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9508 <var>package</var> is the name of the package
9509 that provides these fonts, and
9510 <var>extension</var> is either <tt>scale</tt>
9511 or <tt>alias</tt>, whichever corresponds to
9518 Font packages must declare a dependency on
9519 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9520 or <tt>Pre-Depends</tt> control field.
9524 Font packages that provide one or more
9525 <file>fonts.scale</file> files as described above must
9526 invoke <prgn>update-fonts-scale</prgn> on each
9527 directory into which they installed fonts
9528 <em>before</em> invoking
9529 <prgn>update-fonts-dir</prgn> on that directory.
9530 This invocation must occur in both the
9531 <prgn>postinst</prgn> (for all arguments) and
9532 <prgn>postrm</prgn> (for all arguments except
9533 <tt>upgrade</tt>) scripts.
9537 Font packages that provide one or more
9538 <file>fonts.alias</file> files as described above must
9539 invoke <prgn>update-fonts-alias</prgn> on each
9540 directory into which they installed fonts. This
9541 invocation must occur in both the
9542 <prgn>postinst</prgn> (for all arguments) and
9543 <prgn>postrm</prgn> (for all arguments except
9544 <tt>upgrade</tt>) scripts.
9548 Font packages must invoke
9549 <prgn>update-fonts-dir</prgn> on each directory into
9550 which they installed fonts. This invocation must
9551 occur in both the <prgn>postinst</prgn> (for all
9552 arguments) and <prgn>postrm</prgn> (for all
9553 arguments except <tt>upgrade</tt>) scripts.
9557 Font packages must not provide alias names for the
9558 fonts they include which collide with alias names
9559 already in use by fonts already packaged.
9563 Font packages must not provide fonts with the same
9564 XLFD registry name as another font already packaged.
9570 <sect1 id="appdefaults">
9571 <heading>Application defaults files</heading>
9574 Application defaults files must be installed in the
9575 directory <file>/etc/X11/app-defaults/</file> (use of a
9576 localized subdirectory of <file>/etc/X11/</file> as described
9577 in the <em>X Toolkit Intrinsics - C Language
9578 Interface</em> manual is also permitted). They must be
9579 registered as <tt>conffile</tt>s or handled as
9580 configuration files.
9584 Customization of programs' X resources may also be
9585 supported with the provision of a file with the same name
9586 as that of the package placed in
9587 the <file>/etc/X11/Xresources/</file> directory, which
9588 must be registered as a <tt>conffile</tt> or handled as a
9589 configuration file.<footnote>
9590 Note that this mechanism is not the same as using
9591 app-defaults; app-defaults are tied to the client
9592 binary on the local file system, whereas X resources
9593 are stored in the X server and affect all connecting
9600 <heading>Installation directory issues</heading>
9603 Historically, packages using the X Window System used a
9604 separate set of installation directories from other packages.
9605 This practice has been discontinued and packages using the X
9606 Window System should now generally be installed in the same
9607 directories as any other package. Specifically, packages must
9608 not install files under the <file>/usr/X11R6/</file> directory
9609 and the <file>/usr/X11R6/</file> directory hierarchy should be
9610 regarded as obsolete.
9614 Include files previously installed under
9615 <file>/usr/X11R6/include/X11/</file> should be installed into
9616 <file>/usr/include/X11/</file>. For files previously
9617 installed into subdirectories of
9618 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9619 determine if subdirectories of <file>/usr/lib/</file> and
9620 <file>/usr/share/</file> can be used. If not, a subdirectory
9621 of <file>/usr/lib/X11/</file> should be used.
9625 Configuration files for window, display, or session managers
9626 or other applications that are tightly integrated with the X
9627 Window System may be placed in a subdirectory
9628 of <file>/etc/X11/</file> corresponding to the package name.
9629 Other X Window System applications should use
9630 the <file>/etc/</file> directory unless otherwise mandated by
9631 policy (such as for <ref id="appdefaults">).
9637 <heading>Perl programs and modules</heading>
9640 Perl programs and modules should follow the current Perl policy.
9644 The Perl policy can be found in the <tt>perl-policy</tt>
9645 files in the <tt>debian-policy</tt> package.
9646 It is also available from the Debian web mirrors at
9647 <tt><url name="/doc/packaging-manuals/perl-policy/"
9648 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9653 <heading>Emacs lisp programs</heading>
9656 Please refer to the "Debian Emacs Policy" for details of how to
9657 package emacs lisp programs.
9661 The Emacs policy is available in
9662 <file>debian-emacs-policy.gz</file> of the
9663 <package>emacsen-common</package> package.
9664 It is also available from the Debian web mirrors at
9665 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9666 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9671 <heading>Games</heading>
9674 The permissions on <file>/var/games</file> are mode 755, owner
9675 <tt>root</tt> and group <tt>root</tt>.
9679 Each game decides on its own security policy.</p>
9682 Games which require protected, privileged access to
9683 high-score files, saved games, etc., may be made
9684 set-<em>group</em>-id (mode 2755) and owned by
9685 <tt>root:games</tt>, and use files and directories with
9686 appropriate permissions (770 <tt>root:games</tt>, for
9687 example). They must not be made
9688 set-<em>user</em>-id, as this causes security problems. (If
9689 an attacker can subvert any set-user-id game they can
9690 overwrite the executable of any other, causing other players
9691 of these games to run a Trojan horse program. With a
9692 set-group-id game the attacker only gets access to less
9693 important game data, and if they can get at the other
9694 players' accounts at all it will take considerably more
9698 Some packages, for example some fortune cookie programs, are
9699 configured by the upstream authors to install with their
9700 data files or other static information made unreadable so
9701 that they can only be accessed through set-id programs
9702 provided. You should not do this in a Debian package: anyone can
9703 download the <file>.deb</file> file and read the data from it,
9704 so there is no point making the files unreadable. Not
9705 making the files unreadable also means that you don't have
9706 to make so many programs set-id, which reduces the risk of a
9710 As described in the FHS, binaries of games should be
9711 installed in the directory <file>/usr/games</file>. This also
9712 applies to games that use the X Window System. Manual pages
9713 for games (X and non-X games) should be installed in
9714 <file>/usr/share/man/man6</file>.</p>
9720 <heading>Documentation</heading>
9723 <heading>Manual pages</heading>
9726 You should install manual pages in <prgn>nroff</prgn> source
9727 form, in appropriate places under <file>/usr/share/man</file>.
9728 You should only use sections 1 to 9 (see the FHS for more
9729 details). You must not install a pre-formatted "cat page".
9733 Each program, utility, and function should have an
9734 associated manual page included in the same package. It is
9735 suggested that all configuration files also have a manual
9736 page included as well. Manual pages for protocols and other
9737 auxiliary things are optional.
9741 If no manual page is available, this is considered as a bug
9742 and should be reported to the Debian Bug Tracking System (the
9743 maintainer of the package is allowed to write this bug report
9744 themselves, if they so desire). Do not close the bug report
9745 until a proper man page is available.<footnote>
9746 It is not very hard to write a man page. See the
9747 <url id="http://www.schweikhardt.net/man_page_howto.html"
9748 name="Man-Page-HOWTO">,
9749 <manref name="man" section="7">, the examples created
9750 by <prgn>dh_make</prgn>, the helper
9751 program <prgn>help2man</prgn>, or the
9752 directory <file>/usr/share/doc/man-db/examples</file>.
9757 You may forward a complaint about a missing man page to the
9758 upstream authors, and mark the bug as forwarded in the
9759 Debian bug tracking system. Even though the GNU Project do
9760 not in general consider the lack of a man page to be a bug,
9761 we do; if they tell you that they don't consider it a bug
9762 you should leave the bug in our bug tracking system open
9767 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9771 If one man page needs to be accessible via several names it
9772 is better to use a symbolic link than the <file>.so</file>
9773 feature, but there is no need to fiddle with the relevant
9774 parts of the upstream source to change from <file>.so</file> to
9775 symlinks: don't do it unless it's easy. You should not
9776 create hard links in the manual page directories, nor put
9777 absolute filenames in <file>.so</file> directives. The filename
9778 in a <file>.so</file> in a man page should be relative to the
9779 base of the man page tree (usually
9780 <file>/usr/share/man</file>). If you do not create any links
9781 (whether symlinks, hard links, or <tt>.so</tt> directives)
9782 in the file system to the alternate names of the man page,
9783 then you should not rely on <prgn>man</prgn> finding your
9784 man page under those names based solely on the information in
9785 the man page's header.<footnote>
9786 Supporting this in <prgn>man</prgn> often requires
9787 unreasonable processing time to find a manual page or to
9788 report that none exists, and moves knowledge into man's
9789 database that would be better left in the file system.
9790 This support is therefore deprecated and will cease to
9791 be present in the future.
9796 Manual pages in locale-specific subdirectories of
9797 <file>/usr/share/man</file> should use either UTF-8 or the usual
9798 legacy encoding for that language (normally the one corresponding
9799 to the shortest relevant locale name in
9800 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9801 <file>/usr/share/man/fr</file> should use either UTF-8 or
9802 ISO-8859-1.<footnote>
9803 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9804 use. In future, all manual pages will be required to use
9810 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9811 included in the subdirectory name unless it indicates a
9812 significant difference in the language, as this excludes
9813 speakers of the language in other countries.<footnote>
9814 At the time of writing, Chinese and Portuguese are the main
9815 languages with such differences, so <file>pt_BR</file>,
9816 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9821 If a localized version of a manual page is provided, it should
9822 either be up-to-date or it should be obvious to the reader that
9823 it is outdated and the original manual page should be used
9824 instead. This can be done either by a note at the beginning of
9825 the manual page or by showing the missing or changed portions in
9826 the original language instead of the target language.
9831 <heading>Info documents</heading>
9834 Info documents should be installed in <file>/usr/share/info</file>.
9835 They should be compressed with <tt>gzip -9</tt>.
9839 The <prgn>install-info</prgn> program maintains a directory of
9840 installed info documents in <file>/usr/share/info/dir</file> for
9841 the use of info readers.<footnote>
9842 It was previously necessary for packages installing info
9843 documents to run <prgn>install-info</prgn> from maintainer
9844 scripts. This is no longer necessary. The installation
9845 system now uses dpkg triggers.
9847 This file must not be included in packages. Packages containing
9848 info documents should depend on <tt>dpkg (>= 1.15.4) |
9849 install-info</tt> to ensure that the directory file is properly
9850 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9855 Info documents should contain section and directory entry
9856 information in the document for the use
9857 of <prgn>install-info</prgn>. The section should be specified
9858 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9859 space and the section of this info page. The directory entry or
9860 entries should be included between
9861 a <tt>START-INFO-DIR-ENTRY</tt> line and
9862 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9864 INFO-DIR-SECTION Individual utilities
9865 START-INFO-DIR-ENTRY
9866 * example: (example). An example info directory entry.
9869 To determine which section to use, you should look
9870 at <file>/usr/share/info/dir</file> on your system and choose
9871 the most relevant (or create a new section if none of the
9872 current sections are relevant).<footnote>
9873 Normally, info documents are generated from Texinfo source.
9874 To include this information in the generated info document, if
9875 it is absent, add commands like:
9877 @dircategory Individual utilities
9879 * example: (example). An example info directory entry.
9882 to the Texinfo source of the document and ensure that the info
9883 documents are rebuilt from source during the package build.
9889 <heading>Additional documentation</heading>
9892 Any additional documentation that comes with the package may
9893 be installed at the discretion of the package maintainer.
9894 Plain text documentation should be installed in the directory
9895 <file>/usr/share/doc/<var>package</var></file>, where
9896 <var>package</var> is the name of the package, and
9897 compressed with <tt>gzip -9</tt> unless it is small.
9901 If a package comes with large amounts of documentation which
9902 many users of the package will not require you should create
9903 a separate binary package to contain it, so that it does not
9904 take up disk space on the machines of users who do not need
9905 or want it installed.</p>
9908 It is often a good idea to put text information files
9909 (<file>README</file>s, changelogs, and so forth) that come with
9910 the source package in <file>/usr/share/doc/<var>package</var></file>
9911 in the binary package. However, you don't need to install
9912 the instructions for building and installing the package, of
9916 Packages must not require the existence of any files in
9917 <file>/usr/share/doc/</file> in order to function
9919 The system administrator should be able to
9920 delete files in <file>/usr/share/doc/</file> without causing
9921 any programs to break.
9923 Any files that are referenced by programs but are also
9924 useful as stand alone documentation should be installed under
9925 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9926 <file>/usr/share/doc/<var>package</var></file>.
9930 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9931 link to another directory in <file>/usr/share/doc</file> only if
9932 the two packages both come from the same source and the
9933 first package Depends on the second.<footnote>
9935 Please note that this does not override the section on
9936 changelog files below, so the file
9937 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9938 must refer to the changelog for the current version of
9939 <var>package</var> in question. In practice, this means
9940 that the sources of the target and the destination of the
9941 symlink must be the same (same source package and
9948 Former Debian releases placed all additional documentation
9949 in <file>/usr/doc/<var>package</var></file>. This has been
9950 changed to <file>/usr/share/doc/<var>package</var></file>,
9951 and packages must not put documentation in the directory
9952 <file>/usr/doc/<var>package</var></file>. <footnote>
9953 At this phase of the transition, we no longer require a
9954 symbolic link in <file>/usr/doc/</file>. At a later point,
9955 policy shall change to make the symbolic links a bug.
9961 <heading>Preferred documentation formats</heading>
9964 The unification of Debian documentation is being carried out
9968 If your package comes with extensive documentation in a
9969 markup format that can be converted to various other formats
9970 you should if possible ship HTML versions in a binary
9971 package, in the directory
9972 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9973 its subdirectories.<footnote>
9974 The rationale: The important thing here is that HTML
9975 docs should be available in <em>some</em> package, not
9976 necessarily in the main binary package.
9981 Other formats such as PostScript may be provided at the
9982 package maintainer's discretion.
9986 <sect id="copyrightfile">
9987 <heading>Copyright information</heading>
9990 Every package must be accompanied by a verbatim copy of its
9991 copyright information and distribution license in the file
9992 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9993 file must neither be compressed nor be a symbolic link.
9997 In addition, the copyright file must say where the upstream
9998 sources (if any) were obtained, and should name the original
10003 Packages in the <em>contrib</em> or <em>non-free</em> archive
10004 areas should state in the copyright file that the package is not
10005 part of the Debian distribution and briefly explain why.
10009 A copy of the file which will be installed in
10010 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10011 be in <file>debian/copyright</file> in the source package.
10015 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10016 link to another directory in <file>/usr/share/doc</file> only if
10017 the two packages both come from the same source and the
10018 first package Depends on the second. These rules are important
10019 because <file>copyright</file> files must be extractable by
10024 Packages distributed under the Apache license (version 2.0), the
10025 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10026 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10027 1.3) should refer to the corresponding files
10028 under <file>/usr/share/common-licenses</file>,<footnote>
10031 <file>/usr/share/common-licenses/Apache-2.0</file>,
10032 <file>/usr/share/common-licenses/Artistic</file>,
10033 <file>/usr/share/common-licenses/GPL-1</file>,
10034 <file>/usr/share/common-licenses/GPL-2</file>,
10035 <file>/usr/share/common-licenses/GPL-3</file>,
10036 <file>/usr/share/common-licenses/LGPL-2</file>,
10037 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10038 <file>/usr/share/common-licenses/LGPL-3</file>,
10039 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10040 <file>/usr/share/common-licenses/GFDL-1.3</file>
10041 respectively. The University of California BSD license is
10042 also included in <package>base-files</package> as
10043 <file>/usr/share/common-licenses/BSD</file>, but given the
10044 brevity of this license, its specificity to code whose
10045 copyright is held by the Regents of the University of
10046 California, and the frequency of minor wording changes, its
10047 text should be included in the copyright file rather than
10048 referencing this file.
10050 </footnote> rather than quoting them in the copyright
10055 You should not use the copyright file as a general <file>README</file>
10056 file. If your package has such a file it should be
10057 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10058 <file>README.Debian</file> or some other appropriate place.
10062 All copyright files must be encoded in UTF-8.
10065 <sect1 id="copyrightformat">
10066 <heading>Machine-readable copyright information</heading>
10069 A specification for a standard, machine-readable format
10070 for <file>debian/copyright</file> files is maintained as part
10071 of the <package>debian-policy</package> package. This
10072 document may be found in the <file>copyright-format</file>
10073 files in the <package>debian-policy</package> package. It is
10074 also available from the Debian web mirrors at
10075 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10076 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10080 Use of this format is optional.
10086 <heading>Examples</heading>
10089 Any examples (configurations, source files, whatever),
10090 should be installed in a directory
10091 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10092 files should not be referenced by any program: they're there
10093 for the benefit of the system administrator and users as
10094 documentation only. Architecture-specific example files
10095 should be installed in a directory
10096 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10098 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10099 latter directory itself may be a symbolic link to the
10104 If the purpose of a package is to provide examples, then the
10105 example files may be installed into
10106 <file>/usr/share/doc/<var>package</var></file>.
10110 <sect id="changelogs">
10111 <heading>Changelog files</heading>
10114 Packages that are not Debian-native must contain a
10115 compressed copy of the <file>debian/changelog</file> file from
10116 the Debian source tree in
10117 <file>/usr/share/doc/<var>package</var></file> with the name
10118 <file>changelog.Debian.gz</file>.
10122 If an upstream changelog is available, it should be accessible as
10123 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10124 plain text. If the upstream changelog is distributed in
10125 HTML, it should be made available in that form as
10126 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10127 and a plain text <file>changelog.gz</file> should be generated
10128 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10129 the upstream changelog files do not already conform to this
10130 naming convention, then this may be achieved either by
10131 renaming the files, or by adding a symbolic link, at the
10132 maintainer's discretion.<footnote>
10133 Rationale: People should not have to look in places for
10134 upstream changelogs merely because they are given
10135 different names or are distributed in HTML format.
10140 All of these files should be installed compressed using
10141 <tt>gzip -9</tt>, as they will become large with time even
10142 if they start out small.
10146 If the package has only one changelog which is used both as
10147 the Debian changelog and the upstream one because there is
10148 no separate upstream maintainer then that changelog should
10149 usually be installed as
10150 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10151 there is a separate upstream maintainer, but no upstream
10152 changelog, then the Debian changelog should still be called
10153 <file>changelog.Debian.gz</file>.
10157 For details about the format and contents of the Debian
10158 changelog file, please see <ref id="dpkgchangelog">.
10163 <appendix id="pkg-scope">
10164 <heading>Introduction and scope of these appendices</heading>
10167 These appendices are taken essentially verbatim from the
10168 now-deprecated Packaging Manual, version 3.2.1.0. They are
10169 the chapters which are likely to be of use to package
10170 maintainers and which have not already been included in the
10171 policy document itself. Most of these sections are very likely
10172 not relevant to policy; they should be treated as
10173 documentation for the packaging system. Please note that these
10174 appendices are included for convenience, and for historical
10175 reasons: they used to be part of policy package, and they have
10176 not yet been incorporated into dpkg documentation. However,
10177 they still have value, and hence they are presented here.
10181 They have not yet been checked to ensure that they are
10182 compatible with the contents of policy, and if there are any
10183 contradictions, the version in the main policy document takes
10184 precedence. The remaining chapters of the old Packaging
10185 Manual have also not been read in detail to ensure that there
10186 are not parts which have been left out. Both of these will be
10187 done in due course.
10191 Certain parts of the Packaging manual were integrated into the
10192 Policy Manual proper, and removed from the appendices. Links
10193 have been placed from the old locations to the new ones.
10197 <prgn>dpkg</prgn> is a suite of programs for creating binary
10198 package files and installing and removing them on Unix
10200 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10201 work on or be ported to other systems.
10206 The binary packages are designed for the management of
10207 installed executable programs (usually compiled binaries) and
10208 their associated data, though source code examples and
10209 documentation are provided as part of some packages.</p>
10212 This manual describes the technical aspects of creating Debian
10213 binary packages (<file>.deb</file> files). It documents the
10214 behavior of the package management programs
10215 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10216 they interact with packages.</p>
10219 It also documents the interaction between
10220 <prgn>dselect</prgn>'s core and the access method scripts it
10221 uses to actually install the selected packages, and describes
10222 how to create a new access method.</p>
10225 This manual does not go into detail about the options and
10226 usage of the package building and installation tools. It
10227 should therefore be read in conjunction with those programs'
10232 The utility programs which are provided with <prgn>dpkg</prgn>
10233 for managing various system configuration and similar issues,
10234 such as <prgn>update-rc.d</prgn> and
10235 <prgn>install-info</prgn>, are not described in detail here -
10236 please see their man pages.
10240 It is assumed that the reader is reasonably familiar with the
10241 <prgn>dpkg</prgn> System Administrators' manual.
10242 Unfortunately this manual does not yet exist.
10246 The Debian version of the FSF's GNU hello program is provided as
10247 an example for people wishing to create Debian packages. However,
10248 while the examples are helpful, they do not replace the need to
10249 read and follow the Policy and Programmer's Manual.</p>
10252 <appendix id="pkg-binarypkg">
10253 <heading>Binary packages (from old Packaging Manual)</heading>
10256 The binary package has two main sections. The first part
10257 consists of various control information files and scripts used
10258 by <prgn>dpkg</prgn> when installing and removing. See <ref
10259 id="pkg-controlarea">.
10263 The second part is an archive containing the files and
10264 directories to be installed.
10268 In the future binary packages may also contain other
10269 components, such as checksums and digital signatures. The
10270 format for the archive is described in full in the
10271 <file>deb(5)</file> man page.
10275 <sect id="pkg-bincreating"><heading>Creating package files -
10276 <prgn>dpkg-deb</prgn>
10280 All manipulation of binary package files is done by
10281 <prgn>dpkg-deb</prgn>; it's the only program that has
10282 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10283 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10284 will spot that the options requested are appropriate to
10285 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10290 In order to create a binary package you must make a
10291 directory tree which contains all the files and directories
10292 you want to have in the file system data part of the package.
10293 In Debian-format source packages this directory is usually
10294 <file>debian/tmp</file>, relative to the top of the package's
10299 They should have the locations (relative to the root of the
10300 directory tree you're constructing) ownerships and
10301 permissions which you want them to have on the system when
10302 they are installed.
10306 With current versions of <prgn>dpkg</prgn> the uid/username
10307 and gid/groupname mappings for the users and groups being
10308 used should be the same on the system where the package is
10309 built and the one where it is installed.
10313 You need to add one special directory to the root of the
10314 miniature file system tree you're creating:
10315 <prgn>DEBIAN</prgn>. It should contain the control
10316 information files, notably the binary package control file
10317 (see <ref id="pkg-controlfile">).
10321 The <prgn>DEBIAN</prgn> directory will not appear in the
10322 file system archive of the package, and so won't be installed
10323 by <prgn>dpkg</prgn> when the package is unpacked.
10327 When you've prepared the package, you should invoke:
10329 dpkg --build <var>directory</var>
10334 This will build the package in
10335 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10336 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10337 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10338 build the package.)
10342 See the man page <manref name="dpkg-deb" section="8"> for details of how
10343 to examine the contents of this newly-created file. You may find the
10344 output of following commands enlightening:
10346 dpkg-deb --info <var>filename</var>.deb
10347 dpkg-deb --contents <var>filename</var>.deb
10348 dpkg --contents <var>filename</var>.deb
10350 To view the copyright file for a package you could use this command:
10352 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10357 <sect id="pkg-controlarea">
10358 <heading>Package control information files</heading>
10361 The control information portion of a binary package is a
10362 collection of files with names known to <prgn>dpkg</prgn>.
10363 It will treat the contents of these files specially - some
10364 of them contain information used by <prgn>dpkg</prgn> when
10365 installing or removing the package; others are scripts which
10366 the package maintainer wants <prgn>dpkg</prgn> to run.
10370 It is possible to put other files in the package control
10371 information file area, but this is not generally a good idea
10372 (though they will largely be ignored).
10376 Here is a brief list of the control information files supported
10377 by <prgn>dpkg</prgn> and a summary of what they're used for.
10382 <tag><tt>control</tt>
10385 This is the key description file used by
10386 <prgn>dpkg</prgn>. It specifies the package's name
10387 and version, gives its description for the user,
10388 states its relationships with other packages, and so
10389 forth. See <ref id="sourcecontrolfiles"> and
10390 <ref id="binarycontrolfiles">.
10394 It is usually generated automatically from information
10395 in the source package by the
10396 <prgn>dpkg-gencontrol</prgn> program, and with
10397 assistance from <prgn>dpkg-shlibdeps</prgn>.
10398 See <ref id="pkg-sourcetools">.
10402 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10407 These are executable files (usually scripts) which
10408 <prgn>dpkg</prgn> runs during installation, upgrade
10409 and removal of packages. They allow the package to
10410 deal with matters which are particular to that package
10411 or require more complicated processing than that
10412 provided by <prgn>dpkg</prgn>. Details of when and
10413 how they are called are in <ref id="maintainerscripts">.
10417 It is very important to make these scripts idempotent.
10418 See <ref id="idempotency">.
10422 The maintainer scripts are not guaranteed to run with a
10423 controlling terminal and may not be able to interact with
10424 the user. See <ref id="controllingterminal">.
10428 <tag><tt>conffiles</tt>
10431 This file contains a list of configuration files which
10432 are to be handled automatically by <prgn>dpkg</prgn>
10433 (see <ref id="pkg-conffiles">). Note that not necessarily
10434 every configuration file should be listed here.
10437 <tag><tt>shlibs</tt>
10440 This file contains a list of the shared libraries
10441 supplied by the package, with dependency details for
10442 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10443 when it determines what dependencies are required in a
10444 package control file. The <tt>shlibs</tt> file format
10445 is described on <ref id="shlibs">.
10450 <sect id="pkg-controlfile">
10451 <heading>The main control information file: <tt>control</tt></heading>
10454 The most important control information file used by
10455 <prgn>dpkg</prgn> when it installs a package is
10456 <tt>control</tt>. It contains all the package's "vital
10461 The binary package control files of packages built from
10462 Debian sources are made by a special tool,
10463 <prgn>dpkg-gencontrol</prgn>, which reads
10464 <file>debian/control</file> and <file>debian/changelog</file> to
10465 find the information it needs. See <ref id="pkg-sourcepkg"> for
10470 The fields in binary package control files are listed in
10471 <ref id="binarycontrolfiles">.
10475 A description of the syntax of control files and the purpose
10476 of the fields is available in <ref id="controlfields">.
10481 <heading>Time Stamps</heading>
10484 See <ref id="timestamps">.
10489 <appendix id="pkg-sourcepkg">
10490 <heading>Source packages (from old Packaging Manual) </heading>
10493 The Debian binary packages in the distribution are generated
10494 from Debian sources, which are in a special format to assist
10495 the easy and automatic building of binaries.
10498 <sect id="pkg-sourcetools">
10499 <heading>Tools for processing source packages</heading>
10502 Various tools are provided for manipulating source packages;
10503 they pack and unpack sources and help build of binary
10504 packages and help manage the distribution of new versions.
10508 They are introduced and typical uses described here; see
10509 <manref name="dpkg-source" section="1"> for full
10510 documentation about their arguments and operation.
10514 For examples of how to construct a Debian source package,
10515 and how to use those utilities that are used by Debian
10516 source packages, please see the <prgn>hello</prgn> example
10520 <sect1 id="pkg-dpkg-source">
10522 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10527 This program is frequently used by hand, and is also
10528 called from package-independent automated building scripts
10529 such as <prgn>dpkg-buildpackage</prgn>.
10533 To unpack a package it is typically invoked with
10535 dpkg-source -x <var>.../path/to/filename</var>.dsc
10540 with the <file><var>filename</var>.tar.gz</file> and
10541 <file><var>filename</var>.diff.gz</file> (if applicable) in
10542 the same directory. It unpacks into
10543 <file><var>package</var>-<var>version</var></file>, and if
10545 <file><var>package</var>-<var>version</var>.orig</file>, in
10546 the current directory.
10550 To create a packed source archive it is typically invoked:
10552 dpkg-source -b <var>package</var>-<var>version</var>
10557 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10558 <file>.diff.gz</file> (if appropriate) in the current
10559 directory. <prgn>dpkg-source</prgn> does not clean the
10560 source tree first - this must be done separately if it is
10565 See also <ref id="pkg-sourcearchives">.</p>
10569 <sect1 id="pkg-dpkg-buildpackage">
10571 <prgn>dpkg-buildpackage</prgn> - overall package-building
10576 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10577 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10578 targets <tt>clean</tt>, <tt>build</tt> and
10579 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10580 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10581 source and binary package upload.
10585 It is usually invoked by hand from the top level of the
10586 built or unbuilt source directory. It may be invoked with
10587 no arguments; useful arguments include:
10588 <taglist compact="compact">
10589 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10592 Do not sign the <tt>.changes</tt> file or the
10593 source package <tt>.dsc</tt> file, respectively.</p>
10595 <tag><tt>-p<var>sign-command</var></tt></tag>
10598 Invoke <var>sign-command</var> instead of finding
10599 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10600 <var>sign-command</var> must behave just like
10601 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10603 <tag><tt>-r<var>root-command</var></tt></tag>
10606 When root privilege is required, invoke the command
10607 <var>root-command</var>. <var>root-command</var>
10608 should invoke its first argument as a command, from
10609 the <prgn>PATH</prgn> if necessary, and pass its
10610 second and subsequent arguments to the command it
10611 calls. If no <var>root-command</var> is supplied
10612 then <var>dpkg-buildpackage</var> will use
10613 the <prgn>fakeroot</prgn> command, which is sufficient
10614 to build most packages without actually requiring root
10617 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10620 Two types of binary-only build and upload - see
10621 <manref name="dpkg-source" section="1">.
10628 <sect1 id="pkg-dpkg-gencontrol">
10630 <prgn>dpkg-gencontrol</prgn> - generates binary package
10635 This program is usually called from <file>debian/rules</file>
10636 (see <ref id="pkg-sourcetree">) in the top level of the source
10641 This is usually done just before the files and directories in the
10642 temporary directory tree where the package is being built have their
10643 permissions and ownerships set and the package is constructed using
10644 <prgn>dpkg-deb/</prgn>
10646 This is so that the control file which is produced has
10647 the right permissions
10652 <prgn>dpkg-gencontrol</prgn> must be called after all the
10653 files which are to go into the package have been placed in
10654 the temporary build directory, so that its calculation of
10655 the installed size of a package is correct.
10659 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10660 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10661 variable substitutions created by
10662 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10667 For a package which generates only one binary package, and
10668 which builds it in <file>debian/tmp</file> relative to the top
10669 of the source package, it is usually sufficient to call
10670 <prgn>dpkg-gencontrol</prgn>.
10674 Sources which build several binaries will typically need
10677 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10678 </example> The <tt>-P</tt> tells
10679 <prgn>dpkg-gencontrol</prgn> that the package is being
10680 built in a non-default directory, and the <tt>-p</tt>
10681 tells it which package's control file should be generated.
10685 <prgn>dpkg-gencontrol</prgn> also adds information to the
10686 list of files in <file>debian/files</file>, for the benefit of
10687 (for example) a future invocation of
10688 <prgn>dpkg-genchanges</prgn>.</p>
10691 <sect1 id="pkg-dpkg-shlibdeps">
10693 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10698 This program is usually called from <file>debian/rules</file>
10699 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10700 id="pkg-sourcetree">), in the top level of the source tree.
10704 Its arguments are executables and shared libraries
10707 They may be specified either in the locations in the
10708 source tree where they are created or in the locations
10709 in the temporary build tree where they are installed
10710 prior to binary package creation.
10712 </footnote> for which shared library dependencies should
10713 be included in the binary package's control file.
10717 If some of the found shared libraries should only
10718 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10719 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10720 by using the <tt>-d<var>dependency-field</var></tt> option
10721 before those executable(s). (Each <tt>-d</tt> option
10722 takes effect until the next <tt>-d</tt>.)
10726 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10727 output control file to be modified. Instead by default it
10728 adds to the <file>debian/substvars</file> file variable
10729 settings like <tt>shlibs:Depends</tt>. These variable
10730 settings must be referenced in dependency fields in the
10731 appropriate per-binary-package sections of the source
10736 For example, a package that generates an essential part
10737 which requires dependencies, and optional parts that
10738 which only require a recommendation, would separate those
10739 two sets of dependencies into two different fields.<footnote>
10740 At the time of writing, an example for this was the
10741 <package/xmms/ package, with Depends used for the xmms
10742 executable, Recommends for the plug-ins and Suggests for
10743 even more optional features provided by unzip.
10745 It can say in its <file>debian/rules</file>:
10747 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10748 -dRecommends <var>optionalpart anotheroptionalpart</var>
10750 and then in its main control file <file>debian/control</file>:
10753 Depends: ${shlibs:Depends}
10754 Recommends: ${shlibs:Recommends}
10760 Sources which produce several binary packages with
10761 different shared library dependency requirements can use
10762 the <tt>-p<var>varnameprefix</var></tt> option to override
10763 the default <tt>shlibs:</tt> prefix (one invocation of
10764 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10765 They can thus produce several sets of dependency
10766 variables, each of the form
10767 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10768 which can be referred to in the appropriate parts of the
10769 binary package control files.
10774 <sect1 id="pkg-dpkg-distaddfile">
10776 <prgn>dpkg-distaddfile</prgn> - adds a file to
10777 <file>debian/files</file>
10781 Some packages' uploads need to include files other than
10782 the source and binary package files.
10786 <prgn>dpkg-distaddfile</prgn> adds a file to the
10787 <file>debian/files</file> file so that it will be included in
10788 the <file>.changes</file> file when
10789 <prgn>dpkg-genchanges</prgn> is run.
10793 It is usually invoked from the <tt>binary</tt> target of
10794 <file>debian/rules</file>:
10796 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10798 The <var>filename</var> is relative to the directory where
10799 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10800 is usually the directory above the top level of the source
10801 tree. The <file>debian/rules</file> target should put the
10802 file there just before or just after calling
10803 <prgn>dpkg-distaddfile</prgn>.
10807 The <var>section</var> and <var>priority</var> are passed
10808 unchanged into the resulting <file>.changes</file> file.
10813 <sect1 id="pkg-dpkg-genchanges">
10815 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10816 upload control file
10820 This program is usually called by package-independent
10821 automatic building scripts such as
10822 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10827 It is usually called in the top level of a built source
10828 tree, and when invoked with no arguments will print out a
10829 straightforward <file>.changes</file> file based on the
10830 information in the source package's changelog and control
10831 file and the binary and source packages which should have
10837 <sect1 id="pkg-dpkg-parsechangelog">
10839 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10840 representation of a changelog
10844 This program is used internally by
10845 <prgn>dpkg-source</prgn> et al. It may also occasionally
10846 be useful in <file>debian/rules</file> and elsewhere. It
10847 parses a changelog, <file>debian/changelog</file> by default,
10848 and prints a control-file format representation of the
10849 information in it to standard output.
10853 <sect1 id="pkg-dpkg-architecture">
10855 <prgn>dpkg-architecture</prgn> - information about the build and
10860 This program can be used manually, but is also invoked by
10861 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10862 environment or make variables which specify the build and host
10863 architecture for the package building process.
10868 <sect id="pkg-sourcetree">
10869 <heading>The Debian package source tree</heading>
10872 The source archive scheme described later is intended to
10873 allow a Debian package source tree with some associated
10874 control information to be reproduced and transported easily.
10875 The Debian package source tree is a version of the original
10876 program with certain files added for the benefit of the
10877 packaging process, and with any other changes required
10878 made to the rest of the source code and installation
10883 The extra files created for Debian are in the subdirectory
10884 <file>debian</file> of the top level of the Debian package
10885 source tree. They are described below.
10888 <sect1 id="pkg-debianrules">
10889 <heading><file>debian/rules</file> - the main building script</heading>
10892 See <ref id="debianrules">.
10896 <sect1 id="pkg-srcsubstvars">
10897 <heading><file>debian/substvars</file> and variable substitutions</heading>
10900 See <ref id="substvars">.
10906 <heading><file>debian/files</file></heading>
10909 See <ref id="debianfiles">.
10913 <sect1><heading><file>debian/tmp</file>
10917 This is the canonical temporary location for the
10918 construction of binary packages by the <tt>binary</tt>
10919 target. The directory <file>tmp</file> serves as the root of
10920 the file system tree as it is being constructed (for
10921 example, by using the package's upstream makefiles install
10922 targets and redirecting the output there), and it also
10923 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10924 id="pkg-bincreating">.
10928 If several binary packages are generated from the same
10929 source tree it is usual to use several
10930 <file>debian/tmp<var>something</var></file> directories, for
10931 example <file>tmp-a</file> or <file>tmp-doc</file>.
10935 Whatever <file>tmp</file> directories are created and used by
10936 <tt>binary</tt> must of course be removed by the
10937 <tt>clean</tt> target.</p></sect1>
10941 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10945 As it exists on the FTP site, a Debian source package
10946 consists of three related files. You must have the right
10947 versions of all three to be able to use them.
10952 <tag>Debian source control file - <tt>.dsc</tt></tag>
10954 This file is a control file used by <prgn>dpkg-source</prgn>
10955 to extract a source package.
10956 See <ref id="debiansourcecontrolfiles">.
10960 Original source archive -
10962 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10968 This is a compressed (with <tt>gzip -9</tt>)
10969 <prgn>tar</prgn> file containing the source code from
10970 the upstream authors of the program.
10975 Debian package diff -
10977 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10983 This is a unified context diff (<tt>diff -u</tt>)
10984 giving the changes which are required to turn the
10985 original source into the Debian source. These changes
10986 may only include editing and creating plain files.
10987 The permissions of files, the targets of symbolic
10988 links and the characteristics of special files or
10989 pipes may not be changed and no files may be removed
10994 All the directories in the diff must exist, except the
10995 <file>debian</file> subdirectory of the top of the source
10996 tree, which will be created by
10997 <prgn>dpkg-source</prgn> if necessary when unpacking.
11001 The <prgn>dpkg-source</prgn> program will
11002 automatically make the <file>debian/rules</file> file
11003 executable (see below).</p></item>
11008 If there is no original source code - for example, if the
11009 package is specially prepared for Debian or the Debian
11010 maintainer is the same as the upstream maintainer - the
11011 format is slightly different: then there is no diff, and the
11013 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11014 and preferably contains a directory named
11015 <file><var>package</var>-<var>version</var></file>.
11020 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11023 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11024 Debian source package. However, if it is not available it
11025 is possible to unpack a Debian source archive as follows:
11026 <enumlist compact="compact">
11029 Untar the tarfile, which will create a <file>.orig</file>
11033 <p>Rename the <file>.orig</file> directory to
11034 <file><var>package</var>-<var>version</var></file>.</p>
11038 Create the subdirectory <file>debian</file> at the top of
11039 the source tree.</p>
11041 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11043 <item><p>Untar the tarfile again if you want a copy of the original
11044 source code alongside the Debian version.</p>
11049 It is not possible to generate a valid Debian source archive
11050 without using <prgn>dpkg-source</prgn>. In particular,
11051 attempting to use <prgn>diff</prgn> directly to generate the
11052 <file>.diff.gz</file> file will not work.
11056 <heading>Restrictions on objects in source packages</heading>
11059 The source package may not contain any hard links
11061 This is not currently detected when building source
11062 packages, but only when extracting
11066 Hard links may be permitted at some point in the
11067 future, but would require a fair amount of
11069 </footnote>, device special files, sockets or setuid or
11072 Setgid directories are allowed.
11077 The source packaging tools manage the changes between the
11078 original and Debian source using <prgn>diff</prgn> and
11079 <prgn>patch</prgn>. Turning the original source tree as
11080 included in the <file>.orig.tar.gz</file> into the Debian
11081 package source must not involve any changes which cannot be
11082 handled by these tools. Problematic changes which cause
11083 <prgn>dpkg-source</prgn> to halt with an error when
11084 building the source package are:
11085 <list compact="compact">
11086 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11088 <item><p>Changing the targets of symbolic links.</p>
11090 <item><p>Creating directories, other than <file>debian</file>.</p>
11092 <item><p>Changes to the contents of binary files.</p></item>
11093 </list> Changes which cause <prgn>dpkg-source</prgn> to
11094 print a warning but continue anyway are:
11095 <list compact="compact">
11098 Removing files, directories or symlinks.
11100 Renaming a file is not treated specially - it is
11101 seen as the removal of the old file (which
11102 generates a warning, but is otherwise ignored),
11103 and the creation of the new one.
11109 Changed text files which are missing the usual final
11110 newline (either in the original or the modified
11115 Changes which are not represented, but which are not detected by
11116 <prgn>dpkg-source</prgn>, are:
11117 <list compact="compact">
11118 <item><p>Changing the permissions of files (other than
11119 <file>debian/rules</file>) and directories.</p></item>
11124 The <file>debian</file> directory and <file>debian/rules</file>
11125 are handled specially by <prgn>dpkg-source</prgn> - before
11126 applying the changes it will create the <file>debian</file>
11127 directory, and afterwards it will make
11128 <file>debian/rules</file> world-executable.
11134 <appendix id="pkg-controlfields">
11135 <heading>Control files and their fields (from old Packaging Manual)</heading>
11138 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11139 data in a common format, known as control files. Binary and
11140 source packages have control data as do the <file>.changes</file>
11141 files which control the installation of uploaded files, and
11142 <prgn>dpkg</prgn>'s internal databases are in a similar
11147 <heading>Syntax of control files</heading>
11150 See <ref id="controlsyntax">.
11154 It is important to note that there are several fields which
11155 are optional as far as <prgn>dpkg</prgn> and the related
11156 tools are concerned, but which must appear in every Debian
11157 package, or whose omission may cause problems.
11162 <heading>List of fields</heading>
11165 See <ref id="controlfieldslist">.
11169 This section now contains only the fields that didn't belong
11170 to the Policy manual.
11173 <sect1 id="pkg-f-Filename">
11174 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11177 These fields in <tt>Packages</tt> files give the
11178 filename(s) of (the parts of) a package in the
11179 distribution directories, relative to the root of the
11180 Debian hierarchy. If the package has been split into
11181 several parts the parts are all listed in order, separated
11186 <sect1 id="pkg-f-Size">
11187 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11190 These fields in <file>Packages</file> files give the size (in
11191 bytes, expressed in decimal) and MD5 checksum of the
11192 file(s) which make(s) up a binary package in the
11193 distribution. If the package is split into several parts
11194 the values for the parts are listed in order, separated by
11199 <sect1 id="pkg-f-Status">
11200 <heading><tt>Status</tt></heading>
11203 This field in <prgn>dpkg</prgn>'s status file records
11204 whether the user wants a package installed, removed or
11205 left alone, whether it is broken (requiring
11206 re-installation) or not and what its current state on the
11207 system is. Each of these pieces of information is a
11212 <sect1 id="pkg-f-Config-Version">
11213 <heading><tt>Config-Version</tt></heading>
11216 If a package is not installed or not configured, this
11217 field in <prgn>dpkg</prgn>'s status file records the last
11218 version of the package which was successfully
11223 <sect1 id="pkg-f-Conffiles">
11224 <heading><tt>Conffiles</tt></heading>
11227 This field in <prgn>dpkg</prgn>'s status file contains
11228 information about the automatically-managed configuration
11229 files held by a package. This field should <em>not</em>
11230 appear anywhere in a package!
11235 <heading>Obsolete fields</heading>
11238 These are still recognized by <prgn>dpkg</prgn> but should
11239 not appear anywhere any more.
11241 <taglist compact="compact">
11243 <tag><tt>Revision</tt></tag>
11244 <tag><tt>Package-Revision</tt></tag>
11245 <tag><tt>Package_Revision</tt></tag>
11247 The Debian revision part of the package version was
11248 at one point in a separate control field. This
11249 field went through several names.
11252 <tag><tt>Recommended</tt></tag>
11253 <item>Old name for <tt>Recommends</tt>.</item>
11255 <tag><tt>Optional</tt></tag>
11256 <item>Old name for <tt>Suggests</tt>.</item>
11258 <tag><tt>Class</tt></tag>
11259 <item>Old name for <tt>Priority</tt>.</item>
11268 <appendix id="pkg-conffiles">
11269 <heading>Configuration file handling (from old Packaging Manual)</heading>
11272 <prgn>dpkg</prgn> can do a certain amount of automatic
11273 handling of package configuration files.
11277 Whether this mechanism is appropriate depends on a number of
11278 factors, but basically there are two approaches to any
11279 particular configuration file.
11283 The easy method is to ship a best-effort configuration in the
11284 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11285 handle updates. If the user is unlikely to want to edit the
11286 file, but you need them to be able to without losing their
11287 changes, and a new package with a changed version of the file
11288 is only released infrequently, this is a good approach.
11292 The hard method is to build the configuration file from
11293 scratch in the <prgn>postinst</prgn> script, and to take the
11294 responsibility for fixing any mistakes made in earlier
11295 versions of the package automatically. This will be
11296 appropriate if the file is likely to need to be different on
11300 <sect><heading>Automatic handling of configuration files by
11305 A package may contain a control information file called
11306 <tt>conffiles</tt>. This file should be a list of filenames
11307 of configuration files needing automatic handling, separated
11308 by newlines. The filenames should be absolute pathnames,
11309 and the files referred to should actually exist in the
11314 When a package is upgraded <prgn>dpkg</prgn> will process
11315 the configuration files during the configuration stage,
11316 shortly before it runs the package's <prgn>postinst</prgn>
11321 For each file it checks to see whether the version of the
11322 file included in the package is the same as the one that was
11323 included in the last version of the package (the one that is
11324 being upgraded from); it also compares the version currently
11325 installed on the system with the one shipped with the last
11330 If neither the user nor the package maintainer has changed
11331 the file, it is left alone. If one or the other has changed
11332 their version, then the changed version is preferred - i.e.,
11333 if the user edits their file, but the package maintainer
11334 doesn't ship a different version, the user's changes will
11335 stay, silently, but if the maintainer ships a new version
11336 and the user hasn't edited it the new version will be
11337 installed (with an informative message). If both have
11338 changed their version the user is prompted about the problem
11339 and must resolve the differences themselves.
11343 The comparisons are done by calculating the MD5 message
11344 digests of the files, and storing the MD5 of the file as it
11345 was included in the most recent version of the package.
11349 When a package is installed for the first time
11350 <prgn>dpkg</prgn> will install the file that comes with it,
11351 unless that would mean overwriting a file already on the
11356 However, note that <prgn>dpkg</prgn> will <em>not</em>
11357 replace a conffile that was removed by the user (or by a
11358 script). This is necessary because with some programs a
11359 missing file produces an effect hard or impossible to
11360 achieve in another way, so that a missing file needs to be
11361 kept that way if the user did it.
11365 Note that a package should <em>not</em> modify a
11366 <prgn>dpkg</prgn>-handled conffile in its maintainer
11367 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11368 the user confusing and possibly dangerous options for
11369 conffile update when the package is upgraded.</p>
11372 <sect><heading>Fully-featured maintainer script configuration
11377 For files which contain site-specific information such as
11378 the hostname and networking details and so forth, it is
11379 better to create the file in the package's
11380 <prgn>postinst</prgn> script.
11384 This will typically involve examining the state of the rest
11385 of the system to determine values and other information, and
11386 may involve prompting the user for some information which
11387 can't be obtained some other way.
11391 When using this method there are a couple of important
11392 issues which should be considered:
11396 If you discover a bug in the program which generates the
11397 configuration file, or if the format of the file changes
11398 from one version to the next, you will have to arrange for
11399 the postinst script to do something sensible - usually this
11400 will mean editing the installed configuration file to remove
11401 the problem or change the syntax. You will have to do this
11402 very carefully, since the user may have changed the file,
11403 perhaps to fix the very problem that your script is trying
11404 to deal with - you will have to detect these situations and
11405 deal with them correctly.
11409 If you do go down this route it's probably a good idea to
11410 make the program that generates the configuration file(s) a
11411 separate program in <file>/usr/sbin</file>, by convention called
11412 <file><var>package</var>config</file> and then run that if
11413 appropriate from the post-installation script. The
11414 <tt><var>package</var>config</tt> program should not
11415 unquestioningly overwrite an existing configuration - if its
11416 mode of operation is geared towards setting up a package for
11417 the first time (rather than any arbitrary reconfiguration
11418 later) you should have it check whether the configuration
11419 already exists, and require a <tt>--force</tt> flag to
11420 overwrite it.</p></sect>
11423 <appendix id="pkg-alternatives"><heading>Alternative versions of
11424 an interface - <prgn>update-alternatives</prgn> (from old
11429 When several packages all provide different versions of the
11430 same program or file it is useful to have the system select a
11431 default, but to allow the system administrator to change it
11432 and have their decisions respected.
11436 For example, there are several versions of the <prgn>vi</prgn>
11437 editor, and there is no reason to prevent all of them from
11438 being installed at once, each under their own name
11439 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11440 Nevertheless it is desirable to have the name <tt>vi</tt>
11441 refer to something, at least by default.
11445 If all the packages involved cooperate, this can be done with
11446 <prgn>update-alternatives</prgn>.
11450 Each package provides its own version under its own name, and
11451 calls <prgn>update-alternatives</prgn> in its postinst to
11452 register its version (and again in its prerm to deregister
11457 See the man page <manref name="update-alternatives"
11458 section="8"> for details.
11462 If <prgn>update-alternatives</prgn> does not seem appropriate
11463 you may wish to consider using diversions instead.</p>
11466 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11467 package's version of a file (from old Packaging Manual)
11471 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11472 when it reinstalls the package it belongs to, and to have it
11473 put the file from the package somewhere else instead.
11477 This can be used locally to override a package's version of a
11478 file, or by one package to override another's version (or
11479 provide a wrapper for it).
11483 Before deciding to use a diversion, read <ref
11484 id="pkg-alternatives"> to see if you really want a diversion
11485 rather than several alternative versions of a program.
11489 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11490 and updated by a special program <prgn>dpkg-divert</prgn>.
11491 Please see <manref name="dpkg-divert" section="8"> for full
11492 details of its operation.
11496 When a package wishes to divert a file from another, it should
11497 call <prgn>dpkg-divert</prgn> in its preinst to add the
11498 diversion and rename the existing file. For example,
11499 supposing that a <prgn>smailwrapper</prgn> package wishes to
11500 install a wrapper around <file>/usr/sbin/smail</file>:
11502 dpkg-divert --package smailwrapper --add --rename \
11503 --divert /usr/sbin/smail.real /usr/sbin/smail
11504 </example> The <tt>--package smailwrapper</tt> ensures that
11505 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11506 can bypass the diversion and get installed as the true version.
11507 It's safe to add the diversion unconditionally on upgrades since
11508 it will be left unchanged if it already exists, but
11509 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11510 message, make the command conditional on the version from which
11511 the package is being upgraded:
11513 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11514 dpkg-divert --package smailwrapper --add --rename \
11515 --divert /usr/sbin/smail.real /usr/sbin/smail
11517 </example> where <tt>1.0-2</tt> is the version at which the
11518 diversion was first added to the package. Running the command
11519 during abort-upgrade is pointless but harmless.
11523 The postrm has to do the reverse:
11525 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11526 dpkg-divert --package smailwrapper --remove --rename \
11527 --divert /usr/sbin/smail.real /usr/sbin/smail
11529 </example> If the diversion was added at a particular version, the
11530 postrm should also handle the failure case of upgrading from an
11531 older version (unless the older version is so old that direct
11532 upgrades are no longer supported):
11534 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11535 dpkg-divert --package smailwrapper --remove --rename \
11536 --divert /usr/sbin/smail.real /usr/sbin/smail
11538 </example> where <tt>1.0-2</tt> is the version at which the
11539 diversion was first added to the package. The postrm should not
11540 remove the diversion on upgrades both because there's no reason to
11541 remove the diversion only to immediately re-add it and since the
11542 postrm of the old package is run after unpacking so the removal of
11543 the diversion will fail.
11547 Do not attempt to divert a file which is vitally important for
11548 the system's operation - when using <prgn>dpkg-divert</prgn>
11549 there is a time, after it has been diverted but before
11550 <prgn>dpkg</prgn> has installed the new version, when the file
11551 does not exist.</p>
11556 <!-- Local variables: -->
11557 <!-- indent-tabs-mode: t -->
11559 <!-- vim:set ai sts=2 sw=2 tw=76: -->