1 <!doctype debiandoc system [
2 <!-- include version information so we don't have to hard code it
3 within the document -->
4 <!entity % versiondata SYSTEM "version.ent"> %versiondata;
5 <!-- current Debian changes file format -->
6 <!entity changesversion "1.8">
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> (required),
1992 <tt>build-indep</tt> (required)
1996 The <tt>build-arch</tt> target must
1997 perform all the configuration and compilation required for
1998 producing all architecture-dependant binary packages
1999 (those packages for which the body of the
2000 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2001 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2002 target must perform all the configuration
2003 and compilation required for producing all
2004 architecture-independent binary packages (those packages
2005 for which the body of the <tt>Architecture</tt> field
2006 in <tt>debian/control</tt> is <tt>all</tt>).
2007 The <tt>build</tt> target
2008 should either depend on those targets or take the same
2009 actions as invoking those targets would perform.<footnote>
2010 This split allows binary-only builds to not install the
2011 dependencies required for the <tt>build-indep</tt>
2012 target and skip any resource-intensive build tasks that
2013 are only required when building architecture-independent
2019 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2020 must not do anything that might require root privilege.
2024 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2025 (required), <tt>binary-indep</tt> (required)
2029 The <tt>binary</tt> target must be all that is
2030 necessary for the user to build the binary package(s)
2031 produced from this source package. It is
2032 split into two parts: <prgn>binary-arch</prgn> builds
2033 the binary packages which are specific to a particular
2034 architecture, and <tt>binary-indep</tt> builds
2035 those which are not.
2038 <tt>binary</tt> may be (and commonly is) a target with
2039 no commands which simply depends on
2040 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2043 Both <tt>binary-*</tt> targets should depend on the
2044 <tt>build</tt> target, or on the appropriate
2045 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2046 provided, so that the package is built if it has not
2047 been already. It should then create the relevant
2048 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2049 make their control files and <prgn>dpkg-deb</prgn> to
2050 build them and place them in the parent of the top
2055 Both the <tt>binary-arch</tt> and
2056 <tt>binary-indep</tt> targets <em>must</em> exist.
2057 If one of them has nothing to do (which will always be
2058 the case if the source generates only a single binary
2059 package, whether architecture-dependent or not), it
2060 must still exist and must always succeed.
2064 The <tt>binary</tt> targets must be invoked as
2066 The <prgn>fakeroot</prgn> package often allows one
2067 to build a package correctly even without being
2073 <tag><tt>clean</tt> (required)</tag>
2076 This must undo any effects that the <tt>build</tt>
2077 and <tt>binary</tt> targets may have had, except
2078 that it should leave alone any output files created in
2079 the parent directory by a run of a <tt>binary</tt>
2084 If a <tt>build</tt> file is touched at the end of
2085 the <tt>build</tt> target, as suggested above, it
2086 should be removed as the first action that
2087 <tt>clean</tt> performs, so that running
2088 <tt>build</tt> again after an interrupted
2089 <tt>clean</tt> doesn't think that everything is
2094 The <tt>clean</tt> target may need to be
2095 invoked as root if <tt>binary</tt> has been
2096 invoked since the last <tt>clean</tt>, or if
2097 <tt>build</tt> has been invoked as root (since
2098 <tt>build</tt> may create directories, for
2103 <tag><tt>get-orig-source</tt> (optional)</tag>
2106 This target fetches the most recent version of the
2107 original source package from a canonical archive site
2108 (via FTP or WWW, for example), does any necessary
2109 rearrangement to turn it into the original source
2110 tar file format described below, and leaves it in the
2115 This target may be invoked in any directory, and
2116 should take care to clean up any temporary files it
2121 This target is optional, but providing it if
2122 possible is a good idea.
2126 <tag><tt>patch</tt> (optional)</tag>
2129 This target performs whatever additional actions are
2130 required to make the source ready for editing (unpacking
2131 additional upstream archives, applying patches, etc.).
2132 It is recommended to be implemented for any package where
2133 <tt>dpkg-source -x</tt> does not result in source ready
2134 for additional modification. See
2135 <ref id="readmesource">.
2141 The <tt>build</tt>, <tt>binary</tt> and
2142 <tt>clean</tt> targets must be invoked with the current
2143 directory being the package's top-level directory.
2148 Additional targets may exist in <file>debian/rules</file>,
2149 either as published or undocumented interfaces or for the
2150 package's internal use.
2154 The architectures we build on and build for are determined
2155 by <prgn>make</prgn> variables using the
2156 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2157 You can determine the Debian architecture and the GNU style
2158 architecture specification string for the build architecture as
2159 well as for the host architecture. The build architecture is
2160 the architecture on which <file>debian/rules</file> is run and
2161 the package build is performed. The host architecture is the
2162 architecture on which the resulting package will be installed
2163 and run. These are normally the same, but may be different in
2164 the case of cross-compilation (building packages for one
2165 architecture on machines of a different architecture).
2169 Here is a list of supported <prgn>make</prgn> variables:
2170 <list compact="compact">
2172 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2175 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2178 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2181 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2182 specification string)
2185 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2186 <tt>DEB_*_GNU_TYPE</tt>)
2189 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2190 <tt>DEB_*_GNU_TYPE</tt>)
2192 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2193 the build architecture or <tt>HOST</tt> for specification of the
2198 Backward compatibility can be provided in the rules file
2199 by setting the needed variables to suitable default
2200 values; please refer to the documentation of
2201 <prgn>dpkg-architecture</prgn> for details.
2205 It is important to understand that the <tt>DEB_*_ARCH</tt>
2206 string only determines which Debian architecture we are
2207 building on or for. It should not be used to get the CPU
2208 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2209 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2210 GNU style variables should generally only be used with upstream
2214 <sect1 id="debianrules-options">
2215 <heading><file>debian/rules</file> and
2216 <tt>DEB_BUILD_OPTIONS</tt></heading>
2219 Supporting the standardized environment variable
2220 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2221 contain several flags to change how a package is compiled and
2222 built. Each flag must be in the form <var>flag</var> or
2223 <var>flag</var>=<var>options</var>. If multiple flags are
2224 given, they must be separated by whitespace.<footnote>
2225 Some packages support any delimiter, but whitespace is the
2226 easiest to parse inside a makefile and avoids ambiguity with
2227 flag values that contain commas.
2229 <var>flag</var> must start with a lowercase letter
2230 (<tt>a-z</tt>) and consist only of lowercase letters,
2231 numbers (<tt>0-9</tt>), and the characters
2232 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2233 <var>options</var> must not contain whitespace. The same
2234 tag should not be given multiple times with conflicting
2235 values. Package maintainers may assume that
2236 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2240 The meaning of the following tags has been standardized:
2244 This tag says to not run any build-time test suite
2245 provided by the package.
2249 The presence of this tag means that the package should
2250 be compiled with a minimum of optimization. For C
2251 programs, it is best to add <tt>-O0</tt> to
2252 <tt>CFLAGS</tt> (although this is usually the default).
2253 Some programs might fail to build or run at this level
2254 of optimization; it may be necessary to use
2255 <tt>-O1</tt>, for example.
2259 This tag means that the debugging symbols should not be
2260 stripped from the binary during installation, so that
2261 debugging information may be included in the package.
2263 <tag>parallel=n</tag>
2265 This tag means that the package should be built using up
2266 to <tt>n</tt> parallel processes if the package build
2267 system supports this.<footnote>
2268 Packages built with <tt>make</tt> can often implement
2269 this by passing the <tt>-j</tt><var>n</var> option to
2272 If the package build system does not support parallel
2273 builds, this string must be ignored. If the package
2274 build system only supports a lower level of concurrency
2275 than <var>n</var>, the package should be built using as
2276 many parallel processes as the package build system
2277 supports. It is up to the package maintainer to decide
2278 whether the package build times are long enough and the
2279 package build system is robust enough to make supporting
2280 parallel builds worthwhile.
2286 Unknown flags must be ignored by <file>debian/rules</file>.
2290 The following makefile snippet is an example of how one may
2291 implement the build options; you will probably have to
2292 massage this example in order to make it work for your
2294 <example compact="compact">
2297 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2298 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2299 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2300 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2302 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2307 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2308 INSTALL_PROGRAM += -s
2310 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2311 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2312 MAKEFLAGS += -j$(NUMJOBS)
2317 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2318 # Code to run the package test suite.
2325 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2326 <sect id="substvars">
2327 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2330 When <prgn>dpkg-gencontrol</prgn>
2331 generates <qref id="binarycontrolfiles">binary package control
2332 files</qref> (<file>DEBIAN/control</file>), it performs variable
2333 substitutions on its output just before writing it. Variable
2334 substitutions have the form <tt>${<var>variable</var>}</tt>.
2335 The optional file <file>debian/substvars</file> contains
2336 variable substitutions to be used; variables can also be set
2337 directly from <file>debian/rules</file> using the <tt>-V</tt>
2338 option to the source packaging commands, and certain predefined
2339 variables are also available.
2343 The <file>debian/substvars</file> file is usually generated and
2344 modified dynamically by <file>debian/rules</file> targets, in
2345 which case it must be removed by the <tt>clean</tt> target.
2349 See <manref name="deb-substvars" section="5"> for full
2350 details about source variable substitutions, including the
2351 format of <file>debian/substvars</file>.</p>
2354 <sect id="debianwatch">
2355 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2358 This is an optional, recommended configuration file for the
2359 <tt>uscan</tt> utility which defines how to automatically scan
2360 ftp or http sites for newly available updates of the
2361 package. This is used
2362 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2363 tools to help with quality control and maintenance of the
2364 distribution as a whole.
2369 <sect id="debianfiles">
2370 <heading>Generated files list: <file>debian/files</file></heading>
2373 This file is not a permanent part of the source tree; it
2374 is used while building packages to record which files are
2375 being generated. <prgn>dpkg-genchanges</prgn> uses it
2376 when it generates a <file>.changes</file> file.
2380 It should not exist in a shipped source package, and so it
2381 (and any backup files or temporary files such as
2382 <file>files.new</file><footnote>
2383 <file>files.new</file> is used as a temporary file by
2384 <prgn>dpkg-gencontrol</prgn> and
2385 <prgn>dpkg-distaddfile</prgn> - they write a new
2386 version of <tt>files</tt> here before renaming it,
2387 to avoid leaving a corrupted copy if an error
2389 </footnote>) should be removed by the
2390 <tt>clean</tt> target. It may also be wise to
2391 ensure a fresh start by emptying or removing it at the
2392 start of the <tt>binary</tt> target.
2396 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2397 package, it adds an entry to <file>debian/files</file> for the
2398 <file>.deb</file> file that will be created when <tt>dpkg-deb
2399 --build</tt> is run for that binary package. So for most
2400 packages all that needs to be done with this file is to
2401 delete it in the <tt>clean</tt> target.
2405 If a package upload includes files besides the source
2406 package and any binary packages whose control files were
2407 made with <prgn>dpkg-gencontrol</prgn> then they should be
2408 placed in the parent of the package's top-level directory
2409 and <prgn>dpkg-distaddfile</prgn> should be called to add
2410 the file to the list in <file>debian/files</file>.</p>
2413 <sect id="embeddedfiles">
2414 <heading>Convenience copies of code</heading>
2417 Some software packages include in their distribution convenience
2418 copies of code from other software packages, generally so that
2419 users compiling from source don't have to download multiple
2420 packages. Debian packages should not make use of these
2421 convenience copies unless the included package is explicitly
2422 intended to be used in this way.<footnote>
2423 For example, parts of the GNU build system work like this.
2425 If the included code is already in the Debian archive in the
2426 form of a library, the Debian packaging should ensure that
2427 binary packages reference the libraries already in Debian and
2428 the convenience copy is not used. If the included code is not
2429 already in Debian, it should be packaged separately as a
2430 prerequisite if possible.
2432 Having multiple copies of the same code in Debian is
2433 inefficient, often creates either static linking or shared
2434 library conflicts, and, most importantly, increases the
2435 difficulty of handling security vulnerabilities in the
2441 <sect id="readmesource">
2442 <heading>Source package handling:
2443 <file>debian/README.source</file></heading>
2446 If running <prgn>dpkg-source -x</prgn> on a source package
2447 doesn't produce the source of the package, ready for editing,
2448 and allow one to make changes and run
2449 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2450 without taking any additional steps, creating a
2451 <file>debian/README.source</file> documentation file is
2452 recommended. This file should explain how to do all of the
2455 <item>Generate the fully patched source, in a form ready for
2456 editing, that would be built to create Debian
2457 packages. Doing this with a <tt>patch</tt> target in
2458 <file>debian/rules</file> is recommended; see
2459 <ref id="debianrules">.</item>
2460 <item>Modify the source and save those modifications so that
2461 they will be applied when building the package.</item>
2462 <item>Remove source modifications that are currently being
2463 applied when building the package.</item>
2464 <item>Optionally, document what steps are necessary to
2465 upgrade the Debian source package to a new upstream version,
2466 if applicable.</item>
2468 This explanation should include specific commands and mention
2469 any additional required Debian packages. It should not assume
2470 familiarity with any specific Debian packaging system or patch
2475 This explanation may refer to a documentation file installed by
2476 one of the package's build dependencies provided that the
2477 referenced documentation clearly explains these tasks and is not
2478 a general reference manual.
2482 <file>debian/README.source</file> may also include any other
2483 information that would be helpful to someone modifying the
2484 source package. Even if the package doesn't fit the above
2485 description, maintainers are encouraged to document in a
2486 <file>debian/README.source</file> file any source package with a
2487 particularly complex or unintuitive source layout or build
2488 system (for example, a package that builds the same source
2489 multiple times to generate different binary packages).
2495 <chapt id="controlfields">
2496 <heading>Control files and their fields</heading>
2499 The package management system manipulates data represented in
2500 a common format, known as <em>control data</em>, stored in
2501 <em>control files</em>.
2502 Control files are used for source packages, binary packages and
2503 the <file>.changes</file> files which control the installation
2504 of uploaded files<footnote>
2505 <prgn>dpkg</prgn>'s internal databases are in a similar
2510 <sect id="controlsyntax">
2511 <heading>Syntax of control files</heading>
2514 A control file consists of one or more paragraphs of
2516 The paragraphs are also sometimes referred to as stanzas.
2518 The paragraphs are separated by empty lines. Parsers may accept
2519 lines consisting solely of spaces and tabs as paragraph
2520 separators, but control files should use empty lines. Some control
2521 files allow only one paragraph; others allow several, in
2522 which case each paragraph usually refers to a different
2523 package. (For example, in source packages, the first
2524 paragraph refers to the source package, and later paragraphs
2525 refer to binary packages generated from the source.) The
2526 ordering of the paragraphs in control files is significant.
2530 Each paragraph consists of a series of data fields. Each field
2531 consists of the field name followed by a colon and then the
2532 data/value associated with that field. The field name is
2533 composed of US-ASCII characters excluding control characters,
2534 space, and colon (i.e., characters in the ranges 33-57 and
2535 59-126, inclusive). Field names must not begin with the comment
2536 character, <tt>#</tt>.
2540 The field ends at the end of the line or at the end of the last
2541 continuation line (see below). Horizontal whitespace (spaces
2542 and tabs) may occur immediately before or after the value and is
2543 ignored there; it is conventional to put a single space after
2544 the colon. For example, a field might be:
2545 <example compact="compact">
2548 the field name is <tt>Package</tt> and the field value
2553 A paragraph must not contain more than one instance of a
2554 particular field name.
2558 There are three types of fields:
2562 The field, including its value, must be a single line. Folding
2563 of the field is not permitted. This is the default field type
2564 if the definition of the field does not specify a different
2569 The value of a folded field is a logical line that may span
2570 several lines. The lines after the first are called
2571 continuation lines and must start with a space or a tab.
2572 Whitespace, including any newlines, is not significant in the
2573 field values of folded fields.<footnote>
2574 This folding method is similar to RFC 5322, allowing control
2575 files that contain only one paragraph and no multiline fields
2576 to be read by parsers written for RFC 5322.
2579 <tag>multiline</tag>
2581 The value of a multiline field may comprise multiple continuation
2582 lines. The first line of the value, the part on the same line as
2583 the field name, often has special significance or may have to be
2584 empty. Other lines are added following the same syntax as the
2585 continuation lines of the folded fields. Whitespace, including newlines,
2586 is significant in the values of multiline fields.
2592 Whitespace must not appear
2593 inside names (of packages, architectures, files or anything
2594 else) or version numbers, or between the characters of
2595 multi-character version relationships.
2599 The presence and purpose of a field, and the syntax of its
2600 value may differ between types of control files.
2604 Field names are not case-sensitive, but it is usual to
2605 capitalize the field names using mixed case as shown below.
2606 Field values are case-sensitive unless the description of the
2607 field says otherwise.
2611 Paragraph separators (empty lines) and lines consisting only of
2612 spaces and tabs are not allowed within field values or between
2613 fields. Empty lines in field values are usually escaped by
2614 representing them by a space followed by a dot.
2618 Lines starting with # without any preceding whitespace are comments
2619 lines that are only permitted in source package control files
2620 (<file>debian/control</file>). These comment lines are ignored, even
2621 between two continuation lines. They do not end logical lines.
2625 All control files must be encoded in UTF-8.
2629 <sect id="sourcecontrolfiles">
2630 <heading>Source package control files -- <file>debian/control</file></heading>
2633 The <file>debian/control</file> file contains the most vital
2634 (and version-independent) information about the source package
2635 and about the binary packages it creates.
2639 The first paragraph of the control file contains information about
2640 the source package in general. The subsequent sets each describe a
2641 binary package that the source tree builds.
2645 The fields in the general paragraph (the first one, for the source
2648 <list compact="compact">
2649 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2651 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2652 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2653 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2654 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2655 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2656 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2657 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2662 The fields in the binary package paragraphs are:
2664 <list compact="compact">
2665 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2666 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2667 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2668 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2669 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2670 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2671 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2672 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2673 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2678 The syntax and semantics of the fields are described below.
2682 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2683 generate control files for binary packages (see below), by
2684 <prgn>dpkg-genchanges</prgn> to generate the
2685 <file>.changes</file> file to accompany the upload, and by
2686 <prgn>dpkg-source</prgn> when it creates the
2687 <file>.dsc</file> source control file as part of a source
2688 archive. Some fields are folded in <file>debian/control</file>,
2689 but not in any other control
2690 file. These tools are responsible for removing the line
2691 breaks from such fields when using fields from
2692 <file>debian/control</file> to generate other control files.
2696 The fields here may contain variable references - their
2697 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2698 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2699 when they generate output control files.
2700 See <ref id="substvars"> for details.
2704 <sect id="binarycontrolfiles">
2705 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2708 The <file>DEBIAN/control</file> file contains the most vital
2709 (and version-dependent) information about a binary package. It
2710 consists of a single paragraph.
2714 The fields in this file are:
2716 <list compact="compact">
2717 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2718 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2719 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2720 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2721 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2722 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2723 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2724 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2725 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2726 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2727 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2728 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2729 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2734 <sect id="debiansourcecontrolfiles">
2735 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2738 This file consists of a single paragraph, possibly surrounded by
2739 a PGP signature. The fields of that paragraph are listed below.
2740 Their syntax is described above, in <ref id="controlsyntax">.
2742 <list compact="compact">
2743 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2744 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2745 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2746 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2747 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2748 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2749 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2750 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2751 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2752 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2753 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2754 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2755 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2756 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2761 The Debian source control file is generated by
2762 <prgn>dpkg-source</prgn> when it builds the source
2763 archive, from other files in the source package,
2764 described above. When unpacking, it is checked against
2765 the files and directories in the other parts of the
2771 <sect id="debianchangesfiles">
2772 <heading>Debian changes files -- <file>.changes</file></heading>
2775 The <file>.changes</file> files are used by the Debian archive
2776 maintenance software to process updates to packages. They
2777 consist of a single paragraph, possibly surrounded by a PGP
2778 signature. That paragraph contains information from the
2779 <file>debian/control</file> file and other data about the
2780 source package gathered via <file>debian/changelog</file>
2781 and <file>debian/rules</file>.
2785 <file>.changes</file> files have a format version that is
2786 incremented whenever the documented fields or their meaning
2787 change. This document describes format &changesversion;.
2791 The fields in this file are:
2793 <list compact="compact">
2794 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2795 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2796 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2797 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2798 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2799 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2800 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2801 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2802 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2803 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2804 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2805 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2806 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2807 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2808 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2814 <sect id="controlfieldslist">
2815 <heading>List of fields</heading>
2817 <sect1 id="f-Source">
2818 <heading><tt>Source</tt></heading>
2821 This field identifies the source package name.
2825 In <file>debian/control</file> or a <file>.dsc</file> file,
2826 this field must contain only the name of the source package.
2830 In a binary package control file or a <file>.changes</file>
2831 file, the source package name may be followed by a version
2832 number in parentheses<footnote>
2833 It is customary to leave a space after the package name
2834 if a version number is specified.
2836 This version number may be omitted (and is, by
2837 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2838 the <tt>Version</tt> field of the binary package in
2839 question. The field itself may be omitted from a binary
2840 package control file when the source package has the same
2841 name and version as the binary package.
2845 Package names (both source and binary,
2846 see <ref id="f-Package">) must consist only of lower case
2847 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2848 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2849 (<tt>.</tt>). They must be at least two characters long and
2850 must start with an alphanumeric character.
2854 <sect1 id="f-Maintainer">
2855 <heading><tt>Maintainer</tt></heading>
2858 The package maintainer's name and email address. The name
2859 must come first, then the email address inside angle
2860 brackets <tt><></tt> (in RFC822 format).
2864 If the maintainer's name contains a full stop then the
2865 whole field will not work directly as an email address due
2866 to a misfeature in the syntax specified in RFC822; a
2867 program using this field as an address must check for this
2868 and correct the problem if necessary (for example by
2869 putting the name in round brackets and moving it to the
2870 end, and bringing the email address forward).
2874 See <ref id="maintainer"> for additional requirements and
2875 information about package maintainers.
2879 <sect1 id="f-Uploaders">
2880 <heading><tt>Uploaders</tt></heading>
2883 List of the names and email addresses of co-maintainers of the
2884 package, if any. If the package has other maintainers besides
2885 the one named in the <qref id="f-Maintainer">Maintainer
2886 field</qref>, their names and email addresses should be listed
2887 here. The format of each entry is the same as that of the
2888 Maintainer field, and multiple entries must be comma
2893 This is normally an optional field, but if
2894 the <tt>Maintainer</tt> control field names a group of people
2895 and a shared email address, the <tt>Uploaders</tt> field must
2896 be present and must contain at least one human with their
2897 personal email address.
2901 The Uploaders field in <file>debian/control</file> can be folded.
2905 <sect1 id="f-Changed-By">
2906 <heading><tt>Changed-By</tt></heading>
2909 The name and email address of the person who prepared this
2910 version of the package, usually a maintainer. The syntax is
2911 the same as for the <qref id="f-Maintainer">Maintainer
2916 <sect1 id="f-Section">
2917 <heading><tt>Section</tt></heading>
2920 This field specifies an application area into which the package
2921 has been classified. See <ref id="subsections">.
2925 When it appears in the <file>debian/control</file> file,
2926 it gives the value for the subfield of the same name in
2927 the <tt>Files</tt> field of the <file>.changes</file> file.
2928 It also gives the default for the same field in the binary
2933 <sect1 id="f-Priority">
2934 <heading><tt>Priority</tt></heading>
2937 This field represents how important it is that the user
2938 have the package installed. See <ref id="priorities">.
2942 When it appears in the <file>debian/control</file> file,
2943 it gives the value for the subfield of the same name in
2944 the <tt>Files</tt> field of the <file>.changes</file> file.
2945 It also gives the default for the same field in the binary
2950 <sect1 id="f-Package">
2951 <heading><tt>Package</tt></heading>
2954 The name of the binary package.
2958 Binary package names must follow the same syntax and
2959 restrictions as source package names. See <ref id="f-Source">
2964 <sect1 id="f-Architecture">
2965 <heading><tt>Architecture</tt></heading>
2968 Depending on context and the control file used, the
2969 <tt>Architecture</tt> field can include the following sets of
2973 A unique single word identifying a Debian machine
2974 architecture as described in <ref id="arch-spec">.
2977 An architecture wildcard identifying a set of Debian
2978 machine architectures, see <ref id="arch-wildcard-spec">.
2979 <tt>any</tt> matches all Debian machine architectures
2980 and is the most frequently used.
2983 <tt>all</tt>, which indicates an
2984 architecture-independent package.
2987 <tt>source</tt>, which indicates a source package.
2993 In the main <file>debian/control</file> file in the source
2994 package, this field may contain the special
2995 value <tt>all</tt>, the special architecture
2996 wildcard <tt>any</tt>, or a list of specific and wildcard
2997 architectures separated by spaces. If <tt>all</tt>
2998 or <tt>any</tt> appears, that value must be the entire
2999 contents of the field. Most packages will use
3000 either <tt>all</tt> or <tt>any</tt>.
3004 Specifying a specific list of architectures indicates that the
3005 source will build an architecture-dependent package only on
3006 architectures included in the list. Specifying a list of
3007 architecture wildcards indicates that the source will build an
3008 architecture-dependent package on only those architectures
3009 that match any of the specified architecture wildcards.
3010 Specifying a list of architectures or architecture wildcards
3011 other than <tt>any</tt> is for the minority of cases where a
3012 program is not portable or is not useful on some
3013 architectures. Where possible, the program should be made
3018 In the Debian source control file <file>.dsc</file>, this
3019 field contains a list of architectures and architecture
3020 wildcards separated by spaces. When the list contains the
3021 architecture wildcard <tt>any</tt>, the only other value
3022 allowed in the list is <tt>all</tt>.
3026 The list may include (or consist solely of) the special
3027 value <tt>all</tt>. In other words, in <file>.dsc</file>
3028 files unlike the <file>debian/control</file>, <tt>all</tt> may
3029 occur in combination with specific architectures.
3030 The <tt>Architecture</tt> field in the Debian source control
3031 file <file>.dsc</file> is generally constructed from
3032 the <tt>Architecture</tt> fields in
3033 the <file>debian/control</file> in the source package.
3037 Specifying only <tt>any</tt> indicates that the source package
3038 isn't dependent on any particular architecture and should
3039 compile fine on any one. The produced binary package(s)
3040 will be specific to whatever the current build architecture is.
3044 Specifying only <tt>all</tt> indicates that the source package
3045 will only build architecture-independent packages.
3049 Specifying <tt>any all</tt> indicates that the source package
3050 isn't dependent on any particular architecture. The set of
3051 produced binary packages will include at least one
3052 architecture-dependant package and one architecture-independent
3057 Specifying a list of architectures or architecture wildcards
3058 indicates that the source will build an architecture-dependent
3059 package, and will only work correctly on the listed or
3060 matching architectures. If the source package also builds at
3061 least one architecture-independent package, <tt>all</tt> will
3062 also be included in the list.
3066 In a <file>.changes</file> file, the <tt>Architecture</tt>
3067 field lists the architecture(s) of the package(s) currently
3068 being uploaded. This will be a list; if the source for the
3069 package is also being uploaded, the special
3070 entry <tt>source</tt> is also present. <tt>all</tt> will be
3071 present if any architecture-independent packages are being
3072 uploaded. Architecture wildcards such as <tt>any</tt> must
3073 never occur in the <tt>Architecture</tt> field in
3074 the <file>.changes</file> file.
3078 See <ref id="debianrules"> for information on how to get
3079 the architecture for the build process.
3083 <sect1 id="f-Essential">
3084 <heading><tt>Essential</tt></heading>
3087 This is a boolean field which may occur only in the
3088 control file of a binary package or in a per-package fields
3089 paragraph of a source package control file.
3093 If set to <tt>yes</tt> then the package management system
3094 will refuse to remove the package (upgrading and replacing
3095 it is still possible). The other possible value is <tt>no</tt>,
3096 which is the same as not having the field at all.
3101 <heading>Package interrelationship fields:
3102 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3103 <tt>Recommends</tt>, <tt>Suggests</tt>,
3104 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3105 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3109 These fields describe the package's relationships with
3110 other packages. Their syntax and semantics are described
3111 in <ref id="relationships">.</p>
3114 <sect1 id="f-Standards-Version">
3115 <heading><tt>Standards-Version</tt></heading>
3118 The most recent version of the standards (the policy
3119 manual and associated texts) with which the package
3124 The version number has four components: major and minor
3125 version number and major and minor patch level. When the
3126 standards change in a way that requires every package to
3127 change the major number will be changed. Significant
3128 changes that will require work in many packages will be
3129 signaled by a change to the minor number. The major patch
3130 level will be changed for any change to the meaning of the
3131 standards, however small; the minor patch level will be
3132 changed when only cosmetic, typographical or other edits
3133 are made which neither change the meaning of the document
3134 nor affect the contents of packages.
3138 Thus only the first three components of the policy version
3139 are significant in the <em>Standards-Version</em> control
3140 field, and so either these three components or all four
3141 components may be specified.<footnote>
3142 In the past, people specified the full version number
3143 in the Standards-Version field, for example "2.3.0.0".
3144 Since minor patch-level changes don't introduce new
3145 policy, it was thought it would be better to relax
3146 policy and only require the first 3 components to be
3147 specified, in this example "2.3.0". All four
3148 components may still be used if someone wishes to do so.
3154 <sect1 id="f-Version">
3155 <heading><tt>Version</tt></heading>
3158 The version number of a package. The format is:
3159 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3163 The three components here are:
3165 <tag><var>epoch</var></tag>
3168 This is a single (generally small) unsigned integer. It
3169 may be omitted, in which case zero is assumed. If it is
3170 omitted then the <var>upstream_version</var> may not
3175 It is provided to allow mistakes in the version numbers
3176 of older versions of a package, and also a package's
3177 previous version numbering schemes, to be left behind.
3181 <tag><var>upstream_version</var></tag>
3184 This is the main part of the version number. It is
3185 usually the version number of the original ("upstream")
3186 package from which the <file>.deb</file> file has been made,
3187 if this is applicable. Usually this will be in the same
3188 format as that specified by the upstream author(s);
3189 however, it may need to be reformatted to fit into the
3190 package management system's format and comparison
3195 The comparison behavior of the package management system
3196 with respect to the <var>upstream_version</var> is
3197 described below. The <var>upstream_version</var>
3198 portion of the version number is mandatory.
3202 The <var>upstream_version</var> may contain only
3203 alphanumerics<footnote>
3204 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3206 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3207 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3208 tilde) and should start with a digit. If there is no
3209 <var>debian_revision</var> then hyphens are not allowed;
3210 if there is no <var>epoch</var> then colons are not
3215 <tag><var>debian_revision</var></tag>
3218 This part of the version number specifies the version of
3219 the Debian package based on the upstream version. It
3220 may contain only alphanumerics and the characters
3221 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3222 tilde) and is compared in the same way as the
3223 <var>upstream_version</var> is.
3227 It is optional; if it isn't present then the
3228 <var>upstream_version</var> may not contain a hyphen.
3229 This format represents the case where a piece of
3230 software was written specifically to be a Debian
3231 package, where the Debian package source must always
3232 be identical to the pristine source and therefore no
3233 revision indication is required.
3237 It is conventional to restart the
3238 <var>debian_revision</var> at <tt>1</tt> each time the
3239 <var>upstream_version</var> is increased.
3243 The package management system will break the version
3244 number apart at the last hyphen in the string (if there
3245 is one) to determine the <var>upstream_version</var> and
3246 <var>debian_revision</var>. The absence of a
3247 <var>debian_revision</var> is equivalent to a
3248 <var>debian_revision</var> of <tt>0</tt>.
3255 When comparing two version numbers, first the <var>epoch</var>
3256 of each are compared, then the <var>upstream_version</var> if
3257 <var>epoch</var> is equal, and then <var>debian_revision</var>
3258 if <var>upstream_version</var> is also equal.
3259 <var>epoch</var> is compared numerically. The
3260 <var>upstream_version</var> and <var>debian_revision</var>
3261 parts are compared by the package management system using the
3262 following algorithm:
3266 The strings are compared from left to right.
3270 First the initial part of each string consisting entirely of
3271 non-digit characters is determined. These two parts (one of
3272 which may be empty) are compared lexically. If a difference
3273 is found it is returned. The lexical comparison is a
3274 comparison of ASCII values modified so that all the letters
3275 sort earlier than all the non-letters and so that a tilde
3276 sorts before anything, even the end of a part. For example,
3277 the following parts are in sorted order from earliest to
3278 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3279 <tt>a</tt>.<footnote>
3280 One common use of <tt>~</tt> is for upstream pre-releases.
3281 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3282 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3287 Then the initial part of the remainder of each string which
3288 consists entirely of digit characters is determined. The
3289 numerical values of these two parts are compared, and any
3290 difference found is returned as the result of the comparison.
3291 For these purposes an empty string (which can only occur at
3292 the end of one or both version strings being compared) counts
3297 These two steps (comparing and removing initial non-digit
3298 strings and initial digit strings) are repeated until a
3299 difference is found or both strings are exhausted.
3303 Note that the purpose of epochs is to allow us to leave behind
3304 mistakes in version numbering, and to cope with situations
3305 where the version numbering scheme changes. It is
3306 <em>not</em> intended to cope with version numbers containing
3307 strings of letters which the package management system cannot
3308 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3309 silly orderings.<footnote>
3310 The author of this manual has heard of a package whose
3311 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3312 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3318 <sect1 id="f-Description">
3319 <heading><tt>Description</tt></heading>
3322 In a source or binary control file, the <tt>Description</tt>
3323 field contains a description of the binary package, consisting
3324 of two parts, the synopsis or the short description, and the
3325 long description. It is a multiline field with the following
3331 Description: <single line synopsis>
3332 <extended description over several lines>
3337 The lines in the extended description can have these formats:
3343 Those starting with a single space are part of a paragraph.
3344 Successive lines of this form will be word-wrapped when
3345 displayed. The leading space will usually be stripped off.
3346 The line must contain at least one non-whitespace character.
3350 Those starting with two or more spaces. These will be
3351 displayed verbatim. If the display cannot be panned
3352 horizontally, the displaying program will line wrap them "hard"
3353 (i.e., without taking account of word breaks). If it can they
3354 will be allowed to trail off to the right. None, one or two
3355 initial spaces may be deleted, but the number of spaces
3356 deleted from each line will be the same (so that you can have
3357 indenting work correctly, for example). The line must
3358 contain at least one non-whitespace character.
3362 Those containing a single space followed by a single full stop
3363 character. These are rendered as blank lines. This is the
3364 <em>only</em> way to get a blank line<footnote>
3365 Completely empty lines will not be rendered as blank lines.
3366 Instead, they will cause the parser to think you're starting
3367 a whole new record in the control file, and will therefore
3368 likely abort with an error.
3373 Those containing a space, a full stop and some more characters.
3374 These are for future expansion. Do not use them.
3380 Do not use tab characters. Their effect is not predictable.
3384 See <ref id="descriptions"> for further information on this.
3388 In a <file>.changes</file> file, the <tt>Description</tt>
3389 field contains a summary of the descriptions for the packages
3390 being uploaded. For this case, the first line of the field
3391 value (the part on the same line as <tt>Description:</tt>) is
3392 always empty. It is a multiline field, with one
3393 line per package. Each line is
3394 indented by one space and contains the name of a binary
3395 package, a space, a hyphen (<tt>-</tt>), a space, and the
3396 short description line from that package.
3400 <sect1 id="f-Distribution">
3401 <heading><tt>Distribution</tt></heading>
3404 In a <file>.changes</file> file or parsed changelog output
3405 this contains the (space-separated) name(s) of the
3406 distribution(s) where this version of the package should
3407 be installed. Valid distributions are determined by the
3408 archive maintainers.<footnote>
3409 Example distribution names in the Debian archive used in
3410 <file>.changes</file> files are:
3411 <taglist compact="compact">
3412 <tag><em>unstable</em></tag>
3414 This distribution value refers to the
3415 <em>developmental</em> part of the Debian distribution
3416 tree. Most new packages, new upstream versions of
3417 packages and bug fixes go into the <em>unstable</em>
3421 <tag><em>experimental</em></tag>
3423 The packages with this distribution value are deemed
3424 by their maintainers to be high risk. Oftentimes they
3425 represent early beta or developmental packages from
3426 various sources that the maintainers want people to
3427 try, but are not ready to be a part of the other parts
3428 of the Debian distribution tree.
3433 Others are used for updating stable releases or for
3434 security uploads. More information is available in the
3435 Debian Developer's Reference, section "The Debian
3439 The Debian archive software only supports listing a single
3440 distribution. Migration of packages to other distributions is
3441 handled outside of the upload process.
3446 <heading><tt>Date</tt></heading>
3449 This field includes the date the package was built or last
3450 edited. It must be in the same format as the <var>date</var>
3451 in a <file>debian/changelog</file> entry.
3455 The value of this field is usually extracted from the
3456 <file>debian/changelog</file> file - see
3457 <ref id="dpkgchangelog">).
3461 <sect1 id="f-Format">
3462 <heading><tt>Format</tt></heading>
3465 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3466 files, this field declares the format version of that file.
3467 The syntax of the field value is the same as that of
3468 a <qref id="f-Version">package version number</qref> except
3469 that no epoch or Debian revision is allowed. The format
3470 described in this document is <tt>&changesversion;</tt>.
3474 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3475 Debian source control</qref> files, this field declares the
3476 format of the source package. The field value is used by
3477 programs acting on a source package to interpret the list of
3478 files in the source package and determine how to unpack it.
3479 The syntax of the field value is a numeric major revision, a
3480 period, a numeric minor revision, and then an optional subtype
3481 after whitespace, which if specified is an alphanumeric word
3482 in parentheses. The subtype is optional in the syntax but may
3483 be mandatory for particular source format revisions.
3485 The source formats currently supported by the Debian archive
3486 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3487 and <tt>3.0 (quilt)</tt>.
3492 <sect1 id="f-Urgency">
3493 <heading><tt>Urgency</tt></heading>
3496 This is a description of how important it is to upgrade to
3497 this version from previous ones. It consists of a single
3498 keyword taking one of the values <tt>low</tt>,
3499 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3500 <tt>critical</tt><footnote>
3501 Other urgency values are supported with configuration
3502 changes in the archive software but are not used in Debian.
3503 The urgency affects how quickly a package will be considered
3504 for inclusion into the <tt>testing</tt> distribution and
3505 gives an indication of the importance of any fixes included
3506 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3507 treated as synonymous.
3508 </footnote> (not case-sensitive) followed by an optional
3509 commentary (separated by a space) which is usually in
3510 parentheses. For example:
3513 Urgency: low (HIGH for users of diversions)
3519 The value of this field is usually extracted from the
3520 <file>debian/changelog</file> file - see
3521 <ref id="dpkgchangelog">.
3525 <sect1 id="f-Changes">
3526 <heading><tt>Changes</tt></heading>
3529 This multiline field contains the human-readable changes data, describing
3530 the differences between the last version and the current one.
3534 The first line of the field value (the part on the same line
3535 as <tt>Changes:</tt>) is always empty. The content of the
3536 field is expressed as continuation lines, with each line
3537 indented by at least one space. Blank lines must be
3538 represented by a line consisting only of a space and a full
3543 The value of this field is usually extracted from the
3544 <file>debian/changelog</file> file - see
3545 <ref id="dpkgchangelog">).
3549 Each version's change information should be preceded by a
3550 "title" line giving at least the version, distribution(s)
3551 and urgency, in a human-readable way.
3555 If data from several versions is being returned the entry
3556 for the most recent version should be returned first, and
3557 entries should be separated by the representation of a
3558 blank line (the "title" line may also be followed by the
3559 representation of a blank line).
3563 <sect1 id="f-Binary">
3564 <heading><tt>Binary</tt></heading>
3567 This folded field is a list of binary packages. Its syntax and
3568 meaning varies depending on the control file in which it
3573 When it appears in the <file>.dsc</file> file, it lists binary
3574 packages which a source package can produce, separated by
3576 A space after each comma is conventional.
3577 </footnote>. The source package
3578 does not necessarily produce all of these binary packages for
3579 every architecture. The source control file doesn't contain
3580 details of which architectures are appropriate for which of
3581 the binary packages.
3585 When it appears in a <file>.changes</file> file, it lists the
3586 names of the binary packages being uploaded, separated by
3587 whitespace (not commas).
3591 <sect1 id="f-Installed-Size">
3592 <heading><tt>Installed-Size</tt></heading>
3595 This field appears in the control files of binary packages,
3596 and in the <file>Packages</file> files. It gives an estimate
3597 of the total amount of disk space required to install the
3598 named package. Actual installed size may vary based on block
3599 size, file system properties, or actions taken by package
3604 The disk space is given as the integer value of the estimated
3605 installed size in bytes, divided by 1024 and rounded up.
3609 <sect1 id="f-Files">
3610 <heading><tt>Files</tt></heading>
3613 This field contains a list of files with information about
3614 each one. The exact information and syntax varies with
3619 In all cases, Files is a multiline field. The first line of
3620 the field value (the part on the same line as <tt>Files:</tt>)
3621 is always empty. The content of the field is expressed as
3622 continuation lines, one line per file. Each line must be
3623 indented by one space and contain a number of sub-fields,
3624 separated by spaces, as described below.
3628 In the <file>.dsc</file> file, each line contains the MD5
3629 checksum, size and filename of the tar file and (if
3630 applicable) diff file which make up the remainder of the
3631 source package<footnote>
3632 That is, the parts which are not the <tt>.dsc</tt>.
3633 </footnote>. For example:
3636 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3637 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3639 The exact forms of the filenames are described
3640 in <ref id="pkg-sourcearchives">.
3644 In the <file>.changes</file> file this contains one line per
3645 file being uploaded. Each line contains the MD5 checksum,
3646 size, section and priority and the filename. For example:
3649 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3650 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3651 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3652 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3654 The <qref id="f-Section">section</qref>
3655 and <qref id="f-Priority">priority</qref> are the values of
3656 the corresponding fields in the main source control file. If
3657 no section or priority is specified then <tt>-</tt> should be
3658 used, though section and priority values must be specified for
3659 new packages to be installed properly.
3663 The special value <tt>byhand</tt> for the section in a
3664 <tt>.changes</tt> file indicates that the file in question
3665 is not an ordinary package file and must by installed by
3666 hand by the distribution maintainers. If the section is
3667 <tt>byhand</tt> the priority should be <tt>-</tt>.
3671 If a new Debian revision of a package is being shipped and
3672 no new original source archive is being distributed the
3673 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3674 entry for the original source archive
3675 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3676 but the <file>.changes</file> file should leave it out. In
3677 this case the original source archive on the distribution
3678 site must match exactly, byte-for-byte, the original
3679 source archive which was used to generate the
3680 <file>.dsc</file> file and diff which are being uploaded.</p>
3683 <sect1 id="f-Closes">
3684 <heading><tt>Closes</tt></heading>
3687 A space-separated list of bug report numbers that the upload
3688 governed by the .changes file closes.
3692 <sect1 id="f-Homepage">
3693 <heading><tt>Homepage</tt></heading>
3696 The URL of the web site for this package, preferably (when
3697 applicable) the site from which the original source can be
3698 obtained and any additional upstream documentation or
3699 information may be found. The content of this field is a
3700 simple URL without any surrounding characters such as
3705 <sect1 id="f-Checksums">
3706 <heading><tt>Checksums-Sha1</tt>
3707 and <tt>Checksums-Sha256</tt></heading>
3710 These multiline fields contain a list of files with a checksum and size
3711 for each one. Both <tt>Checksums-Sha1</tt>
3712 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3713 only in the checksum algorithm used: SHA-1
3714 for <tt>Checksums-Sha1</tt> and SHA-256
3715 for <tt>Checksums-Sha256</tt>.
3719 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3720 multiline fields. The first line of the field value (the part
3721 on the same line as <tt>Checksums-Sha1:</tt>
3722 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3723 of the field is expressed as continuation lines, one line per
3724 file. Each line consists of the checksum, a space, the file
3725 size, a space, and the file name. For example (from
3726 a <file>.changes</file> file):
3729 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3730 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3731 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3732 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3734 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3735 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3736 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3737 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3742 In the <file>.dsc</file> file, these fields list all
3743 files that make up the source package. In
3744 the <file>.changes</file> file, these fields list all
3745 files being uploaded. The list of files in these fields
3746 must match the list of files in the <tt>Files</tt> field.
3751 <heading><tt>DM-Upload-Allowed</tt></heading>
3754 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3758 <sect1 id="f-VCS-fields">
3759 <heading>Version Control System (VCS) fields</heading>
3762 Debian source packages are increasingly developed using VCSs. The
3763 purpose of the following fields is to indicate a publicly accessible
3764 repository where the Debian source package is developed.
3767 <tag><tt>Vcs-Browser</tt></tag>
3770 URL of a web interface for browsing the repository.
3775 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3776 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3777 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3782 The field name identifies the VCS. The field's value uses the
3783 version control system's conventional syntax for describing
3784 repository locations and should be sufficient to locate the
3785 repository used for packaging. Ideally, it also locates the
3786 branch used for development of new versions of the Debian
3790 In the case of Git, the value consists of a URL, optionally
3791 followed by the word <tt>-b</tt> and the name of a branch in
3792 the indicated repository, following the syntax of the
3793 <tt>git clone</tt> command. If no branch is specified, the
3794 packaging should be on the default branch.
3797 More than one different VCS may be specified for the same
3807 <heading>User-defined fields</heading>
3810 Additional user-defined fields may be added to the
3811 source package control file. Such fields will be
3812 ignored, and not copied to (for example) binary or
3813 Debian source control files or upload control files.
3817 If you wish to add additional unsupported fields to
3818 these output files you should use the mechanism
3823 Fields in the main source control information file with
3824 names starting <tt>X</tt>, followed by one or more of
3825 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3826 be copied to the output files. Only the part of the
3827 field name after the hyphen will be used in the output
3828 file. Where the letter <tt>B</tt> is used the field
3829 will appear in binary package control files, where the
3830 letter <tt>S</tt> is used in Debian source control
3831 files and where <tt>C</tt> is used in upload control
3832 (<tt>.changes</tt>) files.
3836 For example, if the main source information control file
3839 XBS-Comment: I stand between the candle and the star.
3841 then the binary and Debian source control files will contain the
3844 Comment: I stand between the candle and the star.
3850 <sect id="obsolete-control-data-fields">
3851 <heading>Obsolete fields</heading>
3854 The following fields have been obsoleted and may be found in packages
3855 conforming with previous versions of the Policy.
3858 <sect1 id="f-DM-Upload-Allowed">
3859 <heading><tt>DM-Upload-Allowed</tt></heading>
3862 Indicates that Debian Maintainers may upload this package to
3863 the Debian archive. The only valid value is <tt>yes</tt>. This
3864 field was used to regulate uploads by Debian Maintainers, See the
3865 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3866 name="Endorse the concept of Debian Maintainers"> for more details.
3875 <chapt id="maintainerscripts">
3876 <heading>Package maintainer scripts and installation procedure</heading>
3879 <heading>Introduction to package maintainer scripts</heading>
3882 It is possible to supply scripts as part of a package which
3883 the package management system will run for you when your
3884 package is installed, upgraded or removed.
3888 These scripts are the control information
3889 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3890 and <prgn>postrm</prgn>. They must be proper executable files;
3891 if they are scripts (which is recommended), they must start with
3892 the usual <tt>#!</tt> convention. They should be readable and
3893 executable by anyone, and must not be world-writable.
3897 The package management system looks at the exit status from
3898 these scripts. It is important that they exit with a
3899 non-zero status if there is an error, so that the package
3900 management system can stop its processing. For shell
3901 scripts this means that you <em>almost always</em> need to
3902 use <tt>set -e</tt> (this is usually true when writing shell
3903 scripts, in fact). It is also important, of course, that
3904 they exit with a zero status if everything went well.
3908 Additionally, packages interacting with users
3909 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3910 should install a <prgn>config</prgn> script as a control
3911 information file. See <ref id="maintscriptprompt"> for details.
3915 When a package is upgraded a combination of the scripts from
3916 the old and new packages is called during the upgrade
3917 procedure. If your scripts are going to be at all
3918 complicated you need to be aware of this, and may need to
3919 check the arguments to your scripts.
3923 Broadly speaking the <prgn>preinst</prgn> is called before
3924 (a particular version of) a package is unpacked, and the
3925 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3926 before (a version of) a package is removed and the
3927 <prgn>postrm</prgn> afterwards.
3931 Programs called from maintainer scripts should not normally
3932 have a path prepended to them. Before installation is
3933 started, the package management system checks to see if the
3934 programs <prgn>ldconfig</prgn>,
3935 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3936 and <prgn>update-rc.d</prgn> can be found via the
3937 <tt>PATH</tt> environment variable. Those programs, and any
3938 other program that one would expect to be in the
3939 <tt>PATH</tt>, should thus be invoked without an absolute
3940 pathname. Maintainer scripts should also not reset the
3941 <tt>PATH</tt>, though they might choose to modify it by
3942 prepending or appending package-specific directories. These
3943 considerations really apply to all shell scripts.</p>
3946 <sect id="idempotency">
3947 <heading>Maintainer scripts idempotency</heading>
3950 It is necessary for the error recovery procedures that the
3951 scripts be idempotent. This means that if it is run
3952 successfully, and then it is called again, it doesn't bomb
3953 out or cause any harm, but just ensures that everything is
3954 the way it ought to be. If the first call failed, or
3955 aborted half way through for some reason, the second call
3956 should merely do the things that were left undone the first
3957 time, if any, and exit with a success status if everything
3959 This is so that if an error occurs, the user interrupts
3960 <prgn>dpkg</prgn> or some other unforeseen circumstance
3961 happens you don't leave the user with a badly-broken
3962 package when <prgn>dpkg</prgn> attempts to repeat the
3968 <sect id="controllingterminal">
3969 <heading>Controlling terminal for maintainer scripts</heading>
3972 Maintainer scripts are not guaranteed to run with a controlling
3973 terminal and may not be able to interact with the user. They
3974 must be able to fall back to noninteractive behavior if no
3975 controlling terminal is available. Maintainer scripts that
3976 prompt via a program conforming to the Debian Configuration
3977 Management Specification (see <ref id="maintscriptprompt">) may
3978 assume that program will handle falling back to noninteractive
3983 For high-priority prompts without a reasonable default answer,
3984 maintainer scripts may abort if there is no controlling
3985 terminal. However, this situation should be avoided if at all
3986 possible, since it prevents automated or unattended installs.
3987 In most cases, users will consider this to be a bug in the
3992 <sect id="exitstatus">
3993 <heading>Exit status</heading>
3996 Each script must return a zero exit status for
3997 success, or a nonzero one for failure, since the package
3998 management system looks for the exit status of these scripts
3999 and determines what action to take next based on that datum.
4003 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4008 What follows is a summary of all the ways in which maintainer
4009 scripts may be called along with what facilities those scripts
4010 may rely on being available at that time. Script names preceded
4011 by <var>new-</var> are the scripts from the new version of a
4012 package being installed, upgraded to, or downgraded to. Script
4013 names preceded by <var>old-</var> are the scripts from the old
4014 version of a package that is being upgraded from or downgraded
4019 The <prgn>preinst</prgn> script may be called in the following
4022 <tag><var>new-preinst</var> <tt>install</tt></tag>
4023 <tag><var>new-preinst</var> <tt>install</tt>
4024 <var>old-version</var></tag>
4025 <tag><var>new-preinst</var> <tt>upgrade</tt>
4026 <var>old-version</var></tag>
4028 The package will not yet be unpacked, so
4029 the <prgn>preinst</prgn> script cannot rely on any files
4030 included in its package. Only essential packages and
4031 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4032 available. Pre-dependencies will have been configured at
4033 least once, but at the time the <prgn>preinst</prgn> is
4034 called they may only be in an unpacked or "Half-Configured"
4035 state if a previous version of the pre-dependency was
4036 completely configured and has not been removed since then.
4039 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4040 <var>new-version</var></tag>
4042 Called during error handling of an upgrade that failed after
4043 unpacking the new package because the <tt>postrm
4044 upgrade</tt> action failed. The unpacked files may be
4045 partly from the new version or partly missing, so the script
4046 cannot rely on files included in the package. Package
4047 dependencies may not be available. Pre-dependencies will be
4048 at least unpacked following the same rules as above, except
4049 they may be only "Half-Installed" if an upgrade of the
4050 pre-dependency failed.<footnote>
4051 This can happen if the new version of the package no
4052 longer pre-depends on a package that had been partially
4060 The <prgn>postinst</prgn> script may be called in the following
4063 <tag><var>postinst</var> <tt>configure</tt>
4064 <var>most-recently-configured-version</var></tag>
4066 The files contained in the package will be unpacked. All
4067 package dependencies will at least be unpacked. If there
4068 are no circular dependencies involved, all package
4069 dependencies will be configured. For behavior in the case
4070 of circular dependencies, see the discussion
4071 in <ref id="binarydeps">.
4074 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4075 <var>new-version</var></tag>
4076 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4077 <tt>in-favour</tt> <var>package</var>
4078 <var>new-version</var></tag>
4079 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4080 <tag><var>deconfigured's-postinst</var>
4081 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4082 <var>failed-install-package</var> <var>version</var>
4083 [<tt>removing</tt> <var>conflicting-package</var>
4084 <var>version</var>]</tag>
4086 The files contained in the package will be unpacked. All
4087 package dependencies will at least be "Half-Installed" and
4088 will have previously been configured and not removed.
4089 However, dependencies may not be configured or even fully
4090 unpacked in some error situations.<footnote>
4091 For example, suppose packages foo and bar are installed
4092 with foo depending on bar. If an upgrade of bar were
4093 started and then aborted, and then an attempt to remove
4094 foo failed because its <prgn>prerm</prgn> script failed,
4095 foo's <tt>postinst abort-remove</tt> would be called with
4096 bar only "Half-Installed".
4098 The <prgn>postinst</prgn> should still attempt any actions
4099 for which its dependencies are required, since they will
4100 normally be available, but consider the correct error
4101 handling approach if those actions fail. Aborting
4102 the <prgn>postinst</prgn> action if commands or facilities
4103 from the package dependencies are not available is often the
4110 The <prgn>prerm</prgn> script may be called in the following
4113 <tag><var>prerm</var> <tt>remove</tt></tag>
4114 <tag><var>old-prerm</var>
4115 <tt>upgrade</tt><var>new-version</var></tag>
4116 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4117 <tt>in-favour</tt> <var>package</var>
4118 <var>new-version</var></tag>
4119 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4120 <tt>in-favour</tt> <var>package-being-installed</var>
4121 <var>version</var> [<tt>removing</tt>
4122 <var>conflicting-package</var> <var>version</var>]</tag>
4124 The package whose <prgn>prerm</prgn> is being called will be
4125 at least "Half-Installed". All package dependencies will at
4126 least be "Half-Installed" and will have previously been
4127 configured and not removed. If there was no error, all
4128 dependencies will at least be unpacked, but these actions
4129 may be called in various error states where dependencies are
4130 only "Half-Installed" due to a partial upgrade.
4133 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4134 <var>old-version</var></tag>
4136 Called during error handling when <tt>prerm upgrade</tt>
4137 fails. The new package will not yet be unpacked, and all
4138 the same constraints as for <tt>preinst upgrade</tt> apply.
4144 The <prgn>postrm</prgn> script may be called in the following
4147 <tag><var>postrm</var> <tt>remove</tt></tag>
4148 <tag><var>postrm</var> <tt>purge</tt></tag>
4149 <tag><var>old-postrm</var> <tt>upgrade</tt>
4150 <var>new-version</var></tag>
4151 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4152 <var>overwriter</var> <var>overwriter-version</var></tag>
4154 The <prgn>postrm</prgn> script is called after the package's
4155 files have been removed or replaced. The package
4156 whose <prgn>postrm</prgn> is being called may have
4157 previously been deconfigured and only be unpacked, at which
4158 point subsequent package changes do not consider its
4159 dependencies. Therefore, all <prgn>postrm</prgn> actions
4160 may only rely on essential packages and must gracefully skip
4161 any actions that require the package's dependencies if those
4162 dependencies are unavailable.<footnote>
4163 This is often done by checking whether the command or
4164 facility the <prgn>postrm</prgn> intends to call is
4165 available before calling it. For example:
4167 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4168 . /usr/share/debconf/confmodule
4172 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4173 configuration for the package
4174 if <package>debconf</package> is installed.
4178 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4179 <var>old-version</var></tag>
4181 Called when the old <tt>postrm upgrade</tt> action fails.
4182 The new package will be unpacked, but only essential
4183 packages and pre-dependencies can be relied on.
4184 Pre-dependencies will either be configured or will be
4185 "Unpacked" or "Half-Configured" but previously had been
4186 configured and was never removed.
4189 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4190 <tag><var>new-postrm</var> <tt>abort-install</tt>
4191 <var>old-version</var></tag>
4192 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4193 <var>old-version</var></tag>
4195 Called before unpacking the new package as part of the
4196 error handling of <prgn>preinst</prgn> failures. May assume
4197 the same state as <prgn>preinst</prgn> can assume.
4203 <sect id="unpackphase">
4204 <heading>Details of unpack phase of installation or upgrade</heading>
4207 The procedure on installation/upgrade/overwrite/disappear
4208 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4209 stage of <tt>dpkg --install</tt>) is as follows. In each
4210 case, if a major error occurs (unless listed below) the
4211 actions are, in general, run backwards - this means that the
4212 maintainer scripts are run with different arguments in
4213 reverse order. These are the "error unwind" calls listed
4220 If a version of the package is already installed, call
4221 <example compact="compact">
4222 <var>old-prerm</var> upgrade <var>new-version</var>
4226 If the script runs but exits with a non-zero
4227 exit status, <prgn>dpkg</prgn> will attempt:
4228 <example compact="compact">
4229 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4231 If this works, the upgrade continues. If this
4232 does not work, the error unwind:
4233 <example compact="compact">
4234 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4236 If this works, then the old-version is
4237 "Installed", if not, the old version is in a
4238 "Half-Configured" state.
4244 If a "conflicting" package is being removed at the same time,
4245 or if any package will be broken (due to <tt>Breaks</tt>):
4248 If <tt>--auto-deconfigure</tt> is
4249 specified, call, for each package to be deconfigured
4250 due to <tt>Breaks</tt>:
4251 <example compact="compact">
4252 <var>deconfigured's-prerm</var> deconfigure \
4253 in-favour <var>package-being-installed</var> <var>version</var>
4256 <example compact="compact">
4257 <var>deconfigured's-postinst</var> abort-deconfigure \
4258 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4260 The deconfigured packages are marked as
4261 requiring configuration, so that if
4262 <tt>--install</tt> is used they will be
4263 configured again if possible.
4266 If any packages depended on a conflicting
4267 package being removed and <tt>--auto-deconfigure</tt> is
4268 specified, call, for each such package:
4269 <example compact="compact">
4270 <var>deconfigured's-prerm</var> deconfigure \
4271 in-favour <var>package-being-installed</var> <var>version</var> \
4272 removing <var>conflicting-package</var> <var>version</var>
4275 <example compact="compact">
4276 <var>deconfigured's-postinst</var> abort-deconfigure \
4277 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4278 removing <var>conflicting-package</var> <var>version</var>
4280 The deconfigured packages are marked as
4281 requiring configuration, so that if
4282 <tt>--install</tt> is used they will be
4283 configured again if possible.
4286 To prepare for removal of each conflicting package, call:
4287 <example compact="compact">
4288 <var>conflictor's-prerm</var> remove \
4289 in-favour <var>package</var> <var>new-version</var>
4292 <example compact="compact">
4293 <var>conflictor's-postinst</var> abort-remove \
4294 in-favour <var>package</var> <var>new-version</var>
4303 If the package is being upgraded, call:
4304 <example compact="compact">
4305 <var>new-preinst</var> upgrade <var>old-version</var>
4307 If this fails, we call:
4309 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4316 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4318 is called. If this works, then the old version
4319 is in an "Installed" state, or else it is left
4320 in an "Unpacked" state.
4325 If it fails, then the old version is left
4326 in an "Half-Installed" state.
4333 Otherwise, if the package had some configuration
4334 files from a previous version installed (i.e., it
4335 is in the "configuration files only" state):
4336 <example compact="compact">
4337 <var>new-preinst</var> install <var>old-version</var>
4341 <var>new-postrm</var> abort-install <var>old-version</var>
4343 If this fails, the package is left in a
4344 "Half-Installed" state, which requires a
4345 reinstall. If it works, the packages is left in
4346 a "Config-Files" state.
4349 Otherwise (i.e., the package was completely purged):
4350 <example compact="compact">
4351 <var>new-preinst</var> install
4354 <example compact="compact">
4355 <var>new-postrm</var> abort-install
4357 If the error-unwind fails, the package is in a
4358 "Half-Installed" phase, and requires a
4359 reinstall. If the error unwind works, the
4360 package is in a not installed state.
4367 The new package's files are unpacked, overwriting any
4368 that may be on the system already, for example any
4369 from the old version of the same package or from
4370 another package. Backups of the old files are kept
4371 temporarily, and if anything goes wrong the package
4372 management system will attempt to put them back as
4373 part of the error unwind.
4377 It is an error for a package to contain files which
4378 are on the system in another package, unless
4379 <tt>Replaces</tt> is used (see <ref id="replaces">).
4381 The following paragraph is not currently the case:
4382 Currently the <tt>- - force-overwrite</tt> flag is
4383 enabled, downgrading it to a warning, but this may not
4389 It is a more serious error for a package to contain a
4390 plain file or other kind of non-directory where another
4391 package has a directory (again, unless
4392 <tt>Replaces</tt> is used). This error can be
4393 overridden if desired using
4394 <tt>--force-overwrite-dir</tt>, but this is not
4399 Packages which overwrite each other's files produce
4400 behavior which, though deterministic, is hard for the
4401 system administrator to understand. It can easily
4402 lead to "missing" programs if, for example, a package
4403 is unpacked which overwrites a file from another
4404 package, and is then removed again.<footnote>
4405 Part of the problem is due to what is arguably a
4406 bug in <prgn>dpkg</prgn>.
4411 A directory will never be replaced by a symbolic link
4412 to a directory or vice versa; instead, the existing
4413 state (symlink or not) will be left alone and
4414 <prgn>dpkg</prgn> will follow the symlink if there is
4423 If the package is being upgraded, call
4424 <example compact="compact">
4425 <var>old-postrm</var> upgrade <var>new-version</var>
4429 If this fails, <prgn>dpkg</prgn> will attempt:
4430 <example compact="compact">
4431 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4433 If this works, installation continues. If not,
4435 <example compact="compact">
4436 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4438 If this fails, the old version is left in a
4439 "Half-Installed" state. If it works, dpkg now
4441 <example compact="compact">
4442 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4444 If this fails, the old version is left in a
4445 "Half-Installed" state. If it works, dpkg now
4447 <example compact="compact">
4448 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4450 If this fails, the old version is in an
4457 This is the point of no return - if
4458 <prgn>dpkg</prgn> gets this far, it won't back off
4459 past this point if an error occurs. This will
4460 leave the package in a fairly bad state, which
4461 will require a successful re-installation to clear
4462 up, but it's when <prgn>dpkg</prgn> starts doing
4463 things that are irreversible.
4468 Any files which were in the old version of the package
4469 but not in the new are removed.
4473 The new file list replaces the old.
4477 The new maintainer scripts replace the old.
4481 Any packages all of whose files have been overwritten
4482 during the installation, and which aren't required for
4483 dependencies, are considered to have been removed.
4484 For each such package
4487 <prgn>dpkg</prgn> calls:
4488 <example compact="compact">
4489 <var>disappearer's-postrm</var> disappear \
4490 <var>overwriter</var> <var>overwriter-version</var>
4494 The package's maintainer scripts are removed.
4497 It is noted in the status database as being in a
4498 sane state, namely not installed (any conffiles
4499 it may have are ignored, rather than being
4500 removed by <prgn>dpkg</prgn>). Note that
4501 disappearing packages do not have their prerm
4502 called, because <prgn>dpkg</prgn> doesn't know
4503 in advance that the package is going to
4510 Any files in the package we're unpacking that are also
4511 listed in the file lists of other packages are removed
4512 from those lists. (This will lobotomize the file list
4513 of the "conflicting" package if there is one.)
4517 The backup files made during installation, above, are
4523 The new package's status is now sane, and recorded as
4528 Here is another point of no return - if the
4529 conflicting package's removal fails we do not unwind
4530 the rest of the installation; the conflicting package
4531 is left in a half-removed limbo.
4536 If there was a conflicting package we go and do the
4537 removal actions (described below), starting with the
4538 removal of the conflicting package's files (any that
4539 are also in the package being unpacked have already
4540 been removed from the conflicting package's file list,
4541 and so do not get removed now).
4547 <sect id="configdetails"><heading>Details of configuration</heading>
4550 When we configure a package (this happens with <tt>dpkg
4551 --install</tt> and <tt>dpkg --configure</tt>), we first
4552 update any <tt>conffile</tt>s and then call:
4553 <example compact="compact">
4554 <var>postinst</var> configure <var>most-recently-configured-version</var>
4559 No attempt is made to unwind after errors during
4560 configuration. If the configuration fails, the package is in
4561 a "Failed Config" state, and an error message is generated.
4565 If there is no most recently configured version
4566 <prgn>dpkg</prgn> will pass a null argument.
4569 Historical note: Truly ancient (pre-1997) versions of
4570 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4571 (including the angle brackets) in this case. Even older
4572 ones did not pass a second argument at all, under any
4573 circumstance. Note that upgrades using such an old dpkg
4574 version are unlikely to work for other reasons, even if
4575 this old argument behavior is handled by your postinst script.
4581 <sect id="removedetails"><heading>Details of removal and/or
4582 configuration purging</heading>
4588 <example compact="compact">
4589 <var>prerm</var> remove
4593 If prerm fails during replacement due to conflict
4595 <var>conflictor's-postinst</var> abort-remove \
4596 in-favour <var>package</var> <var>new-version</var>
4600 <var>postinst</var> abort-remove
4604 If this fails, the package is in a "Half-Configured"
4605 state, or else it remains "Installed".
4609 The package's files are removed (except <tt>conffile</tt>s).
4612 <example compact="compact">
4613 <var>postrm</var> remove
4617 If it fails, there's no error unwind, and the package is in
4618 an "Half-Installed" state.
4623 All the maintainer scripts except the <prgn>postrm</prgn>
4628 If we aren't purging the package we stop here. Note
4629 that packages which have no <prgn>postrm</prgn> and no
4630 <tt>conffile</tt>s are automatically purged when
4631 removed, as there is no difference except for the
4632 <prgn>dpkg</prgn> status.
4636 The <tt>conffile</tt>s and any backup files
4637 (<tt>~</tt>-files, <tt>#*#</tt> files,
4638 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4643 <example compact="compact">
4644 <var>postrm</var> purge
4648 If this fails, the package remains in a "Config-Files"
4653 The package's file list is removed.
4662 <chapt id="relationships">
4663 <heading>Declaring relationships between packages</heading>
4665 <sect id="depsyntax">
4666 <heading>Syntax of relationship fields</heading>
4669 These fields all have a uniform syntax. They are a list of
4670 package names separated by commas.
4674 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4675 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4676 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4677 control fields of the package, which declare
4678 dependencies on other packages, the package names listed may
4679 also include lists of alternative package names, separated
4680 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4681 if any one of the alternative packages is installed, that
4682 part of the dependency is considered to be satisfied.
4686 All of the fields except for <tt>Provides</tt> may restrict
4687 their applicability to particular versions of each named
4688 package. This is done in parentheses after each individual
4689 package name; the parentheses should contain a relation from
4690 the list below followed by a version number, in the format
4691 described in <ref id="f-Version">.
4695 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4696 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4697 earlier, earlier or equal, exactly equal, later or equal and
4698 strictly later, respectively. The deprecated
4699 forms <tt><</tt> and <tt>></tt> were confusingly used to
4700 mean earlier/later or equal, rather than strictly earlier/later,
4701 and must not appear in new packages (though <prgn>dpkg</prgn>
4702 still supports them with a warning).
4706 Whitespace may appear at any point in the version
4707 specification subject to the rules in <ref
4708 id="controlsyntax">, and must appear where it's necessary to
4709 disambiguate; it is not otherwise significant. All of the
4710 relationship fields can only be folded in source package control files. For
4711 consistency and in case of future changes to
4712 <prgn>dpkg</prgn> it is recommended that a single space be
4713 used after a version relationship and before a version
4714 number; it is also conventional to put a single space after
4715 each comma, on either side of each vertical bar, and before
4716 each open parenthesis. When opening a continuation line in a relationship field, it
4717 is conventional to do so after a comma and before the space
4718 following that comma.
4722 For example, a list of dependencies might appear as:
4723 <example compact="compact">
4726 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4731 Relationships may be restricted to a certain set of
4732 architectures. This is indicated in brackets after each
4733 individual package name and the optional version specification.
4734 The brackets enclose a non-empty list of Debian architecture names
4735 in the format described in <ref id="arch-spec">,
4736 separated by whitespace. Exclamation marks may be prepended to
4737 each of the names. (It is not permitted for some names to be
4738 prepended with exclamation marks while others aren't.)
4742 For build relationship fields
4743 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4744 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4745 the current Debian host architecture is not in this list and
4746 there are no exclamation marks in the list, or it is in the list
4747 with a prepended exclamation mark, the package name and the
4748 associated version specification are ignored completely for the
4749 purposes of defining the relationships.
4754 <example compact="compact">
4756 Build-Depends-Indep: texinfo
4757 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4758 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4760 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4761 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4762 <tt>gnumach-dev</tt> only on hurd-i386.
4766 For binary relationship fields and the <tt>Built-Using</tt>
4767 field, the architecture restriction
4768 syntax is only supported in the source package control
4769 file <file>debian/control</file>. When the corresponding binary
4770 package control file is generated, the relationship will either
4771 be omitted or included without the architecture restriction
4772 based on the architecture of the binary package. This means
4773 that architecture restrictions must not be used in binary
4774 relationship fields for architecture-independent packages
4775 (<tt>Architecture: all</tt>).
4780 <example compact="compact">
4781 Depends: foo [i386], bar [amd64]
4783 becomes <tt>Depends: foo</tt> when the package is built on
4784 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4785 package is built on the <tt>amd64</tt> architecture, and omitted
4786 entirely in binary packages built on all other architectures.
4790 If the architecture-restricted dependency is part of a set of
4791 alternatives using <tt>|</tt>, that alternative is ignored
4792 completely on architectures that do not match the restriction.
4794 <example compact="compact">
4795 Build-Depends: foo [!i386] | bar [!amd64]
4797 is equivalent to <tt>bar</tt> on the i386 architecture, to
4798 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4799 bar</tt> on all other architectures.
4803 Relationships may also be restricted to a certain set of
4804 architectures using architecture wildcards in the format
4805 described in <ref id="arch-wildcard-spec">. The syntax for
4806 declaring such restrictions is the same as declaring
4807 restrictions using a certain set of architectures without
4808 architecture wildcards. For example:
4809 <example compact="compact">
4810 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4812 is equivalent to <tt>foo</tt> on architectures using the Linux
4813 kernel and any cpu, <tt>bar</tt> on architectures using any
4814 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4815 using a kernel other than Linux.
4819 Note that the binary package relationship fields such as
4820 <tt>Depends</tt> appear in one of the binary package
4821 sections of the control file, whereas the build-time
4822 relationships such as <tt>Build-Depends</tt> appear in the
4823 source package section of the control file (which is the
4828 <sect id="binarydeps">
4829 <heading>Binary Dependencies - <tt>Depends</tt>,
4830 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4831 <tt>Pre-Depends</tt>
4835 Packages can declare in their control file that they have
4836 certain relationships to other packages - for example, that
4837 they may not be installed at the same time as certain other
4838 packages, and/or that they depend on the presence of others.
4842 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4843 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4844 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4845 <tt>Breaks</tt> is described in <ref id="breaks">, and
4846 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4847 rest are described below.
4851 These seven fields are used to declare a dependency
4852 relationship by one package on another. Except for
4853 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4854 depending (binary) package's control file.
4855 (<tt>Enhances</tt> appears in the recommending package's
4856 control file, and <tt>Breaks</tt> appears in the version of
4857 depended-on package which causes the named package to
4862 A <tt>Depends</tt> field takes effect <em>only</em> when a
4863 package is to be configured. It does not prevent a package
4864 being on the system in an unconfigured state while its
4865 dependencies are unsatisfied, and it is possible to replace
4866 a package whose dependencies are satisfied and which is
4867 properly installed with a different version whose
4868 dependencies are not and cannot be satisfied; when this is
4869 done the depending package will be left unconfigured (since
4870 attempts to configure it will give errors) and will not
4871 function properly. If it is necessary, a
4872 <tt>Pre-Depends</tt> field can be used, which has a partial
4873 effect even when a package is being unpacked, as explained
4874 in detail below. (The other three dependency fields,
4875 <tt>Recommends</tt>, <tt>Suggests</tt> and
4876 <tt>Enhances</tt>, are only used by the various front-ends
4877 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4878 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4882 Since <tt>Depends</tt> only places requirements on the order in
4883 which packages are configured, packages in an installation run
4884 are usually all unpacked first and all configured later.
4886 This approach makes dependency resolution easier. If two
4887 packages A and B are being upgraded, the installed package A
4888 depends on exactly the installed package B, and the new
4889 package A depends on exactly the new package B (a common
4890 situation when upgrading shared libraries and their
4891 corresponding development packages), satisfying the
4892 dependencies at every stage of the upgrade would be
4893 impossible. This relaxed restriction means that both new
4894 packages can be unpacked together and then configured in their
4900 If there is a circular dependency among packages being installed
4901 or removed, installation or removal order honoring the
4902 dependency order is impossible, requiring the dependency loop be
4903 broken at some point and the dependency requirements violated
4904 for at least one package. Packages involved in circular
4905 dependencies may not be able to rely on their dependencies being
4906 configured before they themselves are configured, depending on
4907 which side of the break of the circular dependency loop they
4908 happen to be on. If one of the packages in the loop has
4909 no <prgn>postinst</prgn> script, then the cycle will be broken
4910 at that package; this ensures that all <prgn>postinst</prgn>
4911 scripts are run with their dependencies properly configured if
4912 this is possible. Otherwise the breaking point is arbitrary.
4913 Packages should therefore avoid circular dependencies where
4914 possible, particularly if they have <prgn>postinst</prgn>
4919 The meaning of the five dependency fields is as follows:
4921 <tag><tt>Depends</tt></tag>
4924 This declares an absolute dependency. A package will
4925 not be configured unless all of the packages listed in
4926 its <tt>Depends</tt> field have been correctly
4927 configured (unless there is a circular dependency as
4932 The <tt>Depends</tt> field should be used if the
4933 depended-on package is required for the depending
4934 package to provide a significant amount of
4939 The <tt>Depends</tt> field should also be used if the
4940 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4941 require the depended-on package to be unpacked or
4942 configured in order to run. In the case of <tt>postinst
4943 configure</tt>, the depended-on packages will be unpacked
4944 and configured first. (If both packages are involved in a
4945 dependency loop, this might not work as expected; see the
4946 explanation a few paragraphs back.) In the case
4947 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4948 actions, the package dependencies will normally be at
4949 least unpacked, but they may be only "Half-Installed" if a
4950 previous upgrade of the dependency failed.
4954 Finally, the <tt>Depends</tt> field should be used if the
4955 depended-on package is needed by the <prgn>postrm</prgn>
4956 script to fully clean up after the package removal. There
4957 is no guarantee that package dependencies will be
4958 available when <prgn>postrm</prgn> is run, but the
4959 depended-on package is more likely to be available if the
4960 package declares a dependency (particularly in the case
4961 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4962 script must gracefully skip actions that require a
4963 dependency if that dependency isn't available.
4967 <tag><tt>Recommends</tt></tag>
4970 This declares a strong, but not absolute, dependency.
4974 The <tt>Recommends</tt> field should list packages
4975 that would be found together with this one in all but
4976 unusual installations.
4980 <tag><tt>Suggests</tt></tag>
4982 This is used to declare that one package may be more
4983 useful with one or more others. Using this field
4984 tells the packaging system and the user that the
4985 listed packages are related to this one and can
4986 perhaps enhance its usefulness, but that installing
4987 this one without them is perfectly reasonable.
4990 <tag><tt>Enhances</tt></tag>
4992 This field is similar to Suggests but works in the
4993 opposite direction. It is used to declare that a
4994 package can enhance the functionality of another
4998 <tag><tt>Pre-Depends</tt></tag>
5001 This field is like <tt>Depends</tt>, except that it
5002 also forces <prgn>dpkg</prgn> to complete installation
5003 of the packages named before even starting the
5004 installation of the package which declares the
5005 pre-dependency, as follows:
5009 When a package declaring a pre-dependency is about to
5010 be <em>unpacked</em> the pre-dependency can be
5011 satisfied if the depended-on package is either fully
5012 configured, <em>or even if</em> the depended-on
5013 package(s) are only unpacked or in the "Half-Configured"
5014 state, provided that they have been configured
5015 correctly at some point in the past (and not removed
5016 or partially removed since). In this case, both the
5017 previously-configured and currently unpacked or
5018 "Half-Configured" versions must satisfy any version
5019 clause in the <tt>Pre-Depends</tt> field.
5023 When the package declaring a pre-dependency is about to
5024 be <em>configured</em>, the pre-dependency will be treated
5025 as a normal <tt>Depends</tt>. It will be considered
5026 satisfied only if the depended-on package has been
5027 correctly configured. However, unlike
5028 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5029 permit circular dependencies to be broken. If a circular
5030 dependency is encountered while attempting to honor
5031 <tt>Pre-Depends</tt>, the installation will be aborted.
5035 <tt>Pre-Depends</tt> are also required if the
5036 <prgn>preinst</prgn> script depends on the named package.
5037 It is best to avoid this situation if possible.
5041 <tt>Pre-Depends</tt> should be used sparingly,
5042 preferably only by packages whose premature upgrade or
5043 installation would hamper the ability of the system to
5044 continue with any upgrade that might be in progress.
5048 You should not specify a <tt>Pre-Depends</tt> entry for a
5049 package before this has been discussed on the
5050 <tt>debian-devel</tt> mailing list and a consensus about
5051 doing that has been reached. See <ref id="dependencies">.
5058 When selecting which level of dependency to use you should
5059 consider how important the depended-on package is to the
5060 functionality of the one declaring the dependency. Some
5061 packages are composed of components of varying degrees of
5062 importance. Such a package should list using
5063 <tt>Depends</tt> the package(s) which are required by the
5064 more important components. The other components'
5065 requirements may be mentioned as Suggestions or
5066 Recommendations, as appropriate to the components' relative
5072 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5075 When one binary package declares that it breaks another,
5076 <prgn>dpkg</prgn> will refuse to allow the package which
5077 declares <tt>Breaks</tt> to be unpacked unless the broken
5078 package is deconfigured first, and it will refuse to
5079 allow the broken package to be reconfigured.
5083 A package will not be regarded as causing breakage merely
5084 because its configuration files are still installed; it must
5085 be at least "Half-Installed".
5089 A special exception is made for packages which declare that
5090 they break their own package name or a virtual package which
5091 they provide (see below): this does not count as a real
5096 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5097 version clause; such a <tt>Breaks</tt> is introduced in the
5098 version of an (implicit or explicit) dependency which violates
5099 an assumption or reveals a bug in earlier versions of the broken
5100 package, or which takes over a file from earlier versions of the
5101 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5102 will inform higher-level package management tools that the
5103 broken package must be upgraded before the new one.
5107 If the breaking package also overwrites some files from the
5108 older package, it should use <tt>Replaces</tt> to ensure this
5109 goes smoothly. See <ref id="replaces"> for a full discussion
5110 of taking over files from other packages, including how to
5111 use <tt>Breaks</tt> in those cases.
5115 Many of the cases where <tt>Breaks</tt> should be used were
5116 previously handled with <tt>Conflicts</tt>
5117 because <tt>Breaks</tt> did not yet exist.
5118 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5119 See <ref id="conflicts"> for more information about the
5124 <sect id="conflicts">
5125 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5128 When one binary package declares a conflict with another using
5129 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5130 allow them to be unpacked on the system at the same time. This
5131 is a stronger restriction than <tt>Breaks</tt>, which prevents
5132 the broken package from being configured while the breaking
5133 package is in the "Unpacked" state but allows both packages to
5134 be unpacked at the same time.
5138 If one package is to be unpacked, the other must be removed
5139 first. If the package being unpacked is marked as replacing
5140 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5141 normally be used in this case) the one on the system, or the one
5142 on the system is marked as deselected, or both packages are
5143 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5144 automatically remove the package which is causing the conflict.
5145 Otherwise, it will halt the installation of the new package with
5146 an error. This mechanism is specifically designed to produce an
5147 error when the installed package is <tt>Essential</tt>, but the
5152 A package will not cause a conflict merely because its
5153 configuration files are still installed; it must be at least
5158 A special exception is made for packages which declare a
5159 conflict with their own package name, or with a virtual
5160 package which they provide (see below): this does not
5161 prevent their installation, and allows a package to conflict
5162 with others providing a replacement for it. You use this
5163 feature when you want the package in question to be the only
5164 package providing some feature.
5168 Normally, <tt>Breaks</tt> should be used instead
5169 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5170 stronger restriction on the ordering of package installation or
5171 upgrade and can make it more difficult for the package manager
5172 to find a correct solution to an upgrade or installation
5173 problem. <tt>Breaks</tt> should be used
5175 <item>when moving a file from one package to another (see
5176 <ref id="replaces">),</item>
5177 <item>when splitting a package (a special case of the previous
5179 <item>when the breaking package exposes a bug in or interacts
5180 badly with particular versions of the broken
5183 <tt>Conflicts</tt> should be used
5185 <item>when two packages provide the same file and will
5186 continue to do so,</item>
5187 <item>in conjunction with <tt>Provides</tt> when only one
5188 package providing a given virtual facility may be unpacked
5189 at a time (see <ref id="virtual">),</item>
5190 <item>in other cases where one must prevent simultaneous
5191 installation of two packages for reasons that are ongoing
5192 (not fixed in a later version of one of the packages) or
5193 that must prevent both packages from being unpacked at the
5194 same time, not just configured.</item>
5196 Be aware that adding <tt>Conflicts</tt> is normally not the best
5197 solution when two packages provide the same files. Depending on
5198 the reason for that conflict, using alternatives or renaming the
5199 files is often a better approach. See, for
5200 example, <ref id="binaries">.
5204 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5205 unless two packages cannot be installed at the same time or
5206 installing them both causes one of them to be broken or
5207 unusable. Having similar functionality or performing the same
5208 tasks as another package is not sufficient reason to
5209 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5213 A <tt>Conflicts</tt> entry may have an "earlier than" version
5214 clause if the reason for the conflict is corrected in a later
5215 version of one of the packages. However, normally the presence
5216 of an "earlier than" version clause is a sign
5217 that <tt>Breaks</tt> should have been used instead. An "earlier
5218 than" version clause in <tt>Conflicts</tt>
5219 prevents <prgn>dpkg</prgn> from upgrading or installing the
5220 package which declares such a conflict until the upgrade or
5221 removal of the conflicted-with package has been completed, which
5222 is a strong restriction.
5226 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5230 As well as the names of actual ("concrete") packages, the
5231 package relationship fields <tt>Depends</tt>,
5232 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5233 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5234 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5235 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5236 may mention "virtual packages".
5240 A <em>virtual package</em> is one which appears in the
5241 <tt>Provides</tt> control field of another package. The effect
5242 is as if the package(s) which provide a particular virtual
5243 package name had been listed by name everywhere the virtual
5244 package name appears. (See also <ref id="virtual_pkg">)
5248 If there are both concrete and virtual packages of the same
5249 name, then the dependency may be satisfied (or the conflict
5250 caused) by either the concrete package with the name in
5251 question or any other concrete package which provides the
5252 virtual package with the name in question. This is so that,
5253 for example, supposing we have
5254 <example compact="compact">
5257 </example> and someone else releases an enhanced version of
5258 the <tt>bar</tt> package they can say:
5259 <example compact="compact">
5263 and the <tt>bar-plus</tt> package will now also satisfy the
5264 dependency for the <tt>foo</tt> package.
5268 If a relationship field has a version number attached, only real
5269 packages will be considered to see whether the relationship is
5270 satisfied (or the prohibition violated, for a conflict or
5271 breakage). In other words, if a version number is specified,
5272 this is a request to ignore all <tt>Provides</tt> for that
5273 package name and consider only real packages. The package
5274 manager will assume that a package providing that virtual
5275 package is not of the "right" version. A <tt>Provides</tt>
5276 field may not contain version numbers, and the version number of
5277 the concrete package which provides a particular virtual package
5278 will not be considered when considering a dependency on or
5279 conflict with the virtual package name.<footnote>
5280 It is possible that a future release of <prgn>dpkg</prgn> may
5281 add the ability to specify a version number for each virtual
5282 package it provides. This feature is not yet present,
5283 however, and is expected to be used only infrequently.
5288 To specify which of a set of real packages should be the default
5289 to satisfy a particular dependency on a virtual package, list
5290 the real package as an alternative before the virtual one.
5294 If the virtual package represents a facility that can only be
5295 provided by one real package at a time, such as
5296 the <package>mail-transport-agent</package> virtual package that
5297 requires installation of a binary that would conflict with all
5298 other providers of that virtual package (see
5299 <ref id="mail-transport-agents">), all packages providing that
5300 virtual package should also declare a conflict with it
5301 using <tt>Conflicts</tt>. This will ensure that at most one
5302 provider of that virtual package is unpacked or installed at a
5307 <sect id="replaces"><heading>Overwriting files and replacing
5308 packages - <tt>Replaces</tt></heading>
5311 Packages can declare in their control file that they should
5312 overwrite files in certain other packages, or completely replace
5313 other packages. The <tt>Replaces</tt> control field has these
5314 two distinct purposes.
5317 <sect1><heading>Overwriting files in other packages</heading>
5320 It is usually an error for a package to contain files which
5321 are on the system in another package. However, if the
5322 overwriting package declares that it <tt>Replaces</tt> the one
5323 containing the file being overwritten, then <prgn>dpkg</prgn>
5324 will replace the file from the old package with that from the
5325 new. The file will no longer be listed as "owned" by the old
5326 package and will be taken over by the new package.
5327 Normally, <tt>Breaks</tt> should be used in conjunction
5328 with <tt>Replaces</tt>.<footnote>
5329 To see why <tt>Breaks</tt> is normally needed in addition
5330 to <tt>Replaces</tt>, consider the case of a file in the
5331 package <package>foo</package> being taken over by the
5332 package <package>foo-data</package>.
5333 <tt>Replaces</tt> will allow <package>foo-data</package> to
5334 be installed and take over that file. However,
5335 without <tt>Breaks</tt>, nothing
5336 requires <package>foo</package> to be upgraded to a newer
5337 version that knows it does not include that file and instead
5338 depends on <package>foo-data</package>. Nothing would
5339 prevent the new <package>foo-data</package> package from
5340 being installed and then removed, removing the file that it
5341 took over from <package>foo</package>. After that
5342 operation, the package manager would think the system was in
5343 a consistent state, but the <package>foo</package> package
5344 would be missing one of its files.
5349 For example, if a package <package>foo</package> is split
5350 into <package>foo</package> and <package>foo-data</package>
5351 starting at version 1.2-3, <package>foo-data</package> would
5353 <example compact="compact">
5354 Replaces: foo (<< 1.2-3)
5355 Breaks: foo (<< 1.2-3)
5357 in its control file. The new version of the
5358 package <package>foo</package> would normally have the field
5359 <example compact="compact">
5360 Depends: foo-data (>= 1.2-3)
5362 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5363 the files moved into <package>foo-data</package> are not
5364 required for normal operation).
5368 If a package is completely replaced in this way, so that
5369 <prgn>dpkg</prgn> does not know of any files it still
5370 contains, it is considered to have "disappeared". It will
5371 be marked as not wanted on the system (selected for
5372 removal) and not installed. Any <tt>conffile</tt>s
5373 details noted for the package will be ignored, as they
5374 will have been taken over by the overwriting package. The
5375 package's <prgn>postrm</prgn> script will be run with a
5376 special argument to allow the package to do any final
5377 cleanup required. See <ref id="mscriptsinstact">.
5379 Replaces is a one way relationship. You have to install
5380 the replacing package after the replaced package.
5385 For this usage of <tt>Replaces</tt>, virtual packages (see
5386 <ref id="virtual">) are not considered when looking at a
5387 <tt>Replaces</tt> field. The packages declared as being
5388 replaced must be mentioned by their real names.
5392 This usage of <tt>Replaces</tt> only takes effect when both
5393 packages are at least partially on the system at once. It is
5394 not relevant if the packages conflict unless the conflict has
5399 <sect1><heading>Replacing whole packages, forcing their
5403 Second, <tt>Replaces</tt> allows the packaging system to
5404 resolve which package should be removed when there is a
5405 conflict (see <ref id="conflicts">). This usage only takes
5406 effect when the two packages <em>do</em> conflict, so that the
5407 two usages of this field do not interfere with each other.
5411 In this situation, the package declared as being replaced
5412 can be a virtual package, so for example, all mail
5413 transport agents (MTAs) would have the following fields in
5414 their control files:
5415 <example compact="compact">
5416 Provides: mail-transport-agent
5417 Conflicts: mail-transport-agent
5418 Replaces: mail-transport-agent
5420 ensuring that only one MTA can be unpacked at any one
5421 time. See <ref id="virtual"> for more information about this
5426 <sect id="sourcebinarydeps">
5427 <heading>Relationships between source and binary packages -
5428 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5429 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5433 Source packages that require certain binary packages to be
5434 installed or absent at the time of building the package
5435 can declare relationships to those binary packages.
5439 This is done using the <tt>Build-Depends</tt>,
5440 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5441 <tt>Build-Conflicts-Indep</tt> control fields.
5445 Build-dependencies on "build-essential" binary packages can be
5446 omitted. Please see <ref id="pkg-relations"> for more information.
5450 The dependencies and conflicts they define must be satisfied
5451 (as defined earlier for binary packages) in order to invoke
5452 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5454 There is no Build-Depends-Arch; this role is essentially
5455 met with Build-Depends. Anyone building the
5456 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5457 assumed to be building the whole package, and therefore
5458 installation of all build dependencies is required.
5461 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5462 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5463 not yet know how to check for its existence, and
5464 <tt>binary-arch</tt>. The purpose of the original split
5465 between <tt>Build-Depends</tt> and
5466 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5467 wouldn't need to install extra packages needed only for the
5468 binary-indep targets. But without a build-arch/build-indep
5469 split, this didn't work, since most of the work is done in
5470 the build target, not in the binary target.
5474 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5475 <tt>binary-arch</tt></tag>
5477 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5478 fields must be satisfied when these targets are invoked.
5480 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5481 and <tt>binary-indep</tt></tag>
5483 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5484 <tt>Build-Depends-Indep</tt>, and
5485 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5486 these targets are invoked.
5492 <sect id="built-using">
5493 <heading>Additional source packages used to build the binary
5494 - <tt>Built-Using</tt>
5498 Some binary packages incorporate parts of other packages when built
5499 but do not have to depend on those packages. Examples include
5500 linking with static libraries or incorporating source code from
5501 another package during the build. In this case, the source packages
5502 of those other packages are a required part of the complete source
5503 (the binary package is not reproducible without them).
5507 A <tt>Built-Using</tt> field must list the corresponding source
5508 package for any such binary package incorporated during the build
5510 <tt>Build-Depends</tt> in the source package is not adequate since
5511 it (rightfully) does not document the exact version used in the
5514 including an "exactly equal" ("=") version relation on the version
5515 that was used to build that binary package<footnote>
5516 The archive software might reject packages that refer to
5517 non-existent sources.
5522 A package using the source code from the gcc-4.6-source
5523 binary package built from the gcc-4.6 source package would
5524 have this field in its control file:
5525 <example compact="compact">
5526 Built-Using: gcc-4.6 (= 4.6.0-11)
5531 A package including binaries from grub2 and loadlin would
5532 have this field in its control file:
5533 <example compact="compact">
5534 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5541 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5544 Packages containing shared libraries must be constructed with
5545 a little care to make sure that the shared library is always
5546 available. This is especially important for packages whose
5547 shared libraries are vitally important, such as the C library
5548 (currently <tt>libc6</tt>).
5552 This section deals only with public shared libraries: shared
5553 libraries that are placed in directories searched by the dynamic
5554 linker by default or which are intended to be linked against
5555 normally and possibly used by other, independent packages. Shared
5556 libraries that are internal to a particular package or that are
5557 only loaded as dynamic modules are not covered by this section and
5558 are not subject to its requirements.
5562 A shared library is identified by the <tt>SONAME</tt> attribute
5563 stored in its dynamic section. When a binary is linked against a
5564 shared library, the <tt>SONAME</tt> of the shared library is
5565 recorded in the binary's <tt>NEEDED</tt> section so that the
5566 dynamic linker knows that library must be loaded at runtime. The
5567 shared library file's full name (which usually contains additional
5568 version information not needed in the <tt>SONAME</tt>) is
5569 therefore normally not referenced directly. Instead, the shared
5570 library is loaded by its <tt>SONAME</tt>, which exists on the file
5571 system as a symlink pointing to the full name of the shared
5572 library. This symlink must be provided by the
5573 package. <ref id="sharedlibs-runtime"> describes how to do this.
5575 This is a convention of shared library versioning, but not a
5576 requirement. Some libraries use the <tt>SONAME</tt> as the full
5577 library file name instead and therefore do not need a symlink.
5578 Most, however, encode additional information about
5579 backwards-compatible revisions as a minor version number in the
5580 file name. The <tt>SONAME</tt> itself only changes when
5581 binaries linked with the earlier version of the shared library
5582 may no longer work, but the filename may change with each
5583 release of the library. See <ref id="sharedlibs-runtime"> for
5589 When linking a binary or another shared library against a shared
5590 library, the <tt>SONAME</tt> for that shared library is not yet
5591 known. Instead, the shared library is found by looking for a file
5592 matching the library name with <tt>.so</tt> appended. This file
5593 exists on the file system as a symlink pointing to the shared
5598 Shared libraries are normally split into several binary packages.
5599 The <tt>SONAME</tt> symlink is installed by the runtime shared
5600 library package, and the bare <tt>.so</tt> symlink is installed in
5601 the development package since it's only used when linking binaries
5602 or shared libraries. However, there are some exceptions for
5603 unusual shared libraries or for shared libraries that are also
5604 loaded as dynamic modules by other programs.
5608 This section is primarily concerned with how the separation of
5609 shared libraries into multiple packages should be done and how
5610 dependencies on and between shared library binary packages are
5611 managed in Debian. <ref id="libraries"> should be read in
5612 conjunction with this section and contains additional rules for
5613 the files contained in the shared library packages.
5616 <sect id="sharedlibs-runtime">
5617 <heading>Run-time shared libraries</heading>
5620 The run-time shared library must be placed in a package
5621 whose name changes whenever the <tt>SONAME</tt> of the shared
5622 library changes. This allows several versions of the shared
5623 library to be installed at the same time, allowing installation
5624 of the new version of the shared library without immediately
5625 breaking binaries that depend on the old version. Normally, the
5626 run-time shared library and its <tt>SONAME</tt> symlink should
5627 be placed in a package named
5628 <package><var>libraryname</var><var>soversion</var></package>,
5629 where <var>soversion</var> is the version number in
5630 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5631 would be confusing to directly append <var>soversion</var>
5632 to <var>libraryname</var> (if, for
5633 example, <var>libraryname</var> itself ends in a number), you
5635 <package><var>libraryname</var>-<var>soversion</var></package>
5640 To determine the <var>soversion</var>, look at
5641 the <tt>SONAME</tt> of the library, stored in the
5642 ELF <tt>SONAME</tt> attribute. It is usually of the
5643 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5644 example, <tt>libz.so.1</tt>). The version part is the part
5645 which comes after <tt>.so.</tt>, so in that example it
5646 is <tt>1</tt>. The soname may instead be of the
5647 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5648 as <tt>libdb-5.1.so</tt>, in which case the name would
5649 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5653 If you have several shared libraries built from the same source
5654 tree, you may lump them all together into a single shared
5655 library package provided that all of their <tt>SONAME</tt>s will
5656 always change together. Be aware that this is not normally the
5657 case, and if the <tt>SONAME</tt>s do not change together,
5658 upgrading such a merged shared library package will be
5659 unnecessarily difficult because of file conflicts with the old
5660 version of the package. When in doubt, always split shared
5661 library packages so that each binary package installs a single
5666 Every time the shared library ABI changes in a way that may
5667 break binaries linked against older versions of the shared
5668 library, the <tt>SONAME</tt> of the library and the
5669 corresponding name for the binary package containing the runtime
5670 shared library should change. Normally, this means
5671 the <tt>SONAME</tt> should change any time an interface is
5672 removed from the shared library or the signature of an interface
5673 (the number of parameters or the types of parameters that it
5674 takes, for example) is changed. This practice is vital to
5675 allowing clean upgrades from older versions of the package and
5676 clean transitions between the old ABI and new ABI without having
5677 to upgrade every affected package simultaneously.
5681 The <tt>SONAME</tt> and binary package name need not, and indeed
5682 normally should not, change if new interfaces are added but none
5683 are removed or changed, since this will not break binaries
5684 linked against the old shared library. Correct versioning of
5685 dependencies on the newer shared library by binaries that use
5686 the new interfaces is handled via
5687 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5688 or <tt>shlibs</tt> system</qref>.
5692 The package should install the shared libraries under
5693 their normal names. For example, the <package>libgdbm3</package>
5694 package should install <file>libgdbm.so.3.0.0</file> as
5695 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5696 renamed or re-linked by any <prgn>prerm</prgn> or
5697 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5698 of renaming things safely without affecting running programs,
5699 and attempts to interfere with this are likely to lead to
5704 Shared libraries should not be installed executable, since
5705 the dynamic linker does not require this and trying to
5706 execute a shared library usually results in a core dump.
5710 The run-time library package should include the symbolic link for
5711 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5712 the shared libraries. For example,
5713 the <package>libgdbm3</package> package should include a symbolic
5714 link from <file>/usr/lib/libgdbm.so.3</file> to
5715 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5716 linker (for example <prgn>ld.so</prgn> or
5717 <prgn>ld-linux.so.*</prgn>) can find the library between the
5718 time that <prgn>dpkg</prgn> installs it and the time that
5719 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5721 The package management system requires the library to be
5722 placed before the symbolic link pointing to it in the
5723 <file>.deb</file> file. This is so that when
5724 <prgn>dpkg</prgn> comes to install the symlink
5725 (overwriting the previous symlink pointing at an older
5726 version of the library), the new shared library is already
5727 in place. In the past, this was achieved by creating the
5728 library in the temporary packaging directory before
5729 creating the symlink. Unfortunately, this was not always
5730 effective, since the building of the tar file in the
5731 <file>.deb</file> depended on the behavior of the underlying
5732 file system. Some file systems (such as reiserfs) reorder
5733 the files so that the order of creation is forgotten.
5734 Since version 1.7.0, <prgn>dpkg</prgn>
5735 reorders the files itself as necessary when building a
5736 package. Thus it is no longer important to concern
5737 oneself with the order of file creation.
5741 <sect1 id="ldconfig">
5742 <heading><tt>ldconfig</tt></heading>
5745 Any package installing shared libraries in one of the default
5746 library directories of the dynamic linker (which are currently
5747 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5748 listed in <file>/etc/ld.so.conf</file><footnote>
5749 These are currently <file>/usr/local/lib</file> plus
5750 directories under <file>/lib</file> and <file>/usr/lib</file>
5751 matching the multiarch triplet for the system architecture.
5753 must use <prgn>ldconfig</prgn> to update the shared library
5758 The package maintainer scripts must only call
5759 <prgn>ldconfig</prgn> under these circumstances:
5760 <list compact="compact">
5761 <item>When the <prgn>postinst</prgn> script is run with a
5762 first argument of <tt>configure</tt>, the script must call
5763 <prgn>ldconfig</prgn>, and may optionally invoke
5764 <prgn>ldconfig</prgn> at other times.
5766 <item>When the <prgn>postrm</prgn> script is run with a
5767 first argument of <tt>remove</tt>, the script should call
5768 <prgn>ldconfig</prgn>.
5773 During install or upgrade, the preinst is called before
5774 the new files are unpacked, so calling "ldconfig" is
5775 pointless. The preinst of an existing package can also be
5776 called if an upgrade fails. However, this happens during
5777 the critical time when a shared libs may exist on-disk
5778 under a temporary name. Thus, it is dangerous and
5779 forbidden by current policy to call "ldconfig" at this
5784 When a package is installed or upgraded, "postinst
5785 configure" runs after the new files are safely on-disk.
5786 Since it is perfectly safe to invoke ldconfig
5787 unconditionally in a postinst, it is OK for a package to
5788 simply put ldconfig in its postinst without checking the
5789 argument. The postinst can also be called to recover from
5790 a failed upgrade. This happens before any new files are
5791 unpacked, so there is no reason to call "ldconfig" at this
5796 For a package that is being removed, prerm is
5797 called with all the files intact, so calling ldconfig is
5798 useless. The other calls to "prerm" happen in the case of
5799 upgrade at a time when all the files of the old package
5800 are on-disk, so again calling "ldconfig" is pointless.
5804 postrm, on the other hand, is called with the "remove"
5805 argument just after the files are removed, so this is
5806 the proper time to call "ldconfig" to notify the system
5807 of the fact that the shared libraries from the package
5808 are removed. The postrm can be called at several other
5809 times. At the time of "postrm purge", "postrm
5810 abort-install", or "postrm abort-upgrade", calling
5811 "ldconfig" is useless because the shared lib files are
5812 not on-disk. However, when "postrm" is invoked with
5813 arguments "upgrade", "failed-upgrade", or "disappear", a
5814 shared lib may exist on-disk under a temporary filename.
5822 <sect id="sharedlibs-support-files">
5823 <heading>Shared library support files</heading>
5826 If your package contains files whose names do not change with
5827 each change in the library shared object version, you must not
5828 put them in the shared library package. Otherwise, several
5829 versions of the shared library cannot be installed at the same
5830 time without filename clashes, making upgrades and transitions
5831 unnecessarily difficult.
5835 It is recommended that supporting files and run-time support
5836 programs that do not need to be invoked manually by users, but
5837 are nevertheless required for the package to function, be placed
5838 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5839 preferably under <file>/usr/lib/</file><var>package-name</var>.
5840 If the program or file is architecture independent, the
5841 recommendation is for it to be placed in a subdirectory of
5842 <file>/usr/share</file> instead, preferably under
5843 <file>/usr/share/</file><var>package-name</var>. Following the
5844 <var>package-name</var> naming convention ensures that the file
5845 names change when the shared object version changes.
5849 Run-time support programs that use the shared library but are
5850 not required for the library to function or files used by the
5851 shared library that can be used by any version of the shared
5852 library package should instead be put in a separate package.
5853 This package might typically be named
5854 <package><var>libraryname</var>-tools</package>; note the
5855 absence of the <var>soversion</var> in the package name.
5859 Files and support programs only useful when compiling software
5860 against the library should be included in the development
5861 package for the library.<footnote>
5862 For example, a <file><var>package-name</var>-config</file>
5863 script or <package>pkg-config</package> configuration files.
5868 <sect id="sharedlibs-static">
5869 <heading>Static libraries</heading>
5872 The static library (<file><var>libraryname.a</var></file>)
5873 is usually provided in addition to the shared version.
5874 It is placed into the development package (see below).
5878 In some cases, it is acceptable for a library to be
5879 available in static form only; these cases include:
5881 <item>libraries for languages whose shared library support
5882 is immature or unstable</item>
5883 <item>libraries whose interfaces are in flux or under
5884 development (commonly the case when the library's
5885 major version number is zero, or where the ABI breaks
5886 across patchlevels)</item>
5887 <item>libraries which are explicitly intended to be
5888 available only in static form by their upstream
5893 <sect id="sharedlibs-dev">
5894 <heading>Development files</heading>
5897 If there are development files associated with a shared library,
5898 the source package needs to generate a binary development package
5899 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5900 or if you prefer only to support one development version at a
5901 time, <package><var>libraryname</var>-dev</package>. Installing
5902 the development package must result in installation of all the
5903 development files necessary for compiling programs against that
5904 shared library.<footnote>
5905 This wording allows the development files to be split into
5906 several packages, such as a separate architecture-independent
5907 <package><var>libraryname</var>-headers</package>, provided that
5908 the development package depends on all the required additional
5914 In case several development versions of a library exist, you may
5915 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5916 <ref id="conflicts">) to ensure that the user only installs one
5917 development version at a time (as different development versions are
5918 likely to have the same header files in them, which would cause a
5919 filename clash if both were unpacked).
5923 The development package should contain a symlink for the associated
5924 shared library without a version number. For example, the
5925 <package>libgdbm-dev</package> package should include a symlink
5926 from <file>/usr/lib/libgdbm.so</file> to
5927 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5928 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5929 <file>libgdbm.so</file> when compiling dynamically.
5933 If the package provides Ada Library Information
5934 (<file>*.ali</file>) files for use with GNAT, these files must be
5935 installed read-only (mode 0444) so that GNAT will not attempt to
5936 recompile them. This overrides the normal file mode requirements
5937 given in <ref id="permissions-owners">.
5941 <sect id="sharedlibs-intradeps">
5942 <heading>Dependencies between the packages of the same library</heading>
5945 Typically the development version should have an exact
5946 version dependency on the runtime library, to make sure that
5947 compilation and linking happens correctly. The
5948 <tt>${binary:Version}</tt> substitution variable can be
5949 useful for this purpose.
5951 Previously, <tt>${Source-Version}</tt> was used, but its name
5952 was confusing and it has been deprecated since dpkg 1.13.19.
5957 <sect id="sharedlibs-depends">
5958 <heading>Dependencies between the library and other
5962 If a package contains a binary or library which links to a
5963 shared library, we must ensure that, when the package is
5964 installed on the system, all of the libraries needed are also
5965 installed. These dependencies must be added to the binary
5966 package when it is built, since they may change based on which
5967 version of a shared library the binary or library was linked
5968 with even if there are no changes to the source of the binary
5969 (for example, symbol versions change, macros become functions or
5970 vice versa, or the binary package may determine at compile-time
5971 whether new library interfaces are available and can be called).
5972 To allow these dependencies to be constructed, shared libraries
5973 must provide either a <file>symbols</file> file or
5974 a <file>shlibs</file> file. These provide information on the
5975 package dependencies required to ensure the presence of
5976 interfaces provided by this library. Any package with binaries
5977 or libraries linking to a shared library must use these files to
5978 determine the required dependencies when it is built. Other
5979 packages which use a shared library (for example using
5980 <tt>dlopen()</tt>) should compute appropriate dependencies
5981 using these files at build time as well.
5985 The two mechanisms differ in the degree of detail that they
5986 provide. A <file>symbols</file> file documents, for each symbol
5987 exported by a library, the minimal version of the package any
5988 binary using this symbol will need. This is typically the
5989 version of the package in which the symbol was introduced. This
5990 information permits detailed analysis of the symbols used by a
5991 particular package and construction of an accurate dependency,
5992 but it requires the package maintainer to track more information
5993 about the shared library.
5997 A <file>shlibs</file> file, in contrast, only documents the last
5998 time the library ABI changed in any way. It only provides
5999 information about the library as a whole, not individual
6000 symbols. When a package is built using a shared library with
6001 only a <file>shlibs</file> file, the generated dependency will
6002 require a version of the shared library equal to or newer than
6003 the version of the last ABI change. This generates
6004 unnecessarily restrictive dependencies compared
6005 to <file>symbols</file> files if none of the symbols used by the
6006 package have changed. This, in turn, may make upgrades
6007 needlessly complex and unnecessarily restrict use of the package
6008 on systems with older versions of the shared libraries.
6012 <file>shlibs</file> files also only support a limited range of
6013 library SONAMEs, making it difficult to use <file>shlibs</file>
6014 files in some unusual corner cases.<footnote>
6015 A <file>shlibs</file> file represents an SONAME as a library
6016 name and version number, such as <tt>libfoo VERSION</tt>,
6017 instead of recording the actual SONAME. If the SONAME doesn't
6018 match one of the two expected formats
6019 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6020 cannot be represented.
6025 <file>symbols</file> files are therefore recommended for most
6026 shared library packages since they provide more accurate
6027 dependencies. For most C libraries, the additional detail
6028 required by <file>symbols</file> files is not too difficult to
6029 maintain. However, maintaining exhaustive symbols information
6030 for a C++ library can be quite onerous, so <file>shlibs</file>
6031 files may be more appropriate for most C++ libraries. Libraries
6032 with a corresponding udeb must also provide
6033 a <file>shlibs</file> file, since the udeb infrastructure does
6034 not use <file>symbols</file> files.
6037 <sect1 id="dpkg-shlibdeps">
6038 <heading>Generating dependencies on shared libraries</heading>
6041 When a package that contains any shared libraries or compiled
6042 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6043 each shared library and compiled binary to determine the
6044 libraries used and hence the dependencies needed by the
6046 <prgn>dpkg-shlibdeps</prgn> will use a program
6047 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6048 the libraries and the symbols in those libraries directly
6049 needed by the binaries or shared libraries in the package.
6051 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6052 your <file>debian/rules</file> file in the source package.
6053 List all of the compiled binaries, libraries, or loadable
6054 modules in your package.<footnote>
6055 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6056 correctly is to use a package helper framework such
6057 as <package>debhelper</package>. If you are
6058 using <package>debhelper</package>,
6059 the <prgn>dh_shlibdeps</prgn> program will do this work for
6060 you. It will also correctly handle multi-binary packages.
6062 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6063 or <file>shlibs</file> files installed by the shared libraries
6064 to generate dependency information. The package must then
6065 provide a substitution variable into which the discovered
6066 dependency information can be placed.
6070 If you are creating a udeb for use in the Debian Installer,
6071 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6072 should use the dependency line of type <tt>udeb</tt> by adding
6073 the <tt>-tudeb</tt> option<footnote>
6074 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6075 will automatically add this option if it knows it is
6077 </footnote>. If there is no dependency line of
6078 type <tt>udeb</tt> in the <file>shlibs</file>
6079 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6080 regular dependency line.
6084 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6085 into the <file>debian/substvars</file> file by default, which
6086 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6087 to place a <tt>${shlibs:Depends}</tt> variable in
6088 the <tt>Depends</tt> field in the control file of every binary
6089 package built by this source package that contains compiled
6090 binaries, libraries, or loadable modules. If you have
6091 multiple binary packages, you will need to
6092 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6093 compiled libraries or binaries. For example, you could use
6094 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6095 specify a different <file>substvars</file> file for each
6096 binary package.<footnote>
6097 Again, <prgn>dh_shlibdeps</prgn>
6098 and <prgn>dh_gencontrol</prgn> will handle everything except
6099 the addition of the variable to the control file for you if
6100 you're using <package>debhelper</package>, including
6101 generating separate <file>substvars</file> files for each
6102 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6103 the appropriate flags.
6108 For more details on <prgn>dpkg-shlibdeps</prgn>,
6109 see <manref name="dpkg-shlibdeps" section="1">.
6113 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6114 library <tt>libbar</tt> if it is explicitly linked with that
6115 library (that is, the library is listed in the
6116 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6117 to the link line when the binary is created). Other libraries
6118 that are needed by <tt>libbar</tt> are
6119 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6120 linker will load them automatically when it
6121 loads <tt>libbar</tt>. A package should depend on the
6122 libraries it directly uses, but not the libraries it only uses
6123 indirectly. The dependencies for the libraries used
6124 directly will automatically pull in the indirectly-used
6125 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6126 automatically, but package maintainers need to be aware of
6127 this distinction between directly and indirectly using a
6128 library if they have to override its results for some reason.
6130 A good example of where this helps is the following. We
6131 could update <tt>libimlib</tt> with a new version that
6132 supports a new revision of a graphics format called dgf (but
6133 retaining the same major version number) and depends on a
6134 new library package <package>libdgf4</package> instead of
6135 the older <package>libdgf3</package>. If we
6136 used <prgn>ldd</prgn> to add dependencies for every library
6137 directly or indirectly linked with a binary, every package
6138 that uses <tt>libimlib</tt> would need to be recompiled so
6139 it would also depend on <package>libdgf4</package> in order
6140 to retire the older <package>libdgf3</package> package.
6141 Since dependencies are only added based on
6142 ELF <tt>NEEDED</tt> attribute, packages
6143 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6144 having the dependency on an appropriate version
6145 of <tt>libdgf</tt> and do not need rebuilding.
6150 <sect1 id="sharedlibs-updates">
6151 <heading>Shared library ABI changes</heading>
6154 Maintaining a shared library package using
6155 either <file>symbols</file> or <file>shlibs</file> files
6156 requires being aware of the exposed ABI of the shared library
6157 and any changes to it. Both <file>symbols</file>
6158 and <file>shlibs</file> files record every change to the ABI
6159 of the shared library; <file>symbols</file> files do so per
6160 public symbol, whereas <file>shlibs</file> files record only
6161 the last change for the entire library.
6165 There are two types of ABI changes: ones that are
6166 backward-compatible and ones that are not. An ABI change is
6167 backward-compatible if any reasonable program or library that
6168 was linked with the previous version of the shared library
6169 will still work correctly with the new version of the shared
6171 An example of an "unreasonable" program is one that uses
6172 library interfaces that are documented as internal and
6173 unsupported. If the only programs or libraries affected by
6174 a change are "unreasonable" ones, other techniques, such as
6175 declaring <tt>Breaks</tt> relationships with affected
6176 packages or treating their usage of the library as bugs in
6177 those packages, may be appropriate instead of changing the
6178 SONAME. However, the default approach is to change the
6179 SONAME for any change to the ABI that could break a program.
6181 Adding new symbols to the shared library is a
6182 backward-compatible change. Removing symbols from the shared
6183 library is not. Changing the behavior of a symbol may or may
6184 not be backward-compatible depending on the change; for
6185 example, changing a function to accept a new enum constant not
6186 previously used by the library is generally
6187 backward-compatible, but changing the members of a struct that
6188 is passed into library functions is generally not unless the
6189 library takes special precautions to accept old versions of
6194 ABI changes that are not backward-compatible normally require
6195 changing the <tt>SONAME</tt> of the library and therefore the
6196 shared library package name, which forces rebuilding all
6197 packages using that shared library to update their
6198 dependencies and allow them to use the new version of the
6199 shared library. For more information,
6200 see <ref id="sharedlibs-runtime">. The remainder of this
6201 section will deal with backward-compatible changes.
6205 Backward-compatible changes require either updating or
6206 recording the <var>minimal-version</var> for that symbol
6207 in <file>symbols</file> files or updating the version in
6208 the <var>dependencies</var> in <file>shlibs</file> files. For
6209 more information on how to do this in the two formats, see
6210 <ref id="symbols"> and <ref id="shlibs">. Below are general
6211 rules that apply to both files.
6215 The easy case is when a public symbol is added. Simply add
6216 the version at which the symbol was introduced
6217 (for <file>symbols</file> files) or update the dependency
6218 version (for <file>shlibs</file>) files. But special care
6219 should be taken to update dependency versions when the
6220 behavior of a public symbol changes. This is easy to neglect,
6221 since there is no automated method of determining such
6222 changes, but failing to update versions in this case may
6223 result in binary packages with too-weak dependencies that will
6224 fail at runtime, possibly in ways that can cause security
6225 vulnerabilities. If the package maintainer believes that a
6226 symbol behavior change may have occurred but isn't sure, it's
6227 safer to update the version rather than leave it unmodified.
6228 This may result in unnecessarily strict dependencies, but it
6229 ensures that packages whose dependencies are satisfied will
6234 A common example of when a change to the dependency version
6235 is required is a function that takes an enum or struct
6236 argument that controls what the function does. For example:
6238 enum library_op { OP_FOO, OP_BAR };
6239 int library_do_operation(enum library_op);
6241 If a new operation, <tt>OP_BAZ</tt>, is added,
6242 the <var>minimal-version</var>
6243 of <tt>library_do_operation</tt> (for <file>symbols</file>
6244 files) or the version in the dependency for the shared library
6245 (for <file>shlibs</file> files) must be increased to the
6246 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6247 binary built against the new version of the library (having
6248 detected at compile-time that the library
6249 supports <tt>OP_BAZ</tt>) may be installed with a shared
6250 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6251 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6256 Dependency versions in either <file>symbols</file>
6257 or <file>shlibs</file> files normally should not contain the
6258 Debian revision of the package, since the library behavior is
6259 normally fixed for a particular upstream version and any
6260 Debian packaging of that upstream version will have the same
6261 behavior. In the rare case that the library behavior was
6262 changed in a particular Debian revision, appending <tt>~</tt>
6263 to the end of the version that includes the Debian revision is
6264 recommended, since this allows backports of the shared library
6265 package using the normal backport versioning convention to
6266 satisfy the dependency.
6270 <sect1 id="sharedlibs-symbols">
6271 <heading>The <tt>symbols</tt> system</heading>
6274 In the following sections, we will first describe where the
6275 various <file>symbols</file> files are to be found, then
6276 the <file>symbols</file> file format, and finally how to
6277 create <file>symbols</file> files if your package contains a
6281 <sect2 id="symbols-paths">
6282 <heading>The <file>symbols</file> files present on the
6286 <file>symbols</file> files for a shared library are normally
6287 provided by the shared library package as a control file,
6288 but there are several override paths that are checked first
6289 in case that information is wrong or missing. The following
6290 list gives them in the order in which they are read
6291 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6292 the required information is used.
6295 <p><file>debian/*/DEBIAN/symbols</file></p>
6298 During the package build, if the package itself
6299 contains shared libraries with <file>symbols</file>
6300 files, they will be generated in these staging
6301 directories by <prgn>dpkg-gensymbols</prgn>
6302 (see <ref id="providing-symbols">). <file>symbols</file>
6303 files found in the build tree take precedence
6304 over <file>symbols</file> files from other binary
6309 These files must exist
6310 before <prgn>dpkg-shlibdeps</prgn> is run or the
6311 dependencies of binaries and libraries from a source
6312 package on other libraries from that same source
6313 package will not be correct. In practice, this means
6314 that <prgn>dpkg-gensymbols</prgn> must be run
6315 before <prgn>dpkg-shlibdeps</prgn> during the package
6317 An example may clarify. Suppose the source
6318 package <tt>foo</tt> generates two binary
6319 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6320 When building the binary packages, the contents of
6321 the packages are staged in the
6322 directories <file>debian/libfoo2</file>
6323 and <file>debian/foo-runtime</file> respectively.
6324 (<file>debian/tmp</file> could be used instead of
6325 one of these.) Since <tt>libfoo2</tt> provides
6326 the <tt>libfoo</tt> shared library, it will contain
6327 a <tt>symbols</tt> file, which will be installed
6328 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6329 eventually to be included as a control file in that
6330 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6332 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6334 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6335 to determine whether <tt>foo-prog</tt>'s library
6336 dependencies are satisfied by any of the libraries
6337 provided by <tt>libfoo2</tt>. Since those binaries
6338 were linked against the just-built shared library as
6339 part of the build process, the <file>symbols</file>
6340 file for the newly-built <tt>libfoo2</tt> must take
6341 precedence over a <file>symbols</file> file for any
6342 other <tt>libfoo2</tt> package already installed on
6350 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6351 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6355 Per-system overrides of shared library dependencies.
6356 These files normally do not exist. They are
6357 maintained by the local system administrator and must
6358 not be created by any Debian package.
6363 <p><file>symbols</file> control files for packages
6364 installed on the system</p>
6367 The <file>symbols</file> control files for all the
6368 packages currently installed on the system are
6369 searched last. This will be the most common source of
6370 shared library dependency information. These are
6372 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6373 packages should not rely on this and instead should
6374 use <tt>dpkg-query --control-path <var>package</var>
6375 symbols</tt> if for some reason these files need to be
6383 Be aware that if a <file>debian/shlibs.local</file> exists
6384 in the source package, it will override
6385 any <file>symbols</file> files. This is the only case where
6386 a <file>shlibs</file> is used despite <file>symbols</file>
6387 files being present. See <ref id="shlibs-paths">
6388 and <ref id="sharedlibs-shlibdeps"> for more information.
6392 <sect2 id="symbols">
6393 <heading>The <file>symbols</file> File Format</heading>
6396 The following documents the format of
6397 the <file>symbols</file> control file as included in binary
6398 packages. These files are built from
6399 template <file>symbols</file> files in the source package
6400 by <prgn>dpkg-gensymbols</prgn>. The template files support
6401 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6402 do some of the tedious work involved in
6403 maintaining <file>symbols</file> files, such as handling C++
6404 symbols or optional symbols that may not exist on particular
6405 architectures. When writing <file>symbols</file> files for
6406 a shared library package, refer
6407 to <manref name="dpkg-gensymbols" section="1"> for the
6412 A <file>symbols</file> may contain one or more entries, one
6413 for each shared library contained in the package
6414 corresponding to that <file>symbols</file>. Each entry has
6415 the following format:
6420 <var>library-soname</var> <var>main-dependency-template</var>
6421 [| <var>alternative-dependency-template</var>]
6423 [* <var>field-name</var>: <var>field-value</var>]
6425 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6430 To explain this format, we'll use the the <tt>zlib1g</tt>
6431 package as an example, which (at the time of writing)
6433 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6434 lines will be described first, followed by optional lines.
6438 <var>library-soname</var> must contain exactly the value of
6439 the ELF <tt>SONAME</tt> attribute of the shared library. In
6440 our example, this is <tt>libz.so.1</tt>.<footnote>
6441 This can be determined by using the command
6442 <example compact="compact">
6443 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6449 <var>main-dependency-template</var> has the same syntax as a
6450 dependency field in a binary package control file, except
6451 that the string <tt>#MINVER#</tt> is replaced by a version
6452 restriction like <tt>(>= <var>version</var>)</tt> or by
6453 nothing if an unversioned dependency is deemed sufficient.
6454 The version restriction will be based on which symbols from
6455 the shared library are referenced and the version at which
6456 they were introduced (see below). In nearly all
6457 cases, <var>main-dependency-template</var> will
6458 be <tt><var>package</var> #MINVER#</tt>,
6459 where <var>package</var> is the name of the binary package
6460 containing the shared library. This adds a simple,
6461 possibly-versioned dependency on the shared library package.
6462 In some rare cases, such as when multiple packages provide
6463 the same shared library ABI, the dependency template may
6464 need to be more complex.
6468 In our example, the first line of
6469 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6470 <example compact="compact">
6471 libz.so.1 zlib1g #MINVER#
6476 Each public symbol exported by the shared library must have
6477 a corresponding symbol line, indented by one
6478 space. <var>symbol</var> is the exported symbol (which, for
6479 C++, means the mangled symbol) followed by <tt>@</tt> and
6480 the symbol version, or the string <tt>Base</tt> if there is
6481 no symbol version. <var>minimal-version</var> is the most
6482 recent version of the shared library that changed the
6483 behavior of that symbol, whether by adding it, changing its
6484 function signature (the parameters, their types, or the
6485 return type), or changing its behavior in a way that is
6486 visible to a caller.
6487 <var>id-of-dependency-template</var> is an optional
6488 field that references
6489 an <var>alternative-dependency-template</var>; see below for
6494 For example, <tt>libz.so.1</tt> contains the
6495 symbols <tt>compress</tt>
6496 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6497 version and last changed its behavior in upstream
6498 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6499 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6500 upstream version <tt>1:1.2.0</tt>, and has not changed its
6501 behavior. Its <file>symbols</file> file therefore contains
6503 <example compact="compact">
6504 compress@Base 1:1.1.4
6505 compressBound@ZLIB_1.2.0 1:1.2.0
6507 Packages using only <tt>compress</tt> would then get a
6508 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6509 using <tt>compressBound</tt> would get a dependency
6510 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6514 One or more <var>alternative-dependency-template</var> lines
6515 may be provided. These are used in cases where some symbols
6516 in the shared library should use one dependency template
6517 while others should use a different template. The
6518 alternative dependency templates are used only if a symbol
6519 line contains the <var>id-of-dependency-template</var>
6520 field. The first alternative dependency template is
6521 numbered 1, the second 2, and so forth.<footnote>
6522 An example of where this may be needed is with a library
6523 that implements the libGL interface. All GL
6524 implementations provide the same set of base interfaces,
6525 and then may provide some additional interfaces only used
6526 by programs that require that specific GL implementation.
6527 So, for example, libgl1-mesa-glx may use the
6528 following <file>symbols</file> file:
6531 | libgl1-mesa-glx #MINVER#
6532 publicGlSymbol@Base 6.3-1
6534 implementationSpecificSymbol@Base 6.5.2-7 1
6537 Binaries or shared libraries using
6538 only <tt>publicGlSymbol</tt> would depend only
6539 on <tt>libgl1</tt> (which may be provided by multiple
6541 using <tt>implementationSpecificSymbol</tt> would get a
6542 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6547 Finally, the entry for the library may contain one or more
6548 metadata fields. Currently, the only
6549 supported <var>field-name</var>
6550 is <tt>Build-Depends-Package</tt>, whose value lists
6551 the <qref id="sharedlibs-dev">library development
6552 package</qref> on which packages using this shared library
6553 declare a build dependency. If this field is
6554 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6555 the resulting binary package dependency on the shared
6556 library is at least as strict as the source package
6557 dependency on the shared library development
6559 This field should normally not be necessary, since if the
6560 behavior of any symbol has changed, the corresponding
6561 symbol <var>minimal-version</var> should have been
6562 increased. But including it makes the <tt>symbols</tt>
6563 system more robust by tightening the dependency in cases
6564 where the package using the shared library specifically
6565 requires at least a particular version of the shared
6566 library development package for some reason.
6568 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6570 <example compact="compact">
6571 * Build-Depends-Package: zlib1g-dev
6576 Also see <manref name="deb-symbols" section="5">.
6580 <sect2 id="providing-symbols">
6581 <heading>Providing a <file>symbols</file> file</heading>
6584 If your package provides a shared library, you should
6585 arrange to include a <file>symbols</file> control file
6586 following the format described above in that package. You
6587 must include either a <file>symbols</file> control file or
6588 a <file>shlibs</file> control file.
6592 Normally, this is done by creating a <file>symbols</file> in
6594 named <file>debian/<var>package</var>.symbols</file>
6595 or <file>debian/symbols</file>, possibly
6596 with <file>.<var>arch</var></file> appended if the symbols
6597 information varies by architecture. This file may use the
6598 extended syntax documented in <manref name="dpkg-gensymbols"
6599 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6600 part of the package build process. It will
6601 create <file>symbols</file> files in the package staging
6602 area based on the binaries and libraries in the package
6603 staging area and the <file>symbols</file> files in the
6604 source package.<footnote>
6606 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6607 take care of calling either <prgn>dpkg-gensymbols</prgn>
6608 or generating a <file>shlibs</file> file as appropriate.
6613 Packages that provide <file>symbols</file> files must keep
6614 them up-to-date to ensure correct dependencies in packages
6615 that use the shared libraries. This means updating
6616 the <file>symbols</file> file whenever a new public symbol
6617 is added, changing the <var>minimal-version</var> field
6618 whenever a symbol changes behavior or signature in a
6619 backward-compatible way (see <ref id="sharedlibs-updates">),
6620 and changing the <var>library-soname</var>
6621 and <var>main-dependency-template</var>, and probably all of
6622 the <var>minimal-version</var> fields, when the library
6623 changes <tt>SONAME</tt>. Removing a public symbol from
6624 the <file>symbols</file> file because it's no longer
6625 provided by the library normally requires changing
6626 the <tt>SONAME</tt> of the library.
6627 See <ref id="sharedlibs-runtime"> for more information
6628 on <tt>SONAME</tt>s.
6633 <sect1 id="sharedlibs-shlibdeps">
6634 <heading>The <tt>shlibs</tt> system</heading>
6637 The <tt>shlibs</tt> system is a simpler alternative to
6638 the <tt>symbols</tt> system for declaring dependencies for
6639 shared libraries. It may be more appropriate for C++
6640 libraries and other cases where tracking individual symbols is
6641 too difficult. It predated the <tt>symbols</tt> system and is
6642 therefore frequently seen in older packages. It is also
6643 required for udebs, which do not support <tt>symbols</tt>.
6647 In the following sections, we will first describe where the
6648 various <file>shlibs</file> files are to be found, then how to
6649 use <prgn>dpkg-shlibdeps</prgn>, and finally
6650 the <file>shlibs</file> file format and how to create them.
6653 <sect2 id="shlibs-paths">
6654 <heading>The <file>shlibs</file> files present on the
6658 There are several places where <tt>shlibs</tt> files are
6659 found. The following list gives them in the order in which
6660 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6661 one which gives the required information is used.)
6664 <p><file>debian/shlibs.local</file></p>
6667 This lists overrides for this package. This file
6668 should normally not be used, but may be needed
6669 temporarily in unusual situations to work around bugs
6670 in other packages, or in unusual cases where the
6671 normally declared dependency information in the
6672 installed <file>shlibs</file> file for a library
6673 cannot be used. This file overrides information
6674 obtained from any other source.
6679 <p><file>/etc/dpkg/shlibs.override</file></p>
6682 This lists global overrides. This list is normally
6683 empty. It is maintained by the local system
6689 <p><file>DEBIAN/shlibs</file> files in the "build
6693 These files are generated as part of the package build
6694 process and staged for inclusion as control files in
6695 the binary packages being built. They provide details
6696 of any shared libraries included in the same package.
6701 <p><file>shlibs</file> control files for packages
6702 installed on the system</p>
6705 The <file>shlibs</file> control files for all the
6706 packages currently installed on the system. These are
6708 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6709 packages should not rely on this and instead should
6710 use <tt>dpkg-query --control-path <var>package</var>
6711 shlibs</tt> if for some reason these files need to be
6717 <p><file>/etc/dpkg/shlibs.default</file></p>
6720 This file lists any shared libraries whose packages
6721 have failed to provide correct <file>shlibs</file>
6722 files. It was used when the <file>shlibs</file> setup
6723 was first introduced, but it is now normally empty.
6724 It is maintained by the <tt>dpkg</tt> maintainer.
6731 If a <file>symbols</file> file for a shared library package
6732 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6733 in preference to a <file>shlibs</file>, with the exception
6734 of <file>debian/shlibs.local</file>. The latter overrides
6735 any other <file>shlibs</file> or <file>symbols</file> files.
6740 <heading>The <file>shlibs</file> File Format</heading>
6743 Each <file>shlibs</file> file has the same format. Lines
6744 beginning with <tt>#</tt> are considered to be comments and
6745 are ignored. Each line is of the form:
6746 <example compact="compact">
6747 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6752 We will explain this by reference to the example of the
6753 <tt>zlib1g</tt> package, which (at the time of writing)
6755 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6759 <var>type</var> is an optional element that indicates the
6760 type of package for which the line is valid. The only type
6761 currently in use is <tt>udeb</tt>. The colon and space
6762 after the type are required.
6766 <var>library-name</var> is the name of the shared library,
6767 in this case <tt>libz</tt>. (This must match the name part
6768 of the soname, see below.)
6772 <var>soname-version</var> is the version part of the
6773 ELF <tt>SONAME</tt> attribute of the library, determined the
6774 same way that the <var>soversion</var> component of the
6775 recommended shared library package name is determined.
6776 See <ref id="sharedlibs-runtime"> for the details.
6780 <var>dependencies</var> has the same syntax as a dependency
6781 field in a binary package control file. It should give
6782 details of which packages are required to satisfy a binary
6783 built against the version of the library contained in the
6784 package. See <ref id="depsyntax"> for details on the
6785 syntax, and <ref id="sharedlibs-updates"> for details on how
6786 to maintain the dependency version constraint.
6790 In our example, if the last change to the <tt>zlib1g</tt>
6791 package that could change behavior for a client of that
6792 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6793 the <tt>shlibs</tt> entry for this library could say:
6794 <example compact="compact">
6795 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6797 This version restriction must be new enough that any binary
6798 built against the current version of the library will work
6799 with any version of the shared library that satisfies that
6804 As zlib1g also provides a udeb containing the shared
6805 library, there would also be a second line:
6806 <example compact="compact">
6807 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6813 <heading>Providing a <file>shlibs</file> file</heading>
6816 To provide a <file>shlibs</file> file for a shared library
6817 binary package, create a <file>shlibs</file> file following
6818 the format described above and place it in
6819 the <file>DEBIAN</file> directory for that package during
6820 the build. It will then be included as a control file for
6821 that package<footnote>
6822 This is what <prgn>dh_makeshlibs</prgn> in
6823 the <package>debhelper</package> suite does. If your
6824 package also has a udeb that provides a shared
6825 library, <prgn>dh_makeshlibs</prgn> can automatically
6826 generate the <tt>udeb:</tt> lines if you specify the name
6827 of the udeb with the <tt>--add-udeb</tt> option.
6832 Since <prgn>dpkg-shlibdeps</prgn> reads
6833 the <file>DEBIAN/shlibs</file> files in all of the binary
6834 packages being built from this source package, all of
6835 the <file>DEBIAN/shlibs</file> files should be installed
6836 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6845 <chapt id="opersys"><heading>The Operating System</heading>
6848 <heading>File system hierarchy</heading>
6852 <heading>File System Structure</heading>
6855 The location of all files and directories must comply with the
6856 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6857 exceptions noted below, and except where doing so would
6858 violate other terms of Debian Policy. The following
6859 exceptions to the FHS apply:
6864 The optional rules related to user specific
6865 configuration files for applications are stored in
6866 the user's home directory are relaxed. It is
6867 recommended that such files start with the
6868 '<tt>.</tt>' character (a "dot file"), and if an
6869 application needs to create more than one dot file
6870 then the preferred placement is in a subdirectory
6871 with a name starting with a '.' character, (a "dot
6872 directory"). In this case it is recommended the
6873 configuration files not start with the '.'
6879 The requirement for amd64 to use <file>/lib64</file>
6880 for 64 bit binaries is removed.
6885 The requirement for object files, internal binaries, and
6886 libraries, including <file>libc.so.*</file>, to be located
6887 directly under <file>/lib{,32}</file> and
6888 <file>/usr/lib{,32}</file> is amended, permitting files
6889 to instead be installed to
6890 <file>/lib/<var>triplet</var></file> and
6891 <file>/usr/lib/<var>triplet</var></file>, where
6892 <tt><var>triplet</var></tt> is the value returned by
6893 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6894 architecture of the package. Packages may <em>not</em>
6895 install files to any <var>triplet</var> path other
6896 than the one matching the architecture of that package;
6897 for instance, an <tt>Architecture: amd64</tt> package
6898 containing 32-bit x86 libraries may not install these
6899 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6901 This is necessary in order to reserve the directories for
6902 use in cross-installation of library packages from other
6903 architectures, as part of the planned deployment of
6908 Applications may also use a single subdirectory under
6909 <file>/usr/lib/<var>triplet</var></file>.
6912 The execution time linker/loader, ld*, must still be made
6913 available in the existing location under /lib or /lib64
6914 since this is part of the ELF ABI for the architecture.
6919 The requirement that
6920 <file>/usr/local/share/man</file> be "synonymous"
6921 with <file>/usr/local/man</file> is relaxed to a
6926 The requirement that windowmanagers with a single
6927 configuration file call it <file>system.*wmrc</file>
6928 is removed, as is the restriction that the window
6929 manager subdirectory be named identically to the
6930 window manager name itself.
6935 The requirement that boot manager configuration
6936 files live in <file>/etc</file>, or at least are
6937 symlinked there, is relaxed to a recommendation.
6942 The additional directory <file>/run</file> in the root
6943 file system is allowed. <file>/run</file>
6944 replaces <file>/var/run</file>, and the
6945 subdirectory <file>/run/lock</file>
6946 replaces <file>/var/lock</file>, with
6947 the <file>/var</file> directories replaced by symlinks
6948 for backwards compatibility. <file>/run</file>
6949 and <file>/run/lock</file> must follow all of the
6950 requirements in the FHS for <file>/var/run</file>
6951 and <file>/var/lock</file>, respectively, such as file
6952 naming conventions, file format requirements, or the
6953 requirement that files be cleared during the boot
6954 process. Files and directories residing
6955 in <file>/run</file> should be stored on a temporary
6959 Packages must not assume the <file>/run</file>
6960 directory exists or is usable without a dependency
6961 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
6962 stable release of Debian supports <file>/run</file>.
6967 The following directories in the root filesystem are
6968 additionally allowed: <file>/sys</file> and
6969 <file>/selinux</file>. <footnote>These directories
6970 are used as mount points to mount virtual filesystems
6971 to get access to kernel information.</footnote>
6976 On GNU/Hurd systems, the following additional
6977 directories are allowed in the root
6978 filesystem: <file>/hurd</file>
6979 and <file>/servers</file>.<footnote>
6980 These directories are used to store translators and as
6981 a set of standard names for mount points,
6990 The version of this document referred here can be
6991 found in the <tt>debian-policy</tt> package or on <url
6992 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6993 name="FHS (Debian copy)"> alongside this manual (or, if
6994 you have the <package>debian-policy</package> installed,
6996 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6997 (local copy)">). The
6998 latest version, which may be a more recent version, may
7000 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7001 Specific questions about following the standard may be
7002 asked on the <tt>debian-devel</tt> mailing list, or
7003 referred to the FHS mailing list (see the
7004 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7010 <heading>Site-specific programs</heading>
7013 As mandated by the FHS, packages must not place any
7014 files in <file>/usr/local</file>, either by putting them in
7015 the file system archive to be unpacked by <prgn>dpkg</prgn>
7016 or by manipulating them in their maintainer scripts.
7020 However, the package may create empty directories below
7021 <file>/usr/local</file> so that the system administrator knows
7022 where to place site-specific files. These are not
7023 directories <em>in</em> <file>/usr/local</file>, but are
7024 children of directories in <file>/usr/local</file>. These
7025 directories (<file>/usr/local/*/dir/</file>)
7026 should be removed on package removal if they are
7031 Note that this applies only to
7032 directories <em>below</em> <file>/usr/local</file>,
7033 not <em>in</em> <file>/usr/local</file>. Packages must
7034 not create sub-directories in the
7035 directory <file>/usr/local</file> itself, except those
7036 listed in FHS, section 4.5. However, you may create
7037 directories below them as you wish. You must not remove
7038 any of the directories listed in 4.5, even if you created
7043 Since <file>/usr/local</file> can be mounted read-only from a
7044 remote server, these directories must be created and
7045 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7046 maintainer scripts and not be included in the
7047 <file>.deb</file> archive. These scripts must not fail if
7048 either of these operations fail.
7052 For example, the <tt>emacsen-common</tt> package could
7053 contain something like
7054 <example compact="compact">
7055 if [ ! -e /usr/local/share/emacs ]; then
7056 if mkdir /usr/local/share/emacs 2>/dev/null; then
7057 if chown root:staff /usr/local/share/emacs; then
7058 chmod 2775 /usr/local/share/emacs || true
7063 in its <prgn>postinst</prgn> script, and
7064 <example compact="compact">
7065 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7066 rmdir /usr/local/share/emacs 2>/dev/null || true
7068 in the <prgn>prerm</prgn> script. (Note that this form is
7069 used to ensure that if the script is interrupted, the
7070 directory <file>/usr/local/share/emacs</file> will still be
7075 If you do create a directory in <file>/usr/local</file> for
7076 local additions to a package, you should ensure that
7077 settings in <file>/usr/local</file> take precedence over the
7078 equivalents in <file>/usr</file>.
7082 However, because <file>/usr/local</file> and its contents are
7083 for exclusive use of the local administrator, a package
7084 must not rely on the presence or absence of files or
7085 directories in <file>/usr/local</file> for normal operation.
7089 The <file>/usr/local</file> directory itself and all the
7090 subdirectories created by the package should (by default) have
7091 permissions 2775 (group-writable and set-group-id) and be
7092 owned by <tt>root:staff</tt>.
7097 <heading>The system-wide mail directory</heading>
7099 The system-wide mail directory
7100 is <file>/var/mail</file>. This directory is part of the
7101 base system and should not be owned by any particular mail
7102 agents. The use of the old
7103 location <file>/var/spool/mail</file> is deprecated, even
7104 though the spool may still be physically located there.
7108 <sect1 id="fhs-run">
7109 <heading><file>/run</file> and <file>/run/lock</file></heading>
7112 The directory <file>/run</file> is cleared at boot, normally
7113 by being a mount point for a temporary file system. Packages
7114 therefore must not assume that any files or directories
7115 under <file>/run</file> other than <file>/run/lock</file>
7116 exist unless the package has arranged to create those files or
7117 directories since the last reboot. Normally, this is done by
7118 the package via an init script. See <ref id="writing-init">
7119 for more information.
7123 Packages must not include files or directories
7124 under <file>/run</file>, or under the
7125 older <file>/var/run</file> and <file>/var/lock</file> paths.
7126 The latter paths will normally be symlinks or other
7127 redirections to <file>/run</file> for backwards compatibility.
7133 <heading>Users and groups</heading>
7136 <heading>Introduction</heading>
7138 The Debian system can be configured to use either plain or
7143 Some user ids (UIDs) and group ids (GIDs) are reserved
7144 globally for use by certain packages. Because some
7145 packages need to include files which are owned by these
7146 users or groups, or need the ids compiled into binaries,
7147 these ids must be used on any Debian system only for the
7148 purpose for which they are allocated. This is a serious
7149 restriction, and we should avoid getting in the way of
7150 local administration policies. In particular, many sites
7151 allocate users and/or local system groups starting at 100.
7155 Apart from this we should have dynamically allocated ids,
7156 which should by default be arranged in some sensible
7157 order, but the behavior should be configurable.
7161 Packages other than <tt>base-passwd</tt> must not modify
7162 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7163 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7168 <heading>UID and GID classes</heading>
7170 The UID and GID numbers are divided into classes as
7176 Globally allocated by the Debian project, the same
7177 on every Debian system. These ids will appear in
7178 the <file>passwd</file> and <file>group</file> files of all
7179 Debian systems, new ids in this range being added
7180 automatically as the <tt>base-passwd</tt> package is
7185 Packages which need a single statically allocated
7186 uid or gid should use one of these; their
7187 maintainers should ask the <tt>base-passwd</tt>
7195 Dynamically allocated system users and groups.
7196 Packages which need a user or group, but can have
7197 this user or group allocated dynamically and
7198 differently on each system, should use <tt>adduser
7199 --system</tt> to create the group and/or user.
7200 <prgn>adduser</prgn> will check for the existence of
7201 the user or group, and if necessary choose an unused
7202 id based on the ranges specified in
7203 <file>adduser.conf</file>.
7207 <tag>1000-59999:</tag>
7210 Dynamically allocated user accounts. By default
7211 <prgn>adduser</prgn> will choose UIDs and GIDs for
7212 user accounts in this range, though
7213 <file>adduser.conf</file> may be used to modify this
7218 <tag>60000-64999:</tag>
7221 Globally allocated by the Debian project, but only
7222 created on demand. The ids are allocated centrally
7223 and statically, but the actual accounts are only
7224 created on users' systems on demand.
7228 These ids are for packages which are obscure or
7229 which require many statically-allocated ids. These
7230 packages should check for and create the accounts in
7231 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7232 <prgn>adduser</prgn> if it has this facility) if
7233 necessary. Packages which are likely to require
7234 further allocations should have a "hole" left after
7235 them in the allocation, to give them room to
7240 <tag>65000-65533:</tag>
7248 User <tt>nobody</tt>. The corresponding gid refers
7249 to the group <tt>nogroup</tt>.
7256 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7257 not</em> be used, because it is the error return
7266 <sect id="sysvinit">
7267 <heading>System run levels and <file>init.d</file> scripts</heading>
7269 <sect1 id="/etc/init.d">
7270 <heading>Introduction</heading>
7273 The <file>/etc/init.d</file> directory contains the scripts
7274 executed by <prgn>init</prgn> at boot time and when the
7275 init state (or "runlevel") is changed (see <manref
7276 name="init" section="8">).
7280 There are at least two different, yet functionally
7281 equivalent, ways of handling these scripts. For the sake
7282 of simplicity, this document describes only the symbolic
7283 link method. However, it must not be assumed by maintainer
7284 scripts that this method is being used, and any automated
7285 manipulation of the various runlevel behaviors by
7286 maintainer scripts must be performed using
7287 <prgn>update-rc.d</prgn> as described below and not by
7288 manually installing or removing symlinks. For information
7289 on the implementation details of the other method,
7290 implemented in the <tt>file-rc</tt> package, please refer
7291 to the documentation of that package.
7295 These scripts are referenced by symbolic links in the
7296 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7297 runlevels, <prgn>init</prgn> looks in the directory
7298 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7299 execute, where <tt><var>n</var></tt> is the runlevel that
7300 is being changed to, or <tt>S</tt> for the boot-up
7305 The names of the links all have the form
7306 <file>S<var>mm</var><var>script</var></file> or
7307 <file>K<var>mm</var><var>script</var></file> where
7308 <var>mm</var> is a two-digit number and <var>script</var>
7309 is the name of the script (this should be the same as the
7310 name of the actual script in <file>/etc/init.d</file>).
7314 When <prgn>init</prgn> changes runlevel first the targets
7315 of the links whose names start with a <tt>K</tt> are
7316 executed, each with the single argument <tt>stop</tt>,
7317 followed by the scripts prefixed with an <tt>S</tt>, each
7318 with the single argument <tt>start</tt>. (The links are
7319 those in the <file>/etc/rc<var>n</var>.d</file> directory
7320 corresponding to the new runlevel.) The <tt>K</tt> links
7321 are responsible for killing services and the <tt>S</tt>
7322 link for starting services upon entering the runlevel.
7326 For example, if we are changing from runlevel 2 to
7327 runlevel 3, init will first execute all of the <tt>K</tt>
7328 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7329 all of the <tt>S</tt> prefixed scripts in that directory.
7330 The links starting with <tt>K</tt> will cause the
7331 referred-to file to be executed with an argument of
7332 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7337 The two-digit number <var>mm</var> is used to determine
7338 the order in which to run the scripts: low-numbered links
7339 have their scripts run first. For example, the
7340 <tt>K20</tt> scripts will be executed before the
7341 <tt>K30</tt> scripts. This is used when a certain service
7342 must be started before another. For example, the name
7343 server <prgn>bind</prgn> might need to be started before
7344 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7345 can set up its access lists. In this case, the script
7346 that starts <prgn>bind</prgn> would have a lower number
7347 than the script that starts <prgn>inn</prgn> so that it
7349 <example compact="compact">
7356 The two runlevels 0 (halt) and 6 (reboot) are slightly
7357 different. In these runlevels, the links with an
7358 <tt>S</tt> prefix are still called after those with a
7359 <tt>K</tt> prefix, but they too are called with the single
7360 argument <tt>stop</tt>.
7364 <sect1 id="writing-init">
7365 <heading>Writing the scripts</heading>
7368 Packages that include daemons for system services should
7369 place scripts in <file>/etc/init.d</file> to start or stop
7370 services at boot time or during a change of runlevel.
7371 These scripts should be named
7372 <file>/etc/init.d/<var>package</var></file>, and they should
7373 accept one argument, saying what to do:
7376 <tag><tt>start</tt></tag>
7377 <item>start the service,</item>
7379 <tag><tt>stop</tt></tag>
7380 <item>stop the service,</item>
7382 <tag><tt>restart</tt></tag>
7383 <item>stop and restart the service if it's already running,
7384 otherwise start the service</item>
7386 <tag><tt>reload</tt></tag>
7387 <item><p>cause the configuration of the service to be
7388 reloaded without actually stopping and restarting
7391 <tag><tt>force-reload</tt></tag>
7392 <item>cause the configuration to be reloaded if the
7393 service supports this, otherwise restart the
7397 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7398 <tt>force-reload</tt> options should be supported by all
7399 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7404 The <file>init.d</file> scripts must ensure that they will
7405 behave sensibly (i.e., returning success and not starting
7406 multiple copies of a service) if invoked with <tt>start</tt>
7407 when the service is already running, or with <tt>stop</tt>
7408 when it isn't, and that they don't kill unfortunately-named
7409 user processes. The best way to achieve this is usually to
7410 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7415 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7416 scripts. Writing correct <file>init.d</file> scripts requires
7417 accepting various error exit statuses when daemons are already
7418 running or already stopped without aborting
7419 the <file>init.d</file> script, and common <file>init.d</file>
7420 function libraries are not safe to call with <tt>set -e</tt>
7422 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7423 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7424 in effect and echoing status messages to the console fails,
7426 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7427 to not use <tt>set -e</tt> and instead check the result of
7428 each command separately.
7432 If a service reloads its configuration automatically (as
7433 in the case of <prgn>cron</prgn>, for example), the
7434 <tt>reload</tt> option of the <file>init.d</file> script
7435 should behave as if the configuration has been reloaded
7440 The <file>/etc/init.d</file> scripts must be treated as
7441 configuration files, either (if they are present in the
7442 package, that is, in the .deb file) by marking them as
7443 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7444 by managing them correctly in the maintainer scripts (see
7445 <ref id="config-files">). This is important since we want
7446 to give the local system administrator the chance to adapt
7447 the scripts to the local system, e.g., to disable a
7448 service without de-installing the package, or to specify
7449 some special command line options when starting a service,
7450 while making sure their changes aren't lost during the next
7455 These scripts should not fail obscurely when the
7456 configuration files remain but the package has been
7457 removed, as configuration files remain on the system after
7458 the package has been removed. Only when <prgn>dpkg</prgn>
7459 is executed with the <tt>--purge</tt> option will
7460 configuration files be removed. In particular, as the
7461 <file>/etc/init.d/<var>package</var></file> script itself is
7462 usually a <tt>conffile</tt>, it will remain on the system
7463 if the package is removed but not purged. Therefore, you
7464 should include a <tt>test</tt> statement at the top of the
7466 <example compact="compact">
7467 test -f <var>program-executed-later-in-script</var> || exit 0
7472 Often there are some variables in the <file>init.d</file>
7473 scripts whose values control the behavior of the scripts,
7474 and which a system administrator is likely to want to
7475 change. As the scripts themselves are frequently
7476 <tt>conffile</tt>s, modifying them requires that the
7477 administrator merge in their changes each time the package
7478 is upgraded and the <tt>conffile</tt> changes. To ease
7479 the burden on the system administrator, such configurable
7480 values should not be placed directly in the script.
7481 Instead, they should be placed in a file in
7482 <file>/etc/default</file>, which typically will have the same
7483 base name as the <file>init.d</file> script. This extra file
7484 should be sourced by the script when the script runs. It
7485 must contain only variable settings and comments in SUSv3
7486 <prgn>sh</prgn> format. It may either be a
7487 <tt>conffile</tt> or a configuration file maintained by
7488 the package maintainer scripts. See <ref id="config-files">
7493 To ensure that vital configurable values are always
7494 available, the <file>init.d</file> script should set default
7495 values for each of the shell variables it uses, either
7496 before sourcing the <file>/etc/default/</file> file or
7497 afterwards using something like the <tt>:
7498 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7499 script must behave sensibly and not fail if the
7500 <file>/etc/default</file> file is deleted.
7504 Files and directories under <file>/run</file>, including ones
7505 referred to via the compatibility paths <file>/var/run</file>
7506 and <file>/var/lock</file>, are normally stored on a temporary
7507 filesystem and are normally not persistent across a reboot.
7508 The <file>init.d</file> scripts must handle this correctly.
7509 This will typically mean creating any required subdirectories
7510 dynamically when the <file>init.d</file> script is run.
7511 See <ref id="fhs-run"> for more information.
7516 <heading>Interfacing with the initscript system</heading>
7519 Maintainers should use the abstraction layer provided by
7520 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7521 programs to deal with initscripts in their packages'
7522 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7523 and <prgn>postrm</prgn>.
7527 Directly managing the /etc/rc?.d links and directly
7528 invoking the <file>/etc/init.d/</file> initscripts should
7529 be done only by packages providing the initscript
7530 subsystem (such as <prgn>sysv-rc</prgn> and
7531 <prgn>file-rc</prgn>).
7535 <heading>Managing the links</heading>
7538 The program <prgn>update-rc.d</prgn> is provided for
7539 package maintainers to arrange for the proper creation and
7540 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7541 or their functional equivalent if another method is being
7542 used. This may be used by maintainers in their packages'
7543 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7547 You must not include any <file>/etc/rc<var>n</var>.d</file>
7548 symbolic links in the actual archive or manually create or
7549 remove the symbolic links in maintainer scripts; you must
7550 use the <prgn>update-rc.d</prgn> program instead. (The
7551 former will fail if an alternative method of maintaining
7552 runlevel information is being used.) You must not include
7553 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7554 in the archive either. (Only the <tt>sysvinit</tt>
7559 By default <prgn>update-rc.d</prgn> will start services in
7560 each of the multi-user state runlevels (2, 3, 4, and 5)
7561 and stop them in the halt runlevel (0), the single-user
7562 runlevel (1) and the reboot runlevel (6). The system
7563 administrator will have the opportunity to customize
7564 runlevels by simply adding, moving, or removing the
7565 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7566 symbolic links are being used, or by modifying
7567 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7572 To get the default behavior for your package, put in your
7573 <prgn>postinst</prgn> script
7574 <example compact="compact">
7575 update-rc.d <var>package</var> defaults
7577 and in your <prgn>postrm</prgn>
7578 <example compact="compact">
7579 if [ "$1" = purge ]; then
7580 update-rc.d <var>package</var> remove
7582 </example>. Note that if your package changes runlevels
7583 or priority, you may have to remove and recreate the links,
7584 since otherwise the old links may persist. Refer to the
7585 documentation of <prgn>update-rc.d</prgn>.
7589 This will use a default sequence number of 20. If it does
7590 not matter when or in which order the <file>init.d</file>
7591 script is run, use this default. If it does, then you
7592 should talk to the maintainer of the <prgn>sysvinit</prgn>
7593 package or post to <tt>debian-devel</tt>, and they will
7594 help you choose a number.
7598 For more information about using <tt>update-rc.d</tt>,
7599 please consult its man page <manref name="update-rc.d"
7605 <heading>Running initscripts</heading>
7607 The program <prgn>invoke-rc.d</prgn> is provided to make
7608 it easier for package maintainers to properly invoke an
7609 initscript, obeying runlevel and other locally-defined
7610 constraints that might limit a package's right to start,
7611 stop and otherwise manage services. This program may be
7612 used by maintainers in their packages' scripts.
7616 The package maintainer scripts must use
7617 <prgn>invoke-rc.d</prgn> to invoke the
7618 <file>/etc/init.d/*</file> initscripts, instead of
7619 calling them directly.
7623 By default, <prgn>invoke-rc.d</prgn> will pass any
7624 action requests (start, stop, reload, restart...) to the
7625 <file>/etc/init.d</file> script, filtering out requests
7626 to start or restart a service out of its intended
7631 Most packages will simply need to change:
7632 <example compact="compact">/etc/init.d/<package>
7633 <action></example> in their <prgn>postinst</prgn>
7634 and <prgn>prerm</prgn> scripts to:
7635 <example compact="compact">
7636 if which invoke-rc.d >/dev/null 2>&1; then
7637 invoke-rc.d <var>package</var> <action>
7639 /etc/init.d/<var>package</var> <action>
7645 A package should register its initscript services using
7646 <prgn>update-rc.d</prgn> before it tries to invoke them
7647 using <prgn>invoke-rc.d</prgn>. Invocation of
7648 unregistered services may fail.
7652 For more information about using
7653 <prgn>invoke-rc.d</prgn>, please consult its man page
7654 <manref name="invoke-rc.d" section="8">.
7660 <heading>Boot-time initialization</heading>
7663 There used to be another directory, <file>/etc/rc.boot</file>,
7664 which contained scripts which were run once per machine
7665 boot. This has been deprecated in favour of links from
7666 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7667 described in <ref id="/etc/init.d">. Packages must not
7668 place files in <file>/etc/rc.boot</file>.
7673 <heading>Example</heading>
7676 An example on which you can base your
7677 <file>/etc/init.d</file> scripts is found in
7678 <file>/etc/init.d/skeleton</file>.
7685 <heading>Console messages from <file>init.d</file> scripts</heading>
7688 This section describes the formats to be used for messages
7689 written to standard output by the <file>/etc/init.d</file>
7690 scripts. The intent is to improve the consistency of
7691 Debian's startup and shutdown look and feel. For this
7692 reason, please look very carefully at the details. We want
7693 the messages to have the same format in terms of wording,
7694 spaces, punctuation and case of letters.
7698 Here is a list of overall rules that should be used for
7699 messages generated by <file>/etc/init.d</file> scripts.
7705 The message should fit in one line (fewer than 80
7706 characters), start with a capital letter and end with
7707 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7711 If the script is performing some time consuming task in
7712 the background (not merely starting or stopping a
7713 program, for instance), an ellipsis (three dots:
7714 <tt>...</tt>) should be output to the screen, with no
7715 leading or tailing whitespace or line feeds.
7719 The messages should appear as if the computer is telling
7720 the user what it is doing (politely :-), but should not
7721 mention "it" directly. For example, instead of:
7722 <example compact="compact">
7723 I'm starting network daemons: nfsd mountd.
7725 the message should say
7726 <example compact="compact">
7727 Starting network daemons: nfsd mountd.
7734 <tt>init.d</tt> script should use the following standard
7735 message formats for the situations enumerated below.
7741 <p>When daemons are started</p>
7744 If the script starts one or more daemons, the output
7745 should look like this (a single line, no leading
7747 <example compact="compact">
7748 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7750 The <var>description</var> should describe the
7751 subsystem the daemon or set of daemons are part of,
7752 while <var>daemon-1</var> up to <var>daemon-n</var>
7753 denote each daemon's name (typically the file name of
7758 For example, the output of <file>/etc/init.d/lpd</file>
7760 <example compact="compact">
7761 Starting printer spooler: lpd.
7766 This can be achieved by saying
7767 <example compact="compact">
7768 echo -n "Starting printer spooler: lpd"
7769 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7772 in the script. If there are more than one daemon to
7773 start, the output should look like this:
7774 <example compact="compact">
7775 echo -n "Starting remote file system services:"
7776 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7777 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7778 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7781 This makes it possible for the user to see what is
7782 happening and when the final daemon has been started.
7783 Care should be taken in the placement of white spaces:
7784 in the example above the system administrators can
7785 easily comment out a line if they don't want to start
7786 a specific daemon, while the displayed message still
7792 <p>When a system parameter is being set</p>
7795 If you have to set up different system parameters
7796 during the system boot, you should use this format:
7797 <example compact="compact">
7798 Setting <var>parameter</var> to "<var>value</var>".
7803 You can use a statement such as the following to get
7805 <example compact="compact">
7806 echo "Setting DNS domainname to \"$domainname\"."
7811 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7812 for the left and right quotation marks. A grave accent
7813 (<tt>`</tt>) is not a quote character; neither is an
7814 apostrophe (<tt>'</tt>).
7819 <p>When a daemon is stopped or restarted</p>
7822 When you stop or restart a daemon, you should issue a
7823 message identical to the startup message, except that
7824 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7825 or <tt>Restarting</tt> respectively.
7829 For example, stopping the printer daemon will look like
7831 <example compact="compact">
7832 Stopping printer spooler: lpd.
7838 <p>When something is executed</p>
7841 There are several examples where you have to run a
7842 program at system startup or shutdown to perform a
7843 specific task, for example, setting the system's clock
7844 using <prgn>netdate</prgn> or killing all processes
7845 when the system shuts down. Your message should look
7847 <example compact="compact">
7848 Doing something very useful...done.
7850 You should print the <tt>done.</tt> immediately after
7851 the job has been completed, so that the user is
7852 informed why they have to wait. You can get this
7854 <example compact="compact">
7855 echo -n "Doing something very useful..."
7864 <p>When the configuration is reloaded</p>
7867 When a daemon is forced to reload its configuration
7868 files you should use the following format:
7869 <example compact="compact">
7870 Reloading <var>description</var> configuration...done.
7872 where <var>description</var> is the same as in the
7873 daemon starting message.
7880 <sect id="cron-jobs">
7881 <heading>Cron jobs</heading>
7884 Packages must not modify the configuration file
7885 <file>/etc/crontab</file>, and they must not modify the files in
7886 <file>/var/spool/cron/crontabs</file>.
7890 If a package wants to install a job that has to be executed via
7891 cron, it should place a file named as specified
7892 in <ref id="cron-files"> into one or more of the following
7894 <example compact="compact">
7900 As these directory names imply, the files within them are
7901 executed on an hourly, daily, weekly, or monthly basis,
7902 respectively. The exact times are listed in
7903 <file>/etc/crontab</file>.
7907 All files installed in any of these directories must be
7908 scripts (e.g., shell scripts or Perl scripts) so that they
7909 can easily be modified by the local system administrator.
7910 In addition, they must be treated as configuration files.
7914 If a certain job has to be executed at some other frequency or
7915 at a specific time, the package should install a file in
7916 <file>/etc/cron.d</file> with a name as specified
7917 in <ref id="cron-files">. This file uses the same syntax
7918 as <file>/etc/crontab</file> and is processed
7919 by <prgn>cron</prgn> automatically. The file must also be
7920 treated as a configuration file. (Note that entries in the
7921 <file>/etc/cron.d</file> directory are not handled by
7922 <prgn>anacron</prgn>. Thus, you should only use this
7923 directory for jobs which may be skipped if the system is not
7928 Unlike <file>crontab</file> files described in the IEEE Std
7929 1003.1-2008 (POSIX.1) available from
7930 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7931 name="The Open Group">, the files in
7932 <file>/etc/cron.d</file> and the file
7933 <file>/etc/crontab</file> have seven fields; namely:
7935 <item>Minute [0,59]</item>
7936 <item>Hour [0,23]</item>
7937 <item>Day of the month [1,31]</item>
7938 <item>Month of the year [1,12]</item>
7939 <item>Day of the week ([0,6] with 0=Sunday)</item>
7940 <item>Username</item>
7941 <item>Command to be run</item>
7943 Ranges of numbers are allowed. Ranges are two numbers
7944 separated with a hyphen. The specified range is inclusive.
7945 Lists are allowed. A list is a set of numbers (or ranges)
7946 separated by commas. Step values can be used in conjunction
7951 The scripts or <tt>crontab</tt> entries in these directories should
7952 check if all necessary programs are installed before they
7953 try to execute them. Otherwise, problems will arise when a
7954 package was removed but not purged since configuration files
7955 are kept on the system in this situation.
7959 Any <tt>cron</tt> daemon must provide
7960 <file>/usr/bin/crontab</file> and support normal
7961 <tt>crontab</tt> entries as specified in POSIX. The daemon
7962 must also support names for days and months, ranges, and
7963 step values. It has to support <file>/etc/crontab</file>,
7964 and correctly execute the scripts in
7965 <file>/etc/cron.d</file>. The daemon must also correctly
7967 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7970 <sect1 id="cron-files">
7971 <heading>Cron job file names</heading>
7974 The file name of a cron job file should normally match the
7975 name of the package from which it comes.
7979 If a package supplies multiple cron job files files in the
7980 same directory, the file names should all start with the name
7981 of the package (possibly modified as described below) followed
7982 by a hyphen (<tt>-</tt>) and a suitable suffix.
7986 A cron job file name must not include any period or plus
7987 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7988 cause cron to ignore the file. Underscores (<tt>_</tt>)
7989 should be used instead of <tt>.</tt> and <tt>+</tt>
7996 <heading>Menus</heading>
7999 The Debian <tt>menu</tt> package provides a standard
8000 interface between packages providing applications and
8001 <em>menu programs</em> (either X window managers or
8002 text-based menu programs such as <prgn>pdmenu</prgn>).
8006 All packages that provide applications that need not be
8007 passed any special command line arguments for normal
8008 operation should register a menu entry for those
8009 applications, so that users of the <tt>menu</tt> package
8010 will automatically get menu entries in their window
8011 managers, as well in shells like <tt>pdmenu</tt>.
8015 Menu entries should follow the current menu policy.
8019 The menu policy can be found in the <tt>menu-policy</tt>
8020 files in the <tt>debian-policy</tt> package.
8021 It is also available from the Debian web mirrors at
8022 <tt><url name="/doc/packaging-manuals/menu-policy/"
8023 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8027 Please also refer to the <em>Debian Menu System</em>
8028 documentation that comes with the <package>menu</package>
8029 package for information about how to register your
8035 <heading>Multimedia handlers</heading>
8038 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8039 is a mechanism for encoding files and data streams and
8040 providing meta-information about them, in particular their
8041 type (e.g. audio or video) and format (e.g. PNG, HTML,
8046 Registration of MIME type handlers allows programs like mail
8047 user agents and web browsers to invoke these handlers to
8048 view, edit or display MIME types they don't support directly.
8052 Packages which provide programs to view/show/play, compose, edit or
8053 print MIME types should register them as such by placing a file in
8054 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8055 <file>/usr/lib/mime/packages/</file>. The file name should be the
8056 binary package's name.
8060 The <package>mime-support</package> package provides the
8061 <prgn>update-mime</prgn> program, which integrates these
8062 registrations in the <file>/etc/mailcap</file> file, using dpkg
8064 Creating, modifying or removing a file in
8065 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8066 not activate the trigger. In that case, it can be done by calling
8067 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8068 the maintainer script after creating, modifying, or removing
8071 Packages using this facility <em>should not</em> depend on,
8072 recommend, or suggest <prgn>mime-support</prgn>.
8077 <heading>Keyboard configuration</heading>
8080 To achieve a consistent keyboard configuration so that all
8081 applications interpret a keyboard event the same way, all
8082 programs in the Debian distribution must be configured to
8083 comply with the following guidelines.
8087 The following keys must have the specified interpretations:
8090 <tag><tt><--</tt></tag>
8091 <item>delete the character to the left of the cursor</item>
8093 <tag><tt>Delete</tt></tag>
8094 <item>delete the character to the right of the cursor</item>
8096 <tag><tt>Control+H</tt></tag>
8097 <item>emacs: the help prefix</item>
8100 The interpretation of any keyboard events should be
8101 independent of the terminal that is used, be it a virtual
8102 console, an X terminal emulator, an rlogin/telnet session,
8107 The following list explains how the different programs
8108 should be set up to achieve this:
8114 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8118 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8122 X translations are set up to make
8123 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8124 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8125 is the vt220 escape code for the "delete character"
8126 key). This must be done by loading the X resources
8127 using <prgn>xrdb</prgn> on all local X displays, not
8128 using the application defaults, so that the
8129 translation resources used correspond to the
8130 <prgn>xmodmap</prgn> settings.
8134 The Linux console is configured to make
8135 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8136 generate <tt>ESC [ 3 ~</tt>.
8140 X applications are configured so that <tt><</tt>
8141 deletes left, and <tt>Delete</tt> deletes right. Motif
8142 applications already work like this.
8146 Terminals should have <tt>stty erase ^?</tt> .
8150 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8151 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8152 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8156 Emacs is programmed to map <tt>KB_Backspace</tt> or
8157 the <tt>stty erase</tt> character to
8158 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8159 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8160 <tt>^H</tt> to <tt>help</tt> as always.
8164 Other applications use the <tt>stty erase</tt>
8165 character and <tt>kdch1</tt> for the two delete keys,
8166 with ASCII DEL being "delete previous character" and
8167 <tt>kdch1</tt> being "delete character under
8175 This will solve the problem except for the following
8182 Some terminals have a <tt><--</tt> key that cannot
8183 be made to produce anything except <tt>^H</tt>. On
8184 these terminals Emacs help will be unavailable on
8185 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8186 character takes precedence in Emacs, and has been set
8187 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8188 available) can be used instead.
8192 Some operating systems use <tt>^H</tt> for <tt>stty
8193 erase</tt>. However, modern telnet versions and all
8194 rlogin versions propagate <tt>stty</tt> settings, and
8195 almost all UNIX versions honour <tt>stty erase</tt>.
8196 Where the <tt>stty</tt> settings are not propagated
8197 correctly, things can be made to work by using
8198 <tt>stty</tt> manually.
8202 Some systems (including previous Debian versions) use
8203 <prgn>xmodmap</prgn> to arrange for both
8204 <tt><--</tt> and <tt>Delete</tt> to generate
8205 <tt>KB_Delete</tt>. We can change the behavior of
8206 their X clients using the same X resources that we use
8207 to do it for our own clients, or configure our clients
8208 using their resources when things are the other way
8209 around. On displays configured like this
8210 <tt>Delete</tt> will not work, but <tt><--</tt>
8215 Some operating systems have different <tt>kdch1</tt>
8216 settings in their <tt>terminfo</tt> database for
8217 <tt>xterm</tt> and others. On these systems the
8218 <tt>Delete</tt> key will not work correctly when you
8219 log in from a system conforming to our policy, but
8220 <tt><--</tt> will.
8227 <heading>Environment variables</heading>
8230 A program must not depend on environment variables to get
8231 reasonable defaults. (That's because these environment
8232 variables would have to be set in a system-wide
8233 configuration file like <file>/etc/profile</file>, which is not
8234 supported by all shells.)
8238 If a program usually depends on environment variables for its
8239 configuration, the program should be changed to fall back to
8240 a reasonable default configuration if these environment
8241 variables are not present. If this cannot be done easily
8242 (e.g., if the source code of a non-free program is not
8243 available), the program must be replaced by a small
8244 "wrapper" shell script which sets the environment variables
8245 if they are not already defined, and calls the original program.
8249 Here is an example of a wrapper script for this purpose:
8251 <example compact="compact">
8253 BAR=${BAR:-/var/lib/fubar}
8255 exec /usr/lib/foo/foo "$@"
8260 Furthermore, as <file>/etc/profile</file> is a configuration
8261 file of the <prgn>base-files</prgn> package, other packages must
8262 not put any environment variables or other commands into that
8267 <sect id="doc-base">
8268 <heading>Registering Documents using doc-base</heading>
8271 The <package>doc-base</package> package implements a
8272 flexible mechanism for handling and presenting
8273 documentation. The recommended practice is for every Debian
8274 package that provides online documentation (other than just
8275 manual pages) to register these documents with
8276 <package>doc-base</package> by installing a
8277 <package>doc-base</package> control file in
8278 <file>/usr/share/doc-base/</file>.
8281 Please refer to the documentation that comes with the
8282 <package>doc-base</package> package for information and
8287 <sect id="alternateinit">
8288 <heading>Alternate init systems</heading>
8290 A number of other init systems are available now in Debian that
8291 can be used in place of <package>sysvinit</package>. Alternative
8292 init implementations must support running SysV init scripts as
8293 described at <ref id="sysvinit"> for compatibility.
8296 Packages may integrate with these replacement init systems by
8297 providing implementation-specific configuration information about
8298 how and when to start a service or in what order to run certain
8299 tasks at boot time. However, any package integrating with other
8300 init systems must also be backwards-compatible with
8301 <package>sysvinit</package> by providing a SysV-style init script
8302 with the same name as and equivalent functionality to any
8303 init-specific job, as this is the only start-up configuration
8304 method guaranteed to be supported by all init implementations. An
8305 exception to this rule is scripts or jobs provided by the init
8306 implementation itself; such jobs may be required for an
8307 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8308 scripts and may not have a one-to-one correspondence with the init
8311 <sect1 id="upstart">
8312 <heading>Event-based boot with upstart</heading>
8315 Packages may integrate with the <prgn>upstart</prgn> event-based
8316 boot system by installing job files in the
8317 <file>/etc/init</file> directory. SysV init scripts for which
8318 an equivalent upstart job is available must query the output of
8319 the command <prgn>initctl version</prgn> for the string
8320 <tt>upstart</tt> and avoid running in favor of the native
8321 upstart job, using a test such as this:
8322 <example compact="compact">
8323 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8330 Because packages shipping upstart jobs may be installed on
8331 systems that are not using upstart, maintainer scripts must
8332 still use the common <prgn>update-rc.d</prgn> and
8333 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8334 and for starting and stopping services. These maintainer
8335 scripts must not call the upstart <prgn>start</prgn>,
8336 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8337 interfaces directly. Instead, implementations of
8338 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8339 when an upstart job with the same name as an init script is
8340 present, and perform the requested action using the upstart job
8341 instead of the init script.
8344 Dependency-based boot managers for SysV init scripts, such as
8345 <prgn>startpar</prgn>, may avoid running a given init script
8346 entirely when an equivalent upstart job is present, to avoid
8347 unnecessary forking of no-op init scripts. In this case, the
8348 boot manager should integrate with upstart to detect when the
8349 upstart job in question is started or stopped to know when the
8350 dependency has been satisfied.
8359 <heading>Files</heading>
8361 <sect id="binaries">
8362 <heading>Binaries</heading>
8365 Two different packages must not install programs with
8366 different functionality but with the same filenames. (The
8367 case of two programs having the same functionality but
8368 different implementations is handled via "alternatives" or
8369 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8370 <ref id="conflicts"> respectively.) If this case happens,
8371 one of the programs must be renamed. The maintainers should
8372 report this to the <tt>debian-devel</tt> mailing list and
8373 try to find a consensus about which program will have to be
8374 renamed. If a consensus cannot be reached, <em>both</em>
8375 programs must be renamed.
8379 By default, when a package is being built, any binaries
8380 created should include debugging information, as well as
8381 being compiled with optimization. You should also turn on
8382 as many reasonable compilation warnings as possible; this
8383 makes life easier for porters, who can then look at build
8384 logs for possible problems. For the C programming language,
8385 this means the following compilation parameters should be
8387 <example compact="compact">
8389 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8391 INSTALL = install -s # (or use strip on the files in debian/tmp)
8396 Note that by default all installed binaries should be stripped,
8397 either by using the <tt>-s</tt> flag to
8398 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8399 the binaries after they have been copied into
8400 <file>debian/tmp</file> but before the tree is made into a
8405 Although binaries in the build tree should be compiled with
8406 debugging information by default, it can often be difficult to
8407 debug programs if they are also subjected to compiler
8408 optimization. For this reason, it is recommended to support the
8409 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8410 (see <ref id="debianrules-options">). This variable can contain
8411 several flags to change how a package is compiled and built.
8415 It is up to the package maintainer to decide what
8416 compilation options are best for the package. Certain
8417 binaries (such as computationally-intensive programs) will
8418 function better with certain flags (<tt>-O3</tt>, for
8419 example); feel free to use them. Please use good judgment
8420 here. Don't use flags for the sake of it; only use them
8421 if there is good reason to do so. Feel free to override
8422 the upstream author's ideas about which compilation
8423 options are best: they are often inappropriate for our
8429 <sect id="libraries">
8430 <heading>Libraries</heading>
8433 If the package is <strong>architecture: any</strong>, then
8434 the shared library compilation and linking flags must have
8435 <tt>-fPIC</tt>, or the package shall not build on some of
8436 the supported architectures<footnote>
8438 If you are using GCC, <tt>-fPIC</tt> produces code with
8439 relocatable position independent code, which is required for
8440 most architectures to create a shared library, with i386 and
8441 perhaps some others where non position independent code is
8442 permitted in a shared library.
8445 Position independent code may have a performance penalty,
8446 especially on <tt>i386</tt>. However, in most cases the
8447 speed penalty must be measured against the memory wasted on
8448 the few architectures where non position independent code is
8451 </footnote>. Any exception to this rule must be discussed on
8452 the mailing list <em>debian-devel@lists.debian.org</em>, and
8453 a rough consensus obtained. The reasons for not compiling
8454 with <tt>-fPIC</tt> flag must be recorded in the file
8455 <tt>README.Debian</tt>, and care must be taken to either
8456 restrict the architecture or arrange for <tt>-fPIC</tt> to
8457 be used on architectures where it is required.<footnote>
8459 Some of the reasons why this might be required is if the
8460 library contains hand crafted assembly code that is not
8461 relocatable, the speed penalty is excessive for compute
8462 intensive libs, and similar reasons.
8467 As to the static libraries, the common case is not to have
8468 relocatable code, since there is no benefit, unless in specific
8469 cases; therefore the static version must not be compiled
8470 with the <tt>-fPIC</tt> flag. Any exception to this rule
8471 should be discussed on the mailing list
8472 <em>debian-devel@lists.debian.org</em>, and the reasons for
8473 compiling with the <tt>-fPIC</tt> flag must be recorded in
8474 the file <tt>README.Debian</tt>. <footnote>
8476 Some of the reasons for linking static libraries with
8477 the <tt>-fPIC</tt> flag are if, for example, one needs a
8478 Perl API for a library that is under rapid development,
8479 and has an unstable API, so shared libraries are
8480 pointless at this phase of the library's development. In
8481 that case, since Perl needs a library with relocatable
8482 code, it may make sense to create a static library with
8483 relocatable code. Another reason cited is if you are
8484 distilling various libraries into a common shared
8485 library, like <tt>mklibs</tt> does in the Debian
8491 In other words, if both a shared and a static library is
8492 being built, each source unit (<tt>*.c</tt>, for example,
8493 for C files) will need to be compiled twice, for the normal
8498 Libraries should be built with threading support and to be
8499 thread-safe if the library supports this.
8503 Although not enforced by the build tools, shared libraries
8504 must be linked against all libraries that they use symbols from
8505 in the same way that binaries are. This ensures the correct
8506 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8507 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8508 systems and guarantees that all libraries can be safely opened
8509 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8510 option <tt>-Wl,-z,defs</tt> when building a shared library.
8511 Since this option enforces symbol resolution at build time,
8512 a missing library reference will be caught early as a fatal
8517 All installed shared libraries should be stripped with
8518 <example compact="compact">
8519 strip --strip-unneeded <var>your-lib</var>
8521 (The option <tt>--strip-unneeded</tt> makes
8522 <prgn>strip</prgn> remove only the symbols which aren't
8523 needed for relocation processing.) Shared libraries can
8524 function perfectly well when stripped, since the symbols for
8525 dynamic linking are in a separate part of the ELF object
8527 You might also want to use the options
8528 <tt>--remove-section=.comment</tt> and
8529 <tt>--remove-section=.note</tt> on both shared libraries
8530 and executables, and <tt>--strip-debug</tt> on static
8536 Note that under some circumstances it may be useful to
8537 install a shared library unstripped, for example when
8538 building a separate package to support debugging.
8542 Shared object files (often <file>.so</file> files) that are not
8543 public libraries, that is, they are not meant to be linked
8544 to by third party executables (binaries of other packages),
8545 should be installed in subdirectories of the
8546 <file>/usr/lib</file> directory. Such files are exempt from the
8547 rules that govern ordinary shared libraries, except that
8548 they must not be installed executable and should be
8550 A common example are the so-called "plug-ins",
8551 internal shared objects that are dynamically loaded by
8552 programs using <manref name="dlopen" section="3">.
8557 Packages that use <prgn>libtool</prgn> to create and install
8558 their shared libraries install a file containing additional
8559 metadata (ending in <file>.la</file>) alongside the library.
8560 For public libraries intended for use by other packages, these
8561 files normally should not be included in the Debian package,
8562 since the information they include is not necessary to link with
8563 the shared library on Debian and can add unnecessary additional
8564 dependencies to other programs or libraries.<footnote>
8565 These files store, among other things, all libraries on which
8566 that shared library depends. Unfortunately, if
8567 the <file>.la</file> file is present and contains that
8568 dependency information, using <prgn>libtool</prgn> when
8569 linking against that library will cause the resulting program
8570 or library to be linked against those dependencies as well,
8571 even if this is unnecessary. This can create unneeded
8572 dependencies on shared library packages that would otherwise
8573 be hidden behind the library ABI, and can make library
8574 transitions to new SONAMEs unnecessarily complicated and
8575 difficult to manage.
8577 If the <file>.la</file> file is required for that library (if,
8578 for instance, it's loaded via <tt>libltdl</tt> in a way that
8579 requires that meta-information), the <tt>dependency_libs</tt>
8580 setting in the <file>.la</file> file should normally be set to
8581 the empty string. If the shared library development package has
8582 historically included the <file>.la</file>, it must be retained
8583 in the development package (with <tt>dependency_libs</tt>
8584 emptied) until all libraries that depend on it have removed or
8585 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8586 files to prevent linking with those other libraries
8587 using <prgn>libtool</prgn> from failing.
8591 If the <file>.la</file> must be included, it should be included
8592 in the development (<tt>-dev</tt>) package, unless the library
8593 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8594 library. If it is intended for use with <tt>libltdl</tt>,
8595 the <file>.la</file> files must go in the run-time library
8600 These requirements for handling of <file>.la</file> files do not
8601 apply to loadable modules or libraries not installed in
8602 directories searched by default by the dynamic linker. Packages
8603 installing loadable modules will frequently need to install
8604 the <file>.la</file> files alongside the modules so that they
8605 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8606 does not need to be modified for libraries or modules that are
8607 not installed in directories searched by the dynamic linker by
8608 default and not intended for use by other packages.
8612 You must make sure that you use only released versions of
8613 shared libraries to build your packages; otherwise other
8614 users will not be able to run your binaries
8615 properly. Producing source packages that depend on
8616 unreleased compilers is also usually a bad
8623 <heading>Shared libraries</heading>
8625 This section has moved to <ref id="sharedlibs">.
8631 <heading>Scripts</heading>
8634 All command scripts, including the package maintainer
8635 scripts inside the package and used by <prgn>dpkg</prgn>,
8636 should have a <tt>#!</tt> line naming the shell to be used
8641 In the case of Perl scripts this should be
8642 <tt>#!/usr/bin/perl</tt>.
8646 When scripts are installed into a directory in the system
8647 PATH, the script name should not include an extension such
8648 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8649 language currently used to implement it.
8652 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8653 <file>init.d</file> scripts should almost certainly start
8654 with <tt>set -e</tt> so that errors are detected.
8655 <file>init.d</file> scripts are something of a special case, due
8656 to how frequently they need to call commands that are allowed to
8657 fail, and it may instead be easier to check the exit status of
8658 commands directly. See <ref id="writing-init"> for more
8659 information about writing <file>init.d</file> scripts.
8662 Every script should use <tt>set -e</tt> or check the exit status
8663 of <em>every</em> command.
8666 Scripts may assume that <file>/bin/sh</file> implements the
8667 SUSv3 Shell Command Language<footnote>
8668 Single UNIX Specification, version 3, which is also IEEE
8669 1003.1-2004 (POSIX), and is available on the World Wide Web
8670 from <url id="http://www.unix.org/version3/online.html"
8671 name="The Open Group"> after free
8672 registration.</footnote>
8673 plus the following additional features not mandated by
8675 These features are in widespread use in the Linux community
8676 and are implemented in all of bash, dash, and ksh, the most
8677 common shells users may wish to use as <file>/bin/sh</file>.
8680 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8681 must not generate a newline.</item>
8682 <item><tt>test</tt>, if implemented as a shell built-in, must
8683 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8685 <item><tt>local</tt> to create a scoped variable must be
8686 supported, including listing multiple variables in a single
8687 local command and assigning a value to a variable at the
8688 same time as localizing it. <tt>local</tt> may or
8689 may not preserve the variable value from an outer scope if
8690 no assignment is present. Uses such as:
8694 # ... use a, b, c, d ...
8697 must be supported and must set the value of <tt>c</tt> to
8700 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8701 -<var>signal</var></tt>, where <var>signal</var> is either
8702 the name of a signal or one of the numeric signals listed in
8703 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8704 supported if <prgn>kill</prgn> is implemented as a shell
8707 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8708 signals must be supported. In addition to the signal
8709 numbers listed in the extension, which are the same as for
8710 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8713 If a shell script requires non-SUSv3 features from the shell
8714 interpreter other than those listed above, the appropriate shell
8715 must be specified in the first line of the script (e.g.,
8716 <tt>#!/bin/bash</tt>) and the package must depend on the package
8717 providing the shell (unless the shell package is marked
8718 "Essential", as in the case of <prgn>bash</prgn>).
8722 You may wish to restrict your script to SUSv3 features plus the
8723 above set when possible so that it may use <file>/bin/sh</file>
8724 as its interpreter. Checking your script
8725 with <prgn>checkbashisms</prgn> from
8726 the <package>devscripts</package> package or running your script
8727 with an alternate shell such as <prgn>posh</prgn> may help
8728 uncover violations of the above requirements. If in doubt
8729 whether a script complies with these requirements,
8730 use <file>/bin/bash</file>.
8734 Perl scripts should check for errors when making any
8735 system calls, including <tt>open</tt>, <tt>print</tt>,
8736 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8740 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8741 scripting languages. See <em>Csh Programming Considered
8742 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8743 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8744 If an upstream package comes with <prgn>csh</prgn> scripts
8745 then you must make sure that they start with
8746 <tt>#!/bin/csh</tt> and make your package depend on the
8747 <prgn>c-shell</prgn> virtual package.
8751 Any scripts which create files in world-writeable
8752 directories (e.g., in <file>/tmp</file>) must use a
8753 mechanism which will fail atomically if a file with the same
8754 name already exists.
8758 The Debian base system provides the <prgn>tempfile</prgn>
8759 and <prgn>mktemp</prgn> utilities for use by scripts for
8766 <heading>Symbolic links</heading>
8769 In general, symbolic links within a top-level directory should
8770 be relative, and symbolic links pointing from one top-level
8771 directory to or into another should be absolute. (A top-level
8772 directory is a sub-directory of the root
8773 directory <file>/</file>.) For example, a symbolic link
8774 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8775 should be relative (<file>../share/bar</file>), but a symbolic
8776 link from <file>/var/run</file> to <file>/run</file> should be
8778 This is necessary to allow top-level directories to be
8779 symlinks. If linking <file>/var/run</file>
8780 to <file>/run</file> were done with the relative symbolic
8781 link <file>../run</file>, but <file>/var</file> were a
8782 symbolic link to <file>/srv/disk1</file>, the symbolic link
8783 would point to <file>/srv/run</file> rather than the intended
8789 In addition, symbolic links should be specified as short as
8790 possible, i.e., link targets like <file>foo/../bar</file> are
8795 Note that when creating a relative link using
8796 <prgn>ln</prgn> it is not necessary for the target of the
8797 link to exist relative to the working directory you're
8798 running <prgn>ln</prgn> from, nor is it necessary to change
8799 directory to the directory where the link is to be made.
8800 Simply include the string that should appear as the target
8801 of the link (this will be a pathname relative to the
8802 directory in which the link resides) as the first argument
8807 For example, in your <prgn>Makefile</prgn> or
8808 <file>debian/rules</file>, you can do things like:
8809 <example compact="compact">
8810 ln -fs gcc $(prefix)/bin/cc
8811 ln -fs gcc debian/tmp/usr/bin/cc
8812 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8813 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8818 A symbolic link pointing to a compressed file should always
8819 have the same file extension as the referenced file. (For
8820 example, if a file <file>foo.gz</file> is referenced by a
8821 symbolic link, the filename of the link has to end with
8822 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8827 <heading>Device files</heading>
8830 Packages must not include device files or named pipes in the
8835 If a package needs any special device files that are not
8836 included in the base system, it must call
8837 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8838 after notifying the user<footnote>
8839 This notification could be done via a (low-priority)
8840 debconf message, or an echo (printf) statement.
8845 Packages must not remove any device files in the
8846 <prgn>postrm</prgn> or any other script. This is left to the
8847 system administrator.
8851 Debian uses the serial devices
8852 <file>/dev/ttyS*</file>. Programs using the old
8853 <file>/dev/cu*</file> devices should be changed to use
8854 <file>/dev/ttyS*</file>.
8858 Named pipes needed by the package must be created in
8859 the <prgn>postinst</prgn> script<footnote>
8860 It's better to use <prgn>mkfifo</prgn> rather
8861 than <prgn>mknod</prgn> to create named pipes so that
8862 automated checks for packages incorrectly creating device
8863 files with <prgn>mknod</prgn> won't have false positives.
8864 </footnote> and removed in
8865 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8870 <sect id="config-files">
8871 <heading>Configuration files</heading>
8874 <heading>Definitions</heading>
8878 <tag>configuration file</tag>
8880 A file that affects the operation of a program, or
8881 provides site- or host-specific information, or
8882 otherwise customizes the behavior of a program.
8883 Typically, configuration files are intended to be
8884 modified by the system administrator (if needed or
8885 desired) to conform to local policy or to provide
8886 more useful site-specific behavior.
8889 <tag><tt>conffile</tt></tag>
8891 A file listed in a package's <tt>conffiles</tt>
8892 file, and is treated specially by <prgn>dpkg</prgn>
8893 (see <ref id="configdetails">).
8899 The distinction between these two is important; they are
8900 not interchangeable concepts. Almost all
8901 <tt>conffile</tt>s are configuration files, but many
8902 configuration files are not <tt>conffiles</tt>.
8906 As noted elsewhere, <file>/etc/init.d</file> scripts,
8907 <file>/etc/default</file> files, scripts installed in
8908 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8909 configuration installed in <file>/etc/cron.d</file> must be
8910 treated as configuration files. In general, any script that
8911 embeds configuration information is de-facto a configuration
8912 file and should be treated as such.
8917 <heading>Location</heading>
8920 Any configuration files created or used by your package
8921 must reside in <file>/etc</file>. If there are several,
8922 consider creating a subdirectory of <file>/etc</file>
8923 named after your package.
8927 If your package creates or uses configuration files
8928 outside of <file>/etc</file>, and it is not feasible to modify
8929 the package to use <file>/etc</file> directly, put the files
8930 in <file>/etc</file> and create symbolic links to those files
8931 from the location that the package requires.
8936 <heading>Behavior</heading>
8939 Configuration file handling must conform to the following
8941 <list compact="compact">
8943 local changes must be preserved during a package
8947 configuration files must be preserved when the
8948 package is removed, and only deleted when the
8952 Obsolete configuration files without local changes may be
8953 removed by the package during upgrade.
8957 The easy way to achieve this behavior is to make the
8958 configuration file a <tt>conffile</tt>. This is
8959 appropriate only if it is possible to distribute a default
8960 version that will work for most installations, although
8961 some system administrators may choose to modify it. This
8962 implies that the default version will be part of the
8963 package distribution, and must not be modified by the
8964 maintainer scripts during installation (or at any other
8969 In order to ensure that local changes are preserved
8970 correctly, no package may contain or make hard links to
8971 conffiles.<footnote>
8972 Rationale: There are two problems with hard links.
8973 The first is that some editors break the link while
8974 editing one of the files, so that the two files may
8975 unwittingly become unlinked and different. The second
8976 is that <prgn>dpkg</prgn> might break the hard link
8977 while upgrading <tt>conffile</tt>s.
8982 The other way to do it is via the maintainer scripts. In
8983 this case, the configuration file must not be listed as a
8984 <tt>conffile</tt> and must not be part of the package
8985 distribution. If the existence of a file is required for
8986 the package to be sensibly configured it is the
8987 responsibility of the package maintainer to provide
8988 maintainer scripts which correctly create, update and
8989 maintain the file and remove it on purge. (See <ref
8990 id="maintainerscripts"> for more information.) These
8991 scripts must be idempotent (i.e., must work correctly if
8992 <prgn>dpkg</prgn> needs to re-run them due to errors
8993 during installation or removal), must cope with all the
8994 variety of ways <prgn>dpkg</prgn> can call maintainer
8995 scripts, must not overwrite or otherwise mangle the user's
8996 configuration without asking, must not ask unnecessary
8997 questions (particularly during upgrades), and must
8998 otherwise be good citizens.
9002 The scripts are not required to configure every possible
9003 option for the package, but only those necessary to get
9004 the package running on a given system. Ideally the
9005 sysadmin should not have to do any configuration other
9006 than that done (semi-)automatically by the
9007 <prgn>postinst</prgn> script.
9011 A common practice is to create a script called
9012 <file><var>package</var>-configure</file> and have the
9013 package's <prgn>postinst</prgn> call it if and only if the
9014 configuration file does not already exist. In certain
9015 cases it is useful for there to be an example or template
9016 file which the maintainer scripts use. Such files should
9017 be in <file>/usr/share/<var>package</var></file> or
9018 <file>/usr/lib/<var>package</var></file> (depending on whether
9019 they are architecture-independent or not). There should
9020 be symbolic links to them from
9021 <file>/usr/share/doc/<var>package</var>/examples</file> if
9022 they are examples, and should be perfectly ordinary
9023 <prgn>dpkg</prgn>-handled files (<em>not</em>
9024 configuration files).
9028 These two styles of configuration file handling must
9029 not be mixed, for that way lies madness:
9030 <prgn>dpkg</prgn> will ask about overwriting the file
9031 every time the package is upgraded.
9036 <heading>Sharing configuration files</heading>
9039 If two or more packages use the same configuration file
9040 and it is reasonable for both to be installed at the same
9041 time, one of these packages must be defined as
9042 <em>owner</em> of the configuration file, i.e., it will be
9043 the package which handles that file as a configuration
9044 file. Other packages that use the configuration file must
9045 depend on the owning package if they require the
9046 configuration file to operate. If the other package will
9047 use the configuration file if present, but is capable of
9048 operating without it, no dependency need be declared.
9052 If it is desirable for two or more related packages to
9053 share a configuration file <em>and</em> for all of the
9054 related packages to be able to modify that configuration
9055 file, then the following should be done:
9056 <enumlist compact="compact">
9058 One of the related packages (the "owning" package)
9059 will manage the configuration file with maintainer
9060 scripts as described in the previous section.
9063 The owning package should also provide a program
9064 that the other packages may use to modify the
9068 The related packages must use the provided program
9069 to make any desired modifications to the
9070 configuration file. They should either depend on
9071 the core package to guarantee that the configuration
9072 modifier program is available or accept gracefully
9073 that they cannot modify the configuration file if it
9074 is not. (This is in addition to the fact that the
9075 configuration file may not even be present in the
9082 Sometimes it's appropriate to create a new package which
9083 provides the basic infrastructure for the other packages
9084 and which manages the shared configuration files. (The
9085 <tt>sgml-base</tt> package is a good example.)
9089 If the configuration file cannot be shared as described above,
9090 the packages must be marked as conflicting with each other.
9091 Two packages that specify the same file as
9092 a <tt>conffile</tt> must conflict. This is an instance of the
9093 general rule about not sharing files. Neither alternatives
9094 nor diversions are likely to be appropriate in this case; in
9095 particular, <prgn>dpkg</prgn> does not handle diverted
9096 <tt>conffile</tt>s well.
9100 When two packages both declare the same <tt>conffile</tt>, they
9101 may see left-over configuration files from each other even
9102 though they conflict with each other. If a user removes
9103 (without purging) one of the packages and installs the other,
9104 the new package will take over the <tt>conffile</tt> from the
9105 old package. If the file was modified by the user, it will be
9106 treated the same as any other locally
9107 modified <tt>conffile</tt> during an upgrade.
9111 The maintainer scripts must not alter a <tt>conffile</tt>
9112 of <em>any</em> package, including the one the scripts
9118 <heading>User configuration files ("dotfiles")</heading>
9121 The files in <file>/etc/skel</file> will automatically be
9122 copied into new user accounts by <prgn>adduser</prgn>.
9123 No other program should reference the files in
9124 <file>/etc/skel</file>.
9128 Therefore, if a program needs a dotfile to exist in
9129 advance in <file>$HOME</file> to work sensibly, that dotfile
9130 should be installed in <file>/etc/skel</file> and treated as a
9135 However, programs that require dotfiles in order to
9136 operate sensibly are a bad thing, unless they do create
9137 the dotfiles themselves automatically.
9141 Furthermore, programs should be configured by the Debian
9142 default installation to behave as closely to the upstream
9143 default behavior as possible.
9147 Therefore, if a program in a Debian package needs to be
9148 configured in some way in order to operate sensibly, that
9149 should be done using a site-wide configuration file placed
9150 in <file>/etc</file>. Only if the program doesn't support a
9151 site-wide default configuration and the package maintainer
9152 doesn't have time to add it may a default per-user file be
9153 placed in <file>/etc/skel</file>.
9157 <file>/etc/skel</file> should be as empty as we can make it.
9158 This is particularly true because there is no easy (or
9159 necessarily desirable) mechanism for ensuring that the
9160 appropriate dotfiles are copied into the accounts of
9161 existing users when a package is installed.
9167 <heading>Log files</heading>
9169 Log files should usually be named
9170 <file>/var/log/<var>package</var>.log</file>. If you have many
9171 log files, or need a separate directory for permission
9172 reasons (<file>/var/log</file> is writable only by
9173 <file>root</file>), you should usually create a directory named
9174 <file>/var/log/<var>package</var></file> and place your log
9179 Log files must be rotated occasionally so that they don't grow
9180 indefinitely. The best way to do this is to install a log
9181 rotation configuration file in the
9182 directory <file>/etc/logrotate.d</file>, normally
9183 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9184 the facilities provided by <prgn>logrotate</prgn>.
9187 The traditional approach to log files has been to set up
9188 <em>ad hoc</em> log rotation schemes using simple shell
9189 scripts and cron. While this approach is highly
9190 customizable, it requires quite a lot of sysadmin work.
9191 Even though the original Debian system helped a little
9192 by automatically installing a system which can be used
9193 as a template, this was deemed not enough.
9197 The use of <prgn>logrotate</prgn>, a program developed
9198 by Red Hat, is better, as it centralizes log management.
9199 It has both a configuration file
9200 (<file>/etc/logrotate.conf</file>) and a directory where
9201 packages can drop their individual log rotation
9202 configurations (<file>/etc/logrotate.d</file>).
9205 Here is a good example for a logrotate config
9206 file (for more information see <manref name="logrotate"
9208 <example compact="compact">
9209 /var/log/foo/*.log {
9215 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9219 This rotates all files under <file>/var/log/foo</file>, saves 12
9220 compressed generations, and tells the daemon to reopen its log
9221 files after the log rotation. It skips this log rotation
9222 (via <tt>missingok</tt>) if no such log file is present, which
9223 avoids errors if the package is removed but not purged.
9227 Log files should be removed when the package is
9228 purged (but not when it is only removed). This should be
9229 done by the <prgn>postrm</prgn> script when it is called
9230 with the argument <tt>purge</tt> (see <ref
9231 id="removedetails">).
9235 <sect id="permissions-owners">
9236 <heading>Permissions and owners</heading>
9239 The rules in this section are guidelines for general use.
9240 If necessary you may deviate from the details below.
9241 However, if you do so you must make sure that what is done
9242 is secure and you should try to be as consistent as possible
9243 with the rest of the system. You should probably also
9244 discuss it on <prgn>debian-devel</prgn> first.
9248 Files should be owned by <tt>root:root</tt>, and made
9249 writable only by the owner and universally readable (and
9250 executable, if appropriate), that is mode 644 or 755.
9254 Directories should be mode 755 or (for group-writability)
9255 mode 2775. The ownership of the directory should be
9256 consistent with its mode: if a directory is mode 2775, it
9257 should be owned by the group that needs write access to
9260 When a package is upgraded, and the owner or permissions
9261 of a file included in the package has changed, dpkg
9262 arranges for the ownership and permissions to be
9263 correctly set upon installation. However, this does not
9264 extend to directories; the permissions and ownership of
9265 directories already on the system does not change on
9266 install or upgrade of packages. This makes sense, since
9267 otherwise common directories like <tt>/usr</tt> would
9268 always be in flux. To correctly change permissions of a
9269 directory the package owns, explicit action is required,
9270 usually in the <tt>postinst</tt> script. Care must be
9271 taken to handle downgrades as well, in that case.
9277 Control information files should be owned by <tt>root:root</tt>
9278 and either mode 644 (for most files) or mode 755 (for
9279 executables such as <qref id="maintscripts">maintainer
9284 Setuid and setgid executables should be mode 4755 or 2755
9285 respectively, and owned by the appropriate user or group.
9286 They should not be made unreadable (modes like 4711 or
9287 2711 or even 4111); doing so achieves no extra security,
9288 because anyone can find the binary in the freely available
9289 Debian package; it is merely inconvenient. For the same
9290 reason you should not restrict read or execute permissions
9291 on non-set-id executables.
9295 Some setuid programs need to be restricted to particular
9296 sets of users, using file permissions. In this case they
9297 should be owned by the uid to which they are set-id, and by
9298 the group which should be allowed to execute them. They
9299 should have mode 4754; again there is no point in making
9300 them unreadable to those users who must not be allowed to
9305 It is possible to arrange that the system administrator can
9306 reconfigure the package to correspond to their local
9307 security policy by changing the permissions on a binary:
9308 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9309 described below.<footnote>
9310 Ordinary files installed by <prgn>dpkg</prgn> (as
9311 opposed to <tt>conffile</tt>s and other similar objects)
9312 normally have their permissions reset to the distributed
9313 permissions when the package is reinstalled. However,
9314 the use of <prgn>dpkg-statoverride</prgn> overrides this
9317 Another method you should consider is to create a group for
9318 people allowed to use the program(s) and make any setuid
9319 executables executable only by that group.
9323 If you need to create a new user or group for your package
9324 there are two possibilities. Firstly, you may need to
9325 make some files in the binary package be owned by this
9326 user or group, or you may need to compile the user or
9327 group id (rather than just the name) into the binary
9328 (though this latter should be avoided if possible, as in
9329 this case you need a statically allocated id).</p>
9332 If you need a statically allocated id, you must ask for a
9333 user or group id from the <tt>base-passwd</tt> maintainer,
9334 and must not release the package until you have been
9335 allocated one. Once you have been allocated one you must
9336 either make the package depend on a version of the
9337 <tt>base-passwd</tt> package with the id present in
9338 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9339 your package to create the user or group itself with the
9340 correct id (using <tt>adduser</tt>) in its
9341 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9342 the <prgn>postinst</prgn> is to be preferred if it is
9343 possible, otherwise a pre-dependency will be needed on the
9344 <tt>adduser</tt> package.)
9348 On the other hand, the program might be able to determine
9349 the uid or gid from the user or group name at runtime, so
9350 that a dynamically allocated id can be used. In this case
9351 you should choose an appropriate user or group name,
9352 discussing this on <prgn>debian-devel</prgn> and checking
9353 with the <package/base-passwd/ maintainer that it is unique and that
9354 they do not wish you to use a statically allocated id
9355 instead. When this has been checked you must arrange for
9356 your package to create the user or group if necessary using
9357 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9358 <prgn>postinst</prgn> script (again, the latter is to be
9359 preferred if it is possible).
9363 Note that changing the numeric value of an id associated
9364 with a name is very difficult, and involves searching the
9365 file system for all appropriate files. You need to think
9366 carefully whether a static or dynamic id is required, since
9367 changing your mind later will cause problems.
9370 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9372 This section is not intended as policy, but as a
9373 description of the use of <prgn>dpkg-statoverride</prgn>.
9377 If a system administrator wishes to have a file (or
9378 directory or other such thing) installed with owner and
9379 permissions different from those in the distributed Debian
9380 package, they can use the <prgn>dpkg-statoverride</prgn>
9381 program to instruct <prgn>dpkg</prgn> to use the different
9382 settings every time the file is installed. Thus the
9383 package maintainer should distribute the files with their
9384 normal permissions, and leave it for the system
9385 administrator to make any desired changes. For example, a
9386 daemon which is normally required to be setuid root, but
9387 in certain situations could be used without being setuid,
9388 should be installed setuid in the <tt>.deb</tt>. Then the
9389 local system administrator can change this if they wish.
9390 If there are two standard ways of doing it, the package
9391 maintainer can use <tt>debconf</tt> to find out the
9392 preference, and call <prgn>dpkg-statoverride</prgn> in the
9393 maintainer script if necessary to accommodate the system
9394 administrator's choice. Care must be taken during
9395 upgrades to not override an existing setting.
9399 Given the above, <prgn>dpkg-statoverride</prgn> is
9400 essentially a tool for system administrators and would not
9401 normally be needed in the maintainer scripts. There is
9402 one type of situation, though, where calls to
9403 <prgn>dpkg-statoverride</prgn> would be needed in the
9404 maintainer scripts, and that involves packages which use
9405 dynamically allocated user or group ids. In such a
9406 situation, something like the following idiom can be very
9407 helpful in the package's <prgn>postinst</prgn>, where
9408 <tt>sysuser</tt> is a dynamically allocated id:
9410 for i in /usr/bin/foo /usr/sbin/bar
9412 # only do something when no setting exists
9413 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9415 #include: debconf processing, question about foo and bar
9416 if [ "$RET" = "true" ] ; then
9417 dpkg-statoverride --update --add sysuser root 4755 $i
9422 The corresponding code to remove the override when the package
9425 for i in /usr/bin/foo /usr/sbin/bar
9427 if dpkg-statoverride --list $i >/dev/null 2>&1
9429 dpkg-statoverride --remove $i
9439 <chapt id="customized-programs">
9440 <heading>Customized programs</heading>
9442 <sect id="arch-spec">
9443 <heading>Architecture specification strings</heading>
9446 If a program needs to specify an <em>architecture specification
9447 string</em> in some place, it should select one of the strings
9448 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9449 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9450 part is sometimes elided, as when the OS is Linux.
9454 Note that we don't want to use
9455 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9456 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9457 since this would make our programs incompatible with other
9458 Linux distributions. We also don't use something like
9459 <tt><var>arch</var>-unknown-linux</tt>, since the
9460 <tt>unknown</tt> does not look very good.
9463 <sect1 id="arch-wildcard-spec">
9464 <heading>Architecture wildcards</heading>
9467 A package may specify an architecture wildcard. Architecture
9468 wildcards are in the format <tt>any</tt> (which matches every
9469 architecture), <tt><var>os</var></tt>-any, or
9470 any-<tt><var>cpu</var></tt>. <footnote>
9471 Internally, the package system normalizes the GNU triplets
9472 and the Debian arches into Debian arch triplets (which are
9473 kind of inverted GNU triplets), with the first component of
9474 the triplet representing the libc and ABI in use, and then
9475 does matching against those triplets. However, such
9476 triplets are an internal implementation detail that should
9477 not be used by packages directly. The libc and ABI portion
9478 is handled internally by the package system based on
9479 the <var>os</var> and <var>cpu</var>.
9486 <heading>Daemons</heading>
9489 The configuration files <file>/etc/services</file>,
9490 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9491 by the <prgn>netbase</prgn> package and must not be modified
9496 If a package requires a new entry in one of these files, the
9497 maintainer should get in contact with the
9498 <prgn>netbase</prgn> maintainer, who will add the entries
9499 and release a new version of the <prgn>netbase</prgn>
9504 The configuration file <file>/etc/inetd.conf</file> must not be
9505 modified by the package's scripts except via the
9506 <prgn>update-inetd</prgn> script or the
9507 <file>DebianNet.pm</file> Perl module. See their documentation
9508 for details on how to add entries.
9512 If a package wants to install an example entry into
9513 <file>/etc/inetd.conf</file>, the entry must be preceded with
9514 exactly one hash character (<tt>#</tt>). Such lines are
9515 treated as "commented out by user" by the
9516 <prgn>update-inetd</prgn> script and are not changed or
9517 activated during package updates.
9522 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9526 Some programs need to create pseudo-ttys. This should be done
9527 using Unix98 ptys if the C library supports it. The resulting
9528 program must not be installed setuid root, unless that
9529 is required for other functionality.
9533 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9534 <file>/var/log/lastlog</file> must be installed writable by
9535 group <tt>utmp</tt>. Programs which need to modify those
9536 files must be installed setgid <tt>utmp</tt>.
9541 <heading>Editors and pagers</heading>
9544 Some programs have the ability to launch an editor or pager
9545 program to edit or display a text document. Since there are
9546 lots of different editors and pagers available in the Debian
9547 distribution, the system administrator and each user should
9548 have the possibility to choose their preferred editor and
9553 In addition, every program should choose a good default
9554 editor/pager if none is selected by the user or system
9559 Thus, every program that launches an editor or pager must
9560 use the EDITOR or PAGER environment variable to determine
9561 the editor or pager the user wishes to use. If these
9562 variables are not set, the programs <file>/usr/bin/editor</file>
9563 and <file>/usr/bin/pager</file> should be used, respectively.
9567 These two files are managed through the <prgn>dpkg</prgn>
9568 "alternatives" mechanism. Every package providing an editor or
9569 pager must call the <prgn>update-alternatives</prgn> script to
9570 register as an alternative for <file>/usr/bin/editor</file>
9571 or <file>/usr/bin/pager</file> as appropriate. The alternative
9572 should have a slave alternative
9573 for <file>/usr/share/man/man1/editor.1.gz</file>
9574 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9575 corresponding manual page.
9579 If it is very hard to adapt a program to make use of the
9580 EDITOR or PAGER variables, that program may be configured to
9581 use <file>/usr/bin/sensible-editor</file> and
9582 <file>/usr/bin/sensible-pager</file> as the editor or pager
9583 program respectively. These are two scripts provided in the
9584 <package>sensible-utils</package> package that check the EDITOR
9585 and PAGER variables and launch the appropriate program, and fall
9586 back to <file>/usr/bin/editor</file>
9587 and <file>/usr/bin/pager</file> if the variable is not set.
9591 A program may also use the VISUAL environment variable to
9592 determine the user's choice of editor. If it exists, it
9593 should take precedence over EDITOR. This is in fact what
9594 <file>/usr/bin/sensible-editor</file> does.
9598 It is not required for a package to depend on
9599 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9600 package to provide such virtual packages.<footnote>
9601 The Debian base system already provides an editor and a
9607 <sect id="web-appl">
9608 <heading>Web servers and applications</heading>
9611 This section describes the locations and URLs that should
9612 be used by all web servers and web applications in the
9619 Cgi-bin executable files are installed in the
9621 <example compact="compact">
9622 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9624 or a subdirectory of that directory, and should be
9626 <example compact="compact">
9627 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9629 (possibly with a subdirectory name
9630 before <var>cgi-bin-name</var>).
9634 <p>Access to HTML documents</p>
9637 HTML documents for a package are stored in
9638 <file>/usr/share/doc/<var>package</var></file>
9639 and can be referred to as
9640 <example compact="compact">
9641 http://localhost/doc/<var>package</var>/<var>filename</var>
9646 The web server should restrict access to the document
9647 tree so that only clients on the same host can read
9648 the documents. If the web server does not support such
9649 access controls, then it should not provide access at
9650 all, or ask about providing access during installation.
9655 <p>Access to images</p>
9657 It is recommended that images for a package be stored
9658 in <tt>/usr/share/images/<var>package</var></tt> and
9659 may be referred to through an alias <tt>/images/</tt>
9662 http://localhost/images/<package>/<filename>
9669 <p>Web Document Root</p>
9672 Web Applications should try to avoid storing files in
9673 the Web Document Root. Instead they should use the
9674 /usr/share/doc/<var>package</var> directory for
9675 documents and register the Web Application via the
9676 <package>doc-base</package> package. If access to the
9677 web document root is unavoidable then use
9678 <example compact="compact">
9681 as the Document Root. This might be just a symbolic
9682 link to the location where the system administrator
9683 has put the real document root.
9686 <item><p>Providing httpd and/or httpd-cgi</p>
9688 All web servers should provide the virtual package
9689 <tt>httpd</tt>. If a web server has CGI support it should
9690 provide <tt>httpd-cgi</tt> additionally.
9693 All web applications which do not contain CGI scripts should
9694 depend on <tt>httpd</tt>, all those web applications which
9695 <tt>do</tt> contain CGI scripts, should depend on
9703 <sect id="mail-transport-agents">
9704 <heading>Mail transport, delivery and user agents</heading>
9707 Debian packages which process electronic mail, whether mail
9708 user agents (MUAs) or mail transport agents (MTAs), must
9709 ensure that they are compatible with the configuration
9710 decisions below. Failure to do this may result in lost
9711 mail, broken <tt>From:</tt> lines, and other serious brain
9716 The mail spool is <file>/var/mail</file> and the interface to
9717 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9718 the FHS). On older systems, the mail spool may be
9719 physically located in <file>/var/spool/mail</file>, but all
9720 access to the mail spool should be via the
9721 <file>/var/mail</file> symlink. The mail spool is part of the
9722 base system and not part of the MTA package.
9726 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9727 programs (such as IMAP daemons) must lock the mailbox in an
9728 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9729 be combined with dot locking. To avoid deadlocks, a program
9730 should use <tt>fcntl()</tt> first and dot locking after
9731 this, or alternatively implement the two locking methods in
9732 a non blocking way<footnote>
9733 If it is not possible to establish both locks, the
9734 system shouldn't wait for the second lock to be
9735 established, but remove the first lock, wait a (random)
9736 time, and start over locking again.
9737 </footnote>. Using the functions <tt>maillock</tt> and
9738 <tt>mailunlock</tt> provided by the
9739 <tt>liblockfile*</tt><footnote>
9740 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9741 to use these functions.
9742 </footnote> packages is the recommended way to realize this.
9746 Mailboxes are generally either mode 600 and owned by
9747 <var>user</var> or mode 660 and owned by
9748 <tt><var>user</var>:mail</tt><footnote>
9749 There are two traditional permission schemes for mail spools:
9750 mode 600 with all mail delivery done by processes running as
9751 the destination user, or mode 660 and owned by group mail with
9752 mail delivery done by a process running as a system user in
9753 group mail. Historically, Debian required mode 660 mail
9754 spools to enable the latter model, but that model has become
9755 increasingly uncommon and the principle of least privilege
9756 indicates that mail systems that use the first model should
9757 use permissions of 600. If delivery to programs is permitted,
9758 it's easier to keep the mail system secure if the delivery
9759 agent runs as the destination user. Debian Policy therefore
9760 permits either scheme.
9761 </footnote>. The local system administrator may choose a
9762 different permission scheme; packages should not make
9763 assumptions about the permission and ownership of mailboxes
9764 unless required (such as when creating a new mailbox). A MUA
9765 may remove a mailbox (unless it has nonstandard permissions) in
9766 which case the MTA or another MUA must recreate it if needed.
9770 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9771 be setgid mail to do the locking mentioned above (and
9772 must obviously avoid accessing other users' mailboxes
9773 using this privilege).</p>
9776 <file>/etc/aliases</file> is the source file for the system mail
9777 aliases (e.g., postmaster, usenet, etc.), it is the one
9778 which the sysadmin and <prgn>postinst</prgn> scripts may
9779 edit. After <file>/etc/aliases</file> is edited the program or
9780 human editing it must call <prgn>newaliases</prgn>. All MTA
9781 packages must come with a <prgn>newaliases</prgn> program,
9782 even if it does nothing, but older MTA packages did not do
9783 this so programs should not fail if <prgn>newaliases</prgn>
9784 cannot be found. Note that because of this, all MTA
9785 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9786 <tt>Replaces: mail-transport-agent</tt> control fields.
9790 The convention of writing <tt>forward to
9791 <var>address</var></tt> in the mailbox itself is not
9792 supported. Use a <tt>.forward</tt> file instead.</p>
9795 The <prgn>rmail</prgn> program used by UUCP
9796 for incoming mail should be <file>/usr/sbin/rmail</file>.
9797 Likewise, <prgn>rsmtp</prgn>, for receiving
9798 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9802 If your package needs to know what hostname to use on (for
9803 example) outgoing news and mail messages which are generated
9804 locally, you should use the file <file>/etc/mailname</file>. It
9805 will contain the portion after the username and <tt>@</tt>
9806 (at) sign for email addresses of users on the machine
9807 (followed by a newline).
9811 Such a package should check for the existence of this file
9812 when it is being configured. If it exists, it should be
9813 used without comment, although an MTA's configuration script
9814 may wish to prompt the user even if it finds that this file
9815 exists. If the file does not exist, the package should
9816 prompt the user for the value (preferably using
9817 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9818 as well as using it in the package's configuration. The
9819 prompt should make it clear that the name will not just be
9820 used by that package. For example, in this situation the
9821 <tt>inn</tt> package could say something like:
9822 <example compact="compact">
9823 Please enter the "mail name" of your system. This is the
9824 hostname portion of the address to be shown on outgoing
9825 news and mail messages. The default is
9826 <var>syshostname</var>, your system's host name. Mail
9827 name ["<var>syshostname</var>"]:
9829 where <var>syshostname</var> is the output of <tt>hostname
9835 <heading>News system configuration</heading>
9838 All the configuration files related to the NNTP (news)
9839 servers and clients should be located under
9840 <file>/etc/news</file>.</p>
9843 There are some configuration issues that apply to a number
9844 of news clients and server packages on the machine. These
9848 <tag><file>/etc/news/organization</file></tag>
9850 A string which should appear as the
9851 organization header for all messages posted
9852 by NNTP clients on the machine
9855 <tag><file>/etc/news/server</file></tag>
9857 Contains the FQDN of the upstream NNTP
9858 server, or localhost if the local machine is
9863 Other global files may be added as required for cross-package news
9870 <heading>Programs for the X Window System</heading>
9873 <heading>Providing X support and package priorities</heading>
9876 Programs that can be configured with support for the X
9877 Window System must be configured to do so and must declare
9878 any package dependencies necessary to satisfy their
9879 runtime requirements when using the X Window System. If
9880 such a package is of higher priority than the X packages
9881 on which it depends, it is required that either the
9882 X-specific components be split into a separate package, or
9883 that an alternative version of the package, which includes
9884 X support, be provided, or that the package's priority be
9890 <heading>Packages providing an X server</heading>
9893 Packages that provide an X server that, directly or
9894 indirectly, communicates with real input and display
9895 hardware should declare in their <tt>Provides</tt> control
9896 field that they provide the virtual
9897 package <tt>xserver</tt>.<footnote>
9898 This implements current practice, and provides an
9899 actual policy for usage of the <tt>xserver</tt>
9900 virtual package which appears in the virtual packages
9901 list. In a nutshell, X servers that interface
9902 directly with the display and input hardware or via
9903 another subsystem (e.g., GGI) should provide
9904 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9905 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9911 <heading>Packages providing a terminal emulator</heading>
9914 Packages that provide a terminal emulator for the X Window
9915 System which meet the criteria listed below should declare in
9916 their <tt>Provides</tt> control field that they provide the
9917 virtual package <tt>x-terminal-emulator</tt>. They should
9918 also register themselves as an alternative for
9919 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9920 20. That alternative should have a slave alternative
9921 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9922 pointing to the corresponding manual page.
9926 To be an <tt>x-terminal-emulator</tt>, a program must:
9927 <list compact="compact">
9929 Be able to emulate a DEC VT100 terminal, or a
9930 compatible terminal.
9934 Support the command-line option <tt>-e
9935 <var>command</var></tt>, which creates a new
9936 terminal window<footnote>
9937 "New terminal window" does not necessarily mean
9938 a new top-level X window directly parented by
9939 the window manager; it could, if the terminal
9940 emulator application were so coded, be a new
9941 "view" in a multiple-document interface (MDI).
9943 and runs the specified <var>command</var>,
9944 interpreting the entirety of the rest of the command
9945 line as a command to pass straight to exec, in the
9946 manner that <tt>xterm</tt> does.
9950 Support the command-line option <tt>-T
9951 <var>title</var></tt>, which creates a new terminal
9952 window with the window title <var>title</var>.
9959 <heading>Packages providing a window manager</heading>
9962 Packages that provide a window manager should declare in
9963 their <tt>Provides</tt> control field that they provide the
9964 virtual package <tt>x-window-manager</tt>. They should also
9965 register themselves as an alternative for
9966 <file>/usr/bin/x-window-manager</file>, with a priority
9967 calculated as follows:
9968 <list compact="compact">
9970 Start with a priority of 20.
9974 If the window manager supports the Debian menu
9975 system, add 20 points if this support is available
9976 in the package's default configuration (i.e., no
9977 configuration files belonging to the system or user
9978 have to be edited to activate the feature); if
9979 configuration files must be modified, add only 10
9985 If the window manager complies with <url
9986 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9987 name="The Window Manager Specification Project">,
9988 written by the <url id="http://www.freedesktop.org/wiki/"
9989 name="Free Desktop Group">, add 40 points.
9993 If the window manager permits the X session to be
9994 restarted using a <em>different</em> window manager
9995 (without killing the X server) in its default
9996 configuration, add 10 points; otherwise add none.
9999 That alternative should have a slave alternative
10000 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10001 pointing to the corresponding manual page.
10006 <heading>Packages providing fonts</heading>
10009 Packages that provide fonts for the X Window
10011 For the purposes of Debian Policy, a "font for the X
10012 Window System" is one which is accessed via X protocol
10013 requests. Fonts for the Linux console, for PostScript
10014 renderer, or any other purpose, do not fit this
10015 definition. Any tool which makes such fonts available
10016 to the X Window System, however, must abide by this
10019 must do a number of things to ensure that they are both
10020 available without modification of the X or font server
10021 configuration, and that they do not corrupt files used by
10022 other font packages to register information about
10026 Fonts of any type supported by the X Window System
10027 must be in a separate binary package from any
10028 executables, libraries, or documentation (except
10029 that specific to the fonts shipped, such as their
10030 license information). If one or more of the fonts
10031 so packaged are necessary for proper operation of
10032 the package with which they are associated the font
10033 package may be Recommended; if the fonts merely
10034 provide an enhancement, a Suggests relationship may
10035 be used. Packages must not Depend on font
10036 packages.<footnote>
10037 This is because the X server may retrieve fonts
10038 from the local file system or over the network
10039 from an X font server; the Debian package system
10040 is empowered to deal only with the local
10046 BDF fonts must be converted to PCF fonts with the
10047 <prgn>bdftopcf</prgn> utility (available in the
10048 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10049 placed in a directory that corresponds to their
10051 <list compact="compact">
10053 100 dpi fonts must be placed in
10054 <file>/usr/share/fonts/X11/100dpi/</file>.
10058 75 dpi fonts must be placed in
10059 <file>/usr/share/fonts/X11/75dpi/</file>.
10063 Character-cell fonts, cursor fonts, and other
10064 low-resolution fonts must be placed in
10065 <file>/usr/share/fonts/X11/misc/</file>.
10071 Type 1 fonts must be placed in
10072 <file>/usr/share/fonts/X11/Type1/</file>. If font
10073 metric files are available, they must be placed here
10078 Subdirectories of <file>/usr/share/fonts/X11/</file>
10079 other than those listed above must be neither
10080 created nor used. (The <file>PEX</file>, <file>CID</file>,
10081 <file>Speedo</file>, and <file>cyrillic</file> directories
10082 are excepted for historical reasons, but installation of
10083 files into these directories remains discouraged.)
10087 Font packages may, instead of placing files directly
10088 in the X font directories listed above, provide
10089 symbolic links in that font directory pointing to
10090 the files' actual location in the filesystem. Such
10091 a location must comply with the FHS.
10095 Font packages should not contain both 75dpi and
10096 100dpi versions of a font. If both are available,
10097 they should be provided in separate binary packages
10098 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10099 the names of the packages containing the
10100 corresponding fonts.
10104 Fonts destined for the <file>misc</file> subdirectory
10105 should not be included in the same package as 75dpi
10106 or 100dpi fonts; instead, they should be provided in
10107 a separate package with <tt>-misc</tt> appended to
10112 Font packages must not provide the files
10113 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10114 <file>fonts.scale</file> in a font directory:
10117 <file>fonts.dir</file> files must not be provided at all.
10121 <file>fonts.alias</file> and <file>fonts.scale</file>
10122 files, if needed, should be provided in the
10124 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10125 where <var>fontdir</var> is the name of the
10127 <file>/usr/share/fonts/X11/</file> where the
10128 package's corresponding fonts are stored
10129 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10130 <var>package</var> is the name of the package
10131 that provides these fonts, and
10132 <var>extension</var> is either <tt>scale</tt>
10133 or <tt>alias</tt>, whichever corresponds to
10140 Font packages must declare a dependency on
10141 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10142 or <tt>Pre-Depends</tt> control field.
10146 Font packages that provide one or more
10147 <file>fonts.scale</file> files as described above must
10148 invoke <prgn>update-fonts-scale</prgn> on each
10149 directory into which they installed fonts
10150 <em>before</em> invoking
10151 <prgn>update-fonts-dir</prgn> on that directory.
10152 This invocation must occur in both the
10153 <prgn>postinst</prgn> (for all arguments) and
10154 <prgn>postrm</prgn> (for all arguments except
10155 <tt>upgrade</tt>) scripts.
10159 Font packages that provide one or more
10160 <file>fonts.alias</file> files as described above must
10161 invoke <prgn>update-fonts-alias</prgn> on each
10162 directory into which they installed fonts. This
10163 invocation must occur in both the
10164 <prgn>postinst</prgn> (for all arguments) and
10165 <prgn>postrm</prgn> (for all arguments except
10166 <tt>upgrade</tt>) scripts.
10170 Font packages must invoke
10171 <prgn>update-fonts-dir</prgn> on each directory into
10172 which they installed fonts. This invocation must
10173 occur in both the <prgn>postinst</prgn> (for all
10174 arguments) and <prgn>postrm</prgn> (for all
10175 arguments except <tt>upgrade</tt>) scripts.
10179 Font packages must not provide alias names for the
10180 fonts they include which collide with alias names
10181 already in use by fonts already packaged.
10185 Font packages must not provide fonts with the same
10186 XLFD registry name as another font already packaged.
10192 <sect1 id="appdefaults">
10193 <heading>Application defaults files</heading>
10196 Application defaults files must be installed in the
10197 directory <file>/etc/X11/app-defaults/</file> (use of a
10198 localized subdirectory of <file>/etc/X11/</file> as described
10199 in the <em>X Toolkit Intrinsics - C Language
10200 Interface</em> manual is also permitted). They must be
10201 registered as <tt>conffile</tt>s or handled as
10202 configuration files.
10206 Customization of programs' X resources may also be
10207 supported with the provision of a file with the same name
10208 as that of the package placed in
10209 the <file>/etc/X11/Xresources/</file> directory, which
10210 must be registered as a <tt>conffile</tt> or handled as a
10211 configuration file.<footnote>
10212 Note that this mechanism is not the same as using
10213 app-defaults; app-defaults are tied to the client
10214 binary on the local file system, whereas X resources
10215 are stored in the X server and affect all connecting
10222 <heading>Installation directory issues</heading>
10225 Historically, packages using the X Window System used a
10226 separate set of installation directories from other packages.
10227 This practice has been discontinued and packages using the X
10228 Window System should now generally be installed in the same
10229 directories as any other package. Specifically, packages must
10230 not install files under the <file>/usr/X11R6/</file> directory
10231 and the <file>/usr/X11R6/</file> directory hierarchy should be
10232 regarded as obsolete.
10236 Include files previously installed under
10237 <file>/usr/X11R6/include/X11/</file> should be installed into
10238 <file>/usr/include/X11/</file>. For files previously
10239 installed into subdirectories of
10240 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10241 determine if subdirectories of <file>/usr/lib/</file> and
10242 <file>/usr/share/</file> can be used. If not, a subdirectory
10243 of <file>/usr/lib/X11/</file> should be used.
10247 Configuration files for window, display, or session managers
10248 or other applications that are tightly integrated with the X
10249 Window System may be placed in a subdirectory
10250 of <file>/etc/X11/</file> corresponding to the package name.
10251 Other X Window System applications should use
10252 the <file>/etc/</file> directory unless otherwise mandated by
10253 policy (such as for <ref id="appdefaults">).
10259 <heading>Perl programs and modules</heading>
10262 Perl programs and modules should follow the current Perl policy.
10266 The Perl policy can be found in the <tt>perl-policy</tt>
10267 files in the <tt>debian-policy</tt> package.
10268 It is also available from the Debian web mirrors at
10269 <tt><url name="/doc/packaging-manuals/perl-policy/"
10270 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10275 <heading>Emacs lisp programs</heading>
10278 Please refer to the "Debian Emacs Policy" for details of how to
10279 package emacs lisp programs.
10283 The Emacs policy is available in
10284 <file>debian-emacs-policy.gz</file> of the
10285 <package>emacsen-common</package> package.
10286 It is also available from the Debian web mirrors at
10287 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10288 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10293 <heading>Games</heading>
10296 The permissions on <file>/var/games</file> are mode 755, owner
10297 <tt>root</tt> and group <tt>root</tt>.
10301 Each game decides on its own security policy.</p>
10304 Games which require protected, privileged access to
10305 high-score files, saved games, etc., may be made
10306 set-<em>group</em>-id (mode 2755) and owned by
10307 <tt>root:games</tt>, and use files and directories with
10308 appropriate permissions (770 <tt>root:games</tt>, for
10309 example). They must not be made
10310 set-<em>user</em>-id, as this causes security problems. (If
10311 an attacker can subvert any set-user-id game they can
10312 overwrite the executable of any other, causing other players
10313 of these games to run a Trojan horse program. With a
10314 set-group-id game the attacker only gets access to less
10315 important game data, and if they can get at the other
10316 players' accounts at all it will take considerably more
10320 Some packages, for example some fortune cookie programs, are
10321 configured by the upstream authors to install with their
10322 data files or other static information made unreadable so
10323 that they can only be accessed through set-id programs
10324 provided. You should not do this in a Debian package: anyone can
10325 download the <file>.deb</file> file and read the data from it,
10326 so there is no point making the files unreadable. Not
10327 making the files unreadable also means that you don't have
10328 to make so many programs set-id, which reduces the risk of a
10332 As described in the FHS, binaries of games should be
10333 installed in the directory <file>/usr/games</file>. This also
10334 applies to games that use the X Window System. Manual pages
10335 for games (X and non-X games) should be installed in
10336 <file>/usr/share/man/man6</file>.</p>
10342 <heading>Documentation</heading>
10345 <heading>Manual pages</heading>
10348 You should install manual pages in <prgn>nroff</prgn> source
10349 form, in appropriate places under <file>/usr/share/man</file>.
10350 You should only use sections 1 to 9 (see the FHS for more
10351 details). You must not install a pre-formatted "cat page".
10355 Each program, utility, and function should have an
10356 associated manual page included in the same package. It is
10357 suggested that all configuration files also have a manual
10358 page included as well. Manual pages for protocols and other
10359 auxiliary things are optional.
10363 If no manual page is available, this is considered as a bug
10364 and should be reported to the Debian Bug Tracking System (the
10365 maintainer of the package is allowed to write this bug report
10366 themselves, if they so desire). Do not close the bug report
10367 until a proper man page is available.<footnote>
10368 It is not very hard to write a man page. See the
10369 <url id="http://www.schweikhardt.net/man_page_howto.html"
10370 name="Man-Page-HOWTO">,
10371 <manref name="man" section="7">, the examples created
10372 by <prgn>dh_make</prgn>, the helper
10373 program <prgn>help2man</prgn>, or the
10374 directory <file>/usr/share/doc/man-db/examples</file>.
10379 You may forward a complaint about a missing man page to the
10380 upstream authors, and mark the bug as forwarded in the
10381 Debian bug tracking system. Even though the GNU Project do
10382 not in general consider the lack of a man page to be a bug,
10383 we do; if they tell you that they don't consider it a bug
10384 you should leave the bug in our bug tracking system open
10389 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10393 If one man page needs to be accessible via several names it
10394 is better to use a symbolic link than the <file>.so</file>
10395 feature, but there is no need to fiddle with the relevant
10396 parts of the upstream source to change from <file>.so</file> to
10397 symlinks: don't do it unless it's easy. You should not
10398 create hard links in the manual page directories, nor put
10399 absolute filenames in <file>.so</file> directives. The filename
10400 in a <file>.so</file> in a man page should be relative to the
10401 base of the man page tree (usually
10402 <file>/usr/share/man</file>). If you do not create any links
10403 (whether symlinks, hard links, or <tt>.so</tt> directives)
10404 in the file system to the alternate names of the man page,
10405 then you should not rely on <prgn>man</prgn> finding your
10406 man page under those names based solely on the information in
10407 the man page's header.<footnote>
10408 Supporting this in <prgn>man</prgn> often requires
10409 unreasonable processing time to find a manual page or to
10410 report that none exists, and moves knowledge into man's
10411 database that would be better left in the file system.
10412 This support is therefore deprecated and will cease to
10413 be present in the future.
10418 Manual pages in locale-specific subdirectories of
10419 <file>/usr/share/man</file> should use either UTF-8 or the usual
10420 legacy encoding for that language (normally the one corresponding
10421 to the shortest relevant locale name in
10422 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10423 <file>/usr/share/man/fr</file> should use either UTF-8 or
10424 ISO-8859-1.<footnote>
10425 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10426 use. In future, all manual pages will be required to use
10432 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10433 included in the subdirectory name unless it indicates a
10434 significant difference in the language, as this excludes
10435 speakers of the language in other countries.<footnote>
10436 At the time of writing, Chinese and Portuguese are the main
10437 languages with such differences, so <file>pt_BR</file>,
10438 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10443 If a localized version of a manual page is provided, it should
10444 either be up-to-date or it should be obvious to the reader that
10445 it is outdated and the original manual page should be used
10446 instead. This can be done either by a note at the beginning of
10447 the manual page or by showing the missing or changed portions in
10448 the original language instead of the target language.
10453 <heading>Info documents</heading>
10456 Info documents should be installed in <file>/usr/share/info</file>.
10457 They should be compressed with <tt>gzip -9</tt>.
10461 The <prgn>install-info</prgn> program maintains a directory of
10462 installed info documents in <file>/usr/share/info/dir</file> for
10463 the use of info readers.<footnote>
10464 It was previously necessary for packages installing info
10465 documents to run <prgn>install-info</prgn> from maintainer
10466 scripts. This is no longer necessary. The installation
10467 system now uses dpkg triggers.
10469 This file must not be included in packages. Packages containing
10470 info documents should depend on <tt>dpkg (>= 1.15.4) |
10471 install-info</tt> to ensure that the directory file is properly
10472 rebuilt during partial upgrades from Debian 5.0 (lenny) and
10477 Info documents should contain section and directory entry
10478 information in the document for the use
10479 of <prgn>install-info</prgn>. The section should be specified
10480 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10481 space and the section of this info page. The directory entry or
10482 entries should be included between
10483 a <tt>START-INFO-DIR-ENTRY</tt> line and
10484 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10486 INFO-DIR-SECTION Individual utilities
10487 START-INFO-DIR-ENTRY
10488 * example: (example). An example info directory entry.
10491 To determine which section to use, you should look
10492 at <file>/usr/share/info/dir</file> on your system and choose
10493 the most relevant (or create a new section if none of the
10494 current sections are relevant).<footnote>
10495 Normally, info documents are generated from Texinfo source.
10496 To include this information in the generated info document, if
10497 it is absent, add commands like:
10499 @dircategory Individual utilities
10501 * example: (example). An example info directory entry.
10504 to the Texinfo source of the document and ensure that the info
10505 documents are rebuilt from source during the package build.
10511 <heading>Additional documentation</heading>
10514 Any additional documentation that comes with the package may
10515 be installed at the discretion of the package maintainer.
10516 Plain text documentation should be installed in the directory
10517 <file>/usr/share/doc/<var>package</var></file>, where
10518 <var>package</var> is the name of the package, and
10519 compressed with <tt>gzip -9</tt> unless it is small.
10523 If a package comes with large amounts of documentation which
10524 many users of the package will not require you should create
10525 a separate binary package to contain it, so that it does not
10526 take up disk space on the machines of users who do not need
10527 or want it installed.</p>
10530 It is often a good idea to put text information files
10531 (<file>README</file>s, changelogs, and so forth) that come with
10532 the source package in <file>/usr/share/doc/<var>package</var></file>
10533 in the binary package. However, you don't need to install
10534 the instructions for building and installing the package, of
10538 Packages must not require the existence of any files in
10539 <file>/usr/share/doc/</file> in order to function
10541 The system administrator should be able to
10542 delete files in <file>/usr/share/doc/</file> without causing
10543 any programs to break.
10545 Any files that are referenced by programs but are also
10546 useful as stand alone documentation should be installed under
10547 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10548 <file>/usr/share/doc/<var>package</var></file>.
10552 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10553 link to another directory in <file>/usr/share/doc</file> only if
10554 the two packages both come from the same source and the
10555 first package Depends on the second.<footnote>
10557 Please note that this does not override the section on
10558 changelog files below, so the file
10559 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10560 must refer to the changelog for the current version of
10561 <var>package</var> in question. In practice, this means
10562 that the sources of the target and the destination of the
10563 symlink must be the same (same source package and
10570 Former Debian releases placed all additional documentation
10571 in <file>/usr/doc/<var>package</var></file>. This has been
10572 changed to <file>/usr/share/doc/<var>package</var></file>,
10573 and packages must not put documentation in the directory
10574 <file>/usr/doc/<var>package</var></file>. <footnote>
10575 At this phase of the transition, we no longer require a
10576 symbolic link in <file>/usr/doc/</file>. At a later point,
10577 policy shall change to make the symbolic links a bug.
10583 <heading>Preferred documentation formats</heading>
10586 The unification of Debian documentation is being carried out
10590 If your package comes with extensive documentation in a
10591 markup format that can be converted to various other formats
10592 you should if possible ship HTML versions in a binary
10593 package, in the directory
10594 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10595 its subdirectories.<footnote>
10596 The rationale: The important thing here is that HTML
10597 docs should be available in <em>some</em> package, not
10598 necessarily in the main binary package.
10603 Other formats such as PostScript may be provided at the
10604 package maintainer's discretion.
10608 <sect id="copyrightfile">
10609 <heading>Copyright information</heading>
10612 Every package must be accompanied by a verbatim copy of its
10613 copyright information and distribution license in the file
10614 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10615 file must neither be compressed nor be a symbolic link.
10619 In addition, the copyright file must say where the upstream
10620 sources (if any) were obtained, and should name the original
10625 Packages in the <em>contrib</em> or <em>non-free</em> archive
10626 areas should state in the copyright file that the package is not
10627 part of the Debian distribution and briefly explain why.
10631 A copy of the file which will be installed in
10632 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10633 be in <file>debian/copyright</file> in the source package.
10637 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10638 link to another directory in <file>/usr/share/doc</file> only if
10639 the two packages both come from the same source and the
10640 first package Depends on the second. These rules are important
10641 because <file>copyright</file> files must be extractable by
10646 Packages distributed under the Apache license (version 2.0), the
10647 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10648 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10649 1.3) should refer to the corresponding files
10650 under <file>/usr/share/common-licenses</file>,<footnote>
10653 <file>/usr/share/common-licenses/Apache-2.0</file>,
10654 <file>/usr/share/common-licenses/Artistic</file>,
10655 <file>/usr/share/common-licenses/GPL-1</file>,
10656 <file>/usr/share/common-licenses/GPL-2</file>,
10657 <file>/usr/share/common-licenses/GPL-3</file>,
10658 <file>/usr/share/common-licenses/LGPL-2</file>,
10659 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10660 <file>/usr/share/common-licenses/LGPL-3</file>,
10661 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10662 <file>/usr/share/common-licenses/GFDL-1.3</file>
10663 respectively. The University of California BSD license is
10664 also included in <package>base-files</package> as
10665 <file>/usr/share/common-licenses/BSD</file>, but given the
10666 brevity of this license, its specificity to code whose
10667 copyright is held by the Regents of the University of
10668 California, and the frequency of minor wording changes, its
10669 text should be included in the copyright file rather than
10670 referencing this file.
10672 </footnote> rather than quoting them in the copyright
10677 You should not use the copyright file as a general <file>README</file>
10678 file. If your package has such a file it should be
10679 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10680 <file>README.Debian</file> or some other appropriate place.
10684 All copyright files must be encoded in UTF-8.
10687 <sect1 id="copyrightformat">
10688 <heading>Machine-readable copyright information</heading>
10691 A specification for a standard, machine-readable format
10692 for <file>debian/copyright</file> files is maintained as part
10693 of the <package>debian-policy</package> package. This
10694 document may be found in the <file>copyright-format</file>
10695 files in the <package>debian-policy</package> package. It is
10696 also available from the Debian web mirrors at
10697 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10698 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10702 Use of this format is optional.
10708 <heading>Examples</heading>
10711 Any examples (configurations, source files, whatever),
10712 should be installed in a directory
10713 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10714 files should not be referenced by any program: they're there
10715 for the benefit of the system administrator and users as
10716 documentation only. Architecture-specific example files
10717 should be installed in a directory
10718 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10720 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10721 latter directory itself may be a symbolic link to the
10726 If the purpose of a package is to provide examples, then the
10727 example files may be installed into
10728 <file>/usr/share/doc/<var>package</var></file>.
10732 <sect id="changelogs">
10733 <heading>Changelog files</heading>
10736 Packages that are not Debian-native must contain a
10737 compressed copy of the <file>debian/changelog</file> file from
10738 the Debian source tree in
10739 <file>/usr/share/doc/<var>package</var></file> with the name
10740 <file>changelog.Debian.gz</file>.
10744 If an upstream changelog is available, it should be accessible as
10745 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10746 plain text. If the upstream changelog is distributed in
10747 HTML, it should be made available in that form as
10748 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10749 and a plain text <file>changelog.gz</file> should be generated
10750 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10751 the upstream changelog files do not already conform to this
10752 naming convention, then this may be achieved either by
10753 renaming the files, or by adding a symbolic link, at the
10754 maintainer's discretion.<footnote>
10755 Rationale: People should not have to look in places for
10756 upstream changelogs merely because they are given
10757 different names or are distributed in HTML format.
10762 All of these files should be installed compressed using
10763 <tt>gzip -9</tt>, as they will become large with time even
10764 if they start out small.
10768 If the package has only one changelog which is used both as
10769 the Debian changelog and the upstream one because there is
10770 no separate upstream maintainer then that changelog should
10771 usually be installed as
10772 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10773 there is a separate upstream maintainer, but no upstream
10774 changelog, then the Debian changelog should still be called
10775 <file>changelog.Debian.gz</file>.
10779 For details about the format and contents of the Debian
10780 changelog file, please see <ref id="dpkgchangelog">.
10785 <appendix id="pkg-scope">
10786 <heading>Introduction and scope of these appendices</heading>
10789 These appendices are taken essentially verbatim from the
10790 now-deprecated Packaging Manual, version 3.2.1.0. They are
10791 the chapters which are likely to be of use to package
10792 maintainers and which have not already been included in the
10793 policy document itself. Most of these sections are very likely
10794 not relevant to policy; they should be treated as
10795 documentation for the packaging system. Please note that these
10796 appendices are included for convenience, and for historical
10797 reasons: they used to be part of policy package, and they have
10798 not yet been incorporated into dpkg documentation. However,
10799 they still have value, and hence they are presented here.
10803 They have not yet been checked to ensure that they are
10804 compatible with the contents of policy, and if there are any
10805 contradictions, the version in the main policy document takes
10806 precedence. The remaining chapters of the old Packaging
10807 Manual have also not been read in detail to ensure that there
10808 are not parts which have been left out. Both of these will be
10809 done in due course.
10813 Certain parts of the Packaging manual were integrated into the
10814 Policy Manual proper, and removed from the appendices. Links
10815 have been placed from the old locations to the new ones.
10819 <prgn>dpkg</prgn> is a suite of programs for creating binary
10820 package files and installing and removing them on Unix
10822 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10823 work on or be ported to other systems.
10828 The binary packages are designed for the management of
10829 installed executable programs (usually compiled binaries) and
10830 their associated data, though source code examples and
10831 documentation are provided as part of some packages.</p>
10834 This manual describes the technical aspects of creating Debian
10835 binary packages (<file>.deb</file> files). It documents the
10836 behavior of the package management programs
10837 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10838 they interact with packages.</p>
10841 It also documents the interaction between
10842 <prgn>dselect</prgn>'s core and the access method scripts it
10843 uses to actually install the selected packages, and describes
10844 how to create a new access method.</p>
10847 This manual does not go into detail about the options and
10848 usage of the package building and installation tools. It
10849 should therefore be read in conjunction with those programs'
10854 The utility programs which are provided with <prgn>dpkg</prgn>
10855 for managing various system configuration and similar issues,
10856 such as <prgn>update-rc.d</prgn> and
10857 <prgn>install-info</prgn>, are not described in detail here -
10858 please see their man pages.
10862 It is assumed that the reader is reasonably familiar with the
10863 <prgn>dpkg</prgn> System Administrators' manual.
10864 Unfortunately this manual does not yet exist.
10868 The Debian version of the FSF's GNU hello program is provided as
10869 an example for people wishing to create Debian packages. However,
10870 while the examples are helpful, they do not replace the need to
10871 read and follow the Policy and Programmer's Manual.</p>
10874 <appendix id="pkg-binarypkg">
10875 <heading>Binary packages (from old Packaging Manual)</heading>
10878 The binary package has two main sections. The first part
10879 consists of various control information files and scripts used
10880 by <prgn>dpkg</prgn> when installing and removing. See <ref
10881 id="pkg-controlarea">.
10885 The second part is an archive containing the files and
10886 directories to be installed.
10890 In the future binary packages may also contain other
10891 components, such as checksums and digital signatures. The
10892 format for the archive is described in full in the
10893 <file>deb(5)</file> man page.
10897 <sect id="pkg-bincreating"><heading>Creating package files -
10898 <prgn>dpkg-deb</prgn>
10902 All manipulation of binary package files is done by
10903 <prgn>dpkg-deb</prgn>; it's the only program that has
10904 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10905 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10906 will spot that the options requested are appropriate to
10907 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10912 In order to create a binary package you must make a
10913 directory tree which contains all the files and directories
10914 you want to have in the file system data part of the package.
10915 In Debian-format source packages this directory is usually
10916 <file>debian/tmp</file>, relative to the top of the package's
10921 They should have the locations (relative to the root of the
10922 directory tree you're constructing) ownerships and
10923 permissions which you want them to have on the system when
10924 they are installed.
10928 With current versions of <prgn>dpkg</prgn> the uid/username
10929 and gid/groupname mappings for the users and groups being
10930 used should be the same on the system where the package is
10931 built and the one where it is installed.
10935 You need to add one special directory to the root of the
10936 miniature file system tree you're creating:
10937 <prgn>DEBIAN</prgn>. It should contain the control
10938 information files, notably the binary package control file
10939 (see <ref id="pkg-controlfile">).
10943 The <prgn>DEBIAN</prgn> directory will not appear in the
10944 file system archive of the package, and so won't be installed
10945 by <prgn>dpkg</prgn> when the package is unpacked.
10949 When you've prepared the package, you should invoke:
10951 dpkg --build <var>directory</var>
10956 This will build the package in
10957 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10958 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10959 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10960 build the package.)
10964 See the man page <manref name="dpkg-deb" section="8"> for details of how
10965 to examine the contents of this newly-created file. You may find the
10966 output of following commands enlightening:
10968 dpkg-deb --info <var>filename</var>.deb
10969 dpkg-deb --contents <var>filename</var>.deb
10970 dpkg --contents <var>filename</var>.deb
10972 To view the copyright file for a package you could use this command:
10974 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10979 <sect id="pkg-controlarea">
10980 <heading>Package control information files</heading>
10983 The control information portion of a binary package is a
10984 collection of files with names known to <prgn>dpkg</prgn>.
10985 It will treat the contents of these files specially - some
10986 of them contain information used by <prgn>dpkg</prgn> when
10987 installing or removing the package; others are scripts which
10988 the package maintainer wants <prgn>dpkg</prgn> to run.
10992 It is possible to put other files in the package control
10993 information file area, but this is not generally a good idea
10994 (though they will largely be ignored).
10998 Here is a brief list of the control information files supported
10999 by <prgn>dpkg</prgn> and a summary of what they're used for.
11004 <tag><tt>control</tt>
11007 This is the key description file used by
11008 <prgn>dpkg</prgn>. It specifies the package's name
11009 and version, gives its description for the user,
11010 states its relationships with other packages, and so
11011 forth. See <ref id="sourcecontrolfiles"> and
11012 <ref id="binarycontrolfiles">.
11016 It is usually generated automatically from information
11017 in the source package by the
11018 <prgn>dpkg-gencontrol</prgn> program, and with
11019 assistance from <prgn>dpkg-shlibdeps</prgn>.
11020 See <ref id="pkg-sourcetools">.
11024 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11029 These are executable files (usually scripts) which
11030 <prgn>dpkg</prgn> runs during installation, upgrade
11031 and removal of packages. They allow the package to
11032 deal with matters which are particular to that package
11033 or require more complicated processing than that
11034 provided by <prgn>dpkg</prgn>. Details of when and
11035 how they are called are in <ref id="maintainerscripts">.
11039 It is very important to make these scripts idempotent.
11040 See <ref id="idempotency">.
11044 The maintainer scripts are not guaranteed to run with a
11045 controlling terminal and may not be able to interact with
11046 the user. See <ref id="controllingterminal">.
11050 <tag><tt>conffiles</tt>
11053 This file contains a list of configuration files which
11054 are to be handled automatically by <prgn>dpkg</prgn>
11055 (see <ref id="pkg-conffiles">). Note that not necessarily
11056 every configuration file should be listed here.
11059 <tag><tt>shlibs</tt>
11062 This file contains a list of the shared libraries
11063 supplied by the package, with dependency details for
11064 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11065 when it determines what dependencies are required in a
11066 package control file. The <tt>shlibs</tt> file format
11067 is described on <ref id="shlibs">.
11072 <sect id="pkg-controlfile">
11073 <heading>The main control information file: <tt>control</tt></heading>
11076 The most important control information file used by
11077 <prgn>dpkg</prgn> when it installs a package is
11078 <tt>control</tt>. It contains all the package's "vital
11083 The binary package control files of packages built from
11084 Debian sources are made by a special tool,
11085 <prgn>dpkg-gencontrol</prgn>, which reads
11086 <file>debian/control</file> and <file>debian/changelog</file> to
11087 find the information it needs. See <ref id="pkg-sourcepkg"> for
11092 The fields in binary package control files are listed in
11093 <ref id="binarycontrolfiles">.
11097 A description of the syntax of control files and the purpose
11098 of the fields is available in <ref id="controlfields">.
11103 <heading>Time Stamps</heading>
11106 See <ref id="timestamps">.
11111 <appendix id="pkg-sourcepkg">
11112 <heading>Source packages (from old Packaging Manual) </heading>
11115 The Debian binary packages in the distribution are generated
11116 from Debian sources, which are in a special format to assist
11117 the easy and automatic building of binaries.
11120 <sect id="pkg-sourcetools">
11121 <heading>Tools for processing source packages</heading>
11124 Various tools are provided for manipulating source packages;
11125 they pack and unpack sources and help build of binary
11126 packages and help manage the distribution of new versions.
11130 They are introduced and typical uses described here; see
11131 <manref name="dpkg-source" section="1"> for full
11132 documentation about their arguments and operation.
11136 For examples of how to construct a Debian source package,
11137 and how to use those utilities that are used by Debian
11138 source packages, please see the <prgn>hello</prgn> example
11142 <sect1 id="pkg-dpkg-source">
11144 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11149 This program is frequently used by hand, and is also
11150 called from package-independent automated building scripts
11151 such as <prgn>dpkg-buildpackage</prgn>.
11155 To unpack a package it is typically invoked with
11157 dpkg-source -x <var>.../path/to/filename</var>.dsc
11162 with the <file><var>filename</var>.tar.gz</file> and
11163 <file><var>filename</var>.diff.gz</file> (if applicable) in
11164 the same directory. It unpacks into
11165 <file><var>package</var>-<var>version</var></file>, and if
11167 <file><var>package</var>-<var>version</var>.orig</file>, in
11168 the current directory.
11172 To create a packed source archive it is typically invoked:
11174 dpkg-source -b <var>package</var>-<var>version</var>
11179 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11180 <file>.diff.gz</file> (if appropriate) in the current
11181 directory. <prgn>dpkg-source</prgn> does not clean the
11182 source tree first - this must be done separately if it is
11187 See also <ref id="pkg-sourcearchives">.</p>
11191 <sect1 id="pkg-dpkg-buildpackage">
11193 <prgn>dpkg-buildpackage</prgn> - overall package-building
11198 <prgn>dpkg-buildpackage</prgn> is a script which invokes
11199 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
11200 targets <tt>clean</tt>, <tt>build</tt> and
11201 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
11202 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
11203 source and binary package upload.
11207 It is usually invoked by hand from the top level of the
11208 built or unbuilt source directory. It may be invoked with
11209 no arguments; useful arguments include:
11210 <taglist compact="compact">
11211 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
11214 Do not sign the <tt>.changes</tt> file or the
11215 source package <tt>.dsc</tt> file, respectively.</p>
11217 <tag><tt>-p<var>sign-command</var></tt></tag>
11220 Invoke <var>sign-command</var> instead of finding
11221 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
11222 <var>sign-command</var> must behave just like
11223 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
11225 <tag><tt>-r<var>root-command</var></tt></tag>
11228 When root privilege is required, invoke the command
11229 <var>root-command</var>. <var>root-command</var>
11230 should invoke its first argument as a command, from
11231 the <prgn>PATH</prgn> if necessary, and pass its
11232 second and subsequent arguments to the command it
11233 calls. If no <var>root-command</var> is supplied
11234 then <var>dpkg-buildpackage</var> will use
11235 the <prgn>fakeroot</prgn> command, which is sufficient
11236 to build most packages without actually requiring root
11239 <tag><tt>-b</tt>, <tt>-B</tt></tag>
11242 Two types of binary-only build and upload - see
11243 <manref name="dpkg-source" section="1">.
11250 <sect1 id="pkg-dpkg-gencontrol">
11252 <prgn>dpkg-gencontrol</prgn> - generates binary package
11257 This program is usually called from <file>debian/rules</file>
11258 (see <ref id="pkg-sourcetree">) in the top level of the source
11263 This is usually done just before the files and directories in the
11264 temporary directory tree where the package is being built have their
11265 permissions and ownerships set and the package is constructed using
11266 <prgn>dpkg-deb/</prgn>
11268 This is so that the control file which is produced has
11269 the right permissions
11274 <prgn>dpkg-gencontrol</prgn> must be called after all the
11275 files which are to go into the package have been placed in
11276 the temporary build directory, so that its calculation of
11277 the installed size of a package is correct.
11281 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11282 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11283 variable substitutions created by
11284 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11289 For a package which generates only one binary package, and
11290 which builds it in <file>debian/tmp</file> relative to the top
11291 of the source package, it is usually sufficient to call
11292 <prgn>dpkg-gencontrol</prgn>.
11296 Sources which build several binaries will typically need
11299 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11300 </example> The <tt>-P</tt> tells
11301 <prgn>dpkg-gencontrol</prgn> that the package is being
11302 built in a non-default directory, and the <tt>-p</tt>
11303 tells it which package's control file should be generated.
11307 <prgn>dpkg-gencontrol</prgn> also adds information to the
11308 list of files in <file>debian/files</file>, for the benefit of
11309 (for example) a future invocation of
11310 <prgn>dpkg-genchanges</prgn>.</p>
11313 <sect1 id="pkg-dpkg-shlibdeps">
11315 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11320 See <manref name="dpkg-shlibdeps" section="1">.
11324 <sect1 id="pkg-dpkg-distaddfile">
11326 <prgn>dpkg-distaddfile</prgn> - adds a file to
11327 <file>debian/files</file>
11331 Some packages' uploads need to include files other than
11332 the source and binary package files.
11336 <prgn>dpkg-distaddfile</prgn> adds a file to the
11337 <file>debian/files</file> file so that it will be included in
11338 the <file>.changes</file> file when
11339 <prgn>dpkg-genchanges</prgn> is run.
11343 It is usually invoked from the <tt>binary</tt> target of
11344 <file>debian/rules</file>:
11346 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11348 The <var>filename</var> is relative to the directory where
11349 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11350 is usually the directory above the top level of the source
11351 tree. The <file>debian/rules</file> target should put the
11352 file there just before or just after calling
11353 <prgn>dpkg-distaddfile</prgn>.
11357 The <var>section</var> and <var>priority</var> are passed
11358 unchanged into the resulting <file>.changes</file> file.
11363 <sect1 id="pkg-dpkg-genchanges">
11365 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11366 upload control file
11370 This program is usually called by package-independent
11371 automatic building scripts such as
11372 <prgn>dpkg-buildpackage</prgn>, but it may also be called
11377 It is usually called in the top level of a built source
11378 tree, and when invoked with no arguments will print out a
11379 straightforward <file>.changes</file> file based on the
11380 information in the source package's changelog and control
11381 file and the binary and source packages which should have
11387 <sect1 id="pkg-dpkg-parsechangelog">
11389 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11390 representation of a changelog
11394 This program is used internally by
11395 <prgn>dpkg-source</prgn> et al. It may also occasionally
11396 be useful in <file>debian/rules</file> and elsewhere. It
11397 parses a changelog, <file>debian/changelog</file> by default,
11398 and prints a control-file format representation of the
11399 information in it to standard output.
11403 <sect1 id="pkg-dpkg-architecture">
11405 <prgn>dpkg-architecture</prgn> - information about the build and
11410 This program can be used manually, but is also invoked by
11411 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
11412 environment or make variables which specify the build and host
11413 architecture for the package building process.
11418 <sect id="pkg-sourcetree">
11419 <heading>The Debian package source tree</heading>
11422 The source archive scheme described later is intended to
11423 allow a Debian package source tree with some associated
11424 control information to be reproduced and transported easily.
11425 The Debian package source tree is a version of the original
11426 program with certain files added for the benefit of the
11427 packaging process, and with any other changes required
11428 made to the rest of the source code and installation
11433 The extra files created for Debian are in the subdirectory
11434 <file>debian</file> of the top level of the Debian package
11435 source tree. They are described below.
11438 <sect1 id="pkg-debianrules">
11439 <heading><file>debian/rules</file> - the main building script</heading>
11442 See <ref id="debianrules">.
11446 <sect1 id="pkg-srcsubstvars">
11447 <heading><file>debian/substvars</file> and variable substitutions</heading>
11450 See <ref id="substvars">.
11456 <heading><file>debian/files</file></heading>
11459 See <ref id="debianfiles">.
11463 <sect1><heading><file>debian/tmp</file>
11467 This is the canonical temporary location for the
11468 construction of binary packages by the <tt>binary</tt>
11469 target. The directory <file>tmp</file> serves as the root of
11470 the file system tree as it is being constructed (for
11471 example, by using the package's upstream makefiles install
11472 targets and redirecting the output there), and it also
11473 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11474 id="pkg-bincreating">.
11478 If several binary packages are generated from the same
11479 source tree it is usual to use several
11480 <file>debian/tmp<var>something</var></file> directories, for
11481 example <file>tmp-a</file> or <file>tmp-doc</file>.
11485 Whatever <file>tmp</file> directories are created and used by
11486 <tt>binary</tt> must of course be removed by the
11487 <tt>clean</tt> target.</p></sect1>
11491 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11495 As it exists on the FTP site, a Debian source package
11496 consists of three related files. You must have the right
11497 versions of all three to be able to use them.
11502 <tag>Debian source control file - <tt>.dsc</tt></tag>
11504 This file is a control file used by <prgn>dpkg-source</prgn>
11505 to extract a source package.
11506 See <ref id="debiansourcecontrolfiles">.
11510 Original source archive -
11512 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11518 This is a compressed (with <tt>gzip -9</tt>)
11519 <prgn>tar</prgn> file containing the source code from
11520 the upstream authors of the program.
11525 Debian package diff -
11527 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11533 This is a unified context diff (<tt>diff -u</tt>)
11534 giving the changes which are required to turn the
11535 original source into the Debian source. These changes
11536 may only include editing and creating plain files.
11537 The permissions of files, the targets of symbolic
11538 links and the characteristics of special files or
11539 pipes may not be changed and no files may be removed
11544 All the directories in the diff must exist, except the
11545 <file>debian</file> subdirectory of the top of the source
11546 tree, which will be created by
11547 <prgn>dpkg-source</prgn> if necessary when unpacking.
11551 The <prgn>dpkg-source</prgn> program will
11552 automatically make the <file>debian/rules</file> file
11553 executable (see below).</p></item>
11558 If there is no original source code - for example, if the
11559 package is specially prepared for Debian or the Debian
11560 maintainer is the same as the upstream maintainer - the
11561 format is slightly different: then there is no diff, and the
11563 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11564 and preferably contains a directory named
11565 <file><var>package</var>-<var>version</var></file>.
11570 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11573 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11574 Debian source package. However, if it is not available it
11575 is possible to unpack a Debian source archive as follows:
11576 <enumlist compact="compact">
11579 Untar the tarfile, which will create a <file>.orig</file>
11583 <p>Rename the <file>.orig</file> directory to
11584 <file><var>package</var>-<var>version</var></file>.</p>
11588 Create the subdirectory <file>debian</file> at the top of
11589 the source tree.</p>
11591 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11593 <item><p>Untar the tarfile again if you want a copy of the original
11594 source code alongside the Debian version.</p>
11599 It is not possible to generate a valid Debian source archive
11600 without using <prgn>dpkg-source</prgn>. In particular,
11601 attempting to use <prgn>diff</prgn> directly to generate the
11602 <file>.diff.gz</file> file will not work.
11606 <heading>Restrictions on objects in source packages</heading>
11609 The source package may not contain any hard links
11611 This is not currently detected when building source
11612 packages, but only when extracting
11616 Hard links may be permitted at some point in the
11617 future, but would require a fair amount of
11619 </footnote>, device special files, sockets or setuid or
11622 Setgid directories are allowed.
11627 The source packaging tools manage the changes between the
11628 original and Debian source using <prgn>diff</prgn> and
11629 <prgn>patch</prgn>. Turning the original source tree as
11630 included in the <file>.orig.tar.gz</file> into the Debian
11631 package source must not involve any changes which cannot be
11632 handled by these tools. Problematic changes which cause
11633 <prgn>dpkg-source</prgn> to halt with an error when
11634 building the source package are:
11635 <list compact="compact">
11636 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11638 <item><p>Changing the targets of symbolic links.</p>
11640 <item><p>Creating directories, other than <file>debian</file>.</p>
11642 <item><p>Changes to the contents of binary files.</p></item>
11643 </list> Changes which cause <prgn>dpkg-source</prgn> to
11644 print a warning but continue anyway are:
11645 <list compact="compact">
11648 Removing files, directories or symlinks.
11650 Renaming a file is not treated specially - it is
11651 seen as the removal of the old file (which
11652 generates a warning, but is otherwise ignored),
11653 and the creation of the new one.
11659 Changed text files which are missing the usual final
11660 newline (either in the original or the modified
11665 Changes which are not represented, but which are not detected by
11666 <prgn>dpkg-source</prgn>, are:
11667 <list compact="compact">
11668 <item><p>Changing the permissions of files (other than
11669 <file>debian/rules</file>) and directories.</p></item>
11674 The <file>debian</file> directory and <file>debian/rules</file>
11675 are handled specially by <prgn>dpkg-source</prgn> - before
11676 applying the changes it will create the <file>debian</file>
11677 directory, and afterwards it will make
11678 <file>debian/rules</file> world-executable.
11684 <appendix id="pkg-controlfields">
11685 <heading>Control files and their fields (from old Packaging Manual)</heading>
11688 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11689 data in a common format, known as control files. Binary and
11690 source packages have control data as do the <file>.changes</file>
11691 files which control the installation of uploaded files, and
11692 <prgn>dpkg</prgn>'s internal databases are in a similar
11697 <heading>Syntax of control files</heading>
11700 See <ref id="controlsyntax">.
11704 It is important to note that there are several fields which
11705 are optional as far as <prgn>dpkg</prgn> and the related
11706 tools are concerned, but which must appear in every Debian
11707 package, or whose omission may cause problems.
11712 <heading>List of fields</heading>
11715 See <ref id="controlfieldslist">.
11719 This section now contains only the fields that didn't belong
11720 to the Policy manual.
11723 <sect1 id="pkg-f-Filename">
11724 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11727 These fields in <tt>Packages</tt> files give the
11728 filename(s) of (the parts of) a package in the
11729 distribution directories, relative to the root of the
11730 Debian hierarchy. If the package has been split into
11731 several parts the parts are all listed in order, separated
11736 <sect1 id="pkg-f-Size">
11737 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11740 These fields in <file>Packages</file> files give the size (in
11741 bytes, expressed in decimal) and MD5 checksum of the
11742 file(s) which make(s) up a binary package in the
11743 distribution. If the package is split into several parts
11744 the values for the parts are listed in order, separated by
11749 <sect1 id="pkg-f-Status">
11750 <heading><tt>Status</tt></heading>
11753 This field in <prgn>dpkg</prgn>'s status file records
11754 whether the user wants a package installed, removed or
11755 left alone, whether it is broken (requiring
11756 re-installation) or not and what its current state on the
11757 system is. Each of these pieces of information is a
11762 <sect1 id="pkg-f-Config-Version">
11763 <heading><tt>Config-Version</tt></heading>
11766 If a package is not installed or not configured, this
11767 field in <prgn>dpkg</prgn>'s status file records the last
11768 version of the package which was successfully
11773 <sect1 id="pkg-f-Conffiles">
11774 <heading><tt>Conffiles</tt></heading>
11777 This field in <prgn>dpkg</prgn>'s status file contains
11778 information about the automatically-managed configuration
11779 files held by a package. This field should <em>not</em>
11780 appear anywhere in a package!
11785 <heading>Obsolete fields</heading>
11788 These are still recognized by <prgn>dpkg</prgn> but should
11789 not appear anywhere any more.
11791 <taglist compact="compact">
11793 <tag><tt>Revision</tt></tag>
11794 <tag><tt>Package-Revision</tt></tag>
11795 <tag><tt>Package_Revision</tt></tag>
11797 The Debian revision part of the package version was
11798 at one point in a separate control field. This
11799 field went through several names.
11802 <tag><tt>Recommended</tt></tag>
11803 <item>Old name for <tt>Recommends</tt>.</item>
11805 <tag><tt>Optional</tt></tag>
11806 <item>Old name for <tt>Suggests</tt>.</item>
11808 <tag><tt>Class</tt></tag>
11809 <item>Old name for <tt>Priority</tt>.</item>
11818 <appendix id="pkg-conffiles">
11819 <heading>Configuration file handling (from old Packaging Manual)</heading>
11822 <prgn>dpkg</prgn> can do a certain amount of automatic
11823 handling of package configuration files.
11827 Whether this mechanism is appropriate depends on a number of
11828 factors, but basically there are two approaches to any
11829 particular configuration file.
11833 The easy method is to ship a best-effort configuration in the
11834 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11835 handle updates. If the user is unlikely to want to edit the
11836 file, but you need them to be able to without losing their
11837 changes, and a new package with a changed version of the file
11838 is only released infrequently, this is a good approach.
11842 The hard method is to build the configuration file from
11843 scratch in the <prgn>postinst</prgn> script, and to take the
11844 responsibility for fixing any mistakes made in earlier
11845 versions of the package automatically. This will be
11846 appropriate if the file is likely to need to be different on
11850 <sect><heading>Automatic handling of configuration files by
11855 A package may contain a control information file called
11856 <tt>conffiles</tt>. This file should be a list of filenames
11857 of configuration files needing automatic handling, separated
11858 by newlines. The filenames should be absolute pathnames,
11859 and the files referred to should actually exist in the
11864 When a package is upgraded <prgn>dpkg</prgn> will process
11865 the configuration files during the configuration stage,
11866 shortly before it runs the package's <prgn>postinst</prgn>
11871 For each file it checks to see whether the version of the
11872 file included in the package is the same as the one that was
11873 included in the last version of the package (the one that is
11874 being upgraded from); it also compares the version currently
11875 installed on the system with the one shipped with the last
11880 If neither the user nor the package maintainer has changed
11881 the file, it is left alone. If one or the other has changed
11882 their version, then the changed version is preferred - i.e.,
11883 if the user edits their file, but the package maintainer
11884 doesn't ship a different version, the user's changes will
11885 stay, silently, but if the maintainer ships a new version
11886 and the user hasn't edited it the new version will be
11887 installed (with an informative message). If both have
11888 changed their version the user is prompted about the problem
11889 and must resolve the differences themselves.
11893 The comparisons are done by calculating the MD5 message
11894 digests of the files, and storing the MD5 of the file as it
11895 was included in the most recent version of the package.
11899 When a package is installed for the first time
11900 <prgn>dpkg</prgn> will install the file that comes with it,
11901 unless that would mean overwriting a file already on the
11906 However, note that <prgn>dpkg</prgn> will <em>not</em>
11907 replace a conffile that was removed by the user (or by a
11908 script). This is necessary because with some programs a
11909 missing file produces an effect hard or impossible to
11910 achieve in another way, so that a missing file needs to be
11911 kept that way if the user did it.
11915 Note that a package should <em>not</em> modify a
11916 <prgn>dpkg</prgn>-handled conffile in its maintainer
11917 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11918 the user confusing and possibly dangerous options for
11919 conffile update when the package is upgraded.</p>
11922 <sect><heading>Fully-featured maintainer script configuration
11927 For files which contain site-specific information such as
11928 the hostname and networking details and so forth, it is
11929 better to create the file in the package's
11930 <prgn>postinst</prgn> script.
11934 This will typically involve examining the state of the rest
11935 of the system to determine values and other information, and
11936 may involve prompting the user for some information which
11937 can't be obtained some other way.
11941 When using this method there are a couple of important
11942 issues which should be considered:
11946 If you discover a bug in the program which generates the
11947 configuration file, or if the format of the file changes
11948 from one version to the next, you will have to arrange for
11949 the postinst script to do something sensible - usually this
11950 will mean editing the installed configuration file to remove
11951 the problem or change the syntax. You will have to do this
11952 very carefully, since the user may have changed the file,
11953 perhaps to fix the very problem that your script is trying
11954 to deal with - you will have to detect these situations and
11955 deal with them correctly.
11959 If you do go down this route it's probably a good idea to
11960 make the program that generates the configuration file(s) a
11961 separate program in <file>/usr/sbin</file>, by convention called
11962 <file><var>package</var>config</file> and then run that if
11963 appropriate from the post-installation script. The
11964 <tt><var>package</var>config</tt> program should not
11965 unquestioningly overwrite an existing configuration - if its
11966 mode of operation is geared towards setting up a package for
11967 the first time (rather than any arbitrary reconfiguration
11968 later) you should have it check whether the configuration
11969 already exists, and require a <tt>--force</tt> flag to
11970 overwrite it.</p></sect>
11973 <appendix id="pkg-alternatives"><heading>Alternative versions of
11974 an interface - <prgn>update-alternatives</prgn> (from old
11979 When several packages all provide different versions of the
11980 same program or file it is useful to have the system select a
11981 default, but to allow the system administrator to change it
11982 and have their decisions respected.
11986 For example, there are several versions of the <prgn>vi</prgn>
11987 editor, and there is no reason to prevent all of them from
11988 being installed at once, each under their own name
11989 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11990 Nevertheless it is desirable to have the name <tt>vi</tt>
11991 refer to something, at least by default.
11995 If all the packages involved cooperate, this can be done with
11996 <prgn>update-alternatives</prgn>.
12000 Each package provides its own version under its own name, and
12001 calls <prgn>update-alternatives</prgn> in its postinst to
12002 register its version (and again in its prerm to deregister
12007 See the man page <manref name="update-alternatives"
12008 section="8"> for details.
12012 If <prgn>update-alternatives</prgn> does not seem appropriate
12013 you may wish to consider using diversions instead.</p>
12016 <appendix id="pkg-diversions"><heading>Diversions - overriding a
12017 package's version of a file (from old Packaging Manual)
12021 It is possible to have <prgn>dpkg</prgn> not overwrite a file
12022 when it reinstalls the package it belongs to, and to have it
12023 put the file from the package somewhere else instead.
12027 This can be used locally to override a package's version of a
12028 file, or by one package to override another's version (or
12029 provide a wrapper for it).
12033 Before deciding to use a diversion, read <ref
12034 id="pkg-alternatives"> to see if you really want a diversion
12035 rather than several alternative versions of a program.
12039 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12040 and updated by a special program <prgn>dpkg-divert</prgn>.
12041 Please see <manref name="dpkg-divert" section="8"> for full
12042 details of its operation.
12046 When a package wishes to divert a file from another, it should
12047 call <prgn>dpkg-divert</prgn> in its preinst to add the
12048 diversion and rename the existing file. For example,
12049 supposing that a <prgn>smailwrapper</prgn> package wishes to
12050 install a wrapper around <file>/usr/sbin/smail</file>:
12052 dpkg-divert --package smailwrapper --add --rename \
12053 --divert /usr/sbin/smail.real /usr/sbin/smail
12054 </example> The <tt>--package smailwrapper</tt> ensures that
12055 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12056 can bypass the diversion and get installed as the true version.
12057 It's safe to add the diversion unconditionally on upgrades since
12058 it will be left unchanged if it already exists, but
12059 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12060 message, make the command conditional on the version from which
12061 the package is being upgraded:
12063 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12064 dpkg-divert --package smailwrapper --add --rename \
12065 --divert /usr/sbin/smail.real /usr/sbin/smail
12067 </example> where <tt>1.0-2</tt> is the version at which the
12068 diversion was first added to the package. Running the command
12069 during abort-upgrade is pointless but harmless.
12073 The postrm has to do the reverse:
12075 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12076 dpkg-divert --package smailwrapper --remove --rename \
12077 --divert /usr/sbin/smail.real /usr/sbin/smail
12079 </example> If the diversion was added at a particular version, the
12080 postrm should also handle the failure case of upgrading from an
12081 older version (unless the older version is so old that direct
12082 upgrades are no longer supported):
12084 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12085 dpkg-divert --package smailwrapper --remove --rename \
12086 --divert /usr/sbin/smail.real /usr/sbin/smail
12088 </example> where <tt>1.0-2</tt> is the version at which the
12089 diversion was first added to the package. The postrm should not
12090 remove the diversion on upgrades both because there's no reason to
12091 remove the diversion only to immediately re-add it and since the
12092 postrm of the old package is run after unpacking so the removal of
12093 the diversion will fail.
12097 Do not attempt to divert a file which is vitally important for
12098 the system's operation - when using <prgn>dpkg-divert</prgn>
12099 there is a time, after it has been diverted but before
12100 <prgn>dpkg</prgn> has installed the new version, when the file
12101 does not exist.</p>
12106 <!-- Local variables: -->
12107 <!-- indent-tabs-mode: t -->
12109 <!-- vim:set ai sts=2 sw=2 tw=76: -->