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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 Finally, a <qref id="copyrightformat">specification for
285 machine-readable copyright files</qref> is maintained as part of
286 the <package>debian-policy</package> package using the same
287 procedure as the other policy documents. Use of this format is
292 <sect id="definitions">
293 <heading>Definitions</heading>
296 The following terms are used in this Policy Manual:
300 The character encoding specified by ANSI X3.4-1986 and its
301 predecessor standards, referred to in MIME as US-ASCII, and
302 corresponding to an encoding in eight bits per character of
303 the first 128 <url id="http://www.unicode.org/"
304 name="Unicode"> characters, with the eighth bit always zero.
308 The transformation format (sometimes called encoding) of
309 <url id="http://www.unicode.org/" name="Unicode"> defined by
310 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
311 name="RFC 3629">. UTF-8 has the useful property of having
312 ASCII as a subset, so any text encoded in ASCII is trivially
322 <heading>The Debian Archive</heading>
325 The Debian system is maintained and distributed as a
326 collection of <em>packages</em>. Since there are so many of
327 them (currently well over 15000), they are split into
328 <em>sections</em> and given <em>priorities</em> to simplify
329 the handling of them.
333 The effort of the Debian project is to build a free operating
334 system, but not every package we want to make accessible is
335 <em>free</em> in our sense (see the Debian Free Software
336 Guidelines, below), or may be imported/exported without
337 restrictions. Thus, the archive is split into areas<footnote>
338 The Debian archive software uses the term "component" internally
339 and in the Release file format to refer to the division of an
340 archive. The Debian Social Contract simply refers to "areas."
341 This document uses terminology similar to the Social Contract.
342 </footnote> based on their licenses and other restrictions.
346 The aims of this are:
348 <list compact="compact">
349 <item>to allow us to make as much software available as we can</item>
350 <item>to allow us to encourage everyone to write free software,
352 <item>to allow us to make it easy for people to produce
353 CD-ROMs of our system without violating any licenses,
354 import/export restrictions, or any other laws.</item>
359 The <em>main</em> archive area forms the <em>Debian distribution</em>.
363 Packages in the other archive areas (<tt>contrib</tt>,
364 <tt>non-free</tt>) are not considered to be part of the Debian
365 distribution, although we support their use and provide
366 infrastructure for them (such as our bug-tracking system and
367 mailing lists). This Debian Policy Manual applies to these
372 <heading>The Debian Free Software Guidelines</heading>
374 The Debian Free Software Guidelines (DFSG) form our
375 definition of "free software". These are:
377 <tag>1. Free Redistribution
380 The license of a Debian component may not restrict any
381 party from selling or giving away the software as a
382 component of an aggregate software distribution
383 containing programs from several different
384 sources. The license may not require a royalty or
385 other fee for such sale.
390 The program must include source code, and must allow
391 distribution in source code as well as compiled form.
393 <tag>3. Derived Works
396 The license must allow modifications and derived
397 works, and must allow them to be distributed under the
398 same terms as the license of the original software.
400 <tag>4. Integrity of The Author's Source Code
403 The license may restrict source-code from being
404 distributed in modified form <em>only</em> if the
405 license allows the distribution of "patch files"
406 with the source code for the purpose of modifying the
407 program at build time. The license must explicitly
408 permit distribution of software built from modified
409 source code. The license may require derived works to
410 carry a different name or version number from the
411 original software. (This is a compromise. The Debian
412 Project encourages all authors to not restrict any
413 files, source or binary, from being modified.)
415 <tag>5. No Discrimination Against Persons or Groups
418 The license must not discriminate against any person
421 <tag>6. No Discrimination Against Fields of Endeavor
424 The license must not restrict anyone from making use
425 of the program in a specific field of endeavor. For
426 example, it may not restrict the program from being
427 used in a business, or from being used for genetic
430 <tag>7. Distribution of License
433 The rights attached to the program must apply to all
434 to whom the program is redistributed without the need
435 for execution of an additional license by those
438 <tag>8. License Must Not Be Specific to Debian
441 The rights attached to the program must not depend on
442 the program's being part of a Debian system. If the
443 program is extracted from Debian and used or
444 distributed without Debian but otherwise within the
445 terms of the program's license, all parties to whom
446 the program is redistributed must have the same
447 rights as those that are granted in conjunction with
450 <tag>9. License Must Not Contaminate Other Software
453 The license must not place restrictions on other
454 software that is distributed along with the licensed
455 software. For example, the license must not insist
456 that all other programs distributed on the same medium
457 must be free software.
459 <tag>10. Example Licenses
462 The "GPL," "BSD," and "Artistic" licenses are examples of
463 licenses that we consider <em>free</em>.
470 <heading>Archive areas</heading>
473 <heading>The main archive area</heading>
476 The <em>main</em> archive area comprises the Debian
477 distribution. Only the packages in this area are considered
478 part of the distribution. None of the packages in
479 the <em>main</em> archive area require software outside of
480 that area to function. Anyone may use, share, modify and
481 redistribute the packages in this archive area
483 See <url id="http://www.debian.org/intro/free"
484 name="What Does Free Mean?"> for
485 more about what we mean by free software.
490 Every package in <em>main</em> must comply with the DFSG
491 (Debian Free Software Guidelines).
495 In addition, the packages in <em>main</em>
496 <list compact="compact">
498 must not require or recommend a package outside
499 of <em>main</em> for compilation or execution (thus, the
500 package must not declare a "Pre-Depends", "Depends",
501 "Recommends", "Build-Depends", or "Build-Depends-Indep"
502 relationship on a non-<em>main</em> package),
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
518 <heading>The contrib archive area</heading>
521 The <em>contrib</em> archive area contains supplemental
522 packages intended to work with the Debian distribution, but
523 which require software outside of the distribution to either
528 Every package in <em>contrib</em> must comply with the DFSG.
532 In addition, the packages in <em>contrib</em>
533 <list compact="compact">
535 must not be so buggy that we refuse to support them,
539 must meet all policy requirements presented in this
546 Examples of packages which would be included in
547 <em>contrib</em> are:
548 <list compact="compact">
550 free packages which require <em>contrib</em>,
551 <em>non-free</em> packages or packages which are not
552 in our archive at all for compilation or execution,
556 wrapper packages or other sorts of free accessories for
563 <sect1 id="non-free">
564 <heading>The non-free archive area</heading>
567 The <em>non-free</em> archive area contains supplemental
568 packages intended to work with the Debian distribution that do
569 not comply with the DFSG or have other problems that make
570 their distribution problematic. They may not comply with all
571 of the policy requirements in this manual due to restrictions
572 on modifications or other limitations.
576 Packages must be placed in <em>non-free</em> if they are
577 not compliant with the DFSG or are encumbered by patents
578 or other legal issues that make their distribution
583 In addition, the packages in <em>non-free</em>
584 <list compact="compact">
586 must not be so buggy that we refuse to support them,
590 must meet all policy requirements presented in this
591 manual that it is possible for them to meet.
593 It is possible that there are policy
594 requirements which the package is unable to
595 meet, for example, if the source is
596 unavailable. These situations will need to be
597 handled on a case-by-case basis.
606 <sect id="pkgcopyright">
607 <heading>Copyright considerations</heading>
610 Every package must be accompanied by a verbatim copy of its
611 copyright information and distribution license in the file
612 <file>/usr/share/doc/<var>package</var>/copyright</file>
613 (see <ref id="copyrightfile"> for further details).
617 We reserve the right to restrict files from being included
618 anywhere in our archives if
619 <list compact="compact">
621 their use or distribution would break a law,
624 there is an ethical conflict in their distribution or
628 we would have to sign a license for them, or
631 their distribution would conflict with other project
638 Programs whose authors encourage the user to make
639 donations are fine for the main distribution, provided
640 that the authors do not claim that not donating is
641 immoral, unethical, illegal or something similar; in such
642 a case they must go in <em>non-free</em>.
646 Packages whose copyright permission notices (or patent
647 problems) do not even allow redistribution of binaries
648 only, and where no special permission has been obtained,
649 must not be placed on the Debian FTP site and its mirrors
654 Note that under international copyright law (this applies
655 in the United States, too), <em>no</em> distribution or
656 modification of a work is allowed without an explicit
657 notice saying so. Therefore a program without a copyright
658 notice <em>is</em> copyrighted and you may not do anything
659 to it without risking being sued! Likewise if a program
660 has a copyright notice but no statement saying what is
661 permitted then nothing is permitted.
665 Many authors are unaware of the problems that restrictive
666 copyrights (or lack of copyright notices) can cause for
667 the users of their supposedly-free software. It is often
668 worthwhile contacting such authors diplomatically to ask
669 them to modify their license terms. However, this can be a
670 politically difficult thing to do and you should ask for
671 advice on the <tt>debian-legal</tt> mailing list first, as
676 When in doubt about a copyright, send mail to
677 <email>debian-legal@lists.debian.org</email>. Be prepared
678 to provide us with the copyright statement. Software
679 covered by the GPL, public domain software and BSD-like
680 copyrights are safe; be wary of the phrases "commercial
681 use prohibited" and "distribution restricted".
685 <sect id="subsections">
686 <heading>Sections</heading>
689 The packages in the archive areas <em>main</em>,
690 <em>contrib</em> and <em>non-free</em> are grouped further into
691 <em>sections</em> to simplify handling.
695 The archive area and section for each package should be
696 specified in the package's <tt>Section</tt> control record (see
697 <ref id="f-Section">). However, the maintainer of the Debian
698 archive may override this selection to ensure the consistency of
699 the Debian distribution. The <tt>Section</tt> field should be
701 <list compact="compact">
703 <em>section</em> if the package is in the
704 <em>main</em> archive area,
707 <em>area/section</em> if the package is in
708 the <em>contrib</em> or <em>non-free</em>
715 The Debian archive maintainers provide the authoritative
716 list of sections. At present, they are:
772 The additional section <em>debian-installer</em>
773 contains special packages used by the installer and is not used
774 for normal Debian packages.
778 For more information about the sections and their definitions,
779 see the <url id="http://packages.debian.org/unstable/"
780 name="list of sections in unstable">.
784 <sect id="priorities">
785 <heading>Priorities</heading>
788 Each package should have a <em>priority</em> value, which is
789 included in the package's <em>control record</em>
790 (see <ref id="f-Priority">).
791 This information is used by the Debian package management tools to
792 separate high-priority packages from less-important packages.
796 The following <em>priority levels</em> are recognized by the
797 Debian package management tools.
799 <tag><tt>required</tt></tag>
801 Packages which are necessary for the proper
802 functioning of the system (usually, this means that
803 dpkg functionality depends on these packages).
804 Removing a <tt>required</tt> package may cause your
805 system to become totally broken and you may not even
806 be able to use <prgn>dpkg</prgn> to put things back,
807 so only do so if you know what you are doing. Systems
808 with only the <tt>required</tt> packages are probably
809 unusable, but they do have enough functionality to
810 allow the sysadmin to boot and install more software.
812 <tag><tt>important</tt></tag>
814 Important programs, including those which one would
815 expect to find on any Unix-like system. If the
816 expectation is that an experienced Unix person who
817 found it missing would say "What on earth is going on,
818 where is <prgn>foo</prgn>?", it must be an
819 <tt>important</tt> package.<footnote>
820 This is an important criterion because we are
821 trying to produce, amongst other things, a free
824 Other packages without which the system will not run
825 well or be usable must also have priority
826 <tt>important</tt>. This does
827 <em>not</em> include Emacs, the X Window System, TeX
828 or any other large applications. The
829 <tt>important</tt> packages are just a bare minimum of
830 commonly-expected and necessary tools.
832 <tag><tt>standard</tt></tag>
834 These packages provide a reasonably small but not too
835 limited character-mode system. This is what will be
836 installed by default if the user doesn't select anything
837 else. It doesn't include many large applications.
839 <tag><tt>optional</tt></tag>
841 (In a sense everything that isn't required is
842 optional, but that's not what is meant here.) This is
843 all the software that you might reasonably want to
844 install if you didn't know what it was and don't have
845 specialized requirements. This is a much larger system
846 and includes the X Window System, a full TeX
847 distribution, and many applications. Note that
848 optional packages should not conflict with each other.
850 <tag><tt>extra</tt></tag>
852 This contains all packages that conflict with others
853 with required, important, standard or optional
854 priorities, or are only likely to be useful if you
855 already know what they are or have specialized
856 requirements (such as packages containing only detached
863 Packages must not depend on packages with lower priority
864 values (excluding build-time dependencies). In order to
865 ensure this, the priorities of one or more packages may need
874 <heading>Binary packages</heading>
877 The Debian distribution is based on the Debian
878 package management system, called <prgn>dpkg</prgn>. Thus,
879 all packages in the Debian distribution must be provided
880 in the <tt>.deb</tt> file format.
884 A <tt>.deb</tt> package contains two sets of files: a set of files
885 to install on the system when the package is installed, and a set
886 of files that provide additional metadata about the package or
887 which are executed when the package is installed or removed. This
888 second set of files is called <em>control information files</em>.
889 Among those files are the package maintainer scripts
890 and <file>control</file>, the <qref id="binarycontrolfiles">binary
891 package control file</qref> that contains the control fields for
892 the package. Other control information files include
893 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
894 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
895 used to store shared library dependency information and
896 the <file>conffiles</file> file that lists the package's
897 configuration files (described in <ref id="config-files">).
901 There is unfortunately a collision of terminology here between
902 control information files and files in the Debian control file
903 format. Throughout this document, a <em>control file</em> refers
904 to a file in the Debian control file format. These files are
905 documented in <ref id="controlfields">. Only files referred to
906 specifically as <em>control information files</em> are the files
907 included in the control information file member of
908 the <file>.deb</file> file format used by binary packages. Most
909 control information files are not in the Debian control file
914 <heading>The package name</heading>
917 Every package must have a name that's unique within the Debian
922 The package name is included in the control field
923 <tt>Package</tt>, the format of which is described
924 in <ref id="f-Package">.
925 The package name is also included as a part of the file name
926 of the <tt>.deb</tt> file.
931 <heading>The version of a package</heading>
934 Every package has a version number recorded in its
935 <tt>Version</tt> control file field, described in
936 <ref id="f-Version">.
940 The package management system imposes an ordering on version
941 numbers, so that it can tell whether packages are being up- or
942 downgraded and so that package system front end applications
943 can tell whether a package it finds available is newer than
944 the one installed on the system. The version number format
945 has the most significant parts (as far as comparison is
946 concerned) at the beginning.
950 If an upstream package has problematic version numbers they
951 should be converted to a sane form for use in the
952 <tt>Version</tt> field.
956 <heading>Version numbers based on dates</heading>
959 In general, Debian packages should use the same version
960 numbers as the upstream sources. However, upstream version
961 numbers based on some date formats (sometimes used for
962 development or "snapshot" releases) will not be ordered
963 correctly by the package management software. For
964 example, <prgn>dpkg</prgn> will consider "96May01" to be
965 greater than "96Dec24".
969 To prevent having to use epochs for every new upstream
970 version, the date-based portion of any upstream version number
971 should be given in a way that sorts correctly: four-digit year
972 first, followed by a two-digit numeric month, followed by a
973 two-digit numeric date, possibly with punctuation between the
978 Native Debian packages (i.e., packages which have been written
979 especially for Debian) whose version numbers include dates
980 should also follow these rules. If punctuation is desired
981 between the date components, remember that hyphen (<tt>-</tt>)
982 cannot be used in native package versions. Period
983 (<tt>.</tt>) is normally a good choice.
989 <sect id="maintainer">
990 <heading>The maintainer of a package</heading>
993 Every package must have a maintainer, except for orphaned
994 packages as described below. The maintainer may be one person
995 or a group of people reachable from a common email address, such
996 as a mailing list. The maintainer is responsible for
997 maintaining the Debian packaging files, evaluating and
998 responding appropriately to reported bugs, uploading new
999 versions of the package (either directly or through a sponsor),
1000 ensuring that the package is placed in the appropriate archive
1001 area and included in Debian releases as appropriate for the
1002 stability and utility of the package, and requesting removal of
1003 the package from the Debian distribution if it is no longer
1004 useful or maintainable.
1008 The maintainer must be specified in the <tt>Maintainer</tt>
1009 control field with their correct name and a working email
1010 address. The email address given in the <tt>Maintainer</tt>
1011 control field must accept mail from those role accounts in
1012 Debian used to send automated mails regarding the package. This
1013 includes non-spam mail from the bug-tracking system, all mail
1014 from the Debian archive maintenance software, and other role
1015 accounts or automated processes that are commonly agreed on by
1016 the project.<footnote>
1017 A sample implementation of such a whitelist written for the
1018 Mailman mailing list management software is used for mailing
1019 lists hosted by alioth.debian.org.
1021 If one person or team maintains several packages, they should
1022 use the same form of their name and email address in
1023 the <tt>Maintainer</tt> fields of those packages.
1027 The format of the <tt>Maintainer</tt> control field is
1028 described in <ref id="f-Maintainer">.
1032 If the maintainer of the package is a team of people with a
1033 shared email address, the <tt>Uploaders</tt> control field must
1034 be present and must contain at least one human with their
1035 personal email address. See <ref id="f-Uploaders"> for the
1036 syntax of that field.
1040 An orphaned package is one with no current maintainer. Orphaned
1041 packages should have their <tt>Maintainer</tt> control field set
1042 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1043 These packages are considered maintained by the Debian project
1044 as a whole until someone else volunteers to take over
1045 maintenance.<footnote>
1046 The detailed procedure for gracefully orphaning a package can
1047 be found in the Debian Developer's Reference
1048 (see <ref id="related">).
1053 <sect id="descriptions">
1054 <heading>The description of a package</heading>
1057 Every Debian package must have a <tt>Description</tt> control
1058 field which contains a synopsis and extended description of the
1059 package. Technical information about the format of the
1060 <tt>Description</tt> field is in <ref id="f-Description">.
1064 The description should describe the package (the program) to a
1065 user (system administrator) who has never met it before so that
1066 they have enough information to decide whether they want to
1067 install it. This description should not just be copied verbatim
1068 from the program's documentation.
1072 Put important information first, both in the synopsis and
1073 extended description. Sometimes only the first part of the
1074 synopsis or of the description will be displayed. You can
1075 assume that there will usually be a way to see the whole
1076 extended description.
1080 The description should also give information about the
1081 significant dependencies and conflicts between this package
1082 and others, so that the user knows why these dependencies and
1083 conflicts have been declared.
1087 Instructions for configuring or using the package should
1088 not be included (that is what installation scripts,
1089 manual pages, info files, etc., are for). Copyright
1090 statements and other administrivia should not be included
1091 either (that is what the copyright file is for).
1094 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1097 The single line synopsis should be kept brief - certainly
1098 under 80 characters.
1102 Do not include the package name in the synopsis line. The
1103 display software knows how to display this already, and you
1104 do not need to state it. Remember that in many situations
1105 the user may only see the synopsis line - make it as
1106 informative as you can.
1111 <sect1 id="extendeddesc"><heading>The extended description</heading>
1114 Do not try to continue the single line synopsis into the
1115 extended description. This will not work correctly when
1116 the full description is displayed, and makes no sense
1117 where only the summary (the single line synopsis) is
1122 The extended description should describe what the package
1123 does and how it relates to the rest of the system (in terms
1124 of, for example, which subsystem it is which part of).
1128 The description field needs to make sense to anyone, even
1129 people who have no idea about any of the things the
1130 package deals with.<footnote>
1131 The blurb that comes with a program in its
1132 announcements and/or <prgn>README</prgn> files is
1133 rarely suitable for use in a description. It is
1134 usually aimed at people who are already in the
1135 community where the package is used.
1143 <sect id="dependencies">
1144 <heading>Dependencies</heading>
1147 Every package must specify the dependency information
1148 about other packages that are required for the first to
1153 For example, a dependency entry must be provided for any
1154 shared libraries required by a dynamically-linked executable
1155 binary in a package.
1159 Packages are not required to declare any dependencies they
1160 have on other packages which are marked <tt>Essential</tt>
1161 (see below), and should not do so unless they depend on a
1162 particular version of that package.<footnote>
1164 Essential is needed in part to avoid unresolvable dependency
1165 loops on upgrade. If packages add unnecessary dependencies
1166 on packages in this set, the chances that there
1167 <strong>will</strong> be an unresolvable dependency loop
1168 caused by forcing these Essential packages to be configured
1169 first before they need to be is greatly increased. It also
1170 increases the chances that frontends will be unable to
1171 <strong>calculate</strong> an upgrade path, even if one
1175 Also, functionality is rarely ever removed from the
1176 Essential set, but <em>packages</em> have been removed from
1177 the Essential set when the functionality moved to a
1178 different package. So depending on these packages <em>just
1179 in case</em> they stop being essential does way more harm
1186 Sometimes, unpacking one package requires that another package
1187 be first unpacked <em>and</em> configured. In this case, the
1188 depending package must specify this dependency in
1189 the <tt>Pre-Depends</tt> control field.
1193 You should not specify a <tt>Pre-Depends</tt> entry for a
1194 package before this has been discussed on the
1195 <tt>debian-devel</tt> mailing list and a consensus about
1196 doing that has been reached.
1200 The format of the package interrelationship control fields is
1201 described in <ref id="relationships">.
1205 <sect id="virtual_pkg">
1206 <heading>Virtual packages</heading>
1209 Sometimes, there are several packages which offer
1210 more-or-less the same functionality. In this case, it's
1211 useful to define a <em>virtual package</em> whose name
1212 describes that common functionality. (The virtual
1213 packages only exist logically, not physically; that's why
1214 they are called <em>virtual</em>.) The packages with this
1215 particular function will then <em>provide</em> the virtual
1216 package. Thus, any other package requiring that function
1217 can simply depend on the virtual package without having to
1218 specify all possible packages individually.
1222 All packages should use virtual package names where
1223 appropriate, and arrange to create new ones if necessary.
1224 They should not use virtual package names (except privately,
1225 amongst a cooperating group of packages) unless they have
1226 been agreed upon and appear in the list of virtual package
1227 names. (See also <ref id="virtual">)
1231 The latest version of the authoritative list of virtual
1232 package names can be found in the <tt>debian-policy</tt> package.
1233 It is also available from the Debian web mirrors at
1234 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1235 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1239 The procedure for updating the list is described in the preface
1246 <heading>Base system</heading>
1249 The <tt>base system</tt> is a minimum subset of the Debian
1250 system that is installed before everything else
1251 on a new system. Only very few packages are allowed to form
1252 part of the base system, in order to keep the required disk
1257 The base system consists of all those packages with priority
1258 <tt>required</tt> or <tt>important</tt>. Many of them will
1259 be tagged <tt>essential</tt> (see below).
1264 <heading>Essential packages</heading>
1267 Essential is defined as the minimal set of functionality that
1268 must be available and usable on the system at all times, even
1269 when packages are in an unconfigured (but unpacked) state.
1270 Packages are tagged <tt>essential</tt> for a system using the
1271 <tt>Essential</tt> control field. The format of the
1272 <tt>Essential</tt> control field is described in <ref
1277 Since these packages cannot be easily removed (one has to
1278 specify an extra <em>force option</em> to
1279 <prgn>dpkg</prgn> to do so), this flag must not be used
1280 unless absolutely necessary. A shared library package
1281 must not be tagged <tt>essential</tt>; dependencies will
1282 prevent its premature removal, and we need to be able to
1283 remove it when it has been superseded.
1287 Since dpkg will not prevent upgrading of other packages
1288 while an <tt>essential</tt> package is in an unconfigured
1289 state, all <tt>essential</tt> packages must supply all of
1290 their core functionality even when unconfigured. If the
1291 package cannot satisfy this requirement it must not be
1292 tagged as essential, and any packages depending on this
1293 package must instead have explicit dependency fields as
1298 Maintainers should take great care in adding any programs,
1299 interfaces, or functionality to <tt>essential</tt> packages.
1300 Packages may assume that functionality provided by
1301 <tt>essential</tt> packages is always available without
1302 declaring explicit dependencies, which means that removing
1303 functionality from the Essential set is very difficult and is
1304 almost never done. Any capability added to an
1305 <tt>essential</tt> package therefore creates an obligation to
1306 support that capability as part of the Essential set in
1311 You must not tag any packages <tt>essential</tt> before
1312 this has been discussed on the <tt>debian-devel</tt>
1313 mailing list and a consensus about doing that has been
1318 <sect id="maintscripts">
1319 <heading>Maintainer Scripts</heading>
1322 The package installation scripts should avoid producing
1323 output which is unnecessary for the user to see and
1324 should rely on <prgn>dpkg</prgn> to stave off boredom on
1325 the part of a user installing many packages. This means,
1326 amongst other things, using the <tt>--quiet</tt> option on
1327 <prgn>install-info</prgn>.
1331 Errors which occur during the execution of an installation
1332 script must be checked and the installation must not
1333 continue after an error.
1337 Note that in general <ref id="scripts"> applies to package
1338 maintainer scripts, too.
1342 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1343 to another package without consulting the maintainer of that
1344 package first. When adding or removing diversions, package
1345 maintainer scripts must provide the <tt>--package</tt> flag
1346 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1350 All packages which supply an instance of a common command
1351 name (or, in general, filename) should generally use
1352 <prgn>update-alternatives</prgn>, so that they may be
1353 installed together. If <prgn>update-alternatives</prgn>
1354 is not used, then each package must use
1355 <tt>Conflicts</tt> to ensure that other packages are
1356 de-installed. (In this case, it may be appropriate to
1357 specify a conflict against earlier versions of something
1358 that previously did not use
1359 <prgn>update-alternatives</prgn>; this is an exception to
1360 the usual rule that versioned conflicts should be
1364 <sect1 id="maintscriptprompt">
1365 <heading>Prompting in maintainer scripts</heading>
1367 Package maintainer scripts may prompt the user if
1368 necessary. Prompting must be done by communicating
1369 through a program, such as <prgn>debconf</prgn>, which
1370 conforms to the Debian Configuration Management
1371 Specification, version 2 or higher.
1375 Packages which are essential, or which are dependencies of
1376 essential packages, may fall back on another prompting method
1377 if no such interface is available when they are executed.
1381 The Debian Configuration Management Specification is included
1382 in the <file>debconf_specification</file> files in the
1383 <package>debian-policy</package> package.
1384 It is also available from the Debian web mirrors at
1385 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1386 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1390 Packages which use the Debian Configuration Management
1391 Specification may contain the additional control information
1392 files <file>config</file>
1393 and <file>templates</file>. <file>config</file> is an
1394 additional maintainer script used for package configuration,
1395 and <file>templates</file> contains templates used for user
1396 prompting. The <prgn>config</prgn> script might be run before
1397 the <prgn>preinst</prgn> script and before the package is
1398 unpacked or any of its dependencies or pre-dependencies are
1399 satisfied. Therefore it must work using only the tools
1400 present in <em>essential</em> packages.<footnote>
1401 <package>Debconf</package> or another tool that
1402 implements the Debian Configuration Management
1403 Specification will also be installed, and any
1404 versioned dependencies on it will be satisfied
1405 before preconfiguration begins.
1410 Packages which use the Debian Configuration Management
1411 Specification must allow for translation of their user-visible
1412 messages by using a gettext-based system such as the one
1413 provided by the <package>po-debconf</package> package.
1417 Packages should try to minimize the amount of prompting
1418 they need to do, and they should ensure that the user
1419 will only ever be asked each question once. This means
1420 that packages should try to use appropriate shared
1421 configuration files (such as <file>/etc/papersize</file> and
1422 <file>/etc/news/server</file>), and shared
1423 <package>debconf</package> variables rather than each
1424 prompting for their own list of required pieces of
1429 It also means that an upgrade should not ask the same
1430 questions again, unless the user has used
1431 <tt>dpkg --purge</tt> to remove the package's configuration.
1432 The answers to configuration questions should be stored in an
1433 appropriate place in <file>/etc</file> so that the user can
1434 modify them, and how this has been done should be
1439 If a package has a vitally important piece of
1440 information to pass to the user (such as "don't run me
1441 as I am, you must edit the following configuration files
1442 first or you risk your system emitting badly-formatted
1443 messages"), it should display this in the
1444 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1445 prompt the user to hit return to acknowledge the
1446 message. Copyright messages do not count as vitally
1447 important (they belong in
1448 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1449 neither do instructions on how to use a program (these
1450 should be in on-line documentation, where all the users
1455 Any necessary prompting should almost always be confined
1456 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1457 script. If it is done in the <prgn>postinst</prgn>, it
1458 should be protected with a conditional so that
1459 unnecessary prompting doesn't happen if a package's
1460 installation fails and the <prgn>postinst</prgn> is
1461 called with <tt>abort-upgrade</tt>,
1462 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1472 <heading>Source packages</heading>
1474 <sect id="standardsversion">
1475 <heading>Standards conformance</heading>
1478 Source packages should specify the most recent version number
1479 of this policy document with which your package complied
1480 when it was last updated.
1484 This information may be used to file bug reports
1485 automatically if your package becomes too much out of date.
1489 The version is specified in the <tt>Standards-Version</tt>
1491 The format of the <tt>Standards-Version</tt> field is
1492 described in <ref id="f-Standards-Version">.
1496 You should regularly, and especially if your package has
1497 become out of date, check for the newest Policy Manual
1498 available and update your package, if necessary. When your
1499 package complies with the new standards you should update the
1500 <tt>Standards-Version</tt> source package field and
1501 release it.<footnote>
1502 See the file <file>upgrading-checklist</file> for
1503 information about policy which has changed between
1504 different versions of this document.
1510 <sect id="pkg-relations">
1511 <heading>Package relationships</heading>
1514 Source packages should specify which binary packages they
1515 require to be installed or not to be installed in order to
1516 build correctly. For example, if building a package
1517 requires a certain compiler, then the compiler should be
1518 specified as a build-time dependency.
1522 It is not necessary to explicitly specify build-time
1523 relationships on a minimal set of packages that are always
1524 needed to compile, link and put in a Debian package a
1525 standard "Hello World!" program written in C or C++. The
1526 required packages are called <em>build-essential</em>, and
1527 an informational list can be found in
1528 <file>/usr/share/doc/build-essential/list</file> (which is
1529 contained in the <tt>build-essential</tt>
1532 <list compact="compact">
1534 This allows maintaining the list separately
1535 from the policy documents (the list does not
1536 need the kind of control that the policy
1540 Having a separate package allows one to install
1541 the build-essential packages on a machine, as
1542 well as allowing other packages such as tasks to
1543 require installation of the build-essential
1544 packages using the depends relation.
1547 The separate package allows bug reports against
1548 the list to be categorized separately from
1549 the policy management process in the BTS.
1556 When specifying the set of build-time dependencies, one
1557 should list only those packages explicitly required by the
1558 build. It is not necessary to list packages which are
1559 required merely because some other package in the list of
1560 build-time dependencies depends on them.<footnote>
1561 The reason for this is that dependencies change, and
1562 you should list all those packages, and <em>only</em>
1563 those packages that <em>you</em> need directly. What
1564 others need is their business. For example, if you
1565 only link against <file>libimlib</file>, you will need to
1566 build-depend on <package>libimlib2-dev</package> but
1567 not against any <tt>libjpeg*</tt> packages, even
1568 though <tt>libimlib2-dev</tt> currently depends on
1569 them: installation of <package>libimlib2-dev</package>
1570 will automatically ensure that all of its run-time
1571 dependencies are satisfied.
1576 If build-time dependencies are specified, it must be
1577 possible to build the package and produce working binaries
1578 on a system with only essential and build-essential
1579 packages installed and also those required to satisfy the
1580 build-time relationships (including any implied
1581 relationships). In particular, this means that version
1582 clauses should be used rigorously in build-time
1583 relationships so that one cannot produce bad or
1584 inconsistently configured packages when the relationships
1585 are properly satisfied.
1589 <ref id="relationships"> explains the technical details.
1594 <heading>Changes to the upstream sources</heading>
1597 If changes to the source code are made that are not
1598 specific to the needs of the Debian system, they should be
1599 sent to the upstream authors in whatever form they prefer
1600 so as to be included in the upstream version of the
1605 If you need to configure the package differently for
1606 Debian or for Linux, and the upstream source doesn't
1607 provide a way to do so, you should add such configuration
1608 facilities (for example, a new <prgn>autoconf</prgn> test
1609 or <tt>#define</tt>) and send the patch to the upstream
1610 authors, with the default set to the way they originally
1611 had it. You can then easily override the default in your
1612 <file>debian/rules</file> or wherever is appropriate.
1616 You should make sure that the <prgn>configure</prgn> utility
1617 detects the correct architecture specification string
1618 (refer to <ref id="arch-spec"> for details).
1622 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1623 <prgn>configure</prgn> scripts are used, you should edit the
1624 <file>.in</file> files rather than editing the
1625 <prgn>Makefile</prgn> directly. This allows the user to
1626 reconfigure the package if necessary. You should
1627 <em>not</em> configure the package and edit the generated
1628 <prgn>Makefile</prgn>! This makes it impossible for someone
1629 else to later reconfigure the package without losing the
1635 <sect id="dpkgchangelog">
1636 <heading>Debian changelog: <file>debian/changelog</file></heading>
1639 Changes in the Debian version of the package should be
1640 briefly explained in the Debian changelog file
1641 <file>debian/changelog</file>.<footnote>
1643 Mistakes in changelogs are usually best rectified by
1644 making a new changelog entry rather than "rewriting
1645 history" by editing old changelog entries.
1648 This includes modifications
1649 made in the Debian package compared to the upstream one
1650 as well as other changes and updates to the package.
1652 Although there is nothing stopping an author who is also
1653 the Debian maintainer from using this changelog for all
1654 their changes, it will have to be renamed if the Debian
1655 and upstream maintainers become different people. In such
1656 a case, however, it might be better to maintain the package
1657 as a non-native package.
1662 The format of the <file>debian/changelog</file> allows the
1663 package building tools to discover which version of the package
1664 is being built and find out other release-specific information.
1668 That format is a series of entries like this:
1670 <example compact="compact">
1671 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1673 [optional blank line(s), stripped]
1675 * <var>change details</var>
1676 <var>more change details</var>
1678 [blank line(s), included in output of dpkg-parsechangelog]
1680 * <var>even more change details</var>
1682 [optional blank line(s), stripped]
1684 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1689 <var>package</var> and <var>version</var> are the source
1690 package name and version number.
1694 <var>distribution(s)</var> lists the distributions where
1695 this version should be installed when it is uploaded - it
1696 is copied to the <tt>Distribution</tt> field in the
1697 <file>.changes</file> file. See <ref id="f-Distribution">.
1701 <var>urgency</var> is the value for the <tt>Urgency</tt>
1702 field in the <file>.changes</file> file for the upload
1703 (see <ref id="f-Urgency">). It is not possible to specify
1704 an urgency containing commas; commas are used to separate
1705 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1706 <prgn>dpkg</prgn> changelog format (though there is
1707 currently only one useful <var>keyword</var>,
1712 The change details may in fact be any series of lines
1713 starting with at least two spaces, but conventionally each
1714 change starts with an asterisk and a separating space and
1715 continuation lines are indented so as to bring them in
1716 line with the start of the text above. Blank lines may be
1717 used here to separate groups of changes, if desired.
1721 If this upload resolves bugs recorded in the Bug Tracking
1722 System (BTS), they may be automatically closed on the
1723 inclusion of this package into the Debian archive by
1724 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1725 in the change details.<footnote>
1726 To be precise, the string should match the following
1727 Perl regular expression:
1729 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1731 Then all of the bug numbers listed will be closed by the
1732 archive maintenance software (<prgn>dak</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 <prgn>dpkg-architecture</prgn>.
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>
2674 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2679 The syntax and semantics of the fields are described below.
2683 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2684 generate control files for binary packages (see below), by
2685 <prgn>dpkg-genchanges</prgn> to generate the
2686 <file>.changes</file> file to accompany the upload, and by
2687 <prgn>dpkg-source</prgn> when it creates the
2688 <file>.dsc</file> source control file as part of a source
2689 archive. Some fields are folded in <file>debian/control</file>,
2690 but not in any other control
2691 file. These tools are responsible for removing the line
2692 breaks from such fields when using fields from
2693 <file>debian/control</file> to generate other control files.
2697 The fields here may contain variable references - their
2698 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2699 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2700 when they generate output control files.
2701 See <ref id="substvars"> for details.
2705 <sect id="binarycontrolfiles">
2706 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2709 The <file>DEBIAN/control</file> file contains the most vital
2710 (and version-dependent) information about a binary package. It
2711 consists of a single paragraph.
2715 The fields in this file are:
2717 <list compact="compact">
2718 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2719 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2720 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2721 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2722 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2723 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2724 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2725 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2726 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2727 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2728 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2729 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2730 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2735 <sect id="debiansourcecontrolfiles">
2736 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2739 This file consists of a single paragraph, possibly surrounded by
2740 a PGP signature. The fields of that paragraph are listed below.
2741 Their syntax is described above, in <ref id="controlsyntax">.
2743 <list compact="compact">
2744 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2745 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2746 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2747 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2748 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2749 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2750 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2751 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2752 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2753 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2754 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2755 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2756 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2757 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2763 The Debian source control file is generated by
2764 <prgn>dpkg-source</prgn> when it builds the source
2765 archive, from other files in the source package,
2766 described above. When unpacking, it is checked against
2767 the files and directories in the other parts of the
2773 <sect id="debianchangesfiles">
2774 <heading>Debian changes files -- <file>.changes</file></heading>
2777 The <file>.changes</file> files are used by the Debian archive
2778 maintenance software to process updates to packages. They
2779 consist of a single paragraph, possibly surrounded by a PGP
2780 signature. That paragraph contains information from the
2781 <file>debian/control</file> file and other data about the
2782 source package gathered via <file>debian/changelog</file>
2783 and <file>debian/rules</file>.
2787 <file>.changes</file> files have a format version that is
2788 incremented whenever the documented fields or their meaning
2789 change. This document describes format &changesversion;.
2793 The fields in this file are:
2795 <list compact="compact">
2796 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2797 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2798 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2799 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2800 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2801 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2802 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2803 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2804 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2805 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2806 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2807 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2808 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2810 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2816 <sect id="controlfieldslist">
2817 <heading>List of fields</heading>
2819 <sect1 id="f-Source">
2820 <heading><tt>Source</tt></heading>
2823 This field identifies the source package name.
2827 In <file>debian/control</file> or a <file>.dsc</file> file,
2828 this field must contain only the name of the source package.
2832 In a binary package control file or a <file>.changes</file>
2833 file, the source package name may be followed by a version
2834 number in parentheses<footnote>
2835 It is customary to leave a space after the package name
2836 if a version number is specified.
2838 This version number may be omitted (and is, by
2839 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2840 the <tt>Version</tt> field of the binary package in
2841 question. The field itself may be omitted from a binary
2842 package control file when the source package has the same
2843 name and version as the binary package.
2847 Package names (both source and binary,
2848 see <ref id="f-Package">) must consist only of lower case
2849 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2850 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2851 (<tt>.</tt>). They must be at least two characters long and
2852 must start with an alphanumeric character.
2856 <sect1 id="f-Maintainer">
2857 <heading><tt>Maintainer</tt></heading>
2860 The package maintainer's name and email address. The name
2861 must come first, then the email address inside angle
2862 brackets <tt><></tt> (in RFC822 format).
2866 If the maintainer's name contains a full stop then the
2867 whole field will not work directly as an email address due
2868 to a misfeature in the syntax specified in RFC822; a
2869 program using this field as an address must check for this
2870 and correct the problem if necessary (for example by
2871 putting the name in round brackets and moving it to the
2872 end, and bringing the email address forward).
2876 See <ref id="maintainer"> for additional requirements and
2877 information about package maintainers.
2881 <sect1 id="f-Uploaders">
2882 <heading><tt>Uploaders</tt></heading>
2885 List of the names and email addresses of co-maintainers of the
2886 package, if any. If the package has other maintainers besides
2887 the one named in the <qref id="f-Maintainer">Maintainer
2888 field</qref>, their names and email addresses should be listed
2889 here. The format of each entry is the same as that of the
2890 Maintainer field, and multiple entries must be comma
2895 This is normally an optional field, but if
2896 the <tt>Maintainer</tt> control field names a group of people
2897 and a shared email address, the <tt>Uploaders</tt> field must
2898 be present and must contain at least one human with their
2899 personal email address.
2903 The Uploaders field in <file>debian/control</file> can be folded.
2907 <sect1 id="f-Changed-By">
2908 <heading><tt>Changed-By</tt></heading>
2911 The name and email address of the person who prepared this
2912 version of the package, usually a maintainer. The syntax is
2913 the same as for the <qref id="f-Maintainer">Maintainer
2918 <sect1 id="f-Section">
2919 <heading><tt>Section</tt></heading>
2922 This field specifies an application area into which the package
2923 has been classified. See <ref id="subsections">.
2927 When it appears in the <file>debian/control</file> file,
2928 it gives the value for the subfield of the same name in
2929 the <tt>Files</tt> field of the <file>.changes</file> file.
2930 It also gives the default for the same field in the binary
2935 <sect1 id="f-Priority">
2936 <heading><tt>Priority</tt></heading>
2939 This field represents how important it is that the user
2940 have the package installed. See <ref id="priorities">.
2944 When it appears in the <file>debian/control</file> file,
2945 it gives the value for the subfield of the same name in
2946 the <tt>Files</tt> field of the <file>.changes</file> file.
2947 It also gives the default for the same field in the binary
2952 <sect1 id="f-Package">
2953 <heading><tt>Package</tt></heading>
2956 The name of the binary package.
2960 Binary package names must follow the same syntax and
2961 restrictions as source package names. See <ref id="f-Source">
2966 <sect1 id="f-Architecture">
2967 <heading><tt>Architecture</tt></heading>
2970 Depending on context and the control file used, the
2971 <tt>Architecture</tt> field can include the following sets of
2975 A unique single word identifying a Debian machine
2976 architecture as described in <ref id="arch-spec">.
2979 An architecture wildcard identifying a set of Debian
2980 machine architectures, see <ref id="arch-wildcard-spec">.
2981 <tt>any</tt> matches all Debian machine architectures
2982 and is the most frequently used.
2985 <tt>all</tt>, which indicates an
2986 architecture-independent package.
2989 <tt>source</tt>, which indicates a source package.
2995 In the main <file>debian/control</file> file in the source
2996 package, this field may contain the special
2997 value <tt>all</tt>, the special architecture
2998 wildcard <tt>any</tt>, or a list of specific and wildcard
2999 architectures separated by spaces. If <tt>all</tt>
3000 or <tt>any</tt> appears, that value must be the entire
3001 contents of the field. Most packages will use
3002 either <tt>all</tt> or <tt>any</tt>.
3006 Specifying a specific list of architectures indicates that the
3007 source will build an architecture-dependent package only on
3008 architectures included in the list. Specifying a list of
3009 architecture wildcards indicates that the source will build an
3010 architecture-dependent package on only those architectures
3011 that match any of the specified architecture wildcards.
3012 Specifying a list of architectures or architecture wildcards
3013 other than <tt>any</tt> is for the minority of cases where a
3014 program is not portable or is not useful on some
3015 architectures. Where possible, the program should be made
3020 In the Debian source control file <file>.dsc</file>, this
3021 field contains a list of architectures and architecture
3022 wildcards separated by spaces. When the list contains the
3023 architecture wildcard <tt>any</tt>, the only other value
3024 allowed in the list is <tt>all</tt>.
3028 The list may include (or consist solely of) the special
3029 value <tt>all</tt>. In other words, in <file>.dsc</file>
3030 files unlike the <file>debian/control</file>, <tt>all</tt> may
3031 occur in combination with specific architectures.
3032 The <tt>Architecture</tt> field in the Debian source control
3033 file <file>.dsc</file> is generally constructed from
3034 the <tt>Architecture</tt> fields in
3035 the <file>debian/control</file> in the source package.
3039 Specifying only <tt>any</tt> indicates that the source package
3040 isn't dependent on any particular architecture and should
3041 compile fine on any one. The produced binary package(s)
3042 will be specific to whatever the current build architecture is.
3046 Specifying only <tt>all</tt> indicates that the source package
3047 will only build architecture-independent packages.
3051 Specifying <tt>any all</tt> indicates that the source package
3052 isn't dependent on any particular architecture. The set of
3053 produced binary packages will include at least one
3054 architecture-dependant package and one architecture-independent
3059 Specifying a list of architectures or architecture wildcards
3060 indicates that the source will build an architecture-dependent
3061 package, and will only work correctly on the listed or
3062 matching architectures. If the source package also builds at
3063 least one architecture-independent package, <tt>all</tt> will
3064 also be included in the list.
3068 In a <file>.changes</file> file, the <tt>Architecture</tt>
3069 field lists the architecture(s) of the package(s) currently
3070 being uploaded. This will be a list; if the source for the
3071 package is also being uploaded, the special
3072 entry <tt>source</tt> is also present. <tt>all</tt> will be
3073 present if any architecture-independent packages are being
3074 uploaded. Architecture wildcards such as <tt>any</tt> must
3075 never occur in the <tt>Architecture</tt> field in
3076 the <file>.changes</file> file.
3080 See <ref id="debianrules"> for information on how to get
3081 the architecture for the build process.
3085 <sect1 id="f-Essential">
3086 <heading><tt>Essential</tt></heading>
3089 This is a boolean field which may occur only in the
3090 control file of a binary package or in a per-package fields
3091 paragraph of a source package control file.
3095 If set to <tt>yes</tt> then the package management system
3096 will refuse to remove the package (upgrading and replacing
3097 it is still possible). The other possible value is <tt>no</tt>,
3098 which is the same as not having the field at all.
3103 <heading>Package interrelationship fields:
3104 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3105 <tt>Recommends</tt>, <tt>Suggests</tt>,
3106 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3107 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3111 These fields describe the package's relationships with
3112 other packages. Their syntax and semantics are described
3113 in <ref id="relationships">.</p>
3116 <sect1 id="f-Standards-Version">
3117 <heading><tt>Standards-Version</tt></heading>
3120 The most recent version of the standards (the policy
3121 manual and associated texts) with which the package
3126 The version number has four components: major and minor
3127 version number and major and minor patch level. When the
3128 standards change in a way that requires every package to
3129 change the major number will be changed. Significant
3130 changes that will require work in many packages will be
3131 signaled by a change to the minor number. The major patch
3132 level will be changed for any change to the meaning of the
3133 standards, however small; the minor patch level will be
3134 changed when only cosmetic, typographical or other edits
3135 are made which neither change the meaning of the document
3136 nor affect the contents of packages.
3140 Thus only the first three components of the policy version
3141 are significant in the <em>Standards-Version</em> control
3142 field, and so either these three components or all four
3143 components may be specified.<footnote>
3144 In the past, people specified the full version number
3145 in the Standards-Version field, for example "2.3.0.0".
3146 Since minor patch-level changes don't introduce new
3147 policy, it was thought it would be better to relax
3148 policy and only require the first 3 components to be
3149 specified, in this example "2.3.0". All four
3150 components may still be used if someone wishes to do so.
3156 <sect1 id="f-Version">
3157 <heading><tt>Version</tt></heading>
3160 The version number of a package. The format is:
3161 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3165 The three components here are:
3167 <tag><var>epoch</var></tag>
3170 This is a single (generally small) unsigned integer. It
3171 may be omitted, in which case zero is assumed. If it is
3172 omitted then the <var>upstream_version</var> may not
3177 It is provided to allow mistakes in the version numbers
3178 of older versions of a package, and also a package's
3179 previous version numbering schemes, to be left behind.
3183 <tag><var>upstream_version</var></tag>
3186 This is the main part of the version number. It is
3187 usually the version number of the original ("upstream")
3188 package from which the <file>.deb</file> file has been made,
3189 if this is applicable. Usually this will be in the same
3190 format as that specified by the upstream author(s);
3191 however, it may need to be reformatted to fit into the
3192 package management system's format and comparison
3197 The comparison behavior of the package management system
3198 with respect to the <var>upstream_version</var> is
3199 described below. The <var>upstream_version</var>
3200 portion of the version number is mandatory.
3204 The <var>upstream_version</var> may contain only
3205 alphanumerics<footnote>
3206 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3208 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3209 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3210 tilde) and should start with a digit. If there is no
3211 <var>debian_revision</var> then hyphens are not allowed;
3212 if there is no <var>epoch</var> then colons are not
3217 <tag><var>debian_revision</var></tag>
3220 This part of the version number specifies the version of
3221 the Debian package based on the upstream version. It
3222 may contain only alphanumerics and the characters
3223 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3224 tilde) and is compared in the same way as the
3225 <var>upstream_version</var> is.
3229 It is optional; if it isn't present then the
3230 <var>upstream_version</var> may not contain a hyphen.
3231 This format represents the case where a piece of
3232 software was written specifically to be a Debian
3233 package, where the Debian package source must always
3234 be identical to the pristine source and therefore no
3235 revision indication is required.
3239 It is conventional to restart the
3240 <var>debian_revision</var> at <tt>1</tt> each time the
3241 <var>upstream_version</var> is increased.
3245 The package management system will break the version
3246 number apart at the last hyphen in the string (if there
3247 is one) to determine the <var>upstream_version</var> and
3248 <var>debian_revision</var>. The absence of a
3249 <var>debian_revision</var> is equivalent to a
3250 <var>debian_revision</var> of <tt>0</tt>.
3257 When comparing two version numbers, first the <var>epoch</var>
3258 of each are compared, then the <var>upstream_version</var> if
3259 <var>epoch</var> is equal, and then <var>debian_revision</var>
3260 if <var>upstream_version</var> is also equal.
3261 <var>epoch</var> is compared numerically. The
3262 <var>upstream_version</var> and <var>debian_revision</var>
3263 parts are compared by the package management system using the
3264 following algorithm:
3268 The strings are compared from left to right.
3272 First the initial part of each string consisting entirely of
3273 non-digit characters is determined. These two parts (one of
3274 which may be empty) are compared lexically. If a difference
3275 is found it is returned. The lexical comparison is a
3276 comparison of ASCII values modified so that all the letters
3277 sort earlier than all the non-letters and so that a tilde
3278 sorts before anything, even the end of a part. For example,
3279 the following parts are in sorted order from earliest to
3280 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3281 <tt>a</tt>.<footnote>
3282 One common use of <tt>~</tt> is for upstream pre-releases.
3283 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3284 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3289 Then the initial part of the remainder of each string which
3290 consists entirely of digit characters is determined. The
3291 numerical values of these two parts are compared, and any
3292 difference found is returned as the result of the comparison.
3293 For these purposes an empty string (which can only occur at
3294 the end of one or both version strings being compared) counts
3299 These two steps (comparing and removing initial non-digit
3300 strings and initial digit strings) are repeated until a
3301 difference is found or both strings are exhausted.
3305 Note that the purpose of epochs is to allow us to leave behind
3306 mistakes in version numbering, and to cope with situations
3307 where the version numbering scheme changes. It is
3308 <em>not</em> intended to cope with version numbers containing
3309 strings of letters which the package management system cannot
3310 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3311 silly orderings.<footnote>
3312 The author of this manual has heard of a package whose
3313 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3314 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3320 <sect1 id="f-Description">
3321 <heading><tt>Description</tt></heading>
3324 In a source or binary control file, the <tt>Description</tt>
3325 field contains a description of the binary package, consisting
3326 of two parts, the synopsis or the short description, and the
3327 long description. It is a multiline field with the following
3333 Description: <single line synopsis>
3334 <extended description over several lines>
3339 The lines in the extended description can have these formats:
3345 Those starting with a single space are part of a paragraph.
3346 Successive lines of this form will be word-wrapped when
3347 displayed. The leading space will usually be stripped off.
3348 The line must contain at least one non-whitespace character.
3352 Those starting with two or more spaces. These will be
3353 displayed verbatim. If the display cannot be panned
3354 horizontally, the displaying program will line wrap them "hard"
3355 (i.e., without taking account of word breaks). If it can they
3356 will be allowed to trail off to the right. None, one or two
3357 initial spaces may be deleted, but the number of spaces
3358 deleted from each line will be the same (so that you can have
3359 indenting work correctly, for example). The line must
3360 contain at least one non-whitespace character.
3364 Those containing a single space followed by a single full stop
3365 character. These are rendered as blank lines. This is the
3366 <em>only</em> way to get a blank line<footnote>
3367 Completely empty lines will not be rendered as blank lines.
3368 Instead, they will cause the parser to think you're starting
3369 a whole new record in the control file, and will therefore
3370 likely abort with an error.
3375 Those containing a space, a full stop and some more characters.
3376 These are for future expansion. Do not use them.
3382 Do not use tab characters. Their effect is not predictable.
3386 See <ref id="descriptions"> for further information on this.
3390 In a <file>.changes</file> file, the <tt>Description</tt>
3391 field contains a summary of the descriptions for the packages
3392 being uploaded. For this case, the first line of the field
3393 value (the part on the same line as <tt>Description:</tt>) is
3394 always empty. It is a multiline field, with one
3395 line per package. Each line is
3396 indented by one space and contains the name of a binary
3397 package, a space, a hyphen (<tt>-</tt>), a space, and the
3398 short description line from that package.
3402 <sect1 id="f-Distribution">
3403 <heading><tt>Distribution</tt></heading>
3406 In a <file>.changes</file> file or parsed changelog output
3407 this contains the (space-separated) name(s) of the
3408 distribution(s) where this version of the package should
3409 be installed. Valid distributions are determined by the
3410 archive maintainers.<footnote>
3411 Example distribution names in the Debian archive used in
3412 <file>.changes</file> files are:
3413 <taglist compact="compact">
3414 <tag><em>unstable</em></tag>
3416 This distribution value refers to the
3417 <em>developmental</em> part of the Debian distribution
3418 tree. Most new packages, new upstream versions of
3419 packages and bug fixes go into the <em>unstable</em>
3423 <tag><em>experimental</em></tag>
3425 The packages with this distribution value are deemed
3426 by their maintainers to be high risk. Oftentimes they
3427 represent early beta or developmental packages from
3428 various sources that the maintainers want people to
3429 try, but are not ready to be a part of the other parts
3430 of the Debian distribution tree.
3435 Others are used for updating stable releases or for
3436 security uploads. More information is available in the
3437 Debian Developer's Reference, section "The Debian
3441 The Debian archive software only supports listing a single
3442 distribution. Migration of packages to other distributions is
3443 handled outside of the upload process.
3448 <heading><tt>Date</tt></heading>
3451 This field includes the date the package was built or last
3452 edited. It must be in the same format as the <var>date</var>
3453 in a <file>debian/changelog</file> entry.
3457 The value of this field is usually extracted from the
3458 <file>debian/changelog</file> file - see
3459 <ref id="dpkgchangelog">).
3463 <sect1 id="f-Format">
3464 <heading><tt>Format</tt></heading>
3467 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3468 files, this field declares the format version of that file.
3469 The syntax of the field value is the same as that of
3470 a <qref id="f-Version">package version number</qref> except
3471 that no epoch or Debian revision is allowed. The format
3472 described in this document is <tt>&changesversion;</tt>.
3476 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3477 Debian source control</qref> files, this field declares the
3478 format of the source package. The field value is used by
3479 programs acting on a source package to interpret the list of
3480 files in the source package and determine how to unpack it.
3481 The syntax of the field value is a numeric major revision, a
3482 period, a numeric minor revision, and then an optional subtype
3483 after whitespace, which if specified is an alphanumeric word
3484 in parentheses. The subtype is optional in the syntax but may
3485 be mandatory for particular source format revisions.
3487 The source formats currently supported by the Debian archive
3488 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3489 and <tt>3.0 (quilt)</tt>.
3494 <sect1 id="f-Urgency">
3495 <heading><tt>Urgency</tt></heading>
3498 This is a description of how important it is to upgrade to
3499 this version from previous ones. It consists of a single
3500 keyword taking one of the values <tt>low</tt>,
3501 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3502 <tt>critical</tt><footnote>
3503 Other urgency values are supported with configuration
3504 changes in the archive software but are not used in Debian.
3505 The urgency affects how quickly a package will be considered
3506 for inclusion into the <tt>testing</tt> distribution and
3507 gives an indication of the importance of any fixes included
3508 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3509 treated as synonymous.
3510 </footnote> (not case-sensitive) followed by an optional
3511 commentary (separated by a space) which is usually in
3512 parentheses. For example:
3515 Urgency: low (HIGH for users of diversions)
3521 The value of this field is usually extracted from the
3522 <file>debian/changelog</file> file - see
3523 <ref id="dpkgchangelog">.
3527 <sect1 id="f-Changes">
3528 <heading><tt>Changes</tt></heading>
3531 This multiline field contains the human-readable changes data, describing
3532 the differences between the last version and the current one.
3536 The first line of the field value (the part on the same line
3537 as <tt>Changes:</tt>) is always empty. The content of the
3538 field is expressed as continuation lines, with each line
3539 indented by at least one space. Blank lines must be
3540 represented by a line consisting only of a space and a full
3545 The value of this field is usually extracted from the
3546 <file>debian/changelog</file> file - see
3547 <ref id="dpkgchangelog">).
3551 Each version's change information should be preceded by a
3552 "title" line giving at least the version, distribution(s)
3553 and urgency, in a human-readable way.
3557 If data from several versions is being returned the entry
3558 for the most recent version should be returned first, and
3559 entries should be separated by the representation of a
3560 blank line (the "title" line may also be followed by the
3561 representation of a blank line).
3565 <sect1 id="f-Binary">
3566 <heading><tt>Binary</tt></heading>
3569 This folded field is a list of binary packages. Its syntax and
3570 meaning varies depending on the control file in which it
3575 When it appears in the <file>.dsc</file> file, it lists binary
3576 packages which a source package can produce, separated by
3578 A space after each comma is conventional.
3579 </footnote>. The source package
3580 does not necessarily produce all of these binary packages for
3581 every architecture. The source control file doesn't contain
3582 details of which architectures are appropriate for which of
3583 the binary packages.
3587 When it appears in a <file>.changes</file> file, it lists the
3588 names of the binary packages being uploaded, separated by
3589 whitespace (not commas).
3593 <sect1 id="f-Installed-Size">
3594 <heading><tt>Installed-Size</tt></heading>
3597 This field appears in the control files of binary packages,
3598 and in the <file>Packages</file> files. It gives an estimate
3599 of the total amount of disk space required to install the
3600 named package. Actual installed size may vary based on block
3601 size, file system properties, or actions taken by package
3606 The disk space is given as the integer value of the estimated
3607 installed size in bytes, divided by 1024 and rounded up.
3611 <sect1 id="f-Files">
3612 <heading><tt>Files</tt></heading>
3615 This field contains a list of files with information about
3616 each one. The exact information and syntax varies with
3621 In all cases, Files is a multiline field. The first line of
3622 the field value (the part on the same line as <tt>Files:</tt>)
3623 is always empty. The content of the field is expressed as
3624 continuation lines, one line per file. Each line must be
3625 indented by one space and contain a number of sub-fields,
3626 separated by spaces, as described below.
3630 In the <file>.dsc</file> file, each line contains the MD5
3631 checksum, size and filename of the tar file and (if
3632 applicable) diff file which make up the remainder of the
3633 source package<footnote>
3634 That is, the parts which are not the <tt>.dsc</tt>.
3635 </footnote>. For example:
3638 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3639 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3641 The exact forms of the filenames are described
3642 in <ref id="pkg-sourcearchives">.
3646 In the <file>.changes</file> file this contains one line per
3647 file being uploaded. Each line contains the MD5 checksum,
3648 size, section and priority and the filename. For example:
3651 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3652 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3653 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3654 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3656 The <qref id="f-Section">section</qref>
3657 and <qref id="f-Priority">priority</qref> are the values of
3658 the corresponding fields in the main source control file. If
3659 no section or priority is specified then <tt>-</tt> should be
3660 used, though section and priority values must be specified for
3661 new packages to be installed properly.
3665 The special value <tt>byhand</tt> for the section in a
3666 <tt>.changes</tt> file indicates that the file in question
3667 is not an ordinary package file and must by installed by
3668 hand by the distribution maintainers. If the section is
3669 <tt>byhand</tt> the priority should be <tt>-</tt>.
3673 If a new Debian revision of a package is being shipped and
3674 no new original source archive is being distributed the
3675 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3676 entry for the original source archive
3677 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3678 but the <file>.changes</file> file should leave it out. In
3679 this case the original source archive on the distribution
3680 site must match exactly, byte-for-byte, the original
3681 source archive which was used to generate the
3682 <file>.dsc</file> file and diff which are being uploaded.</p>
3685 <sect1 id="f-Closes">
3686 <heading><tt>Closes</tt></heading>
3689 A space-separated list of bug report numbers that the upload
3690 governed by the .changes file closes.
3694 <sect1 id="f-Homepage">
3695 <heading><tt>Homepage</tt></heading>
3698 The URL of the web site for this package, preferably (when
3699 applicable) the site from which the original source can be
3700 obtained and any additional upstream documentation or
3701 information may be found. The content of this field is a
3702 simple URL without any surrounding characters such as
3707 <sect1 id="f-Checksums">
3708 <heading><tt>Checksums-Sha1</tt>
3709 and <tt>Checksums-Sha256</tt></heading>
3712 These multiline fields contain a list of files with a checksum and size
3713 for each one. Both <tt>Checksums-Sha1</tt>
3714 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3715 only in the checksum algorithm used: SHA-1
3716 for <tt>Checksums-Sha1</tt> and SHA-256
3717 for <tt>Checksums-Sha256</tt>.
3721 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3722 multiline fields. The first line of the field value (the part
3723 on the same line as <tt>Checksums-Sha1:</tt>
3724 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3725 of the field is expressed as continuation lines, one line per
3726 file. Each line consists of the checksum, a space, the file
3727 size, a space, and the file name. For example (from
3728 a <file>.changes</file> file):
3731 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3732 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3733 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3734 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3736 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3737 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3738 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3739 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3744 In the <file>.dsc</file> file, these fields list all
3745 files that make up the source package. In
3746 the <file>.changes</file> file, these fields list all
3747 files being uploaded. The list of files in these fields
3748 must match the list of files in the <tt>Files</tt> field.
3753 <heading><tt>DM-Upload-Allowed</tt></heading>
3756 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3760 <sect1 id="f-VCS-fields">
3761 <heading>Version Control System (VCS) fields</heading>
3764 Debian source packages are increasingly developed using VCSs. The
3765 purpose of the following fields is to indicate a publicly accessible
3766 repository where the Debian source package is developed.
3769 <tag><tt>Vcs-Browser</tt></tag>
3772 URL of a web interface for browsing the repository.
3777 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3778 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3779 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3784 The field name identifies the VCS. The field's value uses the
3785 version control system's conventional syntax for describing
3786 repository locations and should be sufficient to locate the
3787 repository used for packaging. Ideally, it also locates the
3788 branch used for development of new versions of the Debian
3792 In the case of Git, the value consists of a URL, optionally
3793 followed by the word <tt>-b</tt> and the name of a branch in
3794 the indicated repository, following the syntax of the
3795 <tt>git clone</tt> command. If no branch is specified, the
3796 packaging should be on the default branch.
3799 More than one different VCS may be specified for the same
3807 <sect1 id="f-Package-List">
3808 <heading><tt>Package-List</tt></heading>
3811 Multiline field listing all the packages that can be built from
3812 the source package, considering every architecture. The first line
3813 of the field value is empty. Each one of the next lines describes
3814 one binary package, by listing its name, type, section and priority
3815 separated by spaces. Fifth and subsequent space-separated items
3816 may be present and parsers must allow them. See the
3817 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3822 <sect1 id="f-Package-Type">
3823 <heading><tt>Package-Type</tt></heading>
3826 Simple field containing a word indicating the type of package:
3827 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3828 packages. Other types not defined here may be indicated. In
3829 source package control files, the <tt>Package-Type</tt> field
3830 should be omitted instead of giving it a value of <tt>deb</tt>, as
3831 this value is assumed for paragraphs lacking this field.
3837 <heading>User-defined fields</heading>
3840 Additional user-defined fields may be added to the
3841 source package control file. Such fields will be
3842 ignored, and not copied to (for example) binary or
3843 Debian source control files or upload control files.
3847 If you wish to add additional unsupported fields to
3848 these output files you should use the mechanism
3853 Fields in the main source control information file with
3854 names starting <tt>X</tt>, followed by one or more of
3855 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3856 be copied to the output files. Only the part of the
3857 field name after the hyphen will be used in the output
3858 file. Where the letter <tt>B</tt> is used the field
3859 will appear in binary package control files, where the
3860 letter <tt>S</tt> is used in Debian source control
3861 files and where <tt>C</tt> is used in upload control
3862 (<tt>.changes</tt>) files.
3866 For example, if the main source information control file
3869 XBS-Comment: I stand between the candle and the star.
3871 then the binary and Debian source control files will contain the
3874 Comment: I stand between the candle and the star.
3880 <sect id="obsolete-control-data-fields">
3881 <heading>Obsolete fields</heading>
3884 The following fields have been obsoleted and may be found in packages
3885 conforming with previous versions of the Policy.
3888 <sect1 id="f-DM-Upload-Allowed">
3889 <heading><tt>DM-Upload-Allowed</tt></heading>
3892 Indicates that Debian Maintainers may upload this package to
3893 the Debian archive. The only valid value is <tt>yes</tt>. This
3894 field was used to regulate uploads by Debian Maintainers, See the
3895 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3896 name="Endorse the concept of Debian Maintainers"> for more details.
3905 <chapt id="maintainerscripts">
3906 <heading>Package maintainer scripts and installation procedure</heading>
3909 <heading>Introduction to package maintainer scripts</heading>
3912 It is possible to supply scripts as part of a package which
3913 the package management system will run for you when your
3914 package is installed, upgraded or removed.
3918 These scripts are the control information
3919 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3920 and <prgn>postrm</prgn>. They must be proper executable files;
3921 if they are scripts (which is recommended), they must start with
3922 the usual <tt>#!</tt> convention. They should be readable and
3923 executable by anyone, and must not be world-writable.
3927 The package management system looks at the exit status from
3928 these scripts. It is important that they exit with a
3929 non-zero status if there is an error, so that the package
3930 management system can stop its processing. For shell
3931 scripts this means that you <em>almost always</em> need to
3932 use <tt>set -e</tt> (this is usually true when writing shell
3933 scripts, in fact). It is also important, of course, that
3934 they exit with a zero status if everything went well.
3938 Additionally, packages interacting with users
3939 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3940 should install a <prgn>config</prgn> script as a control
3941 information file. See <ref id="maintscriptprompt"> for details.
3945 When a package is upgraded a combination of the scripts from
3946 the old and new packages is called during the upgrade
3947 procedure. If your scripts are going to be at all
3948 complicated you need to be aware of this, and may need to
3949 check the arguments to your scripts.
3953 Broadly speaking the <prgn>preinst</prgn> is called before
3954 (a particular version of) a package is unpacked, and the
3955 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3956 before (a version of) a package is removed and the
3957 <prgn>postrm</prgn> afterwards.
3961 Programs called from maintainer scripts should not normally
3962 have a path prepended to them. Before installation is
3963 started, the package management system checks to see if the
3964 programs <prgn>ldconfig</prgn>,
3965 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3966 and <prgn>update-rc.d</prgn> can be found via the
3967 <tt>PATH</tt> environment variable. Those programs, and any
3968 other program that one would expect to be in the
3969 <tt>PATH</tt>, should thus be invoked without an absolute
3970 pathname. Maintainer scripts should also not reset the
3971 <tt>PATH</tt>, though they might choose to modify it by
3972 prepending or appending package-specific directories. These
3973 considerations really apply to all shell scripts.</p>
3976 <sect id="idempotency">
3977 <heading>Maintainer scripts idempotency</heading>
3980 It is necessary for the error recovery procedures that the
3981 scripts be idempotent. This means that if it is run
3982 successfully, and then it is called again, it doesn't bomb
3983 out or cause any harm, but just ensures that everything is
3984 the way it ought to be. If the first call failed, or
3985 aborted half way through for some reason, the second call
3986 should merely do the things that were left undone the first
3987 time, if any, and exit with a success status if everything
3989 This is so that if an error occurs, the user interrupts
3990 <prgn>dpkg</prgn> or some other unforeseen circumstance
3991 happens you don't leave the user with a badly-broken
3992 package when <prgn>dpkg</prgn> attempts to repeat the
3998 <sect id="controllingterminal">
3999 <heading>Controlling terminal for maintainer scripts</heading>
4002 Maintainer scripts are not guaranteed to run with a controlling
4003 terminal and may not be able to interact with the user. They
4004 must be able to fall back to noninteractive behavior if no
4005 controlling terminal is available. Maintainer scripts that
4006 prompt via a program conforming to the Debian Configuration
4007 Management Specification (see <ref id="maintscriptprompt">) may
4008 assume that program will handle falling back to noninteractive
4013 For high-priority prompts without a reasonable default answer,
4014 maintainer scripts may abort if there is no controlling
4015 terminal. However, this situation should be avoided if at all
4016 possible, since it prevents automated or unattended installs.
4017 In most cases, users will consider this to be a bug in the
4022 <sect id="exitstatus">
4023 <heading>Exit status</heading>
4026 Each script must return a zero exit status for
4027 success, or a nonzero one for failure, since the package
4028 management system looks for the exit status of these scripts
4029 and determines what action to take next based on that datum.
4033 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4038 What follows is a summary of all the ways in which maintainer
4039 scripts may be called along with what facilities those scripts
4040 may rely on being available at that time. Script names preceded
4041 by <var>new-</var> are the scripts from the new version of a
4042 package being installed, upgraded to, or downgraded to. Script
4043 names preceded by <var>old-</var> are the scripts from the old
4044 version of a package that is being upgraded from or downgraded
4049 The <prgn>preinst</prgn> script may be called in the following
4052 <tag><var>new-preinst</var> <tt>install</tt></tag>
4053 <tag><var>new-preinst</var> <tt>install</tt>
4054 <var>old-version</var></tag>
4055 <tag><var>new-preinst</var> <tt>upgrade</tt>
4056 <var>old-version</var></tag>
4058 The package will not yet be unpacked, so
4059 the <prgn>preinst</prgn> script cannot rely on any files
4060 included in its package. Only essential packages and
4061 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4062 available. Pre-dependencies will have been configured at
4063 least once, but at the time the <prgn>preinst</prgn> is
4064 called they may only be in an unpacked or "Half-Configured"
4065 state if a previous version of the pre-dependency was
4066 completely configured and has not been removed since then.
4069 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4070 <var>new-version</var></tag>
4072 Called during error handling of an upgrade that failed after
4073 unpacking the new package because the <tt>postrm
4074 upgrade</tt> action failed. The unpacked files may be
4075 partly from the new version or partly missing, so the script
4076 cannot rely on files included in the package. Package
4077 dependencies may not be available. Pre-dependencies will be
4078 at least unpacked following the same rules as above, except
4079 they may be only "Half-Installed" if an upgrade of the
4080 pre-dependency failed.<footnote>
4081 This can happen if the new version of the package no
4082 longer pre-depends on a package that had been partially
4090 The <prgn>postinst</prgn> script may be called in the following
4093 <tag><var>postinst</var> <tt>configure</tt>
4094 <var>most-recently-configured-version</var></tag>
4096 The files contained in the package will be unpacked. All
4097 package dependencies will at least be unpacked. If there
4098 are no circular dependencies involved, all package
4099 dependencies will be configured. For behavior in the case
4100 of circular dependencies, see the discussion
4101 in <ref id="binarydeps">.
4104 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4105 <var>new-version</var></tag>
4106 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4107 <tt>in-favour</tt> <var>package</var>
4108 <var>new-version</var></tag>
4109 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4110 <tag><var>deconfigured's-postinst</var>
4111 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4112 <var>failed-install-package</var> <var>version</var>
4113 [<tt>removing</tt> <var>conflicting-package</var>
4114 <var>version</var>]</tag>
4116 The files contained in the package will be unpacked. All
4117 package dependencies will at least be "Half-Installed" and
4118 will have previously been configured and not removed.
4119 However, dependencies may not be configured or even fully
4120 unpacked in some error situations.<footnote>
4121 For example, suppose packages foo and bar are installed
4122 with foo depending on bar. If an upgrade of bar were
4123 started and then aborted, and then an attempt to remove
4124 foo failed because its <prgn>prerm</prgn> script failed,
4125 foo's <tt>postinst abort-remove</tt> would be called with
4126 bar only "Half-Installed".
4128 The <prgn>postinst</prgn> should still attempt any actions
4129 for which its dependencies are required, since they will
4130 normally be available, but consider the correct error
4131 handling approach if those actions fail. Aborting
4132 the <prgn>postinst</prgn> action if commands or facilities
4133 from the package dependencies are not available is often the
4140 The <prgn>prerm</prgn> script may be called in the following
4143 <tag><var>prerm</var> <tt>remove</tt></tag>
4144 <tag><var>old-prerm</var>
4145 <tt>upgrade</tt><var>new-version</var></tag>
4146 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4147 <tt>in-favour</tt> <var>package</var>
4148 <var>new-version</var></tag>
4149 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4150 <tt>in-favour</tt> <var>package-being-installed</var>
4151 <var>version</var> [<tt>removing</tt>
4152 <var>conflicting-package</var> <var>version</var>]</tag>
4154 The package whose <prgn>prerm</prgn> is being called will be
4155 at least "Half-Installed". All package dependencies will at
4156 least be "Half-Installed" and will have previously been
4157 configured and not removed. If there was no error, all
4158 dependencies will at least be unpacked, but these actions
4159 may be called in various error states where dependencies are
4160 only "Half-Installed" due to a partial upgrade.
4163 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4164 <var>old-version</var></tag>
4166 Called during error handling when <tt>prerm upgrade</tt>
4167 fails. The new package will not yet be unpacked, and all
4168 the same constraints as for <tt>preinst upgrade</tt> apply.
4174 The <prgn>postrm</prgn> script may be called in the following
4177 <tag><var>postrm</var> <tt>remove</tt></tag>
4178 <tag><var>postrm</var> <tt>purge</tt></tag>
4179 <tag><var>old-postrm</var> <tt>upgrade</tt>
4180 <var>new-version</var></tag>
4181 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4182 <var>overwriter</var> <var>overwriter-version</var></tag>
4184 The <prgn>postrm</prgn> script is called after the package's
4185 files have been removed or replaced. The package
4186 whose <prgn>postrm</prgn> is being called may have
4187 previously been deconfigured and only be unpacked, at which
4188 point subsequent package changes do not consider its
4189 dependencies. Therefore, all <prgn>postrm</prgn> actions
4190 may only rely on essential packages and must gracefully skip
4191 any actions that require the package's dependencies if those
4192 dependencies are unavailable.<footnote>
4193 This is often done by checking whether the command or
4194 facility the <prgn>postrm</prgn> intends to call is
4195 available before calling it. For example:
4197 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4198 . /usr/share/debconf/confmodule
4202 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4203 configuration for the package
4204 if <package>debconf</package> is installed.
4208 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4209 <var>old-version</var></tag>
4211 Called when the old <tt>postrm upgrade</tt> action fails.
4212 The new package will be unpacked, but only essential
4213 packages and pre-dependencies can be relied on.
4214 Pre-dependencies will either be configured or will be
4215 "Unpacked" or "Half-Configured" but previously had been
4216 configured and was never removed.
4219 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4220 <tag><var>new-postrm</var> <tt>abort-install</tt>
4221 <var>old-version</var></tag>
4222 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4223 <var>old-version</var></tag>
4225 Called before unpacking the new package as part of the
4226 error handling of <prgn>preinst</prgn> failures. May assume
4227 the same state as <prgn>preinst</prgn> can assume.
4233 <sect id="unpackphase">
4234 <heading>Details of unpack phase of installation or upgrade</heading>
4237 The procedure on installation/upgrade/overwrite/disappear
4238 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4239 stage of <tt>dpkg --install</tt>) is as follows. In each
4240 case, if a major error occurs (unless listed below) the
4241 actions are, in general, run backwards - this means that the
4242 maintainer scripts are run with different arguments in
4243 reverse order. These are the "error unwind" calls listed
4250 If a version of the package is already installed, call
4251 <example compact="compact">
4252 <var>old-prerm</var> upgrade <var>new-version</var>
4256 If the script runs but exits with a non-zero
4257 exit status, <prgn>dpkg</prgn> will attempt:
4258 <example compact="compact">
4259 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4261 If this works, the upgrade continues. If this
4262 does not work, the error unwind:
4263 <example compact="compact">
4264 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4266 If this works, then the old-version is
4267 "Installed", if not, the old version is in a
4268 "Half-Configured" state.
4274 If a "conflicting" package is being removed at the same time,
4275 or if any package will be broken (due to <tt>Breaks</tt>):
4278 If <tt>--auto-deconfigure</tt> is
4279 specified, call, for each package to be deconfigured
4280 due to <tt>Breaks</tt>:
4281 <example compact="compact">
4282 <var>deconfigured's-prerm</var> deconfigure \
4283 in-favour <var>package-being-installed</var> <var>version</var>
4286 <example compact="compact">
4287 <var>deconfigured's-postinst</var> abort-deconfigure \
4288 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4290 The deconfigured packages are marked as
4291 requiring configuration, so that if
4292 <tt>--install</tt> is used they will be
4293 configured again if possible.
4296 If any packages depended on a conflicting
4297 package being removed and <tt>--auto-deconfigure</tt> is
4298 specified, call, for each such package:
4299 <example compact="compact">
4300 <var>deconfigured's-prerm</var> deconfigure \
4301 in-favour <var>package-being-installed</var> <var>version</var> \
4302 removing <var>conflicting-package</var> <var>version</var>
4305 <example compact="compact">
4306 <var>deconfigured's-postinst</var> abort-deconfigure \
4307 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4308 removing <var>conflicting-package</var> <var>version</var>
4310 The deconfigured packages are marked as
4311 requiring configuration, so that if
4312 <tt>--install</tt> is used they will be
4313 configured again if possible.
4316 To prepare for removal of each conflicting package, call:
4317 <example compact="compact">
4318 <var>conflictor's-prerm</var> remove \
4319 in-favour <var>package</var> <var>new-version</var>
4322 <example compact="compact">
4323 <var>conflictor's-postinst</var> abort-remove \
4324 in-favour <var>package</var> <var>new-version</var>
4333 If the package is being upgraded, call:
4334 <example compact="compact">
4335 <var>new-preinst</var> upgrade <var>old-version</var>
4337 If this fails, we call:
4339 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4346 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4348 is called. If this works, then the old version
4349 is in an "Installed" state, or else it is left
4350 in an "Unpacked" state.
4355 If it fails, then the old version is left
4356 in an "Half-Installed" state.
4363 Otherwise, if the package had some configuration
4364 files from a previous version installed (i.e., it
4365 is in the "configuration files only" state):
4366 <example compact="compact">
4367 <var>new-preinst</var> install <var>old-version</var>
4371 <var>new-postrm</var> abort-install <var>old-version</var>
4373 If this fails, the package is left in a
4374 "Half-Installed" state, which requires a
4375 reinstall. If it works, the packages is left in
4376 a "Config-Files" state.
4379 Otherwise (i.e., the package was completely purged):
4380 <example compact="compact">
4381 <var>new-preinst</var> install
4384 <example compact="compact">
4385 <var>new-postrm</var> abort-install
4387 If the error-unwind fails, the package is in a
4388 "Half-Installed" phase, and requires a
4389 reinstall. If the error unwind works, the
4390 package is in a not installed state.
4397 The new package's files are unpacked, overwriting any
4398 that may be on the system already, for example any
4399 from the old version of the same package or from
4400 another package. Backups of the old files are kept
4401 temporarily, and if anything goes wrong the package
4402 management system will attempt to put them back as
4403 part of the error unwind.
4407 It is an error for a package to contain files which
4408 are on the system in another package, unless
4409 <tt>Replaces</tt> is used (see <ref id="replaces">).
4411 The following paragraph is not currently the case:
4412 Currently the <tt>- - force-overwrite</tt> flag is
4413 enabled, downgrading it to a warning, but this may not
4419 It is a more serious error for a package to contain a
4420 plain file or other kind of non-directory where another
4421 package has a directory (again, unless
4422 <tt>Replaces</tt> is used). This error can be
4423 overridden if desired using
4424 <tt>--force-overwrite-dir</tt>, but this is not
4429 Packages which overwrite each other's files produce
4430 behavior which, though deterministic, is hard for the
4431 system administrator to understand. It can easily
4432 lead to "missing" programs if, for example, a package
4433 is unpacked which overwrites a file from another
4434 package, and is then removed again.<footnote>
4435 Part of the problem is due to what is arguably a
4436 bug in <prgn>dpkg</prgn>.
4441 A directory will never be replaced by a symbolic link
4442 to a directory or vice versa; instead, the existing
4443 state (symlink or not) will be left alone and
4444 <prgn>dpkg</prgn> will follow the symlink if there is
4453 If the package is being upgraded, call
4454 <example compact="compact">
4455 <var>old-postrm</var> upgrade <var>new-version</var>
4459 If this fails, <prgn>dpkg</prgn> will attempt:
4460 <example compact="compact">
4461 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4463 If this works, installation continues. If not,
4465 <example compact="compact">
4466 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4468 If this fails, the old version is left in a
4469 "Half-Installed" state. If it works, dpkg now
4471 <example compact="compact">
4472 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4474 If this fails, the old version is left in a
4475 "Half-Installed" state. If it works, dpkg now
4477 <example compact="compact">
4478 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4480 If this fails, the old version is in an
4487 This is the point of no return - if
4488 <prgn>dpkg</prgn> gets this far, it won't back off
4489 past this point if an error occurs. This will
4490 leave the package in a fairly bad state, which
4491 will require a successful re-installation to clear
4492 up, but it's when <prgn>dpkg</prgn> starts doing
4493 things that are irreversible.
4498 Any files which were in the old version of the package
4499 but not in the new are removed.
4503 The new file list replaces the old.
4507 The new maintainer scripts replace the old.
4511 Any packages all of whose files have been overwritten
4512 during the installation, and which aren't required for
4513 dependencies, are considered to have been removed.
4514 For each such package
4517 <prgn>dpkg</prgn> calls:
4518 <example compact="compact">
4519 <var>disappearer's-postrm</var> disappear \
4520 <var>overwriter</var> <var>overwriter-version</var>
4524 The package's maintainer scripts are removed.
4527 It is noted in the status database as being in a
4528 sane state, namely not installed (any conffiles
4529 it may have are ignored, rather than being
4530 removed by <prgn>dpkg</prgn>). Note that
4531 disappearing packages do not have their prerm
4532 called, because <prgn>dpkg</prgn> doesn't know
4533 in advance that the package is going to
4540 Any files in the package we're unpacking that are also
4541 listed in the file lists of other packages are removed
4542 from those lists. (This will lobotomize the file list
4543 of the "conflicting" package if there is one.)
4547 The backup files made during installation, above, are
4553 The new package's status is now sane, and recorded as
4558 Here is another point of no return - if the
4559 conflicting package's removal fails we do not unwind
4560 the rest of the installation; the conflicting package
4561 is left in a half-removed limbo.
4566 If there was a conflicting package we go and do the
4567 removal actions (described below), starting with the
4568 removal of the conflicting package's files (any that
4569 are also in the package being unpacked have already
4570 been removed from the conflicting package's file list,
4571 and so do not get removed now).
4577 <sect id="configdetails"><heading>Details of configuration</heading>
4580 When we configure a package (this happens with <tt>dpkg
4581 --install</tt> and <tt>dpkg --configure</tt>), we first
4582 update any <tt>conffile</tt>s and then call:
4583 <example compact="compact">
4584 <var>postinst</var> configure <var>most-recently-configured-version</var>
4589 No attempt is made to unwind after errors during
4590 configuration. If the configuration fails, the package is in
4591 a "Failed Config" state, and an error message is generated.
4595 If there is no most recently configured version
4596 <prgn>dpkg</prgn> will pass a null argument.
4599 Historical note: Truly ancient (pre-1997) versions of
4600 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4601 (including the angle brackets) in this case. Even older
4602 ones did not pass a second argument at all, under any
4603 circumstance. Note that upgrades using such an old dpkg
4604 version are unlikely to work for other reasons, even if
4605 this old argument behavior is handled by your postinst script.
4611 <sect id="removedetails"><heading>Details of removal and/or
4612 configuration purging</heading>
4618 <example compact="compact">
4619 <var>prerm</var> remove
4623 If prerm fails during replacement due to conflict
4625 <var>conflictor's-postinst</var> abort-remove \
4626 in-favour <var>package</var> <var>new-version</var>
4630 <var>postinst</var> abort-remove
4634 If this fails, the package is in a "Half-Configured"
4635 state, or else it remains "Installed".
4639 The package's files are removed (except <tt>conffile</tt>s).
4642 <example compact="compact">
4643 <var>postrm</var> remove
4647 If it fails, there's no error unwind, and the package is in
4648 an "Half-Installed" state.
4653 All the maintainer scripts except the <prgn>postrm</prgn>
4658 If we aren't purging the package we stop here. Note
4659 that packages which have no <prgn>postrm</prgn> and no
4660 <tt>conffile</tt>s are automatically purged when
4661 removed, as there is no difference except for the
4662 <prgn>dpkg</prgn> status.
4666 The <tt>conffile</tt>s and any backup files
4667 (<tt>~</tt>-files, <tt>#*#</tt> files,
4668 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4673 <example compact="compact">
4674 <var>postrm</var> purge
4678 If this fails, the package remains in a "Config-Files"
4683 The package's file list is removed.
4692 <chapt id="relationships">
4693 <heading>Declaring relationships between packages</heading>
4695 <sect id="depsyntax">
4696 <heading>Syntax of relationship fields</heading>
4699 These fields all have a uniform syntax. They are a list of
4700 package names separated by commas.
4704 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4705 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4706 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4707 control fields of the package, which declare
4708 dependencies on other packages, the package names listed may
4709 also include lists of alternative package names, separated
4710 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4711 if any one of the alternative packages is installed, that
4712 part of the dependency is considered to be satisfied.
4716 All of the fields except for <tt>Provides</tt> may restrict
4717 their applicability to particular versions of each named
4718 package. This is done in parentheses after each individual
4719 package name; the parentheses should contain a relation from
4720 the list below followed by a version number, in the format
4721 described in <ref id="f-Version">.
4725 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4726 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4727 earlier, earlier or equal, exactly equal, later or equal and
4728 strictly later, respectively. The deprecated
4729 forms <tt><</tt> and <tt>></tt> were confusingly used to
4730 mean earlier/later or equal, rather than strictly earlier/later,
4731 and must not appear in new packages (though <prgn>dpkg</prgn>
4732 still supports them with a warning).
4736 Whitespace may appear at any point in the version
4737 specification subject to the rules in <ref
4738 id="controlsyntax">, and must appear where it's necessary to
4739 disambiguate; it is not otherwise significant. All of the
4740 relationship fields can only be folded in source package control files. For
4741 consistency and in case of future changes to
4742 <prgn>dpkg</prgn> it is recommended that a single space be
4743 used after a version relationship and before a version
4744 number; it is also conventional to put a single space after
4745 each comma, on either side of each vertical bar, and before
4746 each open parenthesis. When opening a continuation line in a relationship field, it
4747 is conventional to do so after a comma and before the space
4748 following that comma.
4752 For example, a list of dependencies might appear as:
4753 <example compact="compact">
4756 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4761 Relationships may be restricted to a certain set of
4762 architectures. This is indicated in brackets after each
4763 individual package name and the optional version specification.
4764 The brackets enclose a non-empty list of Debian architecture names
4765 in the format described in <ref id="arch-spec">,
4766 separated by whitespace. Exclamation marks may be prepended to
4767 each of the names. (It is not permitted for some names to be
4768 prepended with exclamation marks while others aren't.)
4772 For build relationship fields
4773 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4774 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4775 the current Debian host architecture is not in this list and
4776 there are no exclamation marks in the list, or it is in the list
4777 with a prepended exclamation mark, the package name and the
4778 associated version specification are ignored completely for the
4779 purposes of defining the relationships.
4784 <example compact="compact">
4786 Build-Depends-Indep: texinfo
4787 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4788 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4790 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4791 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4792 <tt>gnumach-dev</tt> only on hurd-i386.
4796 For binary relationship fields and the <tt>Built-Using</tt>
4797 field, the architecture restriction
4798 syntax is only supported in the source package control
4799 file <file>debian/control</file>. When the corresponding binary
4800 package control file is generated, the relationship will either
4801 be omitted or included without the architecture restriction
4802 based on the architecture of the binary package. This means
4803 that architecture restrictions must not be used in binary
4804 relationship fields for architecture-independent packages
4805 (<tt>Architecture: all</tt>).
4810 <example compact="compact">
4811 Depends: foo [i386], bar [amd64]
4813 becomes <tt>Depends: foo</tt> when the package is built on
4814 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4815 package is built on the <tt>amd64</tt> architecture, and omitted
4816 entirely in binary packages built on all other architectures.
4820 If the architecture-restricted dependency is part of a set of
4821 alternatives using <tt>|</tt>, that alternative is ignored
4822 completely on architectures that do not match the restriction.
4824 <example compact="compact">
4825 Build-Depends: foo [!i386] | bar [!amd64]
4827 is equivalent to <tt>bar</tt> on the i386 architecture, to
4828 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4829 bar</tt> on all other architectures.
4833 Relationships may also be restricted to a certain set of
4834 architectures using architecture wildcards in the format
4835 described in <ref id="arch-wildcard-spec">. The syntax for
4836 declaring such restrictions is the same as declaring
4837 restrictions using a certain set of architectures without
4838 architecture wildcards. For example:
4839 <example compact="compact">
4840 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4842 is equivalent to <tt>foo</tt> on architectures using the Linux
4843 kernel and any cpu, <tt>bar</tt> on architectures using any
4844 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4845 using a kernel other than Linux.
4849 Note that the binary package relationship fields such as
4850 <tt>Depends</tt> appear in one of the binary package
4851 sections of the control file, whereas the build-time
4852 relationships such as <tt>Build-Depends</tt> appear in the
4853 source package section of the control file (which is the
4858 <sect id="binarydeps">
4859 <heading>Binary Dependencies - <tt>Depends</tt>,
4860 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4861 <tt>Pre-Depends</tt>
4865 Packages can declare in their control file that they have
4866 certain relationships to other packages - for example, that
4867 they may not be installed at the same time as certain other
4868 packages, and/or that they depend on the presence of others.
4872 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4873 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4874 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4875 <tt>Breaks</tt> is described in <ref id="breaks">, and
4876 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4877 rest are described below.
4881 These seven fields are used to declare a dependency
4882 relationship by one package on another. Except for
4883 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4884 depending (binary) package's control file.
4885 (<tt>Enhances</tt> appears in the recommending package's
4886 control file, and <tt>Breaks</tt> appears in the version of
4887 depended-on package which causes the named package to
4892 A <tt>Depends</tt> field takes effect <em>only</em> when a
4893 package is to be configured. It does not prevent a package
4894 being on the system in an unconfigured state while its
4895 dependencies are unsatisfied, and it is possible to replace
4896 a package whose dependencies are satisfied and which is
4897 properly installed with a different version whose
4898 dependencies are not and cannot be satisfied; when this is
4899 done the depending package will be left unconfigured (since
4900 attempts to configure it will give errors) and will not
4901 function properly. If it is necessary, a
4902 <tt>Pre-Depends</tt> field can be used, which has a partial
4903 effect even when a package is being unpacked, as explained
4904 in detail below. (The other three dependency fields,
4905 <tt>Recommends</tt>, <tt>Suggests</tt> and
4906 <tt>Enhances</tt>, are only used by the various front-ends
4907 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4908 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4912 Since <tt>Depends</tt> only places requirements on the order in
4913 which packages are configured, packages in an installation run
4914 are usually all unpacked first and all configured later.
4916 This approach makes dependency resolution easier. If two
4917 packages A and B are being upgraded, the installed package A
4918 depends on exactly the installed package B, and the new
4919 package A depends on exactly the new package B (a common
4920 situation when upgrading shared libraries and their
4921 corresponding development packages), satisfying the
4922 dependencies at every stage of the upgrade would be
4923 impossible. This relaxed restriction means that both new
4924 packages can be unpacked together and then configured in their
4930 If there is a circular dependency among packages being installed
4931 or removed, installation or removal order honoring the
4932 dependency order is impossible, requiring the dependency loop be
4933 broken at some point and the dependency requirements violated
4934 for at least one package. Packages involved in circular
4935 dependencies may not be able to rely on their dependencies being
4936 configured before they themselves are configured, depending on
4937 which side of the break of the circular dependency loop they
4938 happen to be on. If one of the packages in the loop has
4939 no <prgn>postinst</prgn> script, then the cycle will be broken
4940 at that package; this ensures that all <prgn>postinst</prgn>
4941 scripts are run with their dependencies properly configured if
4942 this is possible. Otherwise the breaking point is arbitrary.
4943 Packages should therefore avoid circular dependencies where
4944 possible, particularly if they have <prgn>postinst</prgn>
4949 The meaning of the five dependency fields is as follows:
4951 <tag><tt>Depends</tt></tag>
4954 This declares an absolute dependency. A package will
4955 not be configured unless all of the packages listed in
4956 its <tt>Depends</tt> field have been correctly
4957 configured (unless there is a circular dependency as
4962 The <tt>Depends</tt> field should be used if the
4963 depended-on package is required for the depending
4964 package to provide a significant amount of
4969 The <tt>Depends</tt> field should also be used if the
4970 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4971 require the depended-on package to be unpacked or
4972 configured in order to run. In the case of <tt>postinst
4973 configure</tt>, the depended-on packages will be unpacked
4974 and configured first. (If both packages are involved in a
4975 dependency loop, this might not work as expected; see the
4976 explanation a few paragraphs back.) In the case
4977 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4978 actions, the package dependencies will normally be at
4979 least unpacked, but they may be only "Half-Installed" if a
4980 previous upgrade of the dependency failed.
4984 Finally, the <tt>Depends</tt> field should be used if the
4985 depended-on package is needed by the <prgn>postrm</prgn>
4986 script to fully clean up after the package removal. There
4987 is no guarantee that package dependencies will be
4988 available when <prgn>postrm</prgn> is run, but the
4989 depended-on package is more likely to be available if the
4990 package declares a dependency (particularly in the case
4991 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4992 script must gracefully skip actions that require a
4993 dependency if that dependency isn't available.
4997 <tag><tt>Recommends</tt></tag>
5000 This declares a strong, but not absolute, dependency.
5004 The <tt>Recommends</tt> field should list packages
5005 that would be found together with this one in all but
5006 unusual installations.
5010 <tag><tt>Suggests</tt></tag>
5012 This is used to declare that one package may be more
5013 useful with one or more others. Using this field
5014 tells the packaging system and the user that the
5015 listed packages are related to this one and can
5016 perhaps enhance its usefulness, but that installing
5017 this one without them is perfectly reasonable.
5020 <tag><tt>Enhances</tt></tag>
5022 This field is similar to Suggests but works in the
5023 opposite direction. It is used to declare that a
5024 package can enhance the functionality of another
5028 <tag><tt>Pre-Depends</tt></tag>
5031 This field is like <tt>Depends</tt>, except that it
5032 also forces <prgn>dpkg</prgn> to complete installation
5033 of the packages named before even starting the
5034 installation of the package which declares the
5035 pre-dependency, as follows:
5039 When a package declaring a pre-dependency is about to
5040 be <em>unpacked</em> the pre-dependency can be
5041 satisfied if the depended-on package is either fully
5042 configured, <em>or even if</em> the depended-on
5043 package(s) are only unpacked or in the "Half-Configured"
5044 state, provided that they have been configured
5045 correctly at some point in the past (and not removed
5046 or partially removed since). In this case, both the
5047 previously-configured and currently unpacked or
5048 "Half-Configured" versions must satisfy any version
5049 clause in the <tt>Pre-Depends</tt> field.
5053 When the package declaring a pre-dependency is about to
5054 be <em>configured</em>, the pre-dependency will be treated
5055 as a normal <tt>Depends</tt>. It will be considered
5056 satisfied only if the depended-on package has been
5057 correctly configured. However, unlike
5058 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5059 permit circular dependencies to be broken. If a circular
5060 dependency is encountered while attempting to honor
5061 <tt>Pre-Depends</tt>, the installation will be aborted.
5065 <tt>Pre-Depends</tt> are also required if the
5066 <prgn>preinst</prgn> script depends on the named package.
5067 It is best to avoid this situation if possible.
5071 <tt>Pre-Depends</tt> should be used sparingly,
5072 preferably only by packages whose premature upgrade or
5073 installation would hamper the ability of the system to
5074 continue with any upgrade that might be in progress.
5078 You should not specify a <tt>Pre-Depends</tt> entry for a
5079 package before this has been discussed on the
5080 <tt>debian-devel</tt> mailing list and a consensus about
5081 doing that has been reached. See <ref id="dependencies">.
5088 When selecting which level of dependency to use you should
5089 consider how important the depended-on package is to the
5090 functionality of the one declaring the dependency. Some
5091 packages are composed of components of varying degrees of
5092 importance. Such a package should list using
5093 <tt>Depends</tt> the package(s) which are required by the
5094 more important components. The other components'
5095 requirements may be mentioned as Suggestions or
5096 Recommendations, as appropriate to the components' relative
5102 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5105 When one binary package declares that it breaks another,
5106 <prgn>dpkg</prgn> will refuse to allow the package which
5107 declares <tt>Breaks</tt> to be unpacked unless the broken
5108 package is deconfigured first, and it will refuse to
5109 allow the broken package to be reconfigured.
5113 A package will not be regarded as causing breakage merely
5114 because its configuration files are still installed; it must
5115 be at least "Half-Installed".
5119 A special exception is made for packages which declare that
5120 they break their own package name or a virtual package which
5121 they provide (see below): this does not count as a real
5126 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5127 version clause; such a <tt>Breaks</tt> is introduced in the
5128 version of an (implicit or explicit) dependency which violates
5129 an assumption or reveals a bug in earlier versions of the broken
5130 package, or which takes over a file from earlier versions of the
5131 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5132 will inform higher-level package management tools that the
5133 broken package must be upgraded before the new one.
5137 If the breaking package also overwrites some files from the
5138 older package, it should use <tt>Replaces</tt> to ensure this
5139 goes smoothly. See <ref id="replaces"> for a full discussion
5140 of taking over files from other packages, including how to
5141 use <tt>Breaks</tt> in those cases.
5145 Many of the cases where <tt>Breaks</tt> should be used were
5146 previously handled with <tt>Conflicts</tt>
5147 because <tt>Breaks</tt> did not yet exist.
5148 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5149 See <ref id="conflicts"> for more information about the
5154 <sect id="conflicts">
5155 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5158 When one binary package declares a conflict with another using
5159 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5160 allow them to be unpacked on the system at the same time. This
5161 is a stronger restriction than <tt>Breaks</tt>, which prevents
5162 the broken package from being configured while the breaking
5163 package is in the "Unpacked" state but allows both packages to
5164 be unpacked at the same time.
5168 If one package is to be unpacked, the other must be removed
5169 first. If the package being unpacked is marked as replacing
5170 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5171 normally be used in this case) the one on the system, or the one
5172 on the system is marked as deselected, or both packages are
5173 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5174 automatically remove the package which is causing the conflict.
5175 Otherwise, it will halt the installation of the new package with
5176 an error. This mechanism is specifically designed to produce an
5177 error when the installed package is <tt>Essential</tt>, but the
5182 A package will not cause a conflict merely because its
5183 configuration files are still installed; it must be at least
5188 A special exception is made for packages which declare a
5189 conflict with their own package name, or with a virtual
5190 package which they provide (see below): this does not
5191 prevent their installation, and allows a package to conflict
5192 with others providing a replacement for it. You use this
5193 feature when you want the package in question to be the only
5194 package providing some feature.
5198 Normally, <tt>Breaks</tt> should be used instead
5199 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5200 stronger restriction on the ordering of package installation or
5201 upgrade and can make it more difficult for the package manager
5202 to find a correct solution to an upgrade or installation
5203 problem. <tt>Breaks</tt> should be used
5205 <item>when moving a file from one package to another (see
5206 <ref id="replaces">),</item>
5207 <item>when splitting a package (a special case of the previous
5209 <item>when the breaking package exposes a bug in or interacts
5210 badly with particular versions of the broken
5213 <tt>Conflicts</tt> should be used
5215 <item>when two packages provide the same file and will
5216 continue to do so,</item>
5217 <item>in conjunction with <tt>Provides</tt> when only one
5218 package providing a given virtual facility may be unpacked
5219 at a time (see <ref id="virtual">),</item>
5220 <item>in other cases where one must prevent simultaneous
5221 installation of two packages for reasons that are ongoing
5222 (not fixed in a later version of one of the packages) or
5223 that must prevent both packages from being unpacked at the
5224 same time, not just configured.</item>
5226 Be aware that adding <tt>Conflicts</tt> is normally not the best
5227 solution when two packages provide the same files. Depending on
5228 the reason for that conflict, using alternatives or renaming the
5229 files is often a better approach. See, for
5230 example, <ref id="binaries">.
5234 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5235 unless two packages cannot be installed at the same time or
5236 installing them both causes one of them to be broken or
5237 unusable. Having similar functionality or performing the same
5238 tasks as another package is not sufficient reason to
5239 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5243 A <tt>Conflicts</tt> entry may have an "earlier than" version
5244 clause if the reason for the conflict is corrected in a later
5245 version of one of the packages. However, normally the presence
5246 of an "earlier than" version clause is a sign
5247 that <tt>Breaks</tt> should have been used instead. An "earlier
5248 than" version clause in <tt>Conflicts</tt>
5249 prevents <prgn>dpkg</prgn> from upgrading or installing the
5250 package which declares such a conflict until the upgrade or
5251 removal of the conflicted-with package has been completed, which
5252 is a strong restriction.
5256 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5260 As well as the names of actual ("concrete") packages, the
5261 package relationship fields <tt>Depends</tt>,
5262 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5263 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5264 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5265 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5266 may mention "virtual packages".
5270 A <em>virtual package</em> is one which appears in the
5271 <tt>Provides</tt> control field of another package. The effect
5272 is as if the package(s) which provide a particular virtual
5273 package name had been listed by name everywhere the virtual
5274 package name appears. (See also <ref id="virtual_pkg">)
5278 If there are both concrete and virtual packages of the same
5279 name, then the dependency may be satisfied (or the conflict
5280 caused) by either the concrete package with the name in
5281 question or any other concrete package which provides the
5282 virtual package with the name in question. This is so that,
5283 for example, supposing we have
5284 <example compact="compact">
5287 </example> and someone else releases an enhanced version of
5288 the <tt>bar</tt> package they can say:
5289 <example compact="compact">
5293 and the <tt>bar-plus</tt> package will now also satisfy the
5294 dependency for the <tt>foo</tt> package.
5298 If a relationship field has a version number attached, only real
5299 packages will be considered to see whether the relationship is
5300 satisfied (or the prohibition violated, for a conflict or
5301 breakage). In other words, if a version number is specified,
5302 this is a request to ignore all <tt>Provides</tt> for that
5303 package name and consider only real packages. The package
5304 manager will assume that a package providing that virtual
5305 package is not of the "right" version. A <tt>Provides</tt>
5306 field may not contain version numbers, and the version number of
5307 the concrete package which provides a particular virtual package
5308 will not be considered when considering a dependency on or
5309 conflict with the virtual package name.<footnote>
5310 It is possible that a future release of <prgn>dpkg</prgn> may
5311 add the ability to specify a version number for each virtual
5312 package it provides. This feature is not yet present,
5313 however, and is expected to be used only infrequently.
5318 To specify which of a set of real packages should be the default
5319 to satisfy a particular dependency on a virtual package, list
5320 the real package as an alternative before the virtual one.
5324 If the virtual package represents a facility that can only be
5325 provided by one real package at a time, such as
5326 the <package>mail-transport-agent</package> virtual package that
5327 requires installation of a binary that would conflict with all
5328 other providers of that virtual package (see
5329 <ref id="mail-transport-agents">), all packages providing that
5330 virtual package should also declare a conflict with it
5331 using <tt>Conflicts</tt>. This will ensure that at most one
5332 provider of that virtual package is unpacked or installed at a
5337 <sect id="replaces"><heading>Overwriting files and replacing
5338 packages - <tt>Replaces</tt></heading>
5341 Packages can declare in their control file that they should
5342 overwrite files in certain other packages, or completely replace
5343 other packages. The <tt>Replaces</tt> control field has these
5344 two distinct purposes.
5347 <sect1><heading>Overwriting files in other packages</heading>
5350 It is usually an error for a package to contain files which
5351 are on the system in another package. However, if the
5352 overwriting package declares that it <tt>Replaces</tt> the one
5353 containing the file being overwritten, then <prgn>dpkg</prgn>
5354 will replace the file from the old package with that from the
5355 new. The file will no longer be listed as "owned" by the old
5356 package and will be taken over by the new package.
5357 Normally, <tt>Breaks</tt> should be used in conjunction
5358 with <tt>Replaces</tt>.<footnote>
5359 To see why <tt>Breaks</tt> is normally needed in addition
5360 to <tt>Replaces</tt>, consider the case of a file in the
5361 package <package>foo</package> being taken over by the
5362 package <package>foo-data</package>.
5363 <tt>Replaces</tt> will allow <package>foo-data</package> to
5364 be installed and take over that file. However,
5365 without <tt>Breaks</tt>, nothing
5366 requires <package>foo</package> to be upgraded to a newer
5367 version that knows it does not include that file and instead
5368 depends on <package>foo-data</package>. Nothing would
5369 prevent the new <package>foo-data</package> package from
5370 being installed and then removed, removing the file that it
5371 took over from <package>foo</package>. After that
5372 operation, the package manager would think the system was in
5373 a consistent state, but the <package>foo</package> package
5374 would be missing one of its files.
5379 For example, if a package <package>foo</package> is split
5380 into <package>foo</package> and <package>foo-data</package>
5381 starting at version 1.2-3, <package>foo-data</package> would
5383 <example compact="compact">
5384 Replaces: foo (<< 1.2-3)
5385 Breaks: foo (<< 1.2-3)
5387 in its control file. The new version of the
5388 package <package>foo</package> would normally have the field
5389 <example compact="compact">
5390 Depends: foo-data (>= 1.2-3)
5392 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5393 the files moved into <package>foo-data</package> are not
5394 required for normal operation).
5398 If a package is completely replaced in this way, so that
5399 <prgn>dpkg</prgn> does not know of any files it still
5400 contains, it is considered to have "disappeared". It will
5401 be marked as not wanted on the system (selected for
5402 removal) and not installed. Any <tt>conffile</tt>s
5403 details noted for the package will be ignored, as they
5404 will have been taken over by the overwriting package. The
5405 package's <prgn>postrm</prgn> script will be run with a
5406 special argument to allow the package to do any final
5407 cleanup required. See <ref id="mscriptsinstact">.
5409 Replaces is a one way relationship. You have to install
5410 the replacing package after the replaced package.
5415 For this usage of <tt>Replaces</tt>, virtual packages (see
5416 <ref id="virtual">) are not considered when looking at a
5417 <tt>Replaces</tt> field. The packages declared as being
5418 replaced must be mentioned by their real names.
5422 This usage of <tt>Replaces</tt> only takes effect when both
5423 packages are at least partially on the system at once. It is
5424 not relevant if the packages conflict unless the conflict has
5429 <sect1><heading>Replacing whole packages, forcing their
5433 Second, <tt>Replaces</tt> allows the packaging system to
5434 resolve which package should be removed when there is a
5435 conflict (see <ref id="conflicts">). This usage only takes
5436 effect when the two packages <em>do</em> conflict, so that the
5437 two usages of this field do not interfere with each other.
5441 In this situation, the package declared as being replaced
5442 can be a virtual package, so for example, all mail
5443 transport agents (MTAs) would have the following fields in
5444 their control files:
5445 <example compact="compact">
5446 Provides: mail-transport-agent
5447 Conflicts: mail-transport-agent
5448 Replaces: mail-transport-agent
5450 ensuring that only one MTA can be unpacked at any one
5451 time. See <ref id="virtual"> for more information about this
5456 <sect id="sourcebinarydeps">
5457 <heading>Relationships between source and binary packages -
5458 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5459 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5463 Source packages that require certain binary packages to be
5464 installed or absent at the time of building the package
5465 can declare relationships to those binary packages.
5469 This is done using the <tt>Build-Depends</tt>,
5470 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5471 <tt>Build-Conflicts-Indep</tt> control fields.
5475 Build-dependencies on "build-essential" binary packages can be
5476 omitted. Please see <ref id="pkg-relations"> for more information.
5480 The dependencies and conflicts they define must be satisfied
5481 (as defined earlier for binary packages) in order to invoke
5482 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5484 There is no Build-Depends-Arch; this role is essentially
5485 met with Build-Depends. Anyone building the
5486 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5487 assumed to be building the whole package, and therefore
5488 installation of all build dependencies is required.
5491 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5492 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5493 not yet know how to check for its existence, and
5494 <tt>binary-arch</tt>. The purpose of the original split
5495 between <tt>Build-Depends</tt> and
5496 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5497 wouldn't need to install extra packages needed only for the
5498 binary-indep targets. But without a build-arch/build-indep
5499 split, this didn't work, since most of the work is done in
5500 the build target, not in the binary target.
5504 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5505 <tt>binary-arch</tt></tag>
5507 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5508 fields must be satisfied when these targets are invoked.
5510 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5511 and <tt>binary-indep</tt></tag>
5513 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5514 <tt>Build-Depends-Indep</tt>, and
5515 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5516 these targets are invoked.
5522 <sect id="built-using">
5523 <heading>Additional source packages used to build the binary
5524 - <tt>Built-Using</tt>
5528 Some binary packages incorporate parts of other packages when built
5529 but do not have to depend on those packages. Examples include
5530 linking with static libraries or incorporating source code from
5531 another package during the build. In this case, the source packages
5532 of those other packages are a required part of the complete source
5533 (the binary package is not reproducible without them).
5537 A <tt>Built-Using</tt> field must list the corresponding source
5538 package for any such binary package incorporated during the build
5540 <tt>Build-Depends</tt> in the source package is not adequate since
5541 it (rightfully) does not document the exact version used in the
5544 including an "exactly equal" ("=") version relation on the version
5545 that was used to build that binary package<footnote>
5546 The archive software might reject packages that refer to
5547 non-existent sources.
5552 A package using the source code from the gcc-4.6-source
5553 binary package built from the gcc-4.6 source package would
5554 have this field in its control file:
5555 <example compact="compact">
5556 Built-Using: gcc-4.6 (= 4.6.0-11)
5561 A package including binaries from grub2 and loadlin would
5562 have this field in its control file:
5563 <example compact="compact">
5564 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5571 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5574 Packages containing shared libraries must be constructed with
5575 a little care to make sure that the shared library is always
5576 available. This is especially important for packages whose
5577 shared libraries are vitally important, such as the C library
5578 (currently <tt>libc6</tt>).
5582 This section deals only with public shared libraries: shared
5583 libraries that are placed in directories searched by the dynamic
5584 linker by default or which are intended to be linked against
5585 normally and possibly used by other, independent packages. Shared
5586 libraries that are internal to a particular package or that are
5587 only loaded as dynamic modules are not covered by this section and
5588 are not subject to its requirements.
5592 A shared library is identified by the <tt>SONAME</tt> attribute
5593 stored in its dynamic section. When a binary is linked against a
5594 shared library, the <tt>SONAME</tt> of the shared library is
5595 recorded in the binary's <tt>NEEDED</tt> section so that the
5596 dynamic linker knows that library must be loaded at runtime. The
5597 shared library file's full name (which usually contains additional
5598 version information not needed in the <tt>SONAME</tt>) is
5599 therefore normally not referenced directly. Instead, the shared
5600 library is loaded by its <tt>SONAME</tt>, which exists on the file
5601 system as a symlink pointing to the full name of the shared
5602 library. This symlink must be provided by the
5603 package. <ref id="sharedlibs-runtime"> describes how to do this.
5605 This is a convention of shared library versioning, but not a
5606 requirement. Some libraries use the <tt>SONAME</tt> as the full
5607 library file name instead and therefore do not need a symlink.
5608 Most, however, encode additional information about
5609 backwards-compatible revisions as a minor version number in the
5610 file name. The <tt>SONAME</tt> itself only changes when
5611 binaries linked with the earlier version of the shared library
5612 may no longer work, but the filename may change with each
5613 release of the library. See <ref id="sharedlibs-runtime"> for
5619 When linking a binary or another shared library against a shared
5620 library, the <tt>SONAME</tt> for that shared library is not yet
5621 known. Instead, the shared library is found by looking for a file
5622 matching the library name with <tt>.so</tt> appended. This file
5623 exists on the file system as a symlink pointing to the shared
5628 Shared libraries are normally split into several binary packages.
5629 The <tt>SONAME</tt> symlink is installed by the runtime shared
5630 library package, and the bare <tt>.so</tt> symlink is installed in
5631 the development package since it's only used when linking binaries
5632 or shared libraries. However, there are some exceptions for
5633 unusual shared libraries or for shared libraries that are also
5634 loaded as dynamic modules by other programs.
5638 This section is primarily concerned with how the separation of
5639 shared libraries into multiple packages should be done and how
5640 dependencies on and between shared library binary packages are
5641 managed in Debian. <ref id="libraries"> should be read in
5642 conjunction with this section and contains additional rules for
5643 the files contained in the shared library packages.
5646 <sect id="sharedlibs-runtime">
5647 <heading>Run-time shared libraries</heading>
5650 The run-time shared library must be placed in a package
5651 whose name changes whenever the <tt>SONAME</tt> of the shared
5652 library changes. This allows several versions of the shared
5653 library to be installed at the same time, allowing installation
5654 of the new version of the shared library without immediately
5655 breaking binaries that depend on the old version. Normally, the
5656 run-time shared library and its <tt>SONAME</tt> symlink should
5657 be placed in a package named
5658 <package><var>libraryname</var><var>soversion</var></package>,
5659 where <var>soversion</var> is the version number in
5660 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5661 would be confusing to directly append <var>soversion</var>
5662 to <var>libraryname</var> (if, for
5663 example, <var>libraryname</var> itself ends in a number), you
5665 <package><var>libraryname</var>-<var>soversion</var></package>
5670 To determine the <var>soversion</var>, look at
5671 the <tt>SONAME</tt> of the library, stored in the
5672 ELF <tt>SONAME</tt> attribute. It is usually of the
5673 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5674 example, <tt>libz.so.1</tt>). The version part is the part
5675 which comes after <tt>.so.</tt>, so in that example it
5676 is <tt>1</tt>. The soname may instead be of the
5677 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5678 as <tt>libdb-5.1.so</tt>, in which case the name would
5679 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5683 If you have several shared libraries built from the same source
5684 tree, you may lump them all together into a single shared
5685 library package provided that all of their <tt>SONAME</tt>s will
5686 always change together. Be aware that this is not normally the
5687 case, and if the <tt>SONAME</tt>s do not change together,
5688 upgrading such a merged shared library package will be
5689 unnecessarily difficult because of file conflicts with the old
5690 version of the package. When in doubt, always split shared
5691 library packages so that each binary package installs a single
5696 Every time the shared library ABI changes in a way that may
5697 break binaries linked against older versions of the shared
5698 library, the <tt>SONAME</tt> of the library and the
5699 corresponding name for the binary package containing the runtime
5700 shared library should change. Normally, this means
5701 the <tt>SONAME</tt> should change any time an interface is
5702 removed from the shared library or the signature of an interface
5703 (the number of parameters or the types of parameters that it
5704 takes, for example) is changed. This practice is vital to
5705 allowing clean upgrades from older versions of the package and
5706 clean transitions between the old ABI and new ABI without having
5707 to upgrade every affected package simultaneously.
5711 The <tt>SONAME</tt> and binary package name need not, and indeed
5712 normally should not, change if new interfaces are added but none
5713 are removed or changed, since this will not break binaries
5714 linked against the old shared library. Correct versioning of
5715 dependencies on the newer shared library by binaries that use
5716 the new interfaces is handled via
5717 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5718 or <tt>shlibs</tt> system</qref>.
5722 The package should install the shared libraries under
5723 their normal names. For example, the <package>libgdbm3</package>
5724 package should install <file>libgdbm.so.3.0.0</file> as
5725 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5726 renamed or re-linked by any <prgn>prerm</prgn> or
5727 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5728 of renaming things safely without affecting running programs,
5729 and attempts to interfere with this are likely to lead to
5734 Shared libraries should not be installed executable, since
5735 the dynamic linker does not require this and trying to
5736 execute a shared library usually results in a core dump.
5740 The run-time library package should include the symbolic link for
5741 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5742 the shared libraries. For example,
5743 the <package>libgdbm3</package> package should include a symbolic
5744 link from <file>/usr/lib/libgdbm.so.3</file> to
5745 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5746 linker (for example <prgn>ld.so</prgn> or
5747 <prgn>ld-linux.so.*</prgn>) can find the library between the
5748 time that <prgn>dpkg</prgn> installs it and the time that
5749 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5751 The package management system requires the library to be
5752 placed before the symbolic link pointing to it in the
5753 <file>.deb</file> file. This is so that when
5754 <prgn>dpkg</prgn> comes to install the symlink
5755 (overwriting the previous symlink pointing at an older
5756 version of the library), the new shared library is already
5757 in place. In the past, this was achieved by creating the
5758 library in the temporary packaging directory before
5759 creating the symlink. Unfortunately, this was not always
5760 effective, since the building of the tar file in the
5761 <file>.deb</file> depended on the behavior of the underlying
5762 file system. Some file systems (such as reiserfs) reorder
5763 the files so that the order of creation is forgotten.
5764 Since version 1.7.0, <prgn>dpkg</prgn>
5765 reorders the files itself as necessary when building a
5766 package. Thus it is no longer important to concern
5767 oneself with the order of file creation.
5771 <sect1 id="ldconfig">
5772 <heading><tt>ldconfig</tt></heading>
5775 Any package installing shared libraries in one of the default
5776 library directories of the dynamic linker (which are currently
5777 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5778 listed in <file>/etc/ld.so.conf</file><footnote>
5779 These are currently <file>/usr/local/lib</file> plus
5780 directories under <file>/lib</file> and <file>/usr/lib</file>
5781 matching the multiarch triplet for the system architecture.
5783 must use <prgn>ldconfig</prgn> to update the shared library
5788 The package maintainer scripts must only call
5789 <prgn>ldconfig</prgn> under these circumstances:
5790 <list compact="compact">
5791 <item>When the <prgn>postinst</prgn> script is run with a
5792 first argument of <tt>configure</tt>, the script must call
5793 <prgn>ldconfig</prgn>, and may optionally invoke
5794 <prgn>ldconfig</prgn> at other times.
5796 <item>When the <prgn>postrm</prgn> script is run with a
5797 first argument of <tt>remove</tt>, the script should call
5798 <prgn>ldconfig</prgn>.
5803 During install or upgrade, the preinst is called before
5804 the new files are unpacked, so calling "ldconfig" is
5805 pointless. The preinst of an existing package can also be
5806 called if an upgrade fails. However, this happens during
5807 the critical time when a shared libs may exist on-disk
5808 under a temporary name. Thus, it is dangerous and
5809 forbidden by current policy to call "ldconfig" at this
5814 When a package is installed or upgraded, "postinst
5815 configure" runs after the new files are safely on-disk.
5816 Since it is perfectly safe to invoke ldconfig
5817 unconditionally in a postinst, it is OK for a package to
5818 simply put ldconfig in its postinst without checking the
5819 argument. The postinst can also be called to recover from
5820 a failed upgrade. This happens before any new files are
5821 unpacked, so there is no reason to call "ldconfig" at this
5826 For a package that is being removed, prerm is
5827 called with all the files intact, so calling ldconfig is
5828 useless. The other calls to "prerm" happen in the case of
5829 upgrade at a time when all the files of the old package
5830 are on-disk, so again calling "ldconfig" is pointless.
5834 postrm, on the other hand, is called with the "remove"
5835 argument just after the files are removed, so this is
5836 the proper time to call "ldconfig" to notify the system
5837 of the fact that the shared libraries from the package
5838 are removed. The postrm can be called at several other
5839 times. At the time of "postrm purge", "postrm
5840 abort-install", or "postrm abort-upgrade", calling
5841 "ldconfig" is useless because the shared lib files are
5842 not on-disk. However, when "postrm" is invoked with
5843 arguments "upgrade", "failed-upgrade", or "disappear", a
5844 shared lib may exist on-disk under a temporary filename.
5852 <sect id="sharedlibs-support-files">
5853 <heading>Shared library support files</heading>
5856 If your package contains files whose names do not change with
5857 each change in the library shared object version, you must not
5858 put them in the shared library package. Otherwise, several
5859 versions of the shared library cannot be installed at the same
5860 time without filename clashes, making upgrades and transitions
5861 unnecessarily difficult.
5865 It is recommended that supporting files and run-time support
5866 programs that do not need to be invoked manually by users, but
5867 are nevertheless required for the package to function, be placed
5868 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5869 preferably under <file>/usr/lib/</file><var>package-name</var>.
5870 If the program or file is architecture independent, the
5871 recommendation is for it to be placed in a subdirectory of
5872 <file>/usr/share</file> instead, preferably under
5873 <file>/usr/share/</file><var>package-name</var>. Following the
5874 <var>package-name</var> naming convention ensures that the file
5875 names change when the shared object version changes.
5879 Run-time support programs that use the shared library but are
5880 not required for the library to function or files used by the
5881 shared library that can be used by any version of the shared
5882 library package should instead be put in a separate package.
5883 This package might typically be named
5884 <package><var>libraryname</var>-tools</package>; note the
5885 absence of the <var>soversion</var> in the package name.
5889 Files and support programs only useful when compiling software
5890 against the library should be included in the development
5891 package for the library.<footnote>
5892 For example, a <file><var>package-name</var>-config</file>
5893 script or <package>pkg-config</package> configuration files.
5898 <sect id="sharedlibs-static">
5899 <heading>Static libraries</heading>
5902 The static library (<file><var>libraryname.a</var></file>)
5903 is usually provided in addition to the shared version.
5904 It is placed into the development package (see below).
5908 In some cases, it is acceptable for a library to be
5909 available in static form only; these cases include:
5911 <item>libraries for languages whose shared library support
5912 is immature or unstable</item>
5913 <item>libraries whose interfaces are in flux or under
5914 development (commonly the case when the library's
5915 major version number is zero, or where the ABI breaks
5916 across patchlevels)</item>
5917 <item>libraries which are explicitly intended to be
5918 available only in static form by their upstream
5923 <sect id="sharedlibs-dev">
5924 <heading>Development files</heading>
5927 If there are development files associated with a shared library,
5928 the source package needs to generate a binary development package
5929 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5930 or if you prefer only to support one development version at a
5931 time, <package><var>libraryname</var>-dev</package>. Installing
5932 the development package must result in installation of all the
5933 development files necessary for compiling programs against that
5934 shared library.<footnote>
5935 This wording allows the development files to be split into
5936 several packages, such as a separate architecture-independent
5937 <package><var>libraryname</var>-headers</package>, provided that
5938 the development package depends on all the required additional
5944 In case several development versions of a library exist, you may
5945 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5946 <ref id="conflicts">) to ensure that the user only installs one
5947 development version at a time (as different development versions are
5948 likely to have the same header files in them, which would cause a
5949 filename clash if both were unpacked).
5953 The development package should contain a symlink for the associated
5954 shared library without a version number. For example, the
5955 <package>libgdbm-dev</package> package should include a symlink
5956 from <file>/usr/lib/libgdbm.so</file> to
5957 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5958 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5959 <file>libgdbm.so</file> when compiling dynamically.
5963 If the package provides Ada Library Information
5964 (<file>*.ali</file>) files for use with GNAT, these files must be
5965 installed read-only (mode 0444) so that GNAT will not attempt to
5966 recompile them. This overrides the normal file mode requirements
5967 given in <ref id="permissions-owners">.
5971 <sect id="sharedlibs-intradeps">
5972 <heading>Dependencies between the packages of the same library</heading>
5975 Typically the development version should have an exact
5976 version dependency on the runtime library, to make sure that
5977 compilation and linking happens correctly. The
5978 <tt>${binary:Version}</tt> substitution variable can be
5979 useful for this purpose.
5981 Previously, <tt>${Source-Version}</tt> was used, but its name
5982 was confusing and it has been deprecated since dpkg 1.13.19.
5987 <sect id="sharedlibs-depends">
5988 <heading>Dependencies between the library and other
5992 If a package contains a binary or library which links to a
5993 shared library, we must ensure that, when the package is
5994 installed on the system, all of the libraries needed are also
5995 installed. These dependencies must be added to the binary
5996 package when it is built, since they may change based on which
5997 version of a shared library the binary or library was linked
5998 with even if there are no changes to the source of the binary
5999 (for example, symbol versions change, macros become functions or
6000 vice versa, or the binary package may determine at compile-time
6001 whether new library interfaces are available and can be called).
6002 To allow these dependencies to be constructed, shared libraries
6003 must provide either a <file>symbols</file> file or
6004 a <file>shlibs</file> file. These provide information on the
6005 package dependencies required to ensure the presence of
6006 interfaces provided by this library. Any package with binaries
6007 or libraries linking to a shared library must use these files to
6008 determine the required dependencies when it is built. Other
6009 packages which use a shared library (for example using
6010 <tt>dlopen()</tt>) should compute appropriate dependencies
6011 using these files at build time as well.
6015 The two mechanisms differ in the degree of detail that they
6016 provide. A <file>symbols</file> file documents, for each symbol
6017 exported by a library, the minimal version of the package any
6018 binary using this symbol will need. This is typically the
6019 version of the package in which the symbol was introduced. This
6020 information permits detailed analysis of the symbols used by a
6021 particular package and construction of an accurate dependency,
6022 but it requires the package maintainer to track more information
6023 about the shared library.
6027 A <file>shlibs</file> file, in contrast, only documents the last
6028 time the library ABI changed in any way. It only provides
6029 information about the library as a whole, not individual
6030 symbols. When a package is built using a shared library with
6031 only a <file>shlibs</file> file, the generated dependency will
6032 require a version of the shared library equal to or newer than
6033 the version of the last ABI change. This generates
6034 unnecessarily restrictive dependencies compared
6035 to <file>symbols</file> files if none of the symbols used by the
6036 package have changed. This, in turn, may make upgrades
6037 needlessly complex and unnecessarily restrict use of the package
6038 on systems with older versions of the shared libraries.
6042 <file>shlibs</file> files also only support a limited range of
6043 library SONAMEs, making it difficult to use <file>shlibs</file>
6044 files in some unusual corner cases.<footnote>
6045 A <file>shlibs</file> file represents an SONAME as a library
6046 name and version number, such as <tt>libfoo VERSION</tt>,
6047 instead of recording the actual SONAME. If the SONAME doesn't
6048 match one of the two expected formats
6049 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6050 cannot be represented.
6055 <file>symbols</file> files are therefore recommended for most
6056 shared library packages since they provide more accurate
6057 dependencies. For most C libraries, the additional detail
6058 required by <file>symbols</file> files is not too difficult to
6059 maintain. However, maintaining exhaustive symbols information
6060 for a C++ library can be quite onerous, so <file>shlibs</file>
6061 files may be more appropriate for most C++ libraries. Libraries
6062 with a corresponding udeb must also provide
6063 a <file>shlibs</file> file, since the udeb infrastructure does
6064 not use <file>symbols</file> files.
6067 <sect1 id="dpkg-shlibdeps">
6068 <heading>Generating dependencies on shared libraries</heading>
6071 When a package that contains any shared libraries or compiled
6072 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6073 each shared library and compiled binary to determine the
6074 libraries used and hence the dependencies needed by the
6076 <prgn>dpkg-shlibdeps</prgn> will use a program
6077 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6078 the libraries and the symbols in those libraries directly
6079 needed by the binaries or shared libraries in the package.
6081 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6082 your <file>debian/rules</file> file in the source package.
6083 List all of the compiled binaries, libraries, or loadable
6084 modules in your package.<footnote>
6085 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6086 correctly is to use a package helper framework such
6087 as <package>debhelper</package>. If you are
6088 using <package>debhelper</package>,
6089 the <prgn>dh_shlibdeps</prgn> program will do this work for
6090 you. It will also correctly handle multi-binary packages.
6092 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6093 or <file>shlibs</file> files installed by the shared libraries
6094 to generate dependency information. The package must then
6095 provide a substitution variable into which the discovered
6096 dependency information can be placed.
6100 If you are creating a udeb for use in the Debian Installer,
6101 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6102 should use the dependency line of type <tt>udeb</tt> by adding
6103 the <tt>-tudeb</tt> option<footnote>
6104 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6105 will automatically add this option if it knows it is
6107 </footnote>. If there is no dependency line of
6108 type <tt>udeb</tt> in the <file>shlibs</file>
6109 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6110 regular dependency line.
6114 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6115 into the <file>debian/substvars</file> file by default, which
6116 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6117 to place a <tt>${shlibs:Depends}</tt> variable in
6118 the <tt>Depends</tt> field in the control file of every binary
6119 package built by this source package that contains compiled
6120 binaries, libraries, or loadable modules. If you have
6121 multiple binary packages, you will need to
6122 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6123 compiled libraries or binaries. For example, you could use
6124 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6125 specify a different <file>substvars</file> file for each
6126 binary package.<footnote>
6127 Again, <prgn>dh_shlibdeps</prgn>
6128 and <prgn>dh_gencontrol</prgn> will handle everything except
6129 the addition of the variable to the control file for you if
6130 you're using <package>debhelper</package>, including
6131 generating separate <file>substvars</file> files for each
6132 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6133 the appropriate flags.
6138 For more details on <prgn>dpkg-shlibdeps</prgn>,
6139 see <manref name="dpkg-shlibdeps" section="1">.
6143 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6144 library <tt>libbar</tt> if it is explicitly linked with that
6145 library (that is, the library is listed in the
6146 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6147 to the link line when the binary is created). Other libraries
6148 that are needed by <tt>libbar</tt> are
6149 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6150 linker will load them automatically when it
6151 loads <tt>libbar</tt>. A package should depend on the
6152 libraries it directly uses, but not the libraries it only uses
6153 indirectly. The dependencies for the libraries used
6154 directly will automatically pull in the indirectly-used
6155 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6156 automatically, but package maintainers need to be aware of
6157 this distinction between directly and indirectly using a
6158 library if they have to override its results for some reason.
6160 A good example of where this helps is the following. We
6161 could update <tt>libimlib</tt> with a new version that
6162 supports a new revision of a graphics format called dgf (but
6163 retaining the same major version number) and depends on a
6164 new library package <package>libdgf4</package> instead of
6165 the older <package>libdgf3</package>. If we
6166 used <prgn>ldd</prgn> to add dependencies for every library
6167 directly or indirectly linked with a binary, every package
6168 that uses <tt>libimlib</tt> would need to be recompiled so
6169 it would also depend on <package>libdgf4</package> in order
6170 to retire the older <package>libdgf3</package> package.
6171 Since dependencies are only added based on
6172 ELF <tt>NEEDED</tt> attribute, packages
6173 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6174 having the dependency on an appropriate version
6175 of <tt>libdgf</tt> and do not need rebuilding.
6180 <sect1 id="sharedlibs-updates">
6181 <heading>Shared library ABI changes</heading>
6184 Maintaining a shared library package using
6185 either <file>symbols</file> or <file>shlibs</file> files
6186 requires being aware of the exposed ABI of the shared library
6187 and any changes to it. Both <file>symbols</file>
6188 and <file>shlibs</file> files record every change to the ABI
6189 of the shared library; <file>symbols</file> files do so per
6190 public symbol, whereas <file>shlibs</file> files record only
6191 the last change for the entire library.
6195 There are two types of ABI changes: ones that are
6196 backward-compatible and ones that are not. An ABI change is
6197 backward-compatible if any reasonable program or library that
6198 was linked with the previous version of the shared library
6199 will still work correctly with the new version of the shared
6201 An example of an "unreasonable" program is one that uses
6202 library interfaces that are documented as internal and
6203 unsupported. If the only programs or libraries affected by
6204 a change are "unreasonable" ones, other techniques, such as
6205 declaring <tt>Breaks</tt> relationships with affected
6206 packages or treating their usage of the library as bugs in
6207 those packages, may be appropriate instead of changing the
6208 SONAME. However, the default approach is to change the
6209 SONAME for any change to the ABI that could break a program.
6211 Adding new symbols to the shared library is a
6212 backward-compatible change. Removing symbols from the shared
6213 library is not. Changing the behavior of a symbol may or may
6214 not be backward-compatible depending on the change; for
6215 example, changing a function to accept a new enum constant not
6216 previously used by the library is generally
6217 backward-compatible, but changing the members of a struct that
6218 is passed into library functions is generally not unless the
6219 library takes special precautions to accept old versions of
6224 ABI changes that are not backward-compatible normally require
6225 changing the <tt>SONAME</tt> of the library and therefore the
6226 shared library package name, which forces rebuilding all
6227 packages using that shared library to update their
6228 dependencies and allow them to use the new version of the
6229 shared library. For more information,
6230 see <ref id="sharedlibs-runtime">. The remainder of this
6231 section will deal with backward-compatible changes.
6235 Backward-compatible changes require either updating or
6236 recording the <var>minimal-version</var> for that symbol
6237 in <file>symbols</file> files or updating the version in
6238 the <var>dependencies</var> in <file>shlibs</file> files. For
6239 more information on how to do this in the two formats, see
6240 <ref id="symbols"> and <ref id="shlibs">. Below are general
6241 rules that apply to both files.
6245 The easy case is when a public symbol is added. Simply add
6246 the version at which the symbol was introduced
6247 (for <file>symbols</file> files) or update the dependency
6248 version (for <file>shlibs</file>) files. But special care
6249 should be taken to update dependency versions when the
6250 behavior of a public symbol changes. This is easy to neglect,
6251 since there is no automated method of determining such
6252 changes, but failing to update versions in this case may
6253 result in binary packages with too-weak dependencies that will
6254 fail at runtime, possibly in ways that can cause security
6255 vulnerabilities. If the package maintainer believes that a
6256 symbol behavior change may have occurred but isn't sure, it's
6257 safer to update the version rather than leave it unmodified.
6258 This may result in unnecessarily strict dependencies, but it
6259 ensures that packages whose dependencies are satisfied will
6264 A common example of when a change to the dependency version
6265 is required is a function that takes an enum or struct
6266 argument that controls what the function does. For example:
6268 enum library_op { OP_FOO, OP_BAR };
6269 int library_do_operation(enum library_op);
6271 If a new operation, <tt>OP_BAZ</tt>, is added,
6272 the <var>minimal-version</var>
6273 of <tt>library_do_operation</tt> (for <file>symbols</file>
6274 files) or the version in the dependency for the shared library
6275 (for <file>shlibs</file> files) must be increased to the
6276 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6277 binary built against the new version of the library (having
6278 detected at compile-time that the library
6279 supports <tt>OP_BAZ</tt>) may be installed with a shared
6280 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6281 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6286 Dependency versions in either <file>symbols</file>
6287 or <file>shlibs</file> files normally should not contain the
6288 Debian revision of the package, since the library behavior is
6289 normally fixed for a particular upstream version and any
6290 Debian packaging of that upstream version will have the same
6291 behavior. In the rare case that the library behavior was
6292 changed in a particular Debian revision, appending <tt>~</tt>
6293 to the end of the version that includes the Debian revision is
6294 recommended, since this allows backports of the shared library
6295 package using the normal backport versioning convention to
6296 satisfy the dependency.
6300 <sect1 id="sharedlibs-symbols">
6301 <heading>The <tt>symbols</tt> system</heading>
6304 In the following sections, we will first describe where the
6305 various <file>symbols</file> files are to be found, then
6306 the <file>symbols</file> file format, and finally how to
6307 create <file>symbols</file> files if your package contains a
6311 <sect2 id="symbols-paths">
6312 <heading>The <file>symbols</file> files present on the
6316 <file>symbols</file> files for a shared library are normally
6317 provided by the shared library package as a control file,
6318 but there are several override paths that are checked first
6319 in case that information is wrong or missing. The following
6320 list gives them in the order in which they are read
6321 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6322 the required information is used.
6325 <p><file>debian/*/DEBIAN/symbols</file></p>
6328 During the package build, if the package itself
6329 contains shared libraries with <file>symbols</file>
6330 files, they will be generated in these staging
6331 directories by <prgn>dpkg-gensymbols</prgn>
6332 (see <ref id="providing-symbols">). <file>symbols</file>
6333 files found in the build tree take precedence
6334 over <file>symbols</file> files from other binary
6339 These files must exist
6340 before <prgn>dpkg-shlibdeps</prgn> is run or the
6341 dependencies of binaries and libraries from a source
6342 package on other libraries from that same source
6343 package will not be correct. In practice, this means
6344 that <prgn>dpkg-gensymbols</prgn> must be run
6345 before <prgn>dpkg-shlibdeps</prgn> during the package
6347 An example may clarify. Suppose the source
6348 package <tt>foo</tt> generates two binary
6349 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6350 When building the binary packages, the contents of
6351 the packages are staged in the
6352 directories <file>debian/libfoo2</file>
6353 and <file>debian/foo-runtime</file> respectively.
6354 (<file>debian/tmp</file> could be used instead of
6355 one of these.) Since <tt>libfoo2</tt> provides
6356 the <tt>libfoo</tt> shared library, it will contain
6357 a <tt>symbols</tt> file, which will be installed
6358 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6359 eventually to be included as a control file in that
6360 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6362 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6364 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6365 to determine whether <tt>foo-prog</tt>'s library
6366 dependencies are satisfied by any of the libraries
6367 provided by <tt>libfoo2</tt>. Since those binaries
6368 were linked against the just-built shared library as
6369 part of the build process, the <file>symbols</file>
6370 file for the newly-built <tt>libfoo2</tt> must take
6371 precedence over a <file>symbols</file> file for any
6372 other <tt>libfoo2</tt> package already installed on
6380 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6381 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6385 Per-system overrides of shared library dependencies.
6386 These files normally do not exist. They are
6387 maintained by the local system administrator and must
6388 not be created by any Debian package.
6393 <p><file>symbols</file> control files for packages
6394 installed on the system</p>
6397 The <file>symbols</file> control files for all the
6398 packages currently installed on the system are
6399 searched last. This will be the most common source of
6400 shared library dependency information. These are
6402 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6403 packages should not rely on this and instead should
6404 use <tt>dpkg-query --control-path <var>package</var>
6405 symbols</tt> if for some reason these files need to be
6413 Be aware that if a <file>debian/shlibs.local</file> exists
6414 in the source package, it will override
6415 any <file>symbols</file> files. This is the only case where
6416 a <file>shlibs</file> is used despite <file>symbols</file>
6417 files being present. See <ref id="shlibs-paths">
6418 and <ref id="sharedlibs-shlibdeps"> for more information.
6422 <sect2 id="symbols">
6423 <heading>The <file>symbols</file> File Format</heading>
6426 The following documents the format of
6427 the <file>symbols</file> control file as included in binary
6428 packages. These files are built from
6429 template <file>symbols</file> files in the source package
6430 by <prgn>dpkg-gensymbols</prgn>. The template files support
6431 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6432 do some of the tedious work involved in
6433 maintaining <file>symbols</file> files, such as handling C++
6434 symbols or optional symbols that may not exist on particular
6435 architectures. When writing <file>symbols</file> files for
6436 a shared library package, refer
6437 to <manref name="dpkg-gensymbols" section="1"> for the
6442 A <file>symbols</file> may contain one or more entries, one
6443 for each shared library contained in the package
6444 corresponding to that <file>symbols</file>. Each entry has
6445 the following format:
6450 <var>library-soname</var> <var>main-dependency-template</var>
6451 [| <var>alternative-dependency-template</var>]
6453 [* <var>field-name</var>: <var>field-value</var>]
6455 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6460 To explain this format, we'll use the the <tt>zlib1g</tt>
6461 package as an example, which (at the time of writing)
6463 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6464 lines will be described first, followed by optional lines.
6468 <var>library-soname</var> must contain exactly the value of
6469 the ELF <tt>SONAME</tt> attribute of the shared library. In
6470 our example, this is <tt>libz.so.1</tt>.<footnote>
6471 This can be determined by using the command
6472 <example compact="compact">
6473 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6479 <var>main-dependency-template</var> has the same syntax as a
6480 dependency field in a binary package control file, except
6481 that the string <tt>#MINVER#</tt> is replaced by a version
6482 restriction like <tt>(>= <var>version</var>)</tt> or by
6483 nothing if an unversioned dependency is deemed sufficient.
6484 The version restriction will be based on which symbols from
6485 the shared library are referenced and the version at which
6486 they were introduced (see below). In nearly all
6487 cases, <var>main-dependency-template</var> will
6488 be <tt><var>package</var> #MINVER#</tt>,
6489 where <var>package</var> is the name of the binary package
6490 containing the shared library. This adds a simple,
6491 possibly-versioned dependency on the shared library package.
6492 In some rare cases, such as when multiple packages provide
6493 the same shared library ABI, the dependency template may
6494 need to be more complex.
6498 In our example, the first line of
6499 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6500 <example compact="compact">
6501 libz.so.1 zlib1g #MINVER#
6506 Each public symbol exported by the shared library must have
6507 a corresponding symbol line, indented by one
6508 space. <var>symbol</var> is the exported symbol (which, for
6509 C++, means the mangled symbol) followed by <tt>@</tt> and
6510 the symbol version, or the string <tt>Base</tt> if there is
6511 no symbol version. <var>minimal-version</var> is the most
6512 recent version of the shared library that changed the
6513 behavior of that symbol, whether by adding it, changing its
6514 function signature (the parameters, their types, or the
6515 return type), or changing its behavior in a way that is
6516 visible to a caller.
6517 <var>id-of-dependency-template</var> is an optional
6518 field that references
6519 an <var>alternative-dependency-template</var>; see below for
6524 For example, <tt>libz.so.1</tt> contains the
6525 symbols <tt>compress</tt>
6526 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6527 version and last changed its behavior in upstream
6528 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6529 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6530 upstream version <tt>1:1.2.0</tt>, and has not changed its
6531 behavior. Its <file>symbols</file> file therefore contains
6533 <example compact="compact">
6534 compress@Base 1:1.1.4
6535 compressBound@ZLIB_1.2.0 1:1.2.0
6537 Packages using only <tt>compress</tt> would then get a
6538 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6539 using <tt>compressBound</tt> would get a dependency
6540 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6544 One or more <var>alternative-dependency-template</var> lines
6545 may be provided. These are used in cases where some symbols
6546 in the shared library should use one dependency template
6547 while others should use a different template. The
6548 alternative dependency templates are used only if a symbol
6549 line contains the <var>id-of-dependency-template</var>
6550 field. The first alternative dependency template is
6551 numbered 1, the second 2, and so forth.<footnote>
6552 An example of where this may be needed is with a library
6553 that implements the libGL interface. All GL
6554 implementations provide the same set of base interfaces,
6555 and then may provide some additional interfaces only used
6556 by programs that require that specific GL implementation.
6557 So, for example, libgl1-mesa-glx may use the
6558 following <file>symbols</file> file:
6561 | libgl1-mesa-glx #MINVER#
6562 publicGlSymbol@Base 6.3-1
6564 implementationSpecificSymbol@Base 6.5.2-7 1
6567 Binaries or shared libraries using
6568 only <tt>publicGlSymbol</tt> would depend only
6569 on <tt>libgl1</tt> (which may be provided by multiple
6571 using <tt>implementationSpecificSymbol</tt> would get a
6572 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6577 Finally, the entry for the library may contain one or more
6578 metadata fields. Currently, the only
6579 supported <var>field-name</var>
6580 is <tt>Build-Depends-Package</tt>, whose value lists
6581 the <qref id="sharedlibs-dev">library development
6582 package</qref> on which packages using this shared library
6583 declare a build dependency. If this field is
6584 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6585 the resulting binary package dependency on the shared
6586 library is at least as strict as the source package
6587 dependency on the shared library development
6589 This field should normally not be necessary, since if the
6590 behavior of any symbol has changed, the corresponding
6591 symbol <var>minimal-version</var> should have been
6592 increased. But including it makes the <tt>symbols</tt>
6593 system more robust by tightening the dependency in cases
6594 where the package using the shared library specifically
6595 requires at least a particular version of the shared
6596 library development package for some reason.
6598 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6600 <example compact="compact">
6601 * Build-Depends-Package: zlib1g-dev
6606 Also see <manref name="deb-symbols" section="5">.
6610 <sect2 id="providing-symbols">
6611 <heading>Providing a <file>symbols</file> file</heading>
6614 If your package provides a shared library, you should
6615 arrange to include a <file>symbols</file> control file
6616 following the format described above in that package. You
6617 must include either a <file>symbols</file> control file or
6618 a <file>shlibs</file> control file.
6622 Normally, this is done by creating a <file>symbols</file> in
6624 named <file>debian/<var>package</var>.symbols</file>
6625 or <file>debian/symbols</file>, possibly
6626 with <file>.<var>arch</var></file> appended if the symbols
6627 information varies by architecture. This file may use the
6628 extended syntax documented in <manref name="dpkg-gensymbols"
6629 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6630 part of the package build process. It will
6631 create <file>symbols</file> files in the package staging
6632 area based on the binaries and libraries in the package
6633 staging area and the <file>symbols</file> files in the
6634 source package.<footnote>
6636 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6637 take care of calling either <prgn>dpkg-gensymbols</prgn>
6638 or generating a <file>shlibs</file> file as appropriate.
6643 Packages that provide <file>symbols</file> files must keep
6644 them up-to-date to ensure correct dependencies in packages
6645 that use the shared libraries. This means updating
6646 the <file>symbols</file> file whenever a new public symbol
6647 is added, changing the <var>minimal-version</var> field
6648 whenever a symbol changes behavior or signature in a
6649 backward-compatible way (see <ref id="sharedlibs-updates">),
6650 and changing the <var>library-soname</var>
6651 and <var>main-dependency-template</var>, and probably all of
6652 the <var>minimal-version</var> fields, when the library
6653 changes <tt>SONAME</tt>. Removing a public symbol from
6654 the <file>symbols</file> file because it's no longer
6655 provided by the library normally requires changing
6656 the <tt>SONAME</tt> of the library.
6657 See <ref id="sharedlibs-runtime"> for more information
6658 on <tt>SONAME</tt>s.
6663 <sect1 id="sharedlibs-shlibdeps">
6664 <heading>The <tt>shlibs</tt> system</heading>
6667 The <tt>shlibs</tt> system is a simpler alternative to
6668 the <tt>symbols</tt> system for declaring dependencies for
6669 shared libraries. It may be more appropriate for C++
6670 libraries and other cases where tracking individual symbols is
6671 too difficult. It predated the <tt>symbols</tt> system and is
6672 therefore frequently seen in older packages. It is also
6673 required for udebs, which do not support <tt>symbols</tt>.
6677 In the following sections, we will first describe where the
6678 various <file>shlibs</file> files are to be found, then how to
6679 use <prgn>dpkg-shlibdeps</prgn>, and finally
6680 the <file>shlibs</file> file format and how to create them.
6683 <sect2 id="shlibs-paths">
6684 <heading>The <file>shlibs</file> files present on the
6688 There are several places where <tt>shlibs</tt> files are
6689 found. The following list gives them in the order in which
6690 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6691 one which gives the required information is used.)
6694 <p><file>debian/shlibs.local</file></p>
6697 This lists overrides for this package. This file
6698 should normally not be used, but may be needed
6699 temporarily in unusual situations to work around bugs
6700 in other packages, or in unusual cases where the
6701 normally declared dependency information in the
6702 installed <file>shlibs</file> file for a library
6703 cannot be used. This file overrides information
6704 obtained from any other source.
6709 <p><file>/etc/dpkg/shlibs.override</file></p>
6712 This lists global overrides. This list is normally
6713 empty. It is maintained by the local system
6719 <p><file>DEBIAN/shlibs</file> files in the "build
6723 These files are generated as part of the package build
6724 process and staged for inclusion as control files in
6725 the binary packages being built. They provide details
6726 of any shared libraries included in the same package.
6731 <p><file>shlibs</file> control files for packages
6732 installed on the system</p>
6735 The <file>shlibs</file> control files for all the
6736 packages currently installed on the system. These are
6738 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6739 packages should not rely on this and instead should
6740 use <tt>dpkg-query --control-path <var>package</var>
6741 shlibs</tt> if for some reason these files need to be
6747 <p><file>/etc/dpkg/shlibs.default</file></p>
6750 This file lists any shared libraries whose packages
6751 have failed to provide correct <file>shlibs</file>
6752 files. It was used when the <file>shlibs</file> setup
6753 was first introduced, but it is now normally empty.
6754 It is maintained by the <tt>dpkg</tt> maintainer.
6761 If a <file>symbols</file> file for a shared library package
6762 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6763 in preference to a <file>shlibs</file>, with the exception
6764 of <file>debian/shlibs.local</file>. The latter overrides
6765 any other <file>shlibs</file> or <file>symbols</file> files.
6770 <heading>The <file>shlibs</file> File Format</heading>
6773 Each <file>shlibs</file> file has the same format. Lines
6774 beginning with <tt>#</tt> are considered to be comments and
6775 are ignored. Each line is of the form:
6776 <example compact="compact">
6777 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6782 We will explain this by reference to the example of the
6783 <tt>zlib1g</tt> package, which (at the time of writing)
6785 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6789 <var>type</var> is an optional element that indicates the
6790 type of package for which the line is valid. The only type
6791 currently in use is <tt>udeb</tt>. The colon and space
6792 after the type are required.
6796 <var>library-name</var> is the name of the shared library,
6797 in this case <tt>libz</tt>. (This must match the name part
6798 of the soname, see below.)
6802 <var>soname-version</var> is the version part of the
6803 ELF <tt>SONAME</tt> attribute of the library, determined the
6804 same way that the <var>soversion</var> component of the
6805 recommended shared library package name is determined.
6806 See <ref id="sharedlibs-runtime"> for the details.
6810 <var>dependencies</var> has the same syntax as a dependency
6811 field in a binary package control file. It should give
6812 details of which packages are required to satisfy a binary
6813 built against the version of the library contained in the
6814 package. See <ref id="depsyntax"> for details on the
6815 syntax, and <ref id="sharedlibs-updates"> for details on how
6816 to maintain the dependency version constraint.
6820 In our example, if the last change to the <tt>zlib1g</tt>
6821 package that could change behavior for a client of that
6822 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6823 the <tt>shlibs</tt> entry for this library could say:
6824 <example compact="compact">
6825 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6827 This version restriction must be new enough that any binary
6828 built against the current version of the library will work
6829 with any version of the shared library that satisfies that
6834 As zlib1g also provides a udeb containing the shared
6835 library, there would also be a second line:
6836 <example compact="compact">
6837 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6843 <heading>Providing a <file>shlibs</file> file</heading>
6846 To provide a <file>shlibs</file> file for a shared library
6847 binary package, create a <file>shlibs</file> file following
6848 the format described above and place it in
6849 the <file>DEBIAN</file> directory for that package during
6850 the build. It will then be included as a control file for
6851 that package<footnote>
6852 This is what <prgn>dh_makeshlibs</prgn> in
6853 the <package>debhelper</package> suite does. If your
6854 package also has a udeb that provides a shared
6855 library, <prgn>dh_makeshlibs</prgn> can automatically
6856 generate the <tt>udeb:</tt> lines if you specify the name
6857 of the udeb with the <tt>--add-udeb</tt> option.
6862 Since <prgn>dpkg-shlibdeps</prgn> reads
6863 the <file>DEBIAN/shlibs</file> files in all of the binary
6864 packages being built from this source package, all of
6865 the <file>DEBIAN/shlibs</file> files should be installed
6866 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6875 <chapt id="opersys"><heading>The Operating System</heading>
6878 <heading>File system hierarchy</heading>
6882 <heading>File System Structure</heading>
6885 The location of all files and directories must comply with the
6886 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6887 exceptions noted below, and except where doing so would
6888 violate other terms of Debian Policy. The following
6889 exceptions to the FHS apply:
6894 The optional rules related to user specific
6895 configuration files for applications are stored in
6896 the user's home directory are relaxed. It is
6897 recommended that such files start with the
6898 '<tt>.</tt>' character (a "dot file"), and if an
6899 application needs to create more than one dot file
6900 then the preferred placement is in a subdirectory
6901 with a name starting with a '.' character, (a "dot
6902 directory"). In this case it is recommended the
6903 configuration files not start with the '.'
6909 The requirement for amd64 to use <file>/lib64</file>
6910 for 64 bit binaries is removed.
6915 The requirement for object files, internal binaries, and
6916 libraries, including <file>libc.so.*</file>, to be located
6917 directly under <file>/lib{,32}</file> and
6918 <file>/usr/lib{,32}</file> is amended, permitting files
6919 to instead be installed to
6920 <file>/lib/<var>triplet</var></file> and
6921 <file>/usr/lib/<var>triplet</var></file>, where
6922 <tt><var>triplet</var></tt> is the value returned by
6923 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6924 architecture of the package. Packages may <em>not</em>
6925 install files to any <var>triplet</var> path other
6926 than the one matching the architecture of that package;
6927 for instance, an <tt>Architecture: amd64</tt> package
6928 containing 32-bit x86 libraries may not install these
6929 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6931 This is necessary in order to reserve the directories for
6932 use in cross-installation of library packages from other
6933 architectures, as part of the planned deployment of
6938 Applications may also use a single subdirectory under
6939 <file>/usr/lib/<var>triplet</var></file>.
6942 The execution time linker/loader, ld*, must still be made
6943 available in the existing location under /lib or /lib64
6944 since this is part of the ELF ABI for the architecture.
6949 The requirement that
6950 <file>/usr/local/share/man</file> be "synonymous"
6951 with <file>/usr/local/man</file> is relaxed to a
6956 The requirement that windowmanagers with a single
6957 configuration file call it <file>system.*wmrc</file>
6958 is removed, as is the restriction that the window
6959 manager subdirectory be named identically to the
6960 window manager name itself.
6965 The requirement that boot manager configuration
6966 files live in <file>/etc</file>, or at least are
6967 symlinked there, is relaxed to a recommendation.
6972 The additional directory <file>/run</file> in the root
6973 file system is allowed. <file>/run</file>
6974 replaces <file>/var/run</file>, and the
6975 subdirectory <file>/run/lock</file>
6976 replaces <file>/var/lock</file>, with
6977 the <file>/var</file> directories replaced by symlinks
6978 for backwards compatibility. <file>/run</file>
6979 and <file>/run/lock</file> must follow all of the
6980 requirements in the FHS for <file>/var/run</file>
6981 and <file>/var/lock</file>, respectively, such as file
6982 naming conventions, file format requirements, or the
6983 requirement that files be cleared during the boot
6984 process. Files and directories residing
6985 in <file>/run</file> should be stored on a temporary
6989 Packages must not assume the <file>/run</file>
6990 directory exists or is usable without a dependency
6991 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
6992 stable release of Debian supports <file>/run</file>.
6997 The following directories in the root filesystem are
6998 additionally allowed: <file>/sys</file> and
6999 <file>/selinux</file>. <footnote>These directories
7000 are used as mount points to mount virtual filesystems
7001 to get access to kernel information.</footnote>
7006 On GNU/Hurd systems, the following additional
7007 directories are allowed in the root
7008 filesystem: <file>/hurd</file>
7009 and <file>/servers</file>.<footnote>
7010 These directories are used to store translators and as
7011 a set of standard names for mount points,
7020 The version of this document referred here can be
7021 found in the <tt>debian-policy</tt> package or on <url
7022 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7023 name="FHS (Debian copy)"> alongside this manual (or, if
7024 you have the <package>debian-policy</package> installed,
7026 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7027 (local copy)">). The
7028 latest version, which may be a more recent version, may
7030 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7031 Specific questions about following the standard may be
7032 asked on the <tt>debian-devel</tt> mailing list, or
7033 referred to the FHS mailing list (see the
7034 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7040 <heading>Site-specific programs</heading>
7043 As mandated by the FHS, packages must not place any
7044 files in <file>/usr/local</file>, either by putting them in
7045 the file system archive to be unpacked by <prgn>dpkg</prgn>
7046 or by manipulating them in their maintainer scripts.
7050 However, the package may create empty directories below
7051 <file>/usr/local</file> so that the system administrator knows
7052 where to place site-specific files. These are not
7053 directories <em>in</em> <file>/usr/local</file>, but are
7054 children of directories in <file>/usr/local</file>. These
7055 directories (<file>/usr/local/*/dir/</file>)
7056 should be removed on package removal if they are
7061 Note that this applies only to
7062 directories <em>below</em> <file>/usr/local</file>,
7063 not <em>in</em> <file>/usr/local</file>. Packages must
7064 not create sub-directories in the
7065 directory <file>/usr/local</file> itself, except those
7066 listed in FHS, section 4.5. However, you may create
7067 directories below them as you wish. You must not remove
7068 any of the directories listed in 4.5, even if you created
7073 Since <file>/usr/local</file> can be mounted read-only from a
7074 remote server, these directories must be created and
7075 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7076 maintainer scripts and not be included in the
7077 <file>.deb</file> archive. These scripts must not fail if
7078 either of these operations fail.
7082 For example, the <tt>emacsen-common</tt> package could
7083 contain something like
7084 <example compact="compact">
7085 if [ ! -e /usr/local/share/emacs ]; then
7086 if mkdir /usr/local/share/emacs 2>/dev/null; then
7087 if chown root:staff /usr/local/share/emacs; then
7088 chmod 2775 /usr/local/share/emacs || true
7093 in its <prgn>postinst</prgn> script, and
7094 <example compact="compact">
7095 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7096 rmdir /usr/local/share/emacs 2>/dev/null || true
7098 in the <prgn>prerm</prgn> script. (Note that this form is
7099 used to ensure that if the script is interrupted, the
7100 directory <file>/usr/local/share/emacs</file> will still be
7105 If you do create a directory in <file>/usr/local</file> for
7106 local additions to a package, you should ensure that
7107 settings in <file>/usr/local</file> take precedence over the
7108 equivalents in <file>/usr</file>.
7112 However, because <file>/usr/local</file> and its contents are
7113 for exclusive use of the local administrator, a package
7114 must not rely on the presence or absence of files or
7115 directories in <file>/usr/local</file> for normal operation.
7119 The <file>/usr/local</file> directory itself and all the
7120 subdirectories created by the package should (by default) have
7121 permissions 2775 (group-writable and set-group-id) and be
7122 owned by <tt>root:staff</tt>.
7127 <heading>The system-wide mail directory</heading>
7129 The system-wide mail directory
7130 is <file>/var/mail</file>. This directory is part of the
7131 base system and should not be owned by any particular mail
7132 agents. The use of the old
7133 location <file>/var/spool/mail</file> is deprecated, even
7134 though the spool may still be physically located there.
7138 <sect1 id="fhs-run">
7139 <heading><file>/run</file> and <file>/run/lock</file></heading>
7142 The directory <file>/run</file> is cleared at boot, normally
7143 by being a mount point for a temporary file system. Packages
7144 therefore must not assume that any files or directories
7145 under <file>/run</file> other than <file>/run/lock</file>
7146 exist unless the package has arranged to create those files or
7147 directories since the last reboot. Normally, this is done by
7148 the package via an init script. See <ref id="writing-init">
7149 for more information.
7153 Packages must not include files or directories
7154 under <file>/run</file>, or under the
7155 older <file>/var/run</file> and <file>/var/lock</file> paths.
7156 The latter paths will normally be symlinks or other
7157 redirections to <file>/run</file> for backwards compatibility.
7163 <heading>Users and groups</heading>
7166 <heading>Introduction</heading>
7168 The Debian system can be configured to use either plain or
7173 Some user ids (UIDs) and group ids (GIDs) are reserved
7174 globally for use by certain packages. Because some
7175 packages need to include files which are owned by these
7176 users or groups, or need the ids compiled into binaries,
7177 these ids must be used on any Debian system only for the
7178 purpose for which they are allocated. This is a serious
7179 restriction, and we should avoid getting in the way of
7180 local administration policies. In particular, many sites
7181 allocate users and/or local system groups starting at 100.
7185 Apart from this we should have dynamically allocated ids,
7186 which should by default be arranged in some sensible
7187 order, but the behavior should be configurable.
7191 Packages other than <tt>base-passwd</tt> must not modify
7192 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7193 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7198 <heading>UID and GID classes</heading>
7200 The UID and GID numbers are divided into classes as
7206 Globally allocated by the Debian project, the same
7207 on every Debian system. These ids will appear in
7208 the <file>passwd</file> and <file>group</file> files of all
7209 Debian systems, new ids in this range being added
7210 automatically as the <tt>base-passwd</tt> package is
7215 Packages which need a single statically allocated
7216 uid or gid should use one of these; their
7217 maintainers should ask the <tt>base-passwd</tt>
7225 Dynamically allocated system users and groups.
7226 Packages which need a user or group, but can have
7227 this user or group allocated dynamically and
7228 differently on each system, should use <tt>adduser
7229 --system</tt> to create the group and/or user.
7230 <prgn>adduser</prgn> will check for the existence of
7231 the user or group, and if necessary choose an unused
7232 id based on the ranges specified in
7233 <file>adduser.conf</file>.
7237 <tag>1000-59999:</tag>
7240 Dynamically allocated user accounts. By default
7241 <prgn>adduser</prgn> will choose UIDs and GIDs for
7242 user accounts in this range, though
7243 <file>adduser.conf</file> may be used to modify this
7248 <tag>60000-64999:</tag>
7251 Globally allocated by the Debian project, but only
7252 created on demand. The ids are allocated centrally
7253 and statically, but the actual accounts are only
7254 created on users' systems on demand.
7258 These ids are for packages which are obscure or
7259 which require many statically-allocated ids. These
7260 packages should check for and create the accounts in
7261 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7262 <prgn>adduser</prgn> if it has this facility) if
7263 necessary. Packages which are likely to require
7264 further allocations should have a "hole" left after
7265 them in the allocation, to give them room to
7270 <tag>65000-65533:</tag>
7278 User <tt>nobody</tt>. The corresponding gid refers
7279 to the group <tt>nogroup</tt>.
7286 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7287 not</em> be used, because it is the error return
7296 <sect id="sysvinit">
7297 <heading>System run levels and <file>init.d</file> scripts</heading>
7299 <sect1 id="/etc/init.d">
7300 <heading>Introduction</heading>
7303 The <file>/etc/init.d</file> directory contains the scripts
7304 executed by <prgn>init</prgn> at boot time and when the
7305 init state (or "runlevel") is changed (see <manref
7306 name="init" section="8">).
7310 There are at least two different, yet functionally
7311 equivalent, ways of handling these scripts. For the sake
7312 of simplicity, this document describes only the symbolic
7313 link method. However, it must not be assumed by maintainer
7314 scripts that this method is being used, and any automated
7315 manipulation of the various runlevel behaviors by
7316 maintainer scripts must be performed using
7317 <prgn>update-rc.d</prgn> as described below and not by
7318 manually installing or removing symlinks. For information
7319 on the implementation details of the other method,
7320 implemented in the <tt>file-rc</tt> package, please refer
7321 to the documentation of that package.
7325 These scripts are referenced by symbolic links in the
7326 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7327 runlevels, <prgn>init</prgn> looks in the directory
7328 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7329 execute, where <tt><var>n</var></tt> is the runlevel that
7330 is being changed to, or <tt>S</tt> for the boot-up
7335 The names of the links all have the form
7336 <file>S<var>mm</var><var>script</var></file> or
7337 <file>K<var>mm</var><var>script</var></file> where
7338 <var>mm</var> is a two-digit number and <var>script</var>
7339 is the name of the script (this should be the same as the
7340 name of the actual script in <file>/etc/init.d</file>).
7344 When <prgn>init</prgn> changes runlevel first the targets
7345 of the links whose names start with a <tt>K</tt> are
7346 executed, each with the single argument <tt>stop</tt>,
7347 followed by the scripts prefixed with an <tt>S</tt>, each
7348 with the single argument <tt>start</tt>. (The links are
7349 those in the <file>/etc/rc<var>n</var>.d</file> directory
7350 corresponding to the new runlevel.) The <tt>K</tt> links
7351 are responsible for killing services and the <tt>S</tt>
7352 link for starting services upon entering the runlevel.
7356 For example, if we are changing from runlevel 2 to
7357 runlevel 3, init will first execute all of the <tt>K</tt>
7358 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7359 all of the <tt>S</tt> prefixed scripts in that directory.
7360 The links starting with <tt>K</tt> will cause the
7361 referred-to file to be executed with an argument of
7362 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7367 The two-digit number <var>mm</var> is used to determine
7368 the order in which to run the scripts: low-numbered links
7369 have their scripts run first. For example, the
7370 <tt>K20</tt> scripts will be executed before the
7371 <tt>K30</tt> scripts. This is used when a certain service
7372 must be started before another. For example, the name
7373 server <prgn>bind</prgn> might need to be started before
7374 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7375 can set up its access lists. In this case, the script
7376 that starts <prgn>bind</prgn> would have a lower number
7377 than the script that starts <prgn>inn</prgn> so that it
7379 <example compact="compact">
7386 The two runlevels 0 (halt) and 6 (reboot) are slightly
7387 different. In these runlevels, the links with an
7388 <tt>S</tt> prefix are still called after those with a
7389 <tt>K</tt> prefix, but they too are called with the single
7390 argument <tt>stop</tt>.
7394 <sect1 id="writing-init">
7395 <heading>Writing the scripts</heading>
7398 Packages that include daemons for system services should
7399 place scripts in <file>/etc/init.d</file> to start or stop
7400 services at boot time or during a change of runlevel.
7401 These scripts should be named
7402 <file>/etc/init.d/<var>package</var></file>, and they should
7403 accept one argument, saying what to do:
7406 <tag><tt>start</tt></tag>
7407 <item>start the service,</item>
7409 <tag><tt>stop</tt></tag>
7410 <item>stop the service,</item>
7412 <tag><tt>restart</tt></tag>
7413 <item>stop and restart the service if it's already running,
7414 otherwise start the service</item>
7416 <tag><tt>reload</tt></tag>
7417 <item><p>cause the configuration of the service to be
7418 reloaded without actually stopping and restarting
7421 <tag><tt>force-reload</tt></tag>
7422 <item>cause the configuration to be reloaded if the
7423 service supports this, otherwise restart the
7427 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7428 <tt>force-reload</tt> options should be supported by all
7429 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7434 The <file>init.d</file> scripts must ensure that they will
7435 behave sensibly (i.e., returning success and not starting
7436 multiple copies of a service) if invoked with <tt>start</tt>
7437 when the service is already running, or with <tt>stop</tt>
7438 when it isn't, and that they don't kill unfortunately-named
7439 user processes. The best way to achieve this is usually to
7440 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7445 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7446 scripts. Writing correct <file>init.d</file> scripts requires
7447 accepting various error exit statuses when daemons are already
7448 running or already stopped without aborting
7449 the <file>init.d</file> script, and common <file>init.d</file>
7450 function libraries are not safe to call with <tt>set -e</tt>
7452 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7453 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7454 in effect and echoing status messages to the console fails,
7456 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7457 to not use <tt>set -e</tt> and instead check the result of
7458 each command separately.
7462 If a service reloads its configuration automatically (as
7463 in the case of <prgn>cron</prgn>, for example), the
7464 <tt>reload</tt> option of the <file>init.d</file> script
7465 should behave as if the configuration has been reloaded
7470 The <file>/etc/init.d</file> scripts must be treated as
7471 configuration files, either (if they are present in the
7472 package, that is, in the .deb file) by marking them as
7473 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7474 by managing them correctly in the maintainer scripts (see
7475 <ref id="config-files">). This is important since we want
7476 to give the local system administrator the chance to adapt
7477 the scripts to the local system, e.g., to disable a
7478 service without de-installing the package, or to specify
7479 some special command line options when starting a service,
7480 while making sure their changes aren't lost during the next
7485 These scripts should not fail obscurely when the
7486 configuration files remain but the package has been
7487 removed, as configuration files remain on the system after
7488 the package has been removed. Only when <prgn>dpkg</prgn>
7489 is executed with the <tt>--purge</tt> option will
7490 configuration files be removed. In particular, as the
7491 <file>/etc/init.d/<var>package</var></file> script itself is
7492 usually a <tt>conffile</tt>, it will remain on the system
7493 if the package is removed but not purged. Therefore, you
7494 should include a <tt>test</tt> statement at the top of the
7496 <example compact="compact">
7497 test -f <var>program-executed-later-in-script</var> || exit 0
7502 Often there are some variables in the <file>init.d</file>
7503 scripts whose values control the behavior of the scripts,
7504 and which a system administrator is likely to want to
7505 change. As the scripts themselves are frequently
7506 <tt>conffile</tt>s, modifying them requires that the
7507 administrator merge in their changes each time the package
7508 is upgraded and the <tt>conffile</tt> changes. To ease
7509 the burden on the system administrator, such configurable
7510 values should not be placed directly in the script.
7511 Instead, they should be placed in a file in
7512 <file>/etc/default</file>, which typically will have the same
7513 base name as the <file>init.d</file> script. This extra file
7514 should be sourced by the script when the script runs. It
7515 must contain only variable settings and comments in SUSv3
7516 <prgn>sh</prgn> format. It may either be a
7517 <tt>conffile</tt> or a configuration file maintained by
7518 the package maintainer scripts. See <ref id="config-files">
7523 To ensure that vital configurable values are always
7524 available, the <file>init.d</file> script should set default
7525 values for each of the shell variables it uses, either
7526 before sourcing the <file>/etc/default/</file> file or
7527 afterwards using something like the <tt>:
7528 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7529 script must behave sensibly and not fail if the
7530 <file>/etc/default</file> file is deleted.
7534 Files and directories under <file>/run</file>, including ones
7535 referred to via the compatibility paths <file>/var/run</file>
7536 and <file>/var/lock</file>, are normally stored on a temporary
7537 filesystem and are normally not persistent across a reboot.
7538 The <file>init.d</file> scripts must handle this correctly.
7539 This will typically mean creating any required subdirectories
7540 dynamically when the <file>init.d</file> script is run.
7541 See <ref id="fhs-run"> for more information.
7546 <heading>Interfacing with the initscript system</heading>
7549 Maintainers should use the abstraction layer provided by
7550 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7551 programs to deal with initscripts in their packages'
7552 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7553 and <prgn>postrm</prgn>.
7557 Directly managing the /etc/rc?.d links and directly
7558 invoking the <file>/etc/init.d/</file> initscripts should
7559 be done only by packages providing the initscript
7560 subsystem (such as <prgn>sysv-rc</prgn> and
7561 <prgn>file-rc</prgn>).
7565 <heading>Managing the links</heading>
7568 The program <prgn>update-rc.d</prgn> is provided for
7569 package maintainers to arrange for the proper creation and
7570 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7571 or their functional equivalent if another method is being
7572 used. This may be used by maintainers in their packages'
7573 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7577 You must not include any <file>/etc/rc<var>n</var>.d</file>
7578 symbolic links in the actual archive or manually create or
7579 remove the symbolic links in maintainer scripts; you must
7580 use the <prgn>update-rc.d</prgn> program instead. (The
7581 former will fail if an alternative method of maintaining
7582 runlevel information is being used.) You must not include
7583 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7584 in the archive either. (Only the <tt>sysvinit</tt>
7589 By default <prgn>update-rc.d</prgn> will start services in
7590 each of the multi-user state runlevels (2, 3, 4, and 5)
7591 and stop them in the halt runlevel (0), the single-user
7592 runlevel (1) and the reboot runlevel (6). The system
7593 administrator will have the opportunity to customize
7594 runlevels by simply adding, moving, or removing the
7595 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7596 symbolic links are being used, or by modifying
7597 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7602 To get the default behavior for your package, put in your
7603 <prgn>postinst</prgn> script
7604 <example compact="compact">
7605 update-rc.d <var>package</var> defaults
7607 and in your <prgn>postrm</prgn>
7608 <example compact="compact">
7609 if [ "$1" = purge ]; then
7610 update-rc.d <var>package</var> remove
7612 </example>. Note that if your package changes runlevels
7613 or priority, you may have to remove and recreate the links,
7614 since otherwise the old links may persist. Refer to the
7615 documentation of <prgn>update-rc.d</prgn>.
7619 This will use a default sequence number of 20. If it does
7620 not matter when or in which order the <file>init.d</file>
7621 script is run, use this default. If it does, then you
7622 should talk to the maintainer of the <prgn>sysvinit</prgn>
7623 package or post to <tt>debian-devel</tt>, and they will
7624 help you choose a number.
7628 For more information about using <tt>update-rc.d</tt>,
7629 please consult its man page <manref name="update-rc.d"
7635 <heading>Running initscripts</heading>
7637 The program <prgn>invoke-rc.d</prgn> is provided to make
7638 it easier for package maintainers to properly invoke an
7639 initscript, obeying runlevel and other locally-defined
7640 constraints that might limit a package's right to start,
7641 stop and otherwise manage services. This program may be
7642 used by maintainers in their packages' scripts.
7646 The package maintainer scripts must use
7647 <prgn>invoke-rc.d</prgn> to invoke the
7648 <file>/etc/init.d/*</file> initscripts, instead of
7649 calling them directly.
7653 By default, <prgn>invoke-rc.d</prgn> will pass any
7654 action requests (start, stop, reload, restart...) to the
7655 <file>/etc/init.d</file> script, filtering out requests
7656 to start or restart a service out of its intended
7661 Most packages will simply need to change:
7662 <example compact="compact">/etc/init.d/<package>
7663 <action></example> in their <prgn>postinst</prgn>
7664 and <prgn>prerm</prgn> scripts to:
7665 <example compact="compact">
7666 if which invoke-rc.d >/dev/null 2>&1; then
7667 invoke-rc.d <var>package</var> <action>
7669 /etc/init.d/<var>package</var> <action>
7675 A package should register its initscript services using
7676 <prgn>update-rc.d</prgn> before it tries to invoke them
7677 using <prgn>invoke-rc.d</prgn>. Invocation of
7678 unregistered services may fail.
7682 For more information about using
7683 <prgn>invoke-rc.d</prgn>, please consult its man page
7684 <manref name="invoke-rc.d" section="8">.
7690 <heading>Boot-time initialization</heading>
7693 There used to be another directory, <file>/etc/rc.boot</file>,
7694 which contained scripts which were run once per machine
7695 boot. This has been deprecated in favour of links from
7696 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7697 described in <ref id="/etc/init.d">. Packages must not
7698 place files in <file>/etc/rc.boot</file>.
7703 <heading>Example</heading>
7706 An example on which you can base your
7707 <file>/etc/init.d</file> scripts is found in
7708 <file>/etc/init.d/skeleton</file>.
7715 <heading>Console messages from <file>init.d</file> scripts</heading>
7718 This section describes the formats to be used for messages
7719 written to standard output by the <file>/etc/init.d</file>
7720 scripts. The intent is to improve the consistency of
7721 Debian's startup and shutdown look and feel. For this
7722 reason, please look very carefully at the details. We want
7723 the messages to have the same format in terms of wording,
7724 spaces, punctuation and case of letters.
7728 Here is a list of overall rules that should be used for
7729 messages generated by <file>/etc/init.d</file> scripts.
7735 The message should fit in one line (fewer than 80
7736 characters), start with a capital letter and end with
7737 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7741 If the script is performing some time consuming task in
7742 the background (not merely starting or stopping a
7743 program, for instance), an ellipsis (three dots:
7744 <tt>...</tt>) should be output to the screen, with no
7745 leading or tailing whitespace or line feeds.
7749 The messages should appear as if the computer is telling
7750 the user what it is doing (politely :-), but should not
7751 mention "it" directly. For example, instead of:
7752 <example compact="compact">
7753 I'm starting network daemons: nfsd mountd.
7755 the message should say
7756 <example compact="compact">
7757 Starting network daemons: nfsd mountd.
7764 <tt>init.d</tt> script should use the following standard
7765 message formats for the situations enumerated below.
7771 <p>When daemons are started</p>
7774 If the script starts one or more daemons, the output
7775 should look like this (a single line, no leading
7777 <example compact="compact">
7778 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7780 The <var>description</var> should describe the
7781 subsystem the daemon or set of daemons are part of,
7782 while <var>daemon-1</var> up to <var>daemon-n</var>
7783 denote each daemon's name (typically the file name of
7788 For example, the output of <file>/etc/init.d/lpd</file>
7790 <example compact="compact">
7791 Starting printer spooler: lpd.
7796 This can be achieved by saying
7797 <example compact="compact">
7798 echo -n "Starting printer spooler: lpd"
7799 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7802 in the script. If there are more than one daemon to
7803 start, the output should look like this:
7804 <example compact="compact">
7805 echo -n "Starting remote file system services:"
7806 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7807 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7808 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7811 This makes it possible for the user to see what is
7812 happening and when the final daemon has been started.
7813 Care should be taken in the placement of white spaces:
7814 in the example above the system administrators can
7815 easily comment out a line if they don't want to start
7816 a specific daemon, while the displayed message still
7822 <p>When a system parameter is being set</p>
7825 If you have to set up different system parameters
7826 during the system boot, you should use this format:
7827 <example compact="compact">
7828 Setting <var>parameter</var> to "<var>value</var>".
7833 You can use a statement such as the following to get
7835 <example compact="compact">
7836 echo "Setting DNS domainname to \"$domainname\"."
7841 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7842 for the left and right quotation marks. A grave accent
7843 (<tt>`</tt>) is not a quote character; neither is an
7844 apostrophe (<tt>'</tt>).
7849 <p>When a daemon is stopped or restarted</p>
7852 When you stop or restart a daemon, you should issue a
7853 message identical to the startup message, except that
7854 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7855 or <tt>Restarting</tt> respectively.
7859 For example, stopping the printer daemon will look like
7861 <example compact="compact">
7862 Stopping printer spooler: lpd.
7868 <p>When something is executed</p>
7871 There are several examples where you have to run a
7872 program at system startup or shutdown to perform a
7873 specific task, for example, setting the system's clock
7874 using <prgn>netdate</prgn> or killing all processes
7875 when the system shuts down. Your message should look
7877 <example compact="compact">
7878 Doing something very useful...done.
7880 You should print the <tt>done.</tt> immediately after
7881 the job has been completed, so that the user is
7882 informed why they have to wait. You can get this
7884 <example compact="compact">
7885 echo -n "Doing something very useful..."
7894 <p>When the configuration is reloaded</p>
7897 When a daemon is forced to reload its configuration
7898 files you should use the following format:
7899 <example compact="compact">
7900 Reloading <var>description</var> configuration...done.
7902 where <var>description</var> is the same as in the
7903 daemon starting message.
7910 <sect id="cron-jobs">
7911 <heading>Cron jobs</heading>
7914 Packages must not modify the configuration file
7915 <file>/etc/crontab</file>, and they must not modify the files in
7916 <file>/var/spool/cron/crontabs</file>.
7920 If a package wants to install a job that has to be executed via
7921 cron, it should place a file named as specified
7922 in <ref id="cron-files"> into one or more of the following
7924 <example compact="compact">
7930 As these directory names imply, the files within them are
7931 executed on an hourly, daily, weekly, or monthly basis,
7932 respectively. The exact times are listed in
7933 <file>/etc/crontab</file>.
7937 All files installed in any of these directories must be
7938 scripts (e.g., shell scripts or Perl scripts) so that they
7939 can easily be modified by the local system administrator.
7940 In addition, they must be treated as configuration files.
7944 If a certain job has to be executed at some other frequency or
7945 at a specific time, the package should install a file in
7946 <file>/etc/cron.d</file> with a name as specified
7947 in <ref id="cron-files">. This file uses the same syntax
7948 as <file>/etc/crontab</file> and is processed
7949 by <prgn>cron</prgn> automatically. The file must also be
7950 treated as a configuration file. (Note that entries in the
7951 <file>/etc/cron.d</file> directory are not handled by
7952 <prgn>anacron</prgn>. Thus, you should only use this
7953 directory for jobs which may be skipped if the system is not
7958 Unlike <file>crontab</file> files described in the IEEE Std
7959 1003.1-2008 (POSIX.1) available from
7960 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7961 name="The Open Group">, the files in
7962 <file>/etc/cron.d</file> and the file
7963 <file>/etc/crontab</file> have seven fields; namely:
7965 <item>Minute [0,59]</item>
7966 <item>Hour [0,23]</item>
7967 <item>Day of the month [1,31]</item>
7968 <item>Month of the year [1,12]</item>
7969 <item>Day of the week ([0,6] with 0=Sunday)</item>
7970 <item>Username</item>
7971 <item>Command to be run</item>
7973 Ranges of numbers are allowed. Ranges are two numbers
7974 separated with a hyphen. The specified range is inclusive.
7975 Lists are allowed. A list is a set of numbers (or ranges)
7976 separated by commas. Step values can be used in conjunction
7981 The scripts or <tt>crontab</tt> entries in these directories should
7982 check if all necessary programs are installed before they
7983 try to execute them. Otherwise, problems will arise when a
7984 package was removed but not purged since configuration files
7985 are kept on the system in this situation.
7989 Any <tt>cron</tt> daemon must provide
7990 <file>/usr/bin/crontab</file> and support normal
7991 <tt>crontab</tt> entries as specified in POSIX. The daemon
7992 must also support names for days and months, ranges, and
7993 step values. It has to support <file>/etc/crontab</file>,
7994 and correctly execute the scripts in
7995 <file>/etc/cron.d</file>. The daemon must also correctly
7997 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8000 <sect1 id="cron-files">
8001 <heading>Cron job file names</heading>
8004 The file name of a cron job file should normally match the
8005 name of the package from which it comes.
8009 If a package supplies multiple cron job files files in the
8010 same directory, the file names should all start with the name
8011 of the package (possibly modified as described below) followed
8012 by a hyphen (<tt>-</tt>) and a suitable suffix.
8016 A cron job file name must not include any period or plus
8017 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8018 cause cron to ignore the file. Underscores (<tt>_</tt>)
8019 should be used instead of <tt>.</tt> and <tt>+</tt>
8026 <heading>Menus</heading>
8029 The Debian <tt>menu</tt> package provides a standard
8030 interface between packages providing applications and
8031 <em>menu programs</em> (either X window managers or
8032 text-based menu programs such as <prgn>pdmenu</prgn>).
8036 All packages that provide applications that need not be
8037 passed any special command line arguments for normal
8038 operation should register a menu entry for those
8039 applications, so that users of the <tt>menu</tt> package
8040 will automatically get menu entries in their window
8041 managers, as well in shells like <tt>pdmenu</tt>.
8045 Menu entries should follow the current menu policy.
8049 The menu policy can be found in the <tt>menu-policy</tt>
8050 files in the <tt>debian-policy</tt> package.
8051 It is also available from the Debian web mirrors at
8052 <tt><url name="/doc/packaging-manuals/menu-policy/"
8053 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8057 Please also refer to the <em>Debian Menu System</em>
8058 documentation that comes with the <package>menu</package>
8059 package for information about how to register your
8065 <heading>Multimedia handlers</heading>
8068 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8069 is a mechanism for encoding files and data streams and
8070 providing meta-information about them, in particular their
8071 type (e.g. audio or video) and format (e.g. PNG, HTML,
8076 Registration of MIME type handlers allows programs like mail
8077 user agents and web browsers to invoke these handlers to
8078 view, edit or display MIME types they don't support directly.
8082 Packages which provide programs to view/show/play, compose, edit or
8083 print MIME types should register them as such by placing a file in
8084 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8085 <file>/usr/lib/mime/packages/</file>. The file name should be the
8086 binary package's name.
8090 The <package>mime-support</package> package provides the
8091 <prgn>update-mime</prgn> program, which integrates these
8092 registrations in the <file>/etc/mailcap</file> file, using dpkg
8094 Creating, modifying or removing a file in
8095 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8096 not activate the trigger. In that case, it can be done by calling
8097 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8098 the maintainer script after creating, modifying, or removing
8101 Packages using this facility <em>should not</em> depend on,
8102 recommend, or suggest <prgn>mime-support</prgn>.
8107 <heading>Keyboard configuration</heading>
8110 To achieve a consistent keyboard configuration so that all
8111 applications interpret a keyboard event the same way, all
8112 programs in the Debian distribution must be configured to
8113 comply with the following guidelines.
8117 The following keys must have the specified interpretations:
8120 <tag><tt><--</tt></tag>
8121 <item>delete the character to the left of the cursor</item>
8123 <tag><tt>Delete</tt></tag>
8124 <item>delete the character to the right of the cursor</item>
8126 <tag><tt>Control+H</tt></tag>
8127 <item>emacs: the help prefix</item>
8130 The interpretation of any keyboard events should be
8131 independent of the terminal that is used, be it a virtual
8132 console, an X terminal emulator, an rlogin/telnet session,
8137 The following list explains how the different programs
8138 should be set up to achieve this:
8144 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8148 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8152 X translations are set up to make
8153 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8154 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8155 is the vt220 escape code for the "delete character"
8156 key). This must be done by loading the X resources
8157 using <prgn>xrdb</prgn> on all local X displays, not
8158 using the application defaults, so that the
8159 translation resources used correspond to the
8160 <prgn>xmodmap</prgn> settings.
8164 The Linux console is configured to make
8165 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8166 generate <tt>ESC [ 3 ~</tt>.
8170 X applications are configured so that <tt><</tt>
8171 deletes left, and <tt>Delete</tt> deletes right. Motif
8172 applications already work like this.
8176 Terminals should have <tt>stty erase ^?</tt> .
8180 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8181 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8182 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8186 Emacs is programmed to map <tt>KB_Backspace</tt> or
8187 the <tt>stty erase</tt> character to
8188 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8189 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8190 <tt>^H</tt> to <tt>help</tt> as always.
8194 Other applications use the <tt>stty erase</tt>
8195 character and <tt>kdch1</tt> for the two delete keys,
8196 with ASCII DEL being "delete previous character" and
8197 <tt>kdch1</tt> being "delete character under
8205 This will solve the problem except for the following
8212 Some terminals have a <tt><--</tt> key that cannot
8213 be made to produce anything except <tt>^H</tt>. On
8214 these terminals Emacs help will be unavailable on
8215 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8216 character takes precedence in Emacs, and has been set
8217 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8218 available) can be used instead.
8222 Some operating systems use <tt>^H</tt> for <tt>stty
8223 erase</tt>. However, modern telnet versions and all
8224 rlogin versions propagate <tt>stty</tt> settings, and
8225 almost all UNIX versions honour <tt>stty erase</tt>.
8226 Where the <tt>stty</tt> settings are not propagated
8227 correctly, things can be made to work by using
8228 <tt>stty</tt> manually.
8232 Some systems (including previous Debian versions) use
8233 <prgn>xmodmap</prgn> to arrange for both
8234 <tt><--</tt> and <tt>Delete</tt> to generate
8235 <tt>KB_Delete</tt>. We can change the behavior of
8236 their X clients using the same X resources that we use
8237 to do it for our own clients, or configure our clients
8238 using their resources when things are the other way
8239 around. On displays configured like this
8240 <tt>Delete</tt> will not work, but <tt><--</tt>
8245 Some operating systems have different <tt>kdch1</tt>
8246 settings in their <tt>terminfo</tt> database for
8247 <tt>xterm</tt> and others. On these systems the
8248 <tt>Delete</tt> key will not work correctly when you
8249 log in from a system conforming to our policy, but
8250 <tt><--</tt> will.
8257 <heading>Environment variables</heading>
8260 A program must not depend on environment variables to get
8261 reasonable defaults. (That's because these environment
8262 variables would have to be set in a system-wide
8263 configuration file like <file>/etc/profile</file>, which is not
8264 supported by all shells.)
8268 If a program usually depends on environment variables for its
8269 configuration, the program should be changed to fall back to
8270 a reasonable default configuration if these environment
8271 variables are not present. If this cannot be done easily
8272 (e.g., if the source code of a non-free program is not
8273 available), the program must be replaced by a small
8274 "wrapper" shell script which sets the environment variables
8275 if they are not already defined, and calls the original program.
8279 Here is an example of a wrapper script for this purpose:
8281 <example compact="compact">
8283 BAR=${BAR:-/var/lib/fubar}
8285 exec /usr/lib/foo/foo "$@"
8290 Furthermore, as <file>/etc/profile</file> is a configuration
8291 file of the <prgn>base-files</prgn> package, other packages must
8292 not put any environment variables or other commands into that
8297 <sect id="doc-base">
8298 <heading>Registering Documents using doc-base</heading>
8301 The <package>doc-base</package> package implements a
8302 flexible mechanism for handling and presenting
8303 documentation. The recommended practice is for every Debian
8304 package that provides online documentation (other than just
8305 manual pages) to register these documents with
8306 <package>doc-base</package> by installing a
8307 <package>doc-base</package> control file in
8308 <file>/usr/share/doc-base/</file>.
8311 Please refer to the documentation that comes with the
8312 <package>doc-base</package> package for information and
8317 <sect id="alternateinit">
8318 <heading>Alternate init systems</heading>
8320 A number of other init systems are available now in Debian that
8321 can be used in place of <package>sysvinit</package>. Alternative
8322 init implementations must support running SysV init scripts as
8323 described at <ref id="sysvinit"> for compatibility.
8326 Packages may integrate with these replacement init systems by
8327 providing implementation-specific configuration information about
8328 how and when to start a service or in what order to run certain
8329 tasks at boot time. However, any package integrating with other
8330 init systems must also be backwards-compatible with
8331 <package>sysvinit</package> by providing a SysV-style init script
8332 with the same name as and equivalent functionality to any
8333 init-specific job, as this is the only start-up configuration
8334 method guaranteed to be supported by all init implementations. An
8335 exception to this rule is scripts or jobs provided by the init
8336 implementation itself; such jobs may be required for an
8337 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8338 scripts and may not have a one-to-one correspondence with the init
8341 <sect1 id="upstart">
8342 <heading>Event-based boot with upstart</heading>
8345 Packages may integrate with the <prgn>upstart</prgn> event-based
8346 boot system by installing job files in the
8347 <file>/etc/init</file> directory. SysV init scripts for which
8348 an equivalent upstart job is available must query the output of
8349 the command <prgn>initctl version</prgn> for the string
8350 <tt>upstart</tt> and avoid running in favor of the native
8351 upstart job, using a test such as this:
8352 <example compact="compact">
8353 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8360 Because packages shipping upstart jobs may be installed on
8361 systems that are not using upstart, maintainer scripts must
8362 still use the common <prgn>update-rc.d</prgn> and
8363 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8364 and for starting and stopping services. These maintainer
8365 scripts must not call the upstart <prgn>start</prgn>,
8366 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8367 interfaces directly. Instead, implementations of
8368 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8369 when an upstart job with the same name as an init script is
8370 present, and perform the requested action using the upstart job
8371 instead of the init script.
8374 Dependency-based boot managers for SysV init scripts, such as
8375 <prgn>startpar</prgn>, may avoid running a given init script
8376 entirely when an equivalent upstart job is present, to avoid
8377 unnecessary forking of no-op init scripts. In this case, the
8378 boot manager should integrate with upstart to detect when the
8379 upstart job in question is started or stopped to know when the
8380 dependency has been satisfied.
8389 <heading>Files</heading>
8391 <sect id="binaries">
8392 <heading>Binaries</heading>
8395 Two different packages must not install programs with
8396 different functionality but with the same filenames. (The
8397 case of two programs having the same functionality but
8398 different implementations is handled via "alternatives" or
8399 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8400 <ref id="conflicts"> respectively.) If this case happens,
8401 one of the programs must be renamed. The maintainers should
8402 report this to the <tt>debian-devel</tt> mailing list and
8403 try to find a consensus about which program will have to be
8404 renamed. If a consensus cannot be reached, <em>both</em>
8405 programs must be renamed.
8409 By default, when a package is being built, any binaries
8410 created should include debugging information, as well as
8411 being compiled with optimization. You should also turn on
8412 as many reasonable compilation warnings as possible; this
8413 makes life easier for porters, who can then look at build
8414 logs for possible problems. For the C programming language,
8415 this means the following compilation parameters should be
8417 <example compact="compact">
8419 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8421 INSTALL = install -s # (or use strip on the files in debian/tmp)
8426 Note that by default all installed binaries should be stripped,
8427 either by using the <tt>-s</tt> flag to
8428 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8429 the binaries after they have been copied into
8430 <file>debian/tmp</file> but before the tree is made into a
8435 Although binaries in the build tree should be compiled with
8436 debugging information by default, it can often be difficult to
8437 debug programs if they are also subjected to compiler
8438 optimization. For this reason, it is recommended to support the
8439 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8440 (see <ref id="debianrules-options">). This variable can contain
8441 several flags to change how a package is compiled and built.
8445 It is up to the package maintainer to decide what
8446 compilation options are best for the package. Certain
8447 binaries (such as computationally-intensive programs) will
8448 function better with certain flags (<tt>-O3</tt>, for
8449 example); feel free to use them. Please use good judgment
8450 here. Don't use flags for the sake of it; only use them
8451 if there is good reason to do so. Feel free to override
8452 the upstream author's ideas about which compilation
8453 options are best: they are often inappropriate for our
8459 <sect id="libraries">
8460 <heading>Libraries</heading>
8463 If the package is <strong>architecture: any</strong>, then
8464 the shared library compilation and linking flags must have
8465 <tt>-fPIC</tt>, or the package shall not build on some of
8466 the supported architectures<footnote>
8468 If you are using GCC, <tt>-fPIC</tt> produces code with
8469 relocatable position independent code, which is required for
8470 most architectures to create a shared library, with i386 and
8471 perhaps some others where non position independent code is
8472 permitted in a shared library.
8475 Position independent code may have a performance penalty,
8476 especially on <tt>i386</tt>. However, in most cases the
8477 speed penalty must be measured against the memory wasted on
8478 the few architectures where non position independent code is
8481 </footnote>. Any exception to this rule must be discussed on
8482 the mailing list <em>debian-devel@lists.debian.org</em>, and
8483 a rough consensus obtained. The reasons for not compiling
8484 with <tt>-fPIC</tt> flag must be recorded in the file
8485 <tt>README.Debian</tt>, and care must be taken to either
8486 restrict the architecture or arrange for <tt>-fPIC</tt> to
8487 be used on architectures where it is required.<footnote>
8489 Some of the reasons why this might be required is if the
8490 library contains hand crafted assembly code that is not
8491 relocatable, the speed penalty is excessive for compute
8492 intensive libs, and similar reasons.
8497 As to the static libraries, the common case is not to have
8498 relocatable code, since there is no benefit, unless in specific
8499 cases; therefore the static version must not be compiled
8500 with the <tt>-fPIC</tt> flag. Any exception to this rule
8501 should be discussed on the mailing list
8502 <em>debian-devel@lists.debian.org</em>, and the reasons for
8503 compiling with the <tt>-fPIC</tt> flag must be recorded in
8504 the file <tt>README.Debian</tt>. <footnote>
8506 Some of the reasons for linking static libraries with
8507 the <tt>-fPIC</tt> flag are if, for example, one needs a
8508 Perl API for a library that is under rapid development,
8509 and has an unstable API, so shared libraries are
8510 pointless at this phase of the library's development. In
8511 that case, since Perl needs a library with relocatable
8512 code, it may make sense to create a static library with
8513 relocatable code. Another reason cited is if you are
8514 distilling various libraries into a common shared
8515 library, like <tt>mklibs</tt> does in the Debian
8521 In other words, if both a shared and a static library is
8522 being built, each source unit (<tt>*.c</tt>, for example,
8523 for C files) will need to be compiled twice, for the normal
8528 Libraries should be built with threading support and to be
8529 thread-safe if the library supports this.
8533 Although not enforced by the build tools, shared libraries
8534 must be linked against all libraries that they use symbols from
8535 in the same way that binaries are. This ensures the correct
8536 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8537 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8538 systems and guarantees that all libraries can be safely opened
8539 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8540 option <tt>-Wl,-z,defs</tt> when building a shared library.
8541 Since this option enforces symbol resolution at build time,
8542 a missing library reference will be caught early as a fatal
8547 All installed shared libraries should be stripped with
8548 <example compact="compact">
8549 strip --strip-unneeded <var>your-lib</var>
8551 (The option <tt>--strip-unneeded</tt> makes
8552 <prgn>strip</prgn> remove only the symbols which aren't
8553 needed for relocation processing.) Shared libraries can
8554 function perfectly well when stripped, since the symbols for
8555 dynamic linking are in a separate part of the ELF object
8557 You might also want to use the options
8558 <tt>--remove-section=.comment</tt> and
8559 <tt>--remove-section=.note</tt> on both shared libraries
8560 and executables, and <tt>--strip-debug</tt> on static
8566 Note that under some circumstances it may be useful to
8567 install a shared library unstripped, for example when
8568 building a separate package to support debugging.
8572 Shared object files (often <file>.so</file> files) that are not
8573 public libraries, that is, they are not meant to be linked
8574 to by third party executables (binaries of other packages),
8575 should be installed in subdirectories of the
8576 <file>/usr/lib</file> directory. Such files are exempt from the
8577 rules that govern ordinary shared libraries, except that
8578 they must not be installed executable and should be
8580 A common example are the so-called "plug-ins",
8581 internal shared objects that are dynamically loaded by
8582 programs using <manref name="dlopen" section="3">.
8587 Packages that use <prgn>libtool</prgn> to create and install
8588 their shared libraries install a file containing additional
8589 metadata (ending in <file>.la</file>) alongside the library.
8590 For public libraries intended for use by other packages, these
8591 files normally should not be included in the Debian package,
8592 since the information they include is not necessary to link with
8593 the shared library on Debian and can add unnecessary additional
8594 dependencies to other programs or libraries.<footnote>
8595 These files store, among other things, all libraries on which
8596 that shared library depends. Unfortunately, if
8597 the <file>.la</file> file is present and contains that
8598 dependency information, using <prgn>libtool</prgn> when
8599 linking against that library will cause the resulting program
8600 or library to be linked against those dependencies as well,
8601 even if this is unnecessary. This can create unneeded
8602 dependencies on shared library packages that would otherwise
8603 be hidden behind the library ABI, and can make library
8604 transitions to new SONAMEs unnecessarily complicated and
8605 difficult to manage.
8607 If the <file>.la</file> file is required for that library (if,
8608 for instance, it's loaded via <tt>libltdl</tt> in a way that
8609 requires that meta-information), the <tt>dependency_libs</tt>
8610 setting in the <file>.la</file> file should normally be set to
8611 the empty string. If the shared library development package has
8612 historically included the <file>.la</file>, it must be retained
8613 in the development package (with <tt>dependency_libs</tt>
8614 emptied) until all libraries that depend on it have removed or
8615 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8616 files to prevent linking with those other libraries
8617 using <prgn>libtool</prgn> from failing.
8621 If the <file>.la</file> must be included, it should be included
8622 in the development (<tt>-dev</tt>) package, unless the library
8623 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8624 library. If it is intended for use with <tt>libltdl</tt>,
8625 the <file>.la</file> files must go in the run-time library
8630 These requirements for handling of <file>.la</file> files do not
8631 apply to loadable modules or libraries not installed in
8632 directories searched by default by the dynamic linker. Packages
8633 installing loadable modules will frequently need to install
8634 the <file>.la</file> files alongside the modules so that they
8635 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8636 does not need to be modified for libraries or modules that are
8637 not installed in directories searched by the dynamic linker by
8638 default and not intended for use by other packages.
8642 You must make sure that you use only released versions of
8643 shared libraries to build your packages; otherwise other
8644 users will not be able to run your binaries
8645 properly. Producing source packages that depend on
8646 unreleased compilers is also usually a bad
8653 <heading>Shared libraries</heading>
8655 This section has moved to <ref id="sharedlibs">.
8661 <heading>Scripts</heading>
8664 All command scripts, including the package maintainer
8665 scripts inside the package and used by <prgn>dpkg</prgn>,
8666 should have a <tt>#!</tt> line naming the shell to be used
8671 In the case of Perl scripts this should be
8672 <tt>#!/usr/bin/perl</tt>.
8676 When scripts are installed into a directory in the system
8677 PATH, the script name should not include an extension such
8678 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8679 language currently used to implement it.
8682 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8683 <file>init.d</file> scripts should almost certainly start
8684 with <tt>set -e</tt> so that errors are detected.
8685 <file>init.d</file> scripts are something of a special case, due
8686 to how frequently they need to call commands that are allowed to
8687 fail, and it may instead be easier to check the exit status of
8688 commands directly. See <ref id="writing-init"> for more
8689 information about writing <file>init.d</file> scripts.
8692 Every script should use <tt>set -e</tt> or check the exit status
8693 of <em>every</em> command.
8696 Scripts may assume that <file>/bin/sh</file> implements the
8697 SUSv3 Shell Command Language<footnote>
8698 Single UNIX Specification, version 3, which is also IEEE
8699 1003.1-2004 (POSIX), and is available on the World Wide Web
8700 from <url id="http://www.unix.org/version3/online.html"
8701 name="The Open Group"> after free
8702 registration.</footnote>
8703 plus the following additional features not mandated by
8705 These features are in widespread use in the Linux community
8706 and are implemented in all of bash, dash, and ksh, the most
8707 common shells users may wish to use as <file>/bin/sh</file>.
8710 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8711 must not generate a newline.</item>
8712 <item><tt>test</tt>, if implemented as a shell built-in, must
8713 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8715 <item><tt>local</tt> to create a scoped variable must be
8716 supported, including listing multiple variables in a single
8717 local command and assigning a value to a variable at the
8718 same time as localizing it. <tt>local</tt> may or
8719 may not preserve the variable value from an outer scope if
8720 no assignment is present. Uses such as:
8724 # ... use a, b, c, d ...
8727 must be supported and must set the value of <tt>c</tt> to
8730 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8731 -<var>signal</var></tt>, where <var>signal</var> is either
8732 the name of a signal or one of the numeric signals listed in
8733 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8734 supported if <prgn>kill</prgn> is implemented as a shell
8737 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8738 signals must be supported. In addition to the signal
8739 numbers listed in the extension, which are the same as for
8740 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8743 If a shell script requires non-SUSv3 features from the shell
8744 interpreter other than those listed above, the appropriate shell
8745 must be specified in the first line of the script (e.g.,
8746 <tt>#!/bin/bash</tt>) and the package must depend on the package
8747 providing the shell (unless the shell package is marked
8748 "Essential", as in the case of <prgn>bash</prgn>).
8752 You may wish to restrict your script to SUSv3 features plus the
8753 above set when possible so that it may use <file>/bin/sh</file>
8754 as its interpreter. Checking your script
8755 with <prgn>checkbashisms</prgn> from
8756 the <package>devscripts</package> package or running your script
8757 with an alternate shell such as <prgn>posh</prgn> may help
8758 uncover violations of the above requirements. If in doubt
8759 whether a script complies with these requirements,
8760 use <file>/bin/bash</file>.
8764 Perl scripts should check for errors when making any
8765 system calls, including <tt>open</tt>, <tt>print</tt>,
8766 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8770 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8771 scripting languages. See <em>Csh Programming Considered
8772 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8773 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8774 If an upstream package comes with <prgn>csh</prgn> scripts
8775 then you must make sure that they start with
8776 <tt>#!/bin/csh</tt> and make your package depend on the
8777 <prgn>c-shell</prgn> virtual package.
8781 Any scripts which create files in world-writeable
8782 directories (e.g., in <file>/tmp</file>) must use a
8783 mechanism which will fail atomically if a file with the same
8784 name already exists.
8788 The Debian base system provides the <prgn>tempfile</prgn>
8789 and <prgn>mktemp</prgn> utilities for use by scripts for
8796 <heading>Symbolic links</heading>
8799 In general, symbolic links within a top-level directory should
8800 be relative, and symbolic links pointing from one top-level
8801 directory to or into another should be absolute. (A top-level
8802 directory is a sub-directory of the root
8803 directory <file>/</file>.) For example, a symbolic link
8804 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8805 should be relative (<file>../share/bar</file>), but a symbolic
8806 link from <file>/var/run</file> to <file>/run</file> should be
8808 This is necessary to allow top-level directories to be
8809 symlinks. If linking <file>/var/run</file>
8810 to <file>/run</file> were done with the relative symbolic
8811 link <file>../run</file>, but <file>/var</file> were a
8812 symbolic link to <file>/srv/disk1</file>, the symbolic link
8813 would point to <file>/srv/run</file> rather than the intended
8819 In addition, symbolic links should be specified as short as
8820 possible, i.e., link targets like <file>foo/../bar</file> are
8825 Note that when creating a relative link using
8826 <prgn>ln</prgn> it is not necessary for the target of the
8827 link to exist relative to the working directory you're
8828 running <prgn>ln</prgn> from, nor is it necessary to change
8829 directory to the directory where the link is to be made.
8830 Simply include the string that should appear as the target
8831 of the link (this will be a pathname relative to the
8832 directory in which the link resides) as the first argument
8837 For example, in your <prgn>Makefile</prgn> or
8838 <file>debian/rules</file>, you can do things like:
8839 <example compact="compact">
8840 ln -fs gcc $(prefix)/bin/cc
8841 ln -fs gcc debian/tmp/usr/bin/cc
8842 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8843 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8848 A symbolic link pointing to a compressed file should always
8849 have the same file extension as the referenced file. (For
8850 example, if a file <file>foo.gz</file> is referenced by a
8851 symbolic link, the filename of the link has to end with
8852 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8857 <heading>Device files</heading>
8860 Packages must not include device files or named pipes in the
8865 If a package needs any special device files that are not
8866 included in the base system, it must call
8867 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8868 after notifying the user<footnote>
8869 This notification could be done via a (low-priority)
8870 debconf message, or an echo (printf) statement.
8875 Packages must not remove any device files in the
8876 <prgn>postrm</prgn> or any other script. This is left to the
8877 system administrator.
8881 Debian uses the serial devices
8882 <file>/dev/ttyS*</file>. Programs using the old
8883 <file>/dev/cu*</file> devices should be changed to use
8884 <file>/dev/ttyS*</file>.
8888 Named pipes needed by the package must be created in
8889 the <prgn>postinst</prgn> script<footnote>
8890 It's better to use <prgn>mkfifo</prgn> rather
8891 than <prgn>mknod</prgn> to create named pipes so that
8892 automated checks for packages incorrectly creating device
8893 files with <prgn>mknod</prgn> won't have false positives.
8894 </footnote> and removed in
8895 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8900 <sect id="config-files">
8901 <heading>Configuration files</heading>
8904 <heading>Definitions</heading>
8908 <tag>configuration file</tag>
8910 A file that affects the operation of a program, or
8911 provides site- or host-specific information, or
8912 otherwise customizes the behavior of a program.
8913 Typically, configuration files are intended to be
8914 modified by the system administrator (if needed or
8915 desired) to conform to local policy or to provide
8916 more useful site-specific behavior.
8919 <tag><tt>conffile</tt></tag>
8921 A file listed in a package's <tt>conffiles</tt>
8922 file, and is treated specially by <prgn>dpkg</prgn>
8923 (see <ref id="configdetails">).
8929 The distinction between these two is important; they are
8930 not interchangeable concepts. Almost all
8931 <tt>conffile</tt>s are configuration files, but many
8932 configuration files are not <tt>conffiles</tt>.
8936 As noted elsewhere, <file>/etc/init.d</file> scripts,
8937 <file>/etc/default</file> files, scripts installed in
8938 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8939 configuration installed in <file>/etc/cron.d</file> must be
8940 treated as configuration files. In general, any script that
8941 embeds configuration information is de-facto a configuration
8942 file and should be treated as such.
8947 <heading>Location</heading>
8950 Any configuration files created or used by your package
8951 must reside in <file>/etc</file>. If there are several,
8952 consider creating a subdirectory of <file>/etc</file>
8953 named after your package.
8957 If your package creates or uses configuration files
8958 outside of <file>/etc</file>, and it is not feasible to modify
8959 the package to use <file>/etc</file> directly, put the files
8960 in <file>/etc</file> and create symbolic links to those files
8961 from the location that the package requires.
8966 <heading>Behavior</heading>
8969 Configuration file handling must conform to the following
8971 <list compact="compact">
8973 local changes must be preserved during a package
8977 configuration files must be preserved when the
8978 package is removed, and only deleted when the
8982 Obsolete configuration files without local changes may be
8983 removed by the package during upgrade.
8987 The easy way to achieve this behavior is to make the
8988 configuration file a <tt>conffile</tt>. This is
8989 appropriate only if it is possible to distribute a default
8990 version that will work for most installations, although
8991 some system administrators may choose to modify it. This
8992 implies that the default version will be part of the
8993 package distribution, and must not be modified by the
8994 maintainer scripts during installation (or at any other
8999 In order to ensure that local changes are preserved
9000 correctly, no package may contain or make hard links to
9001 conffiles.<footnote>
9002 Rationale: There are two problems with hard links.
9003 The first is that some editors break the link while
9004 editing one of the files, so that the two files may
9005 unwittingly become unlinked and different. The second
9006 is that <prgn>dpkg</prgn> might break the hard link
9007 while upgrading <tt>conffile</tt>s.
9012 The other way to do it is via the maintainer scripts. In
9013 this case, the configuration file must not be listed as a
9014 <tt>conffile</tt> and must not be part of the package
9015 distribution. If the existence of a file is required for
9016 the package to be sensibly configured it is the
9017 responsibility of the package maintainer to provide
9018 maintainer scripts which correctly create, update and
9019 maintain the file and remove it on purge. (See <ref
9020 id="maintainerscripts"> for more information.) These
9021 scripts must be idempotent (i.e., must work correctly if
9022 <prgn>dpkg</prgn> needs to re-run them due to errors
9023 during installation or removal), must cope with all the
9024 variety of ways <prgn>dpkg</prgn> can call maintainer
9025 scripts, must not overwrite or otherwise mangle the user's
9026 configuration without asking, must not ask unnecessary
9027 questions (particularly during upgrades), and must
9028 otherwise be good citizens.
9032 The scripts are not required to configure every possible
9033 option for the package, but only those necessary to get
9034 the package running on a given system. Ideally the
9035 sysadmin should not have to do any configuration other
9036 than that done (semi-)automatically by the
9037 <prgn>postinst</prgn> script.
9041 A common practice is to create a script called
9042 <file><var>package</var>-configure</file> and have the
9043 package's <prgn>postinst</prgn> call it if and only if the
9044 configuration file does not already exist. In certain
9045 cases it is useful for there to be an example or template
9046 file which the maintainer scripts use. Such files should
9047 be in <file>/usr/share/<var>package</var></file> or
9048 <file>/usr/lib/<var>package</var></file> (depending on whether
9049 they are architecture-independent or not). There should
9050 be symbolic links to them from
9051 <file>/usr/share/doc/<var>package</var>/examples</file> if
9052 they are examples, and should be perfectly ordinary
9053 <prgn>dpkg</prgn>-handled files (<em>not</em>
9054 configuration files).
9058 These two styles of configuration file handling must
9059 not be mixed, for that way lies madness:
9060 <prgn>dpkg</prgn> will ask about overwriting the file
9061 every time the package is upgraded.
9066 <heading>Sharing configuration files</heading>
9069 If two or more packages use the same configuration file
9070 and it is reasonable for both to be installed at the same
9071 time, one of these packages must be defined as
9072 <em>owner</em> of the configuration file, i.e., it will be
9073 the package which handles that file as a configuration
9074 file. Other packages that use the configuration file must
9075 depend on the owning package if they require the
9076 configuration file to operate. If the other package will
9077 use the configuration file if present, but is capable of
9078 operating without it, no dependency need be declared.
9082 If it is desirable for two or more related packages to
9083 share a configuration file <em>and</em> for all of the
9084 related packages to be able to modify that configuration
9085 file, then the following should be done:
9086 <enumlist compact="compact">
9088 One of the related packages (the "owning" package)
9089 will manage the configuration file with maintainer
9090 scripts as described in the previous section.
9093 The owning package should also provide a program
9094 that the other packages may use to modify the
9098 The related packages must use the provided program
9099 to make any desired modifications to the
9100 configuration file. They should either depend on
9101 the core package to guarantee that the configuration
9102 modifier program is available or accept gracefully
9103 that they cannot modify the configuration file if it
9104 is not. (This is in addition to the fact that the
9105 configuration file may not even be present in the
9112 Sometimes it's appropriate to create a new package which
9113 provides the basic infrastructure for the other packages
9114 and which manages the shared configuration files. (The
9115 <tt>sgml-base</tt> package is a good example.)
9119 If the configuration file cannot be shared as described above,
9120 the packages must be marked as conflicting with each other.
9121 Two packages that specify the same file as
9122 a <tt>conffile</tt> must conflict. This is an instance of the
9123 general rule about not sharing files. Neither alternatives
9124 nor diversions are likely to be appropriate in this case; in
9125 particular, <prgn>dpkg</prgn> does not handle diverted
9126 <tt>conffile</tt>s well.
9130 When two packages both declare the same <tt>conffile</tt>, they
9131 may see left-over configuration files from each other even
9132 though they conflict with each other. If a user removes
9133 (without purging) one of the packages and installs the other,
9134 the new package will take over the <tt>conffile</tt> from the
9135 old package. If the file was modified by the user, it will be
9136 treated the same as any other locally
9137 modified <tt>conffile</tt> during an upgrade.
9141 The maintainer scripts must not alter a <tt>conffile</tt>
9142 of <em>any</em> package, including the one the scripts
9148 <heading>User configuration files ("dotfiles")</heading>
9151 The files in <file>/etc/skel</file> will automatically be
9152 copied into new user accounts by <prgn>adduser</prgn>.
9153 No other program should reference the files in
9154 <file>/etc/skel</file>.
9158 Therefore, if a program needs a dotfile to exist in
9159 advance in <file>$HOME</file> to work sensibly, that dotfile
9160 should be installed in <file>/etc/skel</file> and treated as a
9165 However, programs that require dotfiles in order to
9166 operate sensibly are a bad thing, unless they do create
9167 the dotfiles themselves automatically.
9171 Furthermore, programs should be configured by the Debian
9172 default installation to behave as closely to the upstream
9173 default behavior as possible.
9177 Therefore, if a program in a Debian package needs to be
9178 configured in some way in order to operate sensibly, that
9179 should be done using a site-wide configuration file placed
9180 in <file>/etc</file>. Only if the program doesn't support a
9181 site-wide default configuration and the package maintainer
9182 doesn't have time to add it may a default per-user file be
9183 placed in <file>/etc/skel</file>.
9187 <file>/etc/skel</file> should be as empty as we can make it.
9188 This is particularly true because there is no easy (or
9189 necessarily desirable) mechanism for ensuring that the
9190 appropriate dotfiles are copied into the accounts of
9191 existing users when a package is installed.
9197 <heading>Log files</heading>
9199 Log files should usually be named
9200 <file>/var/log/<var>package</var>.log</file>. If you have many
9201 log files, or need a separate directory for permission
9202 reasons (<file>/var/log</file> is writable only by
9203 <file>root</file>), you should usually create a directory named
9204 <file>/var/log/<var>package</var></file> and place your log
9209 Log files must be rotated occasionally so that they don't grow
9210 indefinitely. The best way to do this is to install a log
9211 rotation configuration file in the
9212 directory <file>/etc/logrotate.d</file>, normally
9213 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9214 the facilities provided by <prgn>logrotate</prgn>.
9217 The traditional approach to log files has been to set up
9218 <em>ad hoc</em> log rotation schemes using simple shell
9219 scripts and cron. While this approach is highly
9220 customizable, it requires quite a lot of sysadmin work.
9221 Even though the original Debian system helped a little
9222 by automatically installing a system which can be used
9223 as a template, this was deemed not enough.
9227 The use of <prgn>logrotate</prgn>, a program developed
9228 by Red Hat, is better, as it centralizes log management.
9229 It has both a configuration file
9230 (<file>/etc/logrotate.conf</file>) and a directory where
9231 packages can drop their individual log rotation
9232 configurations (<file>/etc/logrotate.d</file>).
9235 Here is a good example for a logrotate config
9236 file (for more information see <manref name="logrotate"
9238 <example compact="compact">
9239 /var/log/foo/*.log {
9245 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9249 This rotates all files under <file>/var/log/foo</file>, saves 12
9250 compressed generations, and tells the daemon to reopen its log
9251 files after the log rotation. It skips this log rotation
9252 (via <tt>missingok</tt>) if no such log file is present, which
9253 avoids errors if the package is removed but not purged.
9257 Log files should be removed when the package is
9258 purged (but not when it is only removed). This should be
9259 done by the <prgn>postrm</prgn> script when it is called
9260 with the argument <tt>purge</tt> (see <ref
9261 id="removedetails">).
9265 <sect id="permissions-owners">
9266 <heading>Permissions and owners</heading>
9269 The rules in this section are guidelines for general use.
9270 If necessary you may deviate from the details below.
9271 However, if you do so you must make sure that what is done
9272 is secure and you should try to be as consistent as possible
9273 with the rest of the system. You should probably also
9274 discuss it on <prgn>debian-devel</prgn> first.
9278 Files should be owned by <tt>root:root</tt>, and made
9279 writable only by the owner and universally readable (and
9280 executable, if appropriate), that is mode 644 or 755.
9284 Directories should be mode 755 or (for group-writability)
9285 mode 2775. The ownership of the directory should be
9286 consistent with its mode: if a directory is mode 2775, it
9287 should be owned by the group that needs write access to
9290 When a package is upgraded, and the owner or permissions
9291 of a file included in the package has changed, dpkg
9292 arranges for the ownership and permissions to be
9293 correctly set upon installation. However, this does not
9294 extend to directories; the permissions and ownership of
9295 directories already on the system does not change on
9296 install or upgrade of packages. This makes sense, since
9297 otherwise common directories like <tt>/usr</tt> would
9298 always be in flux. To correctly change permissions of a
9299 directory the package owns, explicit action is required,
9300 usually in the <tt>postinst</tt> script. Care must be
9301 taken to handle downgrades as well, in that case.
9307 Control information files should be owned by <tt>root:root</tt>
9308 and either mode 644 (for most files) or mode 755 (for
9309 executables such as <qref id="maintscripts">maintainer
9314 Setuid and setgid executables should be mode 4755 or 2755
9315 respectively, and owned by the appropriate user or group.
9316 They should not be made unreadable (modes like 4711 or
9317 2711 or even 4111); doing so achieves no extra security,
9318 because anyone can find the binary in the freely available
9319 Debian package; it is merely inconvenient. For the same
9320 reason you should not restrict read or execute permissions
9321 on non-set-id executables.
9325 Some setuid programs need to be restricted to particular
9326 sets of users, using file permissions. In this case they
9327 should be owned by the uid to which they are set-id, and by
9328 the group which should be allowed to execute them. They
9329 should have mode 4754; again there is no point in making
9330 them unreadable to those users who must not be allowed to
9335 It is possible to arrange that the system administrator can
9336 reconfigure the package to correspond to their local
9337 security policy by changing the permissions on a binary:
9338 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9339 described below.<footnote>
9340 Ordinary files installed by <prgn>dpkg</prgn> (as
9341 opposed to <tt>conffile</tt>s and other similar objects)
9342 normally have their permissions reset to the distributed
9343 permissions when the package is reinstalled. However,
9344 the use of <prgn>dpkg-statoverride</prgn> overrides this
9347 Another method you should consider is to create a group for
9348 people allowed to use the program(s) and make any setuid
9349 executables executable only by that group.
9353 If you need to create a new user or group for your package
9354 there are two possibilities. Firstly, you may need to
9355 make some files in the binary package be owned by this
9356 user or group, or you may need to compile the user or
9357 group id (rather than just the name) into the binary
9358 (though this latter should be avoided if possible, as in
9359 this case you need a statically allocated id).</p>
9362 If you need a statically allocated id, you must ask for a
9363 user or group id from the <tt>base-passwd</tt> maintainer,
9364 and must not release the package until you have been
9365 allocated one. Once you have been allocated one you must
9366 either make the package depend on a version of the
9367 <tt>base-passwd</tt> package with the id present in
9368 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9369 your package to create the user or group itself with the
9370 correct id (using <tt>adduser</tt>) in its
9371 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9372 the <prgn>postinst</prgn> is to be preferred if it is
9373 possible, otherwise a pre-dependency will be needed on the
9374 <tt>adduser</tt> package.)
9378 On the other hand, the program might be able to determine
9379 the uid or gid from the user or group name at runtime, so
9380 that a dynamically allocated id can be used. In this case
9381 you should choose an appropriate user or group name,
9382 discussing this on <prgn>debian-devel</prgn> and checking
9383 with the <package/base-passwd/ maintainer that it is unique and that
9384 they do not wish you to use a statically allocated id
9385 instead. When this has been checked you must arrange for
9386 your package to create the user or group if necessary using
9387 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9388 <prgn>postinst</prgn> script (again, the latter is to be
9389 preferred if it is possible).
9393 Note that changing the numeric value of an id associated
9394 with a name is very difficult, and involves searching the
9395 file system for all appropriate files. You need to think
9396 carefully whether a static or dynamic id is required, since
9397 changing your mind later will cause problems.
9400 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9402 This section is not intended as policy, but as a
9403 description of the use of <prgn>dpkg-statoverride</prgn>.
9407 If a system administrator wishes to have a file (or
9408 directory or other such thing) installed with owner and
9409 permissions different from those in the distributed Debian
9410 package, they can use the <prgn>dpkg-statoverride</prgn>
9411 program to instruct <prgn>dpkg</prgn> to use the different
9412 settings every time the file is installed. Thus the
9413 package maintainer should distribute the files with their
9414 normal permissions, and leave it for the system
9415 administrator to make any desired changes. For example, a
9416 daemon which is normally required to be setuid root, but
9417 in certain situations could be used without being setuid,
9418 should be installed setuid in the <tt>.deb</tt>. Then the
9419 local system administrator can change this if they wish.
9420 If there are two standard ways of doing it, the package
9421 maintainer can use <tt>debconf</tt> to find out the
9422 preference, and call <prgn>dpkg-statoverride</prgn> in the
9423 maintainer script if necessary to accommodate the system
9424 administrator's choice. Care must be taken during
9425 upgrades to not override an existing setting.
9429 Given the above, <prgn>dpkg-statoverride</prgn> is
9430 essentially a tool for system administrators and would not
9431 normally be needed in the maintainer scripts. There is
9432 one type of situation, though, where calls to
9433 <prgn>dpkg-statoverride</prgn> would be needed in the
9434 maintainer scripts, and that involves packages which use
9435 dynamically allocated user or group ids. In such a
9436 situation, something like the following idiom can be very
9437 helpful in the package's <prgn>postinst</prgn>, where
9438 <tt>sysuser</tt> is a dynamically allocated id:
9440 for i in /usr/bin/foo /usr/sbin/bar
9442 # only do something when no setting exists
9443 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9445 #include: debconf processing, question about foo and bar
9446 if [ "$RET" = "true" ] ; then
9447 dpkg-statoverride --update --add sysuser root 4755 $i
9452 The corresponding code to remove the override when the package
9455 for i in /usr/bin/foo /usr/sbin/bar
9457 if dpkg-statoverride --list $i >/dev/null 2>&1
9459 dpkg-statoverride --remove $i
9469 <chapt id="customized-programs">
9470 <heading>Customized programs</heading>
9472 <sect id="arch-spec">
9473 <heading>Architecture specification strings</heading>
9476 If a program needs to specify an <em>architecture specification
9477 string</em> in some place, it should select one of the strings
9478 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9479 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9480 part is sometimes elided, as when the OS is Linux.
9484 Note that we don't want to use
9485 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9486 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9487 since this would make our programs incompatible with other
9488 Linux distributions. We also don't use something like
9489 <tt><var>arch</var>-unknown-linux</tt>, since the
9490 <tt>unknown</tt> does not look very good.
9493 <sect1 id="arch-wildcard-spec">
9494 <heading>Architecture wildcards</heading>
9497 A package may specify an architecture wildcard. Architecture
9498 wildcards are in the format <tt>any</tt> (which matches every
9499 architecture), <tt><var>os</var></tt>-any, or
9500 any-<tt><var>cpu</var></tt>. <footnote>
9501 Internally, the package system normalizes the GNU triplets
9502 and the Debian arches into Debian arch triplets (which are
9503 kind of inverted GNU triplets), with the first component of
9504 the triplet representing the libc and ABI in use, and then
9505 does matching against those triplets. However, such
9506 triplets are an internal implementation detail that should
9507 not be used by packages directly. The libc and ABI portion
9508 is handled internally by the package system based on
9509 the <var>os</var> and <var>cpu</var>.
9516 <heading>Daemons</heading>
9519 The configuration files <file>/etc/services</file>,
9520 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9521 by the <prgn>netbase</prgn> package and must not be modified
9526 If a package requires a new entry in one of these files, the
9527 maintainer should get in contact with the
9528 <prgn>netbase</prgn> maintainer, who will add the entries
9529 and release a new version of the <prgn>netbase</prgn>
9534 The configuration file <file>/etc/inetd.conf</file> must not be
9535 modified by the package's scripts except via the
9536 <prgn>update-inetd</prgn> script or the
9537 <file>DebianNet.pm</file> Perl module. See their documentation
9538 for details on how to add entries.
9542 If a package wants to install an example entry into
9543 <file>/etc/inetd.conf</file>, the entry must be preceded with
9544 exactly one hash character (<tt>#</tt>). Such lines are
9545 treated as "commented out by user" by the
9546 <prgn>update-inetd</prgn> script and are not changed or
9547 activated during package updates.
9552 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9556 Some programs need to create pseudo-ttys. This should be done
9557 using Unix98 ptys if the C library supports it. The resulting
9558 program must not be installed setuid root, unless that
9559 is required for other functionality.
9563 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9564 <file>/var/log/lastlog</file> must be installed writable by
9565 group <tt>utmp</tt>. Programs which need to modify those
9566 files must be installed setgid <tt>utmp</tt>.
9571 <heading>Editors and pagers</heading>
9574 Some programs have the ability to launch an editor or pager
9575 program to edit or display a text document. Since there are
9576 lots of different editors and pagers available in the Debian
9577 distribution, the system administrator and each user should
9578 have the possibility to choose their preferred editor and
9583 In addition, every program should choose a good default
9584 editor/pager if none is selected by the user or system
9589 Thus, every program that launches an editor or pager must
9590 use the EDITOR or PAGER environment variable to determine
9591 the editor or pager the user wishes to use. If these
9592 variables are not set, the programs <file>/usr/bin/editor</file>
9593 and <file>/usr/bin/pager</file> should be used, respectively.
9597 These two files are managed through the <prgn>dpkg</prgn>
9598 "alternatives" mechanism. Every package providing an editor or
9599 pager must call the <prgn>update-alternatives</prgn> script to
9600 register as an alternative for <file>/usr/bin/editor</file>
9601 or <file>/usr/bin/pager</file> as appropriate. The alternative
9602 should have a slave alternative
9603 for <file>/usr/share/man/man1/editor.1.gz</file>
9604 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9605 corresponding manual page.
9609 If it is very hard to adapt a program to make use of the
9610 EDITOR or PAGER variables, that program may be configured to
9611 use <file>/usr/bin/sensible-editor</file> and
9612 <file>/usr/bin/sensible-pager</file> as the editor or pager
9613 program respectively. These are two scripts provided in the
9614 <package>sensible-utils</package> package that check the EDITOR
9615 and PAGER variables and launch the appropriate program, and fall
9616 back to <file>/usr/bin/editor</file>
9617 and <file>/usr/bin/pager</file> if the variable is not set.
9621 A program may also use the VISUAL environment variable to
9622 determine the user's choice of editor. If it exists, it
9623 should take precedence over EDITOR. This is in fact what
9624 <file>/usr/bin/sensible-editor</file> does.
9628 It is not required for a package to depend on
9629 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9630 package to provide such virtual packages.<footnote>
9631 The Debian base system already provides an editor and a
9637 <sect id="web-appl">
9638 <heading>Web servers and applications</heading>
9641 This section describes the locations and URLs that should
9642 be used by all web servers and web applications in the
9649 Cgi-bin executable files are installed in the
9651 <example compact="compact">
9652 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9654 or a subdirectory of that directory, and should be
9656 <example compact="compact">
9657 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9659 (possibly with a subdirectory name
9660 before <var>cgi-bin-name</var>).
9664 <p>Access to HTML documents</p>
9667 HTML documents for a package are stored in
9668 <file>/usr/share/doc/<var>package</var></file>
9669 and can be referred to as
9670 <example compact="compact">
9671 http://localhost/doc/<var>package</var>/<var>filename</var>
9676 The web server should restrict access to the document
9677 tree so that only clients on the same host can read
9678 the documents. If the web server does not support such
9679 access controls, then it should not provide access at
9680 all, or ask about providing access during installation.
9685 <p>Access to images</p>
9687 It is recommended that images for a package be stored
9688 in <tt>/usr/share/images/<var>package</var></tt> and
9689 may be referred to through an alias <tt>/images/</tt>
9692 http://localhost/images/<package>/<filename>
9699 <p>Web Document Root</p>
9702 Web Applications should try to avoid storing files in
9703 the Web Document Root. Instead they should use the
9704 /usr/share/doc/<var>package</var> directory for
9705 documents and register the Web Application via the
9706 <package>doc-base</package> package. If access to the
9707 web document root is unavoidable then use
9708 <example compact="compact">
9711 as the Document Root. This might be just a symbolic
9712 link to the location where the system administrator
9713 has put the real document root.
9716 <item><p>Providing httpd and/or httpd-cgi</p>
9718 All web servers should provide the virtual package
9719 <tt>httpd</tt>. If a web server has CGI support it should
9720 provide <tt>httpd-cgi</tt> additionally.
9723 All web applications which do not contain CGI scripts should
9724 depend on <tt>httpd</tt>, all those web applications which
9725 <tt>do</tt> contain CGI scripts, should depend on
9733 <sect id="mail-transport-agents">
9734 <heading>Mail transport, delivery and user agents</heading>
9737 Debian packages which process electronic mail, whether mail
9738 user agents (MUAs) or mail transport agents (MTAs), must
9739 ensure that they are compatible with the configuration
9740 decisions below. Failure to do this may result in lost
9741 mail, broken <tt>From:</tt> lines, and other serious brain
9746 The mail spool is <file>/var/mail</file> and the interface to
9747 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9748 the FHS). On older systems, the mail spool may be
9749 physically located in <file>/var/spool/mail</file>, but all
9750 access to the mail spool should be via the
9751 <file>/var/mail</file> symlink. The mail spool is part of the
9752 base system and not part of the MTA package.
9756 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9757 programs (such as IMAP daemons) must lock the mailbox in an
9758 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9759 be combined with dot locking. To avoid deadlocks, a program
9760 should use <tt>fcntl()</tt> first and dot locking after
9761 this, or alternatively implement the two locking methods in
9762 a non blocking way<footnote>
9763 If it is not possible to establish both locks, the
9764 system shouldn't wait for the second lock to be
9765 established, but remove the first lock, wait a (random)
9766 time, and start over locking again.
9767 </footnote>. Using the functions <tt>maillock</tt> and
9768 <tt>mailunlock</tt> provided by the
9769 <tt>liblockfile*</tt><footnote>
9770 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9771 to use these functions.
9772 </footnote> packages is the recommended way to realize this.
9776 Mailboxes are generally either mode 600 and owned by
9777 <var>user</var> or mode 660 and owned by
9778 <tt><var>user</var>:mail</tt><footnote>
9779 There are two traditional permission schemes for mail spools:
9780 mode 600 with all mail delivery done by processes running as
9781 the destination user, or mode 660 and owned by group mail with
9782 mail delivery done by a process running as a system user in
9783 group mail. Historically, Debian required mode 660 mail
9784 spools to enable the latter model, but that model has become
9785 increasingly uncommon and the principle of least privilege
9786 indicates that mail systems that use the first model should
9787 use permissions of 600. If delivery to programs is permitted,
9788 it's easier to keep the mail system secure if the delivery
9789 agent runs as the destination user. Debian Policy therefore
9790 permits either scheme.
9791 </footnote>. The local system administrator may choose a
9792 different permission scheme; packages should not make
9793 assumptions about the permission and ownership of mailboxes
9794 unless required (such as when creating a new mailbox). A MUA
9795 may remove a mailbox (unless it has nonstandard permissions) in
9796 which case the MTA or another MUA must recreate it if needed.
9800 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9801 be setgid mail to do the locking mentioned above (and
9802 must obviously avoid accessing other users' mailboxes
9803 using this privilege).</p>
9806 <file>/etc/aliases</file> is the source file for the system mail
9807 aliases (e.g., postmaster, usenet, etc.), it is the one
9808 which the sysadmin and <prgn>postinst</prgn> scripts may
9809 edit. After <file>/etc/aliases</file> is edited the program or
9810 human editing it must call <prgn>newaliases</prgn>. All MTA
9811 packages must come with a <prgn>newaliases</prgn> program,
9812 even if it does nothing, but older MTA packages did not do
9813 this so programs should not fail if <prgn>newaliases</prgn>
9814 cannot be found. Note that because of this, all MTA
9815 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9816 <tt>Replaces: mail-transport-agent</tt> control fields.
9820 The convention of writing <tt>forward to
9821 <var>address</var></tt> in the mailbox itself is not
9822 supported. Use a <tt>.forward</tt> file instead.</p>
9825 The <prgn>rmail</prgn> program used by UUCP
9826 for incoming mail should be <file>/usr/sbin/rmail</file>.
9827 Likewise, <prgn>rsmtp</prgn>, for receiving
9828 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9832 If your package needs to know what hostname to use on (for
9833 example) outgoing news and mail messages which are generated
9834 locally, you should use the file <file>/etc/mailname</file>. It
9835 will contain the portion after the username and <tt>@</tt>
9836 (at) sign for email addresses of users on the machine
9837 (followed by a newline).
9841 Such a package should check for the existence of this file
9842 when it is being configured. If it exists, it should be
9843 used without comment, although an MTA's configuration script
9844 may wish to prompt the user even if it finds that this file
9845 exists. If the file does not exist, the package should
9846 prompt the user for the value (preferably using
9847 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9848 as well as using it in the package's configuration. The
9849 prompt should make it clear that the name will not just be
9850 used by that package. For example, in this situation the
9851 <tt>inn</tt> package could say something like:
9852 <example compact="compact">
9853 Please enter the "mail name" of your system. This is the
9854 hostname portion of the address to be shown on outgoing
9855 news and mail messages. The default is
9856 <var>syshostname</var>, your system's host name. Mail
9857 name ["<var>syshostname</var>"]:
9859 where <var>syshostname</var> is the output of <tt>hostname
9865 <heading>News system configuration</heading>
9868 All the configuration files related to the NNTP (news)
9869 servers and clients should be located under
9870 <file>/etc/news</file>.</p>
9873 There are some configuration issues that apply to a number
9874 of news clients and server packages on the machine. These
9878 <tag><file>/etc/news/organization</file></tag>
9880 A string which should appear as the
9881 organization header for all messages posted
9882 by NNTP clients on the machine
9885 <tag><file>/etc/news/server</file></tag>
9887 Contains the FQDN of the upstream NNTP
9888 server, or localhost if the local machine is
9893 Other global files may be added as required for cross-package news
9900 <heading>Programs for the X Window System</heading>
9903 <heading>Providing X support and package priorities</heading>
9906 Programs that can be configured with support for the X
9907 Window System must be configured to do so and must declare
9908 any package dependencies necessary to satisfy their
9909 runtime requirements when using the X Window System. If
9910 such a package is of higher priority than the X packages
9911 on which it depends, it is required that either the
9912 X-specific components be split into a separate package, or
9913 that an alternative version of the package, which includes
9914 X support, be provided, or that the package's priority be
9920 <heading>Packages providing an X server</heading>
9923 Packages that provide an X server that, directly or
9924 indirectly, communicates with real input and display
9925 hardware should declare in their <tt>Provides</tt> control
9926 field that they provide the virtual
9927 package <tt>xserver</tt>.<footnote>
9928 This implements current practice, and provides an
9929 actual policy for usage of the <tt>xserver</tt>
9930 virtual package which appears in the virtual packages
9931 list. In a nutshell, X servers that interface
9932 directly with the display and input hardware or via
9933 another subsystem (e.g., GGI) should provide
9934 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9935 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9941 <heading>Packages providing a terminal emulator</heading>
9944 Packages that provide a terminal emulator for the X Window
9945 System which meet the criteria listed below should declare in
9946 their <tt>Provides</tt> control field that they provide the
9947 virtual package <tt>x-terminal-emulator</tt>. They should
9948 also register themselves as an alternative for
9949 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9950 20. That alternative should have a slave alternative
9951 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9952 pointing to the corresponding manual page.
9956 To be an <tt>x-terminal-emulator</tt>, a program must:
9957 <list compact="compact">
9959 Be able to emulate a DEC VT100 terminal, or a
9960 compatible terminal.
9964 Support the command-line option <tt>-e
9965 <var>command</var></tt>, which creates a new
9966 terminal window<footnote>
9967 "New terminal window" does not necessarily mean
9968 a new top-level X window directly parented by
9969 the window manager; it could, if the terminal
9970 emulator application were so coded, be a new
9971 "view" in a multiple-document interface (MDI).
9973 and runs the specified <var>command</var>,
9974 interpreting the entirety of the rest of the command
9975 line as a command to pass straight to exec, in the
9976 manner that <tt>xterm</tt> does.
9980 Support the command-line option <tt>-T
9981 <var>title</var></tt>, which creates a new terminal
9982 window with the window title <var>title</var>.
9989 <heading>Packages providing a window manager</heading>
9992 Packages that provide a window manager should declare in
9993 their <tt>Provides</tt> control field that they provide the
9994 virtual package <tt>x-window-manager</tt>. They should also
9995 register themselves as an alternative for
9996 <file>/usr/bin/x-window-manager</file>, with a priority
9997 calculated as follows:
9998 <list compact="compact">
10000 Start with a priority of 20.
10004 If the window manager supports the Debian menu
10005 system, add 20 points if this support is available
10006 in the package's default configuration (i.e., no
10007 configuration files belonging to the system or user
10008 have to be edited to activate the feature); if
10009 configuration files must be modified, add only 10
10015 If the window manager complies with <url
10016 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10017 name="The Window Manager Specification Project">,
10018 written by the <url id="http://www.freedesktop.org/wiki/"
10019 name="Free Desktop Group">, add 40 points.
10023 If the window manager permits the X session to be
10024 restarted using a <em>different</em> window manager
10025 (without killing the X server) in its default
10026 configuration, add 10 points; otherwise add none.
10029 That alternative should have a slave alternative
10030 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10031 pointing to the corresponding manual page.
10036 <heading>Packages providing fonts</heading>
10039 Packages that provide fonts for the X Window
10041 For the purposes of Debian Policy, a "font for the X
10042 Window System" is one which is accessed via X protocol
10043 requests. Fonts for the Linux console, for PostScript
10044 renderer, or any other purpose, do not fit this
10045 definition. Any tool which makes such fonts available
10046 to the X Window System, however, must abide by this
10049 must do a number of things to ensure that they are both
10050 available without modification of the X or font server
10051 configuration, and that they do not corrupt files used by
10052 other font packages to register information about
10056 Fonts of any type supported by the X Window System
10057 must be in a separate binary package from any
10058 executables, libraries, or documentation (except
10059 that specific to the fonts shipped, such as their
10060 license information). If one or more of the fonts
10061 so packaged are necessary for proper operation of
10062 the package with which they are associated the font
10063 package may be Recommended; if the fonts merely
10064 provide an enhancement, a Suggests relationship may
10065 be used. Packages must not Depend on font
10066 packages.<footnote>
10067 This is because the X server may retrieve fonts
10068 from the local file system or over the network
10069 from an X font server; the Debian package system
10070 is empowered to deal only with the local
10076 BDF fonts must be converted to PCF fonts with the
10077 <prgn>bdftopcf</prgn> utility (available in the
10078 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10079 placed in a directory that corresponds to their
10081 <list compact="compact">
10083 100 dpi fonts must be placed in
10084 <file>/usr/share/fonts/X11/100dpi/</file>.
10088 75 dpi fonts must be placed in
10089 <file>/usr/share/fonts/X11/75dpi/</file>.
10093 Character-cell fonts, cursor fonts, and other
10094 low-resolution fonts must be placed in
10095 <file>/usr/share/fonts/X11/misc/</file>.
10101 Type 1 fonts must be placed in
10102 <file>/usr/share/fonts/X11/Type1/</file>. If font
10103 metric files are available, they must be placed here
10108 Subdirectories of <file>/usr/share/fonts/X11/</file>
10109 other than those listed above must be neither
10110 created nor used. (The <file>PEX</file>, <file>CID</file>,
10111 <file>Speedo</file>, and <file>cyrillic</file> directories
10112 are excepted for historical reasons, but installation of
10113 files into these directories remains discouraged.)
10117 Font packages may, instead of placing files directly
10118 in the X font directories listed above, provide
10119 symbolic links in that font directory pointing to
10120 the files' actual location in the filesystem. Such
10121 a location must comply with the FHS.
10125 Font packages should not contain both 75dpi and
10126 100dpi versions of a font. If both are available,
10127 they should be provided in separate binary packages
10128 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10129 the names of the packages containing the
10130 corresponding fonts.
10134 Fonts destined for the <file>misc</file> subdirectory
10135 should not be included in the same package as 75dpi
10136 or 100dpi fonts; instead, they should be provided in
10137 a separate package with <tt>-misc</tt> appended to
10142 Font packages must not provide the files
10143 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10144 <file>fonts.scale</file> in a font directory:
10147 <file>fonts.dir</file> files must not be provided at all.
10151 <file>fonts.alias</file> and <file>fonts.scale</file>
10152 files, if needed, should be provided in the
10154 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10155 where <var>fontdir</var> is the name of the
10157 <file>/usr/share/fonts/X11/</file> where the
10158 package's corresponding fonts are stored
10159 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10160 <var>package</var> is the name of the package
10161 that provides these fonts, and
10162 <var>extension</var> is either <tt>scale</tt>
10163 or <tt>alias</tt>, whichever corresponds to
10170 Font packages must declare a dependency on
10171 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10172 or <tt>Pre-Depends</tt> control field.
10176 Font packages that provide one or more
10177 <file>fonts.scale</file> files as described above must
10178 invoke <prgn>update-fonts-scale</prgn> on each
10179 directory into which they installed fonts
10180 <em>before</em> invoking
10181 <prgn>update-fonts-dir</prgn> on that directory.
10182 This invocation must occur in both the
10183 <prgn>postinst</prgn> (for all arguments) and
10184 <prgn>postrm</prgn> (for all arguments except
10185 <tt>upgrade</tt>) scripts.
10189 Font packages that provide one or more
10190 <file>fonts.alias</file> files as described above must
10191 invoke <prgn>update-fonts-alias</prgn> on each
10192 directory into which they installed fonts. This
10193 invocation must occur in both the
10194 <prgn>postinst</prgn> (for all arguments) and
10195 <prgn>postrm</prgn> (for all arguments except
10196 <tt>upgrade</tt>) scripts.
10200 Font packages must invoke
10201 <prgn>update-fonts-dir</prgn> on each directory into
10202 which they installed fonts. This invocation must
10203 occur in both the <prgn>postinst</prgn> (for all
10204 arguments) and <prgn>postrm</prgn> (for all
10205 arguments except <tt>upgrade</tt>) scripts.
10209 Font packages must not provide alias names for the
10210 fonts they include which collide with alias names
10211 already in use by fonts already packaged.
10215 Font packages must not provide fonts with the same
10216 XLFD registry name as another font already packaged.
10222 <sect1 id="appdefaults">
10223 <heading>Application defaults files</heading>
10226 Application defaults files must be installed in the
10227 directory <file>/etc/X11/app-defaults/</file> (use of a
10228 localized subdirectory of <file>/etc/X11/</file> as described
10229 in the <em>X Toolkit Intrinsics - C Language
10230 Interface</em> manual is also permitted). They must be
10231 registered as <tt>conffile</tt>s or handled as
10232 configuration files.
10236 Customization of programs' X resources may also be
10237 supported with the provision of a file with the same name
10238 as that of the package placed in
10239 the <file>/etc/X11/Xresources/</file> directory, which
10240 must be registered as a <tt>conffile</tt> or handled as a
10241 configuration file.<footnote>
10242 Note that this mechanism is not the same as using
10243 app-defaults; app-defaults are tied to the client
10244 binary on the local file system, whereas X resources
10245 are stored in the X server and affect all connecting
10252 <heading>Installation directory issues</heading>
10255 Historically, packages using the X Window System used a
10256 separate set of installation directories from other packages.
10257 This practice has been discontinued and packages using the X
10258 Window System should now generally be installed in the same
10259 directories as any other package. Specifically, packages must
10260 not install files under the <file>/usr/X11R6/</file> directory
10261 and the <file>/usr/X11R6/</file> directory hierarchy should be
10262 regarded as obsolete.
10266 Include files previously installed under
10267 <file>/usr/X11R6/include/X11/</file> should be installed into
10268 <file>/usr/include/X11/</file>. For files previously
10269 installed into subdirectories of
10270 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10271 determine if subdirectories of <file>/usr/lib/</file> and
10272 <file>/usr/share/</file> can be used. If not, a subdirectory
10273 of <file>/usr/lib/X11/</file> should be used.
10277 Configuration files for window, display, or session managers
10278 or other applications that are tightly integrated with the X
10279 Window System may be placed in a subdirectory
10280 of <file>/etc/X11/</file> corresponding to the package name.
10281 Other X Window System applications should use
10282 the <file>/etc/</file> directory unless otherwise mandated by
10283 policy (such as for <ref id="appdefaults">).
10289 <heading>Perl programs and modules</heading>
10292 Perl programs and modules should follow the current Perl policy.
10296 The Perl policy can be found in the <tt>perl-policy</tt>
10297 files in the <tt>debian-policy</tt> package.
10298 It is also available from the Debian web mirrors at
10299 <tt><url name="/doc/packaging-manuals/perl-policy/"
10300 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10305 <heading>Emacs lisp programs</heading>
10308 Please refer to the "Debian Emacs Policy" for details of how to
10309 package emacs lisp programs.
10313 The Emacs policy is available in
10314 <file>debian-emacs-policy.gz</file> of the
10315 <package>emacsen-common</package> package.
10316 It is also available from the Debian web mirrors at
10317 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10318 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10323 <heading>Games</heading>
10326 The permissions on <file>/var/games</file> are mode 755, owner
10327 <tt>root</tt> and group <tt>root</tt>.
10331 Each game decides on its own security policy.</p>
10334 Games which require protected, privileged access to
10335 high-score files, saved games, etc., may be made
10336 set-<em>group</em>-id (mode 2755) and owned by
10337 <tt>root:games</tt>, and use files and directories with
10338 appropriate permissions (770 <tt>root:games</tt>, for
10339 example). They must not be made
10340 set-<em>user</em>-id, as this causes security problems. (If
10341 an attacker can subvert any set-user-id game they can
10342 overwrite the executable of any other, causing other players
10343 of these games to run a Trojan horse program. With a
10344 set-group-id game the attacker only gets access to less
10345 important game data, and if they can get at the other
10346 players' accounts at all it will take considerably more
10350 Some packages, for example some fortune cookie programs, are
10351 configured by the upstream authors to install with their
10352 data files or other static information made unreadable so
10353 that they can only be accessed through set-id programs
10354 provided. You should not do this in a Debian package: anyone can
10355 download the <file>.deb</file> file and read the data from it,
10356 so there is no point making the files unreadable. Not
10357 making the files unreadable also means that you don't have
10358 to make so many programs set-id, which reduces the risk of a
10362 As described in the FHS, binaries of games should be
10363 installed in the directory <file>/usr/games</file>. This also
10364 applies to games that use the X Window System. Manual pages
10365 for games (X and non-X games) should be installed in
10366 <file>/usr/share/man/man6</file>.</p>
10372 <heading>Documentation</heading>
10375 <heading>Manual pages</heading>
10378 You should install manual pages in <prgn>nroff</prgn> source
10379 form, in appropriate places under <file>/usr/share/man</file>.
10380 You should only use sections 1 to 9 (see the FHS for more
10381 details). You must not install a pre-formatted "cat page".
10385 Each program, utility, and function should have an
10386 associated manual page included in the same package. It is
10387 suggested that all configuration files also have a manual
10388 page included as well. Manual pages for protocols and other
10389 auxiliary things are optional.
10393 If no manual page is available, this is considered as a bug
10394 and should be reported to the Debian Bug Tracking System (the
10395 maintainer of the package is allowed to write this bug report
10396 themselves, if they so desire). Do not close the bug report
10397 until a proper man page is available.<footnote>
10398 It is not very hard to write a man page. See the
10399 <url id="http://www.schweikhardt.net/man_page_howto.html"
10400 name="Man-Page-HOWTO">,
10401 <manref name="man" section="7">, the examples created
10402 by <prgn>dh_make</prgn>, the helper
10403 program <prgn>help2man</prgn>, or the
10404 directory <file>/usr/share/doc/man-db/examples</file>.
10409 You may forward a complaint about a missing man page to the
10410 upstream authors, and mark the bug as forwarded in the
10411 Debian bug tracking system. Even though the GNU Project do
10412 not in general consider the lack of a man page to be a bug,
10413 we do; if they tell you that they don't consider it a bug
10414 you should leave the bug in our bug tracking system open
10419 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10423 If one man page needs to be accessible via several names it
10424 is better to use a symbolic link than the <file>.so</file>
10425 feature, but there is no need to fiddle with the relevant
10426 parts of the upstream source to change from <file>.so</file> to
10427 symlinks: don't do it unless it's easy. You should not
10428 create hard links in the manual page directories, nor put
10429 absolute filenames in <file>.so</file> directives. The filename
10430 in a <file>.so</file> in a man page should be relative to the
10431 base of the man page tree (usually
10432 <file>/usr/share/man</file>). If you do not create any links
10433 (whether symlinks, hard links, or <tt>.so</tt> directives)
10434 in the file system to the alternate names of the man page,
10435 then you should not rely on <prgn>man</prgn> finding your
10436 man page under those names based solely on the information in
10437 the man page's header.<footnote>
10438 Supporting this in <prgn>man</prgn> often requires
10439 unreasonable processing time to find a manual page or to
10440 report that none exists, and moves knowledge into man's
10441 database that would be better left in the file system.
10442 This support is therefore deprecated and will cease to
10443 be present in the future.
10448 Manual pages in locale-specific subdirectories of
10449 <file>/usr/share/man</file> should use either UTF-8 or the usual
10450 legacy encoding for that language (normally the one corresponding
10451 to the shortest relevant locale name in
10452 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10453 <file>/usr/share/man/fr</file> should use either UTF-8 or
10454 ISO-8859-1.<footnote>
10455 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10456 use. In future, all manual pages will be required to use
10462 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10463 included in the subdirectory name unless it indicates a
10464 significant difference in the language, as this excludes
10465 speakers of the language in other countries.<footnote>
10466 At the time of writing, Chinese and Portuguese are the main
10467 languages with such differences, so <file>pt_BR</file>,
10468 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10473 If a localized version of a manual page is provided, it should
10474 either be up-to-date or it should be obvious to the reader that
10475 it is outdated and the original manual page should be used
10476 instead. This can be done either by a note at the beginning of
10477 the manual page or by showing the missing or changed portions in
10478 the original language instead of the target language.
10483 <heading>Info documents</heading>
10486 Info documents should be installed in <file>/usr/share/info</file>.
10487 They should be compressed with <tt>gzip -9</tt>.
10491 The <prgn>install-info</prgn> program maintains a directory of
10492 installed info documents in <file>/usr/share/info/dir</file> for
10493 the use of info readers.<footnote>
10494 It was previously necessary for packages installing info
10495 documents to run <prgn>install-info</prgn> from maintainer
10496 scripts. This is no longer necessary. The installation
10497 system now uses dpkg triggers.
10499 This file must not be included in packages. Packages containing
10500 info documents should depend on <tt>dpkg (>= 1.15.4) |
10501 install-info</tt> to ensure that the directory file is properly
10502 rebuilt during partial upgrades from Debian 5.0 (lenny) and
10507 Info documents should contain section and directory entry
10508 information in the document for the use
10509 of <prgn>install-info</prgn>. The section should be specified
10510 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10511 space and the section of this info page. The directory entry or
10512 entries should be included between
10513 a <tt>START-INFO-DIR-ENTRY</tt> line and
10514 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10516 INFO-DIR-SECTION Individual utilities
10517 START-INFO-DIR-ENTRY
10518 * example: (example). An example info directory entry.
10521 To determine which section to use, you should look
10522 at <file>/usr/share/info/dir</file> on your system and choose
10523 the most relevant (or create a new section if none of the
10524 current sections are relevant).<footnote>
10525 Normally, info documents are generated from Texinfo source.
10526 To include this information in the generated info document, if
10527 it is absent, add commands like:
10529 @dircategory Individual utilities
10531 * example: (example). An example info directory entry.
10534 to the Texinfo source of the document and ensure that the info
10535 documents are rebuilt from source during the package build.
10541 <heading>Additional documentation</heading>
10544 Any additional documentation that comes with the package may
10545 be installed at the discretion of the package maintainer.
10546 Plain text documentation should be installed in the directory
10547 <file>/usr/share/doc/<var>package</var></file>, where
10548 <var>package</var> is the name of the package, and
10549 compressed with <tt>gzip -9</tt> unless it is small.
10553 If a package comes with large amounts of documentation which
10554 many users of the package will not require you should create
10555 a separate binary package to contain it, so that it does not
10556 take up disk space on the machines of users who do not need
10557 or want it installed.</p>
10560 It is often a good idea to put text information files
10561 (<file>README</file>s, changelogs, and so forth) that come with
10562 the source package in <file>/usr/share/doc/<var>package</var></file>
10563 in the binary package. However, you don't need to install
10564 the instructions for building and installing the package, of
10568 Packages must not require the existence of any files in
10569 <file>/usr/share/doc/</file> in order to function
10571 The system administrator should be able to
10572 delete files in <file>/usr/share/doc/</file> without causing
10573 any programs to break.
10575 Any files that are referenced by programs but are also
10576 useful as stand alone documentation should be installed under
10577 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10578 <file>/usr/share/doc/<var>package</var></file>.
10582 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10583 link to another directory in <file>/usr/share/doc</file> only if
10584 the two packages both come from the same source and the
10585 first package Depends on the second.<footnote>
10587 Please note that this does not override the section on
10588 changelog files below, so the file
10589 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10590 must refer to the changelog for the current version of
10591 <var>package</var> in question. In practice, this means
10592 that the sources of the target and the destination of the
10593 symlink must be the same (same source package and
10600 Former Debian releases placed all additional documentation
10601 in <file>/usr/doc/<var>package</var></file>. This has been
10602 changed to <file>/usr/share/doc/<var>package</var></file>,
10603 and packages must not put documentation in the directory
10604 <file>/usr/doc/<var>package</var></file>. <footnote>
10605 At this phase of the transition, we no longer require a
10606 symbolic link in <file>/usr/doc/</file>. At a later point,
10607 policy shall change to make the symbolic links a bug.
10613 <heading>Preferred documentation formats</heading>
10616 The unification of Debian documentation is being carried out
10620 If your package comes with extensive documentation in a
10621 markup format that can be converted to various other formats
10622 you should if possible ship HTML versions in a binary
10623 package, in the directory
10624 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10625 its subdirectories.<footnote>
10626 The rationale: The important thing here is that HTML
10627 docs should be available in <em>some</em> package, not
10628 necessarily in the main binary package.
10633 Other formats such as PostScript may be provided at the
10634 package maintainer's discretion.
10638 <sect id="copyrightfile">
10639 <heading>Copyright information</heading>
10642 Every package must be accompanied by a verbatim copy of its
10643 copyright information and distribution license in the file
10644 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10645 file must neither be compressed nor be a symbolic link.
10649 In addition, the copyright file must say where the upstream
10650 sources (if any) were obtained, and should name the original
10655 Packages in the <em>contrib</em> or <em>non-free</em> archive
10656 areas should state in the copyright file that the package is not
10657 part of the Debian distribution and briefly explain why.
10661 A copy of the file which will be installed in
10662 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10663 be in <file>debian/copyright</file> in the source package.
10667 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10668 link to another directory in <file>/usr/share/doc</file> only if
10669 the two packages both come from the same source and the
10670 first package Depends on the second. These rules are important
10671 because <file>copyright</file> files must be extractable by
10676 Packages distributed under the Apache license (version 2.0), the
10677 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10678 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10679 1.3) should refer to the corresponding files
10680 under <file>/usr/share/common-licenses</file>,<footnote>
10683 <file>/usr/share/common-licenses/Apache-2.0</file>,
10684 <file>/usr/share/common-licenses/Artistic</file>,
10685 <file>/usr/share/common-licenses/GPL-1</file>,
10686 <file>/usr/share/common-licenses/GPL-2</file>,
10687 <file>/usr/share/common-licenses/GPL-3</file>,
10688 <file>/usr/share/common-licenses/LGPL-2</file>,
10689 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10690 <file>/usr/share/common-licenses/LGPL-3</file>,
10691 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10692 <file>/usr/share/common-licenses/GFDL-1.3</file>
10693 respectively. The University of California BSD license is
10694 also included in <package>base-files</package> as
10695 <file>/usr/share/common-licenses/BSD</file>, but given the
10696 brevity of this license, its specificity to code whose
10697 copyright is held by the Regents of the University of
10698 California, and the frequency of minor wording changes, its
10699 text should be included in the copyright file rather than
10700 referencing this file.
10702 </footnote> rather than quoting them in the copyright
10707 You should not use the copyright file as a general <file>README</file>
10708 file. If your package has such a file it should be
10709 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10710 <file>README.Debian</file> or some other appropriate place.
10714 All copyright files must be encoded in UTF-8.
10717 <sect1 id="copyrightformat">
10718 <heading>Machine-readable copyright information</heading>
10721 A specification for a standard, machine-readable format
10722 for <file>debian/copyright</file> files is maintained as part
10723 of the <package>debian-policy</package> package. This
10724 document may be found in the <file>copyright-format</file>
10725 files in the <package>debian-policy</package> package. It is
10726 also available from the Debian web mirrors at
10727 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10728 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10732 Use of this format is optional.
10738 <heading>Examples</heading>
10741 Any examples (configurations, source files, whatever),
10742 should be installed in a directory
10743 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10744 files should not be referenced by any program: they're there
10745 for the benefit of the system administrator and users as
10746 documentation only. Architecture-specific example files
10747 should be installed in a directory
10748 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10750 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10751 latter directory itself may be a symbolic link to the
10756 If the purpose of a package is to provide examples, then the
10757 example files may be installed into
10758 <file>/usr/share/doc/<var>package</var></file>.
10762 <sect id="changelogs">
10763 <heading>Changelog files</heading>
10766 Packages that are not Debian-native must contain a
10767 compressed copy of the <file>debian/changelog</file> file from
10768 the Debian source tree in
10769 <file>/usr/share/doc/<var>package</var></file> with the name
10770 <file>changelog.Debian.gz</file>.
10774 If an upstream changelog is available, it should be accessible as
10775 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10776 plain text. If the upstream changelog is distributed in
10777 HTML, it should be made available in that form as
10778 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10779 and a plain text <file>changelog.gz</file> should be generated
10780 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10781 the upstream changelog files do not already conform to this
10782 naming convention, then this may be achieved either by
10783 renaming the files, or by adding a symbolic link, at the
10784 maintainer's discretion.<footnote>
10785 Rationale: People should not have to look in places for
10786 upstream changelogs merely because they are given
10787 different names or are distributed in HTML format.
10792 All of these files should be installed compressed using
10793 <tt>gzip -9</tt>, as they will become large with time even
10794 if they start out small.
10798 If the package has only one changelog which is used both as
10799 the Debian changelog and the upstream one because there is
10800 no separate upstream maintainer then that changelog should
10801 usually be installed as
10802 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10803 there is a separate upstream maintainer, but no upstream
10804 changelog, then the Debian changelog should still be called
10805 <file>changelog.Debian.gz</file>.
10809 For details about the format and contents of the Debian
10810 changelog file, please see <ref id="dpkgchangelog">.
10815 <appendix id="pkg-scope">
10816 <heading>Introduction and scope of these appendices</heading>
10819 These appendices are taken essentially verbatim from the
10820 now-deprecated Packaging Manual, version 3.2.1.0. They are
10821 the chapters which are likely to be of use to package
10822 maintainers and which have not already been included in the
10823 policy document itself. Most of these sections are very likely
10824 not relevant to policy; they should be treated as
10825 documentation for the packaging system. Please note that these
10826 appendices are included for convenience, and for historical
10827 reasons: they used to be part of policy package, and they have
10828 not yet been incorporated into dpkg documentation. However,
10829 they still have value, and hence they are presented here.
10833 They have not yet been checked to ensure that they are
10834 compatible with the contents of policy, and if there are any
10835 contradictions, the version in the main policy document takes
10836 precedence. The remaining chapters of the old Packaging
10837 Manual have also not been read in detail to ensure that there
10838 are not parts which have been left out. Both of these will be
10839 done in due course.
10843 Certain parts of the Packaging manual were integrated into the
10844 Policy Manual proper, and removed from the appendices. Links
10845 have been placed from the old locations to the new ones.
10849 <prgn>dpkg</prgn> is a suite of programs for creating binary
10850 package files and installing and removing them on Unix
10852 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10853 work on or be ported to other systems.
10858 The binary packages are designed for the management of
10859 installed executable programs (usually compiled binaries) and
10860 their associated data, though source code examples and
10861 documentation are provided as part of some packages.</p>
10864 This manual describes the technical aspects of creating Debian
10865 binary packages (<file>.deb</file> files). It documents the
10866 behavior of the package management programs
10867 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10868 they interact with packages.</p>
10871 This manual does not go into detail about the options and
10872 usage of the package building and installation tools. It
10873 should therefore be read in conjunction with those programs'
10878 The utility programs which are provided with <prgn>dpkg</prgn>
10879 not described in detail here, are documented in their man pages.
10883 It is assumed that the reader is reasonably familiar with the
10884 <prgn>dpkg</prgn> System Administrators' manual.
10885 Unfortunately this manual does not yet exist.
10889 The Debian version of the FSF's GNU hello program is provided as
10890 an example for people wishing to create Debian packages. However,
10891 while the examples are helpful, they do not replace the need to
10892 read and follow the Policy and Programmer's Manual.</p>
10895 <appendix id="pkg-binarypkg">
10896 <heading>Binary packages (from old Packaging Manual)</heading>
10899 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10902 <sect id="pkg-bincreating"><heading>Creating package files -
10903 <prgn>dpkg-deb</prgn>
10907 All manipulation of binary package files is done by
10908 <prgn>dpkg-deb</prgn>; it's the only program that has
10909 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10910 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10911 will spot that the options requested are appropriate to
10912 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10917 In order to create a binary package you must make a
10918 directory tree which contains all the files and directories
10919 you want to have in the file system data part of the package.
10920 In Debian-format source packages this directory is usually
10921 <file>debian/tmp</file>, relative to the top of the package's
10926 They should have the locations (relative to the root of the
10927 directory tree you're constructing) ownerships and
10928 permissions which you want them to have on the system when
10929 they are installed.
10933 With current versions of <prgn>dpkg</prgn> the uid/username
10934 and gid/groupname mappings for the users and groups being
10935 used should be the same on the system where the package is
10936 built and the one where it is installed.
10940 You need to add one special directory to the root of the
10941 miniature file system tree you're creating:
10942 <prgn>DEBIAN</prgn>. It should contain the control
10943 information files, notably the binary package control file
10944 (see <ref id="pkg-controlfile">).
10948 The <prgn>DEBIAN</prgn> directory will not appear in the
10949 file system archive of the package, and so won't be installed
10950 by <prgn>dpkg</prgn> when the package is unpacked.
10954 When you've prepared the package, you should invoke:
10956 dpkg --build <var>directory</var>
10961 This will build the package in
10962 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10963 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10964 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10965 build the package.)
10969 See the man page <manref name="dpkg-deb" section="8"> for details of how
10970 to examine the contents of this newly-created file. You may find the
10971 output of following commands enlightening:
10973 dpkg-deb --info <var>filename</var>.deb
10974 dpkg-deb --contents <var>filename</var>.deb
10975 dpkg --contents <var>filename</var>.deb
10977 To view the copyright file for a package you could use this command:
10979 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10984 <sect id="pkg-controlarea">
10985 <heading>Package control information files</heading>
10988 The control information portion of a binary package is a
10989 collection of files with names known to <prgn>dpkg</prgn>.
10990 It will treat the contents of these files specially - some
10991 of them contain information used by <prgn>dpkg</prgn> when
10992 installing or removing the package; others are scripts which
10993 the package maintainer wants <prgn>dpkg</prgn> to run.
10997 It is possible to put other files in the package control
10998 information file area, but this is not generally a good idea
10999 (though they will largely be ignored).
11003 Here is a brief list of the control information files supported
11004 by <prgn>dpkg</prgn> and a summary of what they're used for.
11009 <tag><tt>control</tt>
11012 This is the key description file used by
11013 <prgn>dpkg</prgn>. It specifies the package's name
11014 and version, gives its description for the user,
11015 states its relationships with other packages, and so
11016 forth. See <ref id="sourcecontrolfiles"> and
11017 <ref id="binarycontrolfiles">.
11021 It is usually generated automatically from information
11022 in the source package by the
11023 <prgn>dpkg-gencontrol</prgn> program, and with
11024 assistance from <prgn>dpkg-shlibdeps</prgn>.
11025 See <ref id="pkg-sourcetools">.
11029 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11034 These are executable files (usually scripts) which
11035 <prgn>dpkg</prgn> runs during installation, upgrade
11036 and removal of packages. They allow the package to
11037 deal with matters which are particular to that package
11038 or require more complicated processing than that
11039 provided by <prgn>dpkg</prgn>. Details of when and
11040 how they are called are in <ref id="maintainerscripts">.
11044 It is very important to make these scripts idempotent.
11045 See <ref id="idempotency">.
11049 The maintainer scripts are not guaranteed to run with a
11050 controlling terminal and may not be able to interact with
11051 the user. See <ref id="controllingterminal">.
11055 <tag><tt>conffiles</tt>
11058 This file contains a list of configuration files which
11059 are to be handled automatically by <prgn>dpkg</prgn>
11060 (see <ref id="pkg-conffiles">). Note that not necessarily
11061 every configuration file should be listed here.
11064 <tag><tt>shlibs</tt>
11067 This file contains a list of the shared libraries
11068 supplied by the package, with dependency details for
11069 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11070 when it determines what dependencies are required in a
11071 package control file. The <tt>shlibs</tt> file format
11072 is described on <ref id="shlibs">.
11077 <sect id="pkg-controlfile">
11078 <heading>The main control information file: <tt>control</tt></heading>
11081 The most important control information file used by
11082 <prgn>dpkg</prgn> when it installs a package is
11083 <tt>control</tt>. It contains all the package's "vital
11088 The binary package control files of packages built from
11089 Debian sources are made by a special tool,
11090 <prgn>dpkg-gencontrol</prgn>, which reads
11091 <file>debian/control</file> and <file>debian/changelog</file> to
11092 find the information it needs. See <ref id="pkg-sourcepkg"> for
11097 The fields in binary package control files are listed in
11098 <ref id="binarycontrolfiles">.
11102 A description of the syntax of control files and the purpose
11103 of the fields is available in <ref id="controlfields">.
11108 <heading>Time Stamps</heading>
11111 See <ref id="timestamps">.
11116 <appendix id="pkg-sourcepkg">
11117 <heading>Source packages (from old Packaging Manual) </heading>
11120 The Debian binary packages in the distribution are generated
11121 from Debian sources, which are in a special format to assist
11122 the easy and automatic building of binaries.
11125 <sect id="pkg-sourcetools">
11126 <heading>Tools for processing source packages</heading>
11129 Various tools are provided for manipulating source packages;
11130 they pack and unpack sources and help build of binary
11131 packages and help manage the distribution of new versions.
11135 They are introduced and typical uses described here; see
11136 <manref name="dpkg-source" section="1"> for full
11137 documentation about their arguments and operation.
11141 For examples of how to construct a Debian source package,
11142 and how to use those utilities that are used by Debian
11143 source packages, please see the <prgn>hello</prgn> example
11147 <sect1 id="pkg-dpkg-source">
11149 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11154 This program is frequently used by hand, and is also
11155 called from package-independent automated building scripts
11156 such as <prgn>dpkg-buildpackage</prgn>.
11160 To unpack a package it is typically invoked with
11162 dpkg-source -x <var>.../path/to/filename</var>.dsc
11167 with the <file><var>filename</var>.tar.gz</file> and
11168 <file><var>filename</var>.diff.gz</file> (if applicable) in
11169 the same directory. It unpacks into
11170 <file><var>package</var>-<var>version</var></file>, and if
11172 <file><var>package</var>-<var>version</var>.orig</file>, in
11173 the current directory.
11177 To create a packed source archive it is typically invoked:
11179 dpkg-source -b <var>package</var>-<var>version</var>
11184 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11185 <file>.diff.gz</file> (if appropriate) in the current
11186 directory. <prgn>dpkg-source</prgn> does not clean the
11187 source tree first - this must be done separately if it is
11192 See also <ref id="pkg-sourcearchives">.</p>
11196 <sect1 id="pkg-dpkg-buildpackage">
11198 <prgn>dpkg-buildpackage</prgn> - overall package-building
11203 See <manref name="dpkg-buildpackage" section="1">.
11207 <sect1 id="pkg-dpkg-gencontrol">
11209 <prgn>dpkg-gencontrol</prgn> - generates binary package
11214 This program is usually called from <file>debian/rules</file>
11215 (see <ref id="pkg-sourcetree">) in the top level of the source
11220 This is usually done just before the files and directories in the
11221 temporary directory tree where the package is being built have their
11222 permissions and ownerships set and the package is constructed using
11223 <prgn>dpkg-deb/</prgn>
11225 This is so that the control file which is produced has
11226 the right permissions
11231 <prgn>dpkg-gencontrol</prgn> must be called after all the
11232 files which are to go into the package have been placed in
11233 the temporary build directory, so that its calculation of
11234 the installed size of a package is correct.
11238 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11239 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11240 variable substitutions created by
11241 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11246 For a package which generates only one binary package, and
11247 which builds it in <file>debian/tmp</file> relative to the top
11248 of the source package, it is usually sufficient to call
11249 <prgn>dpkg-gencontrol</prgn>.
11253 Sources which build several binaries will typically need
11256 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11257 </example> The <tt>-P</tt> tells
11258 <prgn>dpkg-gencontrol</prgn> that the package is being
11259 built in a non-default directory, and the <tt>-p</tt>
11260 tells it which package's control file should be generated.
11264 <prgn>dpkg-gencontrol</prgn> also adds information to the
11265 list of files in <file>debian/files</file>, for the benefit of
11266 (for example) a future invocation of
11267 <prgn>dpkg-genchanges</prgn>.</p>
11270 <sect1 id="pkg-dpkg-shlibdeps">
11272 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11277 See <manref name="dpkg-shlibdeps" section="1">.
11281 <sect1 id="pkg-dpkg-distaddfile">
11283 <prgn>dpkg-distaddfile</prgn> - adds a file to
11284 <file>debian/files</file>
11288 Some packages' uploads need to include files other than
11289 the source and binary package files.
11293 <prgn>dpkg-distaddfile</prgn> adds a file to the
11294 <file>debian/files</file> file so that it will be included in
11295 the <file>.changes</file> file when
11296 <prgn>dpkg-genchanges</prgn> is run.
11300 It is usually invoked from the <tt>binary</tt> target of
11301 <file>debian/rules</file>:
11303 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11305 The <var>filename</var> is relative to the directory where
11306 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11307 is usually the directory above the top level of the source
11308 tree. The <file>debian/rules</file> target should put the
11309 file there just before or just after calling
11310 <prgn>dpkg-distaddfile</prgn>.
11314 The <var>section</var> and <var>priority</var> are passed
11315 unchanged into the resulting <file>.changes</file> file.
11320 <sect1 id="pkg-dpkg-genchanges">
11322 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11323 upload control file
11327 See <manref name="dpkg-genchanges" section="1">.
11331 <sect1 id="pkg-dpkg-parsechangelog">
11333 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11334 representation of a changelog
11338 See <manref name="dpkg-parsechangelog" section="1">.
11342 <sect1 id="pkg-dpkg-architecture">
11344 <prgn>dpkg-architecture</prgn> - information about the build and
11349 See <manref name="dpkg-architecture" section="1">.
11354 <sect id="pkg-sourcetree">
11355 <heading>The Debian package source tree</heading>
11358 The source archive scheme described later is intended to
11359 allow a Debian package source tree with some associated
11360 control information to be reproduced and transported easily.
11361 The Debian package source tree is a version of the original
11362 program with certain files added for the benefit of the
11363 packaging process, and with any other changes required
11364 made to the rest of the source code and installation
11369 The extra files created for Debian are in the subdirectory
11370 <file>debian</file> of the top level of the Debian package
11371 source tree. They are described below.
11374 <sect1 id="pkg-debianrules">
11375 <heading><file>debian/rules</file> - the main building script</heading>
11378 See <ref id="debianrules">.
11382 <sect1 id="pkg-srcsubstvars">
11383 <heading><file>debian/substvars</file> and variable substitutions</heading>
11386 See <ref id="substvars">.
11392 <heading><file>debian/files</file></heading>
11395 See <ref id="debianfiles">.
11399 <sect1><heading><file>debian/tmp</file>
11403 This is the canonical temporary location for the
11404 construction of binary packages by the <tt>binary</tt>
11405 target. The directory <file>tmp</file> serves as the root of
11406 the file system tree as it is being constructed (for
11407 example, by using the package's upstream makefiles install
11408 targets and redirecting the output there), and it also
11409 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11410 id="pkg-bincreating">.
11414 If several binary packages are generated from the same
11415 source tree it is usual to use several
11416 <file>debian/tmp<var>something</var></file> directories, for
11417 example <file>tmp-a</file> or <file>tmp-doc</file>.
11421 Whatever <file>tmp</file> directories are created and used by
11422 <tt>binary</tt> must of course be removed by the
11423 <tt>clean</tt> target.</p></sect1>
11427 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11431 As it exists on the FTP site, a Debian source package
11432 consists of three related files. You must have the right
11433 versions of all three to be able to use them.
11438 <tag>Debian source control file - <tt>.dsc</tt></tag>
11440 This file is a control file used by <prgn>dpkg-source</prgn>
11441 to extract a source package.
11442 See <ref id="debiansourcecontrolfiles">.
11446 Original source archive -
11448 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11454 This is a compressed (with <tt>gzip -9</tt>)
11455 <prgn>tar</prgn> file containing the source code from
11456 the upstream authors of the program.
11461 Debian package diff -
11463 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11469 This is a unified context diff (<tt>diff -u</tt>)
11470 giving the changes which are required to turn the
11471 original source into the Debian source. These changes
11472 may only include editing and creating plain files.
11473 The permissions of files, the targets of symbolic
11474 links and the characteristics of special files or
11475 pipes may not be changed and no files may be removed
11480 All the directories in the diff must exist, except the
11481 <file>debian</file> subdirectory of the top of the source
11482 tree, which will be created by
11483 <prgn>dpkg-source</prgn> if necessary when unpacking.
11487 The <prgn>dpkg-source</prgn> program will
11488 automatically make the <file>debian/rules</file> file
11489 executable (see below).</p></item>
11494 If there is no original source code - for example, if the
11495 package is specially prepared for Debian or the Debian
11496 maintainer is the same as the upstream maintainer - the
11497 format is slightly different: then there is no diff, and the
11499 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11500 and preferably contains a directory named
11501 <file><var>package</var>-<var>version</var></file>.
11506 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11509 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11510 Debian source package. However, if it is not available it
11511 is possible to unpack a Debian source archive as follows:
11512 <enumlist compact="compact">
11515 Untar the tarfile, which will create a <file>.orig</file>
11519 <p>Rename the <file>.orig</file> directory to
11520 <file><var>package</var>-<var>version</var></file>.</p>
11524 Create the subdirectory <file>debian</file> at the top of
11525 the source tree.</p>
11527 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11529 <item><p>Untar the tarfile again if you want a copy of the original
11530 source code alongside the Debian version.</p>
11535 It is not possible to generate a valid Debian source archive
11536 without using <prgn>dpkg-source</prgn>. In particular,
11537 attempting to use <prgn>diff</prgn> directly to generate the
11538 <file>.diff.gz</file> file will not work.
11542 <heading>Restrictions on objects in source packages</heading>
11545 The source package may not contain any hard links
11547 This is not currently detected when building source
11548 packages, but only when extracting
11552 Hard links may be permitted at some point in the
11553 future, but would require a fair amount of
11555 </footnote>, device special files, sockets or setuid or
11558 Setgid directories are allowed.
11563 The source packaging tools manage the changes between the
11564 original and Debian source using <prgn>diff</prgn> and
11565 <prgn>patch</prgn>. Turning the original source tree as
11566 included in the <file>.orig.tar.gz</file> into the Debian
11567 package source must not involve any changes which cannot be
11568 handled by these tools. Problematic changes which cause
11569 <prgn>dpkg-source</prgn> to halt with an error when
11570 building the source package are:
11571 <list compact="compact">
11572 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11574 <item><p>Changing the targets of symbolic links.</p>
11576 <item><p>Creating directories, other than <file>debian</file>.</p>
11578 <item><p>Changes to the contents of binary files.</p></item>
11579 </list> Changes which cause <prgn>dpkg-source</prgn> to
11580 print a warning but continue anyway are:
11581 <list compact="compact">
11584 Removing files, directories or symlinks.
11586 Renaming a file is not treated specially - it is
11587 seen as the removal of the old file (which
11588 generates a warning, but is otherwise ignored),
11589 and the creation of the new one.
11595 Changed text files which are missing the usual final
11596 newline (either in the original or the modified
11601 Changes which are not represented, but which are not detected by
11602 <prgn>dpkg-source</prgn>, are:
11603 <list compact="compact">
11604 <item><p>Changing the permissions of files (other than
11605 <file>debian/rules</file>) and directories.</p></item>
11610 The <file>debian</file> directory and <file>debian/rules</file>
11611 are handled specially by <prgn>dpkg-source</prgn> - before
11612 applying the changes it will create the <file>debian</file>
11613 directory, and afterwards it will make
11614 <file>debian/rules</file> world-executable.
11620 <appendix id="pkg-controlfields">
11621 <heading>Control files and their fields (from old Packaging Manual)</heading>
11624 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11625 data in a common format, known as control files. Binary and
11626 source packages have control data as do the <file>.changes</file>
11627 files which control the installation of uploaded files, and
11628 <prgn>dpkg</prgn>'s internal databases are in a similar
11633 <heading>Syntax of control files</heading>
11636 See <ref id="controlsyntax">.
11640 It is important to note that there are several fields which
11641 are optional as far as <prgn>dpkg</prgn> and the related
11642 tools are concerned, but which must appear in every Debian
11643 package, or whose omission may cause problems.
11648 <heading>List of fields</heading>
11651 See <ref id="controlfieldslist">.
11655 This section now contains only the fields that didn't belong
11656 to the Policy manual.
11659 <sect1 id="pkg-f-Filename">
11660 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11663 These fields in <tt>Packages</tt> files give the
11664 filename(s) of (the parts of) a package in the
11665 distribution directories, relative to the root of the
11666 Debian hierarchy. If the package has been split into
11667 several parts the parts are all listed in order, separated
11672 <sect1 id="pkg-f-Size">
11673 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11676 These fields in <file>Packages</file> files give the size (in
11677 bytes, expressed in decimal) and MD5 checksum of the
11678 file(s) which make(s) up a binary package in the
11679 distribution. If the package is split into several parts
11680 the values for the parts are listed in order, separated by
11685 <sect1 id="pkg-f-Status">
11686 <heading><tt>Status</tt></heading>
11689 This field in <prgn>dpkg</prgn>'s status file records
11690 whether the user wants a package installed, removed or
11691 left alone, whether it is broken (requiring
11692 re-installation) or not and what its current state on the
11693 system is. Each of these pieces of information is a
11698 <sect1 id="pkg-f-Config-Version">
11699 <heading><tt>Config-Version</tt></heading>
11702 If a package is not installed or not configured, this
11703 field in <prgn>dpkg</prgn>'s status file records the last
11704 version of the package which was successfully
11709 <sect1 id="pkg-f-Conffiles">
11710 <heading><tt>Conffiles</tt></heading>
11713 This field in <prgn>dpkg</prgn>'s status file contains
11714 information about the automatically-managed configuration
11715 files held by a package. This field should <em>not</em>
11716 appear anywhere in a package!
11721 <heading>Obsolete fields</heading>
11724 These are still recognized by <prgn>dpkg</prgn> but should
11725 not appear anywhere any more.
11727 <taglist compact="compact">
11729 <tag><tt>Revision</tt></tag>
11730 <tag><tt>Package-Revision</tt></tag>
11731 <tag><tt>Package_Revision</tt></tag>
11733 The Debian revision part of the package version was
11734 at one point in a separate control field. This
11735 field went through several names.
11738 <tag><tt>Recommended</tt></tag>
11739 <item>Old name for <tt>Recommends</tt>.</item>
11741 <tag><tt>Optional</tt></tag>
11742 <item>Old name for <tt>Suggests</tt>.</item>
11744 <tag><tt>Class</tt></tag>
11745 <item>Old name for <tt>Priority</tt>.</item>
11754 <appendix id="pkg-conffiles">
11755 <heading>Configuration file handling (from old Packaging Manual)</heading>
11758 <prgn>dpkg</prgn> can do a certain amount of automatic
11759 handling of package configuration files.
11763 Whether this mechanism is appropriate depends on a number of
11764 factors, but basically there are two approaches to any
11765 particular configuration file.
11769 The easy method is to ship a best-effort configuration in the
11770 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11771 handle updates. If the user is unlikely to want to edit the
11772 file, but you need them to be able to without losing their
11773 changes, and a new package with a changed version of the file
11774 is only released infrequently, this is a good approach.
11778 The hard method is to build the configuration file from
11779 scratch in the <prgn>postinst</prgn> script, and to take the
11780 responsibility for fixing any mistakes made in earlier
11781 versions of the package automatically. This will be
11782 appropriate if the file is likely to need to be different on
11786 <sect><heading>Automatic handling of configuration files by
11791 A package may contain a control information file called
11792 <tt>conffiles</tt>. This file should be a list of filenames
11793 of configuration files needing automatic handling, separated
11794 by newlines. The filenames should be absolute pathnames,
11795 and the files referred to should actually exist in the
11800 When a package is upgraded <prgn>dpkg</prgn> will process
11801 the configuration files during the configuration stage,
11802 shortly before it runs the package's <prgn>postinst</prgn>
11807 For each file it checks to see whether the version of the
11808 file included in the package is the same as the one that was
11809 included in the last version of the package (the one that is
11810 being upgraded from); it also compares the version currently
11811 installed on the system with the one shipped with the last
11816 If neither the user nor the package maintainer has changed
11817 the file, it is left alone. If one or the other has changed
11818 their version, then the changed version is preferred - i.e.,
11819 if the user edits their file, but the package maintainer
11820 doesn't ship a different version, the user's changes will
11821 stay, silently, but if the maintainer ships a new version
11822 and the user hasn't edited it the new version will be
11823 installed (with an informative message). If both have
11824 changed their version the user is prompted about the problem
11825 and must resolve the differences themselves.
11829 The comparisons are done by calculating the MD5 message
11830 digests of the files, and storing the MD5 of the file as it
11831 was included in the most recent version of the package.
11835 When a package is installed for the first time
11836 <prgn>dpkg</prgn> will install the file that comes with it,
11837 unless that would mean overwriting a file already on the
11842 However, note that <prgn>dpkg</prgn> will <em>not</em>
11843 replace a conffile that was removed by the user (or by a
11844 script). This is necessary because with some programs a
11845 missing file produces an effect hard or impossible to
11846 achieve in another way, so that a missing file needs to be
11847 kept that way if the user did it.
11851 Note that a package should <em>not</em> modify a
11852 <prgn>dpkg</prgn>-handled conffile in its maintainer
11853 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11854 the user confusing and possibly dangerous options for
11855 conffile update when the package is upgraded.</p>
11858 <sect><heading>Fully-featured maintainer script configuration
11863 For files which contain site-specific information such as
11864 the hostname and networking details and so forth, it is
11865 better to create the file in the package's
11866 <prgn>postinst</prgn> script.
11870 This will typically involve examining the state of the rest
11871 of the system to determine values and other information, and
11872 may involve prompting the user for some information which
11873 can't be obtained some other way.
11877 When using this method there are a couple of important
11878 issues which should be considered:
11882 If you discover a bug in the program which generates the
11883 configuration file, or if the format of the file changes
11884 from one version to the next, you will have to arrange for
11885 the postinst script to do something sensible - usually this
11886 will mean editing the installed configuration file to remove
11887 the problem or change the syntax. You will have to do this
11888 very carefully, since the user may have changed the file,
11889 perhaps to fix the very problem that your script is trying
11890 to deal with - you will have to detect these situations and
11891 deal with them correctly.
11895 If you do go down this route it's probably a good idea to
11896 make the program that generates the configuration file(s) a
11897 separate program in <file>/usr/sbin</file>, by convention called
11898 <file><var>package</var>config</file> and then run that if
11899 appropriate from the post-installation script. The
11900 <tt><var>package</var>config</tt> program should not
11901 unquestioningly overwrite an existing configuration - if its
11902 mode of operation is geared towards setting up a package for
11903 the first time (rather than any arbitrary reconfiguration
11904 later) you should have it check whether the configuration
11905 already exists, and require a <tt>--force</tt> flag to
11906 overwrite it.</p></sect>
11909 <appendix id="pkg-alternatives"><heading>Alternative versions of
11910 an interface - <prgn>update-alternatives</prgn> (from old
11915 When several packages all provide different versions of the
11916 same program or file it is useful to have the system select a
11917 default, but to allow the system administrator to change it
11918 and have their decisions respected.
11922 For example, there are several versions of the <prgn>vi</prgn>
11923 editor, and there is no reason to prevent all of them from
11924 being installed at once, each under their own name
11925 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11926 Nevertheless it is desirable to have the name <tt>vi</tt>
11927 refer to something, at least by default.
11931 If all the packages involved cooperate, this can be done with
11932 <prgn>update-alternatives</prgn>.
11936 Each package provides its own version under its own name, and
11937 calls <prgn>update-alternatives</prgn> in its postinst to
11938 register its version (and again in its prerm to deregister
11943 See the man page <manref name="update-alternatives"
11944 section="8"> for details.
11948 If <prgn>update-alternatives</prgn> does not seem appropriate
11949 you may wish to consider using diversions instead.</p>
11952 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11953 package's version of a file (from old Packaging Manual)
11957 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11958 when it reinstalls the package it belongs to, and to have it
11959 put the file from the package somewhere else instead.
11963 This can be used locally to override a package's version of a
11964 file, or by one package to override another's version (or
11965 provide a wrapper for it).
11969 Before deciding to use a diversion, read <ref
11970 id="pkg-alternatives"> to see if you really want a diversion
11971 rather than several alternative versions of a program.
11975 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11976 and updated by a special program <prgn>dpkg-divert</prgn>.
11977 Please see <manref name="dpkg-divert" section="8"> for full
11978 details of its operation.
11982 When a package wishes to divert a file from another, it should
11983 call <prgn>dpkg-divert</prgn> in its preinst to add the
11984 diversion and rename the existing file. For example,
11985 supposing that a <prgn>smailwrapper</prgn> package wishes to
11986 install a wrapper around <file>/usr/sbin/smail</file>:
11988 dpkg-divert --package smailwrapper --add --rename \
11989 --divert /usr/sbin/smail.real /usr/sbin/smail
11990 </example> The <tt>--package smailwrapper</tt> ensures that
11991 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11992 can bypass the diversion and get installed as the true version.
11993 It's safe to add the diversion unconditionally on upgrades since
11994 it will be left unchanged if it already exists, but
11995 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11996 message, make the command conditional on the version from which
11997 the package is being upgraded:
11999 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12000 dpkg-divert --package smailwrapper --add --rename \
12001 --divert /usr/sbin/smail.real /usr/sbin/smail
12003 </example> where <tt>1.0-2</tt> is the version at which the
12004 diversion was first added to the package. Running the command
12005 during abort-upgrade is pointless but harmless.
12009 The postrm has to do the reverse:
12011 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12012 dpkg-divert --package smailwrapper --remove --rename \
12013 --divert /usr/sbin/smail.real /usr/sbin/smail
12015 </example> If the diversion was added at a particular version, the
12016 postrm should also handle the failure case of upgrading from an
12017 older version (unless the older version is so old that direct
12018 upgrades are no longer supported):
12020 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12021 dpkg-divert --package smailwrapper --remove --rename \
12022 --divert /usr/sbin/smail.real /usr/sbin/smail
12024 </example> where <tt>1.0-2</tt> is the version at which the
12025 diversion was first added to the package. The postrm should not
12026 remove the diversion on upgrades both because there's no reason to
12027 remove the diversion only to immediately re-add it and since the
12028 postrm of the old package is run after unpacking so the removal of
12029 the diversion will fail.
12033 Do not attempt to divert a file which is vitally important for
12034 the system's operation - when using <prgn>dpkg-divert</prgn>
12035 there is a time, after it has been diverted but before
12036 <prgn>dpkg</prgn> has installed the new version, when the file
12037 does not exist.</p>
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