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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 include
893 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
894 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
895 used to store shared library dependency information and
896 the <file>conffiles</file> file that lists the package's
897 configuration files (described in <ref id="config-files">).
901 There is unfortunately a collision of terminology here between
902 control information files and files in the Debian control file
903 format. Throughout this document, a <em>control file</em> refers
904 to a file in the Debian control file format. These files are
905 documented in <ref id="controlfields">. Only files referred to
906 specifically as <em>control information files</em> are the files
907 included in the control information file member of
908 the <file>.deb</file> file format used by binary packages. Most
909 control information files are not in the Debian control file
914 <heading>The package name</heading>
917 Every package must have a name that's unique within the Debian
922 The package name is included in the control field
923 <tt>Package</tt>, the format of which is described
924 in <ref id="f-Package">.
925 The package name is also included as a part of the file name
926 of the <tt>.deb</tt> file.
931 <heading>The version of a package</heading>
934 Every package has a version number recorded in its
935 <tt>Version</tt> control file field, described in
936 <ref id="f-Version">.
940 The package management system imposes an ordering on version
941 numbers, so that it can tell whether packages are being up- or
942 downgraded and so that package system front end applications
943 can tell whether a package it finds available is newer than
944 the one installed on the system. The version number format
945 has the most significant parts (as far as comparison is
946 concerned) at the beginning.
950 If an upstream package has problematic version numbers they
951 should be converted to a sane form for use in the
952 <tt>Version</tt> field.
956 <heading>Version numbers based on dates</heading>
959 In general, Debian packages should use the same version
960 numbers as the upstream sources. However, upstream version
961 numbers based on some date formats (sometimes used for
962 development or "snapshot" releases) will not be ordered
963 correctly by the package management software. For
964 example, <prgn>dpkg</prgn> will consider "96May01" to be
965 greater than "96Dec24".
969 To prevent having to use epochs for every new upstream
970 version, the date-based portion of any upstream version number
971 should be given in a way that sorts correctly: four-digit year
972 first, followed by a two-digit numeric month, followed by a
973 two-digit numeric date, possibly with punctuation between the
978 Native Debian packages (i.e., packages which have been written
979 especially for Debian) whose version numbers include dates
980 should also follow these rules. If punctuation is desired
981 between the date components, remember that hyphen (<tt>-</tt>)
982 cannot be used in native package versions. Period
983 (<tt>.</tt>) is normally a good choice.
989 <sect id="maintainer">
990 <heading>The maintainer of a package</heading>
993 Every package must have a maintainer, except for orphaned
994 packages as described below. The maintainer may be one person
995 or a group of people reachable from a common email address, such
996 as a mailing list. The maintainer is responsible for
997 maintaining the Debian packaging files, evaluating and
998 responding appropriately to reported bugs, uploading new
999 versions of the package (either directly or through a sponsor),
1000 ensuring that the package is placed in the appropriate archive
1001 area and included in Debian releases as appropriate for the
1002 stability and utility of the package, and requesting removal of
1003 the package from the Debian distribution if it is no longer
1004 useful or maintainable.
1008 The maintainer must be specified in the <tt>Maintainer</tt>
1009 control field with their correct name and a working email
1010 address. The email address given in the <tt>Maintainer</tt>
1011 control field must accept mail from those role accounts in
1012 Debian used to send automated mails regarding the package. This
1013 includes non-spam mail from the bug-tracking system, all mail
1014 from the Debian archive maintenance software, and other role
1015 accounts or automated processes that are commonly agreed on by
1016 the project.<footnote>
1017 A sample implementation of such a whitelist written for the
1018 Mailman mailing list management software is used for mailing
1019 lists hosted by alioth.debian.org.
1021 If one person or team maintains several packages, they should
1022 use the same form of their name and email address in
1023 the <tt>Maintainer</tt> fields of those packages.
1027 The format of the <tt>Maintainer</tt> control field is
1028 described in <ref id="f-Maintainer">.
1032 If the maintainer of the package is a team of people with a
1033 shared email address, the <tt>Uploaders</tt> control field must
1034 be present and must contain at least one human with their
1035 personal email address. See <ref id="f-Uploaders"> for the
1036 syntax of that field.
1040 An orphaned package is one with no current maintainer. Orphaned
1041 packages should have their <tt>Maintainer</tt> control field set
1042 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1043 These packages are considered maintained by the Debian project
1044 as a whole until someone else volunteers to take over
1045 maintenance.<footnote>
1046 The detailed procedure for gracefully orphaning a package can
1047 be found in the Debian Developer's Reference
1048 (see <ref id="related">).
1053 <sect id="descriptions">
1054 <heading>The description of a package</heading>
1057 Every Debian package must have a <tt>Description</tt> control
1058 field which contains a synopsis and extended description of the
1059 package. Technical information about the format of the
1060 <tt>Description</tt> field is in <ref id="f-Description">.
1064 The description should describe the package (the program) to a
1065 user (system administrator) who has never met it before so that
1066 they have enough information to decide whether they want to
1067 install it. This description should not just be copied verbatim
1068 from the program's documentation.
1072 Put important information first, both in the synopsis and
1073 extended description. Sometimes only the first part of the
1074 synopsis or of the description will be displayed. You can
1075 assume that there will usually be a way to see the whole
1076 extended description.
1080 The description should also give information about the
1081 significant dependencies and conflicts between this package
1082 and others, so that the user knows why these dependencies and
1083 conflicts have been declared.
1087 Instructions for configuring or using the package should
1088 not be included (that is what installation scripts,
1089 manual pages, info files, etc., are for). Copyright
1090 statements and other administrivia should not be included
1091 either (that is what the copyright file is for).
1094 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1097 The single line synopsis should be kept brief - certainly
1098 under 80 characters.
1102 Do not include the package name in the synopsis line. The
1103 display software knows how to display this already, and you
1104 do not need to state it. Remember that in many situations
1105 the user may only see the synopsis line - make it as
1106 informative as you can.
1111 <sect1 id="extendeddesc"><heading>The extended description</heading>
1114 Do not try to continue the single line synopsis into the
1115 extended description. This will not work correctly when
1116 the full description is displayed, and makes no sense
1117 where only the summary (the single line synopsis) is
1122 The extended description should describe what the package
1123 does and how it relates to the rest of the system (in terms
1124 of, for example, which subsystem it is which part of).
1128 The description field needs to make sense to anyone, even
1129 people who have no idea about any of the things the
1130 package deals with.<footnote>
1131 The blurb that comes with a program in its
1132 announcements and/or <prgn>README</prgn> files is
1133 rarely suitable for use in a description. It is
1134 usually aimed at people who are already in the
1135 community where the package is used.
1143 <sect id="dependencies">
1144 <heading>Dependencies</heading>
1147 Every package must specify the dependency information
1148 about other packages that are required for the first to
1153 For example, a dependency entry must be provided for any
1154 shared libraries required by a dynamically-linked executable
1155 binary in a package.
1159 Packages are not required to declare any dependencies they
1160 have on other packages which are marked <tt>Essential</tt>
1161 (see below), and should not do so unless they depend on a
1162 particular version of that package.<footnote>
1164 Essential is needed in part to avoid unresolvable dependency
1165 loops on upgrade. If packages add unnecessary dependencies
1166 on packages in this set, the chances that there
1167 <strong>will</strong> be an unresolvable dependency loop
1168 caused by forcing these Essential packages to be configured
1169 first before they need to be is greatly increased. It also
1170 increases the chances that frontends will be unable to
1171 <strong>calculate</strong> an upgrade path, even if one
1175 Also, functionality is rarely ever removed from the
1176 Essential set, but <em>packages</em> have been removed from
1177 the Essential set when the functionality moved to a
1178 different package. So depending on these packages <em>just
1179 in case</em> they stop being essential does way more harm
1186 Sometimes, unpacking one package requires that another package
1187 be first unpacked <em>and</em> configured. In this case, the
1188 depending package must specify this dependency in
1189 the <tt>Pre-Depends</tt> control field.
1193 You should not specify a <tt>Pre-Depends</tt> entry for a
1194 package before this has been discussed on the
1195 <tt>debian-devel</tt> mailing list and a consensus about
1196 doing that has been reached.
1200 The format of the package interrelationship control fields is
1201 described in <ref id="relationships">.
1205 <sect id="virtual_pkg">
1206 <heading>Virtual packages</heading>
1209 Sometimes, there are several packages which offer
1210 more-or-less the same functionality. In this case, it's
1211 useful to define a <em>virtual package</em> whose name
1212 describes that common functionality. (The virtual
1213 packages only exist logically, not physically; that's why
1214 they are called <em>virtual</em>.) The packages with this
1215 particular function will then <em>provide</em> the virtual
1216 package. Thus, any other package requiring that function
1217 can simply depend on the virtual package without having to
1218 specify all possible packages individually.
1222 All packages should use virtual package names where
1223 appropriate, and arrange to create new ones if necessary.
1224 They should not use virtual package names (except privately,
1225 amongst a cooperating group of packages) unless they have
1226 been agreed upon and appear in the list of virtual package
1227 names. (See also <ref id="virtual">)
1231 The latest version of the authoritative list of virtual
1232 package names can be found in the <tt>debian-policy</tt> package.
1233 It is also available from the Debian web mirrors at
1234 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1235 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1239 The procedure for updating the list is described in the preface
1246 <heading>Base system</heading>
1249 The <tt>base system</tt> is a minimum subset of the Debian
1250 system that is installed before everything else
1251 on a new system. Only very few packages are allowed to form
1252 part of the base system, in order to keep the required disk
1257 The base system consists of all those packages with priority
1258 <tt>required</tt> or <tt>important</tt>. Many of them will
1259 be tagged <tt>essential</tt> (see below).
1264 <heading>Essential packages</heading>
1267 Essential is defined as the minimal set of functionality that
1268 must be available and usable on the system at all times, even
1269 when packages are in an unconfigured (but unpacked) state.
1270 Packages are tagged <tt>essential</tt> for a system using the
1271 <tt>Essential</tt> control field. The format of the
1272 <tt>Essential</tt> control field is described in <ref
1277 Since these packages cannot be easily removed (one has to
1278 specify an extra <em>force option</em> to
1279 <prgn>dpkg</prgn> to do so), this flag must not be used
1280 unless absolutely necessary. A shared library package
1281 must not be tagged <tt>essential</tt>; dependencies will
1282 prevent its premature removal, and we need to be able to
1283 remove it when it has been superseded.
1287 Since dpkg will not prevent upgrading of other packages
1288 while an <tt>essential</tt> package is in an unconfigured
1289 state, all <tt>essential</tt> packages must supply all of
1290 their core functionality even when unconfigured. If the
1291 package cannot satisfy this requirement it must not be
1292 tagged as essential, and any packages depending on this
1293 package must instead have explicit dependency fields as
1298 Maintainers should take great care in adding any programs,
1299 interfaces, or functionality to <tt>essential</tt> packages.
1300 Packages may assume that functionality provided by
1301 <tt>essential</tt> packages is always available without
1302 declaring explicit dependencies, which means that removing
1303 functionality from the Essential set is very difficult and is
1304 almost never done. Any capability added to an
1305 <tt>essential</tt> package therefore creates an obligation to
1306 support that capability as part of the Essential set in
1311 You must not tag any packages <tt>essential</tt> before
1312 this has been discussed on the <tt>debian-devel</tt>
1313 mailing list and a consensus about doing that has been
1318 <sect id="maintscripts">
1319 <heading>Maintainer Scripts</heading>
1322 The package installation scripts should avoid producing
1323 output which is unnecessary for the user to see and
1324 should rely on <prgn>dpkg</prgn> to stave off boredom on
1325 the part of a user installing many packages. This means,
1326 amongst other things, using the <tt>--quiet</tt> option on
1327 <prgn>install-info</prgn>.
1331 Errors which occur during the execution of an installation
1332 script must be checked and the installation must not
1333 continue after an error.
1337 Note that in general <ref id="scripts"> applies to package
1338 maintainer scripts, too.
1342 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1343 to another package without consulting the maintainer of that
1344 package first. When adding or removing diversions, package
1345 maintainer scripts must provide the <tt>--package</tt> flag
1346 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1350 All packages which supply an instance of a common command
1351 name (or, in general, filename) should generally use
1352 <prgn>update-alternatives</prgn>, so that they may be
1353 installed together. If <prgn>update-alternatives</prgn>
1354 is not used, then each package must use
1355 <tt>Conflicts</tt> to ensure that other packages are
1356 de-installed. (In this case, it may be appropriate to
1357 specify a conflict against earlier versions of something
1358 that previously did not use
1359 <prgn>update-alternatives</prgn>; this is an exception to
1360 the usual rule that versioned conflicts should be
1364 <sect1 id="maintscriptprompt">
1365 <heading>Prompting in maintainer scripts</heading>
1367 Package maintainer scripts may prompt the user if
1368 necessary. Prompting must be done by communicating
1369 through a program, such as <prgn>debconf</prgn>, which
1370 conforms to the Debian Configuration Management
1371 Specification, version 2 or higher.
1375 Packages which are essential, or which are dependencies of
1376 essential packages, may fall back on another prompting method
1377 if no such interface is available when they are executed.
1381 The Debian Configuration Management Specification is included
1382 in the <file>debconf_specification</file> files in the
1383 <package>debian-policy</package> package.
1384 It is also available from the Debian web mirrors at
1385 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1386 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1390 Packages which use the Debian Configuration Management
1391 Specification may contain the additional control information
1392 files <file>config</file>
1393 and <file>templates</file>. <file>config</file> is an
1394 additional maintainer script used for package configuration,
1395 and <file>templates</file> contains templates used for user
1396 prompting. The <prgn>config</prgn> script might be run before
1397 the <prgn>preinst</prgn> script and before the package is
1398 unpacked or any of its dependencies or pre-dependencies are
1399 satisfied. Therefore it must work using only the tools
1400 present in <em>essential</em> packages.<footnote>
1401 <package>Debconf</package> or another tool that
1402 implements the Debian Configuration Management
1403 Specification will also be installed, and any
1404 versioned dependencies on it will be satisfied
1405 before preconfiguration begins.
1410 Packages which use the Debian Configuration Management
1411 Specification must allow for translation of their user-visible
1412 messages by using a gettext-based system such as the one
1413 provided by the <package>po-debconf</package> package.
1417 Packages should try to minimize the amount of prompting
1418 they need to do, and they should ensure that the user
1419 will only ever be asked each question once. This means
1420 that packages should try to use appropriate shared
1421 configuration files (such as <file>/etc/papersize</file> and
1422 <file>/etc/news/server</file>), and shared
1423 <package>debconf</package> variables rather than each
1424 prompting for their own list of required pieces of
1429 It also means that an upgrade should not ask the same
1430 questions again, unless the user has used
1431 <tt>dpkg --purge</tt> to remove the package's configuration.
1432 The answers to configuration questions should be stored in an
1433 appropriate place in <file>/etc</file> so that the user can
1434 modify them, and how this has been done should be
1439 If a package has a vitally important piece of
1440 information to pass to the user (such as "don't run me
1441 as I am, you must edit the following configuration files
1442 first or you risk your system emitting badly-formatted
1443 messages"), it should display this in the
1444 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1445 prompt the user to hit return to acknowledge the
1446 message. Copyright messages do not count as vitally
1447 important (they belong in
1448 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1449 neither do instructions on how to use a program (these
1450 should be in on-line documentation, where all the users
1455 Any necessary prompting should almost always be confined
1456 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1457 script. If it is done in the <prgn>postinst</prgn>, it
1458 should be protected with a conditional so that
1459 unnecessary prompting doesn't happen if a package's
1460 installation fails and the <prgn>postinst</prgn> is
1461 called with <tt>abort-upgrade</tt>,
1462 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1472 <heading>Source packages</heading>
1474 <sect id="standardsversion">
1475 <heading>Standards conformance</heading>
1478 Source packages should specify the most recent version number
1479 of this policy document with which your package complied
1480 when it was last updated.
1484 This information may be used to file bug reports
1485 automatically if your package becomes too much out of date.
1489 The version is specified in the <tt>Standards-Version</tt>
1491 The format of the <tt>Standards-Version</tt> field is
1492 described in <ref id="f-Standards-Version">.
1496 You should regularly, and especially if your package has
1497 become out of date, check for the newest Policy Manual
1498 available and update your package, if necessary. When your
1499 package complies with the new standards you should update the
1500 <tt>Standards-Version</tt> source package field and
1501 release it.<footnote>
1502 See the file <file>upgrading-checklist</file> for
1503 information about policy which has changed between
1504 different versions of this document.
1510 <sect id="pkg-relations">
1511 <heading>Package relationships</heading>
1514 Source packages should specify which binary packages they
1515 require to be installed or not to be installed in order to
1516 build correctly. For example, if building a package
1517 requires a certain compiler, then the compiler should be
1518 specified as a build-time dependency.
1522 It is not necessary to explicitly specify build-time
1523 relationships on a minimal set of packages that are always
1524 needed to compile, link and put in a Debian package a
1525 standard "Hello World!" program written in C or C++. The
1526 required packages are called <em>build-essential</em>, and
1527 an informational list can be found in
1528 <file>/usr/share/doc/build-essential/list</file> (which is
1529 contained in the <tt>build-essential</tt>
1532 <list compact="compact">
1534 This allows maintaining the list separately
1535 from the policy documents (the list does not
1536 need the kind of control that the policy
1540 Having a separate package allows one to install
1541 the build-essential packages on a machine, as
1542 well as allowing other packages such as tasks to
1543 require installation of the build-essential
1544 packages using the depends relation.
1547 The separate package allows bug reports against
1548 the list to be categorized separately from
1549 the policy management process in the BTS.
1556 When specifying the set of build-time dependencies, one
1557 should list only those packages explicitly required by the
1558 build. It is not necessary to list packages which are
1559 required merely because some other package in the list of
1560 build-time dependencies depends on them.<footnote>
1561 The reason for this is that dependencies change, and
1562 you should list all those packages, and <em>only</em>
1563 those packages that <em>you</em> need directly. What
1564 others need is their business. For example, if you
1565 only link against <file>libimlib</file>, you will need to
1566 build-depend on <package>libimlib2-dev</package> but
1567 not against any <tt>libjpeg*</tt> packages, even
1568 though <tt>libimlib2-dev</tt> currently depends on
1569 them: installation of <package>libimlib2-dev</package>
1570 will automatically ensure that all of its run-time
1571 dependencies are satisfied.
1576 If build-time dependencies are specified, it must be
1577 possible to build the package and produce working binaries
1578 on a system with only essential and build-essential
1579 packages installed and also those required to satisfy the
1580 build-time relationships (including any implied
1581 relationships). In particular, this means that version
1582 clauses should be used rigorously in build-time
1583 relationships so that one cannot produce bad or
1584 inconsistently configured packages when the relationships
1585 are properly satisfied.
1589 <ref id="relationships"> explains the technical details.
1594 <heading>Changes to the upstream sources</heading>
1597 If changes to the source code are made that are not
1598 specific to the needs of the Debian system, they should be
1599 sent to the upstream authors in whatever form they prefer
1600 so as to be included in the upstream version of the
1605 If you need to configure the package differently for
1606 Debian or for Linux, and the upstream source doesn't
1607 provide a way to do so, you should add such configuration
1608 facilities (for example, a new <prgn>autoconf</prgn> test
1609 or <tt>#define</tt>) and send the patch to the upstream
1610 authors, with the default set to the way they originally
1611 had it. You can then easily override the default in your
1612 <file>debian/rules</file> or wherever is appropriate.
1616 You should make sure that the <prgn>configure</prgn> utility
1617 detects the correct architecture specification string
1618 (refer to <ref id="arch-spec"> for details).
1622 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1623 <prgn>configure</prgn> scripts are used, you should edit the
1624 <file>.in</file> files rather than editing the
1625 <prgn>Makefile</prgn> directly. This allows the user to
1626 reconfigure the package if necessary. You should
1627 <em>not</em> configure the package and edit the generated
1628 <prgn>Makefile</prgn>! This makes it impossible for someone
1629 else to later reconfigure the package without losing the
1635 <sect id="dpkgchangelog">
1636 <heading>Debian changelog: <file>debian/changelog</file></heading>
1639 Changes in the Debian version of the package should be
1640 briefly explained in the Debian changelog file
1641 <file>debian/changelog</file>.<footnote>
1643 Mistakes in changelogs are usually best rectified by
1644 making a new changelog entry rather than "rewriting
1645 history" by editing old changelog entries.
1648 This includes modifications
1649 made in the Debian package compared to the upstream one
1650 as well as other changes and updates to the package.
1652 Although there is nothing stopping an author who is also
1653 the Debian maintainer from using this changelog for all
1654 their changes, it will have to be renamed if the Debian
1655 and upstream maintainers become different people. In such
1656 a case, however, it might be better to maintain the package
1657 as a non-native package.
1662 The format of the <file>debian/changelog</file> allows the
1663 package building tools to discover which version of the package
1664 is being built and find out other release-specific information.
1668 That format is a series of entries like this:
1670 <example compact="compact">
1671 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1673 [optional blank line(s), stripped]
1675 * <var>change details</var>
1676 <var>more change details</var>
1678 [blank line(s), included in output of dpkg-parsechangelog]
1680 * <var>even more change details</var>
1682 [optional blank line(s), stripped]
1684 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1689 <var>package</var> and <var>version</var> are the source
1690 package name and version number.
1694 <var>distribution(s)</var> lists the distributions where
1695 this version should be installed when it is uploaded - it
1696 is copied to the <tt>Distribution</tt> field in the
1697 <file>.changes</file> file. See <ref id="f-Distribution">.
1701 <var>urgency</var> is the value for the <tt>Urgency</tt>
1702 field in the <file>.changes</file> file for the upload
1703 (see <ref id="f-Urgency">). It is not possible to specify
1704 an urgency containing commas; commas are used to separate
1705 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1706 <prgn>dpkg</prgn> changelog format (though there is
1707 currently only one useful <var>keyword</var>,
1712 The change details may in fact be any series of lines
1713 starting with at least two spaces, but conventionally each
1714 change starts with an asterisk and a separating space and
1715 continuation lines are indented so as to bring them in
1716 line with the start of the text above. Blank lines may be
1717 used here to separate groups of changes, if desired.
1721 If this upload resolves bugs recorded in the Bug Tracking
1722 System (BTS), they may be automatically closed on the
1723 inclusion of this package into the Debian archive by
1724 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1725 in the change details.<footnote>
1726 To be precise, the string should match the following
1727 Perl regular expression:
1729 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1731 Then all of the bug numbers listed will be closed by the
1732 archive maintenance script (<prgn>katie</prgn>) using the
1733 <var>version</var> of the changelog entry.
1735 This information is conveyed via the <tt>Closes</tt> field
1736 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1740 The maintainer name and email address used in the changelog
1741 should be the details of the person uploading <em>this</em>
1742 version. They are <em>not</em> necessarily those of the
1743 usual package maintainer.<footnote>
1744 If the developer uploading the package is not one of the usual
1745 maintainers of the package (as listed in
1746 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1747 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1748 fields of the package), the first line of the changelog is
1749 conventionally used to explain why a non-maintainer is
1750 uploading the package. The Debian Developer's Reference
1751 (see <ref id="related">) documents the conventions
1753 The information here will be copied to the <tt>Changed-By</tt>
1754 field in the <tt>.changes</tt> file
1755 (see <ref id="f-Changed-By">), and then later used to send an
1756 acknowledgement when the upload has been installed.
1760 The <var>date</var> has the following format<footnote>
1761 This is the same as the format generated by <tt>date
1763 </footnote> (compatible and with the same semantics of
1764 RFC 2822 and RFC 5322):
1765 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1767 <list compact="compact">
1769 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1772 dd is a one- or two-digit day of the month (01-31)
1775 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1778 <item>yyyy is the four-digit year (e.g. 2010)</item>
1779 <item>hh is the two-digit hour (00-23)</item>
1780 <item>mm is the two-digit minutes (00-59)</item>
1781 <item>ss is the two-digit seconds (00-60)</item>
1783 +zzzz or -zzzz is the the time zone offset from Coordinated
1784 Universal Time (UTC). "+" indicates that the time is ahead
1785 of (i.e., east of) UTC and "-" indicates that the time is
1786 behind (i.e., west of) UTC. The first two digits indicate
1787 the hour difference from UTC and the last two digits
1788 indicate the number of additional minutes difference from
1789 UTC. The last two digits must be in the range 00-59.
1795 The first "title" line with the package name must start
1796 at the left hand margin. The "trailer" line with the
1797 maintainer and date details must be preceded by exactly
1798 one space. The maintainer details and the date must be
1799 separated by exactly two spaces.
1803 The entire changelog must be encoded in UTF-8.
1807 For more information on placement of the changelog files
1808 within binary packages, please see <ref id="changelogs">.
1812 <sect id="dpkgcopyright">
1813 <heading>Copyright: <file>debian/copyright</file></heading>
1815 Every package must be accompanied by a verbatim copy of its
1816 copyright information and distribution license in the file
1817 <file>/usr/share/doc/<var>package</var>/copyright</file>
1818 (see <ref id="copyrightfile"> for further details). Also see
1819 <ref id="pkgcopyright"> for further considerations related
1820 to copyrights for packages.
1824 <heading>Error trapping in makefiles</heading>
1827 When <prgn>make</prgn> invokes a command in a makefile
1828 (including your package's upstream makefiles and
1829 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1830 means that <prgn>sh</prgn>'s usual bad error handling
1831 properties apply: if you include a miniature script as one
1832 of the commands in your makefile you'll find that if you
1833 don't do anything about it then errors are not detected
1834 and <prgn>make</prgn> will blithely continue after
1839 Every time you put more than one shell command (this
1840 includes using a loop) in a makefile command you
1841 must make sure that errors are trapped. For
1842 simple compound commands, such as changing directory and
1843 then running a program, using <tt>&&</tt> rather
1844 than semicolon as a command separator is sufficient. For
1845 more complex commands including most loops and
1846 conditionals you should include a separate <tt>set -e</tt>
1847 command at the start of every makefile command that's
1848 actually one of these miniature shell scripts.
1852 <sect id="timestamps">
1853 <heading>Time Stamps</heading>
1855 Maintainers should preserve the modification times of the
1856 upstream source files in a package, as far as is reasonably
1858 The rationale is that there is some information conveyed
1859 by knowing the age of the file, for example, you could
1860 recognize that some documentation is very old by looking
1861 at the modification time, so it would be nice if the
1862 modification time of the upstream source would be
1868 <sect id="restrictions">
1869 <heading>Restrictions on objects in source packages</heading>
1872 The source package may not contain any hard links<footnote>
1874 This is not currently detected when building source
1875 packages, but only when extracting
1879 Hard links may be permitted at some point in the
1880 future, but would require a fair amount of
1883 </footnote>, device special files, sockets or setuid or
1884 setgid files.<footnote>
1885 Setgid directories are allowed.
1890 <sect id="debianrules">
1891 <heading>Main building script: <file>debian/rules</file></heading>
1894 This file must be an executable makefile, and contains the
1895 package-specific recipes for compiling the package and
1896 building binary package(s) from the source.
1900 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1901 so that it can be invoked by saying its name rather than
1902 invoking <prgn>make</prgn> explicitly. That is, invoking
1903 either of <tt>make -f debian/rules <em>args...</em></tt>
1904 or <tt>./debian/rules <em>args...</em></tt> must result in
1909 The following targets are required and must be implemented
1910 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1911 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1912 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1916 Since an interactive <file>debian/rules</file> script makes it
1917 impossible to auto-compile that package and also makes it hard
1918 for other people to reproduce the same binary package, all
1919 required targets must be non-interactive. It also follows that
1920 any target that these targets depend on must also be
1925 The targets are as follows:
1927 <tag><tt>build</tt> (required)</tag>
1930 The <tt>build</tt> target should perform all the
1931 configuration and compilation of the package.
1932 If a package has an interactive pre-build
1933 configuration routine, the Debian source package
1934 must either be built after this has taken place (so
1935 that the binary package can be built without rerunning
1936 the configuration) or the configuration routine
1937 modified to become non-interactive. (The latter is
1938 preferable if there are architecture-specific features
1939 detected by the configuration routine.)
1943 For some packages, notably ones where the same
1944 source tree is compiled in different ways to produce
1945 two binary packages, the <tt>build</tt> target
1946 does not make much sense. For these packages it is
1947 good enough to provide two (or more) targets
1948 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1949 for each of the ways of building the package, and a
1950 <tt>build</tt> target that does nothing. The
1951 <tt>binary</tt> target will have to build the
1952 package in each of the possible ways and make the
1953 binary package out of each.
1957 The <tt>build</tt> target must not do anything
1958 that might require root privilege.
1962 The <tt>build</tt> target may need to run the
1963 <tt>clean</tt> target first - see below.
1967 When a package has a configuration and build routine
1968 which takes a long time, or when the makefiles are
1969 poorly designed, or when <tt>build</tt> needs to
1970 run <tt>clean</tt> first, it is a good idea to
1971 <tt>touch build</tt> when the build process is
1972 complete. This will ensure that if <tt>debian/rules
1973 build</tt> is run again it will not rebuild the whole
1975 Another common way to do this is for <tt>build</tt>
1976 to depend on <prgn>build-stamp</prgn> and to do
1977 nothing else, and for the <prgn>build-stamp</prgn>
1978 target to do the building and to <tt>touch
1979 build-stamp</tt> on completion. This is
1980 especially useful if the build routine creates a
1981 file or directory called <tt>build</tt>; in such a
1982 case, <tt>build</tt> will need to be listed as
1983 a phony target (i.e., as a dependency of the
1984 <tt>.PHONY</tt> target). See the documentation of
1985 <prgn>make</prgn> for more information on phony
1991 <tag><tt>build-arch</tt> (optional),
1992 <tt>build-indep</tt> (optional)
1996 A package may also provide one or both of the targets
1997 <tt>build-arch</tt> and <tt>build-indep</tt>.
1998 The <tt>build-arch</tt> target, if provided, should
1999 perform all the configuration and compilation required for
2000 producing all architecture-dependant binary packages
2001 (those packages for which the body of the
2002 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2003 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2004 target, if provided, should perform all the configuration
2005 and compilation required for producing all
2006 architecture-independent binary packages (those packages
2007 for which the body of the <tt>Architecture</tt> field
2008 in <tt>debian/control</tt> is <tt>all</tt>).
2012 If <tt>build-arch</tt> or <tt>build-indep</tt> targets are
2013 provided in the rules file, the <tt>build</tt> target
2014 should either depend on those targets or take the same
2015 actions as invoking those targets would perform.<footnote>
2016 The intent of this split is so that binary-only builds
2017 need not install the dependencies required for
2018 the <tt>build-indep</tt> target. However, this is not
2019 yet used in practice since <tt>dpkg-buildpackage
2020 -B</tt>, and therefore the autobuilders,
2021 invoke <tt>build</tt> rather than <tt>build-arch</tt>
2022 due to the difficulties in determining whether the
2023 optional <tt>build-arch</tt> target exists.
2028 If one or both of the targets <tt>build-arch</tt> and
2029 <tt>build-indep</tt> are not provided, then invoking
2030 <file>debian/rules</file> with one of the not-provided
2031 targets as arguments should produce a exit status code
2032 of 2. Usually this is provided automatically by make
2033 if the target is missing.
2037 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2038 must not do anything that might require root privilege.
2042 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2043 (required), <tt>binary-indep</tt> (required)
2047 The <tt>binary</tt> target must be all that is
2048 necessary for the user to build the binary package(s)
2049 produced from this source package. It is
2050 split into two parts: <prgn>binary-arch</prgn> builds
2051 the binary packages which are specific to a particular
2052 architecture, and <tt>binary-indep</tt> builds
2053 those which are not.
2056 <tt>binary</tt> may be (and commonly is) a target with
2057 no commands which simply depends on
2058 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2061 Both <tt>binary-*</tt> targets should depend on the
2062 <tt>build</tt> target, or on the appropriate
2063 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2064 provided, so that the package is built if it has not
2065 been already. It should then create the relevant
2066 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2067 make their control files and <prgn>dpkg-deb</prgn> to
2068 build them and place them in the parent of the top
2073 Both the <tt>binary-arch</tt> and
2074 <tt>binary-indep</tt> targets <em>must</em> exist.
2075 If one of them has nothing to do (which will always be
2076 the case if the source generates only a single binary
2077 package, whether architecture-dependent or not), it
2078 must still exist and must always succeed.
2082 The <tt>binary</tt> targets must be invoked as
2084 The <prgn>fakeroot</prgn> package often allows one
2085 to build a package correctly even without being
2091 <tag><tt>clean</tt> (required)</tag>
2094 This must undo any effects that the <tt>build</tt>
2095 and <tt>binary</tt> targets may have had, except
2096 that it should leave alone any output files created in
2097 the parent directory by a run of a <tt>binary</tt>
2102 If a <tt>build</tt> file is touched at the end of
2103 the <tt>build</tt> target, as suggested above, it
2104 should be removed as the first action that
2105 <tt>clean</tt> performs, so that running
2106 <tt>build</tt> again after an interrupted
2107 <tt>clean</tt> doesn't think that everything is
2112 The <tt>clean</tt> target may need to be
2113 invoked as root if <tt>binary</tt> has been
2114 invoked since the last <tt>clean</tt>, or if
2115 <tt>build</tt> has been invoked as root (since
2116 <tt>build</tt> may create directories, for
2121 <tag><tt>get-orig-source</tt> (optional)</tag>
2124 This target fetches the most recent version of the
2125 original source package from a canonical archive site
2126 (via FTP or WWW, for example), does any necessary
2127 rearrangement to turn it into the original source
2128 tar file format described below, and leaves it in the
2133 This target may be invoked in any directory, and
2134 should take care to clean up any temporary files it
2139 This target is optional, but providing it if
2140 possible is a good idea.
2144 <tag><tt>patch</tt> (optional)</tag>
2147 This target performs whatever additional actions are
2148 required to make the source ready for editing (unpacking
2149 additional upstream archives, applying patches, etc.).
2150 It is recommended to be implemented for any package where
2151 <tt>dpkg-source -x</tt> does not result in source ready
2152 for additional modification. See
2153 <ref id="readmesource">.
2159 The <tt>build</tt>, <tt>binary</tt> and
2160 <tt>clean</tt> targets must be invoked with the current
2161 directory being the package's top-level directory.
2166 Additional targets may exist in <file>debian/rules</file>,
2167 either as published or undocumented interfaces or for the
2168 package's internal use.
2172 The architectures we build on and build for are determined
2173 by <prgn>make</prgn> variables using the
2174 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2175 You can determine the Debian architecture and the GNU style
2176 architecture specification string for the build architecture as
2177 well as for the host architecture. The build architecture is
2178 the architecture on which <file>debian/rules</file> is run and
2179 the package build is performed. The host architecture is the
2180 architecture on which the resulting package will be installed
2181 and run. These are normally the same, but may be different in
2182 the case of cross-compilation (building packages for one
2183 architecture on machines of a different architecture).
2187 Here is a list of supported <prgn>make</prgn> variables:
2188 <list compact="compact">
2190 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2193 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2196 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2199 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2200 specification string)
2203 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2204 <tt>DEB_*_GNU_TYPE</tt>)
2207 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2208 <tt>DEB_*_GNU_TYPE</tt>)
2210 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2211 the build architecture or <tt>HOST</tt> for specification of the
2216 Backward compatibility can be provided in the rules file
2217 by setting the needed variables to suitable default
2218 values; please refer to the documentation of
2219 <prgn>dpkg-architecture</prgn> for details.
2223 It is important to understand that the <tt>DEB_*_ARCH</tt>
2224 string only determines which Debian architecture we are
2225 building on or for. It should not be used to get the CPU
2226 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2227 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2228 GNU style variables should generally only be used with upstream
2232 <sect1 id="debianrules-options">
2233 <heading><file>debian/rules</file> and
2234 <tt>DEB_BUILD_OPTIONS</tt></heading>
2237 Supporting the standardized environment variable
2238 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2239 contain several flags to change how a package is compiled and
2240 built. Each flag must be in the form <var>flag</var> or
2241 <var>flag</var>=<var>options</var>. If multiple flags are
2242 given, they must be separated by whitespace.<footnote>
2243 Some packages support any delimiter, but whitespace is the
2244 easiest to parse inside a makefile and avoids ambiguity with
2245 flag values that contain commas.
2247 <var>flag</var> must start with a lowercase letter
2248 (<tt>a-z</tt>) and consist only of lowercase letters,
2249 numbers (<tt>0-9</tt>), and the characters
2250 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2251 <var>options</var> must not contain whitespace. The same
2252 tag should not be given multiple times with conflicting
2253 values. Package maintainers may assume that
2254 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2258 The meaning of the following tags has been standardized:
2262 This tag says to not run any build-time test suite
2263 provided by the package.
2267 The presence of this tag means that the package should
2268 be compiled with a minimum of optimization. For C
2269 programs, it is best to add <tt>-O0</tt> to
2270 <tt>CFLAGS</tt> (although this is usually the default).
2271 Some programs might fail to build or run at this level
2272 of optimization; it may be necessary to use
2273 <tt>-O1</tt>, for example.
2277 This tag means that the debugging symbols should not be
2278 stripped from the binary during installation, so that
2279 debugging information may be included in the package.
2281 <tag>parallel=n</tag>
2283 This tag means that the package should be built using up
2284 to <tt>n</tt> parallel processes if the package build
2285 system supports this.<footnote>
2286 Packages built with <tt>make</tt> can often implement
2287 this by passing the <tt>-j</tt><var>n</var> option to
2290 If the package build system does not support parallel
2291 builds, this string must be ignored. If the package
2292 build system only supports a lower level of concurrency
2293 than <var>n</var>, the package should be built using as
2294 many parallel processes as the package build system
2295 supports. It is up to the package maintainer to decide
2296 whether the package build times are long enough and the
2297 package build system is robust enough to make supporting
2298 parallel builds worthwhile.
2304 Unknown flags must be ignored by <file>debian/rules</file>.
2308 The following makefile snippet is an example of how one may
2309 implement the build options; you will probably have to
2310 massage this example in order to make it work for your
2312 <example compact="compact">
2315 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2316 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2317 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2318 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2320 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2325 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2326 INSTALL_PROGRAM += -s
2328 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2329 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2330 MAKEFLAGS += -j$(NUMJOBS)
2335 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2336 # Code to run the package test suite.
2343 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2344 <sect id="substvars">
2345 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2348 When <prgn>dpkg-gencontrol</prgn>
2349 generates <qref id="binarycontrolfiles">binary package control
2350 files</qref> (<file>DEBIAN/control</file>), it performs variable
2351 substitutions on its output just before writing it. Variable
2352 substitutions have the form <tt>${<var>variable</var>}</tt>.
2353 The optional file <file>debian/substvars</file> contains
2354 variable substitutions to be used; variables can also be set
2355 directly from <file>debian/rules</file> using the <tt>-V</tt>
2356 option to the source packaging commands, and certain predefined
2357 variables are also available.
2361 The <file>debian/substvars</file> file is usually generated and
2362 modified dynamically by <file>debian/rules</file> targets, in
2363 which case it must be removed by the <tt>clean</tt> target.
2367 See <manref name="deb-substvars" section="5"> for full
2368 details about source variable substitutions, including the
2369 format of <file>debian/substvars</file>.</p>
2372 <sect id="debianwatch">
2373 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2376 This is an optional, recommended configuration file for the
2377 <tt>uscan</tt> utility which defines how to automatically scan
2378 ftp or http sites for newly available updates of the
2379 package. This is used
2380 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2381 tools to help with quality control and maintenance of the
2382 distribution as a whole.
2387 <sect id="debianfiles">
2388 <heading>Generated files list: <file>debian/files</file></heading>
2391 This file is not a permanent part of the source tree; it
2392 is used while building packages to record which files are
2393 being generated. <prgn>dpkg-genchanges</prgn> uses it
2394 when it generates a <file>.changes</file> file.
2398 It should not exist in a shipped source package, and so it
2399 (and any backup files or temporary files such as
2400 <file>files.new</file><footnote>
2401 <file>files.new</file> is used as a temporary file by
2402 <prgn>dpkg-gencontrol</prgn> and
2403 <prgn>dpkg-distaddfile</prgn> - they write a new
2404 version of <tt>files</tt> here before renaming it,
2405 to avoid leaving a corrupted copy if an error
2407 </footnote>) should be removed by the
2408 <tt>clean</tt> target. It may also be wise to
2409 ensure a fresh start by emptying or removing it at the
2410 start of the <tt>binary</tt> target.
2414 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2415 package, it adds an entry to <file>debian/files</file> for the
2416 <file>.deb</file> file that will be created when <tt>dpkg-deb
2417 --build</tt> is run for that binary package. So for most
2418 packages all that needs to be done with this file is to
2419 delete it in the <tt>clean</tt> target.
2423 If a package upload includes files besides the source
2424 package and any binary packages whose control files were
2425 made with <prgn>dpkg-gencontrol</prgn> then they should be
2426 placed in the parent of the package's top-level directory
2427 and <prgn>dpkg-distaddfile</prgn> should be called to add
2428 the file to the list in <file>debian/files</file>.</p>
2431 <sect id="embeddedfiles">
2432 <heading>Convenience copies of code</heading>
2435 Some software packages include in their distribution convenience
2436 copies of code from other software packages, generally so that
2437 users compiling from source don't have to download multiple
2438 packages. Debian packages should not make use of these
2439 convenience copies unless the included package is explicitly
2440 intended to be used in this way.<footnote>
2441 For example, parts of the GNU build system work like this.
2443 If the included code is already in the Debian archive in the
2444 form of a library, the Debian packaging should ensure that
2445 binary packages reference the libraries already in Debian and
2446 the convenience copy is not used. If the included code is not
2447 already in Debian, it should be packaged separately as a
2448 prerequisite if possible.
2450 Having multiple copies of the same code in Debian is
2451 inefficient, often creates either static linking or shared
2452 library conflicts, and, most importantly, increases the
2453 difficulty of handling security vulnerabilities in the
2459 <sect id="readmesource">
2460 <heading>Source package handling:
2461 <file>debian/README.source</file></heading>
2464 If running <prgn>dpkg-source -x</prgn> on a source package
2465 doesn't produce the source of the package, ready for editing,
2466 and allow one to make changes and run
2467 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2468 without taking any additional steps, creating a
2469 <file>debian/README.source</file> documentation file is
2470 recommended. This file should explain how to do all of the
2473 <item>Generate the fully patched source, in a form ready for
2474 editing, that would be built to create Debian
2475 packages. Doing this with a <tt>patch</tt> target in
2476 <file>debian/rules</file> is recommended; see
2477 <ref id="debianrules">.</item>
2478 <item>Modify the source and save those modifications so that
2479 they will be applied when building the package.</item>
2480 <item>Remove source modifications that are currently being
2481 applied when building the package.</item>
2482 <item>Optionally, document what steps are necessary to
2483 upgrade the Debian source package to a new upstream version,
2484 if applicable.</item>
2486 This explanation should include specific commands and mention
2487 any additional required Debian packages. It should not assume
2488 familiarity with any specific Debian packaging system or patch
2493 This explanation may refer to a documentation file installed by
2494 one of the package's build dependencies provided that the
2495 referenced documentation clearly explains these tasks and is not
2496 a general reference manual.
2500 <file>debian/README.source</file> may also include any other
2501 information that would be helpful to someone modifying the
2502 source package. Even if the package doesn't fit the above
2503 description, maintainers are encouraged to document in a
2504 <file>debian/README.source</file> file any source package with a
2505 particularly complex or unintuitive source layout or build
2506 system (for example, a package that builds the same source
2507 multiple times to generate different binary packages).
2513 <chapt id="controlfields">
2514 <heading>Control files and their fields</heading>
2517 The package management system manipulates data represented in
2518 a common format, known as <em>control data</em>, stored in
2519 <em>control files</em>.
2520 Control files are used for source packages, binary packages and
2521 the <file>.changes</file> files which control the installation
2522 of uploaded files<footnote>
2523 <prgn>dpkg</prgn>'s internal databases are in a similar
2528 <sect id="controlsyntax">
2529 <heading>Syntax of control files</heading>
2532 A control file consists of one or more paragraphs of
2534 The paragraphs are also sometimes referred to as stanzas.
2536 The paragraphs are separated by empty lines. Parsers may accept
2537 lines consisting solely of spaces and tabs as paragraph
2538 separators, but control files should use empty lines. Some control
2539 files allow only one paragraph; others allow several, in
2540 which case each paragraph usually refers to a different
2541 package. (For example, in source packages, the first
2542 paragraph refers to the source package, and later paragraphs
2543 refer to binary packages generated from the source.) The
2544 ordering of the paragraphs in control files is significant.
2548 Each paragraph consists of a series of data fields. Each field
2549 consists of the field name followed by a colon and then the
2550 data/value associated with that field. The field name is
2551 composed of US-ASCII characters excluding control characters,
2552 space, and colon (i.e., characters in the ranges 33-57 and
2553 59-126, inclusive). Field names must not begin with the comment
2554 character, <tt>#</tt>.
2558 The field ends at the end of the line or at the end of the last
2559 continuation line (see below). Horizontal whitespace (spaces
2560 and tabs) may occur immediately before or after the value and is
2561 ignored there; it is conventional to put a single space after
2562 the colon. For example, a field might be:
2563 <example compact="compact">
2566 the field name is <tt>Package</tt> and the field value
2571 A paragraph must not contain more than one instance of a
2572 particular field name.
2576 There are three types of fields:
2580 The field, including its value, must be a single line. Folding
2581 of the field is not permitted. This is the default field type
2582 if the definition of the field does not specify a different
2587 The value of a folded field is a logical line that may span
2588 several lines. The lines after the first are called
2589 continuation lines and must start with a space or a tab.
2590 Whitespace, including any newlines, is not significant in the
2591 field values of folded fields.<footnote>
2592 This folding method is similar to RFC 5322, allowing control
2593 files that contain only one paragraph and no multiline fields
2594 to be read by parsers written for RFC 5322.
2597 <tag>multiline</tag>
2599 The value of a multiline field may comprise multiple continuation
2600 lines. The first line of the value, the part on the same line as
2601 the field name, often has special significance or may have to be
2602 empty. Other lines are added following the same syntax as the
2603 continuation lines of the folded fields. Whitespace, including newlines,
2604 is significant in the values of multiline fields.
2610 Whitespace must not appear
2611 inside names (of packages, architectures, files or anything
2612 else) or version numbers, or between the characters of
2613 multi-character version relationships.
2617 The presence and purpose of a field, and the syntax of its
2618 value may differ between types of control files.
2622 Field names are not case-sensitive, but it is usual to
2623 capitalize the field names using mixed case as shown below.
2624 Field values are case-sensitive unless the description of the
2625 field says otherwise.
2629 Paragraph separators (empty lines) and lines consisting only of
2630 spaces and tabs are not allowed within field values or between
2631 fields. Empty lines in field values are usually escaped by
2632 representing them by a space followed by a dot.
2636 Lines starting with # without any preceding whitespace are comments
2637 lines that are only permitted in source package control files
2638 (<file>debian/control</file>). These comment lines are ignored, even
2639 between two continuation lines. They do not end logical lines.
2643 All control files must be encoded in UTF-8.
2647 <sect id="sourcecontrolfiles">
2648 <heading>Source package control files -- <file>debian/control</file></heading>
2651 The <file>debian/control</file> file contains the most vital
2652 (and version-independent) information about the source package
2653 and about the binary packages it creates.
2657 The first paragraph of the control file contains information about
2658 the source package in general. The subsequent sets each describe a
2659 binary package that the source tree builds.
2663 The fields in the general paragraph (the first one, for the source
2666 <list compact="compact">
2667 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2668 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2669 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2670 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2671 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2672 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2673 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2674 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2675 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2676 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2681 The fields in the binary package paragraphs are:
2683 <list compact="compact">
2684 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2685 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2686 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2687 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2688 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2689 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2690 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2692 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2697 The syntax and semantics of the fields are described below.
2701 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2702 generate control files for binary packages (see below), by
2703 <prgn>dpkg-genchanges</prgn> to generate the
2704 <file>.changes</file> file to accompany the upload, and by
2705 <prgn>dpkg-source</prgn> when it creates the
2706 <file>.dsc</file> source control file as part of a source
2707 archive. Some fields are folded in <file>debian/control</file>,
2708 but not in any other control
2709 file. These tools are responsible for removing the line
2710 breaks from such fields when using fields from
2711 <file>debian/control</file> to generate other control files.
2715 The fields here may contain variable references - their
2716 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2717 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2718 when they generate output control files.
2719 See <ref id="substvars"> for details.
2723 <sect id="binarycontrolfiles">
2724 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2727 The <file>DEBIAN/control</file> file contains the most vital
2728 (and version-dependent) information about a binary package. It
2729 consists of a single paragraph.
2733 The fields in this file are:
2735 <list compact="compact">
2736 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2737 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2738 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2739 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2740 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2741 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2742 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2743 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2744 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2745 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2746 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2747 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2748 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2753 <sect id="debiansourcecontrolfiles">
2754 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2757 This file consists of a single paragraph, possibly surrounded by
2758 a PGP signature. The fields of that paragraph are listed below.
2759 Their syntax is described above, in <ref id="controlsyntax">.
2761 <list compact="compact">
2762 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2763 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2764 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2765 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2766 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2768 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2769 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2770 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2771 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2772 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2773 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2774 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2775 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2776 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2781 The Debian source control file is generated by
2782 <prgn>dpkg-source</prgn> when it builds the source
2783 archive, from other files in the source package,
2784 described above. When unpacking, it is checked against
2785 the files and directories in the other parts of the
2791 <sect id="debianchangesfiles">
2792 <heading>Debian changes files -- <file>.changes</file></heading>
2795 The <file>.changes</file> files are used by the Debian archive
2796 maintenance software to process updates to packages. They
2797 consist of a single paragraph, possibly surrounded by a PGP
2798 signature. That paragraph contains information from the
2799 <file>debian/control</file> file and other data about the
2800 source package gathered via <file>debian/changelog</file>
2801 and <file>debian/rules</file>.
2805 <file>.changes</file> files have a format version that is
2806 incremented whenever the documented fields or their meaning
2807 change. This document describes format &changesversion;.
2811 The fields in this file are:
2813 <list compact="compact">
2814 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2818 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2820 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2821 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2822 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2823 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2824 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2825 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2826 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2827 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2828 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2829 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2834 <sect id="controlfieldslist">
2835 <heading>List of fields</heading>
2837 <sect1 id="f-Source">
2838 <heading><tt>Source</tt></heading>
2841 This field identifies the source package name.
2845 In <file>debian/control</file> or a <file>.dsc</file> file,
2846 this field must contain only the name of the source package.
2850 In a binary package control file or a <file>.changes</file>
2851 file, the source package name may be followed by a version
2852 number in parentheses<footnote>
2853 It is customary to leave a space after the package name
2854 if a version number is specified.
2856 This version number may be omitted (and is, by
2857 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2858 the <tt>Version</tt> field of the binary package in
2859 question. The field itself may be omitted from a binary
2860 package control file when the source package has the same
2861 name and version as the binary package.
2865 Package names (both source and binary,
2866 see <ref id="f-Package">) must consist only of lower case
2867 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2868 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2869 (<tt>.</tt>). They must be at least two characters long and
2870 must start with an alphanumeric character.
2874 <sect1 id="f-Maintainer">
2875 <heading><tt>Maintainer</tt></heading>
2878 The package maintainer's name and email address. The name
2879 must come first, then the email address inside angle
2880 brackets <tt><></tt> (in RFC822 format).
2884 If the maintainer's name contains a full stop then the
2885 whole field will not work directly as an email address due
2886 to a misfeature in the syntax specified in RFC822; a
2887 program using this field as an address must check for this
2888 and correct the problem if necessary (for example by
2889 putting the name in round brackets and moving it to the
2890 end, and bringing the email address forward).
2894 See <ref id="maintainer"> for additional requirements and
2895 information about package maintainers.
2899 <sect1 id="f-Uploaders">
2900 <heading><tt>Uploaders</tt></heading>
2903 List of the names and email addresses of co-maintainers of the
2904 package, if any. If the package has other maintainers besides
2905 the one named in the <qref id="f-Maintainer">Maintainer
2906 field</qref>, their names and email addresses should be listed
2907 here. The format of each entry is the same as that of the
2908 Maintainer field, and multiple entries must be comma
2913 This is normally an optional field, but if
2914 the <tt>Maintainer</tt> control field names a group of people
2915 and a shared email address, the <tt>Uploaders</tt> field must
2916 be present and must contain at least one human with their
2917 personal email address.
2921 The Uploaders field in <file>debian/control</file> can be folded.
2925 <sect1 id="f-Changed-By">
2926 <heading><tt>Changed-By</tt></heading>
2929 The name and email address of the person who prepared this
2930 version of the package, usually a maintainer. The syntax is
2931 the same as for the <qref id="f-Maintainer">Maintainer
2936 <sect1 id="f-Section">
2937 <heading><tt>Section</tt></heading>
2940 This field specifies an application area into which the package
2941 has been classified. See <ref id="subsections">.
2945 When it appears in the <file>debian/control</file> file,
2946 it gives the value for the subfield of the same name in
2947 the <tt>Files</tt> field of the <file>.changes</file> file.
2948 It also gives the default for the same field in the binary
2953 <sect1 id="f-Priority">
2954 <heading><tt>Priority</tt></heading>
2957 This field represents how important it is that the user
2958 have the package installed. See <ref id="priorities">.
2962 When it appears in the <file>debian/control</file> file,
2963 it gives the value for the subfield of the same name in
2964 the <tt>Files</tt> field of the <file>.changes</file> file.
2965 It also gives the default for the same field in the binary
2970 <sect1 id="f-Package">
2971 <heading><tt>Package</tt></heading>
2974 The name of the binary package.
2978 Binary package names must follow the same syntax and
2979 restrictions as source package names. See <ref id="f-Source">
2984 <sect1 id="f-Architecture">
2985 <heading><tt>Architecture</tt></heading>
2988 Depending on context and the control file used, the
2989 <tt>Architecture</tt> field can include the following sets of
2993 A unique single word identifying a Debian machine
2994 architecture as described in <ref id="arch-spec">.
2997 An architecture wildcard identifying a set of Debian
2998 machine architectures, see <ref id="arch-wildcard-spec">.
2999 <tt>any</tt> matches all Debian machine architectures
3000 and is the most frequently used.
3003 <tt>all</tt>, which indicates an
3004 architecture-independent package.
3007 <tt>source</tt>, which indicates a source package.
3013 In the main <file>debian/control</file> file in the source
3014 package, this field may contain the special
3015 value <tt>all</tt>, the special architecture
3016 wildcard <tt>any</tt>, or a list of specific and wildcard
3017 architectures separated by spaces. If <tt>all</tt>
3018 or <tt>any</tt> appears, that value must be the entire
3019 contents of the field. Most packages will use
3020 either <tt>all</tt> or <tt>any</tt>.
3024 Specifying a specific list of architectures indicates that the
3025 source will build an architecture-dependent package only on
3026 architectures included in the list. Specifying a list of
3027 architecture wildcards indicates that the source will build an
3028 architecture-dependent package on only those architectures
3029 that match any of the specified architecture wildcards.
3030 Specifying a list of architectures or architecture wildcards
3031 other than <tt>any</tt> is for the minority of cases where a
3032 program is not portable or is not useful on some
3033 architectures. Where possible, the program should be made
3038 In the Debian source control file <file>.dsc</file>, this
3039 field contains a list of architectures and architecture
3040 wildcards separated by spaces. When the list contains the
3041 architecture wildcard <tt>any</tt>, the only other value
3042 allowed in the list is <tt>all</tt>.
3046 The list may include (or consist solely of) the special
3047 value <tt>all</tt>. In other words, in <file>.dsc</file>
3048 files unlike the <file>debian/control</file>, <tt>all</tt> may
3049 occur in combination with specific architectures.
3050 The <tt>Architecture</tt> field in the Debian source control
3051 file <file>.dsc</file> is generally constructed from
3052 the <tt>Architecture</tt> fields in
3053 the <file>debian/control</file> in the source package.
3057 Specifying only <tt>any</tt> indicates that the source package
3058 isn't dependent on any particular architecture and should
3059 compile fine on any one. The produced binary package(s)
3060 will be specific to whatever the current build architecture is.
3064 Specifying only <tt>all</tt> indicates that the source package
3065 will only build architecture-independent packages.
3069 Specifying <tt>any all</tt> indicates that the source package
3070 isn't dependent on any particular architecture. The set of
3071 produced binary packages will include at least one
3072 architecture-dependant package and one architecture-independent
3077 Specifying a list of architectures or architecture wildcards
3078 indicates that the source will build an architecture-dependent
3079 package, and will only work correctly on the listed or
3080 matching architectures. If the source package also builds at
3081 least one architecture-independent package, <tt>all</tt> will
3082 also be included in the list.
3086 In a <file>.changes</file> file, the <tt>Architecture</tt>
3087 field lists the architecture(s) of the package(s) currently
3088 being uploaded. This will be a list; if the source for the
3089 package is also being uploaded, the special
3090 entry <tt>source</tt> is also present. <tt>all</tt> will be
3091 present if any architecture-independent packages are being
3092 uploaded. Architecture wildcards such as <tt>any</tt> must
3093 never occur in the <tt>Architecture</tt> field in
3094 the <file>.changes</file> file.
3098 See <ref id="debianrules"> for information on how to get
3099 the architecture for the build process.
3103 <sect1 id="f-Essential">
3104 <heading><tt>Essential</tt></heading>
3107 This is a boolean field which may occur only in the
3108 control file of a binary package or in a per-package fields
3109 paragraph of a source package control file.
3113 If set to <tt>yes</tt> then the package management system
3114 will refuse to remove the package (upgrading and replacing
3115 it is still possible). The other possible value is <tt>no</tt>,
3116 which is the same as not having the field at all.
3121 <heading>Package interrelationship fields:
3122 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3123 <tt>Recommends</tt>, <tt>Suggests</tt>,
3124 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3125 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3129 These fields describe the package's relationships with
3130 other packages. Their syntax and semantics are described
3131 in <ref id="relationships">.</p>
3134 <sect1 id="f-Standards-Version">
3135 <heading><tt>Standards-Version</tt></heading>
3138 The most recent version of the standards (the policy
3139 manual and associated texts) with which the package
3144 The version number has four components: major and minor
3145 version number and major and minor patch level. When the
3146 standards change in a way that requires every package to
3147 change the major number will be changed. Significant
3148 changes that will require work in many packages will be
3149 signaled by a change to the minor number. The major patch
3150 level will be changed for any change to the meaning of the
3151 standards, however small; the minor patch level will be
3152 changed when only cosmetic, typographical or other edits
3153 are made which neither change the meaning of the document
3154 nor affect the contents of packages.
3158 Thus only the first three components of the policy version
3159 are significant in the <em>Standards-Version</em> control
3160 field, and so either these three components or all four
3161 components may be specified.<footnote>
3162 In the past, people specified the full version number
3163 in the Standards-Version field, for example "2.3.0.0".
3164 Since minor patch-level changes don't introduce new
3165 policy, it was thought it would be better to relax
3166 policy and only require the first 3 components to be
3167 specified, in this example "2.3.0". All four
3168 components may still be used if someone wishes to do so.
3174 <sect1 id="f-Version">
3175 <heading><tt>Version</tt></heading>
3178 The version number of a package. The format is:
3179 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3183 The three components here are:
3185 <tag><var>epoch</var></tag>
3188 This is a single (generally small) unsigned integer. It
3189 may be omitted, in which case zero is assumed. If it is
3190 omitted then the <var>upstream_version</var> may not
3195 It is provided to allow mistakes in the version numbers
3196 of older versions of a package, and also a package's
3197 previous version numbering schemes, to be left behind.
3201 <tag><var>upstream_version</var></tag>
3204 This is the main part of the version number. It is
3205 usually the version number of the original ("upstream")
3206 package from which the <file>.deb</file> file has been made,
3207 if this is applicable. Usually this will be in the same
3208 format as that specified by the upstream author(s);
3209 however, it may need to be reformatted to fit into the
3210 package management system's format and comparison
3215 The comparison behavior of the package management system
3216 with respect to the <var>upstream_version</var> is
3217 described below. The <var>upstream_version</var>
3218 portion of the version number is mandatory.
3222 The <var>upstream_version</var> may contain only
3223 alphanumerics<footnote>
3224 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3226 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3227 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3228 tilde) and should start with a digit. If there is no
3229 <var>debian_revision</var> then hyphens are not allowed;
3230 if there is no <var>epoch</var> then colons are not
3235 <tag><var>debian_revision</var></tag>
3238 This part of the version number specifies the version of
3239 the Debian package based on the upstream version. It
3240 may contain only alphanumerics and the characters
3241 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3242 tilde) and is compared in the same way as the
3243 <var>upstream_version</var> is.
3247 It is optional; if it isn't present then the
3248 <var>upstream_version</var> may not contain a hyphen.
3249 This format represents the case where a piece of
3250 software was written specifically to be a Debian
3251 package, where the Debian package source must always
3252 be identical to the pristine source and therefore no
3253 revision indication is required.
3257 It is conventional to restart the
3258 <var>debian_revision</var> at <tt>1</tt> each time the
3259 <var>upstream_version</var> is increased.
3263 The package management system will break the version
3264 number apart at the last hyphen in the string (if there
3265 is one) to determine the <var>upstream_version</var> and
3266 <var>debian_revision</var>. The absence of a
3267 <var>debian_revision</var> is equivalent to a
3268 <var>debian_revision</var> of <tt>0</tt>.
3275 When comparing two version numbers, first the <var>epoch</var>
3276 of each are compared, then the <var>upstream_version</var> if
3277 <var>epoch</var> is equal, and then <var>debian_revision</var>
3278 if <var>upstream_version</var> is also equal.
3279 <var>epoch</var> is compared numerically. The
3280 <var>upstream_version</var> and <var>debian_revision</var>
3281 parts are compared by the package management system using the
3282 following algorithm:
3286 The strings are compared from left to right.
3290 First the initial part of each string consisting entirely of
3291 non-digit characters is determined. These two parts (one of
3292 which may be empty) are compared lexically. If a difference
3293 is found it is returned. The lexical comparison is a
3294 comparison of ASCII values modified so that all the letters
3295 sort earlier than all the non-letters and so that a tilde
3296 sorts before anything, even the end of a part. For example,
3297 the following parts are in sorted order from earliest to
3298 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3299 <tt>a</tt>.<footnote>
3300 One common use of <tt>~</tt> is for upstream pre-releases.
3301 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3302 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3307 Then the initial part of the remainder of each string which
3308 consists entirely of digit characters is determined. The
3309 numerical values of these two parts are compared, and any
3310 difference found is returned as the result of the comparison.
3311 For these purposes an empty string (which can only occur at
3312 the end of one or both version strings being compared) counts
3317 These two steps (comparing and removing initial non-digit
3318 strings and initial digit strings) are repeated until a
3319 difference is found or both strings are exhausted.
3323 Note that the purpose of epochs is to allow us to leave behind
3324 mistakes in version numbering, and to cope with situations
3325 where the version numbering scheme changes. It is
3326 <em>not</em> intended to cope with version numbers containing
3327 strings of letters which the package management system cannot
3328 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3329 silly orderings.<footnote>
3330 The author of this manual has heard of a package whose
3331 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3332 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3338 <sect1 id="f-Description">
3339 <heading><tt>Description</tt></heading>
3342 In a source or binary control file, the <tt>Description</tt>
3343 field contains a description of the binary package, consisting
3344 of two parts, the synopsis or the short description, and the
3345 long description. It is a multiline field with the following
3351 Description: <single line synopsis>
3352 <extended description over several lines>
3357 The lines in the extended description can have these formats:
3363 Those starting with a single space are part of a paragraph.
3364 Successive lines of this form will be word-wrapped when
3365 displayed. The leading space will usually be stripped off.
3366 The line must contain at least one non-whitespace character.
3370 Those starting with two or more spaces. These will be
3371 displayed verbatim. If the display cannot be panned
3372 horizontally, the displaying program will line wrap them "hard"
3373 (i.e., without taking account of word breaks). If it can they
3374 will be allowed to trail off to the right. None, one or two
3375 initial spaces may be deleted, but the number of spaces
3376 deleted from each line will be the same (so that you can have
3377 indenting work correctly, for example). The line must
3378 contain at least one non-whitespace character.
3382 Those containing a single space followed by a single full stop
3383 character. These are rendered as blank lines. This is the
3384 <em>only</em> way to get a blank line<footnote>
3385 Completely empty lines will not be rendered as blank lines.
3386 Instead, they will cause the parser to think you're starting
3387 a whole new record in the control file, and will therefore
3388 likely abort with an error.
3393 Those containing a space, a full stop and some more characters.
3394 These are for future expansion. Do not use them.
3400 Do not use tab characters. Their effect is not predictable.
3404 See <ref id="descriptions"> for further information on this.
3408 In a <file>.changes</file> file, the <tt>Description</tt>
3409 field contains a summary of the descriptions for the packages
3410 being uploaded. For this case, the first line of the field
3411 value (the part on the same line as <tt>Description:</tt>) is
3412 always empty. It is a multiline field, with one
3413 line per package. Each line is
3414 indented by one space and contains the name of a binary
3415 package, a space, a hyphen (<tt>-</tt>), a space, and the
3416 short description line from that package.
3420 <sect1 id="f-Distribution">
3421 <heading><tt>Distribution</tt></heading>
3424 In a <file>.changes</file> file or parsed changelog output
3425 this contains the (space-separated) name(s) of the
3426 distribution(s) where this version of the package should
3427 be installed. Valid distributions are determined by the
3428 archive maintainers.<footnote>
3429 Example distribution names in the Debian archive used in
3430 <file>.changes</file> files are:
3431 <taglist compact="compact">
3432 <tag><em>unstable</em></tag>
3434 This distribution value refers to the
3435 <em>developmental</em> part of the Debian distribution
3436 tree. Most new packages, new upstream versions of
3437 packages and bug fixes go into the <em>unstable</em>
3441 <tag><em>experimental</em></tag>
3443 The packages with this distribution value are deemed
3444 by their maintainers to be high risk. Oftentimes they
3445 represent early beta or developmental packages from
3446 various sources that the maintainers want people to
3447 try, but are not ready to be a part of the other parts
3448 of the Debian distribution tree.
3453 Others are used for updating stable releases or for
3454 security uploads. More information is available in the
3455 Debian Developer's Reference, section "The Debian
3459 The Debian archive software only supports listing a single
3460 distribution. Migration of packages to other distributions is
3461 handled outside of the upload process.
3466 <heading><tt>Date</tt></heading>
3469 This field includes the date the package was built or last
3470 edited. It must be in the same format as the <var>date</var>
3471 in a <file>debian/changelog</file> entry.
3475 The value of this field is usually extracted from the
3476 <file>debian/changelog</file> file - see
3477 <ref id="dpkgchangelog">).
3481 <sect1 id="f-Format">
3482 <heading><tt>Format</tt></heading>
3485 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3486 files, this field declares the format version of that file.
3487 The syntax of the field value is the same as that of
3488 a <qref id="f-Version">package version number</qref> except
3489 that no epoch or Debian revision is allowed. The format
3490 described in this document is <tt>&changesversion;</tt>.
3494 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3495 Debian source control</qref> files, this field declares the
3496 format of the source package. The field value is used by
3497 programs acting on a source package to interpret the list of
3498 files in the source package and determine how to unpack it.
3499 The syntax of the field value is a numeric major revision, a
3500 period, a numeric minor revision, and then an optional subtype
3501 after whitespace, which if specified is an alphanumeric word
3502 in parentheses. The subtype is optional in the syntax but may
3503 be mandatory for particular source format revisions.
3505 The source formats currently supported by the Debian archive
3506 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3507 and <tt>3.0 (quilt)</tt>.
3512 <sect1 id="f-Urgency">
3513 <heading><tt>Urgency</tt></heading>
3516 This is a description of how important it is to upgrade to
3517 this version from previous ones. It consists of a single
3518 keyword taking one of the values <tt>low</tt>,
3519 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3520 <tt>critical</tt><footnote>
3521 Other urgency values are supported with configuration
3522 changes in the archive software but are not used in Debian.
3523 The urgency affects how quickly a package will be considered
3524 for inclusion into the <tt>testing</tt> distribution and
3525 gives an indication of the importance of any fixes included
3526 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3527 treated as synonymous.
3528 </footnote> (not case-sensitive) followed by an optional
3529 commentary (separated by a space) which is usually in
3530 parentheses. For example:
3533 Urgency: low (HIGH for users of diversions)
3539 The value of this field is usually extracted from the
3540 <file>debian/changelog</file> file - see
3541 <ref id="dpkgchangelog">.
3545 <sect1 id="f-Changes">
3546 <heading><tt>Changes</tt></heading>
3549 This multiline field contains the human-readable changes data, describing
3550 the differences between the last version and the current one.
3554 The first line of the field value (the part on the same line
3555 as <tt>Changes:</tt>) is always empty. The content of the
3556 field is expressed as continuation lines, with each line
3557 indented by at least one space. Blank lines must be
3558 represented by a line consisting only of a space and a full
3563 The value of this field is usually extracted from the
3564 <file>debian/changelog</file> file - see
3565 <ref id="dpkgchangelog">).
3569 Each version's change information should be preceded by a
3570 "title" line giving at least the version, distribution(s)
3571 and urgency, in a human-readable way.
3575 If data from several versions is being returned the entry
3576 for the most recent version should be returned first, and
3577 entries should be separated by the representation of a
3578 blank line (the "title" line may also be followed by the
3579 representation of a blank line).
3583 <sect1 id="f-Binary">
3584 <heading><tt>Binary</tt></heading>
3587 This folded field is a list of binary packages. Its syntax and
3588 meaning varies depending on the control file in which it
3593 When it appears in the <file>.dsc</file> file, it lists binary
3594 packages which a source package can produce, separated by
3596 A space after each comma is conventional.
3597 </footnote>. The source package
3598 does not necessarily produce all of these binary packages for
3599 every architecture. The source control file doesn't contain
3600 details of which architectures are appropriate for which of
3601 the binary packages.
3605 When it appears in a <file>.changes</file> file, it lists the
3606 names of the binary packages being uploaded, separated by
3607 whitespace (not commas).
3611 <sect1 id="f-Installed-Size">
3612 <heading><tt>Installed-Size</tt></heading>
3615 This field appears in the control files of binary packages,
3616 and in the <file>Packages</file> files. It gives an estimate
3617 of the total amount of disk space required to install the
3618 named package. Actual installed size may vary based on block
3619 size, file system properties, or actions taken by package
3624 The disk space is given as the integer value of the estimated
3625 installed size in bytes, divided by 1024 and rounded up.
3629 <sect1 id="f-Files">
3630 <heading><tt>Files</tt></heading>
3633 This field contains a list of files with information about
3634 each one. The exact information and syntax varies with
3639 In all cases, Files is a multiline field. The first line of
3640 the field value (the part on the same line as <tt>Files:</tt>)
3641 is always empty. The content of the field is expressed as
3642 continuation lines, one line per file. Each line must be
3643 indented by one space and contain a number of sub-fields,
3644 separated by spaces, as described below.
3648 In the <file>.dsc</file> file, each line contains the MD5
3649 checksum, size and filename of the tar file and (if
3650 applicable) diff file which make up the remainder of the
3651 source package<footnote>
3652 That is, the parts which are not the <tt>.dsc</tt>.
3653 </footnote>. For example:
3656 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3657 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3659 The exact forms of the filenames are described
3660 in <ref id="pkg-sourcearchives">.
3664 In the <file>.changes</file> file this contains one line per
3665 file being uploaded. Each line contains the MD5 checksum,
3666 size, section and priority and the filename. For example:
3669 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3670 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3671 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3672 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3674 The <qref id="f-Section">section</qref>
3675 and <qref id="f-Priority">priority</qref> are the values of
3676 the corresponding fields in the main source control file. If
3677 no section or priority is specified then <tt>-</tt> should be
3678 used, though section and priority values must be specified for
3679 new packages to be installed properly.
3683 The special value <tt>byhand</tt> for the section in a
3684 <tt>.changes</tt> file indicates that the file in question
3685 is not an ordinary package file and must by installed by
3686 hand by the distribution maintainers. If the section is
3687 <tt>byhand</tt> the priority should be <tt>-</tt>.
3691 If a new Debian revision of a package is being shipped and
3692 no new original source archive is being distributed the
3693 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3694 entry for the original source archive
3695 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3696 but the <file>.changes</file> file should leave it out. In
3697 this case the original source archive on the distribution
3698 site must match exactly, byte-for-byte, the original
3699 source archive which was used to generate the
3700 <file>.dsc</file> file and diff which are being uploaded.</p>
3703 <sect1 id="f-Closes">
3704 <heading><tt>Closes</tt></heading>
3707 A space-separated list of bug report numbers that the upload
3708 governed by the .changes file closes.
3712 <sect1 id="f-Homepage">
3713 <heading><tt>Homepage</tt></heading>
3716 The URL of the web site for this package, preferably (when
3717 applicable) the site from which the original source can be
3718 obtained and any additional upstream documentation or
3719 information may be found. The content of this field is a
3720 simple URL without any surrounding characters such as
3725 <sect1 id="f-Checksums">
3726 <heading><tt>Checksums-Sha1</tt>
3727 and <tt>Checksums-Sha256</tt></heading>
3730 These multiline fields contain a list of files with a checksum and size
3731 for each one. Both <tt>Checksums-Sha1</tt>
3732 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3733 only in the checksum algorithm used: SHA-1
3734 for <tt>Checksums-Sha1</tt> and SHA-256
3735 for <tt>Checksums-Sha256</tt>.
3739 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3740 multiline fields. The first line of the field value (the part
3741 on the same line as <tt>Checksums-Sha1:</tt>
3742 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3743 of the field is expressed as continuation lines, one line per
3744 file. Each line consists of the checksum, a space, the file
3745 size, a space, and the file name. For example (from
3746 a <file>.changes</file> file):
3749 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3750 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3751 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3752 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3754 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3755 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3756 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3757 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3762 In the <file>.dsc</file> file, these fields should list all
3763 files that make up the source package. In
3764 the <file>.changes</file> file, these fields should list all
3765 files being uploaded. The list of files in these fields
3766 must match the list of files in the <tt>Files</tt> field.
3770 <sect1 id="f-DM-Upload-Allowed">
3771 <heading><tt>DM-Upload-Allowed</tt></heading>
3774 Indicates that Debian Maintainers may upload this package to
3775 the Debian archive. The only valid value is <tt>yes</tt>. If
3776 the field <tt>DM-Upload-Allowed: yes</tt> is present in the
3777 source section of the source control file of the most recent
3778 version of a package in unstable or experimental, the Debian
3779 archive will accept uploads of this package signed with a key
3780 in the Debian Maintainer keyring. See the General
3781 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3782 name="Endorse the concept of Debian Maintainers"> for more
3787 <sect1 id="f-VCS-fields">
3788 <heading>Version Control System (VCS) fields</heading>
3791 Debian source packages are increasingly developed using VCSs. The
3792 purpose of the following fields is to indicate a publicly accessible
3793 repository where the Debian source package is developed.
3796 <tag><tt>Vcs-Browser</tt></tag>
3799 URL of a web interface for browsing the repository.
3804 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3805 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3806 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3811 The field name identifies the VCS. The field's value uses the
3812 version control system's conventional syntax for describing
3813 repository locations and should be sufficient to locate the
3814 repository used for packaging. Ideally, it also locates the
3815 branch used for development of new versions of the Debian
3819 In the case of Git, the value consists of a URL, optionally
3820 followed by the word <tt>-b</tt> and the name of a branch in
3821 the indicated repository, following the syntax of the
3822 <tt>git clone</tt> command. If no branch is specified, the
3823 packaging should be on the default branch.
3826 More than one different VCS may be specified for the same
3836 <heading>User-defined fields</heading>
3839 Additional user-defined fields may be added to the
3840 source package control file. Such fields will be
3841 ignored, and not copied to (for example) binary or
3842 Debian source control files or upload control files.
3846 If you wish to add additional unsupported fields to
3847 these output files you should use the mechanism
3852 Fields in the main source control information file with
3853 names starting <tt>X</tt>, followed by one or more of
3854 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3855 be copied to the output files. Only the part of the
3856 field name after the hyphen will be used in the output
3857 file. Where the letter <tt>B</tt> is used the field
3858 will appear in binary package control files, where the
3859 letter <tt>S</tt> is used in Debian source control
3860 files and where <tt>C</tt> is used in upload control
3861 (<tt>.changes</tt>) files.
3865 For example, if the main source information control file
3868 XBS-Comment: I stand between the candle and the star.
3870 then the binary and Debian source control files will contain the
3873 Comment: I stand between the candle and the star.
3882 <chapt id="maintainerscripts">
3883 <heading>Package maintainer scripts and installation procedure</heading>
3886 <heading>Introduction to package maintainer scripts</heading>
3889 It is possible to supply scripts as part of a package which
3890 the package management system will run for you when your
3891 package is installed, upgraded or removed.
3895 These scripts are the control information
3896 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3897 and <prgn>postrm</prgn>. They must be proper executable files;
3898 if they are scripts (which is recommended), they must start with
3899 the usual <tt>#!</tt> convention. They should be readable and
3900 executable by anyone, and must not be world-writable.
3904 The package management system looks at the exit status from
3905 these scripts. It is important that they exit with a
3906 non-zero status if there is an error, so that the package
3907 management system can stop its processing. For shell
3908 scripts this means that you <em>almost always</em> need to
3909 use <tt>set -e</tt> (this is usually true when writing shell
3910 scripts, in fact). It is also important, of course, that
3911 they exit with a zero status if everything went well.
3915 Additionally, packages interacting with users
3916 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3917 should install a <prgn>config</prgn> script as a control
3918 information file. See <ref id="maintscriptprompt"> for details.
3922 When a package is upgraded a combination of the scripts from
3923 the old and new packages is called during the upgrade
3924 procedure. If your scripts are going to be at all
3925 complicated you need to be aware of this, and may need to
3926 check the arguments to your scripts.
3930 Broadly speaking the <prgn>preinst</prgn> is called before
3931 (a particular version of) a package is unpacked, and the
3932 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3933 before (a version of) a package is removed and the
3934 <prgn>postrm</prgn> afterwards.
3938 Programs called from maintainer scripts should not normally
3939 have a path prepended to them. Before installation is
3940 started, the package management system checks to see if the
3941 programs <prgn>ldconfig</prgn>,
3942 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3943 and <prgn>update-rc.d</prgn> can be found via the
3944 <tt>PATH</tt> environment variable. Those programs, and any
3945 other program that one would expect to be in the
3946 <tt>PATH</tt>, should thus be invoked without an absolute
3947 pathname. Maintainer scripts should also not reset the
3948 <tt>PATH</tt>, though they might choose to modify it by
3949 prepending or appending package-specific directories. These
3950 considerations really apply to all shell scripts.</p>
3953 <sect id="idempotency">
3954 <heading>Maintainer scripts idempotency</heading>
3957 It is necessary for the error recovery procedures that the
3958 scripts be idempotent. This means that if it is run
3959 successfully, and then it is called again, it doesn't bomb
3960 out or cause any harm, but just ensures that everything is
3961 the way it ought to be. If the first call failed, or
3962 aborted half way through for some reason, the second call
3963 should merely do the things that were left undone the first
3964 time, if any, and exit with a success status if everything
3966 This is so that if an error occurs, the user interrupts
3967 <prgn>dpkg</prgn> or some other unforeseen circumstance
3968 happens you don't leave the user with a badly-broken
3969 package when <prgn>dpkg</prgn> attempts to repeat the
3975 <sect id="controllingterminal">
3976 <heading>Controlling terminal for maintainer scripts</heading>
3979 Maintainer scripts are not guaranteed to run with a controlling
3980 terminal and may not be able to interact with the user. They
3981 must be able to fall back to noninteractive behavior if no
3982 controlling terminal is available. Maintainer scripts that
3983 prompt via a program conforming to the Debian Configuration
3984 Management Specification (see <ref id="maintscriptprompt">) may
3985 assume that program will handle falling back to noninteractive
3990 For high-priority prompts without a reasonable default answer,
3991 maintainer scripts may abort if there is no controlling
3992 terminal. However, this situation should be avoided if at all
3993 possible, since it prevents automated or unattended installs.
3994 In most cases, users will consider this to be a bug in the
3999 <sect id="exitstatus">
4000 <heading>Exit status</heading>
4003 Each script must return a zero exit status for
4004 success, or a nonzero one for failure, since the package
4005 management system looks for the exit status of these scripts
4006 and determines what action to take next based on that datum.
4010 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4015 What follows is a summary of all the ways in which maintainer
4016 scripts may be called along with what facilities those scripts
4017 may rely on being available at that time. Script names preceded
4018 by <var>new-</var> are the scripts from the new version of a
4019 package being installed, upgraded to, or downgraded to. Script
4020 names preceded by <var>old-</var> are the scripts from the old
4021 version of a package that is being upgraded from or downgraded
4026 The <prgn>preinst</prgn> script may be called in the following
4029 <tag><var>new-preinst</var> <tt>install</tt></tag>
4030 <tag><var>new-preinst</var> <tt>install</tt>
4031 <var>old-version</var></tag>
4032 <tag><var>new-preinst</var> <tt>upgrade</tt>
4033 <var>old-version</var></tag>
4035 The package will not yet be unpacked, so
4036 the <prgn>preinst</prgn> script cannot rely on any files
4037 included in its package. Only essential packages and
4038 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4039 available. Pre-dependencies will have been configured at
4040 least once, but at the time the <prgn>preinst</prgn> is
4041 called they may only be in an unpacked or "Half-Configured"
4042 state if a previous version of the pre-dependency was
4043 completely configured and has not been removed since then.
4046 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4047 <var>new-version</var></tag>
4049 Called during error handling of an upgrade that failed after
4050 unpacking the new package because the <tt>postrm
4051 upgrade</tt> action failed. The unpacked files may be
4052 partly from the new version or partly missing, so the script
4053 cannot rely on files included in the package. Package
4054 dependencies may not be available. Pre-dependencies will be
4055 at least unpacked following the same rules as above, except
4056 they may be only "Half-Installed" if an upgrade of the
4057 pre-dependency failed.<footnote>
4058 This can happen if the new version of the package no
4059 longer pre-depends on a package that had been partially
4067 The <prgn>postinst</prgn> script may be called in the following
4070 <tag><var>postinst</var> <tt>configure</tt>
4071 <var>most-recently-configured-version</var></tag>
4073 The files contained in the package will be unpacked. All
4074 package dependencies will at least be unpacked. If there
4075 are no circular dependencies involved, all package
4076 dependencies will be configured. For behavior in the case
4077 of circular dependencies, see the discussion
4078 in <ref id="binarydeps">.
4081 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4082 <var>new-version</var></tag>
4083 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4084 <tt>in-favour</tt> <var>package</var>
4085 <var>new-version</var></tag>
4086 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4087 <tag><var>deconfigured's-postinst</var>
4088 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4089 <var>failed-install-package</var> <var>version</var>
4090 [<tt>removing</tt> <var>conflicting-package</var>
4091 <var>version</var>]</tag>
4093 The files contained in the package will be unpacked. All
4094 package dependencies will at least be "Half-Installed" and
4095 will have previously been configured and not removed.
4096 However, dependencies may not be configured or even fully
4097 unpacked in some error situations.<footnote>
4098 For example, suppose packages foo and bar are installed
4099 with foo depending on bar. If an upgrade of bar were
4100 started and then aborted, and then an attempt to remove
4101 foo failed because its <prgn>prerm</prgn> script failed,
4102 foo's <tt>postinst abort-remove</tt> would be called with
4103 bar only "Half-Installed".
4105 The <prgn>postinst</prgn> should still attempt any actions
4106 for which its dependencies are required, since they will
4107 normally be available, but consider the correct error
4108 handling approach if those actions fail. Aborting
4109 the <prgn>postinst</prgn> action if commands or facilities
4110 from the package dependencies are not available is often the
4117 The <prgn>prerm</prgn> script may be called in the following
4120 <tag><var>prerm</var> <tt>remove</tt></tag>
4121 <tag><var>old-prerm</var>
4122 <tt>upgrade</tt><var>new-version</var></tag>
4123 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4124 <tt>in-favour</tt> <var>package</var>
4125 <var>new-version</var></tag>
4126 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4127 <tt>in-favour</tt> <var>package-being-installed</var>
4128 <var>version</var> [<tt>removing</tt>
4129 <var>conflicting-package</var> <var>version</var>]</tag>
4131 The package whose <prgn>prerm</prgn> is being called will be
4132 at least "Half-Installed". All package dependencies will at
4133 least be "Half-Installed" and will have previously been
4134 configured and not removed. If there was no error, all
4135 dependencies will at least be unpacked, but these actions
4136 may be called in various error states where dependencies are
4137 only "Half-Installed" due to a partial upgrade.
4140 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4141 <var>old-version</var></tag>
4143 Called during error handling when <tt>prerm upgrade</tt>
4144 fails. The new package will not yet be unpacked, and all
4145 the same constraints as for <tt>preinst upgrade</tt> apply.
4151 The <prgn>postrm</prgn> script may be called in the following
4154 <tag><var>postrm</var> <tt>remove</tt></tag>
4155 <tag><var>postrm</var> <tt>purge</tt></tag>
4156 <tag><var>old-postrm</var> <tt>upgrade</tt>
4157 <var>new-version</var></tag>
4158 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4159 <var>overwriter</var> <var>overwriter-version</var></tag>
4161 The <prgn>postrm</prgn> script is called after the package's
4162 files have been removed or replaced. The package
4163 whose <prgn>postrm</prgn> is being called may have
4164 previously been deconfigured and only be unpacked, at which
4165 point subsequent package changes do not consider its
4166 dependencies. Therefore, all <prgn>postrm</prgn> actions
4167 may only rely on essential packages and must gracefully skip
4168 any actions that require the package's dependencies if those
4169 dependencies are unavailable.<footnote>
4170 This is often done by checking whether the command or
4171 facility the <prgn>postrm</prgn> intends to call is
4172 available before calling it. For example:
4174 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4175 . /usr/share/debconf/confmodule
4179 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4180 configuration for the package
4181 if <package>debconf</package> is installed.
4185 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4186 <var>old-version</var></tag>
4188 Called when the old <tt>postrm upgrade</tt> action fails.
4189 The new package will be unpacked, but only essential
4190 packages and pre-dependencies can be relied on.
4191 Pre-dependencies will either be configured or will be
4192 "Unpacked" or "Half-Configured" but previously had been
4193 configured and was never removed.
4196 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4197 <tag><var>new-postrm</var> <tt>abort-install</tt>
4198 <var>old-version</var></tag>
4199 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4200 <var>old-version</var></tag>
4202 Called before unpacking the new package as part of the
4203 error handling of <prgn>preinst</prgn> failures. May assume
4204 the same state as <prgn>preinst</prgn> can assume.
4210 <sect id="unpackphase">
4211 <heading>Details of unpack phase of installation or upgrade</heading>
4214 The procedure on installation/upgrade/overwrite/disappear
4215 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4216 stage of <tt>dpkg --install</tt>) is as follows. In each
4217 case, if a major error occurs (unless listed below) the
4218 actions are, in general, run backwards - this means that the
4219 maintainer scripts are run with different arguments in
4220 reverse order. These are the "error unwind" calls listed
4227 If a version of the package is already installed, call
4228 <example compact="compact">
4229 <var>old-prerm</var> upgrade <var>new-version</var>
4233 If the script runs but exits with a non-zero
4234 exit status, <prgn>dpkg</prgn> will attempt:
4235 <example compact="compact">
4236 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4238 If this works, the upgrade continues. If this
4239 does not work, the error unwind:
4240 <example compact="compact">
4241 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4243 If this works, then the old-version is
4244 "Installed", if not, the old version is in a
4245 "Half-Configured" state.
4251 If a "conflicting" package is being removed at the same time,
4252 or if any package will be broken (due to <tt>Breaks</tt>):
4255 If <tt>--auto-deconfigure</tt> is
4256 specified, call, for each package to be deconfigured
4257 due to <tt>Breaks</tt>:
4258 <example compact="compact">
4259 <var>deconfigured's-prerm</var> deconfigure \
4260 in-favour <var>package-being-installed</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>
4267 The deconfigured packages are marked as
4268 requiring configuration, so that if
4269 <tt>--install</tt> is used they will be
4270 configured again if possible.
4273 If any packages depended on a conflicting
4274 package being removed and <tt>--auto-deconfigure</tt> is
4275 specified, call, for each such package:
4276 <example compact="compact">
4277 <var>deconfigured's-prerm</var> deconfigure \
4278 in-favour <var>package-being-installed</var> <var>version</var> \
4279 removing <var>conflicting-package</var> <var>version</var>
4282 <example compact="compact">
4283 <var>deconfigured's-postinst</var> abort-deconfigure \
4284 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4285 removing <var>conflicting-package</var> <var>version</var>
4287 The deconfigured packages are marked as
4288 requiring configuration, so that if
4289 <tt>--install</tt> is used they will be
4290 configured again if possible.
4293 To prepare for removal of each conflicting package, call:
4294 <example compact="compact">
4295 <var>conflictor's-prerm</var> remove \
4296 in-favour <var>package</var> <var>new-version</var>
4299 <example compact="compact">
4300 <var>conflictor's-postinst</var> abort-remove \
4301 in-favour <var>package</var> <var>new-version</var>
4310 If the package is being upgraded, call:
4311 <example compact="compact">
4312 <var>new-preinst</var> upgrade <var>old-version</var>
4314 If this fails, we call:
4316 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4323 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4325 is called. If this works, then the old version
4326 is in an "Installed" state, or else it is left
4327 in an "Unpacked" state.
4332 If it fails, then the old version is left
4333 in an "Half-Installed" state.
4340 Otherwise, if the package had some configuration
4341 files from a previous version installed (i.e., it
4342 is in the "configuration files only" state):
4343 <example compact="compact">
4344 <var>new-preinst</var> install <var>old-version</var>
4348 <var>new-postrm</var> abort-install <var>old-version</var>
4350 If this fails, the package is left in a
4351 "Half-Installed" state, which requires a
4352 reinstall. If it works, the packages is left in
4353 a "Config-Files" state.
4356 Otherwise (i.e., the package was completely purged):
4357 <example compact="compact">
4358 <var>new-preinst</var> install
4361 <example compact="compact">
4362 <var>new-postrm</var> abort-install
4364 If the error-unwind fails, the package is in a
4365 "Half-Installed" phase, and requires a
4366 reinstall. If the error unwind works, the
4367 package is in a not installed state.
4374 The new package's files are unpacked, overwriting any
4375 that may be on the system already, for example any
4376 from the old version of the same package or from
4377 another package. Backups of the old files are kept
4378 temporarily, and if anything goes wrong the package
4379 management system will attempt to put them back as
4380 part of the error unwind.
4384 It is an error for a package to contain files which
4385 are on the system in another package, unless
4386 <tt>Replaces</tt> is used (see <ref id="replaces">).
4388 The following paragraph is not currently the case:
4389 Currently the <tt>- - force-overwrite</tt> flag is
4390 enabled, downgrading it to a warning, but this may not
4396 It is a more serious error for a package to contain a
4397 plain file or other kind of non-directory where another
4398 package has a directory (again, unless
4399 <tt>Replaces</tt> is used). This error can be
4400 overridden if desired using
4401 <tt>--force-overwrite-dir</tt>, but this is not
4406 Packages which overwrite each other's files produce
4407 behavior which, though deterministic, is hard for the
4408 system administrator to understand. It can easily
4409 lead to "missing" programs if, for example, a package
4410 is unpacked which overwrites a file from another
4411 package, and is then removed again.<footnote>
4412 Part of the problem is due to what is arguably a
4413 bug in <prgn>dpkg</prgn>.
4418 A directory will never be replaced by a symbolic link
4419 to a directory or vice versa; instead, the existing
4420 state (symlink or not) will be left alone and
4421 <prgn>dpkg</prgn> will follow the symlink if there is
4430 If the package is being upgraded, call
4431 <example compact="compact">
4432 <var>old-postrm</var> upgrade <var>new-version</var>
4436 If this fails, <prgn>dpkg</prgn> will attempt:
4437 <example compact="compact">
4438 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4440 If this works, installation continues. If not,
4442 <example compact="compact">
4443 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4445 If this fails, the old version is left in a
4446 "Half-Installed" state. If it works, dpkg now
4448 <example compact="compact">
4449 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4451 If this fails, the old version is left in a
4452 "Half-Installed" state. If it works, dpkg now
4454 <example compact="compact">
4455 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4457 If this fails, the old version is in an
4464 This is the point of no return - if
4465 <prgn>dpkg</prgn> gets this far, it won't back off
4466 past this point if an error occurs. This will
4467 leave the package in a fairly bad state, which
4468 will require a successful re-installation to clear
4469 up, but it's when <prgn>dpkg</prgn> starts doing
4470 things that are irreversible.
4475 Any files which were in the old version of the package
4476 but not in the new are removed.
4480 The new file list replaces the old.
4484 The new maintainer scripts replace the old.
4488 Any packages all of whose files have been overwritten
4489 during the installation, and which aren't required for
4490 dependencies, are considered to have been removed.
4491 For each such package
4494 <prgn>dpkg</prgn> calls:
4495 <example compact="compact">
4496 <var>disappearer's-postrm</var> disappear \
4497 <var>overwriter</var> <var>overwriter-version</var>
4501 The package's maintainer scripts are removed.
4504 It is noted in the status database as being in a
4505 sane state, namely not installed (any conffiles
4506 it may have are ignored, rather than being
4507 removed by <prgn>dpkg</prgn>). Note that
4508 disappearing packages do not have their prerm
4509 called, because <prgn>dpkg</prgn> doesn't know
4510 in advance that the package is going to
4517 Any files in the package we're unpacking that are also
4518 listed in the file lists of other packages are removed
4519 from those lists. (This will lobotomize the file list
4520 of the "conflicting" package if there is one.)
4524 The backup files made during installation, above, are
4530 The new package's status is now sane, and recorded as
4535 Here is another point of no return - if the
4536 conflicting package's removal fails we do not unwind
4537 the rest of the installation; the conflicting package
4538 is left in a half-removed limbo.
4543 If there was a conflicting package we go and do the
4544 removal actions (described below), starting with the
4545 removal of the conflicting package's files (any that
4546 are also in the package being unpacked have already
4547 been removed from the conflicting package's file list,
4548 and so do not get removed now).
4554 <sect id="configdetails"><heading>Details of configuration</heading>
4557 When we configure a package (this happens with <tt>dpkg
4558 --install</tt> and <tt>dpkg --configure</tt>), we first
4559 update any <tt>conffile</tt>s and then call:
4560 <example compact="compact">
4561 <var>postinst</var> configure <var>most-recently-configured-version</var>
4566 No attempt is made to unwind after errors during
4567 configuration. If the configuration fails, the package is in
4568 a "Failed Config" state, and an error message is generated.
4572 If there is no most recently configured version
4573 <prgn>dpkg</prgn> will pass a null argument.
4576 Historical note: Truly ancient (pre-1997) versions of
4577 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4578 (including the angle brackets) in this case. Even older
4579 ones did not pass a second argument at all, under any
4580 circumstance. Note that upgrades using such an old dpkg
4581 version are unlikely to work for other reasons, even if
4582 this old argument behavior is handled by your postinst script.
4588 <sect id="removedetails"><heading>Details of removal and/or
4589 configuration purging</heading>
4595 <example compact="compact">
4596 <var>prerm</var> remove
4600 If prerm fails during replacement due to conflict
4602 <var>conflictor's-postinst</var> abort-remove \
4603 in-favour <var>package</var> <var>new-version</var>
4607 <var>postinst</var> abort-remove
4611 If this fails, the package is in a "Half-Configured"
4612 state, or else it remains "Installed".
4616 The package's files are removed (except <tt>conffile</tt>s).
4619 <example compact="compact">
4620 <var>postrm</var> remove
4624 If it fails, there's no error unwind, and the package is in
4625 an "Half-Installed" state.
4630 All the maintainer scripts except the <prgn>postrm</prgn>
4635 If we aren't purging the package we stop here. Note
4636 that packages which have no <prgn>postrm</prgn> and no
4637 <tt>conffile</tt>s are automatically purged when
4638 removed, as there is no difference except for the
4639 <prgn>dpkg</prgn> status.
4643 The <tt>conffile</tt>s and any backup files
4644 (<tt>~</tt>-files, <tt>#*#</tt> files,
4645 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4650 <example compact="compact">
4651 <var>postrm</var> purge
4655 If this fails, the package remains in a "Config-Files"
4660 The package's file list is removed.
4669 <chapt id="relationships">
4670 <heading>Declaring relationships between packages</heading>
4672 <sect id="depsyntax">
4673 <heading>Syntax of relationship fields</heading>
4676 These fields all have a uniform syntax. They are a list of
4677 package names separated by commas.
4681 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4682 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4683 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4684 control fields of the package, which declare
4685 dependencies on other packages, the package names listed may
4686 also include lists of alternative package names, separated
4687 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4688 if any one of the alternative packages is installed, that
4689 part of the dependency is considered to be satisfied.
4693 All of the fields except for <tt>Provides</tt> may restrict
4694 their applicability to particular versions of each named
4695 package. This is done in parentheses after each individual
4696 package name; the parentheses should contain a relation from
4697 the list below followed by a version number, in the format
4698 described in <ref id="f-Version">.
4702 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4703 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4704 earlier, earlier or equal, exactly equal, later or equal and
4705 strictly later, respectively. The deprecated
4706 forms <tt><</tt> and <tt>></tt> were confusingly used to
4707 mean earlier/later or equal, rather than strictly earlier/later,
4708 and must not appear in new packages (though <prgn>dpkg</prgn>
4709 still supports them with a warning).
4713 Whitespace may appear at any point in the version
4714 specification subject to the rules in <ref
4715 id="controlsyntax">, and must appear where it's necessary to
4716 disambiguate; it is not otherwise significant. All of the
4717 relationship fields can only be folded in source package control files. For
4718 consistency and in case of future changes to
4719 <prgn>dpkg</prgn> it is recommended that a single space be
4720 used after a version relationship and before a version
4721 number; it is also conventional to put a single space after
4722 each comma, on either side of each vertical bar, and before
4723 each open parenthesis. When opening a continuation line in a relationship field, it
4724 is conventional to do so after a comma and before the space
4725 following that comma.
4729 For example, a list of dependencies might appear as:
4730 <example compact="compact">
4733 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4738 Relationships may be restricted to a certain set of
4739 architectures. This is indicated in brackets after each
4740 individual package name and the optional version specification.
4741 The brackets enclose a non-empty list of Debian architecture names
4742 in the format described in <ref id="arch-spec">,
4743 separated by whitespace. Exclamation marks may be prepended to
4744 each of the names. (It is not permitted for some names to be
4745 prepended with exclamation marks while others aren't.)
4749 For build relationship fields
4750 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4751 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4752 the current Debian host architecture is not in this list and
4753 there are no exclamation marks in the list, or it is in the list
4754 with a prepended exclamation mark, the package name and the
4755 associated version specification are ignored completely for the
4756 purposes of defining the relationships.
4761 <example compact="compact">
4763 Build-Depends-Indep: texinfo
4764 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4765 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4767 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4768 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4769 <tt>gnumach-dev</tt> only on hurd-i386.
4773 For binary relationship fields and the <tt>Built-Using</tt>
4774 field, the architecture restriction
4775 syntax is only supported in the source package control
4776 file <file>debian/control</file>. When the corresponding binary
4777 package control file is generated, the relationship will either
4778 be omitted or included without the architecture restriction
4779 based on the architecture of the binary package. This means
4780 that architecture restrictions must not be used in binary
4781 relationship fields for architecture-independent packages
4782 (<tt>Architecture: all</tt>).
4787 <example compact="compact">
4788 Depends: foo [i386], bar [amd64]
4790 becomes <tt>Depends: foo</tt> when the package is built on
4791 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4792 package is built on the <tt>amd64</tt> architecture, and omitted
4793 entirely in binary packages built on all other architectures.
4797 If the architecture-restricted dependency is part of a set of
4798 alternatives using <tt>|</tt>, that alternative is ignored
4799 completely on architectures that do not match the restriction.
4801 <example compact="compact">
4802 Build-Depends: foo [!i386] | bar [!amd64]
4804 is equivalent to <tt>bar</tt> on the i386 architecture, to
4805 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4806 bar</tt> on all other architectures.
4810 Relationships may also be restricted to a certain set of
4811 architectures using architecture wildcards in the format
4812 described in <ref id="arch-wildcard-spec">. The syntax for
4813 declaring such restrictions is the same as declaring
4814 restrictions using a certain set of architectures without
4815 architecture wildcards. For example:
4816 <example compact="compact">
4817 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4819 is equivalent to <tt>foo</tt> on architectures using the Linux
4820 kernel and any cpu, <tt>bar</tt> on architectures using any
4821 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4822 using a kernel other than Linux.
4826 Note that the binary package relationship fields such as
4827 <tt>Depends</tt> appear in one of the binary package
4828 sections of the control file, whereas the build-time
4829 relationships such as <tt>Build-Depends</tt> appear in the
4830 source package section of the control file (which is the
4835 <sect id="binarydeps">
4836 <heading>Binary Dependencies - <tt>Depends</tt>,
4837 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4838 <tt>Pre-Depends</tt>
4842 Packages can declare in their control file that they have
4843 certain relationships to other packages - for example, that
4844 they may not be installed at the same time as certain other
4845 packages, and/or that they depend on the presence of others.
4849 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4850 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4851 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4852 <tt>Breaks</tt> is described in <ref id="breaks">, and
4853 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4854 rest are described below.
4858 These seven fields are used to declare a dependency
4859 relationship by one package on another. Except for
4860 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4861 depending (binary) package's control file.
4862 (<tt>Enhances</tt> appears in the recommending package's
4863 control file, and <tt>Breaks</tt> appears in the version of
4864 depended-on package which causes the named package to
4869 A <tt>Depends</tt> field takes effect <em>only</em> when a
4870 package is to be configured. It does not prevent a package
4871 being on the system in an unconfigured state while its
4872 dependencies are unsatisfied, and it is possible to replace
4873 a package whose dependencies are satisfied and which is
4874 properly installed with a different version whose
4875 dependencies are not and cannot be satisfied; when this is
4876 done the depending package will be left unconfigured (since
4877 attempts to configure it will give errors) and will not
4878 function properly. If it is necessary, a
4879 <tt>Pre-Depends</tt> field can be used, which has a partial
4880 effect even when a package is being unpacked, as explained
4881 in detail below. (The other three dependency fields,
4882 <tt>Recommends</tt>, <tt>Suggests</tt> and
4883 <tt>Enhances</tt>, are only used by the various front-ends
4884 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4885 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4889 Since <tt>Depends</tt> only places requirements on the order in
4890 which packages are configured, packages in an installation run
4891 are usually all unpacked first and all configured later.
4893 This approach makes dependency resolution easier. If two
4894 packages A and B are being upgraded, the installed package A
4895 depends on exactly the installed package B, and the new
4896 package A depends on exactly the new package B (a common
4897 situation when upgrading shared libraries and their
4898 corresponding development packages), satisfying the
4899 dependencies at every stage of the upgrade would be
4900 impossible. This relaxed restriction means that both new
4901 packages can be unpacked together and then configured in their
4907 If there is a circular dependency among packages being installed
4908 or removed, installation or removal order honoring the
4909 dependency order is impossible, requiring the dependency loop be
4910 broken at some point and the dependency requirements violated
4911 for at least one package. Packages involved in circular
4912 dependencies may not be able to rely on their dependencies being
4913 configured before they themselves are configured, depending on
4914 which side of the break of the circular dependency loop they
4915 happen to be on. If one of the packages in the loop has
4916 no <prgn>postinst</prgn> script, then the cycle will be broken
4917 at that package; this ensures that all <prgn>postinst</prgn>
4918 scripts are run with their dependencies properly configured if
4919 this is possible. Otherwise the breaking point is arbitrary.
4920 Packages should therefore avoid circular dependencies where
4921 possible, particularly if they have <prgn>postinst</prgn>
4926 The meaning of the five dependency fields is as follows:
4928 <tag><tt>Depends</tt></tag>
4931 This declares an absolute dependency. A package will
4932 not be configured unless all of the packages listed in
4933 its <tt>Depends</tt> field have been correctly
4934 configured (unless there is a circular dependency as
4939 The <tt>Depends</tt> field should be used if the
4940 depended-on package is required for the depending
4941 package to provide a significant amount of
4946 The <tt>Depends</tt> field should also be used if the
4947 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4948 require the depended-on package to be unpacked or
4949 configured in order to run. In the case of <tt>postinst
4950 configure</tt>, the depended-on packages will be unpacked
4951 and configured first. (If both packages are involved in a
4952 dependency loop, this might not work as expected; see the
4953 explanation a few paragraphs back.) In the case
4954 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4955 actions, the package dependencies will normally be at
4956 least unpacked, but they may be only "Half-Installed" if a
4957 previous upgrade of the dependency failed.
4961 Finally, the <tt>Depends</tt> field should be used if the
4962 depended-on package is needed by the <prgn>postrm</prgn>
4963 script to fully clean up after the package removal. There
4964 is no guarantee that package dependencies will be
4965 available when <prgn>postrm</prgn> is run, but the
4966 depended-on package is more likely to be available if the
4967 package declares a dependency (particularly in the case
4968 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4969 script must gracefully skip actions that require a
4970 dependency if that dependency isn't available.
4974 <tag><tt>Recommends</tt></tag>
4977 This declares a strong, but not absolute, dependency.
4981 The <tt>Recommends</tt> field should list packages
4982 that would be found together with this one in all but
4983 unusual installations.
4987 <tag><tt>Suggests</tt></tag>
4989 This is used to declare that one package may be more
4990 useful with one or more others. Using this field
4991 tells the packaging system and the user that the
4992 listed packages are related to this one and can
4993 perhaps enhance its usefulness, but that installing
4994 this one without them is perfectly reasonable.
4997 <tag><tt>Enhances</tt></tag>
4999 This field is similar to Suggests but works in the
5000 opposite direction. It is used to declare that a
5001 package can enhance the functionality of another
5005 <tag><tt>Pre-Depends</tt></tag>
5008 This field is like <tt>Depends</tt>, except that it
5009 also forces <prgn>dpkg</prgn> to complete installation
5010 of the packages named before even starting the
5011 installation of the package which declares the
5012 pre-dependency, as follows:
5016 When a package declaring a pre-dependency is about to
5017 be <em>unpacked</em> the pre-dependency can be
5018 satisfied if the depended-on package is either fully
5019 configured, <em>or even if</em> the depended-on
5020 package(s) are only unpacked or in the "Half-Configured"
5021 state, provided that they have been configured
5022 correctly at some point in the past (and not removed
5023 or partially removed since). In this case, both the
5024 previously-configured and currently unpacked or
5025 "Half-Configured" versions must satisfy any version
5026 clause in the <tt>Pre-Depends</tt> field.
5030 When the package declaring a pre-dependency is about to
5031 be <em>configured</em>, the pre-dependency will be treated
5032 as a normal <tt>Depends</tt>. It will be considered
5033 satisfied only if the depended-on package has been
5034 correctly configured. However, unlike
5035 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5036 permit circular dependencies to be broken. If a circular
5037 dependency is encountered while attempting to honor
5038 <tt>Pre-Depends</tt>, the installation will be aborted.
5042 <tt>Pre-Depends</tt> are also required if the
5043 <prgn>preinst</prgn> script depends on the named package.
5044 It is best to avoid this situation if possible.
5048 <tt>Pre-Depends</tt> should be used sparingly,
5049 preferably only by packages whose premature upgrade or
5050 installation would hamper the ability of the system to
5051 continue with any upgrade that might be in progress.
5055 You should not specify a <tt>Pre-Depends</tt> entry for a
5056 package before this has been discussed on the
5057 <tt>debian-devel</tt> mailing list and a consensus about
5058 doing that has been reached. See <ref id="dependencies">.
5065 When selecting which level of dependency to use you should
5066 consider how important the depended-on package is to the
5067 functionality of the one declaring the dependency. Some
5068 packages are composed of components of varying degrees of
5069 importance. Such a package should list using
5070 <tt>Depends</tt> the package(s) which are required by the
5071 more important components. The other components'
5072 requirements may be mentioned as Suggestions or
5073 Recommendations, as appropriate to the components' relative
5079 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5082 When one binary package declares that it breaks another,
5083 <prgn>dpkg</prgn> will refuse to allow the package which
5084 declares <tt>Breaks</tt> to be unpacked unless the broken
5085 package is deconfigured first, and it will refuse to
5086 allow the broken package to be reconfigured.
5090 A package will not be regarded as causing breakage merely
5091 because its configuration files are still installed; it must
5092 be at least "Half-Installed".
5096 A special exception is made for packages which declare that
5097 they break their own package name or a virtual package which
5098 they provide (see below): this does not count as a real
5103 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5104 version clause; such a <tt>Breaks</tt> is introduced in the
5105 version of an (implicit or explicit) dependency which violates
5106 an assumption or reveals a bug in earlier versions of the broken
5107 package, or which takes over a file from earlier versions of the
5108 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5109 will inform higher-level package management tools that the
5110 broken package must be upgraded before the new one.
5114 If the breaking package also overwrites some files from the
5115 older package, it should use <tt>Replaces</tt> to ensure this
5116 goes smoothly. See <ref id="replaces"> for a full discussion
5117 of taking over files from other packages, including how to
5118 use <tt>Breaks</tt> in those cases.
5122 Many of the cases where <tt>Breaks</tt> should be used were
5123 previously handled with <tt>Conflicts</tt>
5124 because <tt>Breaks</tt> did not yet exist.
5125 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5126 See <ref id="conflicts"> for more information about the
5131 <sect id="conflicts">
5132 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5135 When one binary package declares a conflict with another using
5136 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5137 allow them to be unpacked on the system at the same time. This
5138 is a stronger restriction than <tt>Breaks</tt>, which prevents
5139 the broken package from being configured while the breaking
5140 package is in the "Unpacked" state but allows both packages to
5141 be unpacked at the same time.
5145 If one package is to be unpacked, the other must be removed
5146 first. If the package being unpacked is marked as replacing
5147 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5148 normally be used in this case) the one on the system, or the one
5149 on the system is marked as deselected, or both packages are
5150 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5151 automatically remove the package which is causing the conflict.
5152 Otherwise, it will halt the installation of the new package with
5153 an error. This mechanism is specifically designed to produce an
5154 error when the installed package is <tt>Essential</tt>, but the
5159 A package will not cause a conflict merely because its
5160 configuration files are still installed; it must be at least
5165 A special exception is made for packages which declare a
5166 conflict with their own package name, or with a virtual
5167 package which they provide (see below): this does not
5168 prevent their installation, and allows a package to conflict
5169 with others providing a replacement for it. You use this
5170 feature when you want the package in question to be the only
5171 package providing some feature.
5175 Normally, <tt>Breaks</tt> should be used instead
5176 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5177 stronger restriction on the ordering of package installation or
5178 upgrade and can make it more difficult for the package manager
5179 to find a correct solution to an upgrade or installation
5180 problem. <tt>Breaks</tt> should be used
5182 <item>when moving a file from one package to another (see
5183 <ref id="replaces">),</item>
5184 <item>when splitting a package (a special case of the previous
5186 <item>when the breaking package exposes a bug in or interacts
5187 badly with particular versions of the broken
5190 <tt>Conflicts</tt> should be used
5192 <item>when two packages provide the same file and will
5193 continue to do so,</item>
5194 <item>in conjunction with <tt>Provides</tt> when only one
5195 package providing a given virtual facility may be unpacked
5196 at a time (see <ref id="virtual">),</item>
5197 <item>in other cases where one must prevent simultaneous
5198 installation of two packages for reasons that are ongoing
5199 (not fixed in a later version of one of the packages) or
5200 that must prevent both packages from being unpacked at the
5201 same time, not just configured.</item>
5203 Be aware that adding <tt>Conflicts</tt> is normally not the best
5204 solution when two packages provide the same files. Depending on
5205 the reason for that conflict, using alternatives or renaming the
5206 files is often a better approach. See, for
5207 example, <ref id="binaries">.
5211 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5212 unless two packages cannot be installed at the same time or
5213 installing them both causes one of them to be broken or
5214 unusable. Having similar functionality or performing the same
5215 tasks as another package is not sufficient reason to
5216 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5220 A <tt>Conflicts</tt> entry may have an "earlier than" version
5221 clause if the reason for the conflict is corrected in a later
5222 version of one of the packages. However, normally the presence
5223 of an "earlier than" version clause is a sign
5224 that <tt>Breaks</tt> should have been used instead. An "earlier
5225 than" version clause in <tt>Conflicts</tt>
5226 prevents <prgn>dpkg</prgn> from upgrading or installing the
5227 package which declares such a conflict until the upgrade or
5228 removal of the conflicted-with package has been completed, which
5229 is a strong restriction.
5233 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5237 As well as the names of actual ("concrete") packages, the
5238 package relationship fields <tt>Depends</tt>,
5239 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5240 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5241 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5242 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5243 may mention "virtual packages".
5247 A <em>virtual package</em> is one which appears in the
5248 <tt>Provides</tt> control field of another package. The effect
5249 is as if the package(s) which provide a particular virtual
5250 package name had been listed by name everywhere the virtual
5251 package name appears. (See also <ref id="virtual_pkg">)
5255 If there are both concrete and virtual packages of the same
5256 name, then the dependency may be satisfied (or the conflict
5257 caused) by either the concrete package with the name in
5258 question or any other concrete package which provides the
5259 virtual package with the name in question. This is so that,
5260 for example, supposing we have
5261 <example compact="compact">
5264 </example> and someone else releases an enhanced version of
5265 the <tt>bar</tt> package they can say:
5266 <example compact="compact">
5270 and the <tt>bar-plus</tt> package will now also satisfy the
5271 dependency for the <tt>foo</tt> package.
5275 If a relationship field has a version number attached, only real
5276 packages will be considered to see whether the relationship is
5277 satisfied (or the prohibition violated, for a conflict or
5278 breakage). In other words, if a version number is specified,
5279 this is a request to ignore all <tt>Provides</tt> for that
5280 package name and consider only real packages. The package
5281 manager will assume that a package providing that virtual
5282 package is not of the "right" version. A <tt>Provides</tt>
5283 field may not contain version numbers, and the version number of
5284 the concrete package which provides a particular virtual package
5285 will not be considered when considering a dependency on or
5286 conflict with the virtual package name.<footnote>
5287 It is possible that a future release of <prgn>dpkg</prgn> may
5288 add the ability to specify a version number for each virtual
5289 package it provides. This feature is not yet present,
5290 however, and is expected to be used only infrequently.
5295 To specify which of a set of real packages should be the default
5296 to satisfy a particular dependency on a virtual package, list
5297 the real package as an alternative before the virtual one.
5301 If the virtual package represents a facility that can only be
5302 provided by one real package at a time, such as
5303 the <package>mail-transport-agent</package> virtual package that
5304 requires installation of a binary that would conflict with all
5305 other providers of that virtual package (see
5306 <ref id="mail-transport-agents">), all packages providing that
5307 virtual package should also declare a conflict with it
5308 using <tt>Conflicts</tt>. This will ensure that at most one
5309 provider of that virtual package is unpacked or installed at a
5314 <sect id="replaces"><heading>Overwriting files and replacing
5315 packages - <tt>Replaces</tt></heading>
5318 Packages can declare in their control file that they should
5319 overwrite files in certain other packages, or completely replace
5320 other packages. The <tt>Replaces</tt> control field has these
5321 two distinct purposes.
5324 <sect1><heading>Overwriting files in other packages</heading>
5327 It is usually an error for a package to contain files which
5328 are on the system in another package. However, if the
5329 overwriting package declares that it <tt>Replaces</tt> the one
5330 containing the file being overwritten, then <prgn>dpkg</prgn>
5331 will replace the file from the old package with that from the
5332 new. The file will no longer be listed as "owned" by the old
5333 package and will be taken over by the new package.
5334 Normally, <tt>Breaks</tt> should be used in conjunction
5335 with <tt>Replaces</tt>.<footnote>
5336 To see why <tt>Breaks</tt> is normally needed in addition
5337 to <tt>Replaces</tt>, consider the case of a file in the
5338 package <package>foo</package> being taken over by the
5339 package <package>foo-data</package>.
5340 <tt>Replaces</tt> will allow <package>foo-data</package> to
5341 be installed and take over that file. However,
5342 without <tt>Breaks</tt>, nothing
5343 requires <package>foo</package> to be upgraded to a newer
5344 version that knows it does not include that file and instead
5345 depends on <package>foo-data</package>. Nothing would
5346 prevent the new <package>foo-data</package> package from
5347 being installed and then removed, removing the file that it
5348 took over from <package>foo</package>. After that
5349 operation, the package manager would think the system was in
5350 a consistent state, but the <package>foo</package> package
5351 would be missing one of its files.
5356 For example, if a package <package>foo</package> is split
5357 into <package>foo</package> and <package>foo-data</package>
5358 starting at version 1.2-3, <package>foo-data</package> would
5360 <example compact="compact">
5361 Replaces: foo (<< 1.2-3)
5362 Breaks: foo (<< 1.2-3)
5364 in its control file. The new version of the
5365 package <package>foo</package> would normally have the field
5366 <example compact="compact">
5367 Depends: foo-data (>= 1.2-3)
5369 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5370 the files moved into <package>foo-data</package> are not
5371 required for normal operation).
5375 If a package is completely replaced in this way, so that
5376 <prgn>dpkg</prgn> does not know of any files it still
5377 contains, it is considered to have "disappeared". It will
5378 be marked as not wanted on the system (selected for
5379 removal) and not installed. Any <tt>conffile</tt>s
5380 details noted for the package will be ignored, as they
5381 will have been taken over by the overwriting package. The
5382 package's <prgn>postrm</prgn> script will be run with a
5383 special argument to allow the package to do any final
5384 cleanup required. See <ref id="mscriptsinstact">.
5386 Replaces is a one way relationship. You have to install
5387 the replacing package after the replaced package.
5392 For this usage of <tt>Replaces</tt>, virtual packages (see
5393 <ref id="virtual">) are not considered when looking at a
5394 <tt>Replaces</tt> field. The packages declared as being
5395 replaced must be mentioned by their real names.
5399 This usage of <tt>Replaces</tt> only takes effect when both
5400 packages are at least partially on the system at once. It is
5401 not relevant if the packages conflict unless the conflict has
5406 <sect1><heading>Replacing whole packages, forcing their
5410 Second, <tt>Replaces</tt> allows the packaging system to
5411 resolve which package should be removed when there is a
5412 conflict (see <ref id="conflicts">). This usage only takes
5413 effect when the two packages <em>do</em> conflict, so that the
5414 two usages of this field do not interfere with each other.
5418 In this situation, the package declared as being replaced
5419 can be a virtual package, so for example, all mail
5420 transport agents (MTAs) would have the following fields in
5421 their control files:
5422 <example compact="compact">
5423 Provides: mail-transport-agent
5424 Conflicts: mail-transport-agent
5425 Replaces: mail-transport-agent
5427 ensuring that only one MTA can be unpacked at any one
5428 time. See <ref id="virtual"> for more information about this
5433 <sect id="sourcebinarydeps">
5434 <heading>Relationships between source and binary packages -
5435 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5436 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5440 Source packages that require certain binary packages to be
5441 installed or absent at the time of building the package
5442 can declare relationships to those binary packages.
5446 This is done using the <tt>Build-Depends</tt>,
5447 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5448 <tt>Build-Conflicts-Indep</tt> control fields.
5452 Build-dependencies on "build-essential" binary packages can be
5453 omitted. Please see <ref id="pkg-relations"> for more information.
5457 The dependencies and conflicts they define must be satisfied
5458 (as defined earlier for binary packages) in order to invoke
5459 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5461 There is no Build-Depends-Arch; this role is essentially
5462 met with Build-Depends. Anyone building the
5463 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5464 assumed to be building the whole package, and therefore
5465 installation of all build dependencies is required.
5468 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5469 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5470 not yet know how to check for its existence, and
5471 <tt>binary-arch</tt>. The purpose of the original split
5472 between <tt>Build-Depends</tt> and
5473 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5474 wouldn't need to install extra packages needed only for the
5475 binary-indep targets. But without a build-arch/build-indep
5476 split, this didn't work, since most of the work is done in
5477 the build target, not in the binary target.
5481 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5482 <tt>binary-arch</tt></tag>
5484 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5485 fields must be satisfied when these targets are invoked.
5487 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5488 and <tt>binary-indep</tt></tag>
5490 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5491 <tt>Build-Depends-Indep</tt>, and
5492 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5493 these targets are invoked.
5499 <sect id="built-using">
5500 <heading>Additional source packages used to build the binary
5501 - <tt>Built-Using</tt>
5505 Some binary packages incorporate parts of other packages when built
5506 but do not have to depend on those packages. Examples include
5507 linking with static libraries or incorporating source code from
5508 another package during the build. In this case, the source packages
5509 of those other packages are a required part of the complete source
5510 (the binary package is not reproducible without them).
5514 A <tt>Built-Using</tt> field must list the corresponding source
5515 package for any such binary package incorporated during the build
5517 <tt>Build-Depends</tt> in the source package is not adequate since
5518 it (rightfully) does not document the exact version used in the
5521 including an "exactly equal" ("=") version relation on the version
5522 that was used to build that binary package<footnote>
5523 The archive software might reject packages that refer to
5524 non-existent sources.
5529 A package using the source code from the gcc-4.6-source
5530 binary package built from the gcc-4.6 source package would
5531 have this field in its control file:
5532 <example compact="compact">
5533 Built-Using: gcc-4.6 (= 4.6.0-11)
5538 A package including binaries from grub2 and loadlin would
5539 have this field in its control file:
5540 <example compact="compact">
5541 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5548 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5551 Packages containing shared libraries must be constructed with
5552 a little care to make sure that the shared library is always
5553 available. This is especially important for packages whose
5554 shared libraries are vitally important, such as the C library
5555 (currently <tt>libc6</tt>).
5559 This section deals only with public shared libraries: shared
5560 libraries that are placed in directories searched by the dynamic
5561 linker by default or which are intended to be linked against
5562 normally and possibly used by other, independent packages. Shared
5563 libraries that are internal to a particular package or that are
5564 only loaded as dynamic modules are not covered by this section and
5565 are not subject to its requirements.
5569 A shared library is identified by the <tt>SONAME</tt> attribute
5570 stored in its dynamic section. When a binary is linked against a
5571 shared library, the <tt>SONAME</tt> of the shared library is
5572 recorded in the binary's <tt>NEEDED</tt> section so that the
5573 dynamic linker knows that library must be loaded at runtime. The
5574 shared library file's full name (which usually contains additional
5575 version information not needed in the <tt>SONAME</tt>) is
5576 therefore normally not referenced directly. Instead, the shared
5577 library is loaded by its <tt>SONAME</tt>, which exists on the file
5578 system as a symlink pointing to the full name of the shared
5579 library. This symlink must be provided by the
5580 package. <ref id="sharedlibs-runtime"> describes how to do this.
5582 This is a convention of shared library versioning, but not a
5583 requirement. Some libraries use the <tt>SONAME</tt> as the full
5584 library file name instead and therefore do not need a symlink.
5585 Most, however, encode additional information about
5586 backwards-compatible revisions as a minor version number in the
5587 file name. The <tt>SONAME</tt> itself only changes when
5588 binaries linked with the earlier version of the shared library
5589 may no longer work, but the filename may change with each
5590 release of the library. See <ref id="sharedlibs-runtime"> for
5596 When linking a binary or another shared library against a shared
5597 library, the <tt>SONAME</tt> for that shared library is not yet
5598 known. Instead, the shared library is found by looking for a file
5599 matching the library name with <tt>.so</tt> appended. This file
5600 exists on the file system as a symlink pointing to the shared
5605 Shared libraries are normally split into several binary packages.
5606 The <tt>SONAME</tt> symlink is installed by the runtime shared
5607 library package, and the bare <tt>.so</tt> symlink is installed in
5608 the development package since it's only used when linking binaries
5609 or shared libraries. However, there are some exceptions for
5610 unusual shared libraries or for shared libraries that are also
5611 loaded as dynamic modules by other programs.
5615 This section is primarily concerned with how the separation of
5616 shared libraries into multiple packages should be done and how
5617 dependencies on and between shared library binary packages are
5618 managed in Debian. <ref id="libraries"> should be read in
5619 conjunction with this section and contains additional rules for
5620 the files contained in the shared library packages.
5623 <sect id="sharedlibs-runtime">
5624 <heading>Run-time shared libraries</heading>
5627 The run-time shared library must be placed in a package
5628 whose name changes whenever the <tt>SONAME</tt> of the shared
5629 library changes. This allows several versions of the shared
5630 library to be installed at the same time, allowing installation
5631 of the new version of the shared library without immediately
5632 breaking binaries that depend on the old version. Normally, the
5633 run-time shared library and its <tt>SONAME</tt> symlink should
5634 be placed in a package named
5635 <package><var>libraryname</var><var>soversion</var></package>,
5636 where <var>soversion</var> is the version number in
5637 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5638 would be confusing to directly append <var>soversion</var>
5639 to <var>libraryname</var> (if, for
5640 example, <var>libraryname</var> itself ends in a number), you
5642 <package><var>libraryname</var>-<var>soversion</var></package>
5647 To determine the <var>soversion</var>, look at
5648 the <tt>SONAME</tt> of the library, stored in the
5649 ELF <tt>SONAME</tt> attribute. It is usually of the
5650 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5651 example, <tt>libz.so.1</tt>). The version part is the part
5652 which comes after <tt>.so.</tt>, so in that example it
5653 is <tt>1</tt>. The soname may instead be of the
5654 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5655 as <tt>libdb-5.1.so</tt>, in which case the name would
5656 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5660 If you have several shared libraries built from the same source
5661 tree, you may lump them all together into a single shared
5662 library package provided that all of their <tt>SONAME</tt>s will
5663 always change together. Be aware that this is not normally the
5664 case, and if the <tt>SONAME</tt>s do not change together,
5665 upgrading such a merged shared library package will be
5666 unnecessarily difficult because of file conflicts with the old
5667 version of the package. When in doubt, always split shared
5668 library packages so that each binary package installs a single
5673 Every time the shared library ABI changes in a way that may
5674 break binaries linked against older versions of the shared
5675 library, the <tt>SONAME</tt> of the library and the
5676 corresponding name for the binary package containing the runtime
5677 shared library should change. Normally, this means
5678 the <tt>SONAME</tt> should change any time an interface is
5679 removed from the shared library or the signature of an interface
5680 (the number of parameters or the types of parameters that it
5681 takes, for example) is changed. This practice is vital to
5682 allowing clean upgrades from older versions of the package and
5683 clean transitions between the old ABI and new ABI without having
5684 to upgrade every affected package simultaneously.
5688 The <tt>SONAME</tt> and binary package name need not, and indeed
5689 normally should not, change if new interfaces are added but none
5690 are removed or changed, since this will not break binaries
5691 linked against the old shared library. Correct versioning of
5692 dependencies on the newer shared library by binaries that use
5693 the new interfaces is handled via
5694 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5695 or <tt>shlibs</tt> system</qref>.
5699 The package should install the shared libraries under
5700 their normal names. For example, the <package>libgdbm3</package>
5701 package should install <file>libgdbm.so.3.0.0</file> as
5702 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5703 renamed or re-linked by any <prgn>prerm</prgn> or
5704 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5705 of renaming things safely without affecting running programs,
5706 and attempts to interfere with this are likely to lead to
5711 Shared libraries should not be installed executable, since
5712 the dynamic linker does not require this and trying to
5713 execute a shared library usually results in a core dump.
5717 The run-time library package should include the symbolic link for
5718 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5719 the shared libraries. For example,
5720 the <package>libgdbm3</package> package should include a symbolic
5721 link from <file>/usr/lib/libgdbm.so.3</file> to
5722 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5723 linker (for example <prgn>ld.so</prgn> or
5724 <prgn>ld-linux.so.*</prgn>) can find the library between the
5725 time that <prgn>dpkg</prgn> installs it and the time that
5726 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5728 The package management system requires the library to be
5729 placed before the symbolic link pointing to it in the
5730 <file>.deb</file> file. This is so that when
5731 <prgn>dpkg</prgn> comes to install the symlink
5732 (overwriting the previous symlink pointing at an older
5733 version of the library), the new shared library is already
5734 in place. In the past, this was achieved by creating the
5735 library in the temporary packaging directory before
5736 creating the symlink. Unfortunately, this was not always
5737 effective, since the building of the tar file in the
5738 <file>.deb</file> depended on the behavior of the underlying
5739 file system. Some file systems (such as reiserfs) reorder
5740 the files so that the order of creation is forgotten.
5741 Since version 1.7.0, <prgn>dpkg</prgn>
5742 reorders the files itself as necessary when building a
5743 package. Thus it is no longer important to concern
5744 oneself with the order of file creation.
5748 <sect1 id="ldconfig">
5749 <heading><tt>ldconfig</tt></heading>
5752 Any package installing shared libraries in one of the default
5753 library directories of the dynamic linker (which are currently
5754 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5755 listed in <file>/etc/ld.so.conf</file><footnote>
5756 These are currently <file>/usr/local/lib</file> plus
5757 directories under <file>/lib</file> and <file>/usr/lib</file>
5758 matching the multiarch triplet for the system architecture.
5760 must use <prgn>ldconfig</prgn> to update the shared library
5765 The package maintainer scripts must only call
5766 <prgn>ldconfig</prgn> under these circumstances:
5767 <list compact="compact">
5768 <item>When the <prgn>postinst</prgn> script is run with a
5769 first argument of <tt>configure</tt>, the script must call
5770 <prgn>ldconfig</prgn>, and may optionally invoke
5771 <prgn>ldconfig</prgn> at other times.
5773 <item>When the <prgn>postrm</prgn> script is run with a
5774 first argument of <tt>remove</tt>, the script should call
5775 <prgn>ldconfig</prgn>.
5780 During install or upgrade, the preinst is called before
5781 the new files are unpacked, so calling "ldconfig" is
5782 pointless. The preinst of an existing package can also be
5783 called if an upgrade fails. However, this happens during
5784 the critical time when a shared libs may exist on-disk
5785 under a temporary name. Thus, it is dangerous and
5786 forbidden by current policy to call "ldconfig" at this
5791 When a package is installed or upgraded, "postinst
5792 configure" runs after the new files are safely on-disk.
5793 Since it is perfectly safe to invoke ldconfig
5794 unconditionally in a postinst, it is OK for a package to
5795 simply put ldconfig in its postinst without checking the
5796 argument. The postinst can also be called to recover from
5797 a failed upgrade. This happens before any new files are
5798 unpacked, so there is no reason to call "ldconfig" at this
5803 For a package that is being removed, prerm is
5804 called with all the files intact, so calling ldconfig is
5805 useless. The other calls to "prerm" happen in the case of
5806 upgrade at a time when all the files of the old package
5807 are on-disk, so again calling "ldconfig" is pointless.
5811 postrm, on the other hand, is called with the "remove"
5812 argument just after the files are removed, so this is
5813 the proper time to call "ldconfig" to notify the system
5814 of the fact that the shared libraries from the package
5815 are removed. The postrm can be called at several other
5816 times. At the time of "postrm purge", "postrm
5817 abort-install", or "postrm abort-upgrade", calling
5818 "ldconfig" is useless because the shared lib files are
5819 not on-disk. However, when "postrm" is invoked with
5820 arguments "upgrade", "failed-upgrade", or "disappear", a
5821 shared lib may exist on-disk under a temporary filename.
5829 <sect id="sharedlibs-support-files">
5830 <heading>Shared library support files</heading>
5833 If your package contains files whose names do not change with
5834 each change in the library shared object version, you must not
5835 put them in the shared library package. Otherwise, several
5836 versions of the shared library cannot be installed at the same
5837 time without filename clashes, making upgrades and transitions
5838 unnecessarily difficult.
5842 It is recommended that supporting files and run-time support
5843 programs that do not need to be invoked manually by users, but
5844 are nevertheless required for the package to function, be placed
5845 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5846 preferably under <file>/usr/lib/</file><var>package-name</var>.
5847 If the program or file is architecture independent, the
5848 recommendation is for it to be placed in a subdirectory of
5849 <file>/usr/share</file> instead, preferably under
5850 <file>/usr/share/</file><var>package-name</var>. Following the
5851 <var>package-name</var> naming convention ensures that the file
5852 names change when the shared object version changes.
5856 Run-time support programs that use the shared library but are
5857 not required for the library to function or files used by the
5858 shared library that can be used by any version of the shared
5859 library package should instead be put in a separate package.
5860 This package might typically be named
5861 <package><var>libraryname</var>-tools</package>; note the
5862 absence of the <var>soversion</var> in the package name.
5866 Files and support programs only useful when compiling software
5867 against the library should be included in the development
5868 package for the library.<footnote>
5869 For example, a <file><var>package-name</var>-config</file>
5870 script or <package>pkg-config</package> configuration files.
5875 <sect id="sharedlibs-static">
5876 <heading>Static libraries</heading>
5879 The static library (<file><var>libraryname.a</var></file>)
5880 is usually provided in addition to the shared version.
5881 It is placed into the development package (see below).
5885 In some cases, it is acceptable for a library to be
5886 available in static form only; these cases include:
5888 <item>libraries for languages whose shared library support
5889 is immature or unstable</item>
5890 <item>libraries whose interfaces are in flux or under
5891 development (commonly the case when the library's
5892 major version number is zero, or where the ABI breaks
5893 across patchlevels)</item>
5894 <item>libraries which are explicitly intended to be
5895 available only in static form by their upstream
5900 <sect id="sharedlibs-dev">
5901 <heading>Development files</heading>
5904 If there are development files associated with a shared library,
5905 the source package needs to generate a binary development package
5906 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5907 or if you prefer only to support one development version at a
5908 time, <package><var>libraryname</var>-dev</package>. Installing
5909 the development package must result in installation of all the
5910 development files necessary for compiling programs against that
5911 shared library.<footnote>
5912 This wording allows the development files to be split into
5913 several packages, such as a separate architecture-independent
5914 <package><var>libraryname</var>-headers</package>, provided that
5915 the development package depends on all the required additional
5921 In case several development versions of a library exist, you may
5922 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5923 <ref id="conflicts">) to ensure that the user only installs one
5924 development version at a time (as different development versions are
5925 likely to have the same header files in them, which would cause a
5926 filename clash if both were unpacked).
5930 The development package should contain a symlink for the associated
5931 shared library without a version number. For example, the
5932 <package>libgdbm-dev</package> package should include a symlink
5933 from <file>/usr/lib/libgdbm.so</file> to
5934 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5935 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5936 <file>libgdbm.so</file> when compiling dynamically.
5940 If the package provides Ada Library Information
5941 (<file>*.ali</file>) files for use with GNAT, these files must be
5942 installed read-only (mode 0444) so that GNAT will not attempt to
5943 recompile them. This overrides the normal file mode requirements
5944 given in <ref id="permissions-owners">.
5948 <sect id="sharedlibs-intradeps">
5949 <heading>Dependencies between the packages of the same library</heading>
5952 Typically the development version should have an exact
5953 version dependency on the runtime library, to make sure that
5954 compilation and linking happens correctly. The
5955 <tt>${binary:Version}</tt> substitution variable can be
5956 useful for this purpose.
5958 Previously, <tt>${Source-Version}</tt> was used, but its name
5959 was confusing and it has been deprecated since dpkg 1.13.19.
5964 <sect id="sharedlibs-depends">
5965 <heading>Dependencies between the library and other
5969 If a package contains a binary or library which links to a
5970 shared library, we must ensure that, when the package is
5971 installed on the system, all of the libraries needed are also
5972 installed. These dependencies must be added to the binary
5973 package when it is built, since they may change based on which
5974 version of a shared library the binary or library was linked
5975 with even if there are no changes to the source of the binary
5976 (for example, symbol versions change, macros become functions or
5977 vice versa, or the binary package may determine at compile-time
5978 whether new library interfaces are available and can be called).
5979 To allow these dependencies to be constructed, shared libraries
5980 must provide either a <file>symbols</file> file or
5981 a <file>shlibs</file> file. These provide information on the
5982 package dependencies required to ensure the presence of
5983 interfaces provided by this library. Any package with binaries
5984 or libraries linking to a shared library must use these files to
5985 determine the required dependencies when it is built. Other
5986 packages which use a shared library (for example using
5987 <tt>dlopen()</tt>) should compute appropriate dependencies
5988 using these files at build time as well.
5992 The two mechanisms differ in the degree of detail that they
5993 provide. A <file>symbols</file> file documents, for each symbol
5994 exported by a library, the minimal version of the package any
5995 binary using this symbol will need. This is typically the
5996 version of the package in which the symbol was introduced. This
5997 information permits detailed analysis of the symbols used by a
5998 particular package and construction of an accurate dependency,
5999 but it requires the package maintainer to track more information
6000 about the shared library.
6004 A <file>shlibs</file> file, in contrast, only documents the last
6005 time the library ABI changed in any way. It only provides
6006 information about the library as a whole, not individual
6007 symbols. When a package is built using a shared library with
6008 only a <file>shlibs</file> file, the generated dependency will
6009 require a version of the shared library equal to or newer than
6010 the version of the last ABI change. This generates
6011 unnecessarily restrictive dependencies compared
6012 to <file>symbols</file> files if none of the symbols used by the
6013 package have changed. This, in turn, may make upgrades
6014 needlessly complex and unnecessarily restrict use of the package
6015 on systems with older versions of the shared libraries.
6019 <file>shlibs</file> files also only support a limited range of
6020 library SONAMEs, making it difficult to use <file>shlibs</file>
6021 files in some unusual corner cases.<footnote>
6022 A <file>shlibs</file> file represents an SONAME as a library
6023 name and version number, such as <tt>libfoo VERSION</tt>,
6024 instead of recording the actual SONAME. If the SONAME doesn't
6025 match one of the two expected formats
6026 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6027 cannot be represented.
6032 <file>symbols</file> files are therefore recommended for most
6033 shared library packages since they provide more accurate
6034 dependencies. For most C libraries, the additional detail
6035 required by <file>symbols</file> files is not too difficult to
6036 maintain. However, maintaining exhaustive symbols information
6037 for a C++ library can be quite onerous, so <file>shlibs</file>
6038 files may be more appropriate for most C++ libraries. Libraries
6039 with a corresponding udeb must also provide
6040 a <file>shlibs</file> file, since the udeb infrastructure does
6041 not use <file>symbols</file> files.
6044 <sect1 id="dpkg-shlibdeps">
6045 <heading>Generating dependencies on shared libraries</heading>
6048 When a package that contains any shared libraries or compiled
6049 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6050 each shared library and compiled binary to determine the
6051 libraries used and hence the dependencies needed by the
6053 <prgn>dpkg-shlibdeps</prgn> will use a program
6054 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6055 the libraries and the symbols in those libraries directly
6056 needed by the binaries or shared libraries in the package.
6058 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6059 your <file>debian/rules</file> file in the source package.
6060 List all of the compiled binaries, libraries, or loadable
6061 modules in your package.<footnote>
6062 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6063 correctly is to use a package helper framework such
6064 as <package>debhelper</package>. If you are
6065 using <package>debhelper</package>,
6066 the <prgn>dh_shlibdeps</prgn> program will do this work for
6067 you. It will also correctly handle multi-binary packages.
6069 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6070 or <file>shlibs</file> files installed by the shared libraries
6071 to generate dependency information. The package must then
6072 provide a substitution variable into which the discovered
6073 dependency information can be placed.
6077 If you are creating a udeb for use in the Debian Installer,
6078 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6079 should use the dependency line of type <tt>udeb</tt> by adding
6080 the <tt>-tudeb</tt> option<footnote>
6081 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6082 will automatically add this option if it knows it is
6084 </footnote>. If there is no dependency line of
6085 type <tt>udeb</tt> in the <file>shlibs</file>
6086 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6087 regular dependency line.
6091 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6092 into the <file>debian/substvars</file> file by default, which
6093 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6094 to place a <tt>${shlibs:Depends}</tt> variable in
6095 the <tt>Depends</tt> field in the control file of every binary
6096 package built by this source package that contains compiled
6097 binaries, libraries, or loadable modules. If you have
6098 multiple binary packages, you will need to
6099 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6100 compiled libraries or binaries. For example, you could use
6101 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6102 specify a different <file>substvars</file> file for each
6103 binary package.<footnote>
6104 Again, <prgn>dh_shlibdeps</prgn>
6105 and <prgn>dh_gencontrol</prgn> will handle everything except
6106 the addition of the variable to the control file for you if
6107 you're using <package>debhelper</package>, including
6108 generating separate <file>substvars</file> files for each
6109 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6110 the appropriate flags.
6115 For more details on <prgn>dpkg-shlibdeps</prgn>,
6116 see <manref name="dpkg-shlibdeps" section="1">.
6120 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6121 library <tt>libbar</tt> if it is explicitly linked with that
6122 library (that is, the library is listed in the
6123 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6124 to the link line when the binary is created). Other libraries
6125 that are needed by <tt>libbar</tt> are
6126 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6127 linker will load them automatically when it
6128 loads <tt>libbar</tt>. A package should depend on the
6129 libraries it directly uses, but not the libraries it only uses
6130 indirectly. The dependencies for the libraries used
6131 directly will automatically pull in the indirectly-used
6132 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6133 automatically, but package maintainers need to be aware of
6134 this distinction between directly and indirectly using a
6135 library if they have to override its results for some reason.
6137 A good example of where this helps is the following. We
6138 could update <tt>libimlib</tt> with a new version that
6139 supports a new revision of a graphics format called dgf (but
6140 retaining the same major version number) and depends on a
6141 new library package <package>libdgf4</package> instead of
6142 the older <package>libdgf3</package>. If we
6143 used <prgn>ldd</prgn> to add dependencies for every library
6144 directly or indirectly linked with a binary, every package
6145 that uses <tt>libimlib</tt> would need to be recompiled so
6146 it would also depend on <package>libdgf4</package> in order
6147 to retire the older <package>libdgf3</package> package.
6148 Since dependencies are only added based on
6149 ELF <tt>NEEDED</tt> attribute, packages
6150 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6151 having the dependency on an appropriate version
6152 of <tt>libdgf</tt> and do not need rebuilding.
6157 <sect1 id="sharedlibs-updates">
6158 <heading>Shared library ABI changes</heading>
6161 Maintaining a shared library package using
6162 either <file>symbols</file> or <file>shlibs</file> files
6163 requires being aware of the exposed ABI of the shared library
6164 and any changes to it. Both <file>symbols</file>
6165 and <file>shlibs</file> files record every change to the ABI
6166 of the shared library; <file>symbols</file> files do so per
6167 public symbol, whereas <file>shlibs</file> files record only
6168 the last change for the entire library.
6172 There are two types of ABI changes: ones that are
6173 backward-compatible and ones that are not. An ABI change is
6174 backward-compatible if any reasonable program or library that
6175 was linked with the previous version of the shared library
6176 will still work correctly with the new version of the shared
6178 An example of an "unreasonable" program is one that uses
6179 library interfaces that are documented as internal and
6180 unsupported. If the only programs or libraries affected by
6181 a change are "unreasonable" ones, other techniques, such as
6182 declaring <tt>Breaks</tt> relationships with affected
6183 packages or treating their usage of the library as bugs in
6184 those packages, may be appropriate instead of changing the
6185 SONAME. However, the default approach is to change the
6186 SONAME for any change to the ABI that could break a program.
6188 Adding new symbols to the shared library is a
6189 backward-compatible change. Removing symbols from the shared
6190 library is not. Changing the behavior of a symbol may or may
6191 not be backward-compatible depending on the change; for
6192 example, changing a function to accept a new enum constant not
6193 previously used by the library is generally
6194 backward-compatible, but changing the members of a struct that
6195 is passed into library functions is generally not unless the
6196 library takes special precautions to accept old versions of
6201 ABI changes that are not backward-compatible normally require
6202 changing the <tt>SONAME</tt> of the library and therefore the
6203 shared library package name, which forces rebuilding all
6204 packages using that shared library to update their
6205 dependencies and allow them to use the new version of the
6206 shared library. For more information,
6207 see <ref id="sharedlibs-runtime">. The remainder of this
6208 section will deal with backward-compatible changes.
6212 Backward-compatible changes require either updating or
6213 recording the <var>minimal-version</var> for that symbol
6214 in <file>symbols</file> files or updating the version in
6215 the <var>dependencies</var> in <file>shlibs</file> files. For
6216 more information on how to do this in the two formats, see
6217 <ref id="symbols"> and <ref id="shlibs">. Below are general
6218 rules that apply to both files.
6222 The easy case is when a public symbol is added. Simply add
6223 the version at which the symbol was introduced
6224 (for <file>symbols</file> files) or update the dependency
6225 version (for <file>shlibs</file>) files. But special care
6226 should be taken to update dependency versions when the
6227 behavior of a public symbol changes. This is easy to neglect,
6228 since there is no automated method of determining such
6229 changes, but failing to update versions in this case may
6230 result in binary packages with too-weak dependencies that will
6231 fail at runtime, possibly in ways that can cause security
6232 vulnerabilities. If the package maintainer believes that a
6233 symbol behavior change may have occurred but isn't sure, it's
6234 safer to update the version rather than leave it unmodified.
6235 This may result in unnecessarily strict dependencies, but it
6236 ensures that packages whose dependencies are satisfied will
6241 A common example of when a change to the dependency version
6242 is required is a function that takes an enum or struct
6243 argument that controls what the function does. For example:
6245 enum library_op { OP_FOO, OP_BAR };
6246 int library_do_operation(enum library_op);
6248 If a new operation, <tt>OP_BAZ</tt>, is added,
6249 the <var>minimal-version</var>
6250 of <tt>library_do_operation</tt> (for <file>symbols</file>
6251 files) or the version in the dependency for the shared library
6252 (for <file>shlibs</file> files) must be increased to the
6253 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6254 binary built against the new version of the library (having
6255 detected at compile-time that the library
6256 supports <tt>OP_BAZ</tt>) may be installed with a shared
6257 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6258 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6263 Dependency versions in either <file>symbols</file>
6264 or <file>shlibs</file> files normally should not contain the
6265 Debian revision of the package, since the library behavior is
6266 normally fixed for a particular upstream version and any
6267 Debian packaging of that upstream version will have the same
6268 behavior. In the rare case that the library behavior was
6269 changed in a particular Debian revision, appending <tt>~</tt>
6270 to the end of the version that includes the Debian revision is
6271 recommended, since this allows backports of the shared library
6272 package using the normal backport versioning convention to
6273 satisfy the dependency.
6277 <sect1 id="sharedlibs-symbols">
6278 <heading>The <tt>symbols</tt> system</heading>
6281 In the following sections, we will first describe where the
6282 various <file>symbols</file> files are to be found, then
6283 the <file>symbols</file> file format, and finally how to
6284 create <file>symbols</file> files if your package contains a
6288 <sect2 id="symbols-paths">
6289 <heading>The <file>symbols</file> files present on the
6293 <file>symbols</file> files for a shared library are normally
6294 provided by the shared library package as a control file,
6295 but there are several override paths that are checked first
6296 in case that information is wrong or missing. The following
6297 list gives them in the order in which they are read
6298 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6299 the required information is used.
6302 <p><file>debian/*/DEBIAN/symbols</file></p>
6305 During the package build, if the package itself
6306 contains shared libraries with <file>symbols</file>
6307 files, they will be generated in these staging
6308 directories by <prgn>dpkg-gensymbols</prgn>
6309 (see <ref id="providing-symbols">). <file>symbols</file>
6310 files found in the build tree take precedence
6311 over <file>symbols</file> files from other binary
6316 These files must exist
6317 before <prgn>dpkg-shlibdeps</prgn> is run or the
6318 dependencies of binaries and libraries from a source
6319 package on other libraries from that same source
6320 package will not be correct. In practice, this means
6321 that <prgn>dpkg-gensymbols</prgn> must be run
6322 before <prgn>dpkg-shlibdeps</prgn> during the package
6324 An example may clarify. Suppose the source
6325 package <tt>foo</tt> generates two binary
6326 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6327 When building the binary packages, the contents of
6328 the packages are staged in the
6329 directories <file>debian/libfoo2</file>
6330 and <file>debian/foo-runtime</file> respectively.
6331 (<file>debian/tmp</file> could be used instead of
6332 one of these.) Since <tt>libfoo2</tt> provides
6333 the <tt>libfoo</tt> shared library, it will contain
6334 a <tt>symbols</tt> file, which will be installed
6335 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6336 eventually to be included as a control file in that
6337 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6339 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6341 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6342 to determine whether <tt>foo-prog</tt>'s library
6343 dependencies are satisfied by any of the libraries
6344 provided by <tt>libfoo2</tt>. Since those binaries
6345 were linked against the just-built shared library as
6346 part of the build process, the <file>symbols</file>
6347 file for the newly-built <tt>libfoo2</tt> must take
6348 precedence over a <file>symbols</file> file for any
6349 other <tt>libfoo2</tt> package already installed on
6357 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6358 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6362 Per-system overrides of shared library dependencies.
6363 These files normally do not exist. They are
6364 maintained by the local system administrator and must
6365 not be created by any Debian package.
6370 <p><file>symbols</file> control files for packages
6371 installed on the system</p>
6374 The <file>symbols</file> control files for all the
6375 packages currently installed on the system are
6376 searched last. This will be the most common source of
6377 shared library dependency information. These are
6379 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6380 packages should not rely on this and instead should
6381 use <tt>dpkg-query --control-path <var>package</var>
6382 symbols</tt> if for some reason these files need to be
6390 Be aware that if a <file>debian/shlibs.local</file> exists
6391 in the source package, it will override
6392 any <file>symbols</file> files. This is the only case where
6393 a <file>shlibs</file> is used despite <file>symbols</file>
6394 files being present. See <ref id="shlibs-paths">
6395 and <ref id="sharedlibs-shlibdeps"> for more information.
6399 <sect2 id="symbols">
6400 <heading>The <file>symbols</file> File Format</heading>
6403 The following documents the format of
6404 the <file>symbols</file> control file as included in binary
6405 packages. These files are built from
6406 template <file>symbols</file> files in the source package
6407 by <prgn>dpkg-gensymbols</prgn>. The template files support
6408 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6409 do some of the tedious work involved in
6410 maintaining <file>symbols</file> files, such as handling C++
6411 symbols or optional symbols that may not exist on particular
6412 architectures. When writing <file>symbols</file> files for
6413 a shared library package, refer
6414 to <manref name="dpkg-gensymbols" section="1"> for the
6419 A <file>symbols</file> may contain one or more entries, one
6420 for each shared library contained in the package
6421 corresponding to that <file>symbols</file>. Each entry has
6422 the following format:
6427 <var>library-soname</var> <var>main-dependency-template</var>
6428 [| <var>alternative-dependency-template</var>]
6430 [* <var>field-name</var>: <var>field-value</var>]
6432 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6437 To explain this format, we'll use the the <tt>zlib1g</tt>
6438 package as an example, which (at the time of writing)
6440 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6441 lines will be described first, followed by optional lines.
6445 <var>library-soname</var> must contain exactly the value of
6446 the ELF <tt>SONAME</tt> attribute of the shared library. In
6447 our example, this is <tt>libz.so.1</tt>.<footnote>
6448 This can be determined by using the command
6449 <example compact="compact">
6450 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6456 <var>main-dependency-template</var> has the same syntax as a
6457 dependency field in a binary package control file, except
6458 that the string <tt>#MINVER#</tt> is replaced by a version
6459 restriction like <tt>(>= <var>version</var>)</tt> or by
6460 nothing if an unversioned dependency is deemed sufficient.
6461 The version restriction will be based on which symbols from
6462 the shared library are referenced and the version at which
6463 they were introduced (see below). In nearly all
6464 cases, <var>main-dependency-template</var> will
6465 be <tt><var>package</var> #MINVER#</tt>,
6466 where <var>package</var> is the name of the binary package
6467 containing the shared library. This adds a simple,
6468 possibly-versioned dependency on the shared library package.
6469 In some rare cases, such as when multiple packages provide
6470 the same shared library ABI, the dependency template may
6471 need to be more complex.
6475 In our example, the first line of
6476 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6477 <example compact="compact">
6478 libz.so.1 zlib1g #MINVER#
6483 Each public symbol exported by the shared library must have
6484 a corresponding symbol line, indented by one
6485 space. <var>symbol</var> is the exported symbol (which, for
6486 C++, means the mangled symbol) followed by <tt>@</tt> and
6487 the symbol version, or the string <tt>Base</tt> if there is
6488 no symbol version. <var>minimal-version</var> is the most
6489 recent version of the shared library that changed the
6490 behavior of that symbol, whether by adding it, changing its
6491 function signature (the parameters, their types, or the
6492 return type), or changing its behavior in a way that is
6493 visible to a caller.
6494 <var>id-of-dependency-template</var> is an optional
6495 field that references
6496 an <var>alternative-dependency-template</var>; see below for
6501 For example, <tt>libz.so.1</tt> contains the
6502 symbols <tt>compress</tt>
6503 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6504 version and last changed its behavior in upstream
6505 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6506 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6507 upstream version <tt>1:1.2.0</tt>, and has not changed its
6508 behavior. Its <file>symbols</file> file therefore contains
6510 <example compact="compact">
6511 compress@Base 1:1.1.4
6512 compressBound@ZLIB_1.2.0 1:1.2.0
6514 Packages using only <tt>compress</tt> would then get a
6515 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6516 using <tt>compressBound</tt> would get a dependency
6517 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6521 One or more <var>alternative-dependency-template</var> lines
6522 may be provided. These are used in cases where some symbols
6523 in the shared library should use one dependency template
6524 while others should use a different template. The
6525 alternative dependency templates are used only if a symbol
6526 line contains the <var>id-of-dependency-template</var>
6527 field. The first alternative dependency template is
6528 numbered 1, the second 2, and so forth.<footnote>
6529 An example of where this may be needed is with a library
6530 that implements the libGL interface. All GL
6531 implementations provide the same set of base interfaces,
6532 and then may provide some additional interfaces only used
6533 by programs that require that specific GL implementation.
6534 So, for example, libgl1-mesa-glx may use the
6535 following <file>symbols</file> file:
6538 | libgl1-mesa-glx #MINVER#
6539 publicGlSymbol@Base 6.3-1
6541 implementationSpecificSymbol@Base 6.5.2-7 1
6544 Binaries or shared libraries using
6545 only <tt>publicGlSymbol</tt> would depend only
6546 on <tt>libgl1</tt> (which may be provided by multiple
6548 using <tt>implementationSpecificSymbol</tt> would get a
6549 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6554 Finally, the entry for the library may contain one or more
6555 metadata fields. Currently, the only
6556 supported <var>field-name</var>
6557 is <tt>Build-Depends-Package</tt>, whose value lists
6558 the <qref id="sharedlibs-dev">library development
6559 package</qref> on which packages using this shared library
6560 declare a build dependency. If this field is
6561 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6562 the resulting binary package dependency on the shared
6563 library is at least as strict as the source package
6564 dependency on the shared library development
6566 This field should normally not be necessary, since if the
6567 behavior of any symbol has changed, the corresponding
6568 symbol <var>minimal-version</var> should have been
6569 increased. But including it makes the <tt>symbols</tt>
6570 system more robust by tightening the dependency in cases
6571 where the package using the shared library specifically
6572 requires at least a particular version of the shared
6573 library development package for some reason.
6575 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6577 <example compact="compact">
6578 * Build-Depends-Package: zlib1g-dev
6583 Also see <manref name="deb-symbols" section="5">.
6587 <sect2 id="providing-symbols">
6588 <heading>Providing a <file>symbols</file> file</heading>
6591 If your package provides a shared library, you should
6592 arrange to include a <file>symbols</file> control file
6593 following the format described above in that package. You
6594 must include either a <file>symbols</file> control file or
6595 a <file>shlibs</file> control file.
6599 Normally, this is done by creating a <file>symbols</file> in
6601 named <file>debian/<var>package</var>.symbols</file>
6602 or <file>debian/symbols</file>, possibly
6603 with <file>.<var>arch</var></file> appended if the symbols
6604 information varies by architecture. This file may use the
6605 extended syntax documented in <manref name="dpkg-gensymbols"
6606 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6607 part of the package build process. It will
6608 create <file>symbols</file> files in the package staging
6609 area based on the binaries and libraries in the package
6610 staging area and the <file>symbols</file> files in the
6611 source package.<footnote>
6613 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6614 take care of calling either <prgn>dpkg-gensymbols</prgn>
6615 or generating a <file>shlibs</file> file as appropriate.
6620 Packages that provide <file>symbols</file> files must keep
6621 them up-to-date to ensure correct dependencies in packages
6622 that use the shared libraries. This means updating
6623 the <file>symbols</file> file whenever a new public symbol
6624 is added, changing the <var>minimal-version</var> field
6625 whenever a symbol changes behavior or signature in a
6626 backward-compatible way (see <ref id="sharedlibs-updates">),
6627 and changing the <var>library-soname</var>
6628 and <var>main-dependency-template</var>, and probably all of
6629 the <var>minimal-version</var> fields, when the library
6630 changes <tt>SONAME</tt>. Removing a public symbol from
6631 the <file>symbols</file> file because it's no longer
6632 provided by the library normally requires changing
6633 the <tt>SONAME</tt> of the library.
6634 See <ref id="sharedlibs-runtime"> for more information
6635 on <tt>SONAME</tt>s.
6640 <sect1 id="sharedlibs-shlibdeps">
6641 <heading>The <tt>shlibs</tt> system</heading>
6644 The <tt>shlibs</tt> system is an simpler alternative to
6645 the <tt>symbols</tt> system for declaring dependencies for
6646 shared libraries. It may be more appropriate for C++
6647 libraries and other cases where tracking individual symbols is
6648 too difficult. It predated the <tt>symbols</tt> system and is
6649 therefore frequently seen in older packages. It is also
6650 required for udebs, which do not support <tt>symbols</tt>.
6654 In the following sections, we will first describe where the
6655 various <file>shlibs</file> files are to be found, then how to
6656 use <prgn>dpkg-shlibdeps</prgn>, and finally
6657 the <file>shlibs</file> file format and how to create them.
6660 <sect2 id="shlibs-paths">
6661 <heading>The <file>shlibs</file> files present on the
6665 There are several places where <tt>shlibs</tt> files are
6666 found. The following list gives them in the order in which
6667 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6668 one which gives the required information is used.)
6671 <p><file>debian/shlibs.local</file></p>
6674 This lists overrides for this package. This file
6675 should normally not be used, but may be needed
6676 temporarily in unusual situations to work around bugs
6677 in other packages, or in unusual cases where the
6678 normally declared dependency information in the
6679 installed <file>shlibs</file> file for a library
6680 cannot be used. This file overrides information
6681 obtained from any other source.
6686 <p><file>/etc/dpkg/shlibs.override</file></p>
6689 This lists global overrides. This list is normally
6690 empty. It is maintained by the local system
6696 <p><file>DEBIAN/shlibs</file> files in the "build
6700 These files are generated as part of the package build
6701 process and staged for inclusion as control files in
6702 the binary packages being built. They provide details
6703 of any shared libraries included in the same package.
6708 <p><file>shlibs</file> control files for packages
6709 installed on the system</p>
6712 The <file>shlibs</file> control files for all the
6713 packages currently installed on the system. These are
6715 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6716 packages should not rely on this and instead should
6717 use <tt>dpkg-query --control-path <var>package</var>
6718 shlibs</tt> if for some reason these files need to be
6724 <p><file>/etc/dpkg/shlibs.default</file></p>
6727 This file lists any shared libraries whose packages
6728 have failed to provide correct <file>shlibs</file>
6729 files. It was used when the <file>shlibs</file> setup
6730 was first introduced, but it is now normally empty.
6731 It is maintained by the <tt>dpkg</tt> maintainer.
6738 If a <file>symbols</file> file for a shared library package
6739 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6740 in preference to a <file>shlibs</file>, with the exception
6741 of <file>debian/shlibs.local</file>. The latter overrides
6742 any other <file>shlibs</file> or <file>symbols</file> files.
6747 <heading>The <file>shlibs</file> File Format</heading>
6750 Each <file>shlibs</file> file has the same format. Lines
6751 beginning with <tt>#</tt> are considered to be comments and
6752 are ignored. Each line is of the form:
6753 <example compact="compact">
6754 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6759 We will explain this by reference to the example of the
6760 <tt>zlib1g</tt> package, which (at the time of writing)
6762 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6766 <var>type</var> is an optional element that indicates the
6767 type of package for which the line is valid. The only type
6768 currently in use is <tt>udeb</tt>. The colon and space
6769 after the type are required.
6773 <var>library-name</var> is the name of the shared library,
6774 in this case <tt>libz</tt>. (This must match the name part
6775 of the soname, see below.)
6779 <var>soname-version</var> is the version part of the
6780 ELF <tt>SONAME</tt> attribute of the library, determined the
6781 same way that the <var>soversion</var> component of the
6782 recommended shared library package name is determined.
6783 See <ref id="sharedlibs-runtime"> for the details.
6787 <var>dependencies</var> has the same syntax as a dependency
6788 field in a binary package control file. It should give
6789 details of which packages are required to satisfy a binary
6790 built against the version of the library contained in the
6791 package. See <ref id="depsyntax"> for details on the
6792 syntax, and <ref id="sharedlibs-updates"> for details on how
6793 to maintain the dependency version constraint.
6797 In our example, if the last change to the <tt>zlib1g</tt>
6798 package that could change behavior for a client of that
6799 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6800 the <tt>shlibs</tt> entry for this library could say:
6801 <example compact="compact">
6802 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6804 This version restriction must be new enough that any binary
6805 built against the current version of the library will work
6806 with any version of the shared library that satisfies that
6811 As zlib1g also provides a udeb containing the shared
6812 library, there would also be a second line:
6813 <example compact="compact">
6814 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6820 <heading>Providing a <file>shlibs</file> file</heading>
6823 To provide a <file>shlibs</file> file for a shared library
6824 binary package, create a <file>shlibs</file> file following
6825 the format described above and place it in
6826 the <file>DEBIAN</file> directory for that package during
6827 the build. It will then be included as a control file for
6828 that package<footnote>
6829 This is what <prgn>dh_makeshlibs</prgn> in
6830 the <package>debhelper</package> suite does. If your
6831 package also has a udeb that provides a shared
6832 library, <prgn>dh_makeshlibs</prgn> can automatically
6833 generate the <tt>udeb:</tt> lines if you specify the name
6834 of the udeb with the <tt>--add-udeb</tt> option.
6839 Since <prgn>dpkg-shlibdeps</prgn> reads
6840 the <file>DEBIAN/shlibs</file> files in all of the binary
6841 packages being built from this source package, all of
6842 the <file>DEBIAN/shlibs</file> files should be installed
6843 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6852 <chapt id="opersys"><heading>The Operating System</heading>
6855 <heading>File system hierarchy</heading>
6859 <heading>File System Structure</heading>
6862 The location of all files and directories must comply with the
6863 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6864 exceptions noted below, and except where doing so would
6865 violate other terms of Debian Policy. The following
6866 exceptions to the FHS apply:
6871 The optional rules related to user specific
6872 configuration files for applications are stored in
6873 the user's home directory are relaxed. It is
6874 recommended that such files start with the
6875 '<tt>.</tt>' character (a "dot file"), and if an
6876 application needs to create more than one dot file
6877 then the preferred placement is in a subdirectory
6878 with a name starting with a '.' character, (a "dot
6879 directory"). In this case it is recommended the
6880 configuration files not start with the '.'
6886 The requirement for amd64 to use <file>/lib64</file>
6887 for 64 bit binaries is removed.
6892 The requirement for object files, internal binaries, and
6893 libraries, including <file>libc.so.*</file>, to be located
6894 directly under <file>/lib{,32}</file> and
6895 <file>/usr/lib{,32}</file> is amended, permitting files
6896 to instead be installed to
6897 <file>/lib/<var>triplet</var></file> and
6898 <file>/usr/lib/<var>triplet</var></file>, where
6899 <tt><var>triplet</var></tt> is the value returned by
6900 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6901 architecture of the package. Packages may <em>not</em>
6902 install files to any <var>triplet</var> path other
6903 than the one matching the architecture of that package;
6904 for instance, an <tt>Architecture: amd64</tt> package
6905 containing 32-bit x86 libraries may not install these
6906 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6908 This is necessary in order to reserve the directories for
6909 use in cross-installation of library packages from other
6910 architectures, as part of the planned deployment of
6915 Applications may also use a single subdirectory under
6916 <file>/usr/lib/<var>triplet</var></file>.
6919 The execution time linker/loader, ld*, must still be made
6920 available in the existing location under /lib or /lib64
6921 since this is part of the ELF ABI for the architecture.
6926 The requirement that
6927 <file>/usr/local/share/man</file> be "synonymous"
6928 with <file>/usr/local/man</file> is relaxed to a
6933 The requirement that windowmanagers with a single
6934 configuration file call it <file>system.*wmrc</file>
6935 is removed, as is the restriction that the window
6936 manager subdirectory be named identically to the
6937 window manager name itself.
6942 The requirement that boot manager configuration
6943 files live in <file>/etc</file>, or at least are
6944 symlinked there, is relaxed to a recommendation.
6949 The additional directory <file>/run</file> in the root
6950 file system is allowed. <file>/run</file>
6951 replaces <file>/var/run</file>, and the
6952 subdirectory <file>/run/lock</file>
6953 replaces <file>/var/lock</file>, with
6954 the <file>/var</file> directories replaced by symlinks
6955 for backwards compatibility. <file>/run</file>
6956 and <file>/run/lock</file> must follow all of the
6957 requirements in the FHS for <file>/var/run</file>
6958 and <file>/var/lock</file>, respectively, such as file
6959 naming conventions, file format requirements, or the
6960 requirement that files be cleared during the boot
6961 process. Files and directories residing
6962 in <file>/run</file> should be stored on a temporary
6968 The following directories in the root filesystem are
6969 additionally allowed: <file>/sys</file> and
6970 <file>/selinux</file>. <footnote>These directories
6971 are used as mount points to mount virtual filesystems
6972 to get access to kernel information.</footnote>
6977 On GNU/Hurd systems, the following additional
6978 directories are allowed in the root
6979 filesystem: <file>/hurd</file>
6980 and <file>/servers</file>.<footnote>
6981 These directories are used to store translators and as
6982 a set of standard names for mount points,
6991 The version of this document referred here can be
6992 found in the <tt>debian-policy</tt> package or on <url
6993 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6994 name="FHS (Debian copy)"> alongside this manual (or, if
6995 you have the <package>debian-policy</package> installed,
6997 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6998 (local copy)">). The
6999 latest version, which may be a more recent version, may
7001 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7002 Specific questions about following the standard may be
7003 asked on the <tt>debian-devel</tt> mailing list, or
7004 referred to the FHS mailing list (see the
7005 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7011 <heading>Site-specific programs</heading>
7014 As mandated by the FHS, packages must not place any
7015 files in <file>/usr/local</file>, either by putting them in
7016 the file system archive to be unpacked by <prgn>dpkg</prgn>
7017 or by manipulating them in their maintainer scripts.
7021 However, the package may create empty directories below
7022 <file>/usr/local</file> so that the system administrator knows
7023 where to place site-specific files. These are not
7024 directories <em>in</em> <file>/usr/local</file>, but are
7025 children of directories in <file>/usr/local</file>. These
7026 directories (<file>/usr/local/*/dir/</file>)
7027 should be removed on package removal if they are
7032 Note that this applies only to
7033 directories <em>below</em> <file>/usr/local</file>,
7034 not <em>in</em> <file>/usr/local</file>. Packages must
7035 not create sub-directories in the
7036 directory <file>/usr/local</file> itself, except those
7037 listed in FHS, section 4.5. However, you may create
7038 directories below them as you wish. You must not remove
7039 any of the directories listed in 4.5, even if you created
7044 Since <file>/usr/local</file> can be mounted read-only from a
7045 remote server, these directories must be created and
7046 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7047 maintainer scripts and not be included in the
7048 <file>.deb</file> archive. These scripts must not fail if
7049 either of these operations fail.
7053 For example, the <tt>emacsen-common</tt> package could
7054 contain something like
7055 <example compact="compact">
7056 if [ ! -e /usr/local/share/emacs ]; then
7057 if mkdir /usr/local/share/emacs 2>/dev/null; then
7058 if chown root:staff /usr/local/share/emacs; then
7059 chmod 2775 /usr/local/share/emacs || true
7064 in its <prgn>postinst</prgn> script, and
7065 <example compact="compact">
7066 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7067 rmdir /usr/local/share/emacs 2>/dev/null || true
7069 in the <prgn>prerm</prgn> script. (Note that this form is
7070 used to ensure that if the script is interrupted, the
7071 directory <file>/usr/local/share/emacs</file> will still be
7076 If you do create a directory in <file>/usr/local</file> for
7077 local additions to a package, you should ensure that
7078 settings in <file>/usr/local</file> take precedence over the
7079 equivalents in <file>/usr</file>.
7083 However, because <file>/usr/local</file> and its contents are
7084 for exclusive use of the local administrator, a package
7085 must not rely on the presence or absence of files or
7086 directories in <file>/usr/local</file> for normal operation.
7090 The <file>/usr/local</file> directory itself and all the
7091 subdirectories created by the package should (by default) have
7092 permissions 2775 (group-writable and set-group-id) and be
7093 owned by <tt>root:staff</tt>.
7098 <heading>The system-wide mail directory</heading>
7100 The system-wide mail directory
7101 is <file>/var/mail</file>. This directory is part of the
7102 base system and should not be owned by any particular mail
7103 agents. The use of the old
7104 location <file>/var/spool/mail</file> is deprecated, even
7105 though the spool may still be physically located there.
7109 <sect1 id="fhs-run">
7110 <heading><file>/run</file> and <file>/run/lock</file></heading>
7113 The directory <file>/run</file> is cleared at boot, normally
7114 by being a mount point for a temporary file system. Packages
7115 therefore must not assume that any files or directories
7116 under <file>/run</file> other than <file>/run/lock</file>
7117 exist unless the package has arranged to create those files or
7118 directories since the last reboot. Normally, this is done by
7119 the package via an init script. See <ref id="writing-init">
7120 for more information.
7124 Packages must not include files or directories
7125 under <file>/run</file>, or under the
7126 older <file>/var/run</file> and <file>/var/lock</file> paths.
7127 The latter paths will normally be symlinks or other
7128 redirections to <file>/run</file> for backwards compatibility.
7134 <heading>Users and groups</heading>
7137 <heading>Introduction</heading>
7139 The Debian system can be configured to use either plain or
7144 Some user ids (UIDs) and group ids (GIDs) are reserved
7145 globally for use by certain packages. Because some
7146 packages need to include files which are owned by these
7147 users or groups, or need the ids compiled into binaries,
7148 these ids must be used on any Debian system only for the
7149 purpose for which they are allocated. This is a serious
7150 restriction, and we should avoid getting in the way of
7151 local administration policies. In particular, many sites
7152 allocate users and/or local system groups starting at 100.
7156 Apart from this we should have dynamically allocated ids,
7157 which should by default be arranged in some sensible
7158 order, but the behavior should be configurable.
7162 Packages other than <tt>base-passwd</tt> must not modify
7163 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7164 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7169 <heading>UID and GID classes</heading>
7171 The UID and GID numbers are divided into classes as
7177 Globally allocated by the Debian project, the same
7178 on every Debian system. These ids will appear in
7179 the <file>passwd</file> and <file>group</file> files of all
7180 Debian systems, new ids in this range being added
7181 automatically as the <tt>base-passwd</tt> package is
7186 Packages which need a single statically allocated
7187 uid or gid should use one of these; their
7188 maintainers should ask the <tt>base-passwd</tt>
7196 Dynamically allocated system users and groups.
7197 Packages which need a user or group, but can have
7198 this user or group allocated dynamically and
7199 differently on each system, should use <tt>adduser
7200 --system</tt> to create the group and/or user.
7201 <prgn>adduser</prgn> will check for the existence of
7202 the user or group, and if necessary choose an unused
7203 id based on the ranges specified in
7204 <file>adduser.conf</file>.
7208 <tag>1000-59999:</tag>
7211 Dynamically allocated user accounts. By default
7212 <prgn>adduser</prgn> will choose UIDs and GIDs for
7213 user accounts in this range, though
7214 <file>adduser.conf</file> may be used to modify this
7219 <tag>60000-64999:</tag>
7222 Globally allocated by the Debian project, but only
7223 created on demand. The ids are allocated centrally
7224 and statically, but the actual accounts are only
7225 created on users' systems on demand.
7229 These ids are for packages which are obscure or
7230 which require many statically-allocated ids. These
7231 packages should check for and create the accounts in
7232 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7233 <prgn>adduser</prgn> if it has this facility) if
7234 necessary. Packages which are likely to require
7235 further allocations should have a "hole" left after
7236 them in the allocation, to give them room to
7241 <tag>65000-65533:</tag>
7249 User <tt>nobody</tt>. The corresponding gid refers
7250 to the group <tt>nogroup</tt>.
7257 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7258 not</em> be used, because it is the error return
7267 <sect id="sysvinit">
7268 <heading>System run levels and <file>init.d</file> scripts</heading>
7270 <sect1 id="/etc/init.d">
7271 <heading>Introduction</heading>
7274 The <file>/etc/init.d</file> directory contains the scripts
7275 executed by <prgn>init</prgn> at boot time and when the
7276 init state (or "runlevel") is changed (see <manref
7277 name="init" section="8">).
7281 There are at least two different, yet functionally
7282 equivalent, ways of handling these scripts. For the sake
7283 of simplicity, this document describes only the symbolic
7284 link method. However, it must not be assumed by maintainer
7285 scripts that this method is being used, and any automated
7286 manipulation of the various runlevel behaviors by
7287 maintainer scripts must be performed using
7288 <prgn>update-rc.d</prgn> as described below and not by
7289 manually installing or removing symlinks. For information
7290 on the implementation details of the other method,
7291 implemented in the <tt>file-rc</tt> package, please refer
7292 to the documentation of that package.
7296 These scripts are referenced by symbolic links in the
7297 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7298 runlevels, <prgn>init</prgn> looks in the directory
7299 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7300 execute, where <tt><var>n</var></tt> is the runlevel that
7301 is being changed to, or <tt>S</tt> for the boot-up
7306 The names of the links all have the form
7307 <file>S<var>mm</var><var>script</var></file> or
7308 <file>K<var>mm</var><var>script</var></file> where
7309 <var>mm</var> is a two-digit number and <var>script</var>
7310 is the name of the script (this should be the same as the
7311 name of the actual script in <file>/etc/init.d</file>).
7315 When <prgn>init</prgn> changes runlevel first the targets
7316 of the links whose names start with a <tt>K</tt> are
7317 executed, each with the single argument <tt>stop</tt>,
7318 followed by the scripts prefixed with an <tt>S</tt>, each
7319 with the single argument <tt>start</tt>. (The links are
7320 those in the <file>/etc/rc<var>n</var>.d</file> directory
7321 corresponding to the new runlevel.) The <tt>K</tt> links
7322 are responsible for killing services and the <tt>S</tt>
7323 link for starting services upon entering the runlevel.
7327 For example, if we are changing from runlevel 2 to
7328 runlevel 3, init will first execute all of the <tt>K</tt>
7329 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7330 all of the <tt>S</tt> prefixed scripts in that directory.
7331 The links starting with <tt>K</tt> will cause the
7332 referred-to file to be executed with an argument of
7333 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7338 The two-digit number <var>mm</var> is used to determine
7339 the order in which to run the scripts: low-numbered links
7340 have their scripts run first. For example, the
7341 <tt>K20</tt> scripts will be executed before the
7342 <tt>K30</tt> scripts. This is used when a certain service
7343 must be started before another. For example, the name
7344 server <prgn>bind</prgn> might need to be started before
7345 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7346 can set up its access lists. In this case, the script
7347 that starts <prgn>bind</prgn> would have a lower number
7348 than the script that starts <prgn>inn</prgn> so that it
7350 <example compact="compact">
7357 The two runlevels 0 (halt) and 6 (reboot) are slightly
7358 different. In these runlevels, the links with an
7359 <tt>S</tt> prefix are still called after those with a
7360 <tt>K</tt> prefix, but they too are called with the single
7361 argument <tt>stop</tt>.
7365 <sect1 id="writing-init">
7366 <heading>Writing the scripts</heading>
7369 Packages that include daemons for system services should
7370 place scripts in <file>/etc/init.d</file> to start or stop
7371 services at boot time or during a change of runlevel.
7372 These scripts should be named
7373 <file>/etc/init.d/<var>package</var></file>, and they should
7374 accept one argument, saying what to do:
7377 <tag><tt>start</tt></tag>
7378 <item>start the service,</item>
7380 <tag><tt>stop</tt></tag>
7381 <item>stop the service,</item>
7383 <tag><tt>restart</tt></tag>
7384 <item>stop and restart the service if it's already running,
7385 otherwise start the service</item>
7387 <tag><tt>reload</tt></tag>
7388 <item><p>cause the configuration of the service to be
7389 reloaded without actually stopping and restarting
7392 <tag><tt>force-reload</tt></tag>
7393 <item>cause the configuration to be reloaded if the
7394 service supports this, otherwise restart the
7398 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7399 <tt>force-reload</tt> options should be supported by all
7400 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7405 The <file>init.d</file> scripts must ensure that they will
7406 behave sensibly (i.e., returning success and not starting
7407 multiple copies of a service) if invoked with <tt>start</tt>
7408 when the service is already running, or with <tt>stop</tt>
7409 when it isn't, and that they don't kill unfortunately-named
7410 user processes. The best way to achieve this is usually to
7411 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7416 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7417 scripts. Writing correct <file>init.d</file> scripts requires
7418 accepting various error exit statuses when daemons are already
7419 running or already stopped without aborting
7420 the <file>init.d</file> script, and common <file>init.d</file>
7421 function libraries are not safe to call with <tt>set -e</tt>
7423 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7424 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7425 in effect and echoing status messages to the console fails,
7427 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7428 to not use <tt>set -e</tt> and instead check the result of
7429 each command separately.
7433 If a service reloads its configuration automatically (as
7434 in the case of <prgn>cron</prgn>, for example), the
7435 <tt>reload</tt> option of the <file>init.d</file> script
7436 should behave as if the configuration has been reloaded
7441 The <file>/etc/init.d</file> scripts must be treated as
7442 configuration files, either (if they are present in the
7443 package, that is, in the .deb file) by marking them as
7444 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7445 by managing them correctly in the maintainer scripts (see
7446 <ref id="config-files">). This is important since we want
7447 to give the local system administrator the chance to adapt
7448 the scripts to the local system, e.g., to disable a
7449 service without de-installing the package, or to specify
7450 some special command line options when starting a service,
7451 while making sure their changes aren't lost during the next
7456 These scripts should not fail obscurely when the
7457 configuration files remain but the package has been
7458 removed, as configuration files remain on the system after
7459 the package has been removed. Only when <prgn>dpkg</prgn>
7460 is executed with the <tt>--purge</tt> option will
7461 configuration files be removed. In particular, as the
7462 <file>/etc/init.d/<var>package</var></file> script itself is
7463 usually a <tt>conffile</tt>, it will remain on the system
7464 if the package is removed but not purged. Therefore, you
7465 should include a <tt>test</tt> statement at the top of the
7467 <example compact="compact">
7468 test -f <var>program-executed-later-in-script</var> || exit 0
7473 Often there are some variables in the <file>init.d</file>
7474 scripts whose values control the behavior of the scripts,
7475 and which a system administrator is likely to want to
7476 change. As the scripts themselves are frequently
7477 <tt>conffile</tt>s, modifying them requires that the
7478 administrator merge in their changes each time the package
7479 is upgraded and the <tt>conffile</tt> changes. To ease
7480 the burden on the system administrator, such configurable
7481 values should not be placed directly in the script.
7482 Instead, they should be placed in a file in
7483 <file>/etc/default</file>, which typically will have the same
7484 base name as the <file>init.d</file> script. This extra file
7485 should be sourced by the script when the script runs. It
7486 must contain only variable settings and comments in SUSv3
7487 <prgn>sh</prgn> format. It may either be a
7488 <tt>conffile</tt> or a configuration file maintained by
7489 the package maintainer scripts. See <ref id="config-files">
7494 To ensure that vital configurable values are always
7495 available, the <file>init.d</file> script should set default
7496 values for each of the shell variables it uses, either
7497 before sourcing the <file>/etc/default/</file> file or
7498 afterwards using something like the <tt>:
7499 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7500 script must behave sensibly and not fail if the
7501 <file>/etc/default</file> file is deleted.
7505 Files and directories under <file>/run</file>, including ones
7506 referred to via the compatibility paths <file>/var/run</file>
7507 and <file>/var/lock</file>, are normally stored on a temporary
7508 filesystem and are normally not persistent across a reboot.
7509 The <file>init.d</file> scripts must handle this correctly.
7510 This will typically mean creating any required subdirectories
7511 dynamically when the <file>init.d</file> script is run.
7512 See <ref id="fhs-run"> for more information.
7517 <heading>Interfacing with the initscript system</heading>
7520 Maintainers should use the abstraction layer provided by
7521 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7522 programs to deal with initscripts in their packages'
7523 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7524 and <prgn>postrm</prgn>.
7528 Directly managing the /etc/rc?.d links and directly
7529 invoking the <file>/etc/init.d/</file> initscripts should
7530 be done only by packages providing the initscript
7531 subsystem (such as <prgn>sysv-rc</prgn> and
7532 <prgn>file-rc</prgn>).
7536 <heading>Managing the links</heading>
7539 The program <prgn>update-rc.d</prgn> is provided for
7540 package maintainers to arrange for the proper creation and
7541 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7542 or their functional equivalent if another method is being
7543 used. This may be used by maintainers in their packages'
7544 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7548 You must not include any <file>/etc/rc<var>n</var>.d</file>
7549 symbolic links in the actual archive or manually create or
7550 remove the symbolic links in maintainer scripts; you must
7551 use the <prgn>update-rc.d</prgn> program instead. (The
7552 former will fail if an alternative method of maintaining
7553 runlevel information is being used.) You must not include
7554 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7555 in the archive either. (Only the <tt>sysvinit</tt>
7560 By default <prgn>update-rc.d</prgn> will start services in
7561 each of the multi-user state runlevels (2, 3, 4, and 5)
7562 and stop them in the halt runlevel (0), the single-user
7563 runlevel (1) and the reboot runlevel (6). The system
7564 administrator will have the opportunity to customize
7565 runlevels by simply adding, moving, or removing the
7566 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7567 symbolic links are being used, or by modifying
7568 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7573 To get the default behavior for your package, put in your
7574 <prgn>postinst</prgn> script
7575 <example compact="compact">
7576 update-rc.d <var>package</var> defaults
7578 and in your <prgn>postrm</prgn>
7579 <example compact="compact">
7580 if [ "$1" = purge ]; then
7581 update-rc.d <var>package</var> remove
7583 </example>. Note that if your package changes runlevels
7584 or priority, you may have to remove and recreate the links,
7585 since otherwise the old links may persist. Refer to the
7586 documentation of <prgn>update-rc.d</prgn>.
7590 This will use a default sequence number of 20. If it does
7591 not matter when or in which order the <file>init.d</file>
7592 script is run, use this default. If it does, then you
7593 should talk to the maintainer of the <prgn>sysvinit</prgn>
7594 package or post to <tt>debian-devel</tt>, and they will
7595 help you choose a number.
7599 For more information about using <tt>update-rc.d</tt>,
7600 please consult its man page <manref name="update-rc.d"
7606 <heading>Running initscripts</heading>
7608 The program <prgn>invoke-rc.d</prgn> is provided to make
7609 it easier for package maintainers to properly invoke an
7610 initscript, obeying runlevel and other locally-defined
7611 constraints that might limit a package's right to start,
7612 stop and otherwise manage services. This program may be
7613 used by maintainers in their packages' scripts.
7617 The package maintainer scripts must use
7618 <prgn>invoke-rc.d</prgn> to invoke the
7619 <file>/etc/init.d/*</file> initscripts, instead of
7620 calling them directly.
7624 By default, <prgn>invoke-rc.d</prgn> will pass any
7625 action requests (start, stop, reload, restart...) to the
7626 <file>/etc/init.d</file> script, filtering out requests
7627 to start or restart a service out of its intended
7632 Most packages will simply need to change:
7633 <example compact="compact">/etc/init.d/<package>
7634 <action></example> in their <prgn>postinst</prgn>
7635 and <prgn>prerm</prgn> scripts to:
7636 <example compact="compact">
7637 if which invoke-rc.d >/dev/null 2>&1; then
7638 invoke-rc.d <var>package</var> <action>
7640 /etc/init.d/<var>package</var> <action>
7646 A package should register its initscript services using
7647 <prgn>update-rc.d</prgn> before it tries to invoke them
7648 using <prgn>invoke-rc.d</prgn>. Invocation of
7649 unregistered services may fail.
7653 For more information about using
7654 <prgn>invoke-rc.d</prgn>, please consult its man page
7655 <manref name="invoke-rc.d" section="8">.
7661 <heading>Boot-time initialization</heading>
7664 There used to be another directory, <file>/etc/rc.boot</file>,
7665 which contained scripts which were run once per machine
7666 boot. This has been deprecated in favour of links from
7667 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7668 described in <ref id="/etc/init.d">. Packages must not
7669 place files in <file>/etc/rc.boot</file>.
7674 <heading>Example</heading>
7677 An example on which you can base your
7678 <file>/etc/init.d</file> scripts is found in
7679 <file>/etc/init.d/skeleton</file>.
7686 <heading>Console messages from <file>init.d</file> scripts</heading>
7689 This section describes the formats to be used for messages
7690 written to standard output by the <file>/etc/init.d</file>
7691 scripts. The intent is to improve the consistency of
7692 Debian's startup and shutdown look and feel. For this
7693 reason, please look very carefully at the details. We want
7694 the messages to have the same format in terms of wording,
7695 spaces, punctuation and case of letters.
7699 Here is a list of overall rules that should be used for
7700 messages generated by <file>/etc/init.d</file> scripts.
7706 The message should fit in one line (fewer than 80
7707 characters), start with a capital letter and end with
7708 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7712 If the script is performing some time consuming task in
7713 the background (not merely starting or stopping a
7714 program, for instance), an ellipsis (three dots:
7715 <tt>...</tt>) should be output to the screen, with no
7716 leading or tailing whitespace or line feeds.
7720 The messages should appear as if the computer is telling
7721 the user what it is doing (politely :-), but should not
7722 mention "it" directly. For example, instead of:
7723 <example compact="compact">
7724 I'm starting network daemons: nfsd mountd.
7726 the message should say
7727 <example compact="compact">
7728 Starting network daemons: nfsd mountd.
7735 <tt>init.d</tt> script should use the following standard
7736 message formats for the situations enumerated below.
7742 <p>When daemons are started</p>
7745 If the script starts one or more daemons, the output
7746 should look like this (a single line, no leading
7748 <example compact="compact">
7749 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7751 The <var>description</var> should describe the
7752 subsystem the daemon or set of daemons are part of,
7753 while <var>daemon-1</var> up to <var>daemon-n</var>
7754 denote each daemon's name (typically the file name of
7759 For example, the output of <file>/etc/init.d/lpd</file>
7761 <example compact="compact">
7762 Starting printer spooler: lpd.
7767 This can be achieved by saying
7768 <example compact="compact">
7769 echo -n "Starting printer spooler: lpd"
7770 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7773 in the script. If there are more than one daemon to
7774 start, the output should look like this:
7775 <example compact="compact">
7776 echo -n "Starting remote file system services:"
7777 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7778 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7779 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7782 This makes it possible for the user to see what is
7783 happening and when the final daemon has been started.
7784 Care should be taken in the placement of white spaces:
7785 in the example above the system administrators can
7786 easily comment out a line if they don't want to start
7787 a specific daemon, while the displayed message still
7793 <p>When a system parameter is being set</p>
7796 If you have to set up different system parameters
7797 during the system boot, you should use this format:
7798 <example compact="compact">
7799 Setting <var>parameter</var> to "<var>value</var>".
7804 You can use a statement such as the following to get
7806 <example compact="compact">
7807 echo "Setting DNS domainname to \"$domainname\"."
7812 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7813 for the left and right quotation marks. A grave accent
7814 (<tt>`</tt>) is not a quote character; neither is an
7815 apostrophe (<tt>'</tt>).
7820 <p>When a daemon is stopped or restarted</p>
7823 When you stop or restart a daemon, you should issue a
7824 message identical to the startup message, except that
7825 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7826 or <tt>Restarting</tt> respectively.
7830 For example, stopping the printer daemon will look like
7832 <example compact="compact">
7833 Stopping printer spooler: lpd.
7839 <p>When something is executed</p>
7842 There are several examples where you have to run a
7843 program at system startup or shutdown to perform a
7844 specific task, for example, setting the system's clock
7845 using <prgn>netdate</prgn> or killing all processes
7846 when the system shuts down. Your message should look
7848 <example compact="compact">
7849 Doing something very useful...done.
7851 You should print the <tt>done.</tt> immediately after
7852 the job has been completed, so that the user is
7853 informed why they have to wait. You can get this
7855 <example compact="compact">
7856 echo -n "Doing something very useful..."
7865 <p>When the configuration is reloaded</p>
7868 When a daemon is forced to reload its configuration
7869 files you should use the following format:
7870 <example compact="compact">
7871 Reloading <var>description</var> configuration...done.
7873 where <var>description</var> is the same as in the
7874 daemon starting message.
7881 <sect id="cron-jobs">
7882 <heading>Cron jobs</heading>
7885 Packages must not modify the configuration file
7886 <file>/etc/crontab</file>, and they must not modify the files in
7887 <file>/var/spool/cron/crontabs</file>.
7891 If a package wants to install a job that has to be executed via
7892 cron, it should place a file named as specified
7893 in <ref id="cron-files"> into one or more of the following
7895 <example compact="compact">
7901 As these directory names imply, the files within them are
7902 executed on an hourly, daily, weekly, or monthly basis,
7903 respectively. The exact times are listed in
7904 <file>/etc/crontab</file>.
7908 All files installed in any of these directories must be
7909 scripts (e.g., shell scripts or Perl scripts) so that they
7910 can easily be modified by the local system administrator.
7911 In addition, they must be treated as configuration files.
7915 If a certain job has to be executed at some other frequency or
7916 at a specific time, the package should install a file in
7917 <file>/etc/cron.d</file> with a name as specified
7918 in <ref id="cron-files">. This file uses the same syntax
7919 as <file>/etc/crontab</file> and is processed
7920 by <prgn>cron</prgn> automatically. The file must also be
7921 treated as a configuration file. (Note that entries in the
7922 <file>/etc/cron.d</file> directory are not handled by
7923 <prgn>anacron</prgn>. Thus, you should only use this
7924 directory for jobs which may be skipped if the system is not
7929 Unlike <file>crontab</file> files described in the IEEE Std
7930 1003.1-2008 (POSIX.1) available from
7931 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7932 name="The Open Group">, the files in
7933 <file>/etc/cron.d</file> and the file
7934 <file>/etc/crontab</file> have seven fields; namely:
7936 <item>Minute [0,59]</item>
7937 <item>Hour [0,23]</item>
7938 <item>Day of the month [1,31]</item>
7939 <item>Month of the year [1,12]</item>
7940 <item>Day of the week ([0,6] with 0=Sunday)</item>
7941 <item>Username</item>
7942 <item>Command to be run</item>
7944 Ranges of numbers are allowed. Ranges are two numbers
7945 separated with a hyphen. The specified range is inclusive.
7946 Lists are allowed. A list is a set of numbers (or ranges)
7947 separated by commas. Step values can be used in conjunction
7952 The scripts or <tt>crontab</tt> entries in these directories should
7953 check if all necessary programs are installed before they
7954 try to execute them. Otherwise, problems will arise when a
7955 package was removed but not purged since configuration files
7956 are kept on the system in this situation.
7960 Any <tt>cron</tt> daemon must provide
7961 <file>/usr/bin/crontab</file> and support normal
7962 <tt>crontab</tt> entries as specified in POSIX. The daemon
7963 must also support names for days and months, ranges, and
7964 step values. It has to support <file>/etc/crontab</file>,
7965 and correctly execute the scripts in
7966 <file>/etc/cron.d</file>. The daemon must also correctly
7968 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7971 <sect1 id="cron-files">
7972 <heading>Cron job file names</heading>
7975 The file name of a cron job file should normally match the
7976 name of the package from which it comes.
7980 If a package supplies multiple cron job files files in the
7981 same directory, the file names should all start with the name
7982 of the package (possibly modified as described below) followed
7983 by a hyphen (<tt>-</tt>) and a suitable suffix.
7987 A cron job file name must not include any period or plus
7988 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7989 cause cron to ignore the file. Underscores (<tt>_</tt>)
7990 should be used instead of <tt>.</tt> and <tt>+</tt>
7997 <heading>Menus</heading>
8000 The Debian <tt>menu</tt> package provides a standard
8001 interface between packages providing applications and
8002 <em>menu programs</em> (either X window managers or
8003 text-based menu programs such as <prgn>pdmenu</prgn>).
8007 All packages that provide applications that need not be
8008 passed any special command line arguments for normal
8009 operation should register a menu entry for those
8010 applications, so that users of the <tt>menu</tt> package
8011 will automatically get menu entries in their window
8012 managers, as well in shells like <tt>pdmenu</tt>.
8016 Menu entries should follow the current menu policy.
8020 The menu policy can be found in the <tt>menu-policy</tt>
8021 files in the <tt>debian-policy</tt> package.
8022 It is also available from the Debian web mirrors at
8023 <tt><url name="/doc/packaging-manuals/menu-policy/"
8024 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8028 Please also refer to the <em>Debian Menu System</em>
8029 documentation that comes with the <package>menu</package>
8030 package for information about how to register your
8036 <heading>Multimedia handlers</heading>
8039 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8040 is a mechanism for encoding files and data streams and
8041 providing meta-information about them, in particular their
8042 type (e.g. audio or video) and format (e.g. PNG, HTML,
8047 Registration of MIME type handlers allows programs like mail
8048 user agents and web browsers to invoke these handlers to
8049 view, edit or display MIME types they don't support directly.
8053 Packages which provide the ability to view/show/play,
8054 compose, edit or print MIME types should register themselves
8055 as such following the current MIME support policy.
8059 The <package>mime-support</package> package provides the
8060 <prgn>update-mime</prgn> program which allows packages to
8061 register programs that can show, compose, edit or print
8066 Packages containing such programs must register them
8067 with <prgn>update-mime</prgn> as documented in <manref
8068 name="update-mime" section="8">. They should <em>not</em> depend
8069 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
8070 they should just put something like the following in the
8071 <tt>postinst</tt> and <tt>postrm</tt> scripts:
8074 if [ -x /usr/sbin/update-mime ]; then
8083 <heading>Keyboard configuration</heading>
8086 To achieve a consistent keyboard configuration so that all
8087 applications interpret a keyboard event the same way, all
8088 programs in the Debian distribution must be configured to
8089 comply with the following guidelines.
8093 The following keys must have the specified interpretations:
8096 <tag><tt><--</tt></tag>
8097 <item>delete the character to the left of the cursor</item>
8099 <tag><tt>Delete</tt></tag>
8100 <item>delete the character to the right of the cursor</item>
8102 <tag><tt>Control+H</tt></tag>
8103 <item>emacs: the help prefix</item>
8106 The interpretation of any keyboard events should be
8107 independent of the terminal that is used, be it a virtual
8108 console, an X terminal emulator, an rlogin/telnet session,
8113 The following list explains how the different programs
8114 should be set up to achieve this:
8120 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8124 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8128 X translations are set up to make
8129 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8130 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8131 is the vt220 escape code for the "delete character"
8132 key). This must be done by loading the X resources
8133 using <prgn>xrdb</prgn> on all local X displays, not
8134 using the application defaults, so that the
8135 translation resources used correspond to the
8136 <prgn>xmodmap</prgn> settings.
8140 The Linux console is configured to make
8141 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8142 generate <tt>ESC [ 3 ~</tt>.
8146 X applications are configured so that <tt><</tt>
8147 deletes left, and <tt>Delete</tt> deletes right. Motif
8148 applications already work like this.
8152 Terminals should have <tt>stty erase ^?</tt> .
8156 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8157 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8158 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8162 Emacs is programmed to map <tt>KB_Backspace</tt> or
8163 the <tt>stty erase</tt> character to
8164 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8165 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8166 <tt>^H</tt> to <tt>help</tt> as always.
8170 Other applications use the <tt>stty erase</tt>
8171 character and <tt>kdch1</tt> for the two delete keys,
8172 with ASCII DEL being "delete previous character" and
8173 <tt>kdch1</tt> being "delete character under
8181 This will solve the problem except for the following
8188 Some terminals have a <tt><--</tt> key that cannot
8189 be made to produce anything except <tt>^H</tt>. On
8190 these terminals Emacs help will be unavailable on
8191 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8192 character takes precedence in Emacs, and has been set
8193 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8194 available) can be used instead.
8198 Some operating systems use <tt>^H</tt> for <tt>stty
8199 erase</tt>. However, modern telnet versions and all
8200 rlogin versions propagate <tt>stty</tt> settings, and
8201 almost all UNIX versions honour <tt>stty erase</tt>.
8202 Where the <tt>stty</tt> settings are not propagated
8203 correctly, things can be made to work by using
8204 <tt>stty</tt> manually.
8208 Some systems (including previous Debian versions) use
8209 <prgn>xmodmap</prgn> to arrange for both
8210 <tt><--</tt> and <tt>Delete</tt> to generate
8211 <tt>KB_Delete</tt>. We can change the behavior of
8212 their X clients using the same X resources that we use
8213 to do it for our own clients, or configure our clients
8214 using their resources when things are the other way
8215 around. On displays configured like this
8216 <tt>Delete</tt> will not work, but <tt><--</tt>
8221 Some operating systems have different <tt>kdch1</tt>
8222 settings in their <tt>terminfo</tt> database for
8223 <tt>xterm</tt> and others. On these systems the
8224 <tt>Delete</tt> key will not work correctly when you
8225 log in from a system conforming to our policy, but
8226 <tt><--</tt> will.
8233 <heading>Environment variables</heading>
8236 A program must not depend on environment variables to get
8237 reasonable defaults. (That's because these environment
8238 variables would have to be set in a system-wide
8239 configuration file like <file>/etc/profile</file>, which is not
8240 supported by all shells.)
8244 If a program usually depends on environment variables for its
8245 configuration, the program should be changed to fall back to
8246 a reasonable default configuration if these environment
8247 variables are not present. If this cannot be done easily
8248 (e.g., if the source code of a non-free program is not
8249 available), the program must be replaced by a small
8250 "wrapper" shell script which sets the environment variables
8251 if they are not already defined, and calls the original program.
8255 Here is an example of a wrapper script for this purpose:
8257 <example compact="compact">
8259 BAR=${BAR:-/var/lib/fubar}
8261 exec /usr/lib/foo/foo "$@"
8266 Furthermore, as <file>/etc/profile</file> is a configuration
8267 file of the <prgn>base-files</prgn> package, other packages must
8268 not put any environment variables or other commands into that
8273 <sect id="doc-base">
8274 <heading>Registering Documents using doc-base</heading>
8277 The <package>doc-base</package> package implements a
8278 flexible mechanism for handling and presenting
8279 documentation. The recommended practice is for every Debian
8280 package that provides online documentation (other than just
8281 manual pages) to register these documents with
8282 <package>doc-base</package> by installing a
8283 <package>doc-base</package> control file in
8284 <file>/usr/share/doc-base/</file>.
8287 Please refer to the documentation that comes with the
8288 <package>doc-base</package> package for information and
8297 <heading>Files</heading>
8299 <sect id="binaries">
8300 <heading>Binaries</heading>
8303 Two different packages must not install programs with
8304 different functionality but with the same filenames. (The
8305 case of two programs having the same functionality but
8306 different implementations is handled via "alternatives" or
8307 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8308 <ref id="conflicts"> respectively.) If this case happens,
8309 one of the programs must be renamed. The maintainers should
8310 report this to the <tt>debian-devel</tt> mailing list and
8311 try to find a consensus about which program will have to be
8312 renamed. If a consensus cannot be reached, <em>both</em>
8313 programs must be renamed.
8317 By default, when a package is being built, any binaries
8318 created should include debugging information, as well as
8319 being compiled with optimization. You should also turn on
8320 as many reasonable compilation warnings as possible; this
8321 makes life easier for porters, who can then look at build
8322 logs for possible problems. For the C programming language,
8323 this means the following compilation parameters should be
8325 <example compact="compact">
8327 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8329 INSTALL = install -s # (or use strip on the files in debian/tmp)
8334 Note that by default all installed binaries should be stripped,
8335 either by using the <tt>-s</tt> flag to
8336 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8337 the binaries after they have been copied into
8338 <file>debian/tmp</file> but before the tree is made into a
8343 Although binaries in the build tree should be compiled with
8344 debugging information by default, it can often be difficult to
8345 debug programs if they are also subjected to compiler
8346 optimization. For this reason, it is recommended to support the
8347 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8348 (see <ref id="debianrules-options">). This variable can contain
8349 several flags to change how a package is compiled and built.
8353 It is up to the package maintainer to decide what
8354 compilation options are best for the package. Certain
8355 binaries (such as computationally-intensive programs) will
8356 function better with certain flags (<tt>-O3</tt>, for
8357 example); feel free to use them. Please use good judgment
8358 here. Don't use flags for the sake of it; only use them
8359 if there is good reason to do so. Feel free to override
8360 the upstream author's ideas about which compilation
8361 options are best: they are often inappropriate for our
8367 <sect id="libraries">
8368 <heading>Libraries</heading>
8371 If the package is <strong>architecture: any</strong>, then
8372 the shared library compilation and linking flags must have
8373 <tt>-fPIC</tt>, or the package shall not build on some of
8374 the supported architectures<footnote>
8376 If you are using GCC, <tt>-fPIC</tt> produces code with
8377 relocatable position independent code, which is required for
8378 most architectures to create a shared library, with i386 and
8379 perhaps some others where non position independent code is
8380 permitted in a shared library.
8383 Position independent code may have a performance penalty,
8384 especially on <tt>i386</tt>. However, in most cases the
8385 speed penalty must be measured against the memory wasted on
8386 the few architectures where non position independent code is
8389 </footnote>. Any exception to this rule must be discussed on
8390 the mailing list <em>debian-devel@lists.debian.org</em>, and
8391 a rough consensus obtained. The reasons for not compiling
8392 with <tt>-fPIC</tt> flag must be recorded in the file
8393 <tt>README.Debian</tt>, and care must be taken to either
8394 restrict the architecture or arrange for <tt>-fPIC</tt> to
8395 be used on architectures where it is required.<footnote>
8397 Some of the reasons why this might be required is if the
8398 library contains hand crafted assembly code that is not
8399 relocatable, the speed penalty is excessive for compute
8400 intensive libs, and similar reasons.
8405 As to the static libraries, the common case is not to have
8406 relocatable code, since there is no benefit, unless in specific
8407 cases; therefore the static version must not be compiled
8408 with the <tt>-fPIC</tt> flag. Any exception to this rule
8409 should be discussed on the mailing list
8410 <em>debian-devel@lists.debian.org</em>, and the reasons for
8411 compiling with the <tt>-fPIC</tt> flag must be recorded in
8412 the file <tt>README.Debian</tt>. <footnote>
8414 Some of the reasons for linking static libraries with
8415 the <tt>-fPIC</tt> flag are if, for example, one needs a
8416 Perl API for a library that is under rapid development,
8417 and has an unstable API, so shared libraries are
8418 pointless at this phase of the library's development. In
8419 that case, since Perl needs a library with relocatable
8420 code, it may make sense to create a static library with
8421 relocatable code. Another reason cited is if you are
8422 distilling various libraries into a common shared
8423 library, like <tt>mklibs</tt> does in the Debian
8429 In other words, if both a shared and a static library is
8430 being built, each source unit (<tt>*.c</tt>, for example,
8431 for C files) will need to be compiled twice, for the normal
8436 Libraries should be built with threading support and to be
8437 thread-safe if the library supports this.
8441 Although not enforced by the build tools, shared libraries
8442 must be linked against all libraries that they use symbols from
8443 in the same way that binaries are. This ensures the correct
8444 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8445 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8446 systems and guarantees that all libraries can be safely opened
8447 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8448 option <tt>-Wl,-z,defs</tt> when building a shared library.
8449 Since this option enforces symbol resolution at build time,
8450 a missing library reference will be caught early as a fatal
8455 All installed shared libraries should be stripped with
8456 <example compact="compact">
8457 strip --strip-unneeded <var>your-lib</var>
8459 (The option <tt>--strip-unneeded</tt> makes
8460 <prgn>strip</prgn> remove only the symbols which aren't
8461 needed for relocation processing.) Shared libraries can
8462 function perfectly well when stripped, since the symbols for
8463 dynamic linking are in a separate part of the ELF object
8465 You might also want to use the options
8466 <tt>--remove-section=.comment</tt> and
8467 <tt>--remove-section=.note</tt> on both shared libraries
8468 and executables, and <tt>--strip-debug</tt> on static
8474 Note that under some circumstances it may be useful to
8475 install a shared library unstripped, for example when
8476 building a separate package to support debugging.
8480 Shared object files (often <file>.so</file> files) that are not
8481 public libraries, that is, they are not meant to be linked
8482 to by third party executables (binaries of other packages),
8483 should be installed in subdirectories of the
8484 <file>/usr/lib</file> directory. Such files are exempt from the
8485 rules that govern ordinary shared libraries, except that
8486 they must not be installed executable and should be
8488 A common example are the so-called "plug-ins",
8489 internal shared objects that are dynamically loaded by
8490 programs using <manref name="dlopen" section="3">.
8495 Packages that use <prgn>libtool</prgn> to create and install
8496 their shared libraries install a file containing additional
8497 metadata (ending in <file>.la</file>) alongside the library.
8498 For public libraries intended for use by other packages, these
8499 files normally should not be included in the Debian package,
8500 since the information they include is not necessary to link with
8501 the shared library on Debian and can add unnecessary additional
8502 dependencies to other programs or libraries.<footnote>
8503 These files store, among other things, all libraries on which
8504 that shared library depends. Unfortunately, if
8505 the <file>.la</file> file is present and contains that
8506 dependency information, using <prgn>libtool</prgn> when
8507 linking against that library will cause the resulting program
8508 or library to be linked against those dependencies as well,
8509 even if this is unnecessary. This can create unneeded
8510 dependencies on shared library packages that would otherwise
8511 be hidden behind the library ABI, and can make library
8512 transitions to new SONAMEs unnecessarily complicated and
8513 difficult to manage.
8515 If the <file>.la</file> file is required for that library (if,
8516 for instance, it's loaded via <tt>libltdl</tt> in a way that
8517 requires that meta-information), the <tt>dependency_libs</tt>
8518 setting in the <file>.la</file> file should normally be set to
8519 the empty string. If the shared library development package has
8520 historically included the <file>.la</file>, it must be retained
8521 in the development package (with <tt>dependency_libs</tt>
8522 emptied) until all libraries that depend on it have removed or
8523 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8524 files to prevent linking with those other libraries
8525 using <prgn>libtool</prgn> from failing.
8529 If the <file>.la</file> must be included, it should be included
8530 in the development (<tt>-dev</tt>) package, unless the library
8531 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8532 library. If it is intended for use with <tt>libltdl</tt>,
8533 the <file>.la</file> files must go in the run-time library
8538 These requirements for handling of <file>.la</file> files do not
8539 apply to loadable modules or libraries not installed in
8540 directories searched by default by the dynamic linker. Packages
8541 installing loadable modules will frequently need to install
8542 the <file>.la</file> files alongside the modules so that they
8543 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8544 does not need to be modified for libraries or modules that are
8545 not installed in directories searched by the dynamic linker by
8546 default and not intended for use by other packages.
8550 You must make sure that you use only released versions of
8551 shared libraries to build your packages; otherwise other
8552 users will not be able to run your binaries
8553 properly. Producing source packages that depend on
8554 unreleased compilers is also usually a bad
8561 <heading>Shared libraries</heading>
8563 This section has moved to <ref id="sharedlibs">.
8569 <heading>Scripts</heading>
8572 All command scripts, including the package maintainer
8573 scripts inside the package and used by <prgn>dpkg</prgn>,
8574 should have a <tt>#!</tt> line naming the shell to be used
8579 In the case of Perl scripts this should be
8580 <tt>#!/usr/bin/perl</tt>.
8584 When scripts are installed into a directory in the system
8585 PATH, the script name should not include an extension such
8586 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8587 language currently used to implement it.
8590 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8591 <file>init.d</file> scripts should almost certainly start
8592 with <tt>set -e</tt> so that errors are detected.
8593 <file>init.d</file> scripts are something of a special case, due
8594 to how frequently they need to call commands that are allowed to
8595 fail, and it may instead be easier to check the exit status of
8596 commands directly. See <ref id="writing-init"> for more
8597 information about writing <file>init.d</file> scripts.
8600 Every script should use <tt>set -e</tt> or check the exit status
8601 of <em>every</em> command.
8604 Scripts may assume that <file>/bin/sh</file> implements the
8605 SUSv3 Shell Command Language<footnote>
8606 Single UNIX Specification, version 3, which is also IEEE
8607 1003.1-2004 (POSIX), and is available on the World Wide Web
8608 from <url id="http://www.unix.org/version3/online.html"
8609 name="The Open Group"> after free
8610 registration.</footnote>
8611 plus the following additional features not mandated by
8613 These features are in widespread use in the Linux community
8614 and are implemented in all of bash, dash, and ksh, the most
8615 common shells users may wish to use as <file>/bin/sh</file>.
8618 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8619 must not generate a newline.</item>
8620 <item><tt>test</tt>, if implemented as a shell built-in, must
8621 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8623 <item><tt>local</tt> to create a scoped variable must be
8624 supported, including listing multiple variables in a single
8625 local command and assigning a value to a variable at the
8626 same time as localizing it. <tt>local</tt> may or
8627 may not preserve the variable value from an outer scope if
8628 no assignment is present. Uses such as:
8632 # ... use a, b, c, d ...
8635 must be supported and must set the value of <tt>c</tt> to
8638 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8639 -<var>signal</var></tt>, where <var>signal</var> is either
8640 the name of a signal or one of the numeric signals listed in
8641 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8642 supported if <prgn>kill</prgn> is implemented as a shell
8645 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8646 signals must be supported. In addition to the signal
8647 numbers listed in the extension, which are the same as for
8648 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8651 If a shell script requires non-SUSv3 features from the shell
8652 interpreter other than those listed above, the appropriate shell
8653 must be specified in the first line of the script (e.g.,
8654 <tt>#!/bin/bash</tt>) and the package must depend on the package
8655 providing the shell (unless the shell package is marked
8656 "Essential", as in the case of <prgn>bash</prgn>).
8660 You may wish to restrict your script to SUSv3 features plus the
8661 above set when possible so that it may use <file>/bin/sh</file>
8662 as its interpreter. Checking your script
8663 with <prgn>checkbashisms</prgn> from
8664 the <package>devscripts</package> package or running your script
8665 with an alternate shell such as <prgn>posh</prgn> may help
8666 uncover violations of the above requirements. If in doubt
8667 whether a script complies with these requirements,
8668 use <file>/bin/bash</file>.
8672 Perl scripts should check for errors when making any
8673 system calls, including <tt>open</tt>, <tt>print</tt>,
8674 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8678 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8679 scripting languages. See <em>Csh Programming Considered
8680 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8681 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8682 If an upstream package comes with <prgn>csh</prgn> scripts
8683 then you must make sure that they start with
8684 <tt>#!/bin/csh</tt> and make your package depend on the
8685 <prgn>c-shell</prgn> virtual package.
8689 Any scripts which create files in world-writeable
8690 directories (e.g., in <file>/tmp</file>) must use a
8691 mechanism which will fail atomically if a file with the same
8692 name already exists.
8696 The Debian base system provides the <prgn>tempfile</prgn>
8697 and <prgn>mktemp</prgn> utilities for use by scripts for
8704 <heading>Symbolic links</heading>
8707 In general, symbolic links within a top-level directory should
8708 be relative, and symbolic links pointing from one top-level
8709 directory to or into another should be absolute. (A top-level
8710 directory is a sub-directory of the root
8711 directory <file>/</file>.) For example, a symbolic link
8712 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8713 should be relative (<file>../share/bar</file>), but a symbolic
8714 link from <file>/var/run</file> to <file>/run</file> should be
8716 This is necessary to allow top-level directories to be
8717 symlinks. If linking <file>/var/run</file>
8718 to <file>/run</file> were done with the relative symbolic
8719 link <file>../run</file>, but <file>/var</file> were a
8720 symbolic link to <file>/srv/disk1</file>, the symbolic link
8721 would point to <file>/srv/run</file> rather than the intended
8727 In addition, symbolic links should be specified as short as
8728 possible, i.e., link targets like <file>foo/../bar</file> are
8733 Note that when creating a relative link using
8734 <prgn>ln</prgn> it is not necessary for the target of the
8735 link to exist relative to the working directory you're
8736 running <prgn>ln</prgn> from, nor is it necessary to change
8737 directory to the directory where the link is to be made.
8738 Simply include the string that should appear as the target
8739 of the link (this will be a pathname relative to the
8740 directory in which the link resides) as the first argument
8745 For example, in your <prgn>Makefile</prgn> or
8746 <file>debian/rules</file>, you can do things like:
8747 <example compact="compact">
8748 ln -fs gcc $(prefix)/bin/cc
8749 ln -fs gcc debian/tmp/usr/bin/cc
8750 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8751 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8756 A symbolic link pointing to a compressed file should always
8757 have the same file extension as the referenced file. (For
8758 example, if a file <file>foo.gz</file> is referenced by a
8759 symbolic link, the filename of the link has to end with
8760 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8765 <heading>Device files</heading>
8768 Packages must not include device files or named pipes in the
8773 If a package needs any special device files that are not
8774 included in the base system, it must call
8775 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8776 after notifying the user<footnote>
8777 This notification could be done via a (low-priority)
8778 debconf message, or an echo (printf) statement.
8783 Packages must not remove any device files in the
8784 <prgn>postrm</prgn> or any other script. This is left to the
8785 system administrator.
8789 Debian uses the serial devices
8790 <file>/dev/ttyS*</file>. Programs using the old
8791 <file>/dev/cu*</file> devices should be changed to use
8792 <file>/dev/ttyS*</file>.
8796 Named pipes needed by the package must be created in
8797 the <prgn>postinst</prgn> script<footnote>
8798 It's better to use <prgn>mkfifo</prgn> rather
8799 than <prgn>mknod</prgn> to create named pipes so that
8800 automated checks for packages incorrectly creating device
8801 files with <prgn>mknod</prgn> won't have false positives.
8802 </footnote> and removed in
8803 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8808 <sect id="config-files">
8809 <heading>Configuration files</heading>
8812 <heading>Definitions</heading>
8816 <tag>configuration file</tag>
8818 A file that affects the operation of a program, or
8819 provides site- or host-specific information, or
8820 otherwise customizes the behavior of a program.
8821 Typically, configuration files are intended to be
8822 modified by the system administrator (if needed or
8823 desired) to conform to local policy or to provide
8824 more useful site-specific behavior.
8827 <tag><tt>conffile</tt></tag>
8829 A file listed in a package's <tt>conffiles</tt>
8830 file, and is treated specially by <prgn>dpkg</prgn>
8831 (see <ref id="configdetails">).
8837 The distinction between these two is important; they are
8838 not interchangeable concepts. Almost all
8839 <tt>conffile</tt>s are configuration files, but many
8840 configuration files are not <tt>conffiles</tt>.
8844 As noted elsewhere, <file>/etc/init.d</file> scripts,
8845 <file>/etc/default</file> files, scripts installed in
8846 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8847 configuration installed in <file>/etc/cron.d</file> must be
8848 treated as configuration files. In general, any script that
8849 embeds configuration information is de-facto a configuration
8850 file and should be treated as such.
8855 <heading>Location</heading>
8858 Any configuration files created or used by your package
8859 must reside in <file>/etc</file>. If there are several,
8860 consider creating a subdirectory of <file>/etc</file>
8861 named after your package.
8865 If your package creates or uses configuration files
8866 outside of <file>/etc</file>, and it is not feasible to modify
8867 the package to use <file>/etc</file> directly, put the files
8868 in <file>/etc</file> and create symbolic links to those files
8869 from the location that the package requires.
8874 <heading>Behavior</heading>
8877 Configuration file handling must conform to the following
8879 <list compact="compact">
8881 local changes must be preserved during a package
8885 configuration files must be preserved when the
8886 package is removed, and only deleted when the
8890 Obsolete configuration files without local changes may be
8891 removed by the package during upgrade.
8895 The easy way to achieve this behavior is to make the
8896 configuration file a <tt>conffile</tt>. This is
8897 appropriate only if it is possible to distribute a default
8898 version that will work for most installations, although
8899 some system administrators may choose to modify it. This
8900 implies that the default version will be part of the
8901 package distribution, and must not be modified by the
8902 maintainer scripts during installation (or at any other
8907 In order to ensure that local changes are preserved
8908 correctly, no package may contain or make hard links to
8909 conffiles.<footnote>
8910 Rationale: There are two problems with hard links.
8911 The first is that some editors break the link while
8912 editing one of the files, so that the two files may
8913 unwittingly become unlinked and different. The second
8914 is that <prgn>dpkg</prgn> might break the hard link
8915 while upgrading <tt>conffile</tt>s.
8920 The other way to do it is via the maintainer scripts. In
8921 this case, the configuration file must not be listed as a
8922 <tt>conffile</tt> and must not be part of the package
8923 distribution. If the existence of a file is required for
8924 the package to be sensibly configured it is the
8925 responsibility of the package maintainer to provide
8926 maintainer scripts which correctly create, update and
8927 maintain the file and remove it on purge. (See <ref
8928 id="maintainerscripts"> for more information.) These
8929 scripts must be idempotent (i.e., must work correctly if
8930 <prgn>dpkg</prgn> needs to re-run them due to errors
8931 during installation or removal), must cope with all the
8932 variety of ways <prgn>dpkg</prgn> can call maintainer
8933 scripts, must not overwrite or otherwise mangle the user's
8934 configuration without asking, must not ask unnecessary
8935 questions (particularly during upgrades), and must
8936 otherwise be good citizens.
8940 The scripts are not required to configure every possible
8941 option for the package, but only those necessary to get
8942 the package running on a given system. Ideally the
8943 sysadmin should not have to do any configuration other
8944 than that done (semi-)automatically by the
8945 <prgn>postinst</prgn> script.
8949 A common practice is to create a script called
8950 <file><var>package</var>-configure</file> and have the
8951 package's <prgn>postinst</prgn> call it if and only if the
8952 configuration file does not already exist. In certain
8953 cases it is useful for there to be an example or template
8954 file which the maintainer scripts use. Such files should
8955 be in <file>/usr/share/<var>package</var></file> or
8956 <file>/usr/lib/<var>package</var></file> (depending on whether
8957 they are architecture-independent or not). There should
8958 be symbolic links to them from
8959 <file>/usr/share/doc/<var>package</var>/examples</file> if
8960 they are examples, and should be perfectly ordinary
8961 <prgn>dpkg</prgn>-handled files (<em>not</em>
8962 configuration files).
8966 These two styles of configuration file handling must
8967 not be mixed, for that way lies madness:
8968 <prgn>dpkg</prgn> will ask about overwriting the file
8969 every time the package is upgraded.
8974 <heading>Sharing configuration files</heading>
8977 If two or more packages use the same configuration file
8978 and it is reasonable for both to be installed at the same
8979 time, one of these packages must be defined as
8980 <em>owner</em> of the configuration file, i.e., it will be
8981 the package which handles that file as a configuration
8982 file. Other packages that use the configuration file must
8983 depend on the owning package if they require the
8984 configuration file to operate. If the other package will
8985 use the configuration file if present, but is capable of
8986 operating without it, no dependency need be declared.
8990 If it is desirable for two or more related packages to
8991 share a configuration file <em>and</em> for all of the
8992 related packages to be able to modify that configuration
8993 file, then the following should be done:
8994 <enumlist compact="compact">
8996 One of the related packages (the "owning" package)
8997 will manage the configuration file with maintainer
8998 scripts as described in the previous section.
9001 The owning package should also provide a program
9002 that the other packages may use to modify the
9006 The related packages must use the provided program
9007 to make any desired modifications to the
9008 configuration file. They should either depend on
9009 the core package to guarantee that the configuration
9010 modifier program is available or accept gracefully
9011 that they cannot modify the configuration file if it
9012 is not. (This is in addition to the fact that the
9013 configuration file may not even be present in the
9020 Sometimes it's appropriate to create a new package which
9021 provides the basic infrastructure for the other packages
9022 and which manages the shared configuration files. (The
9023 <tt>sgml-base</tt> package is a good example.)
9027 If the configuration file cannot be shared as described above,
9028 the packages must be marked as conflicting with each other.
9029 Two packages that specify the same file as
9030 a <tt>conffile</tt> must conflict. This is an instance of the
9031 general rule about not sharing files. Neither alternatives
9032 nor diversions are likely to be appropriate in this case; in
9033 particular, <prgn>dpkg</prgn> does not handle diverted
9034 <tt>conffile</tt>s well.
9038 When two packages both declare the same <tt>conffile</tt>, they
9039 may see left-over configuration files from each other even
9040 though they conflict with each other. If a user removes
9041 (without purging) one of the packages and installs the other,
9042 the new package will take over the <tt>conffile</tt> from the
9043 old package. If the file was modified by the user, it will be
9044 treated the same as any other locally
9045 modified <tt>conffile</tt> during an upgrade.
9049 The maintainer scripts must not alter a <tt>conffile</tt>
9050 of <em>any</em> package, including the one the scripts
9056 <heading>User configuration files ("dotfiles")</heading>
9059 The files in <file>/etc/skel</file> will automatically be
9060 copied into new user accounts by <prgn>adduser</prgn>.
9061 No other program should reference the files in
9062 <file>/etc/skel</file>.
9066 Therefore, if a program needs a dotfile to exist in
9067 advance in <file>$HOME</file> to work sensibly, that dotfile
9068 should be installed in <file>/etc/skel</file> and treated as a
9073 However, programs that require dotfiles in order to
9074 operate sensibly are a bad thing, unless they do create
9075 the dotfiles themselves automatically.
9079 Furthermore, programs should be configured by the Debian
9080 default installation to behave as closely to the upstream
9081 default behavior as possible.
9085 Therefore, if a program in a Debian package needs to be
9086 configured in some way in order to operate sensibly, that
9087 should be done using a site-wide configuration file placed
9088 in <file>/etc</file>. Only if the program doesn't support a
9089 site-wide default configuration and the package maintainer
9090 doesn't have time to add it may a default per-user file be
9091 placed in <file>/etc/skel</file>.
9095 <file>/etc/skel</file> should be as empty as we can make it.
9096 This is particularly true because there is no easy (or
9097 necessarily desirable) mechanism for ensuring that the
9098 appropriate dotfiles are copied into the accounts of
9099 existing users when a package is installed.
9105 <heading>Log files</heading>
9107 Log files should usually be named
9108 <file>/var/log/<var>package</var>.log</file>. If you have many
9109 log files, or need a separate directory for permission
9110 reasons (<file>/var/log</file> is writable only by
9111 <file>root</file>), you should usually create a directory named
9112 <file>/var/log/<var>package</var></file> and place your log
9117 Log files must be rotated occasionally so that they don't grow
9118 indefinitely. The best way to do this is to install a log
9119 rotation configuration file in the
9120 directory <file>/etc/logrotate.d</file>, normally
9121 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9122 the facilities provided by <prgn>logrotate</prgn>.
9125 The traditional approach to log files has been to set up
9126 <em>ad hoc</em> log rotation schemes using simple shell
9127 scripts and cron. While this approach is highly
9128 customizable, it requires quite a lot of sysadmin work.
9129 Even though the original Debian system helped a little
9130 by automatically installing a system which can be used
9131 as a template, this was deemed not enough.
9135 The use of <prgn>logrotate</prgn>, a program developed
9136 by Red Hat, is better, as it centralizes log management.
9137 It has both a configuration file
9138 (<file>/etc/logrotate.conf</file>) and a directory where
9139 packages can drop their individual log rotation
9140 configurations (<file>/etc/logrotate.d</file>).
9143 Here is a good example for a logrotate config
9144 file (for more information see <manref name="logrotate"
9146 <example compact="compact">
9147 /var/log/foo/*.log {
9153 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9157 This rotates all files under <file>/var/log/foo</file>, saves 12
9158 compressed generations, and tells the daemon to reopen its log
9159 files after the log rotation. It skips this log rotation
9160 (via <tt>missingok</tt>) if no such log file is present, which
9161 avoids errors if the package is removed but not purged.
9165 Log files should be removed when the package is
9166 purged (but not when it is only removed). This should be
9167 done by the <prgn>postrm</prgn> script when it is called
9168 with the argument <tt>purge</tt> (see <ref
9169 id="removedetails">).
9173 <sect id="permissions-owners">
9174 <heading>Permissions and owners</heading>
9177 The rules in this section are guidelines for general use.
9178 If necessary you may deviate from the details below.
9179 However, if you do so you must make sure that what is done
9180 is secure and you should try to be as consistent as possible
9181 with the rest of the system. You should probably also
9182 discuss it on <prgn>debian-devel</prgn> first.
9186 Files should be owned by <tt>root:root</tt>, and made
9187 writable only by the owner and universally readable (and
9188 executable, if appropriate), that is mode 644 or 755.
9192 Directories should be mode 755 or (for group-writability)
9193 mode 2775. The ownership of the directory should be
9194 consistent with its mode: if a directory is mode 2775, it
9195 should be owned by the group that needs write access to
9198 When a package is upgraded, and the owner or permissions
9199 of a file included in the package has changed, dpkg
9200 arranges for the ownership and permissions to be
9201 correctly set upon installation. However, this does not
9202 extend to directories; the permissions and ownership of
9203 directories already on the system does not change on
9204 install or upgrade of packages. This makes sense, since
9205 otherwise common directories like <tt>/usr</tt> would
9206 always be in flux. To correctly change permissions of a
9207 directory the package owns, explicit action is required,
9208 usually in the <tt>postinst</tt> script. Care must be
9209 taken to handle downgrades as well, in that case.
9215 Control information files should be owned by <tt>root:root</tt>
9216 and either mode 644 (for most files) or mode 755 (for
9217 executables such as <qref id="maintscripts">maintainer
9222 Setuid and setgid executables should be mode 4755 or 2755
9223 respectively, and owned by the appropriate user or group.
9224 They should not be made unreadable (modes like 4711 or
9225 2711 or even 4111); doing so achieves no extra security,
9226 because anyone can find the binary in the freely available
9227 Debian package; it is merely inconvenient. For the same
9228 reason you should not restrict read or execute permissions
9229 on non-set-id executables.
9233 Some setuid programs need to be restricted to particular
9234 sets of users, using file permissions. In this case they
9235 should be owned by the uid to which they are set-id, and by
9236 the group which should be allowed to execute them. They
9237 should have mode 4754; again there is no point in making
9238 them unreadable to those users who must not be allowed to
9243 It is possible to arrange that the system administrator can
9244 reconfigure the package to correspond to their local
9245 security policy by changing the permissions on a binary:
9246 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9247 described below.<footnote>
9248 Ordinary files installed by <prgn>dpkg</prgn> (as
9249 opposed to <tt>conffile</tt>s and other similar objects)
9250 normally have their permissions reset to the distributed
9251 permissions when the package is reinstalled. However,
9252 the use of <prgn>dpkg-statoverride</prgn> overrides this
9255 Another method you should consider is to create a group for
9256 people allowed to use the program(s) and make any setuid
9257 executables executable only by that group.
9261 If you need to create a new user or group for your package
9262 there are two possibilities. Firstly, you may need to
9263 make some files in the binary package be owned by this
9264 user or group, or you may need to compile the user or
9265 group id (rather than just the name) into the binary
9266 (though this latter should be avoided if possible, as in
9267 this case you need a statically allocated id).</p>
9270 If you need a statically allocated id, you must ask for a
9271 user or group id from the <tt>base-passwd</tt> maintainer,
9272 and must not release the package until you have been
9273 allocated one. Once you have been allocated one you must
9274 either make the package depend on a version of the
9275 <tt>base-passwd</tt> package with the id present in
9276 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9277 your package to create the user or group itself with the
9278 correct id (using <tt>adduser</tt>) in its
9279 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9280 the <prgn>postinst</prgn> is to be preferred if it is
9281 possible, otherwise a pre-dependency will be needed on the
9282 <tt>adduser</tt> package.)
9286 On the other hand, the program might be able to determine
9287 the uid or gid from the user or group name at runtime, so
9288 that a dynamically allocated id can be used. In this case
9289 you should choose an appropriate user or group name,
9290 discussing this on <prgn>debian-devel</prgn> and checking
9291 with the <package/base-passwd/ maintainer that it is unique and that
9292 they do not wish you to use a statically allocated id
9293 instead. When this has been checked you must arrange for
9294 your package to create the user or group if necessary using
9295 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9296 <prgn>postinst</prgn> script (again, the latter is to be
9297 preferred if it is possible).
9301 Note that changing the numeric value of an id associated
9302 with a name is very difficult, and involves searching the
9303 file system for all appropriate files. You need to think
9304 carefully whether a static or dynamic id is required, since
9305 changing your mind later will cause problems.
9308 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9310 This section is not intended as policy, but as a
9311 description of the use of <prgn>dpkg-statoverride</prgn>.
9315 If a system administrator wishes to have a file (or
9316 directory or other such thing) installed with owner and
9317 permissions different from those in the distributed Debian
9318 package, they can use the <prgn>dpkg-statoverride</prgn>
9319 program to instruct <prgn>dpkg</prgn> to use the different
9320 settings every time the file is installed. Thus the
9321 package maintainer should distribute the files with their
9322 normal permissions, and leave it for the system
9323 administrator to make any desired changes. For example, a
9324 daemon which is normally required to be setuid root, but
9325 in certain situations could be used without being setuid,
9326 should be installed setuid in the <tt>.deb</tt>. Then the
9327 local system administrator can change this if they wish.
9328 If there are two standard ways of doing it, the package
9329 maintainer can use <tt>debconf</tt> to find out the
9330 preference, and call <prgn>dpkg-statoverride</prgn> in the
9331 maintainer script if necessary to accommodate the system
9332 administrator's choice. Care must be taken during
9333 upgrades to not override an existing setting.
9337 Given the above, <prgn>dpkg-statoverride</prgn> is
9338 essentially a tool for system administrators and would not
9339 normally be needed in the maintainer scripts. There is
9340 one type of situation, though, where calls to
9341 <prgn>dpkg-statoverride</prgn> would be needed in the
9342 maintainer scripts, and that involves packages which use
9343 dynamically allocated user or group ids. In such a
9344 situation, something like the following idiom can be very
9345 helpful in the package's <prgn>postinst</prgn>, where
9346 <tt>sysuser</tt> is a dynamically allocated id:
9348 for i in /usr/bin/foo /usr/sbin/bar
9350 # only do something when no setting exists
9351 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9353 #include: debconf processing, question about foo and bar
9354 if [ "$RET" = "true" ] ; then
9355 dpkg-statoverride --update --add sysuser root 4755 $i
9360 The corresponding code to remove the override when the package
9363 for i in /usr/bin/foo /usr/sbin/bar
9365 if dpkg-statoverride --list $i >/dev/null 2>&1
9367 dpkg-statoverride --remove $i
9377 <chapt id="customized-programs">
9378 <heading>Customized programs</heading>
9380 <sect id="arch-spec">
9381 <heading>Architecture specification strings</heading>
9384 If a program needs to specify an <em>architecture specification
9385 string</em> in some place, it should select one of the strings
9386 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9387 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9388 part is sometimes elided, as when the OS is Linux.
9392 Note that we don't want to use
9393 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9394 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9395 since this would make our programs incompatible with other
9396 Linux distributions. We also don't use something like
9397 <tt><var>arch</var>-unknown-linux</tt>, since the
9398 <tt>unknown</tt> does not look very good.
9401 <sect1 id="arch-wildcard-spec">
9402 <heading>Architecture wildcards</heading>
9405 A package may specify an architecture wildcard. Architecture
9406 wildcards are in the format <tt>any</tt> (which matches every
9407 architecture), <tt><var>os</var></tt>-any, or
9408 any-<tt><var>cpu</var></tt>. <footnote>
9409 Internally, the package system normalizes the GNU triplets
9410 and the Debian arches into Debian arch triplets (which are
9411 kind of inverted GNU triplets), with the first component of
9412 the triplet representing the libc and ABI in use, and then
9413 does matching against those triplets. However, such
9414 triplets are an internal implementation detail that should
9415 not be used by packages directly. The libc and ABI portion
9416 is handled internally by the package system based on
9417 the <var>os</var> and <var>cpu</var>.
9424 <heading>Daemons</heading>
9427 The configuration files <file>/etc/services</file>,
9428 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9429 by the <prgn>netbase</prgn> package and must not be modified
9434 If a package requires a new entry in one of these files, the
9435 maintainer should get in contact with the
9436 <prgn>netbase</prgn> maintainer, who will add the entries
9437 and release a new version of the <prgn>netbase</prgn>
9442 The configuration file <file>/etc/inetd.conf</file> must not be
9443 modified by the package's scripts except via the
9444 <prgn>update-inetd</prgn> script or the
9445 <file>DebianNet.pm</file> Perl module. See their documentation
9446 for details on how to add entries.
9450 If a package wants to install an example entry into
9451 <file>/etc/inetd.conf</file>, the entry must be preceded with
9452 exactly one hash character (<tt>#</tt>). Such lines are
9453 treated as "commented out by user" by the
9454 <prgn>update-inetd</prgn> script and are not changed or
9455 activated during package updates.
9460 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9464 Some programs need to create pseudo-ttys. This should be done
9465 using Unix98 ptys if the C library supports it. The resulting
9466 program must not be installed setuid root, unless that
9467 is required for other functionality.
9471 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9472 <file>/var/log/lastlog</file> must be installed writable by
9473 group <tt>utmp</tt>. Programs which need to modify those
9474 files must be installed setgid <tt>utmp</tt>.
9479 <heading>Editors and pagers</heading>
9482 Some programs have the ability to launch an editor or pager
9483 program to edit or display a text document. Since there are
9484 lots of different editors and pagers available in the Debian
9485 distribution, the system administrator and each user should
9486 have the possibility to choose their preferred editor and
9491 In addition, every program should choose a good default
9492 editor/pager if none is selected by the user or system
9497 Thus, every program that launches an editor or pager must
9498 use the EDITOR or PAGER environment variable to determine
9499 the editor or pager the user wishes to use. If these
9500 variables are not set, the programs <file>/usr/bin/editor</file>
9501 and <file>/usr/bin/pager</file> should be used, respectively.
9505 These two files are managed through the <prgn>dpkg</prgn>
9506 "alternatives" mechanism. Every package providing an editor or
9507 pager must call the <prgn>update-alternatives</prgn> script to
9508 register as an alternative for <file>/usr/bin/editor</file>
9509 or <file>/usr/bin/pager</file> as appropriate. The alternative
9510 should have a slave alternative
9511 for <file>/usr/share/man/man1/editor.1.gz</file>
9512 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9513 corresponding manual page.
9517 If it is very hard to adapt a program to make use of the
9518 EDITOR or PAGER variables, that program may be configured to
9519 use <file>/usr/bin/sensible-editor</file> and
9520 <file>/usr/bin/sensible-pager</file> as the editor or pager
9521 program respectively. These are two scripts provided in the
9522 <package>sensible-utils</package> package that check the EDITOR
9523 and PAGER variables and launch the appropriate program, and fall
9524 back to <file>/usr/bin/editor</file>
9525 and <file>/usr/bin/pager</file> if the variable is not set.
9529 A program may also use the VISUAL environment variable to
9530 determine the user's choice of editor. If it exists, it
9531 should take precedence over EDITOR. This is in fact what
9532 <file>/usr/bin/sensible-editor</file> does.
9536 It is not required for a package to depend on
9537 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9538 package to provide such virtual packages.<footnote>
9539 The Debian base system already provides an editor and a
9545 <sect id="web-appl">
9546 <heading>Web servers and applications</heading>
9549 This section describes the locations and URLs that should
9550 be used by all web servers and web applications in the
9557 Cgi-bin executable files are installed in the
9559 <example compact="compact">
9560 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9562 or a subdirectory of that directory, and should be
9564 <example compact="compact">
9565 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9567 (possibly with a subdirectory name
9568 before <var>cgi-bin-name</var>).
9572 <p>Access to HTML documents</p>
9575 HTML documents for a package are stored in
9576 <file>/usr/share/doc/<var>package</var></file>
9577 and can be referred to as
9578 <example compact="compact">
9579 http://localhost/doc/<var>package</var>/<var>filename</var>
9584 The web server should restrict access to the document
9585 tree so that only clients on the same host can read
9586 the documents. If the web server does not support such
9587 access controls, then it should not provide access at
9588 all, or ask about providing access during installation.
9593 <p>Access to images</p>
9595 It is recommended that images for a package be stored
9596 in <tt>/usr/share/images/<var>package</var></tt> and
9597 may be referred to through an alias <tt>/images/</tt>
9600 http://localhost/images/<package>/<filename>
9607 <p>Web Document Root</p>
9610 Web Applications should try to avoid storing files in
9611 the Web Document Root. Instead they should use the
9612 /usr/share/doc/<var>package</var> directory for
9613 documents and register the Web Application via the
9614 <package>doc-base</package> package. If access to the
9615 web document root is unavoidable then use
9616 <example compact="compact">
9619 as the Document Root. This might be just a symbolic
9620 link to the location where the system administrator
9621 has put the real document root.
9624 <item><p>Providing httpd and/or httpd-cgi</p>
9626 All web servers should provide the virtual package
9627 <tt>httpd</tt>. If a web server has CGI support it should
9628 provide <tt>httpd-cgi</tt> additionally.
9631 All web applications which do not contain CGI scripts should
9632 depend on <tt>httpd</tt>, all those web applications which
9633 <tt>do</tt> contain CGI scripts, should depend on
9641 <sect id="mail-transport-agents">
9642 <heading>Mail transport, delivery and user agents</heading>
9645 Debian packages which process electronic mail, whether mail
9646 user agents (MUAs) or mail transport agents (MTAs), must
9647 ensure that they are compatible with the configuration
9648 decisions below. Failure to do this may result in lost
9649 mail, broken <tt>From:</tt> lines, and other serious brain
9654 The mail spool is <file>/var/mail</file> and the interface to
9655 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9656 the FHS). On older systems, the mail spool may be
9657 physically located in <file>/var/spool/mail</file>, but all
9658 access to the mail spool should be via the
9659 <file>/var/mail</file> symlink. The mail spool is part of the
9660 base system and not part of the MTA package.
9664 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9665 programs (such as IMAP daemons) must lock the mailbox in an
9666 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9667 be combined with dot locking. To avoid deadlocks, a program
9668 should use <tt>fcntl()</tt> first and dot locking after
9669 this, or alternatively implement the two locking methods in
9670 a non blocking way<footnote>
9671 If it is not possible to establish both locks, the
9672 system shouldn't wait for the second lock to be
9673 established, but remove the first lock, wait a (random)
9674 time, and start over locking again.
9675 </footnote>. Using the functions <tt>maillock</tt> and
9676 <tt>mailunlock</tt> provided by the
9677 <tt>liblockfile*</tt><footnote>
9678 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9679 to use these functions.
9680 </footnote> packages is the recommended way to realize this.
9684 Mailboxes are generally either mode 600 and owned by
9685 <var>user</var> or mode 660 and owned by
9686 <tt><var>user</var>:mail</tt><footnote>
9687 There are two traditional permission schemes for mail spools:
9688 mode 600 with all mail delivery done by processes running as
9689 the destination user, or mode 660 and owned by group mail with
9690 mail delivery done by a process running as a system user in
9691 group mail. Historically, Debian required mode 660 mail
9692 spools to enable the latter model, but that model has become
9693 increasingly uncommon and the principle of least privilege
9694 indicates that mail systems that use the first model should
9695 use permissions of 600. If delivery to programs is permitted,
9696 it's easier to keep the mail system secure if the delivery
9697 agent runs as the destination user. Debian Policy therefore
9698 permits either scheme.
9699 </footnote>. The local system administrator may choose a
9700 different permission scheme; packages should not make
9701 assumptions about the permission and ownership of mailboxes
9702 unless required (such as when creating a new mailbox). A MUA
9703 may remove a mailbox (unless it has nonstandard permissions) in
9704 which case the MTA or another MUA must recreate it if needed.
9708 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9709 be setgid mail to do the locking mentioned above (and
9710 must obviously avoid accessing other users' mailboxes
9711 using this privilege).</p>
9714 <file>/etc/aliases</file> is the source file for the system mail
9715 aliases (e.g., postmaster, usenet, etc.), it is the one
9716 which the sysadmin and <prgn>postinst</prgn> scripts may
9717 edit. After <file>/etc/aliases</file> is edited the program or
9718 human editing it must call <prgn>newaliases</prgn>. All MTA
9719 packages must come with a <prgn>newaliases</prgn> program,
9720 even if it does nothing, but older MTA packages did not do
9721 this so programs should not fail if <prgn>newaliases</prgn>
9722 cannot be found. Note that because of this, all MTA
9723 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9724 <tt>Replaces: mail-transport-agent</tt> control fields.
9728 The convention of writing <tt>forward to
9729 <var>address</var></tt> in the mailbox itself is not
9730 supported. Use a <tt>.forward</tt> file instead.</p>
9733 The <prgn>rmail</prgn> program used by UUCP
9734 for incoming mail should be <file>/usr/sbin/rmail</file>.
9735 Likewise, <prgn>rsmtp</prgn>, for receiving
9736 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9740 If your package needs to know what hostname to use on (for
9741 example) outgoing news and mail messages which are generated
9742 locally, you should use the file <file>/etc/mailname</file>. It
9743 will contain the portion after the username and <tt>@</tt>
9744 (at) sign for email addresses of users on the machine
9745 (followed by a newline).
9749 Such a package should check for the existence of this file
9750 when it is being configured. If it exists, it should be
9751 used without comment, although an MTA's configuration script
9752 may wish to prompt the user even if it finds that this file
9753 exists. If the file does not exist, the package should
9754 prompt the user for the value (preferably using
9755 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9756 as well as using it in the package's configuration. The
9757 prompt should make it clear that the name will not just be
9758 used by that package. For example, in this situation the
9759 <tt>inn</tt> package could say something like:
9760 <example compact="compact">
9761 Please enter the "mail name" of your system. This is the
9762 hostname portion of the address to be shown on outgoing
9763 news and mail messages. The default is
9764 <var>syshostname</var>, your system's host name. Mail
9765 name ["<var>syshostname</var>"]:
9767 where <var>syshostname</var> is the output of <tt>hostname
9773 <heading>News system configuration</heading>
9776 All the configuration files related to the NNTP (news)
9777 servers and clients should be located under
9778 <file>/etc/news</file>.</p>
9781 There are some configuration issues that apply to a number
9782 of news clients and server packages on the machine. These
9786 <tag><file>/etc/news/organization</file></tag>
9788 A string which should appear as the
9789 organization header for all messages posted
9790 by NNTP clients on the machine
9793 <tag><file>/etc/news/server</file></tag>
9795 Contains the FQDN of the upstream NNTP
9796 server, or localhost if the local machine is
9801 Other global files may be added as required for cross-package news
9808 <heading>Programs for the X Window System</heading>
9811 <heading>Providing X support and package priorities</heading>
9814 Programs that can be configured with support for the X
9815 Window System must be configured to do so and must declare
9816 any package dependencies necessary to satisfy their
9817 runtime requirements when using the X Window System. If
9818 such a package is of higher priority than the X packages
9819 on which it depends, it is required that either the
9820 X-specific components be split into a separate package, or
9821 that an alternative version of the package, which includes
9822 X support, be provided, or that the package's priority be
9828 <heading>Packages providing an X server</heading>
9831 Packages that provide an X server that, directly or
9832 indirectly, communicates with real input and display
9833 hardware should declare in their <tt>Provides</tt> control
9834 field that they provide the virtual
9835 package <tt>xserver</tt>.<footnote>
9836 This implements current practice, and provides an
9837 actual policy for usage of the <tt>xserver</tt>
9838 virtual package which appears in the virtual packages
9839 list. In a nutshell, X servers that interface
9840 directly with the display and input hardware or via
9841 another subsystem (e.g., GGI) should provide
9842 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9843 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9849 <heading>Packages providing a terminal emulator</heading>
9852 Packages that provide a terminal emulator for the X Window
9853 System which meet the criteria listed below should declare in
9854 their <tt>Provides</tt> control field that they provide the
9855 virtual package <tt>x-terminal-emulator</tt>. They should
9856 also register themselves as an alternative for
9857 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9858 20. That alternative should have a slave alternative
9859 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9860 pointing to the corresponding manual page.
9864 To be an <tt>x-terminal-emulator</tt>, a program must:
9865 <list compact="compact">
9867 Be able to emulate a DEC VT100 terminal, or a
9868 compatible terminal.
9872 Support the command-line option <tt>-e
9873 <var>command</var></tt>, which creates a new
9874 terminal window<footnote>
9875 "New terminal window" does not necessarily mean
9876 a new top-level X window directly parented by
9877 the window manager; it could, if the terminal
9878 emulator application were so coded, be a new
9879 "view" in a multiple-document interface (MDI).
9881 and runs the specified <var>command</var>,
9882 interpreting the entirety of the rest of the command
9883 line as a command to pass straight to exec, in the
9884 manner that <tt>xterm</tt> does.
9888 Support the command-line option <tt>-T
9889 <var>title</var></tt>, which creates a new terminal
9890 window with the window title <var>title</var>.
9897 <heading>Packages providing a window manager</heading>
9900 Packages that provide a window manager should declare in
9901 their <tt>Provides</tt> control field that they provide the
9902 virtual package <tt>x-window-manager</tt>. They should also
9903 register themselves as an alternative for
9904 <file>/usr/bin/x-window-manager</file>, with a priority
9905 calculated as follows:
9906 <list compact="compact">
9908 Start with a priority of 20.
9912 If the window manager supports the Debian menu
9913 system, add 20 points if this support is available
9914 in the package's default configuration (i.e., no
9915 configuration files belonging to the system or user
9916 have to be edited to activate the feature); if
9917 configuration files must be modified, add only 10
9923 If the window manager complies with <url
9924 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9925 name="The Window Manager Specification Project">,
9926 written by the <url id="http://www.freedesktop.org/wiki/"
9927 name="Free Desktop Group">, add 40 points.
9931 If the window manager permits the X session to be
9932 restarted using a <em>different</em> window manager
9933 (without killing the X server) in its default
9934 configuration, add 10 points; otherwise add none.
9937 That alternative should have a slave alternative
9938 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9939 pointing to the corresponding manual page.
9944 <heading>Packages providing fonts</heading>
9947 Packages that provide fonts for the X Window
9949 For the purposes of Debian Policy, a "font for the X
9950 Window System" is one which is accessed via X protocol
9951 requests. Fonts for the Linux console, for PostScript
9952 renderer, or any other purpose, do not fit this
9953 definition. Any tool which makes such fonts available
9954 to the X Window System, however, must abide by this
9957 must do a number of things to ensure that they are both
9958 available without modification of the X or font server
9959 configuration, and that they do not corrupt files used by
9960 other font packages to register information about
9964 Fonts of any type supported by the X Window System
9965 must be in a separate binary package from any
9966 executables, libraries, or documentation (except
9967 that specific to the fonts shipped, such as their
9968 license information). If one or more of the fonts
9969 so packaged are necessary for proper operation of
9970 the package with which they are associated the font
9971 package may be Recommended; if the fonts merely
9972 provide an enhancement, a Suggests relationship may
9973 be used. Packages must not Depend on font
9975 This is because the X server may retrieve fonts
9976 from the local file system or over the network
9977 from an X font server; the Debian package system
9978 is empowered to deal only with the local
9984 BDF fonts must be converted to PCF fonts with the
9985 <prgn>bdftopcf</prgn> utility (available in the
9986 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9987 placed in a directory that corresponds to their
9989 <list compact="compact">
9991 100 dpi fonts must be placed in
9992 <file>/usr/share/fonts/X11/100dpi/</file>.
9996 75 dpi fonts must be placed in
9997 <file>/usr/share/fonts/X11/75dpi/</file>.
10001 Character-cell fonts, cursor fonts, and other
10002 low-resolution fonts must be placed in
10003 <file>/usr/share/fonts/X11/misc/</file>.
10009 Type 1 fonts must be placed in
10010 <file>/usr/share/fonts/X11/Type1/</file>. If font
10011 metric files are available, they must be placed here
10016 Subdirectories of <file>/usr/share/fonts/X11/</file>
10017 other than those listed above must be neither
10018 created nor used. (The <file>PEX</file>, <file>CID</file>,
10019 <file>Speedo</file>, and <file>cyrillic</file> directories
10020 are excepted for historical reasons, but installation of
10021 files into these directories remains discouraged.)
10025 Font packages may, instead of placing files directly
10026 in the X font directories listed above, provide
10027 symbolic links in that font directory pointing to
10028 the files' actual location in the filesystem. Such
10029 a location must comply with the FHS.
10033 Font packages should not contain both 75dpi and
10034 100dpi versions of a font. If both are available,
10035 they should be provided in separate binary packages
10036 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10037 the names of the packages containing the
10038 corresponding fonts.
10042 Fonts destined for the <file>misc</file> subdirectory
10043 should not be included in the same package as 75dpi
10044 or 100dpi fonts; instead, they should be provided in
10045 a separate package with <tt>-misc</tt> appended to
10050 Font packages must not provide the files
10051 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10052 <file>fonts.scale</file> in a font directory:
10055 <file>fonts.dir</file> files must not be provided at all.
10059 <file>fonts.alias</file> and <file>fonts.scale</file>
10060 files, if needed, should be provided in the
10062 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10063 where <var>fontdir</var> is the name of the
10065 <file>/usr/share/fonts/X11/</file> where the
10066 package's corresponding fonts are stored
10067 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10068 <var>package</var> is the name of the package
10069 that provides these fonts, and
10070 <var>extension</var> is either <tt>scale</tt>
10071 or <tt>alias</tt>, whichever corresponds to
10078 Font packages must declare a dependency on
10079 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10080 or <tt>Pre-Depends</tt> control field.
10084 Font packages that provide one or more
10085 <file>fonts.scale</file> files as described above must
10086 invoke <prgn>update-fonts-scale</prgn> on each
10087 directory into which they installed fonts
10088 <em>before</em> invoking
10089 <prgn>update-fonts-dir</prgn> on that directory.
10090 This invocation must occur in both the
10091 <prgn>postinst</prgn> (for all arguments) and
10092 <prgn>postrm</prgn> (for all arguments except
10093 <tt>upgrade</tt>) scripts.
10097 Font packages that provide one or more
10098 <file>fonts.alias</file> files as described above must
10099 invoke <prgn>update-fonts-alias</prgn> on each
10100 directory into which they installed fonts. This
10101 invocation must occur in both the
10102 <prgn>postinst</prgn> (for all arguments) and
10103 <prgn>postrm</prgn> (for all arguments except
10104 <tt>upgrade</tt>) scripts.
10108 Font packages must invoke
10109 <prgn>update-fonts-dir</prgn> on each directory into
10110 which they installed fonts. This invocation must
10111 occur in both the <prgn>postinst</prgn> (for all
10112 arguments) and <prgn>postrm</prgn> (for all
10113 arguments except <tt>upgrade</tt>) scripts.
10117 Font packages must not provide alias names for the
10118 fonts they include which collide with alias names
10119 already in use by fonts already packaged.
10123 Font packages must not provide fonts with the same
10124 XLFD registry name as another font already packaged.
10130 <sect1 id="appdefaults">
10131 <heading>Application defaults files</heading>
10134 Application defaults files must be installed in the
10135 directory <file>/etc/X11/app-defaults/</file> (use of a
10136 localized subdirectory of <file>/etc/X11/</file> as described
10137 in the <em>X Toolkit Intrinsics - C Language
10138 Interface</em> manual is also permitted). They must be
10139 registered as <tt>conffile</tt>s or handled as
10140 configuration files.
10144 Customization of programs' X resources may also be
10145 supported with the provision of a file with the same name
10146 as that of the package placed in
10147 the <file>/etc/X11/Xresources/</file> directory, which
10148 must be registered as a <tt>conffile</tt> or handled as a
10149 configuration file.<footnote>
10150 Note that this mechanism is not the same as using
10151 app-defaults; app-defaults are tied to the client
10152 binary on the local file system, whereas X resources
10153 are stored in the X server and affect all connecting
10160 <heading>Installation directory issues</heading>
10163 Historically, packages using the X Window System used a
10164 separate set of installation directories from other packages.
10165 This practice has been discontinued and packages using the X
10166 Window System should now generally be installed in the same
10167 directories as any other package. Specifically, packages must
10168 not install files under the <file>/usr/X11R6/</file> directory
10169 and the <file>/usr/X11R6/</file> directory hierarchy should be
10170 regarded as obsolete.
10174 Include files previously installed under
10175 <file>/usr/X11R6/include/X11/</file> should be installed into
10176 <file>/usr/include/X11/</file>. For files previously
10177 installed into subdirectories of
10178 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10179 determine if subdirectories of <file>/usr/lib/</file> and
10180 <file>/usr/share/</file> can be used. If not, a subdirectory
10181 of <file>/usr/lib/X11/</file> should be used.
10185 Configuration files for window, display, or session managers
10186 or other applications that are tightly integrated with the X
10187 Window System may be placed in a subdirectory
10188 of <file>/etc/X11/</file> corresponding to the package name.
10189 Other X Window System applications should use
10190 the <file>/etc/</file> directory unless otherwise mandated by
10191 policy (such as for <ref id="appdefaults">).
10197 <heading>Perl programs and modules</heading>
10200 Perl programs and modules should follow the current Perl policy.
10204 The Perl policy can be found in the <tt>perl-policy</tt>
10205 files in the <tt>debian-policy</tt> package.
10206 It is also available from the Debian web mirrors at
10207 <tt><url name="/doc/packaging-manuals/perl-policy/"
10208 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10213 <heading>Emacs lisp programs</heading>
10216 Please refer to the "Debian Emacs Policy" for details of how to
10217 package emacs lisp programs.
10221 The Emacs policy is available in
10222 <file>debian-emacs-policy.gz</file> of the
10223 <package>emacsen-common</package> package.
10224 It is also available from the Debian web mirrors at
10225 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10226 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10231 <heading>Games</heading>
10234 The permissions on <file>/var/games</file> are mode 755, owner
10235 <tt>root</tt> and group <tt>root</tt>.
10239 Each game decides on its own security policy.</p>
10242 Games which require protected, privileged access to
10243 high-score files, saved games, etc., may be made
10244 set-<em>group</em>-id (mode 2755) and owned by
10245 <tt>root:games</tt>, and use files and directories with
10246 appropriate permissions (770 <tt>root:games</tt>, for
10247 example). They must not be made
10248 set-<em>user</em>-id, as this causes security problems. (If
10249 an attacker can subvert any set-user-id game they can
10250 overwrite the executable of any other, causing other players
10251 of these games to run a Trojan horse program. With a
10252 set-group-id game the attacker only gets access to less
10253 important game data, and if they can get at the other
10254 players' accounts at all it will take considerably more
10258 Some packages, for example some fortune cookie programs, are
10259 configured by the upstream authors to install with their
10260 data files or other static information made unreadable so
10261 that they can only be accessed through set-id programs
10262 provided. You should not do this in a Debian package: anyone can
10263 download the <file>.deb</file> file and read the data from it,
10264 so there is no point making the files unreadable. Not
10265 making the files unreadable also means that you don't have
10266 to make so many programs set-id, which reduces the risk of a
10270 As described in the FHS, binaries of games should be
10271 installed in the directory <file>/usr/games</file>. This also
10272 applies to games that use the X Window System. Manual pages
10273 for games (X and non-X games) should be installed in
10274 <file>/usr/share/man/man6</file>.</p>
10280 <heading>Documentation</heading>
10283 <heading>Manual pages</heading>
10286 You should install manual pages in <prgn>nroff</prgn> source
10287 form, in appropriate places under <file>/usr/share/man</file>.
10288 You should only use sections 1 to 9 (see the FHS for more
10289 details). You must not install a pre-formatted "cat page".
10293 Each program, utility, and function should have an
10294 associated manual page included in the same package. It is
10295 suggested that all configuration files also have a manual
10296 page included as well. Manual pages for protocols and other
10297 auxiliary things are optional.
10301 If no manual page is available, this is considered as a bug
10302 and should be reported to the Debian Bug Tracking System (the
10303 maintainer of the package is allowed to write this bug report
10304 themselves, if they so desire). Do not close the bug report
10305 until a proper man page is available.<footnote>
10306 It is not very hard to write a man page. See the
10307 <url id="http://www.schweikhardt.net/man_page_howto.html"
10308 name="Man-Page-HOWTO">,
10309 <manref name="man" section="7">, the examples created
10310 by <prgn>dh_make</prgn>, the helper
10311 program <prgn>help2man</prgn>, or the
10312 directory <file>/usr/share/doc/man-db/examples</file>.
10317 You may forward a complaint about a missing man page to the
10318 upstream authors, and mark the bug as forwarded in the
10319 Debian bug tracking system. Even though the GNU Project do
10320 not in general consider the lack of a man page to be a bug,
10321 we do; if they tell you that they don't consider it a bug
10322 you should leave the bug in our bug tracking system open
10327 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10331 If one man page needs to be accessible via several names it
10332 is better to use a symbolic link than the <file>.so</file>
10333 feature, but there is no need to fiddle with the relevant
10334 parts of the upstream source to change from <file>.so</file> to
10335 symlinks: don't do it unless it's easy. You should not
10336 create hard links in the manual page directories, nor put
10337 absolute filenames in <file>.so</file> directives. The filename
10338 in a <file>.so</file> in a man page should be relative to the
10339 base of the man page tree (usually
10340 <file>/usr/share/man</file>). If you do not create any links
10341 (whether symlinks, hard links, or <tt>.so</tt> directives)
10342 in the file system to the alternate names of the man page,
10343 then you should not rely on <prgn>man</prgn> finding your
10344 man page under those names based solely on the information in
10345 the man page's header.<footnote>
10346 Supporting this in <prgn>man</prgn> often requires
10347 unreasonable processing time to find a manual page or to
10348 report that none exists, and moves knowledge into man's
10349 database that would be better left in the file system.
10350 This support is therefore deprecated and will cease to
10351 be present in the future.
10356 Manual pages in locale-specific subdirectories of
10357 <file>/usr/share/man</file> should use either UTF-8 or the usual
10358 legacy encoding for that language (normally the one corresponding
10359 to the shortest relevant locale name in
10360 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10361 <file>/usr/share/man/fr</file> should use either UTF-8 or
10362 ISO-8859-1.<footnote>
10363 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10364 use. In future, all manual pages will be required to use
10370 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10371 included in the subdirectory name unless it indicates a
10372 significant difference in the language, as this excludes
10373 speakers of the language in other countries.<footnote>
10374 At the time of writing, Chinese and Portuguese are the main
10375 languages with such differences, so <file>pt_BR</file>,
10376 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10381 If a localized version of a manual page is provided, it should
10382 either be up-to-date or it should be obvious to the reader that
10383 it is outdated and the original manual page should be used
10384 instead. This can be done either by a note at the beginning of
10385 the manual page or by showing the missing or changed portions in
10386 the original language instead of the target language.
10391 <heading>Info documents</heading>
10394 Info documents should be installed in <file>/usr/share/info</file>.
10395 They should be compressed with <tt>gzip -9</tt>.
10399 The <prgn>install-info</prgn> program maintains a directory of
10400 installed info documents in <file>/usr/share/info/dir</file> for
10401 the use of info readers.<footnote>
10402 It was previously necessary for packages installing info
10403 documents to run <prgn>install-info</prgn> from maintainer
10404 scripts. This is no longer necessary. The installation
10405 system now uses dpkg triggers.
10407 This file must not be included in packages. Packages containing
10408 info documents should depend on <tt>dpkg (>= 1.15.4) |
10409 install-info</tt> to ensure that the directory file is properly
10410 rebuilt during partial upgrades from Debian 5.0 (lenny) and
10415 Info documents should contain section and directory entry
10416 information in the document for the use
10417 of <prgn>install-info</prgn>. The section should be specified
10418 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10419 space and the section of this info page. The directory entry or
10420 entries should be included between
10421 a <tt>START-INFO-DIR-ENTRY</tt> line and
10422 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10424 INFO-DIR-SECTION Individual utilities
10425 START-INFO-DIR-ENTRY
10426 * example: (example). An example info directory entry.
10429 To determine which section to use, you should look
10430 at <file>/usr/share/info/dir</file> on your system and choose
10431 the most relevant (or create a new section if none of the
10432 current sections are relevant).<footnote>
10433 Normally, info documents are generated from Texinfo source.
10434 To include this information in the generated info document, if
10435 it is absent, add commands like:
10437 @dircategory Individual utilities
10439 * example: (example). An example info directory entry.
10442 to the Texinfo source of the document and ensure that the info
10443 documents are rebuilt from source during the package build.
10449 <heading>Additional documentation</heading>
10452 Any additional documentation that comes with the package may
10453 be installed at the discretion of the package maintainer.
10454 Plain text documentation should be installed in the directory
10455 <file>/usr/share/doc/<var>package</var></file>, where
10456 <var>package</var> is the name of the package, and
10457 compressed with <tt>gzip -9</tt> unless it is small.
10461 If a package comes with large amounts of documentation which
10462 many users of the package will not require you should create
10463 a separate binary package to contain it, so that it does not
10464 take up disk space on the machines of users who do not need
10465 or want it installed.</p>
10468 It is often a good idea to put text information files
10469 (<file>README</file>s, changelogs, and so forth) that come with
10470 the source package in <file>/usr/share/doc/<var>package</var></file>
10471 in the binary package. However, you don't need to install
10472 the instructions for building and installing the package, of
10476 Packages must not require the existence of any files in
10477 <file>/usr/share/doc/</file> in order to function
10479 The system administrator should be able to
10480 delete files in <file>/usr/share/doc/</file> without causing
10481 any programs to break.
10483 Any files that are referenced by programs but are also
10484 useful as stand alone documentation should be installed under
10485 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10486 <file>/usr/share/doc/<var>package</var></file>.
10490 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10491 link to another directory in <file>/usr/share/doc</file> only if
10492 the two packages both come from the same source and the
10493 first package Depends on the second.<footnote>
10495 Please note that this does not override the section on
10496 changelog files below, so the file
10497 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10498 must refer to the changelog for the current version of
10499 <var>package</var> in question. In practice, this means
10500 that the sources of the target and the destination of the
10501 symlink must be the same (same source package and
10508 Former Debian releases placed all additional documentation
10509 in <file>/usr/doc/<var>package</var></file>. This has been
10510 changed to <file>/usr/share/doc/<var>package</var></file>,
10511 and packages must not put documentation in the directory
10512 <file>/usr/doc/<var>package</var></file>. <footnote>
10513 At this phase of the transition, we no longer require a
10514 symbolic link in <file>/usr/doc/</file>. At a later point,
10515 policy shall change to make the symbolic links a bug.
10521 <heading>Preferred documentation formats</heading>
10524 The unification of Debian documentation is being carried out
10528 If your package comes with extensive documentation in a
10529 markup format that can be converted to various other formats
10530 you should if possible ship HTML versions in a binary
10531 package, in the directory
10532 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10533 its subdirectories.<footnote>
10534 The rationale: The important thing here is that HTML
10535 docs should be available in <em>some</em> package, not
10536 necessarily in the main binary package.
10541 Other formats such as PostScript may be provided at the
10542 package maintainer's discretion.
10546 <sect id="copyrightfile">
10547 <heading>Copyright information</heading>
10550 Every package must be accompanied by a verbatim copy of its
10551 copyright information and distribution license in the file
10552 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10553 file must neither be compressed nor be a symbolic link.
10557 In addition, the copyright file must say where the upstream
10558 sources (if any) were obtained, and should name the original
10563 Packages in the <em>contrib</em> or <em>non-free</em> archive
10564 areas should state in the copyright file that the package is not
10565 part of the Debian distribution and briefly explain why.
10569 A copy of the file which will be installed in
10570 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10571 be in <file>debian/copyright</file> in the source package.
10575 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10576 link to another directory in <file>/usr/share/doc</file> only if
10577 the two packages both come from the same source and the
10578 first package Depends on the second. These rules are important
10579 because <file>copyright</file> files must be extractable by
10584 Packages distributed under the Apache license (version 2.0), the
10585 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10586 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10587 1.3) should refer to the corresponding files
10588 under <file>/usr/share/common-licenses</file>,<footnote>
10591 <file>/usr/share/common-licenses/Apache-2.0</file>,
10592 <file>/usr/share/common-licenses/Artistic</file>,
10593 <file>/usr/share/common-licenses/GPL-1</file>,
10594 <file>/usr/share/common-licenses/GPL-2</file>,
10595 <file>/usr/share/common-licenses/GPL-3</file>,
10596 <file>/usr/share/common-licenses/LGPL-2</file>,
10597 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10598 <file>/usr/share/common-licenses/LGPL-3</file>,
10599 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10600 <file>/usr/share/common-licenses/GFDL-1.3</file>
10601 respectively. The University of California BSD license is
10602 also included in <package>base-files</package> as
10603 <file>/usr/share/common-licenses/BSD</file>, but given the
10604 brevity of this license, its specificity to code whose
10605 copyright is held by the Regents of the University of
10606 California, and the frequency of minor wording changes, its
10607 text should be included in the copyright file rather than
10608 referencing this file.
10610 </footnote> rather than quoting them in the copyright
10615 You should not use the copyright file as a general <file>README</file>
10616 file. If your package has such a file it should be
10617 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10618 <file>README.Debian</file> or some other appropriate place.
10622 All copyright files must be encoded in UTF-8.
10625 <sect1 id="copyrightformat">
10626 <heading>Machine-readable copyright information</heading>
10629 A specification for a standard, machine-readable format
10630 for <file>debian/copyright</file> files is maintained as part
10631 of the <package>debian-policy</package> package. This
10632 document may be found in the <file>copyright-format</file>
10633 files in the <package>debian-policy</package> package. It is
10634 also available from the Debian web mirrors at
10635 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10636 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10640 Use of this format is optional.
10646 <heading>Examples</heading>
10649 Any examples (configurations, source files, whatever),
10650 should be installed in a directory
10651 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10652 files should not be referenced by any program: they're there
10653 for the benefit of the system administrator and users as
10654 documentation only. Architecture-specific example files
10655 should be installed in a directory
10656 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10658 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10659 latter directory itself may be a symbolic link to the
10664 If the purpose of a package is to provide examples, then the
10665 example files may be installed into
10666 <file>/usr/share/doc/<var>package</var></file>.
10670 <sect id="changelogs">
10671 <heading>Changelog files</heading>
10674 Packages that are not Debian-native must contain a
10675 compressed copy of the <file>debian/changelog</file> file from
10676 the Debian source tree in
10677 <file>/usr/share/doc/<var>package</var></file> with the name
10678 <file>changelog.Debian.gz</file>.
10682 If an upstream changelog is available, it should be accessible as
10683 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10684 plain text. If the upstream changelog is distributed in
10685 HTML, it should be made available in that form as
10686 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10687 and a plain text <file>changelog.gz</file> should be generated
10688 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10689 the upstream changelog files do not already conform to this
10690 naming convention, then this may be achieved either by
10691 renaming the files, or by adding a symbolic link, at the
10692 maintainer's discretion.<footnote>
10693 Rationale: People should not have to look in places for
10694 upstream changelogs merely because they are given
10695 different names or are distributed in HTML format.
10700 All of these files should be installed compressed using
10701 <tt>gzip -9</tt>, as they will become large with time even
10702 if they start out small.
10706 If the package has only one changelog which is used both as
10707 the Debian changelog and the upstream one because there is
10708 no separate upstream maintainer then that changelog should
10709 usually be installed as
10710 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10711 there is a separate upstream maintainer, but no upstream
10712 changelog, then the Debian changelog should still be called
10713 <file>changelog.Debian.gz</file>.
10717 For details about the format and contents of the Debian
10718 changelog file, please see <ref id="dpkgchangelog">.
10723 <appendix id="pkg-scope">
10724 <heading>Introduction and scope of these appendices</heading>
10727 These appendices are taken essentially verbatim from the
10728 now-deprecated Packaging Manual, version 3.2.1.0. They are
10729 the chapters which are likely to be of use to package
10730 maintainers and which have not already been included in the
10731 policy document itself. Most of these sections are very likely
10732 not relevant to policy; they should be treated as
10733 documentation for the packaging system. Please note that these
10734 appendices are included for convenience, and for historical
10735 reasons: they used to be part of policy package, and they have
10736 not yet been incorporated into dpkg documentation. However,
10737 they still have value, and hence they are presented here.
10741 They have not yet been checked to ensure that they are
10742 compatible with the contents of policy, and if there are any
10743 contradictions, the version in the main policy document takes
10744 precedence. The remaining chapters of the old Packaging
10745 Manual have also not been read in detail to ensure that there
10746 are not parts which have been left out. Both of these will be
10747 done in due course.
10751 Certain parts of the Packaging manual were integrated into the
10752 Policy Manual proper, and removed from the appendices. Links
10753 have been placed from the old locations to the new ones.
10757 <prgn>dpkg</prgn> is a suite of programs for creating binary
10758 package files and installing and removing them on Unix
10760 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10761 work on or be ported to other systems.
10766 The binary packages are designed for the management of
10767 installed executable programs (usually compiled binaries) and
10768 their associated data, though source code examples and
10769 documentation are provided as part of some packages.</p>
10772 This manual describes the technical aspects of creating Debian
10773 binary packages (<file>.deb</file> files). It documents the
10774 behavior of the package management programs
10775 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10776 they interact with packages.</p>
10779 It also documents the interaction between
10780 <prgn>dselect</prgn>'s core and the access method scripts it
10781 uses to actually install the selected packages, and describes
10782 how to create a new access method.</p>
10785 This manual does not go into detail about the options and
10786 usage of the package building and installation tools. It
10787 should therefore be read in conjunction with those programs'
10792 The utility programs which are provided with <prgn>dpkg</prgn>
10793 for managing various system configuration and similar issues,
10794 such as <prgn>update-rc.d</prgn> and
10795 <prgn>install-info</prgn>, are not described in detail here -
10796 please see their man pages.
10800 It is assumed that the reader is reasonably familiar with the
10801 <prgn>dpkg</prgn> System Administrators' manual.
10802 Unfortunately this manual does not yet exist.
10806 The Debian version of the FSF's GNU hello program is provided as
10807 an example for people wishing to create Debian packages. However,
10808 while the examples are helpful, they do not replace the need to
10809 read and follow the Policy and Programmer's Manual.</p>
10812 <appendix id="pkg-binarypkg">
10813 <heading>Binary packages (from old Packaging Manual)</heading>
10816 The binary package has two main sections. The first part
10817 consists of various control information files and scripts used
10818 by <prgn>dpkg</prgn> when installing and removing. See <ref
10819 id="pkg-controlarea">.
10823 The second part is an archive containing the files and
10824 directories to be installed.
10828 In the future binary packages may also contain other
10829 components, such as checksums and digital signatures. The
10830 format for the archive is described in full in the
10831 <file>deb(5)</file> man page.
10835 <sect id="pkg-bincreating"><heading>Creating package files -
10836 <prgn>dpkg-deb</prgn>
10840 All manipulation of binary package files is done by
10841 <prgn>dpkg-deb</prgn>; it's the only program that has
10842 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10843 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10844 will spot that the options requested are appropriate to
10845 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10850 In order to create a binary package you must make a
10851 directory tree which contains all the files and directories
10852 you want to have in the file system data part of the package.
10853 In Debian-format source packages this directory is usually
10854 <file>debian/tmp</file>, relative to the top of the package's
10859 They should have the locations (relative to the root of the
10860 directory tree you're constructing) ownerships and
10861 permissions which you want them to have on the system when
10862 they are installed.
10866 With current versions of <prgn>dpkg</prgn> the uid/username
10867 and gid/groupname mappings for the users and groups being
10868 used should be the same on the system where the package is
10869 built and the one where it is installed.
10873 You need to add one special directory to the root of the
10874 miniature file system tree you're creating:
10875 <prgn>DEBIAN</prgn>. It should contain the control
10876 information files, notably the binary package control file
10877 (see <ref id="pkg-controlfile">).
10881 The <prgn>DEBIAN</prgn> directory will not appear in the
10882 file system archive of the package, and so won't be installed
10883 by <prgn>dpkg</prgn> when the package is unpacked.
10887 When you've prepared the package, you should invoke:
10889 dpkg --build <var>directory</var>
10894 This will build the package in
10895 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10896 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10897 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10898 build the package.)
10902 See the man page <manref name="dpkg-deb" section="8"> for details of how
10903 to examine the contents of this newly-created file. You may find the
10904 output of following commands enlightening:
10906 dpkg-deb --info <var>filename</var>.deb
10907 dpkg-deb --contents <var>filename</var>.deb
10908 dpkg --contents <var>filename</var>.deb
10910 To view the copyright file for a package you could use this command:
10912 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10917 <sect id="pkg-controlarea">
10918 <heading>Package control information files</heading>
10921 The control information portion of a binary package is a
10922 collection of files with names known to <prgn>dpkg</prgn>.
10923 It will treat the contents of these files specially - some
10924 of them contain information used by <prgn>dpkg</prgn> when
10925 installing or removing the package; others are scripts which
10926 the package maintainer wants <prgn>dpkg</prgn> to run.
10930 It is possible to put other files in the package control
10931 information file area, but this is not generally a good idea
10932 (though they will largely be ignored).
10936 Here is a brief list of the control information files supported
10937 by <prgn>dpkg</prgn> and a summary of what they're used for.
10942 <tag><tt>control</tt>
10945 This is the key description file used by
10946 <prgn>dpkg</prgn>. It specifies the package's name
10947 and version, gives its description for the user,
10948 states its relationships with other packages, and so
10949 forth. See <ref id="sourcecontrolfiles"> and
10950 <ref id="binarycontrolfiles">.
10954 It is usually generated automatically from information
10955 in the source package by the
10956 <prgn>dpkg-gencontrol</prgn> program, and with
10957 assistance from <prgn>dpkg-shlibdeps</prgn>.
10958 See <ref id="pkg-sourcetools">.
10962 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10967 These are executable files (usually scripts) which
10968 <prgn>dpkg</prgn> runs during installation, upgrade
10969 and removal of packages. They allow the package to
10970 deal with matters which are particular to that package
10971 or require more complicated processing than that
10972 provided by <prgn>dpkg</prgn>. Details of when and
10973 how they are called are in <ref id="maintainerscripts">.
10977 It is very important to make these scripts idempotent.
10978 See <ref id="idempotency">.
10982 The maintainer scripts are not guaranteed to run with a
10983 controlling terminal and may not be able to interact with
10984 the user. See <ref id="controllingterminal">.
10988 <tag><tt>conffiles</tt>
10991 This file contains a list of configuration files which
10992 are to be handled automatically by <prgn>dpkg</prgn>
10993 (see <ref id="pkg-conffiles">). Note that not necessarily
10994 every configuration file should be listed here.
10997 <tag><tt>shlibs</tt>
11000 This file contains a list of the shared libraries
11001 supplied by the package, with dependency details for
11002 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11003 when it determines what dependencies are required in a
11004 package control file. The <tt>shlibs</tt> file format
11005 is described on <ref id="shlibs">.
11010 <sect id="pkg-controlfile">
11011 <heading>The main control information file: <tt>control</tt></heading>
11014 The most important control information file used by
11015 <prgn>dpkg</prgn> when it installs a package is
11016 <tt>control</tt>. It contains all the package's "vital
11021 The binary package control files of packages built from
11022 Debian sources are made by a special tool,
11023 <prgn>dpkg-gencontrol</prgn>, which reads
11024 <file>debian/control</file> and <file>debian/changelog</file> to
11025 find the information it needs. See <ref id="pkg-sourcepkg"> for
11030 The fields in binary package control files are listed in
11031 <ref id="binarycontrolfiles">.
11035 A description of the syntax of control files and the purpose
11036 of the fields is available in <ref id="controlfields">.
11041 <heading>Time Stamps</heading>
11044 See <ref id="timestamps">.
11049 <appendix id="pkg-sourcepkg">
11050 <heading>Source packages (from old Packaging Manual) </heading>
11053 The Debian binary packages in the distribution are generated
11054 from Debian sources, which are in a special format to assist
11055 the easy and automatic building of binaries.
11058 <sect id="pkg-sourcetools">
11059 <heading>Tools for processing source packages</heading>
11062 Various tools are provided for manipulating source packages;
11063 they pack and unpack sources and help build of binary
11064 packages and help manage the distribution of new versions.
11068 They are introduced and typical uses described here; see
11069 <manref name="dpkg-source" section="1"> for full
11070 documentation about their arguments and operation.
11074 For examples of how to construct a Debian source package,
11075 and how to use those utilities that are used by Debian
11076 source packages, please see the <prgn>hello</prgn> example
11080 <sect1 id="pkg-dpkg-source">
11082 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11087 This program is frequently used by hand, and is also
11088 called from package-independent automated building scripts
11089 such as <prgn>dpkg-buildpackage</prgn>.
11093 To unpack a package it is typically invoked with
11095 dpkg-source -x <var>.../path/to/filename</var>.dsc
11100 with the <file><var>filename</var>.tar.gz</file> and
11101 <file><var>filename</var>.diff.gz</file> (if applicable) in
11102 the same directory. It unpacks into
11103 <file><var>package</var>-<var>version</var></file>, and if
11105 <file><var>package</var>-<var>version</var>.orig</file>, in
11106 the current directory.
11110 To create a packed source archive it is typically invoked:
11112 dpkg-source -b <var>package</var>-<var>version</var>
11117 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11118 <file>.diff.gz</file> (if appropriate) in the current
11119 directory. <prgn>dpkg-source</prgn> does not clean the
11120 source tree first - this must be done separately if it is
11125 See also <ref id="pkg-sourcearchives">.</p>
11129 <sect1 id="pkg-dpkg-buildpackage">
11131 <prgn>dpkg-buildpackage</prgn> - overall package-building
11136 <prgn>dpkg-buildpackage</prgn> is a script which invokes
11137 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
11138 targets <tt>clean</tt>, <tt>build</tt> and
11139 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
11140 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
11141 source and binary package upload.
11145 It is usually invoked by hand from the top level of the
11146 built or unbuilt source directory. It may be invoked with
11147 no arguments; useful arguments include:
11148 <taglist compact="compact">
11149 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
11152 Do not sign the <tt>.changes</tt> file or the
11153 source package <tt>.dsc</tt> file, respectively.</p>
11155 <tag><tt>-p<var>sign-command</var></tt></tag>
11158 Invoke <var>sign-command</var> instead of finding
11159 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
11160 <var>sign-command</var> must behave just like
11161 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
11163 <tag><tt>-r<var>root-command</var></tt></tag>
11166 When root privilege is required, invoke the command
11167 <var>root-command</var>. <var>root-command</var>
11168 should invoke its first argument as a command, from
11169 the <prgn>PATH</prgn> if necessary, and pass its
11170 second and subsequent arguments to the command it
11171 calls. If no <var>root-command</var> is supplied
11172 then <var>dpkg-buildpackage</var> will use
11173 the <prgn>fakeroot</prgn> command, which is sufficient
11174 to build most packages without actually requiring root
11177 <tag><tt>-b</tt>, <tt>-B</tt></tag>
11180 Two types of binary-only build and upload - see
11181 <manref name="dpkg-source" section="1">.
11188 <sect1 id="pkg-dpkg-gencontrol">
11190 <prgn>dpkg-gencontrol</prgn> - generates binary package
11195 This program is usually called from <file>debian/rules</file>
11196 (see <ref id="pkg-sourcetree">) in the top level of the source
11201 This is usually done just before the files and directories in the
11202 temporary directory tree where the package is being built have their
11203 permissions and ownerships set and the package is constructed using
11204 <prgn>dpkg-deb/</prgn>
11206 This is so that the control file which is produced has
11207 the right permissions
11212 <prgn>dpkg-gencontrol</prgn> must be called after all the
11213 files which are to go into the package have been placed in
11214 the temporary build directory, so that its calculation of
11215 the installed size of a package is correct.
11219 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11220 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11221 variable substitutions created by
11222 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11227 For a package which generates only one binary package, and
11228 which builds it in <file>debian/tmp</file> relative to the top
11229 of the source package, it is usually sufficient to call
11230 <prgn>dpkg-gencontrol</prgn>.
11234 Sources which build several binaries will typically need
11237 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11238 </example> The <tt>-P</tt> tells
11239 <prgn>dpkg-gencontrol</prgn> that the package is being
11240 built in a non-default directory, and the <tt>-p</tt>
11241 tells it which package's control file should be generated.
11245 <prgn>dpkg-gencontrol</prgn> also adds information to the
11246 list of files in <file>debian/files</file>, for the benefit of
11247 (for example) a future invocation of
11248 <prgn>dpkg-genchanges</prgn>.</p>
11251 <sect1 id="pkg-dpkg-shlibdeps">
11253 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11258 See <manref name="dpkg-shlibdeps" section="1">.
11262 <sect1 id="pkg-dpkg-distaddfile">
11264 <prgn>dpkg-distaddfile</prgn> - adds a file to
11265 <file>debian/files</file>
11269 Some packages' uploads need to include files other than
11270 the source and binary package files.
11274 <prgn>dpkg-distaddfile</prgn> adds a file to the
11275 <file>debian/files</file> file so that it will be included in
11276 the <file>.changes</file> file when
11277 <prgn>dpkg-genchanges</prgn> is run.
11281 It is usually invoked from the <tt>binary</tt> target of
11282 <file>debian/rules</file>:
11284 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11286 The <var>filename</var> is relative to the directory where
11287 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11288 is usually the directory above the top level of the source
11289 tree. The <file>debian/rules</file> target should put the
11290 file there just before or just after calling
11291 <prgn>dpkg-distaddfile</prgn>.
11295 The <var>section</var> and <var>priority</var> are passed
11296 unchanged into the resulting <file>.changes</file> file.
11301 <sect1 id="pkg-dpkg-genchanges">
11303 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11304 upload control file
11308 This program is usually called by package-independent
11309 automatic building scripts such as
11310 <prgn>dpkg-buildpackage</prgn>, but it may also be called
11315 It is usually called in the top level of a built source
11316 tree, and when invoked with no arguments will print out a
11317 straightforward <file>.changes</file> file based on the
11318 information in the source package's changelog and control
11319 file and the binary and source packages which should have
11325 <sect1 id="pkg-dpkg-parsechangelog">
11327 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11328 representation of a changelog
11332 This program is used internally by
11333 <prgn>dpkg-source</prgn> et al. It may also occasionally
11334 be useful in <file>debian/rules</file> and elsewhere. It
11335 parses a changelog, <file>debian/changelog</file> by default,
11336 and prints a control-file format representation of the
11337 information in it to standard output.
11341 <sect1 id="pkg-dpkg-architecture">
11343 <prgn>dpkg-architecture</prgn> - information about the build and
11348 This program can be used manually, but is also invoked by
11349 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
11350 environment or make variables which specify the build and host
11351 architecture for the package building process.
11356 <sect id="pkg-sourcetree">
11357 <heading>The Debian package source tree</heading>
11360 The source archive scheme described later is intended to
11361 allow a Debian package source tree with some associated
11362 control information to be reproduced and transported easily.
11363 The Debian package source tree is a version of the original
11364 program with certain files added for the benefit of the
11365 packaging process, and with any other changes required
11366 made to the rest of the source code and installation
11371 The extra files created for Debian are in the subdirectory
11372 <file>debian</file> of the top level of the Debian package
11373 source tree. They are described below.
11376 <sect1 id="pkg-debianrules">
11377 <heading><file>debian/rules</file> - the main building script</heading>
11380 See <ref id="debianrules">.
11384 <sect1 id="pkg-srcsubstvars">
11385 <heading><file>debian/substvars</file> and variable substitutions</heading>
11388 See <ref id="substvars">.
11394 <heading><file>debian/files</file></heading>
11397 See <ref id="debianfiles">.
11401 <sect1><heading><file>debian/tmp</file>
11405 This is the canonical temporary location for the
11406 construction of binary packages by the <tt>binary</tt>
11407 target. The directory <file>tmp</file> serves as the root of
11408 the file system tree as it is being constructed (for
11409 example, by using the package's upstream makefiles install
11410 targets and redirecting the output there), and it also
11411 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11412 id="pkg-bincreating">.
11416 If several binary packages are generated from the same
11417 source tree it is usual to use several
11418 <file>debian/tmp<var>something</var></file> directories, for
11419 example <file>tmp-a</file> or <file>tmp-doc</file>.
11423 Whatever <file>tmp</file> directories are created and used by
11424 <tt>binary</tt> must of course be removed by the
11425 <tt>clean</tt> target.</p></sect1>
11429 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11433 As it exists on the FTP site, a Debian source package
11434 consists of three related files. You must have the right
11435 versions of all three to be able to use them.
11440 <tag>Debian source control file - <tt>.dsc</tt></tag>
11442 This file is a control file used by <prgn>dpkg-source</prgn>
11443 to extract a source package.
11444 See <ref id="debiansourcecontrolfiles">.
11448 Original source archive -
11450 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11456 This is a compressed (with <tt>gzip -9</tt>)
11457 <prgn>tar</prgn> file containing the source code from
11458 the upstream authors of the program.
11463 Debian package diff -
11465 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11471 This is a unified context diff (<tt>diff -u</tt>)
11472 giving the changes which are required to turn the
11473 original source into the Debian source. These changes
11474 may only include editing and creating plain files.
11475 The permissions of files, the targets of symbolic
11476 links and the characteristics of special files or
11477 pipes may not be changed and no files may be removed
11482 All the directories in the diff must exist, except the
11483 <file>debian</file> subdirectory of the top of the source
11484 tree, which will be created by
11485 <prgn>dpkg-source</prgn> if necessary when unpacking.
11489 The <prgn>dpkg-source</prgn> program will
11490 automatically make the <file>debian/rules</file> file
11491 executable (see below).</p></item>
11496 If there is no original source code - for example, if the
11497 package is specially prepared for Debian or the Debian
11498 maintainer is the same as the upstream maintainer - the
11499 format is slightly different: then there is no diff, and the
11501 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11502 and preferably contains a directory named
11503 <file><var>package</var>-<var>version</var></file>.
11508 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11511 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11512 Debian source package. However, if it is not available it
11513 is possible to unpack a Debian source archive as follows:
11514 <enumlist compact="compact">
11517 Untar the tarfile, which will create a <file>.orig</file>
11521 <p>Rename the <file>.orig</file> directory to
11522 <file><var>package</var>-<var>version</var></file>.</p>
11526 Create the subdirectory <file>debian</file> at the top of
11527 the source tree.</p>
11529 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11531 <item><p>Untar the tarfile again if you want a copy of the original
11532 source code alongside the Debian version.</p>
11537 It is not possible to generate a valid Debian source archive
11538 without using <prgn>dpkg-source</prgn>. In particular,
11539 attempting to use <prgn>diff</prgn> directly to generate the
11540 <file>.diff.gz</file> file will not work.
11544 <heading>Restrictions on objects in source packages</heading>
11547 The source package may not contain any hard links
11549 This is not currently detected when building source
11550 packages, but only when extracting
11554 Hard links may be permitted at some point in the
11555 future, but would require a fair amount of
11557 </footnote>, device special files, sockets or setuid or
11560 Setgid directories are allowed.
11565 The source packaging tools manage the changes between the
11566 original and Debian source using <prgn>diff</prgn> and
11567 <prgn>patch</prgn>. Turning the original source tree as
11568 included in the <file>.orig.tar.gz</file> into the Debian
11569 package source must not involve any changes which cannot be
11570 handled by these tools. Problematic changes which cause
11571 <prgn>dpkg-source</prgn> to halt with an error when
11572 building the source package are:
11573 <list compact="compact">
11574 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11576 <item><p>Changing the targets of symbolic links.</p>
11578 <item><p>Creating directories, other than <file>debian</file>.</p>
11580 <item><p>Changes to the contents of binary files.</p></item>
11581 </list> Changes which cause <prgn>dpkg-source</prgn> to
11582 print a warning but continue anyway are:
11583 <list compact="compact">
11586 Removing files, directories or symlinks.
11588 Renaming a file is not treated specially - it is
11589 seen as the removal of the old file (which
11590 generates a warning, but is otherwise ignored),
11591 and the creation of the new one.
11597 Changed text files which are missing the usual final
11598 newline (either in the original or the modified
11603 Changes which are not represented, but which are not detected by
11604 <prgn>dpkg-source</prgn>, are:
11605 <list compact="compact">
11606 <item><p>Changing the permissions of files (other than
11607 <file>debian/rules</file>) and directories.</p></item>
11612 The <file>debian</file> directory and <file>debian/rules</file>
11613 are handled specially by <prgn>dpkg-source</prgn> - before
11614 applying the changes it will create the <file>debian</file>
11615 directory, and afterwards it will make
11616 <file>debian/rules</file> world-executable.
11622 <appendix id="pkg-controlfields">
11623 <heading>Control files and their fields (from old Packaging Manual)</heading>
11626 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11627 data in a common format, known as control files. Binary and
11628 source packages have control data as do the <file>.changes</file>
11629 files which control the installation of uploaded files, and
11630 <prgn>dpkg</prgn>'s internal databases are in a similar
11635 <heading>Syntax of control files</heading>
11638 See <ref id="controlsyntax">.
11642 It is important to note that there are several fields which
11643 are optional as far as <prgn>dpkg</prgn> and the related
11644 tools are concerned, but which must appear in every Debian
11645 package, or whose omission may cause problems.
11650 <heading>List of fields</heading>
11653 See <ref id="controlfieldslist">.
11657 This section now contains only the fields that didn't belong
11658 to the Policy manual.
11661 <sect1 id="pkg-f-Filename">
11662 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11665 These fields in <tt>Packages</tt> files give the
11666 filename(s) of (the parts of) a package in the
11667 distribution directories, relative to the root of the
11668 Debian hierarchy. If the package has been split into
11669 several parts the parts are all listed in order, separated
11674 <sect1 id="pkg-f-Size">
11675 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11678 These fields in <file>Packages</file> files give the size (in
11679 bytes, expressed in decimal) and MD5 checksum of the
11680 file(s) which make(s) up a binary package in the
11681 distribution. If the package is split into several parts
11682 the values for the parts are listed in order, separated by
11687 <sect1 id="pkg-f-Status">
11688 <heading><tt>Status</tt></heading>
11691 This field in <prgn>dpkg</prgn>'s status file records
11692 whether the user wants a package installed, removed or
11693 left alone, whether it is broken (requiring
11694 re-installation) or not and what its current state on the
11695 system is. Each of these pieces of information is a
11700 <sect1 id="pkg-f-Config-Version">
11701 <heading><tt>Config-Version</tt></heading>
11704 If a package is not installed or not configured, this
11705 field in <prgn>dpkg</prgn>'s status file records the last
11706 version of the package which was successfully
11711 <sect1 id="pkg-f-Conffiles">
11712 <heading><tt>Conffiles</tt></heading>
11715 This field in <prgn>dpkg</prgn>'s status file contains
11716 information about the automatically-managed configuration
11717 files held by a package. This field should <em>not</em>
11718 appear anywhere in a package!
11723 <heading>Obsolete fields</heading>
11726 These are still recognized by <prgn>dpkg</prgn> but should
11727 not appear anywhere any more.
11729 <taglist compact="compact">
11731 <tag><tt>Revision</tt></tag>
11732 <tag><tt>Package-Revision</tt></tag>
11733 <tag><tt>Package_Revision</tt></tag>
11735 The Debian revision part of the package version was
11736 at one point in a separate control field. This
11737 field went through several names.
11740 <tag><tt>Recommended</tt></tag>
11741 <item>Old name for <tt>Recommends</tt>.</item>
11743 <tag><tt>Optional</tt></tag>
11744 <item>Old name for <tt>Suggests</tt>.</item>
11746 <tag><tt>Class</tt></tag>
11747 <item>Old name for <tt>Priority</tt>.</item>
11756 <appendix id="pkg-conffiles">
11757 <heading>Configuration file handling (from old Packaging Manual)</heading>
11760 <prgn>dpkg</prgn> can do a certain amount of automatic
11761 handling of package configuration files.
11765 Whether this mechanism is appropriate depends on a number of
11766 factors, but basically there are two approaches to any
11767 particular configuration file.
11771 The easy method is to ship a best-effort configuration in the
11772 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11773 handle updates. If the user is unlikely to want to edit the
11774 file, but you need them to be able to without losing their
11775 changes, and a new package with a changed version of the file
11776 is only released infrequently, this is a good approach.
11780 The hard method is to build the configuration file from
11781 scratch in the <prgn>postinst</prgn> script, and to take the
11782 responsibility for fixing any mistakes made in earlier
11783 versions of the package automatically. This will be
11784 appropriate if the file is likely to need to be different on
11788 <sect><heading>Automatic handling of configuration files by
11793 A package may contain a control information file called
11794 <tt>conffiles</tt>. This file should be a list of filenames
11795 of configuration files needing automatic handling, separated
11796 by newlines. The filenames should be absolute pathnames,
11797 and the files referred to should actually exist in the
11802 When a package is upgraded <prgn>dpkg</prgn> will process
11803 the configuration files during the configuration stage,
11804 shortly before it runs the package's <prgn>postinst</prgn>
11809 For each file it checks to see whether the version of the
11810 file included in the package is the same as the one that was
11811 included in the last version of the package (the one that is
11812 being upgraded from); it also compares the version currently
11813 installed on the system with the one shipped with the last
11818 If neither the user nor the package maintainer has changed
11819 the file, it is left alone. If one or the other has changed
11820 their version, then the changed version is preferred - i.e.,
11821 if the user edits their file, but the package maintainer
11822 doesn't ship a different version, the user's changes will
11823 stay, silently, but if the maintainer ships a new version
11824 and the user hasn't edited it the new version will be
11825 installed (with an informative message). If both have
11826 changed their version the user is prompted about the problem
11827 and must resolve the differences themselves.
11831 The comparisons are done by calculating the MD5 message
11832 digests of the files, and storing the MD5 of the file as it
11833 was included in the most recent version of the package.
11837 When a package is installed for the first time
11838 <prgn>dpkg</prgn> will install the file that comes with it,
11839 unless that would mean overwriting a file already on the
11844 However, note that <prgn>dpkg</prgn> will <em>not</em>
11845 replace a conffile that was removed by the user (or by a
11846 script). This is necessary because with some programs a
11847 missing file produces an effect hard or impossible to
11848 achieve in another way, so that a missing file needs to be
11849 kept that way if the user did it.
11853 Note that a package should <em>not</em> modify a
11854 <prgn>dpkg</prgn>-handled conffile in its maintainer
11855 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11856 the user confusing and possibly dangerous options for
11857 conffile update when the package is upgraded.</p>
11860 <sect><heading>Fully-featured maintainer script configuration
11865 For files which contain site-specific information such as
11866 the hostname and networking details and so forth, it is
11867 better to create the file in the package's
11868 <prgn>postinst</prgn> script.
11872 This will typically involve examining the state of the rest
11873 of the system to determine values and other information, and
11874 may involve prompting the user for some information which
11875 can't be obtained some other way.
11879 When using this method there are a couple of important
11880 issues which should be considered:
11884 If you discover a bug in the program which generates the
11885 configuration file, or if the format of the file changes
11886 from one version to the next, you will have to arrange for
11887 the postinst script to do something sensible - usually this
11888 will mean editing the installed configuration file to remove
11889 the problem or change the syntax. You will have to do this
11890 very carefully, since the user may have changed the file,
11891 perhaps to fix the very problem that your script is trying
11892 to deal with - you will have to detect these situations and
11893 deal with them correctly.
11897 If you do go down this route it's probably a good idea to
11898 make the program that generates the configuration file(s) a
11899 separate program in <file>/usr/sbin</file>, by convention called
11900 <file><var>package</var>config</file> and then run that if
11901 appropriate from the post-installation script. The
11902 <tt><var>package</var>config</tt> program should not
11903 unquestioningly overwrite an existing configuration - if its
11904 mode of operation is geared towards setting up a package for
11905 the first time (rather than any arbitrary reconfiguration
11906 later) you should have it check whether the configuration
11907 already exists, and require a <tt>--force</tt> flag to
11908 overwrite it.</p></sect>
11911 <appendix id="pkg-alternatives"><heading>Alternative versions of
11912 an interface - <prgn>update-alternatives</prgn> (from old
11917 When several packages all provide different versions of the
11918 same program or file it is useful to have the system select a
11919 default, but to allow the system administrator to change it
11920 and have their decisions respected.
11924 For example, there are several versions of the <prgn>vi</prgn>
11925 editor, and there is no reason to prevent all of them from
11926 being installed at once, each under their own name
11927 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11928 Nevertheless it is desirable to have the name <tt>vi</tt>
11929 refer to something, at least by default.
11933 If all the packages involved cooperate, this can be done with
11934 <prgn>update-alternatives</prgn>.
11938 Each package provides its own version under its own name, and
11939 calls <prgn>update-alternatives</prgn> in its postinst to
11940 register its version (and again in its prerm to deregister
11945 See the man page <manref name="update-alternatives"
11946 section="8"> for details.
11950 If <prgn>update-alternatives</prgn> does not seem appropriate
11951 you may wish to consider using diversions instead.</p>
11954 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11955 package's version of a file (from old Packaging Manual)
11959 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11960 when it reinstalls the package it belongs to, and to have it
11961 put the file from the package somewhere else instead.
11965 This can be used locally to override a package's version of a
11966 file, or by one package to override another's version (or
11967 provide a wrapper for it).
11971 Before deciding to use a diversion, read <ref
11972 id="pkg-alternatives"> to see if you really want a diversion
11973 rather than several alternative versions of a program.
11977 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11978 and updated by a special program <prgn>dpkg-divert</prgn>.
11979 Please see <manref name="dpkg-divert" section="8"> for full
11980 details of its operation.
11984 When a package wishes to divert a file from another, it should
11985 call <prgn>dpkg-divert</prgn> in its preinst to add the
11986 diversion and rename the existing file. For example,
11987 supposing that a <prgn>smailwrapper</prgn> package wishes to
11988 install a wrapper around <file>/usr/sbin/smail</file>:
11990 dpkg-divert --package smailwrapper --add --rename \
11991 --divert /usr/sbin/smail.real /usr/sbin/smail
11992 </example> The <tt>--package smailwrapper</tt> ensures that
11993 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11994 can bypass the diversion and get installed as the true version.
11995 It's safe to add the diversion unconditionally on upgrades since
11996 it will be left unchanged if it already exists, but
11997 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11998 message, make the command conditional on the version from which
11999 the package is being upgraded:
12001 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12002 dpkg-divert --package smailwrapper --add --rename \
12003 --divert /usr/sbin/smail.real /usr/sbin/smail
12005 </example> where <tt>1.0-2</tt> is the version at which the
12006 diversion was first added to the package. Running the command
12007 during abort-upgrade is pointless but harmless.
12011 The postrm has to do the reverse:
12013 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12014 dpkg-divert --package smailwrapper --remove --rename \
12015 --divert /usr/sbin/smail.real /usr/sbin/smail
12017 </example> If the diversion was added at a particular version, the
12018 postrm should also handle the failure case of upgrading from an
12019 older version (unless the older version is so old that direct
12020 upgrades are no longer supported):
12022 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12023 dpkg-divert --package smailwrapper --remove --rename \
12024 --divert /usr/sbin/smail.real /usr/sbin/smail
12026 </example> where <tt>1.0-2</tt> is the version at which the
12027 diversion was first added to the package. The postrm should not
12028 remove the diversion on upgrades both because there's no reason to
12029 remove the diversion only to immediately re-add it and since the
12030 postrm of the old package is run after unpacking so the removal of
12031 the diversion will fail.
12035 Do not attempt to divert a file which is vitally important for
12036 the system's operation - when using <prgn>dpkg-divert</prgn>
12037 there is a time, after it has been diverted but before
12038 <prgn>dpkg</prgn> has installed the new version, when the file
12039 does not exist.</p>
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